Effects of Adhesives on Calcium-Release, PH and Bonding of TheraCal

Objectives: The purpose of this study was to evaluate the effects of dental adhesives on calcium-release, PH and shear bond strengths of pulp-capping material, TheraCal (Bisco).

Methods:

Twenty-five light-cured TheraCal discs (diameter 20mm, thickness 1mm) were prepared, coated with various adhesives (Control without adhesive, One-Step(TE), All-Bond3(TE), All-BondSE, Exp Universal Adhesive(SE); Bisco) and light-cured, and stored in de-ionized water (20mL, 37ºC, 24hours). Their pH and calcium concentration (n=5) were measured with a pH/ISE meter, PH and Calcium Ion Selective Electrodes (Thermo-Scientific Orion), respectively. Shear bond strength (n=5) on dentin was tested using the #5-gel cap method (bonding area 15mm²). Twenty-five human dentins were polished by 320SiC paper and rinsed with water. Ten dentin samples (TE groups) were etched (15sec by 37%H₃PO₄) and rinsed with water. The adhesives were applied to the dentin surface except control and light-cured according to manufacturer’s instructions. 1mm of TheraCal was applied and light-cured (20sec/500mW/cm²). A #5 gel post was filled with Universal Bisfil composite (L/C) and placed on TheraCal. Excess material was removed, and the post was light-cured (40s@ 500mW/cm²) on two sides. Bonded specimens were stored in de-ionized water (37ºC, 24 hours), and tested by Instron tester (crosshead speed 5mm/min). The data were analyzed statistically by one-way ANOVA and Tukey Tests (p<0.05).

Results: The test results are shown in the table below. For each row, means with different letters are statistically different at p<0.05.

Average (Standard Deviation)	Control-No Adhesive	One-Step	All-Bond3	All-BondSE	Exp Universal Adhesive
Calcium-Release (µg/cm2)	284.3 (0.0)a	79.6 (23.8)b	31.2 (15.5)c	44.9 (16.4)c	5.7(2.0)d
pH	8.32(0.03)a	8.04(0.18)b	5.48(0.26)d	7.73(0.22)c	6.01(0.50)d
Bond Strength(MPa)	0.8(0.4)a	11.1(3.14)cd	8.16(1.1)bc	7.7(0.5)b	11.4(1.74)d

 Conclusions: The bond strengths of TheraCal were significantly increased by the adhesives tested (p<0.05). The pH of TheraCal was slightly decreased with adhesives. TheraCal coated with adhesives was still able to release calcium.