PURPOSE: This in-vitro study was designed to evaluate retention forces, microleakage and plastic deformation of a prefabricated 2-implant bar attachment system (SFI-Bar, Cendres+Metaux, Switzerland). MATERIALS AND METHODS: Two SFI implant-adapters were torqued with 35 Ncm into two implant analogues. Before the tube bars were finally sealed, the inner cavity of the tube bar was filled with liquid red dye to evaluate microleakage. As tube bar sealing agents three different materials were used (AGC Cem (AGC, resin based), Cervitec Plus (CP; varnish) and Gapseal (GS; silicone based). Four groups with eight specimens each were tested (GS, GS+AGC, AGC, CP). For cyclic loading, the attachment system was assembled parallel to the female counterparts in a chewing simulator. The mean retention forces of the initial and final ten cycles were statistically evaluated (ANOVA, alpha< or =.05). RESULTS: All groups showed a significant loss of retention forces. Their means differed between 30-39 N initially and 22-28 N after 50,000 loading cycles. No significant statistical differences could be found between the groups at the beginning (P=.224), at the end (P=.257) or between the loss of retention forces (P=.288). Microleakage occurred initially only in some groups but after 10,000 loading cycles all groups exhibited microleakage. CONCLUSION: Long-term retention forces of the SFI-Bar remained above 20 N which can be considered clinically sufficient. The sealing agents in this study are not suitable to prevent microleakage.
Female ; Humans ; Mastication ; Plastics* ; Silicones

PURPOSE: This study investigated the strain of implants using a chewing simulator with strain gauges in mandibular implant-supported fixed prostheses under various dynamic loads. MATERIALS AND METHODS: Three implant-supported 5-unit fixed prostheses were fabricated with three different occlusion types (Group I: Canine protected occlusion, Group II: Unilaterally balanced occlusion, Group III: Bilaterally balanced occlusion). Two strain gauges were attached to each implant abutment. The programmed dynamic loads (0 - 300 N) were applied using a chewing simulator (MTS 858 Mini Bionix II systems, MTS systems corp., Minn, USA) and the strains were monitored. The statistical analyses were performed using the paired t-test and the ANOVA. RESULTS: The mean strain values (MSV) for the working sides were 151.83 microepsilon, 176.23 microepsilon, and 131.07 microepsilon for Group I, Group II, and Group III, respectively. There was a significant difference between Group II and Group III (P < .05). Also, the MSV for non-working side were 58.29 microepsilon, 72.64 microepsilon, and 98.93 microepsilon for Group I, Group II, and Group III, respectively. One was significantly different from the others with a 95% confidence interval (P < .05). CONCLUSION: The MSV for the working side of Groups I and II were significantly different from that for the non-working side (Group I: t = 7.58, Group II: t = 6.25). The MSV for the working side of Group II showed significantly larger than that of Group III (P < .01). Lastly, the MSV for the non-working side of Group III showed significantly larger than those of Group I or Group II (P < .01).
Mastication ; Prostheses and Implants ; Sprains and Strains

STATE MENT of PROBLEMS: Although some clinicians report long-term success with fixed partial denture (FPD) that contain cantilever pontic, the use of cantilever FPDs may be hazardous because of unfavorable leverages during mastication. PURPOSE of STUDY: This study aims to compare the stress induced in the periodontium with normal and reduced bone support, and to analyze the stress distribution patterns of anterior cantilevered FPDs using the finite element method. RESULTS: Cantilever bridge with a reduced bone level generated the highest peak stresses in the periodontium. In the models of reduced bone support, a cantilever bridge exhibited the greatest mobility and a 3-unit fixed restorations induced the smallest mobility of canine. The highest peak stress level of a 3-unit bridge in the periodontium is similar to the unrestored situation. But stress distribution in the bone is modified. CONCLUSION: In reduced bone support, a cantilever bridge exhibited the greatest mobility and stress.
Denture, Partial, Fixed ; Mastication ; Periodontium

The purpose of this study was to investigate how cyclic loading influenced the fracture toughness of hot-press lithium disilicate and zirconia core materials and whether there was an increase in the propensity for crown failure. Two types of all-ceramic crowns including the IPS e.max Press system (n=24) and the Lava zirconia system (n=24), were selected. Sectioned specimens were subjected to cyclic loading with the maximum magnitude of 200 N (R=0.1) until two million cycles. The material properties including Young's modulus (E) and hardness (H) and the fracture toughness (KIC) of the core materials were evaluated using indentation methods (n=12 each). The load-bearing capacities of the specimens were examined by means of monotonic load to fracture (n=12 each). It was found that the material properties, including E, H and KIC, of the two types of dental ceramics, were reduced. Statistical analysis indicated that there were no significant influences of fatigue loading on material properties E and H for both types of dental ceramics or KIC for zirconia, while for the IPS e.max Press core, KIC, which was parallel to the direction of the lithium disilicate crystals, was significantly reduced (P=0.001). A conclusion was drawn that zirconia possesses high mechanical reliability and sustainable capacity to resist fatigue loading, while fatigue loading remarkably degraded the anisotropic mechanical behaviour of hot-press lithium disilicate ceramics.
Crowns ; Humans ; Mastication ; Materials Testing

OBJECTIVE: The objective of this study was to investigate the differences in masticatory efficiency among patients with different Angle's classes of malocclusion and to assess the correlation between masticatory efficiency and the occlusal contact area. METHODS: The mixing ability index (MAI) was calculated for measuring masticatory efficiency of 61 adult patients according to Angle's classifications of malocclusion. The study included 25, 15, and 21 patients with Angle's Class I, II, and III malocclusions, respectively. Silicone interocclusal recording material was used to measure the occlusal contact area. RESULTS: Both the MAI and occlusal contact area showed the highest average values in the Class I malocclusion group, followed by the Class II and Class III malocclusion groups. No significant difference was observed in the MAI values between the Class I and Class II malocclusion groups (p > 0.05), whereas a significant difference was observed between the Class I and Class III malocclusion groups (p < 0.01) and between the Class II and Class III malocclusion groups (p < 0.05). A weak positive correlation was also observed between the MAI and occlusal contact area (p < 0.01, r² = 0.13). CONCLUSIONS: The results of this study indicated that masticatory efficiency was the highest in patients with Angle's Class I malocclusion, followed by those with Angle's Class II and Angle's Class III malocclusions. Moreover, a weak positive correlation was observed between masticatory efficiency and the occlusal contact area.
Adult ; Classification ; Humans ; Malocclusion* ; Mastication ; Silicon ; Silicones

PURPOSE: The purpose of this study is to evaluate the stability of interface between Co-Cr-Mo (CCM) UCLA abutment and external hex implant. MATERIALS AND METHODS: Sixteen external hex implant fixtures were assigned to two groups (CCM and Gold group) and were embedded in molds using clear acrylic resin. Screw-retained prostheses were constructed using CCM UCLA abutment and Gold UCLA abutment. The external implant fixture and screw-retained prostheses were connected using abutment screws. After the abutments were tightened to 30 Ncm torque, 5 kg thermocyclic functional loading was applied by chewing simulator. A target of 1.0 × 10⁶ cycles was applied. After cyclic loading, removal torque values were recorded using a driving torque tester, and the interface between implant fixture and abutment was evaluated by scanning electronic microscope (SEM). The means and standard deviations (SD) between the CCM and Gold groups were analyzed with independent t-test at the significance level of 0.05. RESULTS: Fractures of crowns, abutments, abutment screws, and fixtures and loosening of abutment screws were not observed after thermocyclic loading. There were no statistically significant differences at the recorded removal torque values between CCM and Gold groups (P>.05). SEM analysis revealed that remarkable wear patterns were observed at the abutment interface only for Gold UCLA abutments. Those patterns were not observed for other specimens. CONCLUSION: Within the limit of this study, CCM UCLA abutment has no statistically significant difference in the stability of interface with external hex implant, compared with Gold UCLA abutment.
Crowns ; Fungi ; Mastication ; Prostheses and Implants ; Torque

PURPOSE: Direct splinting material should have high flexural strength to withstand force during mastication and low modulus of elasticity to provide some movement while force applied for relief of stress. The purpose of this study was to compare flexural strength and modulus of elasticity of several resinous splinting materials. MATERIALS AND METHODS: Four materials; Super-Bond C&B, G-FIX, G-aenial Universal Flo, FiltekTM Z350 XT; were used in this study. Fifteen rectangular bar specimens of each material were prepared. Three-point bending test were performed to determine physical properties. Maximum load at fracture was recorded and flexural strength and modulus of elasticity were calculated. One-way analysis of variance (ANOVA) and Scheffe's tests at a 0.05 level of significance were conducted on all test results. RESULTS: Statistical analysis reveals that Super-Bond C&B had significant low mean value for flexible strength and the other three materials showed no significant difference. For modulus of elasticity, Super-Bond C&B exhibited statistically lower modulus of elasticity. G-FIX presented intermediate result, showing statistically higher modulus of elasticity than Super-Bond C&B but lower than G-aenial Universal Flo and FiltekTM Z350 XT. There was no significant difference on modulus of elasticity between G-aenial Universal Flo and FiltekTM Z350 XT. CONCLUSION: Using a G-FIX, the newly commercially available splinting material, which shows higher fracture resistance properties comparable to flowable and restorative composite resin and a relatively flexible nature might be a beneficial for stabilizing teeth mobility.
Elastic Modulus* ; Mastication ; Splints* ; Tooth Mobility ; Tooth*

Recently, flexible denture is widely used with some advantages such as esthetics, flexibility and biocompatibility. However, there is an opposite opinion about stability because of the movement of denture by the material's flexibility. As the denture moves to tissue surface during mastication, it irritates the supporting tissue. It can lead to trauma and rapid resorption of residual ridges if this irritation lasts for a long time. In this case, the patient has used flexible denture with insufficient stability, retention and support for several years and thus continuous irritation of the supporting tissue resulted in palate bone exposure. The patient discomfort and palate bone exposure underwent improvements by the new denture with stability and retention. A careful case selection for flexible denture, regular checkup and proper treatment are necessary to prevent the side effects.
Dentures* ; Esthetics ; Humans ; Mastication ; Palate* ; Pliability

The occlusion contact, which is engaged in many dental clinical scopes, is the primary subject in the field of dental occlusion. Prosthodontics is one of the fields that are involved in with this subject, including the static relation (the occlusal contacts in intercuspal occlusion) and the dynamic relation (such as that in chewing movement). Not only the restorations, but also the abutments, that have to be properly managed to obtain a harmony occlusal contact relationship.
Dental Occlusion ; Humans ; Mastication ; Prosthodontics ; Tooth

The lips have important functional and esthetic facial features and the lips are used for relatively simple tasks, such as retaining oral contents, as well as for complex functions such as mastication, speech and expressing emotion. Therefore, it is esthetically and functionally critical to maintain the normal position and contour of the lips during reconstructive surgery. However, the freely movable nature of the vermilion and the cutaneous lip makes this area highly susceptible to distortion. We report here on a case of squamous cell carcinoma on the lower lip and the extensive surgical defect that resulted from total vermilionectomy and wedge resection of the lip was repaired with the tongue flap.
Carcinoma, Squamous Cell ; Humans ; Lip ; Mastication ; Tongue