Purpose: This study investigated the bonding of resin cement to hybrid resin blocks using an experimental primer solution. The combined use of silane coupling and sandblasting was also investigated.

 Methods: Shofu Block HC Hard (SH; Shofu) as a CAD/CAM hybrid resin block and an experimental non-filler type resin block with no filler (NF) were prepared and used in the experiments. Adherends (14×12×2 mm) and specimens (3×3×3 mm) were prepared using either SH or NF. The conditioning of each surface after sandblasting was: HC primer treatment (HC group), 4% silane compounded experimental primer solution (HC+SI group), experimental 4% silane coupling agent (SI group), and no treatment (NT group). After each treatment, the adherend surface and specimen surface were bonded using Block HC Cem (Shofu). After curing, the samples were immersed in 37°C water for 24 h, followed by 5,000 thermal cycles (n=6). A shear bond test was performed using a universal tester and the obtained data was statistically analyzed using one-way analysis of variance (ANOVA) and Tukey’s test. The fractured surface was observed under a scanning electron microscope. To investigate the penetration of HC into the matrix resin, an NF specimen (14×12×3 mm) was prepared, HC was applied to the surface of the specimen and the sample was kept standing for 10 min, after which it was analyzed using a laser Raman microscope.

 Results: There was no significant difference in the bonding strength in each group after immersion of SH and NF in water for 24 h, but after thermal cycling, the bonding strength was significantly higher in the HC and HC+SI groups compared to the SI and NT groups. In addition, no difference was noted after thermal cycling in the HC and HC+SI groups compared with that after 24 h immersion in water. Laser Raman spectroscopic analysis implied the possibility of 4-5 μm superficial penetration of HC into the matrix resin. Thus, when using the experimental primer solution, a high bond strength might be obtained due to the synergistic effect of penetration into the matrix resin and chemical bonding to the filler although further study is needed to clarify the function of the experimental primer solution.

 Conclusion: Within the limitations of this study, the experimental primer solution possibly enhanced the bonding to resin blocks.

 Purpose: This study examined the shear bond strength of self-adhesive resin cement between CAD/CAM ceramic treated with different etching times or sandblasting and the resin composite for core build-up.

 Methods: Seventy-five embedded ceramic blocks were polished using SiC#1200 papers, and were randomly assigned to five groups (n=15). The ceramic surfaces were sandblasted or etched with 9 wt% hydrofluoric acid for 0, 1.5, 5 or 30 min for each group, then the surface roughness (Ra) were measured. Disc specimens made from resin composite were adhered after priming.

 Results: Greater surface roughness was observed for the sandblasting group than the etched groups (p<0.05). The greatest bond strength was observed for the 5 min-etch group (p<0.05). The 5 min-etch group and sandblasting group had greater bond strength than the other groups (p<0.05). Significant positive correlations (r=0.450 for all etching time periods and r=0.879 for the etching time periods up to 5 min) were found between the etching time and the surface roughness. The surface roughness was found to positively correlate (p<0.05) to the bond strength (r=0.460 for all the surface roughness conditions and r=0.571 for the surface roughness obtained by etching time periods up to 5 min). Cohesive failure within the ceramic block was the dominant failure mode in the surface treated groups.

 Conclusion: The study suggested that hydrofluoric acid etching treatments achieved bond strength similar to that generally achieved by sandblasting treatment in the laboratory.

 Purpose: The purpose of this study was to histologically examine the amount of regenerated tissue and the healing of periapical tissue after revascularization following the pulpectomy of rat immature teeth by using mineral trioxide aggregate (MTA) compared with calcium hydroxide (CH).

 Materials and Methods: Six-week-old Wistar male rats were used. The pulp was removed and the root canals were shaped with a Ni-Ti rotary file under rubber dam isolation. An H-file was inserted to induce bleeding over 1 mm from the apical foramen. Blood clot formation in the entire root canal was confirmed and MTA or CH was applied on the canal orifice. The experimental periods were one, two and four weeks after the operation. The specimens were observed histologically by HE staining and immunohistochemically by DMP1 and nestin expression.

 Results: The formation of regenerated tissue was greater in the MTA groups than in the CH groups. Significantly more regenerated tissue was seen in the MTA groups compared with the CH groups at one week (p=0.041) and four weeks (p=0.015) after the operation. Significantly more hard tissue was formed at the cervical third of the MTA group at four weeks compared with the CH group (p=0.004). Each postoperative period of the MTA groups (p=0.004) and each postoperative period of the CH groups (p=0.041) showed a gradually increasing tendency in the formation of hard tissue toward four weeks after the operation. Each postoperative period of the MTA groups (p=0.015) showed a gradually increasing tendency in the formation of bone-like tissue four weeks after the operation. All of the hard tissue formed in the root canal was bone-like tissue. No inflammatory cell infiltration was observed. Expression of DMP1, a regulator of mineralization, was observed underneath the MTA, in the granulation-like tissue under the MTA and around the lumpy structure of the apex side at one week. Expression of nestin, an odontoblast-like cell marker, gradually increased in the apex toward four weeks after the operation.

 Conclusion: This study shows that revascularization using MTA is more effective compared to CH in the formation of regenerated tissue and bone-like mineralized tissue in the root canal following the pulpectomy of vital immature teeth.

 Purpose: Based on the concept of minimal intervention dentistry and developments in adhesive technology, direct resin composite build-up restorations are increasingly performed for endodontically treated teeth. The adhesive systems and dual-cure resin composites use a touch-cure system which contains a special accelerator to promote chemical polymerization. This accelerator enhances the polymerization of the adhesive in deeper areas where light energy is attenuated, such as post cavities. The purpose of this study was to evaluate the influence of the touch-cure system on the micro-tensile bond strength of selected self-etch adhesive systems to root canal dentin.

 Methods: One two-step self-etch adhesive system, Clearfil SE Bond 2 (SE2) with/without Clearfil DC Activator (DCA), and one one-step self-etch adhesive system, Clearfil Universal Bond QuickER (UBQ), were applied to a root canal post cavity (depth 8 mm, diameter 1.5 mm) according to the manufacturer’s instructions followed by a dual-cure resin composite build-up (Clearfil DC Automix ONE). After immersion of the specimens in water for 24 hours, micro-tensile bond strengths in coronal and apical regions were evaluated. The micro-tensile bond strengths were statistically analyzed using a two-way ANOVA and Student’s t-test with Bonferroni correction (α=0.05).

 Results: Pretesting failures of specimens were not observed in this study. Micro-tensile bond strengths in the apical region were significantly lower than those in the coronal region in all adhesive systems. In the coronal region, a significant difference was seen only between SE2+DCA and UBQ, while there was no significant difference among all tested adhesive systems in the apical region.

 Conclusion: Within the limitations of this study, the effect of the touch-cure system on micro-tensile bond strength to root canal dentin was found in neither the one-step nor the two-step self-etch adhesive system.

 Purpose: In cases of a single-tooth edentulous space in the posterior region, we usually consider either a 3-unit fixed partial denture or an implant. However, minimal invasive treatment with resin composite is still the best option in some situations. This case report describes a minimal invasive and simplified direct composite bridge restoration without reinforcing fibers.

 Case: A 29-year-old female patient presented with a missing mandibular left first molar that had been recently extracted because of root fractures that had made the tooth unrestorable. A two-step self-etch adhesive system was applied after additional phosphoric acid etching of enamel surfaces which were slightly cut. Only flowable resin composite was used for the fabrication of the direct resin composite bridge. The prognosis after 9 months was good.

 Conclusion: A technique for using flowable composite resin to construct a direct resin composite bridge was demonstrated. It is important to consider the direct composite restoration option even for single-tooth replacement cases in the posterior region when the clinical and economic circumstances preclude an implant or fixed partial denture as a treatment choice. Direct composite bridge restoration is a valid treatment option for esthetic and functioning dental restoration when used under appropriate clinical circumstances. It is also important to note that the eventual repair or replacement of this restoration is much easier in comparison to dental ceramics as the substrate is composite resin. For clinical patients such as the one presented in this paper, the direct resin composite bridge is satisfactory for their restorative needs. However, further clinical research is necessary to verify the clinical effectiveness of direct bridge restorations.

 Purpose: Due to the poor prognosis for vertical root fracture (VRF), the affected tooth is usually extracted. Recently, however, good clinical progress has been reported when adhesive materials are used to bond the fractured fragments (adhesive therapy). The weaknesses of adhesive therapy are technical difficulty, and occasional inflammation and infection causing persistent deep periodontal pockets. In the present study, a combination method of internal adhesive therapy using resin, and external adhesive therapy using mineral trioxide aggregate (MTA) and intentional replantation was applied to two VRF cases.

 Materials and methods: First, the VRF tooth was extracted, and the infected tooth substance was extensively resected leaving a thin layer of the fracture line on the root surface. Subsequently, the disinfected root canal of the tooth was filled with dual-cure type core resin along with a reinforcing fiber core or metal wire to consolidate the tooth into one piece. A linear-shaped cavity was formed on the fracture line of the root surface, and filled with MTA before replantation. Finally, the treated tooth was replanted in the extraction socket after curettage and irrigation.

 Results: The two VRF cases treated with this method did not show any inflammation or the formation of a residual periodontal pocket, indicating a good prognosis.

 Conclusion: In the two VRF cases treated with the combination method of adhesive therapy with MTA and intentional replantation, greater eradication of the infection source was attained, resulting in the reconstruction of good periodontal tissue. This method is proposed as an innovative treatment for vertical root fracture without acute pain or periodontal pockets.