10-year randomized trial (RCT) of zirconia-ceramic and metal-ceramic fixed dental prostheses.

OBJECTIVES: To monitor zirconia-ceramic and metal-ceramic posterior FDPs with respect to survival and technical/biological complication rates. MATERIALS AND METHODS: Fifty-eight patients received 76 3- to 5-unit posterior FDPs. The sites were randomly assigned to 40 zirconia-based (ZC) and 36 metal-based (MC) FDPs. FDPs were examined at baseline (cementation), at 6 months, at 1 year and then yearly up to 10 years. Technical outcomes were assessed using modified United States Public Health Service (USPHS) criteria. Biologic outcomes included probing depth, plaque, bleeding on probing and tooth vitality. Statistical analysis was performed applying Kaplan-Meier (KM) estimation, log-rank, Mann-Whitney and Fisher exact test. RESULTS: During the 10-year follow-up thirteen patients (17 FDPs) dropped out and 6 FDPs in 6 patients (5 ZC,1 MC) were considered catastrophic failures for technical and/or biological reasons. Forty-four patients with 53 FDPs (29 ZC, 24 MC) were available for examination. The median observation period was 10.3 years (ZC) and 10.0 years (MC). The 10-year KM survival estimate of ZC FDPs was 91.3% (95%CI:69.5;97.8) and 100% of MC FDPs. Minor chipping of the veneering ceramic and occlusal wear were found to a similar extent at ZC and MC FDPs. ZC FDPs demonstrated a significantly higher rate of framework fracture, de-bonding, major fractures of the veneering ceramic and poor marginal adaption. Biological outcomes were similar in both groups and between abutment and control teeth. CONCLUSION: At 10 years, ZC and MC posterior FDPs resulted in similar outcomes for the majority of the outcome measures (p > 0.05).

Influence of recasting on the quality of dental alloys: A systematic review.

STATEMENT OF PROBLEM: Dental alloy manufacturers advise against the reuse of previously melted alloy. However, for economic reasons, dental laboratories often reuse the casting surplus (sprue and metal remaining in the crucible former). Such reuse remains a controversial topic in dental practice. PURPOSE: The purpose of this systematic review was to assess the effects of remelting dental alloys by evaluating the following parameters: reasons for recasting and associated processes, feasible number of recastings, treatment of alloys before recasting and its effects on cytotoxicity, color of opaque porcelain, castability of alloys, marginal accuracy, mechanical properties, porcelain-metal interfaces, and corrosion. MATERIAL AND METHODS: The systematic review included all studies on dental alloy recasting. MEDLINE, Dentistry and Oral Science Source, Science Direct, and ISI Web of Science were searched (up to July 2014). Data were extracted and the quality of studies was assessed. RESULTS: Thirty-four studies published between 1983 and 2014 were included. The number of recastings ranged from 1 to 10. The percentage of new alloy ranged from 0 to 100 wt%, although the mean value was 50 wt%. CONCLUSIONS: Evidence for the feasibility of adding 50% new metal at each recasting is limited. The number of recastings should be limited to a maximum of 4. No general test protocol can be deduced from these studies, which limits the comparison and exploitation of data. Furthermore, no consensus protocol exists for the evaluation of recasting. Future studies should work toward establishing a standard protocol.

Clinical evaluation of fixed partial dentures made in Sweden and China.

The aim of this study was to compare the quality of fixed partial dentures (FPDs) made in a Chinese dental laboratory with corresponding FPDs made in Swedish dental laboratories. Twenty-one patients were fitted with FPDs between March 2007 and December 2008. Single crowns and prostheses of up to seven units were made. All dentures, gold and CoCr alloys covered with ceramic, were produced in duplicate: one by a dental technician in China and the other by a dental technician in Sweden. The dentures were blind-tested with regard to marginal integrity, anatomic form and color, approximal and occlusal contacts, and time taken for adjustments. The composition of dentures was analyzed, and the material used, framework weight, compliance of the laboratories, and costs (material and labour) were recorded. There was no difference in the quality of marginal integrity, anatomic form, color, approximal and occlusal contacts, or in the time taken for adjustments. The bridge frameworks made in China were thinner and lighter (p<0.01) than those made in Sweden. Three FPDs from China showed elastic deformation when tested clinically and were considered too thin for clinical use. In 11 out of 14 orders from the Chinese laboratory, the gold alloy specified was not delivered and the cobalt-chromium alloy contained small amounts (0.19%) of nickel.The prostheses with gold-alloy frameworks from China cost 47% of those from Sweden (p<0.01) and those with cobalt/chromium frameworks 44% (p<0.01). In conclusion, the quality of the FPDs made in Sweden and China was comparable, with the exception of the dimension of the Chinese bridges, which in some cases was considered too weak. The gold alloy ordered from the Chinese laboratory was often not the alloy delivered and the CoCr alloy contained small amounts of nickel. FPDs from China cost less than half the price of those from Sweden.

Análise biomecânica em prótese parcial fixa: método dos elementos finitos / Biomechanics analysis in fixed partial prosthesis: finite elements method

O objetivo deste estudo foi analisar a distribuição de tensões de von Mises em uma prótese parcial fixa de três elementos em metalocerâmica e em dois sistemas de cerâmica pura através de carregamento estático aplicado em modelos matemáticos bidimensionais obtidos pelo método de elementos finitos. A partir da imagem de uma peça anatômica de estudo, os desenhos foram confeccionados e suas imagens vetorizadas foram “exportadas” para o programa MSC/PATRAN e a análise foi feita utilizando-se um carregamento de 100N distribuídos em 17 pontos das superfícies oclusais dos modelos. Em todos os modelos as maiores concentrações de tensões localizaram-se no interior dos pinos e na região médio-inferior dos conectores. Os dois sistemas cerâmicos se comportaram satisfatoriamente em comparação à metalocerâmica.

Evaluation of color duplication in metal-ceramic complexes using visual and instrumental shade-matching systems.

This study was designed to evaluate color differences (DE) between intended and fabricated shades of various metal-ceramic complexes using visual and instrumental shade determination. Forty-two master disks were made to represent every tab in two shade guides. The shades of the master disks were determined visually and instrumentally. Accordingly, 84 experimental disks were fabricated. Color measurements of the master and fabricated disks were performed using a spectrophotometer. Visual shade determination showed a significantly lower DE value than the instrumental shade determination. However, all groups showed DE values exceeding 2.75, which could be considered perceivable and therefore clinically unacceptable. A reliable shade duplication of an existing metal-ceramic restoration cannot be ensured, regardless of the method of shade assessment.

[Development of new approaches for objective dental tissue characteristiсs reproduction for preparation of highly aesthetical restoration].

A new method of color quality control based on spectrophotometry has been developed for dental restoration. A comparative analysis of quality of subjective color control by trained and non-trained observers has been made. Based on comparative analysis of the results of subjective color-control and spectrophotometry the maximum amount of allowed color difference has been set (dE=2.8).

Re-intervention on crowns: what comes next?

AIM: It is the aim of this paper to consider the treatment instituted when re-intervention is deemed necessary on a tooth which has previously been crowned. METHODS: A detailed sample of treatment records of patients has been established at the NHS Business Services Authority (Dental Services Division), consisting of records containing indirectly placed restorations for patients of age 18 years or older from January 1991. For each tooth treated with a crown, the subsequent history of intervention on that tooth was recorded. RESULTS: There were data on 47,474 crowns available for analysis, with metal-ceramic (bonded) crowns dominating the data (overall, 80% of crowns being these). There were 10,426 crowned teeth with re-interventions in the study period, with 36% of the re-interventions involving recementing, 17% being replacement crowns, 13% direct restorations, 12% root treatment, and 19% of crowned teeth being extracted and/or replaced by a denture. The longer the interval since crown placement, the higher the proportion of extractions or direct restoration and the lower the proportion of recementing. CONCLUSIONS: Recementation is the most frequently recorded re-intervention, with the incidence of this decreasing with increasing age of the crown. In 17% of re-interventions, the next intervention was a replacement crown.

[Cr-Ti-Al-N complex coating on titanium to strengthen Ti/porcelain bonding].

OBJECTIVE: To study the feasibility of magnetron sputtering Cr-Ti-Al-N complex coating as an interlayer on titanium to enhance the titanium-ceramic binding strength. METHODS: With a three-point bending test according to ISO 9693, the binding strength of Duceratin (Degussa) to titanium substrate prepared with 4 different surface treatments (polishing, polishing and megnetron sputtering Cr, Ti, Al, and N complex coating, sandblasting, sandblasting and coating) was evaluated. Ti/porcelain interface and fractured Ti surface were examined using scanning electron microscopy with energy-dispersive spectrometry (EDS). RESULTS: The binding strength of polished and coated titanium/Duceratin was significantly higher than polished titanium group (P<0.05). The binding strength of sandblasted and coated titanium/Duceratin did not differ significantly from that of sandblasted titanium group (P>0.05), and the strength in the two sandblasted titanium groups was significantly higher than that in polished and coated titanium group (P<0.05). CONCLUSION: Megnetron sputtering Cr-Ti-Al-N complex on polished titanium can increase the titanium/porcelain binding strength. Megnetron sputtering coating is a promising Ti/porcelain interlayer.

[Effects of investment materials on cast shrinkage of base metal alloys].

OBJECTIVE: To compare the influence of different investment materials, methods and crown height on the cast shrinkage of full crowns made of dental base metal alloy. METHODS: All of the 288 wax patterns were made and divided into three groups according to their crown height. In every group, wax patterns were invested in metal rings and paper rings with three types investment material and cast with base metal alloys. Then the inside diameters of castings were measured and analyzed by statistical package SPSS. RESULTS: Differences between groups invested with the three types of material were significant(P < 0.01). There were significant difference between the groups investing with metal rings and paper rings(P < 0.01). CONCLUSION: The component of investment material and invested ring can affect the cast shrinkage of dental base metal alloy apparently.

Elimination of low-quality ceramic posts by proof testing.

OBJECTIVES: Prosthetic posts made of zirconia ceramics are beneficial because of their esthetic advantages. The mechanical reliability of ceramic posts is limited because of the strength level and the large scatter in strength of ceramic materials. The hypothesis of this study is that the failure of ceramic posts in vivo, which occur on low-quality posts because of critical microscopic defects can be excluded using the so-called proof test technology. METHODS: The theory of the proof test technology is explained in detail in this study. In the experimental part 22 ceramic posts were tested at different proof load levels using a stepwise rotating four-point bending proof test device. RESULTS: The experimental failures deviated from the theoretical failure probabilities by 0.24-12.69%. The deviation would be further reduced in a serial proof test using batches with a greater quantity of posts. The test eliminated those posts, which contained microscopic defects above a critical size of clinical relevance. SIGNIFICANCE: The technology can help to reduce clinical failures of non-vital abutment teeth with ceramic posts, which are caused by critical microscopic defects of the ceramic material as a result of the industrial manufacturing process.

ONLAY DE CROMO-COBALTO UNA ALTERNATIVA PARA LA RESTAURACION DE PRIMEROS MOLARES PERMANENTES EN NIÑOS CON DENTINCION MIXTA

La evolución de la caries puedes llevar a la pérdida de la estructura por tácnicas convencionales solamente sería posible con medidas drásticas. No debe sorprender, por lo tanto, que las condicones en que están muchos de esos dientes permitan el uso de los diseños clásicos de prepración. Con frecuencia es necesario compensar una longitud, cúspide mutilidas o ausentes, e incluso, en casos extremos, una corona clínica ausente. En estas situaciones, el diseño de la preparación puede ser un tes de inventiva del operador, lo cual solo es posible si el dentista tiene sólidos conocimientos básicos de oos principios de la odontología restauradora y un intimo conocimiento de las técnicas

RESTAURACIONES ESTETICAS POSTERIORES EMPLEANDO LA TECNICA DE DOBLE INLAY METAL

Basados en la metodología empleada y frente a lo expuesto se puede concluir establecido que realizar la TECNICA DE DOBLEINLAY METAL CERAMICA. Se garantiza la adaptación, de las restauraciones produciendo un adecuado asentamiento de la restauración al diente. La preparación del bisel, mimétiza esa linea, dando una armonia entre el diente y la restauración aún cuando el color de la restauración es diferente al color del diente

[Study on relationship of different thickness and opaquing capacity of various opaques].

OBJECTIVE: To evaluate the relation between different opaque thickness and color difference. METHODS: Model made of the thin plastic paper was used to control the ceramic thickness. The data of chromaticity was measured by TC-PIIG auto color difference meter and its results were processed by computer. RESULTS: There are two thickness values which can be considered as ideal range of opaque thickness for color opaquing: one is the values of ceramic thickness which is based on the color difference values of the infinite chromaticity thickness (ICT) and the other is the values of ceramic thickness which is depended on the color difference values which is 1.5 compared with ICT. The ideal range for VITA is (0.207-0.152) mm, SHOFO is (0.190-0.160) mm, CARAT is (0.140-0.074) mm and EXCELCO is (0.169-0.144) mm. CONCLUSION: There is a relationship of non linear direct ratio between opaque thickness and its shadow capacity. However, no more increase of color difference values in respect to the thickness was found when the ceramic thickness reach a certain value. Different ceramic porcelain needs different ideal range of thickness.

RESTAURACIONES METALOPLASTICAS PARA EL SECTOR ANTERIOR MEDIANTE REJILLA METALICA CON ANCLAJE RADICULAR Y RESINA - BOND

Conservando la estructura coronaria remanente en dientes anterosuperiores, se consigue mejores resultados estéticos y una mayor resistencia a las fuerzas masticatorias. Los pacientes exigentes en estética mejoran la calidad restaurativa con este tipo de restauración metaloplástica. Si la restauración está bien confeccionada no se presentan problemas posteriores tales como recidiva de caries, fracturas, etc. Es un medio de protección adecuando para las estructuras coronarias remanentes susceptibles a ser eliminadas. Esta técnica es una alternativa más dentro la odontología moderna y restauradora

Thermal stresses in metal-ceramic specimens for the ISO crack initiation test (three-point flexure bond test).

OBJECTIVES: At the October 1996 meeting of the ISO/TC106/SC 2/WG 1 working group, a special three-point flexure test for the characterization of the metal-ceramic bond was incorporated in the standard (ISO CD 9693). Due to the fabrication process, like real porcelain-fused-to-metal (PFM) restorations, the specimens contain thermal (eigen-) stresses upon which the load stresses are superimposed in the actual test. This study is devoted to the determination of these residual thermal stresses. METHODS: The residual thermal stresses in the specimen were calculated with the aid of the finite element method (FEM) using an especially fine mesh in the vicinity of the edge of initial debonding. Young's modulus, EM, of the alloy was varied within the interval 80 GPa < or = EM < or = 220 GPa which covers the spectrum of dental alloys. The analysis also allows the calculation of thermal stresses as a function of the difference delta alpha = alpha M - alpha C of the coefficients of thermal expansion of alloy and ceramic and the glass transition temperature theta G of porcelain. RESULTS: The thermal shear and normal stresses at the bond interface concentrate at the end of the ceramic veneer and practically vanish over about three quarters of the central part of the layer. The larger the Young's modulus, EM, of the alloy, the higher both stresses. SIGNIFICANCE: The results permit a deeper comprehension of the debonding process in the test: shear stress induced by loading increases the overall shear stress at the end of the bond interface, whereas load tensile stress is buffered by thermal compressive stress.

A comparison of the marginal fit of In-Ceram, IPS Empress, and Procera crowns.

The in vitro marginal fit of three all-ceramic crown systems (In-Ceram, Procera, and IPS Empress) was compared. All crown systems were significantly different from each other at P = 0.05. In-Ceram exhibited the greatest marginal discrepancy (161 microns), followed by Procera (83 microns), and IPS Empress (63 microns). There were no significant differences among the various stages of the crown fabrication: core fabrication, porcelain veneering, and glazing. The facial and lingual margins exhibited significantly larger marginal discrepancies than the mesial and distal margins.

Fatigue life of a Nd:YAG laser-welded metal ceramic alloy.

Fifteen laser-welded Olympia alloy samples were divided into three groups of five samples each, with different gap distances between the welded halves. The first group was welded with a 0.0-mm gap distance. The second and third groups had Olympia shims placed in 0.3- and 1.0-mm gaps, respectively, prior to laser welding. Each of the samples was tested to failure in load fatigue at 30 Hz in a fatigue testing device using an applied stress of 35,000 psi (241.4 MPa). The means and standard deviations for the number of cycles required to produce fatigue failure for each group was 494,618 +/- 118,311 cycles for the group welded with 0.0-mm gap distance, and 242,741 +/- 44,623 and 232,021 +/- 55,877 cycles for the 0.3- and 1.0-mm specimens, respectively. A one-way analysis of variance showed that the 0.0-mm gap specimens had the greatest number of cycles to failure (P < or = 0.05). There was no significant difference between the other two groups. With the exception of two specimens that failed at the weld center, all failures occurred at the edge of the weld.