Alternative method for retention and removal of cement-retained implant prostheses

This article describes a simple, quick, and economical technique that makes use of a light-polymerized resin system to facilitate the retention and removal of cement-retained implant prostheses.     

Passivity of fit and marginal opening in screw- or cement-retained implant fixed partial denture designs

The relationship of stress generation upon placement of cement-retained or screw-retained implant restorations has not been thoroughly investigated. Passivity of fit and marginal discrepancies of screw- and cement-retained implant fixed partial denture (FPD) designs were determined using a photoelastic model of a partially edentulous posterior mandibular arch with 3 screw-type implants. Buccal and lingual marginal openings, measured with a traveling microscope before cementation or screw tightening, revealed no statistical difference in adaptation between designs. Screw tightening caused a reduction in marginal opening (changes significant, P < .05). The opening with the cemented FPDs was similar before and after cementation. Photoelastic evaluation of the FPDs showed that cement-retained FPDs exhibited a more equitable stress distribution than did their screw-retained counterparts.     

A new prosthodontic technique for fabricating cement-retained implant-supported prostheses.

This article describes a new technique for fabricating cement-retained implant-supported prostheses. The technique involves cementation of the prostheses over customized gold cylinders. Access channels are incorporated in the prostheses to allow future access of the gold screws. This technique can be used in various clinical situations to achieve total passive fit of the framework without compromising retrievability. The technique overcomes the problems encountered with other previously advocated methods for constructing such prostheses. In addition, maintenance of the resulting prostheses is uncomplicated.     

A technique for retrieval of cement-retained implant-supported prostheses

Predictable retrievability of cement-retained prostheses has been a clinical concern. This article presents a technique that describes an implant restoration design which will allow predictable removal of cement-retained implant-supported prostheses.     

Effects of modifying implant screw access channels on the amount of extruded excess cement and retention of cement-retained implant-supported dental prostheses: A systematic review

Statement of problem

Cement-retained implant-supported prostheses eliminate screw loosening and enhance esthetics. However, retrievability and the possibility of removing extruded excess cement (EEC) have been problematic.

A transfer method for multiple cement-retained implant restorations

This article describes a time-saving method for impression making and abutment preparation performed as a laboratory procedure on multiple cement-retained ITI implants.     

An in vitro study on compensation of mismatch of screw versus cement-retained implant supported fixed prostheses

In common practice a perfect fit of the prosthetic framework with the implant abutments is almost impossible to achieve. The mismatch, which is principally induced by the technological process adopted to manufacture the fixed prostheses, strains the framework thus generating constraint reactions. These are static forces that load the implant components and the bone at the implant–bone interface and may cause the bone remodelling. Depending on the magnitude of such forces, i.e. depending on the magnitude of the mismatch, the bone remodelling may lead to the loosening of the screws and of the implant–bone interface and hence cause implant failure. The present study shows an in vitro comparison of 3 different connecting abutments (standard, EsthetiCone and CerAdapt, Nobel Biocare AB, Göteborg, Sweden) with relation to the mechanical stresses induced by geometrical mismatches (technology induced errors). Two experimental devices were purposely realized and used to assess the ability of the different abutments to compensate errors. One was designed for translation errors and the other for rotation errors. The experimental apparatus set‐up includes 2 freestanding implants supporting a prosthetic structure and the connecting abutments. The implants and the abutments were used as delivered by the manufacturer, while the prostheses were purposely realized and instrumented with strain gauges. The data obtained with the error devices do not give quantitative information on what happens in clinical applications where the implants are connected to living bone, which is a tissue much more deformable than the steel used for the error devices. Results allow direct comparisons of the behaviour of the different investigated abutments with respect to position errors. The CerAdapt system (cement retained ceramic abutments) showed the least strain in presence of translation errors. The standard system (screw retained abutments) showed the least strain in presence of rotation errors.     

Fracture resistance of implant-supported screw- versus cement-retained porcelain fused to metal single crowns: SEM fractographic analysis.

OBJECTIVES: The present in vitro study aimed at evaluating the fracture resistance of both implant-supported screw- and cement-retained porcelain fused to metal (PFM) single crowns. A scanning electron microscope (SEM) evaluation of the mode of failure of the specimens was also performed. METHODS: Forty PFM premolar-shaped identical single crowns were realized. The restorations were divided into two groups: cement-retained (group 1) and screw-retained (group 2) prostheses. Compressive loading tests and SEM fractographic analyses were performed. The data were statistically analysed by means of the Student's t-test, with a confidence interval of 95%. RESULTS: The mean fracture load value was 1657 (+/-725) N in group 1 and 1281 (+/-747) N in group 2; the statistical analysis pointed out no significant differences between the two groups (p=0.115). The mean work at maximum load value was 0.775 (+/-0.619) J in group 1 and 0.605 (+/-0.526) J in group 2; the statistical analysis pointed out no significant differences between the two groups (p=0.355). All the samples were affected by cohesive fractures of the porcelain. Screw-retained crowns showed microcracks at the level of the occlusal access to the screw and extensive fractures in the whole thickness of the ceramics. On the contrary, cement-retained restorations were affected by less wide paramarginal fractures of the porcelain. SIGNIFICANCE: A stronger implant-prosthetic connection was noticed in cemented restorations group than in screw-retained single crowns. Even though negatively influenced by the presence of the occlusal access to the screw, the metal-ceramics bond can be considered predictable in both the implant-prosthetic connection systems analysed.     

Jawbone reduction in immediate prostheses. A comparison between overdentures and complete dentures

In a randomized controlled clinical trial 74 patients who required immediate dentures were randomly treated with immediate overdentures on 2 lower canines or immediate complete dentures. Mandibular bone reduction was measured using oblique lateral cephalometric radiographs made at base-line and the results compared with those of one year and two years after denture treatment. Analysis of the data showed that the average bone reduction in the lower canine regions in the first year was 0.75 in the immediate overdenture group and 1.90 mm in the immediate complete denture group. In the posterior parts of the mandible the bone reduction was respectively 0.77 and 1.77 mm. The differences were statistically significant in all measured regions. The differences in the first two years were significant in all regions except the molar region. Retention of roots of canines beneath a mandibular denture in immediate denture patients, even when they were in poor condition, reduced the collapse of the alveolar processes in all region of the mandible.     

Influence of implant and conventional prostheses on satisfaction and quality of life: A literature review. Part 2: Qualitative analysis and evaluation of the studies

PURPOSE: To review the influence of prosthodontic and dental implant treatment on patient satisfaction and oral health-related quality of life (OHQOL) based on a systematic search of the literature. MATERIALS AND METHODS: A systematic literature search was carried out for articles published between 1960 and February 2003. Details of the search process and results were reported in Part 1 of the study (Int J Prosthodont2004;17:83-93). The included studies were categorized and evaluated according to their level of evidence, following the guidelines of the Agency for Health Care Policy and Research. The characteristics and content of the studies were analyzed and tabulated. RESULTS: Among the 114 included studies, there were 76 publications reaching evidence level III. The results showed that the effects of compromised oral health are not limited to traditional clinical aspects, but can considerably affect patients in various activities of daily life. Twenty-four of the 38 investigations with evidence levels I and II dealt with implant stabilization of complete mandibular prostheses, comparing implant prostheses to conventional complete dentures. Fully edentulous patients experience negative impacts on OHQOL from their condition. They benefit significantly from the use of dental implants to support mandibular prostheses. However, support by more than 2 implants does not appear to further significantly increase patient satisfaction and OHQOL. CONCLUSIONS: To date, research in the field of patient-based outcomes has concentrated on dental implant treatment for the edentulous patient. Other prosthetic treatments such as single crowns, fixed and removable partial dentures, or further treatment concepts (eg, the shortened dental arch concept) are not well represented. The use of patient-centered outcome measures can help to find an individual, patient-oriented prosthetic solution.     

Relationship between implant preload and screw loosening on implant-supported prostheses

The purpose of this study was to determine whether varying the preload on the implant-abutment complex would affect screw loosening under simulated loading conditions. Abutment screws in sample models were tightened to 25, 30, 35, and 40 N-cm. One group of samples was allowed to stand for 3 hours after being torqued and then loosened. Another group of samples was retorqued after 10 minutes with the same initial torque value and then allowed to stand for 3 hours before loosening. For the load group of samples, the abutments were torqued into place, retorqued after 10 minutes, and a load applied for 3 hours before loosening. Cyclic loading was carried out using a servo-hydraulic testing machine with the values cycled between 1 and 26 pounds and the load applied directly to the abutments. Analysis of variance, analysis of covariance, and linear regression analysis was performed. Within the parameters of this in vitro investigation, the following recommendations can be made: (1) retightening abutment screws 10 minutes after the initial torque applications should be routinely performed and (2) increasing the torque value for abutment screws above 30 N-cm can be beneficial for abutment-implant stability and to decrease screw loosening.     

A simple prosthetic approach using cement-retained implant prosthesis after surgical treatment of ameloblastoma

Ameloblastoma is an odontogenic tumor of epithelial origin that manifests itself in the maxillofacial area with marked deformity. After removal of the tumor, prosthetic reconstruction may be challenging because of extensive tissue loss, which necessitates careful treatment planning. We describe a case in which a patient lost considerable supporting tissue after excision of the tumor. The mandible was grafted with autogenous corticocancellous bone harvested from the left anterior iliac crest in a delayed manner. After healing, six implants were placed. After second-stage surgery, a new method was used to reduce thickness of the soft tissue around the implants. A cement-retained nine-unit fixed partial denture was fabricated in three clinical visits. The patient has been monitored for 5 years with no complications despite the use of cement to retain the prosthesis and the unfavorable crown-to-root ratio.     

Longevity of partial, complete and fixed prostheses: a literature review.

A review of the dental literature reveals a lack of consensus as to the longevity of conventional prosthodontic therapy. The reasons for this are suggested and best estimates of the longevity of partial, complete and fixed prostheses are presented based on the available literature. A renewed interest in survival studies, hopefully based on sound parameters that outline the reasons for failure, as well as replacement indicators, is required to update our knowledge of survival rates.     

In vitro stress analyses of dental implants supporting screw-retained and cement-retained prostheses

A photoelastic and strain gauge analysis was performed to evaluate the stress transferred to implants through the provisional-cement-retained, the permanent-cement-retained, and the screw-retained prostheses. The deflections of the prostheses at the time of the loading were also measured. In the single crown test, the provisional-cement-retained crowns transferred less stress. In the two-unit fixed partial denture test, there were no differences between the three different prostheses. In the two-implant supported distal cantilevered prostheses, the screw-type and the permanent-cement-retained prostheses developed more stress around the apex of both implants. The permanent-cement-retained prostheses acted almost the same as the screw-type.     

Mandibular flexure and its significance on implant fixed prostheses: a review

Purpose: The aims of this review are to determine the effect of mandibular flexure on the “implant‐framework system,” and analyze the existing literature on the topic. Materials and Methods: A MEDLINE and PubMed search was conducted to identify any articles in English related to the topic published up to May 2010 using the search words “mandible,”“dental implants,”“dental impression technique,”“jaw movement,”“dental stress analysis,” and “mechanical stress.” Results: The search identified 40 and 36 articles from MEDLINE and PubMed, respectively. Twenty articles met the inclusion criteria. Conclusions: Mandibular flexure is a multifactorial phenomenon, and the effect of the implant‐framework system in this is unclear. Studies have focused mainly on the fully edentulous mandible. These have found that mandibular flexure should be taken into consideration when designing a prosthesis and have suggested that dividing the prosthesis at the symphysis region, or into multiple implant fixed dental prostheses, may minimize the effect of mandibular flexure on the implant prosthesis. At this time, no studies have investigated the effect of mandibular flexure on long‐span, unilateral, implant fixed prostheses. The clinical significance of mandibular flexure on the success of dental implant treatment is at this time unclear, and further research is needed.