The International Journal of Prosthodontics, 05/2009

Purpose: The aim of this study was to review the published literature on in vitro articles investigating the retentive force or wear features of different attachment systems, specifically for mandibular two-implant overdentures using an unsplinted prosthodontic design. Materials and Methods: An electronic search was performed through PubMed, Embase, and Medline databases using Boolean operators to combine the following key words: "retention," "wear," "overdenture attachments," "attachment systems," "implant-retained overdentures," and "implant-supported overdentures." The search was limited to articles written in English published up to October 2008. In addition, a hand search through articles and reference lists retrieved from the electronic search and peer-reviewed journals was also conducted. Results: From a total of 193 articles, only 15 met the specified inclusion criteria for the review. These articles provided evidence that the majority of attachment systems for mandibular two-implant overdentures demonstrate a reduction in their retentive force under in vitro conditions. Wear was unquestionably implicated as the etiologic factor for the loss of retention; however, the specific mechanisms involved in the wear process have not been researched adequately. Findings from the literature have also implicated several factors that influence the retentive force of the attachment system and its wear features; compelling evidence on its precise role however, is still lacking. Conclusions: Further in vitro investigations of the factors involved in the retention and wear of attachment systems for mandibular two-implant overdentures are still needed. These factors must be investigated separately under well-controlled conditions to limit the influence of confounding variables on their outcome.

Purpose: The need to place a restoration's margins on sound tooth material may require crown lengthening or forced eruption. The latter intervention may benefit from a severance of the tooth's circumferential fibers during the orthodontic process in an effort to stabilize the bone level. Orthodontic appliance design for the extrusive action, especially in the absence of neighboring teeth, may require the use of mini-implants, which are a useful adjunct in such situations. Materials and Methods: This case history describes the management of a maxillary left canine that lacked sound tooth material in the cervical zone for a proper ferrule. It was diagnosed as requiring extrusion so as to recruit it into an abutment role for a fixed partial denture design. This treatment modality was considered more favorable compared to the alternative of a crown lengthening procedure. The tooth in question was a strategic abutment in an old and failing porcelain-fused-to-metal fixed prosthesis. Results: Fiberotomy permitted rapid extrusion of the canine and available sound tooth margins for crown preparation with a proper ferrule. Conclusion: Following 28 days of tooth stabilization the implants were easily removed and treatment continued as originally planned.

Purpose: The aim of this study was to evaluate plaque accumulation and peri-implant tissue response adjacent to machined and dual acid-etched (DAE) titanium implant surfaces. Materials and Methods: Two types of implants were used-control implants with a DAE surface in their apical portion and a machined coronal part, and test implants with a DAE surface throughout their entire length. A total of 10 sets of implants were placed in the posterior quadrants of eight patients, with at least 2 implants (1 control and 1 test implant) placed in each site. Machined healing abutments were placed on the control implants and DAE-surfaced healing abutments on the test implants. Plaque Index and bleeding on probing (BOP) were recorded together with histologic and microbiologic analyses of the peri-implant tissues. The healing abutments underwent a scanning electron microscope scan at 5 months postsurgery. Standardized radiographs were also taken at the time of implant placement and 3, 6, and 12 months postsurgery. Results: DAE surfaces accumulated more plaque than machined surfaces (P .0006) and the plaque was assessed as more difficult to remove (P .0143). No histologic abnormalities were seen and the test implants showed significantly lower crestal bone resorption than the control (P .0174). Conclusion: DAE healing abutments showed an increased plaque accumulation, but no significant BOP differences or histologic analyses were found between test and control sites. The test implants showed less interproximal bone resorption than the control ones at the end of a 1-year follow-up evaluation.

This study aimed to evaluate the responsiveness of denture patients to the Liverpool Oral Rehabilitation Questionnaire (LORQ). Changes in scores for 20 core items completed from 2000 to 2005 by 16 patients both before and after oral rehabilitation were assessed. The median age of respondents was 68 years and the median time between questionnaires was 2.6 years. Results indicated that masticatory efficiency impacted both food choice (P = .03) and social life (P = .06). After rehabilitation there was less worry about maxillary prostheses falling out (P = .07), less embarrassment while conversing (P = .02), and less worry about losing self-confidence from embarrassment caused by dentures (P = .06). Also, drooling problems deteriorated (P = .03). This exploratory study reports encouraging findings, but a larger prospective multicenter study is required to determine the responsiveness of the current version of the LORQ (version 3).

Purpose: This paper aims to analyze the demographic and prosthodontic treatment differences between patients who did and did not respond to a mailed questionnaire. Materials and Methods: All living patients who received tooth- and implant-related fixed prosthodontic treatment between January 1984 and June 2005 (n = 986) in one private prosthodontic practice were mailed a questionnaire regarding their prosthodontic treatment. Demographic data (sex, age) and treatment data (survival, type of treatment, time in situ, number of units, number of treatments) for responding and nonresponding patients were collected from patient files and analyzed. Statistical significance was set at P = .05. Results: There were 500 responding patients (50.7%) with 2,702 fixed prosthodontic units (60.02%) and 486 nonresponding patients (49.3%) with 1,800 fixed prosthodontic units (39.98%). Prostheses were in situ from 1 to 20 years, with the average time in situ for respondents of 7.47 ± 5.48 years and 6.5 ± 5.21 years for nonrespondents. Responding and nonresponding patients had similar sex distributions (P = .61), Kaplan-Meier 10-year estimated cumulative survivals (92.2 ± 1.72% and 91.5 ± 1.92%; P = .13), and received a similar distribution of treatment prostheses (implant versus tooth) (P = .24). However, responding patients were significantly older (P .001), had their prostheses in situ for a greater length of time (P = .01), received more prosthetic units (P .001), and underwent more treatment episodes (P .001) than nonresponding patients. Conclusions: Patient questionnaires provide valid and unique research information. Prosthesis outcomes for patients who did and did not respond to the questionnaire were the same. Treatment outcomes of patients who attend review appointments and those who are lost to follow-up cannot be assumed to be different. Demographic- and treatment-related characteristics of responding patients indicated that an enhanced provider-patient rapport was a principal motivator for responding to the questionnaire.

Purpose: This systematic review sought to determine the long-term clinical survival rates of single-tooth restorations fabricated with computer-aided design/computer-assisted manufacture (CAD/CAM) technology, as well as the frequency of failures depending on the CAD/CAM system, the type of restoration, the selected material, and the luting agent. Materials and Methods: An electronic search from 1985 to 2007 was performed using two databases: Medline/PubMed and Embase. Selected keywords and well-defined inclusion and exclusion criteria guided the search. All articles were first reviewed by title, then by abstract, and subsequently by a full text reading. Data were assessed and extracted by two independent examiners. The pooled results were statistically analyzed and the overall failure rate was calculated by assuming a Poisson-distributed number of events. In addition, reported failures were analyzed by CAD/CAM system, type of restoration, restorative material, and luting agent. Results: From a total of 1,957 single-tooth restorations with a mean exposure time of 7.9 years and 170 failures, the failure rate was 1.75% per year, estimated per 100 restoration years (95% CI: 1.22% to 2.52%). The estimated total survival rate after 5 years of 91.6% (95% CI: 88.2% to 94.1%) was based on random-effects Poisson regression analysis. Conclusions: Long-term survival rates for CAD/CAM single-tooth Cerec 1, Cerec 2, and Celay restorations appear to be similar to conventional ones. No clinical studies or randomized clinical trials reporting on other CAD/CAM systems currently used in clinical practice and with follow-up reports of 3 or more years were found at the time of the search.

The aim of this study was to evaluate the surface properties and color of porcelain modified by extraoral polishing sequences. Six different surface treatment regimens (diamond burs, self-glaze, overglaze, reglaze, Pearl Surface polishing system, and Diamond Twist SCL) were applied to 60 porcelain disks (n = 10 per group). Profilometry and atomic force microscopy (AFM) were used for the determination of surface roughness (Ra); color changes (DE*) were investigated by spectrophotometry. Statistical comparisons were made using analysis of variance, the Kruskal-Wallis test, and the Pearson correlation coefficient test. Surface treatments significantly affected Ra values (P .001) but had no effect on color (P > .05). AFM findings were consistent with Ra values. Color did not appear to be correlated with surface roughness (P > .05). The findings concluded that the Pearl Surface system helps to decrease chairside time and may be used as an alternative to overglazing.

The relative hardness (RH) of five composite materials was determined through polymerization via LED lights. Disk specimens were prepared by using composites composed of Artiste, an experimental glass fiber composite, Filtek Supreme, Z100, and LuxaCore. Specimens were polymerized for 10 and 20 seconds from the top surface only with two lights, Smartlite-IQ2 and DEMI LED, with light maintained 8 mm from the surface through a coronal section of the molar tooth. Knoop hardness numbers were determined for the top and bottom surfaces both immediately and 24 hours later. Ten RH values per group were calculated and data were statistically analyzed. Generally, RH increased with increasing polymerization time. The DEMI LED light resulted in RH values that were significantly higher than those obtained with Smartlite IQ2. Z100 had RH values of > 80% under most testing conditions and had the highest hardness values of all composites tested. Therefore, it is considered to be the most appropriate for core buildups.

Purpose: The aim of this study was to investigate the survival rates and technical failures of removable prostheses (RPs) supported by telescopic double crown (TDC)-retained abutment teeth luted with zinc-phosphate or glass-ionomer cement. Materials and Methods: Clinical records of 577 patients (288 women, 289 men) who received 577 TDC-retained RPs supported by 1,807 abutments at the Department of Prosthodontics of the University Hospital Regensburg, Regensburg, Germany, between 1984 and 2007 were analyzed. The 577 prostheses included 200 attached to telescopic crowns with friction fit (FFs), 62 to conical crowns (CCs), and 315 to parallel-sided telescopic crowns with clearance fit (CFs). Survival probabilities were evaluated for the RPs, loss of cementation of the inner copings, secondary caries, and abutment teeth that required endodontic treatment using the Kaplan-Meier method. A Cox regression analysis determined the impact of covariates such as sex, denture location (maxilla/mandible), Eichner classification, number of abutment teeth, and the type of double crown system used. Results: The 10-year survival probability was 98.8% ± 0.09% for FFs, 92.9% ± 0.41% for CCs, and 86.6% ± 0.05% for CFs. During the observation period, loss of cementation was frequently observed (FFs: 32%, CCs: 53.2%, CFs: 21.3%). After 15 years, more than 75% of patients had experienced at least one "loss of cementation" event. In this respect, zinc-oxide phosphate and glass-ionomer cements did not show any significant difference. Conclusion: The long-term successful outcome of the RP experience was not compromised, although numerous clinical visits were required for maintenance. The predominant maintenance procedure was the need for recementation of the inner copings.

Denture stomatitis is a debilitating disease associated with the presence of adherent Candida albicans. This study compared the attachment capacity of C albicans to three different acrylic resin materials (self-curing [SC], conventional pressure-packed [CPP], and injection-molded [IM]) to determine whether the physical properties of the materials influenced candidal attachment. No significant differences in attachment between the isolates were observed for each acrylic resin. However, a comparison of the mean of all isolates showed significantly less attachment to SC than to CPP (P .05). These data indicate that choice of denture acrylic resin material may influence the capacity for developing denture stomatitis.

This prospective study evaluated the clinical outcome of three-unit posterior fixed dental prostheses (FDPs) made of In-Ceram Zirconia. All 65 FDPs were inserted at the Department of Prosthodontics, School of Dentistry, Kiel, Germany, and cemented with glass-ionomer cement. Follow-ups were performed annually. During a mean observation time of 54.4 months, two FDPs failed (one technical and one biologic failure). Two FDPs debonded and the veneering ceramic fractured in four cases. Three abutment teeth needed endodontic treatment and two additional abutment teeth exhibited secondary caries. Results suggest that posterior three-unit all-ceramic FDPs made from In-Ceram Zirconia may be a viable prosthetic treatment option with an outcome comparable to metal-ceramic FDPs.

Purpose: The prosthodontic treatment of dysphagic patients may preclude favorable treatment outcomes due to uncoordinated or discordant oral and pharyngeal functions. Since optimal treatment requires a full understanding of the mechanism of oropharyngeal swallowing, this study seeks to describe the normal temporal pattern of tongue-, jaw-, and swallowing-related muscle coordination during voluntarily triggered swallows in healthy patients. Materials and Methods: Tongue pressure against the hard palate at seven measuring points, swallowing sounds, and surface electromyography (EMG) activity of the masseter, anterior digastric, and infrahyoid muscles during voluntarily triggered swallowing were recorded in seven healthy male volunteers. The order of onset and offset of these parameters was analyzed by repeated-measures two-way analysis of variance. Results: The onset of anterior digastric muscle activity occurred first and was significantly earlier than the onset of the masseter or infrahyoid muscles and tongue pressure. The onset of masseter muscle activity was also significantly earlier than that of the infrahyoid muscle and tongue pressure. Offset of masseter activity was almost simultaneous with the swallowing sound and was significantly earlier than the offset of the anterior digastric and infrahyoid muscles as well as tongue pressure. The EMG burst of the anterior digastric muscle continued until the offset of tongue pressure, and was followed by the offset of infrahyoid muscle activity. Conclusions: The temporal coordination patterns of the tongue, jaw, and oropharyngeal muscles during voluntarily triggered swallowing appear to agree with known safe management of a bolus and offer criteria for evaluating the function of oropharyngeal swallowing.

The selected case history describes a 56-year-old surgical nurse who is very dissatisfied with her existing anterior removable partial denture, especially the presence of anterior diastemas, but she is unaware of any speech impediment. She also dislikes the instability, bulk, and removable nature of both of her removable partial dentures, as well as the soreness of her palatal mucosa. She expresses a desire to receive fixed implant-supported prostheses, if possible, but is open to all treatment options. She explains her need for a predictable, safe, and lifelong treatment outcome.

The selected case history describes a 76-year-old retired housewife who requires dental treatment.