• 대한치과보철학회지
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• 제33권3호
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• pp.397-412
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• 1995

The purpose of this study was to analyze the stress distribution in the dentin and post structures by the various post core materials and the amount of remaining coronal tooth structures. The 2-dimensional finite element models of mandibular 2nd premolars was divided into seven types according to the various amount of remaining coronal tooth structures. All types were modeled using equal length, diameter and shape of the post. 2 types of post and core materials were used : 1) cast gold post and core 2) stainless steel post and compsite resin core 10 Newton force was applied as follows 1) vertical force on occlusal fossa 2) $45^{\circ}$ oblique force on buccal surface of buccal cusp tip The results were as follows : 1. There was no apparent difference in the pattern of stress distribution according to the amount of remaining coronal tooth structure. 2. There was no apparent difference in the pattern of stress distribution within the dentin according to the post and core materials. A cast gold post and core generated lower dentin stress than a stainless steel post and resin core. 3. Max. dentinal stress resulting from vertical force was observed in the lingual side of dentin around the crown margin.This stress resulting from oblique force was observed in the lingual root surface of alveolar bone crest level.

• Restorative Dentistry and Endodontics
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• 제23권2호
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• pp.710-717
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• 1998

The pH changes in 3 cavities prepared at the facial inner dentin and lingual outer dentin of the cervical portion and apical portion of roots filled with calcium hydroxide containing sealers were investigated. 50 extracted permanent teeth with single canal were instrumented with step-back method. An irrigant of 5% NaOCl was used between files. Then 3 small cavities were prepared. The cavity of apical portion and inner dentin cavity of coronal portion was cut a distance of about 1.0mm from the canal wall and outer dentin cavity of coronal portion was cut to a depth of about 0.5mm from root surface. 10 teeth of control group was not filled. 20 teeth were not flushed with 17% EDTA before using root canal sealers and then divided into 2 groups obturated with Sealapex and Apexit. The remaining 20 teeth were flushed with 17% EDTA and 5% NaOCl to remove smear layer and divided into 2 groups obturated with Sealapex and Apexit. The pH change of the dentin in each cavity was measured at 0, 1, 3, 5, 7, 15, 30 days with pH microelectrode(WPI Co., USA). The results were as follows: 1. The groups obturated with Sealapex and Apexit(calcium hydroxide based-sealers) have no increase in the pH level at root dentin. And there is no significant difference in pH level between groups obturated with Sealapex and Apexit(P>0.05). 2. Differences in pH levels between the treated and untreated groups with EDTA were not significant(P>0.05). 3. There is no significant difference in pH level between apical and cervical dentin, inner and outer dentin throughout the duration of the experiment(P>0.05).

• Restorative Dentistry and Endodontics
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• 제40권2호
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• pp.136-142
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• 2015

Objectives: The aim of this study was to evaluate the effects of tri-antibiotic paste (TAP) on microtensile bond strengths (MTBS) of dental adhesives to dentin. Materials and Methods: Sixty extracted molars had their occlusal surfaces flattened to expose dentin. They were divided into two groups, i.e., control group with no dentin treatment and experimental group with dentin treatment with TAP. After 10 days, specimens were bonded using self-etch (Filtek P90 adhesive) or etch-and-rinse (Adper Single Bond Plus) adhesives and restored with composite resin. Teeth were sectioned into beams, and the specimens were subjected to MTBS test. Data were analyzed using two-way ANOVA and post hoc Tukey tests. Results: There was a statistically significant interaction between dentin treatment and adhesive on MTBS to coronal dentin (p = 0.003). Despite a trend towards worse MTBS being noticed in the experimental groups, TAP application showed no significant effect on MTBS (p = 0.064). Conclusions: The etch-and-rinse adhesive Adper Single Bond Plus presented higher mean bond strengths than the self-etch adhesive Filtek P90, irrespective of the group. The superior bond performance for Adper Single Bond when compared to Filtek P90 adhesive was confirmed by a fewer number of adhesive failures. The influence of TAP in bond strength is insignificant.

• Restorative Dentistry and Endodontics
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• 제44권3호
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• pp.25.1-25.10
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• 2019

Objective: The aim of this study was to evaluate discoloration of teeth undergoing regenerative endodontic procedures (REPs) using blood clot or platelet-rich fibrin (PRF) as the scaffolds and different calcium silicate-based materials as the intracanal coronal barriers in an ex vivo model. Materials and Methods: Forty-eight bovine incisors were prepared and disinfected using 1 mg/mL double antibiotic paste (DAP). The specimens were then randomly divided into 2 groups (n = 24) according to the scaffolds (blood or PRF). After placement of scaffolds each group was divided into 2 subgroups (n = 12) according to the intracanal coronal barriers (ProRoot MTA or Biodentine). The pulp chamber walls were sealed with dentin bonding agent before placement of DAP and before placement of scaffolds. The color changes (${\Delta}E$) were measured at different steps. The data were analyzed using 2-way analysis of variance. Results: Coronal discoloration induced by DAP was not clinically perceptible (${\Delta}E{\leq}3.3$). Regarding the type of the scaffold, coronal discoloration was significantly higher in blood groups compared with PRF groups at the end of REP and after 1 month (p < 0.05). However, no significant difference was found between PRF and blood clot after 6 months (p > 0.05). Considering the type of intracanal coronal barrier, no significant difference existed between ProRoot MTA and Biodentine (p > 0.05). Conclusions: With sealing the dentinal tubules of pulp chamber with a dentin bonding agent and application of DAP as an intracanal medicament, coronal color change of the teeth following the use of PRF and blood sealed with either ProRoot MTA or Biodentine was not different at 6-month follow-up.

• Restorative Dentistry and Endodontics
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• 제24권2호
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• pp.337-345
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• 1999

The purpose of this study was to compare the shape of root canal after instrumentation with some engine driven NiTi files. Thirty narrow and curved canals(15-35 degree) of mesial canals of extracted human mandibular first molars were divided into three groups. Group 1: After radicular access with Gates Glidden drill, apical shaping using step back method with Flexo file Group 2: After radicular access with Gates Glidden drill, apical shaping with Profile .04 Group 3: Canal shaping with GT file and Profile .04. Using modified Bramante technique, the root was sectioned at 2 mm from apical foramen, height of curvature, 2 mm from canal orifice. Canal centering ratio, amount of transport, amount of dentin removed, shape of canal were measured and statistical analysis is done using SPSS Program V 7.5. The results were as follows: 1. Canal centering ratio of group 3 was the lowest at coronal part, but there was no statistical difference. Centering ratio of group 2 was the lowest at curve part, and there was statistical difference between group 1(P<0.05). Centering ratio of group 2 was the lowest at apical part, but there was no statistic difference. 2. Amount of transport of group 3 was the lowest at coronal part, but there was no statistical difference. Amount of transport of group 2 was the lowest at curve part, and there was statistical difference between group 1(P<0.05). Amount of transport of group 3 was the lowest at apical part, and there was statistical difference between group 1 and group 2, group 1 and group 3(P<0.05). 3. Amount of dentin removed of group 3 was the lowest at coronal part, bur there was no statistical difference. Amount of dentin removed of group 2 was the lowest at curve part, but there was no statistical difference. Amount of dentin removed or group 2 was the lowest at apical part, and there was statistical difference between group 1 and group 2, group 1 and group 3(P<0.05). 4. The shape of the canals after instrumentation varied among the groups. The majority of canals at coronal and curve part for group 1 were round in shape(7 in 10), those at apical part were oval(8 in 10). The majority of canals at coronal part for group 2 were round in shape(7 in 10) and there was no difference in the number of shape at other part. There was no difference in the number of shape at every part for group 3. As above results, NiTi rotary instrumentation showed a trend to remain more centered in the canal than SS file instrumentation. At using NiTi file, coronal shaping with Gates Glidden drill was not statistically different from shaping with GT file. But shaping with GT file showed tapered canals, so it may be said that shaping with GT file is a safe and valuable instrumentation method.

• 대한소아치과학회지
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• 제41권1호
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• pp.47-53
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• 2014

상아질 이형성증은 매우 드물게 발생하는 상염색체 우성 유전 질환이다. 발생학적 원인에 대해서는 아직 명확하게 알려지지 않았으며 인구 100,000당 1명의 발병률을 나타낸다. 상아질 이형성증은 두 가지 형으로 분류가 되며, 치근부위 상아질 형성이상을 보이는 치근형의 제 1형과 치관부위 상아질 형성이상을 보이는 치관형인 제 2형으로 나눠진다. 제 1형 상아질 이형성증은 임상적으로 정상적인 치관형태을 보이고 있으나 동요도를 가지며 방사선학적으로 치수강과 치근관의 폐쇄, 짧은 원추형의 치근형태 및 자발적으로 형성된 치근단 병소가 특징적으로 관찰된다. 본 논문은 한 가족 내에서 아버지를 제외한 4명의 가족 구성원들에게 발생한 제 1형 상아질 이형성증을 관찰한 바, 이에 대해 이환된 가족 구성원들의 임상, 방사선학 및 조직병리학적 소견을 보고하고자 한다. 제 1형 상아질 이형성증은 방사선학적 검사를 시행하지 않고서는 임상적으로 인지하기 어려우며 조기 진단을 통해 정기적인 구강 위생 관리 및 예방치료를 시행할 경우 이환된 치아의 조기 탈락을 예방하거나 지연시킬 수 있을 것이다.

• Restorative Dentistry and Endodontics
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• 제24권2호
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• pp.322-329
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• 1999

The hydrodynamic theory of dentin sensitivity states that movement of tubular contents or tubular fluid, in either direction of dentinal tubule, causes dentin sensitivity. A corollary of that theory is that anything that can decrease dentinal fluid movement or dentin permeability should decrease dentin sensitivity. A wide variety of physicochemical methods have been used to reduce the permeability and sensitivity of exposed dentin. The purpose of this study was to evaluate the ability of 4 kinds of clinical desensitizing agents(2% NaF, 30% Potassium oxalate, MS Coat$^{(R)}$, Tubulitec system$^{(R)}$) to reduce the rate of fluid flow through dentin in vitro. Sixty coronal dentin discs, 1mm in thickness, were prepared from extracted third molars, free from decay and wear. Dentin discs were treated with 3% EDTA(Tubulicid Plus$^{(R)}$(Dental Therapeutics AB, Sweden)) to remove the smear layer and debris occluding the tubular orifices. After placing the discs in a split chamber device, the rate at which physiologic saline solution could filter across dentin under 150cm $H_2O$ hydrostatic pressure was measured. The occlusal side of the discs were then treated with MS Coat$^{(R)}$, 2% NaF, Tubulitec system$^{(R)}$, and 30% Potassium oxalate, and the filter ratio of the saline solution was measured again. The following conclusions were drawn : 1. Hydraulic conductance which was measured after the application of desensitizing agents was decreased in all the groups(p<0.05). 2. % change of hydraulic conductance was compared but no significant difference was found among the four desensitizing agents(p>0.05). 2% NaF, 30% Potassium oxalate, MS Coat$^{(R)}$ and Tubulitec system$^{(R)}$ decreased the permeability of dentin. It is considered that above four agents can be used in treating the hypersensitive teeth.

• Restorative Dentistry and Endodontics
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• 제23권1호
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• pp.468-476
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• 1998

The purpose of this study was to observe the morphologic change of dentinal surface, adhesion in interface between dentin and bonding agents, and penetration pattern of resin tags into dentinal tubles according to bonding procedure of ONE-STEP universal adhesive system. Ten extracted human molars were mounted in dental stone and sectioned to expose mid-coronal occlusal dentin and again sectioned tooth crown apically. Specimens were randomly assigned to three groups for dentin conditioning with 32% phoshoric acid, two coats of bonding agents after dentin conditioning, and bond of composite resin. The surfaces of dentin were treated with etch ant and applied bonding agent, and bonded composite resin according to the directions of manufacturer. Specimens which were boned composite were sectioned longitudinally for observing interfaces between resin and dentin. Two of specimens which were sectioned longitudinally were immersed in 6 N HCL for 30 seconds and 1% NaOCL for 12 hours to partially demineralize and deproteinize the dentin substrate. Each specimen was mounted on a brass stub, sputter-coated with gold and observed under SEM. The result were as follows : 1. On the dentinal surface which was conditioned with 32% phosphoric acid. the smear layer was completely removed. orifices of dentinal tubules were opened 3-$5{\mu}m$ wide. and dentinal surface was irregular. 2. On the dentinal surface which was applied ONE-STEP. bonding agent. resin particles were observed on the orifices of dentinal tubules and intertubular dentin. 3. There were close adaptation between dentin and resin and were the pattern which composite invaded into dentin. 4. 1-$3{\mu}m$-wide hybrid layer was visible in the interface between dentin and resin. 5. Long and funnel shaped resin tags were observed in demineralized specimens. and the surfaces of tags were rough.

• Restorative Dentistry and Endodontics
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• 제29권3호
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• pp.233-238
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• 2004

The purpose of this study was to evaluate the effect of immediate or delayed composite resin filling on dentinal microtensile bond strength (${\mu}TBS$) after applied the adhesive. The coronal dentin of human third molars was exposed. Single-Bond or One-Step was applied on the dentin surfaces. and composite resin were constructed immediately (group 1) or 5min., 10min., 15min., 20min. and 30min. (groups 2-6) after an adhesive was applied. The specimens were sectioned and made bar-shaped. Each surface area of them was about $1\textrm{mm}^2$. The ${\mu}TBS$ test was performed by EZ test. The results were analysed by One-way ANOVA and Tukey's test at 95% significance level. The results suggested that the ${\mu}TBS$ of Single-Bond to dentin was decreased when the composite resin was constructed 20min. and 30min. after Single-Bond was applied. But the ${\mu}TBS$ of One-Step was not affected by delayed composite resin filling.

• Restorative Dentistry and Endodontics
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• 제42권3호
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• pp.188-199
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• 2017

Objectives: This in vitro study evaluated the effect of dentin biomodifiers on the immediate and long-term bond strengths of a simplified etch and rinse adhesive to dentin. Materials and Methods: Flat coronal dentin surfaces were prepared in 120 extracted human molars. Teeth were randomly divided into 5 groups (n = 24) according to 5 different surface pre-treatments: No pre-treatment (control); 1M carbodiimide (EDC); 0.1% epigallocatechin-3-gallate (EGCG); 2% minocycline (MI); 10% sodium ascorbate (SA). After surface pre-treatment, adhesive (Adper Single Bond 2 [SB], 3M ESPE) was applied. Composite was applied into transparent plastic tubes (2.5 mm in diameter), which was placed over the bonded dentin surface. From each group, 10 samples were subjected to shear bond strength (SBS) evaluation at 24 hours (immediate) and remaining 10 samples were tested after 6 months (delayed). Additionally, 4 samples per group were subjected to scanning electron microscopic analysis for observation of resin-dentin interface. The data were statistically analysed with Shaperio-Wilk W test, 2-way analysis of variance (ANOVA), and post hoc Tukey's test. Results: At 24 hours, SBS of all surface pre-treatment groups were comparable with the control group, with significant differences found between EDC and SA groups only (p = 0.009). After 6 months storage, EDC, EGCG, and MI pre-treatments preserved the resindentin bond strength with no significant fall. Conclusions: Dentin pre-treatment with all the dentin biomodifiers except SA resulted in significant preservation of resin-dentin bond over 6 months storage period, without negatively affecting the immediate bond strength of the etch and rinse adhesive tested.