Behaviour of primary incisor caries: a micromechanical study

Area of Science:

• Dental research
• Materials science
• Biomaterials

Background:

• Smooth-surface carious lesions in primary teeth are common and pose clinical challenges.
• Previous research has not assessed the micromechanical properties of entire carious lesions in primary teeth.

Purpose of the Study:

• To characterize the hardness and modulus of elasticity across smooth-surface carious lesions in primary incisors.
• To understand the impact of caries on the mechanical integrity of primary tooth dentine.

Main Methods:

• An in vitro micromechanical study was performed on carious primary incisor teeth.
• Ultra-micro-indentation was used to measure hardness and elastic modulus in hydrated carious and sound dentine from the pulpal region to the tooth surface.

Main Results:

• Carious dentine exhibited significantly reduced hardness and modulus of elasticity compared to sound dentine.
• Median hardness decreased from 0.28 GPa (inner) to 0.01 GPa (surface) in carious dentine.
• Median modulus of elasticity decreased from 5.98 GPa (inner) to 0.12 GPa (surface) in carious dentine.
• A notable increase in hardness and modulus of elasticity was observed in the outermost 300-500 microm of the carious lesion.

Conclusions:

• The carious process detrimentally affects the mechanical properties of primary incisor dentine, increasing the risk of restorative failure.
• The observed increase in mechanical properties at the lesion surface suggests enhanced mineral content, potentially indicating remineralization.