Auto-cured Glass Ionomer Research Articles

Fluoride rechargability of a non-resin auto-cured glass ionomer cement from a fluoridated dentifrice: An in vitro study

In addition to their fluoride-releasing properties, glass ionomer cement (GICs) have the ability to reuptake and release fluorides from commonly used sources like fluoridated dentifrices. This property has the potential to provide a continuous low concentration of fluoride in the saliva aiding in caries prevention. The superior fluoride-recharging abilities of resin-modified GICs over conventional GICs have been documented. The manufacturer of a non-resin, auto-cured GIC (GC Fuji VII) claims fluoride release from the product to be about six times that of conventional GIC. It was hypothesized that perhaps this high fluoride release could translate into a high reuptake and release, when exposed to a 1 000 ppm fluoridated dentifrice every day, thus providing increased fluoride levels in saliva. This study therefore examined fluoride-recharging abilities of the non-resin, auto-cured glass ionomer cement from a 1 000 ppm fluoridated dentifrice and compared it with resin-modified glass ionomer cement. Twelve glass ionomer discs each of resin-modified glass ionomer cement (GC Fuji II L C, Group 1) and the non-resin, auto-cured glass ionomer cement (GC Fuji VII, Group 2) were prepared with precise dimensions of 9 x 2 mm. The 12 specimens in each group were further subdivided into two subgroups of six each. Subgroup A involved no fluoride treatment (Control). Subgroup B involved application of a 1 000 ppm dentifrice for 2 minutes twice daily with a soft toothbrush. The disc-specimens were then suspended in airtight plastic bottles containing exactly 20 ml double distilled water. The fluoride concentration of the water in which the specimen discs were immersed was measured by means of a fluoride ion selective electrode connected to an ion selective electrode meter/digital ion analyzer at 1, 2, 7, 15, and 30 days. It was performed using the Kruskal-Wallis Test. Fuji VII, despite a high fluoride release, did not significantly recharge when exposed to a 1 000 ppm fluoridated dentifrice.

A resin impression SEM technique for examining the glass–ionomer cement chemical fusion zone

Examination of the auto-cure glass-ionomer cement (GIC)-tooth interface using conventional SEM techniques causes severe dehydration and subsequent fracturing of the GIC, hampering accurate assessment of the GIC-tooth interface. A simple, accurate impression technique was developed to examine the GIC chemical fusion zone. Samples of GIC were bonded to prepared cavities and tooth surfaces that had been conditioned with 10% polyacrylic acid for 10 s and allowed to mature for 24 h in neutral buffered saline, sectioned under water and then acid etched with 37% phosphoric acid for 30 s to remove sectioning smear layer and to highlight surface morphology, rinsed and gently dried. Optibond Solo Plus was then applied and photo-polymerized. Increments of posterior hybrid composite were then bonded onto the Optibond and photo-polymerized. The tooth sections with attached GIC were then dissolved off the bonded composite with 18% HCl for 4 days. Subsequent SEM examination of the resin impressions created with this technique provided high-quality, detailed images of the GIC chemical fusion zone, without the development of the fracture artefacts associated with the desiccation of GIC. The resin impression technique described proved to be a simple and successful method for providing accurate SEM images of the GIC-tooth chemical fusion.

The influence of resin coating on the shear punch strength of a high strength auto-cure glass ionomer

Objectives. The aim of this study is to examine the influence of early water contact on the shear punch strength of a modern, high strength, auto-cure glass ionomer (Fuji IX GP). Methods. Specimens, 8.0 mm in diameter and approximately 1.25 mm thick, were prepared in metal washers, and allowed to remain covered by polyester strips for 7 min, to ensure completion of the initial set. A minimum of 32 specimens was prepared for each set of experiments and they were divided into two equal groups. Following removal of the strips, the surfaces of the specimens in Group 1 were immediately coated on both sides with Fuji Coat LC and light cured for 10 s. In Group 2 the specimens were left uncoated. All specimens were then placed in distilled water at 37 °C, and stored for periods of 24 h, 1, 2, 5, or 8 weeks. The strength of the specimens was measured at each time interval in the shear mode by a punch test in a universal testing machine. Results. The mean strength of the coated specimens in Group 1, which had been protected against exposure to water, increased significantly on ageing from 67.1 (24 h) to 78.0 MPa (1 week), with no further significant change in strength. The mean strength of the specimens in Group 2 increased significantly from 75.7 (24 h) to 83.3 (1 week) and 91.9 MPa (2 weeks), with no further significant change in strength. Uncoated specimens were stronger at all points of time. The difference was statistically significant at 24 h, 2, 5, and 8 weeks ( P<0.05), but not at 1 week ( P=0.061). Significance. The results suggest that, contrary to the usual instructions for placement of glass ionomer, early access to water will positively influence the shear punch strength of Fuji IX GP.

Adaptation to the cavity floor of the light‐cured glass ionomer cement base under a composite restoration

The study attempted to assess methods of prevention of the formation of a contraction gap in a cylindrical enamel and dentine cavity. The influence has been investigated of the tensile bond strength of cement/dentine and cement/composite resin and the direct tensile strength during setting of light-cured glass-ionomer cements. The interface between composite resin/cement and cement/dentine were viewed and photographed by replica techniques under an SEM (Scanning Electron Microscope). The most noticeable finding was that an enamel and dentine cavity applicated with light- and auto-cured glass-ionomer cement generally presented with a small construction gap at the tooth restoration interface. However, the light-cured glass-ionomer base (Vitrabond) exhibited significantly better tensile bond strength to dentine and resin performance than the conventional glass-ionomer tested. This study revealed that there was no clear relationship between the adhesion to dentine and the adaptation to the dentine cavity floor.

Bond strength of a light-cured and two auto-cured glass ionomer liners

Ninety-nine extracted human molar teeth were used in this study comparing the shear bond strengths on dentine of one light-cured and two auto-cured polyalkenoate (glass ionomer) cements. Bond strength can be influenced by differences in tooth structure. A balanced-incomplete block design (Hull and Nie, 1981) was used to reduce variation attributable to such differences. Cements were applied to paired dentine surfaces in combinations such that 66 tooth sides were treated with each material. A light-cured dentinal adhesive and composite resin restorative material were then placed and shear bond strength testing was conducted exactly 24 h after the completion of each specimen. Mean forces (MPa) for the three materials were compared using an appropriate analysis of variance model (balanced-incomplete-blocks) The shear bond strengths (MPa) of the light-cured liner (Espe, Seefeld/Oberbay, FRG) was 4.71 ± 1.16. Vitrabond showed the greatest variance of all three materials tested, however this material's average bond strength was greater than the maximum achieved for the other materials. Student-Newman-Keuls comparison of means showed that all cements differed significantly from each other (α = 0.05).It is concluded that the light-cured glass ionomer liner exhibited significantly better shear bond strength performance than the two auto-cured glass ionomers tested.