The International Journal of Prosthodontics, 06/2009

Purpose: The aim of this study was to test whether posterior fixed dental prostheses (FDPs) with zirconia frameworks exhibit similar survival rates and technical and biologic outcomes as those with metal frameworks. Materials and Methods: Fifty-nine patients in need of 76 FDPs replacing one to three posterior teeth (molars and premolars) were included in the study. The three- to five-unit FDPs were randomly assigned to 38 zirconia-ceramic and 38 metal-ceramic FDPs. At baseline, 6 months, and 1 to 3 years after cementation, the technical outcome of the reconstructions was examined using the United States Public Health Service (USPHS) criteria. The biologic outcome was analyzed at test (abutment) and control (contralateral) teeth by assessing: probing pocket depth (PPD), probing attachment level (PAL), plaque control record (PCR), bleeding on probing (BOP), and tooth vitality. Radiographs of the FDPs were made. Statistical analysis was performed by applying Kaplan-Meier, Pearson chi-square, Fisher exact, and Mann-Whitney U tests. Results: Fifty-three patients with 67 FDPs (36 zirconia-ceramic, 31 metal-ceramic) were examined after a mean observation period of 40.3 ± 2.8 months. Six patients with 9 FDPs were lost to follow-up. The survival of both kinds of FDPs was 100%. No significant differences regarding the technical and biologic outcomes were found. Minor chipping of the veneering ceramic was found in 25% of the zirconia-ceramic and 19.4% of the metal-ceramic FDPs. Extended fracturing of the veneering ceramic occurred solely in zirconia-ceramic FDPs (C: 8.6%, D: 2.8% [USPHS criteria]). Few biologic complications were found. Both types of FDPs rendered the same mean values for the biologic parameters (mean PPD, PCR, and BOP for zirconia-ceramic FDPs = 2.4 ± 0.3, 0.1 ± 0.1, and 0.3 ± 0.2, respectively; mean PPD, PCR, and BOP for metal-ceramic FDPs = 2.4 ± 0.3, 0.1 ± 0.1, and 0.3 ± 0.2, respectively). Conclusion: Zirconia-ceramic FDPs exhibited a similar survival rate to metal-ceramic FDPs at 3 years of function.

The purpose of this study was to investigate the accuracy of diagnosing interproximal subgingival caries at crown margins. A total of 32 subgingival interproximal crown margin areas were examined by 10 clinicians (n = 320) using conventional diagnostic methods on extracted, crowned teeth mounted in a specially designed cast. Crown margins were located 1.5 mm below the level of the artificial gingiva. Clinical and radiographic diagnoses were compared to the histopathologic findings for each site. Both visual-tactile and radiographic evaluations revealed a weak diagnostic accuracy for interproximal subgingival crown margin caries.

Purpose: The restoration of speech after an extensive resection of the soft palate has been a challenge faced by both prosthodontists and surgeons. Few comparisons between prosthetic rehabilitations and surgical reconstructions of large soft palate defects exist in equally matched groups of patients. The purpose of this study was to evaluate speech outcomes in patients with soft palate defects that were rehabilitated with either a pharyngeal obturator or surgical reconstruction. Materials and Methods: Nine patients who were treated via prosthetic obturation were compared to nine patients who underwent surgical reconstruction of the oropharynx with a radial forearm free flap and a soft palate insufficiency repair modification. Speech intelligibility data, perceptual ratings of resonance, and aeromechanical measurements of velopharyngeal function were collected. Results: There were no differences in any of the speech outcome measures between the two groups of patients. Conclusion: Future studies should focus on the patient's perspective on rehabilitative options and potential quality of life issues.

The concept of tooth preparation for ceramic veneers remains controversial regarding whether the use of a palatal chamfer would affect the longevity of restorations. This study aimed to evaluate the load-fatigue testing of ceramic veneers using two different preparation designs-an incisal shoulder finish line with or without a palatal chamfer. A pressable ceramic veneer was bonded to the prepared maxillary central incisor using resin cement. The number of cycles until fatigue failure for each tooth-veneer specimen was recorded. Results revealed that using a palatal chamfer margin design significantly increased the fatigue failure cycle count.

Removable maxillary prostheses (n = 31) rigidly retained on either a one-piece anteriorly located milled bar fixed on four implants located in the anterior maxillary region (group 1, n = 15) or on two bilaterally placed milled bars fixed on six to eight implants located in the posterior maxillary region (group 2, n = 16) were evaluated for prosthodontic maintenance and the calculated bar-generated supporting area. Comparisons of the incidence of prosthodontic maintenance and the supporting area generated by the bars did not differ between groups. Evident advantages were noted for the anterior concept (group 1) with regards to surgical, technical, and prosthodontic aspects, suggesting a preference for this approach versus the more intricate and complex posterior concept (group 2) under particular circumstances and on appropriate indication.

Purpose: The aim of this study was to assess the effect of a palatal lift prosthesis (PLP) on the speech intelligibility of cleft palate patients treated with pharyngeal flap surgery, the minimum duration required for improvement in nasality, and the sustenance of speech improvement after removing the appliance. Materials and Methods: Seven patients ranging between 16 and 26 years of age were recruited for this study. These subjects had velopharyngeal dysfunction secondary to a surgically corrected cleft palate, which failed to improve following pharyngeal flap surgery. A PLP was given to these patients and improvements in speech intelligibility were assessed using two speech examinations: perceptual analysis and nasometry. The nasal resonance, nasal air emission, and articulation were measured prior to the insertion of the prosthesis and at the end of every month for the next 3 months, following which the prosthesis was removed and the tests were repeated. Results: There was a statistically significant decrease in nasalance percentage at the end of the 3 months, and it was found that this improvement in speech persisted even after the removal of the prosthesis. Conclusions: A PLP, when used for a minimum duration of 3 months, causes a significant decrease in nasal resonance, thereby improving speech intelligibility in patients who failed to see improvement following pharyngeal flap surgery for velopharyngeal incompetence.

Purpose: The effectiveness of an appliance for the treatment of obstructive sleep apnea (OSA) shows inordinate interindividual differences. Also, its therapeutic effects still remain unresolved. This study examined and compared the effects of a mandibular advancement splint (MAS) on the masseter and submental muscles of patients with mild and moderate OSA. Materials and Methods: Twenty OSA patients (10 mild and 10 moderate) who refused or did not tolerate nasal continuous positive airway pressure were randomly selected among individuals whose apnea-hypopnea indices (AHIs) were determined at the sleep laboratory of the Department of Chest Diseases, Ege University, before the study. Two polysomnography (PSG) sessions were performed and evaluated: the first without an MAS for the first half of the night to determine baseline muscle activity and the second with an MAS for the other half of the night to follow the condition of muscle activity. Electromyograms (EMGs) of the sum of the submental musculature and masseter muscle were measured with PSGs. The highest EMG amplitudes of the muscles and their AHIs were recorded before and after use of the appliance. Data were analyzed statistically using a t test. Results: After insertion of the MAS device, EMG amplitudes increased significantly in the submental (P .05) and masseter muscles (P .05) of both mild and moderate OSA patients. However, the increase in muscle activity in the mild OSA group was significantly different from the moderate OSA group (P .05). Accordingly, the mean EMG amplitude during moderate apnea episodes was lower than mild both with and without the appliance. After insertion of the MAS, the mean AHI in both mild and moderate OSA patients decreased significantly from baseline recordings (P .05). Patients reported a favorable sleeping pattern and no dislodgement of the appliance during sleep. Conclusion: The MAS activated the masseter and submental muscles during sleep and prevented the upper airway from collapsing. The prosthetic appliance was useful in the treatment of both mild and moderate OSA syndrome.

This study sought to develop treatment strategies for managing percutaneous infection around craniofacial implants. The present general pathogen situation together with a bacterial resistance were determined in 57 infected peri-implant sites. Forty-four implants were randomly assigned for wound cleaning and split into three groups-two with local antibiotics of proven efficacy and one with 3% hydrogen peroxide (H2O2). The pathogen spectrum differed depending on the severity of the infection, with Staphylococcus aureus clearly correlated with the degree of inflammation (positive correlation: R = 0.72). It was observed that the use of additional local antibiotics was not superior to conventional wound cleaning with 3% H2O2. It is suggested that sulcus fluid flow rate measurements could serve as a simple and reliable objective parameter for recall examinations.

Purpose: The aim of this prospective clinical trial was to evaluate the reliability of three- and four-unit posterior fixed partial dentures (FPDs) with zirconia frameworks after 3 years of clinical function. Materials and Methods: Thirty patients, each needing a posterior FPD to restore one or two missing teeth, were included in the study. Preparation guidelines were: occlusal reduction of 1.5 to 2 mm, axial reduction of 1.5 mm, and circumferential chamfer preparation placed 0.5 mm subgingivally. Frameworks were fabricated using a computer-aided design/computer-assisted manufacture technique. All FPDs were cemented with glass-ionomer cement. At baseline and 12, 24, and 36 months after cementation, survival and success of the zirconia framework and the ceramic veneer were evaluated. To analyze the effect of placement of an all-ceramic restoration on the gingival tissue, Gingival Index, Plaque Index, sulcus bleeding index, and pocket depth at abutment (test) and contralateral analogous teeth (control) were assessed. Data were analyzed by descriptive statistics, the Wilcoxon test, and the McNemar test. Results: Of the 30 initial subjects, 27 patients with 27 zirconia FPDs were examined after a mean testing period of 34.2 months. All FPDs were still in use and unfractured, resulting in a 100% survival rate for the frameworks. One FPD exhibited a major chip after 36 months. The cumulative success rate was 96.3%. No significant differences between the periodontal parameters of the test and control teeth were observed. The Plaque Index revealed significantly higher scores for mesial and distal control teeth at baseline and after 12 and 24 months for distal control teeth. Conclusion: Posterior zirconia-based three- and four-unit FPDs present a reliable treatment modality after medium-term clinical use.

This study examined the adhesive stability of screw-retained implant-supported fixed dental prostheses (FDPs) bonded to prefabricated gold cylinders after a load cycling. Five FDP groups (n = 10 per group) that differed either in bonding or loading modality (no loading, loading, moment loading, humidity, silicoating) were compared based on the forces needed to separate the FDP frameworks from the gold cylinders. The mean separating forces for the different groups ranged from 311 N to 501 N. No statistically significant differences could be detected between the five groups (Welch t test, P = .447). Despite the limited transferability into clinical practice, it appears that sufficient bonding stability can be achieved for screw-retained implant-supported FDPs bonded to prefabricated gold cylinders.

Purpose: A nonlinear finite element method was applied to examine the effects of implant diameter and length on the maximum von Mises stresses in the jaw, and to evaluate the maximum displacement of the implant-abutment complex in immediate-loading models. Materials and Methods: The implant diameter (D) ranged from 3.0 to 5.0 mm and implant length (L) ranged from 6.0 to 16.0 mm. Results: The results showed that the maximum von Mises stress in cortical bone was decreased by 65.8% under a buccolingual load with an increase in D. In cancellous bone, it was decreased by 71.5% under an axial load with an increase in L. The maximum displacement in the implant-abutment complex decreased by 64.8% under a buccolingual load with an increase in D. The implant was found to be more sensitive to L than to D under axial loads, while D played a more important role in enhancing its stability under buccolingual loads. Conclusion: When D exceeded 4.0 mm and L exceeded 11.0 mm, both minimum stress and displacement were obtained. Therefore, these dimensions were the optimal biomechanical selections for immediate-loading implants in type B/2 bone.

Purpose: Zirconia was recently introduced as a ceramic implant abutment due to its superior mechanical properties and white color. Nevertheless, it requires careful handling to avoid unexpected failure. The aim of this study was to examine five clinically broken zirconia implant abutments using fractography principles. Materials and Methods: Five clinically fractured zirconia abutments were retrieved for fractographic analysis. The specimens were cleaned, sterilized, and reassembled to allow reconstruction of the broken abutments. Each fragment was gold sputter-coated and individually examined using scanning electron microscopy. The location of the crack origin was identified and the stress at failure was estimated using fracture marks observed on the broken surfaces. Results: For three abutments, the critical crack was located at the internal ring where the abutments met the internal metallic component. The estimated stress at failure ranged between 978 and 1,228 MPa. Friction landmarks were observed on the surface of the fixation screw, which could be responsible for the generation of high internal stresses. Two abutments broke due to overpreparation and thinning of the lateral walls. Conclusion: A confirmatory radiograph is recommended before the final zirconia abutments are screwed into place to prevent improper seating and the generation of damaging internal stresses.

The purpose of this study was to evaluate the occlusion of all-ceramic onlay surfaces generated with a laboratory (LAB) and computer-aided design/computer-assisted manufacturing (COMP) system. The treatment of the mandibular left first molar was simulated on 16 casts. A minimum of three static contacts and their localization were defined beforehand (MIN3). The occlusal contacts obtained (CORR) were analyzed and the mean quotients (MIN3/CORR) for COMP- and LAB-processed restorations were calculated (1.06 ± 0.17 and 1.03 ± 0.13, respectively). The Wilcoxon signed ranks test revealed no significant differences (P .05).

Purpose: A facial prosthesis demands a good visual match with the adjacent skin. Skin color and translucency must be mimicked by the prosthesis. Translucency can be defined as allowing the passage of light, yet diffusing it so as not to render the bodies beyond clearly visible, therefore being semi-transparent. The translucency of skin hampers color measurements of color meters recommended by the Commission Internationale de l'Eclairage (CIE) due to edge loss. The aim of this study was to analyze the translucency of skin at different body sites by measuring volume reflection in a cohort of Caucasian individuals. Materials and Methods: To analyze skin translucency, a volume reflection meter (VRM) was applied to the skin of the forehead, cheek, palm of the hand, and lower forearm. The VRM measures the volume reflection of a small incident light beam at three different distances from the incident beam. To describe the impact of translucency on skin color and the impact of volume reflection at different distances of an incident beam, the VRM spectra were converted into CIE L*a*b* coordinates. Results: VRM measurements were carried out on a cohort of 48 individuals during spring. The mean age was 40.8 years (± 11.7 years). Statistically significant interactions between body site, distance from the light source, and L*, a*, and b* values were found. L* values decreased and a* and b* values increased at longer distances from the incident light beam since the light path was increased. Conclusion: Skin on the forehead, cheek, palm of the hand, and lower forearm each have their own specific volume reflection and thus, translucency, absorption, and scattering characteristics. These location-specific characteristics are due to known local differences in the skin's multilayered structure. For a good visual match between a facial prosthesis and the adjacent skin, volume reflection measurements of the skin close to the intended site of the prosthesis are necessary.