Shaping ability of progressive versus constant taper instruments in curved root canals of extracted teeth

AIM: To compare the shaping ability of progressive versus constant taper shaft instruments in curved root canals of extracted human teeth. METHODOLOGY: A total of 40 root canals of mandibular molars with curvatures ranging between 20 degrees and 40 degrees were divided into two groups of 20 canals each and embedded in a muffle system. The root canals sectioned horizontally at three levels before preparation and then remounted into the mould. All root canals were prepared with ProTaper (progressive taper) or Hero Shaper (constant taper) instruments. Pre- and post-instrumentation radiographs and cross-sectional images were obtained. The parameters evaluated were: working safety (instrument failure, apical blockage and loss of working length) and shaping ability (straightening, cross-sectional area, transportation and centring ability). The data were analysed statistically using Student's t-test. RESULTS: No instrument fractured during preparation. One Hero Shaper instrument permanently deformed. Both instrument systems maintained working length well. The canals prepared with Hero Shaper instruments were straightened to a lesser degree (P < 0.05). ProTaper instruments removed more dentine in the coronal and the middle sections of the canals. Canals prepared with Hero Shaper instruments had less transportation (P < 0.01) and better centring ability (P < 0.05) in the apical section. CONCLUSIONS: Both instrument systems were safe to use and maintained working length well. The canals prepared with Hero Shaper had less transportation and were better centred in the apical region, possibly because their smaller taper reduced instrument stiffness.     

Heterotrophic ossification on a skin graft in a postburn scar of the chin

Some patients who have heterotrophic ossification (HO) in a postburn scar are occasionally seen in the clinic. The occurrence of HO following hip and abdominal surgery is common in males, whereas females are frequently affected following burns. The HO of skin grafts in burn scars of the superior body parts is uncommon, especially on the face. We report a recent case of a male patient in whom HO arose on skin grafts on his chin. The patient presented with a history of a painless chin mass for 48 years. Computed tomography scan suggested that the mass was located within subcutaneous tissue away from the lower jaw. The density of the mass was almost the same as the cortical bone of the lower jaw. The mass was completely resected under general anesthesia. It was a rectangular mass of 3× 0.5× 0.3 cm. Histological examination gave the diagnosis of HO, which was also confirmed by immunohistochemical stainings for vimentin. Recurrence was not found in this case by clinical and radiologic follow-up at 1 year after surgery.     

口呼吸与鼻呼吸儿童牙弓、基骨形态差异的研究

目的：比较口呼吸与鼻呼吸儿童牙弓、基骨形态的差异，探讨呼吸方式与牙弓、基骨形态的关系。方法：通过口鼻气流同步测定系统的随机检测，选择鼻呼吸比例≤70％(口呼吸组)及≥95％(鼻呼吸组)的11～14岁儿童各34人，测量石膏模型，比较其牙弓、基骨形态的差异。结果：①口呼吸儿童与鼻呼吸儿童相比腭盖较高，上颌基骨较窄，形态相对窄长。②口呼吸儿童比鼻呼吸儿童的上颌中、后段牙弓较长，牙弓形态相对窄长，下颌牙弓后段形态也相对窄长。结论：口呼吸可以引起儿童牙弓、基骨形态的改变。     

Activation of vanilloid receptor 1 (VR1) by eugenol

The structural similarity of eugenol with capsaicin suggests that these two agents may share molecular mechanisms to produce their effects. We investigated the effects of eugenol in comparison with those of capsaicin using whole-cell patch clamp and Fura-2-based calcium-imaging techniques in a heterologous expression system and with sensory neurons. In vanilloid receptor 1 (VR1)-expressing human embryonic kidney (HEK) 293 cells and trigeminal ganglion (TG) neurons, eugenol activated inward currents, whereas capsazepine, a competitive VR antagonist, and ruthenium red (RR), a functional VR antagonist, completely blocked eugenol-induced inward currents. Moreover, eugenol caused elevation of [Ca(2+)](i), and this was completely abolished by both capsazepine and ruthenium red in VR1-expressing HEK 293 cells and TG neurons. Our results provide strong evidence that eugenol produces its effects, at least in part, via VR1 expressed by the sensory nerve endings in the teeth.     

Clinical evaluation of ceramic inlay made by CAD/CAM for 3 year]

In this study,ceramic inlays made by CAD/CAM system were used to restore posterior tooth defects.After three years of clinical observation on 21 prostheses no secondary caries was found and patients satisfied with their restoration on aspects of color match and resistance to wear etc.Five cases of inlay fracture and of obvious space between inlay margin and Cavowall were found.The main reason was the insufficient thickness of the inlays meanwhile the selection of bonding agent was not appropriate.The clinical successful rate is 76.20%.As CAD/CAM is a sophisticated technique induced into prosthodontic area just in 1980's,it has still some deficiency to be improved and perfected.     

Bond strength between luting materials and a fiber-reinforced resin composite for indirect restorations

The purpose of the present study was to evaluate the bond strength between a fiber-reinforced composite (FRC) and six luting agents (Panavia F 2.0, Linkmax MC, Chemiace II, Multibond, Super-Bond C&B, and Fuji I). A prosthodontic resin composite material (RC-control) and a luting agent containing no functional monomer (MT) were used as controls. Shear bond strengths between alumina-blasted FRC and the luting agents were determined after 20,000 thermocycles. The FRC showed superior bond strength when compared with the RC-control. Highest bond strengths were achieved when FRC was bonded with Panavia F 2.0, Linkmax MC, Multibond, Super-Bond C&B, and MT, whereas Chemiace II trailed in the list of resin-based luting agents evaluated. Insufficient bonding was obtained with Fuji I. Results of the present study revealed that when fabricating restorations, the clinician should select an appropriate combination of resin composite material and luting agent so as to ensure the longevity of restorations.