Comparison of the two magnetic resonance deartifact techniques in imaging of different porcelain-fused-to-metal crowns / 华西口腔医学杂志

OBJECTIVE@#This study aimed to compare the porcelain-fused-to-metal (PFM) crown artifact in the magnetic resonance imaging (MRI) of the two magnetic resonance deartifact techniques in studying the application value of the propeller-fast spin-echo T2-weighted sequence (FSE T2WI) in troubleshooting PFM crown artifacts.@*METHODS@#A total of 48 patients with right mandible first molar crown who underwent MRI head examination were chosen as subjects in the study. According to different metal substrates, PFM crowns were divided to three types, namely, nickel-chromium alloy crown, cobalt-chromium alloy crown and titanium crown. The patients received two MRI scan sequences, that is, FSE T2WI and propeller-FSE T2WI sequences. The MRI artifacts areas in two sequences were measured.@*RESULTS@#The difference between FSE T2WI and propeller-FSE T2WI sequences in three kinds of PFM crown was significant (P<0.05).@*CONCLUSIONS@#Propeller-FSE T2WI sequence technique can effectively reduce the metal artifacts of various PFM crowns.

Evaluation of clinical effect of porcelain fused for metal crown restoration after root canal therapy / 医疗卫生装备

Objective To investigate the clinical effect of porcelain fused for metal crown restoration after root canal therapy.Methods Totally 90 patients with pulpitis or periapical periodontitis from December 2013 to December 2015 had their clinical data analyzed,who underwent root canal therapy and were divided equally into an observation group and a control group.The observation group took porcelain endocrowns repair and the control group applied ceramic crown.The two groups were compared on the restoration integrity,edge sealing,residual rate,gum,food impaction and color 3 months,6 months and 1 a after treatment.Results The observation group behaved significantly better than the control group in the edge sealing and restoration integrity (P＜0.05).There were significant differences between the residual rates,gum and food impaction in the two groups (P＜0.05).Conclusion Porcelain endocrowns repair gains advantages over ceramic crown repair in edge sealing,integrity,gum,food impaction and color after root canal therapy,though its long-term effect needs further investigation.

Evaluation of clinical effect of porcelain fused for metal crown restoration after root canal therapy / 医疗卫生装备

Objective To investigate the clinical effect of porcelain fused for metal crown restoration after root canal therapy.Methods Totally 90 patients with pulpitis or periapical periodontitis from December 2013 to December 2015 had their clinical data analyzed,who underwent root canal therapy and were divided equally into an observation group and a control group.The observation group took porcelain endocrowns repair and the control group applied ceramic crown.The two groups were compared on the restoration integrity,edge sealing,residual rate,gum,food impaction and color 3 months,6 months and 1 a after treatment.Results The observation group behaved significantly better than the control group in the edge sealing and restoration integrity (P＜0.05).There were significant differences between the residual rates,gum and food impaction in the two groups (P＜0.05).Conclusion Porcelain endocrowns repair gains advantages over ceramic crown repair in edge sealing,integrity,gum,food impaction and color after root canal therapy,though its long-term effect needs further investigation.

Evaluation of effects of porcelain firing on the marginal fit changes of porcelain­ fused-to- metal crown fabricated utilizing two different margin designs and two commercially available base metal alloys

Aim: To find the marginal fit of the porcelain fused to metal crowns by two different margin designs (shoulder and chamfer) and two commercially available base metal alloys. Material and Methods: Tooth preparation of first central incisor for porcelain-fused-to-metal crown with shoulder margin and second incisor for porcelain-fused-to-metal crown with chamfer margin was done. Wax pattern of the same was prepared. Impression of both prepared ivorine incisors was made by light body impression material and poured with pattern resin. Both the patterns were invested and casted with cobalt chromium alloy for making master dies. Two wax patterns of unprepared central incisors were fabricated, one with shoulder margin and another with chamfer margin. These patterns were then cut back to the size of the coping. Four rings were invested. In each ring ten patterns, five with shoulder margin and five with deep chamfer margin were sprued together to ensure that each group would pass through the same investing and casting procedure, followed by ceramic firing and measurement. Results: Marginal fit change or marginal discrepancy (before and after firing) between the groups was highly significant. Conclusions: Veneered crowns exhibited highly significant marginal distortion than non- veneered copings after porcelain firing. Shoulder margin is better in minimizing marginal discrepancy compared to deep chamfer margin. Marginal discrepancy is less when cerabond base metal alloy is used with shoulder margin as compared to commend base metal alloy used for shoulder margin.

Assessment of Porcelain Fused to Metal Crown Preparations by General Practitioners in Saudi Arabia.

Background: Principles for fabricating prosthetic restorations include sufficient axial preparation and adequate occlusal clearance of the prepared teeth. This study measured the convergence angles in the prepared teeth for porcelain fused to metal (PFM) crowns done by general practitioners in different regions of Saudi Arabia. In addition, the presence of planar occlusal reductions, functional cusp bevels and rounded angles in prepared casts were evaluated. Methods: Sixty dies were selected from the working casts of prepared PFM crowns by general dental practitioners. The dies were divided into four equal groups according to the region. All the measured dies were mounted with the occlusal plane of the prepared teeth parallel to the floor. Photographs of buccal and proximal aspects of the dies were taken and then transferred into a personal computer. An AutoCAD software program was used to measure the mesiodistal and buccolingual convergence angles. The planar occlusal reduction, functional cusp bevel and presence of rounded angles of each preparation were evaluated. The data were recorded, then analyzed using SPSS version 20.0. Results: The mean convergence angles were high above the ideal range (4º-14º) in all of the selected regions. The mean mesiodistal convergence angle nearest to the ideal range was registered in teeth prepared in Dammam region, which was lower than tooth preparations from Jeddah, Abha and Jazan regions. Statistically significant differences with buccal, lingual taper and buccolingual convergence existed between the regions. Also significant differences were observed between the teeth preparation samples from four regions with distal taper and mesiodistal convergence angles. Conclusion: The achieved convergence angles of tooth preparations for PFM crowns by different general practitioner were out of the recommended range mentioned in dental literature.

Focal epithelial hyperplasia arising after delivery of metal-ceramic fixed dental prosthesis

Focal epithelial hyperplasia (FEH) is a human papillomavirus (HPV)-induced alteration of the oral mucosa that presents with a clinically distinct appearance. While other HPV-infected lesions such as squamous papilloma, verruca vulgaris, and condyloma acuminatum involve the skin, oral mucosa, and genital mucosa, FEH occurs only in the oral mucosa. The affected oral mucosa exhibits multiple papules and nodules with each papule/nodule being flat-topped or sessile. The affected region resembles the normal color of oral mucosa rather than appearing as a white color since the epithelial surface is not hyperkeratinized. Almost all cases present with multiple sites of occurrence. This rare, benign epithelial proliferation is related to low-risk HPV, especially HPV-13 and -32, and is not transformed into carcinoma. We report a case of FEH that arose on the attached gingiva of an East Asian male adult related to prosthesis without detection of any HPV subtype in HPV DNA chip and sequencing.

Three-dimensional finite element analysis of prosthesis stress variation / 中国组织工程研究

BACKGROUND:Based on variational principle and weighting technology of three-dimensional finite element method, human teeth with a complex morphology can be modeled, which helps to understand the stress distribution of dental hard tissue and prosthesis during the dynamic repair process. OBJECTIVE:To comprehensively analyze the three-dimensional finite element studies concerning biomechanics of dental prostheses, focusing on the effects of metal crown, porcelain thickness, root canal preparation and fil ing on the tooth stress. METHODS:A computer-based search of PubMed (1993-04/2012-09), China Academic Journal Network Publishing Database (2001-2008), and VIP (2001-2008) was performed by the first author to retrieve articles concerning the effects of metal crown, porcelain thickness, root canal preparation and fil ing on the tooth stress. The keywords were“porcelain-fused-to-metal, finite element method, stress analysis, root canal”in English and Chinese. Articles with repetitive contents or meta-analysis were ruled out. Then 40 articles were suitable for further analysis.RESULTS AND CONCLUSION:Finite element method has important significance to establish high-fidelity and high-accuracy models in oral medicine, thereby providing effective biomechanical information for the root canal treatment and post-treatment repair. Scholars continue to explore the stress distribution of dental prostheses during chewing. This review summarizes the stress changes of post and core crowns, supporting reference for further research. Three-dimensional finite element method can be used to build nonlinear three-dimensional finite element models with anisotropic biomechanical characteristics, and can gradual yimprove the transition from static analysis to a dynamic analysis, truly achieving accurate simulation of oral biology and dental morphology as wel as chewing function of the teeth.

Assessment of convergence angle of full-coverage porcelain fused to metal crowns in clinical practice.

Background: Full-coverage porcelain fused to metal crowns is commonly recommended for restoration of extensively damaged teeth. Ability of the dentist to adequately prepare teeth is fundamental to success and longevity of these restorations. Aims: This study was designed to compare recommended convergence angle and taper values of tooth preparation with clinically practiced values and to assess the factors such as tooth position, operator experience, vitality, and restorative status on convergence angle of prepared teeth. Setting and Design: It was a descriptive, cross-sectional study design and held at The Aga Khan University Hospital, Dental Section, for a period of 1 year. Materials and Methods: A minimum of 197 crown preparation models of molar and premolar teeth prepared by residents and specialists were collected in order to achieve the objectives of the study on the basis of convenient sampling technique. Statistical Analysis: One sample t-test used to compare the mean practiced convergence angle values with its recommended values. Independent sample t-test and one-way ANOVA was used to see difference in the convergence angle values of the teeth prepared by different operators, tooth type, vitality status, and restorative status of teeth. Results: Mean reported convergence angle and axial wall taper values were 23.7°±8.9° and 11.3°±7.8°, respectively, which is significantly greater (P<0.001) than the recommended values. Convergence angle values were greater for molars as compared to premolars. Conclusion: There was a considerable disparity between the convergent angles values recorded in this study and the recommended guidelines and are affected by tooth type, vitality, and restorative status of tooth.

The effect of thermocycling on the bonding of different restorative materials to access opening through porcelain fused to metal restorations

PURPOSE: Porcelain fused to metal (PFM) crowns provide the best treatment option for teeth that have a large or defective restoration. More than 20% of teeth with PFM crowns or bridges require non-surgical root canal treatment (NSRCT). This may be due to the effect of restorative procedures and the possible leakage of bacteria and or their by-products, which leads to the demise of the tooth pulp. Thus, this study was planned to compare the ability of the restorative materials to seal perforated PFM specimens. MATERIALS AND METHODS: The study evaluates the ability of amalgam, composite or compomer restorative materials to close perforated PFM specimen's in-vitro. Ninety PFM specimens were constructed using Ni-Cr alloys and feldspathic porcelain, and then they were divided into 3 groups: amalgam (A), composite + Exite adhesive bond (B) and compomer + Syntac adhesive bond (C). All the PFM samples were embedded in an acrylic block to provide complete sealing of the hole from the bottom side. After the aging period, each group was further divided into 3 equal subgroups according to the thermocycling period (one week for 70 cycles, one month for 300 cycles and three months for 900 cycles). Each subgroup was put into containers containing dye (Pelikan INK), one maintained at 5degrees C and the other at 55degrees C, each cycle for 30 sec time. The data obtained was analyzed by SPSS, 2006 using one way ANOVA test and student t-test and significant difference level at (P<.01). RESULTS: The depth of dye penetration was measured at the interfaces of PFM and filling materials using Co-ordinate Vernier Microscope. The lowest levels of the dye penetration for the three groups, as well as subgroups were during the first week. The values of dye leakage had significantly increased by time intervals in subgroups A and C. CONCLUSION: It was seen that amalgam showed higher leakage than composite while compomer showed the lowest level of leakage.

Bond-strength of several metal-meramic alloys and meneered-porcelain / 대한치과보철학회지

PURPOSE: In this study, we evaluated the bond-strength between a few metal ceramic-alloys and veneered-porcelain and found if the bond strength of metal-ceramic alloy with lower gold content than the presently used gold alloy was high enough. MATERIALS AND METHODS: For this study, after plasticizing porcelain only for gold alloy, metal specimen was fabricated using Ni-Cr alloy and gold alloy with different gold content. Three point flexural test were performed to measure their bond-strength. RESULTS: The bonding strength of Group 1 to porcelain was 40.62 +/- 3.32 MPa, which was the highest (P.05), while there was a significant difference between that of Group 2, Group 3 and Group 4 and that of Group 6 (Duncan's test, P<.05). The bonding strength between gold alloy and porcelain increased according to the content of gold. In all experimental groups showed higher value than 25 MPa, which is the least value recommended by ISO 9693. CONCLUSION: In all groups, bonding strength was higher than 25 MPa, which is the least value of ISO9693. Therefore, it is considered that metal gold alloy with low gold content is clinically usable.

Observation for clinical effects of glassfiber post with all-ceramic-crown for incisors restoration / 中国实用护理杂志

Objective To investigate the clinical effect of glassfiber post with all-ceramic-crown for incisors restoration, providing some references for our clinical application. Methods 82 patients (100 teeth defect) in our department from October,2008 to October, 2009 were divided into group A and group B with 50 incisors in each. Glassfiber post with all - ceramic - crown was used in group A, and metal post with porcelain-fused-to-metal in group B. After one year follow-up, we observed the clinical effect. Results 49 cases were effective and 1 case failed in group A. 42 cases were effective and 8 cases failed in group B.There was statistically significant difference between the two groups. Conclusions Glassfiber post with all-ceramic-crown is better in convenient handling and good colour for incisors compared to metal post with porcelain-fused-to-metal.

Influence of nickel-chromium alloy and gold-platinum alloy PFM on canine gingival tissues / 实用口腔医学杂志

Objective: To compare the influence of nickel-chromium alloy and gold-platinum alloy porcelain-fused-to-metal ( PFM ) on ultramicrostructure of canine gingival tissues, to survey the biological effects after PFM full crown restoration, and to provide data for selection of PFM materials. Methods; The nickel-chromium alloy and gold-platinum alloy PFM full crowns were used to repair canines in 3 healthy dogs. The microstructure of canine gingival tissue was observed through light microscope and transmission electron microscope. Apoptosis of canine gingival cells was detected by TUNEL method. Results; Under light microscope, inflammatory cell infiltration and partial bleeding were seen in the nickel-chromium alloy PFM full crown repaired canine gingival tissues. Under transmission electron microscope, large amount of cell apoptosis and neuclear condensation were observed in these tissues,and apoptotic index was 58.63% ±11. 12%. While under light microscope, inflammatory cell infiltration and partial bleeding were not seen in the gold-platinum metal PFM full crown repaired canine gingival tissues. Under transmission electron microscope, only small amount of cell apoptosis was detected in these tissues,and apoptotic index was 26. 90% ± 17. 35%. Statistical significance was found in both nickel-chromium alloy group and gold-platinum metal group compared to control group. There was also statistical significance between nickel-chromium alloy group and gold-platinum metal group in cell apoptosis numbers (P <0. 05). Cell apoptosis number in nickel-chromium alloy group was much higher than that in gold-platinum metal group. Conclusion; The negtive effects on ultramicrostructure of gingival tissue using nickel-chromium alloy PFM are more evident than using gold-platinum metal. When select PFM to repair defect teeth, it is better to select the inactive gold-platinum metal PFM as base crown.

Uso do núcleo metálico fundido na reconstrução de dentes tratados endodonticamente: relato de caso clínico / Casting metallic nucleus use in thereconstruction of endodonticallytreated teeth: a case-report

A restauração de dentes tratados endodonticamente é um aspectoimportante que envolve múltiplas opções de tratamentos de complexidade variável.A decisão do material e da técnica para restaurá-los é um tema polêmicona literatura odontológica. Para dificultar ainda mais a seleção, uma grande variedadede alternativas restauradoras está disponível no mercado atualmente. Oobjetivo deste artigo é mostrar que o núcleo metálico fundido ainda tem sua indicaçãoe apresentar um caso clínico de dente reconstruído com núcleo metálicofundido e coroa metalocerâmica.

The restoration of endodonticallytreated teeth is an important aspect involvingmultiple treatment options with a range of complexity.The choice of the material and the techniqueused to restore the teeth is still controversial in theliterature. To make the selection even more difficulta great variety of restoring alternatives is availablein the market today. The objective of this article isto show that casting metallic nucleus still have itsindication and to present a report case of a toothreconstructed with casting metallic nucleus andporcelain fused to metal crown.

All-ceramic and porcelain-fused-to-metal fixed partial dentures: a comparative study by 2D finite element analyses

All-ceramic fixed partial dentures (FPDs) have an esthetic approach for oral rehabilitation. However, metal-ceramic FPDs are best indicated in the posterior area where the follow-up studies found a lower failure rate. This 2D finite element study compared the stress distribution on 3-unit all-ceramic and metal-ceramic FPDs and identified the areas of major risk of failure. Three FPD models were designed: (1) metal-ceramic FPD; (2) All-ceramic FPD with the veneering porcelain on the occlusal and cervical surface of the abutment tooth; (3) All-ceramic FPD with the veneering porcelain only on the occlusal surface. A 100 N load was applied in an area of 0.5 mm² on the working cusps, following these simulations: (1) on the abutment teeth and the pontic; (2) only on the abutment teeth; and (3) only on the pontic. Relative to the maximum stress values found for the physiological load, all-ceramic FPD with only occlusal veneering porcelain produced the lowest stress value (220 MPa), followed by all-ceramic FPD with cervical veneering porcelain (322 MPa) and metal-ceramic FPD (387 MPa). The stress distribution of the load applied on the abutments was significantly better compared to the other two load simulations. The highest principal stress values were low and limited in a small area for the three types of models under this load. When the load was applied on the pontic, the highest stress values appeared on the connector areas between the abutments and pontic. In conclusion, the best stress values and distribution were found for the all-ceramic FPD with the veneering porcelain only on the occlusal surface. However, in under clinical conditions, fatigue conditions and restoration defects must be considered.

Evaluation of clinical esthetical effect in cervical margin of porcelain-fused-metal crown restoration / 中华医学美学美容杂志

Objective To evaluate the clinical esthetical effect in the cervical margin of the porcelain fused to metal crown restoration.Methods 225 cases with the porcelain fused to metal crown were observed.The evaluator examined these restorations for cervical color,marginal fit,and gingival state.(Results 53) cases of restoration changed in the cervical color.The method and the tooth preparation volume,the procedure and the material,which were all closely relevant to the cervical color change.(Conclusion Using)the correct method,improving the procedure and choosing the proper material would reduce the cervical color change.

Effects of microstructure grinded on the labial face of PFM on esthetic prosthesis for anterior teeth / 中华医学美学美容杂志

Objective To explore the effects of microstructure grinded on the labial face of porcelain fused to metal crown (PFM) in esthetic prosthesis for anterior teeth. Methods 193 patients with single maxillary incisor tooth defects were repaired with 2 crowns for each one. After the crowns being blent colour and molded, the crown A was not grinded particularly on the labial face and the crown B was done according to the records of the microstructure.The patients were allowed to choose the most satisfied one when 2 crowns were cemented temporarily. Results 36 patients chose the crown A and 157 chose B.The difference was significant ( P0.05). Conclusion The crown has great vitality and accordes with the esthetic standards of the patients by way of being grinded microstructure on the labial face.

The influence of repeated firings on the remained porcelain rate / 实用口腔医学杂志

Objective: To study the influence of repeated firings on the PFM bond strength. Methods: 25 specimens of PFM in the diameter of 13.0 mm and thickness of (1.0?0.02) mm were prepared and fired at 920 ℃ for 1, 3, 5, 7 or 9 times(5 samples for each time). The remained porcelain rate(RPR) was measured by Mackert method and used to evaluate the bond strength.Results: After 3 firings, the RPR of PFM decreased obviously, and additional firings had no obvious effect on the RPR. Conclusion: 3 times firing or more may decrease the bond strength of PFM.

Effect of baking temperature of gold-porcelain blended layer on bond strength of porcelain fused to Ni-Cralloy / 实用口腔医学杂志

Objective:To compare the differences of bond strength usi ng gold intermediate layer between Ni-Cr alloy and opaque porcelain(OP) baked at different temperatures. Methods:36 standard samples of Ni-Cr al loy and 36 of gold were prepared. The samples were divided into 4 groups with 9 in each. In group 1,OP was smeared to the surface of the samples and then baked at 950 ℃. In group 2,3 and 4 blendgold neu(a gold past) was put on the surface of the samples, then baked at 820 ℃,890 ℃ and 960 ℃ respectively. The samples were proccessed for further tests.The bond strength was tested by shear bond te st, and the electron probe was used to observe interfacial bond state and diffus ion of interfacial elements. Results:The bond strength(MPa) in g roup 1,2,3 and 4 was 19.66? 1.83,22.34?2.73,21.33?2.75 and 28.02?5.71 res pectively(group 1 vs group 4 P

Contents of Ni and Cr in hair after wearing Ni-Cr based porcelain-fused-metal (PFM) crown / 实用口腔医学杂志

0.05). Conclusion:After Ni-Cr-Based porcelain-fused-to-metal crown application, the metal ion can be released and absorbed by human body. But the content is almost harmless to human body.

The influence of repeated firings on the color of porcelain-fused-to-metal crown restoration / 实用口腔医学杂志

s〕 Objective:To investigate the influence of repeated firings on the color of porcelain fused to metal crown(PFM) . Methods: 5 PFM samples were prepared and fired for 9 times.The color of the samples was measured following firing with CIE1976 L*a*b* color system . The color difference ?E ab *,hue angle h ab * and chroma C ab * were calculated according to the following calculations:?E ab * ={(?L*) 2 +(?a*) 2 +(?b*) 2} 1/2 , C ab * ={(a*) 2+(b*) 2} 1/2 , h ab *=tg 1 b*/ a*, L* presented brightness. Results: After repeated firing, L* value of PFM , C ab * and L* value of dentin layer and h ab * value of opaque layer increased. Conclusion: The color of PFM after repeated firing may become brighter. The color change is resulted from the increase of L* and C ab * of dentin layer.