• The Journal of Korean Academy of Prosthodontics
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• v.54 no.1
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• pp.1-7
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• 2016

Purpose: The aim of this study was to evaluate the effect of increased vertical dimension of occlusion on lower facial changes by facial type. Materials and methods: Lateral cephalograms from 261 patients were obtained and classified by sagittal (Class I, II, and III) and vertical (hypodivergent, normodivergent, and hyperdivergent) facial patterns. Retrusive displacement of soft tissue Pogonion and downward displacement of soft tissue Menton were measured in each group after 2 mm of vertical dimension of occlusion was increased at the lower central incisor using a virtual simulation program. The ratio of both displacements was calculated in all groups. The statistical analysis was done by 2-way ANOVA and Post hoc was done by Tukey test (5% level of significance). Results: Retrusive displacement of soft tissue Pogonion in Class III group was statistically different compared to Class I and II, and in vertical facial groups all 3 groups were significantly different (P<.05). Downward displacement of soft tissue Menton showed statistically significant difference between all sagittal groups and vertical groups (P<.05). The ratio of both displacements showed statistically significant difference in all sagittal groups and vertical groups (P<.05), and Class II hyperdivergent group had the highest value. Conclusion: Lower facial change was statically significant according to the facial type when vertical dimension of occlusion increased. Class II hyperdivergent facial type showed the highest ratio after increase in vertical dimension of occlusion.

• Journal of Dental Rehabilitation and Applied Science
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• v.27 no.1
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• pp.25-39
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• 2011

In animal studies, Magnesium (Mg) - incorporated oxidized implants showed significant enhancement of the bone response. This prospective clinical trial was performed to investigate the success rate, implant stability and marginal bone loss of Mg oxidized clinical implant. The experimental protocol was approved by Institutional Review Board of the Gangneung-Wonju National University Dental Hospital. Fifty healthy patients had partial edentulism were included in this study. Mg oxidized clinical implants (Implant M, Shinhung, Korea) were installed and restored with conventional protocol. The patients were recalled at 1, 3, 6 months after functional loading. Implant stability quotient (ISQ) was measured and periapical radiographic images were obtained. Amount of marginal bone loss was calculated with calibrated images from periapical radiographs. Repeated measured analysis of variance and post hoc Tukey test were used to compare the mean ISQ and bone level. A total of 101 implants were analyzed. The mean ISQ values increased continuously with time lapse from 68.4 at fixture installation to 71.5 at 6 months after loading. Implant stability was correlated with gender, fixture diameter, bone quality and implant sites. The mean marginal bone loss during 6 months after loading was 0.26 mm. There was no failed implant and six-month success rate was 100%. Within the limitations of this study, the six-month success rate of Mg oxidized implant was satisfactory. The implant stability and marginal bone level were excellent. However, further longer clinical studies will be needed to confirm the success of Mg oxidized clinical implant.

• Restorative Dentistry and Endodontics
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• v.25 no.4
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• pp.499-508
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• 2000

The purposes of this study were to evaluate the validity of 2 kinds of digital radiography techniques in evaluating the radiopacity comparison of restorative materials and to determine the relative radiopacities of several kinds of compomer and flow able resin using these techniques. After taking radiographs of an aluminum step wedge, con-elation of optical density calibration curves were evaluated between conventional radiography with transmission densitometer and CD-Dent digital radiography (storage phosphor system) and between conventional one and RVG$^{(R)}$ digital radiography (CCD system). Compomers such as Dyract$^{(R)}$ AP, Compoglass$^{(R)}$, and Dyract flow$^{(R)}$, and flowable resins such as Ultraseal-XT$^{(R)}$ plus$^{TM}$, Revolution$^{TM}$, Aeliteflo$^{TM}$ and Tetric-flow$^{(R)}$ were used. Five specimens of 5mm in diameter and 2 mm thick were fabricated with each material. Radiopacities of the materials were measured using the above radiographic techniques and compared. The results were as follows: 1. When the optical density calibration curves were compared, conventional radiography and both CD-Dent and RVG$^{(R)}$ digital radiographies showed very high inverse correlations (${\gamma}$=-0.95, ${\gamma}$=-0.98 ; p<0.05). 2. All the tested restorative materials showed levels of radiopacity the same as or greater than that of dentin (p<0.05), Radiopacities of Dyract$^{(R)}$ AP, Compoglass$^{(R)}$, and Tetric flow$^{(R)}$ were greater than those of Revolution$^{TM}$, Aeliteflo$^{TM}$, or dentin (p<0.05). 3. Radiopacities of Dyract$^{(R)}$ AP, Compoglass$^{(R)}$, and Tetric flow$^{(R)}$ were shown to be greater than that of enamel when conventional radiography and CD-Dent digital radiography were used (p<0.05). Radiopacity of Dyract flow$^{(R)}$ was shown to be greater than that of Enamel when conventional radiography was used (p<0.05).

• Restorative Dentistry and Endodontics
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• v.32 no.1
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• pp.37-46
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• 2007

The C-shaped canal system is an anatomical variation mostly seen in mandibular second molars, although it can also occur in maxillary and other mandibular molars. The main anatomical feature of C-shaped canals is the presence of fins or web connecting the individual root canals. The complexity of C-shaped canals prevents these canals from being cleaned, shaped, and obturated effectively during root canal therapy, and sometimes it leads to an iatrogenic perforation from the extravagant preparation. The purpose of this study was to provide further knowledge of the anatomical configuration and the minimal thickness of dentinal wall according to the level of the root. Thirty extracted mandibular second molars with fused roots and longitudinal grooves on lingual or buccal surface of the root were collected from a native Korean population. The photo images and radiographs from buccal, lingual, apical direction were taken. After access cavity was prepared, teeth were placed in 5.25% sodium hypochlorite solution for 2 hours to dissolve the organic tissue of the root surface and from the root canal system. After bench dried and all the teeth were embedded in a self-curing resin. Each block was sectioned using a microtome (Accutom-50, Struers, Denmark) at interval of 1 mm. The sectioned surface photograph was taken using a digital camera (Coolpix 995, Nikon, Japan) connected to the microscope. 197 images were evaluated for canal configurations and the minimal thickness of dentinal wall between canal and external wall using 'Root Thickness Gauge Program' designed with Visual Basic. The results were as follows : 1. At the orifice level of all teeth, the most frequent observed configuration was Melton's Type C I (73%), however the patterns were changed to type C II and C III when the sections were observed at the apical third. On the other hand, the type C III was observed at the orifice level of only 2 teeth but this type could be seen at apical region of the rest of the teeth. 2. The C-shaped canal showed continuous and semi-colon shape at the orifice level, but at the apical portion of the canal there was high possibility of having 2 or 3 canals 3. Lingual wall was thinner than buccal wall at coronal, middle, apical thirds of root but there was no statistical differences.