Castable Glass Ceramics Research Articles

キャスタブルセラミックス（ＯＣＣ）の予後調査

The purpose of this study was to evaluate the clinical strength of castable glass-ceramic (OCC, Olympus Optical Co., Japan) restorations.On 38 patients, from February 8, 1994 to December 19, 1996 at Aichi-Gakuin University Dental Hospital, 154 castable glass-ceramic restorations were cemented.These restorations were reexamined February 1998 and an analysis of fractures in the restorations was performed. Observed fractures as well as cracking or chipping and 22.7% of the restorations were considered fractured, and the longest survival time until now has been 48 months. The Kaplan-Meier survival probability calculated for these restorations was 0.86 using Panavia 21 and 0.90 using Panavia EX after a time interval of 24 months, and 0.66 using Panavia 21 and 0.82 using Panavia EX after a time interval of 36 months. There were no significant differences in the survival between the two cements.It was then con cluded that castable glass-ceramic restorations are suitable for clinical use, although some problems remain, especially with the successful lifetime of the castable glass-ceramics.

オールセラミッククラウンの各種支台に対する接着

Although all-ceramic crowns have been recognized as very good esthetic restorations, they need a great deal of tooth substance elimination and a sufficient crown thickness because they are brittle. Many strong and tough ceramics have been developed to overcome this weak point such as a core-strengthened ceramics and a castable glass ceramics. The progress of adhesive dentistry has subsequently contributed so that all-ceramic crowns have been widely used in daily practice. Strong bondings between all-ceramic crowns and abutment teeth as a dentinoenamel junction of the natural tooth have reinforced the brittleness of all-ceramic crowns. Many adhesive resins have been developed to bond restorations to tooth substances (enamel, dentin and cementum), dental alloys, ceramics and composite resins. These bonding systems, however, are very technique-sensitive and can not demonstrate the ability if not applied properly. The most effective surface treatment of abutments for ceramic bonding are presented in this paper.

Bonding effect of adhesive resin cement to ZrO2−Al2O3 composite ceramics (3Y20A)

ZrO2−Al2O3 Composite Ceramics (3Y20A) has been discussed as a reinforcing material for castable glass ceramics. It is a goal of this study to obtain stable adhesive strength of 3Y20A using adhesive resin cement. As for the experimental conditions, four types of adhesive resins and three surface treatment methods were selected, and the effect of their bonding strength was compared. As a result, the surface roughness of 3Y20A was increased and its bonding strengh was improved with a 46% hydrofluoric acid treatment and 5-atm alumina sandblasting. In addition, the use of a silane coupling agent has a tendency to improve bonding strength. After 10,000 thermal cycles, the bonding strength of Panavia 21 was more stable than that of Super Bond C & B, Imperva Dual cement, and Bistite Resin Cement.

鋳造歯冠用結晶化ガラスの色調再現性に関する研究 結晶析出量と透過率について

In recent years, castable glass ceramics have been used clinically as material in crown and bridge restorations. Materials used in such restorations must be not only strong enough to withstand masticatory and biting forces but also aesthetically close to the color of natural teeth.In order to establish a technique for enhancing the color reproducibility of castable glass ceramics, which is an essential factor for clinical application, the relationship between the amount of crystalline phase and total light transmission of the crystal was investigated. The results were as follows:1. Castable glass ceramics showed a high degree of translucency. A crystallization temperature of 910°C was found to be the most appropriate for the amount of HAP crystal, which has a translucency close to that of enamel.2. For enhancement of the color reproducibility of castable glass ceramics, consideration must be given not only to the color of the glass and the stain but also to the influence of the tooth substance and metal as well as the color of the cement.

フルベイクタイプのキャスタブル・ガラス・セラミックス―ポーセレン・ジャケット・クラウンの荷重時の応力解析 三次元光弾性実験による応力解析

The purpose of this study was to investigate the stress distribution of all-ceramic crowns made of castable glass ceramics coping with and completely veneered by dental porcelain, using three-dimensional photoelastic stress analysis technique under a static load. Two-layered photoelastic models were made of epoxy resin. Four different loading sites were chosen, and stress was frozen.The results obtained in each model were as follows:1. Severe stress was observed in the vicinity of loading sites, and there was a strong possibility of fracture.2. Relatively low tensile stress was observed at the incisal half of the labial surface and around the cingulum of the lingual surface.3. Relatively high compressive stress was observed around the labial and lingual cervixes. This is considered to be mesiodistal tensile stress, and may be related to cervical semicircular fracture, with tensile stress around the cingulum.4. Danger of fracture from the internal surface was suggested.5. Compressive and tensile stresses tended to decrease in areas away from loading sites, compared to the partially veneered type, and superiority of complete veneered type was indicated.

Dental castable glass ceramics: ceramming treatment and colour property

The magnitudes of colour change vector and lightness were examined for 20CaO/10P2O5/10MgO/10Al2O3/50SiO2 glass ceramics (B2O3/CaF2=0.01 wt % 0.01 wt %, mass fraction). The glass ceramics were thermally treated (cerammed) for crystallization at each selected temperature (800 to 980°C for each ceramming period) within a steel ring including the investment mould. Cristobalite-quartz investment mould exhibited no adhesive mould interfaces, showing that the magnitudes of colour change vector and lightness ranged from 17.60 (890°C) to 37.05 (980°C) and 55.77 (890°C) to 71.42 (980°C) for glass ceramics, respectively, after thermal treatment for 2 h (sample thickness 2 mm). The thermal treatment controlled the colour property measured by colour analyser as compared the cerammed samples with bovine enamel and human tooth enamel.

Ｃａｓｔａｂｌｅ Ｇｌａｓｓ ＣｅｒａｍｉｃｓとＰｏｒｃｅｌａｉｎの接着に関する研究 第２報試験片の製作と引張試験

Castable glass ceramics-porcelain jacket crown, in which castable glass ceramics are used as a coping and dental porcelain is partially or completely fired, is recommended from an aspect of esthetics. The adhesive strength between two ceramic materials is considered to be important for this jacket crown. The purposes of this study were to evaluate the adhesion of two ceramic materials under tensile load and to establish fabrication of tensile test pieces.The following results were obtained.1. Established method for fabricating tensile test pieces and tensile test are adequate to know the behavior of ceramic materials under a tensile load.2. Dental porcelain used in this study showed favorable adhesion to castable glass ceramic, without detracting the inherent physical properties of castable glass ceramic.3. The white layer, which shows the formation at the surface of castable glass ceramic after the ceraming process, does not affect the adhesion of dental porcelain to castable glass ceramic.4. Reinforcement of the white layer is expected to be obtained by firing dental porcelain.

Ｃａｓｔａｂｌｅ Ｇｌａｓｓ ＣｅｒａｍｉｃｓとＰｏｒｃｅｌａｉｎの接着に関する研究 第１報 試験片形状決定のための応力解析

Prior to the evaluation of the tensile adhesive strength of dental porcelain to castable glass ceramic, stress distribution was analyzed to determine the configuration of the tensile test pieces, by using the photoelastic stress analysis method. On the assumption that 3 type tensile test pieces of dental porcelain baked on castable glass ceramics, 3 photoelastic test models consisting of two layers were made of epoxy resin. A 2 kgf tensile load was added to each model, and the stress was maintained. The stress distribution of the median section was analyzed.The results were as follows:(1) The tensile stress was observed at the castable glass ceramic-porcelain interface of all test models.(2) Stress concentration effects were significant at the periphery of castable glass ceramic-porcelain interface in two of 3 test models.(3) Uniform tensile stress was observed at the castable glass ceramic-porcelain interface in only one of 3 test models.

Influence of Crystallization on Strength and Color of Castable Glass-Ceramics Containing Two Crystals

The mechanical properties, color and transparency of glass-ceramics are highly dependent on the ceramming temperature and/or amount of the crystal phase in the glass matrix. In this study, the influence of crystallization on the strength and color, translucency of castable ceramics containing crystalline apatite and magnesium titanate were measured. It was concluded that magnesium titanate precipitated during ceramming, appeared to be an important factor in decreasing total transmittance and in determination of the color of glass-ceramics.

Effect of crystallization on fracture strength of castable glass-ceramics containing two crystals.

The relationship between fracture strength and crystallization in castable glass-ceramics was studied using castable glass-ceramics which contained crystalline apatite and magnesium titanate. Bending strength was increased with increases in crystal phases; 90, 124, 122 and 162 MPa were recorded for as-cast specimens and specimens cerammed at temperatures of 905 degrees, 925 degrees and 945 degrees C, respectively. The results of bending tests suggest that the crystallization of magnesium titanate is more effective than that of apatite in increasing the strength of glass-ceramics. Fracture toughness in specimens reheated at 905 degrees C was doubled compared with as-cast specimens. The apatite particles precipitated during ceramming treatment were thought to be an important factor in increasing both the fracture toughness and crack pinning effect.

Al2O3-and ZrO2-modified dental glass ceramics

Castable machinable glass-ceramics have been widely considered as aesthetic materials for dental restoration. In order to extend their applications to bridge-work fabrication, it is necessary to increase their fracture strength and fracture toughness. The effects of ziconia and alumina additions on the properties of glass-ceramics, especially on the mechanical properties were studied. It was found that appropriate addition of alumina increases the bending strength due to aluminium strengthening the glass-ceramic by means of incorporation into the glass network. However, additions of ziconia fail to show promising results on the mechanical property. The evolution of recrystallization and the associated microstructure were also studied and are discussed.

Effects of Surface Treatment on Adhesive Strength of Cements to Castable Glass Ceramics

Effects of Surface Treatment on Adhesive Strength of Cements to Castable Glass Ceramics

Castable glass ceramics for veneer restorations

Porcelain veneer restorations are the usual technique chosen for the placement of esthetic veneer restorations. Cast glass ceramic veneers exhibit properties that make them extremely useful for this dental application. They have a hardness, abrasion resistance, coefficient of thermal expansion, and translucency similar to that of enamel. The use of the lost wax casting technique to provide precise anatomic form and margins allows for increased accuracy during veneer fabrication. Chairside time requirements may be decreased as a result of the improved accuracy inherent in the lost wax casting technique. The dentist's ability to maximize esthetics and decrease chairside time make this a technique likely to see increased use in the future.

Ｃａｓｔａｂｌｅ Ｇｌａｓｓ Ｃｅｒａｍｉｃｓ‐Ｐｏｒｃｅｌａｉｎ Ｊａｃｋｅｔ Ｃｒｏｗｎの荷重時の応力解析 三次元光弾性実験による応力解析

A photoelastic stress analysis technique has been conducted for many years as a test to predict the mechanical behaviors of porcelain teeth under a load. The purpose of this study was to investigate the stress distribution of a castable glass ceramics-porcelain jacket crown under a static load and obtain the some informations for producing the jacket crown. On the assumption that the jacket crown consist of two layers (castable glass ceramics coping and dental porcelain), the crown models were made of epoxy resin. Three different loading sites were chosen (lingual porcelain surface, lingual castable glass ceramics surface and incisal porcelain surface) to epoxy resin models.In the case of the model which the load (2.0 kgf) was added to the lingual castable glass ceramics portion, the tensile stress in the labial porcelain portion reached the maximum value. And, when the same load was added to the lingual porcelain portion of the model, the tensile stress in the lingual castable glass ceramics portion reached the maximum value. Furthermore, in the model which was added to the lingual castable glass ceramics portion, the high tensile stress was observed in the lingual castable glass ceramics-porcelain border.

マイカ・クリスタル系ガラス・セラミックスクラウンに関する研究 適合性について

The purpose of this study is to investigate the influence of three marginal shape of abutment teeth (Flat, Moderate and Steep) on the fitness of castable glass ceramics (DICOR) crown clinically. The following results were obtained: 1. The change of width of three marginal shapes showed the same tendency on each firing procedure. 2. The vertical change of three marginal shapes showed the most constant on Flat and decreased on Steep. 3. On the marginal edge, the Labiopalatal gaps were larger than Mesiodistal gaps. 4. On Labiopalatal section, the gaps of Steep were larger than those of Flat and Moderate especially as cast. 5. The gaps Flat were almost same on Labial, Palatal, Mesial and Distal parts.

キャスタブル・ガラス・セラミックス「DICOR TM 」のラミネートベニアテクニックに関する臨床例

キャスタブル・ガラス・セラミックス「DICOR TM 」のラミネートベニアテクニックに関する臨床例