The International Journal of Prosthodontics, 01/2008

The September 2007 Meeting of the International College of Prosthodontists in Fukuoka, Japan yielded an outstanding collection of poster presentations. The results were as follows: The finalists for the Young Prosthodontist Award included Athina A. Bakopoulou (winner) and Dubravka Knezovic Zlataric (runner-up). The category Case History Poster Competition included finalists Ben Lee (winner) and Matjaz Golobic (runner-up). The poster abstracts are presented with a biography of the winning author. Further, each author was asked to provide a brief reply to questions posed by Dr Zarb regarding their research topic. The quality of the poster presentations was exceptional and augurs well for the discipline's research future. It is also worth noting that Dr Bakopoulou was also a winner at the 2005 Meeting in Crete. Hers is indeed an impressive performance, and together with the excellent work of the other winners, deserves the congratulation of the entire editorial staff of the IJP.

Purpose: To investigate the influence of (1) osteoporosis on resorption of edentulous jaws and (2) whether osteoporosis enhances implant loss. Materials and Methods: MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials (CENTRAL) databases were searched for association of osteoporosis and bone resorption/loss of implants. Inclusion and exclusion criteria were defined and quality assessment of the remaining studies after exclusion was performed. The Cochrane approach for cohort studies was applied. Results: Methodologic assessment of the eligible publications using the Cochrane approach resulted in the inclusion of 11 publications in the final evaluation. Most studies dealt with the association between the extent of resorption or atrophy of edentulous jaws and the systemic (femoral, lumbar spine, metacarpal) bone mineral content (BMC) or bone mineral density (BMD) status. Four studies reported a significant association between the extent of resorption and the skeletal BMC and/or BMD. Four studies evaluated the effect of endosseous implants on mandibular BMC or BMD changes and the association between systematic BMD statuses and loss of implants. These studies revealed no association between systemic BMD status, mandibular BMD status, bone quality, and implant loss. Conclusions: Although no firm conclusions could be drawn regarding the effect of osteoporosis on resorption of edentulous jaws, with or without implants, due to the different parameters applied in the various studies, the use of endosseous implants in osteoporosis patients is not contraindicated.

Purpose: Various ceramic implant systems made of yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) have become commercially available in recent years. A systematic search of the literature was performed to assess the clinical success of dental Y-TZP implants and whether the osseointegration of Y-TZP is comparable to that of titanium, the standard implant material. Materials and Methods: The internet database MEDPILOT was searched cumulatively for the keywords zircon* and dent* and implant as well as for zircon* and osseointegration. The last search was conducted on January 31st, 2007. Subsequently, the reference lists of the relevant publications were searched. Furthermore, a letter was sent to the 5 identified manufacturers of zirconia dental implants to ask for peer-reviewed publications. Results: Ninety-six articles were found by the search strategy. No controlled clinical studies in humans regarding clinical outcomes or osseointegration could be identified. Clinical data were restricted to case studies and case series. Only 7 animal studies fulfilled the inclusion criteria. Osseointegration was evaluated at 4 weeks to 24 months after placement in different animal models and sites and under different loading conditions. The mean bone-implant contact percentage was above 60% in almost all experimental groups. In studies that used titanium implants as a control, Y-TZP implants were comparable to or even better than titanium implants. Surface modifications may further improve initial bone healing and resistance to removal torque. Conclusions: Y-TZP implants may have the potential to become an alternative to titanium implants but cannot currently be recommended for routine clinical use, as no long-term clinical data are available.

This study aimed to examine the longitudinal influence of bonded composite resin cingulum rest seats on abutment tooth periodontal tissues in removable partial dentures (RPDs). Twenty-eight patients with RPDs were enrolled in the study. Thirty-one cingulum rest seats were prepared for an anterior tooth using composite resin and a standardized method for each patient. Periodontal indices such as probing pocket depth (PD), bleeding on probing (BoP), and tooth mobility (TM) were measured at the time of denture insertion (baseline) and at least 3 months postinsertion (up to 8 years). Control data were obtained from the remaining nonprepared anterior teeth on the other side of the arch. None of the bonded resin rest seats failed, but slight abrasion was observed in 3 rest seats. No significant differences were found in terms of PD, BoP, and TM between baseline and postinsertion data for abutments with bonded resin rest seats and controls. It is suggested that bonded composite resin cingulum rest seats can be used longitudinally without damaging the periodontal tissues of abutment teeth.

Purpose: The aim of the present study was to evaluate the clinical outcome of extensive Empress onlays retained with resin-bonded cement. Materials and Methods: One hundred thirty extensive ceramic onlays were placed in premolar and molar regions in 91 patients treated by 2 general practitioners between 1997 and 2000. Seventy-seven percent of the constructions were luted with chemically cured resin composite cement and 23% were luted with dual-cured resin cement. Fifty-nine patients with 81 restorations were clinically evaluated independently by 2 calibrated examiners using the California Dental Association protocol. The mean time in function for all restorations at examination was 49 months. Results: Seventy-five (93%) onlays were still in function after 4 years. Six onlays (7.3%) had failed; 1 had lost retention as a result of caries, and 5 had fractured. All failures were in molar regions. Conclusions: Ceramic onlay therapy is an acceptable treatment alternative over a 4-year period, but further long-term data are necessary before this treatment should be considered for general dental practice.

Purpose: The aim of this study was to compare the shear bond strength of a veneering composite to 2 differently treated fiber-reinforced composite (FRC) substrates and to a base metal alloy. Materials and Methods: A veneering composite (SR Adoro) was bonded to the following substrates: (1) a nickel-chromium base metal alloy (control, group A), (2) an FRC substructure (Vectris) with a flat surface (group B), and (3) an FRC substructure (Vectris) with retentive rods 0.5 X 0.5 mm in cross section and 10 mm in length, positioned parallel to each other at a distance of 0.5 mm (group C). Thirty-nine specimens were fabricated and divided into 3 groups of equal size. All specimens were thermocycled for 5,000 cycles at 5°C and 55°C with dwell time of 30 seconds in each bath. Evaluation of shear bond strength was performed at a constant crosshead speed of 0.5 mm/min according to ISO 10477. Results: The mean values for the shear bond strength were 19.29 MPa for the control group (group A), 16.66 MPa for group B, and 16.74 MPa for group C. Despite a tendency to higher bond strength of group A specimens, no statistically significant difference was recorded between the groups (P > .05). Conclusions: No statistically significant difference was found between the metal and FRC substructures. Retentive rods on the FRC substructure do not seem to increase the bond strength significantly.

The 3-dimensional forces exerted on an abutment tooth of a removable partial denture (RPD) were measured in vivo during clenching using a force-measuring device with a piezoelectric transducer. The device was mounted on the mandibular right second premolar of a subject with an edentulous maxilla. The magnitude of the forces was higher and the direction was more posterior without the RPD in place. The direction was most posterior with an RPD with a distal rest only and most anterior with an RPD with a mesial rest only. The 3-dimensional forces exerted on an abutment tooth thus depend on both the presence of a denture and the rest location.

Purpose: The objective of this follow-up study was to examine the performance of Cerec inlays and onlays, all of which were placed by the same clinician, in terms of clinical quality over a functional period of 15 years. Materials and Methods: Of 200 Cerec inlays and onlays placed consecutively in a private practice by one of the authors (TO) between 1989 and early 1991, 187 were closely monitored over a period of 15 years. All ceramic inlays and onlays had been placed chairside using the Cerec 1 method and had been luted with a bonding composite. Up to 17 years after their placement, a follow-up assessment was conducted, and the restorations were classified using modified United States Public Health Service criteria. Results: According to Kaplan-Meier analysis, the success rate of Cerec inlays and onlays was 88.7% after 17 years. A total of 21 failures (11%) were found in 17 patients. Of these failures, 76% were attributed to ceramic fractures (62%) or tooth fractures (14%). The reasons for the remaining failures were caries (19%) and endodontic problems (5%). Restorations of premolars presented a lower failure risk than those of molars. Conclusion: The survival rate probability of 88.7% after up to 17 years of clinical service for Cerec computer-aided design/computer-assisted machining restorations made of Vita Mk I feldspathic ceramic is regarded as a very respectable clinical outcome.

This clinical single-blind study aimed to evaluate the influence of 2 occlusal concepts (OCs) on patient satisfaction in the initial phase after fitting new complete dentures (CDs). Thirty-eight edentulous patients received 1 new maxillary CD and 2 almost identical mandibular CDs, which differed only in their OC (bilateral balanced occlusion vs canine guidance). After 2 weeks, the patients' satisfaction was evaluated and the OC was changed. Two weeks later, the patients' satisfaction was reevaluated. After 2 and 4 weeks, 63% and 47% of the patients preferred bilateral balanced occlusion and 5% and 11% preferred canine guidance, respectively. Thus, a bilateral balanced occlusion primarily facilitates the adaptation of a new CD.

Purpose: This study aimed to assess the persistent presence of microorganisms on patient-derived dental impressions and gypsum casts, while highlighting important human pathogens such as Candida, methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa. Materials and Methods: The practices and opinions regarding cross-infection control from 59 general dentists in Japan were obtained via a questionnaire. Alginate impressions were made from 56 patients. Using a brain heart infusion agar medium, impression and imprint cultures were carried out to visualize the microbial contamination on the surfaces of the impressions and gypsum casts, respectively. The colonies on the surfaces of the 30 impression cultures and 26 imprint cultures were collected by swabbing and then inoculated onto selective agar plates to detect streptococci, staphylococci, Candida, MRSA, and P aeruginosa. Results: The questionnaire showed that only 54% of general dentists had a cross-infection policy in their dental clinics, and only 30% to 40% were aware of the possible persistence of MRSA or P aeruginosa on impressions and gypsum casts. The impression/imprint cultures grew a large number of visible bacterial colonies on all of the impression/gypsum cast samples investigated. Selective agar cultures demonstrated the presence of streptococci (100, 100%), staphylococci (56.7, 65.4%), Candida (30, 46.2%), MRSA (26.7, 15.4%), and P aeruginosa (6.7, 7.7%) on the impressions and the gypsum casts, respectively. Conclusions: This investigation showed that patient-derived dental impressions and gypsum casts are contaminated with numerous microbes, including Candida, MRSA, and P aeruginosa, which are known pathogens responsible for nosocomial and/or life-threatening infection in the immunocompromised host.

This study aimed to analyze the effect of relative humidity (RH) on the initial hydrophilicity of unset elastomeric dental impression materials. Initial water contact angles were studied on thin unset films of 1 polyether and 4 polyvinyl siloxane (PVS) impression materials at 20%, 50%, and 80% RH by high-resolution drop shape analysis. One of 4 PVS materials reached the polyether's initial hydrophilicity. This PVS showed increased hydrophilicity with increasing RH. The initial hydrophilicity of impression materials can be influenced by the RH level. Accounting for RH will enhance the clinical relevance of hydrophilicity studies.

This study aimed to investigate the relationship between missing occlusal units and oral health-related quality of life (OHRQoL) in subjects with shortened dental arches (SDAs). Subjects with SDAs (N = 115) were recruited consecutively from 6 university-based prosthodontic clinics. OHRQoL was measured using the Japanese version of the Oral Health Impact Profile (OHIP-J). An increase of 1 missing occlusal unit was associated with an increase of 2.1 OHIP-J units (95% CI: 0.6-3.5, P = .02) in a linear regression analysis. Missing occlusal units are related to OHRQoL impairment in subjects with SDAs.

Purpose: This study of short-span fixed dental prostheses (Ss-FDPs) versus long-span FDPs (Ls-FDPs) evaluated the long-term efficacy and determined the frequencies and causes of failures. Materials and Methods: A total of 236 Ss-FDPs and 86 Ls-FDPs made in an undergraduate university clinic for 149 and 70 patients, respectively, were evaluated over a 20-year period. Kaplan-Meier analysis with a 95% confidence interval was used to estimate the survival probability. Failures of the FDPs were divided into irreversible (loss of FDPs or finish line involvement) or reversible (FDPs and abutments intact after conservative treatment) complications and into biologic and technical/patient-related failures. Results: The overall survival estimations for Ss-FDPs (70.8%; 95% CI: 63%-79%) and Ls-FDPs (52.8%; 36%-70%) at year 20, were statistically significantly different (P = .030). There was no statistically significant difference (P = .126) for the survival estimations for Ss-FDPs (60.4%; 48%-73%) versus Ls-FDPs (59.0%; 44%-74%) at year 19 in the root-canal treated (RCT) group. For the Ss-FDPs group there was a statistically significant difference (P = .009) between the vital (82.4%; 73%-92%) and RCT (60.4%; 49%-73%) groups at year 20. The reason for failure in the Ss-FDP group was of biologic origin in 55.6% to 66.7% of cases, but for the Ls-FDP group the failures were of technical origin in 56.0% to 84.0% of cases. Conclusion: The survival of Ss-FDPs and Ls-FDPs over a 20-year period was favorable. The overall survival estimation for Ss-FDPs was statistically significantly better than for Ls-FDPs at year 20. The use of an RCT abutment becomes more significant in fixed prosthetic restorations with 4 or more units. Occurrence of a previously reversible complication is a predictive factor for an irreversible complication later on. A reversible complication within the first 2 years for an Ss-FDP will lead to an irreversible complication.

This study aimed to analyze factors related to patients' general satisfaction with removable partial dentures (RPDs), such as esthetics, retention, speech, chewing, and comfort. A total of 103 patients with Kennedy Class I RPDs (34 to 82 years old; mean age: 63; 35 men, 68 women) assessed their satisfaction with dentures. Stepwise multiple regression analysis was used to evaluate the relationship among the factors. Significant correlations were found between general satisfaction and each of the individual components (P .05). The patients' assessment of esthetics explained almost 50% of general satisfaction in both arches (P .05). Esthetics, chewing, and speech had significant effects on the patients' general satisfaction with dentures.