• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제28권1호
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• pp.1-6
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• 2002

When bilateral sagittal split ramus osteotomy or mandibular angle reduction are carried out, we have to consider the position of inferior alveolar nerve. For bone splitting or resection using a saw or an osteotome, the bucco-lingual position of the inferior alveolar nerve plays an important role in the preventing perioperative complications such as paresthesia or anesthesia. Because it is rare to find literatures concerning the mean anatomic position of the inferior alveolar nerve in Koreans, we investigated 30 patients who underwent to take CT and orthopantomogram for implant surgery, and evaluated the bucco-lingual position and vertical relationship of the inferior alveolar nerve at the mandible. The results showed that the distance between inferior alveolar nerve and buccal plate was the farthest at mandibular second molar ($7.1{\sim}7.4mm$) and the nearest at mandibular angle area ($4.4{\sim}4.8mm$). But it was no statistical relationship between the bucco-lingual postion of inferior alveolar nerve on the CT and its vertical position on the OPT. In conclusion, the results suggest that a careful surgical procedure is needed at the mandibular angle area to avoid a nerve damage and there are sufficient bone materials at the mandibular second molar are for bilateral sagittal split ramus osteotomy or mandibular angle reduction or plate fixation. And OPT is not usefull for the evaluation of a relative bucco-lingual position of inferior alveolar nerve in relation to its vertical postion on the OPT.

• 대한치과교정학회지
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• 제46권5호
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• pp.280-289
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• 2016

Objective: The aim of this study was to analyze tooth movement and arch width changes in maxillary dentition following nonextraction treatment with orthodontic mini-implant (OMI) anchorage in Class II division 1 malocclusions. Methods: Seventeen adult patients diagnosed with Angle's Class II division 1 malocclusion were treated by nonextraction with OMIs as anchorage for distalization of whole maxillary dentition. Three-dimensional virtual maxillary models were superimposed with the best-fit method at the pretreatment and post-treatment stages. Linear, angular, and arch width variables were measured using Rapidform 2006 software, and analyzed by the paired t -test. Results: All maxillary teeth showed statistically significant movement posteriorly (p < 0.05). There were no significant changes in the vertical position of the maxillary teeth, except that the second molars were extruded (0.86 mm, p < 0.01). The maxillary first and second molars were rotated distal-in ($4.5^{\circ}$, p < 0.001; $3.0^{\circ}$, p < 0.05, respectively). The intersecond molar width increased slightly (0.1 mm, p > 0.05) and the intercanine, interfirst premolar, intersecond premolar, and interfirst molar widths increased significantly (2.2 mm, p < 0.01; 2.2 mm, p < 0.05; 1.9 mm, p < 0.01; 2.0 mm, p < 0.01; respectively). Conclusions: Nonextraction treatment with OMI anchorage for Class II division 1 malocclusions could retract the whole maxillary dentition to achieve a Class I canine and molar relationship without a change in the vertical position of the teeth; however, the second molars were significantly extruded. Simultaneously, the maxillary arch was shown to be expanded with distal-in rotation of the molars.

• Imaging Science in Dentistry
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• 제50권1호
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• pp.37-43
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• 2020

Purpose: The purpose of this study was to evaluate the accuracy of linear measurements in the horizontal and vertical dimensions based on object position and slice inclination in cone-beam computed tomography (CBCT) images. Materials and Methods: Ten dry sheep hemi-mandibles, each with 4 sites (incisor, canine, premolar, and molar), were evaluated when either centrally or peripherally positioned within the field of view (FOV) with the image slices subjected to either oblique or orthogonal inclinations. Four types of images were created of each region: central/cross-sectional, central/coronal, peripheral/cross-sectional, and peripheral/coronal. The horizontal and vertical dimensions were measured for each region of each image type. Direct measurements of each region were obtained using a digital caliper in both horizontal and vertical dimensions. CBCT and direct measurements were compared using the Bland-Altman plot method. P values <0.05 were considered to indicate statistical significance. Results: The buccolingual dimension of the incisor and premolar areas and the height of the incisor, canine, and molar areas showed statistically significant differences on the peripheral/coronal images compared to the direct measurements (P<0.05). Molar area height in the central/coronal slices also differed significantly from the direct measurements (P<0.05). Cross-sectional images of either the central or peripheral position had no marked difference from the gold-standard values, indicating sufficient accuracy. Conclusion: Peripheral object positioning within the FOV in combination with applying an orthogonal inclination to the slices resulted in significant inaccuracies in the horizontal and vertical measurements. The most undesirable effect was observed in the molar area and the vertical dimension.

• The Journal of Advanced Prosthodontics
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• 제12권5호
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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.

• 대한치과의사협회지
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• 제45권9호통권460호
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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.

• 대한치과교정학회지
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• 제46권4호
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• pp.242-252
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• 2016

Objective: Orthodontic mini-implants (OMI) generate various horizontal and vertical force vectors and moments according to their insertion positions. This study aimed to help select ideal biomechanics during maxillary incisor retraction by varying the length in the anterior retraction hook (ARH) and OMI position. Methods: Two extraction models were constructed to analyze the three-dimentional finite element: a first premolar extraction model (Model 1, M1) and a residual 1-mm space post-extraction model (Model 2, M2). The OMI position was set at a height of 8 mm from the arch wire between the second maxillary premolar and the first molar (low OMI traction) or at a 12-mm height in the mesial second maxillary premolar (high OMI traction). Retraction force vectors of 200 g from the ARH (-1, +1, +3, and +6 mm) at low or high OMI traction were resolved into X-, Y-, and Z-axis components. Results: In M1 (low and high OMI traction) and M2 (low OMI traction), the maxillary incisor tip was extruded, but the apex was intruded, and the occlusal plane was rotated clockwise. Significant intrusion and counter-clockwise rotation in the occlusal plane were observed under high OMI traction and -1 mm ARH in M2. Conclusions: This study observed orthodontic tooth movement according to the OMI position and ARH height, and M2 under high OMI traction with short ARH showed retraction with maxillary incisor intrusion.

• 대한치과보철학회지
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• 제53권2호
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• pp.111-119
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• 2015

목적: 인상재와 석고모형을 사용하지 않고 디지털 영상 만을 사용하여 제작된 수술가이드를 이용한 치과 임플란트 수술의 정확도를 평가하고자 하였다. 재료 및 방법: 상하악 부분 무치악 모델 6개 세트를 본 연구에 사용하였다. 모델을 환자 구강구조로 간주하고 부분 무치악 모델을 Trios 구강스캐너로 디지털 인상을 채득하였다. 수술가이드의 정확도 평가를 위해 제작된 Reference plate를 모델의 교합면에 고정한 상태로 CBCT를 촬영하였다. CBCT에서 얻은 영상과 디지털 인상에서 얻은 영상을 정합하고 정합한 영상에서 임플란트 식립위치를 진단하고 수술가이드를 디자인하였다. 제작된 수술가이드를 이용하여 부분 무치악 모델에서 임플란트를 식립하였다. 시술 후, 시술 전과 동일한 방법으로 CBCT를 촬영하여 시술 전 컴퓨터 소프트웨어에서 측정한 수치와 시술 후 CBCT촬영하여 소프트웨어상에서 측정한 시술 후 수치 사이 차이점을 비교하였다. 결과: 평균거리오차가 임플란트 상단 X축에서 0.27 mm, Y축에서 0.29 mm 였으며, 임플란트 하단(Apex)부위에서는 X축에서 0.11 mm, Y축에서 0.14 mm 평균각도오차가 X축에서 $0.26^{\circ}$, Y축에서 $0.26^{\circ}$ 였다. 평균수직오차는 +0.44 mm로 시술 전 계획한 높이보다 평균 0.44 mm 더 위로 임플란트가 식립되었다. 결론: 본 연구의 결과는 인상재와 석고모형을 사용하지 않고 디지털 영상 만을 사용하여 제작된 수술가이드를 사용하여 임플란트를 시술할 경우 계획한 임플란트 식립 위치와 방향으로 높은 정확도를 가지고 임플란트를 식립할 수 있음을 보여 주었다.

• 구강회복응용과학지
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• 제27권4호
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• pp.437-447
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• 2011

오랜 기간 국소의치를 장착한 부분 무치악 환자에서, 치아가 결손된 부위는 점진적인 치조골의 흡수가 발생되는 반면, 잔존 지대치 부위는 치조골이 유지되어 있는 것을 볼 수 있다. 이는 차후 잔존 지대치를 상실한 후에도 치아 상실의 시점에 따라 수직적인 골 높이의 현저한 차이를 나타낸다. 이와 같이 전체 치아 발거 후 상하악 악간 거리가 좌우측 또는 전후방으로 다르게 나타나는 환자에서 임플란트를 이용한 고정성 보철물이나 임플란트 피개의치의 제작 시 여러 가지 보철적 문제가 야기될 수 있다. 본 논문은 구치부 결손으로 인해 오랫동안 국소의치를 사용했던 환자에서 치아 상실 후 잔존 치조골의 높이를 고려하여 임플란트 지지 국소의치를 제작한 증례로서 잔존 치조골 량이 많아 악간거리가 짧은 전치부는 임플란트를 식립하여 고정성 보철물로, 오랫동안 치조골의 흡수로 인해 악간거리가 긴 구치부는 국소의치로 수복하였다. 본 증례에서의 임플란트 지지 국소의치는 부가적인 수술이 없이 소수의 임플란트를 식립하고 환자에게 기존 보철물의 양식과 유사한 보철물을 제공함으로서 경제적이고 편안한 치료결과를 보여주었다.

• 구강회복응용과학지
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• 제18권4호
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• pp.321-329
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• 2002

Bending moments results from offset overloading of dental implant, which may cause stress concentrations to exceed the physiological capacity of cortical bone and lead to various kinds of mechanical failures. The purpose of this study was to compare the distributing pattern of stress on the finite element models with the different angulated placement of dental implant in mandibular posterior missing areas. The three kinds of finite element model, were designed according to 3 main configurations: Model 1(parallel typed placement of 2 fixtures), Model 2(15. distal angulated placement of one fixture on second molar area), Model 3(15. mesial angulated placement of one fixture on second molar area). The cemented crowns for mandibular first and second molars were made on the two fixtures (4mm 11.5). Three-dimensional finite element models by two fixtures were constructed with the components of the implant and surrounding bone. A 200N vertical static load were applied to the center of central fossa and the point 2mm apart from the center of central fossa on each model. The preprocessing, solving and postprocessing procedures were done by using FEM analysis software NISA/DISPLAY IV Version 10.0((Engineering Mechanics Research Corporation, USA). Von Mises stresses were evaluated and compared in the supporting bone, fixtures, and abutment. The results were as following : (1) Under the point loading at the central fossa, the direction of angulated fixture affected the stress pattern of implants. (2) Under the offset loading, the position of loading affected more on the stress concentration of implants compare to the angulated direction of implants. The results had a tendency to increase the stress on the supporting bone, fixture and screw under the offset loads when the placement angulation of implant fixture is placed toward mesial or distal direction. In designing of the occlusal scheme for angulated placement, placing the occlusal contacts axially during chewing appears to have advantages in a biomechanical viewpoint.

• 대한치과보철학회지
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• 제47권4호
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• pp.365-375
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• 2009

연구목적: 임플란트 보철물의 유지형태 중 나사 및 시멘트 혼합 유지형의 경우 나사 풀림력 등에 영향을 주는 임플란트 구성 성분의 응력에 관한 연구가 부족하였다. 임플란트 상부 보철물의 유지형태, 즉, 시멘트 유지와 나사 유지, 그리고 이 두 가지 유지형태가 서로 연결된 혼합형의 임플란트 보철물의 응력분산의 특징들을 3차원 유한요소분석법을 이용하여 비교하고자 하였다. 연구재료 및 방법: 하악골에서 제1소구치 부위와 제1대구치 부위에 2개의 임플란트 (SS II, Osstem Co. Ltd., Seoul, Korea)를 식립한 가상의 3본 계속가공의치를 모델화하였다. 지대주 종류와 그 위치에 따라, 4가지 모형 군으로 나누어 실험하였다. 모형 1은제1대구치와 제1소구치 각각의 고정체에 모두 동일한 시멘트 유지형 지대주인 Comocta abutment (Osstem Co. Ltd) 를 장착하여 3본 계속가공의치를 합착시킨 경우이고, 모형 2는 제1대구치와 제1소구치 각각의 고정체에 모두 나사 유지형 지대주인 Octa abutment (Osstem Co. Ltd) 를 장착하여 3본 계속가공의치를 나사로 고정시킨 경우이며, 모형 3은 제1대구치의 고정체에는 시멘트 유지형 지대주인 Comocta abutment를 장착하고, 제1소구치에는 나사 유지형 지대주인 Octa abutment를 장착한 후 3본 계속가공의치를 각각 시멘트 합착 및 나사로 고정시킨 경우이다. 그리고 모형 4는 모형 3에서 각각 제1대구치 및 제1소구치의 지대주를 맞바꾼 후 3본 계속가공의치를 나사 및 시멘트로 고정시킨 경우로 나누었다. 평균저작압인 하중을 대구치 565 N과 소구치 288 N의 힘으로 설정하고 수직방향으로 중심와와 협측 교두정에, 그리고 $30^{\circ}$ 경사 하중을 협측 교두정 부위에 준 다음 골, 고정체, 지대주, 그리고 지대주 나사 등에 나타나는 von-Mises stress 양상을 평가하였다. 결과: 네 가지 모형 중 나사 유지형 지대주인 Octa abutment를 제1대구치와 제1소구치 부위에 사용한 모형 2가 전반적으로 가장 낮은 안정적인 응력 분포를 보였다. 네 가지 모형 모두 피질골 및 고정체에 미치는 응력 크기 및 분포는 거의 유사하며, 치조골에 작용하는 응력은 하중의 종류와 상관없이 주로 피질골에 집중되었다. 지대주, 지대주 나사, 그리고 보철물 나사 등에 미치는 응력 크기나 분포는 모형에 관계없이 나사 유지형인 경우가 시멘트 유지형인 경우에 비해 낮은 안정적인 값을 보였다. 제1대구치와 제1소구치의 상부 구조물의 차이에 의한 교호작용 (reciprocal action)은 상대적으로 약하였다. 모든 부위에서 중앙 수 직하중, 교두정 수직하중, 그리고 교두정 경사하중의 순으로 응력값이 증가하였다. 결론: 본 유한 요소실험의 한계내에서 나사 및 시멘트 혼합 유지형의 임플란트 보철물은 시멘트 유지형만 사용하는 경우와 비교하여 주위에 더 큰 응력을 나타내지는 않았다. 이상적인 passive fit의 가정하에서 나사 유지형의 임플란트 보철물이 본체와 주위에 가장 작은 응력을 나타내었다.