Redha, Ola A H; (2023) In-vitro evaluation of peroxide-based tooth whitening agent on the physical, chemical and cellular properties of teeth. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The present in vitro study aimed to evaluate the effects of carbamide peroxide (CP) at concentrations of 5%, 10%, and 35% on dentinal collagen structure, chemical and mechanical properties, and dental cell viability. Teeth were exposed to CP gel for 2 or 4 hours daily for 1 or 2 weeks. Changes in tooth shade were measured using a Spectroshade. Collagen scaffold models and demineralized dentine disc samples were prepared and exposed to CP droplets, and mineralized dentine disc samples were analyzed post-bleaching using Raman spectroscopy and Vickers hardness. Dental pulp stem cells and gingival fibroblast cells were evaluated for changes in morphology and viability after exposure to CP gel or hydrogen peroxide. The results showed that tooth shade changed significantly with 10% and 35% CP/4-h groups having the greatest change. Collagen scaffold models showed gelatinization most severe with 35% CP exposure, indicating that CP freeradical by-products can disrupt collagen's quaternary structure. Demineralized discs also displayed a glassy amorphous layer after exposure. Raman spectra of mineralized dentine discs after CP exposure showed a significant decrease in the integrated area of amide I and amide III values. Tooth hardness was reduced with the 35% CP group showing the most significant reduction. The measurement location nearest to the exposure site was the most affected. Human dental pulp stim cells (HDPSCs) and Human gingival fibroblast cells (HGFCs) viability decreased over time for all groups. The study concludes that even low concentrations of peroxide agents result in deleterious changes in dentine collagen, compromising the physico-chemical properties of teeth and cell viability. Long-term implications on tooth longevity should be observed in-vivo for a potential reversal of changes. These findings raise questions about the safety of tooth-whitening agents and suggest a need for further research into the effects of peroxide agents on dentinal collagen and tooth longevity.

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