Acceleration of Enamel Subsurface Lesion Remineralisation by Intralesion pH Modulation

Remineralisation of demineralised enamel subsurface lesions can be enhanced by pretreatment of the lesions with base (NaOH). The aim of this study was to test the effect of intralesion pH modulation on remineralisation of demineralised enamel subsurface lesions by casein phosphopeptide-stabilised amorphous calcium fluoride phosphate (CPP-ACFP) in vitro. Two remineralisation models were utilised, the first involving 60-min cyclic pH modulation for 105 h and the second involved short-term cyclic pH modulation (12-min cycle, 240 min total duration) compared with the equivalent time of continuous treatment (200 min total duration). The intralesion pH modulation was achieved by cyclic exposure to a pH 12.9 NaOH solution and a CPP-ACFP remineralisation solution at pH 5.5. Percent remineralisation was assessed using transverse microradiography with data statistically analysed using a 2-sample Student t test. For the first model, the intralesion pH modulation group had significantly (p < 0.001) higher remineralisation (43.8 ± 6.9%) than the control group (28.2 ± 5.8%) cycled with water. For the second model, the intralesion pH modulation group had significantly (p < 0.001) higher remineralisation (23.1 ± 3.4%) than the group with continuous equivalent CPP-ACFP treatment time (1.9 ± 1.3%). In both models, intralesion pH modulation significantly accelerated remineralisation, and this was attributed to the effect pH modulation had on the diffusion gradients of ions/ion pairs and the degree of saturation with respect to apatite phases within the lesion fluid.