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Background/purpose: The present study aimed to compare the force decay of invisible aligners for maxillary anterior teeth with 0.1 mm (D1), 0.2 mm (D2), and 0.3 mm (D3) labial movement within a simulated oral environment over 7 days. Materials and methods: The prepared invisible aligners were immersed in saliva (S) and subjected to applied force (F) for 7 days. The aligners were set and placed on the maxillary right central incisor with 0.1 mm (D1), 0.2 mm (D2), and 0.3 mm (D3) labial movement. Thin-film pressure sensors were used to measure the aligner force changes. The data were collected and analyzed by statistical methods. Results: Significant differences were observed in the initial and first-day force between the D2 and D3 groups under simulated oral environment force (SF) (P < 0.05). There was a significant difference in force decay between Day 1 and Day 7 for all groups (P < 0.05). The SFD1 group showed a significant decrease in force on Day 5 (P < 0.05), while the SFD2 and SFD3 groups showed significant force decay on Day 4 (P < 0.05). The force decay ratio on Day 7 was higher in the SFD3 group than in the SFD1 and SFD2 groups, but no significant difference was observed. Conclusion: Larger labial movement of the aligners resulted in higher force decay under artificial saliva environments, and the force decay of invisible aligners was increased by immersion time in artificial saliva.
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Background/purpose: The strength of aligners themselves has a high decay rate and is susceptible to accelerated degradation in the environment. The purpose of this study was to compare three types of invisible aligner films after being immersed in coffee, tea, cola, and red wine for seven days and to evaluate the changes in their strengths. Materials and methods: Three types of invisible aligner plates with a thickness of 0.75 mm, i.e., Duran T (polyethylene terephthalate glycol, PETG), Biolon (polyethylene terephthalate, PET), and Zendura FLX (polyurethane, PU), were soaked in artificial saliva and four drinks (coffee, tea, cola, red wine) for 1, 4, and 7 days. The strength test was performed by using the three-point bending test method. The residual strength ratio for the same type of invisible correction film at the same time was separately recorded. The independent t-test was used to indicate significant differences at P < 0.05. Results: The Biolon invisible correction film soaked in cola, red wine and artificial saliva showed significant differences on the 1st and 4th days (P < 0.05). The Duran T invisible correction film soaked in coffee and artificial saliva showed significant differences on the first day (P < 0.05). The Zendura FLX invisible correction film had a waterproof layer on the surface, and there was no significant difference between soaking in any drink and soaking in saliva (P > 0.05). Conclusion: Invisible correction films with different ingredients soaked in solutions show a strength decay phenomenon, except for those with TPU ingredients.
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Background/purpose: Zirconia crowns (ZrC) without veneering porcelain have become an effective alternative in clinical practice. Monolithic zirconia restorations fabricated by the dry milling method do not have acceptable clinical properties. This study evaluated the periodontal qualities of three-dimensional printed ZrC using the modified United States Public Health Service (USPHS) criteria. Materials and methods: A total of 15 patients who required dental crowns were recruited, and all 15 teeth were restored with digital 3D-printed ZrC. All crowns were assessed at the time of crown placement and 2, 6, and 24 weeks post-placement. Clinical parameters, including plaque index, gingival index, probing depth, crown marginal integrity, and attrition of the antagonist's teeth, were evaluated and recorded. Results: According to the Modified California Dental Association quality evaluation system, 100% of the crowns received satisfactory grades. Despite the significant increase in plaque index and gingival index at two weeks post-ZrC placement, there was no deterioration in probing depth. Moreover, there was discard usage of ZrC on the antagonist's teeth at 24 weeks posttreatment. Of the 15 crowns, one tooth had to be extracted due to a vertical root fracture. Overall, the digital 3D-printed crowns showed no adverse effects on periodontal tissues after 24 weeks of follow-up. Conclusion: The 3D-printed ZrC showed no periodontal problems. It can serve as an alternative for patients, particularly those with high esthetic expectations.
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Background: /purpose: Photobiostimulation (PBS) can affect cellular functions. The objective of the present study was to evaluate the cellular changes in periodontal ligament (PDL) cells that received different carbon dioxide (CO2) laser irradiation parameters under negative pressure culture. Materials and methods: The negative pressure-cultured PDL cells on normal medium and differentiation medium were subjected to continuous irradiation with a CO2 laser at an energy density of 5 J/cm2 or 10 J/cm2. The irradiated PDL cells were harvested at Days 1, 5 and 7, and their viability was analyzed by the Presto Blue assay and the biologic markers alkaline phosphatase (ALP), bone sialopoietin (BSP), osteopontin (OPN), osteocalcin (OC), matrix metalloproteinase-3 (MMP-3) collagen I (Col I) and cyclooxygenase-2 (COX-2) expression by reverse transcription-polymerase chain reaction (RT-PCR). Results: The PDL cell viability showed that the differentiation medium groups were higher than the normal culture groups. The cell morphologies were all expressed as spindle type. The inflammatory markers in the laser-irradiated groups were higher on the first day and decreased on the seventh day (P < 0.05). Osteogenesis markers were highly expressed at different time periods (P < 0.05). The Col I and OPN genes were highly expressed on the first day, and the Col I high expression lasted until the seventh day. The OC gene was highly expressed on the seventh day. The effects of PDL cultured in differential medium and normal medium were the same in the present study. Conclusion: A low-dose CO2 laser continuously irradiating cultured PDL cells can induce osteogenesis and reduce cell inflammatory expression.
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BACKGROUND/PURPOSE: Local anesthesia (LA) application is a routine dental work in clinic. The aim of present study was to evaluate the extent of biologic effects of LA on periodontal ligaments (PDL) or bone cells (MG63). MATERIALS AND METHODS: Local anesthetics (LAs) at different concentrations were added to PDL and MG 63 cells. The viability of the cells was analyzed using an MTT assay. The inflammatory markers, COX-2, IL-1, IL-6 and TNF-A, of PDL and MG63 cells treated with LAs were analyzed with a Western blot assay. The extract medium of the LA-treated PDL cells was added to the MG63 cells for subsequent culture and to examine the RANKL, ALP, and OPG expression. The data were statistically analyzed with p < 0.05 set as an indication of significance. RESULTS: The viability of the PDL and MG63 cells was less 50% at LAs concentrations above the 10 mM. At high LA concentrations, the PDL and MG63 cells treated with LAs became spherical in shape, or vesicles developed in the cytoplasm. The IL-1, IL-6, and TNF-A expression in the PDL groups showed no statistical differences between Septanest and Scandonest (p > 0.05). The RANKL expression in the MG63 cells increased as the Septanest and Scandonest concentrations were increased in the PDL extract medium (p < 0.05) after 48 h of culturing. CONCLUSION: The LAs with adrenaline increased inflammation in the PDL and MG63 cells. The LA-treated PDL extract medium increased the RANKL expression in the MG63 cells.
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The purpose of the present study was to evaluate the physicochemical and cytologic properties of mineral trioxide aggregate (MTA) mixed with distilled water and Na(2)HPO(4) buffer solution. The MTA setting time and pH value were evaluated. An MTA micrograph on scanning electron microscopy (SEM) was observed. Mouse fibroblasts (an L929 cell line) were used to test the toxicity of MTA after the first and seventh day of treatment by mitochondrial colorimetric assay. The results show the Na(2)HPO(4) buffer group reduced the MTA setting time, and the pH value as in the distilled water group is similar with the Na(2)HPO(4) buffer group. The mixed MTA's XRD produced similar peaks of the distilled water and Na(2)HPO(4) buffer solution groups. The L929 cell survival rate of distilled water and H(2)PO(4) buffer solution groups did not exhibit any significant difference (p < 0.05). There are differences in SEM observations both of the MTA surface and of the cells in culture on the surface of the MTA with Na(2)HPO(4) versus distilled water. The results suggest that 15% Na(2)HPO(4) buffer can be successfully used as an accelerator of MTA.