Frank Houston

The fit of cast and premachined implant abutments

STATEMENT OF PROBLEM There is insufficient information regarding the adaptation of abutments to implants. PURPOSE This study assessed the adaptation of premachined, cast, and laboratory modified premachined abutments to implants at two sites: abutment/implant interface and screw to screw seat. MATERIAL AND METHODS Six combinations of abutments and implants were studied: CeraOne abutments joined to Nobel Biocare implants; STR (Implant Innovations Inc.) abutments joined to 31 implants; Cast UCLA (31) abutments subjected to porcelain firing cycles and joined to 31 implants; Cast UCLA abutments subjected to porcelain firing cycles and joined to Nobel Biocare implants; UCLA premachined abutments cast with gold palladium alloy and subjected to porcelain firing cycles (later joined to 31 implants); and UCLA premachined abutments joined to 31 implants. Each group contained five assemblies. RESULTS The adaptation of abutments to implants was closer and the amounts of contact larger for assemblies with premachined and laboratory modified premachined abutments than for those with cast abutments. CONCLUSION The finishing of custom-made abutments requires further refinement.

A comparison of the dimensional accuracy of the splinted and unsplinted impression techniques for the Bone-Lock implant system

STATEMENT OF PROBLEM The precise transfer of intraoral relationships of implants to laboratory working models is central to the success of implant prostheses. PURPOSE In this study a stone master model incorporating five implants (Bone-Lock) was used to compare the dimensional accuracy of a splinted impression technique with an unsplinted impression technique. METHODS A three-factor analysis of variance was used to examine the effect of technique, relative position of the implant on the cast, and plane of measurement. RESULTS All three factors had a significant effect on dimensional accuracy. CONCLUSIONS The splinted technique exhibited more deviation from the master model than the unsplinted technique did. This was primarily associated with rotational discrepancies around the long axes of the implants for the splinted technique.

Comparison of the dimensional accuracy of one- and two-step techniques with the use of putty/wash addition silicone impression materials.

This study compared the putty/wash one-step and two-step techniques for making addition silicone impressions. For each technique 15 impressions were made of a stainless steel base to which three tapered posts were attached. Stone models were made of all impressions. The results indicated that the interabutment distances increased slightly compared with the stainless steel model for both techniques, but the differences between techniques were not considered to be clinically important. The intraabutment measurements for the abutment without undercut increased, whereas abutments with undercuts decreased. These variations from the stainless steel model were also clinically insignificant.

In Vitro Study of Retention of Paired Press-Stud Overdenture Component Attachments

1.1.Statement of problem: Loss of retention of implant overdenture stud attachment assemblies presents maintenance problems to both the patient and dentist. 1.2.Purpose:The purpose of this in vitro study was to investigate effects of repeated separation and reunion cycles on retention of paired overdenture stud attachment assemblies set in acrylic resin. 1.3.Material and methods: Ten pairsof stud attachments were set vertically and parallel to each other (Group 1). Ten other pairs of stud attachments were set with one vertical and the other at a vertical angle of 15°, so that it converged on the first implant (Group 2). Baseline measurements of separation force were made for each of the ten paired attachment assemblies in the two groups. Each assembly was first subjected to a cycle of 100 separations and reunions, followed by measurement of separation force. Then, additional cycles were carried out for a total of 1000 separations and reunions, with measurement of separation force and retightening after each cycle. Repeated-values ANOVA was employed to compare the two groups at the different time intervals, with p<.05 representing statistical significance. 1.4.Results: While significant (p<.0001) decay in the resistance to separation was observed forboth the parallel and converging groups of paired stud attachment assemblies, these decreases were judged to have little clinical importance. 1.5. Conclusion: There was no clinically meaningful difference in retention between the first group of two parallel stud attachments and the second group with one attachment converging at an angle of 15°. Group 1 showed greater retention than Group 2 after the retightening adjustments.

Cost-saving implant training aids.

This article describes a simple step-by-step procedure that uses inexpensive materials to enable those who wish to learn procedures used in the construction of a screw-type implant overdenture to practice these procedures before they use expensive precious metal components. The use of this procedure will result in considerable savings in training costs and affords a greater opportunity to provide practical experience before making this type of an overdenture for patients. It could also provide for a rapid expansion in the number of trained personnel who could make this form of treatment available to a larger number of patients.