INTRODUCTION

The diagnosis and treatment of primary dental caries are common procedures in general dental practice and are topics of extensive research.^1,2 Small-scale studies have shown that substantial variation exists among clinicians in restorative treatment thresholds.^3-8 At present, the only thresholds that can be definitely identified as inappropriate are those that call for surgical treatment when noncavitated caries is confined to enamel, because of the potential for enamel lesions to arrest or reverse.⁹

Previous studies by the Dental Practice-Based Research Network (DPBRN) and Dental PBRN Japan (JDPBRN), which included practitioners from the United States, Scandinavia, and Japan, revealed substantial variation among dentists in restorative treatment thresholds based on radiographic interproximal lesion depth. When the interproximal cavity is located in the enamel, findings for intervention proportions were as follows: Scandinavia, 0%-21%; the United States, 40%-75%¹⁰; and Japan, 47%-74%,¹¹ depending on patients' caries risk status on various clinical scenarios.

Regarding occlusal enamel carious lesions, several studies using a series of clinical photographs of the occlusal surface of a mandibular first molar have documented wide variation in the proportion of dentists who would intervene surgically into enamel when the caries is located in the inner half of the enamel: for adult patients, 6% in Sweden,⁴ 3%-8% in Scandinavian countries, and 63%-77% in the United States.¹² These results show that the treatment thresholds of occlusal primary caries differ among populations. However, no studies conducted in Japan have quantified differences in dentists' treatment thresholds for occlusal carious lesions, nor have they investigated differences between adult and pediatric patients.

The purposes of this study were to 1) quantify Japanese dentists' restorative treatment thresholds for occlusal primary caries; 2) determine if patient's age affects dentists' decisions to surgically treat these carious lesions; and 3) test the hypothesis that patients', dentists', and practices' characteristics are significantly associated with surgical enamel intervention.

METHODS AND MATERIALS

Hypothetical Scenarios With Clinical Photographs and Patient Background Data

Participants indicated their treatment decision from options presented for cases described in the questionnaire. A series of four clinical photographs of the occlusal surface of a mandibular first molar, together with a description, were presented portraying increasing depths of cavitation (Figure 1). We inquired about the treatment decision for each case with high caries risk under two different patient age scenarios (30 and 12 years old). The exact wording of each case scenario is provided in Figure 1. The same photographs showing occlusal surfaces with increasing caries severity were used in previous studies with the following descriptions: Case 1 had a white or discolored enamel surface, no cavitation. No radiographic signs of caries. Case 2 had minor loss of tooth substance with a break in the enamel surface or discolored fissures with gray/opaque enamel and/or caries confined to the enamel. No radiographic signs of caries. Case 3 had moderate loss of tooth substance and/or caries in the outer third of the dentin according to the radiograph. Case 4 had considerable loss of tooth substance and/or caries in the middle third of the dentin according to the radiograph (Figure 1).^4,12,15 Cases 1 and 2 were enamel lesions located in the outer and inner enamel, respectively. Cases 3 and 4 were dentin lesions located in the outer and middle thirds of the dentin.^4,12,15 For each case and each scenario, the respondent provided treatment codes in a “check all that apply” format (see Figure 1).

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RESULTS

Demographic Information of Participants

Questionnaires were distributed to 282 dentists; 189 (67%) were ultimately collected. Demographic characteristics of study participants are shown in Table 1.¹¹ The mean number of years elapsed since graduation from dental school was 18.5 ± 9.9; participants were predominantly male (n=154, 82%). Race/ethnicity was almost entirely Asian (n=186, 99%). With regard to type of practice, 41% (n=77) of participants were employed by another dentist. Regarding practice busyness, 40% (n=72) of dentists were able to provide care to all, but the practice was overburdened, while 33% (n=59) provided care to all, but the practice was not overburdened. Most dentists (n=159, 84%) used a dental explorer to diagnose primary occlusal caries. The percentage of patients who self-pay was 9%.

Table 1:  Distribution of Dentists', Practices', Patients', and Dental Procedures' Characteristics of Participants (Kakudate and others, 2012)¹¹

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Treatment Thresholds

Table 2 shows the distributions of treatment recommendations. In the adult-patient scenario, the percentage of participants who would perform surgical treatment decreased in the following order: case 4 (98%) > case 3 (76%) > case 2 (48%) > case 1 (14%). The same order was reported in the pediatric model: case 4 (97%) > case 3 (65%) > case 2 (34%) > case 1 (9%).

Table 2:  Distribution of Treatment Options Chosen by Dentists for Cases 1 Through 4 for Adult and Pediatric Patient Scenarios

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In case 2, the percentages of participants who would perform surgical treatment for adult and pediatric patients were 48% (n=88) and 34% (n=63), respectively, and 76% (n=140) and 65% (n=121) in Case 3. The proportion of dentists who indicated surgical intervention was significantly higher for the adult patient model than for the pediatric patient model in both case 2 (p<0.01) and case 3 (p<0.05).

Factors Affecting the Decision to Intervene Surgically in Occlusal Inner Enamel Lesions

The results of the multiple logistic regression analysis are shown in Table 3. In the case 2 adult patient model, three factors were significantly associated with the decision to intervene surgically in enamel (odds ratios [95% CI]): type of practice 0.26 (0.11-0.62), percentage of patients who self-pay 1.04 (1.01-1.07), and practice busyness 3.72 (1.05-13.19). In the case 2 pediatric patient model, two factors were significantly associated with dentists' decision to intervene surgically in inner enamel (odds ratio [95% CI]): type of practice 0.38 (0.15-0.93) and using a dental explorer for a primary occlusal caries diagnosis 8.32 (1.84-37.71).

Table 3:  Factors Affecting Dentists' Decision to Intervene Surgically Into Inner Enamel Lesions According to Patient's Age^a

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DISCUSSION

In this study, most dentists chose not to restore an enamel lesion in the absence of dark brown pigmentation (as shown in case 1). Approximately one-third to one-half of participants chose to intervene surgically when the image pictured minor loss of tooth substance with a break in the enamel surface or discolored fissures with gray/opaque enamel (case 2) and most dentists (two-thirds to three-fourths) when the image pictured moderate loss of tooth substance and/or caries in dentin (case 3). Almost all participants chose to intervene surgically when considerable loss of tooth substance with caries involving dentin was visible (case 4).

In the presence of enamel surface integrity, caries lesions present in the enamel and/or dentin can be managed via remineralization therapies,^18,19 although the extent of remineralization is limited by the caries risk of the individual environment, as explained in the concept of caries balance.^20,21 Consensus has been reached regarding the potential for noncavitated enamel lesions to reverse, and the restorative intervention of noncavitated caries confined to enamel is inappropriate.⁹ Therefore, the authors think interventions to the enamel lesion shown in case 1 and 2 are not necessary.

According to the result of the same scenario survey (N=519) by US DPBRN,¹² the percentage of dentists who indicated surgical treatment in patients with high caries risk in cases 1, 2, and 3 were 25% (n=129), 77% (n=394), and 94% (n=482), respectively. However, in that study, subgroup analysis revealed that almost all dentists in Scandinavia chose not to restore lesions that were limited to enamel; restorative treatment was indicated predominantly for occlusal surfaces that involved dentin. A previous study in Scandinavia reported a similar finding.⁴ Given these reports, the Japanese dentists' treatment thresholds may be said to fall somewhere between US and Scandinavia levels. The current treatment strategy in Scandinavia is based on the diagnosis of caries activity, identification of the main causal and predisposing factors in individual cases, and assessment of caries risk.¹² This Scandinavian situation is a result of dental school education about cariology, current restrictive criteria for placement of the first restoration in Scandinavian dental practices, and high and predictable recall frequency among Scandinavians.^12,22

Results of multiple logistic regression analysis suggested that type of practice, percentage of patients who self-pay, practice busyness, and using a dental explorer for primary occlusal caries diagnosis were significantly associated with the decision to intervene surgically in an enamel lesion (case 2). A previous study by the US DPBRN using the same scenario also revealed that decisions to intervene surgically were associated with type of practice.¹² Further, usage of a dental explorer was associated with decisions to intervene surgically into proximal enamel carious lesions.¹¹ Taken together, these findings suggest that further dissemination of information on the appropriate use of dental explorers may help reduce surgical intervention into enamel.

In general, practitioners may treat patients who do not follow directions fully and who may not return for several years, thereby making a remineralization approach less effective.^20,21 That may be the reason why dentists feel hesitant to take a nonsurgical approach with patients, exemplified by the 12-year-old patient scenario. However, in the present study, the proportion of dentists who indicated surgical intervention into enamel was significantly higher for adult patients than for pediatric ones. Elderton's empirical work about the restorative cycle may underly why the profession is concerned about the adverse effects of intervening surgically before it becomes necessary.²³ Previous studies suggested that dentists intervened earlier in adult patients than in pediatric patients^24,25 in the 1980s. In addition, in the early 1990s, the concept of minimally invasive dentistry advanced rapidly.^26,27 Therefore, it is possible that the participants believed that delayed surgical intervention among pediatric patients may improve first molar longevity.

This study featured a relatively wide variety of participants, with respondents hailing from all over Japan. The age and gender distribution of this study sample was similar to the actual distribution in Japan,²⁸ thereby enhancing the generalizability of the findings. However, the study findings should be evaluated with caution. First, participants were not selected by random sampling. Second, given the cross-sectional nature of our study, causative relationships between factors and use of an enamel-based surgical treatment threshold were difficult to assess. Lastly, a clinical photograph and a patient scenario cannot replicate all of the nuances that can be perceived in a real tooth and a patient caries risk status; we therefore cannot state with certainty that the decision-making context provided by this questionnaire entirely duplicated the real-world clinical context.

CONCLUSION

More than one-third of the participants chose to intervene surgically into occlusal enamel. The translation of research findings to clinical practices is a complex matter.^29,30 In an effort to improve dentists' clinical decision-making regarding occlusal enamel intervention, results of this study will be communicated to dentists, and the effect of this dissemination will be evaluated for its impact on routine clinical practice.