Influence of preparation height and cement space on the fit and retention of computer aided design/computer aided manufacturing zirconia crown / 华西口腔医学杂志

OBJECTIVE@#To investigate the effects of preparation height and cement space on the fit and retention of computer aided design (CAD)/computer aided manufacturing (CAM) zirconia crown, and to provide reference for the clinical design and fabrication of CAD/CAM crowns.@*METHODS@#3D printing system was used to fabricate resin abutment teeth with convergence angle of 2° and height of 1-3 mm. The models' optical impressions were collected by the three-shape scanner. Then, the cement spaces were set by Cradle CAD/CAM system at 10-50 μm to create an all-ceramic zirconia crown. The fit of the crowns was measured by using silicone rubber interstitial impression method. The retention of the crowns was measured by pull-off test with uniaxial tensile force after the crown was bonded. The data were analyzed by SPSS 22.0 soft-ware.@*RESULTS@#When the preparation height was fixed, the fitness values of different cement space groups have statistical difference (P0.05). The fitness values of different preparation height groups have no statistical difference (P>0.05), and the retention values of different preparation height groups have statistical difference (P0.05).@*CONCLUSIONS@#When cradle CAD/CAM system is used to create a full crown in the clinic, the preparation height should be set to more than 3 mm, and the cement space should be set at 30 μm.

Progress in restorative treatments of primary incisor defects / 口腔疾病防治

@#Dental caries and trauma are the most common oral diseases in children, which could result in defects of the teeth or detention. Maintenance of the primary dentition in a nonpathologic condition is important for oral health, craniofacial development, and the overall well-being of the children. In contemporary dentistry, primary anterior teeth defects are mainly treated with drugs, restorative treatments, or both. Restorative treatment is the most preferred method and includes direct restoration, full coronal restoration, post-and-core crowns, etc. This article reviews the available information regarding a variety of restorative treatments for primary incisor defects, including their backgrounds, clinical indications, clinical pathways, and related studies. The literature review shows that intraconal direct restoration is widely used on single surfaces. There are many kinds of full coronal restorations, and each has its own advantages. Pediatric resin-bonded strip crowns and zirconia crowns are the most popular and have excellent aesthetics. The use of post-and-core crowns for primary incisors is controversial. The absorbable post may be the next research hotspot. Therefore, treatment of severely destroyed primary incisors poses a challenge for pediatric dentists, as three important considerations must be kept in mind: children′s behavioral management, preservation of the tooth structure and parental satisfaction.

Colorimetric Analysis of Preformed Zirconia Anterior Crowns for Esthetic Restoration / 대한소아치과학회지

The purpose of this study was to identify which combination of zirconia crowns and cements is most similar in color to the maxillary primary incisors by varying the color of zirconia crowns, crown thickness, and shade of cements. Prefabricated zirconia crowns in 3 shades and crowns fabricated using 6 types of zirconia blocks were used in this study. These were filled with A2-shade or translucent-shade resin cement and the L(*), a(*), and b(*) values were calculated using a spectrophotometer. The color differences between the natural teeth and the zirconia crowns were assessed. The shade of the final restoration was more similar to that of the natural teeth using A2-shade than translucent-shade resin cement. Application of A2-shade cement to a 0.5-mm-thick crown fabricated from a smile series 2 zirconia block resulted in the color most similar to that of the natural teeth. A2-shade resin cement is recommended for zirconia crown restoration in anterior primary teeth compared to TR-shade resin cement for more esthetic restoration. Since restorations with Nusmile zirconia crowns were not esthetically favorable in terms of shade, improvement of the shade characteristics of the product or development of a new kind of zirconia crown is required.

Bond Strength of Band on Zirconia Crown with Compomer and Resin Cement / 대한소아치과학회지

The aim of this study was to evaluate the compomer cement and resin cement as an orthodontic band cement on zirconia crown.A total of 30 specimens were prepared. Preformed stainless steel crowns and zirconia crowns of upper right second primary molar were used. Orthodontic bands were cemented on stainless steel crowns (Group I, n = 10) and zirconia crowns (Group II, n = 10) with compomer cement. The other bands were cemented on zirconia crowns with resin cement (Group III, n = 10). The tensile loads were applied to band to measure the bond strength.The mean of bond strengths of group I, II and III were 0.79 MPa, 1.09 MPa and 1.56 MPa respectively. Bond strength of group II is significantly higher than group I. There was no significant difference between group II and III.Compomer cement and resin cement containing functional monomers showed favorable bond strength of orthodontic bands.

Comparison of Crown Shape and Amount of Tooth Reduction for Primary Anterior Prefabricated Crowns / 대한소아치과학회지

The purpose of this study was to obtain instructions for size selection of prefabricated crown and tooth reduction by 3-dimensional analysis of the size and shape of the maxillary primary central and lateral incisors and prefabricated crowns (celluloid strip, resin veneered stainless steel, and zirconia crowns).The maxillary primary central and lateral incisors of 300 Korean children was scanned with three types of prefabricated crown to create standard three-dimensional tooth models and prefabricated crowns. The shapes of the prefabricated crowns and natural teeth were compared according to four parameters (mesio-distal width, height, labio-palatal width, and labial surface curvature coefficient) and calculated the amount of tooth reduction required for each prefabricated crown.The size 2 resin veneered stainless steel crown, size 1 zirconia crown, and size 2 celluloid strip crown were most similar in shape to the primary central incisor. The size 3 rein veneered stainless steel crown, size 2 zirconia crown, and size 3 celluloid strip crown were most similar to the primary lateral incisor.The amount of tooth reduction was similar in both maxillary primary central and lateral incisors. The incisal reduction was greatest for the zirconia crown. At the proximal surface, the zirconia and celluloid strip crowns required a similar amount of tooth reduction, but more than the resin veneered stainless steel crown. The labial surface reduction was greatest for the zirconia crown. The degree of lingual surface reduction was not significant among the three prefabricated crowns.Among the assessment parameters, mesio-distal crown width was the most important for choosing a prefabricated crown closest to the actual size of the natural crown.

Effect of additional firing process after sintering of monolithic zirconia crown on marginal and internal fitness / 대한치과보철학회지

PURPOSE: To evaluate an effect of additional firing process after sintering of monolithic zirconia crown on marginal and internal fit through three-dimensional analysis. MATERIALS AND METHODS: Ten monolithic zirconia crowns were fabricated using titanium abutment model. Monolithic zirconia crowns were designed, milled, and sintered as a control group, and additional firing with coloring was performed as a test group. Three dimensional analysis were performed by using triple-scan protocol, and cross-section analysis on mesio-distal and disto-lingual section was evaluated to measure marginal and internal fitness. Then, three-dimensional surface difference on between two groups was evaluated (α=.05). RESULTS: There was statistically significant difference between the control group (32.0 ± 24.3 µm) and the test group (17.0 ± 10.8 µm) in the mesial axial wall (P < .02) and the control group (60.2 ± 24.3 µm) and the test group (71.8 ± 21.5 µm) in the distal axial wall (P < .01). There was no statistically significant difference at the remaining point. CONCLUSION: There was no statistical significance on the deviation of inner surface of crown according to firing number, and the results of both group were considered clinically acceptable.

Comparison of marginal and internal discrepancies of zirconia crowns fabricated by various digital scan methods / 대한치과재료학회지

In this study, marginal and internal discrepancies of zirconia crowns fabricated with the CAD/CAM (computer aided design

A retrospective study on the clinical outcomes of all-ceramic crowns restoration fabricated by oral digital impression / 口腔疾病防治

Objective @#To evaluate the clinical outcomes of all-ceramic crowns whose oral digital impressions were scanned by 3Shape Trios. @*Methods @#All the impressions were scanned by Trios and all the crowns were fabricated according to the standard procedure. The restoration quality were evaluated using modified United States Public Health Service (USPHS) criteria one year after treatment. Restoration integrity、 marginal adaptation、enamel wear、 color satisfaction and gingival index (GI) of the prostheses were evaluated according to the modified USPHS criteria. @*Results@#The clinical 1 year survival rate of 92 porcelain crowns fabricated by 3-shape Trios digital impression and made by CAD/CAM was 100%. The scored A rates of restoration integrity、 marginal adaptation、 enamel wear、 secondary caries、color satisfaction and gingival index of the prostheses were 100%、91.3%、 98%、95.6%、96.7% and 94.7% after 1 year, respectively.@*Conclusion@#The clinical outcomes of all-ceramic crowns whose oral digital impressions were scanned by 3Shape Trios and whose crowns were made by CAD-CAM are satisfying.

A retrospective study on the clinical outcomes of all-ceramic crowns restoration fabricated by oral digital impression / 口腔疾病防治

Objective @#To evaluate the clinical outcomes of all-ceramic crowns whose oral digital impressions were scanned by 3Shape Trios. @*Methods @#All the impressions were scanned by Trios and all the crowns were fabricated according to the standard procedure. The restoration quality were evaluated using modified United States Public Health Service (USPHS) criteria one year after treatment. Restoration integrity、 marginal adaptation、enamel wear、 color satisfaction and gingival index (GI) of the prostheses were evaluated according to the modified USPHS criteria. @*Results@#The clinical 1 year survival rate of 92 porcelain crowns fabricated by 3-shape Trios digital impression and made by CAD/CAM was 100%. The scored A rates of restoration integrity、 marginal adaptation、 enamel wear、 secondary caries、color satisfaction and gingival index of the prostheses were 100%、91.3%、 98%、95.6%、96.7% and 94.7% after 1 year, respectively.@*Conclusion@#The clinical outcomes of all-ceramic crowns whose oral digital impressions were scanned by 3Shape Trios and whose crowns were made by CAD-CAM are satisfying.

Shear Bonding Strength of Three Cements Luted on Pediatric Zirconia Crowns and Dentin of Primary Teeth / 대한소아치과학회지

The aim of this study was to evaluate the shear bond strength of three luting cements and to identify the effect of thermocycling.Zirconia discs were made similar to the inner surface of a preformed pediatric zirconia crown (NuSmile® ZR crown: ZRCr). The similarity between the zirconia discs and the inner surface of a ZRCr was confirmed by scanning electron microscope. Three luting cements were Ketac™ Cem Permanent Glass Ionomer Luting Cement (KGI), RelyX™ Luting Plus Cement (RLP), RelyX™ Unicem Self-Adhesive Universal Resin Cement (RUR). Three luting cements were bonded according to the manufacturer's instructions for 60 zirconia discs and 60 dentin of primary teeth. Total of 120 specimens were divided into two subgroups: One was not aged, and the other was tested with 5500 thermocycling. Shear bond strength was measured using a universal testing machine, and the fracture patterns were observed with SEM.On the zirconia discs and the dentin of primary teeth, shear bond strength of RUR was higher than that of KGI and RLP, and there were statistically significant differences by cement type. The shear bond strength differences for RUR were not statistically significant depending on thermocycling.

Esthetic Restoration of Deciduous Teeth Using Prefabricated Zirconia Crown in Children with Early Childhood Caries: A Report of Three Cases / 치위생과학회지

Early childhood caries is a widespread condition that requires attention; however, its treatment remains a challenge in terms of child behavior management. This study describes the usefulness of customized zirconia crowns for the restoration of deciduous teeth through the evaluation of some cases. Three cases are described: a 29-month-old girl who presented with severe early childhood caries affecting anterior tooth, a 50-month-old boy who presented with extensive caries of his anterior tooth, and 70-month-old girl who presented with extensive caries of his primary posterior dentition. These prefabricated, zirconium-based ceramic crowns (Nusmile™ NuSmile) are available in various sizes, shapes and colors. Before the treatment, radiographs and intraoral photographs were taken to evaluate the appropriateness of treatment. Our findings indicate that customized zirconia crowns may be appropriate for restoring the deciduous teeth. Further long-term clinical studies are required to clarify the usefulness of this restorative method.

Restoration of partial removable dental prosthesis after fabricating of surveyed crowns utilizing electronic surveying: a case report

Adoption of CAD/CAM milling in dentistry has allowed production of more analytic and precise prosthesis. Such precision enables definite path of insertion and undercut to be provided in removable partial denture especially when designing a surveyed crown on an abutment tooth. This case is about the production of surveyed crown with proper path of insertion utilizing CAD/CAM electronic surveying method on a patient with edentulous maxilla. Resulting removable partial denture fit well and showed acceptable stability and retention with no clinical problem.

Fabrication of a CAD/CAM monolithic zirconia crown to fit an existing partial removable dental prosthesis

Fabricating a surveyed prosthesis beneath an existing partial removable dental prosthesis (PRDP) is a challenging and time-consuming procedure. The computer-aided design/computer-assisted manufacturing (CAD/CAM) technology was applied to fabricate a retrofitted, surveyed zirconia prosthesis to an existing PRDP. CAD/CAM technology enabled precise and easy replication of the contour of the planned surveyed crown on the existing abutment tooth. This technology ensured excellent adaptation and fit of newly fabricated crown to the existing PRDP with minimal adjustments. In this case report, a seventy-year-old male patient presented with fractured existing surveyed crown. Because the existing PRDP was serviceable, new crown was fabricated to the existing PRDP.

Evaluation of marginal fit of 2 CAD-CAM anatomic contour zirconia crown systems and lithium disilicate glass-ceramic crown

PURPOSE: This study was to evaluate the marginal fit of two CAD-CAM anatomic contour zirconia crown systems compared to lithium disilicate glass-ceramic crowns. MATERIALS AND METHODS: Shoulder and deep chamfer margin were formed on each acrylic resin tooth model of a maxillary first premolar. Two CAD-CAM systems (Prettau(R)Zirconia and ZENOSTAR(R)ZR translucent) and lithium disilicate glass ceramic (IPS e.max(R)press) crowns were made (n=16). Each crown was bonded to stone dies with resin cement (Rely X Unicem). Marginal gap and absolute marginal discrepancy of crowns were measured using a light microscope equipped with a digital camera (Leica DFC295) magnified by a factor of 100. Two-way analysis of variance (ANOVA) and post-hoc Tukey's HSD test were conducted to analyze the significance of crown marginal fit regarding the finish line configuration and the fabrication system. RESULTS: The mean marginal gap of lithium disilicate glass ceramic crowns (IPS e.max(R)press) was significantly lower than that of the CAD-CAM anatomic contour zirconia crown system (Prettau(R)Zirconia) (P<.05). Both fabrication systems and finish line configurations significantly influenced the absolute marginal discrepancy (P<.05). CONCLUSION: The lithium disilicate glass ceramic crown (IPS e.max(R)press) had significantly smaller marginal gap than the CAD-CAM anatomic contour zirconia crown system (Prettau(R)Zirconia). In terms of absolute marginal discrepancy, the CAD-CAM anatomic contour zirconia crown system (ZENOSTAR(R)ZR translucent) had under-extended margin, whereas the CAD-CAM anatomic contour zirconia crown system (Prettau(R)Zirconia) and lithium disilicate glass ceramic crowns (IPS e.max(R)press) had overextended margins.

Comparison of occusal aspects in monolithic zirconia crown before and after occlusal adjustment during intraoral try-in: a case report / 대한치과보철학회지

In case of prosthesis fabrication by CAD/CAM, location, area and contour of occlusal contacts can be adjusted so more functional occlusion can be acquired. Also, errors in a manufacturing process is reduced compared to cast metal prostheses and porcelain fused metal prostheses fabricated by conventional methods such as casting and porcelain build up. Therefore, prostheses by CAD/CAM show superior occlusion accuracy. Recently, virtual articulator function has been introduced to CAD/CAM system, which reproduces mandibular movement against maxilla. Thus, it is possible to consider occlusal interference in anterior/lateral movement as well as closing movement. There have been many studies on the marginal and internal fit of prostheses using zirconia but the occlusal fit of zirconia crown fabricated by CAD/CAM has not been researched as much. In this case report, 7 zirconia crowns were designed and fabricated by CAD/CAM for total 5 patients. The models of zirconia crowns before and after occlusal adjustment during intraoral try-in were scanned for occlusal contacts, which were compared to evaluate accuracy of prostheses and understand patterns of occlusal adjustment. Most of the occlusal adjustments were done on functional cusps and slopes of zirconia crown, and the magnitude of occlusal adjustment ranged from 15 microm to 60 microm. In the zirconia crown fabricated with CAD/CAM systems, the occlusal adjustment is a necessary procedure, so additional procedures will be needed for compensating reduced mechanical properties.

Comparative study of fracture strength depending on the occlusal thickness of full zirconia crown / 대한치과보철학회지

PURPOSE: The purpose of this study was to compare the fracture strength of traditional metal-ceramic crowns and full zirconia crowns according to the occlusal thickness. MATERIALS AND METHODS: A mandibular first molar resin tooth was prepared with 1.5 mm occlusal reduction, 1.0 mm rounded shoulder margin and 6degrees taperness in the axial wall. Duplicating the resin tooth, 64 metal dies were fabricated. 48 full zirconia crowns were fabricated using Prettau zirconia blanks by ZIRKONZAHN CAD/CAM and classified into six groups according to the occlusal thickness (0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm). 16 metal-ceramic crowns were fabricated and classified into two groups according to the occlusal porcelain thickness (1.0 mm, 1.5 mm). All crowns were cemented on each metal die and mounted in a universal testing machine. The load was directed at the functional cusp of each specimen until catastrophic failure occurred. One-way ANOVA, Tukey multiple comparison test (alpha=.05) and t-test (alpha=.05) were used. RESULTS: The results were as follows. 1. The test 1 group (646.48 N) showed the lowest fracture strength (P.05). The value of test 6 group (1781.24 N) was significantly higher than those of the other groups (P<.05). 2. There were no significant differences of the fracture strength of metal ceramic crowns according to occlusal porcelain thickness 1.0 mm (2515.71 N) and 1.5 mm (3473.31 N) (P<.05). CONCLUSION: Full zirconia crown needs to be 1.0 mm or over in occlusal thickness for the posterior area to have higher fracture strength than maximum bite force.

Fracture resistance and marginal fidelity of zirconia crown according to the coping design and the cement type / 대한치과보철학회지

PURPOSE: The purpose was to compare the marginal fidelity and the fracture resistance of the zirconia crowns according to the various coping designs with different thicknesses and cement types. Material and METHODS: Zirconia copings were designed and fabricated with various thicknesses using the CAD/CAM system (Everest, KaVo Dental GmbH, Biberach., Germany). Eighty zirconia copings were divided into 4 groups (Group I: even 0.3 mm thickness, Group II: 0.3 mm thickness on the buccal surface and the buccal half of occlusal surface and the 0.6 mm thickness on the lingual surface and the lingual half of occlusal surface, Group III: even 0.6 mm thickness, Group IV: 0.6 mm thickness on the buccal surface and the buccal half of occlusal surface and the 1.0 mm thickness on the lingual surface and the lingual half of occlusal surface) of 20. By using a putty index, zirconia crowns with the same size and contour were fabricated. Each group was divided into two subgroups by type of cement: Cavitec(R) (Kerr Co, USA) and Panavia-F(R) (Kuraray Medical Inc, Japan). After the cementation of the crowns with a static load compressor, the marginal fidelity of the zirconia crowns were measured at margins on the buccal, lingual, mesial and distal surfaces, using a microscope of microhardness tester (Matsuzawa, MXT-70, Japan, x100). The fracture resistance of each crown was measured using a universal testing machine (Z020, Zwick, Germany) at a crosshead speed of 1 mm/min. The results were analyzed statistically by the two-way ANOVA and oneway ANOVA and Duncan's multiple range test at alpha= .05. RESULTS: Group I and III showed the smallest marginal fidelity, while group II demonstrated the largest value in Cavitec(R) subgroup (P .05). Panavia-F(R) subgroup showed significantly higher fracture resistance than Cavitec(R) subgroup in group I and II (P < .05). CONCLUSION: Within the limitation of this study, considering fracture resistance or marginal fidelity and esthetics, a functional ceramic substructure design of the coping with slim visible surface can be used for esthetic purposes, or a thick invisible surface to support the veneering ceramic can be used depending on the priority.