Academic literature on the topic 'Metal-ceramic crowns'
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Journal articles on the topic "Metal-ceramic crowns"
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Swati, Sikka, R. Chowdhary, and P. S. Patil. "Marginal Strength of Collarless Metal Ceramic Crown." International Journal of Dentistry 2010 (2010): 1–5. http://dx.doi.org/10.1155/2010/521470.
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Metal ceramic restorations have been implicated for the discoloration in area of labiogingivalmargin. Attempts to rectify this, by altering the design of metal frameworkswill lead to decrease in fracture strength atmargin. This in vitro study compared the fracture strength at margins of metal ceramic crowns cemented to metal tooth analogs. Crowns evaluated with different marginal configurations, shoulder and shoulder bevel with 0 mm, 0.5 mm, 1 mm, and 1.5 mm, were selected.Methods. Maxillary right canine typhodont tooth was prepared to receive a metal ceramic crown with shoulder margin. This was duplicated to get 20 metal teeth analogs. Then the same tooth was reprepared to get shoulder bevel configuration. These crowns were then cemented onmetal teeth analogs and tested for fracture strength atmargin on an Instron testing machine. A progressive compressive load was applied using 6.3 mm diameter rod with crosshead speed of 2.5 mm per minute. Statisticaly analysis was performed with ANOVA, Student's “t” test and “f” test.Results. The fracture strength of collarless metal ceramic crowns under study exceeded the normal biting force. Therefore it can be suggested that collarless metal ceramic crowns with shoulder or shoulder bevel margins up to 1.5 mm framework reduction may be indicated for anteriormetal ceramic restorations.Significance. k Collarless metal ceramic crowns have proved to be successful for anterior fixed restorations. Hence, it may be subjected to more clinical trials.
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de Jesus Tavarez, Rudys Rodolfo, Mateus R. Tonetto, EM Maia Filho, Valdimar S. Valente, Carlos E. Francischone, CD Vilarinho Soares de Moura, CE Francischone Júnior, Antonio M. Silva, and Izabella S. Ribeiro. "Marginal Fit Metal–Ceramic and In-Ceram Single Crown Cement retained in Implant-supported Abutments." Journal of Contemporary Dental Practice 17, no. 12 (2016): 969–72. http://dx.doi.org/10.5005/jp-journals-10024-1965.
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ABSTRACT Introduction This study evaluated the cervical fit of cemented metal–ceramic and In-Ceram implant-supported crowns, before and after the cementing procedure. Materials and methods Twenty crowns cemented on implant abutments are divided into two groups (n = 10): Group 1 – cemented metal–ceramic crowns and group 2 – cemented In-Ceram crowns. The marginal adaptations before and after cementation were evaluated in a comparison microscope with an error of 1 μm. All crowns were cemented with zinc phosphate cement. Results The cervical misalignment of cemented crowns before cementation (52.65 ± 11.83 and 85.73 ± 14.06 μm) was lower than that after cementation (66.80 ± 15.86 and 89.36 ± 22.66 μm). Conclusion The cementing procedure interferes with the marginal fit of cemented crowns on implant abutments, with the prosthesis having better adaptation before cementation. Cemented metal–ceramic crowns exhibited better cervical adaptation than In-Ceram crowns cemented before and after the cementing procedure. Clinical significance The maintenance of gum health and the longevity of prosthetic restorations are closely related to the restoration's marginal integrity. How to cite this article Valente VS, Francischone CE, Vilarinho Soares de Moura CD, Francischone Júnior CE, Silva AM, Ribeiro IS, Maia Filho EM, Bandéca MC, Tonetto MR, de Jesus Tavarez RR. Marginal Fit Metal–Ceramic and In-Ceram Single Crown Cement retained in Implant-supported Abutments. J Contemp Dent Pract 2016;17(12):969-972.
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Manozzo Kunz, Patrícia Valéria, Gabriela Andrade Serpa, Leonardo Fernandes da Cunha, Gisele Maria Correr, and Carla Castiglia Gonzaga. "Fit of metal-ceramic crowns." Brazilian Journal of Oral Sciences 21 (August 27, 2021): e225136. http://dx.doi.org/10.20396/bjos.v21i00.8665136.
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Aim: To evaluate the influence of cobalt-chromium (Co-Cr) coping fabrication methods and ceramic application on the marginal and internal fit of metal-ceramic crowns. Methods: Co-Cr copings for metal-ceramic crowns were prepared by lost wax casting or CAD-CAM machining of sintered blocks. The fit was analyzed using the silicone replica technique at four assessment points: marginal gap (MG), axial wall (AW), axio-occlusal (AO) angle, and central occlusal (CO) wall. After the initial analysis, the copings were ceramic-veneered with the layering technique, and the fit was again determined. Data were statistically analyzed by paired and unpaired Student’s-t test (α=0.05). Results: Marginal and internal fit before ceramic application according to the coping manufacturing method showed significant differences only at CO (p < 0.001), with milled copings (137.98±16.71 μm) showing higher gap values than cast copings (112.86±8.57 μm). For cast copings, there were significant differences at MG (before 109.13±8.79 μm; after 102.78±7.18 μm) and CO (before 112.86±8.57 μm; after 104.07±10.63 μm) when comparing the fit before and after ceramic firing. For milled copings, there was significant difference only at AO (before 116.39±9.64 μm; after 108.54±9.26 μm). Conclusion: This study demonstrated that the coping fabrication method influenced the internal fit. Ceramic firing maintained or improved the fit of the metal-ceramic crowns. The marginal discrepancy of all restorations, before and after ceramic firing, can be considered clinically acceptable.
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Medic, Vesna, Kosovka Obradovic-Djuricic, Slobodan Dodic, and Renata Petrovic. "In vitro evaluation of microleakage of various types of dental cements." Srpski arhiv za celokupno lekarstvo 138, no. 3-4 (2010): 143–49. http://dx.doi.org/10.2298/sarh1004143m.
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Introduction. Microleakage is defined as the clinically undetectable seepage of oral fluids containing bacteria and debris between cement layer and tooth restoration. Objective. This in vitro study investigated the effect of different dental cements (zinc-phosphate, polycarboxylate, glass-ionomer and resin cement) on microleakage in different ceramic crown systems (metal ceramic crown, metal ceramic crown with a porcelain margin, Empress 2 and In Ceram all-ceramic crowns) fixed on extracted human teeth. Methods. One hundred and sixty intact human premolars were randomized to four groups of forty teeth each, according to the different ceramic crown systems. They were prepared in a standardized manner for metal-ceramic and all-ceramic crowns. Crowns were made following a standard laboratory technique, and each group of crowns were divided into four groups according to the different cement agents and cemented on their respective abutments. The specimens were subjected to thermocycling, placed in methylene blue solutions, embedded in resin blocks and vertically cut in the bucco-oral and meso-distal direction. The microleakage in the area of tooth-cement interface was defined as linear penetration of methylene blue and was determined with a microscope to assign microleakage scores using a five-point scale. Results. A significant association was found between a cement type and degree of microleakage (p=0.001). No statistically significant differences were found among the different ceramic crown systems luted with the same dental cement. The smallest degree of microleakage was observed in specimens luted with resin cement (X=1.73), followed by glass-ionomer cement (X=2.45) and polycarboxylate cement (X=3.20). The greatest degree of microleakage was detected in the crowns fixed with zincphosphate cement (X=3.33). Conclusion. The investigated dental cements revealed different sealing abilities. The use of resin cement resulted in the percentage of 0 microleakage scores. Due to this feature, the resin cement is to be recommended in everyday clinical practice.
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Lee, Ki-Hong, In-Sung Yeo, Benjamin M. Wu, Jae-Ho Yang, Jung-Suk Han, Sung-Hun Kim, Yang-Jin Yi, and Taek-Ka Kwon. "Effects of Computer-Aided Manufacturing Technology on Precision of Clinical Metal-Free Restorations." BioMed Research International 2015 (2015): 1–5. http://dx.doi.org/10.1155/2015/619027.
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Purpose. The purpose of this study was to investigate the marginal fit of metal-free crowns made by three different computer-aided design/computer-aided manufacturing (CAD/CAM) systems.Materials and Methods. The maxillary left first premolar of a dentiform was prepared for all-ceramic crown restoration. Thirty all-ceramic premolar crowns were made, ten each manufactured by the Lava system, Cercon, and Cerec. Ten metal ceramic gold (MCG) crowns served as control. The marginal gap of each sample was measured under a stereoscopic microscope at 75x magnification after cementation. One-way ANOVA and the Duncan’s post hoc test were used for data analysis at the significance level of 0.05.Results. The mean (standard deviation) marginal gaps were 70.5 (34.4) μm for the MCG crowns, 87.2 (22.8) μm for Lava, 58.5 (17.6) μm for Cercon, and 72.3 (30.8) μm for Cerec. There were no significant differences in the marginal fit among the groups except that the Cercon crowns had significantly smaller marginal gaps than the Lava crowns(P<0.001). Conclusions. Within the limitation of this study, all the metal-free restorations made by the digital CAD/CAM systems had clinically acceptable marginal accuracy.
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Vahidi, Farhad, Erwin T. Egloff, and Francis V. Panno. "Evaluation of marginal adaptation of all-ceramic crowns and metal ceramic crowns." Journal of Prosthetic Dentistry 66, no. 4 (October 1991): 426–31. http://dx.doi.org/10.1016/0022-3913(91)90499-m.
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Anusavice, K. J., and B. Hojjatie. "Stress Distribution in Metal-Ceramic Crowns with a Facial Porcelain Margin." Journal of Dental Research 66, no. 9 (September 1987): 1493–98. http://dx.doi.org/10.1177/00220345870660091601.
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The use of metal-ceramic restorations with porcelain butt-joint facial margins has increased in the past several years. Although these crowns exhibit improved esthetics compared with metal-ceramic crowns which display a metal gingival collar or metal knife-edge margin, the effectiveness of this design in resisting intra-oral forces is not known. The objective of this study was to analyze the stress distribution induced by simulated intra-oral loads on crowns with variable coping configurations. The copings, with a thickness of either 0. 1 or 0.3 mm, were modeled with a facial termination of metal at three locations: at the gingival floor, 0.9 mm above the gingival floor, and 4.2 mm above the gingival floor. The coping and crown dimensions were based on a prepared maxillary central incisor with a facial shoulder and a lingual chamfer. Both Ni-Cr and Au-Pd alloy copings were employed in the crown models. Finite element stress analyses were performed on crowns which were subjected to several loading conditions. A cement film thickness of 0.030 mm was assumed. For all cases, the stresses which developed in porcelain and cement near the facial and lingual margins due to a vertical load of 200 N were predominately compressive in nature. For the crowns with Ni-Cr copings, the tensile stress in porcelain ranged from 11.0 MPa (for crowns with a facial metal thickness of 0.3 mm) to 12.5 MPa (for a metal thickness of 0.1 mm). The corresponding stresses for crowns with Au-Pd alloy copings were 8.3 MPa and 8.6 MPa, respectively. Maximum compressive stresses in cement near the lingual margin were 22.3 MPa for the Ni-Cr crowns and 30.0 MPa for the Au-Pd crowns. The maximum tensile stress in porcelain was 29.0 MPa and occurred near the area of loading for the Au-Pd case. The maximum tensile stress in the facial porcelain region (8.3 MPa) developed within the incisal third of the facial surface. Under the conditions assumed in this study, the alloy type, coping thickness, and coping termination point have a negligibly small effect on the stresses induced in porcelain or cement near the facial margin.
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V. Geshoska, Katerina, and Jagoda Bajevska. "Effect of manufacturing protocol on the internal fit and marginal discrepancy of metal ceramic and full ceramic dental crowns." Macedonian Pharmaceutical Bulletin 63, no. 01 (2018): 69–74. http://dx.doi.org/10.33320/maced.pharm.bull.2017.63.01.008.
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The accuracy of internal fit and marginal precision plays important role of clinical quality and success of dental crowns. Complications caused by marginal discrepancies such as caries, gingivitis, hypersensitivity are highlighted in dental literature. Despite marginal fit, internal fit and precision have a significant role in the persistence of full ceramic and metal ceramic crowns. As the technology evolves, it’s questionable which impression and manufacturing method is giving most accurate dental crowns. Therefore, the main purpose of this study is to get some information and data about marginal and internal fitting of dental crowns made by conventional, two-phase impression technique with polyvinyl siloxanes, and using different manufacturing process. Keywords: internal fit, marginal discrepancy, metal ceramic, full ceramic crowns
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Theng, Kai Yuan, Muchtar Andanastuti, Mohamed M. Aboras, Norziha Yahaya, and Mariyam Jamaludin Ghazali. "Properties and Survival Rate of all Ceramics Dental Crown: A Review." Applied Mechanics and Materials 465-466 (December 2013): 857–61. http://dx.doi.org/10.4028/www.scientific.net/amm.465-466.857.
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All-ceramic dental crown restoration is popular because it results in better aesthetic quality than metal alloy restoration. Ceramics also show superior biocompatibility and inertness to human biological systems. However, clinical experience indicates that all-ceramic crowns are not as durable as their porcelain-fused-to-metal counterparts, particularly on molar teeth. New ceramic biomaterials that combine durability with excellent aesthetic qualities have been developed. In this study, several promising bioceramics for dental crown applications are evaluated and compared. The evaluated parameters include strength of the material, survival rate in clinical performance, and aesthetic quality.
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Badran, Noha, Sanaa Abdel Kader, and Fayza Alabbassy. "Effect of Incisal Porcelain Veneering Thickness on the Fracture Resistance of CAD/CAM Zirconia All-Ceramic Anterior Crowns." International Journal of Dentistry 2019 (August 26, 2019): 1–12. http://dx.doi.org/10.1155/2019/6548519.
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Statement of Problem. In some clinical situations, the vertical length of either a prepared tooth or an implant abutment is short, while the occlusal clearance to be restored by a porcelain crown is large. Incisal thickness of the veneering porcelain should be considered to prevent mechanical failure of the crown. Purpose. The aim of this study is to evaluate the effect of two different incisal veneering porcelain thickness on the fracture resistance of the anterior all-ceramic CAD/CAM zirconia crown system as compared with the conventionally used metal ceramic crown system. Method. CAD/CAM zirconia all-ceramic and metal ceramic crowns were fabricated on the prepared dies with standardized dimensions and designs using standardized methods according to the manufacturer’s instructions. All crowns were then adhesively luted with resin-based cement (Multilink cement system), subjected to thermal cycling and cyclic loading, and were loaded until fracture using the universal testing machine to indicate the fracture resistance for each crown material in each veneering thickness. Results. Statistical analysis was carried out, and the results showed that the fracture resistance of the nickel-chromium metal ceramic group was significantly higher than that of the CAD/CAM zirconia all-ceramic group. Also, the fracture resistance of crowns with 1.5 mm incisal veneering thickness was significantly higher than those with 3 mm incisal veneering thickness in both groups. Furthermore, there was no significant difference in the fracture mode of the two groups where 50% of the total specimens demonstrated Mode II (veneer chipping), while 35% demonstrated Mode I (visible crack) and only 15% demonstrated Mode III (bulk fracture). Conclusion. High failure load values were demonstrated by the specimens in this study, which suggest sufficient strength of both incisal veneering thickness in both crown systems to withstand clinical applications; however, the fracture patterns still underline the requirement of a core design that support a consistent thickness of the veneering ceramic, and it is recommended to conduct long-term prospective clinical studies to confirm findings reported in the present study.
Dissertations / Theses on the topic "Metal-ceramic crowns"
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Ismail, Moosa. "Bond strength of metal orthodontic brackets to all ceramic crowns." University of the Western Cape, 2016. http://hdl.handle.net/11394/5608.
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Magister Scientiae Dentium - MSc(Dent)Aim: The aim of this study was to evaluate, in-vitro, the shear bond strength (SBS) and the resultant failure pattern after debonding of metal orthodontic brackets bonded with TransbondTM XT adhesive resin cement and RelyXTM Unicem 2 self-adhesive resin cement to pre-treated (35% ortho-phosphoric acid and silane coupling agent application) IPS eMax and porcelain veneered zirconia crowns. Material and methodology: A Typhodont maxillary lateral incisor was used and prepared in a conventional manner to receive a full ceramic crown. A CAD (computer aided design)/ CAM (computer aided manufacturing) machine was used to scan the prepared tooth and manufacture 40 IPS eMax crowns and 40 porcelain veneered zirconia crowns. Half the number of IPS eMax crown specimens (ie. 20) and half the number of porcelain veneered zirconia crown specimens (ie. 20) were thermocycled (ie. to mimic thermal changes which occur in the mouth), from 5 to 55o for 500 cycles as recommended by the International Organization for Standardization (ISO 6872, 2008). The remaining 20 IPS eMax crown specimens and 20 porcelain veneered zirconia crown specimens remained new and unexposed to thermal changes. The facial surfaces of all the thermocycled and non-thermocycled crown specimens were then etched. Etching of all the ceramic bonding surfaces was performed by the application of 35 per cent ortho-phosphoric acid liquid for 2 minutes, followed by a thin layer of a ceramic primer. A lateral incisor metal bracket with a bracket base area of 9mm2 (as confirmed by the manufacturer) was bonded to each of the etched and silane treated ceramic crown specimens and separated in the following manner: Group 1: (10 thermocycled, etched and silane treated IPS eMax and 10 thermocycled, etched and silane treated porcelain veneered zirconia crown specimens) RelyX™ Unicem 2 self-adhesive resin cement was used to bond the bracket to the ceramic crown specimens, Group 2: (10 thermocycled, etched and silane treated IPS eMax and 10 thermocycled, etched and silane treated porcelain veneered zirconia crown specimens) Transbond™ XT light cure adhesive primer was first applied onto the bonding surface of the crowns and then Transbond™ XT adhesive resin was used to bond the bracket to the ceramic crown specimens, Group 3: (10 non-thermocycled, etched and silane treated IPS eMax and 10 non-thermocycled, etched and silane treated porcelain veneered zirconia crown specimens) RelyX™ Unicem 2 self-adhesive resin cement was used to bond the bracket to the ceramic crown specimens, Group 4: (10 non-thermocycled, etched and silane treated IPS eMax and 10 non-thermocycled, etched and silane treated porcelain veneered zirconia crown specimens) Transbond™ XT light cure adhesive primer was first applied onto the bonding surface of the crowns and then Transbond™ XT adhesive resin cement was used to bond the bracket to the ceramic crown specimens. After bonding all samples were stored in distilled water for 24 hours before being submitted to the shear bond strength test. Debonding forces in Newtons (N) was determined by using a shear testing machine and converted into Mega Pascals (MPa). Results: The results after debonding were compared. The mean shear bond strength for RelyXTM Unicem 2 self-adhesive resin cement bonded to the all ceramic non-thermocycled crowns (Group 3) ranged from a low of 5.1 MPa (45.5 Newtons) when brackets were bonded to the IPS eMax crowns to a high of 5.8 MPa (51.9 Newtons) when brackets were bonded to the porcelain veneered zirconia crowns. The mean shear bond strength for Transbond XT adhesive resin cement bonded to the all ceramic non-thermocycled crowns (Group 4) ranged from a low of 6.4 MPa (57.3 Newtons) when brackets were bonded to the porcelain veneered zirconia crowns to a high of 8.1 MPa (72.7 Newtons) when brackets were bonded to the IPS eMax crowns. The side by side Box-and-Whisker plots of the shear bond strengths show wide and overlapping dispersions of the crown/adhesive resin combinations which consequently lessen the probability of significant differences between the crown/adhesive resin combinations in all 4 groups. According to the Kruskal-Wallis test (p < 0.05), and the Bonferroni Test the non-thermocycled crown/adhesive resin combinations do not differ significantly. Study of the mean ARI (Adhesive Remnant Index) values for the non-thermocycled crown/adhesive combinations shows that brackets bonded with Rely-XTM Unicem 2 to non-thermocycled porcelain veneered zirconia crowns failed entirely at the ceramic/adhesive interface and for all the other non-thermocycled ceramic/adhesive combinations most of the failures of the bond (70%) occurred at the bracket/adhesive interface, ie. cohesive fractures within the composite resin. No cohesive fractures of the porcelain crowns were noted. The results of the thermocycled groups (Group 1 and Group 2) show the TransbondTM XT/non-thermocycled IPS eMax crown combination yielded the highest overall mean shear bond strength of 8.1 MPa (72.7 Newtons) but dropped to a mean shear bond strength of 5.1 MPa (46.1 Newtons) (36.4% drop in shear bond strength) when the crowns were thermocycled prior to bonding. The TransbondTM XT/non-thermocycled porcelain veneerd zirconia crown combination yielded the second highest overall mean shear bond strength of 6.4 MPa (57.3 Newtons) and dropped to a mean shear bond strength of 5.1 MPa (45.8 Newtons) (19.3% drop in shear bond strength) when the crowns were thermocycled prior to bonding. The RelyXTM Unicem 2/non-thermocycled porcelain veneered zirconia crown combination yielded the third highest overall mean shear bond strength of 5.8 MPa (51.9 Newtons) but dropped significantly to a mean shear bond strength of 3.2 MPa (29.1 Newtons) (a significant 43.8% drop in shear bond strength) when the crowns were thermocycled prior to bonding. Lastly, the RelyXTM Unicem 2/non-thermocycled IPS eMax crown combination yielded the fourth highest mean shear bond strength of 5.1MPa (45.5 Newtons) but dropped to a mean shear bond strength of 4.9 MPa (44.5 Newtons) (a drop in shear bond strength of only 3%) when the crowns were thermocyled prior to bonding. Relaxing the significance level (p-value) somewhat demonstrates the negative influence of thermocycling on the shear bond strength of the crown/adhesive combinations. The non-thermocycled all ceramic crown/adhesive combinations showed mean ARI values of between 1.3 and 2.1 indicating cohesive fractures within the composite resin and efficient bonding of the adhesive material to the porcelain surface. However, all the thermocycled all ceramic crown/adhesive treatment combinations showed mean ARI values of between 0 and 0.8 indicating a bond failure between adhesive and porcelain and highlighting the negative influence of thermocycling on bond strength of both adhesive resin cements. Conclusion: Within the limitations of this study, it can be concluded that: 1.There was no significant difference in the shear bond strengths of metal orthodontic brackets bonded with RelyXTM Unicem 2 self-adhesive resin cement and metal orthodontic brackets bonded with TransbondTM XT adhesive resin cement to IPS eMax and porcelain-veneered zirconia crowns which were conditioned with 35 % phosphoric acid and a silane coupling agent. 2. Conditioning the porcelain surface with 35% phosphoric acid and a silane coupling agent (which is safer to use than Hydrofluoric acid) is sufficient for bonding metal orthodontic brackets to all ceramic crowns, and should make it simpler for clinicians to remove the remaining adhesive from the porcelain surface after debonding. 3. The negative influence of thermocycling prior to bonding can be seen on shear bond strength values. 4. Most of the failures of the bond occurred at the ceramic/adhesive interface and cohesive fractures within the composite resin. No cohesive fractures of the porcelain crowns were noted.
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Marashdeh, M. M. "Preparations features and periodontal consequences of metal ceramic crowns (MCCs)." Thesis, Queen's University Belfast, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273254.
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Seymour, Kevin Guy. "Variations in the labial 'shoulder' geometry of teeth prepared to receive metal ceramic crowns." Thesis, Queen Mary, University of London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267746.
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Näpänkangas, R. (Ritva). "Fixed metal ceramic prostheses:treatment need, complications and survival of conventional fixed prosthodontics." Doctoral thesis, University of Oulu, 2001. http://urn.fi/urn:isbn:9514265408.
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Abstract
The aims of this study were to evaluate the treatment need of fixed
bridges according to the distribution of pontics in dentition in different
age groups, and to investigate the primary and late complications and
survival of the conventional fixed metal ceramic prostheses, as well as
patients' satisfaction with the prosthetic treatment.
The whole material consisted of the patients treated with fixed metal
ceramic prostheses by undergraduate students at the Institute of Dentistry
during the years 1984 - 1996. There were altogether 772 patients, 460
women (60 %) and 312 men (40 %). Their mean age was 47 years (23 - 81
years). Altogether 944 single metal ceramic crowns and 543 fixed bridges
(1374 abutments and 807 pontics) were prepared.
It can be concluded that the fixed bridges are most often prepared to
replace upper first premolars and lower first molars also in the future.
The most usual primary complications related to fixed bridges occurred
during preprosthetic endodontic treatment of abutment teeth and during the
preparation of the root canals. Previous restoration of the prepared tooth
does not have any marked effect on the prognosis of single crowns with
dowels, although anatomically complicated upper lateral incisors and upper
first premolars need special attention in the treatment planning. Patients
were satisfied with aesthetics and function of the fixed metal ceramic
prostheses. Late complications found in clinical examinations were few,
and the survival rate for the fixed metal ceramic bridge prostheses was
calculated to be 84 % after 10 years, long fixed bridges having a lower
survival than the shorter ones.
The treatment need for conventional fixed bridges seems to be highest
among patients over 50 years of age in the future. Age does not influence
the longevity of the fixed prostheses, but basic circumstances of the
mouth, especially low secretion of saliva affected by diseases and/or
medications and high scores of lactobacilli and streptococcus mutans of
the saliva seem to decrease the survival.
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Nilsson, Eddie, and Marko Drazic. "Fracture resistance of porcelain-veneered gold-alloy and zirconia molar crowns." Thesis, Malmö högskola, Odontologiska fakulteten (OD), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-19673.
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AbstraktSyfte:Studiens syfte var att utreda maxlasttoleransen mellan yttria-stabiliserad zirkoniumdioxid- (Y-TZP) och metallkeramiska- (MC) molarkronor med en ny design på in vitro belastningsformen. En stålkula användes för att utöva last på kusparna istället för i fissuren för att framställa en sprickbildning liknande den som ses kliniskt. Materialochmetod:26 kronor tillverkades, varav 13 högädla MC och 13presintrade Y-TZP. 7 av MC göts av 50% tidigare icke-gjuten och 50% omgjuten legering medan de kvarvarande 6 göts av 100% tidigare icke gjuten legering. Kronorna täcktes av ett fasadporslinoch cementerades på stansar av ett resinmaterial. Av de 26 kronorna genomgick 24 förbelastingstester och belastades slutligen till fraktur. Resultat: MC klarade signifikant högre belastningar än Y-TZP, P>0,001. Frakturerna skiljde sig också grupperna emellan där MC-gruppen uppvisade enbart adhesiva frakturer av fasadporslinet under det att Y-TZP-gruppen uppvisade kohesiva brott i ytporslinet undantaget en Y-TZP-krona som uppvisade total fraktur. Ingen signifikant skillnad kunde ses mellan MC-kronor bestående av enbart tidigare icke gjuten legering och MC-kronor med 50% omgjuten legering, P=0,370. Konklusion: MC-kronor klararsignifikant högre belastningar än Y-TZP-kronor och testet genererar kliniskt relevanta frakturer av ytporslinet snarare än totala frakturer. Frakturbeteendet skiljer sig mellan MC och Y-TZP där MC uppvisar endast adhesiva fraktureroch Y-TZP främst kohesiva brott av ytporslinet.
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Bayardo-González, Daniel Eduardo. "Avaliação da resistência à fratura em coroas metalocerâmicas e ceramocerâmicas, utilizando infra-estruturas com e sem reforço." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/25/25135/tde-13062007-160803/.
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As restaurações metalocerâmicas apresentam relatos de sucesso clínico a longo prazo e as características de reforço (cinta lingual e poste proximal) das infra-estruturas metálicas parecem ser de grande importância para este sucesso. Estes reforços freqüentemente estão ausentes nas infraestruturas das restaurações ceramocerâmicas. O objetivo deste estudo foi testar a hipótese nula de que coroas confeccionadas com infra-estruturas cerâmicas com desenho com e sem reforço não resultam em valores de resistência à fratura diferentes de coroas com infra-estruturas metálicas confeccionadas com os mesmos desenhos. Para a realização deste trabalho foram fabricadas 40 coroas, dividas em quatro grupos (n=10): (1) coroas metalocerâmicas - infra-estrutura com reforço; (2) coroas metalocerâmicas - infra-estrutura sem reforço; (3) coroas ceramocerâmicas - infra-estrutura com reforço; e (4) coroas ceramocerâmicas - infra-estrutura sem reforço. Os corpos de prova foram cimentados com ionômero de vidro modificado por resina nos troquéis metálicos e submetidos à análise de resistência à fratura usando uma máquina de teste universal Kratos, a uma velocidade de 0,5 mm/min. Todos os corpos de prova foram mantidos sob pressão até a fratura. Os resultados de resistência à fratura (kgf) foram submetidos à análise de variância (ANOVA) a dois critérios e ao teste de Tukey. O nível de significância considerado em todas as análises foi de 5% (p<0,05). Os valores médios de resistência à fratura foram de 237,637 kgf para as coroas metalocerâmicas com infraestruturas com reforço, 171,738 kgf para as coroas metalocerâmicas com infraestruturas com reforço, 127,588 kgf para as coroas ceramocerâmicas com infra-estruturas com reforço e 93,914 kgf para as coroas ceramocerâmicas com infra-estruturas sem reforço, com diferença estatisticamente significante (p<0,05), entre os quatro grupos. As coroas metalocerâmicas com reforço (Grupo 1) apresentaram o maior valor de resistência à fratura e estatisticamente significante, entre todos os grupos. As coroas confeccionadas com infra-estruturas com reforço apresentaram maior resistência à fratura do que as confeccionadas sem reforço, tanto nas coroas metalocerâmicas como nas ceramocerâmicas.Metal-ceramic restorations present reports of long-term clinical success, and the characteristics of reinforcement coping (lingual collar and buttressing shoulder) seem to be of great importance for this success. These reinforcements are often absent in all-ceramic coping restorations. The aim of the current study was to evaluate and compare the in vitro fracture resistance of metal-ceramic and In-Ceram Alumina all-ceramic crowns, with and without reinforced coping design. Forty crowns were fabricated and divided into four groups (n=10): group 1, metal-ceramic crown with reinforced coping design; group 2, metal-ceramic crown without reinforced coping design; group 3, allceramic crown with reinforced coping design and group 4, all-ceramic crown with out reinforced coping design. The forty crowns were cemented on stainless steel dies and axially loaded in a universal testing machine until fracture occurred, and the maximum load (kgf) was recorded. Data were analyzed by one-way analysis of variance (ANOVA) and Tukey test (p<0.05) The results showed a statistical significant superiority (p<0.05) of the reinforcement coping groups (237.637 kgf for metalo-ceramic crowns and 127.588 kgf for all-ceramic crowns), regarding to non reinforcement coping groups (171.738 kgf for metalo ceramic crowns and 93.914 kgf for all-ceramic crowns). These founds denote that: (1) crowns made with reinforcement coping had presented greater fracture resistance than those confectioned without it and (2) metal-ceramic crowns had presented greater fracture resistance than all-ceramic crowns.
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Dias, Ana Paula. "Avaliação da adaptação marginal e rugosidade de superfície de copings confeccionados de Níquel-Cromo e Cobalto-Cromo injetados em moldes de revestimento a temperatura reduzida." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/58/58131/tde-01092017-113233/.
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A adaptação marginal e a rugosidade de superfície são parâmetros fundamentais para o sucesso clinico e longevidade das coroas metalocerâmicas. O primeiro permite o selamento das bordas do preparo, prevenindo contra problemas relacionados a exposição do preparo aos fluidos orais e a placa bacteriana e o segundo, remete ao auxilio de uma boa adaptação a fatores mecânicos e biológicos importantes a qualidade da restauração final. Visto que ambos os aspectos são diretamente relacionados a temperatura em que as ligas são submetidas, o objetivo deste trabalho foi avaliar o desajuste marginal, por meio de microscopia óptica, e rugosidade de superfície, por meio de microscopia confocal, de copings metálicos obtidos com as ligas metalicas de Ni-Cr [Verabond II e experimental (SR)] e Co-Cr (Keragen) injetadas no molde de revestimento a duas diferentes temperaturas de estufagem (900°C e 700°C), de forma a avaliar se a redução da temperatura de estufagem possa causar o melhoramento do resultado das fundições, minimizando os efeitos das altas temperaturas. As leituras foram realizadas em copings confeccionados a partir da fundição de casquetes de munhão calcináveis. Cada coping foi cimentado a uma matriz (munhão) por meio de um padronizador da pressão de assentamento e levado aos respectivos microscópios para leitura de desajuste marginal e rugosidade de superfície. Para a avaliação do desajuste marginal foi calculada a media das distancias da borda da restauração a borda do preparo a partir de um ponto inicial aleatório selecionado sobre a margem cervical do coping. Duas leituras eram realizadas a cada ¼ de volta, totalizando 8 leituras por coping. Para os dados obtidos, que tiveram distribuição não normal, foi utilizado o teste não paramétrico de Kruskal Wallis e foi observado que a liga VB apresentou menor desajuste marginal (56,92µm) quando comparado a liga Keragen (66,75 µm) com p<0,05 e a liga SR apresentou resultado intermediário (49,87µm), sem diferença estatística entre as demais. Para comparação das temperaturas foi utilizado o teste Mann-Whitney e a fundição a 700 °C resultou em melhor adaptação marginal que a 900 °C (50,75 µm e 66,75 µm, respectivamente) com p=0,045. Para a avaliação da rugosidade foi selecionada uma área do coping distante 100 m da borda cervical da peca e realizada a leitura. Os dados de rugosidade de superfície seguiram distribuição normal, sendo utilizado um teste paramétrico (ANOVA), seguindo pelo teste de Bonferroni. Ao se compararem as Ligas, SR apresentou menor rugosidade que Keragen (p=0,002) e que Vera Bond (p=0,001); ao se compararem as temperaturas a fundição a 700 °C resultou em menor rugosidade que a 900 °C (p=0,045). O que se concluiu com a presente metodologia apresentada foi que o comportamento das ligas as diferentes temperaturas varia de acordo com a sua composição tanto em relação a superfície quanto a adaptação marginal e que a fundição a 700 °C proporcionou obtenção dos melhores resultados em ambas as variáveis, sendo possível a otimização da superfície da peca fundida sem o comprometimento da adaptação marginal por meio da redução da temperatura de injeção da liga no molde, favorecendo o resultado final das restaurações.A proper marginal fit and surface roughness are fundamental aspects for the clinical success of metal-ceramic crowns. The first parameter allows to preserve the margins adaptation accuracy of the restaurations, thus preventing issues related to an improper exposition of the dental tissues into the oral fluids and biofilm. The second parameter is related to mechanical and biological important aspects for the restoration quality and is also able to optimize the piece final adaptation. Both parameters are associated to temperature levels and the understanding of their behavior is convenient for the improvement of the Fixed Prostheses, therefore the aim of this study was to mensure the maginal gap by using the optical microscopy and evaluate the surface roughness by confocal microscopy of metallic copings fused with Nickel-Chromium alloys [Verabond II e experimental (SR)] and Cobalt- Chromium (Keragen) under two distinct mold temperature for the alloy injection: 700°C and 900°C. Performing those analysis represents a way to find out if the temperature reduction of the mold can be convenient to increase the quality of the casting patterns`s surface without affect the marginal fidelity, thus minimizing the overheat casting problems. The mensurements were performed in copings fused from resin cylinders for casting and each one, after fused, was cimented in a abutment cylinder analogue with standardized pression and placed under the respective microscopes for marginal fit and surface analyses. For the marginal fit mensurement were selected two equidistant points in a metal coping that representing ¼ turn on the measurement device, in a total of 8 measurements for coping in each step that results in a misfit average. Once it was found a non-normal distribution, the non-parametric Kruskal Wallis test was performed for the data and was observed that the allow VBII conferred lower values of marginal fit (56,92 µm) when compared to Keragen alloy (66,75 µm), p<0,05, and SR conferred average values between the others (49,87 µm),with no statistic difference. In the comparison between the mold temperatures the Mann-Whitney test was implemented and the temperature at 700°C reveled better results of marginal fit than the 900 °C temperature (50,75 µm e 66,75 µm, respectively) with p=0,045.For the surface analysis was selected an anatomic reference line in each coping and was set up a distance of 100 µm from this point to make the quantification. For the surface roughness data, with normal distribution, comparisons were performed using a parametric test for independent data (ANOVA), followed by Bonferroni test. The level of significance was set at 5%. At the comparison of alloys, the SR granted lower values of roughness in its patterns than Keragen (p=0.002) and Verabond II (p=0,001). Comparing the temperatures, the values of roughness of the patterns fused under 700° were lower than those fused under 900° (p=0,045). There was no significant difference for interaction between alloy X temperature (p=0,280). The conclusion of the present study was that the behavior of the alloys regarding the marginal fit and surface roughness vary depending of its composition and the Mold temperature and Pieces injected at 700°C in the mold conferred better results in both parameters, therefore being possible to optimize the fixed photesis casting patterns surfaces without marginal fit commitment by reducing the mold temperature for the alloy injection, thus Contributing to the quality of the metal ceramic restorations.
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Dias, Ana Paula. "Efeito da sinterização da cerâmica no desajuste marginal de coroas metalocerâmicas de níquel-cromo e cobalto-cromo." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/58/58131/tde-06022014-091350/.
Full textAbstract:
A adaptação marginal é fundamental para o sucesso clínico e longevidade das coroas metalocerâmicas. O objetivo deste trabalho foi avaliar, por meio de microscopia óptica, o desajuste marginal de copings metalocerâmicos obtidos com as ligas metálicas de Ni-Cr [Verabond II e experimental (SR)] e Co-Cr (Keragen). As leituras foram realizadas antes da sinterização (T1), após a sinterização do opaco (T2) e após a sinterização da cerâmica (T3). A partir de uma matriz metálica e uma contra-matriz de teflon, encaixada sobre o preparo da matriz, foram obtidos 30 padrões de resina acrílica Duralay/cera com espessura de 0,7 mm (n=30), que foram incluidos em anel com revestimento Microfine (Talladium). Após a fundição, os copings foram desincluídos, jateados e usinados. Cada copings, adaptado à outra matriz metálica por meio de um padronizador da pressão de assentamento, foi levado ao microscópio óptico. Foram selecionados dois pontos equidistantes de um ponto selecionado no copings, que representava ¼ de volta no dispositivo de leitura, totalizando 8 leituras por etapa em cada copings. Os dados de desajuste marginal (μm) foram analisados estatisticamente pelos testes ANOVA e Bonferroni (α=0,05). Os resultados mostraram que houve diferença para os fatores: tempo (p=0,00) e liga metálica (p=0,001). Com relação aos tempos, após a aplicação da cerâmica, houve maior desajuste marginal (132 μm) que após a sinterização de opaco (111,81) e antes da sinterização (90,44), com diferença entre essas duas etapas. Com relação às ligas metálicas, a liga experimental SR apresentou o menor desajuste marginal (79,75 μm) que as ligas de Ni-Cr (120,23 μm) e Co-Cr (134,28 μm) que não apresentaram diferença entre si. Não houve diferença significativa para as interações (p=0,834). Conclui-se que o desajuste marginal aumenta após as sinterizações da cerâmica e a liga experimental SR pode ser utilizada com segurança para confecção de restaurações metalocerâmicas, por apresentar os melhores resultados entre as ligas utilizadas.The good marginal fit is a critical point for the clinical success of metal-ceramic crowns after definitive cementation. The knowledge of alloys properties, their interference factors and materials development allows the creation of new crowns within clinically acceptable marginal fit, factor that enables a good periodontal restorations performance and also prevents caries recurrences in cementation line. The present study evaluated, by optical microscopy, marginal fit in metal-ceramic crowns fused with three different alloys; Nickel-Chromium (Verabond II), Cobalt- Chromium (Keragen) and a experimetal Nickel-Chromium (SR) alloy in three distinct stages; after the cast (T1), after opaque layer application (T2) and after ceramic coating (T3). Were selected two equidistant points in a metal coping that representing ¼ turn on the measurement device, in a total of 8 measurements for coping in each step that results in a misfit average. Comparisons were performed using a parametric test for independent data (ANOVA), followed by Bonferroni test where applicable. The level of significance was set at 5%. The results showed there were statistical differences for such factors: time (p = 0.00) and alloy (p = 0.001). In relation to time, after ceramics application, there was higher marginal misfit (132 μm) than after opaque sintering (111.81 μm) and before sintering (90.44 μm) with differences between these two steps. In relation to alloys, the experimental SR alloy showed the lower marginal misfit (79.75 μm) than Ni-Cr alloys (120.23 μm) and Co- Cr (134.28 μm) and there was no statistical difference for these experimental groups There was no significant difference for interaction (p = 0.834). In conclusion the marginal misfit increases after ceramics sintering. Experimental SR alloy showed the best results among the alloys and can be safely used to metal ceramic restorations.
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Yang, Chao-sen, and 楊朝森. "Characterization of a Copolyester and Six Metal-Ceramic Crowns." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/7mx9k2.
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碩士國立中山大學
材料科學研究所
96
This thesis contains two parts of materials characterization. Part I is a poly(butylene succinate) copolymer with minor amount of 2-methyl-propylene succinate. In the second part, six kinds of implant crowns made from five dental casting alloys and one Zircoina ceramic are studied. Copolyester was synthesized and characterized as having 89.0 mol% butylene succinate units and 11.0 mol% 2-methyl-propylene succinate units in a random sequence, revealed by NMR. Isothermal crystallization kinetics was studied in the temperature range (Tc) from 75 to 91 °C using differential scanning calorimeter (DSC). The melting behavior after isothermal crystallization was studied by using DSC by varying the Tc, the crystallization time and the scanning rate. DSC curves showed triple melting peaks. Multiple melting behaviors indicate that the upper melting peaks are associated with the primary and the recrystallized crystals, or the crystals with different lamellar thickness. As the Tc increases, the contribution of recrystallization slowly decreases and finally disappears. A Hoffman-Weeks linear plot gives an equilibrium melting temperature of 118.4 °C. The spherulitic growth rates of this copolyester were measured at Tc between 69 and 91 °C using an optical microscope equipped with a CCD camera. The kinetic analysis of the growth rates gave a regime II-III transition temperature at about 77.2 °C. Rectangular specimens of 10 × 9 × 4 mm were made of five kinds of casting alloys, separately. They were treated in the same procedures as crowns did. Their surfaces after oxidation were analyzed using x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Rectangular specimens after applying porcelains were ~5.5 mm thick. The cross-section areas were studied by electron probe micro analyzer (EPMA). Standardized maxillary premolar crowns were fabricated with five different alloys and one Zircoina ceramic. The crown specimens were positioned in a custom testing apparatus and vertically loaded on the middle of the occlusal surface with a universal testing machine at a crosshead speed of 0.5 mm/min until fracture. Mean values of load at fracture were calculated in each alloy and compared with a one-way analysis of variance and Tukey test (α=0.05). The fracture surfaces were examined using SEM. The results of XPS, SEM and EPMA indicate that on the surface there was an oxidation layer (or interface between metal and ceramic) of indium (or/and tin, zinc, etc.). The concentration of oxide metal increased, whereas that of precious metal decreased, from bulk to interface. The fracture strength and the fracture path of the crowns were correlated with the metal-ceramic interface of the rectangular specimens that was characterized using XPS, SEM and EPMA.
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Chin, Chun-Cheong, and 錢振昌. "Porcelain Fracture Resistance in Metal-Ceramic Crowns with Different Veneer Thickness." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/83757938300759644694.
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碩士國立臺灣大學
臨床牙醫學研究所
96
Purpose: Fracture of ceramic veneers is frequently observed in clinical practice and poses an esthetic and functional dilemma both for the patient and the dentist. The purpose of this study was to compare the porcelain fracture resistance between two different thickness of porcelain on the cement-retained implant metal-ceramic crowns. Material and methods: Forty (8×8×8 mm, W×H×L) cubic-shaped single metal-ceramic crowns were fabricated with two different thickness (1.5 mm or 2.5 mm) of porcelain and divided into four groups (10 crowns each): Groups 1 & 3 (1.5 mm), Groups 2 & 4 (2.5 mm). All the samples were cemented on 1mm Easy abutment above a Brånemark RP implant analog embedded in a 30×30×84 mm type IV die stone block. Groups 3 & 4 were first exposed to a vertically dynamic loading of 80N for 100,000 cycles to simulate masticatory function at mesial marginal ridge of the occlusal surface. Afterwards, all the samples were positioned in a custom testing apparatus and vertically loaded on the mesial marginal ridge of the occlusal surface with a universal testing machine (Instron 5566) at a crosshead speed of 0.5 mm/min until fracture. SEM fractographic analysis was utilized to determine the fracture patterns. Mean values of load at fracture (kgf) were recorded in each group and compared with a 2-way ANOVA and independent t-test (p＜0.05)(factors: porcelain thickness, with/without dynamic loading). Results: 1. No obvious ceramic fracture except digging pits was observed in Groups 3 & 4 after dynamic loading. 2. Mean values of loads required to fracture the crowns were as follow: Group 1: 129.63 ± 12.65 kgf; Group 2: 116.08 ± 10.83 kgf; Group 3: 84.18 ± 3.98 kgf; Group 4: 66.94 ± 11.05 kgf. 3. Dynamic loading prior to fracture test reduced the mean fracture loads significantly in Groups 3 & 4. 4. Cohesive or adhesive fracture of the porcelain can be observed in all four groups in fracture test. Conclusions: From a clinical viewpoint, to diminish the porcelain thickness of about 1.5mm, can decrease the probability of porcelain fracture of metal-ceramic crowns.
Books on the topic "Metal-ceramic crowns"
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Müterthies, Klaus. Esthetic approach to metal ceramic restoration for the mandibular anterior region. London: Quintessence, 1990.
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Blunn, Gordon. Bearing surfaces. Oxford University Press, 2011. http://dx.doi.org/10.1093/med/9780199550647.003.007006.
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♦ Traditionally bearings were made from polyethylene and cobalt chrome. These bearings are still most commonly used for knee replacements. In hip replacements due to osteolysis caused by polyethylene wear alternative material combinations at the bearing surface are used♦ Highly cross linked plastics have been developed and have been shown to reduce wear. There are a number of different types available which differ in their performance♦ Metal on metal bearings first used in the 1960s have also been developed and show very low wear rates. These bearings are more susceptible to edge loading and the resulting metal ion release can result in adverse biological reactions leading to failure♦ Whilst ceramic on plastic surfaces have been used for a considerable amount of time the reduction in wear is not as great as with well functioning metal on metal bearings♦ Ceramic on ceramic bearings have been used for a considerable time and show even lower wear rates than metal on metal bearings. In the past there has been an incidence of catastrophic fracture of these bearings but developments in materials technology have considerably reduced these events.
Book chapters on the topic "Metal-ceramic crowns"
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Malo, Paulo, Miguel de Araujo Nobre, Joao Borges, and Ricardo Almeida. "Retrievable Metal Ceramic Implant-Supported Fixed Prostheses With Milled Titanium Frameworks And All-Ceramic Crowns." In Journal of Prosthodontics on Complex Restorations, 214–24. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2016. http://dx.doi.org/10.1002/9781119274605.ch29.
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Stevenson, Brian. "Metal–ceramic crowns." In Advanced Operative Dentistry, 129–40. Elsevier, 2011. http://dx.doi.org/10.1016/b978-0-7020-3126-7.00010-7.
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"Ceramic and Modified Metal–Ceramic Crowns." In Esthetic Dentistry and Ceramic Restorations, 215–58. CRC Press, 1998. http://dx.doi.org/10.1201/b14686-11.
Full textConference papers on the topic "Metal-ceramic crowns"
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Petrescu, Emanuela, Cosmin Sinescu, Meda Lavinia Negrutiu, Roxana Rominu, Pop Daniela Maria, and Mihai Rominu. "Non-invasive imagistic investigation of metal-ceramic crowns." In Asia Communications and Photonics Conference and Exhibition. Washington, D.C.: OSA, 2010. http://dx.doi.org/10.1364/acp.2010.79900y.
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Petrescu, Emanuela, Cosmin Sinescu, Meda Lavinia Negrutiu, Roxana Rominu, Daniela Maria Pop, and Mihai Rominu. "Non-invasive imagistic investigation of metal-ceramic crowns." In Asia Communications and Photonics Conference and Exhibition, edited by Qingming Luo, Frank Chuang, Stefan Haacke, and Chih-Chung Yang. SPIE, 2010. http://dx.doi.org/10.1117/12.891278.
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Petrescu, Emanuela, Cosmin Sinescu, Meda Lavinia Negrutiu, Daniela Pop, Roxana Rominu, Marius Enescu, Mihai Rominu, Adrian Bradu, George Dobre, and Adrian Gh Podoleanu. "OCT and RX validation of metal-ceramic crowns repaired with ceramic material." In SPIE Optical Systems Design, edited by Gérard Berginc. SPIE, 2011. http://dx.doi.org/10.1117/12.896770.
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Andrei, M., G. Buica, M. Burlibasa, D. Gheorghe, and C. Pirvu. "Monitoring on short-term the corrosion processes of three different metal-ceramic crowns." In 2014 International Semiconductor Conference (CAS). IEEE, 2014. http://dx.doi.org/10.1109/smicnd.2014.6966403.
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Porojan, Liliana, Cristina Savencu, Adrian Boloș, Lucian Rusu, and Sorin Porojan. "Mechanical approach of metal-ceramic crowns obtained with laser-based additive manufacturing methods." In Seventh International Conference on Lasers in Medicine, edited by Carmen Todea, Adrian Podoleanu, and Virgil-Florin Duma. SPIE, 2018. http://dx.doi.org/10.1117/12.2280228.
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Yin, Ling, Abdur-Rasheed Alao, Xiao-Fei Song, and Richard Stoll. "Manufacturing Reliable Ceramic Crowns: The Role of Abrasive Machining in Digital Dentistry." In ASME 2016 11th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/msec2016-8613.
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Dental caries is a ubiquitous disease and nearly 100% of the population is affected worldwide. Consequently, reliable dental restorations are in high demand. More and more patients expect and request esthetics and biosafety, and desire metal-free prostheses. Both biocompatible and esthetic ceramics and digital processing of prostheses have been developed to meet these demands. This paper reviews the current status of abrasive machining involved in affordable digital dental ceramic restorations with regard to dental ceramic materials, dental CAD/CAM systems, and extra/intraoral dental handpiece adjustments. It highlights the importance and challenge of abrasive machining technologies in manufacturing of affordable and reliable dental restorations with cutting-edge materials.
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Song, Xiao-Fei, Jianhui Peng, Ling Yin, and Bin Lin. "In Vitro Dental Cutting of Feldspar and Leucite Glass Ceramics Using an Electric Handpiece." In ASME 2012 International Manufacturing Science and Engineering Conference collocated with the 40th North American Manufacturing Research Conference and in participation with the International Conference on Tribology Materials and Processing. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/msec2012-7290.
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Glass ceramics are important restorative materials in dentistry. They are used as veneer-core bilayer all-ceramic or metal-fused ceramic restorations or monolithic inlays/onlays/crowns to replace missing or damaged tooth structures for aesthetic and functional purposes. However, glass ceramic materials, such as feldspar and leucite glass ceramics, which are subject to this investigation, are brittle and easily induced microfractures in abrasive cutting using dental handpieces and coarse burs. In this paper, we investigated the dental abrasive cutting characteristics of feldspar and leucite glass ceramics using a high-speed electric handpiece and coarse diamond burs. Cutting forces, specific removal energy, surface roughness and morphology were investigated as functions of specific material removal rate and maximum undeformed chip thickness. The results indicate that increasing the specific material removal rate or the maximum undeformed chip thickness resulted in increases in both tangential and normal forces, but a decrease in specific removal energy for both ceramics. Tangential, normal forces and specific removal energy were significantly larger in up cutting than those in down cutting. Surface roughness for the two ceramics was not affected by the specific removal rate or the maximum undeformed chip thickness. Both microfrature and ductile microcutting morphology were observed in the machined surfaces for both ceramics. There existed a brittle to ductile transition trend when decreasing the specific material removal rate or the maximum undeformed chip thickness for the two ceramics. In comparison with feldspar glass ceramic, leucite glass ceramic generated better surfaces due to its more ductile deformation occurring in dental cutting.
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Sudarev, A. V., A. A. Suryaninov, B. V. Sudarev, and V. G. Konakov. "Development of High Temperature Gas Turbine Matrix Microrecuperator Made of Laser Sintered Ceramic and Metal Structural Materials." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68320.
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Analysis of trends in the development of small gas turbine engines (GTE) has shown that a significant increase in the parameters of the working media required to increase their efficiency and competitiveness in the energy market is limited by the reduced efficiency of small size blading of compressors and turbines [1]. Structural ceramic materials (SCMs), which has high heat resistance and relatively low density, allows development of light-weight and compact heat exchangers for regeneration of heat in the GTE’s which are suitable for continuous operation at the gas temperatures above 1000°C [2]. A design of the heat exchange surface for a countercurrent regenerative AH with a matrix consisting of coaxial cylindrical shells, each of which is made of heat elements (HE) in the form of circular perforated plates of equal width and different diameters, is proposed. The shells are embedded in one another and form a cylindrical matrix with longitudinal channels of circular (air) and semicircular (gas) cross sections. The AH matrix in the area with the gas temperature over 650°C is made of SMC, while within a zone with lower temperature operation it is made of the heat-resistant alloy. The AH metal matrix model was tested with various coolants in model paths: “air-water”, “water-air” and “air-to-air.” The experimental results confirmed the data of the thermal-engineering calculations. Such a sintered heat exchanger was designed for microGTE of 2 kW. At the present time it is being fabricated. Bench tests are scheduled for September-November 2012.
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Fend, Thomas, Bernhard Hoffschmidt, Oliver Reutter, Jo¨rg Sauerhering, and Robert Pitz-Paal. "Gas Flow in Hot Porous Materials: The Solar Air Receiver and Spin-Off Applications." In ASME 4th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2006. http://dx.doi.org/10.1115/icnmm2006-96173.
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This article presents an overview on research results from various projects, which deal with one common problem: gas flow in hot porous materials. First, the solar air receiver, which converts concentrated solar radiation into heat in an air circuit, is described as far as the basic principle and the materials employed are concerned. Then, results from experiments in concentrated solar radiation are presented. Materials employed in these applications are extruded ceramic materials as well as metal and ceramic foams with pore sizes on the milli- and micrometer scale. As it turned out, the material properties significantly influence the efficiency of the solar air receiver. It is shown, that under specific conditions flow instability occurs, which may lead to a thermal overload of the material. Measures to avoid these overloads are proposed. Two approaches how to predict gas flow theoretically are reported. Additionally, it is shown, how material quantities such as pressure drop characteristics influence the flow behaviour and the temperature distribution inside the material. Finally, before a conclusion is given, two further applications, which have been dealt with because similar phenomena occur, are reported: an advanced cross flow particle filter and a gas turbine cooling system.
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Zhang, Wei, Lili Zheng, Hui Zhang, and Sanjay Sampath. "Generic Correlation of Spray Distance With In-Flight Particle Behavior for Different Kinds of Materials in Air Plasma Spraying." In ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference collocated with the ASME 2007 InterPACK Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ht2007-32393.
Full textAbstract:
This paper investigates the influence of spray distance on inflight particle status for Yttria Stabilized Zirconia (YSZ), Mo and NiCrAlY thermal spray powders in Ar-H2 plasma through modeling and experiments. Distributions of individual particle characteristics such as temperature, velocity and size at the point of the maximum particle flux and points of the squared grids were measured for a few plume cross-sections. Numerical simulations were performed using the experimental conditions, and parametric studies were also performed. In-flight particle characteristics and their distributions were presented at different standoff/spray distances to reveal the heating and melting behaviors of different kinds of materials such as metal, alloy and ceramics powders. It can be found that for ceramic, metal and alloy powders, the particle velocity and temperature all increase with spray distance and then decrease after reaching maximum. However the positions of maximum temperature and velocity depend strongly on the material and size of the particles. The statistical distributions of temperature and velocity at different spray distances were also presented. It can be observed that the temperature distribution becomes narrower as spray distance increases. The occurrence of such behavior can be explained by analyzing particle kinetic energy and molten status. The correlations between powder properties and spray conditions have been established and they can serve as guidance for spray distance optimization of air plasma spraying for metal, alloys and ceramics particles.