The International Journal of Prosthodontics, 05/2015

Michael I. MacEntee is Professor Emeritus of Oral Health Sciences in the Division of Prosthodontics and Dental Geriatrics at the University of British Columbia. He is a teacher, researcher, and clinician focused on quality of life and access to care for older people. He has published numerous books, chapters, and peer-reviewed papers on the measurement, distribution, impact, and management of mouth-related disorders. He is a past president of the Royal College of Dentists of Canada and of the International College of Prosthodontists. In 2009, he received a Distinguished Scientist Award from the International Association for Dental Research and a Killam Teaching Prize. He was recently elected a Fellow of the Canadian Academy of Health Sciences. Currently, he is the editor-in-chief of Gerodontology.

Purpose: The aim of this study was to evaluate the relationship between sleep bruxism (SB) and perceived stress through the estimation of stress-related biomarkers (cortisol, α-amylase) in saliva. Materials and Methods: Forty-five volunteers (20 men, 25 women) participated in this study. Participants were divided into two groups (bruxers and nonbruxers) according to their answers in a standard bruxism assessment questionnaire outlined by the American Academy of Sleep Medicine. To confirm the preliminary diagnosis and to determine the severity of SB in the group of patients who had a positive self report for SB, a miniature, single-use electromyographic (EMG) device for SB detection (BiteStrip) was used. The perceived stress of the 45 participants was measured using the Perceived Stress Scale questionnaire. Unstimulated whole saliva was collected and levels of salivary cortisol and α-amylase were determined by enzyme-linked immunosorbent assay test and enzyme kinetic reaction, respectively. Nonparametric statistical methods were applied for data analyses. Results: Bruxers showed higher levels of perceived stress than nonbruxers (P < .001). There was a moderate positive correlation between the 25 bruxers' BiteStrip scores and the salivary cortisol levels (Spearman rank correlation = 0.401, P = .047). Additionally, bruxers showed higher levels of cortisol than nonbruxers (P < .001). On the contrary, salivary α-amylase levels were not significantly different in bruxers and nonbruxers (P = .414). Conclusions: These findings suggest that SB activity was related to higher levels of perceived psychological stress and salivary cortisol. Despite the limitations of the EMG recording device, a moderate positive correlation between BiteStrip score and cortisol levels was observed in bruxers.

Purpose: The aim of this study was to assess the effect of root canal post placement on the restoration of endodontically treated teeth. Materials and Methods: PubMed, the Cochrane Central Register of Controlled Trials (CENTRAL), Scopus, and two Chinese databases (China National Knowledge Internet and the Wan-fang database) were searched to identify randomized or quasi-randomized clinical trials related to post-and-core systems for the restoration of endodontically treated teeth. Studies published prior to August 2013, performed on humans, and written in English or Chinese were considered for inclusion. Two of the authors independently extracted data and assessed the quality of the selected studies. Results: Three studies involving 317 participants were included in the review. Meta-analysis revealed that the risk of overall failure was greater with nonpost (104/271) than with post (78/377) restorations, irrespective of the number of remaining coronal walls (risk ratio [RR] = 0.41; 95% confidence interval [CI], 0.23 to 0.74). The risk of catastrophic failure was greater with nonpost (24/227) than with post (4/329) restorations, irrespective of the remaining coronal walls in restored teeth (RR = 0.11; 95% CI, 0.04 to 0.31). When three or four coronal walls remained, no catastrophic failure occurred in either the post group or the nonpost group. The difference in noncatastrophic failure between the two groups had no statistical significance no matter how many coronal walls remained (P > .05). Conclusions: Post placement appears to have a significant influence on reducing the catastrophic failure rate of endodontically treated teeth. When three or four coronal walls remain, post placement seems to have no influence on the restoration of endodontically treated teeth.

Purpose: The purpose of this study was to determine the implant stress under distalextension removable prostheses (DERPs). Materials and Methods: A mandibular distal-extension cast and denture were fabricated. Strain gauges were attached to the implant, which was placed either parallel to the distal abutment or perpendicular to the ridge crest (inclined). Occlusal load was applied in five directions, and strains were compared using the Kruskal-Wallis test (P = .05). Results: When the implant was parallel, the strain was maximum at 20 degrees applied load direction. When the implant was inclined, the strain was minimum at 20 degrees mesial and maximum at 20 degrees applied distal load direction. Conclusions: Implant bending strain is reduced when the implant is loaded on its long axis and oriented parallel with the long axis of the most distal tooth.

Purpose: Ceramic defects in porcelain-fused-to-metal (PFM) restorations may depend on framework alloy type. This study assessed ceramic defects on cobalt-chromium- (Co-Cr-) and gold-platinum- (Au-Pt-) based PFM restorations. Materials and Methods: In this study, 147 Co-Cr-based and 168 Au-Pt-based PFM restorations inserted between 1998 and 2010 (139 patients) were examined for ceramic defects. Detected defects were assigned to three groups according to clinical defect relevance. Results: Ceramic defect rates (Co-Cr-based: 12.9%; Au-Pt-based: 7.2%) revealed no significant difference but a strong statistical trend (U test, P = .082). Most defects were of little clinical relevance. Conclusions: Co-Cr PFM restorations may be at higher risk for ceramic defects compared to Au-Pt-based restorations.

Purpose: The aim of this study was to evaluate the peri-implant soft and hard tissues and satisfaction in patients with two adjacent implant-supported restorations in the esthetic region, treated with two adjacent implants with a scalloped or flat platform. Materials and Methods: The randomized clinical trial consisted of 40 patients allocated to either a scalloped implant group consisting of 20 patients or a flat implant group of 20 patients. Clinical and radiographic examinations were performed during a 5-year followup period, and patient satisfaction during the same period was assessed. Results: The scalloped implant group showed significantly more marginal bone loss (scalloped: 3.2 ± 1.1 mm; flat: 1.5 ± 0.8 mm) and significantly greater bone loss at the interimplant bone crest (scalloped: 2.4 ± 1.0 mm; flat: 1.3 ± 1.0 mm). Furthermore, peri-implant soft tissues showed significantly more bleeding when provided with scalloped implants than with flat implants. Papilla index scores were low in both groups. Patient satisfaction was high in both groups. Conclusion: More bone loss and compromised interimplant papilla regeneration were noted around scalloped implants in the first year, and stable results were observed in the subsequent 4 years with both systems. Scalloped implants seem to offer no benefit when compared to conventional flat implants in the esthetic region.

Purpose: The aim of this study was to compare, from the patients' perspective, immediate and conventional loading of fixed complete-arch prostheses to rehabilitate mandibles with failing dentition. Materials and Methods: This controlled, prospective, nonrandomized study included 36 consecutive patients: 18 treated with conventional loading (control) and 18 with immediate loading (test). Patient general satisfaction and specific satisfaction with esthetics, chewing, speaking, comfort, self-esteem, ease of cleaning, and treatment duration were evaluated using 10-cm visual analog scales before treatment and 3 and 12 months after treatment. Postoperative pain and swelling were monitored daily for 1 week. Statistical analysis was performed applying Mann-Whitney and Wilcoxon tests (α = .05). Results: Between baseline and 3 months, satisfaction in the test group increased significantly with the exception of speech; in the control group, satisfaction increased significantly for esthetics and decreased significantly for speech, chewing, and comfort, but did not vary for general satisfaction or self-esteem. After 3 months, satisfaction was significantly higher in the test group with the exception of ease of cleaning. Between 3 and 12 months, satisfaction improved in both groups but more so in the control group, so that after 12 months there were no differences. The test group showed lower mean pain, which began after the third day postsurgery. Mean swelling and maximum pain/swelling did not show significant differences at any point. Conclusions: Patient satisfaction was reported as significantly higher with immediate loading. However, at the end of the observation periods, reported functional differences had disappeared. Significant differences were only noted for postoperative pain after the third day.

Purpose: The aim of this study was to analyze the marginal and internal fit of metalceramic and zirconia-based crowns. Materials and Methods: Forty standardized steel specimens were prepared to receive posterior crowns and randomly divided into four groups (n = 10): (1) metal-ceramic, (2) NobelProcera Zirconia, (3) Lava Zirconia, and (4) VITA In-Ceram YZ. All crowns were cemented with glass-ionomer agent and sectioned buccolingually. A scanning electron microscope was used for measurements. Kruskal-Wallis and Wilcoxon signed rank test (α = .05) statistical analyses were conducted. Results: Significant differences (P < .0001) in marginal discrepancies were observed between metal-ceramic and zirconia groups. No differences were found for the axial wall fit (P = .057). Significant differences were shown among the groups in discrepancies at the occlusal cusp (P = .0012) and at the fossa (P = .0062). No differences were observed between surfaces. Conclusions: All zirconia groups showed better values of marginal discrepancies than the metal-ceramic group. Procera Zirconia showed the lowest gaps.

Purpose: The purpose of this retrospective study was to investigate the relationship of specific prosthetic complications in patients with a maxillary complete removable dental prosthesis (CRDP) opposing a mandibular metal-resin implant-fixed complete dental prosthesis (MRIFCDP) with respect to anteroposterior (AP) spread and cantilever length. Materials and Methods: Of the 46 patients contacted for this study, 23 patients responded. All patients had been treated with a maxillary CRDP and a mandibular MRIFCDP. They were reviewed for prosthetic complications, and the AP spread and cantilever length were evaluated. A polyvinyl siloxane impression was made of each MRIFCDP so that cantilever length and AP spread could be measured. The average recall time was 8.5 years. The mechanical complications noted were screw-related complications, including both the prosthetic and the abutment screw, consisting of loosening and/or fracture, and fracture of the metal framework. Three different individuals repeated each measurement three times. Inter- and intrarater reliability was evaluated with the intraclass correlation coefficient, and a linear regression analysis of age and average cantilever length to AP spread ratio was calculated. In addition, calculations using this ratio were divided into two groups (> 2.1 and ≤ 2.1) and examined with each variable individually. A logistic regression analysis was performed for a comparison between the two AP spread ratio groups by age, right cantilever length, left cantilever length, average cantilever length, posterior spread, and failures. Results: None of the predictor values was significant for the linear regression analysis of age, cantilever length, and AP ratio on number of failures. There was no significance in complications between the groups that had an AP spread ratio > 2.1 and groups that had an AP spread ratio ≤ 2.1. Conclusions: There was no statistical significance in predicting whether a screw-related complication would occur in relation to age, cantilever length, or AP spread ratio. There was no increase or decrease in complications whether the AP spread ratio was greater than or less than or equal to 2.1. In mandibular MRIFCDPs opposing maxillary complete denture situations, screw-related complications may be less likely regardless of the patient's age, cantilever length, or AP spread ratio of the prosthesis.

This study aimed to evaluate and compare the marginal and internal gap widths of lithium disilicate computer-aided design / computer-assisted manufacture (LDC) crowns and conventionally produced porcelain-fused-to-metal (PFM) crowns. A convenience sample of 21 patients treated with a single restoration was selected. PFM and LDC crowns were fabricated for each selected abutment tooth, following traditional crown preparation. Silicone replicas were produced, and internal gaps and marginal gaps were measured. Internal gaps were significantly larger for the axial and occlusal surfaces of LDC crowns than for those of PFM crowns (P < .001). Marginal gaps were not significantly different (P > .05). Both LDC crowns and PFM crowns showed clinically acceptable marginal fit.

Purpose: The aim of this retrospective follow-up study was to determine whether implant-supported reconstructions on customized computer-milled abutments will loosen less frequently than those placed on prefabricated abutments. Materials and Methods: Suprastructures on prefabricated abutments (n = 312) were compared with those on customized computer-milled abutments (n = 96) over an observation period of 2 years. In all cases, the suprastructures had been cemented on the abutments with zinc oxide-eugenol cement (ZEC). Both groups were subdivided into single-crown restorations, fixed dental prostheses (FDPs) with two implants, and FDPs with more than two implants. The data were evaluated on the denture level. Results: Of the restorations on prefabricated abutments, 8% loosened, and of those on customized abutments, 3.1% loosened. The difference was not significant. Of the single crowns on prefabricated abutments, 7.7% loosened, and of those on customized abutments, 0% loosened. The difference was significant. For the FDPs with two implants (prefabricated abutments: 9.7%; customized abutments: 10.7%; not significant) and the FDPs with more than two implants (prefabricated abutments: 0%; customized abutments: 11.1%; significance not analyzed), statistical evaluation was difficult because of the small number of cases. Conclusions: Loosening of reconstructions placed on customized abutments can be reduced for single-crown restorations. When ZEC is used, customized abutments offer a valid alternative to prefabricated abutments. The small number of cases of FDPs with two implants and FDPs with more than two implants made statistical evaluation impossible.

Purpose: This study aimed to investigate the precision of mechanical torque wrenches used for implants in dental offices. Materials and Methods: Mechanical torque wrenches (n = 138) with two functional designs and made by three manufacturers were tested by three groups of investigators. Potential influences on accuracy were tested. Relative deviations from targeted torque values and the precision of recorded torque values were analyzed. Results: Most abutment screws were tightened too tightly rather than too weakly. Differences were apparent in the influence of the functional design of torque wrenches on their precision. No significant correlation between absolute frequency of use and relative deviation or precision was detected. Investigators with different levels of experience exhibited significantly different deviations from targeted torque values. Conclusions: Average deviation from intended torque values, and levels of imprecision, are evidently not major problems in implant prosthetics; however, high torque values are a cause for concern.

Purpose: The aim of this study was to explore individual (ie, sociodemographic characteristics, patient personality) and clinical factors (ie, dentist-patient communication, denture quality) associated with complete denture satisfaction among the Taiwanese elderly population. Materials and Methods: A multistage sampling and cross-sectional design was used to collect data. A total of 387 fully edentulous citizens, aged 65 years and older and who had received new sets of complete dentures, were selected. The participants completed clinical dental examinations and questionnaires by personal interview to collect information on denture satisfaction and associated variables. The relationship among three groups of these participants (satisfied, neutral, and dissatisfied) and potential factors were simultaneously examined using polytomous logistic regression analysis. Results: Overall, 36.7% of the participants were dissatisfied with their dentures. Living status (crude odds ratio [COR] = 2.04), personality (COR = 4.86), dentist-patient communication (COR = 7.46), and denture quality (COR = 5.02) were associated with complete denture satisfaction. The multivariate regression model showed that dentist-patient communication (adjusted odds ratio [AOR] = 6.41) and denture quality (AOR = 4.40) were significant complete denture satisfaction factors that diluted the effect of living status and personality. Conclusions: Inadequate dentistpatient communication and low denture quality were associated with the dissatisfaction of patients with dentures. To increase complete denture satisfaction, the importance of training programs aimed at enhancing dentist-patient communication and denture quality cannot be overemphasized.

The influence of repeated system-specific torque tightening on the position stability of the abutment after de- and reassembly of the implant components was evaluated in six dental implant systems with a conical implant-abutment connection. An established experimental setup was used in this study. Rotation, vertical displacement, and canting moments of the abutment were observed; they depended on the implant system (P = .001, P < .001, P = .006, respectively). Repeated torque tightening of the abutment screw does not eliminate changes in position of the abutment.