The International Journal of Prosthodontics, 05/2016

Purpose: This report aims to describe the restorative outcome of 5,491 implant-supported single crowns, fixed partial dentures, and splinted restorations that were prescribed or had implants placed during the study period. Timing of the complications and the relationship between the complications and different factors (practitioner, patient, and restoration) are examined. Materials and Methods: Dental clinicians qualified in or before December 2004, registered in Victoria, and placing and/or restoring implants in private practice were invited to participate in the study. Data extraction was conducted by two trained and calibrated research assistants with specific training in implant terminology and previous research experience extracting data from dental records. Prostheses average time observed/in function was calculated using the difference between the definitive restoration date and the patient record examination date or the date of implant/restoration lost. Both descriptive statistics and generalized linear mixed modeling were used to describe the restorative complications. Results: Over the study period a total of 499 mechanical complications were recorded. Single-implant crowns had the largest sample size (n = 4,760) and a recorded complication rate of 2.56 per 100 prostheses per year. The majority of screw loosenings recorded in this study were inadequately described. In single-implant crowns, abutment screw loosening occurred at a rate of 0.07 per 100 per year while unspecified screw loosening occurred at a rate of 0.53. Lateral screw loosening was more common in lateral screw-retained implant crowns (1.06) than decementation was in cement-retained implant crowns (0.57). Esthetics (0.25), veneer chipping or fracture (0.41), and food packing/contact point issues (0.53) also represent significant portions of the restorative complications. Each type of complication presented with a slightly different timing profile. Clustering within the first year was common. The ratio of screw loosening between the group who prescribed between 1 and 100 during the study period and those who prescribed more than 501 implant restorations was 1:0.15 (P = .005). Patients with operator-reported attrition had double the rate of veneer fracture (P = .005). Contact point issues were approximately three times more common in the posterior segment (P = .001). Conclusion: During the period of January 2005 to December 2009, screw loosening, lateral screw loosening, decementation, esthetic complication, veneer chipping or fracture, and food packing/contact point issues were recorded at different rates for different types of prostheses in the private practices included in this study. Clusters of several complications within the first year were observed. For single-implant crowns, screw-loosening complications were less frequent in the more experienced group. Operator-reported attrition was related to higher rate of veneering material fracture. More contact point complications were found in the posterior regions of the oral cavity.

Purpose: This study was conducted to assess the effect of using a double screw on the prevention of abutment screw loosening. Materials and Methods: Internal connected abutment with a single screw (IS), internal connected abutment with a double screw (ID), external connected abutment with a single screw (ES), and external connected abutment with a double screw (ED) groups were prepared (n = 10 in each group). After 50,000 loading cycles, postload removal torque loss (RTL) percentage was measured. Results: Postload RTL of ID and ED were smaller than those of IS and ES (P = .000 and P = .039, respectively). Conclusion: This study showed that a double screw was more effective in prevention of screw loosening.

Carbon ion radiotherapy, a form of charged particle radiotherapy that has been used to treat various inoperable and radio-resistant tumors, has been associated with less severe late effects than conventional radiotherapy. A 63-year-old woman with a soft palate defect received carbon ion radiotherapy (total dose: 64 Gray equivalents). Several late effects were observed, and osteoradionecrosis was observed not only on the tumor side but also on the other side and gradually expanded during maxillofacial prosthetic rehabilitation. While the definitive prosthesis improved her speech and eating ability, careful adjustments and close follow-up should continue with respect to postradiation effects.

The type of prosthetic restoration used in implant rehabilitation greatly contributes to the recovery of masticatory function as well as quality of life in patients. Frameworks for implant-supported prostheses are typically made by casting metal or milling either titanium or zirconia. Recently, nonmetal, polymer-type materials were suggested as framework materials. Polyetherketoneketone (PEKK), a high-performance polymer, was recently introduced in the dental field with potentially wide-ranging applications. This case history report describes implant- and tooth-supported fixed prostheses created using a new highperformance polymer (Pekkton, Cendres+Metaux) framework for a fully edentulous maxilla and partially edentulous mandible.

Purpose: The aim of this study was to perform an objective and subjective evaluation of the efficacy of positioning stents in radiation-induced xerostomia in patients with tongue carcinoma. Materials and Methods: A total of 30 patients with tongue carcinoma and undergoing conventional radiotherapy were randomly assigned to control (n = 15) and study (n = 15) groups, without and with a positioning stent, respectively. Assessment of salivary output reduction was done before and after radiotherapy, at 3- and 6-month intervals, by measurement of unstimulated and stimulated salivary flow rates (objective evaluation). Xerostomia (subjective evaluation) was noted using six items from the Quality of Life Head and Neck Module (QLQ-H&N35) as proposed by the European Organization for Research and Treatment of Cancer. The significance level was set at .05. Results: Mean unstimulated and stimulated salivary flow rates at 3- and 6-month intervals revealed significantly (P .05) higher scores for the study group as compared with the control group. The mean quality of life scores in the study group were significantly (P .05) lower compared with the control group. Conclusion: The use of a positioning stent minimized radiation-induced xerostomia and its symptoms.

Purpose: Root fracture is a common and serious cause of abutment tooth loss. No studies to date have comprehensively assessed the individual contributions of the factors that increase stress on abutment teeth. The purpose of this study was to analyze the stress distribution in abutment teeth based on a three-dimensional finite element model and to analyze the factors that affect stress distribution. Materials and Methods: Models were generated from the computed tomography data of a single patient, consisting of a mandibular second premolar abutment tooth, bone, residual mucous membrane, and a partial removable dental prosthesis (PRDP). Four models were prepared using different types of endodontic posts and cores. Akers clasps were used for the simulated PRDPs, and a vertical load was applied to the occlusal surface of the PRDPs. Debonding between the post and root was simulated. The Young modulus of the residual ridge was reduced to simulate a poor fit between the denture base and the residual ridge. Stress distribution in the abutment tooth root was observed, and the maximum principal stress was evaluated. Results: The nonmetal post model and the mesial rest model reduced stress concentration in the root. The stress increased in models simulating debonding and poor fit. The results of the multiple linear regression analysis confirmed that debonding and poor fit were significantly associated with root stress. Conclusion: Within the limitations of this study, it is suggested that the bonding integrity of posts and adequate fit of the denture base are important factors affecting the longevity of abutment teeth for PRDPs.

A model with simulated flabby tissue was fabricated by modifying the standard maxillary edentulous acrylic resin cast to evaluate the effect of maxillary impression tray design on the displacement of flabby tissue. Seven groups of trays were fabricated using different combinations of relief spaces and escape holes. After impression taking, test and control casts were scanned and three-dimensional digital models were superimposed. Negative deviations were recorded at the point of the alveolar crest, the posterior part of the flabby tissue, and the middle of the palate, while positive deviations were recorded at the point of the anterior part of flabby tissue. The amount and characteristics of tissue displacement differed with tray design and the relief method used.

Purpose: The aim of this study was to assess functional and esthetic satisfaction plus evaluate changes in oral health-related quality of life (OHRQoL) using the Oral Health Impact Profile (OHIP-14) after insertion of a metal-ceramic (MC-FDP) or a veneered zirconia all-ceramic (AC-FDP) posterior three-unit fixed dental prosthesis (FDP). Additionally, patients' and professionals' esthetic evaluations were compared. Materials and Methods: A convenience sample of 34 patients was randomized to receive a MC-FDP (n = 17) or an AC-FDP (n = 17). Patients were assessed using the OHIP-14 and also answered a questionnaire regarding satisfaction with function and esthetics using visual analog scales (VAS) before treatment and after 2 weeks, after 3 months, and after 1, 2, and 3 years. A fully dentate control group (n = 20) was also assessed using the OHIP-14. The operator and another observer evaluated the esthetics of the FDPs using VAS. Results: The patients assessed the two FDP types similarly for all parameters. In contrast, there was a statistically significant difference in OHIP-14 results between the treated patients and the control group before treatment. After treatment, a statistically significant improvement in OHIP-14 was observed at all examinations. Patients were highly satisfied with the function and esthetics of the FDPs. The overall satisfaction with esthetics was statistically significantly higher among the patients than among the professionals at three out of five examinations. Conclusion: The patients experienced improved OHRQoL and increased satisfaction with function and esthetics after receiving a posterior three-unit FDP. No important differences were observed between the two types of FDPs when evaluated by the patient or the professionals.

The Eysenck Personality Questionnaire's (EPQ) N value (neuroticism) was used to evaluate information from 158 patients before ceramic crown treatment. Patient satisfaction was also evaluated using a satisfaction questionnaire 2 weeks posttreatment. Patient expectations were not correlated with sex, age, or N value, and sex was not correlated with patient satisfaction other than in relation to crown shape. Total esthetic satisfaction and feature improvement were positively correlated with age, while satisfaction for five specific criteria was negatively correlated with N value and overall expectation. These observations underscore the importance of considering the physical and psychologic aspects of patient care when planning dental treatment.

Purpose: The aim of this study was to find the correlation between the number, type, and placement of symmetric functional tooth units and the nutritional status using body mass index (BMI) and Mini Nutritional Assessment (MNA) in patients with both maxillary and mandibular removable partial dentures. Materials and Methods: A randomized study was conducted at the Clinic for Prosthodontics, School of Dentistry, University of Belgrade, Serbia, followed by determination of number of functional tooth units. After insertion of the prostheses, the nutritional status was assessed, using BMI and MNA form. Nutritional status was reviewed 12 months after prosthetic treatment. Number of teeth and age were analyzed using analysis of variance and t test. For other variables such as BMI baseline, BMI follow-up, MNA baseline, MNA follow-up, change in BMI, and change in MNA, Kruskal-Wallis Test or Mann-Whitney Test were used. Results: The results on the MNA changes showed that patients with symmetric natural functional tooth units had significantly higher values (2.9 ± 0.8) compared with patients without natural functional tooth units (1.9 ± 0.6) or with asymmetric natural functional tooth units (1.6 ± 0.4). Patients with asymmetric artificial functional tooth units had significantly lower change in MNA (1.9 ± 0.4) than those with symmetric artificial functional tooth units (2.6 ± 0.9). Conclusion: The findings of this study suggest that adequate rehabilitation with symmetric positioning of the functional tooth units can improve the nutritional status of partially edentulous patients.

Purpose: The aim of this study was to evaluate the effect of gender and knowledge of color in dentistry on the visual shade-matching ability of dental students with no experience in shade matching and without identification skills. Materials and Methods: A total of 32 color-normal participants, 16 female (F) and 16 male (M), completed all phases of the experiment. The control group did not listen to a 60-minute lecture (FNL = females that did not listen; MNL = males that did not listen); the other group listened to a lecture about color in dentistry (FL = females that listened; ML= males that listened). The Toothguide Training Box (TTB) (VITA Zahnfabrik) was used. The final exam consisted of a total of 15 lightness-chroma-hue tasks. The correct selection of lightness (L*), chroma (C*), and hue (h*) was observed, as was the computed shade-matching score, ΣΔE*ab, for each participant. Mann-Whitney U test was used for statistical analysis of the data (α = .05) (SPSS 22.0 for Windows [IBM]). Results: Gender was found to play an important role in shade matching. The FL group selected L* better (L* = 12.11) in comparison with the MNL group (L* = 11.00), which is not significantly different (P = .19). The FL group selected L* better in comparison with the ML group (L* = 10.57), which is not significantly different (P = .10). The FNL group selected C* statistically significantly better (C* = 9.86) than did the ML group (C* = 8.57) (P = .016). The shade-matching score, ΣΔE*ab, for group FL (ΣΔE*ab = 22.50) and group ML (ΣΔE*ab = 31.79) was marginally statistically significant (P = .06). Conclusion: A 60-minute lecture from the field of color in dentistry has a minimal impact on tooth-shade matching, whereas gender plays an important role.

The aim of this in vitro study was to evaluate the influence of two sealants (Kiero Seal, Kuss Dental, and Berutemp 500, Carl-Bechem) and a disinfectant agent (Chlorhexamed gel, GlaxoSmithKline) on bacterial colonization of the implant-abutment interface. Implants were pretreated with the substances or left without sealing before standard abutments were fixed. Half the specimens were subjected to cyclic loading, and the others were not loaded. Following 7 days of incubation in a bacterial solution, bacterial counts of the internal part of the implants were determined by real-time polymerase chain reaction. All pretreatments lowered bacterial counts, but no substance could guarantee sterility of the implants' internal portion.

Purpose: It has long been taught that the hue of a patient can be taken from the canine and applied to other anterior teeth at a lower chroma. This concept does not appear to derive from published work. This study examined color relationships between in vivo maxillary central incisors and canines as a function of age. Materials and Methods: The L*a*b* values and VITA Classical shades of the maxillary central incisor and canine of 62 subjects were determined using a handheld spectrophotometer. Linear regression analysis and t tests were used to describe the relationships of the L*a*b* values of these teeth within each patient and as a function of age. Results: Linear regression demonstrated a significant decrease in ΔE with age (P = .056). Patient age was greater when ΔE (central-canine) > 3.3 (average age = 38.8 years) than when ΔE 3.3 (average age = 58.8 years) (t test; P = .19). ΔC decreases significantly with age (P .001). ΔH demonstrated a trend to decrease as a function of age (P = .2). ΔL remained the same over time (P = .21). Changes with age were due to central incisor differences, while the canine remained constant. Conclusion: ΔE (incisor-canine) significantly decreases with age; mostly due to ΔC. The majority of changes for all three color coordinates are due to alterations in the central incisor. The majority of the patients in this study were found to have a different shade family (VITA Classical) for the central incisor and canine.

Purpose: The aim of the present study was to evaluate the effect of the build angle and the support configuration (thick versus thin support) on the dimensional accuracy of 3D-printed full-coverage dental restorations. Materials and Methods: A full-coverage dental crown was digitally designed and 3D-printed using stereolithography-additive manufacturing (SLA-AM) technology. Nine different angles were used during the build process: 90, 120, 135, 150, 180, 210, 225, 240, and 270 degrees. In each angle, the crown was printed using a thin and a thick support type, resulting in 18 specimens. The specimens were digitally scanned using a highresolution optical surface scanner (IScan D104i; Imetric 3D). The dimensional accuracy was evaluated by digital subtraction technique. The 3D digital files of the scanned printed crowns (test model), exported in standard tessellation language (STL) format, were superimposed with the STL file of the designed crown (reference model) using Geomagic Studio 2014 (3D Systems). Results: The root mean square estimate value and color map results suggest that the build angle and support structure configuration have an influence on the dimensional accuracy of 3D-printed crown restorations. Among the tested angles, the 120-degree build angle showed a minimal deviation of 0.029 mm for thin support and 0.031 mm for thick support, indicating an accurate fit between the test and reference models. Furthermore, the deviation pattern observed in the color map was homogenously distributed and located further away from the critical marginal area. Conclusions: Within the limitations of this study, the selection of build angle should offer the crown the highest dimensional accuracy and self-supported geometry. This allows for the smallest necessary support surface area and decreases the time needed for finishing and polishing. These properties were mostly observed with a build angle of 120 degrees combined with a thin support type.

Monolithic zirconia restorations increasingly have been used in dental practice in recent years and demonstrate superior mechanical performance compared with porcelain-veneered zirconia restorations. Recent advances in manufacturing technology have made possible the fabrication of translucent monolithic zirconia ceramics. This case report describes three clinical examples of monolithic zirconia fixed dental prostheses being used in the anterior and posterior regions and exhibiting acceptable esthetic results.

Purpose: The aim of this study was to detail and assess the capability of a novel methodology to 3D-quantify tooth wear progression in a patient over a period of 12 months. Materials and Methods: A calibrated stainless steel model was used to identify the accuracy of the scanning system by assessing the accuracy and precision of the contact scanner and the dimensional accuracy and stability of casts fabricated from three different types of impression materials. Thereafter, the overall accuracy of the 3D scanning system (scanner and casts) was ascertained. Clinically, polyether impressions were made of the patient's dentition at the initial examination and at the 12-month review, then poured in type IV dental stone to assess the tooth wear. The anterior teeth on the resultant casts were scanned, and images were analyzed using 3D matching software to detect dimensional variations between the patient's impressions. Results: The accuracy of the 3D scanning system was established to be 33 μm. 3D clinical analysis demonstrated localized wear on the incisal and palatal surfaces of the patient's maxillary central incisors. The identified wear extended to a depth of 500 μm with a distribution of 4% to 7% of affected tooth surfaces. Conclusion: The newly developed 3D scanning methodology was found to be capable of assessing and accounting for the various factors affecting tooth wear scanning. Initial clinical evaluation of the methodology demonstrates successful monitoring of tooth wear progression. However, further clinical assessment is needed.

Purpose: The aim of this study was to evaluate the clinical performance of glass fiber-reinforced composite-based resin-bonded fixed partial dentures (GFRC-RBFPDs) as periodontal splints for periodontal support-reduced anterior partially edentulous dentition and for replacing lost teeth. Materials and Methods: A total of 39 subjects were enrolled who required fixed restorations for lost mandibular anterior teeth where the adjacent teeth offered severely reduced periodontal support. GFRC-RBFPDs were cemented to replace the lost teeth and to stabilize the adjacent teeth. The survival rates were recorded, and the periodontal condition (bone height, bleeding index, and probing depth) was evaluated at 1, 2, 3, and 4 years after the restorations. The results were statistically analyzed with single-factor variance analysis and chi-square tests (α = .05). Results: The complete survival rate was 89.7%, and the functional survival rate was 92.3% at the fourth year. The main reason for failure was fracture of the connector of the GFRC-RBFPDs. In 21.7% of adjacent teeth, the bone height decreased; in the other 78.3%, it increased from 1 year after the restoration to the end of the observation period and the heights were statistically different from the initial values. The periodontal condition of the adjacent teeth was improved after the restoration. Conclusions: This 4-year clinical evaluation indicated that GFRC-RBFPDs may be useful as fixed prostheses to replace one to three lost anterior teeth with damaged periodontal support in adjacent teeth.