The Impact of Enamel Microdamage on Tooth Appearance

Objectives: This study aimed to investigate the influence of enamel microdamage (acid or physically derived) on tooth appearance in vitro.
Methods: Two aspects of tooth appearance (stain accumulation and gloss) were studied, and four sets of experiments performed on polished bovine enamel blocks with acid damage or physical damage (microcracks or microabrasions). Staining with acid damage was studied by acid etching enamel blocks with 1% citric acid (pH = 3.6) and exposing the blocks to acidic or neutral stain solution. The final microhardness was recorded to reflect the damage levels. Staining with physically damaged enamel blocks was studied with natural cracks or induced microscatches, and specimens were exposed to a neutral stain solution. In both experiments, ΔW was evaluated by measuring the L*, a*, b* values before and after staining. In separate experiments, the surface roughness and gloss values were measured on acid etched enamel blocks (1% citric acid, pH = 3.6) or, in another study, the enamel surface with microscatches and compared to sound enamel.
Results: The presence of initial erosive damage and acidic stain solution led to decreased hardness and increased staining (~180HK, ΔW~8.2), which demonstrated that more acid damage led to higher stain accumulation. Enamel blocks with microcracks or microabrasions also exhibited a higher propensity for staining (ΔW~17.5) than sound enamel (ΔW~10) . Microdamage was also found to impact the gloss of enamel. The value of surface gloss decreases with increasing enamel acid damage (99GU - 32GU), and microabrasions roughen the enamel surface reducing gloss value (111GU - 51GU).
Conclusions: Enamel microdamage (acid or physically derived) acts as entry points for stain penetration and accumulation, while also causing a loss of gloss and shine, therefore directly impacting tooth appearance.