Tamotsu Yamaga

CLINICAL OBSERVATIONS OF NONCOPING OVERDENTURE ABUTMENTS PROTECTED BY TANNIN-FLUORIDE PREPARATION

STATEMENT OF PROBLEM The exposed dentin of overdenture abutments can lead to caries. Therefore chemical protection is needed to prevent caries. Considering that dentin contains both organic and inorganic components, reinforcement of both components should give reasonable results. Tannin-fluoride preparation strengthens both the organic and inorganic components of teeth. PURPOSE This study examined whether the tannin-fluoride preparation protects noncoping abutments. MATERIAL AND METHODS Thirty-one subjects aged 36 to 86 years participated in the clinical trial. A trial autopolymerizing resin containing the preparation or a conventional autopolymerizing resin was applied to the inner surface of the denture base, which was in contact with the abutments. When there were autopolymerizing resin group abutments, there was also at least one preparation group abutment under the overdenture. RESULTS The incidence of caries in the preparation and autopolymerizing resin groups were 0% and 0%, respectively, for the first 2 years, 4.5% and 0%, respectively, during the 3- to 4-year period, 13.8% and 75%, respectively, during the 5- to 8-year period, and 10% and 15%, respectively, in total. Gingival crevicular fluid demonstrated a tendency to decrease in both groups over time. CONCLUSION The trial autopolymerizing resin containing the preparation has a long-term caries prevention effect, and helps to maintain gingival health. Without adding clinical steps, abutments can be protected by the tannin-fluoride preparation.

Clasping system with rotational path of insertion. Part 1. Retention of denture

The rotational path of insertion differs substantially from the conventional path or the straight path of insertion. In the use of the rotational path, one segment of the partial denture is seated first, then the remainder of the prosthesis is rotated into position. One segment of this system is the rigid retentive component with long rest and the other the conventional clasp.This study examined the influence of point and direction of displacing force and the proximal undercut of rigid retainer on retention of this system. Then this system was applied in clinical field. The following results were obtained:1) Retention of denture is the smallest when displacing force was applied at the conventional clasp part.2) Direction of displacing force (± 10deg;) has no significant effect on the retention.3) The value of retention showed a tendency to increase in order when proximal undercut of rigid retainer was 0.3, 0.7 and 1.0 mm respectively.4) The effects of the point and direction of displacing force on retention of mesio-disto rests and reciprocal arms design are similar to those of original long rest design.5) When a severly tilted posterior tooth is used as an abutment tooth, this system could provide adequate retention.

Clinical Studies on Crevicular Fluid of Abutment Tooth. Part 4. Effects of Proximal Minor Connector Design.

The purpose of this study was to investigate the relationship between gingival health around abutment teeth and design of proximal minor connector. Twenty-two subjects who have not worn dentures for at least 6 months participated in this study. Four types of proximal minor connector were investigated. Gingival health such as gingival crevicular fluid (GCF) flow, gingival index (GI), plaque index (PlI) and probing depth were examined just before and 12 months after insertion of dentures. The results were as follows:1. In the conventional design of the proximal minor connector, gingival health had a tendency to worse.2. In the open design of the proximal minor connector, gingival health had a tendency to improve.3. On both open and closed sides of the rotational path clasping system, gingival health had a tendency to be unchanged.

Clinical studies on crevicular fluid of abutment tooth. Part II. Gingival condition around proximal area adjacent to edentulous spaces

Sixty subjects (42 subjects with dentures and 18 subjects without dentures) were participated in this study. Crevicular fluid flow (Periotron unit: GCF), gingival index (GI), plaque index (PH) and probing depth (PD) of 209 marginal gingiva around natural and crowned abutment teeth were measured to evaluate gingival condition.The following results were obtained.1. The GI, PII and PD in subjects with dentures were higher than those in subjects without dentures. The GCF in subjects with dentures was inclined to be high comparing with those in subjects without dentures.2. The GCF, GI and PD of crowned teeth in the subjects with dentures were higher than those of natural teeth. On the other hand, the GCF, GI and PD of crowned teeth in the subjects without dentures were almost equal to those of natural teeth.3. The coefficient of correlation between GCF and other indices (GI, PII, PD) were+0.66 (p<0.01), +0.38 (p<0.01) and+0.38 (p<0.01), respectively.

[Caries-reduction of overdenture abutment. Part 2. Solubility of the embedded tannin-fluoride preparation].

We tried to embed HY-preparation with the zinc oxide eugenol cement as the base material to the inner surface of denture base to which the abutment might contact. We reported that it was useful to prevent caries of the overdenture abutment teeth. But we anticipated solubility of the embedded HY-preparation might gradually decrease.In this study we measured the F-ion solubility in the HY-preparation and examined the gradual change of its solubility in vitro, and examined clinically the caries activity of five subjects with overdenture and obtained the following results.1) The F-solubility in both distilled water and artificial saliva almost had the same increasing tendency.2) The F-solubility of the preparation, with zinc oxide eugenol cement in powder-liquid ratio of 6: 1 and 12: 1, had almost the same increasing tendency.3) The solubility of HY-preparation to artificial saliva per day was larger in the early stage and gradually decreased thereafter, but after 24 weeks the solubility was almost nil. The solubility period of R2-group with larger surface area was longer than that of R1-group.4) We examined clinically caries activity with the Cariostat. It was lower after 3 months than on the time we had embedded the HY-preparation in the cavity.

[Filling materials with a tannin-fluoride preparation in denture base. Part 1. In relation to the mixing ratio of preparation to the autopolymerizing resin].

We embedded tannin-fluoride preparation with the zinc oxide eugenol cement as the filling material to the inner surface of denture base to which the abutment might contact, and reported that it was useful to prevent caries of the overdenture abutment teeth. But we anticipated the weakness of mechanical strength of the denture.In this study we produced autopolymerizing resin containing the preparation, and the F-ion solubility, setting time, Knoop Hardness, adhesive strength and compressive strength were measured. The following results were obtained:1) The F-ion solubility was increased as the mixing ratio increased.2) Setting time was increased as the mixing ratio increased.3) The values of Knoop Hardness from 10 to 50% groups were lower than that of 0% group, and there was no statistical difference between the values from 10 to 50% groups.4) The values of adhesive strength of mixing ratio from 10 to 30% groups showed almost the same value as that of 0% group.5) The values of proportional limit of compressive strength of 10 and 20% groups showed almost the same value as that of 0% group.

Dynamical Studies on Major Connector in Partial Denture

口蓋部連結装置は,上 顎局部床義歯 において広 く用い られてお り,両 側の義歯床間 あるいは義歯床 と間接維持 装置 とを連結 して義歯 の維持,安 定をはか り,義 歯 に加 え られた荷重 を維持歯や顎堤粘膜に分散する役割 を果た している.し たが ってこの連結装置の設計を誤まると, 連結装置 のこれ らの役割 を十分に果 たす ことができず, 患者に不快 な装着感 を与 えた り1),義 歯床の回転 を引き 起 こした り2,3),維 持歯に対 して 有害 な側方力 を与えた りする4)と いわれている.し たがって,臨 床 においてこ の連結装置 の設計条件 とその装置 の力学的性質 との関係 について把握するこ とはきわめて重要な ことである. 従来,連 結装置に関す る力学的研究 としては,連 結装 置の応力分布に関する一連の研 究5~9)や,咬合圧下 に お ける装置 の応力分布10,11)などが報告 されている.特 に連 結装置の設計条件 と力学的性質 との関係について検討 し た もの としては,床 の回転量が連結装置 の厚径の増大 に 伴 って対数比例的 に減少する と報告 した もの2,3),さらに は連結装置の幅,厚 さ,断 面形状,材 質 とその力学的性 質 との関係について理論的考察 をした もの12~14)や実験 的 に研究 した もの15)などがある. このよ うに,こ れ までの研究 によって,連 結装置の力 学的性質に対す るその形態的条件の影響が次第に明らか にな りつつあるが,臨 床 における個々の症例 に対 してこ れ らの成果 を利用する うえでは,複 雑 な計算 を必要 とす るなどの不便 さが ある.こ の点に関 して,野 首 ら14)は, 口蓋の形態を円弧型に想 定す ることにより,そ の荷重 変位関係が簡単 に求め られる ノモグラム を作 成 して い る. 今回,著 者 らは,さ らに計算精度の向上 と操作の簡略 化 をはかるため,小 型計算機を用 いて連結装置 の荷重 変位関係 な らびに各部の応力を計算する ソフ トウェアー を作成 した.そ して口蓋形態の実測値15)を参考 にした連 結装置試料の これ らの実測値 とこの ソフ トウェアーを用 いて得た値 とを比較 し,さ らに円弧型以外の形態に関 し て も,そ の応力分布を調べ臨床的応用への可能性 につい て も検討 を加 えた.