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

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

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

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

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 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

PURPOSE: The purpose of this study was to compare the functional abilities of the low bulb obturators with those of high bulb obturators in terms of patients' evaluation. MATERIAL AND METHODS: This study included 11 maxillectomy patients who underwent postoperative prosthodontic rehabilitations. Two obturators of the same design except for different bulb heights, were fabricated for each of the maxillectomy patient. After two months of alternate use, the functions of the obturators were measured by investigating the patients' subjective evaluations in terms of convenience, speech, nasality, leakage, and mastication and identifying their preferred prostheses. Wilcoxon signed rank test was used as a statistical method (P < .05). RESULTS: There were no significant differences in patient evaluations of low and high bulb obturators (P >.05). And patients' preferences varied. CONCLUSION: In extreme situation such as in mouth opening limitation, the use of low bulb obturators can be recommended and result in comparable speech function to that of obturators with high lateral walls.
Humans ; Mastication ; Mouth ; Prostheses and Implants ; Prosthodontics

Chewing simulator, which can partly mimic the motion of chewing motion of human, has been successfully developed. The purpose of its development was to make a new machine which can anticipate the clinical results of restoration in the human teeth more accurately in vitro condition It is composed of 4 major parts; chewing part, motor part, water bath, controlling part. The controlling part control the chewing force, frequency, the temperature and running time of water. Additionally, the actual chewing force and remaining time is shown in the monitor of controlling part. At present, the chewing cycle is composed depending on the pre-published data of foreign people. Long term clinical data should be additionally collected for the simulator to mimic the clinical results more accurately.
Baths ; Humans ; Mastication* ; Running ; Tooth ; Water

OBJECTIVE: To investigate the inter-rater agreement for the clinical dysphagia scale (CDS). METHOD: Sixty-seven subjects scheduled to participate in a video-fluoroscopic swallowing study (VFSS) were pre-examined by two raters independently within a 24-hour interval. Each item and the total score were compared between the raters. In addition, we investigated whether subtraction of items showing low agreement or modification of rating methods could enhance inter-rater agreement without significant compromise of validity. RESULTS: Inter-rater agreement was excellent for the total score (intraclass correlation coefficient (ICC): 0.886). Four items (lip sealing, chewing and mastication, laryngeal elevation, and reflex coughing) did not show excellent agreement (ICC: 0.696, 0.377, 0.446, and kappa: 0.723, respectively). However, subtraction of each item either compromised validity, or did not improve agreement. When redefining 'history of aspiration' and 'lesion location' items, the inter-rater agreement (ICC: 0.912, 0.888, respectively) and correlation with new videofluoroscopic dysphagia score (PCC: 0.576, 0.577, respectively) were enhanced. The CDS showed better agreement and validity in stroke patients compared to non-stroke patients (ICC: 0.917 vs 0.835, PCC: 0.663 vs 0.414). CONCLUSION: The clinical dysphagia scale is a reliable bedside swallowing test. We can improve inter-rater agreement and validity by refining the 'history of aspiration' and 'lesion location' item.
Deglutition ; Deglutition Disorders ; Humans ; Mastication ; Reflex ; Stroke

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*