• The Journal of Advanced Prosthodontics
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• v.12 no.5
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• pp.307-315
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• 2020

PURPOSE. The purpose of this study was to evaluate the occurrence of displacement while tightening the screw of scan bodies, which were compared according to the material type. MATERIALS AND METHODS. Three types of scan bodies whose base regions were made up of polyether ether ketone (PEEK) material [Straumann Group, Dentium Group, and Myfit (PEEK) Group] and another scan body whose base region was made up of titanium material [Myfit (Metal) Group] were used (15 per group). The reference model was fabricated by aligning the scan body library on the central axis of the implant, and moving this position by the resin model. The screws of the scan bodies were tightened to the implant fixture with torques of 5 Ncm, 10 Ncm, and a hand tightening torque. After the application of the torque, the scan bodies were scanned using a laboratory scanner. To evaluate the vertical, horizontal, and 3-dimensional (3D) displacements, a 3D inspection software program was used. To examine the difference among groups, one-way analysis of variance and Tukey's HSD post hoc test were used (α=.05). RESULTS. There were significant differences in 3D, vertical, and horizontal displacements among the different types of scan bodies (P<.001). There was a significantly lower displacement in the Straumann group than in the Myfit (PEEK) and Dentium groups (P<.05). CONCLUSION. The horizontal displacement in all groups was less than 10 ㎛. With the hand tightening torque, a high vertical displacement of over 100 ㎛ occurred in PEEK scan bodies (Myfit and Dentium). Therefore, it is recommended to apply a tightening torque of 5 Ncm instead of a hand tightening torque.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.1
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• pp.67-76
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• 2008

Implant requires long lasting, strong osseointegration using bio-mechanical interlocking by bone ingrowth. In regarding the size level for bone ingrowth, the micro-patterning would enhance bone response. Micro-patterning can increase the area contacting the bone tissues. Therefore, it may distribute the load to the surrounding bone tissue, more effectively. This study compared and analyzed the load distributing effect with the shape and number of micro-patterning. For the optimal comparison of threads, the assumptions different from general finite element analysis model were made. It was assumed that the implant was axisymmetric and infinitely long. The implant was assumed to be completely embedded in the infinitely long cortical bone and to have 100% bone apposition. The implant-bone interface had completely fixed boundary conditions and received an infinitely big axial load. The condition of threads were as follows. The reference model 1 had conventional thread. Model 2 had 2 micro-patterns on the upper flank of the thread. Model 3 had 2 micro-patterns on the lower flank of the thread. Model 4 had 2 micro-patterns on the upper and lower flanks of the thread. Model 5 had 3 micro patterns on the upper and lower flanks of the thread. The results were as follows: 1. The thread with micro-patterns distributed stress better than the conventional thread. 2. The thread with micro-patterns on the lower flank distributed stress better than that with micro-patterns on the upper flank. 3. The thread with 3 micro-patterns distributed stress better than that with 2 micro-patterns, However, an area with stress concentration occurred.

• The korean journal of orthodontics
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• v.39 no.3
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• pp.146-158
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• 2009

Objective: The purpose of this study was to reveal the position of the incisive foramen in relation to the incisive papilla and cusp tips. Methods: Plaster models and CT images of 25 adult orthodontic patients were used to measure the width of the incisive canal and positions of the anterior and posterior borders of the incisive foramen in relation to the incisive papilla. Results: The palatal surface distance from the interdental papilla between the maxillary central incisors to the posterior border of the incisive foramen along the palatal surface was 1.7 fold of the distance from the interdental papilla between the central incisors to the posterior border of the incisive papilla. The distance between the posterior border of the incisive papilla and posterior border of the incisive foramen along the palatal surface was 6.15 ${\pm}$ 1.75 mm. The anteroposterior position of the posterior border of the incisive foramen was slightly anterior to the lingual cusp tips of the maxillary 1st premolars. The width of the incisive foramen was 4.03 ${\pm}$ 0.64 mm, therefore it is recommended to position the mini-implant more than 3 mm laterally when placing a mini-implant lateral to the incisive foramen, from the center. Conclusions: These results can be used as a reference in presuming the position of the incisive foramen when placing mini-implant in the anterior palate area.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.4
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• pp.300-306
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• 2013

Purpose: This study was to evaluate the accuracy of how to use the Mechanical Torque-Limiting Devices. Materials and methods: Three different implant manufacturers (Dentium, Osstem, Shinhung) were prepared for each two implant torque controllers. Divided into two groups depending on the method used for removal torque was measured. Repeated measures of ANOVA test (${\alpha}=.05$) was used as statistics to evaluate the effect of repeated loading number on the removal torque. Independent t-test was used to evaluate the difference in removal torque of two groups. Results: The removal torque significantly decreased as the number of loading repetition increased (P<.05). There was significant difference between two groups. Conclusion: Loosen the handle part of the implant torque controllers spring resilience to recover one group compared to the group that did not, showed a little more closed to the reference value.

• The Journal of Advanced Prosthodontics
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• v.9 no.5
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• pp.341-349
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• 2017

PURPOSE. This study evaluated the accuracies of different bite registration techniques for implant-fixed prostheses using three dimensional file analysis. MATERIALS AND METHODS. Implant fixtures were placed on the mandibular right second premolar, and the first and second molar in a polyurethane model. Aluwax (A), Pattern Resin (P), and Blu-Mousse (B) were used as the bite registration materials on the healing abutments (H) or temporary abutments (T). The groups were classified into HA, HP, HB, TA, TP, and TB according to each combination. The group using the bite impression coping was the BC group; impression taking and bite registration were performed simultaneously. After impression and bite taking, the scan bodies were connected to the lab analogs of the casts. These casts were scanned using a model scanner. The distances between two reference points in three-dimensional files were measured in each group. One-way ANOVA and Duncan's test were used at the 5% significance level. RESULTS. The smallest distance discrepancy was observed in the TB group using the temporary abutments. The Blu-Mousse and HP groups showed the largest distance discrepancy. The TB and BC groups showed a lower distance discrepancy than the HP group (P=.001), and there was no significant difference between the groups using the temporary abutments and healing abutments (P>.05). CONCLUSION. Although this study has limitations as an in-vitro investigation, the groups using the temporary abutments to hold the Blu-Mousse record and bite impression coping showed greater accuracy than the group using the healing abutments to hold the pattern resin record.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.5
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• pp.644-652
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• 2007

Statement of problem: Resonance frequency analysis is evaluated as the non-invasive and objective method for the evaluation of implant stability and has been increasingly used. It is necessary to evaluate the factors affect the ISQ measurement stability. Purpose: This study was performed to evaluate the effect of the autoclave sterilization and reuse of $Smartpeg^{TM}$ on ISQ measurement. Material and methods: $SmartPeg^{TM}$ (Integration Diagnostics Ltd., $G\ddot{o}teborg$, Sweden) of autoclave group (A) was autoclave sterilized 9 times and $Smartpeg^{TM}$ of reuse group (R) was reused 9 times. Ten $SmartPeg^{TM}s$ were allocated to each group and after each autoclave sterilization and reuse, implant stability quotient (ISQ) values were measured 3 times from the two directions a and b at a right angle. $Osstell^{TM}$ mentor (Integration Diagnostics Ltd. $G\ddot{o}teborg$, Sweden) was used and type 1 (article no. 100353) $Smartpeg^{TM}$ was selected according to $Smartpeg^{TM}$ reference list. Osstem Implant US II future (Osstem Co., Seoul, Korea) in $4.0mm{\times}11.5mm$ was embedded in the self-curing acrylic resin ($Orthojet^{(R)}$, Lang Dental, U.S.A.). Data was statistically analyzed by one-way ANOVA $({\alpha}=.05)$ and scheffe test was done where a significant difference exist. Correlation test was also done between ISQ value and the number of autoclave sterilization or reuse. Results: 1. In autoclave group, the means and sd. of ISQ value before autoclave sterilization were $84.97{\pm}0.41,\;84.93{\pm}0.74$ at direction a and b. There was significant differences between autoclave groups at direction a and b (P=.000). 2. In reuse group, the means and sd. of ISQ value before reuse were $85.40{\pm}0.62,\;85.50{\pm}0.57$ at direction a and b. There was no significant difference between reuse groups at direction a and b (P>.05). 3. There was a weak positive correlation between the number of reuse and ISQ value at direction a and b (${\gamma}=.207$ and .246, P<.01). Conclusion: Within the limitations of this study, the following conclusions were drawn. Till ninth reuse of $Smartpeg^{TM}$, the ISQ measurement stability did not be affected. After twice autoclave sterilization of $Smartpeg^{TM}$ the ISQ measurement stability was affected.

• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.4
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• pp.277-288
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• 2002

Seven finite element models were constructed in mandible having single screw-type implant fixture connected to the premolar superstructure, in order to evaluate how the length, diameter and platform shape of a screw-type fixture influence the stress in the supporting tissue around fixtures. Each finite element model was varied in terms of length, diameter, and platform shape of the fixture. In each model, 250N of vertical load was placed on the central pit of an occlusal plane and 250N of oblique load placed on the buccal cusp. The stress distribution in the supporting tissue and the other components was analysed using 2-dimensional finite element analysis and the maximum von Mises stress in each reference area was compared. Under lateral loading, the stress was larger at the abutment/fixture interface, and in the crestal bone, compared to the stress pattern under vertical loading. The amount of stress at the superstructure was similar regardless of the length, diameter and platform shape of a fixture. Around the longer fixture, the stress was decreased at the bone crest and subjacent cancellous bone and increased in the cancellous bone area apical to the fixture. Around the wider fixture, the stress was decreased at the abutment/fixture interface, and the bone crest and increased in the cancellous bone area apical to the fixture. Around the fixture having wider platform, less stress was produced at the abutment/fixture interface and the upper part of the cortical bone, compared to the fixture having standard platform. In conclusion, the stress distribution of the supporting tissue was affected by length, diameter, and platform shape of a fixture, and the fixture which was larger in diameter and length could reduce the stress in the supporting tissues at the bone-fixture interface and bone crest area.

• The Journal of Korean Academy of Prosthodontics
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• v.31 no.3
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• pp.423-446
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• 1993

Titanium and its alloys are finding increasing use in medical devices and dental implants. The strong selling point of titanium is its resistance to the highly corrosive body fluids in which an implant must survive. This corrosion resistance is due to a tenacious passive oxide or film which exists on the metal's surface and renders it passive. Potentiodynamic polarization measurement is one of the most commonly used electro-chemical methods that have been applied to measure corrosion rates. And the potentiodynamic polarization test supplies detailed information such as open circuit, rupture, and passivation potential. Furthermore, it indicates the passive range and sensitivity to pitting corrosion. This study was designed to compare the corrosion resistance of the commonly used dental implant materials such as CP Ti, Ti-6A1-4V, Co-Cr-Mo alloy, and 316L stainless steel. And the effects of galvanic couples between titanium and the dental alloys were assessed for their useful-ness-as. materials for superstructure. The working electrode is the specimen , the reference electrode is a saturated calomel electrode (SCE), and the counter electrode is made of carbon. In $N_2-saturated$ 0.9% NaCl solutions, the potential scanning was performed starting from -800mV (SCE) and the scan rate was 1 mV/sec. At least three different polarization measurements were carried out for each material on separate specimen. The galvanic corrosion measurements were conducted in the zero-shunt ammeter with an implant supraconstruction surface ratio of 1:1. The contact current density was recorded over a 24-hour period. The results were as follows : 1. In potential-time curve, all specimens became increasingly more noble after immersion in the test solution and reached between -70mV and 50mV (SCE) respectively after 12 hours. 2. The Ti and Ti alloy in the saline solution were most resistant to corrosion. They showed the typical passive behavior which was exhibited over the entire experimental range. Therefore no breakdown potentials were observed. 3. Comparing the rupture potentials, Ti and Ti alloy had the high(:st value (because their break-down potentials were not observed in this study potential range ) followed by Co-Cr-Mo alloy and stainless steel (316L). So , the corrosion resistance of titanium was cecellent, Co-Cr-Mo alloy slightly inferior and stainless steel (316L) much less. 4. The contact current density sinks faster than any other galvanic couple in the case of Ti/gold alloy. 5. Ag-Pd alloy coupled with Ti yielded high current density in the early stage. Furthermore, Ti became anodic. 6. Ti/Ni-Cr alloy showed a relatively high galvanic current and a tendency to increase.

• Imaging Science in Dentistry
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• v.51 no.3
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• pp.243-250
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• 2021

Purpose: The objective of this study was to evaluate the amount of height available for a maxillary sinus augmentation procedure without blocking the ostium and jeopardizing the drainage of the ostiomeatal complex using cone-beam computed tomography (CBCT) imaging. Materials and Methods: A total of 200 sinonasal complexes comprising 100 dentate and 100 edentulous scans were retrospectively assessed using CBCT. Invivo 5.0, a CBCT reconstruction program, was used for image evaluation. The coronal section demonstrating the ostiomeatal complex was selected as a reference view to perform measurements of the sinus. The measurements were done by 2 evaluators in separate sessions. Comparative analyses of measurements were performed between dentate and edentulous patients and between male and female patients. Results: The safe height to which the sinus can be elevated without compromising the integrity of the ostiomeatal complex was calculated for each sinus. In the presence of significant mucosal thickening, the height available for augmentation was calculated by subtracting the height of mucosal thickening from the sinus floor to the location of the ostium. In this study, the available height was approximately 27.05 mm for dentate and 23.40 mm for edentulous patients. The inter-operator reliability was excellent for all the parameters evaluated. Conclusion: This retrospective study with a limited number of patients from a single university-based site shows that CBCT is valuable in evaluating the location and patency of the ostium for planning sinus augmentation procedures for dental implant placement.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.41
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• pp.33.1-33.7
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• 2019

Background: The concept of the ideal morphology for the alveolar bone form is an important element to reconstruct or restore the in maximizing esthetic profile and functional alveolar bone restoration. The purpose of this preliminary study is to evaluate the normal alveolar bone structure to provide the standard reference and guide template for use in diagnosing for implant placement, determining the correct amount of bone augmentation in actual clinical practice and producing prostheses based on three-dimensional imaging assessment of alveolar bone. Methods: This study was included 11 men and 11 women (average age, 22.6 and 24.5 years, respectively) selected from among 127 patients. The horizontal widths of alveolar bone of maxilla and mandible were measured at the crestal, mid-root, and root apex level on MDCT (multi-detector computed tomography) images reconstructed by medical imaging software. In addition, tooth dimensions of the central incisors, canines, second premolars, and first molars of maxilla and mandible, including the horizontal width of the interdental alveolar bone crest, were also measured and statistically analyzed. Results: The horizontal alveolar bone width of the palatal side of maxilla showed a distinct increment from the alveolar bone crest to the apical region in both anterior and posterior areas. The average widths of the maxillary alveolar ridge were as follows: central incisor, 7.43 mm; canine, 8.91 mm; second premolar, 9.57 mm; and first molar, 12.38 mm. The average widths of the mandibular alveolar ridge were as follows: central incisor, 6.21 mm; canine, 8.55 mm; second premolar, 8.45 mm; and first molar, 10.02 mm. In the buccal side, the alveolar bone width was not increased from the crest to the apical region. The horizontal alveolar bone width of an apical and mandibular border region was thinner than at the mid-root level. Conclusions: The results of the preliminary study are useful as a clinical guideline when determining dental implant diameter and position. And also, these measurements can also be useful during the production of prefabricated membranes and customized alveolar bone scaffolds.