Takayoshi Igarashi

Faculty-supervised measurements of the face and of mandibular movements on young adults

PURPOSE The purpose of this study was to determine the average facial proportions and mandibular movement capacity of 316 first-year dental students who carefully recorded them on each other. MATERIALS AND METHODS This early exacting clinical experience was closely supervised by the authors in Columbus, Ohio during 1969-70. Five vertical and six horizontal distances were measured on each subjects face. An ala-tragus line and an occlusal line were drawn on the left side of the face to determine if these two lines were parallel. Measurements of mandibular movements involved maximum normal and hinge opening at the incisors and maximum amounts of right, left lateral and protrusive excursions of the mandible. RESULTS The ala width and distance between the tips of upper right and left canine cusps averaged (35.2 mm and 34.8 mm) but with very large individual variations. The distance between ala to occlusal plane lines was 29.9 mm at the tragus and 31.3 mm near the ala. The angle between orbitale and ala-tragus averaged 13.6 degrees. CONCLUSION The upper lip length was the most variable and the distance between the pupils was the most stable of the eleven facial measurements. The ala-tragus line and the occlusal plane lines were for all practical purposes parallel. Maximum jaw opening averaged 51.2 mm which was 3.0 times larger than maximal hinge opening of 17.2 mm. The maximum right plus left side jaw excursions (9.2 and 9.4 mm) totaled 18.6 mm, 2.3 times more than the 8.0 mm mean maximum forward protrusion.

Distortion and other errors in oblique cephalometric radiography.

An evaluation of image distortion and serial variation in oblique cephalometric radiography. Reduction of inaccuracies from these sources is best achieved by aligning images of the inferior border of the mandible directly underlying the structures under study.

Bond Strength to Dentin Subjected to Temporary Cementation of Resin Based Luting Agents

目的: リン酸を表面処理剤とするレジン系装着材料の仮着した象牙質に対する接着強さの影響を明らかにするために, 比較検討を行った.方法: HY-Bond Temporary Cement Hard (以下HYB), Freegenol Temporary Pack (以下FTP) およびNeodyne T (以下NDT) の3種類の仮着材で, レジンプレートを牛歯象牙質に仮着した.Variolink II (以下V2) およびRely X ARC (以下RX) を用いて, IPS Empressを接着して勢断接着試験用試料を作製した.仮着を行っていないものをコントロール (以下CON) とした.仮着した象牙質およびIPS Empressに対する表面処理は, 製造者指示に従って行った.試料を37℃ で24時間精製水中保管後, 勇断接着強さを測定した.結果: V2の接着強さは, CON (11.4MPa, a, b), HYB (12.7MPa, a), FTP (7.6MPa, b, c) およびNDT (5.9MPa, c) であった.CONと比較してNDTが有意に (P<0.05) 低い値を示したが, HYBおよびFTPでは有意差が認められなかった.一方, RXの接着強さは, CON (21.7 MPa, d), HYB (11.3MPa, e), FTP (6.0MPa, f) およびNDT (11.2MPa, e) であった.CONと比較してすべての仮着材で有意に低い値を示した.最も低い値を示したFTPでは, CONの27.5%であった.同一文字は多重比較において危険率5%で有意差がないことを示す.結論: V2とRXは, 接着強さが低下した仮着材がそれぞれで異なったことから, リン酸処理を行うレジン系装着材料の接着強さは, 組合せによって影響が異なることが明らかとなった.

A Study on Repair Restoration with High Filler Containing Indirect Composites-Surface Treatment for Light Cured Type Resins-

目的: 光重合タイプの高フィラー型硬質レジンの補修時における有効な表面処理方法を知ることを目的とした.方法: ArtglassおよびGradia (エナメル色ペーストAEおよびGE, デンチン色ペーストADおよびGD) を用い, 製造者指示に従い重合した被着体 (2×2×12.5mm) に, 処理なし (NT), シラン処理 (S), ボンディング処理 (B), シラン処理とボンディング処理を併用 (SB) の4条件で表面処理を行った.追加築盛は, 直接法および間接法のそれぞれで, 製造者指示の補修用レジンを用いて曲げ接着試験用試験体 (2×2×25mm) を重合して作製した.試験体は, 37℃ で24時間水中保管後に3点曲げ試験を行い, 曲げ接着強さを得た.結果: 被着体AEは直接法ではSB>S>B>NT, 間接法ではSB≧S>B>NTの順で, 被着体ADは直接法および間接法の両者で, SB>S>B>NTの順で有意に大きな曲げ接着強さを示した.一方, 被着体GEは, 直接法ではSB>B≧S>NT, 間接法ではSB≧S≧B>NTの順で, 被着体GDは, 直接法ではSB≧B>S>NT, 間接法ではSB≧B≧S>NTの順で有意に大きな曲げ接着強さを示した.結論: 最適な表面処理は, AEが直接法でSB, 間接法でSBおよびS, ADが直接法および間接法の両者でSB, GEが直接法ではSB, GDがSBおよびB, GEおよびGDともに間接法ではS, BおよびSBであった.

Thickness of the Metal Frame by Electroforming-Influence of Positioning Die in the Electroplating Solution-

目的: ゴールドエレクトロフォーミング法は, メタルコーピングを回転する電解溶液中で製作するため, 電鋳歯型の位置づけがコーピングの厚さに影響を及ぼすと考えられる. そこで, 電解槽内での水平的位置づけを変化させ, その影響を検討した.方法: フルベークタイプの陶材焼付冠製作用に形成した上顎中切歯支台歯模型 (松風) を原型とし, 複製電鋳歯型を製作した. 電解槽装置 (GAMMATeasy, Gramm) のビーカー (内径56.0mm) 内で, 垂直的に電極上縁から切縁中央までを20.0mmとし, 水平的に1.ビーカー中心, 2.中心から11.0mm, 3.中心から22.0mm (以下, P0, P1, P2) の3条件に位置づけした. その後, 厚さ200μmに設定しエレクトロフォーミングを行い試料とした. 試料を包埋し, 唇舌的に切断し, 走査型レーザー顕微鏡 (Laser microscope 1 LM 21 W, Lasertec) にてコーピングの厚さを測定した. 測定部位は唇面中央部, 切端部, 舌面中央部, 基底結節上部, 舌側軸面中央部 (以下, a, b, c, d, e) の5点とした. 試料数は各条件5個とし, 統計にはKruskal-Wallis testとBonferroni Correctionを用い, 各測定部位での比較を行った.結果: コーピングの厚さは, P0では全測定部位で最大値を示し, 設定値に近似した値を示した.そのほかは設定値より小さな値を示した. d, eにおいてはP0>P1>P2の順に大きな値を示し, bではP0>P1≧P2の順に大きな値を示した.結論: ビーカー内での電鋳歯型の位置づけがコーピングの厚さに影響を及ぼし, 設定した厚さより薄くなることが判明した.

A Study on Thermal Properties of All Ceramic Restorations. All Ceramics.

This study was conducted to investigate the thermal properties (thermal diffusivity, specific thermal capacity and thermal conductivity) of all ceramic restorative materials. Measurement of thermal properties of IPS Empress®, DiCOR® and adhesive resin cement Variolink II were performed by the Xenon flash method. The results obtained were as follows. Thermal diffusivity (×10-2cm2s-1) was 0.372-0.423 for IPS Empress®, 0.614 for DiCOR® and 0.191-0.193 for Variolink. Specific thermal capacity (Jg-1K-1) ranged from 0.695 to 0.872 for IPS Empress®, 1.119 for DiCOR® and 0.733-4.114 for Variolink. Thermal conductivity (Wm-1K-1) was 0.644-0.770 for IPS Empress®, 1.721 for DiCOR® and 0.297-0.475 for Variolink. Thermal conductivity of IPS Empress® was found to be less than that of human enamel, while that of DiCOR® was greater than that of human enamel. Thermal conductivity of Variolink was smaller than those of human enamel and dentin.The above results indicated that IPS Empress® had greater thermal insulation capability than human enamel and dentin and that DiCOR® had less.

Chromatic Study of IPS Empress. The Effect of Various Adhesive Resin Cements on Layering Technique.

IPS Empress® is an all-ceramic crown system which provides a color tone and light transmittance resembling those of natural teeth. However, because of the translucency of all-ceramic crowns, the color of the adhesive resin cements and the abutment teeth can affect the color of the final crowns.This study examined the effects of IPS Empress® on the layering technique and color of the adhesive resin cements on various background color by comparison and examination.The color difference from the standard color was calculated, and it was judged to have color appearance when ΔE*ab≤2.0.The conclusions were as follows:1. For A 2 background, the color appearance to standard color were obtained using translucent type cements VW and VB (Variolink).2. For Au background, the color appearance to standard color were all of translucent type cements, while for Pd background, opaque type cements YO (Variolink) insertion with better color appearance.3. For H background, using translucent type cements Tr (LA cement) containing dentin color tone and opaque type cements VO (Variolink) with lower values of lightness yielded ΔE*ab≤2.0 with color appearance.The above results suggested that appropriate intermediate cements used in the layering techniqueof IPS Empress® decrease the influence of the background color, achieving a color tone approximating the target color.

A Study on the Fine Particle Glass Ionomer Cements for Luting. Setting Characteristics and Disintegration Rate.

For improvement of film thickness of final cementation, 2 brands (Shofu HY-BOND GLASS-IONOMER CX and GC Fuji-I) of Glass Ionomer Cement were milled and the experimental fine particlepowder was produced. Ohmae et al. reported the retention, total film thickness, and physical properties in aprevious study. In this study, the setting characteristics of these experimental cements, specific surface areaof particle, and disintegration rate were investigated. The results were as follows: Peak time of reaction ofexperimental cements using a differential scanning calorimeter were shorter than normal GICs. The startingpoint of dissappearance of fluidity of experimental cements using a thermomechanical analyzer were shorteras the perticle size became smaller. The specific surface area of experimental particle increased as theparticle size became smaller. The disintegration rate of experimental cements increased compared to normal GICs.

A Study of Toothbrush Abrasion on Adhesive Resin Cement. Filler Contents of the Routing Cement.

Although there have been reports on the abrasion of resin cements, cement film thickness was hardly considered.Takamisawa evaluated the influence of the cement film thickness on the abrasion of non-filler type resin cement, and concluded that there was a close relationship between number of times and depth of abrasion. The rate of increase of the wear depth was affected by the cement film thickness.Since most resin cements contained microfiller, Variolink (Vivadent) was examined and it was IPSEmpress (Vivadent) cem kit.Newly-designed appliances to prescribe 3 cement film thicknesses were used, namely 50, 100, and 200 μm, and the abrasion for each thickness in toothbrush abrasion test was observed.Continuous measurements were made of the sectional profile, wear depth, and surface roughness by scanning laser microscope.In SEM observation, the abrasion surface showed different aspects between non-filler and microfiller types.While there was a close relationship between number of times and depth of abrasion as in the case of non-filler type, the amount of increase of the wear depth varied with the cement film thickness.Test results indicated that the cement film thickness had influence on the abrasion of resin cement, and resistance of abrasion was influenced by filler type and resin matrix.

A Study on the Retention Force of Crowns. Influence to the Changes in the Powder Particle Size Distribution of Glass Ionomer Luting Cement on the Retention Force of Crowns.

When cementing a crown, the amount of final seating is affected by the film thickness of the dental cement. To decrease the film thickness of glass ionomer cement (GIC), a GIC powder (Shofu Hybond Glass ionomer CX) was milled and three experimental fine particle powders were produced. The purpose of this study was to investigate the physical properties of fine particle GICs (ISO-9917, compressive strength, setting time, film thickness) and retention force of the crown cemented. The powder was milled with Centrifugal Fluidized Milling Machine (CF-160 Ube Kousan Co.) to produce the particle size (CX-01: maximum particle size:∅6μm, CX-02: 8μm, CX-03: 12μm). The results were as follows: In specimen containing a large amount of fine particles (CX-01), the best seating of a crown was accomplished (total film thickness: 8.0μm), though both compressive strength and film thickness was reduced to some extent. On the other hand, there was no significant difference between the retention force of normal GIC and fine particle cement (CX-01, 02, 03). The setting time of CX-01, 02, 03 was slightly longer than that of normal GIC.