• The korean journal of orthodontics
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• v.30 no.4 s.81
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• pp.475-481
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• 2000

The purpose of this study was to evaluate the effect of oral environment on the strength of resin bracket wings by comparing fracture mode according to water immersion and thermocycling. Seventy-five resin brackets(Spirit MB, Ormco, California) were divided into three groups and treated for six months as follows; (1) untreated, (2) water immersion in distilled water at $37^{\circ}C$, (3) water immersion in distilled water at $37^{\circ}C$ with total 2,100 times of thermocycling taken 350 times each month. Fracture mode of the wing was tested on universal testing machine. In addition to resin brackets, 25 metal brackets were used as controls. Through the statistical analyses, following results were obtained. 1. Resin bracket wings showed significantly lower fracture strength than metal brackets(p<0.001). 2. Water immersion and water immersion with thermocycling groups showed significantly lower fracture strength than open air condition group(p<0.001). 3. Water immersion with thermocycling group showed significantly lower fracture strength than water immersion group(p<0.001). The above results suggest that the mechanical property of resin bracket wing nay be influenced by oral environment and further research is needed to improve the strength of the wing in the resin bracket.

• 대한치과보철학회:학술대회논문집
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• 2005.11a
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• pp.75-75
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• 2005

• Restorative Dentistry and Endodontics
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• v.35 no.4
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• pp.257-266
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• 2010

The purpose of this study was to determine the effect of post types and sizes on fracture resistance in immature tooth model with various restorative techniques. Bovine incisors were sectioned 8 mm above and 12 mm below the cementoenamel junction to simulate immature tooth model. To compare various post-and-core restorations, canals were restored with gutta-percha and resin core, or reinforced dentin wall with dual-cured resin composite, followed by placement of D.T. LIGHT-POST, ParaPost XT, and various sizes of EverStick Post individually. All of specimens were stored in the distilled water for 72 hours and underwent 6,000 thermal cycles. After simulation of periodontal ligament structure with polyether impression material, compressive load was applied at 45 degrees to the long axis of the specimen until fracture was occurred. Experimental groups reinforced with post and composite resin were shown significantly higher fracture strength than gutta-percha group without post placement (p < 0.05). Most specimens fractured limited to cervical third of roots. Post types did not influence on fracture resistance and fracture level significantly when cement space was filled with dual-cured resin composite. In addition, no statistically significant differences were seen between customized and standardized glass fiber posts, which cement spaces were filled with resin cement or composite resin individually. Therefore, root reinforcement procedures as above in immature teeth improved fracture resistance regardless of post types and sizes.

• Journal of the korean academy of Pediatric Dentistry
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• v.47 no.2
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• pp.205-212
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• 2020

The purpose of this study is to evaluate the validity of primary anterior zirconia crown made with Computer Aided Design/Computer Aided Manufacturing (CAD/CAM) technology by analyzing fracture strength and translucency parameter. Zirconia crown was designed with CAD software, using 3D scanned data of #61 tooth model. Crown fabrication was performed with CAM machine using zirconia block. Zirconia crowns were divided into 3 groups according to thickness(0.3, 0.5, and 0.7 mm), and fracture strength was compared with 1.0 mm thickness of resin strip crown. The compressive force was applied with universal testing machine at 30° along the incisal edge at increments of 1 mm/min. For translucency evaluation, 0.3, 0.5, and 0.7 mm thickness of zirconia specimens were fabricated and translucency was measured with spectrophotometer. Among zirconia groups, there was a significant increase in fracture strength as thickness increased (p < 0.05). The fracture strength of zirconia crown was significantly higher than resin strip crown in all groups (p < 0.05). Translucency parameter was highest in 0.3 mm group, and significantly decreased as thickness increased to 0.5 and 0.7 mm (p < 0.05). Thin primary anterior zirconia crown can be designed and fabricated according to individual needs by using CAD/CAM. Restoration with thin crown would reduce the amount of tooth reduction, risk of pulp exposure, and make more esthetic restoration possible.

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

• Journal of Dental Rehabilitation and Applied Science
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• v.37 no.4
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• pp.232-243
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• 2021

Purpose: The purpose of this study was to evaluate the shear bond strength of various 3D printed denture base resins and the conventional denture base resin to various denture relining materials. Materials and Methods: For denture base materials, a heatcured (Vertex RS) and two types of 3D printed DENTCA Denture base II, NextDent^TM Base) were used. And 4 types denture relining materials (Tokuyama Rebase II fast, Kooliner, Denture Liner, Denture Liner, Lang Jet Denture Repair Kit) with different components were used. It was classified into 12 groups. Adhesion was performed between the resin base and the relining materials in accordance with ISO/TS 11405 standard. The shear bonding strength was measured, and then the adhesion interface was observed with a stereoscopic microscope and a scanning electron microscope. The fracture pattern was investigated through the analysis of the fragment. Results: In the 3D printed denture resin group, the shear bonding strength with relining materials was significantly lower than that of the heat-cured resin group (P < 0.05). The group of polymethyl methacrylate -based relining materials, high shear bonding strength was shown regardless of the type of denture. As for the fracture pattern, adhesive fracture appeared in most groups, and cohesive, mixed fracture appeared in some groups. Conclusion: The polymethyl methacrylate -based denture relining materials showed high shear bonding strength values compared to other denture relining materials. But, for direct methods, it is considered advantageous in terms of shear bonding strength to use a isobutyl methacrylate-based denture relining materials.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.4
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• pp.595-607
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• 1999

The purpose of this in vitro study was to evaluate the efficacy of self-etching primer which was developed to simplify the bonding procedures by measuring the shear bond strength and observing the interfacial morphology. 90 flat dentinal surfaces were prepared by grinding the buccal and lingual areas of caries-free human deciduous molars. After bonding of composite resin to sample surfaces according to the manufacturer's direction and thermocycling, shear bond strengths were measured using Universal testing machine(Instron). Another groups of specimens were treated by hydrochloric acid to secure the resin only and those tags were evaluated under SEM for their length and forms and the morphology of the bonding sites were also observed. The result as follows. 1. Group III showed higher shear bond strength than group I and II but no statistically significant difference was founded between group I and II(p>.05). 2. Adhesive failure was predominant in group II whereas dentin detachment was the main failure pattern in group I and III. 3. Relating long resin tags of $100-200{\mu}m$ were observed in samples of all groups under SEM. In group I, homogeneously long resin tags were arranged rather tight whereas rather loosely arranged resin tags of various length were found in group II. Lateral branching of resin tags was the characteristic finding observed in group III.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.3
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• pp.225-235
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• 2009

A common procedure of restoration of endodonticlly treated tooth with fiber-reinforced post is followed by core build-up after post cementation. However, this technique is complex and time-consuming. The aim of this study was to compare fracture strength of premolar, restored with various methods of core fabrications on fiber-reinforced posts and casting metal restoration. Forty five freshly extracted human mandibular premolars were obtained and devided into 5 groups acconding to the type of post and methods of core build-up. In Group A, D.T. $Light-post^{(R)}$ were cemented with $DUO-LINK^{TM}$ and then $LIGHT-CORE^{TM}$ was used for core restoration. In Group B, D.T. $Light-post^{(R)}$ and $DUO-LINK^{TM}$ were used for cementing in the postspace, and $DUO-LINK^{TM}$ was used again for core restoration. In Group C, $Light-post^{(R)}$ bonding and the core build-up were performed simultaneously by using $DUO-LINK^{TM}$. In Group D, $LuxaPost^{(R)}$ was bonded by using $LuxaCore^{(R)}-Dual$. Again, $LuxaCore^{(R)}-Dual$ was used for core restoration. In Group E, $LuxaPost^{(R)}$ bonding and the core build-up were performed simultaneously by using $LuxaCore^{(R)}-Dual$. Axial reduction was formed parallelly as possible and 45 degree bevel was made at buccal occlusal surface. Crowns were fabricated and cemented. Each tooth was embedded in self-curing acrylic resin to the level of 2mm below the CEJ. Specimens were fixed on universal testing machin such that the axis of the tooth was at 45 degree inclination to the horizontal plane, and compressive force was applied at a crosshead speed of 1mm/min until failure occurred. The mean fracture strength was the highest in group A followed by descending order in group B, D, E and C. However, there were no statistically significant differences between groups with regard to the fracture strength. The type of the post or build-up methods of the core does not seem to influence the fracture strength.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.1
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• pp.22-30
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• 2008

Purpose: The purpose of this study is to compare three different CAD/CAM systems through the fracture strength of zirconia core and to evaluate the clinical availability of each system. Material and methods: The following three groups of 30 maxillary mesial incisor core for all-ceramics(each group 10) were fabricated as follows: group 1. $Adens^{(R)}$ CAD/CAM system, group 2. $Cerasys^{(R)}$ CAD/CAM system, group 3. 3M $Lava^{(R)}$ CAD/CAM system. All specimens were manufactured consistently thickness 0.5mm and relief $40{\mu}m$. Specimens were subjected to compressive loading on the lingual area by Z250/$SN5S^{(R)}$. Each group's mean and standard deviation were calculated and Kruskal Waillis test, Wilcoxon Rank Sum test were utilized to find out the relationship among the groups. Results: The results were as follows: 1. The mean fracture strength of $Adens^{(R)}$ system was $615.89{\pm}156.1N$, the $Cerasys^{(R)}$ system was $863.98{\pm}151.5N$, and the 3M $Lava^{(R)}$ system was $1143.1{\pm}286.6N$. 2. The fracture strength of the systems showed the significant statistical differences in order of 3M $Lava^{(R)}$ system, $Cerasys^{(R)}$ system, $Adens^{(R)}$ system. Conclusion: In this study, in spite of the differences among the groups, every group showed clinically useful results. It is necessary to study further clinical experiments on a long term basis.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.3
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• pp.231-242
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• 2008

Purpose: The purpose of this study was to investigate the bond strength of the core-veneer interface in all ceramic systems. Material and Methods: The all ceramic systems tested with their respective veneer were IPS Empress 2 with IPS Eris, IPS e.max Press with IPS e.max Ceram and IPS-e.max ZirCAD with IPS e.max Ceram. Cores (N=36, N=12/group, diameter: 10mm, thickness: 3mm) were fabricated according to the manufacturer's instruction and cleaned with ultrasonic cleaner. The veneer(diameter: 3mm, thickness: 2mm) were condensed in stainless steel mold and fired on to the core materials. After firing, they were again ultrasonically cleaned and embedded in acrylic resin. The specimens were stored in distilled water at $37^{\circ}C$ for 1 week. The specimens were placed in a mounting jig and subjected to shear force in a universal testing machine(Z020, Zwick, Germany). Load was applied at close to the core-veneer interface as possible with crosshead speed of 1.00mm/min until failure. Average shear bond strengths(MPa) were analyzed with a one-way analysis of variance and the Tukey test(${\alpha}=.05$). The failed specimens were examinated by scanning electron microscopy(JSM-6360, JEOL, Japan). The pattern of failure was classified as cohesive in core, cohesive in veneer, mixed or adhesive. Results: The mean shear bond strength($MPa{\pm}SD$) were IPS e.max Press $32.85{\pm}6.75MPa$, IPS Empress 2 $29.30{\pm}6.51MPa$, IPS e.max ZirCAD $28.10{\pm}4.28MPa$. IPS Empress 2, IPS e.max Press, IPS e.max ZirCAD were not significantly different from each others. Scanning electron microscopy examination revealed that adhesive failure did not occur in any all ceramic systems. IPS Empress 2 and IPS e.max Press exhibited cohesive failure in both the core and the veneer. IPS e.max ZirCAD exhibited cohesive failure in veneer and mixed failure.