Effect of microstructure of reinforced CAD/CAM hybrid composite resin block on shear bond strength of composite resin / 대한치과재료학회지

The shear bond strength of the composite resin to a CAD/CAM hybrid composite resin block (CRB) can be affected by the composition and microstructure of the hybrid CRB, surface treatment and the properties of the applied adhesive. In this study, the shear bond strengths between composite resin and the hybrid CRBs were measured to evaluate the effect of microstructure differences in hybrid CRBs on the bond strength. Ten conventional and reinforced hybrid CRBs developed by five domestic and international manufacturersand five universal adhesives currently used in dentistry were selected. After polishing the hybrid CRB surface, the specimens were divided into two groups. The first group was HF-treated to observe the microstructure by FE-SEM, and the second group was sandblasted with alumina, measured the surface roughness by CLSM, bonded with composite resin (diameter = 2.0mm) using universal adhesive, and stored in a 37 ℃ water bath for 24 hours, and measured the shear bond strength using a universal testing machine. The measured values were statistically analyzed using the Tukey-multiple comparison test (α= 0.05). It was observed that the size, type, and fraction of the filler particles contained in the regular and reinforced hybrid CRBs affected the microstructure, but the differences did not affect the shear bond strength. All five universal adhesives containing 10-MDP as the main functional monomer met the minimum bond strength (>20 MPa) required for clinical applications.

Evaluation of component release and oxygen-inhibited layer removal on cytotoxicity of syringe-type bis-acryl composites for provisional restorations / 대한치과재료학회지

This study aimed to analyze the eluted components of syringe-type bis-acryl composites and to evaluate the effect of removing the oxygen-inhibited layer on cytotoxicity. Four different bis-acryl provisional composite materials-Protemp 4 (PT), Structur 2 SC (ST), Luxatemp Automix Plus (LT), and Hexa-Temp (HT)-were evaluated. Gas chromatography/mass spectrometry was used to analyze the composite eluate after 24 h of immersion in methanol. An agar overlay test and a live/dead assay were performed on the polymerized disc-shaped specimens after 24 h. To evaluate the effect of removing the oxygen-inhibited layer, samples were prepared with a surface oxygen-inhibited layer. The surface oxygen-inhibited layer of the disc-shaped specimens was removed with alcohol only (subgroup A) or with polishing and alcohol (subgroup PA), and their cytotoxicities were compared with those of “as received” (subgroup N) specimens using the WST-1 assay. Statistical significance was assessed using analyses of variance, followed by Bonferroni multiple comparison tests (α=0.05). Different components were detected by gas chromatography/mass spectrometry analysis among the groups. The agar overlay assay confirmed severe cytotoxicity in HT, LT, and ST groups, whereas PT showed moderate cytotoxicity. The effect of removing the oxygen-inhibited layer on cell viability was significantly higher in PA than in N in all composite groups. In HT and ST, the cell viability was significantly higher in PA than in A. Syringe-type bis-acryl composites for provisional restorations may elute various components into the oral cavity, which may cause cytotoxicity in adjacent structures. The cytotoxicity of the materials is reduced by the removal of the oxygen-inhibited layer.

A study on the Korean dental education system II: the need for integrated education system / 대한구강보건학회지

Objectives@#With the rapid changes in society, there are more arguments for redefining dental education system. This study aimed to review and analyze the problems in the current dental education system in Korea and then propose an integrated education system based on those findings. @*Methods@#A narrative review of the problems confronting the dental education system in Korea was carried out. Accordingly, full-text screening and specialists’ discussions were extracted from the review. The purpose of the review was to summarize the strengths and weaknesses of Korean dental education systems to offer perspectives on an integrated education system in accordance with the specialists’ opinions. @*Results@#The results revealed that the problems of the current dental education system were identified in clinical education, basic science, and humanities and social sciences. Dental schools should provide clinical education so that dental students can be exposed to the clinical environment at an early stage and perform patient-based clinical practice. It is also imperative to encourage participation in research programs to train dental scientists, as well as to reflect on courses that can adapt to changes brought about by new technologies. It is recommended that education opportunities for integrated humanities and social sciences be provided. @*Conclusions@#It will be critical in the future for dental schools to embrace a flexible education system from various perspectives. It is vital that dental schools play a role in developing students’ critical thinking, problem-solving, and decision-making skills. Finally, as part of an integrated education system, an improvement program should be devised.

A study on the Korean dental education system II: the need for integrated education system / 대한구강보건학회지

Objectives@#With the rapid changes in society, there are more arguments for redefining dental education system. This study aimed to review and analyze the problems in the current dental education system in Korea and then propose an integrated education system based on those findings. @*Methods@#A narrative review of the problems confronting the dental education system in Korea was carried out. Accordingly, full-text screening and specialists’ discussions were extracted from the review. The purpose of the review was to summarize the strengths and weaknesses of Korean dental education systems to offer perspectives on an integrated education system in accordance with the specialists’ opinions. @*Results@#The results revealed that the problems of the current dental education system were identified in clinical education, basic science, and humanities and social sciences. Dental schools should provide clinical education so that dental students can be exposed to the clinical environment at an early stage and perform patient-based clinical practice. It is also imperative to encourage participation in research programs to train dental scientists, as well as to reflect on courses that can adapt to changes brought about by new technologies. It is recommended that education opportunities for integrated humanities and social sciences be provided. @*Conclusions@#It will be critical in the future for dental schools to embrace a flexible education system from various perspectives. It is vital that dental schools play a role in developing students’ critical thinking, problem-solving, and decision-making skills. Finally, as part of an integrated education system, an improvement program should be devised.

Periodontal regenerative therapy in endo-periodontal lesions: a retrospective study over 5 years

PURPOSE: The aim of this study was to evaluate clinical and radiographic changes and the survival rate after periodontal surgery using deproteinized bovine bone mineral (DBBM) with 10% collagen or DBBM with a collagen membrane in endo-periodontal lesions. METHODS: A total of 52 cases (41 patients) with at least 5 years of follow-up were included in this study. After scaling and root planing with or without endodontic treatment, periodontal regenerative procedures with DBBM with 10% collagen alone or DBBM with a collagen membrane were performed, yielding the DBBM + 10% collagen and DBBM + collagen membrane groups, respectively. Changes in clinical parameters including the plaque index, bleeding on probing, probing pocket depth, gingival recession, relative clinical attachment level, mobility, and radiographic bone gains were evaluated immediately before periodontal surgical procedures and at a 12-month follow-up. RESULTS: At the 12-month follow-up after regenerative procedures, improvements in clinical parameters and radiographic bone gains were observed in both treatment groups. The DBBM + 10% collagen group showed greater probing pocket depth reduction (4.52±1.06 mm) than the DBBM + collagen membrane group (4.04±0.82 mm). However, there were no significant differences between the groups. Additionally, the radiographic bone gain in the DBBM + 10% collagen group (5.15±1.54 mm) was comparable to that of the DBBM + collagen membrane group (5.35±1.84 mm). The 5-year survival rate of the teeth with endo-periodontal lesions after periodontal regenerative procedures was 92.31%. CONCLUSIONS: This study showed that regenerative procedures using DBBM with 10% collagen alone improved the clinical attachment level and radiographic bone level in endo-periodontal lesions. Successful maintenance of the results after regenerative procedures in endo-periodontal lesions can be obtained by repeated oral hygiene education within strict supportive periodontal treatment.

A case report of multiple bilateral dens invaginatus in maxillary anteriors

The present report presents a case of dens invaginatus (DI) in a patient with 4 maxillary incisors. A 24-year-old female complained of swelling of the maxillary left anterior region and discoloration of the maxillary left anterior tooth. The maxillary left lateral incisor (tooth #22) showed pulp necrosis and a chronic apical abscess, and a periapical X-ray demonstrated DI on bilateral maxillary central and lateral incisors. All teeth responded to a vitality test, except tooth #22. The anatomic form of tooth #22 was similar to that of tooth #12, and both teeth had lingual pits. In addition, panoramic and periapical X-rays demonstrated root canal calcification, such as pulp stones, in the maxillary canines, first and second premolars, and the mandibular incisors, canines, and first premolars bilaterally. The patient underwent root canal treatment of tooth #22 and non-vital tooth bleaching. After a temporary filling material was removed, the invaginated mass was removed using ultrasonic tips under an operating microscope. The working length was established, and the root canal was enlarged up to #50 apical size and obturated with gutta-percha and AH 26 sealer using the continuous wave of condensation technique. Finally, non-vital bleaching was performed, and the access cavity was filled with composite resin.

Comparison of mechanical and biological properties of zirconia and titanium alloy orthodontic micro-implants / 대한치과교정학회지

OBJECTIVE: The aim of this study was to compare the initial stability as insertion and removal torque and the clinical applicability of novel orthodontic zirconia micro-implants made using a powder injection molding (PIM) technique with those parameters in conventional titanium micro-implants. METHODS: Sixty zirconia and 60 titanium micro-implants of similar design (diameter, 1.6 mm; length, 8.0 mm) were inserted perpendicularly in solid polyurethane foam with varying densities of 20 pounds per cubic foot (pcf), 30 pcf, and 40 pcf. Primary stability was measured as maximum insertion torque (MIT) and maximum removal torque (MRT). To investigate clinical applicability, compressive and tensile forces were recorded at 0.01, 0.02, and 0.03 mm displacement of the implants at angles of 0°, 10°, 20°, 30°, and 40°. The biocompatibility of zirconia micro-implants was assessed via an experimental animal study. RESULTS: There were no statistically significant differences between zirconia micro-implants and titanium alloy implants with regard to MIT, MRT, or the amount of movement in the angulated lateral displacement test. As angulation increased, the mean compressive and tensile forces required to displace both types of micro-implants increased substantially at all distances. The average bone-to-implant contact ratio of prototype zirconia micro-implants was 56.88 ± 6.72%. CONCLUSIONS: Zirconia micro-implants showed initial stability and clinical applicability for diverse orthodontic treatments comparable to that of titanium micro-implants under compressive and tensile forces.

Effects of silanation time on shear bond strength between a gold alloy surface and metal bracket / 대한치과교정학회지

OBJECTIVE: We aimed to investigate the effects of silanation time on the shear bond strength (SBS) of metal brackets on gold alloy in a silicoating procedure and compare the SBS of metal brackets on gold alloy and enamel. METHODS: Type III gold alloy plates were sandblasted with 30-microm silicon dioxide. Excess particles were removed with gentle air after silica coating, and silane was applied. Maxillary central-incisor metal brackets were bonded to each conditioned alloy surface with a light curing resin adhesive for 1 s, 30 s, 60 s, or 120 s after applying silane. The brackets were also bonded to 36 upper central incisors with the same adhesive. All samples were cured for 40 s with a light emitting diode curing light. The SBS was tested after 1 h and after 24 h. The adhesive remnant index (ARI) of the samples was also compared. RESULTS: The 60-s and 120-s silanation time groups showed a higher SBS than the other groups (p < 0.05). Samples tested after 24 h showed a significantly higher SBS than did the samples tested after 1 h (p < 0.05). The 1-s group showed higher ARI scores. The one-way analysis of variance and Student-Newman-Keuls test showed that the SBS values of the 60-s and 120-s silanation time groups were not significantly different from the SBS values of enamel. CONCLUSIONS: Adequate silanation time is required to produce sufficient bond strength during silicoating.

Clinical efficacy of serum human epididymis protein 4 as a diagnostic biomarker of ovarian cancer: A pilot study

OBJECTIVE: To compare accuracy of serum human epididymis protein 4 (HE4) levels with cancer antigen 125 (CA-125) levels as biomarkers for ovarian cancer. METHODS: The study population included 94 Korean women, including 32 patients with a diagnosis of ovarian cancer and 62 patients with a diagnosis of benign ovarian tumor. All diagnoses were confirmed by histopathological analysis. Serum HE4 levels were assessed using an HE4 enzyme immunoassay, which were performed according to the manufacturer's instructions. Serum CA-125 levels were determined using a Modular analytics E170 module. RESULTS: The median serum CA-125 and HE4 levels were significantly higher in patients with ovarian cancer than those with other benign tumors (CA-125, 394.1 U/mL vs. 22.7 U/mL; HE4, 56.7 pM vs. 18.5 pM; P < 0.05 in both). An additional comparison revealed that the patients with endometriosis had greater median serum CA-125 levels than those with other benign ovarian tumors (32.0 U/mL vs. 17.9 U/mL, P = 0.03). Conversely, the median serum HE4 levels were similar among the two benign ovarian tumor groups, with no statistically significant difference observed (19.0 pM vs. 18.2 pM, P = 0.49). The receiver operating characteristics curve analysis for the benign ovarian tumor and ovarian cancer patients showed that HE4 showed a greater area under the curve with borderline significance when compared with CA-125 in both groups (0.93 vs. 0.85). CONCLUSION: Serum HE4 levels may not only allow for the detection of ovarian cancer, but also allow for better differentiation of cases of ovarian cancer versus other benign ovarian tumors compared with serum CA-125.

Shear bond strength between gold alloy and orthodontic metal bracket using light emitting diode curing light / 대한치과교정학회지

OBJECTIVE: The need to bond orthodontic brackets onto various alloys has increased because of the increasing demand for adult orthodontic treatment. This study tried to evaluate the shear bond strength between gold alloy and metal bracket using light emitting diode (LED) light curing after metal primer and silicoating surface conditioning. METHODS: Half of the type III gold alloy plates were treated with sandblasting with aluminum oxide and metal primer containing 4-META, the other half were treated with silica and silane. Metal brackets were bonded with Transbond XT light curing adhesive on these plates and shear bond strength were evaluated 1 hour, 6 hours, and 24 hours later. The differences of shear bond strength between groups were evaluated with two-way ANOVA. RESULTS: The results showed higher bond strength in the silicoating group and a tendency of bond strength increase over time. CONCLUSIONS: When using LED curing lights for metal bracket bonding to alloy surfaces, long curing time and silicoating can produce a reliable bonding strength.

Clinical study of shade improvement and safety of polymer-based pen type BlancTic Forte whitening agent containing 8.3% Carbamide peroxide / 대한치과보존학회지

This clinical study evaluated the whitening effect and safety of polymer based-pen type BlancTis Forte (NIBEC) containing 8.3% carbamide peroxide. Twenty volunteers used the BlancTis Forte whitening agent for 2 hours twice a day for 4 weeks. As a control, Whitening Effect Pen (LG) containing 3% hydrogen peroxide was used by 20 volunteers using the same protocol. The change in shade (DeltaE*, color difference) was measured using Shadepilot(TM) (DeguDent) before, during, and after bleaching (2 weeks, 4 weeks, and post-bleaching 4 weeks). A clinical examination for any side effects (tooth hypersensitivity or soft tissue complications) was also performed at each check-up. The following results were obtained. 1. Both the experimental and control groups displayed a noticeable change in shade (DeltaE) of over 2. No significant differences were found between the two groups (p > 0.05), implying that the two agents have a similar whitening effect. 2. The whitening effect was mainly due to changes in a and b values rather than in L value (brightness). The experimental group showed a significantly higher change in b value, thus yellow shade, than the control (p < 0.05). 3. None of the participants complained of tooth hypersensitivity or soft tissue complications, confirming the safety of both whitening agents.