Laboratorial method proposal to obtain caries-affected dentin

Author(s)

Cynthia Soares de Azevedo

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Odontologia (FO/SDO)
• Defense date: 2012-06-14

Examining board members

Adriana Bona Matos; Maria Aparecida Alves de Cerqueira Luz; Ricardo Scarparo Navarro

• Advisor: Adriana Bona Matos

Abstract

The aim of this in vitro study was to validate a protocol for obtaining standard caries affected-dentine by dentine demineralization process induced by Streptoccocus mutans biofilm (microbiological approach). Validation methods performed were optical coherence tomography (OCT), visual inspection, laser fluorescence and digital radiography. As all methods were nondestructive, all analysis were performed in the same specimens. A total of 48 human molars (24 erupted and 24 unerupted) were grounded in the occlusal surface to remove enamel and obtain a flat dentin surface. The roots of the teeth were removed and the specimens were cut in the bucco-lingual direction yielding two fragments that were randomized into experimental groups. The dental fragments were protected with acid resistant varnish in half of the occlusal surface (control) and in the other half was produced carious lesions. The experimental groups were composed from two variation factors: period of cariogenic challenge (7, 14 and 21 days) and type of dentin (from erupted or unerupted teeth). Thus six experimental groups were formed: with dentin from erupted teeth - G1 (7 days of cariogenic challenge), G2 (14 days), G3 (21 days), and with dentin from unerupted teeth - G4 (7 days), G5 (14 days) and G6 (21 days). After different periods of cariogenic challenge, the specimens were evaluated on their healthy and caries-affected portions using different diagnostic methods and the results were compared. Visual inspection proved the formation of caries affected dentin as characteristics of the tissue as yellowing, loss of surface gloss and consistency elastic were observed. The digital radiography was able to detect the presence of radiolucent image, suggesting caries. Three calibrated examiners viewed all the images obtained by visual inspection and digital radiography, and were able to distinguish healthy from caries affected dentin. We used the Fisher exact statistical test with a significance level of 5% which confirmed no difference between groups in both visual inspection (G1 and G4 - p=0.6; G2 and G5 - p=1 and G3 and G6 - p=1) and digital radiography (G1 and G4 - p=1, G2 and G5 - p=1 and G3 and G6 - p=1). Both laser fluorescence values and depth of demineralization (OCT) were subjected to statistical test Analysis of Variance (ANOVA) (p<0.05). Regarding the values obtained by laser fluorescence, a statistically significant difference can be observed for the factor type of substrate (p=0.001), with the erupted teeth specimens with higher fluorescence compared to specimens from unerupted teeth. For OCT, we can observe that there was no statistically significant difference for the factor type of substrate (p=0.163), for the factor length of cariogenic challenge (p=0.512) and interaction between factors (p=0.148). Finally, photomicrographs were obtained by scanning electron microscopy which confirmed the presence of caries affected tissue produced artificially at all demineralization times tested, however a more uniform demineralization surface was observed in caries affected dentin of unerupted teeth. Thus, we conclude that 7 days of cariogenic challenge is sufficient to obtain standard caries affected dentin to be used in laboratory tests and unerupted teeth provided a more suitable substrate for use in this proposed protocol. (AU)

• FAPESP's process: 10/12910-3 - Laboratorial method proposal to obtain caries-affected dentin
• Grantee: Cynthia Soares de Azevedo
• Support Opportunities: Scholarships in Brazil - Master