• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.3
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• pp.370-377
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• 2018

Although the frequency of composite resin restoration in children is gradually increasing, there are insufficient researches about the rate of composite resin repair in children. The purpose of this study was to evaluate the repair rate of composite resin restorations in the permanent first molar in children under 12 years old. This study retrospectively analyzed 169 children treated with composite resin restoration in the permanent first molar from May 2014 to April 2015. According to the location of the tooth, the repair rate was higher in the mandible than maxilla and in the left than right. In the classification of restoration, the repair rate was the highest in the class II cavity, and the repair rate was the lowest in the restoration of the occlusal surface only. Repair rate in two years was 14.8%, and repair hazard ratio decreased with age. The most common reason of composite resin restoration replacement was the secondary caries (74.1%). Within the limits of study, the repair rate of children was higher than that of adult due to the characteristics of children. Therefore, dentists should understand these characteristics and try to reduce the repair rate of composite resin composite restorations.

• Advanced Composite Materials
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• v.16 no.3
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• pp.207-221
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• 2007

The filling process of resin injection/compression molding (I/CM) can be divided into injection and compression phases. During the resin injection the mold is kept only partially closed and thus a gap is present between the reinforcements and the upper mold. The gap results in preferential flow path. After the gap is filled with the resin, the compression action initiates and forces the resin to penetrate into the fiber preform. In the present study, the resin flow in the gap is simplified by using the Stokes approximation, while Darcy's law is used to calculate the flow field in the fiber mats. Results show that most of the injected resins enter into the gap during the injection phase. The resin injection time is extremely short so the duration of the filling process is determined by the final closing action of the mold cavity. Compared with resin transfer molding (RTM), I/CM process can reduce the mold filling time or injection pressure significantly.

• Proceedings of the KACD Conference
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• 2002.05a
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• pp.348-349
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• 2002

• Proceedings of the KACD Conference
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• 2006.05a
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• pp.250-250
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• 2006

• The Journal of the Korean dental association
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• v.42 no.9 s.424
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• pp.632-637
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• 2004

• Composites Research
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• v.30 no.6
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• pp.393-398
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• 2017

The shrinkage distribution of a dental composite (Clearfil AP-X, Kuraray, Japan) used for dental restoration was observed using a digital image correlation method. In order to analyze the shrinkage distribution formed during and after light irradiation, digital images were taken with different photographing conditions for each period. Optimal photographing conditions during LED irradiation were obtained through a preliminary experiment in which the exposure time was applied from 0.15 ms to 0.55 ms in 0.05 ms intervals. The DIC analysis results showed that the strain was non-uniform. For the initial 20 s of light irradiation the composite resin shrank to the level of 50~60% of the final curing shrinkage. Such large shrinkage amount of the composite resin lump affected the tensile stress concentration near the adhesive region between the composite resin and the substrate.

• Restorative Dentistry and Endodontics
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• v.13 no.1
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• pp.131-137
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• 1988

The purpose of this study was to investigate the interfacial bond strength of repaired composite resins, Lite-Fil P and Bis-Fil II, under different interfacial conditions. The matured composite resin specimen were prepared as Table I and divided into 9 groups. All specimens were stored in distilled water at $37^{\circ}C$ for 24 hours before testing. The results were as follows; 1. The bond strength of the groups that bonding agent was applicated was greater than that of the groups that bonding agent was not applicated. 2. The bond strength of the saliva contaminated groups was the lowest. 3. The bond strength of the group that chemical cured composite resin bonded to chemical cured composite resin was greater than that of the other groups. 4. The bond strength of the no-treated group was greater than that of saliva contaminated group, and lesser than that of the bonding agent applicated groups.

• Restorative Dentistry and Endodontics
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• v.25 no.3
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• pp.446-458
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• 2000

In this study, compressive strengths of three condensable composite resins(ALERT, SureFil, Solitaire), conventional hybrid composite resin(Z-100) and amalgam(HI-Aristaloy 21) according to the 6 types of cavity design(cylinder, trapezoidal, butt-joint, round bevel, long bevel and short bevel) were measured and appearance of fracture surfaces were observed with SEM, thus evaluated clinical applications of condensable composite resins according to the cavity designs. The results were as follows; 1. Compressive strengths according to experimental materials were the highest in SureFil, and Z-100, ALERT, Solitaire, HI-Aristaloy 21 in order. 2. SureFil showed the highest compressive strength(p<0.05). compressive strengths of ALERT and Solitaire were lower than that of Z-100, hybrid composite(p<0.05). 3. Compressive strengths according to specimen design were the highest in trapezoidal shape(p<0.05) and no significant difference was detected between other specimen designs. 4. The appearance of condensable composite resin under SEM was of a diverse configuration according to component of resin matrix, shapes of filler and surface treatments between resin and filler.

• Restorative Dentistry and Endodontics
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• v.42 no.1
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• pp.39-47
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• 2017

Objectives: Although the coating of surface sealants to dental composite resin may potentially reduce bacterial adhesion, there seems to be little information regarding this issue. This preliminary in vitro study investigated the adhesion of Streptococcus mutans (S. mutans) on the dental composite resins coated with three commercial surface sealants. Materials and Methods: Composite resin (Filtek Z250) discs (8 mm in diameter, 1 mm in thickness) were fabricated in a mold covered with a Mylar strip (control). In group PoGo, the surfaces were polished with PoGo. In groups PS, OG, and FP, the surfaces polished with PoGo were coated with the corresponding surface sealants (PermaSeal, PS; OptiGuard, OG; Fortify Plus, FP). The surfaces of the materials and S. mutans cells were characterized by various methods. S. mutans adhesion to the surfaces was quantitatively evaluated using flow cytometry (n = 9). Results: Group OG achieved the lowest water contact angle among all groups tested (p < 0.001). The cell surface of S. mutans tested showed hydrophobic characteristics. Group PoGo exhibited the greatest bacterial adhesion among all groups tested (p < 0.001). The sealant-coated groups showed statistically similar (groups PS and FP, p > 0.05) or significantly lower (group OG, p < 0.001) bacterial adhesion when compared with the control group. Conclusions: The application of the surface sealants significantly reduced S. mutans adhesion to the composite resin polished with the PoGo.

• Restorative Dentistry and Endodontics
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• v.35 no.2
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• pp.69-79
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• 2010

The purpose of this study was to evaluate the effect of film thickness of various resin cements on bonding efficiency in indirect composite restoration by measurement of microtensile bond strength, polymerization shrinkage, flexural strength and modulus, fractographic FE-SEM analysis. Experimental groups were divided according to film thickness (< $50\;{\mu}m$-control, $50\;{\mu}m$-T50, $100\;{\mu}m$-T100, $150\;{\mu}m$-T150) using composite- based resin cements (Variolink II, Duo-Link) and adhesive-based resin cements (Panavia F, Rely X Unicem). The data was analyzed using ANOVA and Duncan's multiple comparison test (p < 0.05). The results were as follows ; 1. Variolink II showed higher microtensile bond strength than that of adhesive-based resin cements in all film thickness (p < 0.05) but Duo-Link did not show significant difference except control group (p > 0.05). 2. Microtensile bond strength of composite-based resin cements were decreased significantly according to increasing film thickness (p < 0.05) but adhesive-based resin cements did not show significant difference among film thickness (p > 0.05). 3. Panavia F showed significantly lower polymerization shrinkage than other resin cements (p < 0.05). 4. Composite-based resin cements showed significantly higher flexural strength and modulus than adhesive-based resin cements (p < 0.05). 5. FE-SEM examination showed uniform adhesive layer and well developed resin tags in composite-based resin cements but unclear adhesive layer and poorly developed resin tags in adhesive-based resin cements. In debonded surface examination, composite-based resin cements showed mixed failures but adhesive-based resin cements showed adhesive failures.