Comparison of fracture resistance in post restorations in primary maxillary incisors.

AIM: This in vitro study aimed to test the fracture resistance of 4 different posts used in the restoration of severely decayed primary incisors. MATERIALS AND METHODS: Fifty primary incisors were selected for this study and sectioned 1 mm above the CEJ. After filing and irrigation of the root canal space, the canals were obturated with Metapex and 3 mm of post space was prepared inside the canals. Intact glass fiber posts, split-ended glass fiber posts, composite resin posts, and orthodontic γ 'gamma' wire posts were used as intracanal posts and the final composite resin restoration was placed using a paediatric strip crown. After thermocycling of the specimens, the fracture resistance was measured using a universal testing machine. RESULTS: The mean fracture resistance of split- ended glass fiber posts was higher than the other groups, however, there was no significant difference between any of the groups (P>0.05). CONCLUSION: Split-ended glass fiber posts seem to be a more appropriate option for full coverage restorations in primary incisors.

Microleakage and marginal gap of adhesive cements for noble alloy full cast crowns.

Very limited comparative information about the microleakage in noble alloy full cast crowns luted with different types of adhesive resin cements is available. The purpose of this study was to evaluate the microleakage and marginal gap of two self-adhesive resin cements with that of other types of adhesive luting cements for noble alloy full cast crowns. Fifty noncarious human premolars and molars were prepared in a standardized manner for full cast crown restorations. Crowns were made from a noble alloy using a standardized technique and randomly cemented with five cementing agents as follows: 1) GC Fuji Plus resin-modified glass ionomer cement, 2) Panavia F 2.0 resin cement, 3) Multilink Sprint self-adhesive resin cement, 4), Rely X Unicem self-adhesive resin cement with pretreatment, and 5) Rely X Unicem with no pretreatment. The specimens were stored in distilled water at 37°C for two weeks and then subjected to thermocycling. They were then placed in a silver nitrate solution, vertically cut in a mesiodistal direction and evaluated for microleakage and marginal gap using a stereomicroscope. Data were analyzed using a nonparametric Kruskal-Wallis test followed by Dunn multiple range test at a p<0.05 level of significance. The Rely X Unicem (with or with no pretreatment) exhibited the smallest degree of microleakage at both tooth-cement and cement-crown interfaces. The greatest amount of microleakage was found for Panavia F 2.0 resin cement followed by GC Fuji Plus at both interfaces. No statistically significant difference in the marginal gap values was found between the cementing agents evaluated (p>0.05). The self-adhesive resin cements provided a much better marginal seal for the noble alloy full cast crowns compared with the resin-modified glass ionomer or dual-cured resin-based cements.

Assessment of Bond Strength between Metal Brackets and Non-Glazed Ceramic in Different Surface Treatment Methods.

OBJECTIVE: The aim of this study was to evaluate the bond strength between metal brackets and non-glazed ceramic with three different surface treatment methods. MATERIALS AND METHODS: Forty-two non-glazed ceramic disks were assigned into three groups. Group I and II specimens were etched with 9.5% hydrofluoric acid. Subsequently in group I, silane and adhesive were applied and in group II, bonding agent was used only. In group III, specimens were treated with 35% phosphoric acid and then silane and adhesive were applied. Brackets were bonded with light-cured composites. The specimens were stored in water in room temperature for 24 hours and then thermocycled 500 times between 5°C and 55°C. RESULTS: The difference of tensile bond strength between groups I and III was not significant (P=0.999). However, the tensile bond strength of group II was significantly lower than groups I, and III (P<0.001). The adhesive remnant index scores between the three groups had statistically significant differences (P<0.001). CONCLUSION: With the application of scotch bond multi-purpose plus adhesive, we can use phosphoric acid instead of hydrofluoric acid for bonding brackets to non-glazed ceramic restorations.

XPS analysis of the surface of leucite-reinforced feldspathic ceramics.

OBJECTIVE: The bond of a silane-coupling agent to a ceramic surface is expected to be influenced by the composition and chemical state of the ceramic surface. The purpose of this study was to determine the variation in the composition and the chemical states of the surfaces of a range of leucite-reinforced feldspathic (LRF) ceramics using X-ray photoelectron spectroscopy (XPS). METHODS: Five LRF ceramic discs (IPS Empress,Optec HSP,VMK 68, Mirage, and a modified Mirage) were produced and polished to a 1 microm finish. A further nine discs of the modified Mirage were produced. The discs were stored for 48h in a vacuum oven at 110 degrees C to remove absorbed water. The surfaces of these discs were analysed by XPS. Survey scans at 30 degrees take-off angle were taken and surface composition (in at%) was calculated from the narrow scans for Si 2p, O 1s, Al 2p, Mg 2s, K 2p, Na 1s, Ca 2p and N 1s. RESULTS: Atomic concentration of elements (after exclusion of C) for the five LRF ceramics were in the range: O, 45.0-51.6%; Si, 26.7-35.6%; Al, 6.3-9.7%; Mg, 4.9-8.8%; K, 0.5-2.2%; N, 0.9-2.9% and less than 1% of Na and Ca. The shapes of the O 1s and Si 2p narrow scan core lines of the five LRF ceramics were virtually identical. SIGNIFICANCE: All five LRF ceramics were found to have a silica-rich surface layer due to a reduction in K and Na relative to the bulk composition. Both the composition and chemical states of the surfaces for the five LRF ceramics were very similar.

Intercondylar width as a guide to setting up complete denture teeth.

A clinical study was designed to investigate the relationship between intercondylar width (ICW) and inter-dental widths of the upper and lower canines and first molars to aid in denture teeth positioning. The study was divided into two parts so that the results of the first part could be verified in the second part. In the first part, 27 adult subjects were selected according to the exclusion criteria of the study. A kinematic hinge axis locator was used to locate the true point of condylar rotation. The distance between these points was considered to be the ICW. A strong correlation was found between ICW and interdental measurements, with ICW and upper first molars being the strongest (r=0.612, P= 0.004). A set of indices developed from the results was recommended for the positioning of complete denture teeth. In the second part of the study, inter-dental measurements were estimated using the indices obtained in the first part. The estimated inter-dental widths showed no significant differences compared with the real widths (P= 0.109, P=0.849, P=0.353, P=0.41). Based on the results of this study, ICW measurements can be used for setting up canines and first molars in complete dentures.