Evaluation of flexure strength and vertical marginal gap distance of 3 unit all-ceramic bridges using a modified technique

The proposed study was designed to determine the feasibility of jointing procedure for Inceram fixed partial dentures combining the slip casting technique and machinable ceramic. Twenty Inceram bridges were constructed. The bridges were divided into two equal groups as follows: Group [1]: Anterior group: Ten anterior bridges replacing maxillary central incisor were constructed from Inceram alumina. Group [2] Posterior group: Ten posterior bridges replacing mandibular second premolar were constructed from Inceram zirconia. The samples from each group were further subdivided into two equal subgroups according to the technique used as follows: Subgroup [A]: Conventional technique: five anterior and five posterior bridges were constructed using the conventional technique. In this technique, the retainers and the pontic were constructed using the slip casting technique. Subgroup [B]: Modified technique: five anterior and five posterior bridges were constructed using a modified technique. In this technique, the pontic was constructed using the Celay system, then connected to the two retainers by the slip mix. The bridges constructed in this study were evaluated through the following tests: [1] vertical marginal gap distance using the traveling microscope. [2] Flexural strength using the universal testing machine. The obtained results were collected, tabulated and statistically analyzed using analysis of variance ANO-VA. There was no significant difference in the vertical marginal gap distance measurements between the conventional and modified technique among the tested groups. There was no significant difference in the flexural strength values between the anterior conventional and modified techniques. The posterior modified technique recorded a great reduction in the flexural strength values than the posterior conventional technique. The technique of jointing the milled Inceram pontic to the slip cast retainers was successful for Inceram alumina [3 units anterior bridges], but was not met with a great success for the posterior bridges from Inceram zirconia considering the flexural strength. Marginal gap distance was not affected

Influence of different PH levels on cement/alloy shear bond strength and interfacial pore count

The present study aimed to investigate the effect of different storage media with different pH levels on the cement/alloy shear bond strength and interfacial pore count. A total of 186 disc shaped samples were cast from Au-Pt-Pd, Pd-Ag and Ni-Cr alloy [62 samples for each alloy] using a copper mold former with a hole of 2 mm thickness and 5 mm diameter. Two representative samples from each alloy were selected for surface topographic assessment using a scanning electron microscope [SEM]. The 60 samples for each tested alloy were divided into 2 groups according to the type of luting cement used. Group 1:15 twin alloy samples were cemented with resin modified glass ionomer cement [RMGIC]. Group 2: 15 twin alloy samples for each tested alloy were cemented with adhesive resin cement. Each group, for each tested alloy, was divided into 3 subgroups according to the type of storage media used. Subgroup A: 5 twin cemented samples [for each alloy] were stored in normal saline for 1 week. Subgroup B: 5 twin cemented samples [for each alloy] were stored in lactic acid [pH:4] for 8 hours followed by storage in buffer solution for 16 hours then this procedure was repeated for a period of 1 week. Subgroup C: 5 twin cemented samples were stored in citric acid for 8 hours followed by 16 hours in buffer solution and the procedure was repeated for a period of 1 week. A stereomicroscope was employed to measure the pore count at the cement/alloy interface. Shear bond strength values were measured using a universal testing machine. All data were collected and statistically analyzed using ONE WAY ANO-VA. The mean interfacial pore count of the three tested alloys cemented with either RMGIC or resin cement was significantly less in lactic and citric acid storage media compared to those stored in normal saline. The mean shear bond strength values of Ni-Cr and Pd-Ag alloys cemented with RMGIC were significantly higher in citric acid compared to those stored in saline or lactic acid storage media. However, for Au-Pt-Pd alloy, cemented with RMGIC, shear bond strength values were significantly higher in lactic and citric acid storage media compared to those stored in normal saline. The mean shear bond strength values of the tested alloys cemented with adhesive resin cement were significantly reduced when stored in lactic and citric acid compared to those stored in normal saline. Meanwhile, irrespective of the type of storage media, Ni-Cr samples cemented with either resin modified glass ionomer or adhesive resin cement recorded significant higher shear bond strength values than Pd-Ag and Au-Pt-Pd alloys. 1- Resin modified glass ionomer cement can be successfully used in cementation of indirect restorations in patients with low oral pH levels either from plaque, dietary fermentable products or citrus fruits. However resin cement is not recommended in these situations. 2- Base metal alloys, luted with either resin-modi tied glass ion-omer or resin cement, are more preferable than Au-Pt-Pd and Pd-Ag alloys in all the investigated storage media

Effect of different surface treatments to two all-ceramic systems luted with adhesive cements on the interfacial fore size and shear bond strength

This study was designed to study the effect of different surface treatments on ceramic/ cement bond strength

Material and Methods: Sixty six disc shaped Duceram LFC as well as 66 Inceram samples [3mm thickness and 6 mm diameter] were constructed and divided into 3 groups according to the type of surface treatment employed. Group 1 was Al[2]O[3] blasted, group 2 was HF etched and group 3 was copper coated. Each group of the tested ceramic was divided into 2 subgroups according to the type of cement used. Subgroup 1: twin samples were cemented with glass ionomer cement, subgroup 2: twin samples were cemented with resin cement. A stereomicroscope was used to measure the surface roughness of the differently treated ceramics and calculated the interfacial mean pore count and average pore size of cemented samples. A scanning electron microscope was used to study the surface topographic changes of the differently treated ceramics and calculated the interfacial mean pore count and average pore size of cemented samples. A scanning electron microscope was used to study the surface topographic changes of the differently treated ceramics. Shear bond strength values were measured using a universal testing machine. For the copper coated samples, optical measurement were taken using a spectrophotometer [N = 5 for each material] and color change delta E was calculated. All data were statistically analyzed using ONE WAY ANOVA

Results: The highest bond strength was obtained with the blasted and copper coated groups of the tested ceramics when glass ionomer cement was used. With resin cement, the HF etched Duceram and the blasted Inceram groups exhibited the highest shear bond values due to the increased surface roughness [Ra]. However the blasted Inceram recorded the highest shear bond values compared to the HF etched and copper coated groups with resin cement. Spectrophotometric measurements revealed no color changes [delta E] before and after copper coating

Conclusions: blasting and copper coating Duceram LFC and Inceram exhibited a high shear bond values with glass ionomer cement. Blasting or HF etching is recommended for Duceram LFC when resin cement is to be used. However, blasting of inceram is recommended when resin cement is to be used