Minimally Invasive FullMouth Rehabilitation Adapting Digital Dentistry QUINTESSENCE OF DENTAL TECHNOLOGY 2018

Minimally Invasive Full-Mouth Rehabilitation Adapting Digital DentistryThe traditional approach for opening the VDO by using a familiar articulator to mount the master casts and com-plet

One of the most complex tasks of any esthetic oral rehabilitation is the development

of a treatment plan Assembling all the data gathered from multiple sources—such

as medical and dental history, patient’s chief complaint, radiographs, cone beam puted tomography (CBCT), casts, bite registrations, occlusal analysis, tooth shade analysis, just to name a few—and then interpreting the data, coming to a conclusion, and fabricating visually acceptable prototypes (virtual or not) for communication with the patient and restorative team is not a easy task

com-Although it is clear that the advances in digital technology in recent years have made a highly positive impact, information remains fragmented The restorative team still needs to collect different pieces of information using digital and nondigital for-mats and combine them using different digital platforms or analog methods to pre-pare an appropriate treatment plan Not to mention that there are so many variables involved in an oral rehabilitation that the process of establishing a final treatment plan itself is very stressful and intricate Minimal errors in data gathering can lead to unpredictable outcomes, and the lack of predictability is one of the most challenging fears in dentistry

We urgently need digital tools that allow us to record, in an all-in-one single form, patient data dynamically (lips at rest, teeth display during smile and exaggerated smile, occlusal excursions and movements), statically (intraoral scan, extraoral scan, digital dental shade analysis, and CBCT), and historically (medical and dental history) While many systems provide the op-portunity to design smiles, plan restorations, determine implant placement, or evaluate underlying structures, most of the systems available still lack full integration Furthermore, many digital platforms remain based in traditional dentistry, where teeth still need to cut in order for the software algorithms to design and propose an acceptable restoration Ideally we need fully digital data sequencing, where all digitally recorded data would allow complete analysis and study of occlusion (includ-ing vertical dimension of occlusion), dental esthetics, tooth position, enamel and dentin thickness, edentulous space, root canal therapy, and gingival esthetics to create the ultimate virtual patient

plat-With the assistance of this technology, the human brain would then design a successful treatment plan with a minimally invasive approach in mind and monitor its outcome over time in the same digital platform As the machine stores more information, better decisions could be drawn This technology is already available in other fields In medicine, for instance,

a surge of interest in machine learning has resulted in an array of successful data-driven applications, ranging from cal image processing and diagnosis of specific diseases, to the broader tasks of decision support and outcome prediction Through an artificial neural network—which resembles a biologic brain in the sense that it learns by responding to the environment and stores the acquired knowledge for future decisions—digital technology could help to predict the success

medi-of a given treatment or suggest its limitations Dentistry could truly benefit from artificial intelligence and artificial neural networks, or at minimum all-in-one digital platforms offered at a reasonable cost

Digital workflow is clearly the theme of this year’s Quintessence of Dental Technology, with its collection of essays and cases demonstrating a combination of human ingenuity, artistry, and technology to promote better and high-quality dentistry I welcome you to take the time to explore the possibilities shown in this book, to be curious, and to crave for knowledge with the excitement of all new possibilities

Sillas Duarte, Jr, DDS, MS, PhD

Copyright of Quintessence of Dental Technology (QDT) is the property of Quintessence Publishing Company Inc and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission However, users may print, download, or email articles for individual use.

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Minimally Invasive Full-Mouth

Rehabilitation Adapting Digital Dentistry

1 Private Practice, Daikanyama Address Dental Clinic, Tokyo, Japan.

2 Osaka Ceramic Training Center, Osaka, Japan.

3 Private Practice, Yamamoto Dental Clinic, Osaka, Japan.

Correspondence to: Dr Masayuki Okawa, Daikanyama

Address Dental Clinic, 17-1-301 Daikanyama-cho, Shibuya-ku, Tokyo 150-0034, Japan

mechanics of tooth structure.

Since Magne and Belser introduced various anterior

bonded porcelain restoration cases in 2002,2 many

clini-cians, including the author, have been publishing

well-documented successful results for anterior teeth.3,4 Magne

et al5,6 and Dietschi and Argente7 later published direct

and indirect adhesive restorative techniques with the

mini-mally invasive concept for posterior teeth Since then,

Duarte et al,8 Fradeani et al,9 Vailati et al,10 Okawa,11 and

other clinicians have published minimally invasive full-mouth

rehabilitation cases.12 New clinical workflows and materials

for minimally invasive restorations also continue to be

in-troduced Moreover, the author has presented clinically

successful minimally invasive restorations fabricated using

a microscope to avoid technical errors.13

Since the introduction of digital dentistry—the recent

paradigm shift in dentistry—it is important to understand

its application in the minimally invasive restoration

work-flow.14 In this article, several important aspects of

execut-ing minimally invasive restorations are discussed through

the presentation of full-mouth minimally invasive

restora-tions for a case of severely acid-worn dentition

CLINICAL GOAL OF INDIRECT

MINIMALLY INVASIVE TREATMENT

As previously noted, the author has been having excellent

case outcomes and prognoses by working under the

micro-scope In the patient shown in Figs 1 to 6, the fractured

anterior teeth were treated under the microscope with

bonded porcelain restorations Marginal integrity was

sta-ble, with no sign of marginal porcelain chipping or

discolor-ation 9 years posttreatment

The author did not have much exposure to digital

den-tistry at the time of treating this patient However, with

micro dentistry (treatment under the microscope), high

ac-curacy can be obtained and prosthetic errors avoided, with

Clinical Questions/Concerns Regarding Minimally Invasive Full-Mouth Rehabilitation

1 Recently, cases of minimally invasive or noninvasive mouth rehabilitations of severely worn dentition (due to chemical erosion, occlusal abrasion,15 enamel dysplasia, etc) have been presented widely Is tooth reduction necessary for those cases?16 If necessary, how much reduction is needed for different types of cases? What type of finish line is appropriate?

full-2 Polymer versus all-ceramics: What is required to obtain accuracy of fit of restorations using a digital workflow? What kind of material choice is appropriate for milling the restoration? Should material choice be different de-pending on the location of the restoration, ie, anterior or posterior?

3 The provisional stage is extremely important for mouth rehabilitation cases in order to evaluate function and esthetics Since adhesive restoration preparation does not require retention and resistance form, how can

full-we choose the provisional restoration material? How do

we cement the provisional restoration? What kind of temporary cement can be used?

RESTORATIVE TREATMENT FOR SEVERELY WORN DENTITION

Severely worn dentition can be caused by acid erosion, parafunctional habits such as bruxism, malocclusion, or a combination of these Severely worn dentition can cause esthetic, functional, and biologic issues, and this can lead

to complete bite collapse Restorative treatment is tant to prevent further deterioration.17 Adhesive restoration

impor-to preserve the remaining impor-tooth structure should be the treatment of choice in such cases.18

Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry

CASE PRESENTATION

Chief Complaints

The patient, a 21-year-old fashion model, was concerned

with the esthetics of her thin and short central incisors

She also complained of sensitivity in the anterior teeth and muscle pain caused by her clenching habit A later inter-view revealed that she had an eating disorder (bulimia) The patient wanted treatment to improve the anterior es-thetics and posterior occlusion as well as eliminate teeth sensitivity

Fig 1 Preoperative photograph of patient with four fractured

maxillary anterior teeth.

Fig 2 Teeth preparation.

Fig 3 After completion of restorative treatment under

micro-scope.

Fig 4 Three-year postoperative radiographs There is no

detect-able gap between the teeth and restoration margins even

though radiopaque resin cement was used.

Figs 5a and 5b Nine-year postoperative photographs There is

no discoloration on the anterior restoration supragingival

margins.

Fig 6 Magnification of supragingival margin under the

micro-scope No significant clinical negative changes can be observed

Initial Clinical Work-up

Analysis of facial features and lip and teeth relationship

The incisal edge position was concave and did not match

the smile line The mandibular anterior teeth were slightly

extruded (Figs 7a to 7c)

Intraoral photograph analysis. Figures 8a to 8c show the

anterior teeth in occlusion, anterior rest position, and

ante-rior protrusive movement There was no significant

con-cern in terms of the maxillary cervical gingival levels, but

the occlusal plane was canted to the right The midline of

the maxillary central incisors matched the facial midline

The midline of the mandibular central incisors was shifted

to the right; therefore, the left canine relationship was

Class III The path of teeth guidance can be analyzed by

examining the anterior teeth working contacts and wear

pattern This case was diagnosed as pathway to

end-to-end wear Spear noted that overjet should be deeper and

overbite shallower for cases such as this, with teeth

con-tacts in functional movement until the end of the

mandibu-lar envelope movement.19

The four maxillary incisors appeared very thin (Figs 9a

and 9b) All six maxillary anterior teeth showed incisal

chip-ping and significant wear, so those teeth appeared to be very short There was no decay or restorations on these teeth The occlusal view (Fig 9b) shows the typical acid enamel erosion pattern and shiny worn-down occlusal sur-faces.17 This wear pattern confirmed that acid erosion caused the dentin exposure, and the mandibular anterior labial incline and bruxism caused additional wear of the maxillary anterior teeth

Study model analysis The acid erosion and occlusal wear

of the palatal surfaces of the maxillary anterior teeth could

be seen on the initial study models (Figs 10a to 10d) Hard tissue defects caused by the acid erosion and occlusal wear were more prominent on the anterior teeth than the posterior teeth The maxillary left first molar seemed to have been lost much earlier and left unrestored The sec-ond and third molars were tilted mesially and closed the space of the first molar The maxillary molars showed sig-nificant wear on the functional cusps, and the mandibular molars showed occlusal concavities, corresponding with the patient’s complaint of right molar clenching There also was pain on palpation of the posterior belly of the digastric muscle This implies that the right condyle could locate on the more posterior position

7c

Figs 7a to 7c Clinical evaluation of facial esthetics and face-to-tooth relationships The incisal edge position of the maxillary anterior teeth is shorter than the lower lip smile line, and the mandibular anterior teeth are slightly extruded Those are the major esthetic issues.

Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry

Figs 8a to 8c Initial preoperative photographs.

Figs 9a and 9b Initial preoperative facial and occlusal views of the maxillary anterior teeth.

Figs 10a to 10d Evaluation of initial preoperative study casts (a) Maxillary anterior teeth, palatal view; (b) maxillary teeth, entire

occlusal view; (c) maxillary right first and second molars, occlusal view; (d) mandibular right first and second molars, occlusal view.

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Radiographic analysis. All teeth were vital (Fig 11) Dental

decay was found on the interproximal surfaces of the

man-dibular right first and second molars There were no

peri-odontal concerns The maxillary left second molar was

mesially tilted

Restorative Treatment Objectives and

Treatment Planning

An organized and sequenced treatment plan was

estab-lished along with eliminating the risk factors of the acid

erosion.17 The treatment plan objectives for patients with

acid erosion should be to recover proper anatomical

fea-tures; reestablish proper occlusion and function; improve

esthetics, such as the smile line; and eliminate teeth

sensi-tivity.11 This particular patient had more significant anterior

teeth wear compared to posterior wear Since the anterior teeth were already labially inclined, the ideal treatment choice preferably included either orthodontic intrusion or crown lengthening to create space for the future restora-tions rather than opening the vertical dimension of occlu-sion (VDO), in order not to create too much postoperative anterior teeth display Orthodontic treatment,20 including uprighting the maxillary left second molar, was discussed with the patient However, due to her occupational commit-ment, she could not undertake the suggested orthodontic treatment Therefore, full-mouth rehabilitation with open-ing of the VDO became the final treatment plan

A predictable treatment outcome with opening of the VDO has been shown by Abduo.21 Spear stated that the ideal VDO21,22 does not exist; VDO can change and adapt

to the patient’s condition, so an appropriate VDO for each individual patient needs to be determined.20 The restor-

Fig 11 Preoperative full-mouth radiographs.

Fig 12 Anatomy of thick enamel structure of anterior tooth’s lingual and interproximal areas It is important to preserve those structures for tooth flexure control.

11

12

Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry

ative treatment should bring back anatomy of the

individu-al tooth by increasing VDO and then restore function and

esthetics by preserving as much of the remaining tooth

structure (Fig 12)

Workflow of Minimally Invasive

Full-Mouth Rehabilitation

The method to determine the ideal VDO for this patient was

to fabricate a diagnostic wax-up on the articulator The

inter-occlusal record was acquired and mounted on the lator Esthetic and functional requirements were eval uated

articu-in this order: maxillary central articu-incisors, lateral articu-incisors and canines, maxillary premolars and molars, mandibular ante-rior teeth, mandibular premolars and molars The diagnostic wax-up should exhibit the ideal treatment plan goal visu-ally Meeting the patient’s esthetic demands and the op-erator’s functional goal should be the most important determinants of a new VDO Figures 13 to 21 demonstrate the mounting of casts on the articulator, the diagnostic wax-up technique, and determination of the new VDO

9.5 mm

Fig 13 Two sets of study casts were mounted on the articulator by using the same centric relation registration One set was for

fabrication of the diagnostic wax-up and the other for fabrication of the provisional restorations and anterior guidance index.

Fig 14 Esthetic evaluation and wax-up of the maxillary central incisors according to the patient’s request Ideal incisal position was created by adding wax after evaluating the central incisors and upper lip position during a smile General length, width, and tooth

proportions were also taken into consideration Patients with acid erosion tend to get used to the appearance of short teeth and

usually do not request long teeth 23

Fig 15 Establishing the ideal occlusal plane according to proper occlusal plane concepts and esthetic requirements In this case, the ideal occlusal plane was created by correcting the mesially tilted maxillary left first molar alignment.

Fig 16 Palatal surfaces of the anterior teeth were recontoured in the wax-up The maxillary left molars were also waxed and

idealized.

10 mm

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17 18

19

Fig 17 Ideal protrusive movement path provided on the articulator With the pathway to end-to-end wear in this case, overjet should be created deep and overbite shallow 19

Fig 18 New established VDO appreciated by closing the articulator.

Fig 19 Mandibular movement paths defined by touring the maxillary anterior lingual surface wax.

Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry

The traditional approach for opening the VDO by using

a familiar articulator to mount the master casts and

com-pleting diagnostic wax-up was selected for this treatment

However, after this step, digital dentistry was implemented

The microscope was used for restorative steps, such as

teeth preparations, in order to minimize technical errors

Following are the five main treatment steps for this patient

Step 1: Full-Mouth Provisional

Restorations (Digital Approach)

As shown in Figs 22 to 36, the full-mouth provisional

res-torations for this patient were fabricated digitally using the

noninvasive approach, as was the goal

This case was categorized as Class IV according to the

ACE analysis by Vailati and Belser.18 The author selected

the sandwich veneer technique, with separate buccal and palatal veneers, for the six maxillary anterior teeth to pre-serve interproximal sound tooth structure, which has an important role in controlling the tooth flexure in teeth that have lost significant hard tissue due to acid erosion and occlusal wear

Anterior provisional restorations were cemented with provisional resin cement (Telio CS Link, Ivoclar Vivadent)

by applying spot acid etch and bond Posterior overlay provisional restorations do not have traditional “retention and resistance” form and yet receive heavy vertical and lat-eral occlusal loads, so regular provisional resin cement would not hold those restorations for long Therefore, the inner surfaces of the posterior overlay provisional restora-tions were treated with primer (HC primer, Shofu), and non–self-adhesive resin cement (HC cement, Shofu) was used (Figs 32a and 32b)

24b 24a

Figs 22a and 22b Preoperative

study casts and diagnostic

wax-up models were scanned

using a tabletop scanner and the

images then superimposed.

Figs 23a and 23b

Superim-posed images There is adequate

space on the buccal, incisal, and

palatal areas of the maxillary

anterior teeth

Figs 24a and 24b The palatal

veneer restorations for the

maxillary anterior teeth and

occlusal overlay restorations for

the maxillary left molars were

digitally created with the software

after scanning of the preoperative

study casts.

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Figs 26a and 26b Labial provisional veneer restorations for the maxillary anterior teeth were digitally created.

Fig 27a Maxillary anterior labial veneer provisional restorations milled from PMMA disk.

Fig 27b Maxillary labial and palatal provisional veneer restorations polished and ready for insertion.

Figs 28a and 28b Fabricated sandwich veneer provisional restorations tried on the stone master casts.

Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry

Figs 29a and 29b Posterior

provisional overlay veneer

restorations (a) designed and (b)

fabricated The VDO was not

raised much in this case, so the

posterior overlay provisional

resto-rations were thin These

restora-tions were splinted in order to

avoid stability issues during the

provisional phase.

Figs 30a and 30b Provisional

restorations for the mandibular

molars were fabricated using the

direct bonding technique using a

clear silicone matrix (Reveal,

Bisco) since there was not

enough clearance to fabricate

PMMA provisional restorations

with the noninvasive approach

Direct bonding was applied on the

mandibular right first and second

molars and first premolar and on

the left first molar and second

premolar.

Figs 31a to 31c After setting preoperative casts with the new VDO on the articulator, an anterior index was fabricated to keep

posterior interocclusal space with the new VDO during fabrication of the provisional restorations The index is used to transfer the provisionals from the articulator to the patient’s mouth It acts as an intraoral vertical stop After inserting posterior provisional

restorations with the index, the anterior sandwich technique provisional veneer restorations were inserted and anterior stop and

33a 33b

35

challenging to perform without error.

Figs 36a and 36b Final restoration casts created from the duplicated provisional restoration casts with some minor waxing and recontouring after the intraoral adjustments After adjustment of the casts, both arches were scanned for the digital wax-up of the final restorations.

Fig 35 Provisional restorations fabricated for the noninvasive full-mouth rehabilitation.

Figs 34a and 34b Working under the microscope is extremely useful for insertion of palatal provisional veneer restorations on the unprepared tooth surface because

it is concave.

Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry

When occlusal rehabilitation treatment for heavy

brux-ists is carried out with altered VDO, there is a tendency for

muscle activity to become more active 2 to 3 months into

the treatment and for the patient to begin to break down

the provisional restorations.24,25 In this patient, accordingly,

there was chipping and wear of the provisional direct

com-posite restorations on the mandibular right molars The

right condyle was also deviated forward after opening the

VDO This gave the assumption that the condyle was

devi-ated posteriorly due to too much compressive stress

After several anterior and posterior occlusal adjustments,

the patient became accustomed to the altered VDO and

occlusion The frequency of mandibular right-side

provision-al restoration repair was reduced and pprovision-alpation pain in the

posterior belly of the digastric muscle disappeared

Facial-ly, the patient noticed less muscle bulk on the mandibular

angle and she did not clench as much as previously

After these positive outcomes with the provisional

res-torations, it was decided to proceed to the final restorations

But first, impressions of both arches were taken for the

digital wax-up of the final restorations, and the casts were

refined using a curving and waxing technique

Step 2: Molar Teeth Preparation

(Microscope Technique)

The full-mouth provisional restoration was accomplished

with the completely noninvasive approach However,

be-cause the direct composite provisional restorations on the mandibular right first and second molars were constantly chipping and wearing due to the patient’s strong bruxism, milled lithium disilicate (IPS e.max, Ivoclar Vivadent) was selected as the material of choice for the final restorations given its high strength and capability for etch and bond This material will prevent the future loss of VDO and non-ideal posterior rotation of the TMJ The author has been using lithium disilicate clinically for minimally invasive mo-lar restorations below the manufacturer’s recommended thickness (thinner than 0.8 mm); however, chipping or shear fracture has been occurring in patients with heavy bruxism The author also believes that the press technique

is an effective fabrication method for those extremely thin molar occlusal veneer restorations For this case, prepara-tion of the first and second molars was done to provide 0.8

to 1.00 mm thickness for the ceramic restorations.9 ever, the preparation was kept in the enamel since inter-occlusal space was automatically created by increasing the VDO Final preparations of the maxillary left first and second molars were done by preparing the PMMA provi-sional restorations under the microscope, and the final preparations of the mandibular first and second molars were done by preparing a direct composite resin mock-up under the microscope.26 The direct composite bonded res-torations on the mandibular right and left second premo-lars and left first molar were in great condition; therefore, it was decided they would be the final restorations (Figs 37

How-to 40)

Fig 37 After preparation of the mandibular right first and second molars A great deal of occlusal wear was noted on the provisional restorations; interproximal decay was also detected Therefore, those teeth needed to be prepared for lithium disilicate (IPS e.max CAD, Ivoclar Vivadent) final restorations.

Fig 38 Measuring the material thickness of the final restoration is an important step With digital dentistry, this task is performed

easily After tooth preparation, prepared teeth and the entire arch are scanned by the intraoral scanner (Trios 3, 3Shape) and final

restorations designed by digitally superimposing the scans with the software.

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Step 3: Fabrication and Insertion of

Posterior Final Restorations (Digital

Approach)

The posterior final restorations were fabricated digitally

using IPS e.max CAD HT A1 block e.max CAD was chosen

as the restorative material for this case due to its wear

re-sistance and esthetics e.max CAD ceramic block can be milled as thin as 0.3 mm with the use of a new milling bur and setting milling time longer, although there are some small variations in results It is rather easy to mill e.max CAD ceramic block since it is milled in the green stage If the margin needs to be as thin as 0.2 to 0.3 mm, it should

be milled thicker and then adjusted on the 3D-printed die model (Figs 41 to 43)

Figs 39a and 39b Mandibular right first and second molar PMMA provisional restorations: (a) intraoral view and (b) preinsertion views of the four PMMA provisional restorations The mandibular right first and second molar restorations were splinted for retention and had a holding notch applied on the individual restorations for easy removal These PMMA restorations had great fit; however, possible material distortion during milling could occur because the restorations are very thin Cementation was done with HC cement Figs 40a and 40b Digital image of final restoration wax-up cast (provisional restorations modified casts) and digital image of prepared teeth are double scanned.

Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry

Figs 41a to 41d (a) 3D-printed model is required

for adjustment of occlusion, surface texturing,

staining, margin adjustment, and polishing IPS e.max

CAD HT A1 block (a, b) before crystallization and (c)

after crystallization (d) Abutment dies produced by

3D printer and completed ceramic overlay

restora-tions after staining.

Fig 42a Lava Ultimate HT A1 block (3M ESPE),

which is a polymer block, was milled under the same

setting experimentally It was milled as thin as 0.3 mm

without problem However, e.max CAD presented

better light transmittance in the same HT A1 block

Fig 42b Try-in of Lava Ultimate overlay restorations

The stability and fit of the overlay restorations from

the polymer block was satisfactory.

Figs 43a and 43b IPS e.max CAD ceramic overlay restorations inserted on the mandibular right first and second molars Rubber dam should be used for the bonding procedure to control moisture Highly filled composite resin (ENA HRi, Micerium) was softened

by heat and used as the bonding material due to its high bond strength and hardness The ceramic overlay restorations on molars fabricated digitally were as accurate and esthetic as those using the traditional approach.

Palatal Ceramic

Fig 44 Data from the wax-up model of final restorations, which was refined from the provisional model and the data before abutment preparation, were superimposed to simulate the final restorations The sandwich veneer technique was employed for the maxillary anterior teeth to preserve enamel in the proximal area, which is important for tooth flexure control.

Figs 45a and 45b Cervical area was prepared 0.2 mm under the microscope.

Fig 46 After completion of abutment preparation

Figs 47a and 47b Shape of prepared abutments and acquired material space was measured on the software.

46

44

Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry

Step 4: Abutment Preparation of

Anterior Teeth (Under Microscope)

Sandwich veneer restoration was chosen for the maxillary

anterior teeth Non-preparation provisional restoration was

possible because enough material space was secured at

the time of diagnostic wax-up When evaluating the

provi-sionals, it was found that the restorations tended to slip

away during the seating procedure due to the labial convex

surface A 0.2-mm feather-edge chamfer finish line was

placed at the gingival level of the labial cervical area

Hence, the bonding procedure could be performed with

control and the seating position checked under the

micro-scope This subtle tooth reduction should not affect the

deflection of the tooth Preparation of the incisal edge and

lingual aspect involved only rounding the sharp edges

A microscope is required to perform minimal

prepara-tion accurately And for the intraoral digital scanning, not

limited to subgingival but for the veneer restorations, it is

difficult to scan the tooth surfaces at adjacent contact

points, so stripping reduction of the contact points should

be done within the tolerance to avoid violating tooth

flex-ure.Labial veneers of maxillary anterior teeth can be thin

as long as abutment flexure is minimum and bonding is in enamel without complications such as chipping or fracture Many anterior teeth can be restored without any abutment preparation Consideration of strength and direction of occlusal force and required material space is more critical

in posterior teeth restoration (Figs 44 to 47)

Step 5: Fabrication and Insertion of Anterior Restorations (Digital and Traditional Approaches)

Two sets of restorations were fabricated by two dental technicians using two different fabrication approaches for study purposes to compare the workflows and the results The digitally fabricated restorations were designed using the digital data obtained by an intraoral scanner After mill-ing, they were stained and final adjustments were made on the model generated by the 3D printer (Figs 48 to 58) The second set of restorations used a combination of tradition-

al and digital approaches Labial veneers were fabricated

Fig 49 Palatal veneers were first designed after superimposing the data from the provisional modified cast wax-up for final tions and the data from intraoral scanning after abutment preparation.

restora-Fig 50 Milled palatal veneer restorations using IPS e.max CAD block according to the design shown in restora-Fig 49.

Figs 51a and 51b Palatal veneer restorations were tried on the 3D-printed model after crystallization and staining Once fit was confirmed, scanning with a desktop scanner was carried out with the palatal veneer restorations seated on the 3D-printed model Fig 52 Maxillary anterior labial veneers were designed on the superimposed data of the wax-up model of final restorations and scanned data of the 3D-printed model with palatal veneers seated Individual dies were fabricated by sectioning the 3D-printed model and superimposed on the image to reproduce accurate veneer margins of the proximal area.

Fig 53 Milled labial veneers using e.max CAD block from the data of Fig 52.

Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry

Fig 55 Completed anterior labial veneer restorations after crystallization and staining.

Figs 56a and 56b Maxillary anterior sandwich veneer restorations completed using the digital approach (technician: Mr Takahiro Aoki, Osaka Ceramic Training Center).

Fig 57 Try-in of sandwich veneer restorations Natural shade and esthetics were achieved using the digital approach.

Fig 58 Highly accurate marginal fit was achieved using the digital approach Gingival margins cannot be distinguished by visually comparing the veneers before and after try-in.

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on a refractory cast using feldspathic porcelain and

fin-ished on the stone master model obtained by silicone

im-pression The stone master model was scanned and palatal

veneers were designed digitally They were milled, stained, and finished on the master model (Figs 59 to 64)

Fig 61 Labial veneer restorations were fabricated using the porcelain layering technique on the refractory die (technician: Mr Shigeo Kataoka, Osaka Ceramic Training Center) Despite the progress in materials for digital fabrication, such as gradation monolithic block and staining technique, limitations in detailed coloring and light transmittance remain The shape of mamelons, incisal halos, and creation of internal structure such as fluorescence still require the creative hand of the master technician, which will not change in the near future.

Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry

Fig 62 Completed labial veneer restorations using refractory model technique Surface texture was finished by

the master ceramist.

Fig 63 Completed sandwich veneer restorations using the traditional and digital approaches.

Fig 64 Fit of labial veneer and palatal veneer restorations is confirmed on the stone model.

62

63

64

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Superior accuracy of fit and esthetics were achieved in

both restorations (Fig 65) The result of the digital approach

was better than expected preoperatively after utilizing

orig-inal techniques and technology After discussion with both

technicians, it was decided to have the patient choose

which of the two to be inserted as the final restorations

The patient chose the restorations fabricated using the

combination of traditional and digital approaches (Fig 66)

However, the restorations fabricated using only the digital approach would have achieved the same treatment goal satisfactorily The patient was happy with the result of the restorations both esthetically and functionally (Figs 67 to 72) Again, the same level of result would have been achieved with the restorations fabricated using only the digital approach

Traditional combined with digital approach

Fig 65 Comparison of two different sets of maxillary anterior veneer restorations fabricated using only the digital approach and the traditional with the digital approach

Fig 66 The patient chose the restorations fabricated by Mr Kataoka using a combination of the traditional and digital approaches

Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry

Fig 67 Natural esthetics was achieved even at the palatal junction area.

Figs 68a to 68c Frontal and maxillary/mandibular occlusal views of the final minimally invasive full-mouth rehabilitation using the traditional and digital approaches

67

68a

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70

71 Fig 69 Postoperative full-mouth radiographs It is evident that the maximum possible amount of tooth structure was preserved Fig 70 Postoperative panoramic radiograph The mandibular occlusal plane was well leveled by increasing VDO.

Fig 71 With the treatment performed under enlarged view of the microscope, 27 the cervical labial margin of the veneer restoration fabricated on the refractory model was so well fitted that it was undetectable even under microscopic view and achieved superior

Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry

CONCLUSION

Digital technology can be applied to minimally invasive

full-mouth rehabilitation because of factors such as

supra gingival margins, accurate intraoral scan data, and

reproducibility of PMMA provisional restorations The

den-tist and technician have to be somewhat creative and be

able to acclimatize their steps and procedures, such as

abutment preparation, veneer design, milling, and

3D-printed model fabrication Technical procedures such as

creating particular surface textures, staining, adjustment of

occlusion and margins are required and performed

manu-ally using a 3D-printed or CAD/CAM model

It is clear that minimally invasive treatment will be the mainstream of restorative dentistry The dentist and the technician need to figure out how to utilize digital technol-ogy and incorporate it into the traditional workflow to main-tain or improve treatment quality Progress in digital software, milling machines, and materials will not stop Master-quality work is still created by the hands of the clinician and tech-nician, which will not change Our patients’ satisfaction is achieved by adding a truly natural appearance to the artifi-cial restoration

Fig 72 The patient’s new natural-looking smile and dramatically improved smile line.

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4 Okawa M, Yamamoto S Exzellente dentale asthetik Quintessenz

Zahntech 2013;39:11–12.

5 Magne P, Knezevic A Simulated fatigue resistance of composite

resin versus porcelain CAD/CAM overlay restorations on

endodonti-cally treated molars Quintessence Int 2009;40:125–133.

6 Magne P, Belser UC Rationalization of shape and related stress

dis-tribution in posterior teeth: A finite element study using nonlinear

contact analysis Int J Periodontics Restorative Dent 2002;22:425–

433.

7 Dietschi D, Argente A A comprehensive and conservative approach

for the restoration of abrasion and erosion Part II: Clinical

proce-dures and case report Eur J Esthet Dent 2011;6:142–159.

8 Duarte S, Sartori N, Cascione D, Phark JH Ceramic-reinforced

poly-mers: Overview of CAD/CAM hybrid restorative materials

Quintes-sence Dent Technol 2014;27:32–48.

9 Fradeani M, Barducci G, Bacherini L, Brennan M Esthetic

rehabilita-tion of a severely worn dentirehabilita-tion with minimally invasive prosthetic

procedures (MIPP) Int J Periodontics Restorative Dent 2012;32:

135–147.

10 Vailati F, Brugera A, Belser U Minimally invasive treatment of initial

dental erosion using pressed lithium disilicate glass-ceramic

restora-tions: A case report Quintessence Dent Technol 2012;35:65–78.

11 Okawa M Minimally invasive full-mouth rehabilitation for dental

ero-sion Quintessence Dent Technol 2016;39:57–77.

12 Duarte S Sartori N Biomaterials update: The adhesive restorative

complex (ARC) Concept Quintessence Dent Technol 2017;40:48–

65.

13 Okawa M Efficacy of working under a microscope for bonded

porce-lain restorations [in Japanese] Quintessence Microdentistry Yearbook

2011 Tokyo: Quintessence, 2011:66–78.

for the restoration of abrasion and erosion Part I: Concepts and ical rationale for early intervention using adhesive techniques Eur J Esthet Dent 2011;6:20–33.

clin-18 Vailati F, Belser UC Classification and treatment of the anterior illary dentition affected by dental erosion: The ACE classification Int

max-J Periodontics Restorative Dent 2010;30:559–571.

19 Spear F Facially Generated Treatment Planning Scottsdale: Spear Education, 2005.

20 Spear F, Kinzer G Approach to vertical dimension In: Cohen M (ed) Interdisciplinary Treatment Planning: Principles, Design, Implementa- tion Berlin: Quintessence, 2010:213–246.

21 Abduo J Safety of increasing vertical dimension of occlusion: A tematic review Quintessence Int 2012;43:369–380.

sys-22 Walther W Determinants of a healthy aging dentition: Maximum ber of bilateral centric stops and optimum vertical dimension of oc- clusion Int J Prosthodont 2003;16(suppl):77–79.

num-23 Vailati F, Carciofo S Treatment planning of adhesive additive tations: The progressive wax-up of the three-step technique Int J Esthet Dent 2016;11:356–377.

rehabili-24 Maxwell LC, Carlson DS, McNamara JA Jr, Faulkner JA Adaptation

of the masseter and temporalis muscles following alteration in length with or without surgical detachment Anat Rec 1981;200:127–137.

25 Helsing G Functional adaptation to change in vertical dimension J Prosthet Dent 1984;52:867–870.

26 Bacherini L, Brennan M, Bocabella L, Vigiani P Esthetic rehabilitation

of a severely discolored dentition with minimally invasive prosthetic procedures (MIPP) Quintessence Dent Technol 2013;36:59–76.

27 Massironi D, Pascetta R, Romeo G Precision in Dental Esthetics: Clinical and Laboratory Procedures Milan: Quintessenza Edizioni, 2006:126–141.

Copyright of Quintessence of Dental Technology (QDT) is the property of Quintessence Publishing Company Inc and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission However, users may print, download, or email articles for individual use.

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1 Adjunct Professor, Department of Preventive and Restorative Sciences,

University of Pennsylvania School of Dental Medicine, Philadelphia,

Pennsylvania, USA, and Private Practice, San Sebastián, Spain.

2 Shinbi Laboratory, San Sebastián, Spain.

3 Professor of Restorative Dentistry and Chairman, Department of

Preventive and Restorative Sciences, University of Pennsylvania

School of Dental Medicine, Philadelphia, Pennsylvania, USA.

Correspondence to: Dr Iñaki Gamborena, C/ resurrección M Azkue

#6 -4, 20018 San Sebastián, Guipúzcoa, Spain

Email: Gambmila@telefonica.net, www.Drgamborena.com

As described in the authors’ previous article

pub-lished in QDT 2017, the Slim concept provides

the unique ability to create an abundance of soft

tissue volume in the early surgical stages of implant

resto-ration It involves protocols and components, the Slim

heal-ing abutment beheal-ing the most important, that enable long-term esthetic and functional success The following case details further the clinical steps of the Slim concept in

a patient ideally restored with implant crown restorations along with veneers in the anterior maxilla

Clinical Steps to Ultimate Success

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CASE PRESENTATION

A female patient presented with a removable partial

denture replacing the maxillary right central and lateral

incisors and first premolar as well as the maxillary left

premolars (Fig 1) Her request was to have

implant-supported fixed dental prostheses replace those teeth

The panoramic radiograph and cone beam computed

tomography (CBCT) scan revealed the magnitude of the

bone loss, especially on the buccal aspect, when compared

to the adjacent central and lateral incisors (Fig 2) The

heights of the papillae on the mesial and distal aspects of

the defect were almost ideal, except for the volume loss on

the buccal aspect (Fig 3) The large buccal and vertical

defect in the edentulous area was caused by excessive

pressure from the base of the removable denture, which

replaced the teeth extracted about 10 years earlier

Graft, Implant, and Slim Placement (Figs 4 to 9)

CBCT examination of maxillary tuberosities indicated ficient soft tissue thickness to serve as preferred donor sites for subepithelial connective tissue grafts Connective tissue from the tuber areas is more dense and provides better long-term stability than palatal tissue; however, it re-quires complete coverage to ensure adequate vasculariza-tion and avoid necrotizing

suf-Since bone augmentation procedures add another level

of complexity and unpredictability, it was decided to ment the deficient sites solely with a connective tissue graft A buccal and crestal incision was made on the eden-tulous ridge, and a partial-thickness flap was elevated to increase the volume and tissue height, especially between the implants and buccolingually A sulcular incision was

3

The Slim Concept—Clinical Steps to Ultimate Success

made around the mesial and distal aspects of the teeth,

and the papillae adjacent to the defect were elevated

Fi-nally, the partial-thickness flap was prepared and raised

above the mucogingival junction (MGJ) until it reached the

desired coronal position No vertical releasing incisions

were made and the periosteum was left on the bone A

NobelActive NP 3.5 × 13-mm implant (NobelBiocare) was

placed in the area of the maxillary right central incisor and

a NobelActive 3.0 × 13-mm implant in the area of the

lateral incisor Slim healing abutments with 7-mm heights

were selected to maximize crestal tissue grafting and

en-able primary flap closure A large free tissue graft was

harvested from the maxillary tuberosity and carefully

de-epithelialized The connective tissue graft was sutured in

position to the palatal aspect of the flap The buccal flap

was then sutured exactly to the initial incision to close the

wound Monofilament suture material (6-0 PTFE) was used

to secure the tissues in place, and a 6-0 monopropylene

suture was used for precise flap closure This type of

sur-gery should always be performed in one stage together

with implant placement

Implant Planning and Execution (Fig 10)

Bone morphology, implant selection, and surgical ment were assessed and determined with digital implant planning software Virtual implant selection and placement suggested two NobelActive NP implants (3.5 × 13 mm) The yellow line indicates the bone level on the adjacent teeth and assists in the determination if bone or soft tissue augmentation is needed About 3.7 mm of tissue depth for the central and 3 mm for the lateral incisor would be nec-essary to control tissue scallop and volume to mimic the adjacent site Due to the thin buccal plate, the implant for the lateral incisor was selected to have a 3.0-mm diameter

place-Healing Phase (Figs 11 to 13)

The removable partial denture served as a provisional toration and was adjusted to avoid any contact with the augmented site The 3-month follow-up showed that the

res-10

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original goal of creating a soft tissue contour similar to the

adjacent site was achieved The Slim healing abutments

were initially completely covered with soft tissue, indicating

the great volume gained

Provisional Impression/Slim

Manage-ment (Figs 14 to 17)

Three months after surgery, an impression of the implants

was made under local anesthesia Removal of the healing

abutments and connection of the impression copings were

done carefully due to the large amount of tissue to

dis-place, the bone depth, and the diameter of the impression

copings—the smaller the better Due to their wider base,

Slim healing abutments must be removed with pliers The

impression coping was inserted with vertical pressure,

and seating was verified radiographically A diagnostic

full-contour wax-up was made to replicate the natural

tooth and duplicate its diameter, especially in the gingival

third A line was drawn on the master cast following the

ideal scallop of the wax-up, and the desired emergence

profile was carved from that line to the abutment head

Polyvinyl siloxane (PVS) matrices were made to visualize

the full-contour wax-up and fabricate the composite

abut-ment The stone was carved with hand instruments until

a divergent cone was created from the implant head

Com-posite abutments were then scanned and transformed in

zirconia

Provisional Restoration/Adaptation (Figs 18 to 20)

After the Slim abutments were removed with the patient under anesthesia, the final zirconia (Zr) abutments were connected and verified radiographically Some interproxi-mal bone had to be trimmed with diamond burs until final adaptation No flap was deflected and all bone recontour-ing was done through the tissue hole created by the Zr abutments The abutment screw of the 3.0 NobelActive implant should not be torqued beyond 15 Ncm Ischemia

is related to pressure and blanching of the tissues, which reduces blood supply and may cause necrosis of the sur-rounding tissues The provisional crowns were then relined chairside to establish ideal fit and proper interproximal contact areas The abutments were disconnected to adapt the margins and polish the provisional crown restorations extraorally

Papilla Loss/Second Graft (Figs 21 to 25)

During the healing process (3 months), papilla between the two implants was lost, which was likely caused by a loosening of the provisional and trauma due to incorrect occlusion Buccal tissue volume was adequate A second connective tissue graft was placed in the papilla area to improve the volume and density of the lost papilla Zr abut-

14

15

The Slim Concept—Clinical Steps to Ultimate Success

ments were modified to allow more space for grafting A

tunnel incision on the papilla and adjacent implants was

prepared to attach the second connective tissue graft

buc-copalatally A 6-0 PTFE monofilament suture material was used for that, while a 6-0 monopropylene suture was used for exact flap closure adaptation and positioning

Prosthetic Phase Healing (Figs 26 to 28)

After 9 months, the healing process of the grafted site

around the Zr abutments and provisional restorations was

reevaluated The soft tissue situation with respect to

vol-ume, interproximal height, and buccal/palatal support was

almost ideal Some additional pressure was needed on

the buccal aspect to control and blend the scallop of

the implant restoration with the adjacent central incisor

The original Zr abutments were replaced by an ASC

(angu-lated screw channel) Zr abutment on the central and a new

titanium/Zr abutment on the lateral incisor, due to fracture

of the Zr abutment as seen on the periapical radiograph A

pick-up impression of the provisional restorations was

made and poured in stone while the patient was waiting

This impression is helpful to transfer the emergence

pro-files but lacks accuracy in the interproximal contact areas

Veneers: Preparation/Final Impression (Figs 29 to 31)

The maxillary left central and lateral incisors were prepared for porcelain laminate veneers to improve the overall es-thetic outcome The veneers were completed first and the veneered teeth would be used to match the implant crowns

to their exact shade, value, and translucency The tion was approximately 1.4 mm in depth at the middle third

prepara-of the tooth to create sufficient space for the ceramist to mask the dark shade of the natural abutment teeth Since the interproximal contact areas were not completely opened, clear matrices were placed to facilitate sectioning

of the individual dies in the laboratory during master cast fabrication A two-cord technique was applied for the de-finitive impression, with a #000 retraction cord carefully placed into the sulcus first for margin location and to con-

The Slim Concept—Clinical Steps to Ultimate Success

trol intracrevicular fluids and bleeding, and a #00 cord

placed on top to further deflect the soft tissue and capture

the finishing line The top cord was removed immediately

before the impression material was applied while the first

cord stayed in the sulcus

Customized dies were fabricated for the prepared teeth

with flowable composite These dies were then stained

chairside to replicate the shade of the natural abutment

teeth as closely as possible These customized dies allow

dental technicians to adapt their porcelain layering

tech-nique individually and simulate the esthetic outcome in the

laboratory

Veneers: Model Work, Porcelain Buildup (Figs 32 to 35)

A “Geller model” was made from the definitive impression

to fabricate the two porcelain laminate veneers The clear matrices in the interproximal areas allow the technician to trim the dies more efficiently and delicately without dam-aging the interproximal finish lines The trimmed dies are placed back in the impression and secured into position to then pour the rest of the impression with stone, creating a master cast that allows the prepared dies to be removed while keeping the soft tissue contour of the model intact.During layering of the porcelain, the dental technician can simulate and verify the expected outcome on the cus-tomized composite dies in terms of final shade, value, chro-

ma, and translucency

Zr Abutment Fabrication

(Figs 36 and 37)

The new Zr abutments were fabricated to provide better

support of the soft tissues after the second connective

tis-sue graft Modifications were also necessary to meet the

goal of having the soft tissues supported 90% by the

abut-ment and 10% by the crown A two-piece Zr abutabut-ment was

fabricated for the lateral incisor since there was no metal

connection available for the specific implant (3.0 mm

No-belActive) The Zr abutment part was bonded to a titanium

abutment to maximize the esthetic outcome It was first

built in composite to the ideal contour The composite and

supporting titanium abutments were then scanned to

de-sign and fabricate the Zr component The Zr abutment was

perforated to facilitate the bonding process and limit voids

in the resin cement

To block out the dark color of the titanium, three ent resin cements were selected and tested with respect

differ-to their level of opacity Of those, the high-opacity (Ho0) Multilink Hybrid abutment cement (Ivoclar Vivadent) seemed

to provide the best ability to mask the titanium

Abutment Scanning (Fig 38)

The plastic ASC wax-up sleeve engaging abutment was connected to the laboratory analog, and composite resin was placed between the conically carved stone and the plastic sleeve until the ideal contour was achieved The composite abutment was light cured and prepared to create a 1-mm subgingival margin on the buccal aspect

of the ideally carved scallop and a slightly supragingival margin on the palatal aspect The composite abutment was