• Journal of Periodontal and Implant Science
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• v.49 no.2
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• pp.127-135
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• 2019

Purpose: The aim of this study was to evaluate the computed tomography (CT) imaging findings and clinical symptoms of patients who complained of neurosensory disturbances after mandibular implant surgery, and to investigate the relationships of these parameters with the prognosis for recovery. Methods: CT scans were reviewed in 56 patients with nerve disturbance after mandibular implant surgery. Two oral radiologists classified the imaging findings into intrusion, contact, close, and separate groups according to the distance from the inferior border of the implant to the roof of the mandibular canal (MC). The symptoms of 56 patients were classified into 8 groups and the frequency of each group was investigated. Patients were categorized according to symptom improvement into no recovery and recovery groups, and the relationships of recovery with the CT classification and specific symptom groups were analyzed. Results: Thirty-eight of the 56 nerve disturbance cases showed improvement. The close and separate groups in the CT classification had a strong tendency for recovery (90.9% and 81.8%, respectively) (P<0.05). Although the lowest recovery rate was found in the intrusion group, it was non-negligible, at 50%. The 6 patients with a worm crawling feeling all improved, while the 8 cases with a tightening sensation showed the lowest recovery rate, at 12.5%, and the symptom of a tightening sensation occurred only in the intrusion and contact groups. Conclusions: The closer the implant fixture was to the MC on CT images, the less likely the patient was to recover. Regarding paresthesia symptoms, while a worm crawling feeling is thought to be a predictor of recovery, a tightening sensation appeared to be associated with a lower recovery rate.

• Imaging Science in Dentistry
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• v.54 no.2
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• pp.171-180
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• 2024

Purpose: This study was conducted to identify the typical sites and patterns of peri-implant bone defects on cone-beam computed tomography (CBCT) images, as well as to evaluate the detectability of the identified bone defects on panoramic images. Materials and Methods: The study population included 114 patients with a total of 367 implant fixtures. CBCT images were used to assess the presence or absence of bone defects around each implant fixture at the mesial, distal, buccal, and lingual sites. Based on the number of defect sites, the presentations of the peri-implant bone defects were categorized into 3 patterns: 1 site, 2 or 3 sites, and circumferential bone defects. Two observers independently evaluated the presence or absence of bone defects on panoramic images. The bone defect detection rate on these images was evaluated using receiver operating characteristic analysis. Results: Of the 367 implants studied, 167 (45.5%) had at least 1 site with a confirmed bone defect. The most common type of defect was circumferential, affecting 107 of the 167 implants(64.1%). Implants were most frequently placed in the mandibular molar region. The prevalence of bone defects was greatest in the maxillary premolar and mandibular molar regions. The highest kappa value was associated with the mandibular premolar region. Conclusion: The typical bone defect pattern observed was a circumferential defect surrounding the implant. The detection rate was generally higher in the molar region than in the anterior region. However, the capacity to detect partial bone defects using panoramic imaging was determined to be poor.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.36 no.5
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• pp.224-229
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• 2014

The maxillary posterior area is the most challenging site for the dental implant. Although the sinus graft is a predictable and successful technique for rehabilitation of atrophic and pneumatized posterior maxilla, when there is severe destruction of alveolar bone, a very long crown length remains challenging after successful dental implants installation with sinus graft. We performed vertical augmentation of the maxillary posterior alveolar ridge using the allogenic block bone graft with a simultaneous sinus graft using allogenic and heterogenic bone chips. After about six months, we installed the dental implant. After this procedure, we achieved a more favorable crown-implant fixture ratio and better results clinically and biomechanically. This is a preliminary report of vertical augmentation of maxillary posterior alveolar ridge using allogenic block bone graft and simultaneous maxillary sinus graft. Further research requires longer observation and more patients.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.40 no.3
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• pp.117-122
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• 2014

Objectives: The purpose of this study was to evaluate the sinus bone graft resorption over 3 years after two-stage implant placement. Materials and Methods: The subjects for this study included 30 patients whose maxillary posterior ridges were too atrophic for implants. Bone-added osteotome sinus floor elevation was used in 15 maxillary sinuses, while the bone graft by lateral approach technique was used in 25 maxillary sinuses. The height from the top of the fixture to the sinus floor was estimated immediately after implant placement and the follow-up period was over 3 years. The surgery was classified with two groups: sinus bone grafting with and without autogenous bone. All implants were placed simultaneously. Results: The mean vertical bone loss was $3.15{\pm}2.95mm$. The survival rate of implants was 94.7%. Conclusion: The amount of bone resorption was not significantly associated with the surgical methods, the type of bone graft materials used, or sinus perforation during surgery.

• The Journal of the Korean dental association
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• v.45 no.9 s.460
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• pp.562-570
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• 2007

Many dentists and patients expect that implant function and esthetics will not change over time. However, even the most successful implant restorations with ideal position, vertical height, and occlusion can be aesthetically pleasing, but may hide a common problem. Many dentists noticed that there can be some circumferential bone loss around the neck of the implants. To circumvent this bone loss, a "platform switching" concept was introduced recently. The basic concept of platform switching is by moving the fixture-abutment interface further away from the crestal bone to minimize crestal bone loss. Since crestal bone loss is a multifactor problem, it is important to consider microgap formation and micromotion between the implant and abutment because platform switching does not solve the problem on its own. In this article, we reviewed studies concerning platform switching and discussed the clinical application and the problems that may occur with its use.

• Journal of the Korean institute of surface engineering
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• v.48 no.6
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• pp.283-291
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• 2015

The purpose of this study was to investigate effects of TiN coating on the fatigue fracture of dental implant system with various cyclic loads. TiN coated abutment screw, the fixture, and abutment of internal hex type were prepared for fatigue test. The fatigue test was carried out according to ISO 14801:2003(E) using tensile and compression tester with repeated load from 30% to 80% of static fracture force. Morphology and fractured surface was observed by field emission scanning electron microscope(FE-SEM) and energy dispersive X-ray spectroscope(EDS). The fracture cycle drastically decreased as repeated load increased. Especially, in the case of TiN-coated abutment screw, fracture cycle increased compared to non-coated abutment screw. The fatigue crack was propagated fast as repeated load increased. The plastic deformation region decreased, whereas, cleavage fracture region increased as repeated load increased.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.23 no.5
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• pp.406-414
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• 2001

In recent decade, there has been a very rapid development in technical possibilities to provide patients with maxillofacial prostheses. Dr. Brenemark first introduced possibility of use of maxillofacial interosseous implant in patients with ablative tumor surgery in 1979. He did introduce the new type of maxillofacial implants system which widen the fixture flange on top of the bone. The advantages of fixed prostheses with implants were well known to various ways, easy to attach, keep clean prostheses, and not to disturb recipient bed. But there are some problems to install implants on maxillofacial regions, because mostly facial bone has very thin cortical bone and poor bone quality. It needs more retention between implant and bone which overcome that fault with fixture flange. To make maxillofacial prostheses, it should be understood general procedure of maxillofacial laboratory work. Ear and midface maxillofacial fabrication which include nose and eye defects will be described step by step.

• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.4
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• pp.251-276
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• 2002

The purpose of this study was to compare and analyze the stress distribution and displacement of the fully bone anchored bridge and implant-supported overdenture in edentulous mandible on certain conditions such as number of implants, different design of superstructure. Three dimensional analysis was used and nine kinds of models designed for this study. FEM models were created using commercial software[$Rhinoceros^{(R)}$ (Ver. 1.0 Robert McNeel & Associates, USA)], and analyze using commercial software [Cosmos/$Works^{TM}$(Ver. 4.0 Structural Research & Analysis Corp., US A)]. A vertical load and $45^{\circ}$ oblique load of 17kgf were applied at the left 1st. molar. The results were as follows : (1) In the group of OVD, the displacement was reduced as increasing the number of fixture under vertical loading but there was no specific difference in Von Mises stress. Under oblique loading, the displacement was same at the vertical loading but Von Mises stress was reduced in order of OVD-3, OVD-4, OVD-2. But, bending moment reduced according to increasing the number of fixture. (2) In the group of FBAB, under vertical and oblique loading, the magnitude of Von Mises stress and displacement reduced according to increasing the number of fixtures. FBAB-4 and FBAB-5 showed similar score and distribution, but FBAB-6 showed lower value relatively. (3) In cantilever design, the maximum displacement reduced under vertical loading but increased under oblique loading. However, von mises stresses on fixtures increased under vertical and oblique loading. (4) In comparing OVD-group with FBAB-group, FBAB showed low magnitude of displacement in respect of oblique loading. However OVD-group was more stable in respect of stress distribution.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.4
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• pp.458-470
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• 2004

Statement of problem: Br${\aa}$nemark or ITI are two currently most widely used implant systems but with contrasting design, surgical and restoration methods. Purpose: The purpose of this study was to compare changes and its statistical significance in bone height and shape which may rise due to the differences between two implant systems. Also to analyse the effect of inter-implant distance on annual bone height changes. Material & Method: Those patients who were treated with two or more of either Br${\aa}$nemark or ITI implants at posterior mandibular area at Yonsei University Dental Hospital, Implant Clinic were selected. At annual examination appointments, standardised radiographs using parallel technique were taken. Marginal bone and inter-implant crestal bone changes were measured and following results were obtained. Results: 1) When ITI and Br${\aa}$nemark system were compared, both annual marginal and inter-implant crestal bone height changes in ITI system in the first two years were smaller than Br${\aa}$nemark and they were statistically significant. On the third year, however, there was no statistical difference between two implant systems on their annual bone level changes (p>0.05). 2) The Marginal and inter-implant crestal bone changes were compared when inter-implant distance was less than 4mm. Statistically significant bone level changes were noted on the first year only for ITI implants but in the first and second year for Br${\aa}$nemark implants (p>0.05). 3) When comparing angulation changes between marginal bone and implant fixture, ITI system had smaller angulation changes but the annual changes were not statistically significant (p>0.05). Conclusion: Within the limitation of this study, it could be concluded that Br${\aa}$nemark implant systems had more changes in marginal and inter-implant crestal bone level in the first and second year after loading with statistical significance. Further studies are recommended to see the effects of these bone loss during the first and second year after loading on the long term prognosis of Br${\aa}$nemark Implants.

• Journal of Periodontal and Implant Science
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• v.36 no.2
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• pp.531-554
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• 2006

Oral implants must fulfill certain criteria arising from special demands of function, which include biocompatibility, adequate mechanical strength, optimum soft and hard tissue integration, and transmission of functional forces to bone within physiological limits. And one of the critical elements influencing the long-term uncompromise functioning of oral implants is load distribution at the implant- bone interface, Factors that affect the load transfer at the bone-implant interface include the type of loading, material properties of the implant and prosthesis, implant geometry, surface structure, quality and quantity of the surrounding bone, and nature of the bone-implant interface. To understand the biomechanical behavior of dental implants, validation of stress and strain measurements is required. The finite element analysis (FEA) has been applied to the dental implant field to predict stress distribution patterns in the implant-bone interface by comparison of various implant designs. This method offers the advantage of solving complex structural problems by dividing them into smaller and simpler interrelated sections by using mathematical techniques. The purpose of this study was to evaluate the stresses induced around the implants in bone using FEA, A 3D FEA computer software (SOLIDWORKS 2004, DASSO SYSTEM, France) was used for the analysis of clinical simulations. Two types (external and internal) of implants of 4.1 mm diameter, 12.0 mm length were buried in 4 types of bone modeled. Vertical and oblique forces of lOON were applied on the center of the abutment, and the values of von Mises equivalent stress at the implant-bone interface were computed. The results showed that von Mises stresses at the marginal. bone were higher under oblique load than under vertical load, and the stresses were higher at the lingual marginal bone than at the buccal marginal bone under oblique load. Under vertical and oblique load, the stress in type I, II, III bone was found to be the highest at the marginal bone and the lowest at the bone around apical portions of implant. Higher stresses occurred at the top of the crestal region and lower stresses occurred near the tip of the implant with greater thickness of the cortical shell while high stresses surrounded the fixture apex for type N. The stresses in the crestal region were higher in Model 2 than in Model 1, the stresses near the tip of the implant were higher in Model 1 than Model 2, and Model 2 showed more effective stress distribution than Model.