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Understanding Dentists’ Restorative Treatment Decisions James D. Bader, DDS, MPH Daniel A. Shugars, DDS, PhD, MPH School of Dentistry, CEW7450 University of North Carolina Chapel Hill, NC 27599-7450 and Pew Health Professions Commissions, Duke University

It is widely acknowledged that when confronted with the same clinical situation, not all dentists will make the same decisions regarding the need for treatment and the choice of treatment when intervention is indicated. The variation in these decisions often is attributed to “clinical judgment” and to personal pFeference based on ”clinical experience.“ Although the extent of variation has been termed ”striking” (l),neither its precise nature nor the reasons for it have received much careful examination. This situation reflects recent events in medicine, where investigation of variation in physicians’ practice patterns began in earnest only about a decade ago (2).

Since restoration and replacement of teeth account for a large portion of dentist treatment time (3)and dental expenditures (4), variations in decisions to provide these services and in types of services provided can have substantial cost and policy implications. Similarly, it is likely that such variation also introduces some inappropriate treatment at the extremes, i.e., both over- and undertreatment (5), both of which can have long-term economicand health implications.Unfortunately, we know little about variation in dental treatment decisions, and even less about how these decisions are made and what factors influence decisions. Our inability to understand, and thus predict, dentists’ treatment decisions renders it impossible to define the normative, or professionally defined, ”treatment needs” of a population (6). Also, without knowledge of the factors that influence dentists’ decisions, the American Dental Association’s recently initiated program to develop ”practiceparameters”-i.e., information to help guide dentists‘treatment decisionsmay not achieve the effectsits sponsors anticipate (7). Because technological development will lead to more restorative treatment alternatives for a wider range of ”treatable” conditions, dentists will face more decisions, perhaps with greater implicationsfor cost and appropriateness. Thus, it is imperative that dentishy begin to understand the nature of dentists’ treatment decisions, and the factors that influence these decisions. This paper reviews the available information describingvariation in dentists’ restorative treatment decisions and associated factors, and describes a model to facilitate additional investigation of these decisions. The review is divided into four sections. The first three sections review variation in dentists’ assessment of clinical conditions, decisions to intervene, and treatment recommendations. These sections reflect conceptually the sequence of the treatment planning process (8) and represent a slight modification of the traditional sequence of steps in problem-solving models (9). The fourth section reviews knowledge of factors associated with variation in these steps in the decision process.

Send correspondenceand reprint requests to Dr. Bader. Reparation of this review was supported by grant H506669 from the Agency for Health Care Policy and Research. Manuscript received 3/25/91; returned toauthorsfor revision:5/7/91;acceptedforpublication:6/6/91.

Assessment of Clinical Conditions For restorative treatment, an assessment of clinical conditions is devoted primarily to detecting caries, eval-

Abstract A critical review of the literature is presented that examines variation in dentists’ restorative treatment decisions and the factors associated with this variation. Substantial variation has been documented in dentists’ assessment of caries, in dentists’ decisions to intervene, and in the selection of treatment recommended to the patient. However, the factors associated with this variation are not well documented. Following discussionof this review, a model is proposed to help guide further studies of dentists’ restorative treatment decisions. This explanatory model incorporates the factors identified in the review, as well as others either observed informally or found in the medical literature. The implications of variation in dentists’ treatment decisions highlight the importance of a full explicationof the process dentists follow in making treatment decisions. Understandingthis process, which heretofore has been examined only superficially because it has been regarded as a function of “clinical judgment,“is fundamental to determinationsof normative treatment needs, to interventions designed to reduce the frequency of inappropriate treatment,and to the development of valid practice parameters. Key Words: diagnosis, decision making, treatment planning, treatment needs, quality of care. ~~~~~~

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uating existing restorations, and identifymg missing and damaged teeth. Additional assessments usually made at the same time include evaluation of functional, occlusal, and periodontal conditions. These additional assessments tend to furnish information useful in selection among treatment alternatives, rather than in defining the need for interventions. Three of the four primary assessments, detection of caries, evaluation of existing restorations, and detection of damaged teeth, are problematic in terms of either the existence of evaluation criteria, or consistent application of these criteria among practicing dentists. Epidemiologists have developed a widely accepted set of criteria for the presence of caries using visual-tactile examination techniques (10). Experience with these criteria indicates that calibration is difficult, that examiners must be recalibrated regularly, and that achieving acceptable levels of intra- and interexaminer reliability takes careful practice and attention to detail (11).No single set of criteria to assess the condition of previously placed restorations is in widespread use. While inspection for caries seems to be the most important part of an assessment of existing restorations, other criteria involving marginal conditions, contour, and color and smoothness of the restorative material are also considered (12,13). There is far less standardization among these criteria, although most represent some modification of the original Ryge-Snyder criteria (14). Finally, no standardized, widely accepted criteria for damage to tooth structure (erosion,attrition, fracture)are available. With the exception of reports of examiner reliability associated with clinical trials and epidemiologic examinations, the literature contains few reports of the degree to which dentists vary on caries diagnoses for individual teeth. A significant difference was found in the mean number of caries diagnoses per patient made by 12 Finnish clinical dental educators examining the same ten patients, with a threefold range in mean number of diagnoses made by individual teachers (15).In a study of 228 extracted teeth in which practitioners’ attention was directed to a particular aspect of an existing restoration, all nine examiners agreed on the presence of caries in only two teeth (16). In 38 teeth, one of nine examiners diagnosed canes. The range of total caries diagnoses per examiner was from 11 to 57 teeth. In another study of extracted teeth examined by 86 dentists, a similar degree of variation was noted across48 surfaces evaluated visually (from three to 33 surfaces), and radiographically (from seven to 36 surfaces) (17). Assessment of existing restorations is a crucial issue because their replacement constitutes a majority of all restorative treatment effort (18-20). Despite the frequency with which replacement occurs, there is little information that describes the criteria employed in these assessments that lead to condemnation, and none describing variation among dentists in their application.

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Caries is the most frequently cited reason for replacement, although the rate is highly variable (18,21-26),and recent reports tend to show increased rates of replacement due to various perceived mechanical shortcomings of the restorations (1323-26). Finally, there is no information available describing assessment of damage to the tooth. Because no standardized indices or rating scales for recording such damage are in use, comparisons of assessments among dentists are not possible. Decisions to Initiate Treatment The information gathered during assessments of clinical conditions is assumed to be an important input to the second step in the restorative treatment decision sequence: deciding whether intervention is necessary. One study of practicing British dentists presents direct comparisons of dentists’ decisions to treat individual teeth. Fifteen dentists examined 18 subjects, indicating which teeth they would treat and the reason for treatment for each tooth (27,28). Overall, 41 percent of all teeth indicated for treatment by at least one dentist received such an indication by the majority of dentists. There was a tendency for treatment recommendations supported by a larger proportion of dentists to be associated with caries, rather than restoration condition, suggesting that agreement for identificationof caries requiring treatment was more consistent than agreement for restorations needing replacement for mechanical reasons. A similar study, also of British dentists, focused only on decisions to restore carious teeth (17). From visual examinations of extracted teeth, between 0 and 46 percent of surfaces were indicated for restoration by the 86 examining dentists. From radiographs, between 6 percent and 50 percent of surfaces were so indicated. Ten Scottish dental educators showed a greater than fourfold range (six to 27 teeth) in decisions to recommend restorations for 30 extracted teeth with possible occlusal decay (29). When decisions to seal teeth for which restorations were not recommended were also considered, the range was from 18to 27 interventions for the 30 teeth. Scottish dentists in the General Dental Service indicated no majority consensus on thresholds for treatment based on radiographic lesion depth (30). An additional study yielded similar information about the extent of variation among dentists in decisions regarding the initiation of treatment, although the information did not stem from direct comparison between dentists (31). Treatment received over a three-year period in a British population was identified for teeth determined be carious at a baseline epidemiologic examination. Although all of the patients had one or more courses of treatment during the three-year period, 44 percent of teeth classified as carious at baseline were not treated during the subsequent three years. In addition, when compared to thenumber of teeth deemed carious at baseline that subsequently received

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treatment, three times as many teeth deemed sound at the baseline examination received treatment. Finally, a similar variation in mean number of decisions to treat individual teeth was reported among Finnish clinical dental educators (15). Because there are no widely accepted objective criteria for restoration conditions, there are also no standards for "restoration failures." One study of restoration replacement was based on examinationsof 13 extracted, restored teeth without clinically or radiographically detectable caries (32). Variation among 62 dentists in decisions to replace the existing restorations was substantial, with between 0 and 13 restorations indicated for replacement. Across all 13 restorations, 37 percent of all recommendations for treatment were minority recommendations, i.e., made by fewer than half of the dentists examining the teeth. In a similar study where teeth were carious in some instances, decisions to replace restorations exhibited more variation than did caries diagnoses, with a fourfold difference in replacement rates (16).The most frequently mentioned reasons for replacement (other than caries) are breakdown of the margin and fracture of the restoration. The subjectivity in detection of marginal discrepancies is illustrated by comparison of results from the epidemiologic determination of restoration acceptability

"Assessment of existing restorations is a crucial issue because their replacement constitutes a majority of all restorative treatment effort."

among Dutch adults, with reported reasons for restoration replacement in Scandinavian studies. In the Dutch study, 23 percent of restorations were deemed unacceptable, and 43 percent of those determinations were due to overhangs at the gingival margin (33). Yet overhangs were not cited frequently enough in Scandinavian studiesas a reason for replacement to merit separate mention, and all "other" reasons accounted for less than 10percent of reasons for replacement in these studies (21). Two additional studies furnish further evidence of substantial variation among dentists regarding decisions to intervene. In a study of randomly selected records of 37 volunteer general dentists, Bailit found substantial variation in amalgam replacement rates (34). After two years, some dentists had replaced 30 percent of two- and three-surface amalgams, while other dentists had replaced only 5 percent. In a study of the decisions made by seven dental consultants from two insurance carriers, Bailit found overall agreement rates for approval/denial of restorative procedures to be around .40, as measured by the kappa statistic (35).

Journal of Public Health Dentistry

Selection Among Treatment Alternatives Few reports have described dentists' selection of alternative treatments, given that a decision to intervene has been made. None have compared dentists' choices for specific teeth under clinical conditions. A single study reports variation in total treatment decisions for the patient, with treatment being quantified as standard fees (36). Two patients were examined by 16 and 15 Illinois dentists, respectively, with the range of total costs for recommended treatment being over fivefold for each patient. The principal source of the variation in both patients was associated with restorative treatment alternatives,both to restore existing teeth and to replace missing teeth. The author noted relatively little variation in decisions not to replace missing teeth. Analyses of claims data have been used to assess variations in patterns of restorative treatment in two studies. Grembowski found a tenfold difference between highest and lowest mean patient-service-provision rates for operative (nonprosthetic) treatment, and a fourfold range for the ten highest and ten lowest rates, among 200 general dentists in the northwest (4). These distributions were based on claims from a relatively homogeneous patient population, which was assumed to reduce possible influences of individual patient and plan variations on the distributions. Correlations between established treatment alternatives (e.g., crown vs three-surfaceamalgam) were not inverse, suggesting that selection of one restorative treatment from among alternatives is not necessarily constant across patients within a practice. Bailit found that the amount of variation among claims from 227 dentists in the northeast was also extensive (1).Variation in mean service-provision rates for common individual restorative services was as much as fortyfold among dentists. Variation in mean total servicesreceived per patient was on the order of fourfold. These serviceprovision rates were adjusted for differences in patient age as well as insurance deductibles and prosthesis coverage. However, there was no assurance that the patients seen by the dentists were similar in terms of sociodemographic characteristicsand clinical circumstances. Also, it should be noted that despite the magnitude of the variation, no testing was performed in these studies, or any cited earlier, to determine if such variation could occur by chance alone (37).

Factors Associated with Variation in Dentists' Decisions The extent to which variation in dentists' detection of caries, evaluation of existing restorations, and identification of damaged teeth are associated with characteristics of the dentist, the practice, and the patient is almost completely unknown. One study found that dentists graduating more than 25 years earlier tended to detect fewer carious lesions upon visual examination of mounted teeth than dentists with less experience,but that

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the difference was less when the same diagnoses were based solely on radiographs (1 7). While the fracture of a restoration usually can be established objectively, marginal breakdown is an extremely subjective detennination, and probably depends on previous training (12), economic factors (18), dentists’ expectations of acceptable performance of various types of restorative material (24), and dentists’ individual criteria and skills (38,391. This latter factor has received little attention, although there are indications that dentists’ abilities to detect marginal discrepancies (39), and the criteria for declaring them unsatisfactory (38) are far from uniform. Although dentists’ characteristics that are associated with decisions to intervene have not been studied directly, one study of Scandinavian dentists found that younger dentists were less likely to initiate treatment for caries confined to the enamel as visualized on radiographs (40), while a second study found no age association (41). This tendency among younger dentists toward conservatismin decisionsto initiate treatment isopposite that found in a British study where dentists in practice more than 25 years were less likely than their younger colleagues to initiate treatment for caries upon visual examination only, even though rates based on radiographic examination were not different (17). This latter finding is in agreement with a Scottish study where no associations were found between a variety of dentist characteristics and radiographically determined treatment thresholds (30).Reviews of records of 37 US general dentists indicated that the length of time amalgam restorations survived before replacement was highly variable, but not strongly associated with any measured technical factors, practice busyness, average patient income, or dentist age (34).The investigators suggested that differences were related to dentist preferences, or style. Several patient characteristics have been associated with decisions to treat. Among British adults, patients who changed dentists received twice as many restorations as patients who did not change dentists (42). A survey of US dentists indicated that they are more suspicious of restorations placed by other dentists (19), and this suspicion may account for some of the increase shown in the British study, which included treatment on previously untreated teeth, as well as on teeth with existing restorations. Also, from US claims data, patient profiles of services indicated that more services were provided in early courses of treatment with a dentist than in later encounters (43). Patient age has been shown to be associated with more aggressive treatment decisions based on lesion depth (30,44).Finally, in an epidemiologic survey of Dutch adults, the proportion of existing restorations classified as needing replacement by trained examiners was greater among older patients and patients who visited thedentist less frequently (33).Both of these factors are associated with the age of the restoration, which was a major determinant of amalgam replacement

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(21). A variety of studies offer some information concerning factors associated with the amount of restorative care provided to patients, an indicator that may be related both to assessmentsand decisions to intervene, as well as to selectionamongalternative treatments. Among British patients, there was a strong relationship between the number of filled surfaces at baseline and the number of restorations received over the next five years (45). The patients with more filled surfaces at baseline also tended to be younger and to have more teeth. They received more courses of treatment over the five-year period and received both more new restorations and more replacement restorations.The degree to which restorative needs were met was studied in a group of US adult males classified as having or not having intact dentitions (14 or more teeth on at least one side of the mouth) (46). Those subjects with intact dentitions had a greater proportion of their restorative needs met through restorativecare, as opposed to the alternative of needs being met through extractions or needs not being met. Finally, in the study of dentists in the northwest, dentist age and practice busyness were both inversely related to mean number of restorative procedures provided (47). A survey that requested dentists to identify and rank the three most important factors in selectingamong three sets of two alternative treatments found substantial variation among the specific factors ranked as most important, and among those ranked as one of the three most important (48). Two general observations were consistent across the three sets of alternative restorative decisions, however. First, the periodontal status of the tooth was either the first or second most common principal consideration, as well as the most commonly cited factor overall. Second, most dentists tended to rank technical, or clinical, factors as more important than patient factors. When included as independent variables in a regression on dentists’ rates of provision of various restorative procedures, these technical factors appeared to be less influential than dentists’ consideration of patient factors, particularly cost (49). Patient preferences may also be reflected more directly through the preparation of alternative treatment plans, as shown in a study of Tennessee dentists, where fewer than half of the patients received a single treatment recommendation (50). Typically, dentists reported providing a “best care” recommendation accompanied or followed by another set of recommendations, typically a cost-modified plan of treatment. The availability of dental insurance has been shown to influence the treatment dentists recommend. In a study using hypothetical, or simulated cases, the presence of increasingly liberal benefits led to nonlinear increases in cost of treatment recommended, but the strength and nature of the association varied substantially across the cases(51).Also,the vanationamongdentists’ recommen-

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dations for a given case was greater than the variation attributable to insurance benefits. Results of the Rand Health Insurance study suggest that increased benefits influence restorative treatment decisions primarily through receipt of treatment and the timeliness of treatment for caries detected at baseline (5233). Only a small effectfor provision of more costly treatment was noted, with no tendency toward overtreatment. The effect of insurance was quite pronounced on both the presentation and acceptanceof the ”best care” plan in the Tennessee study, however. Patients with insurance were more likely to receive a ”best care” recommendation as the primary treatment plan, and were more likely to accept that plan (50).This cost effect is reinforced by findings of an analysis of health insurance data from the National Medical Care Expenditure Survey. Lower patient copayments were associated with greater utilization of more costly restorative services (54). Finally, in the comparison of recommended treatment costs among Illinois dentists, mean costs were higher when dentists thought they would be reimbursed under fee-for-servicearrangements, compared to when dentists thought the patient was a member of a part of a prepaid capitation plan (36).

“The extent t o which variation in dentists, detection of caries, evaluation of existing restorations, and identification of damaged teeth are associated with characteristics of the dentist, the practice, and the patient is completely unknown.” Awareness of alternative treatments and, more specifically, knowledge of outcomes of care, are held to be strongly associated with variations in utilization of specific procedures in medicine (55).While this association could also hold for single-tooth restorative decisions, outcomes for most treatment alternatives are not well documented. Thus, individual beliefs are substituted for knowledge of outcomes, and differences in these beliefs among dentists undoubtedly explain some of the observed variation. However, dental sealant, arguably a restorativedental procedure, represents perhaps the only example in dentistry where both the outcome of care and provider knowledge and awareness of the procedure are well studied. Although general awareness of the procedure and specific knowledge of outcomes have been assumed to be important determinants in practitioners’ decisions to use this procedure (56,571, a recent national survey found that neither factor was associated with utilization in multivariate analyses where a variety of determinants were considered (58). A final suggestion of a source of variability in dentists’ choice of treatment alternatives, as well as decisions to recommend treatment, is found in reports describing the

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development of indices of oral health status. In studies where expert panels used paired-preference (59) and profile-ranking (60)approaches to determining an index score, caries and restoration status of the dentition did not emerge as important factors in overall ratings of oral health. Primary determinants were clinical factors with implications for long-term prognoses, such as periodontal disease and number and pattern of missing teeth. This result supportsdentists’ perceptionsthat periodontal status is an important factor in restorative treatment decisions (48). Discussion of the Available Information The available information supports the conventional wisdom that there is considerable variation in practitioners’treatment decisions.Reports describesubstantial variation in dentists’ assessments of clinical conditions, in their decisions to initiate treatment, and in their selections of the amount and type of restorative treatment to recommend. The methods, themselves, used to examine and report the extent of variation varied widely among the studies, as did the conditions under which dentists were asked to make their assessments. Thus, comparisons among studies are not possible, especially among studies examining different aspects of the decision process. Studies in several countries reported variation in diagnostic and treatment-provision rates, supporting other observations that variability is not strongly related to particular methods of financing and organizing the delivery of medical care (61). Although most of the evidence for variation in assessments of clinical conditions comes from studies of caries diagnoses, the absence of criteria for other clinical conditions suggests that even greater variation in identification of conditions may be occurring. Logically, variation in decisions to initiate treatment will stem from variation in assessments, but additional factors also seem to be involved, namely the patients’ previous experience in retaining teeth and receiving restorations, the longevity of the dentist-patient relationship, and the “ownership” of restorations being considered for replacement. To some extent, the fact that increased frequency of restoration replacements is associated with more teeth and more existing restorations may be simply a result of increased risk of restoration and re-restoration. However, the association may also reflect the practice styles of patients’ current and formerdentists, as well as the number of times the patient has changed dentists. The factors associated with variation in selection among treatment alternatives suggest that most dentists develop their principal treatment recommendations without considering many nonclinical patient factors, except reimbursement arrangements. Patient nonclinical characteristicsand preferences seem to be considered only after a principal recommendation has been formulated. Thus, clinical factorsand dentists’ pref-

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TABLE 1 Nature of Associations Reported in the Literature Between Dentist and Patient Factors and 3 Steps in Dentists’ Restorative Treatment Decisions ~~

Steps in Dentists’ Restorative Decision-making Process Factors

Assessment

Decision to Treat

Fewer conditions with greater age Imputed‘ Imputed

Mixed effects

Treatment Selection

Dentist factors Age Criteria and skills Training, preferences, style Practice busyness

Imputed More intervention with reduced busyness

Imputed

Patient factors Age

No. of existing restorations Age of existing restorations Operator for existing restoration, length of time in practice Frequency of visits

More suspicion of others’ restorations

Insurance coverage

Imputed

Periodontal status

More intervention with greater age More intervention with more restorations More intervention with older restorations More intervention with new patients, others‘ restorations More intervention for infrequent visitors More intervention with coverage Imputed

More costly treatment with coverage Imputed

‘Effect of the factor not identified, or factor not preasely defined.

erences probably drive most initial treatment decisions. Table 1 summarizes the factors for which associations have been found with dentists’ assessments,intervention decisions, and treatment selections. The number of factors that have been explored is not large, and few conclusions can be reached about the influence of these factors because, in most instances, each has been investigated in one, or at best, a few studies. Also, study designs and samples seldom permit comparisons, and external validity is problematic both in studies using simulated cases and in studies performed in an era of different materials and caries rates. Because many of the studies in which these factors are identified have been based on insurance data or record reviews, comparisons of dentists’ “decisions” are often based on practitioners’ overallprocedure provision rates, rather than on assessment, intervention decision, and treatment selection for specific patients. Thus, many of the associationsin Table 1are listed in the intervention decision category, even though the comparison inevitably also reflects the effects of the factor on assessment and selection processes. The inability of many of the reports to specify precisely which step in the treatment-decision process is influenced by the factor studied is a major barrier in attempts to understand the process. For example, associations hypothesized between dentists’ treatment preferences and service provi-

sion rates (49) may be masked by differences in the assessment process (e.g., criteria for evaluating tooth damage are not the same among respondents) or in the intervention process (e.g., a patient‘s periodontal status affectsdecisionsto intervene to a varying degree depending on practitioners’ expectations for tooth longevity), even if the practitioners are treating patients with similar clinical conditions. As suggested at the beginning of this review, the examination of dentists’ treatment decisionsand the factors associated with those decisions is in its infancy. The profession is not sophisticated in its methods of measuring dentists’ decision-making processes. Two reasons may account for much of the profession’s lack of progress: the difficult access to decision making in the relative isolation of dentists’ offices, and the lack of any knowledge of comparativeoutcomes for most dental treatment, which fosters the assumption that all alternatives are appropriate and reduces concern over variation among dentists. That so little is known about the distributions of decisions and their variation among practicing dentists, let alone the reasons for the choices, is a powerful reminder that the dental profession has tended to deal with the issue by assuming that it is best left to the individual practitioner. It would seem advantageous to abandon this assumption and begin to examine practitioners’

Journal of Public Health Dentistry

108 FIGURE 1 Proposed Explanatory Model of Dentists' Restorative Treatment Decisions ~~

Personal

Dentist Factors Practice

Enining M I S

I

preferences expeirences

busyness scale/personnel lab arrangements equtpment

I

Patient Factors Clinical Conditions Other Condifions caries

Chief complaint

cane5 risk fanor3 resforalion risk faders IraR~m rlsk factors

lnSuranCB BtatUS

arch Integrity functional status periodontal status

utilization history practice history preferences

age SOCioeCOnomiC status

treatment decisions in earnest. A Proposed Model of the Decision Process A model would be useful for helping structure the further investigation of factors associated with dentists' treatment decisions. Grembowski (48) has suggested using Starfield's model of medical practice (62),in which both structural and process factors, including both patient and provider considerations,are seen as influencing outcomes. In this model, one can visualize the broad range and interaction of structural, environmental, and patient factors influencing both "provision of care" and "receipt of care." However, the model offers little guidance in describing the decision-making process, or specific factors that influence decisions. Eisenberg has framed the investigation of physicians' practice patterns as sets of factors influencing each of three motivations influencing physicians' treatment behaviors (63). These sets of factors in turn each suggest a set of definable independent variables to be explored in both cross-sectional and longitudinal investigations of dentists' treatment decisions. Drawing from both the Starfield model and Eisenberg's motivations and factors, as well as the utilization literature (64)and the meager information from the studies reviewed here, we suggest that the conceptual model outlined in Figure 1could prove useful in guiding subsequent investigations of dentists' restorative decisions. The model treats the three steps of assessment, decision to treat, and selection of treatment as separate elements in the decision-makingsequence.Anecdotal information from informal discussions with practitioners indicates that these steps are often compressed--e.g., a deteriorated amalgam restoration is immediately visualized by an examining dentist as needing a crown. This tendency

to skip steps in a model of the decision making process was noted in an earlier examinationof dentists' treatment planning (65).Nevertheless, it is useful for purposes of explication of the process and design of subsequent interventions to consider the steps in the decision model separately. In this simplisticconceptualization,a variety of dentist and patient factors are shown as generally influencing the decision-makingprocess. More precise identification of which factors affect which steps must await further investigations.All of the factors listed were identified by studies reported in the preceding review, although often in the discussion section of the report, rather than in the results. In many instances, individual dentist and patient factors listed in the model represent groups of conceptually or empirically related measures. For example, "restoration risk factors" might comprisemeasures of current conditions found to be associated with replacement decisions, such as restoration integrity, margins, contours, and color, as well as the identity of the operator, the age of the restoration, and the patient's previous experience under similar circumstances. Some factors listed, such as socioeconomic status, insurance status, and utilization history, are familiarelementsin existing models of dental services utilization that explain events preceding and following the restorative decision-making process (64,66).The factors are included in this model because they are known, or expected, to affectdentists' intervention decisions and treatment. We acknowledge that this model lacks a definitive theoretical structure to support the proposed relationships. This has been the norm for explanatory research into variation in practice patterns, which has been largely empirical with reliance on simple assumptions concerning the processes involved and their order of occurrence. Decision-analytic theory is used to support portions of some current models of practice variation, with uncertainty about outcomes cited as an explanation for observed variation (55). A different theory of cognitive development in medicine, illness scripting, suggests that among experienced physicians, the approach to diagnosis and to selection of treatment is less likely to be an ordered, analytical process than a rapid recognition of previously encountered conditionsand subsequent decisions (67).According to this theory, because "physicians' experiencesare idiosyncratic, it is not surprising that it is difficult to achieve consensus among experts" (67).Elements of both decision analysis and illness scripting are represented in the proposed model through training and previous experience factors. The model is intended to be an explanatory model that represents factors associated with individual dentists' decisions concerning individual patients. Thus, some structural or environmental factors that exert a fairly uniform effect over all patients and practitioners in an area are excluded, such as community fluoridation status

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or local market conditions. Others, such a s practice busyness and practice scale, are treated simply as additional dentist descriptors. Finally, the model represents only a dentist’s initial decision-makingprocess. It is the fruits of this process that are presented to the patient as the dentist’s recommendations. Depending on the circumstances, these recommendations may be accepted, or a negotiation process may ensue. That process may well depend on many of the same factors, but sufficient additional influences also may be active to suggest that an expansion of this model would not be appropriate (66). If the model is to prove useful in furthering our understanding of dentists’ restorative treatment decisions, the task is to refine and define the lists of factors, and to identify the relationships between specific influencing factors and specific steps in the decision-makingprocess. Importance of Understanding Dentists‘ Treatment Decisions Three types of benefits would accrue from a better understanding of these dentists’ restorative treatment decisions. First, simply by gaining knowledge of the distribution of relatively common decisions and the factors that influence these distributions, it would be possible to predict the intensity and mix of restorative treatment that dentists would provide to a population, using only field examinationand interview data from a sample of these patients. Thus, professionally defined treatment needscould be determined from epidemiologic examinations, a translation that is not possible now (6,623). Such treatment needs estimates would be useful in program and personnel planning as well as in programevaluation. Second, an understanding of the factors dentists currently incorporate in their decision processes will be useful in identifymg inappropriate decision-making behaviors. As noted in examinations of physicians’ decisions, “uncertaintybiases, errors, and differences of opinions, motives, and values weaken every link in the chain that connects a patient’s actual condition to selection of a diagnostic test or treatment” (69). In medicine, the wide variation in the type of treatment used for a clinical condition has been explained by a combination of appropriate and inappropriate treatment decisions (5). Moreover, inappropriate treatment has been linked to adverse health outcomes (70). It is likely that a similar situation exists in dentistry, with the variation noted in dentists’ decisions leading to some degree of inappropriate care, with suboptimal economic and health outcomes. Third, the assumptions upon which many treatment decisions are based-i.e., the reasons certain factors are associated with treatment decisions-represent hypotheses urgently in need of testing in dental practice. Although the studies in this review did not address these assumptions directly, many of the decisions to initiate treatment, and many of the choices among alternative treatments, stem from firmly held, but essentiallyunsub-

stantiated, beliefs concerning the superiority of one material over another, or the inevitability of an adverse outcome under certain circumstances. Most of these assumptions have not been tested in controlled clinical trials or, perhaps more importantly, in more realistic demonstration projects in dental practice (71).For example, the long-cherished assumption that cast restorations enjoy markedly superior longevity seems challenged by a review of several studies of restoration longevity (72). Thus, a careful review of the assumptions or factors upon which treatment decisions and choices are based should direct thedevelopment of a hierarchy of needed outcome assessments within dentistry. Those assumptions that drive the greatest number of decisions and for which the least objective support is available would merit the earliest examination and testing. Dentistry is plagued by the lack of knowledge of comparative long-term outcomesof the treatments it provides. Such an ordered approach to the development of knowledge of outcomes is long overdue. The dental profession has approved a plan to establish parameters of care that define boundaries of acceptable dental care (7). The development of parameters will be based on these unproven assumptions in the absence of better information. Thus, it is essential that the assumptions needing examination be identified through studies of dentists’ treatment decisions. Examinationsof the efficacy, effectiveness, and cost effectiveness of the treatments, as well as the appropriateness of dentists’ treatment decisions must be components of the profession’s approach to maintaining the quality of care in the future (73). References 1. Bailit H, Clive J. The development of dental practice profiles. Med

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