The International Journal of Prosthodontics, 06/2010

Purpose: The aim of this review was to systematically evaluate and compare the frequency of veneer chipping and core fracture of zirconia fixed dental prostheses (FDPs) and porcelain-fused-to-metal (PFM) FDPs and determine possible influencing factors. Materials and Methods: The SCOPUS database and International Association of Dental Research abstracts were searched for clinical studies involving zirconia and PFM FDPs. Furthermore, studies that were integrated into systematic reviews on PFM FDPs were also evaluated. The principle investigators of any clinical studies on zirconia FDPs were contacted to provide additional information. Based on the available information for each FDP, a data file was constructed. Veneer chipping was divided into three grades (grade 1 = polishing, grade 2 = repair, grade 3 = replacement). To assess the frequency of veneer chipping and possible influencing factors, a piecewise exponential model was used to adjust for a study effect. Results: None of the studies on PFM FDPs (reviews and additional searching) sufficiently satisfied the criteria of this review to be included. Thirteen clinical studies on zirconia FDPs and two studies that investigated both zirconia and PFM FDPs were identified. These studies involved 664 zirconia and 134 PFM FDPs at baseline. Follow-up data were available for 595 zirconia and 127 PFM FDPs. The mean observation period was approximately 3 years for both groups. The frequency of core fracture was less than 1% in the zirconia group and 0% in the PFM group. When all studies were included, 142 veneer chippings were recorded for zirconia FDPs (24%) and 43 for PFM FDPs (34%). However, the studies differed extensively with regard to veneer chipping of zirconia: 85% of all chippings occurred in 4 studies, and 43% of all chippings included zirconia FDPs. If only studies that evaluated both types of core materials were included, the frequency of chipping was 54% for the zirconia-supported FDPs and 34% for PFM FDPs. When adjusting the survival rate for the study effect, the difference between zirconia and PFM FDPs was statistically significant for all grades of chippings (P = .001), as well as for chipping grade 3 (P = .02). If all grades of veneer chippings were taken into account, the survival of PFM FDPs was 97%, while the survival rate of the zirconia FDPs was 90% after 3 years for a typical study. For both PFM and zirconia FDPs, the frequency of grades 1 and 2 veneer chippings was considerably higher than grade 3. Veneer chipping was significantly less frequent in pressed materials than in hand-layered materials, both for zirconia and PFM FDPs (P = .04). Conclusions: Since the frequency of veneer chipping was significantly higher in the zirconia FDPs than PFM FDPs, and as refined processing procedures have started to yield better results in the laboratory, new clinical studies with these new procedures must confirm whether the frequency of veneer chipping can be reduced to the level of PFM.

The aim of this study was to evaluate the prevalence of sleep-disordered breathing (SDB) and its relationship with nocturnal denture wear in edentulous subjects. Sixty-two edentulous subjects completed questionnaires to ascertain their risk for SDB; 25 subjects wore dentures during sleep. The prevalence of SDB was 40.3% based on the results of the Berlin Questionnaire. There was no significant difference between high- and low-risk groups with respect to age, Body Mass Index, or denture use, except for a history of self-reported high blood pressure. The prevalence of suspected SDB in edentulous subjects was higher than in the general population.

Purpose: The aim of this study was to report the short-term clinical- and patient-based results of an early loading protocol using two Fixture Original implants with a mandibular overdenture. Materials and Methods: Fifteen consecutively treated patients were enrolled in this study. Each patient received 2 implants; one patient received an additional implant during the observation period, yielding a total of 31 implants used in this study. All patients were treated with overdentures supported by a resilient ovoid bar mechanism. Clinically based outcomes were documented throughout the study, while patient-based outcomes were recorded at baseline and at the 1-year follow-up using the Denture Satisfaction and the Oral Health Impact Profile. Results: Patients were followed for an average of 28.87 ± 5.04 months. The overall success rate was 100% for the implants and 93% for the original prosthetic treatment plan, since an overdenture was converted to a fixed prosthesis for one patient throughout follow-up. The mean bone loss measured during the first year of loading was 0.11 mm (standard deviation: 0.14 mm). Prosthetic maintenance events were mainly related to the acrylic superstructure. Patient-based treatment outcomes showed a statistically significant improvement with the prosthetic treatment and in their quality of life (Wilcoxon signed rank rest, P .05). Conclusions: This short-term longitudinal study suggests that Fixture Original implants can be loaded early using mandibular overdentures. Additionally, modified prosthetic and surgical protocols led to minimal postinsertion prosthodontic maintenance. The results underscore the effectiveness of the overdenture technique in rectifying patients' complaints with conventional mandibular prostheses.

Purpose: The aim of this article was to demonstrate a novel approach to designing facial prostheses using the transplantation concept and computer-assisted technology for extensive, large, maxillofacial defects that cross the facial midline. Materials and Methods: The three-dimensional (3D) facial surface images of a patient and his relative were reconstructed using data obtained through optical scanning. Based on these images, the corresponding portion of the relative's face was transplanted to the patient's where the defect was located, which could not be rehabilitated using mirror projection, to design the virtual facial prosthesis without the eye. A 3D model of an artificial eye that mimicked the patient's remaining one was developed, transplanted, and fit onto the virtual prosthesis. A personalized retention structure for the artificial eye was designed on the virtual facial prosthesis. The wax prosthesis was manufactured through rapid prototyping, and the definitive silicone prosthesis was completed. Results: The size, shape, and cosmetic appearance of the prosthesis were satisfactory and matched the defect area well. The patient's facial appearance was recovered perfectly with the prosthesis, as determined through clinical evaluation. Conclusion: The optical 3D imaging and computer-aided design/computer-assisted manufacturing system used in this study can design and fabricate facial prostheses more precisely than conventional manual sculpturing techniques. The discomfort generally associated with such conventional methods was decreased greatly. The virtual transplantation used to design the facial prosthesis for the maxillofacial defect, which crossed the facial midline, and the development of the retention structure for the eye were both feasible.

Purpose: Eichner Indices (A, B, and C), especially the Eichner subgroups (A1-A3, B1-B4, C1-C3), have not been validated in relation to oral functions. The purpose of this study was to investigate the association of posterior occlusal contact loss with occlusal force and masticatory performance in subjects who had a normal dentition or partially edentulous arches restored with removable prostheses. Materials and Methods: The study sample consisted of 1,288 independently living patients over the age of 60 years. Subjects were grouped into 10 subgroups by posterior occlusal contacts according to the Eichner Index. Bilateral maximum occlusal force in the intercuspal position was measured using pressure-sensitive sheets. Masticatory performance was determined by the concentration of dissolved glucose obtained from comminuted gummy jellies. Results: Occlusal force and masticatory performance were significantly associated with posterior occlusal contacts. Occlusal force measured in subgroups A2 to B2 and B3 to C3 did not differ statistically, although overall occlusal force decreased significantly as the loss of occlusal contacts increased. Similarly, masticatory performance was reduced with decreasing occlusal contact, although the decline was more gradual. Masticatory performance among subgroups A1 to B1, A3 to B2, B2 to B3, B4 to C2, and C1 to C3 did not differ significantly. Conclusions: The Eichner Index subgroups were significantly associated with reduced oral functions, even if the teeth were restored with removable prostheses. Preservation of occlusal contacts of the bilateral (B2) and unilateral (B3) premolars was critical for occlusal force and masticatory performance, respectively.

A master cast representing a completely edentulous mandible was fabricated in polyurethane resin and had four implants secured to the anterior interforaminal area. Impressions were made using six technique-material combinations. Ten definitive casts were fabricated for each technique. Linear distances between implants were measured using a traveling microscope. There was no statistically significant difference between the direct unsplinted and splinted techniques (P > .05), while the indirect technique was statistically significantly different from the other two techniques (P .05). There was no statistically significant difference between the two impression materials.

Purpose: The Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) axis II for psychosocial assessment was adopted to grade chronic pain severity and to correlate that severity with levels of depression and somatization in a population of chronic TMD patients. Materials and Methods: A series of 111 consecutive patients who sought treatment for TMD symptoms lasting longer than 6 months were recruited and underwent assessment using the RDC/TMD axis II instrument. The frequencies of the different scores from the Graded Chronic Pain Scale (GCPS) and the Symptoms Checklist-90R Depression (SCL-DEP) and Somatization (SCL-SOM) scales in the study population were recorded. Correlation between categories of patients identified by the GCPS items and the SCL-DEP and SCL-SOM scales was assessed by means of the Spearman rank correlation test. Results: Severe or moderate somatization was shown by 47.7% and 26.1% of patients, and severe or moderate depression scores were recorded by 39.6% and 1.8% of the sample, respectively. GCPS scores showed that the vast majority of patients had a low disability or no disability at all, with only 5.4% of patients showing a severely limiting high disability. A significant correlation was found between SCL-SOM and GCPS scores, but not between SCL-DEP and GCPS, even if raw depression scores of patients with a high disability were greater than those of subjects with a low disability. Conclusions: Within the limitations of the present investigation, the external validity of which is far from optimal and should be improved in future studies on more representative samples, the RDC/TMD axis II for psychosocial assessment has provided interesting data regarding the prevalence of the different degrees of chronic pain severity and their relation with levels of depression and somatization.

Purpose: The aim of this study was to clarify the aspects of loss of interproximal contact (IC) between fixed implant prostheses and the adjacent teeth. Materials and Methods: A total of 146 implant prostheses in 105 patients were investigated. The loss of IC between fixed implant prostheses and adjacent teeth was evaluated using a 50-µm-thick contact gauge, and the IC was regarded as lost when the gauge was inserted into an IC without resistance at follow-up visits. Statistical analyses were performed to clarify the IC loss rate and factors affecting it. Results: Eighty of 186 ICs (43%) were regarded as lost. The IC loss rate at the mesial aspect was significantly greater than that at the distal aspect (P = .000, Wilcoxon test). Age, the condition of the opposing dentition, the vitality of the adjacent teeth, and the state of splinting of the adjacent teeth affected the loss of IC at the mesial aspect significantly (P .05, Cox regression analysis). Conclusion: Loss of IC between fixed implant prostheses and adjacent teeth was observed frequently at follow-up visits, especially at the mesial aspects of the prostheses. It is considered that this phenomenon may induce food impaction and cause an adverse effect on the peri-implant tissue. Hence, appropriate informed consent and careful maintenance at follow-up visits regarding IC between implants and adjacent teeth are important, and the loss of IC should be recovered if observed.

This study considered the need and demand for complete dentures in a select group of 600 Jordanian adults and the relationship between complete edentulism and sociodemographic variables by means of a pilot-tested questionnaire. Both maxillary and mandibular dentures were fabricated for 505 subjects, while 95 needed complete dentures in only one arch. Significantly more men than women requested complete dentures. Approximately 80% (28 of 35) of subjects who required replacement dentures for esthetic reasons were women, while over 85% (18 of 21) of subjects who required a spare set of dentures were men. The findings suggest a significant relationship between sociodemographic variables and edentulism, with age, education level, and socioeconomic status playing vital roles in edentulism and denture demand.

Purpose: The objectives of this preliminary, longitudinal, and explorative cohort study were to assess changes in and the onset of osteoarthrosis (OA)-related pain in the temporomandibular joint (TMJ) and to address factors that might impact the development or reduction of associated pain symptoms. Materials and Methods: In this sex-matched study, 60 women were recruited (30 asymptomatic with a magnetic resonance imaging [MRI] diagnosis of OA-related TMJ changes, 30 symptomatic with accompanying MRI evidence of OA of the TMJ). All subjects underwent a baseline clinical examination and MRI assessment and were subsequently referred to a dental practitioner, who was informed of the diagnosis and further treatment where required. Not all subjects underwent dental treatment interventions. Following a mean 4-year period, subjects were reexamined clinically. Spearman rank correlation and Mann-Whitney U tests were used to evaluate possible correlations in reported pain level changes with the number of posterior occlusal contacts and new dental restorations placed between baseline and recall appointments. Results: The dropout rate was 28% (6.7% for symptomatic, 50% for asymptomatic). OA-related TMJ pain in symptomatic subjects decreased with time (pain reduction: −3.6 ± 3.4 on a 0 to 10 numeric rating scale); asymptomatic patients rarely developed pain. Conclusion: These preliminary results suggest that factors other than dental occlusion might play a role in the reduction of pain.

The aim of this study was to compare the initial hydrophilicity of unset and set elastomeric impression materials. Initial water contact angles were studied on thin unset and set films of one polyether and six polyvinyl siloxane (PVS) impression materials using high-resolution drop shape analysis at drop ages of 1 and 3 seconds. All unset PVS materials were very hydrophobic initially but showed different kinetics of hydrophilization. In contrast, the unset polyether was more hydrophilic initially but lacked distinct hydrophilization. All impression materials showed statistically significant contact angle differences between unset and set surfaces (P .05). Dependent on the drop age, two PVS materials reached or exceeded the hydrophilicity of the polyether (P .05). It can be concluded that studies on the wetting behavior of elastomeric impression materials should consider both the experimental drop age and set and unset material surfaces.

Purpose: The aim of this study was to evaluate the clinical performance of two- to five-unit implant-supported all-ceramic restorations and to compare the results of two different all-ceramic systems, Denzir (DZ) and In-Ceram Zirconia (InZ). Materials and Methods: Eighteen patients were treated with a total of 25 two- to five-unit implant-supported fixed dental prostheses. Nine patients were given DZ system restorations and 9 were given InZ system restorations. The restorations were cemented with zinc phosphate cement onto customized titanium abutments and were evaluated after 1, 3, and 5 years. Results: At the 5-year follow-up, all restorations were in function; none had fractured. However, superficial cohesive (chip-off) fractures were observed in 9 of 18 patients (11 of 25 restorations). Sixteen units in the DZ group (9 of 13 restorations) and 3 in the InZ group (2 of 12 restorations) had chip-off fractures. The difference between the two groups regarding frequency of chip-off fractures was statistically significant (P .05 at the FDP level and P .001 at the unit level). Conclusion: The results suggest that all-ceramic implant-supported fixed dental prostheses of two to five units may be considered a treatment alternative. The DZ system, however, exhibited an unacceptable amount of veneering porcelain fractures and thus cannot be recommended for the type of treatment evaluated in this trial. Poor compatibility or problems with the bond mechanisms between the veneer and framework could not explain the chip-off fractures. Stress distribution, as well as other factors concerning the veneering porcelain, need to be evaluated further.

The aim of this study was to investigate the applicability of zirconium dioxide (zirconia) as a substitute for metal alloys in a group of metal allergy patients. Fourteen patients (eight women, six men) who had been restored with porcelain-fused-to-metal fixed partial dentures (FPDs) and had exhibited hypersensitivity lesions to dental alloys were enrolled in this study. Patients were previously patch-tested using standard testing substances authorized by the International Contact Dermatitis Research Group. Patients received FPDs with zirconia frameworks and occurrences of oral symptoms were evaluated. No hypersensitivity lesions in the mouth or on the skin were encountered during the follow-up period of 3 years. Zirconia FPDs may be an alternative to porcelain-fused-to-metal FPDs in patients with metal allergies.

Purpose: The aim of this study was to evaluate the axial forces (AFs) and bending moments (BMs) on implants supporting a fixed dental prosthesis (FDP) with a distal cantilever (10 mm) compared to an FDP supported by a tilted or short (7 mm instead of 13 mm) posterior implant by means of in vitro strain gauge measurements. Materials and Methods: Nine titanium Brånemark implants were placed in an edentulous composite mandible. The mechanical loading conditions were evaluated for the following three situations: (1) short distal implants supporting a cantilever, (2) long tilted distal implants, and (3) no distal implants supporting a cantilever. A vertical load of 50 N was applied at the first molar position, and the resultant AFs and BMs were measured for the three different situations, three different numbers of supporting implants (three, four, or five), and three different prosthesis materials (titanium, acrylic, and fiber-reinforced acrylic). Results: The mean BMs, as well as the maximum AFs and BMs, were significantly higher in the model with a cantilever compared to that having the tilted or short distal implants (P .001). There was no significant difference between the models with a distally tilted implant versus a short distal implant. Conclusion: The use of posterior implants reduced the AFs and BMs on implants supporting an FDP compared to that with a distal cantilever. No difference in mechanical loading was observed between short tilted distal implants.