We investigated the effect of Er,Cr:YSGG laser cutting on the micro-tensile bond strength (MTBS) of resin composite to dentin. The occlusal surfaces of extracted human molars were ground using silicon carbide paper to obtain flat dentin surfaces. For Groups 1 to 6, the superficial dentin surfaces were cut using an Er,Cr:YSGG laser. A plastic tube was attached to each dentin surface and was used to apply the following: bonding agent (Clearfil Mega Bond/Bond: SEB, Group 1); self-etching primer (Clearfil Mega Bond/Primer: SEP) and SEB (Group 2 and control); phosphoric acid (K-etchant Gel: KET), SEP and SEB (Group 3); KET, sodium hypochlorite (AD Gel: ADG), SEP and SEB (Group 4); all-in-one adhesive (Tri-S Bond: TRI, Group 5); KET, ADG and TRI (Group 6). After each bonding procedure, resin composite (Clearfil Majesty) was placed in the tube and photo-cured. The specimens were cut into beams for micro-tensile bond testing. Data were statistically analyzed with one-way ANOVA and post-hoc Tukey test. The MTBS values (MPa, mean ± SD) for each group were: Group 1: 22.0±11.0, Group 2: 21.8±4.9, Group 3: 40.7±6.3, Group 4: 39.0±10.0, Group 5: 29.4±9.6, Group 6: 34.8±9.0, and control: 52.7±8.7. Preconditioning using phosphoric acid or sodium hypochlorite may be effective for improving the dentin bond strength of resin composite in cavities prepared using an Er,Cr:YSGG laser.

View full abstract

The objectives of this study were to evaluate the interfacial ultrastructure of PrimeFil (Tokuyama Dental) under SEM/TEM, and to evaluate the clinical performance in vivo. For SEM observation, human extracted molars were used. The crown was horizontally cut to expose the flat enamel and dentin surface. The surface was ground with #1000 SiC paper and treated with either PrimeFil or Bond Force (Tokuyama Dental) which served as a control, and filled with composites. The specimen was cut into halves and embedded. After the cut surface was polished, argon-ion beam etched and Pt-sputtered, the bonding interface with enamel and dentin was observed by SEM. For TEM observation, the bonded specimens prepared as above were ultra-thinned without demineralization. We also employed this new restorative system in daily practice. SEM images showed that the bonding agent created a tight junction and no gap with enamel and dentin. In the superficial dentin layer, the hybrid layer was clearly observed compared with the Bond Force interface. TEM images revealed that fewer hydroxyapatite crystallites remained in the hybrid layer than in the Bond Force interface. The innovative self-etching adhesive showed satisfactory adhesion to tooth tissues and is thought to be promising for clinical use.

View full abstract

The purpose of the present study was to reduce the application time of the Shining Bond Star (SBS, Yudent) containing phosphoric ester monomers. Using an improved version of SBS (i-SBS), tensile bond strengths to bovine enamel/dentin were measured after storage in water for 24 hours. Further, the bonding interfaces between i-SBS and human enamel/dentin were observed under SEM. The tensile bond strengths to bovine enamel and dentin were 23.5±3.5 MPa and 19.5±2.4 MPa for the 10-second application, and 21.0±2.7 MPa and 19.7±2.2 MPa for the 20-second application, respectively. There was no significant difference among the four groups (p<0.05). The SEM figures revealed the tight adhesive interface to both human enamel and dentin. To conclude, i-SBS, an improved version of SBS, reduces the application time and produces good adhesion to both enamel and dentin.

View full abstract