Surgical template for completely edentulous patients.

Implant angulation is of utmost importance for fabrication of esthetic, hygienic, and functional prostheses, even in the treatment of completely edentulous patients. Most mandibular surgical templates are not reliable because of a lack of stability resulting either from severe resorption of the mandible or from the interference of mucoperiosteal flaps elevated during surgery. This article describes a technique for fabrication and surgical application of a stable template for the completely edentulous mandible. By combining the mandibular template with a maxillary duplicate denture, the problem of lack of stability can be overcome. A consistently reliable reference for implant placement in the edentulous mandible, specifically in relation to implant angulation (trajectory), can be obtained.

Microleakage of multi-step and simplified-step bonding systems.

PURPOSE: To measure and compare the microleakage of Class V resin composite restorations using the following three pairs of multi- and simplified-step dentin bonding systems (DBS): OptiBond vs. OptiBond FL, All-Bond 2 vs. One-Step, and Tenure vs. Tenure Quik. MATERIALS AND METHODS: V-shaped cavities were prepared in the mesial and distal surfaces of 30 extracted human mandibular molars with margins in both enamel and cementum, and randomly assigned into three equal groups of 10 each. All DBSs were applied strictly following manufacturers' specifications before three incremental layers of resin composite (Pertac-Hybrid) were applied in all cavities. Specimens were stored for 7 days in 37 degrees C water, thermocycled for 300 cycles between 5 degrees C and 55 degrees C, immersed in 0.5% basic fuchsin solution for 24 hours, and embedded in resin before being sectioned longitudinally in multiple sections. Dye solution penetration at the tooth/composite interface was scored from 0 to 4 under a microscope at x100 at both enamel (E) and cementum (C) margins. Data were analyzed by Kruskal-Wallis and Mann-Whitney U tests with alpha = 0.05. RESULTS: OptiBond FL and One-Step showed less microleakage at the cementum margins compared to their multi-step versions. At the enamel margins Tenure Quik showed less microleakage compared to Tenure, and none of the other DBSs tested showed significant dye penetration at that interface. All DBSs showed significantly less microleakage at the enamel margins compared to the cementum margins except for OptiBond FL and One-Step that did not show any significant dye penetration at the cementum margins as well.

Bond strength of multi-step and simplified-step systems.

PURPOSE: To measure and compare the in vitro shear bond strength (SBS) of the following three pairs of multi- and simplified-step dentin bonding systems: OptiBond vs. OptiBond FL, All-Bond 2 vs. One-Step, and Tenure vs. Tenure Quik. MATERIALS AND METHODS: 60 extracted human mandibular molars were sectioned perpendicular to the long axis 1 mm above the CEJ to expose the dentin bonding surface. After being wet-ground to 600 grit with SiC abrasive papers, rinsed and dried, the teeth were individually mounted in phenolic rings with epoxy resin, and randomly assigned into six equal groups of 10 each. The dentin surfaces were treated with the above mentioned dentin bonding systems, and a gelatin cylinder filled with resin composite (Pertac-Hybrid) was directly bonded to each pretreated surface. After 7-day storage in 37 degrees C water followed by thermocycling, the specimens were shear tested to failure on an Instron machine. Data were analyzed by independent t-tests, one-way ANOVA, and Duncan's Multiple Comparison tests at alpha = 0.05. RESULTS: Except for the pair Tenure/Tenure Quik, the differences between the pairs All-Bond 2/One-Step and OptiBond/OptiBond FL were statistically significant with All-Bond 2 and OptiBond FL yielding higher shear bond strength (P < 0.05). Findings of this study indicated that OptiBond FL was the only simplified-step system showing improved bond strength.

Temperature rise in pulpal chamber during fabrication of provisional resinous crowns.

STATEMENT OF PROBLEM: The heat generated during the exothermic polymerization reaction of autopolymerizing resinous materials and the heat generated by ultraviolet lamps during irradiation of photopolymerizing resinous materials could cause pulpal damage when a direct technique is used to fabricate provisional restorations. This could occur if temperature elevations overcome the physiological heat dissipating mechanisms of the dental-periodontal system. PURPOSE: This in vitro study compared the rise in temperatures in the pulpal chamber during fabrication of provisional complete veneer crowns by direct method with different autopolymerizing and photopolymerizing resins. The effect of curing resinous crowns in different matrices, such as a polyvinyl siloxane impression and a vaccuum-formed polypropylene sheet, was also evaluated. RESULTS: The results demonstrated that the amount of heat generated during resin polymerization and transmitted to the pulpal chamber could be damaging to pulpal tissues including odontoblasts. When curing of provisional resinous crowns was performed in the polyvinyl siloxane impression, significantly lower temperatures were recorded compared with curing in the vacuum-formed polypropylene sheet. CONCLUSIONS: To prevent pulpal damage, effective cooling procedures are strongly recommended when directly fabricating resinous provisional crowns.

Marginal fidelity of crowns fabricated from six proprietary provisional materials.

STATEMENT OF PROBLEM: The most important requirement for an interim crown is suitable marginal adaptation. PURPOSE: This in vitro study compared vertical discrepancies of margins for complete crowns made with six provisional materials (Provipont, Protemp Garant, Unifast LC, Triad VLC, Splintline, and Jet). MATERIAL AND METHODS: A direct technique was used to fabricate 60 provisional complete crowns on prepared molars with a polyvinyl siloxane impression and a vacuum-formed polypropylene sheet as matrices. A measuring microscope was used to measure vertical marginal discrepancies at x 100. Data were analyzed with Kruskal-Wallis one-way analysis of variance and Mann-Whitney U tests (alpha = 0.05). RESULTS: Significant differences were found between resinous materials tested (p = 0.0002) and multiple comparisons tests indicated no significant difference between Splintline and Protemp Garant; Provipont, Unifast LC, and Triad VLC; and Unifast LC, Triad and Jet provisional materials. CONCLUSIONS: This study indicated that provisional crowns fabricated with Splintline and Protemp Garant interim restorative materials recorded the least marginal discrepancies.

Fracture load and mode of failure of ceramic veneers with different preparations.

STATEMENT OF PROBLEM: Fracture is a clinical failure modality for ceramic veneers. Whether design of tooth preparation can affect the strength of ceramic veneers remains controversial. PURPOSE: This in vitro study evaluated fracture load and mode of failure of ceramic veneers, with 4 tooth preparation designs, that were bonded on extracted human maxillary central incisors. Identical parameters were also measured on unrestored intact teeth for comparison. MATERIAL AND METHODS: Fifty maxillary central incisors were randomly divided into 5 equal groups. Each group was assigned a different tooth preparation design: (1) no incisal reduction, (2) 2 mm incisal reduction without palatal chamfer (butt joint), (3) 1 mm incisal reduction and 1 mm height palatal chamfer, (4) 4 mm incisal reduction and 1 mm height palatal chamfer, and (5) unrestored (control). Forty teeth were prepared to accommodate ceramic veneers of equal thickness and incisocervical length. Stone dies were fabricated and veneers made from IPS Empress ceramic. Ceramic veneers were bonded and all teeth mounted in phenolic rings with epoxy resin. Fracture loads were recorded with a mechanical testing machine. RESULTS: Mean fracture loads (SD) in kgf were as follows: group 1, 23.7 (6.11); group 2, 27.4 (9.63); group 3, 16.4 (3.44); group 4, 19.2 (6.18); and group 5, 31.0 (10.38). Modes of failure were also analyzed for both ceramic veneers and teeth. One-way ANOVA with multiple comparisons revealed 3 significant subsets: groups 1-2-5, groups 4-1, and groups 3-4 (P <.05). Groups 1 and 2 had no ceramic veneer fractures; group 3 had 3 ceramic veneer fractures, and group 4 had 6 ceramic veneer fractures. CONCLUSION: Groups 1 and 2 recorded the greatest fracture loads that were comparable to an unrestored control.