• The Journal of Korean Academy of Prosthodontics
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• v.58 no.4
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• pp.313-320
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• 2020

Purpose: The purpose of this study was to evaluate the machining precision and the marginal and internal fit of single restorations fabricated with three types of lithium disilicate ceramic blocks and to evaluate the correlation. Materials and methods: Single restorations were designed using a CAD software program. The crown designed model file was extracted from the CAD software program. Three types of lithium disilicate blocks (Rosetta; HASS, IPS e.max CAD; Ivoclar vivadent, VITA Suprinity; VITA) were milled using a milling machine. For the fabrication of the crown scanned model file, the intaglio surface of the restoration was digitized using a contact scanner. Then, using the three-dimensional inspection software (Geomagic control X; 3D Systems), the process of the overlap of the crown designed model and the scanned model and 3-dimensional analysis was conducted. In addition, the marginal and internal fit of the crowns was evaluated by a silicone replication method. The difference among three types of single ceramic crown was analyzed using a Kruskal-Wallis H test, and Spearman correlation analysis was performed to analyze the correlation between machining precision and fitness (α=.05). Results: There was a significant difference in the machining precision and the marginal and internal fit according to the type of ceramic block (P<.001). In addition, the machining precision and the marginal and internal fit were positively correlated (P<.001). Conclusion: The marginal fit of crowns fabricated according to the types of ceramic blocks was within the clinically acceptable range (< 120 ㎛), so it can be regarded as appropriate machining precision applicable to all clinical as aspects in terms of the marginal fit.

• Journal of Dental Rehabilitation and Applied Science
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• v.34 no.4
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• pp.280-289
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• 2018

Purpose: The purpose of this randomized clinical trial is to determine whether implant length and the crown-to-implant (C/I) ratio influence implant stability and peri-implant marginal bone loss (MBL). Materials and Methods: 46 patients with single tooth missing in the posterior molar region of the mandible were included in this study. 19 implants (CMI IS-III $active^{(R)}$ long implant) of 5.0 mm diameter and 10 mm length were installed for the control group, while 27 implants (CMI IS-III $active^{(R)}$ short implant) of 5.5 mm diameter and 6.6, 7.3 or 8.5 mm length were placed for the experimental group. Each implant was inserted and immediately loaded using the digitally pre-fabricated surgical template and provisional restoration. The CAD-CAM monolithic zirconia crown was fabricated at 3 months after the surgery as a definitive restoration. The ISQ value and the MBL was measured at 48 weeks after the surgery. The correlation between the C/I ratio, MBL, and secondary implant stability was analyzed. Results: Successful results in terms of ISQ and MBL were achieved with both groups. There was no significant difference between the groups in terms of ISQ values and MBL at 48 weeks after the surgery (P > 0.05). No significant correlation was found between the C/I ratio and secondary stability as well as the C/I ratio and the MBL (P > 0.05). Conclusion: The influence of C/I ratio in both groups was not shown on the stability nor the marginal bone loss in implants supporting single crown of the mandible. Short implant could be a preferable alternative option in the reduced bone height mandible under the limited condition despite its higher C/I ratio.

• The Journal of Korean Academy of Prosthodontics
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• v.54 no.3
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• pp.210-217
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• 2016

Purpose: The aim of this study was to evaluate the marginal and internal adaptation of monolithic zirconia restoration made without physical model by digital intraoral scanner. Materials and methods: A prospective clinical trial was performed on 11 restorations as a pilot study. The monolithic zirconia restorations were fabricated after digital intraoral impression taking by intraoral scanner (TRIOS, 3shape, Copenhagen, Denmark), computer-aided designing, and milling manufacturing process. Completed zirconia crowns were tried in the patients' mouth and a replica technique was used to acquire the crown-abutment replica. The absolute marginal discrepancy, marginal gap, and internal gap of axial, line angle, and occlusal part were measured after sectioning the replica in the mesiodistal and buccolingual direction. Statistical analysis was performed using Kruskal-Wallis and Mann-Whitney U test (${\alpha}=.05$). Results: From the adaptation analysis by replica, the statistically significant difference was not found between mesiodistal and buccolingual sections (P>.05), but there was significant difference among the measurement location (P<.01). The amount of absolute marginal discrepancy was larger than those of marginal gap and internal gap (P<.01). Conclusion: Within the limitations of this study, the adaptation accuracy of model-free monolithic zirconia restoration fabricated by intraoral scanner exhibited clinically acceptable result. However, the margin of zirconia crown showed tendency of overcontour and cautious clinical application and follow up is necessary.

• The Journal of Korea Assosiation for Disability and Oral Health
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• v.15 no.1
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• pp.50-54
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• 2019

Muscular dystrophy (MD) is a heterogeneous group of inherited neuromuscular disorders, characterized by progressive muscle weakness. Severity of the disease ranges from mild to severe, and the disease is mostly caused by mutations in a number of genes. These genetic mutations cause lack of proteins which are essential for muscle cell stability. Muscle fibers are gradually replaced by fat and fibrous tissue. The muscles of the head and neck are affected in several types of MD that manifest as altered craniofacial morphology and dental malocclusion. A 3-year-10-month old, 15.0 kg boy with MD presented to Seoul National University Dental Hospital, Seoul, South Korea because of extensive carious teeth. A number of dental caries in primary dentition were identified during clinical oral examination. Due to dental anxiety and underlying systemic disease, general anesthesia was considered. General anesthesia was induced and maintained with intravenous anesthetics, propofol and remifentanil. Caries treatments - resin restoration, pulpectomy, zirconia crown restoration, stainless steel crown restoration - were performed. Under general anesthesia, successful dental procedure was done. Total intravenous anesthesia (TIVA) was performed instead of inhalation anesthesia in order to avoid risk of complications such as malignant hyperthermia and life-threatening rhabdomyolysis. With decreasing muscle function, plaque control becomes more difficult and leads to gingivitis. Especially, the open-mouth posture worsens gingivitis and can leads to malocclusions and problems in swallowing. Regular and periodic dental care is essential for maintaining oral health for patients with MD.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.1
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• pp.91-95
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• 2009

The use of stainless steel crowns are indicated for restoration of primary or permanent molars with proximal dental caries, extensive dental caries, or previous pulp treatment with increased danger of tooth fracture. Stainless steel crowns were introduced by Humphrey in 1950. For their improved durability, longevity, and success rate, they have been strongly considered for restoring extensive and multi-surfaced dental caries of molars in pediatric dentistry. However, they also have shortcomings, such as possibility of pulpal exposure or damaging proximal surface of adjacent teeth. In addition, when oversized stainless steel crowns are used, eruption of the adjacent permanent teeth may be disturbed by their prominent margin. As a means to compensate the shortcomings of stainless steel crowns, use of orthodontics bands may be considered. It is an alternative restoration method, where an orthodontic band is placed on a tooth first and cavity is restored with filling material, such as composite resin, glass ionomer, or amalgam. The use of an orthodontic band is indicated for molar restoration with cervical dental caries, extensive dental caries, enamel hypoplasia, or previous pulp treatment. Because it requires shorter chair time compared to stainless steel crown, its application is very useful for children with poor behavior. However, restoration using an orthodontic band requires good oral hygiene after its application. This case report illustrates the conservative restoration of primary molars and permanent molars with extensive dental caries using orthodontic bands.

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.5
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• pp.429-440
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• 2002

Current dental restorations present a relatively weak resistance to fracture. Owing to their unique mechanical properties, fibre-reinforced polymers are now being considered. Unidirectional or woven continuous fibres, made of glass, polyethylene, carbon or Kevlar, have been evaluated. This study focused on the use of glass fibre knitted fabrics to reinforce acrylate resins, in order to investigate the possibility to construct single crowns as well as three unit bridges. Some points affecting the final composite system were tested ; 1) static strength, with focus on the stress transfer under a occlusal contact point ; 2) modelling of a three nit bridge ; 3) fatigue strength as a posterior three unit bridge material. The study demonstrated that knitted fabric reinforcements are showing an interesting compromise between stiffness, static strength for single crown. For three unit bridge applications in the posterior arch, however knitted glass fabric reinforcements were not strong enough in fatigue An additional reinforcement in the posterior arch fixed partial denture design was recommended.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.7 no.3
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• pp.73-77
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• 2004

The purpose of this study was to improve the ornamental value of Perilla frutescens var. acuta. The growth of Perilla frutescens var. acuta was significantly varied as according to light intensities. The plant height, crown width, petiole length, leaf length, leaf width, stem diameter, and chlorophyll content were the greatest with 30% shade treatment. All of growth characteristics decreased as increasing shading levels. The anthocyanin contents also decreased with 70% shading level. The leaf color turned from dark purplish red to deep yellowish green, and the growth rate and ornamental value were the lowest with 70% shading condition.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.17 no.2
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• pp.73-83
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• 2014

This study was conducted to evaluate defects in Zelkova serrata trees using an ultrasonic tomograph (PICUS) and suggest a management plan to maintain it as a natural and cultural resource. In previous study, health information of 16 protected trees were obtained by surveying the following categories; tree appearance, crown, bark, root exposure, water and nutrition, deterioration, pest, vitality, ground status, and pollutant. The average score of health was 16.5 in 16 trees, which means that general monitor is needed for management. In this study, the evaluation result of tree's inside defects using an ultrasonic tomograph showed that 43.8% of decay rate has been found in 16 trees. In fact, some trees look to be good even though they actually have a defects causing broken by natural disaster such as strong wind. Therefore, it is urgent to put some support to the trees and come up with a protective plan. The results of this study would be useful as basic data in developing a guideline for the efficient conservation and management of big and old trees.

• Restorative Dentistry and Endodontics
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• v.8 no.1
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• pp.45-51
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• 1982

An endodontically treated tooth is likely to be brittle than a vital tooth. Internal structure of the tooth has been weakened due to a significant removal of dentin by coronal access, canal preparation. There are many controversies concerning with various methods of reinforcing an intact anterior tooth that has endodontic treatment. In this experiment, 128 extracted maxillary anterior teeth were endodontically treated, and prepared with 4 methods of restorations; Composite resin filling with zinc phosphate cement, composite resin filling without zinc phosphate cement, composite resin filling with post, and metal crown with post. An Instron testing machine was used to measure the fracture loads of the specimens. The means of the failure loads for the 4 groups were compared by F-test statistically and the failure modes were observed. The results were as follows; 1. There were no statistically significant difference between the failure loads of the four methods of restoration. 2. Teeth without post were fractured in a horizontal or oblique plane through upper or middle third of the root. 3. In the posted teeth, fractures were occurred around the post. 4. In the metal crowned teeth with post, the fracture were occurred around the post or coronal area.

• The Journal of the Korean dental association
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• v.54 no.3
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• pp.191-197
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• 2016

In the past, restoration of implant crown, ready-made abutment produced by implant manufacturer could only be used. Using straight, angled abutment, there was a limit in adaptation multiple implants. Recently, with the development of implant and CAD/CAM technology, CAD/CAM customized abutment use has become possible which is different from the past when restoration was possible with only prefabricated abutment. Not only it makes emergence profile possible which is similar to natural teeth, but also it makes insertion path possible on CAD in multiple implant restorations. However, on anterior teeth which dental esthetics is very important, another restorations which are formed with natural colored gingiva area could be required. Titanium-based zirconia prostheses which have titanium connection and zirconia structure from 1mm above fixture platform are alternative. Therefore, the purpose of this review is to analyze the characteristics, advantages and disadvantages of the abutment which is used in multiple implant restorations, and to choose right abutment when clinical trials.