• The Journal of Advanced Prosthodontics
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• 제4권1호
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• pp.37-42
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• 2012

PURPOSE. The influence of the modified process in the fiber-reinforced post and resin core foundation treatment on the fracture resistance and failure pattern of premolar was tested in this study. MATERIALS AND METHODS. Thirty-six human mandibular premolars were divided into 4 groups (n = 9). In group DCT, the quartz fibre post (D.T. Light-post) was cemented with resin cement (DUO-LINK) and a core foundation was formed with composite resin (LIGHT-CORE). In group DMO and DMT, resin cement (DUO-LINK) was used for post (D.T. Lightpost) cementation and core foundation; in group DMO, these procedures were performed simultaneously in one step, while DMT group was accomplished in separated two steps. In group LCT, the glass fiber post (LuxaPost) cementation and core foundation was accomplished with composite resin (LuxaCore-Dual) in separated procedures. Tooth were prepared with 2 mm ferrule and restored with nickel-chromium crowns. A static loading test was carried out and loads were applied to the buccal surface of the buccal cusp at a 45 degree inclination to the long axis of the tooth until failure occurred. The data were analyzed with MANOVA (${\alpha}$= .05). The failure pattern was observed and classified as either favorable (allowing repair) or unfavorable (not allowing repair). RESULTS. The mean fracture strength was highest in group DCT followed in descending order by groups DMO, DMT, and LCT. However, there were no significant differences in fracture strength between the groups. A higher prevalence of favorable fractures was detected in group DMT but there were no significant differences between the groups. CONCLUSION. The change of post or core foundation method does not appear to influence the fracture strength and failure patterns.

• 대한기계학회논문집A
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• 제25권6호
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• pp.972-979
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• 2001

Tool fracture index(TFI) was developed in order not only to detect tool fracture but also to predict the amount of tool fracture in face milling. TFI is calculated by using peak-to-valley values of cutting force acting on teeth and their ratio between the adjacent teeth. When the tool fractures, a large value of TFI proportional to the amount of tool fracture was obtained periodically and decreased gradually. It was found that TFI is independent of cutter runout and it almost does not vary during transient cutting such as cutting condition change during machining. The threshold of tool fracture can be analytically determined by TFI developed in this paper, because the magnitude of TFI was shown to be dependent on the ratio of the amount of tool fracture to feed per tooth and immersion ratio. It was possible to predict the amount of tool fracture in experiments by using the proposed TFI.

• 대한치과교정학회지
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• 제21권2호
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• pp.259-272
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• 1991

Orthodontic traction has been suggested as the treatment of choice for intrusive luxation injuries. Prior research has shown orthodontic forces to be ineffective in the presence of ankylosis or in cases with zero mobility following the injury. If orthodontic traction is to be effective, it must be initiated prior to the onset of ankylosis. The purpose of this study was to describe the effects of intrusive luxation at various times following the injury, and to determine the time of the onset of ankylosis, and to examine what effect immediate partial luxation has on the onset of ankylosis. Eight young mongrel dogs were utilized for this study. Intrusive luxation was produced with an axial impact using a gravity hammer and a specially designed holding device on 4 teeth (2 max. and 2 man. first premolars) in each dog. The teeth were intruded approximately 3-4mm in an axial direction. One maxillary and one mandibular premolars were partially luxated with the other two teeth being untouched. Pre and posttrauma tooth position was documented with plaster models and radiographs taken with an individualized X-ray jig. Dogs were sacrificed immediately following the injury and at 1, 2, 4, 7, 10, 14 and 21 days respectively. Tetracycline was administered as a vital bone marker 24 hours before sacrifice. Block sections of the tooth and alveolus were prepared for decalcified and non decalcified histologic sections. The effects of traumatic intrusion were analyzed by means of model casts, radiographs, tetracycline bone marking and histologic preparations. The results obtained were as follows: 1. The animal sacrificed immediately following the injury displayed alveolar fractures, torn periodontal ligaments, and areas of direct tooth-bone contact. 2. The odontoblastic layer of the pulp was disorganized as early as 24 hours after the injury. 3. Bony remodeling was noted at 4 days along with active surface resorption. 4. Ankylosis was first seen 7 days after the injury. 5. Osteogenesis in the dentin (thick tetracycline bands) was observed 7 days after the injury. 6. There was no progressive root resorption and ankylosis where the periodontal ligament has been healed. 7. The Luxated group showed significantly more root resolution and ankylosis than the Nonluxated group with increased observation periods. The results suggest that ankylosis may occur within the first week following the injury, and hence orthodontic traction should be initiated as soon after the injury as possible.

• 대한소아치과학회지
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• 제34권1호
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• pp.156-161
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• 2007

소아치과 임상에서는 외상성 손상에 의하거나 발치 도중 우발적으로 유치의 치근이 파절되는 경우가 종종 있다. 이런 경우 임상의들은 치근 파절편을 발치할지, 남겨둘지에 대해 간혹 고민하게 된다. 이같은 상황에서 잔근이나 파절편의 발치 시도가 계승치 배를 손상시킬 우려가 있을 경우에는 일반적으로 치근 파절편을 남겨두는 것이 추천되고 있다. 본 연구는 유치 잔근이나 파절편을 술자 의도적으로 잔존시킨 경우, 계승치의 맹출경로에 장애를 가하지 않고 소멸될 것인지의 예후를 확인해 볼 목적으로 잔근이나 치근 파절편을 의도적으로 남긴 3세 8개월${\sim}6$세 1개월 어린이 6명을 대상으로 $7{\sim}37$개월 동안 $2{\sim}3$개월 주기의 내원을 통하여 임상검사와 방사선검사를 시행하고 예후를 장기 관찰하였다. 관찰 결과, 5 증례에서 치근측 파절편은 생리적인 흡수과정을 통하여 크기가 축소되거나 소멸되었고, 1 증례에서는 계승치와 함께 밀려 출은하였으며 계승치의 맹출을 현저하게 지장을 초래한 경우는 나타나지 않았다. 본 관찰을 통하여 치조골 내에 남은 유치근 파절편이 계승치배에 근접한 경우, 이를 무리하게 발치하려 시도하기보다는 치배의 손상 가능성을 고려하여 잔존시키고 주기적인 검진을 통해 흡수 여부를 판단하며 예후 관리를 하는 방법의 타당성을 확인할 수 있었다.

• 구강회복응용과학지
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• 제35권4호
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• pp.206-213
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• 2019

목적: 굴곡파절의 대부분 연구들이 협측에 한정되어있다. 본 연구에서는 상악 구치부에서 구개측 굴곡파절의 빈도 조사를 통해 굴곡파절의 원인을 분석해보고자 한다. 연구 재료 및 방법: 총 3193개의 상악 구치를 대상으로 조사를 진행하였다. 구내 관찰과 모형 관찰, 그리고 모형 스캔을 통해 제작된 가상 모형을 관찰하는 방법으로 조사를 진행하였다. 그 결과를 치아, 연령, 성별, 악궁에 따라 분류하였다. 통계적 유의성의 평가를 위해 Chi-square test를 시행하였다(α = 0.05). 결과:상악 소구치(6.8%)보다 대구치(10.8%)에서 구개측 굴곡파절이 높은 빈도로 관찰되었고, 그중 제1대구치(39.1%)에서 가장 높은 빈도로 관찰되었다. 연령이 증가할수록 구개측 굴곡파절이 높은 빈도로 관찰되었으며 이는 통계적으로 유의성이 있었다(P < 0.05). 구개측 굴곡파절의 빈도는 성별에 따른 차이에서는 통계적으로 유의성이 없었으며(P > 0.05), 악궁에 따른 차이에서는 좌측에서 더 높은 빈도로 나타났고 통계적으로 유의성이 있었다(P < 0.05). 결론: 상악 구치에서 구개측 굴곡파절은 상악 제1대구치에서 높은 빈도로 관찰되었고, 연령의 증가에 따라 증가하는 양상을 보였다. 이와 같은 결과는 굴곡파절의 가장 주된 원인이 교합력임을 의미한다.

• 대한소아치과학회지
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• 제36권2호
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• pp.288-292
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• 2009

치관-치근 파절(crown-root fracture)은 법랑질, 상아질, 백악질에 파급된 파절이며 치수노출을 수반하는 것과 수반하지 않는 것이 있다. 치근부위만 파절된 경우와 달리 치관-치근 파절의 경우 치수와 치주조직을 통해 세균감염이 발생하기 때문에 치유를 기대하기 힘들다. 파절은 치근을 따라 다양한 부위에서 일어나기 때문에 치료방법은 파절 정도에 따라 결정된다. 치근의 파절선이 치관부에 근접 한 경우 느슨한 치아 파절편을 제거 한 후, long junctional epithelium이 형성되도록 치은을 노출된 상아질에 맞게 적합시키거나, 외과적으로 파절 부위를 노출시키거나, 교정적 또는 외과적으로 치아를 정출시키는 방법 등을 고려해 볼 수 있지만 파절선이 깊은 경우 발치가 일반적이다. 그러나 최근 논문에서 수직 치관-치근 파절된 치아에 대해 발치대신 레진으로 파절선을 수복한 후 재식하여 성공한 사례가 발표되었다. 이 방법으로 치아를 보존할 수 있으며 이러한 방법이 전치 부에서는 예후가 좋다고 보고되었다. 본 증례에서는 외상으로 인하여 상악중절치의 치관-치근 파절이 발생한 10세 환아에서 해당 치아를 발치하여 레진으로 파절부위를 재부착한 후 재식하였다. 그러나 18개월간 주기적으로 관찰한 결과 문헌에서와 같은 좋은 결과를 나타내지는 않았다.

• 대한소아치과학회지
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• 제43권2호
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• pp.200-206
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• 2016

상아질, 백악질, 치수를 포함하는 파절로 정의되는 치근파절은 영구치에서 발생하는 외상 중 0.5-7%를 차지하며, 대부분 11-20세군의 상악 전치부에 호발한다. 영구치 치근파절의 처치는 기본적으로 변위된 치관부 파절편을 정복시키고 고정하는 것이다. 60-80%는 치수생활력이 유지되나 치수괴사나 염증성 치근흡수의 징후가 나타난다면 근관치료를 시행하게 되며 대부분에서 치근부 파절편의 치수생활력은 유지되기 때문에 근관치료는 치관부 파절편에 한하여 수행한다. 그러나 치관부 파절편에서 적절한 apical stop을 얻는 것은 어렵다. 의도적 재식술이란 통제된 환경에서 의도적으로 치아를 발거한 후 구강 외에서 치근단 치료를 시행하고 재식립하는 방법으로 완벽한 근관치료와 수복을 목표로 한다. 통상적인 근관치료가 실패한 경우, 기존의 수복물이 존재하거나 석회화된 근관으로 인해 재근관치료가 어려운 경우, 공간적으로 접근이 불가능하여 치근단 수술을 시행하지 못하는 증례에서 의도적 재식술이 계획될 수 있다. 본 증례에서는 이전의 외상으로 인해 석회화된 근관을 보이는 상악 중절치에서 발생한 수평 치근파절을 치료하기 위해 의도적 재식술을 이용하였고 임상적, 기능적으로 만족할만한 결과를 얻었기에 이를 보고하는 바이다.

• The Journal of Advanced Prosthodontics
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• 제8권3호
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• pp.194-200
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• 2016

PURPOSE. The prospective follow-up aimed to assess the performance of lithium disilicate crowns and clinical reasons of adverse events compromising survival and quality. MATERIALS AND METHODS. 58 patients were treated with 375 heat-pressed monolithic crowns, which were bonded with resin cement. Annual recalls up to five years included a complete dental examination as well as quality assessment using CDA-criteria. Any need for clinical intervention led to higher complication rate and any failure compromised the survival rate. Kaplan-Meier-method was applied to all crowns and a dataset containing one randomly selected crown from each patient. RESULTS. Due to drop-outs, 45 patients (31 females, 14 males) with the average age of 43 years (range = 17-73) who had 327 crowns (176 anterior, 151 posterior; 203 upper jaw, 124 lower jaw) were observed and evaluated for between 4 and 51 months (median = 28). Observation revealed 4 chippings, 3 losses of retention, 3 fractures, 3 secondary caries, 1 endodontic problem, and 1 tooth fracture. Four crowns had to be removed. Survival and complication rate was estimated 98.2% and 5.4% at 24 months, and 96.8% and 7.1% at 48 months. The complication rate was significantly higher for root canal treated teeth (12%, P<.01) at 24 months. At the last observation, over 90% of all crowns showed excellent ratings (CDA-rating Alfa) for color, marginal fit, and caries. CONCLUSION. Heat pressed lithium disilicate crowns showed an excellent performance. Besides a careful luting, dentists should be aware of patients' biological prerequisites (grade of caries, oral hygiene) to reach full success with these crowns.

• The Journal of Advanced Prosthodontics
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• 제3권2호
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• pp.90-95
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• 2011

PURPOSE. To compare the fracture resistance and the mode of failure of endodontically treated teeth restored with different post-core systems. MATERIALS AND METHODS. Root canal treatment was performed on 40 maxillary incisors and the samples were divided into four groups of 10 each. For three experimental groups post space preparation was done and teeth were restored with cast post-core (Group B), stainless steel post with composite core (Group C) and glass fiber post with composite core using adhesive resin cement (Group D). Control group (A) samples were selected with intact coronal structure. All the samples were prepared for ideal abutment preparation. All the samples were subjected to a load of 0.5 mm/min at $130^{circ}$.until fracture occurred using the universal testing machine. The fracture resistance was measured and the data were analyzed statistically. The fracture above the embedded resin was considered to be favorable and the fracture below the level was considered as unfavorable. The statistical analysis of fracture resistance between different groups was carried out with t-test. For the mode of failure the statistical analysis was carried out by Kruskal-Wallis test and Chi-Square test. RESULTS. For experimental group Vs control group the fracture resistance values showed significant differences (P<.05). For the mode of failure the chi-square value is 16.1610, which means highly significant (P=.0009) statistically. CONCLUSION. Endodontically treated teeth without post core system showed the least fracture resistance demonstrating the need to reinforce the tooth. Stainless steel post with composite core showed the highest fracture resistance among all the experimental groups. Teeth restored with the Glass fiber post showed the most favorable fractures making them more amenable to the re-treatment.

• Imaging Science in Dentistry
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• 제44권2호
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• pp.89-94
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• 2014

Purpose: Vertical root fracture (VRF) is a common complication in endodontically treated teeth. Considering the poor prognosis of VRF, a reliable and valid detection method is necessary. Cone beam computed tomography (CBCT) has been reported to be a reliable tool for the detection of VRF; however, the presence of metallic intracanal posts can decrease the diagnostic values of CBCT systems. This study evaluated and compared the effects of intracanal stainless steel or titanium posts on the sensitivity, specificity, and accuracy of VRF detection using a NewTom VG CBCT system. Materials and Methods: Eighty extracted single-rooted teeth were selected and sectioned at the cemento-enamel junction. The roots were divided into two groups of 40. Root fracture was induced in the test group by using an Instron machine, while the control group was kept intact. Roots were randomly embedded in acrylic blocks and radiographed with the NewTom VG, both with titanium and stainless steel posts and also without posts. Sensitivity, specificity, and accuracy values were calculated as compared to the gold standard. Results: The sensitivity, specificity, and accuracy of VRF diagnosis were significantly lower in teeth with stainless steel and titanium posts than in those without posts. Interobserver agreement was the highest in teeth without posts, followed by stainless steel posts, and then titanium posts. Conclusion: Intracanal posts significantly decreased the VRF diagnostic values of CBCT. The stainless steel posts decreased the diagnostic values more than the titanium posts.