| 1. |
- Fernandes, Cláudio Pinheiro, et al.
(författare)
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A Novel Sensor for Bite Force Determinations
- 2003
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Ingår i: Dental Materials. - 0109-5641 .- 1879-0097. ; 19:2, s. 118-126
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- OBJECTIVES: The clinical usefulness, accuracy and precision of a novel bite force sensor based on force sensing resistors were tested in six subjects wearing maxillary removable partial dentures retained by conical crowns. METHODS: The surfaces of the sensor were manufactured in a silicone material that had mechanical properties similar to those of tough foodstuffs. In two separate series of standardized bite force tests, submaximum force levels were recorded with the sensor and with a strain gaged bite fork. Subjects were assisted in the loading tests with visual feedback instrumentation. Reliability estimates for the bite force sensor were calculated in order to show their reproducibility. Strain gages attached to the prostheses were used to determine the pattern of force distribution during loading tests. The bite force results obtained with the new bite force sensor and with the bite fork were analyzed with ANOVA and Scheffes tests. The strain patterns registered with strain gages were analyzed with F-test. RE-SULTS: The bite force sensor and the bite fork transducer showed no statistically significant differences in respect of intra-individual bite force levels (range 50-300N). The bite forces registered with the new sensor were dependent on the loading position (p<0.05), sex (p<0.05) and test subject (p<0.05). The reliability of the new sensor for sub-maximum bite forces was calculated to be 93%. Strain gage results showed that the new sensor generated strain patterns of less variance (p<0.05) than the bite fork and therefore allowed for higher precision during biting tests. SIGNIFICANCE: The presented instrument has such clinical merits, as to favor its use in experimental clinical studies on the biomechanics of prosthetic appliances.
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| 2. |
- Fernandes, Cláudio Pinheiro, et al.
(författare)
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On the Accuracy of Some In Vitro Models for Mechanical Studies of Maxillary Removable Partial Dentures
- 2003
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Ingår i: Dental Materials. - 0109-5641 .- 1879-0097. ; 19:2, s. 127-136
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- OBJECTIVES: Comparative in vitro/in vivo studies show wide differences in functional strain magnitudes and patterns of functional strain distribution in prosthetic devices. The aim of this study was to evaluate the accuracy of three in vitro models for biomechanical studies of prosthetic devices. METHODS: Strain gages were attached to the test RPDs of six subjects. In vitro maxillary models with simple (model A), intermediate (model B) and advanced (model C) features for the anatomical simulation of supporting structures were manufactured for each subject. The dentures were subjected to two separate series of standardized functional and laboratorial loading tests. The principal maximum strain value (epsilon (1)) obtained for each gage and experiment was used to calculate the intra-experiment variance and inter-experiment variance for the in vivo and in vitro experiments. The integrated strain gage difference value between the in vitro and in vivo data (Sigma(diff)) was calculated for every loading test and compared to the in vivo inter-experiment variance with ANOVA and Scheffes test. RESULTS: The bite forces recorded were similar for each subject and loading position and between the two loading sessions. The inter- and intra-experiment variance was found to be higher for in vivo loadings than for in vitro. Results showed that the (Sigma(diff)) values for model B and model C were significantly different from the in vivo strain interexperiment variance (p<0.05). SIGNIFICANCE: This study showed that the anatomical simulation of in vitro models is insufficient to allow for accurate mechanical analyses of maxillary RPDs and that only simple verifications of the strain levels in prosthetic appliances can be attained in vitro.
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| 3. |
- Pinheiro Fernandes, Cláudio
(författare)
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Comparative in vivo and in vitro studies on the biomechanics of maxillary partial dentures. A methodological and experimental study.
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biomechanical aspects are generally agreed to be significant, particularly during the planning of restorative treatments and the design of prosthetic appliances. However, comparative in vivo/in vitro studies show wide differences in the magnitudes and patterns of functional strains in prosthetic devices. The general aim of this study was to investigate some aspects of the biomechanical behavior of maxillary partial dentures in vivo and in vitro. This study also verified the validity, precision and accuracy of in vivo reflection photoelasticity and bite force sensors based on force sensing resistors. Conical crown retained dentures of 7 subjects were prepared for reflection photoelasticity and strain gauge recordings. Three in vitro models with simple, intermediate and advanced anatomical simulation features were manufactured for each subject. In vivo and in vitro loading experiments were performed using bite force sensors. Several variables were tested in this study such as the occlusal loading position, sex, distribution of abutment teeth, palatal height index, in vitro models, and denture structural design. The results indicate that the bite force sensor was able to accurately detect bite force levels in the range of 50 N to 300 N. The bite forces registered with the new sensor were dependent on the loading position, sex and test subject. The reliability of the new sensor for submaximum bite forces was calculated to be 93%. Strain gauge results showed that the new sensor generated strain patterns of low variance during biting tests. In vivo reflection photoelasticity experiments showed that coated areas accessible to normally incident light produced valid, reliable and accurate data of the stress/strain distribution in prosthetic appliances. Comparative in vivo/in vitro data showed that all the studied models failed to reproduce the in vivo functional strain patterns. Anatomical simulation of in vitro models is insufficient to allow for accurate mechanical analyses of maxillary RPDs, therefore, only simple verifications of the strain levels in prosthetic appliances can be attained in vitro. The magnitudes and distribution of stress fields in dentures with different structural design revealed that the palatal major connector and the denture bases mucosal contacts contribute significantly to the rigidity and stability of RPDs retained by conical crowns. Patients with a high palatal height index are less dependent on major connectors for denture stability and rigidity than patients with a low palatal height index.
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