• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.1
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• pp.34-41
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• 2017

Anticonvulsants, calcium channel blockers and immunosuppressants are representative drugs related with gingival enlargement. Clinical signs and symptoms caused by drug-induced gingival enlargment frequently appear within 1 to 3 months after medication. At initial stage, it is limited to attached gingiva but may extend coronally and interfere with esthetics, mastication and speech. Interproximal spaces are common beginning area and pathologic teeth migration could be occurred by the lesion. Withdrawal or substitution of medication would be the most effective treatment of drug-induced gingival enlargement. However, periodontal treatment and further supportive periodontal therapy should be provided where change in medication is impossible. The present study reports the cases which show the resolution of inflammation with spontaneous teeth migration without change in medication. In all cases discussed in this report could be efficiently managed with proper periodontal treatment and further supportive periodontal therapy.

• Journal of Dental Rehabilitation and Applied Science
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• v.19 no.4
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• pp.269-279
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• 2003

This study investigated the mechanical properties of precious metal-ceramic alloy joined by the laser-welding and the soldering compared with the parent metal. Twenty-four tensile specimens were cast in precious metal-ceramic alloy and divided into three groups of eight. All specimens in the control group(group 1) were left in the as-cast condition. Group 2 and 3 were the test specimens, which were sectioned at the center. Eight of sectioned specimens were joined by soldering with a propane-oxygen torch, and the remaining specimens were joined by laser-welding. After joining, each joint diameter was measured, and then tested to tensile failure on an Instron machine. Failure loads were recorded, and then fracture stress(ultimate tensile strength), 0.2% yield strength and % elongation calculated. These data for three groups were subjected to a one-way analysis of variance(ANOVA). Neuman-Keuls post hoc test was then used to determine any significant differences between groups. The fracture locations, fracture surfaces were examined by SEM(scanning electron microscope). The results were as follows: 1) The tensile strength and 0.2% yield strength of the soldered group($280.28{\pm}49.35MPa$, $160.24{\pm}26.67MPa$) were significantly less than both the as-cast group($410.99{\pm}13.07MPa$, $217.82{\pm}17.99MPa$) and the laser-welded group($383.56{\pm}59.08MPa$, $217.18{\pm}12.96MPa$). 2) The tensile strength and 0.2% yield strength of the laser-welded group were about each 98%, 99.7% of the as-cast group. There were no statistically significant differences in these two groups(p<0.05). 3) The percentage elongations of the soldered group($3.94{\pm}2.32%$) and the laser-welded group($5.06{\pm}1.08%$) were significantly less than the as-cast group($14.25{\pm}4.05%$) (p<0.05). 4) The fracture of the soldered specimens occurred in the solder material and many porosities were showed at the fracture site. 5) The fracture of the laser-welded specimens occurred also in the welding area, and lack of fusion and a large void was observed at the center of the fracture surface. However, the laser-welded specimens showed a ductile failure mode like the as- cast specimens. The results of this study indicated that the tensile strengths of the laser-welded joints were comparable to those of the as-cast joints and superior to those of the soldered joints.

• Journal of Dental Rehabilitation and Applied Science
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• v.27 no.4
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• pp.393-403
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• 2011

The purpose of this study was to analyze and compare survival rates of resorbable blast media(RBM) surface and acid-etched surface implants being usually used in clinics. RBM surface implants (USII, Osstem, Busan, Korea) or acid-etched surface implants ($Osseotite^{(R)}$, Biomet $3i^{[TM]}$, FL, USA) were placed in edentulous area of 140 patients between January of 2005 and March of 2007. The number of implants was 304, and 152 out of them were RBM surface implants while another 152 were acid-etched surface implants. According to the evaluation items, the survey was performed before and after the implants installations. The 3-year survival rates of both kind of implants were calculated. 1. Total of 152 RBM surface implants were placed. Among them, one implant was failed, which was implanted in the posterior mandible with D2 bone quality. The failure was resulted from fracture of the fixture. Others showed good results and survival rate of RBM surface implant was 99.34%. 2. Total of 152 acid-etched surface implants were placed. Seven implants of them were failed, thus, survival rate was 95.39%. The causes of the failures were considered as infection, overheat and the lack of initial stability. In this research, both implants showed good 3-year survival rate, although RMB surface implant represented a better result.

• Journal of Dental Rehabilitation and Applied Science
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• v.27 no.3
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• pp.293-304
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• 2011

The purpose of this study was to investigate the displacement and pattern of stress distribution on periodontal ligaments of maxillary first and second molar, and on orthodontic mini-implant (OMI) surface, according to three different insertion angles to the bone surface of OMI using Dragon helix appliance, which is a newly introduced scissors-bite correcting appliance. OMI were placed between second premolar and first molar with three different insertion angles (45, 60, 90 degrees). Displacement and maximum stress distribution area (MSDA) were analyzed by finite element analysis. When the insertion angle to the alveolar bone surface was 90 degrees, maxillary first and second molar both exhibited MSDA at the palatal root apex. Maxillary first molar did not show any significant displacement, while the second molar exhibited intrusive and palatal displacement. On the OMI, as the insertion angle decreased, the MSDA shifted towards the tip, and the amount of displacement had increased. When the OMI was inserted at a 90 degree angle, anchor loss was minimized and scissors-bite correcting effect was maximized.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.3
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• pp.255-265
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• 2009

Recently many studies have been published on application of immediate loaded implants. However, the immediate loading protocol has not been well documented. The purpose of the present study was to evaluate the stress distribution between bone-implant interfaces and the effect of implant length in the anterior maxilla using 3 dimensional finite element analyses. The diameter 4.0 mm threaded type implants with different length(8.5 mm, 10.0 mm, 11.5 mm, 13.0 mm, 15.0 mm) were used in this study. The bone quality of anterior maxillary bone block was assumed to D3 bone. Bone-implant interfaces of immediately loaded implant were constructed using a contact element for simulating the non osseointegration status. For simplification of all the processing procedures, all of the material assumed to be homogenous, isotropic, and linearly elastic. The 178 N of static force was applied on the middle of the palatoincisal line angle of the abutment with $120^{\circ}$ angle to the long axis of abutment. Maximum von Mises stress were concentrated on the labial cortical bone of the implant neck area, especially at the cortical-cancellous bone interfaces. Compared the different length, highest peak stress value was observed at the 8.5 mm implants and the results indicated a tendency towards favorable stress distribution on the bone, when the length was increased. Presence of cortical bone was very important to immediate loading, and it appears that implants of a length more than 13 mm are preferable for immediate loading at the anterior maxilla.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.1
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• pp.39-46
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• 2010

To assess the stress distribution of implant prosthesis induced by intentional misfit using photoelastic model. Stress was measured at the surrounding bone after applying vertical load to the implant. Three implants were placed in each of three photoelastic resin blocks. No misfits were used for the control group, while for the experimental group $100{\mu}m$ misfit after cutting the crown was used. The photoelastic stress analysis was performed. In control group, stress concentration was not shown when the load was not applied, whereas stress concentration was shown only in the loaded part even when load was applied and the stress was distributed in anterior-posterior direction when applying a load in the middle. When intentional misfits were given, stress around the fixture was incurred when tightening the screw even if load was not applied. If the load was applied, stress was concentrated around the implants including areas where the load was applied. In particular, the prosthesis made of UCLA showed more stress concentration as compared with a conical abutment. In the UCLA case, concentration was shown from the apex following through the axis to the cervical area. Prosthesis with misfit makes the stress concentrated though the load was not applied and it induces even more severe stress concentration when the load was applied. This founding demonstrates the importance of the correct prosthesis production.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.3
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• pp.189-198
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• 2017

Purpose: This study aims to analyze the stress distribution of mandibular molar restoration supported by the implants with external hex and internal taper abutment connection design. Materials and Methods: Models of external connection (EXHEX) and internal connection (INCON) implants, corresponding abutment/crowns, and screws were developed. Supporting edentulous mandibular bony structures were designed. All the components were assembled and a finite element analysis was performed to predict the magnitude and pattern of stresses generated by occlusal loading. A total of 120 N static force was applied both by axial (L1) and oblique (L2) direction. Results: Peak von Mises stresses produced in the implants by L2 load produced 6 - 15 times greater than those by L1 load. The INCON model showed 2.2 times greater total amount of crown cusp deflection than the EXHEX model. Fastening screw in EXHEX model and upside margin of implant fixture in INCON model generated the peak von Mises stresses by oblique occlusal force. EXHEX model and INCON model showed the similar opening gap between abutment and fixture, but intimate sealing inside the contact interface was maintained in INCON model. Conclusion: Oblique force produced grater magnitudes of deflection and stress than those by axial force. The maximum stress area at the implant was different between the INCON and EXHEX models.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.44 no.1
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• pp.94-104
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• 2007

Iris recognition is biometric technology which uses a unique iris pattern of user in order to identify person. In the captured iris image by conventional iris recognition camera, it is often the case with eyelid occlusion, which covers iris information. The eyelids are unnecessary information that causes bad recognition performance, so this paper proposes robust algorithm in order to detect eyelid. This research has following three advantages compared to previous works. First, we remove the detected eyelash and specular reflection by linear interpolation method because they act as noise factors when locating eyelid. Second, we detect the candidate points of eyelid by using mask in limited eyelid searching area, which is determined by searching the cross position of eyelid and the outer boundary of iris. And our proposed algorithm detects eyelid by using parabolic hough transform based on the detected candidate points. Third, there have been many researches to detect eyelid, but they did not consider the rotation of eyelid in an iris image. Whereas, we consider the rotation factor in parabolic hough transform to overcome such problem. We tested our algorithm with CASIA Database. As the experimental results, the detection accuracy were 90.82% and 96.47% in case of detecting upper and lower eyelid, respectively.

• Journal of the korean academy of Pediatric Dentistry
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• v.40 no.4
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• pp.296-305
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• 2013

For the purpose of evaluating the prevalence of malocclusion and self-esteem in adolescents, 1,380 middle-school students in the Yangsan area were surveyed by oral examination and questionnaires and the obtained results were as follows: The distribution of 1st molar occlusion by Angle's classification was 69.0, 19.4, 10.6% for Class I, II and III respectively. In the horizontal relationship, the prevalence of normal overjet and crossbite was 86.9% and 5.6% respectively whereas larger and extremely larger overjet was found in 6.6% and 0.8%. In the vertical relationship of anterior teeth, normal, deep overbite and openbite was shown in 94.1%, 4.7%, and 1.2%. For the midline discrepancy, the distribution of groups with 0~1 mm, 2~4 mm and over 5 mm was 98.2%, 1.4%, and 0.4%. Crowding only in the maxilla was found in 9.6%, while that only in the mandible and in both arches was 14.1% and 24.1% respectively. Spacing only in the maxilla was seen in 3.0%, while that only in the mandible and in both arches was 2.4% and 1.7% respectively. Significant difference in self-esteem was revealed in female and malocclusion groups of crossbite and openbite(p < 0.05).

• Journal of Dental Rehabilitation and Applied Science
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• v.32 no.2
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• pp.117-122
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• 2016

Purpose: Gingival whitening is one of dental treatment purposes which is close to treating aesthetic disorders. Initial gingival whitening treatment was done by dermabrasion using a high power Diode Laser. However, this treatment method cannot be free from any infection or pain after the treatment. Therefore, we have decided to progress gingival whitening treatment using a low power LED laser. Materials and Methods: The laser was irradiated on pork meat then the safety of output power, temperature change and skin denaturalization was measured. Bison 365 nm LED laser was irradiated on oral mucosal pigment of a 15 - 20 kg beagle for 15 min for 1 - 2 weeks, one or two times each. Any pigment loss was checked through Hematoxyline-Eosin staining. Results: The melanin pigments at the area of 365 nm LED Laser irradiation were decreased. Conclusion: The 365 nm LED Laser proposed in this study is considered to compensate the bleaching effect achieved by either using Diode laser or surgical methods.