The International Journal of Prosthodontics, 03/2007

Purpose: This study investigated the long-term survival of posts and cores on root canal-treated (RCT) teeth restored with complete crowns, fixed dental prostheses (FDPs), 3-unit FDPs, and cantilever FDPs (C-FDPs) made over a period of 16 to 20 years in an undergraduate clinic. Materials and Methods: Complete treatment and follow-up records of 1,037 complete crowns, 134 three-unit FDPs, 322 FDPs, and 168 C-FDPs were available for analysis. All RCT teeth studied had a post-and-core buildup. Kaplan-Meier survival curves were used to evaluate the different types of fixed restorations. Results: For complete crowns, the estimated survival rates at year 18 were 74.9% for the vital group and 79.4% for the RCT group (P = .602). For 3-unit FDPs, the survival rate at year 20 was 83.2% for the vital group and 60.5% for the RCT group (P = .108). For the FDPs, the survival rate at year 20 was 77.4% for the vital group, while for the RCT group with at least 1 RCT abutment, the survival rate was 56.7% (P = .002). For C-FDPs with vital abutments, the survival rate was 73.5% at year 16, while for the RCT group with at least 1 RCT abutment, the survival rate was 52.3% at year 18 (P .01). Conclusions: There was no statistically significant difference in the long-term survival of complete crowns on vital abutments versus post-and-core complete crowns or in the survival of 3-unit FDPs on vital abutments versus those with at least 1 RCT abutment. For FDPs with more than 3 units and C-FDPs, the use of a post-and-core abutment led to significantly more failures.

This study was designed to test the hypothesis that normal lines on the occlusal surface of a superstructure allow estimation of the functional load direction to an implant. Micro-occlusal surface data were obtained using a 3-dimensional laser scanner to identify the normal lines, and strains on the abutment surface were measured with strain gauges under static load using an in vitro model. Measurements were repeated following alterations of the occlusal surface cusp angle. Statistically significant correlations were found between the 2 measurements (P .05), suggesting that normal lines on the occlusal surface can be used to estimate the load direction to an implant.

The aim of this prospective clinical study was to investigate the long-term survival of Procera AllCeram all-ceramic crowns in the anterior and posterior regions. Between 1997 and 2005, 155 Procera crowns with aluminum oxide cores were placed in 50 patients. Patients were recalled in 2005 for a clinical assessment. Thirty-nine patients with 135 crowns attended the recall examination. Of the 135 total crowns, 103 were located in the posterior region and 32 were located in the anterior region. The cumulative survival rate was 100% in the anterior region and 98.8% in the posterior region (1 crown fracture) after 5 and 7 years. Clinical success was achieved irrespective of the tooth position, cement used (resin composite or glass-ionomer cement), or the core design with reduced or conventional margins. Procera AllCeram seems to be a predictable technique for esthetic all-ceramic single crown restorations in the anterior and posterior regions.

This study aimed to assess the correlation between self-rated denture function and oral health-related quality of life (OHRQoL) in different age groups. Subjects' OHRQoL was measured using the Oral Health Impact Profile, and self-ratings of denture function were assessed on a Likert-type scale for patients with fixed and removable partial dentures in 3 age groups (N = 253). For subjects with fixed partial dentures, all correlations were significant for the younger patients but not for higher age groups, whereas the opposite was true for subjects with removable partial dentures. The importance of self-perception of denture function in OHRQoL is different in various groups of patients, depending on age and dental status.

Purpose: Clinically excellent dentures have shown a limited influence on the function of denture wearers, suggesting that patient factors, such as salivary flow or oral sensory ability, may play an important role in oral function. The purpose of this study was to examine the oral sensory ability of aged edentulous patients in relation to masticatory performance. Materials and Methods: Subjects were 30 edentulous elderly patients with no oral symptoms or pathologies. Oral stereognostic ability (OSA) tests were conducted with test pieces of 12 shaped forms. The duration time for recognition was noted and the answers were recorded using a 3-point scale. Masticatory performance was determined by the concentration of dissolved glucose obtained from test gummy jellies, which are a standardized food developed for measuring masticatory performance. Bilateral maximum occlusal force in the intercuspal position was measured with pressure-sensitive sheets. Stimulated whole saliva was collected using the mastication method. A multiple linear regression analysis for masticatory performance was carried out. Statistical significance was set at P .05. Results: The stepwise multiple linear regression analysis showed that masticatory performance was significantly associated with maximum occlusal force (b = .65, P .001), OSA score (b = .51, P .001), and hyposalivation (b = -.26, P = .042). The R2 of the model was 0.67, indicating that about two thirds of the variation in masticatory performance could be statistically explained by this model. Conclusion: Reduced oral sensory function, low occlusal force, and hyposalivation appear to be associated with impairment of masticatory performance in aged complete denture wearers.

Purpose: The aim of this study was to determine if the amount of alcohol intake is associated with masseter muscle activity recorded during sleep. Materials and Methods: Sixty healthy young female subjects (average age, 23.0 ± 1.9 years; range, 21 to 32 years) participated in the study. Subjects were asked to perform 6 consecutive nightly masseter electromyography (EMG) recordings by using a portable EMG recording system in their homes. Using a minimum threshold criterion, which was set at 20% of the maximum voluntary contraction level, the total duration of muscle activity per hour of sleep was calculated. EMG data obtained on the first night were excluded from the analysis to avoid the first-night effect, and the data of the remaining 5 nights were averaged. Further, the subjects were asked to fill out questionnaires regarding their daily alcohol intake during the recording period. The total ethanol content of the consumed alcohol was calculated using a standard conversion table for alcoholic beverages. The ethanol concentration of each type of alcohol was multiplied by the reported amount consumed on each day, and the average value for 5 days was calculated. The EMG data were considered as a dependent variable, while the alcohol data were considered as an independent variable. Linear regression analysis was used to assess a possible association between these variables. Results: The subjects who did not consume alcohol during the recording period (n = 28) or who provided incomplete data sets as a result of missing data (n = 9) were excluded. The data of the remaining 23 subjects (n = 23) were exclusively analyzed. The result of this analysis revealed that the total ethanol content of the consumed alcohol was significantly and positively related to the EMG duration variable (coefficient = 0.51, 95% confidence interval: 0.20 to 0.82, adjusted R2 = 0.33, P .01). Conclusion: The results suggest that the amount of alcohol intake is substantially associated with masseter muscle activity levels during sleep in young women

A 49-year-old patient presented with an Angle Class III malocclusion with a partially edentulous mandible, as diagnosed by orofacial examination and radiographic and cephalometric analyses. The patient refused orthognathic surgery; therefore, the treatment plan included the preparation of all teeth and fabrication of provisional restorations to reestablish optimal occlusion. To allow for the placement of 3 implants, the edentulous posterior mandibular ridge was improved via alveolar distraction. The patient was recalled 3, 6, 12, and 24 months after prosthodontic treatment. The oral situation was stable and patient satisfaction was reported as high.

This study proposes a new clinical procedure for measuring the closest speaking space (CSS) and compares it with an instrumental method. The study population included 15 edentulous and 10 dentulous subjects free of systemic disease, speech defects, or masticatory system dysfunction. For all subjects, the CSS was measured using clinical and instrumental methods. The clinical method utilized polyvinyl siloxane, commonly used for interocclusal records, injected on the occlusal surface of the premolars just before the pronunciation of a word containing the consonant sound "s" 3 times. The instrumental method used a kinesiograph. Statistical analysis was performed using 1-way repeated-measures analysis of variance and the Student t test for paired data. There was no statistical difference between the clinical and instrumental methods of determining CSS. Within the limitations of this study, based on a small sample, the new simpler and less expensive method to record the CSS should be considered and further investigated.

Purpose: The purpose of this study was to compare 3 veneering ceramics for zirconia frameworks regarding color stability and predictability of the esthetic result. Materials and Methods: Six patients with 1 maxillary central incisor to be restored were enrolled in the study. The contralateral incisor had to be nonrestored and vital to serve as a reference tooth. For each patient, 4 single crowns with zirconia frameworks were fabricated. Three veneering ceramics were assessed and masked to eliminate bias. Choice of the veneering ceramics was done at random. The veneering was performed by 4 dental technicians. Three veneering ceramics were compared: ceramic A (Initial, GC), ceramic B (Triceram, Esprident), and ceramic C (Cercon Ceram S, DeguDent). The color of the crowns and reference teeth was captured using spectrophotometric analysis (SpectroShade, MHT), and the color difference (DE) was calculated (objective method). In addition, the crowns and reference teeth were compared subjectively by 11 observers blind to the ceramic used for veneering. Statistical analysis was performed with analysis of variance (ANOVA). Results: Regardless of the veneering ceramic used, all crowns showed a high color deviation from the reference teeth when applying the objective analysis (DEA 6.8 ± 2.5, DEB 5.6 ± 1.2, DEC 5.7 ± 2.1). In addition, no significant differences were found between the ΔE of crowns and teeth for the 3 ceramics. In the framework-supported area, ceramic B showed a significantly lower difference in value (DL) compared to the reference teeth than the other 2 ceramics (DLA 4.9 ± 2.3, DLB 1.1 ± 2.1, DLC 4.1 ± 1.5; P .01 ANOVA). When performing the subjective analysis, ceramic B was chosen as the best match by a majority of observers (> 60%) in 4 of 6 patients. Conclusions: All 3 ceramics met the esthetic demands only to a limited extent. Ceramic B allowed for the most predictable result in terms of color stability.

Purpose: This study aimed to evaluate the clinical success of a hydrophilic polyvinyl siloxane impression material for fixed dental restorations under various clinical conditions. Materials and Methods: A total of 1,466 preparations for fixed restorations in maxillary and mandibular anterior and posterior teeth were evaluated. The study contained inlay, onlay, crown, veneer, post, and adhesive-wing preparations and implants for gold, porcelain-fused-to-metal, and ceramic restorations. The preparation finish line relative to the crest of the marginal gingiva, type of restoration, and position of the teeth were recorded. Three categories were established to rate impression quality: perfect impressions, with an absence of any voids or bubbles and perfect reproduction of the preparation finish line, were rated Criteria I; acceptable impressions, with minimal defects (£ 2 mm) not involving the preparation finish line, were rated Criteria II; and unacceptable impressions, with larger voids or bubbles (> 2 mm) or defects involving the preparation finish line, were rated Criteria III. Results: Overall, 96.86% of the final impressions were clinically acceptable, 89.43% of which were rated Criteria I and 7.43% of which were rated Criteria II. Only 3.14% of the impressions were unacceptable and rated Criteria III. A significant influence on impression quality was found when the preparation finish line was more than 2 mm subgingival (P .004), as well as when a beveled preparation was used (P .004). The position of the teeth (P > .404) had no significant effect. Conclusion: Surface-activated polyvinyl siloxane impression material offers high predictability to avoid bubbles and voids in the final impression.

Purpose: To compare the dimensional measurements and surface topography of stereolithographic models generated from computerized tomography (CT), magnetic resonance imaging (MRI), and laser scanning (LS) data with the same subjects' natural ears and ear casts. Materials and Methods: Stereolithographic models were manufactured from images of the subjects' ears and ear casts recorded by CT, MRI, and LS, and dimensional measurements were compared. In the second part of the study, all stereolithographic models were CT scanned and reconstructed in an STL file format. A comparison of the surface topography of the CT, MRI, and LS model ears was made. Results: Intraclass correlation coefficients indicated that dimensions could be reliably measured on the CT, MRI, and LS stereolithographic models. A 2-way analysis of variance revealed no statistical differences between the various sources of data (P = .991). The smallest differences of surface topography were observed on the MRI/CT superimpositions. Conclusion: The dimensional measurements on the stereolithographic models were similar to those from the original source. Only small differences were apparent between the surface topography of the CT, MRI, and LS models. MRI may be particularly appropriate to fabricate a prosthesis because it involves no radiation for the patient and internal form can be reproduced. The use of this technique in clinical practice requires further study.

This study evaluated the effects of recasting on high noble, noble, and nickel-based alloys, as well as on titanium. Four specimens of each material were cast and recast 7 times. Chemical composition, microstructure, microhardness, and ion release were determined before and after the first cast and following each recast. Zinc and tin concentrations in the high noble alloy decreased significantly with recasting; consequently, the release of these ions decreased as well. A significant increase in Vickers hardness appeared in the fifth recast in both the high noble alloy and titanium. The noble alloy and the nickel-based alloy demonstrated great stability after 7 recasts. The results suggest not recasting titanium.

This study aimed to compare the effect of precementation desensitizing laser treatment and conventional desensitizing agents on crown retention. Crowns were fabricated for 50 molar teeth, and specimens were assigned to 5 groups based on treatment method: untreated control group (CON), laser group (LAS), sodium fluoride group (FLU), Oxagel oxalate group (OXA), and Gluma primer group (GLU). All crowns were luted with glass-ionomer cement. Tensile force was applied for crown dislodgement. Recorded forces and calculated retentive strengths were as follows: CON (261 N) > LAS (223 N) = FLU (208 N) > GLU (161 N) = OXA (147 N) (P .05). The differences in force magnitudes between all groups were significant (P .05), except for LAS versus FLU and GLU versus OXA. The retention decrease was 15% for LAS, 20% for FLU, 38% for GLU, and 44% for OXA. Laser treatment had a less negative effect on retention for crowns luted with glass-ionomer cement than the other treatment modalities, and it may be a more suitable desensitization method if crown retention can be moderately sacrificed.

Purpose: This study evaluated the 2-year outcome of post-and-core restorative procedures in endodontically treated teeth. The effect of baseline factors (tooth type, number of residual coronal walls, and type of definitive restoration) on restoration failure was assessed. Materials and Methods: The consecutive sample design included 150 patients. A total of 162 teeth (57 anterior and 105 posterior) were restored. Sixty-nine teeth had 3 or 4 residual coronal walls, while 93 teeth had 2 or fewer walls. Crowns and direct resin composite restorations were placed in 121 and 41 teeth, respectively. After 23 to 25 months, all patients were evaluated. Logistic regression was used to identify the joint effect of variables recorded at baseline (P .05). Results: The only failure modes observed were post debonding (4.3%, 2 in anterior teeth and 5 in posterior teeth) and endodontic failure (3.0%, 2 in anterior teeth and 3 in posterior teeth). All post debondings occurred in teeth with 2 or fewer coronal walls that were crown covered. All endodontic failures occurred in crown-covered teeth (1 failure in a tooth with 3 walls and the remaining 4 failures in teeth with 2 or fewer walls). Logistic regression found no statistical significance for any of the variables recorded at baseline. Conclusion: Restorations placed with the use of a fiber post and core resulted in 4.3% post debondings and 3.0% endodontic failures after 2 years of clinical service

Purpose: Dental impressions often carry microorganisms that may cause cross infection from patients to dental staff. The aim of the current study was to determine the effectiveness of 4 different disinfectant solutions on 3 commonly used impression materials-alginate, polyether, and polyvinyl siloxane-to establish a protocol for disinfection of these impression materials after clinical exposure and prior to handling in the dental laboratory. Materials and Methods: A total of 45 impressions were taken from the maxillary dentate arches of 15 dental staff participants at the Department of Dentistry, Prince Rashid Hospital, Irbid, Jordan. For each participant, 3 successive impressions were recorded in the different impression materials. For each impression, 6 specimens were dissected from 6 different locations and exposed to 6 different regimens: 1 was left untreated, 1 was immersed in sterile water for 10 minutes to serve as a control, and the remaining 4 specimens were exposed to 4 different disinfection treatments (Dimenol, Perform-ID, MD 520, and Haz-tabs). Serial dilutions of the suspension were carried out and counted by the Miles-Misra technique (inoculation on Columbia blood agar for quantification). The dilutions were aerobically incubated at 37°C for 48 hours. Results: The disinfectants were able to completely eliminate microorganisms carried by the impressions. For those undisinfected specimens, the results showed that untreated alginate impressions appear to carry more microorganisms (P .05) than the other 2 rubber impression materials used in the study. For those specimens immersed in sterile water for 10 minutes (control group), the number of microorganisms eliminated was increased from 62% to 90% compared to those left untreated. Conclusion: Impression materials may act as a vehicle for the transfer of microorganisms from the patient's mouth to dental personnel. Impressions should be disinfected to eliminate the risk of cross contamination

This study aimed to determine the influence of surface roughness (Ra), surface free energy (SFE), saliva, and bacteria on Candida adhesion to denture materials. The Ra and SFE of 2 acrylic resin specimens and 2 denture liner specimens were measured and assayed in a flow chamber for bacteria culture perfusion plus Candida albicans or C glabrata cultures. Adhesion was determined by counting under light microscopy. Candida adhesion showed significant differences depending on the factors involved. The overall colonization was significantly decreased by saliva and influenced by bacteria. Candida adhesion was strongly affected by Ra, saliva, and bacteria, but not by SFE.

The aim of this pilot study was to evaluate the mechanical strength of an acrylic resin palatal denture base reinforced with a mesh or bundle of glass fibers. Silicon and stone casts of an edentulous maxilla (Frasaco) were used to manufacture palatal denture bases (n = 20) using heat-polymerized acrylic resin (SR Triplex Hot). The denture bases were reinforced with either 1 or 3 layers of glass-fiber mesh (Stick Net) or with a bundle of unidirectional glass fibers (Stick). Denture bases without reinforcement served as the control group. Fracture tests were carried out on a universal testing machine to determine each material's mechanical strength. The highest mean fracture values of 919 N were obtained in samples with 3 layers of Stick Net, with mean values of 677 N in the control samples. The differences between these 2 groups were statistically significant (P .05). The applied glass-fiber reinforcement increased the mechanical strength of the acrylic resin palatal denture bases.

This study aimed to determine how facial measurements explain the variability of dental proportions. The following measurements were obtained from 90 subjects: width and length of each maxillary anterior tooth, length of the nose, length of the upper lip, facial length (including the lengths of the facial thirds), intercanthal width, interalar width, intercommisural width while smiling, and maximum central incisor exposure while smiling. The combination of all facial measurements explained the variability of maxillary anterior teeth width/length ratios by only 20% to 38% in men and 16% to 27% in women. Within the population tested, the results suggest that the use of facial measurements for the selection of artificial denture teeth is generally inaccurate.