The effect of reduced thickness in different regions on the fracture resistance of monolithic zirconia crowns / 대한치과보철학회지

Purpose@#. This study aims to evaluate the combined effect of reduced thickness in different regions on the fracture resistance of monolithic zirconia crowns. @*Materials and methods@#. Seven nickel-chromium dies were generated from a 3D model of mandibular first molar using the digital scanner with the following geometries:1.5 mm occlusal reduction, 1.0 mm deep chamfer. Based on the abutment model, Zirconia blocks (Luxen Zirconia) were selected to fabricate Sixty-three zirconia crowns with occlusal thicknesses of 0.3 mm, 0.5 mm, and 1.5 mm, and different axial thicknesses of 0.3 mm, 0.5 mm, and 1.0 mm. All crowns were cemented by resin cement. Next, the crowns were subjected to load-to-fracture test until fracture using an electronic universal testing machine. In addition, fracture patterns were observed with a scanning electron microscope (SEM). Two-way ANOVA and the Tuckey HSD test for post hoc analysis were used for statistical analysis (P < .05). @*Results@#. The mean values of fracture resistancerecorded was higher than the average biting force in the posterior region. The two-way ANOVA showed that the occlusal and axial thickness affected the fracture resistance significantly (P < .05). However, the effect of axial thickness on fracture resistance did not show a statistical difference when thicker than 0.5 mm. The observed failure modes were partial or complete fracture depending on the severity of crack propagation. @*Conclusion@#. Within the limitations of the present study, the CAD-CAM monolithic zirconia crown with extremely reduced thickness showed adequate fracture resistance to withstand occlusal load in molar regions. In addition, both occlusal and axial thickness affected the fracture resistance of the zirconia crown and showed different results as combined.

Comparison of the outcomes of three-dimensional finite element analysis under arbitrary and realistic occlusal loading conditions in mandibular posterior region

Purpose@#The purpose of this study was to compare the biomechanical outcome in the mandibular posterior region between two different loading conditions by finite element analysis. @*Materials and Methods@#The mandibular posterior teeth model and the implant model were generated for the study. And 2 different types of loading conditions were provided: Arbitrary occlusion and natural occlusion obtained from the digital occlusal analyzer, Accura (Accura, Dmetec Co. Ltd., Seoul, Korea). Total load of 100 N was evenly distributed over arbitrary occlusion points, and 100 N load was differentially distributed over natural occlusion points according to Accura data. The biomechanical outcome was evaluated by the finite element analysis software. @*Results@#The result of finite element analysis showed considerable difference in both von Mises stress pattern and displacement under different loading conditions. @*Conclusion@#In finite element analysis, it is recommended to simulate a realistic occlusal loading pattern that is based on accurate measurement.

An assessment of accuracy of half-guided implant surgery using implant surgical guide: A case report / 대한치과보철학회지

Nowadays, dental implant is one of the widely used treatment options for edentulous patients. Recently, a method of improving the accuracy of implant surgery using an implant surgical guide has been introduced and widely used in order to accurately place the implant in a proper position. Full-guided and half-guided implant surgery can be distinguished according to the level of surgical guide application during the implant surgery. It is true that full-guided implant surgery exhibits higher accuracy, but half-guided implant surgery is often performed in a clinical situation due to the factors such as the circumstances of the operation. A partially edentulous patient who lost teeth due to tooth fracture and periodontal disease was treated using implant and fixed prosthesis. Half-guided implant surgery was performed using an implant surgical guide during implant surgery, the accuracy of implant placement was analyzed.

Factors that affect the bite force measurement

Mastication is the process to help digestion by chewing or grinding food. Masticatory system consists of maxilla, mandible, temporomandibular joints, ligaments, dentitions, and musculatures. Assessing the bite force can be one of the methods to estimate the masticatory system. Bite force is influenced by facial morphology, age, sex, periodontal status, temporomandibular joint disorder and dental condition, and so forth. In general, higher maximum bite force is seen in those who have a square-shaped face and in male rather than female. In addition, bite force tends to be increased by age 20, maintained constantly until age 40 - 50, and then decreased. Periodontal disease is known as a causative factor for decreased bite force while temporomandibular disorder (TMD) remains controversial as to whether it affects the force. The status of teeth is considered as an important factor to determine the maximum bite force.

The Significance of ALIP in Acute Myeloid Leukemia after Chemotherapy : A Retrospective Study of Clinical and Histopathologic Aspects / 대한혈액학회지

BACKGROUND: Bone marrow biopsies following the completion of remission-induction chemotherapy for patients of acute myelogenous leukemia (AML) whose blasts on bone marrow smear are counted less than 5%, show abnormal localization of immature precursors (the so-called ALIP defined as clusters or aggregates of small mononuclear elements with a narrow rim of light blue stained agranular cytoplasm) occasionally. The importance of ALIP in bone marrow section after antileukemic therapy is not determined yet. The purpose of this study is to elucidate the significance of ALIP on patients' remission duration and survival. METHODS: The bone marrow slides from adult AML patients who achieved complete remission (CR) after receiving first antileukemic therapy between January 1987 and April 1996 in Seoul National University Hospital were reviewed. Among them, 24 patients showed ALIP findings in their bone marrow biopsy sections and 8 patients' bone marrow were rebiopsied before next chemotherapy.We analyzed them on the histopathologic aspects. The patients who achieved CR after receiving first antileukemic therapy using Ara- C and daunorubicin were analyzed about their remission duration and survival duration according to ALIP positiveness (ALIP+ group : 16 patients, ALIP- group : 39patients. RESULTS: 1) Among eight rebiopsied bone marrow sections, six patients showed disappearance of ALIP findings spontaneously and none showed the increase of blast counts more than 5%.2) No statistically significant difference about patient characteristics between ALIP+ group and ALIP- group was shown except intervals between first antileukemic chemotherapy and biopsy of bone marrow (ALIP+ vs. ALIP-, 28 days vs. 34 days, P=0.001). The actuarial risk of relapse and CR duration were similar in both groups (P=0.44). The median duration of remission for the ALIP+ patients was 7 months and 12 months for ALIP- patients. Also the overall survival was similar in both groups (P=0.37). The median duration ofsurvival was 12 months for ALIP+ patients and 21 months for ALIP- patients. CONCLUSION: We did not find any statistically significant differences between ALIP+ group and ALIP- group for remission duration and overall survival, and observed ALIP findings in earlier bone marrow biopsies afterchemotherapy. We concluded ALIP findingmight be a indirect evidence of bone marrow regeneration, but further studies with cytogenetics or FISH method should be followed.