The influences of implant angulations in one and two directions on the retentive properties of overdenture attachments: an in vitro study.

Implant alignment is an important factor in overdentures retained by solitary abutments. In this study, the effect of implant angulations in two directions, on the amount of retention of attachments was evaluated. Ninety models were divided into nine groups of two blocks each; one for two implants and one for two attachments. The implants were placed either parallel to, at 5°, or at 10° relative to the reference plane. The attachments were related to the implants with a 0, 5, or 10° angulations. The direction of the implant was either labial or distolabial. The initial and the subsequent retention values of each sample were measured after each 500 cycles of insertion and removal. The measurements were repeated for five consecutive 3,000 cycles, and the results were analyzed by means of one-way ANOVA and Tukey HSD tests. Group 9 with a 10° distolabial tilt of the implants and of their attachments showed the highest initial retention, whereas group 1 with a 0° angulations and parallel attachments showed the lowest (6.9 ± 0.28 and 3.88 ± 0.19 N, respectively). The initial retention and the final loss of retention was significantly higher in those groups with the distolabial tilt of the implants (p < 0.05). Within the limitations of this study, it was demonstrated that the more divergent the implants and their retentive components, the higher their initial retention and the lower their final retention may be.

Prevalence of oral mucosal lesions in a group of Iranian dependent elderly complete denture wearers.

AIM: Oral mucosal lesions are frequently observed in institutionalized elderly patients more than other age groups. The aim of this study was to determine the prevalence of epulis fissuratum and denture stomatitis and their associated causes in dependent elderly complete denture wearers. MATERIALS AND METHODS: This study was conducted in dependent elderly complete denture's wearers living in four randomly selected nursing homes located in Tehran. Associated factors such as gender, age, use of medication, site of nursing home, denture quality and denture-wearing habit were studied. RESULTS: Overall, 674 patients were examined; 201 had complete denture. The prevalence of denture stomatitis was 36%. There was significant relationship among the prevalence of denture stomatitis with gender and denture wearing period (p < 0.05). The prevalence of epulis fissuratum was 16.4%. There was significant relationship among the prevalence of epulis fissuratum with gender, denture quality and denture wearing habit (p < 0.05). CONCLUSION: In this particular dependent age group, the prevalence of oral mucosal lesions is high and the mentioned associated factors should be noticed. CLINICAL SIGNIFICANCE: Dependent elderly complete denture wearers need more support and motivation for reducing the prevalence of these particular denture-associated oral mucosal lesions.

The effects of two attachment types on the stresses introduced to the mandibular residual ridge: a 3D finite element analysis.

PURPOSE: Two commonly used attachment systems for implant-retained overdentures are bar and ball systems. The aim of this study was to compare these two types of attachments on the basis of the stresses introduced to the mandibular posterior residual ridge by an overdenture retained by two implants. METHOD AND MATERIALS: A basic model was generated from the data provided by a CT scan of a patient's mandible, the diagnostic casts, and the existing overdenture. Two root-form implants were placed in the anterior mandible. Models were used to simulate two situations: The first model represented an edentulous mandible supporting an overdenture retained by two implants connected with a bar and plastic clip system, and in the second model two ball attachments with nylon caps were used as the retention mechanism. A 35 N vertical load was introduced to the first molar region of each group to simulate the occlusal forces of the maxillary complete denture. The stresses in the mandibular residual ridges under the first molar region were measured using Ansys software. RESULTS: The bar-retained overdenture introduced higher stresses to the posterior mandibular residual ridge compared to the ball-retained overdenture (0.4 MPa and 0.1 MPa, respectively). CONCLUSION: Within the limitations of this study, the ball system was shown to introduce a lower amount of stress to the posterior mandibular residual ridge compared to a bar and clip system.

Influence of the fast-processing technique on the number of the occlusal contacts and occlusal vertical dimension of complete dentures.

AIM: Occlusal errors during acryl processing affect the retention and stability of complete dentures. The aim of the present study was to assess the influence of a short curing technique on the number of occlusal contacts and the occlusal vertical dimension (OVD) of complete dentures. MATERIALS AND METHODS: Complete dentures were prepared. The number of occlusal contacts was recorded in centric relation (CR) using 60 µ articulation paper. The OVD was recorded with the waxed trial denture in place. Dentures were then invested and processed with compression molding and short cure water bath technique. The number of occlusal contacts was recorded again. The amount of pin opening was measured for all of the complete dentures on the articulator. Data were analyzed with paired t-test to determine the alterations. RESULTS: The mean number of occlusal contacts before and after processing was 10.9 ± 2.4 and 6.3 ± 3.1 respectively (4.7 ± 1.9 decrease; p < 0.001). A 2 mm mean increase in OVD was observed in 47.7% of the dentures with < 6 occlusal contact changes and 88.9% of the dentures with ≥ 6 occlusal contact changes (p < 0.003). A significant change in the number of occlusal contacts was associated with an OVD increased up to two times. CONCLUSION: The short curing technique seems to be related to the decreased occlusal contacts and increased OVD. CLINICAL SIGNIFICANCES: More time is needed to adjust the occlusal errors of this method, because it has a negative effect on the morphologic pattern of artificial teeth of complete dentures and thus should be used carefully.

The prevalence of occlusal disharmony and its associated causes in complete dentures.

AIM: Occlusal disharmony is frequently observed among edentulous patients. With the side effects of occlusal disharmony in mind, the goal of this research was to investigate the prevalence of occlusal disharmony in inserted complete dentures and its associated causes. METHODS AND MATERIALS: This cross-sectional study was conducted on 107 selected patients. Factors such as age, gender, ridge relationship on the articulator, occlusal scheme, and the performance of a clinical remount from patients' treatment records were investigated. The presence and/or status of any occlusal disharmony was determined by a calibrated prosthodontist extraorally and qualitatively. Occlusal disharmony is defined as the absence of simultaneous bilateral contacts between the opposing posterior teeth in centric relation. The prevalence of occlusal disharmony was determined and the roles of the aforementioned factors were studied and analyzed using a Chi-square analysis. The results were considered significant at p<0.05. RESULTS: Out of 107 patients, 31 patients (28.8%) showed occlusal disharmony. No statistically significant relationship was found between occlusal disharmony and age, gender, ridge relationships, or occlusal scheme (p<0.5). Twenty-five (81%) out of 31 complete dentures with occlusal disharmony were not clinically remounted. There was a highly significant relationship between the absence of clinical remounting and occlusal disharmony (p<0.001). CONCLUSION: Within the limits of this study, the prevalence of occlusal disharmony was noticeable. A randomized clinical trial is strongly recommended to investigate factors related to the incidence of occlusal disharmony. CLINICAL SIGNIFICANCE: It is important to refine the occlusion of a complete denture after laboratory processing of the denture before it is delivered to the patient.