The International Journal of Prosthodontics, 04/2009

Purpose: This randomized clinical trial tested hypotheses that there are no differences in patient satisfaction, component costs, or treatment and maintenance times when mandibular overdentures are retained by one or two implants. Materials and Methods: Subjects wearing conventional complete dentures were randomized to receive either one midline or two bilateral mandibular implants followed by a mandibular denture reline to incorporate implant retention. They indicated on a visual analog scale satisfaction with their dentures before implants and at 2 months and 1 year after implant retention. Satisfaction outcomes between the two groups were compared using the Wilcoxon/Mann-Whitney nonparametric rank test, while changes within each group were analyzed using signed-rank tests. Component costs and times for surgery, prosthodontic treatment, and maintenance were compared using nonparametric and t tests. Results: Eighty-six subjects enrolled in this study and 85 completed the 1-year follow-up, at which median satisfaction was 93 (maximum 100) in the single-implant group and 94 in the two-implant group (P > .5). Within each group, median improvement in satisfaction was similarly dramatic (~44) and significant (P .001). Prosthodontic maintenance time was similar for both groups (P > .37), but the singleimplant group had significantly lower component costs (P .001) and lower times for surgery (P = .002), postsurgical denture maintenance (P = .021), and denture reline (P .001). Five implants failed in four subjects, all in the two-implant group and all before denture reline. Conclusion: Lower component costs and treatment times, with comparable satisfaction and maintenance time over the first year, indicate that a mandibular overdenture retained by a single midline implant may be an alternative to the customary two-implant overdenture for maladaptive denture patients.

The purpose of this study was to compare the probability of failure, expressed as B10 strength, of three systems of machined zirconia ceramics (Lava, DC-Zirkon, and Cercon) with a zirconia-reinforced aluminum ceramic (In-Ceram Zirconia). Ten rectangular specimens of each material were subjected to a three-point flexural strength test. The B10 strength of Lava was significantly lower than that of DC-Zirkon but significantly higher than that of Cercon and In-Ceram Zirconia. The B10 strength of Cercon and In-Ceram Zirconia were not significantly different from one another. The machined zirconia ceramics appeared to fail primarily with intergranular fracture.

Purpose: This study investigated whether the presence of tooth wear in young adults can help to discriminate patients with sleep bruxism (SB) from control subjects. Materials and Methods: The tooth wear clinical scores and frequency of sleep masseter electromyographic activity of 130 subjects (26.6 ± 0.5 years) were compared in this case-control study. Tooth wear scores (collected during clinical examination) for the incisors, canines, and molars were pooled or analyzed separately for statistics. Sleep bruxers (SBrs) were divided into two subgroups according to moderate to high (M-H-SBr; n = 59) and low (L-SBr; n = 48) frequency of masseter muscle contractions. Control subjects (n = 23) had no history of tooth grinding. The sensitivity and specificity of tooth wear versus SB diagnosis, as well as positive and negative predictive values (PPV and NPV), were calculated. One-way analysis of variance and the Mann-Whitey U test were used to compare groups. Results: Both SBr subgroups showed significantly higher tooth wear scores than the control group for both pooled and separated scores (P .001). No difference was observed between M-H-SBr and L-SBr frequency groups (P = .14). The pooled sum of tooth wear scores discriminates SBrs from controls (sensitivity = 94%, specificity = 87%). The tooth wear PPV for SB detection was modest (26% to 71%) but the NPV to exclude controls was high (94% to 99%). Conclusions: Although the presence of tooth wear discriminates SBrs with a current history of tooth grinding from nonbruxers in young adults, its diagnostic value is modest. Moreover, tooth wear does not help to discriminate the severity of SB. Caution is therefore mandatory for clinicians using tooth wear as an outcome for SB diagnosis.

The aim of this study was to measure in vitro retention of cast gold crowns cemented with traditional and resin cements. Forty-eight human molars were prepared on a lathe to produce complete crown preparations with a consistent taper and split into six groups, eight crowns in each group. Crowns were cast in a high-gold alloy and then cemented. After 24 hours, the retention force (N) was recorded and mean values were analyzed by one-way analysis of variance and the Fisher post-hoc least significant difference (PLSD) multiple comparisons test (α = .05). Failure sites were examined under x100 magnification and recorded. Mean values (SD) for each group in increasing order of retention force were: Harvard Cement: 43 N (27), TempoCem: 59 N (16), PermaCem Dual: 130 N (42), RelyX Luting Cement: 279 N (26), Contax and PermaCem Dual: 286 N (38), and TempoCem with Contax and PermaCem Dual: 340 N (14). The Fisher PLSD interval (P = .05) for comparing cements was 29 N. Zincphosphate cement and provisional resin cements had the lowest retention forces. Resin cement with a bonding agent and the hybrid-ionomer cement had similar retention forces. Resin cement with a bonding agent applied after use of a provisional resin cement had a significantly higher retention force than the other cements tested.

Purpose: The aim of this study was to review the current knowledge regarding dental barotrauma. Methods: A search using the PubMed Bibliographic Index and Index- Medicus was performed to identify articles in English that were published between 1930 and 2007. The reference lists of the resulting articles were searched to find publications relating to dental barotrauma. Results: Only a few scientific publications reported this phenomenon. Moreover, a significant part of the relevant literature was from more than 60 years ago. There was no published study on the current incidence rate of this phenomenon. Conclusion: Besides other oral manifestations of barometric pressure changes, such as barodontalgia (barometric pressure-related oral pain), a clinician should be familiar with this entity and take preventive measures as well as periodically examine his or her patients who fly planes or scuba dive. The clinician should also search for occult pathologies such as leaking restorations or secondary caries lesions. In addition, the clinician should be aware of the possible influence of pressure changes on the retention of prosthetic devices and plan treatment accordingly.

The goal of this study was to research the wear shown by a material (Cristobal+) offered as an alternative to ceramics in the covering of an implant-supported fixed prosthesis. Twenty-six active cusps were used in this study; the control group consisted of 12 cusps adjacent to restorations composed of Cristobal+. Five images were obtained from each sample and analyzed using computer software that creates an arch along each cusp, so each image gives the value of the radius described by that arch. If a sample showed any sign of wear, the values for the successive radii would be increasingly larger since a flattened arch would produce a larger radius. An analysis of the paired Student t test was applied. After assessing the results, a statistically significant difference in wear was noted (P .05). Within the limitations of this study, it can be concluded that the wear of the cusps under function made with Cristobal+ reinforced composite was greater than that of the natural adjacent cusps.

Purpose: The aim of this study was to compare the efficacy of two denture adhesives in edentulous patients wearing complete maxillary and mandibular dentures. Materials and Methods: Twenty-four edentulous patients were treated with complete dentures following a standardized protocol. Resistance to dislodgement of both dentures was measured in simulated functional movements by means of a gnathometer and a dynamometer. These outcome measurements were assessed first without the adhesive and then after two successive 2-week periods of using a randomly assigned denture adhesive in a crossover experimental design. The adhesives used were a standard one (Kukident Classic) and a new adhesive with a similar formulation but different physical characteristics (Kukident Pro). Results: Twenty-four patients (mean age: 58 years) participated in this study. Gnathometer results demonstrated significant differences between the nonadhesive group and both the experimental adhesive (P = .008) and the control adhesive groups (P = .021). Differences between both adhesive groups were not significant (P = .161). Dynamometer results showed highly significant differences between the maxillary and mandibular dentures in both the nonadhesive group and the two adhesive groups (P = .0001). Similarly, highly significant differences were found when any of the adhesive groups were compared with the nonadhesive group (P = .0001). The patient subjective evaluation was very favorable for both adhesives. Conclusions: This study confirms the predicted and expected improvement in the stability and retention of wellfitting complete dentures with the adjunctive use of adhesives. The observed and recorded improvements with the new adhesive as compared to the traditional one were not statistically significant.

Purpose: The aim of this report is to present the clinical and patient-based outcomes of an immediate-loading protocol of TiUnite implants with mandibular overdentures in edentulous patients 5 years following initial placement. Materials and Methods: The study comprised two groups of edentulous patients. In the experimental group, 35 consecutively treated patients received 70 TiUnite implants that were loaded immediately, as well as 69 Brånemark machined implants as a backup treatment. One patient received one Brånemark implant. The control group comprised patients who were treated previously with conventional two-stage implant procedures, but were all case matched to the intervention group and served as a historical cohort. This group included 42 patients who received 111 Brånemark implants. Both groups of patients were treated with overdentures that were supported with a standardized resilient bar mechanism. Clinical and patient-based outcomes in the immediate group were recorded for the first 5 years following the initial placement of implants and were measured at various stages of treatment using two questionnaires: the Denture Satisfaction Scale and the Oral Health Impact Profile (OHIP-20). Results: Just over 98% of implants were found to be successful in both groups (Fisher exact test: P = 1.000). A statistically significant improvement in patients' total, mandibular, and functional satisfaction scores was found when comparing baseline data to the data obtained 5 years following loading in the experimental group (P .001). There were no significant differences between the 1- and 5-year total, mandibular, and functional satisfaction scores, or between baseline and 5-year maxillary denture satisfaction scores. A statistically significant and positive correlation was found between baseline and 1-year maxillary satisfaction scores (P = .002). Any improvement in the patients' quality of life (QoL) was maintained during the first 5 years of loading. Conclusion: The results of this longitudinal study suggest that immediate loading of two dental implants by means of bar-retained mandibular overdentures is a predictable treatment option and leads to substantial improvement in patients' satisfaction and QoL. Importantly, this mirrors the outcomes found for patients subjected to the more commonly accepted two-stage implant procedure.

The purpose of this study was to compare two measurement methods for the external marginal fit of zirconia posterior fixed partial dentures (FPDs) fabricated using computer-aided design/manufacturing technology and metal-ceramic posterior FPDs fabricated using the conventional lost-wax technique. The null hypothesis was that there would be no differences between the measurement methods. Forty standardized steel specimens were prepared to receive posterior three-unit FPDs. Specimens were divided into four groups (n = 10): (1) metal-ceramic, (2) Procera Bridge Zirconia, (3) Lava AllCeramic System, and (4) Vita In-Ceram YZ 2000. All FPDs were luted with glass-ionomer cement (Ketac Cem EasyMix, 3M ESPE). Two measurement methods were used to analyze marginal fit: an image analysis (IA) program and a scanning electron microscope (SEM) (JEOL JSM-6400) with magnifications of x40 and x1,000, respectively. Marginal fit was measured at the same point on each abutment. Significant interaction was observed between measurement method and material (P = .0019). Therefore, the measurement method is not independent of the restoration material. Differences among groups were observed for IA (P = .0001) and SEM (P = .0013). Significant differences were observed for the Procera (P = .0050) and metalceramic (P = .0039) specimen groups when both measurement methods were evaluated separately. Accuracy of fit achieved by the four groups analyzed was within the range of clinical acceptance, yielding Procera Bridge Zirconia to have the best marginal fit using both measurement methods.

Purpose: A systematic review and meta-analysis of studies that specifically compared immediate to conventional loading of single implant crowns was conducted and the overall treatment effect was estimated. Materials and Methods: MEDLINE, the Cochrane Controlled Trials Register, and bibliographies of relevant primary and review articles were searched. Randomized and nonrandomized controlled studies that compared immediate with conventional loading of single implant crowns were selected according to strict criteria. From the 105 articles screened, five studies with 248 implants were analyzed. The meta-analysis was prepared in accordance with the Quality of Reporting of Meta-analyses (QUOROM) statement. Descriptive and outcome data were extracted using specially designed data extraction forms. The data were entered into MIX software for meta-analysis using a fixed effects model, relative risk, and 95% confidence interval (CI). Results: Immediate loading of single implant crowns was associated with a significantly higher risk of implant failure (relative risk: 5.07, 95% CI: 2.00 to 12.84, P .001). Pooling of randomized controlled trials showed similar results, although the difference was not statistically significant. Immediate nonocclusal loading was also associated with worse outcomes when compared to conventional loading (relative risk: 4.76, 95% CI: 1.74 to 13.02, P = .002). Conclusions: This systematic review and meta-analysis shows that better outcomes are currently achieved using conventional loading of single implants with crowns, as opposed to immediately loaded ones, which are at a higher risk of failure. Further adequately powered clinical trials are needed. Caution with immediate loading of implants with crowns as a standard of care for single tooth replacement is recommended.

The reliability of a newly developed tooth wear grading system was assessed both clinically and on dental casts by two observers using 20 participants. The reliability of clinical occlusal/incisal tooth wear grading was fair-to-good to excellent, while that of most of the clinical nonocclusal/nonincisal grades was at least fair-to-good. Dental cast assessment frequently yielded poor reliabilities, especially for nonocclusal/nonincisal surfaces. Hence, occlusal/incisal wear could be graded more reliably than nonocclusal/nonincisal wear, while the clinical assessment of tooth wear was more reliable than the grading of dental casts.

Purpose: Nonpassive fit frameworks are believed to lead to implant overload and consequently loss of osseointegration. This is one of the most commonly reported failures of implant prostheses. In an ideal situation of passive fit, when torque is applied to bring the abutment-cylinder interface together some amount of deformation can be expected, and it should be homogeneous along the periphery of the abutment. The aim of this study was to verify the amount of abutment deformation that can be expected when a free-standing cylinder is screwed into place. This could give insight into what should be accepted as passive fit. Materials and Methods: Strain gauges were bonded to the sides of five standard abutments that had machined palladiumsilver cylinders or cobalt-chromium cast cylinders screwed into place. Measurements were taken to verify the deformation at each site. Results: Values of abutment deformation after abutment screw tightening ranged from -127.70 to -590.27 µε. The deformation recorded for palladium-silver prosthetic cylinder tightening ranged from 56.905 to -381.50 µε (mean: 173.298 µε) and from -5.62638 to -383.86 µε (mean: 200.474 µε) for cobalt-chromium cylinders. There was no statistically significant difference among the two groups. Conclusion: Both abutment screw tightening and prosthetic cylinder screw tightening result in abutment deformation, which is compressive most of the time.

The aim of this study was to investigate the contact angles of six different type 3 dental impression materials (DIMs). Contact angles (n = 3) were continuously determined for 20 seconds after placing 4 µL of deionized water onto a thin layer (50 µm) of freshly mixed DIM (polyvinyl siloxane, C-silicone, polyether, and hybrid DIMs). Data were subjected to parametric statistics (P .05). Contact angles ranged from 76.1 ± 5.6 degrees to 119.5 ± 1.8 degrees at 0 seconds and from 11.7 ± 1.6 degrees to 74.7 ± 1.1 degrees at 5 seconds after droplet deposition. The siloxanes showed significantly higher contact angles at 0 and 5 seconds compared to all other DIMs tested (P .05). The newly introduced DIMs with a polyether backbone showed promising results regarding their hydrophilicity.

Purpose: The aim of this study was to evaluate the effect of an oral rehabilitation program on masticatory performance and ability as a function of the number of masticatory cycles. Subjects with a mandibular fixed implant-supported prosthesis (ISP), complete dentures (CDs), or a natural dentition (ND) were evaluated. Materials and Methods: Masticatory performance was tested with an artificial test food (Optocal). Optocal was provided to subjects in two portions of 17 cubes and collected after both 20 and 40 masticatory cycles. The particles were collected on stacks of eight sieves. The geometric mean diameter of the chewed particles was calculated using the sieves. Questionnaires were used to assess masticatory ability before and after the fixed mandibular rehabilitation program. The geometric mean diameter of the chewed particles was compared by two-way analysis of variance followed by the Tukey test (P .05). Results: The geometric mean diameter for all groups was lower after 40 cycles versus 20 cycles. When compared to the ND group, masticatory performance for the CD and ISP groups was 12% and 28% after 20 cycles and 31% and 61% after 40 cycles, respectively. The data for the masticatory ability of the ISP group before and after fixed mandibular rehabilitation were compared by the McNemar test (P .05), and showed that 100% of these subjects were satisfied with their chewing capacity after fixed mandibular rehabilitation. Conclusions: These results quantify the differences in masticatory function among different types of dentition. Greater masticatory function for fixed mandibular rehabilitation versus CDs was demonstrated.

Purpose: The aim of this study was to investigate the optimal design of a fiberreinforced composite (FRC) framework to obtain the maximum reinforcement for fixed partial dentures (FPDs) under three different loading conditions using threedimensional finite element (FE) analysis. Materials and Methods: A three-unit FPD replacing the maxillary right lateral incisor was constructed using FE analysis software (ANSYS 10.0, ANSYS). A fiber framework of the pontic was designed with three variations: with the main framework curved labially (FRC1), located in the center (FRC2), or curved lingually (FRC3). Each framework was compared with a hybrid composite FPD without any fiber reinforcement (C-FPD). A lateral load was applied to the three different loading points of the pontic 0 mm, 3 mm, and 6 mm from the incisal edge, each representing loading conditions 1, 2, and 3, respectively. Results: Localized high stress concentration was observed around the connectors under all loading conditions. In all FRC-FPD models, the FRC framework showed stress-bearing capacity for the FPD. The highest stress reduction ratio under all loading conditions was obtained using the FRC1 model. The FRC1 framework also best reduced displacement of the framework. Conclusion: This study suggests that the optimum design of an FRC framework is to labially curve the FRC of the main framework at the region of the pontic.