The effect of repeated microwave irradiation on the dimensional stability of a specific acrylic denture resin.

PURPOSE: To determine the dimensional stability of a poly(methyl methacrylate) (PMMA) acrylic resin when subjected to multiple sessions of repeated microwave irradiation at power settings of 700 and 420 W. MATERIALS AND METHODS: Twenty standardized denture bases were fabricated using a PMMA resin. Points of measurement were marked on each denture base with a standardized template, and the distances between points were recorded using a digital microscope. The denture bases were randomly placed into two experimental groups of 10 bases each. Individual denture bases were placed into a glass beaker containing 200 ml of room temperature deionized water and then exposed to either 700 or 420 W of microwave radiation for 3 minutes. The denture bases were allowed to cool to room temperature, and measurements between points were recorded. This process was carried out for two microwave periods with measurements being completed after each period. The data were then analyzed for any significant changes in distances between points using a Student's t-test. RESULTS: All denture bases experienced 1.0 to 2.0 mm or approximately 3% linear dimensional change after each period of microwaving. Results were significant with all t-tests having values of p < 0.05. CONCLUSION: This report showed that the denture bases deformed significantly under experimental conditions at either 700 W for 3 minutes in 200 ml of water or 420 W for 3 minutes in 200 ml of water.

Measuring mobility of 2 dental implant fixtures of different configurations: an in vitro study.

OBJECTIVES: To our knowledge, it has not as yet been determined if mini-dental implants can be used as a long-term treatment method compared to endosseous standard root-form dental implant fixtures. This in vitro study investigates the stability of 2 different implants, 1 mini-dental implant and 1 endosseous standard root form dental implant, under lateral forces. METHODS: There were 2 different screw-type dental implants with the O-ring/ball attachment prosthetic heads used. A mini-dental implant (Sendax MDI MAX; IMTEC, Corp., Ardmore, OK) 13 mm in length and 2.2 mm in diameter, and root form implant (Brånemark; Nobel Biocare AB, Goteborg, Sweden) 13 mm in length and 4 mm in diameter. These implants were then embedded into a matrix mixture of pumice, two-fifths BaSO4 powder and one-fifth plaster. Parallel periapical radiographs were taken pretest and after lateral forces were applied. The implants were vibrated using electric toothbrushes. They were attached to O-rings on the implants. Periapical radiographs were secured periodically every 5 minutes. The first discrepancy was observed at the 35th minute. Mobility and discrepancy values were recorded at the instances of 35th, 60th, 90th, and 120th minutes. Stability was measured and recorded using a manual stress and tension gauge. Radiographic discrepancy values were measured using a stereomicroscope. RESULTS: The Brånemark implant showed less mobility and discrepancy values than the mini-dental implant. The discrepancies were observed mostly at the cervical region of the 2 implants. CONCLUSIONS: According to the experimental results of this study, the Brånemark implant was more stable than the mini-dental implant at the end of 2 minutes.

Retrofitting a cast dowel-core on salvaged dental implants.

Dental implant screw fracture involves attempting to retrieve the screw fragment or, as an alternative, attempting to salvage the dental implant. Circumstances that do not allow for screw retrieval require a solution in which the internal configuration of the dental implant can provide for a custom direct dowel fabrication. The proposed technique is to retrofit the fabrication of a custom cast dowel-core and provisional use of a direct procedure, which provides accuracy of fit, retention, and ease of production.

One-piece dowel-crown on single endosseous implants.

The unitized (one-piece) dowel-crown technique described in this article uses routine clinical and laboratory procedures, minimizes clinical appointments, and provides a simplified prosthetic restoration for a single dental implant.