• Journal of Korean society of Dental Hygiene
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• v.14 no.5
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• pp.617-622
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• 2014

With the explosive increase of esthetic demands by patients, many dental materials for the esthetic restoration have been introduced. Recently, zirconia based restorations are using for the cases of single crown, bridges, implant prostheses etc. Zirconia have superior mechanical properties and biocompatibility. Owing to the properties of high strength, zirconia has to be manufactured by CAD/CAM system. Dental CAD/CAM system is a futuristic treatment and technical system which makes it possible to produce the precision and uniform prosthesis and also standardize the treatments. This article introduces the characteristics of zirconia, fabrication procedure using CAD/CAM system and procedure for the cementation of zirconia based restoration.

• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.4
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• pp.399-406
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• 2013

Reports about the intrusion of a natural tooth bounded by implants are very rare, although some concerns have been discussed on the intrusion of teeth connected to implants. A female aged 56 years received an implant (mandibular right first premolar) and post/core onto root rest (mandibular right second premolar) and was restored by single zirconia crown, respectively. Molars were implant restorations. Four month after loading, second premolar was intruded and prominent gap was shown between opposite tooth. Because nonspecific discomfort was expressed, observation was decided after explanation of prognosis of tooth without treatment. Three month later reversal to original position was detected on the periapical radiographs and fully recovered position with intimate contact was completed 11 more months later. Till now 2 years and 3 month observation is being performed. Through the observation of spontaneous recovery of a natural tooth bounded by implants, the cause of intrusion and a mechanism of spontaneous recovery could be estimated.

• Journal of Periodontal and Implant Science
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• v.34 no.2
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• pp.303-315
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• 2004

The success and failure of dental implants depends on various factors such as patient's systemic status, quantity and quality of surrounding bone, presence or absence of marginal infection and mechanical loading condition. The measurement of crestal bone changes around the implants is implemental to evaluate the success and long-term prognosis of the implant. This study was to evaluate the cumulative survival rate of the implants which had been placed in the Department of Periodontics, Chonnam National University Hospital between 1992 and 2003, and to observe the crestal bone loss around the implants which had at least 2 consecutive periapical radiographs after connecting the transmucosal abutment. The radiographs were scanned and digitalized, and the crestal bone levels on the mesial and distal surface of implants were measured using Image analyzer (Image Pro Plus, Media Cybernetics, USA), immediately after implant placement, at 2nd surgery, and 3 months, 6 months, 1 year, and every year thereafter. Any bone loss was not observed during the period between the 1stand 2nd surgery, and the bone loss was 0.86 ${\pm}$ 0.92 mm for the first year of loading after connecting the transmucosal abutment. After 1 year of loading, annual bone loss was 0.1 ${\pm}$ 0.27 mm, and total bone loss was 0.90 ${\pm}$ 0.80 mm (during the average follow-up periods of 22.5 ${\pm}$ 25.6 Mos), The implant, with smooth surface, in the mandible, and with the fixed bridge prosthesis showed greater bone loss, compared to those, with the rough surface, in the maxilla and with single crown. In systemically diseased patients (including DM or osteoporosis), the greater bone loss was observed. The cumulative survival rate among 432 implants was 94.10% for 7 years. Among 15 failed implants, 9 implants were removed due to mobility from disintegration of bone-implant interface. From this results, crestal bone loss around the implants were greatest during 1 year after transmucosal abutment connection, and various factors could affect peri-implant bone loss. To prevent and predict the bone loss around the implants and improve the prognosis, further comprehensive maintenance and follow-up schedules are required.

• 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.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.4
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• pp.457-462
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• 2009

Purpose: The objective of this systematic review was to obtain the comprehensive survival rates of short implants. Then it was examined that whether treatment using short implants has favorable results. Methods: A MEDLINE search was performed, the data obtained from many articles about length, diameter, site of placement, surface treatment and prosthetic design were analyzed. Results and discussion: The data obtained from many articles were analyzed, and it was found that the survival rate of short implants was 95.87%, short implants has similar outcomes to those reported for standard implants. On the other hand, in the comparison the survival rate of 3 groups divided by the diameter of implants under 4 mm, 4-5 mm, and above 5 mm, a statistically significant difference was detected in under 4mm group. In implant group with 6-7 mm length, a group with 5-6 mm diameter has survival rate of 97.01%, groups with 3.1-4.8 mm diameter has survival rate of 92.96%, which was statistically significantly different. In the result of surface feature, the roughed surface groups of short implant showed a higher survival rate by approximately 6.3% than machined surface group. In the result of prosthetic design, survival rate of short implant was considerably lower for the single implant crown group (94.3%) than splinting group (99.4%).

• The Journal of Advanced Prosthodontics
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• v.10 no.1
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• pp.65-72
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• 2018

PURPOSE. The aim of this in vitro study was to investigate the fracture resistance under chewing simulation of implant-supported posterior restorations (crowns cemented to hybrid-abutments) made of different all-ceramic materials. MATERIALS AND METHODS. Monolithic zirconia (MZr) and monolithic lithium disilicate (MLD) crowns for mandibular first molar were fabricated using computer-aided design/computer-aided manufacturing technology and then cemented to zirconia hybrid-abutments (Ti-based). Each group was divided into two subgroups (n=10): (A) control group, crowns were subjected to single load to fracture; (B) test group, crowns underwent chewing simulation using multiple loads for 1.2 million cycles at 1.2 Hz with simultaneous thermocycling between $5^{\circ}C$ and $55^{\circ}C$. Data was statistically analyzed with one-way ANOVA and a Post-Hoc test. RESULTS. All tested crowns survived chewing simulation resulting in 100% survival rate. However, wear facets were observed on all the crowns at the occlusal contact point. Fracture load of monolithic lithium disilicate crowns was statistically significantly lower than that of monolithic zirconia crowns. Also, fracture load was significantly reduced in both of the all-ceramic materials after exposure to chewing simulation and thermocycling. Crowns of all test groups exhibited cohesive fracture within the monolithic crown structure only, and no abutment fractures or screw loosening were observed. CONCLUSION. When supported by implants, monolithic zirconia restorations cemented to hybrid abutments withstand masticatory forces. Also, fatigue loading accompanied by simultaneous thermocycling significantly reduces the strength of both of the all-ceramic materials. Moreover, further research is needed to define potentials, limits, and long-term serviceability of the materials and hybrid abutments.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.36 no.6
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• pp.247-252
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• 2014

Purpose: This study compares the prognosis (the survival rate and marginal bone loss) of resorbable blasting media (RBM) surface implants and sandblasting with large-grit and acid-etching (SLA) surface implants in the early loading. Methods: This study targeted 123 patients treated by implants installation from January 2008 to March 2010. The loading was initiated in the maxilla within three to four months and in the mandible within one to two months. The types of restoration were single crown and fixed partial prosthesis. Those functioned over one year. The implants were classified by the surface of implants as Group 1: RBM surface (GS III; OSSTEM, Busan, Korea) and, Group 2: SLA surface (Superline; Dentium, Seoul, Korea). The groups were categorized by maxilla and mandible and compared by survival rate, marginal bone loss through clinical records evaluation, and radiographic measurements. Results: The marginal bone loss in the maxilla was $0.14{\pm}0.34mm$ (Group 1) and $0.30{\pm}0.37mm$ (Group 2), a statistically significant difference (P<0.05). In the mandible those were $0.28{\pm}0.54mm$ (Group 1) and $0.20{\pm}0.33mm$ (Group 2), not significant (P>0.05). There was no significant difference of marginal bone loss between maxilla and mandible by groups. During observation there was no implant failure, a survival rate of 100%. Conclusion: Both surfaces showed an excellent survival rate, and the marginal bone loss was not substantial.

• The Journal of Advanced Prosthodontics
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• v.7 no.3
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• pp.183-190
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• 2015

PURPOSE. This study evaluated the fracture load of customized zirconia abutments with titanium insert according to preparation depths, with or without 5-year artificial aging. MATERIALS AND METHODS. Thirty-six identical lithium disilicate crowns (IPS e.max press) were fabricated to replace a maxillary right central incisor and cemented to the customized zirconia abutment with titanium insert on a $4.5{\times}10$ mm titanium fixture. Abutments were fabricated with 3 preparation depths (0.5 mm, 0.7 mm, and 0.9 mm). Half of the samples were then processed using thermocycling (temperature: $5-55^{\circ}C$, dwelling time: 120s) and chewing simulation (1,200,000 cycles, 49 N load). All specimens were classified into 6 groups depending on the preparation depth and artificial aging (non-artificial aging groups: N5, N7, N9; artificial aging groups: A5, A7, A9). Static load was applied at 135 degrees to the implant axis in a universal testing machine. Statistical analyses of the results were performed using 1-way ANOVA, 2-way ANOVA, independent t-test and multiple linear regression. RESULTS. The fracture loads were $539.28{\pm}63.11$ N (N5), $406.56{\pm}28.94$ N (N7), $366.66{\pm}30.19$ N (N9), $392.61{\pm}50.57$ N (A5), $317.94{\pm}30.05$ N (A7), and $292.74{\pm}37.15$ N (A9). The fracture load of group N5 was significantly higher than those of group N7 and N9 (P<.017). Consequently, the fracture load of group A5 was also significantly higher than those of group A7 and A9 (P<.05). After artificial aging, the fracture load was significantly decreased in all groups with various preparation depths (P<.05). CONCLUSION. The fracture load of a single anterior implant restored with lithium disilicate crown on zirconia abutment with titanium insert differed depending on the preparation depths. After 5-year artificial aging, the fracture loads of all preparation groups decreased significantly.

• The Journal of Korean Academy of Prosthodontics
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• v.56 no.3
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• pp.258-268
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• 2018

Purpose: This study systematically examines literatures on the suitability of prostheses and accuracy of obtained impressions to see if digital impressions using intraoral scanners can replace traditional impressions. Materials and methods: A MEDLINE/PubMed search and manual search was performed for studies written in English about accuracy of digital impression published in dental journals from August 1, 1997, to July 31, 2017. Depending on criteria, the data for the selected articles were independently organized into standardized spreadsheets by 2 reviewers. Results: Among the total 35 studies met the inclusion criteria, there were 26 studies comparing the suitability of prostheses, and 9 studies comparing the accuracy of impressions through scan data without prostheses. Most studies used prostheses to compare the accuracy of impression techniques. Conclusion: This review suggests that making single crown or mesio-distally short prostheses with digital impressions is clinically reliable in natural teeth. However, there is still a limit to making mesio-distally long prostheses with digital impressions from the lack of related studies. Digital impression cannot fully replace traditional impressions in implant prostheses yet.

• The korean journal of orthodontics
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• v.39 no.1
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• pp.43-53
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• 2009

Objective: The purpose of this study was to compare the difference in three dimensional tooth movement using three different wire sizes($0.018{\times}0.025-in,\;0.016{\times}0.022-in$ 0.016-in) on a NiTi scissors-bite corrector. Methods: Computed tomography(CT) images of the experimental model before and after tooth movement were taken and reconstructed into three dimensional models for superimposition. The direction and the amount of tooth movement were measured and analyzed statistically. Results: The lingual and intrusive movements of the crown of the maxillary second molar were increased as the size of the NiTi wire increased. The roots of the maxillary second metals moved buccally except for the 0.016-in group. The intrusive movement of the roots of the maxillary second molars was increased as the size of the NiTi wire increased. Due to the use of orthodontic mini-implants, anchorage loss was under 0.2 mm on average. Conclusions: The $0.018{\times}0.025-in$ NiTi wire was most effective in lingual and intrusive movement of the maxillary second molar which was in scissors-bite position. Indirect skeletal anchorage with a single orthodontic mini-implant was rigid enough to prevent anchorage loss.