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1.
J Prosthodont ; 22(5): 367-76, 2013 Jul.
Article in English | MEDLINE | ID: mdl-23387412

ABSTRACT

PURPOSE: A precise transfer of the position and orientation of the antirotational mechanism of an implant to the working cast is particularly important to achieve optimal fit of the final restoration. This study evaluated and compared the accuracy of metal and plastic impression copings for use in a full-arch mandibular edentulous simulation with four implants. MATERIALS AND METHODS: Metal and plastic impression transfer copings for two implant systems, Nobel Biocare™ Replace and Straumann SynOcta®, were assessed on a laboratory model to simulate clinical practice. The accuracy of producing stone casts using these plastic and metal impression transfer copings was measured against a standard prosthetic framework consisting of a cast gold bar. A total of 20 casts from the four combinations were obtained. The fit of the framework on the cast was tested by a noncontact surface profilometer, the Proscan 3D 2000 A, using the one-screw test. The effects of implant/system and impression/coping material on gap measurements were analyzed using repeated measures ANOVA. RESULTS: The findings of this in vitro study were as follows: plastic copings demonstrated significantly larger average gaps than metal for Straumann (p = 0.001). Plastic and metal copings were not significantly different for Nobel (p = 0.302). Nobel had significantly larger average gaps than Straumann for metal copings (p = 0.003). Nobel had marginally smaller average gaps than Straumann (p = 0.096) for plastic copings. The system-by-screw location interaction was significant as well (p < 0.001), indicating significant differences among the four screw locations, but the location differences were not the same for the two systems. A rank transformation of the data was necessary due to the nonnormal distribution of the gap measurements. No adjustments were made for multiple comparisons. CONCLUSIONS: The metal impression copings were more accurate than plastic copings when using the Straumann system, and there was no difference between metal and plastic copings for the Nobel Replace system. The system-by-screw location was not conclusive, showing no correlation within each system.


Subject(s)
Dental Alloys/chemistry , Dental Implants , Dental Impression Technique/instrumentation , Plastics/chemistry , Dental Casting Technique , Dental Implant-Abutment Design , Dental Impression Materials/chemistry , Dental Marginal Adaptation , Dental Materials/chemistry , Gold Alloys/chemistry , Humans , Jaw, Edentulous/rehabilitation , Mandible/pathology , Materials Testing , Methylmethacrylates/chemistry , Models, Dental , Polyvinyls/chemistry , Siloxanes/chemistry , Surface Properties , Titanium/chemistry
2.
Compend Contin Educ Dent ; 27(7): 396-401; quiz 402, 421, 2006 Jul.
Article in English | MEDLINE | ID: mdl-16909519

ABSTRACT

This article discusses the fracture resistance of 4 post and core systems including a combined obturator/post system before and after fatigue loading. The obturator/post demonstrated the highest fracture resistance values. The use of a combined obturator/post with a single resin endodontic sealer/luting cement seems promising.


Subject(s)
Dental Materials , Post and Core Technique , Tooth Fractures , Tooth, Nonvital , Humans , Acid Etching, Dental , Composite Resins/chemistry , Crowns , Dental Materials/chemistry , Dental Prosthesis Design , Dental Stress Analysis/instrumentation , Dentin-Bonding Agents/chemistry , Gold Alloys/chemistry , Materials Testing , Post and Core Technique/instrumentation , Resin Cements/chemistry , Root Canal Filling Materials/chemistry , Root Canal Preparation , Stress, Mechanical , Tooth Fractures/physiopathology , Tooth, Nonvital/physiopathology , Zinc Phosphate Cement/chemistry
3.
J Prosthodont ; 11(2): 98-108, 2002 Jun.
Article in English | MEDLINE | ID: mdl-12087547

ABSTRACT

PURPOSE: This study evaluated the influence on dimensional accuracy of dental casts made with different types of trays and impression materials and poured at different and multiple times. MATERIALS AND METHODS: Two types of stock trays (plastic stock tray, perforated metal stock tray) and 4 types of custom tray materials (autopolymerizing acrylic resin, thermoplastic resin, and 2 types of light-polymerized acrylic resins) were used with 2 types of impression materials (addition polymerizing silicone and polyether), to make impressions of a metal master model. Each tray and impression material was used to make 5 impressions. Casts were made by multiple pourings at 30 minutes, 6 hours, 24 hours, and 30 days after impression making. Using a measuring microscope, 12 distances were calculated based on measurements of 8 reference points. The absolute value of the difference of each measurement was calculated, as was the corresponding measurement on the master model. A Bayesian model using a simple noninformative prior was used to analyze these data. RESULTS: Statistical differences within 6 microm were found only with thermoplastic resin tray material for addition silicone, and for thermoplastic resin tray material and 1 type of light-polymerized acrylic resin for polyether. Neither stock trays nor custom trays contributed to the differences in accuracy of the casts. All deviations in casts made with silicone impression material were within a clinically acceptable range. For the polyether, distortions occurred that were clinically unacceptable. Impressions made from polyether distorted over time. Silicone impression material has dimensional stability up to 30 days. CONCLUSION: Accurate casts can be made with either stock trays or custom trays. An impression made from polyether should be poured only once and within 24 hours after impression making, because of the distortion of the material over time. Silicone impression material has better dimensional stability than polyether. .


Subject(s)
Dental Impression Materials/chemistry , Dental Impression Technique/instrumentation , Models, Dental , Acrylic Resins/chemistry , Adhesives/chemistry , Alloys/chemistry , Bayes Theorem , Calcium Sulfate/chemistry , Dental Casting Investment/chemistry , Dental Casting Technique , Equipment Design , Ethers/chemistry , Humans , Materials Testing , Plastics/chemistry , Silicone Elastomers/chemistry , Statistics as Topic , Surface Properties , Surface-Active Agents/chemistry , Time Factors
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