• Journal of Technologic Dentistry
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• v.33 no.1
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• pp.7-14
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• 2011

Purpose: As the demand and importance of aesthetic aspects in dental treatment become higher, much attention is paid to materials used for dental prostheses. Thus, the marginal fidelity of most-commonly used alloy, IPS - Empress and ZrO2 ceramic is compared. Methods: The alloy core made by casting, IPS - Empress core made by pressing and ZrO2 ceramic core made by CAD/CAM are used to make 10 samples respectively. For each core, three points were measures and the optical microscope (Axio Imager.Alm,Zeiss co., Oberkochen, Germany) was used to observe the cores with a magnification of 100. Results: As for alloy, IPS - Empress and ZrO2 ceramic, the average and deviation of their marginal distance are $29.91\;{\pm}11.93{\mu}m$ for alloy, $33.45\;{\pm}8.61{\mu}m$ for IPS - Empress, and $31.55\;{\pm}9.85{\mu}m$ for ZrO2. The one-way ANOVA test was conducted to compare them. However, there was no statistically significant difference among them. Conclusion: The study on marginal fidelity of alloy, IPS - Empress, and ZrO2 ceramic shows they have no marginal fidelity problem clinically. Therefore, if a system is selected based on the patient's condition or treatment method, there will be no problem.

• Journal of Digital Convergence
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• v.20 no.2
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• pp.317-323
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• 2022

This study aimed to qualitative analyze the cusp variation pattern of the mandibular second premolars using a three-dimensional virtual models, and to analyze the left-right bilateral symmetry with a quantitative analysis of the tooth surface area according to the cusp variation. 127 virtual mandibular second premolars were prepared and individual absolute/relative cusp area, total crown area and groove form were analyzed using RapidForm2004(INUS technology INC, Seoul, Korea). Independent t-test, Kruskal-Wallis test and chi-square were performed. As a result, the groove form showed high bilateral symmetry between the left and right sides. Based on the left side of groove form, the bilateral symmetry was 100.0% for the U pattern, and 73.7% for the H patterned, and 78.9% for the Y pattern(p<.001). The finding could be as a meaningful reference for manufacturing CAD/CAM dental prostheses, and it is expected that further studies will be conducted on more samples including the mandibular second premolar immediately after eruption.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.25 no.2
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• pp.68-78
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• 2016

Recently, digital technology has become increasingly prevalent in the dental clinic. Using a milling machine for clinic, it is possible to produce provisional restoration inside the clinic. This can promote large clinical cases such as full mouth rehabilitation with the help of a tabletop scanner, which is capable of semi-adjustable articulator equipment, and a powerful dental CAD software with excellent user convenience. In this case report, a full-mouth rehabilitation was done with digital technology to a 55 year-old female patient, who has lost vertical dimension through the attrition, and has got inclined occlusal plane with unplanned and repeated dental reconstruction. Through the design and milling of the provisional restoration in the clinic and the duplication of these provisionals by double scanning technique, a good functional and esthetic result could be achieved.

• The Journal of Advanced Prosthodontics
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• v.7 no.3
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• pp.207-213
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• 2015

PURPOSE. The purpose of this study was to examine the abutment screw stability of screw- and cement-retained implant-supported dental prosthesis (SCP) after simulated cement washout as well as the stability of SCP cements after complete loosening of abutment screws. MATERIALS AND METHODS. Thirty-six titanium CAD/CAM-made implant prostheses were fabricated on two implants placed in the resin models. Each prosthesis is a two-unit SCP: one screw-retained and the other cemented. After evaluating the passive fit of each prosthesis, all implant prostheses were randomly divided into 3 groups: screwed and cemented SCP (Control), screwed and non-cemented SCP (Group 1), unscrewed and cemented SCP (Group 2). Each prosthesis in Control and Group 1 was screwed and/or cemented, and the preloading reverse torque value (RTV) was evaluated. SCP in Group 2 was screwed and cemented, and then unscrewed (RTV=0) after the cement was set. After cyclic loading was applied, the postloading RTV was measured. RTV loss and decementation ratios were calculated for statistical analysis. RESULTS. There was no significant difference in RTV loss ratio between Control and Group 1 (P=.16). No decemented prosthesis was found among Control and Group 2. CONCLUSION. Within the limits of this in vitro study, the stabilities of SCP abutment screws and cement were not significantly changed after simulated cement washout or screw loosening.

• Journal of Technologic Dentistry
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• v.35 no.1
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• pp.49-56
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• 2013

Purpose: The deformation characteristics induced by non-destructive stresses using piezoelectric transducer(PZT) were analyzed for 3-unit fixed partial dentures manufactured PFM, Everest(CAD/CAM) and Zirkonzahn(copy milling, MAD/MAM) by electron speckle pattern interferometery(ESPI). Methods: The ESPI analysis after loading the restoration with PZT by applying electric voltage of 900mV at the points of 10 mm above the base of the prostheses. Results: PFM and All-Ceramic Everest prostheses showed about 0.1 ${\mu}m$ while that of All- Ceramic Zirkonzahn prostheses showed 0.085 ${\mu}m$, demonstrating that Zirkonzahn displaced less. For PFM and All-Ceramic Zirkonzahn prostheses, the displacements were large at just below the loading point, while generalize displacement was shown over the loading point and weak connector areas for All-Ceramic Everest prostheses. Conclusion: We could find that the deformation characteristics induced by non-destructive stresses using PZT analyzed by ESPI were similar to the fracture strengths evaluated using universal testing machine.

• The Journal of the Korean dental association
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• v.54 no.2
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• pp.108-122
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• 2016

Prosthetic-driven implant placement is a concept considering the dental implant restoration first based on the final form of that prosthesis to be restored. The latest development of the imaging technology and digital dentistry was able to be obtained the high quality images of CBCT with low radiation exposure and it has also enabled the process to reconstruct the intraoral state in three dimensions due to the development of the intraoral, model and impression scanner. Computer-guided implant placement simulations and template production was able to be more widely used in this context. In this narrative review, the features and the types of implant surgical guides will be introduced. It will also be described the diagnosis and treatment plan using computerguided implant software to reduce the number of visit and to increase the accuracy of the implant surgery through the top-down approach based on the shape and location of the final prosthesis.

• Journal of Technologic Dentistry
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• v.38 no.4
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• pp.273-280
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• 2016

연구목적: 본 연구의 목적은 통상적으로 사용되는 글라스 세라믹과 고분자를 침투시킨 지르코니아 소재로 제작된 코어와 레진 시멘트의 굴곡강도 및 결합강도를 비교하여 하이브리드 기술이 치과 재료의 물리적인 성질에 미치는 영향을 조사하기 위함이다. 연구방법: 본 두 가지의 통상적으로 사용되는 세라믹소재[Vita PM9(GC) and I-JAM(ZC)] 와 다른 두 가지 하이브리드 세라믹 소재 [CELTRA Duo(ZRC) and Vita Enamic(RIZ)] 를 평가하였다. 각 그룹의 소재를 선택하여 결합강도와 굴곡강도, 그리고 scanning electron microscopy(SEM)을 이용하여 표면분석을 시행하였다. 도출된 결과 데이터는 일원분산분석(One-way ANOVA)을 통해 분석되었으며, 제1종 오류의 수준은 0.05로 하였다. 연구결과: RIZ 그룹에서 가장 높은 결합강도를 보였으며(p<0.05), ZC 그룹이 가장 낮은 결과를 보였다. 상대적으로 굴곡강도는 ZC 그룹이 가장 높은 수치를 나타내었으며, RIZ 그룹이 가장 취약했다. 연구결론: 하이브리드 기술로 제작된 소재(RIZ 그룹)는 우수한 레진 시멘트와의 결합강도를 보였지만, 그에 비해 굴곡강도는 상대적으로 통상적인 지르코니아 소재보다 비교적 취약한 결과를 보였다.

• Journal of Technologic Dentistry
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• v.42 no.4
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• pp.307-312
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• 2020

Application of ceramic materials for fabrication of dental restoration materials has been a focus of interest in the field of esthetic dentistry. The ceramic materials of choice are glass ceramics, spinel, alumina, and zirconia. The development of yttrium tetragonal zirconia polycrystal (YTZP)-based systems is a recent addition to all-ceramic systems that have high strength and are used for crowns and fixed partial dentures. Computer-aided design/computer-aided manufacturing (CAD/CAM)-produced, YTZP-based systems are popular with respect to their esthetic appeal for use in stress-bearing regions. The highly esthetic nature of zirconia and its superior physical properties and biocompatibility have enabled the development of restorative systems that meet the demands of today's patients. Many in vitro trials have been performed on the use of zirconia; however, relatively fewer long-term clinical studies have been published on this subject. The use of zirconia frameworks for long-span fixed partial dentures is currently being evaluated; in the future, more in vivo research and long-term clinical studies are required to provide scientific evidence for drawing solid guidelines. Further clinical and in vitro studies are required to obtain data regarding the long-term clinical use of zirconia-based restorations.

• Restorative Dentistry and Endodontics
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• v.46 no.2
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• pp.18.1-18.13
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• 2021

Composite resins are the most commonly used dental restorative materials after minimally invasive dental procedures, and they offer an aesthetically pleasing appearance. An ideal composite restorative material should have wear properties similar to those of tooth tissues. Wear refers to the damaging, gradual loss or deformation of a material at solid surfaces. Depending on the mechanism of action, wear can be categorized as abrasive, adhesive, fatigue, or corrosive. Currently used composite resins cover a wide range of materials with diverse properties, offering dental clinicians multiple choices for anterior and posterior teeth. In order to improve the mechanical properties and the resistance to wear of composite materials, many types of monomers, silane coupling agents, and reinforcing fillers have been developed. Since resistance to wear is an important factor in determining the clinical success of composite resins, the purpose of this literature review was to define what constitutes wear. The discussion focuses on factors that contribute to the extent of wear as well as to the prevention of wear. Finally, the behavior of various types of existing composite materials such as nanohybrid, flowable, and computer-assisted design/computer-assisted manufacturing materials, was investigated, along with the factors that may cause or contribute to their wear.

• Journal of Dental Rehabilitation and Applied Science
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• v.32 no.1
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• pp.47-59
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• 2016

Purpose: The aim of this study was to investigate the changes in occlusal force after loss of the lower first molar depending on the inclination and extrusion of the adjacent and opposing teeth by using a strain gauge. Materials and Methods: Anatomic teeth were used to reconstruct the normal dental arch with loss of the lower right first molar. A uniformly thick layer of silicone was applied to the root to mimic the periodontal ligament. Four stages of dies with varying degrees of inclination and extrusion of the adjacent and opposing teeth were constructed and attached to master model interchangeably by using a CAD/CAM fabricated customized die system. The strain gauges were attached to teeth and a universal testing machine was used to determine the changes in occlusal force. An independent t-test and one-way ANOVA were performed (${\alpha}=.05$). Results: While simulating chewing food, the upper first, second premolar and lower second molar showed greater occlusal force than before extraction. When the change of adjacent teeth's occlusal force with their progressive movement after molar loss was evaluated, the difference among four die models was significant and was in the decreasing aspect (P < 0.05). Conclusion: When the lower first molar was lost and the adjacent teeth did not move yet, the occlusal force in adjacent teeth was higher than that when the lower first molar still existed. In addition, the occlusal force in the upper premolars and lower second molar decreased significantly with the progressive movement of adjacent teeth.