• Applied Chemistry for Engineering
• /
• v.16 no.5
• /
• pp.672-676
• /
• 2005

To improve the application of polymeric dental restorative composite (PDRC) for the posterior and anterior restoration, silica bridged with siloxane unit was firstly prepared by heat-treating a silica filler at various temperatures. Degree of conversion (DC), depth of cure, and dynamic volumetric polymerization shrinkage values of PDRC filled with silica bridged with siloxane unit were investigated to study the effect of heat-treated silica on the polymerization behavior of PDRC. From the experimental result, it was found that depth of cure was decreased with an increase of heat treatment temperature. on the other hand, both DC and polymerization shrinkage values were uniformly enhanced with increasing the heat treatment temperature. This phenomenon can be explained from the study that showed decrease of average particle size of silica resulted in the increase of relative amount of resin matrix in PDRC.

• Journal of Dental Anesthesia and Pain Medicine
• /
• v.24 no.4
• /
• pp.265-272
• /
• 2024

Effective pain management is crucial for the successful performance of various endodontic procedures. Painless treatments are made possible by anesthetizing the tooth to be treated using various nerve-block techniques. However, certain circumstances necessitate supplemental anesthetic techniques to achieve profound anesthesia, especially in situations involving a "hot tooth" in which intrapulpal anesthesia (IPA) is employed. IPA is a technique that involves the injection of an anesthetic solution directly into the pulp tissue and is often utilized as the last resort when all other anesthetic techniques have been unsuccessful in achieving complete pulpal anesthesia. This review focuses on the IPA procedure and the factors that influence its success. Additionally, the advantages, limitations, disadvantages, and future directions of IPA are discussed.

• The Journal of Advanced Prosthodontics
• /
• v.6 no.1
• /
• pp.22-29
• /
• 2014

PURPOSE. This study aimed to investigate the potential clinical application of digitized silicone rubber impressions by comparing the accuracy of zirconia 3-unit fixed partial dentures (FPDs) fabricated from 2 types of data (working model and impression) obtained from a laser scanner. MATERIALS AND METHODS. Ten working models and impressions were prepared with epoxy resin and vinyl polysiloxane, respectively. Based on the data obtained from the laser scanner (D-700; 3Shape A/S, Copenhagen, Denmark), a total of 20 zirconia frameworks were prepared using a dental CAD/CAM system (DentalDesigner; 3shape A/S, Copenhagen, Denmark / Ener-mill, Dentaim, Seoul, Korea). The silicone replicas were sectioned into four pieces to evaluate the framework fit. The replicas were imaged using a digital microscope, and the fit of the reference points (P1, P2, P3, P4, P5, P6, and P7) were measured using the program in the device. Measured discrepancies were divided into 5 categories of gaps (MG, CG, AWG, AOTG, OG). Data were analyzed with Student's t-test ($\alpha$=0.05), repeated measures ANOVA and two-way ANOVA (${\alpha}=0.05$). RESULTS. The mean gap of the zirconia framework prepared from the working models presented a narrower discrepancy than the frameworks fabricated from the impression bodies. The mean of the total gap in premolars (P=.003) and molars (P=.002) exhibited a statistical difference between two groups. CONCLUSION. The mean gap dimensions of each category showed statistically significant difference. Nonetheless, the digitized impression bodies obtained with a laser scanner were applicable to clinical settings, considering the clinically acceptable marginal fit ($120{\mu}m$).

• Tribology and Lubricants
• /
• v.21 no.6
• /
• pp.268-271
• /
• 2005

In this study, the wear characteristics of five different dental composite resins cured by conventional halogen light and LED light sources were investigated. Five different dental composite resins of Surefil, Z100, Dyract AP, Fuji II LC and Compoglass were worn against a zirconia ceramic ball using a pin-on-disk type wear tester with 15N contact force in a reciprocal sliding motion of sliding distance of 10mm/cycle at 1Hz under the room temperature dry condition. The wear variations of dental composite resins were linearly increased as the number of cycles increased. It was observed that the wear resistances of these specimens were in the order of Dyract AP > Surefil > Compoglass > Z100 > Fuji II LC. On the morphological observations by SEM, the large crack formation on the sliding track of Fuji II LC specimen was the greatest among all resin composites. Dyract AP showed less wear with few surface damage. There is no significant difference in wear performance between conventional halogen light curing and light emitting diodes curing sources. It indicates that a light emitting diodes (LED) source can replace a halogen light source as curing unit for composite resin restorations.

• The korean journal of orthodontics
• /
• v.46 no.3
• /
• pp.171-179
• /
• 2016

Objective: The primary aim of the study was to generate new prediction equations for the estimation of maxillary and mandibular canine and premolar widths based on mandibular incisors and first permanent molar widths. Methods: A total of 2,340 calculations (768 based on the sum of mandibular incisor and first permanent molar widths, and 1,572 based on the maxillary and mandibular canine and premolar widths) were performed, and a digital stereomicroscope was used to derive the the digital models and measurements. Mesiodistal widths of maxillary and mandibular teeth were measured via scanned digital models. Results: There was a strong positive correlation between the estimation of maxillary (r = 0.85994, $r^2=0.7395$) and mandibular (r = 0.8708, $r^2=0.7582$) canine and premolar widths. The intraclass correlation coefficients were statistically significant, and the coefficients were in the strong correlation range, with an average of 0.9. Linear regression analysis was used to establish prediction equations. Prediction equations were developed to estimate maxillary arches based on $Y=15.746+0.602{\times}sum$ of mandibular incisors and mandibular first permanent molar widths (sum of mandibular incisors [SMI] + molars), $Y=18.224+0.540{\times}(SMI+molars)$, and $Y=16.186+0.586{\times}(SMI+molars)$ for both genders, and to estimate mandibular arches the parameters used were $Y=16.391+0.564{\times}(SMI+molars)$, $Y=14.444+0.609{\times}(SMI+molars)$, and $Y=19.915+0.481{\times}(SMI+molars)$. Conclusions: These formulas will be helpful for orthodontic diagnosis and clinical treatment planning during the mixed dentition stage.

• Journal of dental hygiene science
• /
• v.15 no.2
• /
• pp.196-201
• /
• 2015

The purpose of this study was to evaluate marginal gap of 3 unit fixed dental prostheses (FDPs) fabricated by 3-dimensional (3D) printing technology and to compare marginal gap of its by a conventional method (lost wax technique and casting method). Ten study models were manufactured. Three unit FDPs were fabricated by 3D printing technique (3D group) and conventional methods (CV group). Marginal gaps were measured by silicone replica technique and digital microscope (${\times}160$). Mann-Whitney test was executed (${\alpha}=0.05$). The mean${\pm}$standard deviation of marginal gap for premolars and molars were $112.5{\pm}8.6{\mu}m$ and $110.2{\pm}7.0{\mu}m$ in the 3D group and $83.2{\pm}4.4{\mu}m$ and $82.2{\pm}4.6{\mu}m$ in the CV group. There were statistically significant differences (p<0.05). As results, clinical application further improvement of 3D printing technique may be required.

• Journal of dental hygiene science
• /
• v.19 no.1
• /
• pp.39-47
• /
• 2019

Background: Light-emitting diodes curing unit (LCU), which emit blue light, is used for polymerization of composite resins in many dentistry. Although the use of LCU for light-cured composite resin polymerization is considered safe, it is still controversial whether it can directly or indirectly have harmful biological influences on oral tissues. The aim of this study was to elucidate the biological effects of LCU in wavelengths ranging from 440 to 490 nm, on the cell viability and secretion of inflammatory cytokines in MDPC-23 odontoblastic cells and inflammatory-induced MDPC-23 cells by lipopolysaccharide (LPS). Methods: The MTT assay and observation using microscope were performed on MDPC-23 cells to investigate the cell viability and cytotoxic effects on LCU irradiation. Results: MDPC-23 cells and LPS stimulated MDPC-23 cells were found to have no effects on cell viability and cell morphology in the LCU irradiation. Nitric oxide (NO) and prostaglandin $E_2$ which are the pro-inflammatory mediators, and interleukin-$1{\beta}$ and tumor necrosis factor-${\alpha}$ (TNF-${\alpha}$) which are the proinflammatory cytokines were significantly increased in MCPD-23 cells after LCU irradiation as time increased in comparison with the control. LCU irradiation has the potential to induce inflammation or biological damages in normal dental tissues, including MDPC-23 cells. Conclusion: Therefore, it is necessary to limit the use of LCU except for the appropriate dose and irradiation time. In addition, LCU irradiation of inflammatory-induced MDPC-23 cells by LPS was reduced the secretion of NO compared to the LPS alone treatment group and was significantly reduced the secretion of TNF-${\alpha}$ in all the time groups. Therefore, LCU application in LPS stimulated MDPC-23 odontoblastic cells has a photodynamic therapy like effect as well as inflammation relief.

• The Journal of Advanced Prosthodontics
• /
• v.15 no.4
• /
• pp.171-178
• /
• 2023

PURPOSE. The purpose of this study was to determine the effect of the connector configuration on the fracture load in conventional and translucent zirconia of three-unit fixed dental prostheses (FDPs). MATERIALS AND METHODS. Six different three-unit FDPs were prepared (n = 6) from three types of zirconia (3Y-TZP (Katana ML^®), 4Y-TZP (Katana STML^®), and 5Y-TZP (Katana UTML^®)) in combination with two connector configurations (4 × 2.25, 3 × 3 mm). The CoCr master models were scanned, and the FDPs were designed and fabricated using CAD-CAM. The FDPs were cemented on the metal model and then loaded with a UTM at a crosshead speed of 1 mm/min until failure. Two-way ANOVA and Tukey's test were used for statistical analysis (α = .05). RESULTS. Fracture loads of 3Y-TZP (2740.6 ± 469.2 and 2718.7 ± 339.0 N for size 4 × 2.25 mm and 3 × 3 mm, respectively) were significantly higher than those of 4Y-TZP (1868.3 ± 281.6 and 1663.6 ± 372.7 N, respectively) and 5Y-TZP (1588.0 ± 255.0 and 1559.1 ± 110.0 N, respectively) (P < .05). No significant difference was found between fracture loads of 4Y-TZP and 5Y-TZP (P > .05). The connector configuration within 9 mm² was found to have no effect on the fracture loads on all three types of zirconia (P > .05). CONCLUSION. Fracture loads of three-unit FDPs were affected by the type of zirconia. The fracture loads of conventional zirconia were higher than those of translucent zirconia. However, it was not affected by the connector configuration when the connector had a cross-sectional area of 9 mm².

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.50 no.2
• /
• pp.80-85
• /
• 2024

Objectives: To access the knowledge of undergraduate and postgraduate students of the dental college on basic anatomy, physiology, clinical examination, and pathology of the temporomandibular joint (TMJ). Materials and Methods: A total of 610 undergraduate and postgraduate students of dental college, were included in this study. The questionnaire was pretested for validation and distributed online through Google forms. Results: A pairwise comparison showed that the percentage of correct answers for interns significantly differed from that of IV Bachelor of Dental Surgery (P=0.050) and postgraduate students (P=0.048) (below average: up to 6 correct answers, good: 7-11 correct answers, excellent: 12 or more correct answers). Conclusion: TMJ diseases are common in daily life but frequently go undiagnosed and untreated due to a lack of clinical expertise. This demonstrates the necessity of providing instructions that give students in-depth knowledge and abilities for TMJ issues in clinical practice.

• The Journal of the Korean dental association
• /
• v.54 no.5
• /
• pp.374-383
• /
• 2016

The purpose of this study is to analyze the determinants of pay satisfaction of dental employees. The questionnaire used in this study consists of personal characteristics, characteristics of workplace, administration of pay, Pay satisfaction questionnaire (PSQ). PSQ was translated, and backward translation into korean was implemented. A pilot test was conducted with 25 dental employees to complete the questionnaire. Survey was conducted from February to July in 2015, receiving 323 valid responses. Anova or t-test was conducted with categorized characteristics, by calculating pay satisfaction scores. Principal factor analysis which is an exploratory factor analysis was conducted to investigate the consistency of pay satisfaction. Multiple regression analysis was conducted to investigate how much effect the variables have on pay satisfaction. The result of principal factor analysis showed that pay satisfaction consists of 3 factors which are 'paying system', 'pay level', 'benefits'. 'Pay raise' which was one of 4 factors of original PSQ was not the factor of pay satisfaction of dental employees. The result of analysis of characteristics showed that the scores of paying system between dental clinic and dental hospital had significant difference. The result of multiple regression analysis showed tendencies pay satisfaction increases when age and monthly income increases and whole career and the number of unit chairs decreases. Increasing the autonomy of employees and simplification of paying system would improve pay satisfaction efficiently. When age increases, the pay level increases because of the seniority-based pay structure, and this leads to the higher satisfaction. The higher amount of pay leads to higher satisfaction. The expectation over pay increases relatively higher than the increase of pay level and this leads to the less satisfaction. When the number of unit chairs is fewer, the workplace is smaller, so the employees have more autonomy, and this leads to higher satisfaction.