The Effect of Carbamide Peroxide (CP) Whitening Agent on Tooth Vitality

Objectives: To evaluate the impact of CP whitening agent on the tooth viability by focussing on the dentinal collagen matrix nativity and the dental pulp and gingal fibroblast cell survivability.

Methods: Intact extracted teeth were assigned to different time-dependent whitening protocols 2& 4 hours groups using 5,10& 35%CP. The experimental protocol was designed to duplicate the conditions of standard whitening clinical application. The impact of CP on dentinal collagen was characterised spectroscopically by, mechanically by Vickers Hardness and structurally by Electron Microscopy. Cell viability assay (GFs : Gingival Fibroblasts & DPCs: Dental Pulp Cells) when exposed to CP was performed using an in-house perfusion model mimicking tooth anatomy
Results: Following tooth whitening protocol, the relative intensities of dentinal collagen Amide I & III bands were greatly reduced for the 35% when compared with to a lesser extent for the 5% and 10%. A gradient of apparent denaturation could be observed from the buccal side (exposure to CP) to the lingual side (not exposed). This apparent denaturation of the internal collagen structure was supported histologically and confirmed by hardness reduction of the dentine. Finally, DPCs and GFs survivability was increasingly reduced as function of CP exposure after short time exposure (<2hrs).

Conclusions: Within the limit of this in-vitro studies, significant correlations were found between the concentration of CP, its application time, and its effect on dentine structure and the survivability of relevant dental cells.