Time-course of the effect of potassium oxalate in the treatment of hypersensitive dentine in man

Iontophoresis effects of two-step self-etch and total-etch systems on dentin permeability and sealing of composite restoration under simulated pulpal pressure

BACKGROUND

Studies demonstrated the bond strength enhancement and the decrease in degradation of the adhesive interface after applying either self-etch adhesives or two-step, etch-and-rinse adhesives under an electric field. However, the presence of dentinal fluid driven by the pulpal pressure in vivo is a profounding factor affecting both the sealing ability and bond strength of adhesives. This study aimed to evaluate the effect of three-step etch-and-rinse and two-step self-etch adhesives when applied with iontophoresis under simulated pulpal pressure on the permeability of dentin, resin infiltration, and the sealing ability of resin composite.

METHODS

The experiments were done on 32 recently extracted premolars, randomly assigned into four groups (n = 8) according to two adhesive systems (SBMP and SE), applied following the manufacturer's instructions (control) for two groups or with iontophoresis for the others (SBMPi and SEi). For the iontophoresis, the anodal current was applied at 75 μA for 20 s through the cavity electrode during the bond. The fluid flow rate of dentin was recorded after cavity preparation (smear-layer-covered dentin; T1), bonding (T2), and composite restoration (T3) during the maintained pulpal pressure of 20 mm Hg. The flow rates were expressed as a percentage relative to the initial smear-layer-covered value for each specimen. Results were analyzed using repeated measures ANOVA. Scanning electron microscopy (SEM) was performed to observe the resin/dentin interface.

RESULTS

There were no significant increases in the mean flow rates from T1 to T3 in the SBMP (P = 0.355), while these changes in the SE were significant between T1 (100%) and T2 (166.77%) and T1 and T3 (221.16%) (P = 0.002; one-way RM ANOVA; Holm-Sidak test). For the iontophoresis groups, the mean flow rates decreased significantly from T1 to T2 and T1 to T3 of both SBMPi (T2 = 86.43, and T3 = 79.53; P < 0.001) and SEi groups (T2 = 87.96, and T3 = 81.48; P = 0.004). The iontophoresis of both adhesives produced the optimal resin infiltration with improved quality of the hybrid layer and resin tags.

CONCLUSIONS

SBMP bonded with or without iontophoresis performed better sealing ability than SE under the same condition. Both adhesives applied with anodal iontophoresis significantly decreased the dentin permeability, contributing to the improved resin infiltration.

Clinical efficacy of nanohydroxyapatite-containing toothpaste at relieving dentin hypersensitivity: an 8 weeks randomized control trial

Objective

The objective of this study was to investigate and compare the effectiveness of several toothpastes containing nanohydroxyapatite (nano-HAP) to relieve dentin hypersensitivity (DHS) with that of a commercial desensitizing dentifrice containing calcium sodium phosphosilicate (CSPS).

Materials and methods

In this double-blind, randomized, parallel-group clinical trial, patients diagnosed with DHS and qualified to participate were randomized into four groups: toothpaste containing 10% nano-HAP (10%nano-HAP), 15% nano-HAP (15%nano-HAP), 10% nano-HAP supplemented with potassium nitrate (KNO₃) (10%nano-HAPKN), or CSPS. Subjects’ baseline and post-treatment sensitivities were assessed using visual analog scale (VAS) after the application of ice-cold and air stimuli. Subjects used their assigned toothpaste for routine toothbrushing twice daily. Post-treatment sensitivity was assessed every 2 or 8 weeks. Mean change in VAS (mm) from baseline at each time point were compared using random-intercept, mixed-model analysis and Duncan test (P < 0.05).

Results

With either air or cold stimulus, VAS indicated a significant (P < 0.001) reduction from baseline DHS at each time point with all test toothpastes. Among the nano-HAP toothpastes, 15%nano-HAP and 10%nano-HAPKN were consistent in DHS reduction with both stimuli. With either stimuli, the CSPS did not significantly differ from 15%nano-HAP and 10%nano-HAPKN at any time point.

Conclusions

Toothpaste containing nano-HAP (10 or 15%) alone or supplemented with KNO₃ was as effective as CSPS for relief of DHS symptoms when used at least twice daily.