Abstract : Purpose : The aim of this study was to evaluate the effects of intra-radicular moisture conditions before obturation on the physical properties of Well-Pulp ST as root canal sealer using the push-out bond strength test.

 Methods : Thirty human single-rooted teeth were prepared using niti-rotary instruments and then divided into three groups with respect to the moisture condition tested : (1) the dry group, (2) the moist group, and (3) the wet group. The roots were obturated by the single-point technique with Well-Pulp ST as root canal sealer. One-mm-thick slices were obtained from each root sample (n=10). Bond strengths of the test materials to root canal dentin were measured using a push-out test. The data were analyzed statistically by one-way analysis of variance, followed by Tukey-Kramer multiple tests. Failure modes were analyzed under a scanning electron microscope to detect the mode of fracture.

 Results : The moist group showed higher bond strength than the dry and the wet groups when using Well-Pulp ST as root canal sealer. Also, the dry group showed higher bond strength than the wet group (p<0.05). Under dry and moist conditions, the most common type of failure was adhesive failure along the sealer and gutta-percha interface. Under wet conditions, the majority of specimens showed adhesive failure along the sealer and dentin interface.

 Conclusion : The degree of residual moisture significantly affects the bond strength of Well-Pulp ST as root canal sealer to radicular dentin.

Abstract : Purpose : The aim of this study was to compare the cyclic fatigue resistance of two different NiTi files on rotary movement within an artificial curved canal.

 Methods : NEX-NiTi files (Co group) (ISO size : #25, taper : 0.06, length : 21mm, n=10) and NEX-NiTi Ms files (MS group) (ISO size : #25, taper : 0.06, length : 21mm, n=10) were tested. All files were tested by rotary movement and the testing device was a stainless-steel artificial canal with a 35° angle of curvature.

 To simulate the clinical setting, the tests were done with up-and-down motion at 0.5sec/4mm. All samples were loaded with rotary movement until fracture.

 Time to fracture and the lengths of broken fragments were recorded. After the cyclic fatigue resistance tests were completed, the fractured surface was inspected by a scanning electron microscope. The data were analyzed using Student's test.

 Results : The time to fracture of the MS group was significantly longer than that of the Co group (p<0.01). The average length of broken fragments was 2.12-2.13mm, and there was no statistical significance between the two.

 Scanning electron microscopic observations showed a crater-like formation along with numerous dimples and micro-bubbles in both groups.

 Conclusion : NEX-NiTi Ms files showed higher cyclic fatigue resistance than NEX-NiTi files with continuous rotary movement.

Abstract : This study aimed to identify the root and root canal morphology of mandibular incisors in Japanese patients using computed tomography (CT).

 Materials and methods : Multi-detector CT (MDCT) images of mandibular central incisors (I1) and lateral incisors (I2) in 200 Japanese subjects (100 men and 100 women), aged 20 to 29 years, who visited Nihon University Matsudo Hospital. Both I1 and I2 showed a single root. One root canal was observed in as many as 91.5% of I1 root canals. Two root canals were observed in only 8.5%, and type Ⅲ Vertucci classification was found in both males and females. In the root canal of I2, one root canal was observed in 73.5% and two root canals in 26.5%. According to the classification of Vertucci, for two root canals typeⅡ accounted for 1.0%, type Ⅲ23.0%, type Ⅳ 0.5%, and type Ⅴ 2.0%. Bifurcation of the root canal was observed in almost one third of the root. In this study, we could not observe compound roots. From the results, CT images allow non-invasive imaging and a better understanding of the complex anatomical root canal morphology ; such information on root fusion and root canal morphology should improve the success rate of endodontic therapy.

Abstract : Oxytocin (OT) is a neurohypophysical hormone that plays a role in lactation and parturition. Recently, several papers reported that OT stimulates bone formation in osteoporosis. We hypothesized that OT can also stimulate dentinogenesis via a canonical pathway in dental pulp tissues as well as bone tissues. The aim of the study was to confirm the effects of OT on dentinogenesis using cultured rat dental pulp cells. The cells treated with OT (OT group) presented larger numbers of mineralized nodules than those in control cells (control group) on day 21. The cells of the OT group expressed much higher levels of mRNAs of both dentin sialophosphoprotein and bone-gla protein than the cells in the control group. Furthermore, a higher level of Wnt10a mRNA expression was induced in the cells in the OT group than the cells in the control group. Along with this, the expressions of Axin 2, Lef-1, and ectodin mRNAs, which are related with Wnt canonical pathways, were also much higher in the OT group than those in the control group. We confirmed the expression of OT receptor in odontoblasts in rat dental pulp tissue by using immunohistochemistry. These results indicate that OT directly influences dentinogenesis in rat dental pulp cells via Wnt canonical pathways.

Abstract : Tri Auto ZX2 can be used for patency and glide path according to the manufacturer's instruction manual. However, no reports have verified these details. This study examined whether Tri Auto ZX2 can achieve patency and a glide path.

 The orifice of extracted human premolars was enlarged using #35. 08 EndoWave. Patency and glide path were prepared using OGP mode 180°, 300rpm in Tri Auto ZX2.

Group 1 : Patency was possible with D-finder #10, but not with D-finder #15. EndoWave MGP #15 was used for the glide path.

Group 2 : Patency was possible with D-finder #10, but not with D-finder #15. Superfile #15 was used for the glide path.

Group 3 : Patency was not possible with D-finder #10 or #15. EndoWave MGP #10 was used for patency.

Group 4 : Patency was not possible with D-finder #10 or #15. Superfile #10 was used for patency.

 A glide path could be prepared in all root canals in groups 1 and 2. Patency was possible in 49.1% of root canals in group 3 using Endowave MGP#10 with Tri Auto ZX2 OGP mode. Patency was possible in 68.7% of root canals in group 4 using superfile #10 with Tri Auto ZX2 OGP mode. 31.3% of stainless-steel files in group 4 broke when using OGP mode.

 It is suggested that Tri Auto ZX2 is a good motor for achieving patency and glide path after negotiation using D-finder #10.