Yasuko Takayama

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 Discoloration of Ag-Pd-Au Alloy Part 3 Effect of Heat Treatment

目的: 日常臨床において, 金銀パラジウム合金による鋳造鉤の変色がしばしば観察される. 本研究は, 溶体化処理後, 急冷あるいは空冷を行った金銀パラジウム合金製鋳造鉤を用いた部分床義歯を患者に装着し, 変色の経時変化を測定し, 溶体化処理の効果について明らかにすることを目的としたものである.方法: 装着中の義歯の鋳造鉤が, 高度の変色を示している10名を被験者として選択した. 12%金銀パラジウム合金を用いて, 1) 800℃1時間係留後水中で急冷, 2) 800℃1時間係留後, 室温で空冷, 3) 熱処理なし, の3条件の鋳造鉤を用いた部分床義歯を装着し, 装着時, 6ヵ月後, 1年後に鋳造鉤の輝度の測定を行った.結果: 義歯装着時の鋳造鉤の平均輝度は, 3種とも1, 000cd/m2以上の高い平均輝度を示した. 6ヵ月後の鋳造鉤は, 各条件とも装着時の約1/5-1/8と急激な輝度の低下が認められた. 1年後ではさらに輝度は低下し, 装着時の約1/7-1/12となった. 6ヵ月, 1年後ともに急冷を行ったほうが熱処理なし, 空冷に比べ輝度が高く有意差が認められた.結論: 熱処理の方法により鋳造鉤の輝度に有意差が認められたが, いずれも輝度は大幅に低下しており, 口腔内における金銀パラジウム合金の腐食性の高い患者では, 今回行った溶体化処理では耐変色性が十分でないことが示唆された.

A Study on Discoloration of Ag-Pd-Au Alloy Part 2. Relationship between the Composition of Ag-Pd-Au Alloys and Prevention of Discoloration

目的: 現在市販されている金銀パラジウム合金の組成と耐変色性との関係を明らかにすることを目的に, in vitroおよびin vivo両面から検討を加えた.方法: Fusobacterium nucleatumまたはStreptococcus mutansを加えたTHB (Todd Hewitt Broth) 培地に4種類の金銀パラジウム合金試料を入れ, 37℃ で嫌気培養を4週間行った.培養後, 輝度および色調の測定を行った. また使用義歯に6種類の金属試料 (金銀パラジウム合金, Ti, 14K金合金) を2カ月間埋入し, 撤去後に色差を算出した.結果: 金銀パラジウム合金は, メチルメルカプタンならびに硫化水素産生量の多いF.nucleatum培養環境下で, 大きな変色を示す傾向にあった. Cuを20.0mass%含む12%金銀パラジウム合金の変色は大きく, Tiや14K金合金の色差は小さかった. 組成の異なる4種類の金銀パラジウム合金 (Cu: 10.0-20.0mass%, Au: 12.0, 20.0mass%) は, in vitroおよびin vivoともに色差10以上の変色を認めた.結論: 市販の金銀パラジウム合金の耐変色性は合金組成の影響を受けるが, 口腔内の腐食性が高い患者では, いずれの組成の合金においても耐変色性が十分でなく, 著しい変色を示すことが確認された.

Prevalence of Bone Change in the Condyle with Panorama Radiographic Findings-For Patients Having No Complaint in Temporomandibular Joint-

目的: 本研究は, 顎関節症を主訴とせず, 歯や歯周組織などの観察を目的に撮影されたパノラマX線像を対象に, 下顎頭骨変化の出現頻度を調査し, 骨変化と年齢, 性別, 欠損型や咬合の支持との関連について検討を加えたものである.方法: 1999年12月から2000年3月の間に鶴見大学歯学部附属病院で, 各科から依頼され, 画像検査部においてパノラマX線撮影を行った25歳以上の患者, 970名を対象として調査を行った. 下顎頭の骨変化としてErosion, Osteophyte, Deformityを評価し, さらに年齢, 性別, 欠損型, 咬合の支持 (Eichnerの分類に準じた分類) について検討を加えた.結果: 調査対象970名中, 骨変化を認めたものは113名 (11.6%) で, 出現頻度は男性よりも女性に高かった (有意差あり, 女性14.4%, 男性7.8%).女性では, 骨変化の出現頻度は各年代ともに大きな差はなく, 年齢, 欠損型, 咬合の支持では有意差は認められなかった. 男性では咬合の支持の減少と65歳以上の年齢で骨変化の出現頻度が高くなる傾向にあった. 骨変化所見はDeformityが最も多く, Deformity, Erosionは若い層に, Osteophyteは高齢者層に多かった.結論: 顎関節症を主訴としない患者の11.6%に下顎頭の骨変化が認められ, 出現頻度は性別によって大きく異なることが判明した.

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.