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Untersuchung des Haftverbundes zwischen Zirkoniumdioxid und einem Verblend- Komposit
Abstract
Ziel dieser In vitro- Studie war die Beurteilung der Scherfestigkeit zwischen industriell hergestellter Zirkoniumdioxidkeramik (Y-TZP) und einem Verblendmaterial, bestehend aus einem Mikro- Hybridkomposit. nach unterschiedlicher Vorbehandlung der Oberflächen.
Hierzu wurden 72 Y-TZP Proben hergestellt, in sechs Gruppen (n=12) eingeteilt und unterschiedlich vorbehandelt. Gruppe A (Kontrolle): Sandstrahlen mit 110μ Al2O3 Partikeln, Gruppe B: Oberfläche zusätzlich mit Panavia F 2.0 (Kuraray, D) beschichtet, Gruppe C: beschichtet mit Rely X Unicem (3M Espe, D), Gruppe D: beschichtet mit Triceram Liner (Esprident, D), Gruppe E: beschichtet mit Triceram Bonder (Esprident, D), Gruppe F: beschichtet mit Glasur einer niederschmelzenden Keramik. Anschließend wurde ein Kompositzylinder (Durchmesser 2,4 mm) auf die vorbehandelte Oberfläche polymerisiert. Die Proben wurden einer thermischen Wechsellast (1000x 4°C-55°C) unterzogen und die Scherkraft in einer Universalprüfmaschine gemessen. Die Bruchmodi wurden unter dem Lichtmikroskop beurteilt. Die durchschnittliche Verbundstärke der Proben wurde statistisch mittels ANOVA und der verbesserten Statistik für paarweisen Vergleich analysiert.
Ergebnis dieser Untersuchung war, dass alle zusätzlichen Behandlungen zum Sandstrahlen die Scherfestigkeit signifikant (p≤0.001) verbesserten. Die Verbundfestigkeit in [N] waren in Gruppe D> Gruppe E> Gruppe B> Gruppe F> Gruppe C> Gruppe A.
Die Verbundfestigkeit in [MPa] waren in Gruppe D > Gruppe E> Gruppe F > Gruppe B > Gruppe C > Gruppe A. Die statistische Auswertung der Verbundfestigkeitswerte in [N] ergab signifikante Unterschiede zwischen den experimentellen Gruppen, außer zwischen Gruppe B und C, B und F, C und F, D und E. Die statistische Auswertung der Verbundfestigkeitswerte in [MPa] ergab nur signifikante Unterschiede zwischen den experimentellen Gruppen A und B-F, D und C, D und F.
Daraus folgt, dass das Beschichten einer industriell hergestellten Y-TZP Keramik mit adhäsiven Befestigungsmaterialien oder verschiedenen Keramikschichten signifikant höhere Scherverbundfestigkeiten zum Verblendkomposit liefert, als die alleinige Behandlung mit Sandstrahlen durch Aluminiumdiioxid und eine Beschichtung mit einem keramischen Liner oder Bonder und Opaker als empfehlenswert anzusehen ist.
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Aim of the investigation was to assess the effect of different surface treatments on the bond strength of veneering ceramics to zirconia. In a shear test, the influences of polishing, sandblasting, and silica-coating of the zirconia surface on bonding were assessed with five different veneering ceramics. In addition the effect of liner application was examined. With one veneering ceramic, the impact of regeneration firing of zirconia was also evaluated. Statistical analysis was performed with one-way ANOVA and post hoc Scheffé's test. Failure in every case occurred in the veneering ceramic adjacent to the interface with a thin layer of ceramic remaining on the zirconia surface, indicating that bond strength was higher than the cohesive strength of the veneering ceramic. Shear strength ranged from 23.5 +/- 3.4 MPa to 33.0 +/- 6.8 MPa without explicit correlation to the respective surface treatment. Regeneration firing significantly decreased the shear strength of both polished and sandblasted surfaces. Findings of this study revealed that bonding between veneering ceramics and zirconia might be based on chemical bonds. On this note, sandblasting was not a necessary surface pretreatment to enhance bond strength and that regeneration firing was not recommended.
Zirconia ball heads have been implanted successfully from the late 1980s, but reports of wear and fractures have raised concerns about this ceramic biomaterial. This paper reviews the literature on clinical wear of zirconia-polyethylene bearings, zirconia head degradation and fractures, analysing the different factors that have led to clinical failure, such as material source, manufacturing process and type of polyethylene. The results underline the need for more homogeneous clinical series. Careful follow-up of patients with zirconia-polyethylene bearings is recommended.
In diesem Beitrag werden die mineralogischen, kristallographischen und chemischen Eigenschaften des Korunds dargestellt. Auf dieser grundlage wird der geschichtliche Einzug und derzeitige Einsatz dieses Minerals in der Zahnheilkunde erläutert: In der Vollkeramik werden spezielle Verbindungen mit dem Korund für hochfeste Gerüststrukturen eingesetzt.
This study examines the behavior of cracks approaching interfaces in all-ceramic dental crown-like bilayers. Flat specimens are fabricated by fusing porcelain veneers onto yttria-tetragonal-zirconia-polycrystal (Y-TZP) and alumina core ceramic plates, with veneer/core matching to minimize residual thermal expansion mismatch stresses. Vickers indentations are placed on either side of the interfaces, at systematically decreasing distances, so that the lead corner cracks approach and intersect the interfaces in a normal orientation. Cracks originating in the porcelain arrest at the boundaries and, after further diminution in indentation distance, deflect along the interface without penetration into the tough core ceramic. Cracks initiating in the core ceramic pass unimpeded into the weaker porcelain without deflection, and with abrupt increase in crack size. These latter cracks, because of their lack of containment within the core layer, are regarded as especially dangerous. Implications concerning the design of optimal dental crowns in relation to materials optimization are considered.
Zugl.: Aachen, Techn. Hochsch., Diss. : 1994.
Objectives:
Among contemporary adhesives, self-etch adhesives have been adopted by general practitioners for routine adhesive restorative purposes, mainly because of their ease of use. However, many versions that differ for their clinical application procedure, pH, number of components, etc., are currently available on the market. The purpose of this study was to determine the bonding effectiveness of two new self-etch adhesives (Adper Easy Bond and Adper ScotchBond SE, 3M ESPE) to enamel and dentin using a micro-tensile bond strength (microTBS) protocol and to characterise the interfacial ultra-structure at enamel and dentin using transmission electron microscopy (TEM).
Methods:
The adhesives were applied onto coronal human enamel and dentin surfaces and built up with the micro-hybrid resin composite Z100 (3M ESPE). The 'gold-standard' two-step self-etch adhesive Clearfil SE Bond (Kuraray) served as control. Specimens were sectioned to sticks and trimmed at the interface to a cylindrical hour-glass shape ('trimmed' micro-specimens). Non-demineralized and demineralized TEM sections through the adhesive-dentin/enamel interface were prepared by ultra-microtomy.
Results:
The microTBS of the two self-etch adhesives to enamel was statistically significantly lower than that of the control. To dentin, the microTBS of Adper Easy Bond was significantly lower than that of Adper ScotchBond SE and the control. TEM showed a tight interface to enamel for all three self-etch adhesives. A relatively thick, completely demineralized and acid-resistant hybrid layer was formed at dentin by Adper ScotchBond SE, whereas the interaction of Adper Easy Bond was much shallower, and comparable to that of so-called 'ultra-mild' self-etch adhesives. Some degree of spot- and cluster-like nano-leakage was observed for both adhesives, but did not differ in extent and form from that observed for the control.
Conclusions:
Although the new two self-etch adhesives revealed a tight interaction at both enamel and dentin, their bond strength to both tooth tissues was generally lower than that of the control adhesive. Nevertheless, their bonding effectiveness appears in line with other simplified self-etch adhesives.
The zirconia-resin bond strength was enhanced using novel engineered zirconia primers in combination with selective infiltration etching as a surface pre-treatment. The aim of this study was to evaluate the effect of artificial aging on the chemical stability of the established bond and to understand the activation mechanism of the used primers.
Selective infiltration etched zirconia discs (Procera; NobelBiocare) were coated with one of four novel engineered zirconia primers containing reactive monomers and were bonded to resin-composite discs (Panavia F2.0). Fourier transform infrared spectroscopy (FT-IR) was carried out to examine the chemical activation of zirconia primers from mixing time and up to 60min. The bilayered specimens were cut into microbars (1mm(2) in cross-section area) and zirconia-resin microtensile bond strength (MTBS) was evaluated immediately and after 90 days of water storage at 37 degrees C. Scanning electron microscopy (SEM) was used to analyze the fracture surface.
There was a significant drop in MTBS values after 90 days of water storage for all tested zirconia primers from ca. 28-41MPa to ca. 15-18MPa after completion of artificial aging. SEM revealed increase in percentage of interfacial failure after water storage. FTIR spectra suggested adequate activation of the experimental zirconia primers within 1h of mixing time.
The novel engineered zirconia primers produced initially high bond strength values which were significantly reduced after water storage. Long-term bond stability requires developing more stable primers.
This study sought to evaluate the long-term bond strength of etch-and-rinse and self-etch adhesive systems to dentin after one year of water storage. Crown fragments from the buccal surface of extracted bovine incisors were ground flat to expose dentin surfaces. Four etch-and-rinse and two self-etch bonding agents were used according to manufacturers' instructions. Bonded specimens were stored in water for either 24 hours or one year at 37 delete C. After elapsed storage times, specimens were tested for shear bond strength (SBS) at 0.5 mm/min. Data were analyzed by ANOVA and Tukey's tests (p < 0.05). Both evaluated factors (adhesive system and storage time) and their interactions were statistically significant. Single Bond produced the highest SBS regardless of the water degradation period. One-year water storage reduced the SBS of Prime & Bond NT and One-Up Bond F significantly; the other adhesives performed similarly. Long-term bond strengths of etch-and-rinse and self-etch adhesive systems are susceptible to hygroscopic and hydrolytic effects to varying extents, depending on their chemistry and structure. The presence of monomers with different properties might induce preferential degradation of specific adhesive polymer systems.
Successful long-term bonding to zirconia ceramic remains a challenge, requiring special cements and surface roughening by airborne-particle abrasion, which might negatively affect the ceramic.
The purpose of this study was to evaluate the shear bond strength (SBS) of composite resin cylinders to a modified zirconia surface using different luting techniques after thermal cycling.
Composite resin (TPH3) cylinders with a diameter of 3 mm were bonded to zirconia ceramics (Procera Zirconia) with a modified surface (RZ) and a machined surface (MZ). Three different adhesive luting cements (Panavia F2.0, RelyX ARC, RelyX Unicem) in combination with and without airborne-particle abrasion (50-microm and 110-microm Al(2)O(3)) were used. RZ was bonded using all 3 cements with (50 mum) and without airborne-particle abrasion; with 110 microm, only Panavia F2.0 was used. MZ was bonded using only Panavia F2.0 with (50 microm, 110 microm) and without airborne-particle abrasion. SBS was tested in a universal testing machine (Instron) before and after 90 days of water storage and 20,000 thermal cycles (dwell time, 15 seconds). Statistical analysis was performed using a multifactorial ANOVA model with alpha=.05.
Mean SBS ranged from 10.1 to 20.0 MPa after 3 days and from 0.16 to 14.8 MPa after thermal cycling. Thermal cycling decreased SBS significantly. Airborne-particle abrasion significantly decreased SBS to the modified surface, regardless of cements used. SBS to the modified zirconia surface was significantly higher than to the machined surface.
SBS to the modified zirconia surface is higher than to airborne-particle-abraded, machined zirconia. Airborne-particle abrasion of the modified zirconia surface is not recommended.
Clinical Relevance
Air abrasion and pretreatment with a metal primer seem to be an appropriate method for improving the bond strength of RelyX Unicem resin composite cement to hot isostatic pressed yttrium-oxide partially stabilized zirconia.
To evaluate the hydrolytic stability of different dual-cure resin cements when luted to zirconia ceramic.
Eighteen cylinder-shaped zirconia blocks (Cercon Zirconia, Dentsply) were conditioned with: Group 1, no treatment; Group 2, sandblasting (125microm alumina-Al(2)O(3)-particles); Group 3, tribochemical silica coating (50microm silica-modified Al(2)O(3) particles). Ceramic blocks were duplicated in composite resin (Tetric Evo Ceram, Ivoclar-Vivadent). Composite disks were luted to pre-treated ceramic surfaces using: (1) Clearfil Esthetic Cement (CEC; Kuraray); (2) Rely X Unicem (RXU; 3M ESPE); (3) Calibra (CAL; Dentsply Caulk). After 24h, bonded samples were cut into microtensile sticks (1mm(2)). Half of the sticks were loaded in tension until failure (cross-head speed of 0.5mm/min). The remaining half was tested after 6 months of water storage at 37 degrees C. Data was analyzed with three-way ANOVA and Tukey's test (P<0.05). Fractographic analysis was performed by SEM.
After 24h, bond strength of CEC to zirconia was significantly higher than that of RXU and CAL, independently from the ceramic pre-treatment (P<0.001). Using CAL, all samples failed prematurely except when luting to sandblasted surfaces. After 6 months of water aging, bond strength of CEC significantly decreased. RXU did not significantly alter bond strengths. Adhesion of sandblasted specimens luted with CAL fell over time. Micromorphological alterations were evident after water storage.
Resin-ceramic interfacial longevity depended on cement selection rather than on surface pre-treatments. CEC and RXU were both suitable for luting zirconia. Water aging played an important role in the durability of zirconia-to-composite chemical bonds.
A technique has been described which permits the fabrication and attachment of an anterior fixed partial denture without tooth preparation. The fixed partial denture is attached to the lingual surfaces of the abutment teeth utilizing a composite resin and acid-etched enamel. Conservation of tooth structure and minimal chair time and patient expense are the primary advantages of this technique.
The mechanical strength of the new oxide ceramic system In-Ceram introduced by Vita (Bad Säckingen, Germany) was investigated by an in-vitro study for its mechanical strength and suitabilities for use as posterior three-unit bridges. The transverse strength value measured by a three-point bending test (DIN 13,927) is 320 MPa and the maximum vertical load on three-unit bridges until brittle failure occurs is in the range of 1000 to 1350 N. This is up to four times higher than corresponding values of other ceramics, e.g. Dicor (Dentsply) or Optec (Jeneric). The dental bridges were luted to metallic pontics, and a layer of silicon rubber simulating the periodontal membrane, separated the pontic from a resin base in the testing machine. Life value tests were performed before and after 10 days of thermocycling at temperatures alternating between 5 and 55 degrees C in artificial saliva. Although the pontics had a much higher mobility than normal teeth, the fatigue limit was found to be above 600 N which is much higher than the average biting forces acting on the first and second molars.
The objective of this study was to investigate whether water storage causes permanent damage to composites by determining how the tensile strength of nine different composite materials changes with both water storage and water storage followed by dehydration. Eighteen samples (ASTM-D Specification 1708-66) of each of the nine materials were prepared and divided into three groups of six samples each. Group I was stored dry at 60 degrees C, while Groups II and III were stored in distilled water at 60 degrees C. After six months, Groups I and II were subjected to tensile testing, while Group III was transferred to a desiccator and dehydrated for two weeks at 60 degrees C before this group was tested in tension. Mean values, pooled by storage group independent of material, revealed a significant (p less than 0.05) reduction in strength for both Groups II and III relative to Group I. These findings prove that water has an irreversible effect on most dental composites. A comparison of Group II with Group III data revealed that the samples which were aged in water and tested (Group II) were significantly (p less than 0.05) weaker than the dehydrated samples (Group III). However, some products within Group III did not show any tendency to recover their strength after dehydration.
Metal ceramic restorations are popular in restorative dentistry. Although bonding mechanisms are understood, defining compatibility of alloy and porcelain has been illusive. Chemical compatibility implies a chemical bond between ceramic and alloy that resists stresses resulting from thermal and mechanical incompatibility without compromising esthetics. Research has attempted to predict and test compatibility with varying degrees of success. Despite the success of metal ceramic restorations over the years, compatibility remains undefined without standardized testing procedures. For optimal results, the dentist should communicate with experienced laboratory personnel to meet the specific needs of the patient.
The flexural strengths of porcelain bonded to composite resin specimens using four organosilane materials were compared. Eighty hand-condensed Vita porcelain specimens were stored in distilled water or ambient humidity before sectioning. Three groups (n = 30) of hydrated specimens were repaired to their original dimensions by using Silux composite resin with Kerr Ultrafine Porcelain Repair Bonding system, 3M Porcelain Kit with ScotchPrimer, or Fusion materials. A fourth group (n = 30) of hydrated specimens was repaired with the DenMat Ultrabond Restorative kit. Four groups (n = 10) of unhydrated specimens were repaired the same as the hydrated specimens. Fracture occurred at the porcelain-to-composite resin interface with three-point loading on the repair interface at 3 x 10(2) mm/min. No difference between Kerr, 3M, and Fusion products, when used with Silux composite resin, was found. The DenMat product had lower strengths. The unhydrated specimens had significantly higher bond strengths than the hydrated specimens with all products.
The effects of thermocycling and water penetration on the bond strength of resin-metal-systems and improvements using bonding agents have been tested by shear, bending and tensile tests. After 10,000 cycles within 10 days in different water-baths with 5-37-55 degrees C, there is a decrease in bond strength by 40 to 60%. The use of bonding agents increases the adhesion of the resin to the metal by more than 100%. No significant differences were found between the three bonding agents Silicoater, Sebond MKV and OVS.
The Rocatec procedure as a novel acrylic/metal bonding system is presented. This procedure is based on the tribochemical application of a layer of a ceramic bonding agent by sand blasting, followed by the application of a silane solution. Its particular advantages are the speed and accuracy of coating, the fact that the adhesive layer can be visually checked, and that thermal stresses to the metallic framework are avoided. Shear/compression and tensile tests reveal increased bonding strength values with the Rocatec bonding system than with mechanical bead retention, even after thermocycling and storage in water for one year.
This report describes a technique for fabricating a splint or fixed partial prosthesis splint on mandibular anterior teeth without tooth reduction. The fixation is attained by applying a coupling agent to the gold and etching the enamel to enhance attachment with Sevriton. Clinical experience and judgment provide the final standard.
The leakage of filler elements from four composites after storage in water was investigated by use of atomic absorption spectrophotometry. The results confirmed previous findings that leaching of silicon from different composites is strongly dependent on filler composition. Consideration of the total filler surface of each composite material indicated that quartz as well as pyrolytic silica-containing composites leached less silicon than did composites containing fillers of strontium and/or barium glasses. A correlation between leakage and crack formation in the matrix appeared to exist for all composites except for the microfilled resin. These cracks were explained as a result of osmotic pressure built up at the matrix-filler interface due to hydrolytic degradation of the filler.
Of the investigated materials, the microfilled resin was found to be the most stable material in a wet environment with respect to crack formation. This finding was explained by filler composition, filler form, and the specific structure of the microfilled resin.
The design, fabrication, and bonding factors relating to resin-bonded retainers for posterior teeth have been described. When indicated, these retainers provide an alternative to the usual fixed prosthodontic retainers. In addition to having the qualities of a fixed appliance, these retainers enable the therapeutic procedure to be conservative, esthetically acceptable, economical, and reversible.
The aim of this investigation was to study the chemical solubility of 3 new low-fusing ceramics (Duceram-LFC, Duceragold and Vita Omega 800) in comparison with a conventional PFM-ceramic (Vita Omega) together with different surface treatments. Additionally, the three-point flexure strengths were measured. Although the test conditions were very stringent in comparison to the standard solubility test, all ceramics comply with ISO/DIS 6872 specifications, and are thus deemed to be well tolerated in the oral environment. Vita Omega demonstrated the lowest chemical solubility. Mechanical polishing of the surfaces of LFC and Duceragold ceramics produced lower solubility results as compared to glazing. Vita Omega and Omega 800 behaved contrarily. After repeated hydrolysis testings Ducera-LFC demonstrated the highest disintegration resistance. The three-point flexure strengths of low-fusing ceramics were generally higher than that of the conventional PFM-ceramic. As opposed to the other ceramic materials tested, the flexure strength of Duceram-LFC increased significantly after hydrolysis testing.
In this paper, bond strength and various important factors in bond strength testing are discussed as well as the limitations in the interpretation and clinical relevance of such tests. Standardisation of bond strength testing is needed, and the solutions found in the new ISO document, ISO CD TR 11405 Dental Materials--Guidance on testing of adhesion to tooth structure, are referred to. Tensile and shear test methods are discussed and the bond strength values obtained with these methods compared. The influence of dentine substrate variations, such as remaining dentine thickness and surface treatment or removal of smear layer, are discussed as well as the storage conditions of specimens for in vitro tests, that is, short term, long term and thermocycling, and their relevance to the clinical situation. The information obtained from microscopical studies of fractured surfaces indicates that some adhesives may, under optimal conditions, obtain a bond strength sufficient to fracture the dentine.
This study evaluated the effect of veneering Dicor castable ceramic with Vitadur N and Dicor Plus feldspathic porcelains. A biaxial flexure test was conducted on five groups of specimens (Dicor castable ceramic, Vitadur N dentinal porcelain, Dicor Plus dentinal porcelain, Dicor core veneered with Vitadur N and Dicor core veneered with Dicor Plus castable ceramic). Each group consisted of 10 disks of nearly identical dimensions with a 1.98 +/- 0.04 mm thickness and 15.7 +/- 0.35 mm in diameter. Statistical analysis indicated that there was neither significant difference (p > 0.05) between mean flexural strength of Dicor Plus and Vitadur N ceramic or Vitadur N and Dicor/Vitadur N ceramic specimens. The mean flexural strength of Dicor/Vitadur N specimens was significantly lower than the mean flexural strength of Dicor ceramic specimens. Conversely, there was no significant difference between mean flexural strength of Dicor ceramic and Dicor/Dicor Plus ceramic specimens. Scanning electron microscope (SEM) examinations of Dicor/Dicor Plus ceramic specimens suggested better wetting of Dicor core by Dicor Plus ceramic with lower incidence of porosity at the interface. However, Dicor/Vitadur N ceramic specimens exhibited a higher incidence of porosity at the interface. This indicated that lamination of Dicor castable ceramic material with feldspathic porcelain for esthetics could be attained without sacrificing strength of the original material, provided that appropriate veneering material was selected.
To test the shear bond strengths obtained when orthodontic brackets were bonded ex vivo using a composite resin and a compomer orthodontic adhesive.
Specimens were tested in a special jig made to fit an Instron testing machine. After debonding, the adhesive remaining on bracket bases and enamel surfaces was mapped.
Bond strengths ranged from 8 to 23 MPa with the composite resin producing higher strengths than the compomer for similar combinations of variables. Bond strength was increased by longer curing and a longer debond interval and was higher for brackets with mesh bases than undercut bases. More compomer remained on the enamel surface after debonding than did the composite resin.
The compomer produced bond strengths within the range considered to be clinically acceptable in other studies. If it was clinically successful as an orthodontic adhesive a compomer would confer the advantage that fluoride release would help to minimize the onset of early caries around bonded brackets.
This study evaluated the effects of four adhesive primers on the shear bond strength of a self curing resin to cobalt-chromium alloy.
The adhesive primers Acryl Bond (AB), Cesead Opaque Primer (COP), Metal Primer II (MPII), and MR Bond (MRB) were used. A brass ring placed over the casting alloy disk surface nonprimed or primed with each primer was filled with the self-curing methyl methacrylate polymethyl methacrylate resin. The specimens were stored in water at 37 degrees C for 24 hours and then alternately immersed in water baths at 4 degrees C and 60 degrees C for 1 minute each for up to 20,000 thermal cycles before shear mode testing at a crosshead speed of 0.5 mm/min.
All the primers examined improved the shear bond strength between the resin and cobalt chromium alloy compared with nonprimed specimens before thermal cycling. However, after 20,000 thermal cycles, the bond strengths of resin to cobalt chromium alloy primed with COP or MPII primers were significantly greater than those of specimens primed with AB or MRB primers and nonprimed controls.
This study indicated that COP and MPII are effective primers to obtain higher bond strength between resin and cobalt-chromium alloy.
After 0 years of intermittent reports in the literature, the use of fiber reinforcement is just now experiencing rapid expansion in dentistry.
This article describes the development and use of a continuous, unidirectional fiber reinforced composite as a framework for the fabrication of fixed prostheses.
By using various matrix materials and fibers, a number of fiber-reinforced composite formulations were evaluated with the goal of creating a system with optimized mechanical properties and handling characteristics. Fiber-reinforced composite based on a light polymerized BIS-GMA matrix has been used clinically to make 2-phase prostheses comprised of an internal glass fiber-reinforced composite substructure covered by a particulate composite. The clinical and laboratory procedures required for the fabrication and use of reinforced composite fixed prostheses are described for laboratory-fabricated complete or partial coverage fixed prosthesis and chairside prosthesis.
Although additional clinical experience is needed, fiber-reinforced composite materials can be used to make metal-free prostheses with excellent esthetic qualities.
The objectives of this study were to investigate the repair potential of two commercially available composite resins in terms of bond strength, and the effectiveness of two commercially available adhesive systems used as intermediary materials in the repaired specimens. The repair strength of Helio Progress (HP) and Herculite XRV (XRV) was tested using two bonding agents: DenTASTIC (DT) and All Bond 2 (AB2). The effect of surface abrasion of specimens and the effect of time on repair strength were also investigated. Surface abrasion significantly improved the bond strength (P < 0.001) and the use of bonding agents further enhanced bond strength but not significantly. Use of bonding agents alone improved the repair bond strength significantly (P < 0.001). Repair of HP with HP after surface abrasion and application of DT produced the highest repair bond strength which was 99% of the cohesive strength of the control (unrepaired) specimens. Although there were some differences in the bond strength over the time period of the study (one month) none of these was statistically significant. It is concluded that surface abrasion coupled with the application of bonding agent produces the highest repair strength. It seems likely that clinically acceptable bond strengths are possible after repair of anterior composite resins.
Zirconia ceramics have several advantages over other ceramic materials, due to the transformation toughening mechanisms operating in their microstructure that can give to components made out of them, very interesting mechanical properties. The research on the use of zirconia ceramics as biomaterials started about twenty years ago, and now zirconia (Y-YZP) is in clinical use in THR, but developments are in progress for application in other medical devices. Recent developments have concentrated on the chemistry of precursors, in forming and sintering processes, and on surface finish of components. Today's main applications of zirconia ceramics is in THR ball heads. This review takes into account the main results achieved up to now, and is focused on the role that microstructural characteristics play on the TZP ceramics behaviour in ball heads, namely mechanical properties and their stability, wear of the UHMWPE paired to TZP, and their influence on biocompatibility.
In this in vitro study fracture strength and marginal adaptation of adhesive-fixed three-unit posterior fixed partial dentures made with two different fabrication modifications--with and without the retainer material "Single"--of the new fibreglass system Vectris/Targis and from the metal-free Al2O3-ceramic In-Ceram were examined. The quality of the marginal adaptation was characterised using SEM evaluation and dye penetration techniques. In-Ceram and Vectris/Targis with "Single" showed good marginal adaptation, both statistically significantly better than the modification without "Single". After thermal cycling and mechanical loading the fibreglass reinforced systems showed a significantly higher fracture strength than the In-Ceram.
Objectives:
Resin bonding to yttrium-oxide--partially-stabilized zirconia ceramic (YPSZ) cannot be established by standard methods that are utilized for conventional silica-based dental ceramics. It was our hypothesis that adhesive bonding methods suitable for glass-infiltrated alumina ceramic can also be used to bond successfully to YPSZ. To prove this hypothesis, bonding methods suitable for alumina ceramic were used on YPSZ and the tensile bond strength and their durability evaluated in vitro.
Methods:
Plexiglass tubes filled with resin composite were bonded to YPSZ discs following various adhesion protocols. Groups of 16 samples were bonded using seven different bonding methods. Subgroups of eight bonded samples were tested for tensile strength following storage in distilled water (37 degrees C) for either 3 or 150 days. In addition, the 150 day samples were thermal cycled 37,500 times as a method to stress the bond interface. The statistical analysis was made with the Kruskal-Wallis test followed by multiple pair-wise comparisons of the groups using the Wilcoxon rank sum test.
Results:
Sandblasting alone, the additional use of a silane or acrylizing resulted in an initial bond of a conventional BisGMA resin composite to YPSZ which failed spontaneously over storage time. The use of the BisGMA resin composite after tribochemical silica coating of YPSZ and the use of a polyacid-modified resin composite after sandblasting of YPSZ resulted in an initial bond which decreased significantly over storage time (p = 0.05). A durable resin bond to YPSZ was achieved only after sandblasting the ceramic and using one of two resin composites containing a special phosphate monomer.
Significance:
A durable bond to YPSZ was achieved only by using resin composites with a special adhesive monomer. Therefore, the hypothesis of the study was partially proved as a durable bond to alumina ceramic is achieved with the same resin composites. However, it was partially disproved as tribochemical silica coating of YPSZ did not result in a durable resin bond as it does on glass-infiltrated alumina ceramic.
To determine the stiffness, elastic limit, and strength of a selection of endodontic posts recently introduced onto the market.
Endodontic posts of zirconia (Biopost, Cerapost), titanium (PCR), and carbon fiber (Composipost) were cemented in a brass block and loaded at an angle of 45 degrees in an Instron Testing Machine. From the recorded relationship between force and deflection the three mechanical properties were determined (n = 10 in each group).
The ceramic posts were very stiff and strong, with no plastic behavior. The PCR post was as strong as, but less stiff than, the ceramic posts. Composipost had the lowest values for stiffness, elastic limit, and strength of the posts investigated.
The posts under investigation differed significantly with respect to mechanical properties.
The flexural strength of six recently introduced dental ceramic materials was measured using a three-point-bend test. Conventional feldspathic porcelain and soda-lime glass were used as controls. All six of the new materials had significantly greater breaking strength than the controls. The alumina-based crystalline-reinforced materials exhibited the highest breaking strengths. The silica-based crystalline-reinforced materials resulted in ceramic materials with more moderate strength but still with significantly greater strength than the controls. Scanning electron microscopic analysis of the fractured surfaces indicated crack deflection appeared to be the principal strengthening mechanism in the highly crystalline materials.
This study was conducted to evaluate the effect of grinding and sandblasting on the microstructure, biaxial flexural strength and reliability of two yttria stabilized tetragonal zirconia (Y-TZP) ceramics.
Two Y-TZP powders were used to produce fine grained and coarse grained microstructures. Sixty discs from each material were randomly divided into six groups of ten. For each group, a different surface treatment was applied: dry grinding, wet grinding, sandblasting, dry grinding + sandblasting, sandblasting + dry grinding and a control group. Biaxial flexural strength was determined and data were analyzed using one-way ANOVA, followed by Tukey's HSD test (p < 0.05). In addition, Weibull statistics was used to analyze the variability of flexural strength. The relative amount of transformed monoclinic zirconia, corresponding transformed zone depth (TZD) and the mean critical defect size Ccr were calculated.
There was no difference in mean strength between the as sintered fine and coarse grained Y-TZP. Significant differences (p < 0.05) were found between the control group and ground fine grained material for both wet and dry grinding. Sandblasting significantly increased the strength in fine and coarse grained materials. All surface treatment procedures reduced the Weibull modulus of Y-TZP. For both materials, the highest amount of the monoclinic phase and the largest TZD was found after sandblasting. Lower amounts of the monoclinic phase were obtained after both grinding procedures, where the highest mean critical defect size Ccr was also calculated.
Our results indicate that sandblasting may provide a powerful technique for strengthening Y-TZP in clinical practice. In contrast, grinding may lead to substantial strength degradation and reduced reliability of prefabricated zirconia elements, therefore, sandblasting of ground surfaces is suggested.
This work was undertaken to evaluate the effects of dental grinding and sandblasting on the biaxial flexural strength and Weibull modulus of various Y-TZP ceramics containing 3 mol% yttria. In addition, the susceptibility of pristine and mechanically treated materials to low-temperature degradation under the conditions adopted for testing the chemical solubility of dental ceramics was investigated. The results revealed that surface grinding and sandblasting exhibit a counteracting effect on the strength of Y-TZP ceramics. Dental grinding lowered the mean strength and Weibull modulus, whereas sandblasting provided a powerful method for strengthening, but at the expense of somewhat lower reliability. The finest-grained material exhibited the highest strength after sintering, but it was less damage tolerant than tougher, coarse-grained materials. Upon extraction with the acetic acid solution and the ammonia solution, a significant amount of tetragonal zirconia had transformed to monoclinic, but extensive microcracking and attendant strength degradation had not yet occurred. Standard grade Y-TZP ceramics are more resistant in an alkaline than in an acidic environment, and there was a strong grain-size dependence of the diffusion-controlled transformation. Since a special Y-TZP grade containing a small amount of alumina exhibited the highest damage tolerance and superior stability in an acidic environment, this material shows considerable promise for dental applications.