The Journal of Prosthetic Dentistry publication standards of ethical conduct.
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Animal Experimentation↗
Biomedical subjects
Brien R Lang
Publications and source records attributed to Brien R Lang.
Complete denture occlusion.
Lingualized articulation has been advocated by many practitioners over the past 60 years. It can be achieved using a variety of tooth molds arranged in a number of ways that seem to provide the least complicated approach to occlusal rehabilitation and to satisfy the needs of the edentulous patient. Clinical experience has supported its use during functional and nonfunctional activities [17, 18]. The different combinations of tooth molds available from one particular tooth manufacturer, and now specific molds designed for lingualized articulation by other manufacturers, allows the practitioner to improve the likelihood of maximal intercuspation, avoid deflective occlusal contacts, determine cusp height for selective occlusal reshaping, and achieve a natural and pleasing appearance. The articulation and arrangement of the posterior teeth in lingualized articulation assures a standardized arrangement.
Bicuspid↗
Shear strength of core-veneer interface in bi-layered ceramics.
STATEMENT OF PROBLEM: Delamination of veneering porcelain from underlying ceramic substrates has been reported for all-ceramic restorations. Whether this phenomenon is an inherent weakness of the veneering porcelain due to a weak interface between the veneering and the core porcelains, or merely a fracture through the veneering porcelain itself, has not been explored. PURPOSE: The purpose of this study was to investigate the strength of the substructure and veneering porcelain interface in all-ceramic systems. METHODS: The all-ceramic systems tested with their respective veneering porcelains were IPS-Empress2 with Eris (IE), Procera AllCeram with AllCeram (PA), Procera AllZircon with CZR (PZ), and DC-Zircon with Vita D (DC). The veneering porcelain recommended by the manufacturer for each material was fired to the ceramic core. A metal ceramic (MC) combination was tested as a control group. Sixty specimens, 12 for each system and control, were made from 1 master die. A cylinder of veneering porcelain 2.4 mm in diameter was applied using a specially designed aluminum split mold. After firing, the specimens were placed in a mounting jig and subjected to shear force in a universal testing machine. Load was applied at a crosshead speed of 0.50 mm/min until failure. Average shear strengths (MPa) were analyzed with a 1-way analysis of variance and the Tukey test (alpha=.05). The failed specimens were examined microscopically at original magnification x20 to classify the mode of failure as cohesive in the core, cohesive in the veneer, or adhesive at the interface. RESULTS: The mean shear strengths (+/-SD) in MPa were MC control 30.16 +/- 5.88; IE bonded to Eris 30.86 +/- 6.47; PZ bonded to CZR 28.03 +/- 5.03; DC bonded to Vita D 27.90 +/- 4.79; and PA bonded to AllCeram 22.40 +/- 2.40. IE, PZ, and DC were not significantly different from the MC control. Microscopic examination showed that adhesive failure, or complete delamination, did not occur between the compatible ceramic core and veneering materials. Failure primarily occurred near the interface with residual veneering porcelain remaining on the core. IE with Eris exhibited cohesive failure in both the core and the veneer. CONCLUSION: The bond strengths of 3 of the tested all-ceramic materials (IE, PZ, and DC) were not significantly different from the control (MC) group.
Aluminum Oxide↗
Finite element analysis to determine implant preload.
STATEMENT OF PROBLEM: The nature of the forces used to clamp implant components together, and how they are generated and sustained, is lacking in the literature. PURPOSE: This study examined the dynamic nature of developing the preload in an implant complex using finite element analysis. METHODS: The implant complex was modeled in accordance with the geometric designs for the Nobel Biocare implant systems. A thread helix design for the abutment screw and implant screw bore was modeled to create the geometric design for these units of the implant systems. Using the software programs HyperWorks and LS3D-Dyna, 2 3-dimensional finite element models of (1) a Branemark System 3.75 x 10-mm titanium Mark III implant, a CeraOne titanium abutment, a Unigrip gold alloy abutment screw, and (2) a Replace Select System 4.30 x 10-mm titanium implant, a Straight Esthetic titanium abutment, and a TorqTite titanium abutment screw were created. Modeling the threads to the machining specifications permitted simulation of screw tightening. The abutment screws were subjected to a tightening torque in increments of 1 Ncm from 0 to 64 Ncm using ABAQUS software. Using these models, the effect of the coefficient of friction on the development of preload amount in the implant complex during and after abutment screw tightening was determined. In the first experiment, the coefficient of friction was set to 0.20 between the titanium bearing surface of the abutments and the implant bearing surfaces, and 0.26 between the gold abutment screw and the titanium implant screw bore. In the second experiment, the coefficient of friction was varied; the titanium implant and titanium abutment bearing surfaces were set to a coefficient of friction of 0.20, whereas the Mark III gold and the Replace Select titanium abutment screws and their respective titanium screw bores in the implants were set to 0.12. The preload amount (N) was determined from the finite element analysis. RESULTS: The stress distribution pattern clearly demonstrated a transfer of preload force from the screw to the implant during tightening. A preload of 75% of the yield strength of the abutment screw was not established using the recommended tightening torques. CONCLUSION: Using finite element analysis, a torque of 32 Ncm applied to the abutment screws in the implant assemblies studied in the presence of a coefficient of friction of 0.26 resulted in a lower than optimum preload for the abutment screws. To reach the desired preload of 75% of the yield strength, using a torque of 32 Ncm applied to the abutment screws in the implant assemblies studied, the coefficient of friction between the implant components should be 0.12.
Dental Abutments↗
In vitro evaluation of long-term bonding of Procera AllCeram alumina restorations with a modified resin luting agent.
STATEMENT OF PROBLEM: Bonded densely sintered aluminum oxide ceramic restorations such as Procera AllCeram laminates rely on a strong and long-term durable resin bond. Air particle abrasion and a phosphate-modified resin luting agent have the potential to provide such bonds to aluminum oxide ceramics, but their efficacy on the Procera AllCeram intaglio surface is unknown. The inherent microroughness of this surface may influence bond strengths, because micromechanical interlocking is a main contributor for adhesion of resins to ceramic materials. PURPOSE: This study evaluated the bond strength of a phosphate-modified resin luting agent with and without silanization to an air particle-abraded Procera AllCeram intaglio surface compared with a conventional resin-bonding system before and after artificial aging. MATERIAL AND METHODS: Sixty square (10 x 10 x 2 mm) specimens of Procera AllCeram alumina ceramic with the Procera intaglio surface were air particle abraded with aluminum oxide. Composite cylinders (2.9 mm in diameter and 3.0 mm in width) were fabricated with Z-250 composite and bonded to the ceramic specimens with either Panavia 21 TC or Rely X ARC (control) and their corresponding bonding/silane coupling agents. In addition, Panavia was used without silanization as suggested in similar studies. Subgroups of 10 specimens were stored in distilled water for either 3 or 180 days before shear bond strength was tested with a universal testing machine (MPa) until fracture. The 180-day specimens were subjected to thermocycling at 2000 cycles every 30 days (12,000 cycles total). Data were analyzed with 1-way analysis of variance and Tukey's multiple comparison (alpha=.05). Failure modes were examined with a light microscope (original magnification x 25). RESULTS: Differences between short-term and long-term groups were highly significant (P=.000). Bond strength with Rely X ARC and its silane coupling agent (22.75 +/- 4 MPa) decreased significantly (P=.000) after artificial aging (3.32 +/- 3.62 MPa). Panavia 21 after silanization revealed significantly different (P=.003) early (21.42 +/- 4.3 MPa) and late (16.09 +/- 2.37 MPa) bond strengths but achieved the highest bond strength after artificial aging. Bond strengths of Panavia without silanization both early (8.06 +/- 2.1 MPa) and late (6.91 +/- 2.49 MPa) were not significantly different. Failure modes were mainly adhesive at the ceramic surface for all groups. CONCLUSION: Panavia 21 in combination with its corresponding bonding/silane coupling agent can achieve an acceptable resin bond to the air particle-abraded intaglio surface of Procera AllCeram restorations after artificial aging, which had mixed effects on the other investigated groups. The conventional resin luting agent revealed the most dramatic decrease in bond strength.
Adhesiveness↗
[The preparation procedure of TiAdapt abutment effect on the implant to abutment joint stability].
OBJECTIVE: This study was designed to determine the difference in the implant to abutment joint stability resulting from the preparation procedure in adjusting the TiAdapt abutment. METHODS: Thirty Branemark implants (10RP, 10NP, 10WP) and 10 TiAdapt RP, TiAdapt NP and TiAdapt WP abutments formed the experimental populations of 3 groups. Samples in each groups were further divided into subgroups A and B. Subgroup A was operated with preparation procedure whereas the other served as control. The torque required and the gap between abutment and implant before and after preparation were measured. RESULTS: There were no significant differences in group RP and group WP; there were significant differences in group NP at the significance level of 0.05. CONCLUSION: These results indicate that the implant to abutment joint stability has been strengthened by the abutment preparation procedure.
Dental Abutments↗