Microhardness and cutting resistance in enamel of primary molars among various caries experience groups in vitro

Abstract

Introduction: The differences in each child's caries experiences due to the different individual's enamel properties have not been well established. Objective: To investigate cutting resistance, microhardness, and their correlation with primary teeth enamel from different caries experience groups in vitro. Methods: Forty-five extracted primary molars were collected. They were divided equally into three groups using the dmft/dmft+DMFT index; low, moderate, and high caries experience groups. Each tooth was divided into 2 parts for testing cutting resistance and microhardness. The buccal part was mounted on stainless steel rod equipped with strain gauge devices for testing cutting resistance. The enamel surface was set to define the same amount of the enamel to be cut by airotor handpiece with a new diamond bur mounted on a constant speed stepping motor. The lingual part was tested with a Vickers microhardness tester. All data were compared statistically among various caries experiences using one-way ANOVA. The correlations were investigated using Spearman's and Pearson's correlation. Results: High caries experience group had significantly lower microhardness enamel (295.8 ±12.73 VHN) than the moderate and low caries experience groups (315.01±16.13 VHN and 325.96±9.91 VHN, respectively). The cutting resistance of enamel from the high caries experience group (87.23±15.06 grams) was also significantly less than those from moderate and low caries experience groups (112.78±16.02 grams and 111.67±24.75 grams, consecutively). There were negative correlations between caries experience and cutting resistance (r = -0.46) and between caries experience and microhardness(r = -0.71) but a positive correlation between cutting resistance and microhardness (r= 0.39). Conclusion: Enamel of primary teeth from the high caries experience group had less microhardness and cutting resistance than moderate and low caries experience groups. Further investigation is required to correlate other enamel physical properties with caries experience in both dentitions.