Background: The diagnostic assessment of the level of difficulty in treating patients who need prosthodontic care is useful to establish a medico-economically efficient system with primary care dentists and prosthodontic specialists.
Materials and methods: A multi-axis assessment protocol was established using the newly established treatment difficulty indices. The protocol contains Axis I: oral physiological conditions (e.g., teeth damage and/or missing teeth); Axis II: general health and sociological conditions (e.g., medical disorders); Axis III: oral health-related quality of life (OHRQOL; e.g., oral health impact profile: OHIP); and Axis IV: psychological health (e.g., mood, anxiety, somatoform disorders). A preliminary study on the test–retest consistency of the protocol was conducted to check the levels of reliability of the indices prior to a large-scale, multi-center cohort study on the validity of the protocol.
Results: The test–retest consistency in terms of the oral physiological condition (Axis I) after data reduction was 0.63 for patients with teeth problems, 0.95 for partially edentulous patients, and 0.62 for edentulous patients. The reliability for general health and sociological conditions (Axis II), OHRQOL (Axis III), and psychological health (Axis IV) were 0.88, 0.74, and 0.61, respectively. These values reflect either “sufficient agreement” or “excellent agreement” in accordance with the criteria established by Landis and Koch (Biometrics 1977;33:363-374).
Conclusion: This protocol is the first multi-axis assessment scheme introduced for prosthodontic treatment with sufficient reliability. This new system is therefore expected to have a significant impact on future dental diagnostic nomenclature systems.

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Purpose: The aim of this study was to examine the effect of nonfunctional tooth contact on sensory threshold (tactile detection threshold: TDT) and pain thresholds (filament-prick pain detection threshold: FPT; pressure pain threshold: PPT) in the orofacial region of patients with myofascial pain of the jaw muscles.
Methods: The study was performed on 36 subjects: 20 normal subjects and 16 patients. Using a stair-case method, TDT and FPT were measured by Semmes–Weinstein monofilaments, on the cheek skin (CS) overlying the masseter muscles (MM) and on the skin overlying the palm side of the thenar skin (TS). PPT was measured at the central part of the MM using a pressure algometer. Each parameter was measured before and after keeping light tooth contact for 5 min (session 1) and keeping the jaw relaxed for 5 min (session 2) as a control.
Results: There were significant effects of experimental condition (before–after 5 min) on the TDT and FPT at several sites: after 5 min, TDT was higher in all measurement sites except the left CS of the patients in session 2. As for the FPT, the reactions between CS and TS were quite opposite in both sessions: after 5 min, the FPT at the CS decreased and/or remained, but the FPT at the TS increased and/or remained. Significant session effects (session 1–session 2) were only found on the FPT at the CS in patients.
Conclusion: Sensitivity to FPT was more susceptible to tooth contact condition, especially in the patients.

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Purposes: The aim of this study was to assess the effect of differences in the thermal expansion behaviour of veneering ceramics on the adhesion to Y-TZP, using a fracture mechanics approach.
Methods: Seven veneering ceramics (VM7, VM9, VM13, Lava Ceram, Zirox, Triceram, Allux) and one Y-TZP ceramic were investigated. Thermal expansion coefficients and glass transition temperatures were determined to calculate residual stresses (σ_R, MPa) between core and veneer. Subsequently, the veneering ceramics were fired onto rectangular shaped zirconia specimens, ground flat and notched on the veneering porcelain side. Then specimens were loaded in a four-point bending test and load-displacement curves were recorded. The critical load to induce stable crack extension at the adhesion interface was evaluated to calculate the strain energy release rate (G, J/m²) for each system.
Results: Residual stresses ranged from −48.3 ± 1.5 MPa (VM7) to 36.1 ± 4.8 MPa (VM13) with significant differences between all groups (p < 0.05). The strain energy release rate of the Y-TZP/veneer specimens ranged from 8.2 ± 1.7 J/m² (Lava Ceram) to 17.1 ± 2.8 J/m² (VM9). Values for G could not be obtained with the VM7, Allux and VM13 specimens, due to spontaneous debonding or unstable crack growth. Except for Triceram and Zirox specimens, strain energy release rate was significantly different between all groups (p < 0.05).
Conclusion: Thermal residual stresses and strain energy release rates were correlated. Slight compressive stresses in the region of −20 MPa were beneficial for the Y-TZP/veneer interfacial adhesion. Stresses higher or lower than this value exhibited decreased adhesion.

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Purpose: To assess the implication of vertical misfit on strain within implant frameworks manufactured in titanium or zirconia.
Methods: A master model was fabricated by inserting a Brånemark implant in left side of a mandibular model in the area of the first premolar and the first molar. This model was used to fabricate identical frameworks, five in titanium and five in zirconia. A single strain gauge was mounted on the occlusal surface of each framework to assess strain development as a result of framework fitting. In addition, the peak-to-peak strain amplitude was measured for each framework to determine the strain pattern fluctuation. The vertical gap of the framework–implant interface was measured using a measuring microscope, when only one screw was tightened (1-screw test) and when both screws were tightened (2-screw test). The vertical fit of the frameworks was altered by adding one to three layers of 30 µm steel shims on one of the implants.
Results: For all fitting conditions, measurable amount of strains were recorded, however, as the vertical misfit was introduced, linear increase in framework strain was detected. The titanium and zirconia frameworks exhibited similar strain activities. A direct relationship was observed between the framework strain and vertical gap.
Conclusions: Framework misfit clearly influenced the framework strain magnitude and pattern. The framework material did not affect the framework strain for a similar level of misfit.

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Purpose: There is much controversy about the minimum number of implants and maximum cantilever length in mandible prosthetic restoration. Finite elements analysis of three and four implant-supported prostheses was performed to determine the stresses in the superstructure, implants and cortical bone and, therefore, the failure prediction for each restoration.
Methods: An edentulous mandible was modeled from CT scan images. Two finite element models of three and four implant-supported prostheses with cantilever lengths of 10 and 15 mm were created. Occlusal loads in different parts of the superstructure were applied and shear and normal stresses were calculated.
Results: Two failure criteria were analyzed: the von Mises criterion for isotropic materials (superstructure and implants) and the Tsai-Wu criterion for transversely isotropic material (cortical bone). Both criteria predict failure in the three implant-supported prosthesis for all cases analyzed. The same applies for the four-implant prosthesis of 15 mm cantilever length. However, four implants and a cantilever length of 10 mm passed the failure criteria and were considered safe.
Conclusions: The results from the patient analyzed showed that fixed support prostheses on three implants are not recommended from a structural point of view because they do not adequately support occlusal loads. Excessive stress in the superstructure and the cortical bone can be expected, which would anticipate the failure of the restoration. Fixed support prostheses on four implants with a cantilever length of 10 mm properly resist occlusal loading.

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Purpose: Poly(methyl methacrylate), PMMA, is widely used for fabrication of removable orthodontic appliances. Silver nano particles (AgNps) have been added to PMMA because of their antimicrobial properties. The aim of this study is to investigate the effect of AgNps on the flexural strength of PMMA.
Methods: Acrylic liquid containing 0.05% and 0.2% AgNps was prepared for two kinds of acrylic resins: Rapid Repair & Selecta Plus. Two groups without AgNps were used as control groups. For each one, flexural strength was investigated via Three Point Bending method for the 15 acrylic blocks. Two-way ANOVA, one way ANOVA and Tukey tests were used for statistical analysis.
Results: Rapid Repair without AgNps showed the highest flexural strength. Addition of 0.05% AgNps to Rapid Repair, significantly decreased its flexural strength while, continuing the addition up to 0.2% increased it nearly up to its primary level. In contrast, addition of AgNps to Selecta Plus increased its flexural strength but addition of 0.05% nano particles was more effective than 0.2%.
Conclusions: The effect of AgNps on flexural strength of PMMA depends on several factors including the type of acrylics and the concentrations of nano particles.

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Purpose: The purpose of this study was to clarify whether differences in masticating conditions affected masticatory path stabilities of healthy subjects and TMD patients.
Methods: Twenty healthy female subjects as the healthy group, and 20 female Temporomandibular Disorders (TMD) patients as the TMD group, were selected. Incisal point movement of during mastication of both masticating condition 1 (mc1; crispy bread chewed until swallowing on the free side) and masticating condition 2 (mc2; softened chewing-gum chewed for 20 s on the habitual side) were recorded by MKG. As for mc1, out of all cycles during mastication only those cycles on the habitual chewing side were analyzed. As for mc2, the ten cycles from the fifth cycle were analyzed. For these analyzed sections, the indicators representing movement path stability were calculated and compared between the two groups.
Results: As for mc1, though the values of the indicators representing path stability were larger for the TMD group, there were cases where no significant differences were found between the two groups. As for mc2, the values were significantly larger for the TMD group (SDs; P < 0.05, SD/ODs; P < 0.01).
Conclusions: From these results, it was suggested that the differences in masticating conditions affected the assessment of masticatory path stabilities of healthy subjects and TMD patients and the conditions should be considered for analyzing masticatory movement.

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Purpose: We studied the relationship between tapping point reproducibility and stability of occlusal contacts at maximum intercuspation.
Methods: Tapping movements of 12 adult volunteers who had dentition with natural teeth were recorded, and distances between the tapping point (TP) and the intercuspal position (ICP) at the incisal point were calculated. Occlusal contacts at the ICP of individual subjects were also evaluated with black-colored silicone impression material. The correlation between TP–ICP distance and occlusal contact stability was studied.
Results: TP–ICP distance exhibited negative correlations with the total number of teeth showing occlusal contact at the ICP. Standard deviations of TP–ICP distance also negatively correlated with the extension of occlusal contact area over dentition.
Conclusions: This finding indicates that occlusal contacts at the ICP affect the kinematic behavior of tapping movements. The results of this study also suggest that jaw movement data may provide useful clinical information for the evaluation of occlusal contact at ICP.

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Purpose: The purpose of this study was to determine the durability of the peel bond of commercial resilient denture liners to a denture base resin using a thermal cycling test.
Methods: Eight commercial resilient denture liners (five silicone and three acrylic) were used in the study. The samples were exposed to thermal cycles between 5 °C and 55 °C for 1 min for 0, 1,250, 2,500, 5,000 and 10,000 cycles. The test samples were placed under tension until failure in a materials testing machine using a crosshead speed of 20 mm/min. The modes of debonding were characterized as tear, peel or snap. Statistical analysis was performed using one-way and two-way analysis of variance and Student–Newman–Keuls multiple comparison tests (α = .05).
Results: A significant difference was found between different resilient denture liners for peel bond strength at 0 cycles. No extreme influence on the peel bond strength was observed under any of the thermal cycles. The snap mode of debonding was observed in most samples of all materials for all cycles.
Conclusion: All resilient denture liners tested had a sufficiently strong bond to the denture base resin. Within the limitations of this study, the results show that all of the materials were acceptable for clinical use, having met the accepted adequate bond strength for resilient denture liners of 0.45 MPa.

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Objectives: The present paper aims to review the literature on various approaches in the tray designs and different techniques used to overcome difficulties in making impressions of patients with severely limited mouth opening published from 1984 to 2009.
Study design: A search in the National Library of Medicine's Pub Med database, Google search and Science Direct was performed to include all case reports and reviews on prosthodontic rehabilitation of patients with microstomia. A total of 17 articles were included for discussion in the review out of the 22 articles found to be giving new tray designs.
Conclusions: Different tray designs and impression techniques which can be useful in management of difficult cases causing little discomfort to the patient and help in getting back such patients to a comfortable social living.

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Purpose: In many cases dentist tries to satisfy the patient with stock prosthesis that comes in standard sizes, shapes and colors. However, most of the patients complain of discomfort even after appropriate adjustment because of insufficient adaptation to underlying soft tissues. The rehabilitation of a patient with loss of eye as a result of congenital defect, pathology or accidental trauma is a challenge in terms of re-establishment of the esthetics of the patient. The purpose of this technical procedure is to provide a well fitting prosthesis to the patient, reducing the number of laboratory steps and appointments for fabrication of ocular prosthesis.
Method: A suitable stock eye shell was modified to fit the eye socket, followed by relining with low fusing compound and making a final impression with polyvinyl siloxane impression material. The impression was poured in die stone, flasking procedure was accomplished. After dewaxing, molten wax was flown in the lower half of the flask followed by repositioning of the upper half. The flask was reopened, the stock eye shell along with the hardened wax on tissue surface was tried in the patient's eye. Finally processing was done.
Conclusion: This technique describes an impression procedure, followed by a wax pattern try-in in the same appointment and also the detailed laboratory procedure for fabrication of the ocular prosthesis, taking into consideration positioning of iris as a result enhancing the esthetic appearance of the patient.

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