Clinical success in impacted third molar extraction Tiểu Phẫu Răng Khôn

Sách hướng dẫn chi tiết nhổ răng khôn, là sách gối đầu của các bác sĩ Tiểu phẫuPhẫu thuật trong miệng. Sách hướng dẫn chi tiết nhổ răng khôn, là sách gối đầu của các bác sĩ Tiểu phẫuPhẫu thuật trong miệng. Sách hướng dẫn chi tiết nhổ răng khôn, là sách gối đầu của các bác sĩ Tiểu phẫuPhẫu thuật trong miệng.

J.-F ANDREANI M.D.

Maxillofacial SurgeonParis, France

C DUNGLAS D.D.S.

Qualified OrthodontistAssistant ProfessorFaculty of DentistryUniversity Paris 5, France

Translation

M.-P HIPPOLYTE

PeriodontistAssistant ProfessorUniversity of Reims, France

Paris, Chicago, Berlin,Tokyo, Copenhagen, London, Milan, Barcelona,

Istanbul, São Paulo, New Delhi, Moscow, Prague, and Warsaw

University Paris 5, France

First published in French in 2002 by Quintessence International, Paris

L’extraction de la dent de sagesse

All rights reserved This book or any part thereof may not be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, or otherwise, without

prior written permission of the publisher.

The computerized radiographic imagesand the CT examination presented in this textbookwere provided by Drs Pascal Guinet, Alain Lacan,

Philippe Katz and Danielle Pajoni

We gratefully acknowledge their contribution

and the quality of their documentation

Table of Contents

Cover

Table of Contents

1 Third molar extraction: Why and when?

Embryology and eruption of the third molars

Developmental prognosis and eruption axis of the third molar

Indications requiring the use of orthodontic techniques

Third molar and DMD

Therapeutic occlusion and third molars

Relapse of anterior tooth crowding and its effect on the third molar

The mandibular third molar

3 Selection of radiographic examinations

Dental panoramic radiograph

Periapical radiograph

The shape of the tooth

The anatomic situation of the tooth

5 Nerve block anesthesia: Technique and failure assessment

Anesthesia of the inferior alveolar nerve

Additional anesthesia

Anesthetic procedures for the upper oral regions

6 Surgical protocol: Basic principles

Instrumentation

Incision lines

Elevation of a full-thickness flap

Bone removal

Sectioning the retained tooth

Alveolar socket evaluation

Suture

7 Germectomy

Indications for germectomy

At what age should treatment start?

Surgical protocol

8 The mesially inclined third molar

Radiographic interpretation

Degree of surgical difficulty

9 The horizontal third molar

Radiographic interpretation

Surgical protocol

Degree of surgical difficulty

10The vertical third molar

Radiographic interpretation

Degree of surgical difficulty

11The distally inclined third molar

Radiographic interpretation

Degree of surgical difficulty

The maxillary third molar

12The maxillary third molar: Examination and extraction

Anatomic specificities

Degree of surgical difficulty

Anesthesia in the maxilla

Third molar

extraction:

Why and when?

Extraction of third molars is one of the most common procedures indentistry Studies aimed at obtaining a better understanding of the reasonsleading to the extraction of one or several third molars have been reported inthe English and Scandinavian literature.

The National Institute of Health (NIH) has published the conclusions of theconsensus development conference held in 1979 and, while waiting for anoverall consensus on the indications for extractions, made the followingrecommendations:

• Evidence of hypertrophy, cyst or tumor development of the dental follicle

• Repeated episodes of pericoronitis

• Irreversible carious lesions

• Distal periodontal defect on the second molar

• Distal carious lesion of the second molar in relation to the third molar

Despite the accumulated experience in dealing with diagnosis andtreatment of developmental anomalies concerning the third molars,extraction still remains controversial when patients are asymptomatic.Indeed, the proportion of prophylactic extractions is increasing andrepresents from 18% to 40% of the overall third molar extractions carriedout in developed countries (Liedholm et al; Lysel and Rohlin) The majority ofthird molar extractions take place between the ages of 20 and 29 years(Liedholm et al) The main reasons for deciding on this course of action are:

• To reduce the risk of sequelae, surgical morbidity, and complications

involving the neighboring teeth in the elderly patients

• To improve oral health in younger patients who have completed their

growth phase

The quality of the outcome of this procedure is determined by a series offactors:

However, as yet it has not been possible to establish universal guidelinesconcerning the relevant indications for prophylactic extractions because ofthe widely varying criteria used in different countries by differentpractitioners and different scientific communities (Worrall et al).

Furthermore, even from a review of the current literature, it is not possible

to establish a significant risk-benefit ratio In addition, the decision toproceed with an extraction is often made during a single consultation usingonly one radiographic examination in young patients who have completedtheir growth phase

In order to establish a diagnosis it is essential to fully understand and beable to estimate the stage of eruption of the third molar The latter is related

to the evaluation of the prognosis in terms of impaction, partial retention orenclavement, tooth and periodontal lesions on the second and/or third molar,and the risk of anterior tooth crowding, which should always be avoided.The English clinical practice consensus committees have suggested threefactors that should be considered in the decision-making process forextraction of third molars (Liedholm et al):

• The age of the patient

• The angle formed between the great axis of the tooth and the occlusalplane, as well as the uprighting dynamics of this axis•

• The eruptive position

Some additional factors should also be taken into account:

• Oral hygiene

• Carious and periodontal indexes

The angulation of the axis of the third molar can be classified as follows,depending on the degree of distortion (Liedholm et al; Winter; see chapter4):

• Totally covered with soft tissue

• Totally covered with bone

The NIH has established that (NIH; Worrall et al):

• The surgical procedure and postoperative effects are more favorable in

the case of younger patients

• However, in the young adolescent, the indication for enucleation of the

third molar buds before root formation becomes evident

radiographically is not recommended because of the surgical risk thatwould be incurred

• Distally inclined molars are more likely to develop complications during

eruption than are molars with other angulations

• Molars that are partially or totally covered with soft tissue are more

prone to complications than are totally impacted molars

In the context of orthodontic treatment, the extraction indication ratios

for so-called prophylactic extractions are continually increasing, whichnaturally leads us to question this indication

In orthodontics, an indication for third molar extraction usually refers to thethird mandibular molar Many practitioners support the current view of therelationship between the occurrence of anterior mandibular crowding andthe eruption of the third molars at the end of adolescence and willtherefore often recommend extraction Once the decision has been made

to extract the mandibular molar, this invariably implies the removal of themaxillary molars in order to create a Class I occlusion

Embryology and eruption of the third molars

Like all human molars, the third molar is an accessional tooth, as distinct from the other teeth, which are known as replacement or successional

teeth The third molar originates from the primitive dental lamina and the bud

eruption depends on the growth of the posterior region of the arch.Emergence into the oral cavity occurs between 17 and 21 years of age Thetooth drifts along the distal aspect of the second molar in order to reach thelevel of the occlusal plane Root formation is completed between the ages of

18 and 25 years

The third molar encounters some difficulty in correcting its eruptive curve

to the upright position because the direction of its growth often brings itunder the cervical line of the second molar, thus causing it to becomepartially retained within the tissue

As a general rule, the third mandibular molar usually fills the space formed

by the retromolar triangle distal to the second molar.

In the maxilla, the complete absence of any bone obstruction allows thethird molar to erupt in either the correct position or a labial position The onlyobstacle to the smooth eruption of the third maxillary molar is the muscle-tendon-aponeurotic component (pterygoids, buccinator, or ligaments)

Developmental prognosis and eruption axis of the third molar

Most studies have shown that the eruption of the third molar is amultifactorial mechanism None of these studies has established anysignificant correlation between the angulation of mandibular third molar andits impaction

In the early stages of calcification, the mandibular third molar presents aphysiologic mesial and lingual orientation The change in angulation thatleads to the vertical positioning of the tooth should occur between theages of 14 and 16 years (Richardson, 1978) Establishing this vertical axis

may occur during differential growth events in the crown surface and the

mesial root in relation to the distal aspect.

According to Richardson, if growth occurs predominantly in the mesialarea of the crown, vertical positioning of the tooth will result; but if growth

of the distal root predominates, then the tooth bud will develop in ahorizontal position (Fig 1-1)

In summary, it appears that the developmental prognosis for the third

molar can be established from the age of 16 years.

Björk correlates the lack of appropriate space for the eruption of the thirdmolar with three factors:

• The direction of vertical condylar growth

• Reduced mandibular length

• Backward orientation of tooth eruption

1-1 Differential growth between the mesial and distal aspects of the right mandibular third molar.

Silling notes that Class II skeletal relationships (ie, mandible positioned in

an excessively posterior sagittal position in relation to the maxilla) with ashort mandible and a closed mandibular angle are associated withimpaction Conversely, the percentage of impaction decreases in the case

of a hyperdeveloped mandible (skeletal Class III)

Indications requiring the use of orthodontic

techniques

Some techniques indicate the need for extraction before treatment isinitiated

Crowding is measured by comparing the available space with that required

to accommodate the second and third mandibular molars The available

space is the distance between the anterior border of the ramus and the

distal aspect of the first molar, parallel to the occlusal plane The required

space is the sum of the respective mesiodistal diameters of the second and

third molars as measured with a lateral cephalogram The difference

determines the degree of crowding and the need for extraction

1-2a Panoramic radiograph prior to orthodontic treatment showing evidence of posterior crowding in

a male patient.

1-2bTwenty-one months later, the panoramic radiograph shows the resorption of the anterior border

of the ramus, which has allowed the eruption of the second molar Note the differential root

development between the mesial and distal aspects.

In a growing patient, starting from the age of 8 years, an average of 1.5

mm per hemiarch per year should be added to the value for the availablespace, taking into account that cessation of growth occurs approximately atthe age of 17 years for boys and 15 years for girls (Tweed) This extraspace results from the resorption of the anterior border of the mandibularramus during growth (Figs 1-2a and 1-2b) However, according to Tweed,estimations of the increase in the available posterior space can be affected

by several factors:

• The degree of mesio-occlusal drift of the first mandibular molar

• The degree of resorption of the anterior border of the ramus

• The cessation of mesial molar drift

• In the mandible, the probability of eruption must be assessed using mean

measurements of the Xi distance (ie, the cephalometric point constructedgeometrically at the center of the ramus) to the distal edge of the secondmolar, parallel to the occlusal plane Turley and Chaconas constructed acurve in order to assess the likelihood of impaction in relation to theavailable space The following values are approximations of these meanmeasurements:

1 21 mm for impacted teeth

2 25 mm for marginal third molars

3 30 mm for third molars in functional occlusion

The need for maximum anchorage preparation

In the Tweed-Merrifield technique, correcting a dental Class II situation inpatients who are still growing requires maximum anchorage preparation, ie,therapeutic distal tipping of the mandibular molars before initiation ofinterarch mechanical treatment, in order to reduce any possible side effects.This leads to the possible risk of impaction of the third molar The presence

of the third molar may indeed limit the possibility of therapeutic distal tipping

of the second molar It thus leads to a dentomaxillary disharmony (DMD)with a secondary or induced posterior position According to these authors,orthodontic anchorage preparations should only be considered if there is noposterior crowding to jeopardize the success of distal tipping of the first andsecond molars The same principle applies to orthodontic distalization of thefirst maxillary molar

Third molar and DMD

Spontaneous DMD is the consequence of two biologic mechanisms:

• The growth process, which leads to a decrease in the volume of the faceand is species specific and genetically determined

• The genetically determined distance between the teeth and osseousbases

The need for premolar extraction will depend on the size of an anteriorlyexpressed DMD, anterior tooth crowding, and excessive buccal inclination ofthe mandibular incisor, regardless of whether there is also a hyperdivergentskeletal pattern, ie, any divergence between the base of the cranium or the

Frankfort plane and the inferior edge of the mandibular body as measuredradiographically The extra space made by moving the posterior segmentdistally will accommodate the third molar According to Schulhof, eachadditional millimeter of available space will increase the chance of themandibular third molar erupting normally by 10%.

Studies undertaken by Ricketts (1979) and Richardson (1975) haveshown that a greater percentage of impactions occurred in cases where noextraction was carried out versus cases where premolar extraction hadbeen undertaken and in cases where the first premolars had been extractedcompared to those where the second premolars had been extracted

However, extracting a premolar does not ensure that the third molar willerupt Thus, there is no evidence to suggest that the extraction ofpremolars will resolve an anteriorly expressed DMD

Finally, the decision to extract one or several third molars may depend onwhether there are any eruption anomalies of the second molars (Figs 1-3aand 1-3b)

1-3a Mesioversion of a retained left mandibular second molar.

1-3b Extraction of the left mandibular third molar has allowed orthodontic uprighting of the second

molar shown in Fig 1-3a.

Therapeutic occlusion and third molars

Achieving Class II therapeutic occlusion using maxillary premolarextractions in the presence of posterior mandibular crowding does notautomatically require the removal of all third molars Extraction of only themandibular third molars may be sufficient in most cases

Relapse of anterior tooth crowding and its effect

on the third molar

Orthodontic treatment should be planned to provide the optimumdevelopmental outcome for the third molars

Treating DMD, when present, and establishing a functional occlusion doesnot prevent the occurrence or relapse of tooth malposition, which can quitefrequently occur in the anterior region This leads to the conclusion that otherfactors may be involved in this partial relapse

According to Van der Linden, late mandibular growth may be the onlyfactor responsible for anterior crowding and would occur even in theabsence of the third molars.

According to Charron, the most plausible explanation for this crowding isthe late growth of the mandible at around 17 or 18 years of age.Concomitant changes, mostly in the occlusal relationship, take place at alater stage and are also involved in crowding, probably due to mesial driftand occlusal interference

Björk acknowledges the influence of the third molars, but suggests thatmandibular growth is mainly responsible for crowding The effects ofmandibular growth continue to influence the positioning of the maxillaryincisor even when growth of the maxilla is complete

Several authors (Darqué and Langlade, followed by Bolender, Deblock,Raberin, and Brunner [cited in Darqué]) have suggested that the followingfactors may lead to crowding:

• The direction of tooth eruption is closely correlated with the type ofmandibular growth rotation; if the rotation is anterior, ie, if the angleformed by the mandibular body and the ramus closes up, the mandibularincisors will erupt in the buccal direction with a mesial drift of the otherteeth, which may lead to anterior crowding

• Late post-therapeutic growth of the mandible after completion of growth

of the anterior and upper part of the face, combined with anterior rotationpatterns of the mandible (which is the most commonly observed growthpattern) will also give rise to overcrowding

• With regard to neuromuscular aspects of development, contractions in thelip membrane will influence the vertical positioning of the incisor axes, andwill therefore reduce the available space for a correct alignment

• The presence of DMDs (lack of parity in the volume ratios of the maxillaryand mandibular incisors) will also affect crowding

• The noticeable change in the mandibular intercanine distance, whichdecreases noticeably after therapy and thus reduces the available space

• The rate of periodontal healing, which is slower in the adult patient andtherefore may lead to relapse.

It appears that the etiology of post-therapy tooth crowding is not entirely due to the development of the third molars The late growth and mean anterior rotation of the mandible and the labiomental muscle tone are among the factors that should be considered before making the decision to extract the third molars.

For the majority of cases, the decision to extract asymptomatic thirdmolars should not be made before the age of 16 years and should follow

a complete assessment of the prognosis for their development

anomalies

Anomalies in the development of third molars are due to the orientation ofthe tooth bud and to the dental and skeletal environment The two main

types of pathologies discussed in this chapter are pericoronitis and

dentigerous cysts.

Terminology

Anomalies of dentition are caused by retained teeth This term includes

impacted and partially erupted teeth and applies to any tooth that is not in itscorrect functional position after its normal eruption time, taking into accountthe age of the patient (Fig 2-1)

• A retained tooth is considered to be impacted if the pericoronal follicledoes not connect with the oral cavity

• A retained tooth is considered to have partially erupted if the folliclemembrane opens partially or totally into the oral cavity (Figs 2-2a and 2-2b)

Thus, an impacted tooth may either still be totally enclosed inside its bonecrypt or the roof of the bone crypt may already be perforated The crownand its follicular membrane then come into contact with the inner aspect ofthe fibromucosa, which completely covers the cortical bone; at this stage oferuption the tooth is in a submucosal position The tooth, however, remainsimpacted as long as its follicular membrane is not perforated

The emergence of the tooth occurs when the reduced epithelium and thegingival epithelium fuse together; the crown then breaks through thisepithelial layer to erupt into the oral cavity If emergence cannot occurnormally and the crown is retained, the tooth is considered to be submerged

or partially retained rather than partially impacted

The precision of these definitions is important because it enables adistinction to be made between the two types of pathology:

• A follicular cyst (dentigerous cyst) appears when the tooth bud is

dystopic or indeed ectopic and the eruption of the tooth is obstructed.The bone crypt is distorted and its walls are pushed back due to thethickening of the follicular tissue

• Conversely, pericoronitis occurs after the emergence of the tooth, when

the pericoronal space opens up into the oral cavity

The follicular cyst

The apex of the dental follicle produces the tissues that support the tooth:

the cementum, the periodontal ligament, and the alveolar bone wall (Cahilland Marks) This means that part of the dental follicle disappears as rootformation occurs On the other hand, the coronal portion of the follicleremains until the tooth emerges At this stage, osteoclasts form to ensuresufficient bone resorption for the tooth to erupt (Marks and Cahill) Thisoccluded portion of the follicle, which completely surrounds the crown, is inclose contact with the reduced epithelium Note that the follicular tissue isnot inserted into the anatomic collar, but remains attached to the roots awayfrom the enamel (Figs 2-3 to 2-6) The supracrestal ligament, whichdevelops only after the tooth has emerged, is then inserted into the exposedroot area (Korbendau and Guyomard)

The development of a cyst or tumor in the follicle occurs when the tooth

i s retained This type of odontogenic cyst occurs quite frequently About

50% of such cysts are associated with the mandibular third molars Like themaxillary canine or the mandibular premolars, the eruption of a mandibularthird molar is often impeded by a lack of space in the dental arch(Korbendau and Guyomard) The pathogenesis of the development of thistype of cyst is still unknown, although the buildup of cystic fluid between theenamel and the follicular tissue is a characteristic of cyst development

2-1 (1) Impacted retained tooth: The crown is completely enclosed within the bone crypt (2)

Impacted retained tooth: The crown is in a submucosal position (3) Partially retained tooth: The bone

crypt has an opening into the oral cavity.

2-2a Partially retained tooth.

2-2b The mesial inclination of the right mandibular third molar positions the mesial alveolar border at

the cementoenamel junction This partial retention has led to the exposure of the proximal root.

The presence of a follicular cyst in its latent phase cannot be detected by

clinical examination because the lesions are generally asymptomatic.

Lesions may be discovered in the second decade of life, in the dentition adolescent, or in the young adult, sometimes followinginflammatory events, but are most often detected during routine radiographicexaminations:

mixed-• Small-sized cysts accompany the teeth, which are impacted in theretromolar triangle area (Fig 2-7)

• Voluminous cysts develop in the follicle of the ectopic teeth, which aregenerally distal to the dental arch (Main) (Figs 2-8a and 2-8b)

2-3 Extraction of the right mandibular third molar shows the follicle insertion in the completed roots.

2-4 The occlusal end of the follicle completely surrounds the crown Cell degeneration and thickening

of this wall lead to osteolysis and to the enlargement of the bone crypt in the case of cyst formation.

2-5 The follicular membrane has been pushed back, possibly beyond the boundary of the enamel.

2-6 This root area, located between the enamel and the follicle insertion, is free of periodontal

ligament fibers The supracrestal fibers will develop as the tooth reaches the occlusal plane.

2-7 Posterior marginal cyst Growth into the distal area of the follicle is a result of the partial retention

of the tooth under the temporal ridge of the ramus.

Radiographic examination is not always sufficient to diagnose a

follicular cyst because:

• Pathological enlargement of the pericoronal space, which indicates thedevelopment of a cyst in the follicular wall, may be less than 2 mm (Fig 2-9)

• Other lesions (which occur less frequently) such as keratocysts, dermoidcysts, ameloblastoma, or carcinoma may give similar unilocular images

Histologic examination must always be undertaken after surgical

removal of these lesions because pathological changes occur more oftenthan is generally supposed (Glosser and Campbell) Cell degeneration(which occurs very rapidly in some cases) indicates the need for asystematic histologic examination in order to establish the final diagnosis(Craig et al)

Decisions regarding treatment

Enlargement of the pericoronal space is a diagnostic factor that thepractitioner must take into account The conservative treatment planadvocated for the canines and premolars is not appropriate for the thirdmolars

With regard to ectopic teeth, a sudden extension of the lesion may invadethe mandibular body or the ramus as well as the sinus antrum in the maxilla.Surgical removal of the cyst and extraction of the molar is always indicated(Figs 2-10a to 2-10e) For cases in which surgical extraction is refused bythe patient, radiographic follow-up is always recommended in the absence

of clinical symptoms (Figs 2-11a and 2-11b) The practitioner will naturallyinform the patient of the possible consequences of refusing an extraction:fractures, secondary infections, and local damage due to invasion of the softtissue (eg, muscle blocks and cell spaces) It is strongly recommended thatpatients sign a discharge form or that their refusal to do so is noted in theirmedical records

2-8a This follicular cyst in a 60-year-old female patient developed from the right mandibular third

molar, which is impacted within the ramus The cyst was observed on a radiograph taken during

treatment of the adjacent second molar.

2-8b The wall of the cyst surrounds the crown of the right mandibular third molar and extends

beyond the cementoenamel junction.

2-9 The left maxillary and mandibular third molars are impacted The pericoronal space of the left

maxillary third molar is enlarged; these changes may indicate cyst formation.

2-10a In this 45-year-old male patient, the panoramic radiograph indicates that the left mandibular

third molar is impacted within the ramus with a marked mesial inclination A radiolucent cavity indicates

a voluminous pericoronal dentigerous cyst Note the backward inclination of the dental canal toward the

basal border.

2-10b This figure shows a 33 × 25–mm cavity that encloses the impacted tooth and occupies the

total height of the mandibular body The basilar border is intact and the radiolucent cavity can be seen

cross-2-10c Three-dimensional axial section parallel to the basilar border that crosses the roots of the left

mandibular second molar, as well as the adjacent third molar, close to its main axis.

2-10d Section across the mesial aspect of the impacted tooth At this level, the anterior extension of

the defect crosses the roots of the left mandibular second molar in a labial direction close to the lingual

cortical bone.

2-10e Deeper axial section showing the apices of the left mandibular second molar This section

shows the severity of the transversal invasion of the defect, which at that level occupies the entire depth

of the mandibular body Note the blistering of the inner cortical bone and its thinning without any rupture

of the wall (red arrow).

Characteristics

• The inflammatory reaction due to the eruption of the third molar frequentlyoccurs in 17- to 25-year-olds It may be acute or subacute, but is mostoften chronic (Lee and Kim)

• The dimensions of the opening of the pericoronal space, which is filledwith the follicular tissue, may be very small, but the mesial cusps aremore often totally exposed (Fig 2-12a)

• The congestive phase, which occurs during eruption, encourages bacterialcolonization of the pericoronal space If the tooth fails to eruptcompletely, the infection will continue and the site will remain inaccessiblefor cleaning

• When anaerobic bacterial flora invade this space, the presence of

Bacteroides forsythus and Porphyromonas gingivalis indicates that

serious inflammatory gingivitis is developing (Blakey et al)

• The retromolar space, which is located between the second molar and theramus, is generally smaller than the mesiodistal diameter of the crown(Class II; see chapter 4)

• The pericoronal space is often larger on the distal aspect Inflammation ofthe follicular tissue induces a typical crescent-shaped bone loss (Fig 2-12b)

• The axis of the tooth is most often vertical (Punwutikorn et al)

• The affected teeth have reached—or grown beyond—the occlusal plane

in 80% of cases (Halverson and Anderson)

Clinical aspects

A spontaneous and quite acute pain appears in the retromolar region and

often radiates outward toward the ear Chewing becomes painful becausethe soft tissue cap, which partially covers the crown, is damaged by the

The presence of inflammatory gingivitis can be established with an

intraoral examination The retromolar tissues will appear severely

congested The soft tissue cap, which masks the distal part of the crown,often appears edematous and is marked with the imprints of the opposingteeth This redness sometimes spreads toward the anterior tonsil pillar andthe gingival-cheek sulcus Pressure on the soft tissue cap is painful and maylead to a purulent serous discharge The intraoral examination must alwaysinclude a bilateral finger exploration of the oral cavity floor in order todiagnose possible induration

Following local treatment of the inflammation and antibiotic prescription,the overall clinical symptoms may disappear; however, this period of healing

is often short lived Relapse is the rule when the tooth is retained As long

as the tooth remains in situ, pericoronitis may become chronic At this stage,radiographic examination is essential to assess the need for surgery

2-11a Another tooth has developed in the same bone crypt as the left mandibular third molar.

2-11b The pericoronal space of these two teeth is widened The common follicular tissue has

thickened by several millimeters and may possibly develop into a follicular cyst.

2-12a The soft tissue cap that partially covers the crown is compressed by the opposite dentition

during chewing.

2-12b Widening of the pericoronal space under the lower border of the temporal ridge Note that

pericoronitis is mainly due to a distal partial eruption and that the tooth axis is most often vertical.

Complications

Necrotizing gingivitis (NG), also called necrotizing ulcerative gingivitis, is

an acute inflammation that destroys the superficial periodontal tissues as aresult of bacterial plaque (Lindhe) In the presence of poor hygiene, stress,and heavy tobacco smoking, a painful necrotizing ulceration appears in theretromolar area and sometimes on the interdental soft tissue papillae of thehemiarch, extending as far as the canine tooth on the opposite side (Figs 2-13a and 2-13b) The ulcerated area is covered with a grayish coating anddivides the gingival papilla into a buccal and a lingual portion as the centralcrater deepens In addition, the connective tissue becomes hemorrhagic (Fig2-13c)

Plaque and soft deposits are always present under the subgingivalcalculus The bacteria responsible for the necrotizing gingivitis are fusiform

bacilli and spirilla, spirochetes, and Bacteroides species Under these

conditions, the general symptoms that appear with pericoronitis are moreseverely marked and the infra-angular adenopathy becomes painful

Before considering a surgical approach, the practitioner must ensure thatthe treatment is appropriate for the presenting symptoms and that thediagnosis is correct and the symptoms of NG have not been confused withthe oral symptoms of hematologic disorders and AIDS (Charon et al).Where there is doubt, a blood test and a serologic test should be carriedout Treatment for NG may include:

• Antibiotic therapy

• Prescription of antiseptic mouthwashes (2% chlorhexidine)

• Patient motivation and hygiene recommendations

• Curettage and debridement using ultrasonic devices

Spread of infection

Acute pericoronitis may be the starting point for the spread of bacterialinfection and inflammation, the clinical forms of which vary according to thecondition of the third molar that is already present on the arch or has beenretained (Fig 2-14) The anatomic situation of the neighboring muscleinsertions anchored to the cortical bone plates plays an important role indetermining the direction in which microorganisms and serous fluids spread.Other anatomic structures may also be involved in the infection: sinuses,salivary glands, orbits, and the calvaria (Alling et al)

The inflammation-induced trismus appears as a temporary jaw

constriction and is often one of the clinical manifestations indicatingproblems with the eruption of the third molar One of the three main elevatormuscles of the mandible—temporal, masseter, or medial pterygoid—isinvolved Inflammation that spreads toward the muscle blocks in thepresence of suppurating pericoronitis may induce a very tight trismus, whichwill require treatment with antibiotics before surgery can be considered

2-13b Inflammation of the gingival pad that still covers the crown of the left mandibular third molar

induces throbbing pains that make oral hygiene very difficult and painful.

2-13c The tips of the papillae are rapidly eroded by necrosis, and the whole gingival papillary tissue

increases in volume Note the presence of bacterial plaque.

2-14 The infection may spread to the neighboring anatomic regions of the third molar starting from a

periapical lesion (red arrows) or from pericoronitis (black arrows) (according to Alling et al).

of radiographic

examinations