ACE Class I - · PDF fileACE Class I ACE Class II ACE Class III ACE Class IV ACE Class V ACE...

The International Journal of Periodontics & Restorative Dentistry

Thinning of palatal enamel

Dentin exposure on the palatalaspect (contact areas), no damage to incisal edges

Dentin exposure on the palatalaspect, damage to incisal edges(< 2 mm)

Extended dentin exposure on the palatal aspect, loss of toothlength (> 2 mm), preserved facial enamel

Extended dentin exposure on the palatal aspect, loss of toothlength (> 2 mm), loss of facial enamel

Advanced loss of tooth structureleading to pulp necrosis

Treatment:No restorative treatment

Treatment:Direct or indirect palatal composites

Treatment:Palatal veneers

Treatment:Sandwich approach

Treatment:Sandwich approach (experimental)

Treatment:Sandwich approach (highly experimental)

ACE Class I

ACE Class II

ACE Class III

ACE Class IV

ACE Class V

ACE Class VI

2 mm

2 mm

© 2010 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART OF THIS ARTICLE MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.

In modern society, dental erosion hasbecome one of the major causes ofthe loss of mineralized tooth struc-ture. Several surveys have pointedout a high and still increasing preva-lence, especially among young indi-viduals (eg, 37% of 14-year-olds inthe United Kingdom present signs ofpalatal enamel erosion).1–12 Signs ofdental erosion that may be easily evi-dent at an early stage include:“glossy” (smooth, glazed) enamel,yellowing of the teeth from the under-lying dentin, increased incisal translu-cency, and cupping of the occlusalsurfaces. While the presence of den-tal caries normally leads clinicians totake action immediately, in the caseof dental erosion, many clinicians pre-fer to postpone any dental treatmentuntil the patient is older, even thoughliterature confirms that direct clinicalobservation is an unreliable methodfor monitoring the rates of toothwear.13,14 To play down this problemis frequently the preferred approach,which is understandable since manyclinicians do not feel comfortableproposing an extensive dental reha-bilitation to young individuals whoare still asymptomatic and unaware of

Classification and Treatment of theAnterior Maxillary Dentition Affected byDental Erosion: The ACE Classification

Francesca Vailati, MD, DMD, MSc*Urs Christoph Belser, DMD, Prof Dr Med Dent**

Erosive tooth wear is a serious problem with very costly consequences.Intercepting patients at the initial stages of the disease is critical to avoid signifi-cant irreversible damages to their dentition and to benefit from still favorableconditions when it comes to clinical performance of the restorative measures proposed. In this article, a new classification is proposed to quantify the severityof the dental destruction and to guide clinicians and patients in the therapeuticdecision-making process. The classification is based on several parameters relevant for both the selection of treatment and the assessment of the prognosis,such as dentin exposure in the palatal tooth contact areas, alterations at the levelof the incisal edges, and ultimately, loss of pulp vitality. (Int J PeriodonticsRestorative Dent 2010;30:559–571.)

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Volume 30, Number 6, 2010

*Senior Lecturer, Department of Fixed Prosthodontics and Occlusion, School of DentalMedicine, University of Geneva, Geneva, Switzerland; Private Practice, Geneva,Switzerland.

**Chairman, Department of Fixed Prosthodontics and Occlusion, School of DentalMedicine, University of Geneva, Geneva, Switzerland.

Correspondence to: Dr Francesca Vailati, rue Barthélemy-Menn 19, Geneva, Switzerland1205; email: [email protected].


the problem. What such clinicians arenot considering, however, is thatthese patients sooner or later willneed to restore their jeopardizeddentition anyway. The debate overwhether it is preferable to start earli-er with a lighter, less invasive rehabil-itation or later with a highlyaggressive but eventually more resis-tant one is still open.

The aim of this article is to con-vince clinicians that in the specific caseof dental erosion, hesitation in under-taking the adequate treatment willinevitably lead to further degradationof the patient’s dentition. To persuadethe patients and to obtain informedconsent for treatment, it is necessaryto quantify the dental destruction andto make a prognosis on the futureprogression of the disease if no treat-ment would be undertaken. It wouldappear that the existing erosionassessment indices and classificationshave not led to a broad respectiveawareness among dental careproviders to date. This may bebecause these tools are rather com-plex and difficult to use in a daily prac-tice set-up, since they have beenprimarily designed for scientific pur-poses. Furthermore, practical experi-ence indicates that all relevant signslinked to the various progressionstages of generalized dental erosioncould be assessed clinically by main-ly examining the anterior dentition.This finding may help to simplify thediagnostic process significantly.

Consequently, a new classifica-tion, the anterior clinical erosive clas-sification (ACE), has been proposedto provide clinicians with a practicaltool to grade the dental status of

each patient and to subsequentlyrelate it to the appropriate treatment.

Maxillary anterior teeth anddental erosion

Disease progression

In the case of dental erosion, thepalatal aspect of the maxillary anteri-or teeth usually appears to be themost affected portion of the denti-tion, particularly in patients with anintrinsic etiology (eg, gastric reflux,psychiatric diseases). At an early stage,acid-caused destruction can be verysubtle and thus difficult to discoverbecause of the somewhat hiddenlocation of the palatal tooth surfaces,especially if the disease progressesslowly. Patients frequently do not pre-sent signs of tooth sensitivity, even inthe presence of dentin exposure.Often, the erosive wear will manifesttoo late, when irreversible damagehas already taken place and costlyrestorative treatments are required.

At the initial stage, only an atten-tive and trained eye can detect themore yellowish color resulting fromthe thinning of the enamel in the cen-tral palatal portion of the clinicalcrown. The cingula appear flatter andtheir surfaces are very shiny.

The next step of erosive wearleads to a weakening of the incisaledges, which is first noticeable by anincrease in translucency. Furthermore,the presence of caries or Class IIIrestorations may contribute addition-ally to the weakening of the facialaspect of the tooth. In extremeinstances, a complete loss of the

incisal edge may result, whichdepends strongly on the original over-bite and overjet configuration and onthe location of the occlusal contactarea. For example, in a patient with aslight vertical overlap (overbite), therisk of incisal fracture is very highbecause of the destructive combina-tion of erosion and the focal attritionof the antagonist teeth. In fact, at anearly stage of enamel erosion, chip-ping is frequently visible in the form ofirregularities at the incisal edges. Onthe other hand, in patients with adeep bite interarch configuration, themaxillary anterior teeth may present apronounced concave morphology ontheir palatal aspect before any effecton the length of the clinical crownmanifests. In extreme situations, theloss of the tooth structure maybecome so extensive that the pulpchamber (or its original extent) can beidentified on the palatal aspect.Surprisingly, such teeth frequentlykeep their vitality; however, they mayrespond less quickly to the vitality test.

In advanced stages, when thelabial tooth structure has been under-mined too much, the facial surfacesfracture and the clinical crowns sud-denly appear reduced in length.Finally, especially in deep bitepatients, the vertical overlap may beaggravated by the supraeruption ofthe anterior segments.

Traditional reconstructive versusadhesive therapy

Following the guidelines for conven-tional oral rehabilitation concepts,structurally compromised teeth

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should receive complete crown cov-erage. To place the associatedrestoration margins at the gingivallevel, a significant amount of theremaining volume of the clinical crownhas to be removed during toothpreparation to provide the requiredvertical path of insertion for the crown.In other terms, preparing such teethfor crowns will substantially aggravatethe destruction of mineralized tissuethat was initiated by the erosiveprocess. Not infrequently, electiveendodontic treatment will be neces-sary, mostly accompanied by the useof posts, to assure intraradicular reten-tion of the crowns to be cemented.

To avoid these types of invasivetreatment modalities and to keep theteeth vital, an experimental approachto restoring the maxillary anteriorteeth of patients affected by severedental erosion is currently underinvestigation at the University ofGeneva School of Dental Medicine(Geneva Erosion study) by the authorsof this research. A minimally invasivetreatment concept that consists ofreconstructing the palatal aspect withcomposite restorations, followed bythe restoration of the facial aspectwith ceramic veneers, is promoted.The treatment objective is reachedby the most conservative approachpossible, since the remaining toothstructure is preserved and located inthe center between two differentrestorations (the sandwich approach)and performed at two different timepoints. When it comes to the preser-vation of mineralized tooth structure,such an ultraconservative approachcannot be matched by any type ofcomplete crown coverage.

preparation for all-ceramic crownscould not achieve this level of toothpreservation.

ACE classification

Assessment of the severity of dentalerosion is complicated because of thesubjectivity of the methods of evalu-ation and the possible presence ofwear cofactors (parafunctional habits,hyposalivation, wear resulting fromtooth malposition, aging, coarse diet,inappropriate tooth-brushing tech-niques, abrasive toothpastes, etc). Inaddition, the rating scales selectedby investigators may be somewhatcomplicated to translate in a clinicalenvironment, and early alterations aredifficult to locate, even with the sup-port of photography, study casts, andattentive clinical examination.18–26

Several authors have proposedclassifications and indices addressingeither tooth wear in general25 orincluding diagnostic criteria for erosivetooth wear specifically.26 Most recent-ly, Bartlett et al18 published a newscoring system, termed basic erosivewear examination (BEWE), designedfor both scientific and clinical purpos-es. It was the authors’ twofold objec-tive to provide a simple tool for use ingeneral practice and to permit morescientifically oriented comparisonswith already existing indices.Furthermore, the BEWE aimed toaugment the awareness of tooth ero-sion among general practitioners andto provide a respective guide for treat-ment when indicated. Finally, theBEWE was intended to stop the con-tinued proliferation of new indices, as

The type of restoration best indi-cated to restore the palatal aspect ofthe eroded maxillary anterior teeth(direct or indirect composite restora-tions) is selected according to theamount of the anterior interocclusalspace obtained after an increase inthe vertical dimension of occlusion. Ifthe space is limited (< 1 mm), thecomposite restorations can be fabri-cated free-hand, saving time andmoney (there is no laboratory fee forthe palatal onlays and only one clini-cal appointment is required). If theinterocclusal distance between theanterior teeth is significant, however,free-hand resin composites couldprove to be rather challenging.

When the teeth present a com-bination of compromised palatal,incisal, and facial aspects, it is difficultto visualize the optimal final mor-phology of the teeth, particularlywhile restoring only the palatalaspect with rubber dam in place.Thus, the results may be unpre-dictable and highly time consuming.Under such conditions, fabricatingpalatal onlays in a laboratory clearlypresents some advantages, includingsuperior wear resistance and higherprecision during fabrication of thedefinitive form. A series of articleson full-mouth adhesive rehabilitationaddress this in detail.15–17 One of thecriticisms to the sandwich approachis the work and cost associated withthe fabrication of two separaterestorations for each tooth. However,only with two independent restora-tions are two different paths of inser-tion possible, and the toothpreparation can therefore be keptminimal. Even the most conservative

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it was hoped to represent a consensuswithin the specialized scientific com-munity. Nevertheless, there is still anundisputable need for a classificationthat directly and specifically focuseson the anterior maxillary dentition,where loss of mineralized tissuebecause of erosion, as minute as itmay be at an early stage of the dis-ease, can be assessed easily.

Clinicians not involved in epi-demiologic surveys clearly need theleast complicated approach to clas-sify each patient rapidly and todecide on the most appropriatetreatment plan. Thus, the prerequi-site for a precise and rapid assess-ment is a diagnostic instrument thatis based on a limited number of key

parameters and that guides the clin-ician in a logical and systematic way.As a consequence, these two funda-mental paradigms have been instru-mental in the development andfinalization of the proposed ACE clas-sification (Table 1).

The ACE classification is strictlyrelated to the clinical observation ofthe status of the anterior maxillaryteeth, which are generally the mostdamaged. Patients are grouped intosix classes, and for each class, a den-tal treatment plan is suggested. Theclassification is based on five para-meters relevant for the selection ofthe treatment and the assessment ofthe prognosis: the dentin exposure inthe contact areas, the preservation of

the incisal edges, the length of theremaining clinical crown, the pres-ence of enamel on the vestibular sur-faces, and the pulp vitality.

ACE Class I: Flattened cingula without dentin exposure

Suggested therapy: No restorative treatmentThis is the earliest stage of dentalerosion. The enamel is present butthinner. The palatal aspect of theteeth may appear more yellowish inthe central portion of the underlyingdentin and more white at the periph-ery with the presence of thicker enam-el (Fig 1).

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Table 1 The ACE classification

Palatal Palatal Incisal edge Facial Pulp Suggestedenamel dentin length enamel vitality therapy

Class I Reduced Not exposed Preserved Preserved Preserved No restorative treatmentClass II Lost in contact Minimally exposed Preserved Preserved Preserved Palatal composites

areasClass III Lost Distinctly exposed Lost ≤ 2 mm Preserved Preserved Palatal onlaysClass IV Lost Extensively exposed Lost > 2 mm Preserved Preserved Sandwich approachClass V Lost Extensively exposed Lost > 2 mm Distinctively Preserved Sandwich approach

reduced/lost (experimental)Class VI Lost Extensively exposed Lost > 2 mm Lost Lost Sandwich approach

(highly experimental)

Fig 1 ACE Class I: (left) Frontal and (right)occlusal views. Very early detection of theerosive problem. All the cingula lost theirmicroanatomical details. The enamelappears very shiny. Even though there is notyet dentin exposure, small chipping of theenamel at the incisal edge is visible (minimalvertical overlap). Considering the patient’sage (25 years) and etiology (bulimia), thispatient has a high risk of deterioratingtoward a more severe stage in a short periodof time.


For patients in this category, norestorative treatment is recommend-ed. However, preventive measures(eg, occlusal guard, fluoride gel) aremandatory. Most of all, the etiologyshould be investigated and the causeof the dental erosion eliminated.Since the enamel layer is still intact,100% recovery is possible at thisstage if the patient is capable of pre-venting further tissue loss.

ACE Class II: Dentin exposureon the palatal aspect (contactareas), no damage to the incisaledges

Suggested therapy: Direct or indirect palatal onlaysIn this group of patients, the enamelat the level of the palatal aspect of themaxillary teeth is more compromisedand small areas of dentin areexposed, generally related to thecontact points of the opposing den-tition (Fig 2). Since the mandibularanterior teeth are rarely affected byerosion, their incisal edges, com-posed of enamel, typically remain

intact and act like chisels, damagingthe maxillary anterior teeth in a veryaggressive manner (focal attrition).Since the occlusal contacts are nowcomposed of softer dentin, it is rea-sonable to anticipate that the loss oftooth structure will worsen at a fasterrate, especially if the cause of the ero-sion is not under control. This is thereason why the dental status ofpatients affected by dental erosionmay deteriorate quickly after an initialslow start (Fig 3). Nobody can predictexactly how each patient will evolve;nevertheless, parameters such as ageand etiology of the dental erosioncan guide the clinician to predict thesteepness of the curve of the diseaseprogression and to justify early inter-vention. A bulimic patient in his or herearly 20s who already presentsexposed areas of dentin (Class II) is ata higher risk of deteriorating the den-tition compared to a patient in his orher 50s who suffers from gastric refluxthat is kept under medical control.The first patient should be treatedimmediately, even though severalauthors recommend controlling thedisease first.27–29

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Fig 2 ACE Class II: Pretreatment (left) frontal and (center) occlusal views and (right) posttreatment occlusal view. In this patient, the palatalaspects present areas of dentin exposure at the level of the contact points. The incisal edges were still intact. An early conservative rehabilita-tion was planned, and all maxillary anterior teeth were restored using an indirect approach (palatal veneers), while the posterior teethreceived direct composite restorations.


Since a psychologic problem isnot often resolved quickly, protectingthe remaining enamel and theexposed dentin from further dam-age is recommended, even thoughthe restorations may have a lessfavorable prognosis under these spe-cific conditions.30–32 In the opinionof the authors of this paper, thepalatal aspect of Class II patientsshould be restored as soon as possi-ble, either by means of direct or indi-rect composite restorations (early notinvasive rehabilitation).

If the palatal wear has not yetaffected the strength of the incisaledges and the length of the facial sur-faces of the teeth is still intact, restora-tion of the palatal aspect of themaxillary anterior teeth could be theonly treatment required. To obtain thenecessary interocclusal space, adjunc-

tive orthodontic treatment could beadvocated, which allows the posteri-or teeth to be excluded from the treat-ment. However, not every patientaccepts this possibility. A secondoption to obtain the anterior spaceneeded consists of increasing thepatient’s vertical dimension of occlu-sion. In this case, all the posteriorteeth, at least in one arch, are restoredwith direct composite restorationswithout any tooth preparation. Sincethe dental destruction is interceptedat an early stage, there is not enoughspace for thicker, indirect posteriorrestorations; removing tooth structureto create the space for thicker restora-tions goes against the principles ofminimal invasiveness. This early andextensive rehabilitation based ondirect composites is not well accept-ed among clinicians, who think that

restoring so many teeth with so-called”weak” restorations is an overtreat-ment for which a sufficient longevitywould not be guaranteed. As a con-sequence, many clinicians prefer towait until further damage has takenplace to justify a full-mouth rehabili-tation based on stronger restorations(onlays or crowns). Unfortunately,there are no clinical studies availableto date showing which choice may bethe most beneficial in the long term toACE Class II patients: an immediaterehabilitation with weaker direct com-posites and no tooth preparation, ora later treatment with more resistantrestorations but a more compromiseddentition and more aggressive toothpreparation. Thus, further clinicalresearch is needed.

In the current investigationbeing undertaken by the authors of

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Fig 3 Correlation between loss of toothstructure and the patient’s age in cases ofdental erosion. The change in the steepnessof the curve is related to the loss of enameland the consequent dentin exposure in thecontact areas. Several factors can add tothe aggravation of the steepness of thecurve (parafunctional habits, hyposalivation,lack of erosion control, acidic diet, etc).

Enamel

Coronal dentin

Radiculardentin

Toot

h st

ruct

ure

Loss of tooth vitality

Conventional therapy

No restorative treatment

Adhesive therapy, ACE Class IV patient

Adhesive therapy, ACE Class III patient

Adhesive therapy, ACE Class II patient

10 20 30 40 50 60 70 80 90 100

Age (y)


this research in Geneva, all patients(ACE Class II) involved were treatedas early as possible. Since thisprospective clinical study does nothave a control group of patients whowere left untreated and restoredlater with conventional therapy, com-parison between the two differenttreatment plans is not possible. Onthe other hand, this clinical study willprovide the first set of data helpingto confirm (or reject) the clinicalvalidity of this ultraconservativeadhesive approach.

ACE Class III: Distinct dentin exposure on the palatal aspect,damage of the incisal edgelength (≤ 2 mm)

Suggested therapy: Palatal veneersIf patients are left untreated, erosionand focal attrition will eventually leadto a weakening of the thickness ofthe incisal edges of the maxillaryanterior teeth, especially if the verti-cal overlap (overbite) is not signifi-cant (Fig 4). When the incisal edgesare affected, attentive patients startseeking help, driven mostly by esthet-ic concerns. Patients in this categoryare generally in their late 20s or early30s. Since not all of them are willingto receive orthodontic treatment tocreate interarch space in the anteriorsegments of their mouth, an increaseof the vertical dimension of occlusion

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Fig 4 ACE Class III: (left) Pretreatmentand (right) posttreatment views. In this deepbite patient, a severe loss of tooth structureat the level of the palatal aspect weakenedthe vestibular surfaces (note the hightranslucency), but the facial surface wasalmost intact (shortening of the clinicalcrown less than 2 mm). This patientrequired only palatal onlays. No furthertreatment was necessary to restore the maxillary anterior teeth. Note that all teethwere vital and maintained vitality after treatment.


is necessary and involves the recon-struction of the posterior teeth,which, at this stage, may presentsigns of erosion as well. The choicebetween indirect or direct compositerestorations is based on the severityof the loss of tooth structure andsometimes on the financial status ofthe patient.

The final restorative choice for theposterior quadrants (direct compositerestorations or onlays) must alwaysbe driven by minimally invasive prin-ciples. Following the three-steptechnique to increase the verticaldimension of occlusion, the anteriormaxillary teeth are restored with indi-rect restorations (composite palatalveneers), especially if the anteriorspace created with the increase inthe vertical dimension of occlusion ismore than 1 mm. Due to the minimaldamage to the vestibular aspect ofthese anterior teeth, there is often noneed for further treatment.

If the vestibular surfaces of themaxillary anterior teeth are intact oronly slightly damaged at the level ofthe incisal edges, facial veneers maybe considered an overtreatment sincethe length could be reestablished bymeans of palatal veneers. An attemptshould be made to match the color ofthe natural tooth with the palatal

veneers, since the horizontal flat junc-tion between the tooth and palatalveneers may be difficult in terms ofcolor blending. Shade modificationcould always be attempted later ifnecessary. The clinician should havea discussion with each patient todetermine if the patient could be sat-isfied esthetically without veneers.

Even though no long-term follow-up data are available currently on thelongevity of palatal veneers used toreplace damaged incisal edges, theserestorations have an acceptable prog-nosis for ACE Class III patients. Often,all the margins of palatal veneers arebonded to enamel. Furthermore, theteeth involved still preserve theirenamel frame. In fact, looking fromthe palatal aspect, this frame could beidentified and comparable to theframe of a tennis racket (tennis rackettheory, Fig 5).

The mesial and distal walls ofsuch erosion-affected teeth are gen-erally still intact (unless Class IIIrestorations are present). The cervicalpalatal enamel is also mostly presentas a band of 1 to 2 mm next to thegingival margin. Finally, the enamel atthe vestibular aspect of the tooth isalmost completely intact in this classof patients (less than a 2-mm loss ofincisal edge length).

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Fig 5 When the enamel frame is still pres-ent (mesial, distal, cervical, and vestibularaspects), the tooth presents a higher resis-tance to tensile forces. Adhesive restora-tions restoring the palatal aspect aresubject to less bending forces, and theirclinical performance is enhanced (tennisracket theory)


According to the tennis rackettheory, compromised teeth with analmost intact enamel frame will showsurprisingly high resistance to flexureduring function (mastication or occlu-sion). As a consequence, palatalcomposite restorations, subject toless tensile forces, will last longer.

Several studies have demon-strated the importance of the mar-ginal ridges for posterior teeth.Restorations that extend to the mesialand distal aspect, such as mesialocclusal distal restorations, greatlyaffected the strength of the restoredposterior teeth.33–35 In the opinion ofthe current authors, the mesial anddistal marginal ridges of the anteriorteeth may have similar importance tothat described for posterior teeth.Since their removal during palatalveneer preparation could dramatical-ly compromise the flexure resistanceof the tooth, the interproximal contactpoint should be removed minimallyby means of an interproximal dia-mond strip or not be removed at all.

ACE Class IV: Extended dentinexposure on the palatal aspect,loss of the incisal length of thetooth (> 2 mm), preserved facialenamel

Suggested therapy: Sandwich approachMost patients in this category areaware of their dental problem sincethey have noticed the shortening oftheir clinical crowns and an increase inthe translucency of the incisal edges,even though they might not realizethe extent of the tooth destruction

option, the technician should not beconcerned with the final estheticresult (as for the crowns), since theseteeth are generally still alive and theiroriginal color should not need heavymodification.

ACE Class V: Extended dentin exposure on the palatal aspect,loss of the incisal length of thetooth (> 2 mm), distinct reduc-tion/loss of the facial enamel

Suggested therapy: Sandwichapproach (experimental)Patients who are treated at this laterstage, unfortunately, may not have afavorable long-term prognosis if theirmaxillary anterior teeth are restoredusing the sandwich approach (Fig 7).In addition to the reduced length ofthe remaining clinical crown, the lackof enamel on the facial aspect of theteeth compromises the quality of thebond of the definitive veneers andthe flexure resistance.

There are no long-term clinicalstudies reporting on the longevity ofa sandwich approach in Class Vpatients. At the University of Geneva,patients in this category were treat-ed following the adhesive techniquesince the alternative option (conven-tional therapy) would require devi-talization of all compromised teeth.Preliminary data from the GenevaErosion study show very promisingresults: the capacity of the sandwichapproach to keep the vitality of alltreated teeth, all rehabilitationsachieved a very pleasing estheticresult, and tooth preservation wasmaximal. Nevertheless, patients

(Figs 6a to 6d). At this stage, the pos-terior teeth are often involved, espe-cially the premolars. Since an increasein the vertical dimension of occlusionis mandatory to create the necessaryinterarch space for the restorativematerials in the anterior and posteri-or segments, the three-step techniqueshould be followed.

To restore the anterior maxillaryteeth, the sandwich approach is rec-ommended. After the restoration ofthe palatal aspect with compositeveneers, the treatment should becompleted with ceramic facialveneers. The veneers are necessarynot only because palatal veneersoften do not match the color of thenatural teeth, but also because thereare no studies to document the long-term performance of such a largecomposite restoration in case thefacial veneers are not placed.

Some patients in the ongoingGeneva study have decided not toobtain facial veneers and are understrict monitoring. If the palatalveneers degrade at a quick rate,ceramic facial veneers could be fab-ricated at a later date. On the otherhand, the remainder of ACE Class IVpatients all received the two anteriorrestorations, and the preliminaryresults (up to 4 years of follow-upwithout any clinical problems) are veryencouraging (Figs 6e to 6h). Whilepreparing these damaged teeth forfacial veneers, attention should begiven to not remove the facial enam-el and transform these patients intoACE Class V cases. Additive tech-niques (tested by the diagnosticmock-up) or very thin veneers shouldbe advocated.36 For this second

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should be intercepted and treatedwhenever possible for an optimalclinical performance of their rehabil-itation.

ACE Class VI: Advanced loss oftooth structure leading to pulpnecrosis

Suggested therapy: Sandwichapproach (highly experimental)Patients at this stage present a severe-ly compromised dentition (Fig 8).Generally, even in the case of signifi-cant loss of palatal tooth structure,the pulp has time to withdraw and

compromised teeth surprisingly pre-serve their vitality, a result of the slowprogression of the erosive process.For a tooth to lose vitality because ofdental erosion, a very severe and fre-quent acid attack (eg, bulimic oranorexic patients) is necessary, whichovercomes the capacity of the pulp toprotect itself, or simply an extremedestruction of its coronal dentin. Inboth cases, treatment prognosis may

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Fig 6 ACE Class IV

Figs 6a to 6d (left) Pretreatment and(right) postreatment views of an anteriormaxillary restoration. This patient required asandwich approach (composite palatal andceramic facial veneers).

Figs 6e to 6h (left) Pretreatment and(right) posttreatment views. In this patient,the combination of erosion and focal attri-tion led to a complete loss of the incisaledges (more than 2 mm). Compositeveneers were used to restore the palatalaspect; even though ceramic facial veneerswere planned to complete the treatment ofthese teeth, the patient decided to waitsince the difference in shade was not visibleat a normal communication distance (1-yearfollow-up). Note that all teeth kept theirvitality after treatment.


be poor, especially if the erosion can-not be controlled.

In the authors’ opinion, adhesivetechniques should still be attempted,even though long-term results arelacking. The sandwich approach hasthe advantage of preserving themaximum tooth structure and, inmost cases, the tooth vitality of theremaining teeth.

.

in cases of a later loss of vitality is thatinternal bleaching procedures couldbe done easily. On the contrary, incases with conventional therapy, theoption to change the shade of a dis-colored root visible after gingivalrecession is not available because ofthe presence of the post cementedin the root.

So far, in the Geneva Erosionstudy, patients in this category havemaintained the vitality of all treatedteeth. If loss of vitality occurs as aresult of the severely affected pulp ofthese teeth, endodontic access willbe made easier through the palatalveneer without damaging the facialveneer. This would be more difficultin cases of full coverage. Anotheradvantage of the adhesive technique

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Fig 7 ACE Class V: (left) Pretreatment and(right) posttreatment views (2-year follow-up). The dental destruction had involvedalmost two thirds of the crown length andthe dentin was exposed on the facialaspect. The sandwich approach is consid-ered experimental in these cases, since theceramic facial veneers are bonded mainly toa reduced surface of dentin.

Fig 8 ACE Class VI: (left) Pretreatmentand (right) posttreatment views. The dentaltissue destruction in this patient was sosevere that two teeth were not vital at thetime of the first consultation. Since thealternative was the extraction of the fourmaxillary incisors, the patient was treatedfollowing the sandwich approach. The 2-year clinical follow-up results are presented.Note that the palatal composite restora-tions were made directly in the mouth, andthe veneers were fabricated by a laboratorytechnician selected by the patient for per-sonal reasons (completed in collaborationwith Dr H. Gheddaf Dam).


Conclusion

Dental erosion is a frequently under-estimated pathology that affects anincreasing number of young individ-uals. Intercepting patients at the ini-tial stages of the disease is critical toavoid irreversible damage to theirdentition and to guarantee a betterclinical performance of the restora-tions selected. In this article, a newclassification is proposed to quantifythe severity of the dental destructionand to guide clinicians and patients inthe decision-making process. Theclassification is based on several para-meters relevant for both the selec-tion of the treatment and theassessment of the prognosis, such asdentin exposure in the palatal toothcontact areas, alterations at the levelof the incisal edges, and ultimately,loss of pulp vitality. Patients aregrouped into six classes, and for each,a dental treatment plan is suggested.For patients in whom the severityvaries depending on location, themost compromised anterior tooth isselected to decide which class thepatient belongs to. Finally, with theexception of ACE Class II, whereminor orthodontic tooth movementmay be considered, treatment of theerosion requires a distinct augmen-tation of the existing vertical dimen-sion of occlusion to create thenecessary space to restore the max-illary anterior teeth. Consequently,direct or indirect restorations of theposterior quadrants must also beplanned as an integral part of thedefinitive oral rehabilitation.

Acknowledgment

The authors would like to thank the followinglaboratory technicians and ceramists for theirintegral support in completing these complexcases: Alwin Schönenberger, Patrick Schnider,Pascal Müller, Serge Erpen, Sylvan Carciofo,and Sophie Zweiacker. Finally, the authors wouldlike to acknowledge the collaboration of DrHamasat Gheddaf Dam, Dr Giovanna Vaglio, DrFederico Prando, Dr Linda Grutter, Dr TommasoGiovanni Rocca, and Dr Julian Luraschi.

References

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