Occlusal force transmission by overdenture attachments.
ABSTRACT This investigation utilized a composite photoelastic model to examine the load-transfer characteristics of several overdenture attachments. Tissue bar (Hader and King Connector) and stud (extracoronal) attachments (Rotherman, Gerber, and Ancrofix) were studied. The following observations may provide guidelines for the selection of overdenture attachments. 1. The more retentive tissue bar and extracoronal attachments produced higher stress concentrations. 2. Of the tissue bars tested, the Hader Bar produced less torquing forces on the abutment teeth. 3. The Ancrofix appeared to share the forces of occlusion between abutments and the posterior edentulous regions. 4. It must be emphasized that several other factors will also influence the choice of overdenture attachments, such as the judgment of the dentist, economics with respect to the patient, and the availability of laboratory expertise.
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ABSTRACT: The aim of this in vitro study was to evaluate, using the photoelastic analysis method, the stress distribution in mandibular bone surrounding a bar-clip overdenture when 2 implant angulations were simulated. Two mandibular photoelastic models were manufactured, with 2 implants embedded in the interforaminal region: model 1 - PAPI, a photoelastic analysis model with parallel implants; and model 2 - PAAI, a photoelastic analysis model with angled implants. A bar-clip retention system and an overdenture were positioned over the implants, and loads of 1.0, 2.0 and 3.0 bars were applied. The resultant stresses that developed in the supporting structure were photoelastically monitored and were recorded photographically. The results showed that there were no similarities in the areas of stress among the photoelastic resin models when the angulation of the implants was evaluated. Model 1 - PAPI presented a higher stress concentration at the implant apex, while in model 2 - PAAI, there were higher stress concentrations on the mesial and distal implant faces. Within the limitations of this study, it was concluded that the PAPI photoelastic model demonstrated better stress transfer compared to the PAAI model, since the forces oriented along the axis were better absorbed by the bone.Brazilian Oral Research 12/2012; · 0.77 Impact Factor
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ABSTRACT: Nine subjects treated with overdentures on osseointegrated implants in the mandible were functionally evaluated before and after treatment. The last recordings were performed 1 yr after treatment. The evaluation comprised a subjective and a clinical examination. Measurements of bite force and of chewing efficiency were also performed. The bite force was measured during gentle biting, biting as when chewing and biting with maximal effort. Almonds were used as test food. All subjects improved subjectively as well as clinically after treatment. The bite force during gentle biting increased on average from 17.3 N before treatment to 24.0 N 1 yr after treatment. A corresponding improvement of biting as when chewing was also found, from on average 24.0 N before to 38.7 N after treatment. The maximal bite force increased from on average 74.6 N at the baseline examination to 131.5 N at the 1-yr follow-up. The chewing efficiency improved from Ci = 4 (Median value) before treatment to Ci = 2.8 (Median value) after treatment. It is concluded that treatment with an overdenture supported by osseointegrated implants in the mandible improves oral function compared to the situation before treatment.Scandinavian journal of dental research 07/1988; 96(3):235-42.
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ABSTRACT: A space between the denture base and a root cap can effectively control the distribution ratio of occlusal force to abutment teeth and an alveolar ridge. The purpose of this study on abutments was to analyse the effect of variation in space (0 mm (no space), 0.3 mm and 0.6 mm) on the above ratio. Six subjects, 38-65 years of age, each with an edentulous maxilla and several teeth remaining in the mandible, were selected for this experiment. The lower experimental denture had embedded a transducer which could detect a change in the vertical force applied to the experimental tooth. This transducer was capable of changing the vertical space between a denture base and an experimental tooth. Each subject was asked to increase the occlusal force applied to the denture from zero to the maximum loading rate of 5 kgf s-1. The occlusal force and the force exerted on the experimental tooth were recorded in each space 1 month after insertion of new dentures. The following results were obtained: (i) when the occlusal force was applied to the artificial tooth just above the abutment tooth, the mean ratio in the 0 mm space was 60% of the force applied to the denture, the ratio in the 0.3 mm space was 50%, and the ratio in the 0.6 mm space was 30%; (ii) if the occlusal force was applied to the point 10 mm distant from the point just above the experimental tooth, the magnitude of the ratio was decreased by 60-80%.Journal of Oral Rehabilitation 08/1990; 17(4):335-42. · 1.93 Impact Factor