Craniomaxillofacial Reconstructive and Corrective Bone Surgery - part 3 docx

Localized Ridge Augmentation Using Guided Bone Regeneration in Deficient Implant Sites Daniel A.. One augmentation technique is based on the principle of guided tissue regeneration using

140 H.-P Weber, D.A Buser, and D Weingart

sink depth They are press-fit implants, which achieve the

re-quired primary stability with the preparation of a precise,

con-gruent implant bed The instruments necessary for bone

prepa-ration are in part the same as for the HS implant (Figure 15.5):

three round burs of increasing diameters, predrill, trephine

mill, and a color-coded depth gauge However, tap, ratchet,

and guidance key are not necessary To insert the implant, the

insertion device is attached to the implant top in the sterile

ampoule The implant is then removed from the ampoule and

placed into the bone cavity until a slight resistance is

de-tectable Subsequently, the inserting device is removed, and

the implant is tapped to its final position using a special

tap-ping instrument and a mallet The gentle press-fit after

inser-tion allows for good primary stability in recipient sites with

a firm bone structure

ITI Implant Material and Tissue Reactions

ITI implants are endosseous implants that are anchored in the

bone and penetrate the soft tissue cover Therefore, the

im-plant surface is not only in contact with the bone but also withthe mucosa

Since their inception 20 years ago, ITI implants have beenmade of commercially pure titanium with a TPS surface in thebone-anchoring section This coating procedure, first described

by Hahn and Palich,11was introduced in implant dentistry forthe first time with ITI implants in 1974 It creates a rough andmicroporous implant surface, with a porosity between 30 and

50␮m (Figure 15.6) The oxide film responsible for the compatibility of titanium forms on this sprayed layer There-fore, the biocompatibility of the TPS surface is equivalent to

bio-a solid titbio-anium body Technicbio-al detbio-ails of this procedure bio-andthe TPS surface were described by Steinemann.12

BoneDirect bone apposition onto TPS surfaces was clearly shown

at the beginning of the research project in animal experiments,and results were reported by Schroeder and coworkers in 1976and 1978 using a new histologic technique with nondecalci-fied sections.13,14 This phenomenon of direct bone-implant

contact is often termed osseointegration,15or functional

anky-losis.16Light-microscopic images demonstrate the anchorage

of titanium implants with osseointegration (Figure 15.7) The

F IGURE 15.5 Instruments for hollow cylinder site preparation.

F 15.6 Titanium-plasma-sprayed surface (TPS) in a close-up view.

F IGURE 15.7 Micrograph demonstrating direct bone-to-implant tact (osseointegration) to TPS surface (experimental sample from primate).

con-higher magnification reveals the direct apposition of newly

formed bone onto the surface of titanium implants with a TPS

surface without an intervening layer of connective tissue The

vitality of the bone is demonstrated by the presence of

os-teocytes and blood vessels close to the implant surface

(Fig-ure 15.8) Osseointegration was also confirmed on a few

hu-man implants, which had to be removed (e.g., due to recurrent

peri-implant infections in the crestal area; see Figure 15.9)

Furthermore, direct bone-implant contact was also

demon-strated in scanning electron-microscopic analyses, as well as

in a transmission electron-microscopic study by Listgarten et

al.17using titanium evaporated epoxy resin implants (Figure

15.10) Osseointegration is generally not observed to have

100% bone contact along a given implant surface The extent

of bone-implant interface depends mainly on three factors: (1)

the implant and surface material used; (2) the roughness of

the implant surface; and (3) the density of the surrounding

bone

As mentioned earlier, ITI implants have been coated with a

TPS surface since their inception in 1974 as this porous

tita-nium surface offers several advantages from a clinical point

of view An animal study in rats demonstrates that the TPS

surface accelerates bone apposition during early wound

heal-ing.18 TPS implants revealed the first visible bone-implantcontact after 7 days of healing, whereas smooth titanium im-plants demonstrated the first contacts after 21 days In a study

of miniature pigs, titanium implants with TPS coatings

demon-F IGURE 15.9 Osseointegration in apical section of hollow-cylinder implant, cross-sectional view (human explant).

F IGURE 15.10 Direct bone apposition to TPS surface in electron croscopic view (magnification 16,000, sample from canine experi- ment with TPS coated epoxy implants).

mi-F IGURE 15.8 Direct bone-implant contact without interpositioning of

soft tissue Blood vessels in contact with implant surface

(experi-mental sample from canine model).

142 H.-P Weber, D.A Buser, and D Weingart

strated a significantly higher percentage of direct bone-implant

contact in cancellous bone when compared to smooth- or

fine-structured titanium surfaces.19 And finally, a study in sheep

revealed significantly higher removal torques for TPS implants

when compared with smooth- or fine-structured titanium

im-plants.20Summarizing these studies, it can be concluded that

titanium implants with TPS surfaces achieve significantly

faster and better bone anchorage when compared with titanium

implants with smooth- or fine-structured surfaces

To achieve osseointegration of ITI implants, four

prereq-uisites need to be fulfilled: (1) biocompatible material; (2)

atraumatic surgical technique using a slow drilling technique

to prevent overheating of the bone; (3) primary implant

sta-bility; and (4) a healing period of 3 to 4 months without

di-rect loading.7As already mentioned, ITI implants were

de-signed as nonsubmerged implants If placed as such, they

are not covered by the oral mucosa during healing and

pen-etrate the crestal mucosa from the time of implant

place-ment In contrast to the frequently stated requirement for a

submerged implant placement,15 nonsubmerged ITI

im-plants achieve osseointegration with high predictability if

the aforementioned prerequisites are followed.7,21–25 This

clinical fact observed over more than 20 years has been

con-firmed in the recent past by several experimental

if long-term function is to be expected.26

As demonstrated above, bone as mineralized connective sue adheres to the rough TPS surface Therefore, it could beexpected that a similar reaction would occur when the non-mineralized supracrestal connective tissue directly contactedthe TPS surface, and when the implant post is located in ker-atinized attached mucosa Light-microscopic experiments onTPS-coated implants placed in monkeys16 or beagle dogs28

tis-demonstrated a fiber orientation perpendicular to the implantsurface (Figure 15.11) However, studies in beagle dogs eval-uating titanium implants with smooth or sandblasted sur-faces17,29revealed no evidence of perpendicular fiber attach-

F IGURE 15.11 Supracrestal connective tissue fibers in perpendicular

orientation to TPS coated implant surface (cross-sectional view).

F IGURE 15.12 Absence of perpendicular fibers close to the implant surface Collagen fibers with a parallel orientation distant from the implant surface Blood vessel and cell-free zone in contact with im- plant surface.

ment to the tested nonporous titanium surfaces The

connec-tive tissue in direct contact with the implant post was mainly

dominated by circularly oriented collagen fibers This inner

zone of connective tissue was free of blood vessels and

re-sembled most likely an inflammation-free scar-tissue

forma-tion (Figure 15.12) The obvious difference to the

aforemen-tioned studies with perpendicular fiber attachment can

probably be explained by the difference in the surface

char-acteristics

Based on biological considerations for successful

mainte-nance of healthy peri-implant soft tissues, ITI implants have

a smoothly machined titanium surface in the transmucosal

section to reduce the risk of plaque accumulation Thus it has

to be expected that a similar arrangement of circularly

ori-ented connective tissue fibers is predominantly present around

ITI implants in patients due to the smooth surface in the

supracrestal area (Figure 15.13)

Different light-microscopic studies using nonsubmerged

ti-tanium implants in different animal models16,28–30

demon-strated no evidence of an epithelial downgrowth to the

bone-crest level The micrographs revealed the formation of a

peri-implant sulcus, with the most apical epithelial cells

be-ing located approximately 1 mm above the bone-crest level

(Figure 15.14) The epithelial structures around titanium

im-plants are similar to those found around teeth (i.e., sulcular

epithelium-like and, more apically, junctional epithelium-likecell layers along the implant surface; see Figure 15.15)

Prosthodontic Concept

Abutments

Various abutments are available for the two-part ITI implants.They consist of a number of conical abutments for screw-retained and/or cemented restorations including an angledabutment (Figure 15.16), an octagonal abutment for screw-retained restorations only, and the retentive anchor used forimplant treatments with overdentures The abutments all havethe same apical portion fitting to the inner top portion of theimplant with an M2 (2-mm) screw and an 8° cone (Figure15.17) This cone-to-screw interface serves as a nonrotationalfriction fit or mechanical lock on the basis of the Morse ta-per principle It has shown to be three to four times as strong

as a conventional, flat-coupling screw connection.31 To cure the abutments into this nonrotational fit, they are insertedwith a torque of 35 Ncm using a special torque instrument(Figure 15.18)

se-F IGURE 15.13 Circular fibers around implant post in cross-sectional

view (canine experiment).

F IGURE 15.14 Microradiograph demonstrating peri-implant soft sue morphology At the top apical extension of peri-implant epithe- lium At the bottom is the crestal bone height Connective tissue con- tact height extends from the crestal bone height to the epithelium.

tis-F IGURE 15.19 Solid conical abutments (4-mm, 5.5-mm, and 7-mm height) for cemented restorations.

F IGURE 15.15 Peri-implant epithelium resembling sulcular and

junc-tional epithelium at natural teeth.

F IGURE 15.16 ITI abutments From left to right: Solid abutments,

angled abutment retentive anchor, and octa-abutment.

F IGURE 15.17 Cone-to-screw design (Morse taper principle) for tation safe anchorage of abutment in implant.

ro-F IGURE 15.18 Torque instrument for abutment insertion (35 Ncm) and tightening of occlusal screws (20 Ncm).

F IGURE 15.20 Schematic overview of restorative steps for cemented

restorations.

Conical Abutments

The conical abutments come as solid abutments without

in-ternal screw threads in heights of 4, 5.5, and 7 mm, for

ce-mentation of restorations (Figure 15.19) They are especially

easy to use and, therefore, save time and reduce costs After

placement of the conical abutment, an impression is made, a

stone cast is poured, and the crowns or fixed partial dentures

are waxed directly to the stone model and then completed as

conventional crown-bridge work (Figure 15.20)

Octa-abutment for Screw-Retained Restorations

For screw-retained prostheses, the Octa-system with different

prefabricated parts for accurate transfer and laboratory

proce-dures has been added to the ITI armamentarium in the more

recent past.31The top of the Octa-abutment has eight sides and

is 1.5 mm high (Figure 15.21), with an M2 screw hole in its

top to retain the restoration This 2-mm occlusal screw limits

the occurrences of screw loosening or fractures commonly

re-ported for implant restorations The Octa-abutment is anchored

in the implant with the same cone-to-screw interface as the

con-ical abutments described earlier, and they provide a tional friction fit Transfer copings are used for impressions.Once an impression is made, one-piece analogs are secured intothe transfer copings and die stone poured After the stone hasset, the transfer copings are removed Prefabricated gold cop-ings made from nonoxidizing, high gold-content alloys with ahigh melting range are placed on the analogs Long wax-up orguide screws are used to secure the copings on the analogs and

nonrota-to create the space for the future occlusal screw access canal.The frame of the future restoration is then waxed and cast tothe copings In case of porcelain-fused-to-gold restorations, theporcelain is added thereafter It is important that for suchrestorations, a layer of gold compatible with the ceramic ma-terial to be used is cast onto the copings Gold copings with anoctagonal inside are chosen for single-tooth cases, whereas goldcopings with rounded insides are used for fixed partial dentures.The step-by-step procedure for screw-retained restorations issummarized in Figure 15.22a,b The prefabricated gold copingshave an outstanding precision, which can be documented inSEM images (Figure 15.23) The resistance of the implant-abutment-superstructure complex to lateral forces is superiordue to the precise component fit and even enhanced by the 45°inclination of the implant shoulder Angled abutments and atransversal screw retention concept have been added to theprosthodontic concept more recently For instructions on theiruse, the reader is referred to the respective, detailed system lit-erature They assist the restorative dentist in overcoming im-

F IGURE 15.22 (a,b) Schematic overview of procedural steps for screw-retained restorations with the octa-abutment concept and its prefabricated components.

a

bCemented Restorative Technique

F IGURE 15.21 Octa-abutment for screw-retained restoration in

close-up view.

Non-RepositionableTransfer Technique

146 H.-P Weber, D.A Buser, and D Weingart

F IGURE 15.23 Precise fit of gold coping to 45° implant shoulder.

F IGURE 15.24 Angled abutments to correct angulation problems in

fixed partial denture cases.

F IGURE 15.25 Transverse screw coping for single-tooth restorations.

F IGURE 15.26 Octa-abutments on four implants for bar-retained denture.

over-plant angulation and/or divergence problems (Figures 15.24

and 15.25)

Overdentures on Bars

In cases in which support for dentures is needed, two to four

implants can be placed and restored with a gold bar and an

overdenture after completion of implant healing.9,10

Prefabri-cated gold copings, gold bars with round or oval profile, and

gold clips or bar sleeves are the available components Note

that these gold copings are different from the ones used for

cast restorations The bar-retaining copings are only to be used

to affix prefabricated bar segments via soldering procedure, inthat they are fit tightly onto the bars and fitted into the denture

as retentive elements (Figures 15.26–15.28)

Overdenture on Retentive Anchors

When moderate additional retention is required for a lar or maxillary denture, two implants can be placed, andround (retentive) anchors are inserted in the implants after the3- to 4-month healing period.32Because no reopening surgery

mandibu-is necessary, the restorative phase begins at the end of thmandibu-ishealing period Female matrices are processed into the den-ture to fit tightly to the retentive anchors with a simple im-pression and pick-up method (Figures 15.29–15.31)

Case ReportsFigures 15.32 to 15.37 show illustrative examples from casereports

F IGURE 15.27 Gold bar in place Bar segments are soldered to gold

copings different from the ones used for cast restorations.

F IGURE 15.28 Finished overdenture demonstrating bar clips in situ.

A metal lingual plate for strength and minimizing interference with

tongue function is recommended as shown.

F IGURE 15.29 Retentive anchor in close-up view.

F IGURE 15.30 Schematic illustration of function of gold matrix on retentive anchor The presence of the polyethylene sleeve around the matrix is important for proper retentive function of the matrix.

F IGURE 15.31 Tissue side of overdenture with retentive matrices in place.

148 H.-P Weber, D.A Buser, and D Weingart

F IGURE 15.32 (a) Master cast with dies of conical abutments for mented crowns (b) Finished restorations on dies (c) Lingual view of cemented restorations (d) Buccal view of cemented resotrations (e) Radiographic control 3 years after implant placement.

e

F IGURE 15.33 (a) Custom-angled abutment in case with

maxil-lary alveolar protrusion in right canine area Note the placement

of the implant below tissue level for aesthetic crown emergence.

(b) View of custom angled abutment on an HS implant The

cus-tom angled abutment was waxed and cast on an octogonal gold

coping and then custom milled (c) Procelain-fused-to-metal

crown in place (d) Radiographic control at 3 years after crown

insertion.

150 H.-P Weber, D.A Buser, and D Weingart

F IGURE 15.34 (a) Octa-abutment placed for screw-retained restoration

in area of the right canine Note again the deeper implant placement for aesthetic purposes (b) Final restoration in place (c) Radiographic control 2 years after insertion.

b

ca

F IGURE 15.35 (a) Crown post inserted in octa-abutment for fixation of crown via versal screw in area of missing upper left central incisor (b) Close-up view of crown post and SCS screwdriver (c) Fixation of crown with transversal screw (d) Aesthetic appearance of completed tooth replacement (e) Radiographic control 2 years after crown insertion.

e

152 H.-P Weber, D.A Buser, and D Weingart

F IGURE 15.36 (a) Octa-abutments on four implants placed in

maxil-lary edentulous patient (b) High-profile milled bar in situ (c)

Palate-free overdenture with bilateral custom fabricated locks which can be

easily opened and closed by the patient (d) Close-up view of one

of the locks (e) Frontal view of final prosthesis (f) Radiographic control at 1 year.

F IGURE 15.37 (a) Retentive anchors in place (b) Radiographic control at 4 years (c) Retentive anchor matrices processed in lower denture (d) Frontal view of final prostheses (i.e., lower overdenture, upper complete denture).

References

1 Sutter F, Schroeder A, Straumann F ITI Hohlzylinder Systeme.

Prinzipien Methodik Swiss Dent 1983;4:21.

2 Babbush CA, Kent JN, Misiek DJ Titanium plasma-sprayed

(TPS) screw implants for the reconstruction of the edentulous

mandible J Oral Maxillofac Surg 1986;44:274.

3 Sutter F, Schroeder A, Buser D The new concept of ITI

hol-low cylinder and holhol-low screw implants Part I: Engineering and

design Int J Oral Maxillofac Implants 1988;3:161.

4 Buser D, Schroeder A, Sutter F, Lang NP The new concept of

ITI hollow-cylinder and hollow-screw implants: Part 2, Clinical

aspects, indications, and early clinical results Int J Oral

Max-illofac Implants 1988;3:173.

5 Sutter F, Schroeder A, Buser D Das neue ITI-Implantatkonzept.

Technische Aspekte und Methodik Quintessenz 1988;39: (Teil

1)1875–XX; (Teil 2)2057.

6 Sutter F, Krekeler G, Schwammberger AE, Sutter FJ Das

ITI-Bonefitimplantatsystem: Implantatbettgestaltung Quintessenz.

1991;42:541.

7 Buser D, Weber HP, Brägger U The treatment of partially

en-dentulous patients with ITI hollow-screw implants: Pre-surgical

evaluation and surgical procedures Int J Oral Maxillofac

Im-plants 1990;5:165.

8 Sutter F Raveh J Titanium-coated hollow screw and tion plate system for bridging of lower jaw defects: Biomechani-

reconstruc-cal aspects Int J Oral Maxillofac Surg 1988;17:267.

9 Schroeder A, Maeglin B, Sutter F Das plantat Typ-F zur Prothesenretention beim zahnlosen Kiefer.

ITI-Hohlzylinderim-Scheiz Monatsschr Zahnheilk 1983;93:720.

10 ten Bruggenkate CM, Muller K, Oosterbeek HS Clinical

eval-uation of the ITI (F-type) hollow cylinder implant Oral Surg

Oral Med Oral Pathol 1990;70:693.

11 Hahn H, Palich W Preliminary evaluation of porous metal

sur-faced titanium for orthopedic implants J Biomed Mater Res.

1970;4:571.

12 Steinemann S The properties of titanium In: Schroeder A,

Sut-ter F, Krekeler G, eds Oral Implantology: Basics-ITI Hollow

Cylinder New York: Thieme Medical Publishers; 1991:37–58.

13 Schroeder A, Pohler O, Sutter F Gewebsreaktion auf ein

Titan-Hohlzylinderimplantat mit Titan-Spritzschichtoberfläche Schweiz

Monatsschr Zahnheilk 1976;86:713.

14 Schroeder A, Stich H, Straumann F, Sutter F Über die lagerung von Osteozement an einen belasteten Implantatkörper.

An-Schweiz Monatsschr Zahnheilk 1978;88:1051.

15 Brånemark PI, Hansson BO, Adell R, et al Osseointegrated plants in the treatment of the edentulous jaw Experience from a

im-10-year period Scand J Plast Reconstruct Surg II (suppl 16), 1977.

25 Mericske-Stern R, Steinlin-Schaffner T, Marti P, Geering AH Peri-implant mucosal aspects of ITI implants supporting over-

dentures A five-year longitudinal study Clin Oral Implants Res.

1994;5:9–18.

26 McKinney R, Steflik DE, Koth DL Per, peri, or trans? A

con-cept from improved dental terminology J Prosthet Dent 1984;

plants A histologic and histometric study in beagle dogs Clin

Oral Implants Res 1996;7:11.

31 Sutter F, Weber HP, Sorensen J, Belser U The new restorative concept of the ITI Dental Implant System: engineering and de-

sign Int J Periodont Rest Dent 1993;13:408.

32 Mericske-Stern R, Geering AH Implantate in der Totalprothetik: Die Verankerung der Totalprothese im zahnlosen Unterkiefer

durch zwei Implantate mit Einzelattachment Schweiz

Monatss-chr Zahnmed 1988;98:871.

16 Schroeder A, van der Zypen E, Stich H, Sutter F The reactions

of bone, connective tissue and epithelium to endosteal implants

with titanium-sprayed surfaces J Maxillofac Surg 1981;9:15.

17 Listgarten MA, Buser D, Steinemann S, Donath K, Lang NP,

We-ber HP Light and transmission electron microscopy of the intact

interface between bone, gingiva and non-submerged

titanium-coated epoxy resin implants J Dent Res 1992;71:364–371.

18 Kirsch A, Donath K Tierexperimentelle Untersuchungen zur

Bedeutung der Mikromorphologie von

Titanimplantatober-flächen Fortschr Zahnärztl Implantol 1984;1:35.

19 Buser D, Schenk RK, Steinemann S, Fiorellini JP, Fox C, Stich

H Influence of surface characteristics on bone reactions to

ti-tanium implants: a histomorphometric study in miniature pigs.

J Biomed Mater Res 1991;25:889.

20 Wilke HJ, Claes L, Steinemann S The influence of various

ti-tanium surfaces on the interface shear strength between implants

and bone Adv Biomater 1990;9:309.

21 Buser D, Weber HP, Lang NP Tissue integration of

non-sub-merged implants Clin Oral Implants Res 1990;1:33.

22 Buser D, Weber HP, Brägger U, Balsiger C Tissue integration

of one-stage ITI implants: 3-year results of a longitudinal study

with hollow-cylinder and hollow-screw implants Int J Oral

Maxillofac Implants 1991;6:405.

23 Buser D, Sutter F, Weber HP, Belser U, Schroeder A The ITI

Dental Implant System: basics, indications, clinical procedures

and results Clark’s Clin Dentistry 1992;5:1–22.

24 Mericske-Stern R Clinical evaluation of overdenture

restora-tions supported by osseointegrated implants: a retrospective

study Int J Oral Maxillofac Implants 1990;5:375.

Localized Ridge Augmentation Using Guided

Bone Regeneration in Deficient Implant Sites

Daniel A Buser, Dieter Weingart, and Hans-Peter Weber

The use of osseointegrated implants anchored in the jawbone

with direct bone-implant contact has become an increasingly

important treatment modality for the replacement of missing

teeth.1,2To expect a predictable long-term prognosis for

os-seointegrated implants, a sufficient volume of healthy bone

should be available at possible recipient sites Thus a careful

presurgical evaluation is essential to obtain the necessary

in-formation about the quality of the bone, the vertical bone

height, and the orofacial bone width When this analysis

re-veals that the width of the alveolar ridge is insufficient at

de-sired implant locations, reconstructive surgery is needed if

en-dosseous implants are to be used One augmentation technique

is based on the principle of guided tissue regeneration using

barrier membranes, which was initially developed for

peri-odontal regeneration.3,4A comprehensive text on guided bone

regeneration in implant dentistry has been published by Buser

et al.5

This principle has been tested for the regeneration of bone

tissue in different types of bone defects as well as around

den-tal implants.4–23These studies have in common that barrier

membranes were placed over bone defects and closely adapted

to the surrounding bone surface, creating a secluded space

be-tween the bone and the membrane With the placement of a

barrier membrane, preference is given to bone-forming cells

that originate from adjacent bone to populate and regenerate

these defects with bone, since competing soft tissue cells from

the mucosa are excluded from these defects Control sites

without membranes demonstrate incomplete bone

regenera-tion and the presence of soft tissue within the defects For the

regeneration of bone defects using barrier membranes, the

term guided bone regeneration (GBR) is preferable since this

term describes the purpose of the membrane application more

precisely than does the term guided tissue regeneration (GTR).

In combination with the placement of endosseous implants,

two different applications of GBR are possible: (1) the

si-multaneous approach using membranes to regenerate bone

de-fects around an inserted implant; and (2) the staged approach

using membranes for localized ridge augmentation and

place-ment of implants 6 months later into the newly regenerated

alveolar ridge in a separate surgical procedure

The clinical testing of GBR in patients for implant tions started at the University of Bern in 1988, and the poten-tial of both treatment options was demonstrated.11,12From theseearly experiences it could be concluded that the biological prin-ciple of GBR for ridge enlargement is predictable However,factors such as soft tissue management, placement of mem-branes with the provision of sufficient space for bone regener-ation, primary flap closure, and postsurgical infection controlinfluence the prognosis to a great degree and must be optimized.Consequently, the surgical procedures were refined andtechnical modifications developed to improve the predict-ability of the GBR technique.21–23

indica-In implant patients with an insufficient bone volume, thesurgical approach to be chosen depends on three selection cri-teria If the intrasurgical status demonstrates: (1) an implantcannot be inserted with primary stability; (2) an implant can-not be inserted in an appropriate position from a prostheticpoint of view; or (3) the peri-implant bone defect would berelatively extended, the simultaneous application of a barriermembrane, and an implant would have certain risks There-fore, the staged approach is preferred in these situations since

it reduces the risk for compromise or failure of the result.The goal of the staged approach is a localized ridge aug-mentation and subsequent placement of endosseous implantsinto the newly formed alveolar ridge after a healing period of

6 months

Based on current experimental and clinical knowledge, ahealthy individual with normal healing capacity and an alveo-lar bone (defect) site rendering the opportunity for vasculariza-tion and colonization with bone-forming cells is a good candi-date for GBR procedure Additionally, the following clinicaland/or technical prerequisites need to be fulfilled for predictablesuccess with ridge augmentation procedures

Appropriate Barrier Membrane

An appropriate membrane to serve as a barrier is necessary.The mostly used e-PTFE (Teflon) membrane (GTAM, W.L.Gore and Associates, Flagstaff, AZ) is a nondegradable mem-

155

brane The structure of this membrane does not allow the

penetration of cells through the membrane, which is an

im-portant factor for its success as a physical barrier

Numer-ous experimental studies in animals have demonstrated that

this membrane material is bioinert and allows

complication-free tissue integration, provided that submerged healing

without direct contact to the oral cavity can be achieved

(for review, see Buser et al.5) Biodegradable membranes

have also been tested in animals and humans with

success-ful outcomes for periodontal indications.24–28 In these

in-dications, the use of biodegradable membranes gains from

the advantage of avoiding a second surgical procedure for

membrane removal However, the advantage of using

biodegradable membranes for implant indications is not

considerable since most surgical sites have to be reopened

anyway, either for abutment connection (simultaneous

ap-proach) or for implant placement (staged apap-proach)

Biodegradable membranes may have an advantage over

nondegradable, bioinert membranes for implant indications,

with further research needed for outcomes

Primary Soft Tissue Healing

It has been clearly demonstrated in clinical applications and

confirmed in experimental studies (for review, see Buser et

al.5) that a closed healing of the regeneration site is a

pre-requisite for a predictable result When a soft tissue

dehis-cence occurs, the exposure of the membrane leads to its

contamination with bacteria from the oral cavity and

fre-quently to an infection in the membrane site within 2 to 3

months, when the membrane remains in place Since

in-fected membranes cited have an increased risk for a

com-promised surgical result, early membrane removal is

gen-erally recommended in cases of soft tissue dehiscences.23

Therefore, an appropriate flap design has to be chosen for

predictable achievement of primary soft tissue healing

Placement of a barrier membrane changes the conditions

for the healing of a soft tissue wound In the presence of a

barrier membrane, the soft tissue flap is separated from the

bone As a consequence, the primary soft tissue healing

de-pends mainly on a sufficient vascular supply of the

soft-tissue flaps, and the soft soft-tissue wound cannot be supported

by granulation tissue derived from the underlying bone

Clinical experience has demonstrated that crestal incisions

do not allow the predictable achievement of primary

soft-tissue healing The modified incision technique using a

lat-eral incision on the palatal aspect with a combined

split-thickness and full-split-thickness flap design clearly reduced the

frequency of postoperative soft tissue complications Other

important factors for primary soft tissue healing are

care-ful handling of the soft tissue flap using fine surgical

in-struments and retraction sutures during surgery as well as

tension-free wound closure with appropriate mattress andinterrupted sutures Furthermore, a perioperative medica-tion with nonsteroidal anti-inflammatory drugs and the lo-cal extraoral application of cold packs in the surgical areaare useful to reduce postoperative swelling

Membrane Adaptation and Fixation

to Surrounding BoneClose adaptation is necessary to achieve a sealing effect toprevent the ingrowth of soft tissue cells derived from the gin-gival connective tissue because these cells are able to com-pete with bone-forming cells in the created space underneaththe membrane In addition, stabilization of the membrane isuseful for maintaining close adaptation of the membrane tothe bone during wound closure Clinical applications with thespecially designed mini-screws (Memfix System, InstitutStraumann AG, Waldenburg, Switzerland)21–23 or pins29,30

have documented their effectiveness for membrane tion and stabilization

adapta-Creation and Maintenance of Secluded Space

A membrane-protected space allows the ingrowth of genic and osteogenic cells so that bone regeneration is undis-turbed by competing nonosteogenic soft tissue cells.14 It isimportant to differentiate between space-making defects, such

angio-as an extraction socket with intact bone walls, and making defects Non–space-making defects, including sitesfor localized ridge augmentation, are more demanding be-cause the membrane is not supported by local bone walls Inthese defects, standard e-PTFE membranes are susceptible topartial collapse caused by the soft tissue cover during heal-ing.14,23Therefore, membrane support for space maintenance

non–space-is important

Attempts have been made to solve this clinical problem inrecent years One possible solution is the use of stiffer mem-branes (i.e., reinforced e-PTFE membranes with titaniummesh) as recommended for periodontal indications.31 How-ever, clinical testing must demonstrate if stiffer membranesalso have value for ridge augmentation procedures Mem-brane-supporting devices such as mini-screws21–23or pins29,30

have been used The surgical results were improved, but tial membrane collapse lateral to the support posts still posed

par-a problem It becpar-ame obvious thpar-at par-an par-appropripar-ate filling mpar-a-terial was needed in non–space-making defects Autogenousbone is still considered the material of first choice for bonedefect grafting.32,33 Consequently, autografts were used to

further optimize the ridge augmentation procedure It was

ex-pected that the combination of autogenous bone grafts and

e-PTFE augmentation material would improve the outcome of

ridge augmentation procedures because the autograft would

not only serve as a membrane-supporting device to maintain

the created space but also act as an osteoconductive scaffold

to accelerate bone regeneration

It is important to understand the biological behavior of

au-tografts with respect to graft incorporation and repair and the

differences between cortical and cancellous autografts These

details have been intensively studied in numerous

experi-mental studies in orthopedic surgery (for review, see

Bur-chardt32,33) Cancellous autografts are rapidly revascularized,

and they are completely repaired by creeping substitution In

contrast, revascularization of cortical autografts is slow and

occurs through existing haversian canals Remodeling of

cor-tical autografts is also slow and results in a mixture of necrotic

and new viable bone

Based on this biological knowledge of graft incorporation

and graft repair, corticocancellous block grafts placed in the

center of the augmentation area and combined with smaller

bone particles surrounding the block graft were subsequently

used This surgical approach is based on two assumptions

First, the cortical portion of the graft facing to the buccal

as-pect of the crest is used to reestablish the missing buccal

cor-tex Although this new cortex will be a mixture of necrotic

and new viable bone, it offers good mechanical stability and

is less susceptible to resorption than cancellous bone Second,

the cancellous portion of the graft is placed in direct contact

to the host bone in the area where the implant will be placed

during second surgery The host bone surface is perforated

during the surgical procedure to activate bone formation and

to open the marrow space, allowing fast ingrowth of blood

vessels It can be expected that this portion of the graft will

undergo rapid revascularization and graft remodeling In

ad-dition, the preparation of an implant bed during second

surgery will further activate bone remodeling in this area

These assumptions, however, are based on orthopedic

litera-ture, and histologic details of graft incorporation and repair

underneath barrier membranes are not yet documented

Ex-perimental studies evaluating these aspects are currently in

progress

Corticocancellous block grafts can be harvested either in

the retromolar area of the mandible or in the chin, where the

cortical layer normally has an appropriate thickness of 2 to 3

mm The harvesting is uncomplicated and feasible within the

extension of the same surgical flap The block graft should

be appropriately applied to the recipient site First, rigid

fix-ation of the graft is important A bone-graft fixfix-ation screw

should be used because it allows precise positioning of the

graft and prevents micromovements of the graft underneath

the membrane during healing Second, the block graft must

be placed with its cortical layer facing buccally and the

can-cellous portion of the graft in direct contact of the host bone,

as discussed previously Based on more than 6 years of perience with the combination of 3-PTFE membranes and au-tografts, treatment outcome can clearly be optimized in bothmaxillary and mandibular sites,21–23 as demonstrated in theclinical examples presented at the end of this section Whenautografts and the GBR technique are combined, the mem-brane has a double function First, it serves as a physical bar-rier to protect the created space against nonosteogenic cellsderived from the mucosa Second, the membrane serves as agraft preservation device, protecting the autograft from post-operative resorption It has been documented that autogenousbone graft applied in ridge augmentation procedures withoutmembranes show resorption of up to 50% after 6 months ofhealing.34 Resorption in ridge augmentation cases has notbeen observed when bone grafts were protected by a mem-brane This clinical observation has been confirmed in pa-tients undergoing vertical alveolar ridge augmentation utiliz-ing autografts from the iliac crest.35 As an alternative toautografts, mineralized and demineralized freeze-dried boneallografts have been used as a membrane-supporting device

ex-in ridge augmentation procedures as well,15, 36–40and some

of these publications have presented encouraging clinical sults.37,39,40Allografts have the advantage that no harvestingprocedure is necessary However, histologic details of allo-graft incorporation and their substitution underneath barriermembranes and adjacent to implants are not sufficientlyknown for each material at present and need further investi-gation to provide information concerning their predictabilityfor clinical outcomes

re-Healing Time

A last factor important for achieving predictable results is

a sufficiently long healing period It has been demonstratedthat sites of early membrane removal attain less gain in boneheight.41–43 However, the exact healing period for ridgeaugmentation procedures with the GBR technique is notknown at present A histologic study involving extendeddefects in the alveolar ridge in foxhounds revealed almostcomplete cortical and cancellous bone repair and an onset

of bone remodeling after 4 months of healing in covered defects.14These defects are surgically created and

membrane-no osteoconductive filler was used The study confirmedthat bone regeneration and bone maturation is a time-dependent process, even in an animal known for its rapidhealing Based on this fact, a healing period of 9 monthshas been used during the development of this technique forridge augmentation procedures in large bone defects Clin-ical experience has proven this length of time to be effica-cious.12, 21–23However, it can be speculated that the heal-ing period may be shortened when membranes combined

with autogenous bone grafts are used because of the

excel-lent osteoconductive properties of autografts This

expec-tation has been confirmed in more than 30 cases with a

heal-ing period of 6 months

Summary

Over the past several years, the ridge augmentation procedure

using e-PTFE membranes and autografts has proven to be an

efficient and predictable surgical technique.21–23 This

tech-nique uses a staged approach, which has numerous advantages

over a simultaneous approach in large bone defects in the olar process First, it provides a larger bone surface available

alve-to contribute alve-to new bone formation, because no implant is serted in the defect area With a simultaneous approach, theinserted implant reduces the exposed bone surface and its mar-row space as a source of angiogenic and osteogenic cells Sec-ond, the implant positioning can be optimized from a pros-thetic point of view because the implant is placed when thenew crest is already reestablished Following confirmation ofthe treatment outcome, this allows a much easier preparation

in-of the recipient site and a better initial stability for the implant.Third, the staged approach offers advantages with respect to

F IGURE 16.1 Staged approach of guided bone regeneration (a)

Schematic overview of staged approach to augment a deficient

alve-olar ridge Note lateral split-thickness/full-thickness incision and

wound-closing technique (b) Patient with missing right lateral

in-cisor Compromised width of alveolar site (c) Mucoperiosteal flap

elevated; deficient alveolar bone site does not allow placement of implant (d) Corticocancellous bone block graft secured with bone fixation screw Small autologous bone chips are arranged around block graft

bone maturation because new bone formation is activated

twice by the local release of growth factor.44The first

activa-tion occurs during membrane surgery, when the cortical layer

is perforated prior to graft placement The second activation

occurs during implant placement, when the implant recipient

site is prepared in the newly formed alveolar crest Finally, it

can be assumed that better bone apposition to the titanium

sur-face can be achieved with a staged approach because the

“travel distance” for osteogenic elements to the implant

sur-face is much shorter Thus the staged approach should be the

treatment of choice for large bone defects in the alveolar

process, whereas the simultaneous approach can be used in

smaller defects The question of whether bone regenerated ing the barrier technique is “for real” has recently been an-swered in two dog experiments.14, 45These studies have shownthat the newly regenerated bone closely resembled the struc-ture of preexisting alveolar bone,14,45and osseointegration ofunloaded and loaded implants in these regenerated bone sitesoccurred identically as for preexisting bone.45

us-Case ReportsFigures 16.1 and 16.2 show illustrative examples from casereports

F IGURE16.1 Continued (e) GTAM membrane adapted and secured

with miniature fixation screws (Memfix System, Institut Straumann

AG, Waldenburg, Switzerland) (f) Primary flap closure with

Gore-Tex sutures (g) Postoperative follow-up at 7 months (h) ing surgery, Memfix screws and membrane removed

Reopen-Continued.

160 D.A Buser, D Weingart, and H.-P Weber

k

m

l

F IGURE16.1 Continued (i) Result of alveolar augmentation in an occlusal view.

Site prepared for ITI Hollow-Cylinder (HC) implant in ideal position (j) Implant placed to correct vertical level (i.e., shoulder apical to cementoenamel junction of neighbor teeth) (k) HC implant in proper axis direction for screw-retained restora- tion with screw access in the cingulum area of the future crown (l) Final restora- tion (porcelain-fused-to-metal) in place (m) Radiographic control.

a b

F IGURE 16.2 Simultaneous approach of guided bone regeneration (a)

Schematic overview on simultaneous approach for alveolar ridge

augmentation Note incision technique as in staged approach (b)

Im-plant placed in area of lower left first molar Note buccal alveolar

dehiscence Surrounding bone is perforated with a small round bur

to promote bleeding and a source for cells with bone-forming

po-tential (c) Autologous bone particles obtained from implant bed preparation (bone core) placed in area of dehiscence Small closure screw placed in implant (d) GTAM membrane adapted as “poncho” over implant and secured with two Memfix screws (e) Primary wound closure (f) Postoperative follow-up at 1 month

Continued.

162 D.A Buser, D Weingart, and H.-P Weber

References

1 Brånemark P-I, Zarb GA, Albrektsson T, eds Tissue-Integrated

Prostheses: Osseointegration in Clinical Dentistry Chicago:

Quintessence; 1985.

2 Schroeder A, Sutter F, Krekeler G, eds Oral Implantology

Gen-eral Basics and ITI-Hollow-Cylinder System New York: Thieme

Medical; 1991.

3 Nyman S, Lindhe J, Karring T Reattachment-new attachment.

In: Lindhe J, ed Textbook of Clinical Periodontology 2nd ed.

Copenhagen: Munksgard; 1989:450–476.

4 Dahlin C, Linde A, Gottlow J, et al Healing of bone defects by

guided tissue regeneration Plast Reconstr Surg 1988;81:

672–676.

5 Buser D, Dahlin C, Schenk RK, eds Guided Bone

Regenera-tion in Implant Dentistry Chicago: Quintessence; 1994.

6 Dahlin C, Sennerby L, Lekholm, et al Generation of new bone

around titanium implants using a membrane technique: An

ex-perimental study in rabbits Int J Oral Maxillofac Implants.

1989;4:19–25.

7 Dahlin C, Gottlow J, Linde A, et al Healing of maxillary and

mandibular bone defects using a membrane technique Scand J

Plast Reconstr Hand Surg 1990;24:13–19.

8 Seibert J, Nyman S Localized ridge augmentation in dogs: a

pi-lot study using membranes and hydroxylapatite J Periodontol.

10 Lazarra RJ Immediate implant placement into extraction sites:

Surgical and restorative advantages Int J Periodont Rest Dent.

1989;9:333–343.

11 Nyman S, Lang NP, Buser D, et al Bone regeneration adjacent

to titanium dental implants using guided tissue regeneration: a

report of two cases Int J Oral Maxillofac Implants 1990;5:

9–14.

12 Buser D, Brägger U, Lang NP, et al Regeneration and

en-largement of jaw bone using guided tissue regeneration Clin

Oral Implants Res 1990;1:22–32.

13 Jovanovic S, Spiekermann H, Richter EJ Bone regeneration around titanium dental implants in dehisced defect sites: a clin-

ical study Int J Oral Maxillofac Implants 1992;7:233–241.

14 Schenk RK, Buser D, Hardwick WR, Dahlin C Healing pattern

of bone regeneration in membrane-protected defects A

histo-logic study in the canine mandible Int J Oral Maxillofac

Im-plants 1994;9:13–29.

15 Gotfredsen K, Warrer K, Hjøerting-Hansen E, et al Effect of

F IGURE16.2 Continued (g) Reopening surgery at 6 months (h) Result of augmentation Small implant closure screw replaced with

trans-mucosal healing cap (i) Postoperative follow-up 3 weeks after reopening surgery (j) Radiographic control 1 year after crown insertion.

membranes and hydroxyapatite on healing in bone defects

around titanium implants An experimental study in the

mon-key Clin Oral Implants Res 1991;2:172–178.

16 Warrer K, Gotfredsen K, Hjøerting-Hansen E, et al Guided

tis-sue regeneration allowing immediate implantation of dental

im-plants into extraction sockets An experimental study in the

mon-key Clin Oral Implants Res 1991;2:166–171.

17 Wachtel HC, Langford A, Bernimoulin JP, et al Guided bone

regeneration next to osseointegrated implants in humans Int J

Oral Maxillofac Implants 1991;6:127–135.

18 Becker W, Becker B Guided tissue regeneration for implants

placed into extraction sockets and for implant dehiscences:

sur-gical techniques and case reports Int J Periodont Rest Dent.

1990;10:377–392.

19 Jovanovic SA, Giovannoli JL New bone formation by the

prin-ciple of guided tissue regeneration for peri-implant osseous

le-sions J Parodontol 1992;11:29–39.

20 Magnusson I, Batich C, Collins BR New attachment formation

following controlled tissue regeneration using biodegradable

membranes J Periodontol 1988;59:1–12.

21 Buser D, Dula K, Belser U, Hirt HP, Berthold H Localized ridge

augmentation using guided bone regeneration I Surgical

pro-cedure in the maxilla Int J Periodont Rest Dent 1993;13:29–45.

22 Buser D, Dula K, Belser U, Hirt HP, Berthold H Localized ridge

augmentation using guided bone regeneration II Surgical

pro-cedure in the mandible Int J Periodont Rest Dent 1995;15:

13–29.

23 Buser D, Dula K, Hirt HP, Schenk RK Lateral ridge

augmen-tation using autografts and barrier membranes A clinical study

in 40 partially edentulous patients J Oral Maxillofac Surg.

1996;54:420–432.

24 Fleisher N, De Waal H, Bloom A Regeneration of lost

attach-ment in the dog using Vicryl absorbable mesh (polyglactin 910).

Int J Periodont Rest Dent 1988;8(2):45–54.

25 Chung KM, Lakin LM, Stein MD, et al Clinical evaluation of

a biodegradable collagen membrane in guided tissue

regenera-tion J Periodontol 1990;61:732–741.

26 Schultz AJ, Gager AH Guided tissue regeneration using

ab-sorbable membrane (polyglactin 910) and osseous grafting Int

J Periodont Rest Dent 1990;10:8–15.

27 Zappa U Resorbierbare Membranen I Parodontale

Gewebere-generation unter Verwendung von resorbierbaren

Membranen-klinische Aspekte Schweiz Monatsschr Zahnmed 1991;101:

1147–1155.

28 Zappa U Resorbierbare Membranen II Parodontale

Gewe-beregeneration unter Verwendung von resorbierbaren

Membra-nen—Histologische Aspekte Schweiz Monatsschr Zahnmed.

1991;101:1321–1331.

29 Fugazzotto P Ridge augmentation with titanium screws and

guided tissue regeneration: Technique and report of a case Int

J Periodont Rest Dent 1993;13:335–339.

30 Becker W, Becker BE, McGuire MK Localized ridge

augmen-tation using absorbable pins and e-PTFE barrier membranes: a

new surgical technique Case reports Int J Periodont Rest Dent.

1994;14:49–61.

31 Tinti C, Vincenzi G, Cochetto R Guided tissue regeneration in

mucogingival surgery J Periodontol 1993;64:1184–1191.

32 Burchardt H Biology of bone transplantation Orthodont Clin

North Am 1987;18:187–196.

33 Burchardt H Biology of bone graft repair Clin Orthop Relat

Res 1983;174:28–42.

34 ten Bruggenkate CM, Kraajenhagen HA, van der Kwast WAM,

et al Autogenous maxillary bone grafts in conjunction with

placement of ITI endosseous implants A preliminary report Int

J Oral Maxillofac Surg 1992;21:81–84.

35 Jensen O Guided bone graft augmentation In: Buser D, Dahlin

C, Schenk RK, eds Guided Bone Regeneration in Implant

Den-tistry Chicago: Quintessence; 1994:235–264.

36 Buser D, Berthold H Knochendefektfüllung im Kieferbereich

mit Kollagenvlies Dtsch Z Mund Kiefer Gesichtschir 1986;10:

with either PDGF and IGF-I, or DFDB J Periodontol 1992;63:

929–940.

39 Shanaman RH The use of guided tissue regeneration to

facili-tate ideal prosthetic placement of implants Int J Periodont Rest

Dent 1992;12:226–265.

40 Nevins R, Mellonig JT The advantages of localized ridge

aug-mentation prior to implant placement: a staged event Int J

Pe-riodont Rest Dent 1994;14:97–111.

41 Simion M, Baldoni M, Rossi P, Zaffe D A comparative study

of the effectiveness of e-PTFE membranes with and without

early exposure during the healing period Int J Periodont Rest

Dent 1994;14:167–180.

42 Becker W, Dahlin C, Becker BE, et al The use of e-PTFE rier membranes for bone promotion around titanium implants placed into extraction sockets: a prospective multicenter study.

bar-Int J Maxillofac Implants 1994;9:31–40.

43 Lekholm U, Becker W, Dahlin C, et al The role of early vs late removal of GTAM membranes on bone formation around oral implants placed in immediate extraction sockets: an experi-

mental study in dogs Clin Oral Implants Res 1993;4:121–129.

44 Schenk RK Bone regeneration: biologic basis In: Buser D,

Dahlin C, Schenk RK, eds Guided Bone Regeneration in

Im-plant Dentistry Chicago: Quintessence; 1994:49–100.

45 Buser D, Ruskin J, Higginbottom F, Hardwick R, Dahlin C, Schenk RK Osseointegration of titanium implants in bone re- generated in membrane-protected defects: a histologic study in

the canine mandible Int J Oral Maxillofac Implants 1995;10:

666–681.

The ITI Dental Implant System

in Maxillofacial Applications

Dieter Weingart, Daniel A Buser, and Hans-Peter Weber

In severe trauma cases, after jaw resection in tumor surgery,

and especially in cases of severe atrophy of the maxillary or

mandibular alveolar ridge, a direct implant placement using

the one-stage approach with ITI implants as described in

Chapter 15 is often not possible Also, the technique of guided

bone regeneration discussed in that chapter would not be an

efficient method to restore areas of such extended and severe

alveolar atrophy Therefore, a vertical augmentation with

bone grafts most frequently obtained from the iliac crest is

the method of choice in patients presenting with such

condi-tions (Figures 17.1–17.4) As with guided bone regeneration,

two methods regarding timing of implant placement may be

differentiated: (1) implant insertion simultaneously with the

bone grafts in which instance the implants serve to stabilize

the grafts to the basal bone; and (2) stage approach, that is,

the bone grafts are stabilized by means of miniplates or

screws, which are removed after graft healing at which time

the implants are inserted (Figures 17.1 and 17.2)

As a prerequisite for the use of free bone grafts, a maximum

wound closure during the healing phase is required

Accord-ingly, the implants in this indication need to be inserted to the

bone level, and the mucoperiosteal flap must cover the implants

after suturing A modification of the standard ITI Dental

Im-plant System was necessary to allow that at the time of

second-stage surgery (i.e., after bone-graft healing and

osseointegra-tion of the implants) transmucosal extensions can be attached

For this purpose, the ITI Extender System was developed.1–5

The available extensions allow the adaptation of the

peri-implant mucosa to this transmucosal component (Figure 17.5d)

After completion of soft tissue healing following

second-stage surgery, any of the prosthetic abutments of the regular

ITI system may be placed on top of the extensions, and the

superstructure is fabricated according to standard procedures

Surgical Procedure

As outlined earlier, the implants used for the stabilization of

bone grafts are to be inserted into the transplants in a

sub-merged manner, mainly for reasons of infection prophylaxis

and prevention of graft resorption The ITI full-body screws,available in lengths of 6 to 16 mm, are used for these indi-cations Owing to their flared neck, the ITI screw implantsfunction as tension screws, building up an interfragmentarycompression between the natural bone bed of the jaw boneand the bone transplant (Figure 17.6e)

The surgical augmentation procedure and the implantationwith ITI screw implants as well as the use of the transgingi-val extension system is documented step by step in Figures17.5 and 17.6 At first surgery, the implant (ITI FS) is inserted

to its shoulder into the bone graft and covered with a smallclosure screw The mucoperiosteal flap is then positioned overthe bone graft and implants (Figure 17.6g) At second-stagesurgery following a healing phase of 3 to 6 months, the im-plants are exposed, the healing caps removed, and the basalscrews and the mucosa cylinders are inserted and covered withhealing caps (Figures 17.5a–d) After completion of woundhealing (3 to 4 weeks), the prosthetic phase is started with theinsertion of the abutments after removal of the healing caps

Mechanical Aspects

At second-stage surgery, it is important to consider that thebasal screw and the mucosa cylinder are used in correspond-ing pairs and in accordance with the standard lengths (Figure17.7) The microgaps between the implant and the extensionparts are kept as small as technically possible

This transgingival unit of the extender system has been chanically tested under different loading conditions As a re-sult of preliminary tests with different designs, an integratedattachment (basal screw) was chosen As usual for ITI sec-ondary components, its apical portion comprises an 8° coneand a 2-mm screw for attachment to the implant This cone-to-screw design provides a frictional fit, eliminating the risk

me-of loosening me-of the basal screw The design me-of the coronalportions of the basal screw consists of a threaded part to whichthe corresponding mucosa cylinder is attached (Figure 17.7)

It is preferably tightened with a torque meter adjusted to proximately 35 Ncm

ap-164

F IGURE 17.1 (a) Situation after a comminuted fracture of the mandible with a defect in the region of the right alveolar ridge sta- bilized with an AO 2.7 reconstruction plate (b) The defect is ex- posed The remaining vertical bone height in the premolar area is only 3 to 4 mm (c) An autogenous corticocancellous iliac bone graft

is adapted with two lag screws (d) Radiological control 6 months after bone grafting before implant placement (e) Situation after mandibular reconstruction and implant placement of ITI full-body screw For transgingival elongation, the ITI Extender System is inserted.

dc

e

166 D Weingart, D.A Buser, and H.-P Weber

F IGURE 17.2 (a) Bone resection because of an ameloblastoma of the mandible (b,c) After pathohistological evaluation of the resection border, reconstruction of the mandible with an autogenous cortico- cancellous iliac bone graft Fixation of the graft with AO 2.0 mini- plates, and stabilization of the mandible with an AO 2.4 universal plate The alveolar nerve was preserved and lateralized (d,e) The ITI full-body screw implants are inserted 5 to 6 months after bone grafting.

dc

e

F IGURE 17.3 (a) Situation after resection in the left mandible because

of a carcinoma of the floor of the mouth (b) Restoration by

micro-surgically revascularized iliac crest bone graft (c) The implants are

inserted into the bone graft during a second-stage approach (d) Good

osseointegration of the implants in the grafted bone with only

min-imal vertical resorption The ITI Extender System was inserted 3

months following implant placement (e) Preoperative extraoral pect of the patient, with perforation of the reconstruction plate through the skin (f) Postoperative extraoral aspect of the patient fol- lowing mandibular reconstruction with revascularized iliac bone graft and implant placement.

as-d

fc

e

168 D Weingart, D.A Buser, and H.-P Weber

F IGURE 17.4 (a) Extreme atrophy of the mandibular alveolar ridge.

Measurements for evaluating the vertical height were performed

Pa-tient refused an augmentation procedure (b) Situation 2 years later.

Increase of alveolar ridge atrophy Patient came back with a

frac-ture of the extremely atrophied left mandible (c) Intraoperative

sit-uation after an extraoral approach: Fracture and dislocation occurred because there was no bone in the middle of the mandibular ridge (d) Initial stabilization of fracture with miniplate fixation to allow anatomic segment positioning for reconstruction plate application in the same operation.

dc

F IGURE17.4 Continued (e) Stabilization of the fracture with an AO

2.4 reconstruction plate and simultaneous bone grafting with

auto-genous iliac bone (f) Radiological control 6 months after fracture

treatment and augmentation on the left side of the mandible (g)

Aug-mentation on the anterior and right region of the mandible: the

im-plants are inserted through the corticocancellous bone graft into the

mandible (see Figure 17.6) Good interfragmentary compression

be-tween the natural bone bed of the jaw bone and the bone transplant due to implant configuration and a certain lag-screw effect (h) Sit- uation after posthodontic treatment with a bar suprastructure: the ITI Extender System in place Compare the bony situation with (b) In- crease in vertical bone height and titanium microplate for fracture adaption still in place.

hg

fe

170 D Weingart, D.A Buser, and H.-P Weber

F IGURE 17.5 (a) After the healing phase, the implants are exposed either by incision or by punching The basal screw (b) and the mucosa cylinder (c) are inserted with a special insertion instrument (d) The assembled transgingival elongation system.

dc

F IGURE 17.6 Step-by-step representation of the surgical sequence.

After vestibular incision and adoption of the transplant, the implant

bed is prepared in the usual way (a) Marking with the round bur.

dc

(b) Drilling to the desired depth with three spiral drills (c) ing of the neck portion (d) The next step is to pretap the thread in accordance with the depth

Profil-Continued.

172 D Weingart, D.A Buser, and H.-P Weber

F IGURE17.6 Continued (e) The implant is introduced with a standard insertion instrument through the bone graft into the ridge (f)

Inser-tion of the closure screw into the subgingival posiInser-tioned implant (g) The situaInser-tion after suturing the periosteum and the mucosa.

g

With regard to their coronal configuration, the prosthetic

components of the extender system correspond to those of the

standard ITI Dental Implant System (conical abutment,

re-tentive anchor, and octa-abutment) and are also manufactured

from pure titanium Any of these abutments can be attached

to the mucosa cylinder

Maximum tightening moments of more than 400 Ncm

could be achieved with the new transgingival unit compared

with 125 Ncm observed with a conventional 2-mm flat

cou-pling screw Additional dynamic loading tests proved that the

loosening moment remained approximately 10% above the

tightening moment after 2,000,000 cycles.4

Summary

Positive experience and results with endosteal implants in the

field of standard oral implantology led to an extension of the

indication to implantations into transplants In these cases, the

simultaneous use of screw implants facilitated optimal graft

adaptation and fixation Originally, ITI implants were

de-signed for a transmucosal (one-stage) implant placement

Us-ing bone-graft procedures, it is necessary to cover the bone

graft with a soft tissue flap to get satisfactory incorporation

of the bone These cases need second-stage surgery and a cial abutment device

spe-The extender system presented here provides a simple method

of restoring ITI implants placed in combination with nous bone transplants with various prosthetic superstructures

autoge-References

1 Asikainen P, Sutter F The new distance system for the

sub-mergible use of the ITI-Bonefit Implants J Oral Implantol.

1990;4:48–54.

2 Sutter F, Weingart D, Mundwiler U, Sutter F, Asikainen P ITI implants in combination with bone grafts: design and biome-

chanical aspects Clin Oral Implants Res 1990;5:164–172.

3 Weingart D, Strub JR, Schilli W Kieferchirurgisch-prothetisches Konzept zur implantologischen Versorgung bei unter-

schiedlichem Atrophiegrad des zahnlosen Patienten Z Stomatol.

1992;3:137–145.

4 Sutter F, Weber HP, Sorensen J, Belser U The new restorative concept of the ITI Dental Implant System: design and engineer-

ing Int J Periodont Rest Dent 1993;13:409–431.

5 Weingart D, Strub JR, Schilli W, Schenk R, Kleinheinz J, Hürzeler B Mandibular ridge augmentation combining onlay il-

iac bone graft with endosseous implant placement in dogs J Dent

Maxillary Sinus Grafting and

Osseointegration Surgery

Jeffrey I Stein and Alex M Greenberg

Posterior maxillary dental implant reconstruction for

ad-vanced alveolar ridge atrophy has become possible through

bone grafting procedures involving the maxillary sinus This

procedure involves augmentation of either the internal or the

external aspects of the sinus, or both Bone grafting of the

ex-ternal aspect is usually performed with guided bone

regener-ation using allogeneic, autogenous cortical, or

corticocancel-lous grafts as onlays with immediate or delayed implant

placement.1 Sandwich techniques of bone grafting both the

external ridge and the internal sinus with simultaneous

den-tal implant placement has also been reported.2 Sailer and

Keller et al have reported the use of iliac crest bone grafts

with the immediate placement of dental implants with Le Fort

I osteotomies.3,4However, this is a more extensive technique

with increased possibilities for morbidity in this older patient

population

What has become the most common procedure for this

re-gion of reconstruction, however, is the sinus lift graft

proce-dure, which was first reported in 1976 at the Alabama

Im-plant Congress by Tatum et al.5 This procedure is further

supported by Jensen et al., who prefer sinus grafting as

op-posed to onlay grafts, which tend to have greater resorption.6

In this technique, a bony window in the lateral sinus wall is

infractured, and the sinus membrane is preserved intact and

elevated superiorly Initially, Tatum’s technique involved the

use of autologous bone A bone graft of various reported

com-positions is placed, and immediate or delayed dental implant

placement is performed A review of the literature reveals that

this new procedure has various reports and that several

meth-ods of bone grafts have been proposed The reports of sinus

lifting technique are basically the same with regard to the type

of incisions, lateral sinus wall osteotomy, sinus membrane

el-evation, and use of root form implants It is with regard to

various types of bone grafts that numerous authors report

dif-ferences in their methods

Tatum et al reported more than 1500 cases using either

100% autogenous bone of iliac crest origin, demineralized

freeze-dried bone, or irradiated bone and some experience

with mixtures of these types with various forms of

hydroxy-apatite.5Jensen et al reported only the use of 100%

autoge-nous iliac crest cancellous bone grafts.6Raghoebar et al ported 25 patients who had various autogenous bone grafts ofiliac crest (22), symphysis (2), and maxillary tuberosity (1)origin.7Block and Kent advocate the use of a 1:1 mixture ofautogenous bone with demineralized bone.8

re-Vlassis et al reported using a mixture of demineralized allogeneic bone gel (Grafton; Musculoskeletal TransplantFoundation, Little Silver, NJ, USA) and resorbable hydroxy-apatite (Osteogen; Stryker, Kalamazoo, MI, USA).9 Fugaz-zotto reported the use of a 1:1 mixture of demineralized boneand resorbable tricalcium phosphate (Augmen; Miter andCo.).10 Moy et al have performed a comprehensive histo-morphometric investigation regarding four different maxillarysinus grafting materials, which consisted of autogenous sym-physis bone (44.4% bone), hydroxyapatite (20.3% bone), hy-droxyapatite and demineralized bone, 7:1 (4.6% bone), andhydroxyapatite and autogenous symphysis bone, 1:1 (59.4%bone).11

Treatment Planning

A multitude of prosthetic and surgical alternatives exist fortreatment of the partially or completely edentulous posteriormaxilla It must first be determined if conventional nonim-plant dentistry is a viable alternative Numerous questionsneed to be addressed In the partially edentulous patients, arethe remaining teeth in sufficient number, periodontally fit, andstrategically located to serve as abutments for a traditionalfixed bridge or removable partial denture? In complete eden-tulism, a determination must be made whether a denture can

be fabricated with satisfactory retention If not, would an plant supported overdenture be acceptable to the patient? Inthe presence of advanced atrophy with altered ridge relation-ships, will esthetic and occlusal demands be reasonably metwithout skeletal correction?

im-If implant treatment is to be considered, initial factors to beevaluated are the patient’s age, medical history, and psycho-logic status The patient’s tolerance for surgery and a pro-longed treatment time with the possibility of an extended pe-174

riod without a prosthesis needs to be assessed The

surgical-restorative team must have a clear comprehension of the

pa-tient’s complaints and desires and of each other’s vision of the

final restoration Many individuals may not wish to further

compromise remaining teeth to serve as abutments (Figure

18.1) Frequently, the only desire stated may be for a plan that

would allow for a fixed rather than a removable prosthesis

Load requirements must be delineated Nonaxial loading

from malaligned abutments/fixtures as well as long

edentu-lous spans, more posterior locations, parafunctional habits,

in-crease in crown/root (implant) ratio, and an opposing natural

dentition all place a greater strain on the restoration This

problem is further compounded because the posterior

maxil-lary bone density, especially in long-standing edentulism, is

spongy with fewer trabeculae Compromised stress-bearing

capacity is inherent Modification of the treatment plan needs

to account for these biomechanical demands If inadequate

natural abutments are present, the use of fixture(s) generally

restored as a free-standing unit should be considered (Figure

18.1) Fixture load tolerances are elevated by positioning

im-plants along the long axis of force vectors as well as by

in-creasing fixture number, length, diameter, and available

sur-face area for osseointegration This plan may be accomplished

by altering the implant surface coating via plasma spraying

These and future determinations are made on the basis of

the initial patient discussion, examination, mounted cast

eval-uation, and diagnositc setup These casts can later be utilized

for fabrication of a surgical guide stent (Figure 18.2) graphic assessment is an essential element of the workup.Minimally, a panoramic radiograph supplemented by peri-apical films is necessary The magnification factors must beknown either by comparison to a standard measure placed inthe region under examination or by use of a film with a measured grid From these radiographs, the periodontal-endodontic status of the remaining teeth are first considera-tions Short- and long-term prognostic determinations as tothe viability of teeth individually and whether they may serve

Radio-as abutments needs to be judged Edentulous areRadio-as Radio-as well Radio-asthe tuberosity-pterygoid plate region should be surveyed forpathology and quantitatively assessed for vertical boneheights A qualitative assessment of bone type may also beapproximated If no panoramic machine is available, the max-illary sinus may be screened with a Waters’ view (Figure18.3)

Should further radiographic data be necessary, or to lineate sinus pathology or septae detected on plain films, a

de-F IGURE 18.1 Maxillary sinus bone graft and placement of three

den-tal implants to prevent fracture of a long span fixed bridge and

fail-ure of natural tooth abutments.

F IGURE 18.2 Surgical guide stent for bilateral maxillary sinus bone graft and dental implant placement.

F IGURE 18.3 Waters’ view demonstrating bilateral air/fluid levels dicating sinus infection (black arrows).

in-176 J.I Stein and A.M Greenberg

computed tomographic (CT) study should be ordered.12,13

Pa-tients with a significant history of sinus disease or smoking

considering a sinus lift procedure also are required to obtain

CT scanning Reformatted CT utilizing specialized dental

software will clearly demonstrate the residual bone length,

width, and angulation Qualitative bone assessment is also

en-hanced Stents with radiopaque markers may be used to

de-lineate prosthetically desirable implant locations in all views

Study and cross-referencing of the various dimensions will

demystify and facilitate treatment planning (Figures 18.4a–c)

Availability, cost, and additional radiation exposure dictate

the need for CT scanning are made on an individual

case-by-case basis

Once it is evident that the residual dentition cannot serve

as abutments and a fixed or removable restoration is desired,

an implant treatment plan must be developed Assessment of

bone density and volume of individualized implant sites in

light of biomechanical demands is critical Generally, bone

rising vertically 10 mm or more with adequate width to

en-case the fixture circumferentially permits utilization of the

standard surgical approach Minor vertical deficiencies may

be compensated for by placing the fixture apex slightly yond the sinus floor and allowing for secondary bony dom-ing This can also be accomplished by localized apical sinuslifts which enhance length by imploding the fixture site sinusfloor via an osteotome technique described later.14,15Local-ized width deficiencies may be augmented via a guided tis-sue regeneration procedure with simultaneous fixture place-ment or as a staged procedure Fixture sites approximating 7

be-mm of height, particularly if poor bone quality is evident, quire alternative planning In this intermediary range, if bio-mechanical forces are not excessive, bony ridge inadequaciesmay be compensated by increasing the number or the diam-eter of fixtures utilized

re-Unfortunately, minimum bony thresholds are frequently notmet Posterior maxillary atrophy inferiorly (crestally) and lat-erally results from periodontal disease and postextraction dis-use resorption Pneumatization of the maxillary sinus furthercompromises the residual alveolus This expansion of themaxillary antrum results from a slight increase in intrasinuspressure during expiration, inducing osteoclastic activity inthe periosteal layer of the Schneiderian membrane The resid-

a

b

c

F IGURE 18.4 Computerized tomography scan reformatted with

den-tal software (a) Axial plane with numerically identified 3-mm

sec-tional cuts correlated to each cross-secsec-tional view (b) Chronic left

maxillary sinus membrane thickening and subantral bone atrophy (c) Cross-sectional view also demonstrating left maxillary sinus membrane thickening and advanced subantral alveolar bone atrophy.

ual ridge may be narrow with a medial inclination and of

min-imal osseous volume

If inadequate bone is present for traditional fixture

place-ment, an alternative to subantral grafting to be considered is

to bypass this region and place a fixture within the maxillary

tuberosity, possibly extending into the pterygoid plates16–18

(Figures 18.5a–c and 18.6a–c) This will provide a distal

abut-ment for bridge fabrication This option is only viable for short

spans and if mesial and distal fixtures are of sufficient length

and diameter Excessive angulation of the distal fixture as well

as other unfavorable biomechanical factors will commonly

preclude implementation of this procedure

The use of a distal cantilevered pontic is often entertained

at this junction Commonly, this is at the misguided prodding

of the patient in their desire “to keep it simple” and avoid a

graft procedure The strain placed on the distal fixture in a

cantilevered situation, especially if it is short or in poor

qual-ity bone, may lead to fixture failure or fracture (Figures

18.7a,b), or possible frequent abutment–prosthetic screw

loos-ening or fracture Similar considerations contraindicate the

use of excess anterior lever arms when only posterior fixtures

are available in the totally edentulous situation

Restoration of the severely atrophic posterior maxilla

b

quires graft augmentation by either Le Fort I osteotomy with

an autogenous interpositional corticocancellous graft,3,4,19anonlay corticocancellous graft, or a maxillary antrostomy withmembrane elevation and a subantral graft, commonly referred

to as a sinus lift or sinus inlay graft procedure Limited cation exists for the Le Fort I approach Because of the pro-cedure’s complexity and its lowest success rate of osseointe-gration at 68%,20the Le Fort I approach should be reservedfor those patients who require a major correction of a classIII ridge relationship The maxillary onlay graft is a proce-dure of potentially greater complexity and postoperative com-plications, with a lower osseointegration success rate than thesinus inlay graft Inital onlay results reported range from 50%

indi-to 90% but appear indi-to approach 80% indi-to 90% with ence.2,19–24An onlay graft procedure is indicated in lieu ofthe sinus inlay approach in the following circumstances: whensevere buccal alveolar resorption would necessitate palatalimplant placement or angulation, excessive interocclusalspace would result in an unfavorable prosthesis/implant ratio,maxillary anterior augmentation is required, or when the pa-tient has significant sinus disease or smoking addiction Itshould be noted that anterior atrophy or posterior buccal at-rophy may be alternatively addressed with adjunctive graft-

experi-178 J.I Stein and A.M Greenberg

ing procedures (i.e., nasal inlay graft, localized guided tissue

regeneration) in combination with the sinus lift technique

The sinus lift procedure has, comparatively, the highest

success rate and may be of less complexity and morbidity

Contraindications to sinus elevation and augmentation include

sinusitis, presence of a cyst, tumor, or displaced root tip These

conditions may interfere with normal sinus drainage through

the ostium, leading to a mucopurulent accumulation within

the antrum Sinus pathology must be resolved before grafting

to permit a well-ventilated, draining, aseptic antrum Sinus lay grafting alone will not address excess intermaxillary space

in-or cin-orrect majin-or skeletal discrepancies in the transverse in-or teroposterior dimension Alternative or adjunctive proceduresshould be considered Smoking may be a relative to absolutecontraindication depending on severity Bain and Moy25re-ported smokers have more than twice the failure rate, 11.3%versus 4.8%, compared to nonsmokers in standard implantcases Impaired polymorphonuclear neutrophil (PMN) func-

F IGURE 18.7 Failure of bilateral cantilevered prosthesis with

resul-tant implant fractures (a) Panoramic radiograph demonstrates right

single cantilever and left double cantilever (b) Panoramic radiograph

following removal of fixed bridge Right distal implant removed with retained implant apex, and left two distal implants with retained im- plant apices.

warm and debride inhaled air, as well as acting as a resonancechamber for voice modulation Normal sinus function requiresthe patency of the ostium, a functioning ciliary apparatus, andsecretions qualitatively and quantitatively appropriate.The arterial vasculature to the maxillary antrum derives frombranches of the internal maxillary artery (ethmoidal, infraor-bital, facial, and palatine) Venous drainage medially is into thesphenopalatine vein while the remaining walls drain throughthe pterygomaxillary plexus Innervation is provided bybranches of the trigeminal nerve, second division (lateral pos-terior superior nasal, superior alveolar, and infraorbital nerves).Sinus inlay grafting in reports discussed previously hasdemonstrated success rates generally well in excess of 90% Inmanaging the severely atrophic posterior maxilla, this proce-dure most frequently fulfills a cardinal goal of surgery, which

is to obtain a successful if not optimal long-term outcome withthe least amount of intervention, complications, and risks Thisstatement is particularly valid if the procedure morbidity can

be further decreased by performing it in one stage ous graft and implant insertion) and if the graft material uti-lized does not necessitate an iliac crest or mandibular sym-physeal donor site Various graft materials that have beensuccessfully used independently or in combination are autoge-nous, allogeneic, alloplastic, and xenogeneic

(simultane-Selection of Graft MaterialThe graft material selected must be able to provide long-termsupport for an implant-borne prosthesis Present materials uti-lized alone or in combination include autologous, allogeneic(demineralized freeze-dried bone), alloplastic (synthetic hy-droxyapatite), and xenogeneic grafts A potential additionalclass of bone substitutes likely to be available in the near fu-ture are genetically engineered osteoinductive bone mor-phogenic proteins The characteristics of the ideal subantralgraft material are that it be nontoxic, nonantigenic, nonmi-gratory, infection resistant, readily available, easily fabri-cated, inexpensive, strong, resilient, capable of functional re-modeling, provide ease of manipulation, minimize surgicaltime, eliminate donor morbidity, eliminate need for generalanesthesia, enhance early stability of implants, and permitlong-term osseointegration

Bone HealingAutologous bone grafts may be cortical, cancellous, or cor-ticocancellous in composition These type of grafts containmany live cells capable of osteogenesis Success of any graft

is dependent on a variety of host and surgical factors In lecting which graft material to utilize, whether autologous innature or a substitute, the healing process of autogenous bonegrafts must be clearly comprehended.30

se-tion as well as local and systemic vasoconstrictive effects are

believed responsible Increased complications and failure

have been evident in heavy smokers undergoing the sinus

el-evation procedure.26–28 It is recommended that smoking be

discontinued 2 months preoperatively and throughout the

healing period.29Clinical data have yet to clearly define

nec-essary time parameters Patient compliance with such

re-quirements is frequently difficult to monitor and achieve,

de-spite new spoking cessation treatments

Anatomy

The maxillary sinus is a paired, pyramidally shaped,

pneu-matic cavity occupying the body of the maxilla The base of

the pyramid lies medially, serving as the lateral nasal wall

This medial sinus wall–lateral nasal wall merges with the

an-terior wall to form the tallest vertical strut of the maxilla

Pos-teriorly, the maxillary antrum abuts the pterygoid plates The

lateral sinus wall is contiguous with the buccal plate of the

alveolar bone Superiorly, the sinus roof helps form the

or-bital floor Inferiorly, the floor of the maxillary sinus extends

below the level of the nasal cavity Bony septae (buttress)

fre-quently join the medial or the lateral walls to reinforce the

sinus cavity These septae may divide the sinus into two or

more cavities that may or may not communicate

The dimensions and capacity of the sinus demonstrate

marked variability, dependent on sinus expansion It is the

largest of the four paranasal sinuses, with an approximate

height at the base of 35 mm The mediolateral base width is

35 mm, which tapers to 25 mm in the first molar regions Its

anteroposterior depth is generally in excess of 30 mm The

maxillary antrum has an average volume capacity of 15 ml

The sinus is lined with a thin delicate pseudostratified

cil-iated cuboidal to columnar epithelium tightly bound to and

indistinguishable from the underlying periosteum The

pe-riosteum has few elastic fibers and is loosely bound to bone,

facilitating surgical elevation In the lining there are three

glandular cell types—goblet, mucous, and serous—with the

latter two concentrated near the ostium Approximately 2

liters of fluid is produced per day The fluid layer is divided

into an outer gel-like mucous layer for transport that overlies

a less viscous serous fluid layer surrounding the cilia The

cilia beat in a coordinated undulating manner, propelling a

blanket of mucus and intrasinus debris toward the ostium for

drainage into the nose

The ostium is located along the superior aspect of the

me-dial wall, 25 to 35 mm above the antral floor, and drains through

the anterior aspect of the middle meatus The ostium is a

duct-like orifice 3.5⫻ 6 mm in cross section, extending

superome-dially 3.5 to 10 mm in length The ostium position, high on the

medial wall, is further hindered by the ductlike configuration,

making passive (gravitational) drainage ineffective

The sinus functions to lighten the weight of the skull and to