Restorative Dentistry

Tooth wear: Attrition, erosion, and abrasion

Luis A, Litonjua, DMDVSebastiano Andreana, DDS, MS=/Peter J. Bush, BS /Robert E, Cohen, DDS, PhD"

Attrition, erosion, and abrasion rGsult in alterations to the tooth and manifest as tooth wear. Each ciassiti-cation acts through a distinct process that is associated with unique clinical characteristics. Accurateprevalence data for each classification are not auaiiabie since indices do not necessarily measure onespecific etiology, or the study populations may be too diverse in age and characteristics. The treatment ofteeth in each classification will depend on identifying the factors associated with each etioiogy. Somecases may require specific restorative procedures, while others wili not require treatment. A review of theliterature points to fhe interaction of the three entities in the initiation and progression of lesions that mayact synchronously or sequentiaiiy, synergisficaliy or additiveiy, or in conjunction with other entities to maskthe true nature of tootti wear, which appears to be mulfifacfcriai. (Quintessence int 2003:34:435^46)

Key words: abrasion, attrition, cervicai abrasion, dentifrice, erosion, toothbrush abrasion, tooth surfaceloss, tooth wear

Loss of tooth structure may occur through noncari-ous processes. Regressive alterations may vary in

etiology, extent, and clinical presentation among indi-viduals and may be associated with physiologic orpathologic processes. Traditionally, those entities havebeen classified as attrition, erosion, and abrasion (Figs1 to 3), Attrition is defined as the physiologic loss oftooth structure as a result of the masticatory proces-ses; erosion is the chemical dissolution of structurethat does not involve the carious process; and abra-sion is the mechanical wearing away of structure,

Eccles' suggested that the term tooth surface iossbe used to encompass all those descriptions hecause asingle etiologic factor is usually difficult to identify.Later, Smith and Knight-^ proposed the term tooth

'Periodontics Resident, Department ol Penodontics and Endodontics,

Stale University of New York at Butlalo, Buffalo. New York.

^Clinicai Assistant Professor, Department of Periodontics and Endodortcs,

State University of New York at Buffaio, Buffalo, New York,

^Director, South Campus Instrumentation Center, State University of New

York at Buffaio. Buffalo. New York.

"Professor, Department of Peiiodontics and Endodontics, State University

of New York at Buffaio, Buffalo, New York.Reprint requesls; Dr Luis A, Litonjua, Department of Periodontics andEndodontios, State University of New York a( Buffaio. 250 Squire Hail, 3435fularn Street, Buffaio, NY 14214-3008. E-maii: laldmd® yahoo com

wear to embrace all those conditions and their combi-nations whether or not the etiology is known. Theycontended that the term tooth surface loss did not ad-equately reflect the severity of the condition and advo-cated the use of the term tooth wear.-'

ATTRITION

The term attrition is derived from the Latin verb attri-tum which describes the action of rubbing againstsomething,^ Dental attrition is defined as the physio-logic wearing of teeth resulting from tooth to toothcontact as in mastication,^'' This is an age-relatedprocess that can occur at the incisai or occlusal sur-faces and sometimes on the proximal surfaces.Clinically, the first manifestation is the appearance ofa small polished facet on a cusp tip or ridge or an in-cisal edge. Severe attrition may lead to dentinal expo-sure, which may increase the rate of wear,''' -"

Tooth wear occurs at an ultrastructural level andcan be caused by direct contact between surfaces orthe action of an intervening slurry.' Attrition may behastened by a coarse diet and abrasive dust.•'•"•" Dahlet al'' found high levels of inorganic compounds andsalts in snuff while Bowles et al** found silica particlesto be abrasive in tobacco chewing. However, some au-

disagree with this classification of attrition

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• Litonjua et ai

Fig 1 Severe attrition on mandibular incisors and oanines as aresult of bruxism.

Fig 2 Erosion at palatal and occlurai iurlacfcs a i a result olchronic vomiting.

Fig 3 Abrasion aL buccal surfaoes of premola.'s. Patient reporteda history of incorrect and excessive toothbrushing.

where an intervening bolus of food is invoived.Instead, they use the tenn demastication to describethe wearing away of tooth substance during mastica-tion of food influenced by the ahrasiveness of the indi-vidual food particles.

Some paraftinctionai habits (bruxism and clench-ing) may also contribute to attrition.*"' While theprevalence of bruxism is unclear, studies report be-tween 5% to 96% of the population may be affected.*In contrast, Seligman et al'* reported that the preva-lence of dental attrition was not associated with thepresence or absence of temporomandibular jointsyrnptomatology. While a certain amount of attrition isphysiologic, excessive destruction of tooth structure isnot physiologic.

RusselF distinguished physiologic and normal frompathologic and abnormal attrition. He contended thatocclusal wear that renders itself vulnerable even tonormai functional loading cannot be regarded as nor-mal. In addition, if occlusal wear occurs at a ratefaster than compensatory physiologic mechanisms.

this is not physiologic. He also reported that labelingof tooth wear must be viewed in the context of thecultural environment under which it has occurred.

Epidemiologie surveys on the prevalence of attri-tion have been reported as tooth wear or tooth surfaceloss. The exact prevalence of tooth wear or tooth sur-face loss is unclear, primarily due to different assess-ment criteria, but has been reported to range from13% to 98%.'""" One problem of tooth wear surveysis the definition of the condition and parameter ofmeasure. Thus, reports are confusing and incompara-ble because some researchers have reported erosionand attrition singly, or together as tooth wear.^Furthermore, the use of different indices with differentcriteria adds to the confusion reported in the NorthAmerican and the European literature. NorthAmerican literature has concentrated more on attri-tion rather than on erosion, while European literaturehas reported that the most common and destructivecause of tooth wear is erosion.^ Tables 1 to 4 are ex-amples of different criteria or indices.

The studies of measurement of rate, pattern, anddegree of tooth wear are numerous, but it was Broca's1879 method that initially divided wear into degrees. ^Recent authors have patterned their subjective scoringmethod after Broca, and depend primarily on theamount of exposed dentin on the occlusal table to de-rive their methodology. Subsequent methods have uti-lized photographic and planimetric methods to ad-dress quantitative criteria. ^ A more recent method byMayhall and Kageyama * combined three-dimensionaland digital imagery for describing molar wear.

The value of tooth wear surveys comes into ques-tion when one wants to know the progress of attrition,since the data is a cumulative record. It is here wherelongitudinal studies play a vital role in describing thedisease process. Unfortunately, these studies are rarelargely because wear occurs slowly.' ' ' Vertical loss of

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TABLE 1 An attrition index^'

0 = No wear1 = Minimal wear2 = Noticeable flattening parallel to the occluding planes3 = Flattening of cusps ot grooves4 = Total loss of contour and/or dentin exposure when identiliableModiflea from Richaids and Biown.^°

TABLE 2

Ciass 1Class II

Class III

Classification of dental erosion^'

Superficial lesions involving enamel only.oca 1 i zed lesions involving dentin for less than onethird ol ttie surfaceGeneralized lesions involving dentin for more than onethird ot the surfaces•Facial surfaces•Lingual and palatal surfaces•Incisai and occlusal surtaces•Severe multisurtace involvement

enamel rarely exceeds 50 pm/year'' with one report at68 pm/year.-* One should bear in mind that the occur-rence and pattern of tooth wear is likely related to ed-ucational, cultural, dietary, occupational, and geo-graphic factors in the population studied.* Otherimportant factors that should be added are age andthe function of occlusion.

Dental attrition has been used in archeology and theforensic sciences to estimate human age. While thereare some measurement methods (see example on Table5) that have been suggested by authors, estimationshould be based upon several teeth or the entire denti-tion.'" Seligman and Pullinger' concluded that attritionhas a multifaetorial etiology with age and canine guid-ance having signlGcant influence (in addition to para-function, including crowding, occlusal slides, crossbites,chewing habits, and diet). Controlled in vitro experi-ments show that enamel wear is affected by cbanges inlubricating conditiotis, acidity, and loads. ' In addition,enamel wear differs from dentin wear and progressiveincrease of dentin wear is associated witb increasingload." Finally, it should be noted that attrition is a con-tinuing process. Newman," in his review, concludedthat teeth continue to erupt in adulthood even in the ab-sence of masticatory function and concomitant attrition.

Normal attrition requires no treatment since forma-tion of secondary dentin and the eruption processkeep tbe wear process in balance. Where there is lossof posterior support, malocclusion, and bruxism. oc-clusal adjustment and splint therapy may be indicatedfor the remaining dentition."'^ The treatment of severeattrition where teeth are worn to the gingival marginmay require restoration of the vertical dimension toimprove function and esthetics. Treatment options in-clude extraction of affected teeth and replacementwith conventional dentures, overdentures, overlayprosthesis, amalgam or composite buildups, and fixedor removable prostheses.'^

EROSION

The term erosion is derived from the Latin verb erosum(to corrode) which describes the process of gradual

TABLE 3 Tooth wear in general with erosion as one

Rating Operational explanation

SatisfactoryR (Romeo)S (Sierra)

M (Mike)

Not acceptableT (Tango)

V (Victor)

No visible wear or change in anatomic form.Limited (normal) wear. Limited change inanatomic to'mConsiderable wea; with obvicus change otanatomic form, but does not require treatment

Considerable wear with marked change manatomic torm. Further damage to the toothand/or its surrounding tissues is likely to occur.Excessive wear. Extreme change of anatomicform, esttiefics, and function. Pain on chewing.Damage to the tooth and/or its surrounding tis-sues occurs.

Based or Ryge and Snydsr'' syslen

TABLE 4 Tooth Wear Index^

Score/surtace

B/L/O/l No loss ot enamel surface characteristicsC No change of contour

1B/L/O/l Loss of enamel surface characteristicsC Minimal loss of contour

2B/L/0 Loss ot enamel exposing dentin tor less than one

third ot the surfaceI Loss ot enamel |ust exposing dentinC Detect less than 1 mm deep

3B/LJO Loss of enamel exposing denlin greater than one

third ot the surfaceI Loss of enamel and substantial loss of dentin, but

not exposing pulp or secondary dentinC Delect 1 to 2 mm deep

4B/L/0 Complete loss of enamel, or pulp exposure, or expo-

sure ot secondary dentinI Pulp e5(posure or exposure ol secondary dentinC Delect greater than 2 mm deep, or pulp exposure, or

exposure of secondary dentin

B = bjccal or labial; L = lingual or palatal, O = occlusal; I ^ incisai; C ^ cer-

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TABLE 5 Classification of point values of comparison to age changes inattrition, secondary dentin, periodontosis, cementum, and root résorption,according to degree of development ^

An = no attrition

S„ = no secondarydentin

A, = attrition withinenamelS| - seoondarydentin has tiegunto form in upperpart ot puip cavity

P(, = no periodontcsis P, = periodontosis

CQ = normai iayerof oementum iaiddownR.j = No tootrésorption visible

just beginningC, - apposition alittle greater thannormalRi = Root resorptioonly on smaflisoiated spots

Aj = attrition reachingdentinSj - pulp cavity ishaiftiliedwith secondary dentin

Aj = attrition reachingpuipS3 = pulp cavity isnearly or wholiy fiiledwith secondary dentin

Pj = periodontosis aiong P, = periodontosis hastirst one third ot rootCj = great layer ofcementum

Rj = Greater iossofsubstance

passed two thirds of rootCj - Heavy layer ofcetnentum

Rj = Great areas ofboth oementum anddentin affeoted

destruction of a surface, usually by a chemical or elec-trolytic process, Dental erosion is defined as the loss oftooth structure hy a nonhacterial chemical process,^'The soluhility of enamel is pH dependent, and the rateat which apatite precipitates depends on certain fac-tors, such as calcium binding in saliva. Saliva containscalcium and phosphate ions and exists in a supersatu-rated state at neutral pH with respect to enamel hy-droxi'apatite. As the pH of saliva decreases, it crossesthe saturation line at a point known as the critical pH.Since the critical pH of enamel is approximately 5.5,any solution with a lower pH may cause erosion, par-ticularly if the attack is lengthy and intermittent overtime. ^ Tbe inorganic dental matrix is demincralizcd byacid, which may originate from a diet including tbingssuch as fruit juices, from gastric acid in individuals ex-periencing bulimia, or from industrial acids in the work

Clinically, dental erosion is primarily a surface phe-nomenon, wbile earies originates as a suhsurfacedemineralization of enamel structure." Erosion gener-ally presents as concave and rounded defects withoutthe roughness normally associated with caries. In earlystages, erosion affects enamel resulting in smooth,glazed surfaces lacking in developmental ridges andstain lines. The involved dentin may also show a pol-ished surface while some teeth may have a dull mattedappearance.**" In advanced cases, restorations mayprojeet above occlusal surfaces and cusps of posteriorteeth {and incisai edges of anterior teeth) exhihitingconcavities known as cupping. Erosion associatedwith gastrointestinal reflux are evident as concave de-pressions on the palatal and oeclusal surfaces of max-illary teeth, as well as huccal and oeclusal surfaces ofmandibular posterior teeth, and have been termed per-imolysis or perimylolysis^'^ Erosion associated withdiet may be evident on labial surfaces of maxillary an-terior teeth and present as scooped-out depressions.^"

Mannerberg^' described two types of erosive lesionsusing the scanning electron microscope (SEM). Theactive lesion shows distinctly etched enamel prisms re-sembling a honeycomb, while latent or inactive ero-sions are faint with unrecognizable characteristics.Further ultrastruetural studies have demonstrated ir-regular patterns of enamel dissolution. As the lesionprogresses to dentin, the first area to be affected isperituhular dentin. Dentinal tubules tben become en-larged, affecting intertubular areas as well. Rapidprocesses may lead to sensitive teeth, while slowerprogression may be asymptomatic."

In 1995, a European workshop on dental erosionswas undertaken specifically to discuss current knowl-edge on etiology, mechanisms, and implications of thisproblem.'*' Among topics discussed was the etiologicclassification of erosion, which is one of four bases fornomenclature and classification of erosion (the otherthree are clinical severity, progression, and localiza-tion). Thus, etiologic classification of tooth erosionmay fall under extrinsic (exogenous), intrinsic (en-dogenous), or idiopathic (unknown).^ Extrinsic etiol-ogy of dental erosion can'further be subdivided intoenvironmental, diet, medication, and lifestyle,'^ thecharacteristics of which are summarized in Table 6.

Environmental erosion occurs when individuals areexposed to acids in their work place or during leisureactivities, although bealth and safety laws have mostlikely reduced this risk.'" The process predominantlyaffects the labial surfaces of maxillary or mandibularincisors.' Surveys in industrial environments havedemonstrated that workers exposed to acid fumes andaerosols experience more dental erosion compared toacid-free department employees. Among groups stud-ied were battery factory workers exposed to sulfuricacid, galvanizing factory workers exposed to hy-drochloric acid, and workers in etching and cleaningprocesses involving those acids. Other occupations

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that may increase the risk of dental erosion includemunitions manufacturing, commereial printing, andlaboratory workers. Some case reports have showncompetitive swimmers at gas-chlorinated pools suffer-ing from dental erosion.' * One study« reported thatprofessional wine tasters had an associated increasedrisk of tooth erosion due to the frequent exposure towines with erosive potential (pH range of 3.0 to 3.6).Although the latter is an occupation, il is also relatedto diet-a factor that has received the most attention.

The extrinsic etiology of diet has been extensively in-vestigated, but the actual evidence linking a particularaeidie food or beverage as the primary agent is limited,Coliectively, however, the evidence strongly supportsthe role of acidic foods and beverages as a contributingfactor in dentai erosion,'* The erosive potential offoods and beverages are significantly associated withtheir acidity, pH, phosphate and fluoride contents, aswell as the baseline surface microhardness and iodidepermeability values of the exposed enamel,^' Amongthe foods and beverages implicated are citric acid,acidic and citrus fruits and their juices, carbonated softdrinks and diet drinks, sports drinks, and vinegar con-serves,5«-"-'s Acidic foods and beverages have been im-plicated based on eiinical studies, animal studies, andin vitro investigations. Epidemiologic studies and clini-cal trials have provided the strongest evidence for therole of acidic foods and beverages. However, animalstudies are vulnerable to differences in physiologicmechanisms and properties between speeies. ^

In vitro investigations may not address the dif-ferences in hard tissues, the role of saliva, and the roleof soft tissue and physiologic soft tissue move-ments,'* •' "•' !n vitro and in situ experiments havedemonstrated the protective role of saliva against min-eral loss by erosion for enamel and dentin. This maybe attributed to the chemical composition of saliva,the quantity of saliva protecting the specimens, thepresence of organic layers covering the specimens,and the potential effect of fluoride in situ.'*'

There also have been some reports associating med-ications and over-the-counter dental products withdental erosion. Those products have a low pH and,upon frequent and/or sustained contact with the den-tition, will have a marked effect on dentai erosion.Among medications implicated are aspirin, vitamin C,and oral hygiene products with calcium cheiators.'^

Although acidic foods and beverages have thestrongest association with dental erosion, the quantityand frequency of how these arc ingested is modifiedby lifestyle and behavior factors,'' Dieting and the ob-session for a healthier lifestyle may lead one to ingestmore fruits and diet drinks. The quest for beauty maylead to more frequent product use. Toothbrushing im-mediately after an acid attack has been shown to ac-

TABLE 6 Nomenclature and classification ofe ros I on ä' '

EtiologyExtrinsic (exogenous)Environmentai/ocoupationalDielMedicationLifestyle

Intrinsic (endogenous)Idiopathic (unknown)

Clinieal severity on tooth surfaceSuperficiaiLocalized lesionGeneraiized lesion

Pattiogenic activity ot progressionManitest or aetiwLatent or inactive

Loealization of erosion (perimolysis/perimylolysis)Paiatal and occlusai surface ot maxiilary teethBuccal ana oeelusal surface ot mandibular teeth

TABLE 7 Intrinsic factors associated with chronicvomiting or persistent gastroesophageal refiux^'

t. Alimentary tract disorders (peptic uleer, ehronic gastiitis, in-testinal obstruction)

2. Central nervous system disorders (encephalitis, neoplasms)3. Neuroiogic disorders (migraine, diabetic poly neu ropa thia)4. Metabolic and endoerme disorders (adrenal insufficiency, hy-

perthyroid crisis)5. Drug side-eftects (central emetic ettects, gastnc irntation)6. Psychosomatie disorders (stress-induced vomiting, eating

disorders)

celerate loss of tooth substance, and bleaching agentsmay increase susceptibility to acid erosion.^' In addi-tion, two case reports cite the use of intraora! cocainein inducing dental erosion, "

Dental erosion from intrinsic factors is causedmainly by gastric acid reaching the dentition and oralcavity frequently and consistently. This may be a resultof chronic vomiting, persistent gastroesophageal reflux,régurgitation, or rumination." Long-term, regular vom-iting results in dental erosion and is caused by disordersof the alimentary tract, metabolic and endocrine disor-ders, as well as indirect drug side effects including theuse of alcohol,'•"'•• However, in most cases the underly-ing cause of dental erosion and vomiting is due to a bu-limic eating disorder. This affects mostly young womenwhere the prevalence of dental erosion is high,5i Othercommon disorders related to dental erosion are gas-troesophageal reflux and régurgitation. Those arecaused by the incompetence of the gastroesophagealsphincter due to disease, drugs, increased intra-abdomi-nal pressure, and intragastric volume^'''-" (Table 7),

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Prevalence surveys are few in number, while case re-ports or small case series occupy most of the epidemio-logic literature on dental erosion. It is also difficult tocompare prevalence studies because of different indicesand different sampled teeth. * There are many indicesfor the grading of erosion that have been formulatedand appiied in animal and human studies. Some ofthese describe very fine morphologic changes, whichare not ideal for epidemiologic data.^' Azzopardi et a Freviewed techniques to measure tooth wear and ero-sion. They concluded that in vitro tediniques may havelittle direct clinical relevance, but they may lead tonovel and accurate methods. Moreover, in vivo studiesmay have problems with reference points and accuratevalidation of the techniques.

Another source of variation is the way in whichdamage to the teeth has been recorded, estimated, andreported. Some give general guidelines on case historyand clinical examination, whereas others define sever-ity categories and classifications of erosion," In addi-tion, the indices appear to measure only enamel lossand not the specific action of erosion or cause of theerosion. Identification of the prevalence per se is diffi-cult because of the multifactorial etiology', which maycomplicate the situation in the population,^" Never-theless, depcndahie methods exist for the assessment oferosive potential of dental erosion, but the prospectiveuser would need to study the method and learn thespecialized techniques required.-- Azzopardi et aF°concluded that there is need for a simple and reliabletechnique to quantify tooth wear due to erosion. Sup-porting this is a case-control study that reported preva-lence of erosion at 5"* of a Finnish population.=*^'Conversely, a review of epidemiologic studies of ero-sion reported that prevalence in children varied widelybetween 2°/o to 57%, probably due to a small number ofsubjects and different criteria for diagnosis, ^

In contrast, a recent International Dental Feder-ation (FDI) commission report'^ reviewed and ana-lyzed the past data. It concluded that tooth enamelerosion is rare, easily misdiagnosed, and occurs onlyin susceptible individuals regardless of food and bever-age consumption patterns. Therefore, consumption ofacidic food or beverage alone is highly unlikely tocause erosion. Moreover, susceptibility is highly vari-able from one individual to another, and erosion ismultifactorial in nature.

The prevention of erosion can be attempted in twoways, specifically by weakening the erosive potentialof acid challenge and by increasing resistance of thedentition,^' Reducing the frequency of contact withacidic foods and beverages is the most effective ad-vice.* ' * Referral to {and comanagement with) the pa-tient's physician should be considered if erosion bygastric acid is suspected, -*^ Dietary advice and oral

therapy may be performed to increase the protectiveproperties of saliva and alter consumption of poten-tially harmful foods. These include the consumption ofacidic drinks quickly or through a straw, rather thansipped slowly; and the consumption of products withhigh content of calcium, phosphate, and buffering sub-stances, such as milk and cheese. ' "* Additionally,other recommendations are prescription of buffer-containing chewing gum, oral health instructions toprevent further erosion, and fluoride therapy, ''•^^Modification of food and beverage for content andacidity is theoretically possible but not feasible be-cause of food regulatory constraints and consumer ac-ceptance such as altered taste,^' It also has beenshown that calcium and phosphate salts added tofoods and beverages cause less enamel and dentindemineralization.sis« Aside from calcium and phos-phate supplementation, other studies on food and bev-erage modification have explored other salts that varycalcium and phosphate levels; reduction of acidity lev-els and addition of calcium citrate malate to softdrinks; and the applications of fluoride, bicarbonates,and certain milk constituents.*''

Restorative therapy includes glass ionomers, resincomposites, composite or porcelain veneers, andplacement of crowns and bridges. Sensitive teeth maybe treated with desensitizing agents and dentifrices.Unless the etiology of erosive lesions is eliminated,restorations that are abrasive to the antagonistic teeth,such as porcelain, should not be used. - ' ^™

ABRASION

Abrasion is derived from the Latin verb abrasum (toscrape off), which describes the wearing away of asubstance or structure through mechanical process,^Dental abrasion is the pathologic wearing of teeth asa result of abnormal processes, hahit, or abrasivesubstance,^"

Forms of dental abrasion may be related to habit oroccupation,^''-" Notching of incisai edges may becaused by pipe smoking, nut and seed cracking, nailbiting, and hairpin biting. Carpenters, tailors, and musi-cians may exhibit similar notched teeth due to nails,tacks, and instrument mouthpieces, respectively. Thelocation and pattern of abrasion may be dependentupon the cause.^" Proximal root abrasion may be dueto improper flossing and toothpicks. However, themost common cause of dental abrasion found at thecervical areas is toothbrushing, which may be related totechnique, zealous and vigorous methods, time and fre-quency, bristle design, and abrasive dentifrices,^*''"'''This is termed toothbrush abrasion and has merited themost attention.

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Bptdemiologic studies have dealt mainly with tooth-brush abrasions, or cervical abrasions attributed totoothbrushing and interrelated factors. Unlike attritionand erosion, these are easier seen, classified, and iden-tified. Historically, these lesions have been clinicallydescribed as wedge-shaped, dish-shaped, flattened ir-regular, and concave, and can be further characterizedaccording to depth and size." An SEM study by Bradyand Woody'- delineated morphology into two groups:angular and deep versus rounded and shallow.Bevenius et al" used microendoscopy and SEM to de-fine two distinct forms {saucer and wedge-shaped) ofcervical lesions.

The prevalence of toothbrush abrasions varies any-where from 5% to 85%, depending on the populationstudied. Remarkably, there are reported conflicts onthe role of contributing factors, liitchin'^ divided 200individuals aged 20 to 59 into four age classes andfound 42% of tbe 20-to-29-year age group with abra-sions, while the 40-to-49-ycar age group exhibited76 0 with abrasions. Deep lesions were found in theolder groups, and good oral hygiene was associatedwith frequency of abrasion, Radentz et al" found halfof the subjects aged 17 to 45 with cervical abrasionsrelated to dentifrice use. However, they found no rela-tionship of the lesions to toothbrush technique andfrequency. Sangnes and Gjermo'* found 32% of theiryoungest age group and 50% of subjects over 30 yearswith at least one toolh with wedge-shaped defects.The higher prevalence of lesions was associated withhigher frequency of toothbrushing. Tbe tendency of le-sions to appear on the left side of the mouth was at-tributed to having more right-handed people. Thesmaller number of left-handed subjects likewise pre-sented with more lesions on the right side of themouth. Brady and Woody" found 5% of 900 dentistsshowing cervical lesions, with premolars exhibitingthe most frequency. Bergström and Lavstedt" found30% of 81S people with cervical abrasions (with 12%of those also demonstrating wedge-shaped and deepdepressions). Moreover, they concluded that horizon-tal brushing technique versus vertical roll and fre-quency (more than twice per day) had a strong corre-lation to abrasion, while brush stiffness and dentifriceabrasivity were weak. Hand et aP^ found 56% of an el-derly population exbibited cervical abrasions, 30% ofwhich was described as greater than 1 mm deep.Premolars were more frequently affected, and dataanalysis implicated vigorous toothbrushing as themajor etiologic factor. Bergström and Eliasson'^ founda high occurrence rate of 85% in subjects aged 21 to60 years old. No significant differences were foundwith regard to tootbbrush technique, nor dentifriceswith different abrasivily. Furthermore, there was nosignificant difference between subjects using soft.

medium, or hard bristies to the presence of cervicalabrasions (Table 8).

Altbough studies show a strong association of cer-vical abrasions to toothbrushing, some authors con-tend that dental erosion plays a role in this toothwear.-'-'." In experiments where teeth were subjectedto acid attacks and toothbrush abrasion, it was foundthat rate of abrasion resistance of eroded enamel con-tinued with remineralization time. In addition, it wasrecommended that a 1-hour interval be allowed beforetoothbrushing is initiated after an acid attack to allowa period of remineralization needed to re-establish theresistance of eroded enamel against brushingabrasion.*""' By an SEM study, Mannerberg^' notedthat toothbrusb scratches in tooth surfaces disap-peared after some time presumably from the repara-tive effects of inorganic substance precipitation fromsaliva onto the scratches.

There have been a number of in vitro and in vivoinvestigations regarding toothbrushing and toothwear; however, most of these were conducted morethan two decades ago. In vitro studies have employedtoothbrusbing tnachines and have studied wear, bristledesign, and dentifrices.

Toothbrush force and technique

Pbaneuf et al*- reported a development of a power ormechanical toothbrush. Using strain gauges attacbedto tbe subject's toothbrush, they found that the averagemanual brushing force was 318 gm and the averagepower brushing force was 106 gm. In addition, the rateof hand brushing averaged 235 strokes per minute.Björn and Lindhe'' exarnined brushing technique andshowed that the mean maximum force applied duringvertical one-way rotating toothbrushing was 770 ponds(grams of force) for females and 790 ponds for males.The mean maximum force during horizontal brushingwas 450 and 475 ponds, respectively Correspondingly,they found that horizontal toothbrushing gives alonger time of contact between bristles and teetb ver-stis vertical brushing. In a subsequent study,*-* tbey setthe toothbrush force In a toothbrushing macbine at200 g and found the formation of V-sbaped grooves asfundamental characteristics of dentin by linear cross-brushing movement after 1 hour of brushing. This con-trasted with another investigation'*' wherein verticalbrushing tended to produce U-shaped notches.Padbury and Asb ^ reported greater loss of substancewhen employing a simulated roll technique comparedwith scrub technique in vitro, but localized groovingwas more evident in the latter. Fraleigh et al**' com-pared power and tnanual toothbrushes with differentbristle design and found that the maximum normalforce ranged from 260 g for the powerbrush to 1,310 g

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TABLE 8 Prevalence and factors of cervical abrasions

Study

Kite h in'"

Radentz et a l "

Sangnes andGiermo'*

Brady andWoody'^

Bergström andLavstedt"

Hand et al'=

Bergström andËiiasson''

No.otsubjects

200

80

533

900dentists

818

520

250

Age groups(prevalence)

20-29 (42%)30-39 (-45%)40^9 (76%)50-59 (-73%)17-45 (50%)

18-29(32%)30+ (50%)overall (45%)

(5%)

18-25(15.9%)26-35 (37.6%)36-45 (4t.1%)46-55 (40.3%)55-65 (40.8%)65+ (56%)

21-30(67%)31-40(90%)41-50(90%)51-60(90%)Overall (85%)

Type andlocation of lesion

Deeper lesions found onolder people

Abrasions more prevalentat premolars and maxillarytirst molars

Wedge-shaped defects onone or several teeth

Located more on cuspids.premolars, first molarsTwo morphologic groups:angular and deep versusrounded and shallowTwelve percent ot abrasionlesions were wedge-shapedor deep depressions(> 1 mm)

Highest prevalence at max-illary premolars, followed bycaninesSuperficial or deep lesionsTwenty-two percent weredeep or wedge-shapeddepressions

Contributingfactors

Those with good oral hygiene had twice thepercentage of lesion occurrence compared tothose with poor oral hygiene

•Correlation of greater amount ol dentilrice use topresence of abrasion•No reiationship between abrasion and tooth-brushing technique, frequency, brand of dentitriceand toothbrush, and salivary pH•Cervical abrasion related to age and gingivalrecession•Good oral hygiene and brushing more than twicedaily showed higher trequency ot lesions•Toothbrushing technique had no influence onthe occurrence of lesionsFactors not studied

•Strong correlation ot horizontal technique andfrequency to abrasion•Weak correlation to brush stiffness and dentitriceabrasivlty

Vigorous toothbrushing as major eliologic factor

•Prevalence and severity increased with age•No association of abrasion to toothbrushingtechnique and frequency, toothbrush bristle, anddentifrice abrasivity•No association between plaque and abrasion

for a multitufted soft nylon manual brush. They con-cluded that forces applied during toothbrushing variedto such a degree that atiy arbitrarily set bypotheticalstandards for such forces would be meaningless. Theirdata on brush forces agreed with other previously con-ducted studies.

Recent investigations^*-^' utilizing toothbrushingmachines continue to use a brush force of 200 g. Nostudies have analyzed or set the maximum force toprevent toothbrush abrasions in vitro or in vivo.Recently, a toothbrush'^'^ containing a sensor thatalerts the user if brushing force exceeds a preset limit,was introduced into the market. This limit of forcewas based on Phaneufs 1962 paper."

Dentifrice and brush design

An early study*'' showed that the abrasive potential oftoothbrush bristles on dentin is insignificant and thatabrasion depends entirely on the properties of denti-frices. Sangnes^' concluded that abrasion of dentin andcementum can be produced by tootbbrusbing in vitro

if abrasives are used, and that small and insignificantchanges are caused by the tootbbrush itself. Sangnesand Gjermo"' speculated tbat dentifrices available 30years prior may have been more abrasive tban at thetime of tbeir writing. Thereafter, additional studies in-vestigated the properties of dentifrices in vitro.

Harte and Manlv "* concluded that concentrationand temperature were significant influences in denti-frice abrasiveness. An SEM study^^ showed that ce-mentum abrasion principally resulted from toothpasteeven while employing a soft brusb. Dc Boer et al "showed that larger particle size in dentifrices lead tohigher abrasion rate, and that a medium brush wasmore abrasive tban soft brush. Davis and Winter'^demonstrated eariier that fine powder is less abrasivethan coarse powder of the same mineral. Their studyalso concluded that enamel abrasivity has no fixedratio to dentin abrasivity because of the difference inchemical composition. An in vitro experiment** con-cluded that toothbrush filaments vary in their abilityto carry toothpaste and thereby abrade a surface.According to the authors, hard bristles caused the

442 Volume 34, Number 6. 2003

Lilonjua et al

least amount of abrasion while soft bristles caused themost amount of abrasion. This could be explained bythe increased retention of toothpaste by smaller diam-eter filaments and denser tufts, and the greater flexionof filaments increasing tbe area of contact with thesurface. Slop et al^' investigated the rate of enamelabrasion by experimental toothhrushing and foundthat, initially, enamel is removed rapidly and slowsdown after 500 strokes most likely due to the crys-talline structure and organic matrix of enamel. Note-worthy though, was that this was a continuousstroking motion. A pilot study^^ testing a profilometricmethod concluded in vivo wear rates of 0.2 to 0.3 pmper week for enamel, depending on dentifrice and sub-ject. In comparison, dentin values were 4 to 35 pm perweek. A two-year laboratory and clinical study ' ondentin wear at the cementoenamel juntion (CE|)showed certain laboratory methods couid be corre-lated with clinical data. The conclusion of the workestablished that dentifrice abrasivity per se is not themajor factor in progression of dentin wear. A 54-month chnical study''^ concluded that factors otherthan dentifrice abrasivity may play an important rolein tooth wear.

There have also been studies on prophylaxis agents.An in vitro investigation^* on pumice prophylaxis de-termined dentin removal at 1.57 pm/10 mmVlO sec-onds and enamel removal at 0.08 pm/IO mmVlO sec-onds. The data also indicated that enamel is 20 timesmore resistant to abrasives than is dentin. An in vivoreplica study on enamel and dentin polishing estab-lished that immediate effects were the removal ofsmall amounts of tooth structure and scratching hutthe latter was resolved after 21 days for unknown rea-sons.'"" Moreover, the researchers ascertained thatdentin was removed 26 to 71 times more in volumethan enamel. Brascb et al,'"' using rotating rubbercups under controlled in vivo conditions, demon-strated that the dentifrices tested had a much lowerabrading effect on enamel than prophylaxis pastes[pumice and zirconium silicate). Barbakow et al'"^ re-viewed methods to determine relative abrasion of den-tifrices and prophylaxis pastes and noted that there ex-ists a wide variety of methods used by researchers andmanufacturers, and they suggested that a particularmethod be used consistently to score abrasivencss.

In the early 1980s, some clinicians^"-"" speculatedthat there may be other factors intrinsic to the tooththat have played a significant role in the etiology of cer-vical lesions, such as tensile and compressive stressesfrom masticatory and parafunctional habits. This ledone author'"* to create a fourth term abfraction.However, data supporting this term as a discrete clinicalentity aré not yet available.'"' Bader et al'«« concludedthat factors such as brushing, diet, and tooth flexure

may act independently or at different points in the initi-ation and progression of cervical lesions. They also ad-vocated the use of the term noncarious cervical lesionto denote a multifactorial etiology and that multiplemechanisms operate in the progression of such lesions.

Cervical lesions present in a variety of forms de-pending on type and severity of the etioiogic factor,and not all these lesions require restorations.'"' Thedecision to restore noncarious cervical lesions include:strengthening the tooth and decreasing the hypotheti-cal stress concentration and fiexure; preventing hyper-sensitivity and pulp involvement; modifying oral hy-giene maintenance; and improving esthetics.""'"Treatment measures are resin composites and glassionomer or a combination; metal restoration in poste-rior teeth; dentin bonding agents and copai varnishes;fluoride therapy and desensitizing agents; nightguardand occlusal adjustments; and dietary modificationand oral habit cessation.'"''"^-"^

CONCLUSION

There are three disfinct efiologies for tooth wear; how-ever, a review of the literature points to a multifactor-ial efiology which clouds the delineation of each etiol-ogy. Those etiologies may act synchronously orsequentially, synergistically or additively, or in con-junction with other entities to mask the true nature oftooth wear. In some cases, treatment may be necessaryto halt the progression of tooth wear.

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Volume 34, Number 6. 2003

Osseointegration andEsthetics In Single

Tooth Rehabilitation

C. E. Frandschone,L.W. Vasconcelos,andP.-I. Brânemark

220 pp700 coior itiustrationsISBN 85-87425-35-8US $100

This book arms clinicians wüth the knowledgethey need to perform esthetic single-toothrestoration procedures, particularly in the an-terior region. Achieving an ideal esthetic rc-stilt reqtiires attention to factors such asreverse planning, choosing the ideal abut-ment, and careful management of the gingivato guide papillae formation. Chapters onbone augmentation, solutions for partial an-odontia, and increasing patient comfort,amotig others, address the needs of patientswith special considerations.

Contents• Osseointegration and its Benefits• Osseointegration and General Considerations in

Single Tooth Rehabilitation• Abutment Selection• Impression Techniques• CeraOne• Esthetic Optimization• C er Ad apt• integrated Clinical Procedures• Prosthetic Solutions• TiAdapt• Autogenous Bone Grafts• Fixture Indexing at Stage One Surgery• Procera System

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