Effects of implant system, impression technique, and impression material on accuracy of the working cast.

PURPOSE: This in vitro study aimed to identify the effects of the implant system, impression technique, and impression material on the transfer accuracy of implant impressions. The null hypothesis tested was that, in vitro and within the parameters of the experiment, the spatial relationship of a working cast to the placement of implants is not related to (1) the implant system, (2) the impression technique, or (3) the impression material. MATERIALS AND METHODS: A steel maxilla was used as a reference model. Six implants of two different implant systems (Standard Plus, Straumann; Semados, Bego) were fixed in the reference model. The target variables were: three-dimensional (3D) shift in all directions, implant axis direction, and rotation. The target variables were assessed using a 3D coordinate measuring machine, and the respective deviations of the plaster models from the nominal values of the reference model were calculated. Two different impression techniques (reposition/pickup) and four impression materials (Aquasil Ultra, Flexitime, Impregum Penta, P2 Magnum 360) were investigated. In all, 80 implant impressions for each implant system were taken. Statistical analysis was performed using multivariate analysis of variance. RESULTS: The implant system significantly influenced the transfer accuracy for most spatial dimensions, including the overall 3D shift and implant axis direction. There was no significant difference between the two implant systems with regard to rotation. Multivariate analysis of variance showed a significant effect on transfer accuracy only for the implant system. CONCLUSIONS: Within the limits of the present study, it can be concluded that the transfer accuracy of the intraoral implant position on the working cast is far more dependent on the implant system than on the selection of a specific impression technique or material.

Alternative procedure to improve the stability of mandibular complete dentures: a modified neutral zone technique.

The aim of this report is to describe an alternative technique to record the neutral zone. An acrylic resin base with posterior occlusal rims was applied using a thermoplastic denture adhesive. After being worn for 2 days, the base was transferred into an acrylic resin complete denture. Most patients reported an improvement in denture stability and a reduction of pressure sores. This procedure seems to be helpful to improve denture function, especially in the mandible, in patients who cannot be treated with implants. However, because of its complexity, this neutral zone technique cannot be recommended for routine clinical use.

Influence of two functional complete-denture impression techniques on patient satisfaction: dentist-manipulated versus patient-manipulated.

This preliminary clinical study aimed to identify the impact of two border-molding techniques (dentist-manipulated and patient-manipulated) on patient satisfaction, the occlusal force at denture dislodgment, and number of pressure sores. Salivary flow rate and residual ridge resorption were analyzed as covariates. Thirty-six edentulous patients in need of a relining of their existing maxillary denture were included. After relining, no significant influence of the border-molding technique on any of the variables investigated could be identified. It can be concluded that the impact of the border-molding technique on patient satisfaction and denture function probably has been overestimated in the past.