• Restorative Dentistry and Endodontics
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• v.38 no.1
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• pp.11-20
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• 2013

Objectives: In most retrospective studies, the clinical performance of restorations had not been considered in survival analysis. This study investigated the effect of including the clinically unacceptable cases according to modified United States Public Health Service (USPHS) criteria into the failed data on the survival analysis of direct restorations as to the longevity and prognostic variables. Materials and Methods: Nine hundred and sixty-seven direct restorations were evaluated. The data of 204 retreated restorations were collected from the records, and clinical performance of 763 restorations in function was evaluated according to modified USPHS criteria by two observers. The longevity and prognostic variables of the restorations were compared with a factor of involving clinically unacceptable cases into the failures using Kaplan-Meier survival analysis and Cox proportional hazard model. Results: The median survival times of amalgam, composite resin and glass ionomer were 11.8, 11.0 and 6.8 years, respectively. Glass ionomer showed significantly lower longevity than composite resin and amalgam. When clinically unacceptable restorations were included into the failure, the median survival times of them decreased to 8.9, 9.7 and 6.4 years, respectively. Conclusions: After considering the clinical performance, composite resin was the only material that showed a difference in the longevity (p < 0.05) and the significantly higher relative risk of student group than professor group disappeared in operator groups. Even in the design of retrospective study, clinical evaluation needs to be included.

• Restorative Dentistry and Endodontics
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• v.42 no.3
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• pp.157-167
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• 2017

This systematic review aims to summarize the current clinical studies that investigated survival rates against fracture of endodontically treated posterior teeth restored with crowns or resin composite restorations. Literature search were performed using keywords. Publications from 1980 to 2016 were searched in PubMed, ScienceDirect, ISI Web of SCIENCE, MEDLINE, and SCOPUS. Included studies were selected based on inclusion and exclusion criteria. Three clinical studies were included: 1 randomized controlled trial and 1 prospective and 1 retrospective cohort studies. Pooled survival rates ranged from 94%-100% and 91.9%-100% for crowns and resin composite, respectively. The majority of teeth had no more than 3 surface loss of tooth structure. The studies included were heterogeneous, and were not appropriate for further meta-analysis. Current evidence suggested that the survival rates against the fracture of endodontically treated posterior teeth restored with crowns or resin composites were not significantly different in the teeth with minimum to moderate loss of tooth structure.

• Restorative Dentistry and Endodontics
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• v.37 no.3
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• pp.165-169
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• 2012

Closure of interdental spaces using proximal build-ups with resin composite is considered to be practical and conservative. However, a comprehensive approach combining two or more treatment modalities may be needed to improve esthetics. This case report describes the management of a patient with multiple diastemas, a peg-shaped lateral incisor and midline deviation in the maxillary anterior area. Direct resin bonding along with orthodontic movement of teeth allows space closure and midline correction, consequently, creating a better esthetic result.

• Restorative Dentistry and Endodontics
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• v.44 no.4
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• pp.41.1-41.13
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• 2019

Objectives: This paper presents a systematic review and meta-analysis of the effect of preheating on the hardness of nanofilled, nanoceramic, nanohybrid, and microhybrid resin composites. Materials and Methods: An electronic search of papers on MEDLINE/PubMed, ScienceDirect, and EBSCOhost was performed. Only in vitro studies were included. Non-English studies, case reports, clinical trials, and review articles were excluded. A meta-analysis of the reviewed studies was conducted to quantify differences in the microhardness of the Z250 microhybrid resin composite using the Comprehensive Meta-Analysis software. Results: Only 13 studies met the inclusion criteria for this systematic review. The meta-analysis showed that there were significant differences between the non-preheated and preheated modes for both the top and bottom surfaces of the specimens (p < 0.05). The microhardness of the Z250 resin composite on the top surface in the preheated mode (78.1 ± 2.9) was higher than in the non-preheated mode (67.4 ± 4.0; p < 0.001). Moreover, the microhardness of the Z250 resin composite on the bottom surface in the preheated mode (71.8 ± 3.8) was higher than in the non-preheated mode (57.5 ± 5.7, p < 0.001). Conclusions: Although the results reported in the reviewed studies showed great variability, sufficient scientific evidence was found to support the hypothesis that preheating can improve the hardness of resin composites.

• Restorative Dentistry and Endodontics
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• v.36 no.3
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• pp.219-230
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• 2011

Objectives: The aim of this study was to evaluate the optical characteristics such as color and translucency changes before and after light curing, to quantify the CQ and to measure refractive indices of body and opaque shade of resin composites materials. Materials and Methods: Resin composites used in this study were A2 body and A2 opaque shade of Esthet-X, Filtek supreme, Gradia Direct, Clearfil Majesty and Beautifil II. Color and translucency changes before and after light curing were evaluated by colorimeter, the CQ was quantified by GC-MS and refractive index changes were measured by spectroscopic ellipsometer. Results: Translucency parameter (TP) was significantly increased after curing. The CQ content of body shades are higher than that of opaque shades in all resin composites. Refractive index increased after polymerization in all materials and significant difference in ${\Delta}$refractive index was found between body and opaque shade (significance level 0.05). Conclusions: For an accurate shade match, direct shade matching of resin composite should be performed by using the cured material.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.1
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• pp.13-22
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• 2009

The composite resin, due to its esthetic quality, is considered the material of choice for restoration of anterior teeth. To get a satisfactory result in the composite resin restorations, it is necessary to choose right shade. At present, most of the commercial composite resins are based on the Vita Lumin shade guides or shade guides that are provided by their company, but color differences among them might be expected even using the same shade in various materials. This study is to measure color differences between various light-cured composite resins and shade guides and to provide the clinicians with information which may aid in improved color match of esthetic restoration. Four kinds of light-cured composite resins (Gradia Direct (GD), Z250 (Z250), Clearfil AP-X (AP-X), Esthet X (E X)) and shade guides with A2 and A3 shade were used. Three specimens of each material and one specimen of each shade guide were made. Each composite resin was filled into the Teflon mold (1.35 mm depth, 8 mm diameter), followed by compression, polymerization and polishing with wet sandpaper. Shade guides were grinded with polishing stones and rubber points to a thickness of approximately 1.35 mm. Color characteristics were performed with a spectrophotometer(color i5, GretagMacbeth, USA). A computer-controlled spectrophotometer was used to determine CIELAB coordinates ($L^*$, $a^*$, $b^*$) of each specimen and shade guide. The CIELAB measurements made it possible to evaluate the amount of the color difference values (${\Delta}E^*ab$) between composite resins and shade guides. CIE standard D65 was used as the light source. The results were as follows : 1. Among the $L^*$, $a^*$, $b^*$ values of most of 4 kinds of composite resin specimens which are produced by same shade, there were significant differences(p<0.05). 2. Among all 4 kinds of composite resin specimens which are produced by same shade, there were color differences that is perceptible to human eye(${\Delta}E^*>3.3$). 3. Between most of composite resin specimens investigated and their corresponding shade guides, there were color differences that is perceptible to human eye(${\Delta}E^*>3.3$). 4. In the clinical environment, it is recommended that custom shade guides be made from resin material itself for better color matching. Shade guides supplied by manufacturers or Vita Lumin shade guide may not provide clinicians a accurate standard in matching color of composite resins, and there are perceptible color differences in most of products. Therefore, it is recommended that custom shade guides be made from resin material itself and used for better color matching.

• Restorative Dentistry and Endodontics
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• v.25 no.1
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• pp.17-40
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• 2000

Resin cements are used for cementing indirect esthetic restorations such as resin or porcelain inlays. Because of its limitations in curing of purely light cured resin cements due to attenuation of the curing light by intervening materials, dual cured resin cements are recommended for cementing restorations. The physical properties of resin cements are greatly influenced by the extent to which a resin cures and the degree of cure is an important factor in the success of the inlay. The purpose of this study was to evaluate the influence of porcelain thickness and exposure time on the polymerization of resin cements by measuring the microhardness and the degree of conversion, to investigate the nature of the correlation between two methods mentioned above, and to determine the exposure time needed to harden resin cements through various thickness of porcelain. The degree of resin cure was evaluated by the measurements of microhardness [Vickers Hardness Number(VHN)] and degree of conversion(DC), as determined by Fourier Transform Infrared Spectroscopy(FTIR) on one light cured composite resin [Z-100(Z)] and three dual cured resin cements [Duo cement(D), 3M Resin cement(R), and Dual cement(DA)] which were cured under porcelain discs thickness of 0mm, 1mm, 2mm, 3mm with light exposure time of 40sec, 80sec, 120sec, and regression analysis was performed to determine the correlation between VHN and DC. In addition, to determine the exposure time needed to harden resin cements under various thickness of porcelain discs, the changes of the intensity of light attenuated by 1mm, 2mm, and 3mm thickness of porcelain discs were measured using the curing radiometer. The results were obtained as follows ; 1. The values of microhardness and the degree of conversion of resin cements without intervening porcelain discs were 31~109VHN and 51~63%, respectively. In the microhardness Z was the highest, followed by R, D, DA. In the degree of conversion, D and DA was significantly greater than Z and R(p<0.05). 2. The microhardness and the degree of conversion of the resin cements decreased with increasing thickness of porcelain discs, and increased with increasing exposure time, D and R showed great variation with inlay thickness and exposure time, whereas, DA showed a little variation. 3. The intensity of light through 1mm, 2mm, and 3mm porcelain inlays decreased by 0.43, 0.25, and 0.14 times compared to direct illumination, and the respective needed exposure times are 53 sec, 70 sec, and 93 sec. In D and R, 40 sec of light irradiation through 2mm porcelain disc and 80 sec of light irradiation through 3mm porcelain disc were not enough to complete curing. 4. The microhardness and the degree of conversion of the resin cements showed a positive correlationship(R=0.791~0.965) in the order of R, D, Z, DA. As the thickness of porcelain discs increased, the decreasing pattern of microhardness was different from that of the degree of conversion, however.

• Restorative Dentistry and Endodontics
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• v.39 no.2
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• pp.109-114
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• 2014

Objectives: Recurrent caries was partly ascribed to lack of antibacterial properties in composite resin. Silver and zinc nanoparticles are considered to be broad-spectrum antibacterial agents. The aim of the present study was to evaluate the antibacterial properties of composite resins containing 1% silver and zinc-oxide nanoparticles on Streptococcus mutans and Lactobacillus. Materials and Methods: Ninety discoid tablets containing 0%, 1% nano-silver and 1% nano zinc-oxide particles were prepared from flowable composite resin (n = 30). The antibacterial properties of composite resin discs were evaluated by direct contact test. Diluted solutions of Streptococcus mutans (PTCC 1683) and Lactobacillus (PTCC 1643) were prepared. 0.01 mL of each bacterial species was separately placed on the discs. The discs were transferred to liquid culture media and were incubated at $37^{\circ}C$ for 8 hr. 0.01 mL of each solution was cultured on blood agar and the colonies were counted. Data was analyzed with Kruskall-Wallis and Mann-Whitney U tests. Results: Composites containing nano zinc-oxide particles or silver nanoparticles exhibited higher antibacterial activity against Streptococcus mutans and Lactobacillus compared to the control group (p < 0.05). The effect of zinc-oxide on Streptococcus mutans was significantly higher than that of silver (p < 0.05). There were no significant differences in the antibacterial activity against Lactobacillus between composites containing silver nanoparticles and those containing zinc-oxide nanoparticles. Conclusions: Composite resins containing silver or zinc-oxide nanoparticles exhibited antibacterial activity against Streptococcus mutans and Lactobacillus.

• Restorative Dentistry and Endodontics
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• v.18 no.1
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• pp.103-113
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• 1993

The purpose of this study was to evaluate the tensile bond strength of composite resin inlays according to the their internal surface treatment and types of luting cement and compared them with the conventional direct resin filling thchnique. Class II cavities were prepared in 50 extracted human molar teeth, and then equally divided into five groups. Group 1 : Cavities of control group were directly filled with P-50. Group 2 : Cavities of resin inlay group were luted with resin cement. Group 3 : Cavities of resin inlay group were luted with luting G-I cement. Group 4 : Cavities of resin inlay group were luted with resin cement after sandblasting. Group 5 : Cavities of resin inlay group were luted with luting G-I cement after sandblasting. All specimens were polished with same method and stored in normal saline for 24 hours before testing. An Universal Testing machine(Model No. AGS-100A, Shimadzu, Japan) was used to apply tensile loads in the vertical direction, and the force required for separation was recorded with a cross-head speed of 5mm/min and 100kg in full scale. The results were as follows : 1. The mean tensile bond strength was lowest in group luted with luting G-I cement, with measurements of $14.45{\pm}0.78(kg/cm^2)$ and highest in group luted with resin cement after sandblasting, with measurements of $49.6{\pm}2.74(kg/cm^2)$. 2. The tensile bond strength was greater in resin inlay groups luted with resin cement than in control group and resin inlay groups luted with luting G-I cement(P<0.05). 3. The tensile bond strength was lower in resin inlay groups luted with luting G-I cement than in control group(P<0.05). 4. The tensile bond strength was greater in resin inlay groups luted with resin cement or luting G-I cement after sandblasting than without that(P<0.05).

• The Journal of Advanced Prosthodontics
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• v.11 no.1
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• pp.7-15
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• 2019

PURPOSE. The aim of this study was to identify the effects of three aesthetic restorative materials on the wear between tooth and restoration by a pin-on-disk manner. MATERIALS AND METHODS. Six aesthetic restorative materials were used to prepare disk specimens for wear test, which were Lava Zirconia as zirconia group, Vintage MP and Cerabien ZR as veneering porcelain group, Gradia Direct microhybrid composite containing prepolymerized fillers, Filtek Z250 microhybrid composite containing zirconia glass and colloidal silica particles, and Filtek Z350 nanocomposite as composite resin group. Vertical loss of the worn cusp, change of the surface roughness of the restoration materials, and the surface topography were investigated after wear test under 9.8-N contact load. RESULTS. The porcelain groups (Vintage MP and Cerabien ZR) caused the largest vertical loss of teeth when compared with those of the composite resin and zirconia groups, and Filtek Z250 microhybrid composite results in the second-largest vertical loss of teeth. The surface of Filtek Z350 nanocomposite was deeply worn out, but visible wear on the surface of the zirconia and Gradia Direct microhybrid composite was not observed. When the zirconia surface was roughened by sand-blasting, vertical loss of teeth considerably increased when compared with that in the case of fine polished zirconia. CONCLUSION. It was identified that microhybrid composite resin containing a prepolymerized filler and zirconia with reduced surface roughness by polishing were the most desirable restorative materials among the tested materials to prevent the two-body wear between aesthetic restorative material and tooth.