Fujio Tsuchida

Survey on use of titanium dentures in Tsurumi University Dental Hospital for 11 years

PURPOSE The purpose of this study was to survey the production of titanium dentures in Tsurumi University Dental Hospital and to study the actual use of titanium dentures in our university. METHODS The survey was based on the metal base dentures produced at Tsurumi University Dental Hospital during an 11-year period between April 1995 and March 2006, with relation to the types of metals used in the dentures, types of dentures, dental condition, and the number of artificial teeth. RESULTS 1871 metal base dentures were produced in the study period. The dentures consisted of 1290 cobalt-chromium alloy dentures (68.9%), 350 titanium dentures (18.7%) and 231 platinum-added gold alloy dentures (12.3%). Within the titanium denture groups, 132 were complete dentures (37.7%), 55 were complete overdentures (15.7%) and 163 were removable partial dentures (46.6%). JIS type 3 pure titanium was used in the titanium base of 252 dentures (72.0%). The average number of artificial teeth was 10.9, which was the highest among the three types of metal bases, exhibiting significant differences (P<0.01). CONCLUSION Approximately 32 titanium dentures per year on average were delivered at our university and they were applied to almost edentulous arch compared with the other metal base dentures.

Non-destructive three-dimensional evaluation of pores at different welded joints and their effects on joints strength

OBJECTIVES The purpose of this study was to measure the porosity in different laser welded cast alloys non-destructively using X-ray micro-focus computerized tomography (micro-CT) and to evaluate the effect of porosity on the tensile strength of the welded joints. MATERIALS AND METHODS The welding procedure was conducted in rectangular cast metals, CoCr, Ti and platinum added gold alloy (AuPt). The metal plates were butted CoCr to CoCr (CoCr/CoCr) or Ti to Ti (Ti/Ti) for welding of similar metals and Ti to AuPt (Ti/AuPt) for welding of dissimilar metals. Specimens were welded under several laser-welding conditions; with groove (normal), without groove (no groove), spatter, crack, or no overlapped welding (no overlap) (n=5). Porosity in the welded area was evaluated using a micro-CT. Tensile strength of the welded specimens was measured at a crosshead speed of 1mm/min. Multiple comparisons of the group means were performed using ANOVA and Fishers multiple comparisons test (α=.05). The relationship between the porosity and the tensile strength was investigated with a regression analysis. RESULTS Three-dimensional images of Ti/AuPt could not be obtained due to metal artifacts and the tensile specimens of Ti/AuPt were debonded prior to the tensile test. All other welded specimens had porosity in the welded area and the porosities ranged from 0.01% to 0.17%. The fractures of most of the CoCr/CoCr and Ti/Ti specimens occurred in the parent metals. Joint strength had no relationship with the porosity in the welded area (R(2)=0.148 for CoCr/CoCr, R(2)=0.088 for Ti/Ti, respectively). SIGNIFICANCE The small amount of porosity caused by the laser-welding procedures did not affect the joint strength. The joint strength of Ti/AuPt was too weak to be used clinically.

A Study on a Relationship between Clinical Findings and Disc Disorders in Patients with Eichner Classification C1(Surechigai Occlusion).

Thirty patients who visited our hospital with a chief complaint of mismatched dentures and were subsequently diagnosed as class C 1 according to Eichners classification (mean age: 66.6 years) were the subjects. The oral cavity of each patient was examined. In addition, questions were asked and X-rays and MRI were taken to investigate the relationship between disc displacement and factors such as condyle position and the state of the oral cavity.Fishers exact probability test and multivariate analysis utilizing Hayashis quantification theory were applied for statistical analysis.The results were as follows:1. MRI imaging revealed disc displacement in 20 joints of 13 patients (43.3%).2. Condylar bone changes were seen in 11 joints of 8 patients.3. A lateral or bilateral posterior shift of the condyle position was seen in 54% of the patients with disc displacement.4. Statistical analysis revealed significant difference in the type of artificial teeth, deviations in the opening and closing movements of the mouth, past history of temporomandibular arthrosis, and joint click between the patients with disc displacement and healthy individuals.5. The presence of disc displacement most strongly correlated with the past history of temporomandibular arthrosis, followed by deviations in the opening and closing movements of the mouth.

The Effect of Positioning for Measurement of Mandibular Corpus Height in Edentulous Jaw by Rotational Panoramic Radiography.

A new mandibular positioner for quantitative analysis of mandibular bone resorption by rotational panoramic. radiography enabled measurement of the mandibular corpus height. The purpose of this study was to investigate the effect of positioning for edentulous mandible by rotational panoramic radiography.Five dry mandibles were used in this study, and each mandible was tilted up to 30° using the mandibular positioner. Metal tubes were set vertically to the crest of the mandibular corpus of another mandible. The angle of mandibular plane and the angle of inclination of metal tubes were measured using rotational panoramic radiograms.There was a high correlation between the actual size and the measurement by rotational panoramic radiogram.It was possible that the mandibular corpus height was measured within 15° about the inclination of standard metal tubes. This study indicates that the angle measurements of mandibular plane and of the standard metal tubes on rotational panoramic radiogram were useful for accurate positioning.