Gonial Angle Measured by Orthopantomography as a Predictor of Maximum Occlusal Force.

PURPOSE: To establish the accuracy of measuring the gonial angle on an orthopantomogram (GAO), as defined by the anatomic relationship between the inferior and posterior borders of the mandible. Furthermore, to examine the relationship between GAO and maximum occlusal force (MOF) in the premolar and molar regions of healthy young adults. MATERIALS AND METHODS: Orthopantomograms of dry mandibles were obtained in three orientations in the sagittal plane, to represent variation in image acquisition in clinical settings. The GAO was measured using image-processing software, and reliability was analyzed using the intraclass correlation coefficient. Then, GAO, MOF, gender, and body mass index (BMI) were measured in a cohort of healthy young adult volunteers. MOF was measured using an Occlusal Force Meter GM 10 device. The relationships between GAO, MOF, sex, and BMI were examined using the Pearson correlation coefficient and multiple regression analysis. RESULTS: In five dry mandibles, there was a high correlation between the GAOs measured in the different orientations (p < 0.001). In 58 healthy volunteers (31 women and 27 men, mean age 24.6 years), the mean GAO was 123.3° ± 7.5°. The mean MOFs at the first premolar, second premolar, and first molar teeth were 256.4 N ± 128.3 N, 319.0 N ± 171.7 N, and 487.5 N ± 227.2 N, respectively. Men had significantly greater MOF than women at all teeth. The GAO was significantly inversely correlated with MOF at the second premolar (r = -0.376, p = 0.005) and first molar teeth (r = -0.479, p < 0.001). Multiple regression analysis showed that GAO was a significant explanatory factor for MOF at the second premolar and first molar teeth (p = 0.012 and 0.001, respectively). CONCLUSIONS: GAOs were measured accurately on the orthopantomograms taken in this study and were a reliable predictor of MOF between the second premolar and first molar teeth. A smaller GAO was associated with a greater MOF at the second premolar and first molar teeth.

A prospective study of the relationship between patient character and blood pressure in dental implant surgery.

BACKGROUND: Patients often suffer from physical and mental stress in dental implant surgery. The aim of this prospective study is to investigate the relationship between patient character and blood pressure in dental implant surgery. METHODS: Fifteen patients were recruited for the present study. All patients had never received implant treatment in the past. To evaluate the patients' personality trait, NEO-Five Factor Inventory (NEO-FFI) was used. All patients answered 50 questions at the first visit and divided in five dimensions: neuroticism, extraversion, openness, agreeableness, and conscientiousness. The index of physical stress was evaluated by blood pressure and pulse rate. RESULTS: Ten females and five males (mean 55.5 ± 10.6 years) were evaluated in this study. A significant positive correlation was found between elevation rate of diastolic blood pressure/mean blood pressure and neuroticism score (rs = 0.584, 0.526, p < 0.05). On the other hand, there was no significant correlation between systolic blood pressure elevation and neuroticism score. CONCLUSIONS: In this limited study, there was significant correlation between neuroticism character and diastolic blood pressure or mean blood pressure rising in patients who received implant surgery.

The Evaluation of the Heat Generated by the Implant Osteotomy Preparation Using a Modified Method of the Measuring Temperature.

PURPOSE: To establish a method for measuring the heat generated when preparing an osteotomy site, and to assess for correlations of rotational speed, proceeding speed, loading value of the drill (contact pressure), motion pattern, and bone density with temperature increases. MATERIALS AND METHODS: A thermocouple was placed in the internal irrigation hole of a 2.0-mm-diameter twist drill used for measuring osteotomy site temperature. In the artificial blocks, two different densities were used to drill under varying conditions including drill proceeding, rotating speed, and motion pattern. The drilling procedure was repeated five times for each combination, and the data collected were statistically analyzed using multiple regression analysis. RESULTS: Strong positive correlations were found among bone density, drill motion pattern, and maximum temperature, and a positive correlation was found in proceeding speed (P < .001). Rotation speed and maximum temperature were not correlated (P < .001). Conversely, loading values of the drill increased with the lower rotation speed and higher proceeding speed, which were effective in controlling the temperature rise. CONCLUSION: When preparing a simulated bone for an osteotomy with a thermocouple inserted into a twist drill with internal irrigation, the drilling motion pattern, bone density, drill speed, and proceeding rate affected bone temperature, in descending order. It was also observed that bone temperature correlated positively with speed and negatively with proceeding speed, independent of density. This indicates that lower drill speed and higher proceeding speed without excessive loading values minimize the bone temperature heat.

The relationship between the bone characters obtained by CBCT and primary stability of the implants.

BACKGROUND: The aim of this study is to investigate the correlation between the thickness of the cortical bone or the voxel values that are obtained by cone beam CT (CBCT) and the insertion torque values (ITVs) or the implant stability quotient (ISQ) values. METHODS: A pig's ilium was used as the implant placement site. The implants used in this study were two kinds of diameters (3.8 mm, 5.0 mm) and two kinds of lengths (7.0 mm, 12.0 mm) having a general threadlike shape with a mechanically polished surface. To measure the bone density and the cortical thickness around the implants accurately, the CBCT scanning was performed immediately just after the formation of the implant cavity. The initial stabilities were evaluated by the ITVs and the ISQ values. The bone density and cortical thickness around the implants were measured by an implant simulation software (Landmarker ver. 5.0 with special specifications for this study). The relationships of the thickness of the cortical bone and the voxel values with the ITVs and the ISQ values were analyzed using Pearson's correlation coefficient. To evaluate the influence on the ITVs and the ISQ values among multiple factors, multiple regression analysis was performed. P < 0.05 was considered statistically significant. RESULTS: A significant positive correlation was found between the thickness of the cortical bone and the ITVs or the ISQ values in all kinds of implants. In addition, a significant positive correlation was also found between the voxel values and the ITVs. From the multiple regression analysis, the thickness of the cortical bone and the voxel values had a positive influence on the ITVs and the ISQ values. In addition, the length of the implant had a positive influence on the ISQ values at the 3.8-mm-diameter implant. CONCLUSIONS: In this limited study, there were correlations between the thickness of the cortical bone or the voxel values obtained from the CBCT scanning and the implant stabilities. Besides, it was confirmed that the thickness of the cortical bone, the voxel value, and the implant length had positive correlations with the ITVs and the ISQ values.