Histological and microhardness evaluation of early artificial carious lesions in human and bovine enamel: in vitro study

Allan Kenji Masuda,Mayra Fidelis Zamboni Quitero,Maria Aparecida Alves Cerqueira Luz,Luciana Cardoso Espejo-Trung

doi:10.14295/bds.2013.v16i4.929

Abstract

Objective: Early carious lesions in bovine and humanenamel developed in vitro using a pH cycling regimenwere compared. Material and Methods: Fifteencentral bovine incisors and fifteen recently extractedhuman third molars were randomly divided into twogroups: ten for the cross-sectional microhardness test(MT) and five for polarized light microscopy (PLM)analysis. Enamel blocks measuring 5 x 5 mm weremade from the buccal face of the teeth. The blocksused for the MT were sliced into two halves: “A” and“B”. “A” slices were embedded in acrylic resin, withthe face of the dentin-enamel junction left exposedfor the MT prior to pH cycling. “B” slices and wholeblocks were coated with acid-resistant varnish,except a 3 x 3 mm central window, and submitted tothe pH cycling regimen (demineralizing solution for3 h and remineralizing solution for 21 h) over fiveconsecutive days. The “B” slices were then submittedto the MT and the whole blocks were processed forthe PLM study. Results: The PLM analysis revealedshallow, extensive lesions in the bovine enamel,hardly showing the superficial, dark and translucentzones, as well as deep cavity lesions in the humanenamel, with the body of the lesion and the darkzone evident. The MT revealed a significant decreasein microhardness in the superficial levels of thebovine enamel caries and at all depth levels of thehuman enamel caries. Conclusion: The pH cyclingregimen adopted led to the development of deeperand more demineralized carious lesions in humanenamel than bovine enamelKeywordsDental caries; Dental enamel; Microhardness tests; Polarization microscopy.

Highlights

The crystals of human enamel are densely packed and arranged in rods extending from the dentin to the enamel surface
The pH cycling regimen simulates the development of carious lesions in vitro, alternating pH solutions, which is similar to what occurs in the demineralizing and remineralizing processes in the oral environment [16]
PH cycling led to the development of early carious lesions in bovine enamel, using the same methodology described by Featherstone (1996) [17] and modified by Gama-Teixeira (2007) [18] and Argenta, Tabchoury and Cury (2003) [9] for human teeth

Summary

Introduction

The crystals of human enamel are densely packed and arranged in rods extending from the dentin to the enamel surface. The demineralization of human enamel in early carious lesions leads to more superficial mineral deposition than inner sub-surface mineral deposition. Cross-sectional microhardness tests are used to evaluate specific changes in mineral content at different depths in carious lesions [10].

Results

Conclusion