Dentin bond strength of a new adhesive system containing calcium phosphate experimentally developed for direct pulp capping.

The purpose of this study was to evaluate the microtensile bond strength (microTBS) to human dentin of an experimental bonding agent containing calcium phosphates experimentally developed for direct pulp capping. Different concentrations of four types of calcium phosphates were added to an experimental bonding monomer, and six experimental bonding agents were thus prepared. Clearfil SE Bond/Bond was used as the control. Flat dentin surfaces of human molars were assigned to the experimental adhesive systems and the control. After Clearfil SE Bond/Primer was applied to the dentin surface, each experimental bonding agent was applied and photopolymerized, and then a resin composite paste was placed and photopolymerized. The specimens were subjected to microTBS testing. Results revealed that there were no significant differences among the microTBS values of the experimental bonding agents and the control. In other words, the calcium phosphate-containing experimental adhesives did not adversely affect the microTBS to dentin.

Effects of attrition, prior acid-etching, and cyclic loading on the bond strength of a self-etching adhesive system to dentin.

The purpose of this study was to evaluate the effects of dentin attrition, phosphoric acid etching, and cyclic loading on the microtensile bond strength (microTBS) of a self-etching adhesive system to dentin. Flat dentin surfaces of human molars were assigned to eight experimental groups based on those with or without attrition, prior acid-etching, and cyclic loading. Resin composite paste was placed and polymerized after the bonding procedure according to manufacturer's instructions. The specimens were subjected to microTBS testing at a crosshead speed of 0.5 mm/min. Results showed that the minimum mean value of microTBS was 14.9 MPa in the group without attrition and acid-etching but with loading, while the maximum mean value of microTBS was 40.0 MPa in the group without attrition and loading but with acid etching. Therefore, the value of microTBS to dentin without attrition was significantly decreased by cyclic loading but that to dentin with attrition was not affected.

Effects of an experimentally developed adhesive resin system and CO2 laser irradiation on direct pulp capping.

This study examined the wound healing process of rat pulp directly capped with various experimentally developed adhesive resin systems and treated with CO2 laser irradiation. The experimental adhesive resins used in this study were made from Clearfil Mega Bond (MB). The adhesive resin groups were capped with a combination of the following primers and bonding agents: commercially available MB primer (MBP), experimental MB primer containing 2wt% N-methacryloyl 5-aminosalicylic acid (5-NMSA: MP3) and 5wt% 12-methacryloyloxydodecylpyridinium bromide (MDPB: ABP); and commercially available MB bonding agent (MBB), experimental MB bonding agent containing 5wt% and 10wt% hydroxyl-calcium phosphate (hydroxyapatite: MB1, MB2) and 5wt% dicalcium phosphate dihydrate (brushite: MB3) as a reparative dentin-promoter. The combination of the three primers and four bonding agents yielded the 12 adhesive resin groups used in this study. The CO2 laser group was irradiated with a laser and directly capped with MB. The CO2 laser used was an Opelaser 03S II SP, and irradiation conditions were as follows: a power output of 0.5 W, superpulse mode 1, repeat pulse mode (a cycle of 10 msec irradiation and 10 msec interval), defocused beam (approximately distance 20 mm from pulp exposure surface) and an irradiation time of three seconds, with air cooling. The control group was capped with Dycal (DY) and MB. After the direct pulp capping procedures were undertaken, all cavities were restored with Clearfil AP-X resin composite. The rats were sacrificed on the 14th post-operative day. The specimens were alternately stained with Mayer's H & E, Hucker-Conn bacterial stain and the ABC method on TGF-beta1. These stained sections were observed using light microscopy and the following parameters were evaluated: pulp tissue disorganization, inflammatory cell infiltration, reparative dentin formation and bacterial penetration. The results of this study include the following: all experimentally developed bonding agent groups showed reparative dentin formation; whereas, the MBB-capped groups showed very little reparative dentin formation. The descending order regarding the amount of reparative dentin formation was MB2 > MB3 > MB1 >>> MBB, which tended to be dependent on the concentration of the blended reparative dentin-promoter. In terms of the quality of the formed dentin, it was observed that MB1-capped teeth tended to form tubular dentin; whereas, MB2- and MB3-capped teeth formed irregular and osteodentin types of dentin. Among the primers used, the descending order regarding the amount of reparative dentin and tubular type dentin formation was MP3 > MBP > ABP. The descending order of migration of macrophages and leukocytes was ABP > MBP > MP3. The CO2 laser group showed a very irregular fibrous dentin matrix in the vicinity of the denatured and carbonized tissue but definite reparative dentin formation was not observed. The control group showed reparative dentin, which was very thick, compared with the other groups. In all the groups, pulp tissue showed almost normal morphology. Positive staining of TGF-beta1 was only observed slightly in some specimens of all groups. There was no difference in the staining of each group. Based on the results of this study, it was concluded that the combination of MP3 (containing 2wt% 5-NMSA) and MB1 (containing 5wt% hydroxyapatite) was effective in initiating an early repair process after direct pulp capping. CO2 laser irradiation is effective for field control, but a longer observation time will be required to determine findings concerning dentin bridge formation.

Effect of surface conditioning and restorative material on the shear bond strength and resin-dentin interface of a new one-bottle nanofilled adhesive.

OBJECTIVES: To determine the effect of different combinations of surface conditioning (DeTrey Conditioner 36, NRC, no etching) and restorative materials (Dyract AP, Spectrum TPH) on the shear bond strength of Prime and Bond NT to enamel and dentin, and to characterize the resin-dentin interface produced by these combinations. METHODS: Shear bond strength was tested on 30 enamel and 30 dentin flat labial surfaces of extracted bovine teeth. The enamel and dentin specimens were randomly assigned to six groups of five teeth each and treated using different combinations of surface conditioners and restorative materials with Prime and Bond NT. Scanning electron microscope (SEM) observation of argon-ion-etched specimens was done to evaluate the resin-dentin interface. RESULTS: The type of surface conditioning and restorative material had significant effects on dentin bond strengths. Etching the dentin prior to application of Prime and Bond NT significantly increased bond strength and caused formation of a hybrid layer for Spectrum TPH. For Dyract AP, dentin etching generally did not improve bond strength despite the formation of a hybrid layer. On enamel, Prime and Bond NT had consistently high bond strengths on etched specimens. SIGNIFICANCE: The results showed that Dyract AP and Spectrum TPH, when used with Prime and Bond NT have different bonding mechanisms and the effect of surface conditioning on their shear bond strength differs. Clinicians should be aware of these effects in order to optimize bonding.

Histopathologic study on pulp response to single-bottle and self-etching adhesive systems.

This study compared the pulp response to seven adhesive resins (three single-bottle and four self-etching primers) and their companion resin composite systems with a commercial calcium hydroxide material when applied to exposed monkey pulps. The control group was capped with Dycal (DY), while the experimental groups were capped with one of the following adhesive resin systems: AQ Bond (AQ), Single Bond (SB), Imperva Fluorobond (IF), One Step (OS), Prime&Bond NT (PBNT), Perme Bond F (PBF) and One-up Bond F (OBF). Histopathologic evaluation of pulp tissue disorganization, inflammatory cell infiltration, reparative dentin formation and bacterial penetration at the 3rd, 30th and 90th post-operative days was done using light microscopy. Data were analyzed using the Kruskal-Wallis test followed by the Least Significant Difference Test to determine differences between the control group and the experimental groups at each observation period. The correlation of inflammatory cell infiltration and bacterial presence was investigated by the Kendall correlation analysis. All tests were performed at a 95% level of confidence. The pulpal responses of groups DY, SB, OS, PBF and OBF were generally characterized by none-to-mild pulp tissue disorganization and inflammatory cell infiltration. Also, initiation of reparative dentin formation was found earlier in Group DY, resulting in more complete dentin bridges at the 30- and 90-day observation periods. Groups AQ, IF and PBNT had significantly more inflammatory cell infiltration and a lower incidence of reparative dentin formation than Group DY. A significant correlation was detected between inflammatory cell infiltration and the presence of bacteria. It is concluded that the pulp response to SB, OS, PBF and OBF is not significantly different from the calcium hydroxide preparation. However, calcium hydroxide capping resulted in a higher incidence and faster rate of reparative dentin formation.