Castable Glass Research Articles

Evolution and clinical applications of esthetic ceramic materials in dentistry

The guest editor of this special supplement to JADA provides a brief overview of the evolution of all-ceramic materials in dentistry.

Circularly Polarized Dielectric‐Loaded Antennas: Current Technology and Future Challenges

AbstractIn the last few years, dielectric loaded antennas (DLAs) have emerged as a viable solution for high‐gain reception at microwave frequencies for handheld devices such as satellite phones, radios, and global positioning systems. This article compares the performance, cost, and volumetric efficiencies of the two dominant designs, namely the dielectrically loaded quadrifilar‐helix and microstrip patch antennas. The current and future material requirements for DLAs are discussed and an example is given of a recently developed castable glass ceramic based on BiNbO4, which is suitable in terms of properties and glass formability for the single‐step fabrication of net‐shape antenna cores.magnified image

Indirect selective laser sintering of an apatite-mullite glass-ceramic for potential use in bone replacement applications

The feasibility of using indirect selective laser sintering (SLS) to produce parts from glass-ceramic materials for bone replacement applications has been investigated. A castable glass based on the system SiO2 x Al2O3 x P2O5 x CaO x CaF2 that crystallizes to a glass-ceramic with apatite and mullite phases was produced, blended with an acrylic binder, and processed by SLS. Green parts with good structural integrity were produced using a wide range of processing conditions, allowing both monolayer and multilayer components to be constructed. Following SLS the parts were post-processed to remove the binder and to crystallize fully the material, evolving the apatite and mullite phases. The parts were heated to 1200 degrees C using a number of different time-temperature profiles, following which the processed material was analysed by differential thermal analysis, X-ray diffraction, and scanning electron microscopy, and tested for flexural strength. An increase in strength was achieved by infiltrating the brown parts with a resorbable phosphate glass, although this altered the crystal phases present in the material.

Fitness and Endurance Castable Glass Ceramic Inlay

Fitness and Endurance Castable Glass Ceramic Inlay

The effect of investment material and ceramming regime on the surface roughness of two castable glass–ceramic materials

Objective: To assess the surface roughness ( R a) of two castable glass–ceramic materials, cast using four different investment materials and employing different ceramming regimes. Methods: Forty discs, each 12 mm diameter and 2 mm thick were produced from two castable glass–ceramic materials, one a glass ionomer derivative based on 1.5SiO 2–1Al 2O 3–0.53P 2O 5–1CaO–0.67CaF 2 (LG112), the other a fluorcanasite material based on 0.60SiO 2–0.05K 2O–0.10Na 2O–0.15CaO–0.10CaF 2 (SG3). The discs were made using four dental investments, two gypsum-bonded (Whip-Mix Cristobalite (WMC), Degussa California (DC)) and two phosphate-bonded (Fujivest Super (FS), Techceram Glass (TG)). A Ni–Cr metal/ceramic alloy (Wiron 99) was also used as a control. Each investment was used to produce 10 discs for each glass–ceramic material, five left in the as-cast, glass state, the other five cerammed. Ceramming was carried out either within the investment mold or after de-vesting from the investment mold. The discs had their surface roughness values measured using a stylus, surface contact measuring instrument. Results: For the Ni–Cr alloy the phosphate-bonded investments produced discs significantly smoother than those produced by the two gypsum-bonded investments ( p<0.05). The FS investment produced the smoothest discs ( p<0.05), but there was no significant difference between the discs produced by the two gypsum-bonded investments ( p>0.05). For the SG3 material no significant differences were seen between the as-cast glass and cerammed discs ( p>0.05), with the WMC investment producing the smoothest discs ( p<0.05), and the TG investment the roughest ( p<0.05). The LG112 material showed a significant difference between glass and cerammed discs for the gypsum-bonded investments ( p<0.05) but not when using phosphate-bonded investments ( p>0.05). With LG112 the WMC investment produced smoother discs than the DC and TG investments ( p<0.05). The DC investment produced rougher discs than the two phosphate-bonded investments ( p<0.05). Significance: The selection of investment material can have a significant effect on the as-cast surface finish of castable glass–ceramic materials. A gypsum-bonded investment material gave smoother surface finishes compared to phosphate-bonded investments. The ceramming process significantly increases surface roughness.

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.

The effect of casting conditions on the biaxial flexural strength of glass–ceramic materials

Objective. To assess the effect of mould and glass casting temperatures on the biaxial flexural strength (BFS) of two different types of castable glass–ceramic, using existing laboratory equipment and techniques. Methods. Two castable glass–ceramic materials were evaluated. One glass (LG3) is based on SiO 2–Al 2O 3–P 2O 5–CaO–CaF 2, and is similar in composition to glasses used in the manufacture of glass–ionomer cements. The other glass (SG3) is based on SiO 2–K 2O–Na 2O–CaO–CaF 2, and is a canasite-based material. Both materials were used to produce discs of 12 mm diameter and 2 mm thickness using the same lost-wax casting process as used for metal castings. Mould temperatures of between 500°C and 1000°C and glass casting temperatures of between 1100°C and 1450°C were evaluated. The cast discs were cerammed and the biaxial flexural strength determined with a Lloyd 2000 R tester. Results. A significant difference was found for the BFS in the range of mould temperatures evaluated, with the optimum investment mould temperature being 590°C for LG3 and 610°C for SG3 ( p=0.0002 and p=0.019, respectively). No significant differences were seen between any of the glass casting temperatures evaluated. Significance. The mould temperature for castable glass–ceramic materials produced using the lost-wax casting process can have a significant effect on BFS. The optimum mould temperature may differ slightly depending on the type of material being used. The glass casting temperature of these materials does not appear to have a significant effect on BFS.

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.

Influence of lamination on the flexural strength of a dental castable glass ceramic

This study evaluated the effect of veneering Dicor castable ceramic with Vitadur N and Dicor Plus feldspathic porcelains. A biaxial flexure test was conducted on five groups of specimens (Dicor castable ceramic, Vitadur N dentinal porcelain, Dicor Plus dentinal porcelain, Dicor core veneered with Vitadur N and Dicor core veneered with Dicor Plus castable ceramic). Each group consisted of 10 disks of nearly identical dimensions with a 1.98 ± 0.04 mm thickness and 15.7 ± 0.35 mm in diameter. Statistical analysis indicated that there was neither significant difference ( p > 0.05) between mean flexural strength of Dicor Plus and Vitadur N ceramic or Vitadur N and Dicor/Vitadur N ceramic specimens. The mean flexural strength of Dicor/Vitadur N specimens was significantly lower than the mean flexural strength of Dicor ceramic specimens. Conversely, there was no significant difference between mean flexural strength of Dicor ceramic and Dicor/Dicor Plus ceramic specimens. Scanning electron microscope (SEM) examinations of Dicor/Dicor Plus ceramic specimens suggested better wetting of Dicor core by Dicor Plus ceramic with lower incidence of porosity at the interface. However, Dicor/Vitadur N ceramic specimens exhibited a higher incidence of porosity at the interface. This indicated that lamination of Dicor castable ceramic material with feldspathic porcelain for esthetics could be attained without sacrificing strength of the original material, provided that appropriate veneering material was selected.

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.

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.

Effect of acid etching on the flexural strength of a feldspathic porcelain and a castable glass ceramic

This project studied the effect of altering surface topography by chemical etching on the strength of a feldspathic porcelain and castable glass ceramic. Fifty specimens of each ceramic material were subjected to five different etch times (in groups of 10). A silane coupling agent and composite resin cement were applied. Specimens were then subjected to a three-point flexural strength test. Representative specimens were examined under scanning electron microscope to elucidate more information on the effect and the depth of etch. There was no significant difference in the mean flexural strengths between the etched and nonetched groups and no significant difference between the different etching times for either material. Photomicrographs revealed dissimilar etch depths and selective dissolution of the phases. It appears that chemical etching can improve the retention of ceramic laminate veneers without significant loss of strength.

Wear of ceramic inlays, their enamel antagonists, and luting cements

The wear of ceramic inlay materials and antagonist enamel cups was measured in vitro. Per group, six MOD inlays were adhesively cemented in extracted molars. Castable glass ceramic, pressed glass ceramic, and feldspathic porcelain were used as inlay materials. A microfilled and a fine hybrid composite served as luting agents. The restorations were exposed to an in vitro wear test that corresponds to approximately 5 years of clinical service. The wear in the occlusal contact area was quantified during and at the end of the test with a three-dimensional scanner. Final wear measurements on the inlays (mean ± SD) ranged from 21.8 ± 8.8 μm for pressed glass ceramic to 59.0 ± 37.9 μm for castable glass ceramic. The mean wear of the enamel antagonists ranged from 74.6 ± 32.9 μm for pressed glass ceramic to 153.2 ± 61.5 μm for feldspathic porcelain. The wear of the luting composites at the end of the test ranged from 4.9 ± 5.1 μm for microfilled to 12.3 ± 6.3 μm for fine hybrid.

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.

Castable glass ceramic crowns and their reaction to endodontic therapy

The purpose of this investigation was to determine how castable glass (Dicor) crowns would react to both cold testing and endodontic access intervention. Full crown preparations were made on six extracted maxillary teeth. The teeth were then forwarded to Dentsply International, York, Pa. Six castable glass crowns were fabricated to fit these teeth and returned to us. Subsequently the teeth were dried and the crowns were cemented. Scanning electron micrographs of the cemented crowns were made, and endodontic access openings were drilled. The teeth were also cold tested with standard methods. The teeth were then again subjected to scanning electron microscopy to determine any changes the crowns might have undergone. One crown cracked around the gingival collar as scanning electron microscopy was performed. The other crowns did not exhibit any problems such as cracking or crazing from either the access openings or the cold testing.