Tensile bond strengths of provisional luting agents used with an implant system.

STATEMENT OF PROBLEM: Retrievability of cemented implant-supported fixed prostheses is desirable. Retentive strengths of new provisional luting agents have not been reported. PURPOSE: This study compared the tensile bond strengths of 6 provisional luting agents when used with cemented superstructures and 1 implant system. MATERIAL AND METHODS: Ten castings were fabricated and randomly paired with abutment specimens. Castings were cemented and the assemblies were stored in distilled water at 37 degrees C for 48 hours. Tensile bond strength necessary to remove each casting was measured with a 500-kg load and a crosshead speed of 0.5 cm/min. Crown/abutment specimens were cleaned after testing, and the testing procedure was repeated for a total of 6 luting agents (n = 10). Data were analyzed with 1-way analysis of variance and Scheffé's analysis (alpha=.05). RESULTS: Tensile bond strengths ranged between 1.29 and 4.08 MPa. The lowest tensile bond strengths were found to be statistically similar between Temp Bond and Provilink luting agents. Neo-Temp luting agent exhibited the highest tensile bond strength (P <.01). CONCLUSIONS: Temp Bond and Provilink luting agents exhibited the lowest mean tensile bond strengths. Neo-Temp luting agent exhibited a tensile bond strength more than 3 times that of Temp Bond luting agent.

Vertical height loss: an investigation of four restorative materials opposing enamel.

PURPOSE: The objective of this in vitro investigation was to compare the vertical wear produced by cone-shaped styli of three ceramic restorative materials and a Type III gold alloy opposing flattened human enamel. Vertical wear was measured as enamel height loss, material stylus height loss, and total vertical height loss (the sum of the enamel height loss and the restorative material height loss). MATERIALS AND METHODS: Ten cone-shaped styli were fabricated from each of four restorative materials, which included two machined ceramics, a pressed ceramic, and a Type III gold alloy. To maintain the standardized shape, styli were not polished or glazed. Specimens were subjected to wear in the presence of water for 100,000 cycles at 1.2 Hz under a load of 75 N using a wear simulation device. Enamel wear was evaluated by profilometry, and stylus wear was evaluated by computer imaging. Vertical wear was reported as enamel height loss, material stylus height loss, and total vertical height loss (the sum of the enamel height loss and material height loss). Data were compared using one-way analysis of variance and Scheffe's analysis (alpha = 0.05). RESULTS: Significant differences existed among materials based on material height loss (p = .0001), enamel height loss (p = .0001), and total vertical height loss (p = .0118). No significant difference among the three ceramics was found in mean total height loss, which ranged from 0.280 to 0.305 mm. However, the Type III gold exhibited less mean total wear (0.231 +/- 0.082) than the pressed and one machineable ceramic. This machined ceramic exhibited the most material height loss (0.249 +/- 0.044 mm). With the other ceramics, mean enamel wear was significantly more (0.211 and 0.216 mm, respectively). CONCLUSIONS: During wear simulation, pressed or machineable ceramics opposing flattened enamel exhibited a similar degree of total vertical height loss. One machined ceramic material wore significantly more than the other materials. The other machineable ceramic and the pressed ceramic wore the opposing enamel significantly more.

In vitro mechanical property comparison of four resins used for fabrication of provisional fixed restorations.

PURPOSE: This study recorded and compared the flexural elastic moduli and moduli of rupture of four materials (Provipont DC resin, Triad provisional restorative material, Jet acrylic resin, and a 50:50 mixture of Jet acrylic resin and orthodontic resin) used to make provisional restorations. MATERIAL AND METHODS: Thirty-nine identical 63 x 10 x 3 mm specimens were made from each of the four materials. After 24 hours, 30 days, and 60 days of water storage at 37 degrees C (13 specimens each), standard three-point bend tests were conducted on an Instron universal testing machine at a crosshead speed of 0.5 cm/minute. Stress strain curves were generated, and values for the flexural elastic moduli and moduli of rupture were calculated. Data were subjected to two-way and one-way analyses of variance (alpha = 0.05). RESULTS: Provipont DC resin exhibited significantly higher flexural elastic moduli and moduli of rupture values at the 24-hour test time. However, Provipont DC resin exhibited the greatest decrease in these values over time.

Tooth structure loss apical to preparations for fixed partial dentures when using self-limiting burs.

STATEMENT OF PROBLEM: Burs with guide pins may be used to limit the depth of tooth preparation for fixed partial dentures. The effects of guide pins on tooth structure apical to the finish line after tooth preparation for fixed partial dentures has not been recorded. PURPOSE: This in vitro study recorded loss of tooth structure within 1.0 mm apical to the finish line of teeth prepared with straight cylinder and tapered cylinder self-limiting burs and one conventional bur. MATERIAL AND METHODS: Forty-five extracted human teeth were randomly divided into three groups. The facial surface of each tooth was prepared with two types of diamond burs with guide pins and a conventional diamond for the control. The surface was profiled before and after tooth preparation. Profiled surfaces were analyzed and the groups were compared using analysis of variance and the Tukey-Kramer HSD test (alpha = 0.05). RESULTS: No significant difference was recorded between the control group and the group prepared with a round-ended tapered cylinder self-limiting pin. However, there was a statistically significant difference between the control and cylindrical pin groups, and between the two groups prepared with self-limiting diamonds. CONCLUSION: This study revealed abrasion apical to the finish line of the preparation in all groups. The cylindrical guide pin group exhibited the greatest loss of tooth surface.

Evaluation of wear: enamel opposing three ceramic materials and a gold alloy.

STATEMENT OF PROBLEM: The wear of human enamel and of the restorative material is often a critical concern when selecting a restorative material for any given clinical restorative treatment. PURPOSE: This in vitro wear investigation evaluated three ceramic restorative materials and one type III gold (the control) opposing enamel. MATERIAL AND METHODS: The area of enamel lost at specified time intervals, the stylus area lost, and the combined stylus and enamel vertical height lost were evaluated. RESULTS: Enamel wear opposing one type III gold was statistically similar to that of Dicor MGC, which was lower than that of Vita Mark II and IPS Empress, which were also statistically similar in value. CONCLUSIONS: The total vertical height lost from the type III gold specimens and opposing enamel was statistically lower than that of Dicor MGC and IPS Empress (alpha < 0.05).