• The korean journal of orthodontics
• /
• v.34 no.4 s.105
• /
• pp.333-342
• /
• 2004

The purpose of this study was to evaluate the clinical effectiveness of a plasma arc light and light emitting diode (LED), compared with shear bond strength and the failure pattern of brackets bonded with visible light in direct bonding. Brackets were bonded with Transbond XT to 60 human premolars embedded in the resin blocks according to different light-curing methods. Then, the shear bond strength of each group was measured using a universal testing machine (Instron) and the adhesive failure pattern after debonding was visually examined by light microscope. The results were as follows: 1. The shear bond strength showed no significant difference between the visible light and light emitting diode, but the plasma arc light exhibited a significantly lower shear bond strength compared with the visible light and light emitting diode. 2. In the visible light and light emitting diode, adhesive failure patterns were similar. Bond failure occurred more frequently at the enamel-adhesive interface. 3. The bonding failure of brackets bonded with plasma arc light occurred more frequently at the bracket-adhesive interface. The results of this study suggest that plasma arc light, light emitting diode and visible light are all clinically useful in the direct bonding of orthodontic brackets.

• The korean journal of orthodontics
• /
• v.28 no.4 s.69
• /
• pp.659-668
• /
• 1998

The purpose of this study was to evaluate the possibility of the decrease of bond strength due to increased thickness of resin base in indirect bracket bonding technique. Metal brackets were bonded to the resin blocks involving bovine lower incisors and the thickness of resin bases was increased by increments of 0.5 mm from 0.0 mm to 2.0 mm. They were divided into two groups, one group is that the thickness of resin base was increased but the loading point from the tooth surface was maintained constantly, the other group is that the loading point from the tooth surface and the resin base thickness were increased concomitantly. The shear bond strength was tested on universal testing machine and the failure patterns were assessed with the adhesive remnant index(ARI). The results were as follows: 1. When the distance from the tooth surface to the loading point was maintained constantly, shear bond strength was increased significantly according to the decrease of distance from the bracket base to the loading point and the increase of resin base thickness. 2. When the distance from the tooth surface to the loading point and the resin base thickness were increased concomitantly, shear bond strength was decreased according to the increase of resin base thickness but significant differences were ignorable. 3. There were no significant differences in ARI scores according to the change in the thickness of resin base. The results of the present study indicated that shear bond strength was not much affected by the thickness of resin base, whereas was decreased according to the increase of distance from bracket base to the loading point.

• The Journal of the Korea Contents Association
• /
• v.10 no.11
• /
• pp.228-234
• /
• 2010

Ni-Cr and Co-Cr alloy uncontained Be element for using as dental porcelain alloy were analyzed the mechanical properties through bonding strength and fracture test after the bonding with porcelain. The bonding strengths between alloy and ceramic were measured through the shear bond strength test. Consequently, the T-3 group contained Be element that had shear strength of 41.13(${\pm}5.11$)MPa was showed the highest shear strength than the other groups. The second highest group was a verabond contained Be element that had shear strength of 40.72(${\pm}5.98$)MPa. The results of the other groups according to the shear strength were Wirobond(38.40(${\pm}9.66$)MPa) belonged to Co-Cr alloy, and Verabond 2V(32.77(${\pm}4.31$)MPa), Bellabond N(28.63(${\pm}6.39$)MPa), Bellabond plus(24.97(${\pm}6.13$)MPa), Argeloy N.P. Star(22.69(${\pm}3.41$)MPa) uncontained Be element, respectively. The morphological aspects of the fracture surface between alloys and ceramic were observed that all groups were caused mixed failure as conformation attached ceramic fragments to metallic surface by fracture process.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.4
• /
• pp.2585-2592
• /
• 2015

The purpose of this study was to evaluate the shear bond strength between metal core fabricated by 3D printing and dental porcelain. Thirty metal cores were fabricated(cast 15ea, 3D printing 15ea). The porcelain for each group was builded to the metal core. Sample was loaded to shear force(crosshead speed 1mm/min) in a universal material testing machine. The fracture samples were analyzed failure aspect. The means were statistical analyzed using by Mann-whitney test(${\alpha}=0.05$). The period of experimental(metal cores fabrication, dental porcelain build up, data analysis, statistical analysis, failure aspect analysis and others) for this study took six months. The $mean{\pm}SDs$ of shear bond strength was $50.14{\pm}1.60MPa$ for the cast group, and $54.36{\pm}3.18MPa$ for the 3D printing group(p=0.035). The failure aspect showed mixed failure. As a results, metal cores fabricated by 3D printing method were clinically acceptable range.

• Restorative Dentistry and Endodontics
• /
• v.36 no.1
• /
• pp.50-58
• /
• 2011

Objectives: The purpose of this study was to compare the microshear bond strength (uSBS) of two totaletch and four self-etch adhesive systems and a flowable resin to enamel. Materials and Methods: Enamels of sixty human molars were used. They were divided into one of six equal groups (n = 10) by adhesives used; OS group (One-Step Plus), SB group (Single Bond), CE group (Clearfil SE Bond), TY group (Tyrian SPE/One-Step Plus), AP group (Adper Prompt L-Pop) and GB group (G-Bond). After enamel surfaces were treated with six adhesive systems, a flowable composite resin (Filek Z 350) was bonded to enamel surface using Tygon tubes. the bonded specimens were subjected to uSBS testing and the failure modes of each group were observed under FE-SEM. Results: 1. The uSBS of SB group was statistically higher than that of all other groups, and the uSBS of OS, SE and AP group was statistically higher than that of TY and GB group (p < 0.05). 2. The uSBS for TY group was statistically higher than that for GB group (p < 0.05). 3. Adhesive failures in TY and GB group and mixed failures in SB group and SE group were often analysed. One cohesive failure was observed in OS, SB, SE and AP group, respectively. Conclusions: Although adhesives using the same step were applied the enamel surface, the uSBS of a flowable resin to enamel was different.

• The Journal of Korean Academy of Prosthodontics
• /
• v.57 no.2
• /
• pp.127-133
• /
• 2019

Purpose: The purpose of present study was to investigate fracture strength and mode of failure of endodontically treated teeth restored with metal cast post-core system, prefabricated fiber post system, and newly introduced polyetherketoneketone (PEKK) post-core system. Materials and methods: A total of 21 mandibular premolar were randomly grouped into 3 groups of 7 each according to the post material. Group A was for metal cast post core; Group B for prefabricated glass fiber post and resin core; and Group C for milled PEKK post cores. All specimens were restored with metal crown. The fracture strength of each specimen was measured by applying a static load of 135-degree to the tooth at 2 mm/min crosshead speed using a universal testing machine. After the fracture strength measurement, the mode of failure was observed. The results were analyzed using Kruscal-Wallis test and post hoc Mann-Whitney U test at confidence interval ${\alpha}=.05$. Results: Fracture resistance of PEKK post core was lower than those of cast metal post and fiber reinforced post with composite resin core. In the aspect of fracture mode most of the root fracture occurred in the metal post core, whereas the post detachment occurred mainly in the fiber reinforced post. In the case of PEKK post core, teeth and post were fractured together. Conclusion: It is necessary to select appropriate materials of post for extensively damaged teeth restoration and clinical application of the PEKK post seems to require more research on improvement of strength.

• Restorative Dentistry and Endodontics
• /
• v.30 no.3
• /
• pp.184-192
• /
• 2005

Intracanal separation of the rotary files is a serious concern in modern endodontic practice. The objective of this study was to compare the life span and fracture patterns of three NiTi rotary files in molar teeth Mesiobuccal roots of upper molar (n = 150) and mesial roots of lower molar (n = 150) were divided into three groups and each group was prepared with Profile, ProTaper, and K3 respectively. Every file was used until separation and/or deterioration of the cutting blade was happened, and then the number of canals to separation and/or unwinding were recorded. Radiographs and Scanning electon microscope (SEM) photographs were taken to evaluate the patterns of separation. The results were as follows: 1. There were no significant differences in numbers of canals to separation and/or unwinding among the groups. 2. Comparing between flaring files, K3 showed significant lower numbers of canals to separation and/or unwinding (p < 0.05), and there was no significant difference between shaping files 3. Separations of instruments were occurred at the midpoint of curvatures within the canals 4. In SEM observations, ductile fractures were seen in most of cases, characterized by shallow dimples. Additional researches is needed to provide a new guideline that informs the appropriate number of times to use NiTi files.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2017.05a
• /
• pp.76-76
• /
• 2017

Ni-Ti 파일은 근관치료 시 근관형성에 사용되며 근관계 내 조직 잔사와 세균 을 포함한 모든 내용물을 제거하고 미세누출이 생기지 않도록 성공적으로 근관충전을 할 수 있는 근관의 형태를 만드는데 사용된다. Ni-Ti 파일은 수동형 파일처럼 날이 풀어지거나 예각으로 꺾이는 등 시각적으로 나타나는 파일의 피로도나 손상정도를 인지하기 어려워 파일이 근관 내에서 부러지는 것을 막기가 어렵다. Ni-Ti 파일은 육안으로 관찰 할 수 있는 구부러짐이나 풀림 등의 소성변형 없이 기구의 탄성한계 내에서 갑작스럽게 파절되는 경우가 있는데, 이는 만곡 근관 내에서 기구가 회전하는 동안 만곡의 안쪽에는 압축응력이, 만곡의 바깥쪽에는 인장응력이 반복적으로 가해짐으로써 파절의 표면에 미세 파절과 균열이 발생하고 전파되어 결국 피로파절(fatigue fracture)을 야기하게 된다. 또한 Ni-Ti파일이 반복응력을 받으면 균열이 형성되면서 파절이 야기되며 연성파절(ductile fracture) 양상을 나타낸다고 보고하였다. Ni-Ti 파일을 이용한 피로파절에 대한 이전의 연구에서는 파일의 직경이나 경사도 (taper), 단면 형태 및 회전속도, 표면결함 등이 파절에 영향을 미친다고 보고되고 있다. 사용하지 않은 Ni-Ti파일을 구부려 응력을 가 한 상태에서 주사전자현미경으로 관찰한 결과 기계 가공 과정에서 발생한 균열, 미세 결함, 긁힌 자국 및 불균질성 등이 원인으로 알려져 있다. 따라서 본 연구발표에서는 표면결함을 최소화하고 기구의 회전응력 하에서 피로파절저항성을 향상시키기 위한 방법에 대하여 알아보고자 한다.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.35 no.3
• /
• pp.153-159
• /
• 2019

Purpose: Aims to analyze the occlusal wear patterns in maxillary posterior teeth with palatal side abfractions and study the association between occlusal force and abfractions. Materials and Methods: This study was conducted in a total of 308 teeth from 148 patients with palatal side abfractions in maxillary posterior teeth. The occlusal wears in maxillary premolars and molars with palatal side abfractions were classified and recorded. The classification was done by type of teeth, age, and gender, and in order to evaluate the statistical significance between groups, chi-square test was conducted (${\alpha}=0.05$). Results: Palatal side abfractions in maxillary posterior teeth were observed at the highest frequency in the 1st molars, and in all teeth with palatal side abfractions, more than one occlusal wear was observed. In classification by type of teeth, by age, and by gender, the occlusal wears in teeth with palatal side abfractions were observed at high frequency in cuspal inclined plane, central fossa, and marginal ridge, and there was a statistical significance (P < 0.05). Conclusion: Palatal side abfractions were observed at the highest frequency in maxillary 1st molars, and in all maxillary posterior teeth where palatal side abfractions were found, the occlusal wears were observed. And the occlusal wears were observed at high frequency in cuspal inclined plane, central fossa and marginal ridge. Such results show that abfraction is associated with occlusal force.

• Restorative Dentistry and Endodontics
• /
• v.26 no.5
• /
• pp.443-446
• /
• 2001

급격한 치아외상은 치아 경조직에 손상을 주기도 하지만 치수와 치주조직에도 손상을 입힌다. 탈구(luxation)의 경우, 외상에 의해 치근단공 부위에서 신경혈관계의 파괴가 초래되지만 치근파절의 경우에는 파절전 부위에서 이와 유사한 손상이 나타난다. 그러므로 치근파절을 파절선 상부의 치관부에 대한 일종의 탈구로 보기도 한다. 본 증례보고는 외상에 의한 치근파절의 두 가지 치유양상을 비교한 것으로, 한 증례는 특정한 치과적 처치없이 스스로 치유된 경우이고 다른 한 증례는 치아고정 및 근관치료를 포함한 치과치료후에 치유된 경우이다. 수평치근파절의 치유에는 여러 가지 요인이 관여하지만 특히 치아동요도 및 치수생활력이 큰 영향을 미친다. 본 증례에서와 같이 치아의 동요도가 있는 경우에는 고정을 통해서 치유를 촉진하고 치수의 괴사가 초래된 경우에는 근관치료를 포함한 적절한 치과치료를 통해서 치유가 일어날 수 있다. 따라서 치근이 파절된 경우에는 장기간의 관찰을 통해 파절부 치유 및 치수손상 여부를 관찰, 진단하고 그에 따른 적절한 처치를 시행해야 할 것이다.