Clinical Evaluation of Implant-Supported Removable Partial Dentures With a Stress-Breaking Attachment.

PURPOSE: The stress-breaking ball (SBB) attachment can distribute the occlusal force equally between the alveolar ridge and the implants. The purpose of this study was to evaluate the implant-supported distal extension removable partial dentures (RPDs) with SBB attachment in 10 patients who were partially edentulous. METHODS: This randomized crossover study was designed to compare the function of RPDs with and without healing abutments and SBB attachments to support the posterior aspects of the RPDs. Mandibular jaw movements during mastication and the occlusal force and contact area were measured with a commercially available tracking device and pressure-sensitive sheets. Using a visual analog scale, 4 criteria-chewing, retention, stability, and comfort-were evaluated. All of the data obtained were analyzed using a 1-way analysis of variance (α = 0.05). RESULTS: There were no significant differences in either the mean time or the coefficient of variation among the SBB attachments and healing abutments of implant-supported removable partial dentures (ISRPDs) and conventional removable partial dentures (CRPDs). SBB attachments and healing abutments of ISRPDs had greater forces and contact areas than those of CRPDs with significant differences. For all criteria, patients preferred SBB attachments to healing abutments and CRPDs. CONCLUSIONS: The implant-supported distal extension RPDs with SBB attachment improved denture stability and patients' satisfaction.

In vitro assessment of mandibular single/two implant-retained overdentures using stress-breaking attachments.

OBJECTIVE: This study investigated the strain surround implants and the pressure distribution of the alveolar ridge related to implant overdentures with stress-breaking ball (SBB) attachments. METHODS: Simulation models of edentulous mandibles were embedded with 1 and 2 implants to simulate a single implant-retained overdenture (S-IOD) and a two-implant-retained overdenture (T-IOD), respectively. The implants were connected to the denture base with the following conditions: complete separation between the denture base and implant with cover screws as a conventional complete denture (CD), 3 types of settlements with an SBB attachment between them, and a conventional ball attachment (BALL). Strain surround the implant, pressure at 5 different soft tissue areas, and displacement of the denture base were measured with loading up to 50 N. RESULTS: In S-IOD and T-IOD, the strain of each SBB attachment was less than the strain shown by the BALL. The pressure at each region of the SBB attachment was less than the pressure shown with the CD and BALL. CONCLUSIONS: SBB attachments prevented strain surround the implants in loading and provided optimal stress distribution.

Influence of marginal bone resorption on two mini implant-retained mandibular overdenture: An in vitro study.

PURPOSE: To investigate the biomechanical effect of marginal bone resorption (MBR) on the mandibular mini implant (MI)-retained overdenture (MI-OD) on the edentulous model. MATERIALS AND METHODS: The experimental mandibular edentulous model was modified from a commercial model with 2 mm thick artificial soft tissue under denture base. Two MIs (Φ2.6 mm × 10 mm) were bilaterally placed between the lateral incisor and the canine area and attached with magnetic attachments. Three groups were set up as follows: 1) alveolar bone around the MI without MBR (normal group), 2) with MBR to 1/2 the length of the implant (resorption group), and 3) complete denture (CD) without MI (CD group). Strain around the MI, pressure near the first molar area, and displacement of denture were simultaneously measured, loading up to 50 N under bilateral/unilateral loading. Statistical analysis was performed using independent-samples t test and one-way ANOVA (α=.05). RESULTS: The strain around the MI with MBR was approximately 1.5 times higher than that without MBR. The pressure in CD was higher than in MI-ODs (P <.05), while there was no statistical difference between the normal and resorption group (P >.05). Similarly, the CD demonstrated a greater displacement of the denture base than did the MI-ODs during bilateral and unilateral loadings (P <.05). CONCLUSION: The strain around the MI with MBR was approximately 1.5 times higher than that without MBR. The pressure on posterior alveolar ridge and denture displacement of MI-ODs significantly decreased compared to CDs, even when MBR occurs. Bilateral balanced occlusion was recommended for MI-ODs, especially when MBR occurred.

Pressure distribution of implant-supported removable partial dentures with stress-breaking attachments.

PURPOSE: This in vitro study investigated the pressure distribution of the implant-supported removable partial dentures (RPDs) with the stress-breaking attachments under the occlusal force. METHODS: The experimental model of bilateral missing premolars and molars was modified from a commercial simulation model. Five pressure sensors were embedded near the bilateral first molars, first premolars, and medio-lingual alveolar crest. Two implants were placed near the second molars, and they were connected to the denture base using the following conditions: complete separation between the denture base and implant with cover screws (CRPD), flexible connection with a stress-breaking ball (SBB) attachment, and rigid connection without stress breaking with healing caps (HC). The pressure at five different areas of the soft tissue and the displacement of the RPDs were simultaneously measured, loading up to 50 N. The coefficient of variation (CV) for each connection was calculated from all data of the pressure at five areas to evaluate the pressure distribution. RESULTS: The pressure on medio-lingual alveolar crest and molars of the HC was less than SBB and CRPD. In contrast, the pressure on premolars of SBB was greater than for the HC and CRPD. The CV of SBB was less than that of HC and CRPD. Denture displacement of HC and SBB was less than for CRPD. CONCLUSIONS: Within the in vitro limitations, precise denture settlements and pressure distribution under the denture base could be controlled using an SBB attachment. An SBB attachment might be able to protect the implant from harmful force.