• Journal of the Korean Academy of Esthetic Dentistry
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• v.26 no.2
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• pp.68-83
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• 2017

With the increasing popularity of dental CAD / CAM, the kinds of materials that can be used and the range that can be utilized are also increasing. One of the biggest advantages of a dental CADCAM is that you can make a final prosthesis with one visit, but in case of zirconia or a complex aesthetic prosthesis, it is often difficult to make it in one day. In this case, temporary PMMA material can be used to provide a temporary crown with aesthetic and functional properties to the patient and can be used as a test crown or template for the final prosthesis. And if you are with a 5-axis milling machine in a clinic, you can make a temporary crown precisely to a large extent in a short time. In this article, various applications and clinical cases of PMMA temporary crown in the clinic will be presented.

• The Journal of Advanced Prosthodontics
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• v.11 no.5
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• pp.271-279
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• 2019

PURPOSE. The newest technologies for digital implant impression (DII) taking are developing rapidly and showing acceptable clinical results. However, scientific literature is lacking data from clinical studies about the accuracy of DII. The aim of this study was to compare digital and conventional dental implant impressions (CII) in a clinical environment. MATERIALS AND METHODS. Twenty-four fixed zirconia restorations supported by 2 implants were fabricated using conventional open-tray impression technique with splinted transfers (CII group) and scan with Trios 3 IOS (3Shape) (DII group). After multiple verification procedures, master models were scanned using laboratory scanner D800 (3Shape). 3D models from conventional and digital workflow were imported to reverse engineering software and superimposed with high resolution 3D CAD models of scan bodies. Distance between center points, angulation, rotation, vertical shift, and surface mismatch of the scan bodies were measured and compared between conventional and digital impressions. RESULTS. Statistically significant differences were found for: a) inter-implant distance, b) rotation, c) vertical shift, and d) surface mismatch differences, comparing DII and CII groups for mesial and distal implant scan bodies ($P{\leq}.05$). CONCLUSION. Recorded linear differences between digital and conventional impressions were of limited clinical significance with two implant-supported restorations.

• Journal of Korean society of Dental Hygiene
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• v.22 no.4
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• pp.225-230
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• 2022

Objectives: Patients with excessive tooth wear should first be diagnosed for the etiology of the tooth wear. Causes of tooth wear include bruxism, clenching, and taking medications for systemic diseases. After identifying the cause of tooth attrition, the final prosthesis should be restored with an appropriate vertical dimension. Methods: A 79-year-old man with worn out teeth desired a whole dental treatment. He was on medications for high blood pressure and asthma. The treatment proceeded with a consultation with a medical doctor. The medications for asthma evoked multiple teeth wear and a loss of the vertical dimension. After recovery of 3 mm of vertical dimension, 2 months of evaluation was followed by an interim prosthesis. Results: The increased vertical dimension caused no problem in function and esthetics, and the final restoration was performed with a full monolithic zirconia crown. Group function, adequate anterior guidance, and the occlusal plane were determined. Conclusions: After the final restoration, the patient was both esthetically and functionally satisfied, and a night guard splint was delivered to prevent prosthesis fracture. The patient was informed about the potential tooth wear associated with asthma drugs and educated to visit the clinic regularly.

• The Journal of Korean Academy of Prosthodontics
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• v.56 no.2
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• pp.173-178
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• 2018

The direct metal laser sintering (DMLS) technique would be promising for the full-arch implant-supported restorations due to reduced cost and manufacturing time without potential human errors and casting defects. The aims of this case report were to describe the successful outcome of an implant-supported fixed dental prosthesis in the edentulous maxilla by using the DMLS technology and computer-aided design and computer-aided manufacturing (CAD/CAM) monolithic zirconia crowns, and to describe its clinical implications. A healthy 51-year-old Korean woman visited Seoul National University Dental Hospital and she was in need of a rehabilitation of her entire maxilla due to severe tooth mobility. In this case, all maxillary teeth were extracted and an implant-supported fixed dental prosthesis was fabricated that involved a cobalt-chromium (Co-Cr) framework with the DMLS technique and CAD/CAM monolithic zirconia crowns. Six months after delivery, no distinct mechanical and biological complications were detected and the prosthesis exhibited satisfactory esthetics and function. In this case report, with the DMLS system, the three-dimensional printed prosthesis was created without additional manual tooling and thus, reliable accuracy and passive fit were obtained.

• Journal of the Korean Ceramic Society
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• v.39 no.11
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• pp.1055-1062
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• 2002

The phase stability and the Low Temperature Degradation(LTD) mechanism of Tetragonal Zirconia Polycrystals(TZP), sintered specimens of $Y_2O_3$-Stabilized Zirconia(2Y-TZP), doped with trivalent cations, were evaluated by investigating meachnical properties, Raman spectra, lattice parameter variation and the oxygen vacancy behavior under applied electric field. XRD observation was put forward on 2Y-TZP doped with trivalent cation whose ionic radii were larger than $Zr^{4+}(Sc^{3+},\;Yb^{3+},\;Y^{3+},\;Sm^{3+},\;Nd^{3+},\;La^{3+})$ up to 2 mol% and sintered at 1500 h for 1h. For $La^{3+}$ doping, the stability of tetragonal phase was degraded due to the formation of the pyrochlore phase $(La_2Zr_2O_7)$ as the dopant content increased above exceeded 0.5 mol%. As the dosage increased, tetragonal phase maintained for the case of $Sc^{3+}$, whose radius was similar to $Zr^{4+}$, on the other hand, the cubic phase was formed for the cases of $Yb^{3+},\;Y^{3+},\;Sm^{3+},\;Nd^{3+}$. As the radii of dopant cation increased, c/a ratio increased and it was experimentally observed that the amount of monoclinic phase decreased when the specimens were annealed at $220{\circ}C$ for 500 h.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.1
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• pp.47-51
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• 2013

With the introduction of dental implants, restoration of missing teeth with conventional fixed or removable partial dentures is being replaced with implants. Especially, with young patients, not only longevity but also esthetic factors need to be considered. Implant restorations provide long-term success functionally but, esthetic complications such as, marginal exposure due to gingival recession, loss of the papilla and dark color of metal abutments may occur. Recently, zirconia restorations with CAD/CAM technology provide functional, biocompatible and esthetic restorations possible. All-ceramic restorations using the pressed ceramic technique show better fracture toughness values than those of the conventional porcelain veneering technique. Pressed ceramic technique creates the veneer design in wax and the lost wax technique is used to create the restoration. The final contour of the restoration may be controlled during wax-up. A 22-year old female patient was restored with dental implants and zirconia restorations using the pressed ceramic technique presenting short-term but optimistic prognosis.

• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.3
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• pp.209-223
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• 2013

This study was to evaluate the stress distributions of prefabricated, customized abutments and fixtures according to their material and shape by three-dimensional finite element analysis. And to investigate the fatigue life and fracture characteristics. Mandibular models were fabricated by reconstruction of the CT scan of patients with normal occlusion. A total of six finite element models were designed, a load of 100 N was applied on the buccal cusps vertically, and 30 degree obliquely. 10 specimens each were fabricated for the more clinically widely used 4 type abutments and were loaded according to ISO 14801. Differences in stress distribution patterns were not found according to the materials of the abutments and fixtures. But a slight difference in the stress level was detected. Customized abutment groups showed lower crown stress levels. One-piece zirconia implant showed the lowest bone stress levels. In the fatigue test, highest values were measured in group 7. Prefabricated abutments showed less variation of fatigue life (P<0.05). Use of customized abutments can improve the fracture resistance of restorations. Especially, use of customized zirconia abutments reinforced by titanium screw connecting parts is recommended.

• The Journal of Advanced Prosthodontics
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• v.10 no.4
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• pp.321-327
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• 2018

PURPOSE. The purpose of this study was to compare the cutting method and the lamination method to investigate whether the CAD data of the proposed inlay shape are machined correctly. MATERIALS AND METHODS. The Mesial-Occlusal shape of the inlay was modeled by changing the stereolithography (STL). Each group used SLS (metal powder) or SLA (photocurable resin) in the additive method, and wax or zirconia in the subtractive method (n=10 per group, total n=40). Three-dimensional (3D) analysis program (Geomagic Control X inspection software; 3D systems) was used for the alignment and analysis. The root mean square (RMS) in the 2D plane state was measured within $50{\mu}m$ radius of eight comparison measuring points (CMP). Differences were analyzed using one-way analysis of variance and post-hoc Tukey's test were used (${\alpha}=.05$). RESULTS. There was a significant difference in RMS only in SLA and SLS of 2D section (P<.05). In CMP mean, CMP 4 ($-5.3{\pm}46.7{\mu}m$) had a value closest to 0, while CMP 6 ($20.1{\pm}42.4{\mu}m$) and CMP 1 ($-89.2{\pm}61.4{\mu}m$) had the greatest positive value and the greatest negative value, respectively. CONCLUSION. Since the errors obtained from the study do not exceed the clinically acceptable values, the lamination method and the cutting method can be used clinically.

• The Journal of Korean Academy of Prosthodontics
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• v.55 no.3
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• pp.305-310
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• 2017

Nowadays, the development of dental scanner and CAD/CAM technology can facilitate the fabrication of hybrid prosthesis. Double scanning technique, scanning a trial prosthesis and master model, made it possible to realize virtual design and simplify the laboratory work. Instead of using the metal or zirconia framework with composite, ceramic or denture tooth, the new high performance polymer Polyetherketoneketone (Pekkton, Cendres+$M{\acute{e}}taux$, Biel, Switzerland) as a framework with Polymethyl methacrylate (PMMA) veneering teeth (Visio-lign, Bredent, Senden, Germany) was used in this case. This case report showed an acceptable treatment outcome and satisfaction of patient using Pekkton and Visio-lign. However, long term clinical evaluation is needed.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.350-354
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• 2004

In this study, the wear characteristics of five different dental composite resins cured by conventional halogen light and LED light sources were investigated. Five different dental composite resins of Surefil, Z100, Dyract AP, Fuji II LC and Compoglass were worn against a zirconia ceramic ball using a pin-on-disk type wear tester with 15 N contact force in a reciprocal sliding motion of sliding distance of 10 mm/cycle at 1Hz under the room temperature dry condition. The wear variations of dental composite resins were linearly increased as the number of cycles increased. It was observed that the wear resistances of these specimens were in the order of Dyract AP > Surefil > Compoglass > Z100 > Fuji II LC. On the morphological observations by SEM, the large crack formation on the sliding track of Fuji ?LC specimen was the greatest among all resin composites. Dyract AP showed less wear with few surface damage. There is no significant difference in wear performance between conventional halogen light curing and light emitting diodes curing sources. It indicates that a light emitting diodes (LED) source can replace a halogen light source as curing unit for composite resin restorations.