• The Journal of Advanced Prosthodontics
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• v.16 no.4
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• pp.231-243
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• 2024

PURPOSE. The objective of the study was to analyze the impact of cement, bonding pretreatment, and ceramic abutment material on the overall color results of CAD-CAM ceramic crowns bonded to titanium-based hybrid abutments. MATERIALS AND METHODS. For single implant restoration of a maxillary lateral incisor a total of 51 CAD-CAM-fabricated monolithic lithium disilicate crowns were fabricated and subsequently bonded onto 24 lithium disilicate Ti-base abutments, 24 zirconia Ti-base abutments and 3 resin abutment replicas as a control group. The 48 copings were cemented with three definitive and one provisional cement on both grit-blasted and non-blasted Ti-bases. The color of each restoration and surrounding artificial gingiva was measured spectrophotometrically at predefined measuring points and the CIELAB (ΔE_ab) color scale values were recorded. RESULTS. The color outcome of ceramic crowns bonded to hybrid abutments and soft tissues was affected differently by cements of different brands. Grit-blasting of Ti-bases prior to cementing CAD-CAM copings affected the color results of allceramic crowns. There was a significant difference (P = .038) for the median ΔE value between blasted and non-blasted reconstructions at the cervical aspect of the crown. Full-ceramic crowns on zirconia Ti-base abutments exhibited significantly lower ΔE values below the threshold of visibility (ΔE 1.8). In all subcategories tested, the use of a highly opaque temporary cement demonstrated the lowest median ΔE for both the crown and the artificial gingiva. CONCLUSION. Various cements, core ceramic materials and airborne particle abrasion prior to bonding can adversely affect the color of Ti-base supported ceramic crowns and peri-implant soft tissue. However, zirconia CAD-CAM copings and an opaque cement can effectively mask this darkening.

• The Journal of Korean Academy of Prosthodontics
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• v.54 no.3
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• pp.234-238
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• 2016

Purpose: Increasing use of computer aided design-computer aided manufacturing (CAD-CAM) system and number of design software made design of restoration easy and quick. Outcome of restoration has been dependent on dental technician's wax up proficiency, dentists can design restoration for themselves now. This study aims to investigate the outcome of restoration designs, according to handling skill of CAD-CAM design tool. Materials and methods: A patient's mandibular right 1st molar was prepared. After taking impression, stone model was made, scanned the stone model with 3 shape intra-oral scanner, stereolithography (STL) file was extracted. With 3shape dental designer, one dental technician with more than 5 years work experience (designer 0) and three dental technicians with less than 2years work experience (designer 1, 2, 3-group DT) and 4 1st year residents (designer 4, 5, 6, 7-group RT) designed gold crown on the same STL file. Designed crown's MD (mesio-distal) and BL (bucco-lingual) diameter, height of crown, inter-cuspal distance, number of occlusal contact points were compared. Statistical analysis was carried out, test of normality within each group, using independent t-test. Number of contact points were compared, using Wilcoxon signed-rank test. Results: There was no significant difference between group DT and group RT. Number of contact points also resulted in no significant difference. Conclusion: The outcome of each designed crowns showed no statistical differences, in values which can be expressed as numbers. Subjective factors were different. With increasing proficiency in handling designing software, fabrication of restorations according to each designer's occlusal concept can be made easy.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.2
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• pp.267-272
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• 2004

This case report describes an uncommon treatment method for crown-root fractured incisor with immature root. A 7-year-old girl was referred for treatment of crown-root fractured maxillary central incisor. The fracture line extended to 1/2 of the total tooth length with incomplete root formation. The prognosis of crown-root fracture is usually poor and extraction is usually undertaken. But, in the mixed dentition, extraction of maxillary permanent incisor results in many complications, such as resorption of alveolar bone, poor esthetics, pronunciation and mastication. Conservative therapy in the permanent dentition comprises of few treatment modalities; supragingival restoration, gingivectomy, orthodontic extraction of apical fragment, surgical extrusion of apical fragment with or without rotational replantation. However, in this case, these indications are not applicable, so intentional replantation with adhesive resin system is the treatment of choice. The tooth was followed-up for 12 months. Currently, there are no symptoms. Since this modality adopts the respective advantages of both intentional replantation and adhesive treatment, it might be the treatment of choice in cases of vertical crown-root fracture.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.2
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• pp.153-158
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• 2004

Preformed stainless steel crown is an useful restorative material for the treatment of badly broken down primary teeth. However iatrogenic damage to adjacent teeth might occur during the process of tooth reduction. Such damages might lead to plaque accumulation and increase the risks of caries initiation. Especially the damage can make a problem in the first permanent molar. Purpose of this study was to investigate an iatrogenic damage to the first permanent molar during preparation of second primary molar for preformed stainless steel crown. Twelve children restored with preformed stainless steel crown to second primary molar were selected. Contact areas were separated with separation elastics, and tooth surfaces were cleaned. After taking negative impression using vinylpolysiloxane impression material, the specimens were examined by scanning electron microscope for the detection of iatrogenic damage. The prevalence of iatrogenic damage was 66.7% and variable appearances and So we can suggest that when preparing teeth for preformed stainless steel crown, we should be careful about adjacent teeth not to make an iatrogenic damage.

• The Journal of Advanced Prosthodontics
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• v.8 no.5
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• pp.354-362
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• 2016

PURPOSE. The trueness and precision of acquired images of intraoral digital scanners could be influenced by restoration type, preparation outline form, scanning technology and the application of power. The aim of this study is to perform the comparative evaluation of the 3-dimensional reproducibility of intraoral scanners (IOSs). MATERIALS AND METHODS. The phantom containing five prepared teeth was scanned by the reference scanner (Dental Wings) and 5 test IOSs (E4D dentist, Fastscan, iTero, Trios and Zfx Intrascan). The acquired images of the scanner groups were compared with the image from the reference scanner (trueness) and within each scanner groups (precision). Statistical analysis was performed using independent two-samples t-test and analysis of variance (${\alpha}=.05$). RESULTS. The average deviations of trueness and precision of Fastscan, iTero and Trios were significantly lower than the other scanners. According to the restoration type, significantly higher trueness was observed in crown and inlay than in bridge. However, no significant difference was observed among four sites of preparation outline form. If compared by the characteristics of IOS, high trueness was observed in the group adopting the active triangulation and using powder. However, there was no significant difference between the still image acquisition and video acquisition groups. CONCLUSION. Except for two intraoral scanners, Fastscan, iTero and Trios displayed comparable levels of trueness and precision values in tested phantom model. Difference in trueness was observed depending on the restoration type, the preparation outline form and characteristics of IOS, which should be taken into consideration when the intraoral scanning data are utilized.

• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.1
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• pp.111-118
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• 2019

Post-endodontic restorations are both important and challenging for clinical success in endodontically treated posterior teeth. Several options have been proposed to restore endodontically treated molars. In pediatric dentistry, restoration using conventional single crowns, especially for partially erupted molars with insufficient retentive tooth structure, has proven to be difficult. However, the endocrown presents a conservative and esthetic restorative alternative to conventional crowns with post-and-core, as it acquires additional retention within the pulp chamber. The tooth preparation consists of a circular, equigingival, butt-joint margin and a central retention cavity in the pulp chamber that helps to construct both the crown and core as a single unit. This case report describes the esthetic and conservative endocrown restorations of erupting permanent first molars with extensive coronal destruction.

• The Journal of Korean Academy of Prosthodontics
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• v.59 no.1
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• pp.107-115
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• 2021

Excessive pathological attrition over the entire dentition can cause decreased masticatory function, and pathological problems of the temporomandibular joint and the muscular nervous system. In this case, 71 year-old male patient with severe attrition and fracture across the entire tooth was treated by full mouth rehabilitation for regaining space of restoration. In order to determine the appropriate vertical dimension of the patient's occlusion, facial appearance, aesthetics, restoration space were evaluated, and provisional restoration of the raised vertical dimension was made. After 4 months of evaluation, the entire restoration of monolithic zirconia crown using CAD-CAM was completed. Through the above process, satisfactory aesthetic and functional results were obtained.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.4
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• pp.780-790
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• 1996

The endodontically treated tooth is generally restored with post and core, owing to the brittleness and the loss of large amount of tooth structure. Although there have been lots of studies about the endodontically treated teeth, the three-dimensional quantitative studies about the stress distribution of them are in rare cases. In this study, it was assumed that the coronal portion of the upper incisor had extensively damaged. After the root canal therapy it was post cored, and restored with PFG crown. The three-dimensional model, in which the root was supported with a normal alveolar bone, was constructed. Force was applied to the centric stop point with the angle of 135 degrees to the long axis of the tooth. Force was assumed to be 250N as functional maximum bite force of upper central incisors. The results analyzed with three-dimensional finite element method were as follows : 1. Stress was concentrated on the middle portion of the labial side dentin and the apical portion of the dentin. 2. Stress in the post was more concentrated on the post apex. 3. The displacement of the post at the post-cement interface was almost symmetrical la-bio-lingually. 4. It assumed that restoring extensively damaged tooth with a post-core and PFG crown is an adequate method of restoration.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.22 no.1
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• pp.30-46
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• 2013

Porcelain fused to metal crown has been used mostly over the last 50 years for restorations in dentistry. However, the patients' awareness of aesthetic aspect, biocompatibility and the problems such as an allergy to metals led to the growing interest in the 'metal free restoration'. In particular, the price of the precious metals that have been mainly used to date has risen drastically, which made them impossible to play their role as oral restorative materials anymore, and in addition, the PFM restoration has intrinsic problems of chipping and fracture. Therefore, the CAD/CAM has been drawing more attention than ever due to the popular needs for the material that is more aesthetic and stronger for restoration of the molar implant. Considerations in carrying out the full zirconia restoration are as follows: 1) strength, 2) combination work, 3) light penetrability, 4) treatment of cracks, 5) the color reproducibility of the block, 6) the abrasivity of antagonistic tooth, 7) low temperature degradation. In this presentation, the color reproducibility of the block will be discussed. One of the biggest reasons for avoiding the full zirconia restoration is that it is difficult to reproduce the natural color compared to the conventional PFM restoration. Thus, many clinicians show reluctance due to the exposure of the ugly block when the coloring on the surface is removed after occlusal adjustment. From the experience of using blocks by Zirkonzahn for more than 4 years, it is considered that these problems can be addressed to some degrees. Accordingly, how to make restorations that are well in harmony with surrounding prosthesis or natural teeth will be discussed.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.14 no.1
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• pp.77-88
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• 2011

This study was carried out to investigate the effects of soil depth and planting density on the growth of lettuce, crown daisy, and strawberry on a rooftop condition using artificial soil as a growth media. The vegetable crops showed better growth for plant height (cm), plant width (cm), plant fresh weight (g), and Fo, Fm and Fv/m on 20cm depth soil than 10cm depth soil except strawberry. Planting density of $16/m^2$ and $64/m^2$ did not show significant differences on the growth of the crops. Soil moisture content and EC were low for 10cm depth soil in lettuce plots, whereas there was no significant differences on soil moisture and EC between two soil depth in strawberry plots. Hunter's L, a, and b values showed the leaf color of lettuce dark green on 20cm depth soil and reddish on 10cm depth soil. Results showed that soil depth suitable for crop growth on rooftop conditions was 20cm rather than 10cm. Growth response of the crops showed no significant difference between $16/m^2$ and $64/m^2$, indicating that planting density of 64 $plants/m^2$ could be practiced on rooftop conditions. Lettuce growth rapidly changed in control treatment in which leaves were not pinched out, while slowly changed in plants which leaves were periodically pinched out. In the case of control plot, it was impossible to harvest because withering of lower leaves after blossom on June 22. The plant of crown daisy in which pinching was not conducted, blossomed on June 7, and the plants were removed since its aesthetical value was lost. Strawberry seemed to be a suitable vegetable crop for rooftop conditions based on its high covering rate and extended growth period until late October. The soil depth 20cm and planting density 64 $plants/m^2$ were suitable for vegetable crops on green roof system using artificial soil.