Cottmnmity Dem Orat Eptdemtot 1997: 25: 97 103Printed in Denmark . Att rights reserved

Copyrigtu © Munksgaard 1997

Communify Dentistryand Oral Epidemiology

ISSN 0301-5661

What do we know about how dentistsmake caries-related treatmentdecisions?

James D, Bader andDaniel A. ShugarsSchool of Dentistry, University of North Carolina,Chapel Hill, NC, USA

Bader ,ID, Shugars DA: What do we know about how dentists tnake caries-relatedtreatment decisions? Community Dent Oral Fpidemiol 1997; 25: 97-103.© Munksgaard, 1997

Abstract - A conceptual model of dentists' treatment decision-making is dis-cussed. The model suggests that dentists do not use a hypothetico-deductiveprocess for the diagnosis of caries. Rather, caries is idetitified through a processof pattern recognition that in most instances is inextricably linked to interven-tion decisions. Individual dentists have inventories of caries scripts that, whenmatched by a particular clinical presentation, lead to decisions to treat. Thescripts comprise salient factors that are dependent on individual dentist's charac-teristics and biases, and thus vary substantially across dentists. The scripts tend tobe complex, highly visual, and difficult to describe. All of these characteristicssuggest that efforts to improve dentists' caries-related treatment decisionsshould acknowledge this knowledge structure and be designed to change the sa-lient factors or interpretations of salient factors within the context of the cariesscript.

Key wcrds: dental caries, diagnosis; dentalcaries, therapy; decision making; dentists,psychology; observer variation; patient careplanning

J, Bader, Sheps Center, CB#7590, University ofNorth Caroiina, Chapei Hill, NC 27599-7590,USA

Accepted for publication t996

When Dr, Fejerskov originally invitedus to participate in this workshop, hesuggested we address the topic of "howdo dentists utilize criteria in makingtreatment decisions?" In agreeing toprepare a paper, we indicated that if wetackled this suggested topic, the paperwould be quite short, and the conclu-sion would consist of three words, i,e.,"we don't know." For that reason webroadened the title to include morethan just criteria and we added the ten-tative phrase "what do we know about"to the suggested title. While we couldnow condense our conclusion into thesingle word "nothing," we chose to in-terpret the concept of "knowing" a bitmore leniently for the purposes of thispresentation. Thus, this paper describeswhat we consider to be clues, hints, andincomplete insights into the complexquestion of how dentists tnake caries-related treatment decisions. It reflectsour opinions and experiences, bolstered

where convenient by support from theliterature. In short, our approach to ad-dressing this topic resembles our viewof how dentists make treatment deci-sions.

The presentation is based on a con-ceptual model of dentists' treatment de-cision-making (Fig. 1), We originallydeveloped the model to help guide ourinvestigations in a project that soughtto "predict" dentists' restorative treat-ment plans as a measure of normativetreatment needs (1). We subsequentlymodified the model for a presentationat a conference on caries diagnosis (2).We have respecified the model to focuson caries-related treatment decisionsfor this discussion. We emphasize thatthis is a conceptual model. It is notbased on a single underlying theoreticalframework. Rather, it borrows fromseveral theories of decision-making andincorporates our empirical observa-tions, A final caveat is that the model

reflects the decision-making processeswe think are employed by experienceddentists, as opposed to learners or nov-ices. The model outlines a process ofdentists' decision-making that may behelpful both in understanding why den-tists show such variation in their deci-sions and in guiding attempts to reducethe variation and thereby, it is assumed,improve the appropriateness of such de-cisions overall.

Diagnosis of cariesThe traditional view of how dentistsmake caries-related treatment decisionsinvolves a diagnosis of caries, followedby a decision concerning treatment. Incontrast, the model suggests that den-tists do not "diagnose" caries in theclassic sense of making a differential di-agnosis (3, 4), There is no distinct pro-cess that is akin to the standard hypo-thetico-deductive method. Upon reflec-

98 BADER & SHUGARS

Characteristicsage/experienceskills/diligencetolerance for

uncertaintyknowledge

Dentist FactorsBiases

restoration utiiitytreatmenl preferencesdiagnostic techniquesoutiier experiences

Practice Characteristicsbusynessscalepersonnei

delivery systemguidGlJnesequipment

InitialExamination

Script Match Automatic

Uncertaint] LAddition:Scrutiny

Decision to Treat

Dedsionto Treat

TreatmentSeiection andRecommendation

No Script Matcii bio Treatment Recommended

TreatmentNegotiation

andAcceptance

Tooth Levet

Patient Factors

MoLittt Levet Pattent Levetvisual signs tactiie signs- discontinuity - contour- color - conststency- contour - "catch"- shadow radioiucencies

caries- tiistory (FS)- status (DS)oral hygiene

• ttow rate- conststencygingival recess

maiaiignment R,P,D,

diet diseasesfluoride exposure prerererioes- history SES- current status insurancemedications

Eig. I. Conceptual model of dentists' caries-related treatment decisions.

tion, it is not altogether surprising thatthis method is not evident because thediagnostic problem is different. Theusual situation where the hypothetico-deductive process is applied to arrive ata differential diagnosis involves a pa-tient presenting with signs and symp-toms of unknown origin. Data aregathered through questioning and ex-amination and, in so doing, a numberof alternative hypotheses explaining theorigin of the signs and symptoms froma pathophysiological perspective aregenerated and evaluated. The processconcludes with the selection of one ofthe alternative hypotheses as probable.At that point, the diagnostic processends and a process of treatment selec-tion begins. In contrast, when a patientpresents for a dental examination, thediagnostic problem is rarely identifying"what the patient has." Usually, thequestion is "does the tooth have any-thing?" and the question is repeated forevery tooth or tooth surface. We'll sug-gest later that this question might moreaccurately be phrased as "does thetooth need anything?"

If the hypothetico-deductive processis not a principal feature of caries diag-nosis, should this repetitious searchprocess be termed "diagnosis"? To theextent that the term diagnosis refers tothe process of postulating and evalu-ating alternative explanatiotis for a set

of clinical observations, the answer isno. However, to the extent that the termrefers to deciding whether the survivinghypothesis is probable, the answer maybe yes, although we think that the term"detection" is a more appropriate de-scription of the process. Ideally, a singleunstated hypothesis is always beingevaluated whenever a tooth is examinedfor caries. Depending on the orienta-tion of the exatnitier, the hypothesismay be null, that the tooth in questiondoes not have caries, or the alternative,that the tooth does have caries. In ei-ther event, a search for clinical and ra-diological signs usually comprises thedata-gathering activity that leads to adecision concerning the probability ofthe presence of caries. Realistically, asindicated by the tnodel (Fig. 1) we be-lieve that both the initial evaluation ofthe hypothesis and the ultimate deter-mination of a probability are largelyunconscious or automatic and inextri-cably linked to the decision to in-tervene. Thus, for most teeth, the actualprocess of diagnosis, if it occurs, is noteasily distinguishable. The results of theprocess are expressed only in terms ofthe decision to intervene. We will arguethat the absence of a definitive diagnos-tic step contributes to the extensivevariation among practitioners whenthey are asked to provide caries diag-noses (5),

There is some anecdotal support forthis model of how caries diagnosis ordetection is integrated into the treat-ment decision process, A similar viewhas been described by ETTtNGER (6),who based his arguments on his ownobservations and those presented in anunpublished paper by PROSHEK. Den-tists who have treatment-planned pa-tients for our projects often have iden-tified a diagnostic finding by naming itsintended treatment, e.g., pointing to aradiolucency and stating "that's a DOamalgam" (2), Also, when describingtheir plans for treatment of each toothto recorders during clinical examina-tions, dentists were often unable to im-mediately state a reason for the recom-mended treatment when this informa-tion was requested by the recorder (2).Finally, both the sheer paucity of avail-able alternative diagnoses for the signsassociated with caries and the technicalorientation of the profession also sup-port a view of the process where differ-ential diagnosis is de-emphasized and aconfirmed hypothesis (or a rejected nullhypothesis) is expressed in terms of sub-sequent treatment.

Note that an extended diagnosticpathway is also available in the model.This pathway involves the collection ofadditional data prior to a decision con-cerning ititervention being made whenuncertainty is present. In a narrowsense, this pathway more closely resem-bles the classic diagnostic process, inthat evaluation of the hypothesis al-ternates with data collection. However,note too that the outcome of this path-way is also a treatment decision, not adiagnosis.

Carles scripts

If there is no discrete analytical diag-nostic step in the caries examination,what does happen during the examina-tion? We think a process of pattern re-cognition, or non-analytical processing,occurs. Recognition that caries is pres-ent depends on the similarity of what isseen on examination with presentationsencountered previously that have beendeemed to be caries requiring treat-ment. The particular mechanism ofpattern recognition operative in cariesdiagnosis is unknown. We suggest thatpresentations of caries are stored inpractitioners' memories in a form sim-

Detttists' caries-rektted treattnettt decisions 99

ilar to illness scripts (7), Illness scriptsare highly summarized versions of aprovider's cumulative experience withsimilar clinical presentations of healthand disease. They differ from a con-densed form of the traditional differen-tial diagnosis because they minimize orexclude the pathophysiological basis ofthe disease in question and they sequen-tially emphasize sets of salient features,i.e., predisposing factors, limiting con-ditions, signs, and symptoms.

The scripts that we suggest practi-tioners employ in their caries examina-tions, i.e., caries scripts, differ from ill-ness scripts described in medical prac-tice in that caries scripts end with adecision regarding intervention, ratherthan a probable diagnosis. Also, thesigns contained in the script are usuallyvisual and less frequently tactile. Symp-toms are rarely an important feature.Like illness scripts, caries scripts consistof salient features, i,e,, the distinguish-ing characteristics of the particular ex-pression of caries, A caries script mighthave very few salient features, such as acotie-shctped proxitnal shadow on a ra-diograph, or a perntattettt tooth with a"sticky" fissure aitd associated gray/browtt .shadow. Alternatively a cariesscript might be highly focused with sev-eral factors, such as a two-sttrface atttal-gittn restoratiott iti a molar e.xhihititig tioradiological evidence of carles hut havittgseveral ttncrofraetures of the occlusaltitargiti that have resulted itt shallowditching, an adult patietit with moderateplaque aecuntulatioti. a cavitated lesiottelsewhere itt the tnouth, and severalantalgatn resioratiotts ttot placed by theexatnltiittg dentist that have itttperfecttnargins. If these features are closelymatched by a particular tooth in a par-ticular patient, then the practitioner will"automatically" recommend an inter-vention. No diagnosis has been made,and no explicit estimation of the prob-ability of caries being present or occur-ring in the future has been made. Thepractitioner has simply matched the pa-tient's tooth with a pattern for which heor she routinely recotnmends treatment.The absence of a specific distinction be-tween the probability of current and fu-ture caries may explain practitioners'synonymous use of the terms "second-ary caries" and "defective margin,"

The model reflects our assumptionthat during a caries examination, car-

ies-related treatment decisions are me-diated by these scripts most of the time.Thus, as each tooth is inspected, eitherclinically or radiographically, any de-parture from "normal" triggers an un-conscious and rapid review ofthe inven-tory of relevant caries scripts to deter-mine if one of them matches thepresentation. No conscious reflectionon any of the specific salient factors isinvolved, and caries pathophysiology isnot at issue. Although the number ofcaries scripts in a practitioner's invento-ry is presumably large, presorting andordered review by frequency of preseti-tation permits the expression of mosttreatment decisions after almost imper-ceptible pauses. The time spent in den-tal examinations is consumed principal-ly in collecting the visual and tactiledata needed for matching scripts.

Only occasionally does an abnormalpresentation not result in a satisfactorymatch with an existing caries script.When such uncertainty arises, a dentistusually seeks more information. It isnot clear whether the additional infor-mation is used to strengthen a possiblematch with an existing caries script, orwhether the dentist has entered an ana-lytical mode where the probability ofcaries is addressed more directly andthe pathophysiology of disease againfiecomes relevant. In any event, the con-clusion of this additional process also isa decision regarding intervention.

Most but not all caries scripts willend in a decision to intervene. Examplesof "non-intervention" caries scripts arethose leading to watches, i.e., notationsin the treatment record indicating theneed for future comparisons with cur-rent conditions to detect change (8),and those where a practitioner has re-cently abandoned what was once a rovi-tine decision to intervene. Watches areplaced most frequently when uncertain-ty is present. We think that abandonedintervention scripts linger in the inven-tory, and are only gradually lost to thematching process. Some anecdotal sup-port for this view is found in commentswe have heard in our treatment-plan-ning sessions frotn practitioners dis-cussing why their treatment decisionsdiffered from those of colleagues, A notinfrequent explanation would be theobservation that "1 used to treat those."

Caries scripts are not necessarily as-sociated with the demonstrable pres-

ence of caries, simply the probabilitythat it is present. As evident in the pre-vious example, a caries script associatedwith a treatment decision to intervenedue to caries might comprise a set oftooth-level salient factors that pertainonly to visual and tactile assessments ofan existing restoration. For the dentistetnploying the script, these factors maybe associated with some presumed highlikelihood that caries is present or soonwill be present. Agreement among den-tists on the presence of secondary cariesrequiring treatment that is associatedwith restoration margins is weaker thanagreement on the presence of primarycaries (9). Also, agreement among den-tists that a treatment intervention is in-dicated for a given tooth is strongerthan agreement that caries is the pri-mary reason for the intervention (2, 9).These observations suggest that in theabsence of "definitive" signs of caries,dentists' caries scripts have varyingprobafiilities for caries being associatedwith specific indirect signs such asditching or staining. Thus, while cariesneed not be evident, caries scripts arecharacterized by some probability thatcaries is present, or that caries forma-tion will occur.

Factors influencing interventiondecisionsThe model indicates that a variety ofpatient and practitioner factors may af-fect decisions regarding treattnetit inter-vention, either the decision to interveneor the selection of a specific interven-tion. The factors in the model havebeen included largely on the basis of re-ports in the literature identifying an as-sociation with treattnent decisions (1),although some factors are iticluded be-cause they are routinely discussed in theliterature even in the absence of any for-mal evidence of an association. Whileexplanations for how these factors in-fluence treattnent decisions seem obvi-ous in most instances, for many factorsthe actual mechanism has never beenevaluated formally. For example, differ-ences among dentists in their aliility todetect small marginal gaps have beendemonstrated (10), but whether suchdifferences lead to differences in cariestreatment decisions is unknown. In thissame vein, it is worth noting that whilecaries signs are largely visual in clinical

100 BADER & SHUGARS

examinations and wholly visual in ra-diographic examinations, practitioners'visual acuity has received little attentionas a factor explaining variation amongdentists in caries diagnoses (11).

Many of the influencing facfors in-cluded in the model are poorly defined.For example, differences in practitionerdiligence are cited anecdotally as caus-ing variation in diagnoses and treat-ment decisions. However, no measure ofdiligence has been suggested, and theprecise nature of diligence remains un-defined. Another example is the conceptof patients being at "high risk" for car-ies. The constellation of factors denot-ing elevated risk of caries varies acrosspractitioners (12), Also, the measure-ment of any given factor, such as "oralhygiene," can be problematic and themagnitude of risk associated with dif-ferent values of the factor is generallyunknown. We argue that the ill-definednature of many of these factors leads tothe development of highly individualis-tic caries scripts, which contributes inturn to substantial variation amongdentists in their treatment decisions.

The model lists three types of patientfactors thought to influence the caries-related decision-making process. Thetypes are identified by their "level," i,e,,those involving a specific tooth or toothsurface, those describing general intra-oral conditions, and those related to pa-tient history, behavior, preferences, andsocioeconomic status. We suggest thatthe tooth- and mouth-level factors arelikely to be included in caries scripts,while most patient-level factors aremore likely to play a role in decisionsinvolving the extended pathway andtreatment selection. Clearly, many ofthese factors will also operate in the ne-gotiation and acceptance phase that fol-lows the presentation of a treatment re-commendation to a patient.

Three types of dentist factors also arelisted in the model; biases, personalcharacteristics, and practice-relatedcharacteristics. We suggest that thesefactors, which remain constant acrosspatients, exert their effects on treatmentdecisions indirectly by influencing whichsalient factors are included in a cariesscript and the magnitude of the prob-ability of caries associated with a specificcaries script. Biases arc opinions or pref-erences held by individual dentists. Wehave termed these opinions and prefer-

ences "biases" under the assumptionthat they introduce subjective variationinto what is otherwise an objective pro-cess. While the objectivity of the un-derlying process is open to debate, wechose this terminology to emphasize therole of probability and perceptions ofprobability in influencing treatment de-cision-making.

The biases included in the model arebeliefs about treatment utilities, person-al treatment preferences, the diagnosticmethods they employ, and "outlier ex-periences," Obviously, dentists' beliefsabout the absolute and relative utility ofvarious types of restorations in terms ofoutcomes such as longevity, effec-tiveness in restoring function, and pre-venting further disease, will play a rolein decisions to intervene as well as deci-sions concerning the nature ofthe inter-vention. Treatment preferences, whichare presumably based on the aforemen-tioned beliefs as well as personal experi-ence in treatment provision and out-comes, will also influence these treat-ment decisions. Personal preferences fordiagnostic techniques (e,g., use of ra-diographs, other diagnostic measures, aprobe) can influence the presentation ofdisease as perceived by a practitioner(13). "Outlier experiences," which areunusual or unexpected outcomes oftreattnent decisions, often with seriousconsequences, can affect subsequenttreatment decisions by being givengreater consideration or weight by thepractitioner than their incidence wouldsuggest they merit.

The personal characteristics that areincluded in the model are skills/dili-gence, age/experience, knowledge, andtolerance for uncertainty. As noted, weknow little about how and even whetherdentist tactile and visual skills and dih-gence operate to influence treatment de-cisions. Also, we have not defined, letalone measured diligence. We do knowthat age is associated with differences intreatment decisions (1), although it isnot completely clear whether observedage differences are due entirely to theeffects of maturation (experience), orwhether history also is involved (14). Ithas been common to find that olderpractitioners are less aggressive in theirdiagnoses and decisions to intervene(1). Presumably older practitioners'greater experience has led them uncon-sciously to alter the probabilities for

caries presence or caries progressionthat are associated with decisions to in-tervene. Knowledge is a function of ini-tial professional education and subse-quent formal and informal learning. Asused in the model, knowledge refers toaccurate information describing the ep-idemiology and pathophysiology of car-ies and the outcomes of its treatments.

The characteristic of tolerance of un-certainty has received no attention inthe dental diagnostic literature. Dentistswith a low tolerance for uncertaintymay be more likely to recommend "do-ing something," i.e., intervening whenuncertainty arises simply because in-tervening lowers their anxiety over"not doing anything" (15), Establishingwatches for uncertain situations repre-sents a means of lowering anxiety with-out intervention. Uncertainty toleranceplays a yet-to-be-elucidated role in es-tablishing so-called "treatment thresh-olds," which can be thought of as themagnitudes of the perceived probabilityof caries at which various dentists willintervene.

Making decisions to interveneA decision to intervene can be viewed inthe abstract as a complex probabilisticjudgment. Ideally, the judgment includesa Baysian approach to the determina-tion of the probability of disease basedon certain criteria, followed by a deci-sion analytic approach to weighting therelative merits of intervention and non-intervention given that probability. Thedecision analysis process is dependenton information about outcomes of treat-ment, usually also expressed in terms ofprobability. In actuality, these judgmentsare too complex and cumbersome to becompleted de novo for each new tooth.We suggest that practitioners routinelyrely on caries scripts to free themselvesof the necessity for repetitive high-levelcognitive activity. However, proposingthe presence of caries scripts begs thequestion of how practitioners associateparticular scripts, or presentations, withdecisions to recommend treatment in thefirst place. Also, we have posited anumber of factors that may influencethese decisions, but we have not de-scribed the mechanisms through whichthese influences operate. The unfortu-nate truth is that little is known about

Detitists' caries-related treatment decisions 101

the mechanisms or criteria dentists usefor making treatment decisions.

What is becoming clear is that themechanisms are complex and the criter-ia are both several and situational. Forexample, some evidence is available tosuggest that dentists' stated physiologi-cal criteria for caries they regard as re-quiring treatment, the aforementionedtreatment thresholds, are not supportedby their treatment decisions tnade onthe basis of radiographs (16, 17), Thisfinding has been viewed as a possibleindication of the tnisinterpretation ofthe radiographic representation of thecaries process, the inability of dentiststo adequately verbalize their treatmentthresholds, and the relative unimport-ance of a specific depth of penetrationcriterion among all other factors in-volved in treatment decisions. As addi-tional analyses are reported (18, 19), thelatter explanation gains additionalstrength. Thus, the use of stated thresh-olds as predictors of practitioners'treatment decisions will probably notbe successful. The explanation of onegroup of investigators for why practi-tioners may have had difficulty describ-ing their treatment thresholds essen-tially duplicates our view of cariesscripts in all but name; "There may be... a complex web of cues and signs as-sociated with a lesion judged to need afilling, which the dentist may be un-aware of" (16),

We do not know precisely where orwhen dentists begin to create and relyon their personal caries scripts. Presum-ably, the process begins in the preclini-cal operative laboratory when instruc-tion and demonstration are based onnatural teeth, and development contin-ues during courses in oral diagnosis andthroughout students' clinical experi-ences. Practitioners at this formativestage are likely to already possessunique individual scripts based on theirown experiences and their interactionswith a variety of unstandardized in-structors. It is virtually certain thatpractitioners' subsequent clinical expe-riences play a powerful continuing rolein first elaborating and then tnodifyingthese nascent caries scripts over a life-titne. It is probable that virtually all ofthe other dentist factors that can influ-ence these scripts must act through thefilter of personal experience.

We suspect that there are several

types of experience-based feedback thatact to modify caries scripts. Clearly, im-mediate feedback on the presence orabsence of caries associated with re-storations will arise from decisions tointervene in such circumstances. Thatthe behavior of replacing "suspicious"restorations has not been extinguishedin the face of the fact that, upon remov-al, many of these restorations cannot beassociated with caries (20) suggests thatfairly low perceived probabilities of car-ies are sufficient to trigger decisions tointervene, at least for dentists with alow tolerance for uncertainty. This ob-servation also illustrates the imperfectnature of feedback with respect to risk.The absence of caries is not "negative"feedback if the practitioner intervenedbecause of concern over future caries.Rather, the practitioner may regard theabsence of disease as positive feedback,i.e., that the intervention was per-formed "in titne." Two longer-termtypes of feedback, the outcomes of deci-sions to intervene and not to intervene,also will modify intervention decisions.For example, if the observations thatpractitioners become more conservativein their intervention decisions are valid,it would seem that with experiencecomes feedback that restorative inter-ventions are not without their own ad-verse outcomes. Also, decisions not tointervene under uncertainty would seemto be frequently rewarded with longperiods of quiescence.

The mechanism through which feed-back acts to modify intervention deci-sions is not established, but is likely somecombination of gradual change in theperceived probability of caries or partic-ular outcomes of treatment associatedwith a particular caries script andchange in contents of the script itself,i.e., the inclusion or exclusion of salientfactors in an existing script. Changes inknowledge as well as increased confi-dence in the accuracy of perceived prob-abilities are likely to be itivolved in thisprocess as well. As noted, decision-mak-ing is an exercise in probabilistic judg-ment, and in dentistry a great many ofthe probabilities involved in this judg-ment are simply not known (21). Thusuncertainty is introduced. An informalset of assumptions has been adoptedover time, the "uncertainty hypothesis"(15), that describes physician behaviorunder conditions of uncertainty, i.e., the

lack of definitive knowledge of probabil-ities. The hypothesis states that the moreuncertainty is tolerated, the less likely adecision to intervene will be made. Acorollary is that, given a fixed tolerance,more uncertainty is likely to lead to moreintervention. Thus, increased confidencein perceived probability estimatesbrought about by increased experiencewould have the effect of reducing uncer-tainty, and hence, the tendency to in-tervene. New knowledge regarding cariesprobability could have the same effect ifconfidence in the new knowledge wasgreater than confidence in personal ex-perience.

One additional type of experientialfeedback also influences caries proba-bilities associated with specific cariesscripts. This type of feedback is listedin the model as outlier experiences. Infact, the effect is more widely known asthe availability heuristic (4, 15), Thistype of experiential feedback leads tobiased estimates of probability, either ofcaries or of particular outcomes associ-ated with treatment. Heuristics areshortcuts to analytical thinking pro-cesses (4). The availability heuristic op-erates whenever experience is used toassess the plausibility of a particular de-velopment (such as a white spot lesionof a particular size and location pro-gressing to cavitation). In theory morefrequent events are more easily recalled,so that probability of occurrence is as-sociated with ease of recall. Unfortu-nately, ease of recall is also associatedwith other characteristics such as thevividness of an event, the consequencesof an event for the patient or for thepractitioner, or the recentness of theevent. Thus, although the interventiondecision associated with a specific cariesscript may be based on long experiencewith the outcomes of the decision in thepast, a single spectacular instance whenthe intervention decision led to an un-fortunate outcome will bias future deci-sions in the short term by inflating theperceived probability of the occurrenceof such outcomes.

Implications for changeKnown changes in the prevalence, inci-dence, and progression of dental caries,coupled with variation in dentists' car-ies diagnoses and caries-related treat-ment decisions and the lack of evidence

102 BAt:)ER & St^uGARS

supporting the need for much of thecaries-related treatment currently pro-vided, have fostered a general attitudethat the entire process of caries diagno-sis and treatment decision-makingneeds improvement (22), It would ap-pear that if the concept of caries scriptsis a reasonable approximation of howcaries diagnoses and treatment deci-sions arc integrated by practicing den-tists, attempts to improve these pro-cesses must be designed specifically tohelp dentists abandon old scripts andadopt new ones if they are to be fullysuccessful.

The typical continuing education ap-proach to improving the process wouldbe to provide information "from the ex-perts" about new interpretations to beassociated with specific signs of caries,or about new diagnostic tests and theirinterpretations. In the extreme, completedecision trees would be taught togetherwith the pathophysiological basis for se-lecting alternatives at each decisionnode. There are several reasons why it islikely that such approaches will not beeffective in changing practitioners' diag-nostic behaviors. First, the continuingeducation literature would suggest thatstraightforward educational interven-tions are the least effective of all avail-able means to influence practitioner be-havior (23). Second, as we have just ar-gued, practitioners typically do notpursue straightforward deductive diag-nostic strategies based on the patho-physiology ofthe disease. Thus, teachingnew techniques from this perspectivemay actually place an obstacle in thepath of learning and acceptance. Third,rightly or wrongly, our model suggeststhat dentists place a high degree of con-fidence in their previous clinical experi-ence. We argue that if new informationdocs not agree with this experience, it ismore likely to be disregarded.

If these arguments are correct, then itseems clear that those who wish tochange dentists' diagnostic and treat-ment decision behaviors must select oneof two possible levels at which theywould achieve change. At one level, thegoal might be to have dentists incorpo-rate into their caries scripts an addition-al salient factor such as a new diagnostictest, or a re-intcrpretation of an existingsalient factor such as the prognosis asso-ciated with proximal radioiucencies pen-etrating to but not into the dentin. At the

other level, the goal is more ambitious,i.e., having dentists change the frame-work they use to diagnose caries.

Strategies to achieve the first level ofchange are fairly clear-cut. The new in-formation should be presented in thecontext of caries scripts. Thus, the newtest or the re-interpretation should bepresented and discussed in the presenceof other specific salient factors includedin most practitioners' caries scripts. Thepresentation should be visually based tothe maximum extent possible because itis unlikely that written descriptions pro-vide adequate representations, or eveninclude all important salient factors. Ar-guments intended to support the adop-tion ofthe new information should showexplicitly what old information is beingreplaced, and why. The old informationrepresents practitioners' experience,which they trust. If it is to be replaced,practitioners need to have equal confi-dence in the replacement. Thus, not onlyare results of empirical studies necessary,but also they should be accompanied bymaterial explaining why previous experi-ence no longer can be assumed to repre-sent unbiased truth.

Strategies to achieve the second levelof change must be more ambitious. Itis unlikely that the process of patternrecognition that we hypothesize as theprincipal process in diagnosis and treat-ment decision-making will be aban-doned. This repetitive task of inspectionand assessment detnatids an efficientprocess, and some variation on cariesscripts would seem to be the inevitableresult. Thus, the framework underlyinga practitioner's inventory of cariesscripts must be the target for change.Perhaps the greatest improvement pos-sible would be to ensure that the scriptsare based on the "medical model" ofcaries treatment (24), An inspection ofthe salient factors in the model suggeststhat caries scripts are composed almostexclusively of signs of the consequencesof caries, rather than signs of thedisease itself. A new set of scripts thatincorporates salient factors associatedwith the infectious status of the patientwould be based on the pathophysiologyof the disease. The scripts themselveswould not involve pathophysiology, butwould be founded upon a broad base ofmicrobiological, iinmunological, genet-ic, dietetic, and epidemiological knowl-edge as well as new information now

beginning to appear that describes theoutcomes of treatment for caries.

Within this framework, effectivescripts would have readily distinguisha-ble salient clinical factors, would befirmly linked to appropriate treatmentoptions, and would be based on themost current evidenced-based under-standing of the disease process and itsmanagement. For example, PITTS hasproposed a scheme that links the stagesof the caries process with appropriatetreatment options based on currentknowledge (25). A set of replacementscripts might be based on the salientclinical factors that characterize thestages in PITTS' scheme, and might alsobe further differentiated by additionalsalient factors that represent assess-ments of the risk of progression.

A closing observation seems appro-priate. Our ability to improve the ap-propriateness of dentists' caries-relatedtreatment decisions will be limited untilwe better understand the process. Wecan identify some obvious weak points,such as the lack of standardization forassessment of fundamental conceptslike oral hygiene, risk, and even caries,and the lack of outcome informationassociated with various treatment stra-tegies. But there is far more that we donot understand, such as how dentists'characteristics and biases interact, howthe environment of practice affectstreatment decisions, ancf how (and if)dentists incorporate the values and uti-lities of their patients into their treat-ment decisions. Without a deeper un-derstanding of the mechanisms un-derlying the diagnostic and decision-making processes, as well as the factorsthat affect them, the chaos that charac-terizes the current scene will continue(21). This paper has described onemodel of these mechanisms and factors.Other models are certainly possible, butthey remain to be proposed. The profes-sion has an obligation to devote the ef-fort and resources necessary to under-stand how its members make perhapsthe most basic of all patient-relatedprotessional decisions.

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