• Restorative Dentistry and Endodontics
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• 제44권3호
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• pp.33.1-33.12
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• 2019

Objectives: To evaluate the influence of the restorative technique on the mechanical response of endodontically-treated upper premolars with mesio-occluso-distal (MOD) cavity. Materials and Methods: Forty-eight premolars received MOD preparation (4 groups, n = 12) with different restorative techniques: glass ionomer cement + composite resin (the GIC group), a metallic post + composite resin (the MP group), a fiberglass post + composite resin (the FGP group), or no endodontic treatment + restoration with composite resin (the CR group). Cusp strain and load-bearing capacity were evaluated. One-way analysis of variance and the Tukey test were used with ${\alpha}=5%$. Finite element analysis (FEA) was used to calculate displacement and tensile stress for the teeth and restorations. Results: MP showed the highest cusp (p = 0.027) deflection ($24.28{\pm}5.09{\mu}m/{\mu}m$), followed by FGP ($20.61{\pm}5.05{\mu}m/{\mu}m$), CR ($17.62{\pm}7.00{\mu}m/{\mu}m$), and GIC ($17.62{\pm}7.00{\mu}m/{\mu}m$). For load-bearing, CR ($38.89{\pm}3.24N$) showed the highest, followed by GIC ($37.51{\pm}6.69N$), FGP ($29.80{\pm}10.03N$), and MP ($18.41{\pm}4.15N$) (p = 0.001) value. FEA showed similar behavior in the restorations in all groups, while MP showed the highest stress concentration in the tooth and post. Conclusions: There is no mechanical advantage in using intraradicular posts for endodontically-treated premolars requiring MOD restoration. Filling the pulp chamber with GIC and restoring the tooth with only CR showed the most promising results for cusp deflection, failure load, and stress distribution.

• Imaging Science in Dentistry
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• 제45권2호
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• pp.95-101
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• 2015

Purpose: This study used cone-beam computed tomography (CBCT) to characterize mandibular molar root and canal morphology and its variability in Belgian and Chilean population samples. Materials and Methods: We analyzed the CBCT images of 515 mandibular molars (257 from Belgium and 258 from Chile). Molars meeting the inclusion criteria were analyzed to determine (1) the number of roots; (2) the root canal configuration; (3) the presence of a curved canal in the cross-sectional image of the distal root in the mandibular first molar and (4) the presence of a C-shaped canal in the second mandibular molar. A descriptive analysis was performed. The association between national origin and the presence of a curved or C-shaped canal was evaluated using the chi-squared test. Results: The most common configurations in the mesial root of both molars were type V and type III. In the distal root, type I canal configuration was the most common. Curvature in the cross-sectional image was found in 25% of the distal canals of the mandibular first molars in the Belgian population, compared to 11% in the Chilean population. The prevalence of C-shaped canals was 10% or less in both populations. Conclusion: In cases of unclear or complex root and canal morphology in the mandibular molars, CBCT imaging might assist endodontic specialists in making an accurate diagnosis and in treatment planning.

• Restorative Dentistry and Endodontics
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• 제37권1호
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• pp.41-49
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• 2012

Objectives: The internal adaptation of composite restorations with or without resin modified glass ionomer cement (RMGIC) was analyzed non-destructively using Microcomputed tomography (micro-CT). Materials and Methods: Thirty intact human teeth were used. The specimens were divided into 3 groups. In the control group, the cavities were etched with 10% phosphoric acid for 15 sec. Composite resin was filled into the cavity without adhesive. In group 1, light cured glass ionomer cement (GIC, Fuji II LC, GC) was applied as a base. The cavities were then etched, bonded, light cured and filled with composites. In group 2, the cavities were then etched, bonded, light cured and filled with composites without base application. They were immersed in a 25% silver nitrate solution. Micro-CT was performed before and after mechanical loading. One-way ANOVA with Duncan analysis was used to compare the internal adaptation between the groups before or after loading. A paired t-test was used to compare internal adaptation before and after mechanical loading. All statistical inferences were made within the 95% confidence interval. Results: The silver nitrate solution successfully penetrated into the dentinal tubules from the pulp spaces, and infiltrated into the gap between restoration and pulpal floor. Group 2 showed a lower adaptation than the control group and group 1 (p < 0.05). There was no significant difference between the control group and group 1. For all groups, there was a significant difference between before and after mechanical loading (p < 0.05). Conclusions: The internal adaptation before and after loading was better when composites were bonded to tooth using adhesive than composites based with RMGIC.

• Restorative Dentistry and Endodontics
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• 제28권5호
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• pp.363-368
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• 2003

The purpose of this study is to evaluate the effect of additional enamel etching with phosphoric acid on the microleakage of the adhesion of self-etching primer system. Class V cavity($4mm{\times}3mm{\times}1.5mm$) preparations with all margins in enamel were prepared on buccal surface of 42 extracted human upper central incisor teeth. Prepared teeth were randomly divided into 3 groups. Group 1：no additional pretreatment with 37% phosphoric acid (NE). Group 2：additional pretreatment with 37% phosphoric acid for 10 seconds (E10s). Group 3：additional pretreatment with 37% phosphoric acid for 20 seconds (E20s). The adhesives(Clearfil SE $Bond^{\circledR}$, Kuraray, Osaka, Japan) and composite resins(Clearfil $AP-X^{\circledR}$, Osaka, Kuraray, Japan) were applied following the manufacturer's instructions. All the specimens were finished with the polishing disc(3M dental product, St Paul, MN, USA), thermocycled for 500 cycles between $5^{\circ}C$ and $55^{\circ}C$ and resected apical 3-mm root. 0.028 stainless steel wire was inserted apically into the pulp chamber of each tooth and sealed into position with sticky wax. Surrounding tooth surface was covered with a nail varnish 2 times except areas 1mm far from all the margins. After drying for one day, soaked the samples in the distilled water. Microleakage was assessed by electrochemical method(System 6514, $Electrometer^{\circledR}$), Keithley, USA) in the distilled water. In this study, the microleakage was the lowest in group 1 (NE) and the highest in group 3(E20s)(NE

• Imaging Science in Dentistry
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• 제51권4호
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• pp.383-388
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• 2021

Purpose: The aim of this study was to evaluate the root canal morphology of mesial roots of mandibular first molars. Materials and Methods: Forty extracted mandibular first molars were used in this study. The morphological examination of root canals was conducted in accordance with the Vertucci classification using micro-computed tomography (micro-CT). Any aberrant root canal configurations not included in the Vertucci classification were recorded, and their frequency was established using descriptive statistics. Intra-observer reliability was assessed using the Wilcoxon signed-rank test, while inter-observer reliability was assessed using the Cohen kappa test. Significance was evaluated at the P<0.05 level. Results: The mesial roots of mandibular first molars had canal configurations of type I (15%), type II (7.5%), type III (25%), type IV (10%), type V (2.5%), type VI (7.5%), and type VII (7.5%). The images showed 10 (25%) additional configuration types that were not included in the Vertucci classification. These types were 1-3-2-3, 1-2-3-2-3, 2-3-1, 2-3, 1-2-3-1, 2-1-2-3, 3-2-1, 1-2-3-1, 2-3-2-3, and 1-2-1-2-1. The intra-observer differences were not statistically significant(P>0.05) and the kappa value for inter-observer agreement was found to be 0.957. Conclusion: Frequent variations were detected in mesial roots of mandibular first molars. Clinicians should take into consideration the complex structure of the root canal morphology before commencing root canal treatment procedures to prevent iatrogenic complications. Micro-CT was a highly suitable method to provide accurate 3-dimensional visualizations of root canal morphology.

• Imaging Science in Dentistry
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• 제53권1호
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• pp.77-82
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• 2023

Purpose: This study evaluated anatomical variations in the root canals of the lower premolars and molars in a Brazilian sub-population using cone-beam computed tomography (CBCT). Materials and Methods: In total, 121 CBCT images of patients were selected from a database. All images contained lower first and second premolars and molars on both sides of the arch, fully developed roots, and no treatment, resorption, or calcifications. In each image, the root canals of the lower premolars and molars were evaluated according to the Vertucci classification in On-Demand 3D software in the multiplanar reconstruction with dynamic navigation. Twenty-five percent of the images were re-assessed to analyze intraobserver confidence with the kappa test. Data were statistically evaluated with linear regression to evaluate the correlations of anatomic variations with age and sex, and the Wilcoxon test to analyze the laterality of variations, with a significance level of 5%. Results: The intraobserver agreement (0.94) was excellent. In general, the root canals of lower premolars and molars showed a higher prevalence of type I than other Vertucci classification types, followed by type V in premolars and type II in molars. When the molar roots were evaluated separately, type II was more frequent in mesial roots and type I in distal roots. Although age showed no correlations with the results, sex and laterality showed correlations with tooth 45 and the lower second premolars, respectively. Conclusion: The lower premolars and molars of a Brazilian sub-population showed a wide range of root canal anatomic variations.

• Restorative Dentistry and Endodontics
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• 제46권4호
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• pp.56.1-56.11
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• 2021

Objectives: This study evaluated 2 nickel-titanium rotary systems and a complementary protocol with an ultrasonic tip and a small-diameter instrument in flattened root canals. Materials and Methods: Thirty-two human maxillary second premolars with flattened canals (buccolingual diameter ≥4 times larger than the mesiodistal diameter) at 9 mm from the radiographic apex were selected. The root canals were prepared by ProDesign Logic (PDL) 30/0.01 and 30/0.05 or Hyflex EDM (HEDM) 10/0.05 and 25/0.08 (n = 16), followed by application of the Flatsonic ultrasonic tip in the cervical and middle thirds and a PDL 25/0.03 file in the apical third (FPDL). The teeth were scanned using micro-computed tomography before and after the procedures. The percentage of volume increase, debris, and uninstrumented surface area were analyzed using the Kruskal-Wallis, Dunn, Wilcoxon, analysis of variance/Tukey, and paired and unpaired t-tests (α = 0.05). Results: No significant difference was found in the volume increase and uninstrumented surface area between PDL and HEDM (p > 0.05). PDL had a higher percentage of debris than HEDM in the middle and apical thirds (p < 0.05). The FPDL protocol resulted in less debris and uninstrumented surface area for PDL and HEDM (p < 0.05). This protocol, with HEDM, reduced debris in the middle and apical thirds and uninstrumented surface area in the apical third (p < 0.05). Conclusions: High percentages of debris and uninstrumented surface area were observed after preparation of flattened root canals. The HEDM, Flatsonic tip, and 25/0.03 instrument protocol enhanced cleaning in flattened root canals.

• Journal of Oral Medicine and Pain
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• 제30권3호
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• pp.375-381
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• 2005

기존의 치과용 핸드피스를 대체할 수 있는 효과적인 치아 삭제 방법인 Er:YAG 레이저를 이용하여 보다 효과적으로 치아를 삭제하기 위해 여러 가지 변수들, 즉 펄스에너지, 조사반복율 및 레이저 조사 동안의 물분사량에 대한 다양한 연구가 진행되어 왔다. 특히 이 중에서도 물분사량은 삭제 효율이 높이면서 치수를 보호할 수 있는 중요한 요소로 여겨지고 있다. 레이저 조사 동안 분사되는 물의 양이 적으면 치아에 균열이나 탄화를 유발하고 치수손상을 야기할 수 있는 위험이 있는 반면, 물의 양이 지나치게 많으면 삭제효율이 저하되고 레이저 시술동안 치과의사의 시야확보를 방해할 수 있으므로, 조사조건에 따른 가장 적절한 물 분사량을 결정하는 것이 아주 중요하다. 본 연구에서는 특정조사조건에서 치아법랑질 삭제에 가장 효과적인 물분사량을 결정하고, 그 물분사량을 적용하였을 때 치수내에서 발생하는 온도변화를 측정하여 안전성 여부를 함께 평가하고자 하였다. 발거된 건전치아를 표본으로 하여, 20 Hz의 조사반복율, 200 mJ 및 300 mJ의 펄스에너지의 조사조건에서 1.6, 3.0, 5.0, 7.0, 10.0 ml/min의 서로 다른 물분사량을 적용하여 치아삭제 효과를 평가하였다. 이때 레이저 조사시간은 3초로 고정하였다. 삭제효율은 조사 전후의 치아무게를 측정하여 그 차이로 결정하였으며 온도측정을 위해서는 별도의 치아를 준비하여 온도측정장치를 조사측과 반대측의 치수벽에 위치하여 레이저조사 동안의 온도변화를 추적하였다. 실험결과, 200 mJ과 300 mJ 모두에서 1.6 ml/min의 가장 적은 물분사량이 치아삭제효율이 가장 좋았다. 또한 이 조건에서의 온도변화를 측정한 경우에도 치수손상을 일으키지 않을 정도의 미미한 온도상승만을 보여주었다. ANOVA 분석의 결과 조사부위(조사측과 비조사 반대측)에 따른 유의한 차이가 나타났으나(p<0.05), 펄스에너지에 따라 각각 비교하였을 때는 유의한 차이를 보여주지 않았다. 그러므로 본 실험의 결과에 따르면, 1.6 ml/min의 비교적 적은 양의 물을 레이저 조사시에 함께 분사해 준다면 200$\sim$300 mJ의 펄스에너지, 20 Hz의 조사반복율, 3초의 레이저조사시간이라는 조건에서는 치수손상을 일으키지 않는 안전한 범위에서 가장 효과적으로 치아를 삭제할 수 있을 것으로 생각된다.

• 대한소아치과학회지
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• 제36권2호
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• pp.275-280
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• 2009

치근단 낭은 염증 등에 의한 자극으로 치수가 실활되어 치근단에 있는 상피로부터 형성되는 낭종으로 주된 기원은 말라세즈 상피판사이지만 치은열구 상피나 상악동 이장 상피 누공의 싱피에 의한 것도 보고 되었다. 구강악안면 영역에서 가장 흔히 발생되는 낭종의 하나이지만 유치열기에서의 발생 빈도는 낮은 것으로 알려져 있다. 악골 내의 치성 낭종든 크기가 커지면서 주위 조직의 파괴나 구조의 변형을 초래할 수 있으며 유치의 경우에서는 후속 영구치배의 변위를 유발할 수 있다. 이런 큰 크기의 치성 낭종을 외과적으로 제거하면 해부학적 구조의 손상 및 안모의 변형, 치아 흡수, 신경손상 등의 후유증을 일으킬 수 있으므로 조대술이나 감압술 후 적출하는 술식이 권장되고 있다. 이 증례는 하악 우측 부위의 동통을 주소로 연세대학교 치과대학병원 소아치과에 내원한 8세 남아로, 임상 및 방사선학적 검사 결과 치수치료 후 기성금속관의 수복을 시행한 하악 우측 제1유구치와 치근단 하방에 방사선투과성 병변과 견치와 제1소구치의 변위를 발견하였다. 병소가 있는 하악 우측 제1유구치를 발거하였고, 조직학적 검사에서 치근단 낭으로 진단되었다. 감압술 및 공간유지장치를 시행하고 병소의 크기 변화와 하악 우측 견치와 제1소구치의 맹출 양상을 정기적으로 관찰한 결과 양호한 치유 양상과 정상적인 맹출을 보였기에 이를 보고하고자 한다.

• Restorative Dentistry and Endodontics
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• 제23권2호
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• pp.701-709
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• 1998

Many dental composites are Bis-GMA based resin which diluted with the more fluid monomer triethylenglycol dimethacrylate(TEGDMA). TEGDMA is often present in exess so that some quantity remains unreacted following photo-initiated polymerization. TEGDMA is a component of some resin composites which contributes to their cytotoxicity. The presence of dentin between resin composite and pulp space reduce the cytotoxicity in vitro. The root system from extrcted human third molar was removed and then a circular occlusal cavity 4mm in diameter was prepared, leaving a remaining dentinal thickness to the roof of the pulpal chamber within the range 1.0-1.5mm. Dentine was treated with 37% phosphoric acid prior to Z 100 placement without using bonding resin(group 1). In group 2, SMP(Scotchbond Multi Purpose) primer, bonding resin prior to Z 100 placement were applied sequently. In group 3, moulds with internal dimensions 4mm diameter by 2mm depth were used to contain the composite alone with an equvalent mass on tooth model, and then they were immersed directly into water. The purpose of this study is to evaluate the release rate and quantity of TEGDMA with or without the application of bonding resin. Both release rate and total cumulative amount of TEGDMA for the three groups were determined using reversed-phase HPLC at times up to 10 days. The results were as follows: 1. All experimental groups showed the highest rate of release was in the first sample period(0-4.32 min) and the rate of release declined exponentially thereafter. 2. The maximum release rate and total cumulative account of TEGDMA in the tooth model of group 1 and group 2 with the use of SMP bonding resin were reduced however ther were no significant differences between these groups(P>0.05). 3. In the first sample period(0-4.32 min), the rate of release of TEGDMA from composite resin in group 3 immersed directly into water was significantly higher than that in group 1 and group 2 of tooth model(P<0.05). Conclusively, TEGDMA diffusion from Z 100 resin was not effectively prevented by the presence of dentin in spite of using the SMP bonding resin.