The International Journal of Prosthodontics, 05/2005

Purpose: Long-span, resin-bonded fixed partial dentures (FPDs) have been associated with higher debonding rates than short-span prostheses. The use of modified nonrigid connectors that allow movement between the abutments in long-span resin-bonded prostheses may reduce harmful interabutment forces that stress the metal framework and resin-bonded interface. This preliminary investigation aimed to evaluate the longevity of long-span resin-bonded FPDs of 4 or more units with a modified nonrigid connector and increased extension of the retainer framework around the major abutment. Materials and Methods: Thirty-eight patients attended a clinical examination; each had been provided with 1 or more resin-bonded FPD of 4 or more units (43 prostheses). For each patient, the following data were recorded: gender, age, cementation date, and endodontic treatment, if performed. Data regarding the occurrence of any debondings and patient expectations were also recorded. Results: The mean service life for the 43 prostheses was 46.9 months (SD 22.0), with a range of 12 days to 87 months. Three prostheses had debonded, resulting in a clinical retention rate of 92.2%. Conclusion: Long-span resin-bonded FPDs incorporating nonrigid connectors that allow independent movement between the major and minor retainer, combined with increased framework extension on the major abutment, appear successful in the short term. Further research is required to determine their long-term efficacy.

Purpose: This study evaluated the antibacterial activity of water-activated zinc polycarboxylate cement with adjunctive 0.12% chlorhexidine gluconate on the subgingival microbiota in fixed partial dentures. Materials and Methods: Thirty-six teeth prepared as fixed partial denture abutments in 9 patients were cemented randomly using water-activated zinc polycarboxylate cement (control group) or water-activated zinc polycarboxylate cement, including 0.12% chlorhexidine gluconate (test group). A total of 108 subgingival plaque samples were analyzed at baseline, immediately before permanent cementation (5 weeks), and 8 weeks later (at 13 weeks). Results: In the control group, the subgingival microbiota altered to closely resemble the flora of chronic gingivitis (increased proportions of gram-negative anaerobes such as Prevotella intermedia, Fusobacterium nucleatum) by 13 weeks. In contrast, the microflora at test sites comprised predominantly gram-positive facultative cocci and rods at 13 weeks. Conclusion: This study demonstrated that the addition of 0.12% chlorhexidine gluconate may enhance the antimicrobial action of polycarboxylate cements to ensure the maintenance of a microflora compatible with periodontal health, at least up to 13 weeks post-cementation.

Purpose: The aim of the study was to assess implant survival and complications with implants and prostheses in patients exhibiting a variety of systemic diseases and congenital defects. Materials and Methods: Patients with specific medical conditions are regularly treated at the Department of Prosthodontics, University of Bern, Switzerland. All those who had received implant-prosthodontic treatment during the past 12 years were reexamined for this study. Among these patients the following diseases were observed: cleft lip/palate (n = 8), Down syndrome (n = 3), Sjögren syndrome and scleroderma (n = 2), ectodermal dysplasia (n = 4), developmental retardation (n = 2), chronic leukemia (n = 2), lichen planus (n = 1), cerebral palsy (n = 1), deaf-muteness (n = 1), amyotrophic lateral sclerosis (n = 1). At the time of the treatment the mean age was 55.6 years. ITI implants had been placed according to a standard protocol with local anesthesia, except for one patient in whom full anesthesia was used. One hundred three implants were loaded and supported a total of 34 fixed or removable prostheses. All patients were appointed to a regular maintenance care program. In the context of the present study, all but 1 patient were reexamined clinically. New radiographs were obtained, and the implants and prostheses assessed. Additional information was obtained from regular records in the patients' charts. Results: Three implants were lost in the healing phase, and 1 implant was replaced. Only 1 patient with 4 implants was lost from the study (she had passed away). The survival rate of the loaded implants was 100%. In 1 patient, peri-implant bony defects were detected around all 3 intraforaminal implants. The prosthetic plan was maintained in all patients, and they continued to wear the originally planned type of prosthesis. Complications included insufficient hygiene, soft tissue hyperplasia, extraction of remaining teeth, and minor maintenance or repair of the prostheses. Conclusions: So far, the mostly unknown implications and possible risks for the process of osseointegration and long-term maintenance in patients with such rare diseases and defects has resulted in a rather restricted application of implants. However, from the present results, it appears that implants can successfully be placed and maintained. This is ascribed in part to a strict maintenance care program provided by the caregivers and to a high compliance of the patients who participated in this program to perform good oral hygiene.

Purpose: This study aimed to compare the marginal fit of 2 kinds of metal-ceramic crowns-crowns cast from commercially pure titanium and Procera titanium crowns. Materials and Methods: Ten copings of each type were prepared, veneered with low-fusing porcelain, and bonded with glass-ionomer cement. Marginal fit was assessed before and after cementation, and the data were analyzed statistically. Results: There were significant differences among mean values of marginal fit between the groups. Cementation increases discrepancies in both groups. Conclusion: Casting titanium has resulted in the highest discrepancies in marginal fit of both groups.

Purpose: This study aimed to determine whether small variations in the composition of the polymethylmethacrylate (PMMA) of widely used dentures produce differences in the degree of Candida albicans adherence and to relate any differences found to the surface energy of the resins, which appears to play a major role in the initial phases of microorganism adhesion. Materials and Methods: A reference strain of C albicans (18.804 ATCC) and 11 different PMMAs (Vacalon, Inkotherm 85, Veracril, Probase Cold, Inkotherm Press, Inkotherm 85 T, Ruthinium, Vertex, SR Ivocap, Idoacryl, Lucitone) were used. Fifty specimens (15 3 10 3 1 mm) of each type were prepared. C albicans adhesion was determined by microorganism count under fluorescent optical microscope, and the surface energy of the resins was calculated by the contact angle method. P .05 was regarded as significant. Results: C albicans adhesion on the resins ranged from 7.12 cells/mm2 to 330.8 cells/mm2, with statistically significant (P > .05) differences in some cases. Despite small variations in the composition of the resins, their surface energy values were very similar (38.78 to 41.2 mJ/m2), and no relationship was found between C albicans adhesion and surface energy. Conclusion: The adhesion of C albicans to different resins varied in vitro, possibly as a result of the action of residual postpolymerization products. According to these results, variations in surface energy that result from differences in the composition of the different PMMA resins appear to have no influence on the adhesion of C albicans or, therefore, on the onset of denture stomatitis.

Purpose: Restoration of root-treated teeth is routinely performed in clinical practice with a choice of therapeutic options, considering many factors to provide optimal mechanical properties, esthetics, and longevity. The aim of the present work was to present a preliminary clinical report on the use of fiber posts and direct resin composites for restoring root-treated teeth. Materials and Methods: Thirty-eight anterior and 62 posterior endodontically treated teeth were selected from 3 private prosthodontic offices. The protocol used included endodontic treatment, with translucent fiber posts (DT post) bonded to the post-space using a '1-bottle' adhesive (One-Step, Bisco) and a dual-cure resin cement (DuoLink, Bisco). Direct resin restorations were performed using a micro-hybrid resin composite (Gradia Direct, GC) and a layering technique. Both opaque dentin and enamel and translucent enamel shades were used. Results: Patients were recalled after 6, 12, 24, and 30 months, and the restorations assessed according to predetermined clinical and radiographic criteria. These clinician-mediated evaluation methods confirmed the good clinical performance of the restorations. Conclusion: Restoration of endodontically treated teeth with fiber posts and direct resin composites is a treatment option, that in the short term conserves remaining tooth structure and results in good patient compliance.

Purpose: The study's aim was to compare dimensional measurements on computer images generated from data captured digitally by 3 different methods of the surfaces of a plastic cube of known form to those obtained directly from the cube itself. Materials and Methods: Three-dimensional images were reconstructed of a plastic cube obtained by computerized tomography (CT), magnetic resonance imaging (MRI), and laser scanning. Digital calipers were used to record dimensional measurements between the opposing faces of the plastic cube. Similar dimensional measurements were recorded between the cube faces on each of the reconstructed images. The data were analyzed using a 2-way ANOVA to determine whether there were differences between dimensional measurements on the computer images generated from the digitization of the cube surfaces by the different techniques, and the direct measurement of the cube itself. Results: A significant effect of how the measurements were taken (ie, direct, CT, MRI, and laser scanning) on the overall variation of dimensional measurement (P .0005) was observed. Post hoc tests (Bonferroni) revealed that these differences were due principally to differences between the laser-scanned images compared to other sources (ie, direct, CT, and MRI). The magnitude of these differences was very small, up to a maximum mean difference of 0.71 mm (CI ± 0.037 mm). Conclusion: All 3 methods of imaging would be of value in further studies, not only for the fabrication of complex shapes such as prosthetic ears, but also for other facial prostheses.

Purpose: It is important to know whether tooth loss has an impact on an individual's quality of life, since tooth loss is common. The aim of this study was to determine whether oral status is associated with general health and related to quality of life. Materials and Methods: Data of 1,406 subjects aged 60 to 79 years were taken from the Study of Health in Pomerania (SHIP). Sociodemographic (age, sex, and education level) and medical information (including the most common diseases in Germany) were gathered through an interview, and income data were obtained from a self-administered questionnaire. The prosthetic status in the maxilla and mandible was classified into complete denture or removable partial denture or with >= 10 natural teeth including teeth replaced with fixed prosthodontics (>= 10T) or with = 9 natural teeth including fixed prosthodontics (= 9T). The health-related quality of life was measured using the Short Form (SF-12) questionnaire. Multiple linear logistic regression analyses were used to identify the nonstandardized beta coefficient using physical and psychologic indices from the SF-12 as dependent variables and sociodemographic information, prosthetic status, and disease state as independent variables. Results: Prosthetic status is related to the physical scale of the SF-12. Additionally, we found that = 9T had a significant effect on the physical index of general health¨Crelated quality of life. Conclusion: Reduced dentition without replacement of missing teeth by removable or fixed prosthodontics reduces the physical index of quality of life to the same extent as cancer or renal diseases.

Purpose: The aim of this study was to determine the original water content of a supplied acrylic resin powder and a monomer and of dry heat-processed acrylic bars. The effect of the original water content of acrylic resin on processing shrinkage was also investigated. Materials and Methods: Ten bar specimens were fabricated using dried and as-supplied (control) acrylic resins. The resins were polymerized and cooled, then weighed and measured to determine the amount of shrinkage. The initial water content of the specimens was determined by thorough drying, and results were compared with the Student t test. Results: The initial water content and processing shrinkage of the dried acrylic resin bars were both significantly lower (P .0001) than those of the as-supplied acrylic resin bars. Conclusion: The processing shrinkage of acrylic resin made from dried constituents was significantly less than that of resin made from products as supplied by the manufacturer. However, it is not known if this change is of clinical significance.

Purpose: The objective of this study was to investigate whether a systematically arranged shade guide system (Vita 3D-Master) allows clinicians to achieve a better shade match of a restoration, as compared to a conventional shade guide with a design based on empirical values (Vita Classical). Materials and Methods: Fifty-nine restorations in 42 patients being treated by student clinicians were assessed. Using 1 of the 2 shade systems assigned randomly, each student independently determined the tooth shade. With the aid of a visual rating scale, the accuracy of the shade match of the finished restoration was assessed. Results: All restorations whose shades had been determined with the 3D-Master could be placed without any further shade corrections. In contrast, almost 17% of restorations determined with the conventional system required subsequent shade modifications. The match of the shades selected with the 3D-Master was judged significantly better by the clinicians. Conclusion: Within the limitations of the study, clinicians with less clinical experience who use a system that guides them through the shade-taking procedure in a relatively systematic manner will be more successful in selecting the correct tooth shade and in avoiding shade corrections. Clinical assessment of the restoration shades showed significant differences between the shade guide with a systematic design and that based on empirical values.

Purpose: In a retrospective study, the radiographs of 39 patients with Applegate-Kennedy Class I or II in the posterior mandible who had been treated with screw-anchored fixed partial dentures supported by IMZ implants and natural teeth were examined for the presence of radiologically detectable peri-implant bone loss. Furthermore, the results were correlated with a mathematical model. Materials and Methods: The radiographs of the implants were digitized, and the areas of bone atrophy mesial and distal to the implants were determined semi-automatically. The data obtained were correlated with the distance between the implant and the abutment tooth. The connection between the tooth-supported crown and the implant-supported denture was made with a vertical screw-lock precision attachment. In a mathematical analysis it was assumed that the fixed partial prosthesis was a rigid beam with 3 elastically embedded supports. Results: The mean distance between the tooth and the first implant was 11.02 mm (SD: 4.24), and between the tooth and the second implant was 20.25 mm (SD: 5.16). Peri-implant bone loss significantly followed a rational function (mesial implant: P = .03, distal implant: P = .02), meaning that, as the tooth-implant distance increased, the area of atrophy became rapidly larger and then diminished gradually. Distances of 8 to 14 mm between the tooth and the first implant and of 17 to 21 mm between the tooth and the second implant were associated with a more pronounced bone loss. These results were also confirmed mathematically. Conclusion: A tooth-implant distance of 8 to 14 mm for the first implant and 17 to 21 mm for the second implant should be avoided for implant placement if prosthetic rehabilitation is planned using a fixed partial denture supported by a premolar and 2 IMZ implants in the mandible. Although this investigation was done on IMZ implants only, the results were confirmed by a mathematical model, which indicated that the observed bone loss may be the same in other types of implants placed in the same positions.

Purpose: To determine the intensity of quartz-tungsten-halogen light polymerization units in dental offices in El Salvador, Brazil. Materials and Methods: A team of researchers visited 100 offices in 2003. The team measured light intensity with a radiometer. The age and make of the units and the availability of light meters were recorded. Results: One hundred twenty quartz-tungsten-halogen units were tested. Intensity ranged from 10 to 1,000 mW/cm2, with mean of 255.8 mW/cm2. Almost half (48%) of the units had values equal to or less than 200 mW/cm2. Their age ranged from 1 to 21 years. None of the offices had light meters. Conclusions: Clinicians should periodically monitor light intensity and carry out maintenance on their light polymerization units.

This study presents a method of using shadow-speckle correlation to reconstruct a 3-dimensional (3D) tooth model. Compared with other methods based on laser or optical geometric measurements, the shadow-speckle method overcomes their limitations by using a digital image correlation to reconstruct a 3D tooth model. Using plaster models 4 times the normal tooth size showed that the accuracy of the reconstructed model was estimated at roughly 30 µm, which potentially could be used in direct intraoral applications.