Removal of Infected Dentin Guided by Carious Dentin Hardness Testing

Objectives: A hardness testing system for measuring carious dentin, “Cariotester” (SaneiME Corp), is a portable devise for determining Knoop hardness (KHN) based on indentation depth. This study compared removal of infected dentin by dental students and dentists, using a Cariotester.
Methods: The subjects were seven students and seven dentists. Before the experiment, both dentists and students were taught the proper use of the Cariotester, and practiced with it. Extracted human teeth with carious dentin were selected and the superficial enamel removed with a diamond bur. Students and dentists measured the indentation hardness, before carious dentin removal (Control), after carious dentin removal guided by unaided direct subjective observation (A group), and after carious dentin removal guided by a caries detecting dye following A (B group). These operations used (i) only an excavator, and (ii) both round bur and excavator. Ten sites in carious dentin were tested by each operator. Data were evaluated by two-way ANOVA and Fisher’s PLSD test (p<0.05).
Results: The mean values of indentation depth (KHN) for each group were as follows. Control; (i) Student: 224.0µm, Dentist: 223.1µm, (ii) Student: 212.0µm, Dentist: 210.1µm (too soft to convert to KHN), A group; (i) Student: 66.7µm (7KHN), Dentist: 34.2µm (18KHN), (ii) Student: 47.3µm (11.5KHN), Dentist: 29.3µm (23KHN), B group; (i) Student: 35.3µm (17.5KHN), Dentist: 26.1µm (27KHN), (ii) Student: 29.4µm (23KHN), Dentist: 23.3µm (32KHN). There were significant differences between dentists and students, and between caries-removal methods, with no interactions.
Conclusions: The goal for removal of infected dentin is 20KHN or higher. Dentists removed significantly more infected dentin than did students when guided by unaided observation. However dentists also had difficulty in judging when uninfected dentin had been reached, and infected dentin removal was significantly improved by using the caries detecting dye. Use of a round bur removed significantly more infected dentin than use of an excavator alone, and can decrease any remaining infected dentin.