• The Journal of Korean Academy of Prosthodontics
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• v.50 no.1
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• pp.29-35
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• 2012

Purpose: The purpose of this study was to analyze temperature change along the implant-bone interface induced by grinding the occlusal surface of implant gold prosthesis and to compare the temperature generated by grinding of prosthesis with different cooling methods. Materials and methods: The experimental gold prostheses were fabricated with dental gold alloy and castable abutment. The prostheses had 3 cylindrical protrusions on the occlusal surface with 1mm in height. Temperature was measured using 16 thermocouple wires attached to the implant fixture surface and the fixture was embedded in an acrylic resin block inside the $37^{\circ}C$ water bath. Cylinders were grinded for a period of 30 second with a low-speed handpiece with green stone point. One cylindrical protrusion was grinded without cooling, the second one was grinded with air blow, and the third one was grinded with water-spray. Results: The mean maximum temperature was measured more than $47^{\circ}C$ of the implant and the maximum temperature was measured at the cervical portion of the implant in the group without cooling. There was statistically significant difference between the group without cooling and the groups with cooling (P<.05). However, there was no significant difference at all portion of implant in the groups with cooling (P>.05). Conclusion: The results of this study support that the grinding of implant gold prosthesis without cooling may damage the peri-implant tissue. The continuous use of air blow and water-spray adjacent to prosthesis during the grinding of implant gold prosthesis may prove to be beneficial for cooling of the implant.

• Journal of Dental Rehabilitation and Applied Science
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• v.19 no.4
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• pp.291-296
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• 2003

The use of resonance frequency analysis (RFA) provides a possibility to clinically measure implant stability and osseointegration. The implant stability quotient (ISQ) value of RFA is well known that influenced by effective abutment length and stiffness of the implant in the surrounding tissues. Among these factors stiffness is not accurately defined histologically yet. And the purpose of this study was to find the histolgical relationship of RFA. 17 implants in 3 beagle dogs were used for this study. Among these implants 10 were survived for 7 months, 4 were survived for 3 months and 3 were immediate status after placement. Resonance frequency analyses were conducted and the dogs were sacrificed. Percentage of the bone to implant contact (BIC) in the interface, percentage of the mineralized bone (bone area) within the threads of the implant, and marginal bone level were measured under light microscopy. The correlation between resonance frequency and histomorphometric measurements were analysed and following results were obtained. 1. There was statistically significant correlation between ISQ value and BIC on healed implants. But ISQ value and BIC of all implants were not significantly correlated. (P<0.01) 2. Significant correlation between ISQ value and bone area was not found in this study. 3. There was statistically significant correlation between ISQ value and marginal bone level on all implants as well as on healed implants. (P<0.01).

• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.3
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• pp.272-279
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• 2013

The concept of implant stability was basically originated from the relative condition of bone-implant interface and has some meanings for evaluation of that interface. In addtion, it has been used for the investigation of initial bone healing process after fixture installation because a degree of micromotion around interface can affect unfavorable clinical results. The purpose of this study is to investigate the mode of initial bone healing from fixture installation through prospective trial. Thirty fixtures were consecutively installed in mandibles of 26 patients with single tooth loss area and then healing abutment were secured for one-stage surgery meothod. Resonance frequency analysis was performed with one week interval during 12 weeks and periapical radiographs were taken at each month. Although marginal bone level change was not shown through observation period (P>0.05), statistical difference of implant stability was shown through 4 and 6 week (P<0.05) and was not shown after 6 week (P>0.05) according to the bone quality. Initial bone healing process is a successive process of bone resorption and favorable bone healing result might be postulated at 4 week interval after installation through RFA.

• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.3
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• pp.259-271
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• 2013

The purpose of this study was to make the stress distribution produced by simulated different load under two types of internal connection implant system (stepped and tapered type) by means of 3D finite element analysis, The finite element model was designed with the parallel placement of the one fixtures ($4.0mm{\times}11.5mm$) with reverse buttress thread on the mandibular 1st molar. Two models were loaded with 200 N magnitude in the vertical direction on the central position of the crown, the 1.5 mm and 3 mm buccal offset point from the central position of the fixture. The oblique load was applied at the angle of $30^{\circ}$ on the crown surface. Von Mises stress value was recorded and compared in the fixture-bone interface in the bucco-lingual dimension. The results were as follows; 1. The loading conditions of two internal connection implant systems (stepped and tapered type) were the main factor affecting the equivalent bone strain, followed by the type of internal connections. 2. The stepped model had more mechanical stability with the reduced max. stress compared to $11^{\circ}$ tapered models under the distributed oblique loading. 3. The more the contact of implant-abutment interface to the inner wall of implant fixture, the less stress concentration was reduced.

• Journal of Dental Rehabilitation and Applied Science
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• v.36 no.4
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• pp.211-221
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• 2020

The typical biomechanical properties of an internal conical connection (ICC) are axial displacement and loss of preload. The axial displacement of an ICC without a vertical stop can cause the loss of preload and a lowered occlusion. The stress of an ICC is concentrated on the contact interface of the abutment and not on the screw, and during placement, it is important to choose a wider coronal wall thickness as much as possible. The ICC should also be placed below the level of the bone crest. During the restoration of an ICC, care should be taken to ensure an appropriate abutment shape and an accurate connection. To get the best clinical results, it is important to select its wall thickness and place it in the appropriate position to restore it adequately.

• Journal of Dental Rehabilitation and Applied Science
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• v.21 no.2
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• pp.153-167
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• 2005

The purpose of this study was to compare the v-shape thread with the square shape thread of fixture in the view of stress distribution pattern using finite element stress analysis. The finite element model was designed with the parallel placement of two standard fixtures(4.0 mm diameter ${\times}$ 11.5 mm length) on the region of mandibular 1st and 2nd molars. Three dimensional finite element model was created with the components of the implant and surrounding bone. This study simulated loads of 200 N at the central fossa in a axial direction (load A), 200 N at the buccal offset load that is 2 mm apart from central fossa in a axial direction (load B), 200 N at the buccal offset load that was 4 mm apart from central fossa in a axial direction (load C). These forces of load A',B',C' were applied to a $15^{\circ}$ inward oblique direction at that same site with 200 N. Von Mises stress values were recorded and compared in the supporting bone, fixture, and abutment screw. The following results have been made based on this study : 1. The highest stress concentration occurred at the cervical region of the implant fixture. 2. Von Mises stress value of off-site region was higher than that of central fossa region. 3. Square shape thread type showed more even stress distribution in the vertical and oblique force than V-shape thread type. 4. Stress distribution was the most effective in the case of buccal offset load (2, 4 mm distance from central fossa) in the square shape thread type. 5. V-shape thread type revealed higher von Mises stress value than square shape thread type in all environmental condition. The results from numerical analyses concluded that square shape thread type had the lower destructive stress and more stress distribution between the fixture and bone interface than V-shape thread type. Therefore, square shape thread type was regarded as optimal thread configuration in biomechanical concepts.