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

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

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

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

OBJECTIVETo study the mechanism in masticatory muscle dysfunctional induced by hemimastication.

METHODSCa2+ contents were measured with atomic absorption spectrometry; calcinuerin were measured with colorimetric method; muscle fiber types were measured with adenosine-triphosphate (ATPase) staining.

RESULTS(1) Compared with the controls, Ca2+ contents in experimental group had the higher level except 8 weeks (P < 0.05). (2) The ratio of slow fiber in experimental group increased, higher than the match groups (P < 0.05). (3) With Ca2 contents rise, the activities of calcinuerin present a bell-like shape. (4) The ratio of slow-type fiber was positively correlated to the activities of calcinuerin (r = 0.876, P < 0.05).

CONCLUSIONThe signal way of muscle fiber growth and fiber transformation were activated by high concentration of calcium, then, muscle fiber transferred from fast to slow type. It may play an important role in the mechanism that hemimastication result in masticatory muscles dysfunction.

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 aim of this study was to evaluate the interface accuracy of computer-assisted designed and manufactured (CAD/CAM) titanium abutments and implant fixture compared to gold-cast UCLA abutments. MATERIALS AND METHODS: An external connection implant system (Mark III, n=10) and an internal connection implant system (Replace Select, n=10) were used, 5 of each group were connected to milled titanium abutment and the rest were connected to the gold-cast UCLA abutments. The implant fixture and abutment were tightened to torque of 35 Ncm using a digital torque gauge, and initial detorque values were measured 10 minutes after tightening. To mimic the mastication, a cyclic loading was applied at 14 Hz for one million cycles, with the stress amplitude range being within 0 N to 100 N. After the cyclic loading, detorque values were measured again. The fixture-abutment gaps were measured under a microscope and recorded with an accuracy of +/-0.1 microm at 50 points. RESULTS: Initial detorque values of milled abutment were significantly higher than those of cast abutment (P<.05). Detorque values after one million dynamic cyclic loadings were not significantly different (P>.05). After cyclic loading, detorque values of cast abutment increased, but those of milled abutment decreased (P<.05). There was no significant difference of gap dimension between the milled abutment group and the cast abutment group after cyclic loading. CONCLUSION: In conclusion, CAD/CAM milled titanium abutment can be fabricated with sufficient accuracy to permit screw joint stability between abutment and fixture comparable to that of the traditional gold cast UCLA abutment.
Computer-Aided Design ; Joints ; Mastication ; Titanium* ; Torque

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

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