• The Journal of Korean Academy of Prosthodontics
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• v.54 no.4
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• pp.379-386
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• 2016

Purpose: The present study aims at researching the subjective satisfaction of patients who have experienced both conventional impression taking and digital impression taking to measure the possibility of wide clinical application of digital impression. Materials and methods: The study surveyed 170 adult patients over the age of 20, between October 2015 and April 2016, who voluntarily consented to participation and who experienced both conventional impression and digital impression at five dental hospitals that use intraoral digital impression. A total of 128 surveys were used for data analysis, involving frequency analysis, multiple response frequency analysis, descriptive statistics, and contingency table analysis, with the significance level set at 0.05. Results: Responses on the reason for taking impressions using the digital method appeared in the order of 'for implant treatment' (43.8%), 'for crown treatment' (30.5%), and 'for inlay treatment' (15.6%). Patients satisfaction was higher for digital impression taking than conventional impression taking (P<.05). As the preferred choice of impression, digital impression (60.2%) was higher than conventional impression (11.7%). Responses on the reason for choosing digital impression taking appeared in the order of 'no vomiting reflex' (35.1%), 'reliability of 3D digital scanning' (33.8%), and 'short time' (33.8%). Conclusion: The patients preferred digital impression taking to conventional impression taking in terms of satisfaction.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.3
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• pp.562-570
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• 2008

Amelogenesis imperfecta is a group of hereditary defects of enamel, unassociated with any other generalized defects. It is classified into 14 subtypes according to different clinical and genetic features. According to its clinical features, it is classified into hypoplastic type, hypocalcified type and hypomaturation type. However, these features tend to co-exist often. Dental features associated with amelogenesis imperfecta include quantitative and qualitative enamel deficiencies, pulpal calcification, root malformations, abnormal eruption, impaction of permanent teeth, progressive resorption of root and crown, congenital missing teeth and anterior and posterior open bite occlusions. The first case patient is a 16 month-old child with discoloration of deciduous teeth. All of her deciduous and permanent dentition has shown amelogenesis imperfecta. The restorational, orthodontic and recent prosthodontic treatments have been completed. Another patient is a 9 year and 3 month-old child with amelogenesis imperfecta in both deciduous and permanent dentition. The restoration has been done and the prosthodontic treatment is planned after the completion of growth. Above cases indicate that amelogenesis imperfecta occurs both in deciduous and permanent dentition, and it requires the long term treatment and care.

• The Journal of the Korea Contents Association
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• v.10 no.11
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• pp.228-234
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• 2010

Ni-Cr and Co-Cr alloy uncontained Be element for using as dental porcelain alloy were analyzed the mechanical properties through bonding strength and fracture test after the bonding with porcelain. The bonding strengths between alloy and ceramic were measured through the shear bond strength test. Consequently, the T-3 group contained Be element that had shear strength of 41.13(${\pm}5.11$)MPa was showed the highest shear strength than the other groups. The second highest group was a verabond contained Be element that had shear strength of 40.72(${\pm}5.98$)MPa. The results of the other groups according to the shear strength were Wirobond(38.40(${\pm}9.66$)MPa) belonged to Co-Cr alloy, and Verabond 2V(32.77(${\pm}4.31$)MPa), Bellabond N(28.63(${\pm}6.39$)MPa), Bellabond plus(24.97(${\pm}6.13$)MPa), Argeloy N.P. Star(22.69(${\pm}3.41$)MPa) uncontained Be element, respectively. The morphological aspects of the fracture surface between alloys and ceramic were observed that all groups were caused mixed failure as conformation attached ceramic fragments to metallic surface by fracture process.

• The Journal of Korean Academy of Prosthodontics
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• v.56 no.3
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• pp.212-217
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• 2018

Purpose: This study was to assess clinically the incidence of abutment screw loosening of posterior implant-supported fixed prosthesis and its affecting factors. Materials and methods: 391 implant-supported crowns restored from January 2013 to January 2016 were included in this study. All restorations were fabricated with either a single crowns or a splinted crown, and cemented with temporary cement. The incidence of abutment screw loosening is investigated and gender, restoration position, opposing teeth, restoration type, abutment connection type were assessed as possible factors affecting abutment screw loosening. Results: During the observation period (2 - 5 years), abutment screw loosening was found in 29 restorations (7.4%). It took 3 to 48 months (means 19.5 months) to loose the screw, and three of these implants were fractured. Among the factors considered, there were statistically significant differences at abutment screw loosening rate between molar group (9.4%) and premolar group (2.6%) (P<.019). According to the type of opposing teeth, there were statistically significant differences between nature teeth (74.7%) and implant (25.0%), removable denture (3%) (P<.019). The other possible factors did not have a significant effect on loosening of the abutment. Conclusion: The incidence of abutment screw loosening in posterior restoration was 7.4%. Abutment screw loosening were more likely to occur in molars group than premolar group, and according to the opposing teeth, there were the greatest frequency in nature teeth than implant and removal denture. There was a statistically significant difference.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.3
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• pp.480-487
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• 2001

In children and adolescents, oral and maxillofacial trauma is one of the most common causes of dental and periodontal damage, which often induces crown fracture of the permanent anterior teeth. Frequently, these traumatized teeth lose their vitality, and require routine endodontic treatment if their root apices are closed. However if their apices are not fully closed, further root formation should be promoted by apexification or apexogenesis. Calcium hydroxide is a biocompatible & bacteriostatic material, and is widely used for apexification. However it has several disadvantages which include the need for multiple visits and patient cooperation, low strength and technical sensitivity in a broad apex. In one-visit apexification using IRM or SuperEBA, patient's visits can be minimized. However, their biocompatibility is questionable. Mineral trioxide aggregate(MTA) is a relatively new material. It is considered biocompatible with periapical hard tissue and has good marginal sealing ability. MTA is also known to help facillitate the growth of the cementum around it. In this case report, apexification with MTA was attempted on traumatized maxillary central incisors with immature root apices, and favorable clinical results were achieved.

• Journal of the korean academy of Pediatric Dentistry
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• v.40 no.4
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• pp.260-267
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• 2013

The aim of this study was to analyze the three dimensional characteristics of the size, shape and location of mesiodens and their effect on permanent teeth arrangement using Cone-beam computed tomography(CBCT). 191 patients under 15 years old who had visited the hospital between June 2006 and December 2012 and taken CBCT were investigated. Among them, 43 patients with diastema were analyzed to investigate the correlation between the amount of diastema and the mesiodens. The results showed that mesiodens were found in males 3.9 times more than females and found most in 7 years old. The mean length of mesiodens was 13 mm and the width was 6.8 mm. The conical shape comprised of 52.9%. Many mesiodens were located in the palatal side rather than the labial side and located vertically near the crown. 63.0% of mesiodens were reversed and the common complications were delayed eruption followed by diastema, and teeth rotation. And the amount of diastema had correlation with size and mesiodistal position of the mesiodens. The current study used 3D analysis to show the size and position of mesiodens and occurrence distribution of complication. Among these, the amount of diastema had shown the correlation with the size and mesiodistal position of mesiodens.

• Restorative Dentistry and Endodontics
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• v.18 no.2
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• pp.357-367
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• 1993

The purpose of this study was to evaluate the fracture strength of class II restored premolars with amalgam, posterior composite, amalgam - Ketac silver, resin - Ketac silver restorations at marginal ridge. Fifty extacted maxillary and mandibular premolar teeth that were caries free, fracture free, and restoration free were selected and randomly divided into five groups : Group 1 : 10 intact teeth, Group 2 : 10 teeth with class II cavities and restored with, amalgam, Group 3: 10 teeth with class II cavities and restored with posterior resin, Group 4 : 10 teeth with class II cavities and restored with amalgam - ketac silver, Group 5 : 10 teeth with class II cavities and restored with resin - Ketac silver. All teeth were mounted in base of dental stone within metal rings of 2cm diameter, exposing only the crown portion. Class II mesio - occlusal or disto - occlusal cavities were prepared into specimens of Group 2 through 5 by using a No. 710 fissure bur. The occlusal portion was prepared to a faciolingual width of 1.5mm and a pulpal depth of 1.5mm. The proximal protion was prepared to a faciolingual width of 4mm, a occlusogingival height of 4mm, and a gingival floor of 1.5mm. The teeth in Group 2 and 3 were resotored with silver amalgam apd posterior resin respectively. In Group 4 and 5, proximal portions were first filled with Ketac silver 1.5mm gingivally and remaining cavities were restored with amalgam and posterior resin respectively. All specimens were stored in 100 % relative humidity at $37^{\circ}C$ for 48 hours before testing. All teeth were subjected to a compressive load in a Universal Instron Testing Machine at marginal ridges. The loads required to fracture the restorations were recorded in killograms and the data obtained were subjected to statisticall analysis. The results were all follows : 1. The fracture strength of Group 1 which were unprepared were $100{\pm}10.1\;kg$ and the higher values than Group 2, 3, 4, 5 which were prepared and resotred. 2. In restored groups, Group 2 had the higher fracture strength($81.8{\pm}12.4\;kg$) than other groups and Group 4 had the lowest fracture strength($66.8{\pm}9.2kg$). 3. There were significant differences between fracture strength of between Group 1 and Group 3, 4, 5(P<0.05), but not significant difference between fracture strength of Group 2, 3, 4, 5(P>0.05).

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.2
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• pp.256-261
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• 2004

Pulp canal obliteration(PCO) is seen commonly in dental pulp after traumatic tooth injuries and is recognized clinically as early as 3 monthly after injury. Pulp canal obliteration is characterized by deposition of hard tissue within the root canal space and yellow discoloration of the clinical crown. Opinion differs among practitioners as to whether to treat these cases upon early detection of PCO or to observe them until symptoms or radiographic signs of pulpal necrosis are detected. PCO may make root canal treatment necessary because of the development of apical periodotitis or for cosmetic reasons. If carefully executed, root canal treatment in teeth with an PCO is hightly successful and may act as a basis for internal bleaching. During a game, a 12-year-old girl was hit in the face. At that time, she was diagnosis a subluxation of the maxillary right central incisor. At the 24-month recall examination, a root canal of the tooth had been calcified and discolored gradually. We performed endodontic treatment to prevent perfect pulp canal obliteration and internal bleaching.

• Journal of the korean academy of Pediatric Dentistry
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• v.38 no.1
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• pp.62-67
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• 2011

Early eruption refers to an accelerated eruption of a tooth beyond the normal eruption period. The clinical findings of an early erupted tooth with little formation of crown and/or root include severe mobility, pain on chewing, hypocalcification of the enamel, and inclination, displacement, and rotation of the tooth. The radiographic findings include underdeveloped root and insufficient bone support. Early eruption of a permanent tooth can cause several complications such as chronic trauma, pain, edema, an increased rate of premolar impaction and tooth displacement and/or rotation. Therefore, when a permanent tooth erupts earlier than its normal eruption period with accompanying symptoms, appropriate treatments should be done as soon as possible. A female patient of age 7 without any systemic disease was referred from a local dental clinic with chief complaint of severe mobilities and pain in both upper first premolars. According to the clinical and radiographic examinations, the permanent teeth erupted earlier with barely formed roots, severe mobilities, edema, and pain. This case is to report the successful accomplishment of root formations and stabilization of teeth after applying intraoral fixed appliances using bands and spurs for 14 months.

• Journal of Dental Rehabilitation and Applied Science
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• v.22 no.3
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• pp.221-230
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• 2006

Recently, the need for esthetic results has increased the interest for all-ceramic crown prosthesis. Furthermore, the development of zirconium core via CAD/CAM system has allowed the all ceramic restorations to be applied to almost all fixed prosthesis situations. But, the increased strength has been reported to increase in proportion with the bond strength of cement, and recently, the tribochemical system which increases the bond strength through, silica coating and silanization has been introduced. The purpose of this study was to compare the $Rocatec^{TM}$ system and $CoJet^{TM}$ system with the traditional acid etching and silanization method of the irconium based ceramic. The surface character was observed via SEM(X2000), and the bond strength with the resin cement were measured. 50 In-Ceram Zirconia (Adens, Korea) discs were fabricated and embedded in resin, group 1 was treated with glass-bead blasting and cleaning, group 2 was treated with 20% HF for 10 minutes and silanized, group 3 was treated with the $Rocatec^{TM}$ system, and group 4 was treated with the $CoJet^{TM}$ system. Each group was comprised of 10 specimens. The specimens were cemented to a $3mm{\times}5mm$ resin block with Super-Bond C&B. The shear bond strength was measured with the $Instron^{(R)}$ 8871 at a crosshead speed of 0.5mm/min. The results were as follows. 1. According to SEM results, there were little difference between group 1 & group 2, but in group 3 and 4, silica coating was detected and there was increase in surface roughness. 2. The shear bond strength decreased in the order of group 3(46.28MPa), group 4(42.04MPa), group 2(31.56MPa), and group 1(27.46MPa). 3. There was significant differnce between group 1&2 and group 3&4(p<0.05). From the results above, it can be considered that the conventional method of acid etching and silane treatment cannot increase the bond strength with resin cements, and that by applying the tribochemical system of $Rocatec^{TM}$ system and $CoJet^{TM}$ system, we can achieve a stronger all ceramic restoration. Further studies on surface treatments to increase the bond strength are thought to be needed.