No abstract available.
Bite Force*

STATEMENT OF PROBLEM: The cumulative success rate of wide implant is still controversial. Some previous reports have shown high success rate, and some other reports shown high failure rate. PURPOSE: The aim of this study was to analyze, and compare the biomechanics in wide implant system embeded in different width of crestal bone under different occlusal forces by finite element approach. MATERIAL AND METHODS: Three-dimensional finite element models were created based on tracing of CT image of second premolar section of mandible with one implant embedded. One standard model(6mm-crestal bone width, 4.0mm implant diameter, central position) was created. Varied crestal dimension(4, 6, 8 mm), different diameter of implants(3.3, 4.0, 5.5, 6.0mm), and buccal position implant models were generated. A 100-N vertical(L1) and 30 degree oblique load from lingual(L2) and buccal(L3) direction were applied to the occlusal surface of the crown. The analysis was performed for each load by means of the ANSYS V.9.0 program. CONCLUSION: 1. In all cases, maximum equivalent stress that applied 30.oblique load around the alveolar bone crest was larger than that of the vertical load. Especially the equivalent stress that loaded obliquely in buccal side was larger. 2. In study of implant fixture diameter, stress around alveolar bone was decreased with the increase of implant diameter. In the vertical load, as the diameter of implant increased the equivalent stress decreased, but equivalent stress increased in case of the wide implant that have a little cortical bone in the buccal side. In the lateral oblique loading condition, the diameter of implant increased the equivalent stress decreased, but in the buccal oblique load, there was not significant difference between the 5.5mm and 6.0mm as the wide diameter implant. 3. In study of alveolar bone width, equivalent stress was decreased with the increase of alveolar bone width. In the vertical and oblique loading condition, the width of alveolar bone increased 6.0mm the equivalent stress decreased. But in the oblique loading condition, there was not a difference equivalent stress at more than 6.0mm of alveolar bone width. 4. In study of insertion position of implant fixture, even though the insertion position of implant fixture move there was not a difference equivalent stress, but in the case of little cortical bone in the buccal side, value of the equivalent stress was most unfavorable. 5. In all cases, it showed high stress around the top of fixture that contact cortical bone, but there was not a portion on the bottom of fixture that concentrate highly stress and play the role of stress dispersion. These results demonstrated that obtaining the more contact from the bucco-lingual cortical bone by installing wide diameter implant plays an important role in biomechanics.
Bicuspid ; Bite Force ; Crowns ; Mandible

The stress distribution generated in the surrounding bone was calculated and compared for various geometry of the dental implants by means of the finite element methods. The models were designed to represent the screw type endosseous implants (varing the size, shape, direction of the screw thread and the angle of the body) with supporting bone and the cylinder type endosseous implants (varing the lower portion-Round type, tapered type) with supporting bone. Static mean bite forces were applied 100N vertically and 25N horizontally on the center of the implant and three dimensional finite analysis was undertaken using software ANSYS 5.1 Version. The result demonstrated that different implant shape leads to significant variations in stress distribution in the bone. In the case of variation of the screw size, direction and shape the implant model with normally directional and triangular screw implied lower stress than with upper directional or lower directional and quadrangular screw but among models a different screw size, within a variation of 0.2mm there was no meaningful difference in maximum stress. In the case of variation of angle of body the straight implied lower stress than the tapered. As a result of analysis of cylinder type, the implants with larger radius of curvature of the round form and larger diameter of the tapered form implied lower stress.
Bite Force ; Dental Implants ; Radius

STATEMENT OF PROBLEM: Targis/Vectris restorations provide excellent esthetics. Marginal accuracy is significantly influenced by the preparation design. There were no studies to examine the effect of preparation design on the marginal discrepancy and fracture strength of Targis/Vectris crowns. PURPOSE: This study evaluated the marginal accuracy before and after cementation, and the fracture strength of FRC/Ceromer(Targis/Vectris) crowns according to different preparation design. MATERIAL AND METHOD: Three metal dies with different convergence angles(6degrees, 10degrees, 15degrees) were prepared. Total 30 (10 for each angle) Targis/Vectris crowns were made. The restorations were evaluated for adaptation of the margin before and after cementation, then were compressively loaded to failure. Fracture surfaces of the crowns were examined using a SEM. Results. The mean marginal gap was 49micrometer for 6degrees, 55micrometer for 10degreesand 70micrometer for 15degreesand in clinically acceptable level. The mean marginal gap increased significantly after cementation. The increasing amount during cementation was the largest in the 6degrees group. The crowns on 6o convergence angle had a significantly higher fracture strength than the crowns on 15degrees angle. Mean fracture strength of total crowns regardless of convergence angle was 1390 N, which was higher than all-ceramic crowns. SEM observation showed two-mode fracture pattern. CONCLUSION: From the results of this study, all of the FRC/Ceromer crowns had clinically acceptable marginal accuracy and could withstand the bite force. Moreover, less convergent angle than all-ceramic crown might be recommended for preparation procedure.
Bite Force ; Cementation ; Crowns* ; Esthetics

OBJECTIVETo investigate the effect of occlusal force on the etiology of open bite patients who suffer from temporomandibular disorders (TMD).

METHODSOne hundred and two women patients with open bite were divided into TMD (+) group and TMD (-) group according to patients with or without TMD. Occlusal force, occlusal contact areas, occlusal average pressure and occlusal center were evaluated with pressure sensitive sheets. The results were analyzed by SPSS 11.0 statistic software.

RESULTSOcclusal force and occlusal contact areas in TMD (+) group were significantly lower than that in TMD (-) group. Occlusal average pressure and occlusal center had no significance between two groups.

CONCLUSIONThe results indicate that the decrease of occlusal force and occlusal contact areas may have some relationships with TMD in open bite patients.

PURPOSE: This study aims to analyze the stress distribution of mandibular molar restoration supported by the implants with external hex and internal taper abutment connection design. MATERIALS AND METHODS: Models of external connection (EXHEX) and internal connection (INCON) implants, corresponding abutment/crowns, and screws were developed. Supporting edentulous mandibular bony structures were designed. All the components were assembled and a finite element analysis was performed to predict the magnitude and pattern of stresses generated by occlusal loading. A total of 120 N static force was applied both by axial (L1) and oblique (L2) direction. RESULTS: Peak von Mises stresses produced in the implants by L2 load produced 6 – 15 times greater than those by L1 load. The INCON model showed 2.2 times greater total amount of crown cusp deflection than the EXHEX model. Fastening screw in EXHEX model and upside margin of implant fixture in INCON model generated the peak von Mises stresses by oblique occlusal force. EXHEX model and INCON model showed the similar opening gap between abutment and fixture, but intimate sealing inside the contact interface was maintained in INCON model. CONCLUSION: Oblique force produced grater magnitudes of deflection and stress than those by axial force. The maximum stress area at the implant was different between the INCON and EXHEX models.
Bite Force ; Crowns ; Finite Element Analysis* ; Molar

PURPOSE: Current trend in implant dentistry is changing from external connection to internal connection. To evaluate the splinting of external and internal connection implant on screw loosening, 2-units prosthesis was fabricated with BioPlant System(R) of external connection type and Lifecore STAGE-1 Single Stage Implant System(R) of internal connection type. MATERIAL AND METHOD: Experimental group is classified into three groups. 1) G1-EE: 2-units prosthesis was fabricated with two BioPlant System. of external connection type. 2) G1-EI: 2-units prosthesis was fabricated with one BioPlant System(R) of external connection type and one Lifecore STAGE-1 Single Stage Implant System(R) of internal connection type. 3) G1-II: 2-units prosthesis was fabricated with two Lifecore STAGE-1 Single Stage Implant System(R) of internal connection type. In fabricating 2-units prosthesis, two hexed abutments are recommended when two implants are installed parallel, otherwise one hexed abutment is used on major occlusal force area and one nonhexed abutment is used on the other area. Since it is rare to find two implants being parallel, it is hard to fabricate prosthesis with passive adaptation using two hexed abutments. It is much more difficult to acquire passive adaptation when using hex abutment compared to nonhex abutment. To evaluate the influence of hexed and nonhexed abutment on screw loosening, 2-units prosthesis was fabricated with hexed and nonhexed abutment. Experimental group is classified into three groups. 1) G2-HH: 2-units prosthesis was fabricated with two hexed abutments. 2) G2-HN: 2-units prosthesis was fabricated with one hexed abutment and one nonhexed abutment. 3) G2-NN: 2-units prosthesis was fabricated with two nonhexed abutments. RESULT: The results of comparing the detorque value after loading on a each prosthesis periodically are as follows. 1. In splinting group of external and internal connection implant, G1-II group demonstrated the biggest detorque value, followed by G1-EI group and G1-EE group. 2. There is no notable significance between external connection implant of G1-EI group and G1-EE group and also no significance between internal connection implant of G1-EI group and G1-II group. 3. G2-HH group showed higher detorque value than G2-HN and G2-NN group. From the results, we can concluded that using both external connection and internal connection implant together is clinically acceptable and in order to acquire a good passive adaptation in fabricating 2-units implant prosthesis we can use two nonhexed abutments.
Bite Force ; Dentistry ; Prostheses and Implants ; Splints

PURPOSE: Articulation paper mark size is widely accepted as an indicator of forceful tooth contacts. However, mark size is indicative of contact location and surface area only, and does not quantify occlusal force. The purpose of this study is to determine if a relationship exists between the size of paper marks and the percentage of force applied to the same tooth. MATERIALS AND METHODS: Thirty dentate female subjects intercuspated into articulation paper strips to mark occlusal contacts on their maxillary posterior teeth, followed by taking photographs. Then each subject made a multi-bite digital occlusal force percentage recording. The surface area of the largest and darkest articulation paper mark (n = 240 marks) in each quadrant (n = 60 quadrants) was calculated in photographic pixels, and compared with the force percentage present on the same tooth. RESULTS: Regression analysis shows a bi-variant fit of force % on tooth (P<.05). The correlation coefficient between the mark area and the percentage of force indicated a low positive correlation. The coefficient of determination showed a low causative relationship between mark area and force (r2 = 0.067). The largest paper mark in each quadrant was matched with the most forceful tooth in that same quadrant only 38.3% of time. Only 6 2/3% of mark surface area could be explained by applied occlusal force, while most of the mark area results from other factors unrelated to the applied occlusal force. CONCLUSION: The findings of this study indicate that size of articulation paper mark is an unreliable indicator of applied occlusal force, to guide treatment occlusal adjustments.
Bite Force ; Female ; Humans ; Occlusal Adjustment ; Tooth

PURPOSE: Articulation paper mark size is widely accepted as an indicator of forceful tooth contacts. However, mark size is indicative of contact location and surface area only, and does not quantify occlusal force. The purpose of this study is to determine if a relationship exists between the size of paper marks and the percentage of force applied to the same tooth. MATERIALS AND METHODS: Thirty dentate female subjects intercuspated into articulation paper strips to mark occlusal contacts on their maxillary posterior teeth, followed by taking photographs. Then each subject made a multi-bite digital occlusal force percentage recording. The surface area of the largest and darkest articulation paper mark (n = 240 marks) in each quadrant (n = 60 quadrants) was calculated in photographic pixels, and compared with the force percentage present on the same tooth. RESULTS: Regression analysis shows a bi-variant fit of force % on tooth (P<.05). The correlation coefficient between the mark area and the percentage of force indicated a low positive correlation. The coefficient of determination showed a low causative relationship between mark area and force (r2 = 0.067). The largest paper mark in each quadrant was matched with the most forceful tooth in that same quadrant only 38.3% of time. Only 6 2/3% of mark surface area could be explained by applied occlusal force, while most of the mark area results from other factors unrelated to the applied occlusal force. CONCLUSION: The findings of this study indicate that size of articulation paper mark is an unreliable indicator of applied occlusal force, to guide treatment occlusal adjustments.
Bite Force ; Female ; Humans ; Occlusal Adjustment ; Tooth

STATEMENT OF PROBLEM: Unlike screw-retention type, fixture-abutment retention in Locking taper connection depends on frictional force so it has possibility of abutment to sink. PURPOSE: In this study, Bicon(R) Implant System, one of the conical internal connection implant system, was used with applying loading force to the abutments connected to the fixture. Then the amount of sinking was measured. MATERIAL AND METHODS: 10 Bicon(R) implant fixtures were used. First, the abutment was connected to the fixture with finger force. Then it was tapped with a mallet for 3 times and loads of 20 kg corresponding to masticatory force using loading application instrument were applied successively. The abutment state, slightly connected to the fixture without pressure was considered as a reference length, and every new abutment length was measured after each load's step was added. The amount of abutment sinking (mm) was gained by subtracting the length of abutment-fixture under each loading condition from reference length. RESULTS: It was evident, that the amount of abutment sinking in Bicon(R) Implant System increased as loads were added. When loads of 20 kg were applied more than 5 - 7 times, sinking stopped at 0.45 +/- 0.09 mm. CONCLUSION: Even though locking taper connection type implant shows good adaption to occlusal force, it has potential for abutment sinking as loads are given. When locking taper connection type implant is used, satisfactory loads are recommended for precise abutment location.
Bite Force ; Fingers ; Friction ; Retention (Psychology)