Cyclic loading of implant-supported prostheses: comparison of gaps at the prosthetic-abutment interface when cycled abutments are replaced with as-manufactured abutments.

STATEMENT OF PROBLEM: Implant-supported prostheses are mechanically connected to implants. When this connection is a screw joint, it is likely that the fit will be imperfect. Previous studies demonstrate that deformation can occur at the interface between the prosthesis and implant following cyclic loading. This deformation alters the fit of components. If implant connection components, abutments, were to be reoriented or replaced, it is likely that deformed surfaces would no longer approximate each other. Likewise, it is possible that the deformation may deleteriously alter the fit to replacement components. PURPOSE: This study evaluated the changes in prosthesis-implant abutment fit when gold cylinders that have been cyclically loaded are mated to as-manufactured abutments. MATERIAL AND METHODS: Fifteen implant-supported frameworks were fabricated using conventional casting techniques and were cyclically loaded under 3 different loading conditions: anterior region, unilaterally on posterior cantilever, and bilaterally on posterior cantilever. A cyclical load of 200 N was applied to each framework for 200,000 cycles. The abutments and frameworks were returned to the definitive casts for measurements. Linear measurements (microm) of the gap between the prosthetic cylinder and the implant-supported abutment at 4 predetermined reference points were made. The cycled abutments were replaced with as-manufactured abutments, and the gaps were measured at the same reference points. The Mann-Whitney rank-sum test was applied to the 2 sets of data to determine whether significant changes in fit were observed following component replacement (alpha = .05). RESULTS: Although minor changes in component fit were seen, the data failed to show that gaps at the prosthetic-abutment interface of cycled abutments were significantly different from those of as-manufactured abutments. CONCLUSIONS: Within the limitations of this study, differences in the fit between the implant-supported prosthesis and the abutments were not significantly different when abutments worn through loading were replaced with new as-manufactured abutments.

Cyclic loading of implant-supported prostheses: changes in component fit over time.

STATEMENT OF PROBLEM: Dental literature suggests that an implant-supported prosthesis must exhibit a passive fit to prevent implant fracture, component breakage, and screw loosening. From a practical standpoint, passive fit is impossible to achieve; instead, minimal misfit may be the clinical goal. To date no specific range of misfit (below which problems are minimal and above which catastrophic failure occurs) has been established. PURPOSE: The purpose of this study was to determine whether the fit of an implant-supported prosthesis changes through cyclic loading and to quantify the amount of change between the gold cylinder and implant abutment over time. MATERIAL AND METHODS: Fifteen implant-supported frameworks were fabricated with conventional casting techniques and were cyclically loaded under 3 different loading conditions. Five frameworks were loaded on the anterior portion of the framework, 5 were loaded on the left unilateral posterior cantilever, and 5 were loaded bilaterally on the posterior cantilevers with a servohydraulic testing machine. A cyclical load of 200 N was applied to each framework for up to 200,000 cycles. Linear measurements were made in micrometers of the gap between the prosthetic cylinder and the implant-supported abutment at 4 predetermined reference points. These measurements were recorded before the application of the cyclical load, after 50,000 cycles, and after 200,000 cycles. A repeated measures of variance model was fit separately to the data for each load location (P<.05). RESULTS: There was a significant (P=.024) decrease in gap dimensions at individual reference points and a significant (P=.031) decrease in the average gap when the load was applied to the anterior portion of the framework. When the load was applied unilaterally or bilaterally on the posterior cantilever, significant gap closure was not observed (P=.33 and P=.35, respectively). CONCLUSION: Within the limitations of this study, the fit between the prosthetic superstructure and the implant-supported abutment changed when simulated functional loading of the anterior portion of the prosthesis was performed. Simulated functional loading applied unilaterally or bilaterally to the posterior cantilever portion of the prosthesis did not result in changes in the measured gap sizes.

Maxillofacial rehabilitation of a large facial defect resulting from an arteriovenous malformation utilizing a two-piece prosthesis.

Large facial defects involving the oral cavity can be difficult to restore prosthetically because of a lack of anatomic undercuts, limited means of retention, mobility of soft tissue margins, and the weight of the prosthesis. Use of skin adhesives may be precluded because of the presence of persistent moisture and saliva. The maxillofacial rehabilitation, including the design and fabrication of a 2-piece silicone prosthesis retained by the teeth, of a patient with a large facial defect as a result of treatment for an arteriovenous malformation is described. The pathogenesis and therapeutic alternatives for arteriovenous malformations is also discussed.

Can we assess quality of life in patients with head and neck cancer? A preliminary report from the American Academy of Maxillofacial Prosthetics.

Survival statistics alone may no longer be valid when used as evidence of effective outcomes. Patient satisfaction is an end point that needs further evaluation and should be included in the outcomes assessment. A 133-item questionnaire has been designed by a special committee of the American Academy of Maxillofacial Prosthetics (AAMP) to assess the quality of life of patients with head and neck cancer impacting the orofacial region. This survey will be distributed to the entire population of 7 geographically dispersed treatment centers in the United States for a 2-year period. Patients will be stratified into several subgroups, including radiation/nonradiation, maxillary/mandibular, and surgical reconstruction/prostheses. Separate analyses will be conducted for each subgroup, and comparisons will be made within subgroups to test the sensitivity of the questionnaire to a known difference. A revised version of the AAMP questionnaire, limited to 50 items of interest to patients, will be validated against 2 established head and neck cancer questionnaires. This article provides background on previous quality-of-life studies and reviews the need for and aims of the AAMP assessment instrument.