Short implant의 식립 후 1년간의 골흡수 비교연구

Based on the rapid progress made in research concerning implant fixture designs and surface treatments, modern implant treatments have progressed significantly and are now capable of overcoming anatomical limitations and ensuring a stable prognosis. But for cases where patients suffer severe alveolar bone loss in molar areas, many problems still exist. Therefore, short implants (less than 10mm in fixture length) are increasingly being accepted as an alternative option. In spite of the extensive number of studies reporting high success rates using short implants, there are still many risk factors, including 1) reduced bone-implant contact area and 2) reduced stress distribution around the implant fixture and 3) poor prognosis due to poor bone quality. The present study evaluated marginal bone changes in radiographic images of 40 single short implant cases selected from among 389 short implant cases installed in Yongdong Severance Dental Hospital from 2003. Comparisons with standard implants (more than 10mm in length) with 1-year follow up were performed. Additionally, the effects of crown-to-implant ratio in short implants were also evaluatedope

임프란트와 인접 자연치 사이의 근심 접촉 소실에 관한 임상연구

Proximal contact loss between an adjacent natural tooth and fixed implant prosthesis can be experienced during treatment, especially in the case of posterior prostheses following implant placement. Since the implant prostheses are fixed in the jaw bone, contact loss is most likely caused by mesial migration of the anterior adjacent tooth. It could be considered that there is some reason beyond the natural mesial drift after implant prostheses delivery, since contact loss is not often observed in the natural dental arch. Food impaction caused by proximal contact loss frequently leads to patient discomfort and periodontal disease. According to Hua Wei(2008), occlusal force distribution, periodontal status, and masticatory habits affect proximal contact loss between the adjacent natural tooth and the fixed implant prosthesis. This study examined the records of patients who received implant treatment at the Department of Prosthodontics in Kangnam Severance Hospital. The ratio, period, and area of proximal contact loss were evaluated.ope

Histomophometric and Resonance frequency analysis of bone healing around titanium implants with two different surface treatment

Titanium and titanium alloy are widely used as materials for dental implants because of the advantages of their mechanical properties and excellent anchorage into the jaw bone. In the clinical application of dental implant, many attempts have been made to improve bone anchorage of dental implants to reduce the treatment time and improve the success rate in areas with poor bone quality. Recent studies have shown that the existence of a certain surface roughness increase bone-to-implant contact, mainly in the earlier phases of the osseointegration. The purposes of this study were to investigate the bone response around dental implants with two different surface treatment to evaluate the biocompatability. In this study, ABE(Advanced Blasting and Etching) H-R8.5 implants(Warantec, Seoul, Korea) and SLA(Sandblasted, Large-grit, and Acid-etched) ITI implants(Straumann, Waldenburg, Switzerland) were placed in rabbit tibia. The resonance frequency was measured every 1 month during 3 months after implant placement. After 3 months, the bone response around implants was evaluated with histomorphometric analysis. The results obtained was as follows 1. The histomorphometric analysis in 3 months after implant placement revealed that both H-R8.5 implants and ITI implants showed relatively even bone contact from the bottom to the top of implants. No foreignbody reaction and inflammatory cell infiltration were observed. 2. As a result of the histomorphometric analysis, bone to implant contact percentages for ITI implants and H-R8.5 implants were 74%, 72% respectively. 3. As a result of the RFA value measured every 1 month, H-R8.5 implants showed relatively higher RFA value than ITI implants through the observation period from the implant placement to 3 months after. 4. RFA value for H-R8.5 implants showed a tendency to decrease from 4 weeks to 8 weeks, and increase from 8 weeks to 12 weeks. For ITI implants, RFA value showed a tendency to increase with time but was relatively lower than that of H-R8.5 implants after 12 weeksope

A new method to evaluate trueness and precision of digital and conventional impression techniques for complete dental arch

Purpose: The aim of this study was to present a new method to analyze the three-dimensional accuracy of complete-arch dental impressions and verify the reliability of the method. Additionally, the accuracies of conventional and intraoral digital impressions were compared using the new method. Methods: A master model was fabricated using 14 milled polyetheretherketone cylinders and a maxillary acrylic model. Each cylinder was positioned and named according to its corresponding tooth position. Twenty-five definitive stone casts were fabricated using conventional impressions of the master model. An intraoral scanner was used to scan the master model 25 times to fabricate 25 digital models. A coordinate measuring machine was used to physically probe each cylinder in the master model and definitive casts. An inspection software was used to probe cylinders of digital models. A three-dimensional part coordinate system was defined and used to compute the centroid coordinate of each cylinder. Intraclass correlation coefficient (ICC) was evaluated to examine the reliability of the new method. Independent two sample t-test was performed to compare the trueness and precision of conventional and intraoral digital impressions (α = 0.05). Results: ICC results showed that, the new method had almost perfect reliability for the measurements of the master model, conventional and digital impression. Conventional impression showed more accurate absolute trueness and precision than intraoral digital impression for most of the tooth positions (p < 0.05). Conclusions: The new method was reliable to analyze the three-dimensional deviation of complete-arch impressions. Conventional impression was still more accurate than digital intraoral impression for complete arches.ope

Aesthetic implant restoration with alveolar bone graft and digital method on maxillary central incisor: a case report

In case of gingival recession or bone defect in maxillary anterior implant treatment, it is not easy to obtain satisfactory clinical results. In this case, loss of the labial alveolar plate was diagnosed in the maxillary right central incisor, so after tooth extraction, soft tissue was secured and implant placement with bone graft was planned. In addition, digital guide surgery was performed for the ideal implant position, and GBR (Guided Bone Regeneration) was accompanied with the xenogeneic bone and the autologous bone collected from the mandibular ramus since alveolar bone defects were extensive. After a sufficient period of osseointegration of the implant, a temporary prosthesis was fabricated through secondary stage surgery and impression taking, and through periodic external adjustment, the shape of soft tissue was improved. In the final prosthesis fabrication, a color tone of natural teeth was induced by an gold anodized customized abutment, and an aesthetic and functional zirconia prosthesis with reproducing the shape of the temporary prosthesis through intraoral scan was delivered.ope

Submucosal zirconia implant prosthesis fabricated with CAD/CAM

They have been recently introduced many aesthetic implant prosthesis using with zirconia and CAD/CAM. However, there are many limitations in their gingival and occlusal region. In this case, submucosal zirconia implant prosthesis were fabricated with CAD/CAM system. The connection of these screw cement retained prosthesis and titanium abutment was designed to 1mm above the fixture. The clinical results were satisfactory on the aesthetics and function.ope

The effet of cooling rate on the residual stresses in the veneer ceramics of zirconia-ceramic restorations: a literature review

Nowadays, dental zirconia is widely used as a framework material for a fixed dental prosthesis as well as a single restoration. However, clinical studies have reported high incidence of veneer chipping of zirconia-ceramic restorations compared to that of metal-ceramics. Several factors were raised as the possible causes of veneer ceramic chipping, however, it is still in debate. Recently, residual stresses in the veneer ceramics after cooling process gathers attention as one possible cause of chipping and many studies reported that the rate of cooling significantly influenced the types and the amount of residual stress. The purpose of current review was to briefly describe the effect of cooling rate on the residual stress in zirconia-ceramics. It was also described that the different behavior of residual stress between zirconia-ceramics and metal-ceramics following different cooling rate.ope

Considerations and clinical appliances of various abutments in implant prostheses

In the past, restoration of implant crown, ready-made abutment produced by implant manufacturer could only be used. Using straight, angled abutment, there was a limit in adaptation multiple implants. Recently, with the development of implant and CAD/CAM technology, CAD/CAM customized abutment use has become possible which is different from the past when restoration was possible with only prefabricated abutment. Not only it makes emergence profile possible which is similar to natural teeth, but also it makes insertion path possible on CAD in multiple implant restorations. However, on anterior teeth which dental esthetics is very important, another restorations which are formed with natural colored gingiva area could be required. Titanium-based zirconia prostheses which have titanium connection and zirconia structure from 1mm above fixture platform are alternative. Therefore, the purpose of this review is to analyze the characteristics, advantages and disadvantages of the abutment which is used in multiple implant restorations, and to choose right abutment when clinical trials.ope

Displacements of implant components from impressions to definitive casts : a three dimensional analysis

Dept. of Dental Science/박사[한글] 임프란트 인상채득 과정에서는 모두 4번의 부속품의 변위가 발생 가능하다. 첫째, 지대주에 인상 코핑 연결 시 두 부속품 간 공차에 의한 인상 코핑의 위치변화. 둘째, 인상재나 인상방법 자체에서 발생하는 인상 코핑의 위치변화. 셋째, 인상 트레이 내 인상 코핑에 아나로그를 연결할 때 이 두 부속품간의 공차에 의해 발생하는 아나로그의 위치변화. 마지막으로 석고모형 제작 시 석고의 경화팽창에 의한 아나로그의 위치변화이다. 이 중 둘째와 넷째 변위가 실제로 인상법에 의한 변위며 첫 번째와 세 번째 변위는 임상가로서는 조절이 불가능하다. 현재까지 발표된 임프란트 인상에 관한 거의 모든 연구들은 환자모형과 인상 채득 후 제작된 작업모형을 단순히 비교하는 것이었기 때문에 인상의 어떤 단계에서 얼마만큼의 변위가 일어나는지에 대한 고찰은 전혀 이뤄지지 않았으며 무엇보다 임프란트 부속품간의 공차에 의한 변위를 고려하지 않았기 때문에 인상법 자체의 정확도를 평가할 수 없었다. 이에 저자는 임상에서 흔하게 이용되는 2가지 임프란트 인상 채득법, 즉 비 연결 고정법과 광중합형 레진을 이용한 연결 고정법을 사용하여 각각의 인상채득 단계에서 발생하는 부속품의 위치변화를 전산화 3차원 측정기로 측정함으로써 인상채득 과정에서 발생 할 수 있는 4가지 변위량을 비교하였다. 첫 번째와 세 번째 변위인 연결과정에서 발생하는 변위량의 비교에선 인상 코핑 연결 시 와 아나로그 연결 시 각각 31.3±15.5, 30.4 ±15.6㎛의 변위를 초래하였다. 3차원적 선형 변위량 총계의 비교에선 두 번째 변위인 인상 채득 과정동안의 변위량은 비 연결 고정법 (23.6±14.2㎛) 이 광중합 레진 연결 고정법 (43.7±20.3㎛)에 비해 유의성 있게 작았다. 그러나 네 번째 변위인 석고모형을 제작하는 과정에서는 반대의 결과를 보였다 (36.4±19.2 대 20.7±8.3㎛). 인상채득과 석고모형 제작과정 동안에 발생한 총 변위량은 두 가지 인상법 간에 차이를 보이지 않았다 (36.8±18.5 대 37.6±16.5㎛). 현재까지 발표된 논문들과 달리 본 연구에서는 인상과정에서 부속품을 연결하는 동안 부속품 간 공차에 의해 필연적으로 발생하는 변위량을 배제한 채 실제로 인상채득 방법의 차이에 의해 발생하는 변위량을 비교하였다. 단순히 인상 코핑이나 아나로그를 연결하는 과정동안에 작업모형의 정확도에 영향을 미치는 정도의 변위가 발생한다는 것을 알 수 있으며 지금까지 공차에 의한 변위량을 배제하지 않은 채 인상법의 정확도를 평가한 과거 연구들의 결과에 대한 재평가가 필요하다고 사료된다. [영문]Purpose: The aim of the present study was to assess the amount of four possible displacements of implant components from making an impression to fabricate a definitive cast.Materials and Methods: A mandibular master model with 5 parallel implants was fabricated. Performing each of non-splinted and light curing resin splinted open tray impression technique, 5 definitive casts were fabricated per each technique. Using a computerized coordinate measuring machine, 5 part coordinate systems were established and 7 sets of data were obtained for each sample. From the data, the amount of displacement while connecting components, the linear and angular displacement of component during impressions and cast fabrications were calculated.Results: The average displacements while connecting impression copings and abutment replicas were 31.3 and 30.4㎛ each. Non-splinted group resulted smaller displacement compared to splinted group during impressions (23.6 versus 43.7㎛) but greater displacement during cast fabrications (36.4 versus 20.7㎛).Discussion: In contrast to previous studies, current study excluded the displacement resulted from connecting an impression coping or an abutment replica and measured the displacement solely resulted from the impression and the cast fabrication to compare the accuracy of impression techniques because the displacement from connecting components had no relation to the impression technique used and could not be controlled.Conclusions: Connecting a component produced as great as the displacement solely resulted from an impression or a cast fabrication. Non-splinted group was more accurate during impressions but less accurate during cast fabrications.ope

Superimposition: a simple method to minimize occlusal adjustment of monolithic restoration

The development of translucent zirconia enabled clinicians to choose a monolithic zirconia crown as one treatment modality in the posterior dentition. Careful occlusal adjustments are recommended for monolithic zirconia crowns because grinding zirconia inevitably causes phase transformation, which may deteriorate mechanical properties. intraoral scanners enable the clinician to scan and superimpose a complete tooth structure before preparation onto the prepared abutment. This technique helps to reproduce the original tooth form and occlusion of the patient. In this case report, prostheses were fabricated for patients with cracked or fractured tooth by applying intraoral scanner, Computer aided design-computer aided manufacturing (CAD-CAM) and monolithic zirconia crown to reproduce the occlusion of original tooth and to minimize occlusal adjustment. The clinical results were satisfactory in both esthetic and functional aspects.ope