Evaluation of the marginal accuracy of different all-ceramic crown systems after simulation in the artificial mouth

The in vitro marginal fit of five different all-ceramic crown systems (In-Ceram, Empress staining technique, Empress veneering technique, Celay feldspathic system, Celay In-Ceram system) was evaluated before and after cyclic preloading in an artificial mouth. The crowns were adhesively luted to extracted natural maxillary incisors prepared with a 90 degrees shoulder. The results were compared to those for porcelain-fused-to-metal (PFM) crowns with circular porcelain-butt margins which were cemented with zinc phosphate cement. The analysis of the marginal discrepancies showed significant (P < 0.001) differences among the groups. Crown cementation increased the marginal gaps significantly (P < 0.01). Empress staining technique crowns showed the smallest marginal gaps (median 47 microm), followed by conventional In-Ceram crowns (median 60 microm) and Empress veneer technique crowns (median 62 microm). Celay In-Ceram crowns displayed marginal openings with a median of 78 microm, followed by Celay feldspathic crowns with a median of 99 microm. The marginal gap of the PFM control crowns showed a median of 64 microm. Ageing in the chewing simulator had no significant influence on the marginal fit of all specimens. The study indicates that all the tested all-ceramic crowns have clinically acceptable margins. However, in vivo investigations of all all-ceramic crown systems should be made before clinical routine.     

Influence of firing cycles on the margin distortion of 3 all-ceramic crown systems

STATEMENT OF PROBLEM: Although all-ceramic restorations are widely used, there is a lack of information about how the fit is affected by fabrication procedures. The adequacy of the fit of all-ceramic restorations has been questioned. PURPOSE: This study examined the effect of porcelain and glaze firing cycles on the fit of 3 types of all-ceramic crowns. MATERIAL AND METHODS: Ten standardized all-ceramic crowns were fabricated on a metal die from each of 3 systems: conventional In-Ceram, copy-milled In-Ceram, and copy-milled feldspathic crowns. Copings of the conventional and copy-milled In-Ceram crowns and nonglazed copy-milled feldspathic crowns served as the control. A device was used to apply a uniform load on specimens during measurement and to reposition the specimens on the measurement device after each manufacturing process. The specimens were not cemented and were measured on the metal die using a profile projector. Measurements were recorded at 18 points selected along horizontal and vertical planes. The crown systems were compared by use of the Student t test and 1-way analysis of variance (ANOVA). Data of measurements repeated at identical locations were analyzed with a multivariate repeated-measures ANOVA. The Bonferroni post hoc test was used for multiple comparisons (alpha=.05). RESULTS: The conventional In-Ceram (57 +/- 24 microm) and copy-milled In-Ceram (57 +/- 32 microm) crowns demonstrated nearly identical marginal discrepancy values, followed by the copy-milled feldspathic crowns with a mean of 17 +/- 12 microm in the vertical plane. The copy-milled In-Ceram crowns had a mean horizontal discrepancy value of -12 +/- 4 microm, followed by the copy-milled feldspathic crowns with a mean of -4 +/- 5 microm and the conventional In-Ceram crowns with a mean of -6 +/- 4 microm. Statistical analyses demonstrated no significant differences in the marginal discrepancy values among the 3 all-ceramic crown systems, except for the horizontal discrepancy values between the conventional and copy-milled In-Ceram crowns after the porcelain firing cycle. Results indicated that the addition of porcelain to the copings caused a significant change ( P <.05) in the marginal fit of the crowns, except for the fit in the horizontal plane of the conventional In-Ceram crowns. However, no significant changes occurred in the fit of the 3 all-ceramic crowns after the glaze firing cycle. There were significant differences in the marginal discrepancy values among the measurement locations ( P <.05), and the discrepancy value at each location was independent of the mean of the entire crown. CONCLUSIONS: Within the limitations of this study, it was concluded that the 3 all-ceramic crown systems demonstrated a comparable and acceptable marginal fit. The porcelain firing cycle affected the marginal fit of the all-ceramic crowns. However, the glaze firing cycle had no significant effect on fit. The conventional and copy-milled In-Ceram crowns demonstrated medial deformations at the labial and palatal surfaces that might result in occlusal displacement of the crown.     

Fracture Resistances of Cast Metal and Ceramic Dowel and Core Restorations: A Pilot Study

PURPOSE: The purpose of this study was to compare fracture strengths of teeth restored with cast metal and ceramic dowel and cores supporting all-ceramic crowns. MATERIALS AND METHODS: Eighteen recently extracted teeth were randomly divided into 3 equal groups. Metal dowel and cores (MDC) were fabricated for 1 group using a base metal alloy, and served as the control. The other groups received In-Ceram Spinell (ICS) and IPS Empress 2 (IPS) dowel and cores. IPS Empress 1 crowns were fabricated for all samples. Each tooth was subjected to a shear force at a crosshead speed of 2 mm/min on a universal testing machine until failure occurred. RESULTS: The mean fracture strengths and standard deviations of MDC, ICS, and IPS restorations were 1101 N (361), 832 N (288), and 1137 N (367), respectively. The differences between groups were insignificant (p < 0.05). Fractures of the all-ceramic crowns were observed in the MDC group, whereas the failure of ceramic dowel and core restorations was associated with root fracture at the cervical region. CONCLUSIONS: Due to improved mechanical properties, In-Ceram Spinell and IPS Empress 2 ceramic dowel and cores may be candidates for the restoration of endodontically treated anterior teeth.     

In vitro evaluation of fit of adhesively luted ceramic inlays

PURPOSE: The purpose of this study was to evaluate both marginal and overall adaptation of 4 adhesively luted ceramic inlay systems. MATERIALS AND METHODS: A total of 40 extracted teeth were restored with mesio-occlusodistal ceramic inlays using 4 different techniques: Colorlogic, IPS Empress, Celay direct, and Celay indirect. After cementation with a resin luting agent, the samples were sectioned along a mesiodistal line passing through the center of the restoration. The thickness of the cement was measured at the margins and at several points along the inside of the restorations by means of a stereomicroscope fitted with a measuring grid. RESULTS: The results were analyzed by one-way analysis of variance. The marginal precision of IPS Empress and Colorlogic inlays averaged below 50 microns. Marginal precision of Celay inlays averaged between 110 and 130 microns. IPS Empress and Celay inlays showed a uniform distribution of the cement along the entire prepared surface. Colorlogic inlays showed an uneven distribution of the cement film. CONCLUSION: IPS Empress inlays showed the best clinical features compared to Colorlogic and Celay inlays.     

Resistance to Fracture of Three All-Ceramic Systems

Abstract: All-ceramic restorations have become an attractive alternative to porcelain-fused-to-metal crowns, but their strength is still an important issue. The purpose of this study was to compare the in vitro fracture resistance of three all-ceramic systems: IPS Empress, In-Ceram, and Procera AllCeram. Thirty dies were replicated from a master die using high filler resin with a modulus of elasticity similar to dentin. Ten cores each of In-Ceram and Procera were fabricated to a thickness of 0.5 mm. The remaining porcelain was applied using a sculpting device to produce a crown with a final thickness of 1.0 mm axially and 2.5 mm occlusally. Ten IPS Empress crowns were waxed to the same dimensions and were pressed by the manufacturer. The internal surfaces of all the crowns were etched and silanated prior to cementation with a resin cement (Panavia 21). The cemented samples were loaded in an Instron machine until fracture. The mean fracture loads were: IPS Empress, 222.45 (±49) kg; In-Ceram, 218.8 (±36) kg; Procera AllCeram, 194.20 (±37) kg. Tukey's test showed no statistically significant differences among the three all-ceramic systems at p < .05.     

Fracture strength of 5 different all-ceramic crown systems

PURPOSE: The purpose of this study was to evaluate the fracture resistance of 5 different all-ceramic crown systems (In-Ceram, Empress staining technique, Empress veneering technique, Celay feldspathic system, and Celay In-Ceram system) before and after cyclic preloading in an artificial mouth. MATERIALS AND METHODS: Extracted natural maxillary incisors were prepared with a 90-degree shoulder. The crowns were adhesively luted to the abutments using dual-cured composite cement. Half of the specimens were artificially aged via a chewing simulation and thermocycling, and all specimens were tested for fracture strength. The results were compared with those of porcelain-fused-to-metal (PFM) crowns with circular porcelain-butt margins that were cemented with zinc phosphate cement. RESULTS: The chewing simulation and the thermocycling significantly decreased the fracture strength of all tested crown systems (P < 0.01). There were no statistically significant differences between the all-ceramic crown groups and the PFM crowns. CONCLUSION: All-ceramic crowns can be used for anterior restorations. However, in vivo investigations of all-ceramic crown systems should be undertaken before introducing them into routine clinical use.     

The influence of internal surface treatments on tensile bond strength for two ceramic systems

STATEMENT OF THE PROBLEM: The ceramic composition and surface microstructure of all-ceramic restorations are important components of an effective bonding substrate. Hydrofluoric acid and sandblasting are well-known procedures for surface treatment; however, surface treatment for high alumina-containing and lithium disilicate ceramics have not been fully investigated. PURPOSE: This in vitro study evaluated the tensile bond strength of resin cement to two types of ceramic systems with different surface treatments. METHODS AND MATERIALS: Thirty specimens of each ceramic system were made according to the manufacturer's instructions and embedded in polyester resin. Specimens of In-Ceram Alumina [I] and IPS Empress 2 [E] were distributed to three groups with differing surface treatments (n = 10): sandblasting with 50 microm aluminum oxide (APA); sandblasting with 110 microm aluminum oxide modified with silica particles (ROCATEC System-RS); a combination of sandblasting with APA and 10% hydrofluoric acid etching (HA) for two minutes on In-Ceram and for 20 seconds for IPS Empress 2. After the respective surface treatments, all the specimens were silanated, and Rely-X resin cement was injected onto the ceramic surface and light polymerized. The specimens were stored in distilled water at 37 degrees C for 24 hours and thermally cycled 1,100 times (5 degrees C/55 degrees C). The tensile bond strength test was performed in a universal testing machine at a 0.5 mm/minute crosshead speed. RESULTS: The mean bond strength values (MPa) for IPS Empress 2 were 12.01 +/- 5.93 (EAPA), 10.34 +/- 1.77 (ERS) and 14.49 +/- 3.04 (EHA). The mean bond strength values for In-Ceram Alumina were 9.87 +/- 2.40 (IAPA) and 20.40 +/- 6.27 (IRS). All In-Ceram specimens treated with 10% hydrofluoric acid failed during thermal cycling. CONCLUSION: The Rocatec system was the most effective surface treatment for In-Ceram Alumina ceramics; whereas, the combination of aluminum oxide sandblasting and hydrofluoric acid etching for 20 seconds worked more effectively for Empress 2 ceramics.     

Influence of finish line design on marginal adaptation of electroformed metal-ceramic crowns

STATEMENT OF PROBLEM: Gold electroformed metal-ceramic restorations have been promoted as alternatives to conventional metal-ceramic restorations. However, little is known about the relationship between tooth preparation design and marginal adaptation for this type of crown. PURPOSE: This study evaluated the influence of 3 different finish line designs on the marginal adaptation of electroformed metal copings and metal-ceramic crowns. MATERIAL AND METHODS: Three steel dies were prepared for maxillary central incisor crowns with 3 finish line designs: shoulder, rounded shoulder, and deep chamfer preparations. Eight standardized electroformed metal-ceramic crowns were fabricated for each group. Marginal discrepancies were measured at 60 points for each specimen along the circumferential margin at 4 sites (labial, mesial, lingual, and distal surfaces, with 15 points for each site) before and after firing procedures using a laser microscope. Data among the 3 different groups were statistically analyzed using the Kruskal-Wallis test and the Mann-Whitney U test with the Bonferroni correction. Marginal discrepancies between prefiring and postfiring procedures were evaluated using the Wilcoxon signed-ranks test (alpha = .05). RESULTS: Significant differences in the marginal discrepancies of electroformed metal copings without porcelain and metal-ceramic crowns were found among all groups. The lowest range of median marginal discrepancy values (P < .05) at 4 sites, both before and after firing, occurred with the deep chamfer preparation (17.64-21.78 microm and 23.96-25.72 microm, respectively). The highest range values were observed in the shoulder preparation (38.13-49.89 microm and 73.87-89.44 microm, respectively). In all situations, the marginal discrepancies of the postfiring procedures were significantly greater (P = .02 or less) than those of the prefiring procedures. CONCLUSION: Within the limitations of this study, the marginal adaptation of electroformed metal copings or metal-ceramic crowns is affected by finish line design and sequentially diminished by porcelain firing procedures.     

Relative translucency of six all-ceramic systems. Part I: core materials

STATEMENT OF PROBLEM: All-ceramic restorations have been advocated for superior esthetics. Various materials have been used to improve ceramic core strength, but it is unclear whether they affect the opacity of all-ceramic systems. PURPOSE: This study compared the translucency of 6 all-ceramic system core materials at clinically appropriate thicknesses. MATERIALS AND METHODS: Disc specimens 13 mm in diameter and 0.49 +/- 0.01 mm in thickness were fabricated from the following materials (n = 5 per group): IPS Empress dentin, IPS Empress 2 dentin, In-Ceram Alumina core, In-Ceram Spinell core, In-Ceram Zirconia core, and Procera AllCeram core. Empress and Empress 2 dentin specimens also were fabricated and tested at a thickness of 0.77 +/- 0.02 mm (the manufacturer's recommended core thickness is 0.8 mm). A high-noble metal-ceramic alloy (Porc. 52 SF) served as the control, and Vitadur Alpha opaque dentin was used as a standard. Sample reflectance (ratio of the intensity of reflected light to that of the incident light) was measured with an integrating sphere attached to a spectrophotometer across the visible spectrum (380 to 700 nm); 0-degree illumination and diffuse viewing geometry were used. Contrast ratios were calculated from the luminous reflectance (Y) of the specimens with a black (Yb) and a white (Yw) backing to give Yb/Yw with CIE illuminant D65 and a 2-degree observer function (0.0 = transparent, 1.0 = opaque). One-way analysis of variance and Tukey's multiple-comparison test were used to analyze the data (P<.05). RESULTS: Contrast ratios in order of most translucent to most opaque were as follows: Vitadur Alpha 0.60 +/- 0.03, Empress (0.5 mm) 0.64 +/- 0.01, In-Ceram Spinell 0.67 +/- 0.02, Empress 2 (0.5 mm) 0.68 +/- 0.02, Empress (0.8 mm) 0.72 +/- 0.01, Procera 0.72 +/- 0.01, Empress 2 (0.8 mm) 0.74 +/- 0.01, In-Ceram Alumina 0.87 +/- 0.01, In-Ceram Zirconia 1.00 +/- 0.01, and 52 SF alloy 1.00 +/- 0.00. CONCLUSION: Within the limitations of this study, there was a range of ceramic core translucency at clinically relevant core thicknesses. In order of decreasing translucency, the ranges were Vitadur Alpha dentin (standard) > In-Ceram Spinell > Empress, Procera, Empress 2 > In-Ceram Alumina > In-Ceram Zirconia, 52 SF alloy.     

Effect of etching and airborne particle abrasion on the microstructure of different dental ceramics

STATEMENT OF PROBLEM: The ceramic composition and microstructure surface of all-ceramic restorations are important components of an effective bonding substrate. Both hydrofluoric acid etching and airborne aluminum oxide particle abrasion produce irregular surfaces necessary for micromechanical bonding. Although surface treatments of feldspathic and leucite porcelains have been studied previously, the high alumina-containing and lithium disilicate ceramics have not been fully investigated. PURPOSE: The purpose of this study was to assess the surface topography of 6 different ceramics after treatment with either hydrofluoric acid etching or airborne aluminum oxide particle abrasion. MATERIAL AND METHODS: Five copings each of IPS Empress, IPS Empress 2 (0.8 mm thick), Cergogold (0.7 mm thick), In-Ceram Alumina, In-Ceram Zirconia, and Procera (0.8 mm thick) were fabricated following the manufacturer's instructions. Each coping was longitudinally sectioned into 4 equal parts by a diamond disk. The resulting sections were then randomly divided into 3 groups depending on subsequent surface treatments: Group 1, specimens without additional surface treatments, as received from the laboratory (control); Group 2, specimens treated by use of airborne particle abrasion with 50-microm aluminum oxide; and Group 3, specimens treated with 10% hydrofluoric acid etching (20 seconds for IPS Empress 2; 60 seconds for IPS Empress and Cergogold; and 2 minutes for In-Ceram Alumina, In-Ceram Zirconia, and Procera). RESULTS: Airborne particle abrasion changed the morphologic surface of IPS Empress, IPS Empress 2, and Cergogold ceramics. The surface topography of these ceramics exhibited shallow irregularities not evident in the control group. For Procera, the 50-microm aluminum oxide airborne particle abrasion produced a flattened surface. Airborne particle abrasion of In-Ceram Alumina and In-Ceram Zirconia did not change the morphologic characteristics and the same shallows pits found in the control group remained. For IPS Empress 2, 10% hydrofluoric acid etching produced elongated crystals scattered with shallow irregularities. For IPS Empress and Cergogold, the morphologic characteristic was honeycomb-like on the ceramic surface. The surface treatment of In-Ceram Alumina, In-Ceram Zirconia, and Procera did not change their superficial structure. CONCLUSION: Hydrofluoric acid etching and airborne particle abrasion with 50-microm aluminum oxide increased the irregularities on the surface of IPS Empress, IPS Empress 2, and Cergogold ceramics. Similar treatment of In-Ceram Alumina, In-Ceram Zirconia, and Procera did not change their morphologic microstructure.     

Marginal fit of leucite-glass pressable ceramic restorations and ceramic-pressed-to-metal restorations

STATEMENT OF PROBLEM: Fabricating a feldspathic porcelain margin on a metal-ceramic restoration with a clinically acceptable marginal fit has proven to be a technique-sensitive procedure. Pressable ceramics are advocated to solve this problem. PURPOSE: The purpose of this in vitro study was to compare the marginal adaptation of a pressable ceramic system when used with both all-ceramic and metal-ceramic crowns, with a traditional metal-ceramic restoration. MATERIAL AND METHODS: A 1.5-mm, 360-degree chamfer margin was prepared on a typodont maxillary central incisor. Polyether impressions were made and poured in a Type IV dental stone, and the following crowns were fabricated on individual dies: 15 metal ceramic restorations (MCR) (Ceramco II, Ceramco, and Argelite 60), 15 pressed-to-metal restorations (PTM) (CPC-MK, and Argelite 60), and 15 pressed ceramic restorations (PCR) (CPC-MK). The marginal fit of the crowns was evaluated every 90 degrees around the crown margin circumference under a microscope at original magnification x 45. A 1-way analysis of variance (ANOVA) was used to compare data (alpha=.05). RESULTS: The mean marginal discrepancy for MCRs was 94 +/- 41 microm, for PTMs, 88 +/- 29 microm, and for PCRs, 81 +/- 25 microm. The 1-way ANOVA showed no significant difference between groups ( P =.568). CONCLUSION: The marginal fit of pressed-to-metal (PTMs) and pressed all-ceramic crowns (PCRs) was similar to that of traditional metal-ceramic crowns (MCRs).     

Resistance to staining, flexural strength, and chemical solubility of core porcelains for all-ceramic crowns

PURPOSE: The increased demand for tooth-colored restorations has prompted the use of ceramics in areas that are subject to masticatory stresses. To maximize the strength of these restorations, manufacturers and clinicians advocate placement of core materials in lieu of veneering materials in areas that are more susceptible to fracture. The objectives of this study were to determine the: resistance to staining of three core porcelains used for all-ceramic restorations, Procera, IPS Empress, and In-Ceram, through the use of colorimetry and visual observation; flexural strength of these porcelains under a three-point bend test; and chemical solubility in a controlled environment. MATERIALS AND METHODS: L*a*b* values were obtained for each specimen before and after immersion in a saturated solution of methylene blue in ethanol for 24 hours. Visual observation was also performed to ascertain color differences before and after staining. A three-point bend test was used to determine flexural strength. A reflux-condenser type, three-piece extraction apparatus was used with 4% acetic acid solution for 16 hours to determine solubility. Each sample was weighed before and after the reflux procedure to ascertain percentage weight loss. RESULTS: The mean delta E obtained for IPS Empress was 14.5; In-Ceram was 9.2, and Procera was 9.0. Flexural strength obtained for IPS Empress, In-Ceram, and Procera was 176.9 MPa, 323.4 MPa, and 464.3 MPa, respectively. Weight loss of IPS Empress, In-Ceram, and Procera was 0.056%, 0.734%, and 0.003%, respectively. CONCLUSION: IPS Empress showed the least resistance to staining. IPS Empress had the lowest flexural strength, while Procera had the highest. In-Ceram demonstrated the highest chemical solubility.     

Investigation of the fracture resistance of three types of zirconia posts in all-ceramic post-and-core restorations

PURPOSE: All-ceramic post-and-core restorations offer a number of advantages compared with systems that use metal cores. In certain clinical cases, however, fractures at the junction between the post and the core have been reported. The objective is therefore to improve the strength between the post and the core. MATERIALS AND METHODS: Three different methods were used to fabricate all-ceramic post-and-core restorations: pressing IPS Empress cores directly to CosmoPost zirconia posts, adhesively luting IPS Empress cores to CosmoPost zirconia posts, and Celay milling In-Ceram zirconia blanks to one-piece post-and-core restorations. Ten restorations were prepared with each of the three methods. The post-and-core complexes were tested to failure with the load applied perpendicular to the post axis. The load and deflection at fracture were recorded. RESULTS: The highest breaking load and highest deflection were recorded for the luting technique, with values of 25.3 N and 394 microns, respectively. The corresponding values for the pressed cores and the milled zirconia cores were 22 N and 301 microns, and 13 N and 160 microns. All differences were statistically significant at P < .05. Regarding the load dependence of the deflection, the luted cores again demonstrated the highest mean value, with 15.5 microns/N, while this value was 13.6 microns/N and 13 microns/N for the pressed-on and milled cores, respectively. These differences were not statistically significant. CONCLUSION: Adhesively luted all-ceramic cores on zirconia posts offer a viable alternative to the conventional pressed technique.     

Marginal adaptation of different types of all-ceramic partial coverage restorations after exposure to an artificial mouth

OBJECTIVES: To determine the influence of the preparation design and the dimensions of all-ceramic partial coverage restorations (PCR) on the marginal accuracy before and after masticatory simulation. METHODS: In this in vitro study 80 extracted human maxillary molars were restored with MOD inlay restorations and four different modified PCR restorations using a new press ceramic IPS e.max Press (IPS e.max Press VP 1989). The teeth were divided into five groups of 16 specimens each and prepared as follows: Group A received an MOD inlay preparation and Group B, C, D and E received modified PCR. The restorations were adhesively luted and exposed to a mastication simulator. The discrepancies of the marginal fit were examined on epoxy replicas before and after luting as well as after masticatory simulation at 200x magnification. RESULTS: The mean (geometrical) [95% confidence limits] marginal gap decreased from Group A to E before cementation (A-83[77-90]microm, B-68[65-70]microm, C-59[55-64]microm, D-56[52-61]microm, E-50[45-55]microm). Group A had significantly higher marginal gap values than group B (p = 0.017) and the other groups (p<0.0001). After cementation the marginal accuracy was recorded as following: A-103[93-114]microm, B-101[94-108]microm, C-93[89-98]microm, D-102[98-105]microm and E-99[96-102]microm. Cementation increased the marginal gap in groups B-E significantly (p<0.00001), not significantly in group A (p = 0.059). Artificial ageing (A-116[106-127]microm, B-114[109-120]microm, C-106[103-110]microm, D-109[100-118]microm and E-109[105-112]microm) led to further significant decrease of marginal accuracy in Group B (p = 0.029) and C (p = 0.026) only. After cementation and masticatory simulation of the ceramic restorations, the marginal gap values of Groups A, B, C, D and E did not significantly differ from each other (p = 1.00). CONCLUSIONS: The result of this in vitro study showed that IPS e.max Press can be used to fabricate all-ceramic inlays and PCR which meet the requirements in terms of a clinically acceptable marginal gap, irrespective of the preparation design used. However, the preparation design and dimensions of the restorations appeared to affect the initial marginal fit and flowing off of luting material during the cementation process. The factors responsible for these findings require further substantiation.     

Compressive strength of two modern all-ceramic crowns.

This study investigated the compressive strength of all-ceramic crowns manufactured using two recently introduced systems. The mean forces of fracture were 964 N for In-Ceram crowns, 814 N for paint-on IPS Empress crowns, and 750 N for layered IPS Empress crowns, compared with 1,494 N for metal ceramic crowns veneered on a nickel-chromium coping. The results indicate that clinical testing of these all-ceramic crowns is reasonable. Controlled, clinical, long-term evaluation is necessary to assess the safe application of these new crown systems.     

Comparison of marginal integrity of ceramic and composite veneer restorations luted with two different resin agents: an in vitro study

PURPOSE: The aim of the present study was to examine the marginal integrity of a composite veneer, Artglass, in comparison to a ceramic veneer, IPS Empress, by using two different luting agents. The study also aimed to evaluate the effect of grit blasting on marginal integrity of IPS Empress ceramic veneers. MATERIALS AND METHODS: A total of 42 human maxillary incisors were used to construct 14 veneers for each experimental group: (1) Artglass veneers, (2) IPS Empress veneers with grit blasting, and (3) IPS Empress veneers without grit blasting. Veneers were luted with Variolink II High Viscosity and Variolink Ultra. The restored teeth were sectioned buccolingually and mesiodistally, and marginal gap width measurements were made at 200x magnification. The data were statistically analyzed with analysis of variance. RESULTS: The mean marginal gap width varied from 105 to 182 microns. No significant differences were recorded between the marginal gap widths in relation to different types of veneers or luting agents. However, significantly higher marginal discrepancies were observed for the incisal margins of IPS Empress veneers without grit blasting. CONCLUSION: In view of the higher marginal discrepancy of IPS Empress veneers divested without grit blasting, the use of this alternative technique was not beneficial. The use of a highly filled resin luting agent (Variolink Ultra) did not cause an increase in marginal gap widths of the veneers.     

Marginal and internal fit of all-ceramic CAD/CAM crown-copings on chamfer preparations

Evaluation of the marginal and internal fit of all-ceramic molar crown-copings hypothesizing that Computer Aided Design/Computer Aided Manufacturing (CAD/CAM) fabrication shows the same accuracy of fit as conventional techniques. A set of six individual crown preparations was duplicated 12 times yielding 72 plaster dies. Slip-cast (In-Ceram Zirconia), heat-pressing (Empress II) and CAD/CAM crown-copings (Cerec inLab, DCS, Decim and Procera) were seated on 12 dies each. Marginal and internal gap width was measured in the SEM at 120x magnification. Marginal gap of slip-cast (25 +/- 18 microm) was significantly (P < 0.05) smaller than that of Empress II (44 +/- 23 microm) copings. Procera (17 +/- 16 microm) and Decim (23 +/- 17 microm) did not differ (P > 0.05) from slip-cast (25 +/- 18 microm) but were smaller (P < 0.001/P < 0.01) than Empress II (44 +/- 23 microm) and Cerec inLab (43 +/- 23 microm) (P < 0.001/P < 0.05). DCS (33 +/- 20 microm) did not differ (P > 0.05) from any of the others. The internal mid-orobuccal gap width of Procera (136 +/- 68 microm) was larger (P < 0.001) than that of Decim (81 +/- 30 microm) and slip-cast (94 +/- 84 microm) (P < 0.05) while Empress II (105 +/- 53 microm), DCS (110 +/- 79 microm) and Cerec inLab (114 +/- 58 microm) did not differ significantly (P > 0.05) from Decim, Procera and slip-cast. Internal mesiodistal gap width was similar. The fit of conventional and CAD/CAM all-ceramic molar crown-copings covered the same range of gap width confirming the assumed hypothesis.     

A study on the fracture strength of implant-supported restorations using milled ceramic abutments and all-ceramic crowns

PURPOSE: The purpose of this study was to compare five different abutment-crown combinations for single implant-supported restorations regarding their capabilities to withstand loads. MATERIALS AND METHODS: Fifty implants were placed into resin blocks, and the restorations were connected to the implants. The five tested restorations were: (1) metal-ceramic crowns cemented to titanium abutments, (2) In-Ceram crowns cemented to titanium abutments, (3) Celay feldspathic crowns cemented to titanium abutments, (4) In-Ceram crowns cemented to milled ceramic abutments, and (5) Celay feldspathic crowns cemented to milled ceramic abutments. The specimens were loaded at 0- and 45-degree angles to the long axis, and the load values at the moment of failure were recorded using a universal testing machine. RESULTS: The fracture strengths under vertical loading were greater than those under oblique loading. The fracture strengths of metal-ceramic crowns cemented to the titanium abutments were higher than those of all-ceramic crowns cemented on the milled ceramic abutments, regardless of loading direction. There were no differences in the fracture strengths of the ceramic crowns between the two different abutment types under oblique loading. CONCLUSION: All-ceramic crowns on the milled ceramic abutments were weaker than the metal-ceramic crowns on the titanium abutments under oblique loading.     

3种全瓷系统冠边缘适合性的比较(英文)

目的:比较临床常用3种全瓷系统(Kavo Everest、IPS e.max、In-Ceram alumina)冠的边缘适合性,为临床应用提供理论依据。方法:选取1颗无龋的离体前磨牙行牙体预备,其中牙合面预备2mm,颈部凹槽肩台,宽度为0.8mm,牙合聚合度为6°。双重印模法取模,每种系统分别制作10个冠修复体。然后采用双色硅橡胶印模法复制间隙模型,应用光学显微镜采集间隙图像及使用Auto CAD2006软件对其水平边缘间隙、垂直边缘间隙和绝对边缘间隙进行测量,将所得数据使用SPSS13.0软件包进行单因素方差分析。结果:3种全瓷系统制作的上颌前磨牙冠的水平边缘间隙的平均值在41.1～44.9μm,垂直边缘间隙的平均值在51.4～71.7μm,绝对边缘间隙的平均值在66.2～85.1μm。结论:本研究中,3种全瓷系统冠的绝对边缘间隙、垂直边缘间隙和水平边缘间隙均在临床可接受范围;然而,与In-Ceramalumina系统相比,IPS e.max和Kavo Everest系统制作的全瓷冠显示出较好的边缘适合性。     

Fracture resistance of three all-ceramic restorative systems for posterior applications

STATEMENT OF PROBLEM: The failure loads of all-ceramic crowns are influenced not only by the fracture resistance of the component materials but also by prosthesis geometry and size and location of flaws, thus there is a need for a study that compares the fracture resistance of all-ceramic systems using a simple and reproducible specimen geometry that includes flaws occurring at material interfaces. PURPOSE: The research aim was to compare the in vitro fracture resistance and origin of failure of simulated first molar crowns fabricated using 3 all-ceramic systems, IPS Empress 2, Procera AllCeram, and In-Ceram Zirconia. MATERIAL AND METHODS: Twenty axisymmetric crowns of each system were fabricated to fit a preparation with 1.5- to 2.0-mm occlusal reduction. The center of the occlusal surface on each of 15 specimens per ceramic system was axially loaded to fracture in a universal testing machine, and the maximum load (N) was recorded. Fractured surfaces were examined using optical and electron microscopy to determine the most prevalent origin of failure in each ceramic system. Five crowns per system were sectioned, and thickness of the luting agent, core material, and veneer porcelain layers were measured. The 95% confidence intervals of the Weibull modulus and characteristic failure load were compared between the 3 systems. Two-way multivariate analysis of variance was used to analyze the thickness of the luting agent, ceramic core, and veneer porcelain layers (alpha=.05). RESULTS: The 95% confidence intervals for Weibull modulus were 1.8 to 2.3 (IPS Empress 2), 2.8 to 3.6 (Procera AllCeram), and 3.9 to 4.9 (In-Ceram Zirconia). The 95% confidence intervals for characteristic failure load were 771 to 1115 N (IPS Empress 2), 859 to 1086 N (Procera AllCeram), and 998 to 1183 (In-Ceram Zirconia). The origin of failure was most commonly found at the interface between the ceramic core and veneer porcelain for IPS Empress 2 and between the ceramic core and luting agent layer for the other systems. CONCLUSIONS: There was no significant difference in fracture resistance; however, there was a significant difference in failure origin between the all-ceramic systems studied.