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P Assal

Publications and source records attributed to P Assal.

4 recordsLinked to original sources
PubMed2001

[Modification of some occlusion concepts in implant dentistry: thoughts inspired by clinical experience].

Implantology is nowadays a common tool in dentistry. While studying a case and selecting the future restoration, implants have to be considered when possible. Due to the functional differences between an implant and a natural tooth, the classical occlusion principles need to be considered. The prostheses have to be built according to the magnitude and direction of the forces that will be applied on the abutments. The prosthetic work and the occlusal equilibration are different in a patient with implants than in a patient with natural dentition. The occlusal concept will not be the same in the case of single implants surrounded by natural teeth, in the case of a mixed implant-tooth-supported fixed reconstruction and in the case of a full fixed bridge on implants. The purpose of this paper is to discuss the clinical consequences of these differences.

Biomechanical Phenomena↗
PubMed1996

Simultaneous force measurements in 3 dimensions on oral endosseous implants in vitro and in vivo. A methodological study.

A novel piezo-electric force transducer was developed that is mounted directly on ITI-implants and allows for simultaneous force measurements in 3 dimensions. The reliability of this measuring method in vitro and in vivo was evaluated. For test and calibration measurements 5 edentulous patients with 2 mandibular implants were selected and master casts obtained with original implants in situ. Preload of the abutment screw was measured with a torque controller by repeated tightening and loosening. The introduction of additional preloads when bar connectors or telescopes were mounted was examined on the casts and in the mouth. Tests were carried out to identify the influence of screw tensions on force measurements by loading the implants in vertical and transverse directions. Calibration measurements in vivo and in vitro were carried out by means of a spring balance. A regression model was calculated to analyze the influence of the applied preload on measured forces. The mean preload value was 315, ranging from 200 to 480N. A significant correlation of applied loads to measured forces was found (r = 0.99). It was independent of the preload in vertical direction but dependent in transverse direction. No additional tension of the abutment screw was ever observed when bars were mounted. Calibration measurements with the spring balance showed that bars contribute to load sharing between the implants. Comparable results were found for all measurements in vitro and in vivo. It was concluded that the new piezo-electric transducer is an adequate instrument to measure forces in 3 dimensions on ITI-implants.

Dental Abutments↗
PubMedDate not supplied

Occlusal force and oral tactile sensibility measured in partially edentulous patients with ITI implants.

Maximal occlusal force and oral tactile sensibility were recorded in (1) a group of partially edentulous patients restored with ITI implants supporting fixed prostheses or single crowns and (2) a control group consisting of fully dentate subjects with healthy natural teeth. Maximal occlusal force was measured with a miniature force transducer placed between antagonistic implant/tooth pairs in the test group and antagonistic teeth in the control group. The detection threshold of minimal pressure (ie, passive tactile sensibility) was recorded with dynamometers, and minimal perceived thickness (active tactile sensibility) was assessed using steel foils with a thickness from 100 to 10 microns. Highest maximal occlusal force was measured in fully dentate subjects on second premolars (average 450 N). A significant reduction on the first premolars (300 N) was observed. With fixed prostheses supported by implants, the average value of maximal occlusal force was distinctly lower, about 200 N for first premolars and for molars, and 300 N for second molars. The maximum force was again found on second premolars. The detection threshold of minimal pressure was significantly higher on implants than on natural teeth. The average number of wrong assessments when testing steel foils was 3.2 for antagonistic implant/tooth pairs and 2.6 for natural teeth. The comparison of test sides (with implants) and control sides (without implants) in patients of the test group did not reveal significant differences of measurements. It seems that patterns of oral function depend primarily on the state of dentition, type of prosthodontic restorations, and on psychological aspects, and secondarily on the presence of implants.

Adult↗