Procera® Aluminum Oxide
Crown

Abstract: Aluminum oxide material used for the Procera‚ AllCeram coping cannot be altered by acid etching. Yet, it is claimed that resin cements may be bonded to the surface. The purpose of this in-vitro study was to evaluate the maximum load to fracture of several commonly used resin cements when cemented to this densely sintered aluminum oxide. Sixty specimens of (Procera‚) densely sintered aluminum oxide as disks 10 mm X 10 mm X 4 mm. One side of the disk was fabricated in accordance with the technique used to create a coping. The samples were acid etched and bonded agent applied according to the manufacturer’s specifications for the cements used n the study. Rely X-arc (3M), Variolink II (Vivadent), Nexus (Kerr), PermaFlo (Ultradent), Choice (Bisco), and LinkMax (GC America) were dispensed using a standard mold to develop a consistent bonding area of 2.379 mm for testing. The cements were light-cured and stored for 24 hours. A shear load was applied at the junction between the ceramic samples and the cement with a knife-edge rod at a cross-head speed of 0.5 mm/min in a Universal Instron testing machine. The maximum load to fracture data from all samples was then analyzed using a 2-way ANOVA. The hightest maximum load to fracture was obtained with Variolink II. There was no statistically significant difference between Variolink II and Choice (P=0.05). The mean maximum load to fracture of each cement was: Permaflo (24.623 MPa), LinkMax (26.372 MPa), RelY-X arc (29.438 MPa), Nexus (29.526 MPa), Choice (31.83 MPa), and Variolink II (43.601 MPa).
Conclusions: Variolink II exhibited he highest maximum load to fracture when used with densely sintered aluminum oxide.

Abstract: It has been shown that cementation of all ceramic restorations increases the fracture resistance of the over-all restoration. With the number of luting agents available, the question arises: Is there a significant difference between the various cements as to the added strength provided to the restoration? To begin investigating this question, a study was completed testing the ultimate compressive strength of PROCERA® aluminum oxide copings cemented with two luting agents verses the copings alone. Three test groups were selected, each containing six samples. The copings were cemented to pre-milled titanium dies using poly-vinyl siloxane impression material, as a control (Group A), 3M Vitremer (Group B) and G.C. Fuji Plus (Group C). Samples were visually inspected to insure that there were no detectable fractures. The samples were loaded to fracture at the rate of 0.5mm/min using the Instron machine, provided the following results: The mean ultimate compressive strength was: A=35.83+3.26kg (S.D.), B=59.94+6.07kg (SD), C=87.67 +9.37kg (S.D.). Scheffe's test showed that there was a statistical difference between all groups (sig. level = .05).
Conclusions: Under the conditions of this study, the ultimate compressive strength of the PROCERA® copings is increased by the luting agent, with Fuji Plus providing a significantly higher compressive strength.

Abstract: Determining the strength of aluminum oxide, a substrate for all-ceramic restorations, has involved disk samples fabricated to dimensions required for ISO/DIS 6872 Standard. For this standard specifically dimensioned disk samples are fabricated for determining the load to fracture value by the Piston-On-Three Ball and Ring-On-Ring tests. Using the load to fracture value determined by the Instron machine and other material characteristic data, the flexural strength is calculated by a specific ISO mathematical formula. The mean flexural strength of the aluminum oxide is reported in MPa. Earlier studies using this approach have reported flexural strength values for aluminum oxide that have varied as much as 117 MPa. Using the load to fracture data reported in each of the earlier studies and the dimensions of their specific disk samples, this study measured the flexural strength of the aluminum oxide using the finite element methodology. The analysis of each modeled disk sample was performed using ABAQUS®.
Conclusions: For all modeled disks the flexural strength was determined to be same or 510 MPa. For more reliable and valid data both mechanical test and finite element analysis results should be used in the evaluation of flexural strength of ceramic disk samples.

Abstract: The Procera System embraces the concept of computer-assisted design and computer-assisted machining to fabricate an all-ceramic crown composed of a densely sintered, high-purity aluminum oxide coping combined with a compatible veneering porcelain. Strength, precision of fit, color stability, cementation, and wear characteristics are among the many factors that concern clinicians when fabricating all-ceramic restorations with this new crown system. This article presents, in summary form, the data from the many studies on Procera AllCeram crowns that have been conducted at clinical and laboratory centers around the world. The evidence reported in these studies clearly demonstrates that the Procera AllCeram crown represents a combination of computer technology and creativity for which a positive prognosis can be made. Today its application is restricted to single crowns; however, with continued development, multiple unit all-ceramic anterior and posterior fixed partial dentures are clearly in the future.
Conclusions: Procera AllCeram crowns can be used successfully as all-ceramic restorations in all areas of the mouth, and their length of service will reach 5 years or more without complications.

Abstract: The availability of high-technology systems that use computer-aided design and computer-aided machining is on the increase. One such system is the Procera system, which is currently providing cost-effective, high-quality dental restorative services to dental laboratories and to dentists. A reduction in cost to the dentist, and ultimately to the patient, is a major advantage of the Procera system.
Conclusions: Cost benefits combined with its continued success in producing crowns and fixed partial dentures that meet professional standards of care should enhance the acceptance of this new technology.

Abstract: This is a report on Procera AllCeram crowns in a prospective multicenter study. The aim of the study was to evaluate AllCeram crowns in dental practice over a 5- to 10.5-year period. Some of the AllCeram crowns were among the very first that were placed. The crowns were placed between 1989 and 1995. Twelve clinicians at nine clinics placed 87 crowns in 50 patients. The California Dental Association quality evaluation system was used for assessment of marginal integrity and esthetics. After 5 and 10 years a cumulative survival rate of 97.7% and 93.5 %, respectively, and a cumulative success rate of 97.7% and 92.2%, respectively, was recorded. Six crowns (7%) were recorded as failures; five of these crowns (6%) had to be remade. The marginal integrity was considered excellent or acceptable for 92% of the crowns. Bleeding was somewhat more often recorded at teeth with AllCeram crowns (39%) than at contralateral teeth (27%). Endodontic treatment was performed for a low number (2%) of the AllCeram crowns. The patients found the esthetics to be excellent.
Conclusions: The results of this study demonstrated about the same clinical outcome as has been reported by similar studies on all-ceramic crowns built on a core of alumina. The outcome is also in agreement with that reported for metal-ceramic crowns. The results indicate a good prognosis for Procera AllCeram crowns when used for posterior teeth.

Abstract: The purpose of this investigation was to examine the effect of different techniques for surface alteration on the Procera All-Ceramic core material. CeraOne blanks were obtained from the Procera/Sandvik Laboratory in Stockholm, Sweden. Forty samples were divided into four groups with one group serving as the control (surface unaltered following completion of porcelain firing). The remaining groups were each assigned a surface treatment technique. The techniques included: 1) etching with 9.6% hydrofluoric acid, 2) air abrasion (sandblasting) with 50 µm aluminum oxide for 15 seconds, and 3) roughening surface with a diamond followed by etching with 37% phosphoric acid. Each sample was evaluated using scanning electron photomicrographs before and after altering the sample surface.
Conclusions: The SEM analysis of the surfaces indicated that air abrasion (sand blasting) with 50 µm aluminum oxide produced a unique morphology where the crystals seemed to be flattened possibly increasing the surface area.

Abstract: The purpose of this investigation was to examine the influence of selected surface alteration techniques on the bond strength of a luting agent when used with the Procera All-Ceramic core material. The Procera/Sandvik Laboratory in Stockholm, Sweden provided CeraOne blanks. Forty samples were divided into four groups with one group serving as the control (surface unaltered). The remaining groups were each assigned a surface treatment technique. The techniques included: 1) etching with 9.6% hydrofluoric acid, 2) air abrasion (sandblasting) with 50 µm aluminum oxide for 15 seconds, and 3) roughening surface with a diamond followed by etching with 37% phosphoric acid. Enforce resin cement (LD Caulk Co.) was applied to the altered surface of each sample using the manufacturers’ recommendations and silane agents prior to testing. A standard shear bond test was conducted to determine the strength of the bond. The resin was applied and photopolymerized according to the manufacturer’s directions. All specimens were kept in 100% humidity at room temperature for seven days. Following storage, each sample was subjected to a shear load in a Universal testing machine (Instron Corporation) at a cross-head speed of 0.5 mm/minute and using a knife-edge blade placed parallel to the bonded surfaces. Recording was made of shear load at the point of failure.
Conclusions: Acceptable bond strengths were achieved and the sandblasted surface with 50 µm aluminum oxide was the best of the four surface treatments tested at 11.99 MPa with a standard deviation of 3.11 MPa.

Abstract: This study compared changes in CIE L*a*b* color coordinates of simulated veneers made from aluminum oxide core material veneered with feldspathic porcelain after 300 hours of accelerated photothermal aging (weathering). Fifteen aluminum oxide disks (Procera) were divided into 3 groups. Each of the 5 disks was veneered with All-Ceram porcelain of the Vita shades Al and B4, respectively. Five disks remained unfinished as controls. The disks were bonded to composite substrates simulating stained teeth. The color of the specimens was measured with a colorimeter. All specimens were subjected to 300 hours of accelerated aging under light exposure and thermocycling. Color measurements were repeated, and the data were statistically evaluated with multiple paired t tests. Color changes in the test groups involved an increase in lightness and a decrease in chroma. The calculated total color differences were not statistically significant compared with a level 3 DE units..
Conclusions: The results of this study indicate that aluminum oxide shells can be used as the core of double-layer veneers. This veneer system provides the clinician and patient with a lasting and therefore predictable shared match.

Abstract: The purpose of this study was to investigate the possibility that hygroscopic expansion of luting agents may cause micro-cracks in all-ceramic restorations over time. These micro-cracks in turn may contribute to the weakening of the restoration leading to crown fracture. To investigate this hypothesis, the compressive strengths of aluminum oxide copings cemented to titanium dies were compared between two sample groups cemented sixty weeks apart. Each group contained ten (10) samples. All samples were Procera® aluminum oxide copings cemented onto pre-milled titanium dies. Within each group there were two subgroups. One subgroup of 5 samples was cemented with Vitremer and the other subgroup of 5 samples was cemented with Fuji Plus. Group 1 was cemented sixty weeks prior to testing, and Group 2 was cemented 7 days prior to testing. All samples were stored in 100% humidity prior to testing. All of the samples were inspected under 20X microscopic magnification prior to testing and found to be free of any detectable micro-cracks. The die/coping samples were positioned within the Instron testing machine and the compressive strength determined. The compressive strength of the 7 day samples cemented with Vitremer was 59.94 ± 6.07 kg., and the 7-day samples cemented with Fuji Plus was 87.67 ± 9.34 kg. The compressive strength of the 60 week samples cemented with Vitremer was 83.08 ± 11.49 kg., and the 60 week samples cemented with Fuji Plus was 175.87 ± 33.45 kg.
Conclusions: The Scheffé’s test indicated a significant difference between the mean load to fracture values of the two groups. It was concluded under the conditions of this study that the copings were not weakened over time due to hygroscopic expansion and potential micro-crack development, and that the ultimate compressive strength is significantly greater in the samples cemented sixty weeks prior to testing than the samples cemented 7 days before testing.

Abstract: The purpose of this study was to measure the biaxial flexural strength of the various layers of material that formed the Procera® AllCeram Porcelain. Data provided by the Ducera Company producers of the veneering porcelain were to be used for comparison with the data measured during this study. The three layers of the Procera AllCeram Porcelain were the Translucent, Dentine, and the Opaque porcelains. Five bar samples of each layer were fabricated by the Ducera Company for testing. A special testing stand was design to support the bars at each end for the biaxial bending test. Each bar was positioned in the testing stand and a loading piston was placed equally distanced from the sides and ends of the bar. A load was applied to the piston using the Universal Instron machine until the bar fractured. The fracture strength of each bar was then calculated using the load to fracture values. The mean biaxial flexural strengths reported by the Ducera Company for the Translucent porcelain was 103 MPa and 79 MPa for the Dentine porcelain. The Ducera Company provided no data for the Opaque porcelain. The mean biaxial flexural strengths measured by investigators for this study were: Translucent porcelain 86.90 ± 7.63 MPa, Dentine Porcelain 55.26 ± 12.7 MPa, and the Opaque porcelain 94.55 ± 10.59 MPa. Although the data from this investigation differed with the Ducera reported data; the magnitude of the differences between the different veneering porcelain layers is a more important finding. In the Procera AllCeram crown the strong aluminum oxide coping forms the substrate layer. On top of the coping the layered Procera AllCeram Porcelain is placed beginning with the Opaque layer followed by the Dentine and Translucent layers. On the basis of the measured strength data the layering would be: Opaque 94.55, Dentine 55.26, and Translucent layer 86.90 MPa. Recognizing that layered structures can be significantly influenced by the strengths of their individual layers, the question to be pursued is the influence of the weaker Dentine layer on the overall strength of the veneering porcelain.
Conclusions: The biaxial flexural strengths of the layers of the Procera® AllCeram Porcelain were: Opaque 94.55, Dentine 55.26, and Translucent layer 86.90 MPa. The influenced of the strength of the individual layers on the overall strength of the veneering porcelain needs further study.

Abstract: Most porcelains are subject to brittle fracture and adhesive bonding of these ceramics to dentin using a resin cement has been recommended for reinforcement and improved retention. The purpose of this study was to conduct an in-vivo study to evaluate a new unit-dose mechanically mixed resin cement. The test material was Compolute™ (ESPE American) used with a chemically matched self-curing bonding system (EDS Multi™). The control material used for comparison was Variolink II™ with the Syntac™ Bonding system (Ivoclar North America). Both luting materials were dual-cure luting agents. Thirty-eight (38) patients requiring fifty-nine (59) full-crown restorations formed the experimental population for this investigation. The distribution of the crown restorations by material was IPS-Empress (34), In-Ceram (10), OPC (5), Targis (5), Procera (4) and CEREC (1). Assignment of the restorative materials to test and control groups was randomized and reveal only at the cementation appointment. The cementation procedure followed the manufacturer’s instructions and all preparations were acid etched for only 15 seconds. Baseline and six-month data were collected for post-operative sensitivity, color match, margin discoloration and margin adaptation. A telephone interview was also conducted 48 hours following cementation for patient-reporting sensitivity. Post-operative sensitivity was reported for 4 control teeth/crowns (12.9%), and 12 test teeth/crowns (42.9%). There were 45 teeth available for the six-month evaluations with 3 test teeth/crowns (16.6%) and 3 control teeth/crowns (12.0%) demonstrating continued sensitivity.
Conclusions: Using the Chi Square test, no significant differences were found between the test and control teeth/crowns for shade match with 89% test and 84% control teeth/crowns receiving an Alpha rating. No significant differences were found between test and control teeth/crowns for margin adaptation with 71% test and 74% control teeth/crowns receiving an Alpha rating. No significant differences were found between test and control teeth/crowns for margin discoloration for the test or control teeth/crowns. The restorations were considered clinically acceptable at the six-month recall appointment with the exception of one test and one control teeth/crowns sample which were both removed because of extreme sensitivity.

Abstract: Nobel Biocare has developed a new two-layered laminate restoration consisting of a densely sintered aluminum oxide core veneered with an outer layer of feldspathic porcelain. A thin aluminum oxide core layer (approximately 0.2 mms) is created using the Procera® CAD/CAM technology. An outer layer of veneer porcelain (approximately 0.4 to 0.6 mms in thickness) is fused to the aluminum oxide using a shade that matches the color of adjacent teeth to achieve the desired esthetic result. The question of clinical interested is whether or not the resulting color of this rather thin laminate will be effected by a dark substrate (tooth) and can the dark substrate be masked by the color of the luting agent used in cementation. The purpose of this study was to measure the color of the surface of the laminate sample when covering a dark substrate material and to compare the color data with measures from the surface of two-layered veneer when a try-in paste is placed between the laminate sample and the substrate. Aluminum oxide 0.2 mm thick disks were fabricated for this study by Nobel Biocare. The disks were veneered with Vita Lumin Shade B4 porcelain. Five (5) samples were prepared with a veneer thickness of 0.4 mm and 5 samples with a veneer thickness of 0.6mm. Color data were recorded using a Minolta Chromameter II. Color baseline data was collected when the substrate was covered by the 0.4 mm and 0.6 mm two-layered samples for comparison with data collected when dark, light and neutral try-in pastes were placed between the substrate and the two-layered samples.
Conclusions: Significant differences were found in the C.I.E. color coordinate data measured from the surface of the core plus 0.4 mm and 0.6 mm veneer thickness samples when covering the dark substrate. The light and dark try-in pastes produced significant differences in the C.I.E. color coordinate values when placed between the substrate and both the 0.4 mm and 0.6 mm veneer thickness two-layered laminate groups (P<0.001). The color of two-layered porcelain veneers as seen clinically will be altered by changing the color of the luting agent used during cementation procedures.

Abstract: The purpose of this study was to determine if micro-cracks would appear at the margins of Procera® aluminum oxide copings when cemented with the resin-reinforced glass-ionomer cements Fuji Plus and 3M – Vitremer. Thirty (30) Procera copings were fabricated using the Nobel Biocare CAD/CAM system. The samples were divided into two groups of 15 samples. One group was cemented with Fuji Plus and the second group was cemented with 3M –Vitremer onto pre-milled titanium dies. The samples were stored for six weeks in 100% humidity at room temperature (approximately 70°F.). The samples were first inspected for micro-cracks by two Prosthodontists using 2.50 magnification surgical loupes. The investigators under 20X microscopic magnification then inspected the samples. None of the 30 samples showed any signs of fracture by either of the inspection techniques.
Conclusions: Under the conditions of this study, there was no evidence to support the hypothesis that expansion of the resin reinforced cements tested caused micro-cracks of Procera® AllCeram copings.

Abstract: The flexural strength of the Procera® AllCeram Crown has been reported as greater than other all-ceramic crowns. However the influence of the cement thickness on the fracture strength of this crown has not been investigated. The purpose of this study was to evaluate the effect of the cement space on the load to fracture strength of the Procera aluminum oxide coping. A master die was created using a maxillary first molar preparation. The master die was duplicated in a resin material with a modulus of elasticity similar to dentin and would fracture consistently at 173 ± 69Kg. The dies were used to fabricate Procera copings with the standard 1X (60 µm) cement space and 2X (120 µm) cement space. Three cements were selected for the tests. Ten (10) copings were made for each cement with five (5) copings assigned to each of the two (2) cement spaces. After cementing the copings to the dies each specimen was loaded until fracture using an Instron machine at a crosshead speed of 0.5 mm/min. The load to fracture results were:

A Pairwise contrast test on the cement space/cement interaction showed a significant difference (p=0.05) when the cement used was ZnPO4.
Conclusions: When the cement space between the die and the Procera coping was increased from the standard 1X (60 µm) cement space to a 2X (120 µm) cement space the load need to fracture the coping was significantly decreased.

Abstract: The purpose of this study was to evaluate the masking ability of the Procera® AllCeram aluminum oxide coping material when covering a number of core build-up materials used in the rehabilitation of a natural tooth. Ten (10) aluminum oxide disks were manufactured by the Procera Sandvik facility in Stockholm, Sweden. The disks were 10.0 mm in diameter and 0.600 mm in thickness. Core build-up material samples 10.0 mm in diameter and 2.0 mm in thickness were created in the following materials: Amalgam (Tytin, Kerr, USA), Gold (Meracast, Ney USA) Titanium (Nobel Biocare, Sweden), Ti-Core Silver (Essential Dental Systems, USA), and Ti-Core Natural (Essential Dental Systems USA). Each core build-up samples was covered by each of the 10 aluminum oxide disks and CIE L*a*b* color coordinates were read from the surface of each Procera disk using a Minolta ChromaMeter CR-300 (Minolta Inc Japan). Three (3) readings were made for each disk/core build-up sample. Data was collected in the “Lab” and “Yxy” modes. The mean measurement were:

Conclusions: The L*a*b* chromameter data demonstrated no significant differences when the Procera® AllCeram aluminum oxide disks of 0.600 mm thickness covered the five core build-up materials indicating a masking of the color differences of these substrates.

Abstract: The applications for ceramic dental materials are limited by low toughness. The traditional dental porcelains typically have values lower than 1 MPa m1/2. In this study, the toughness values of three ceramic core materials were evaluated using the indentation technique described by Ansti et al. Disk-shaped specimens (2 mm thick and 16 mm in diameter) were prepared of Procera AllCeram (Nobel Biocare), In-Ceram (Vita), and IPS-Empress (Ivoclar) in accordance with manufacturers’ instructions. Loads of 9.8 N to 196 N were applied to the specimens with a Vickers hardness indenter on a Tukon hardness testing machine (Wilson Co., NY). Optimum testing load for each material was determined by comparing crack length (from the center of the indent) to indent half-diagonal ratios at several different loads; a load must be used that produces a ratio greater than 2. It was determined that 196 N of load should be used for Procera AllCeram and IPS-Empress, and 98 N load for In-Ceram. Ten readings were taken for each material and the fracture toughness was calculated with the equation described by Anstis et al. ANOVA and Scheffé tests were used to calculate levels of significance at a = 0.05. The results showed that there was no significant difference between the fracture toughness of Procera AllCeram (4.48 MPa m1/2 SD=0.59) and In-Ceram (4.49 MPa m1/2 SD=0.57). Both are significantly higher (p<0.005) than the fracture toughness of IPS-Empress (1.74 MPa m1/2 SD=0.26).
Conclusions: Under the same loading conditions, higher energy is required to fracture Procera AllCeram or In-Ceram than to fracture IPS-Empress.

Abstract: The traditional gold and porcelain fused to metal crowns are being challenged by the more esthetic all ceramic crown materials. Only previous experience with poor mechanical properties and processing obstacles has prevented a universal acceptance of all ceramic crowns. However, stronger and tougher ceramics and unique processing methods have been developed in the last 20 years. In this study, three of the newest ceramic crown materials were tested to compare their biaxial flexural strength. Ten specimens of each material, Empress, In-Ceram, and Procera AllCeram were prepared following the respective manufacturer's instructions. Significant differences in flexural strength were found for the three materials.
Conclusions: The Procera AllCeram (687 MPa) had 95% and 413% higher strength than In-Ceram (352 MPa) and Empress (134 MPa) respectively.

Abstract: In previous studies, Procera AllCeram coping material was shown to have very high biaxial flexure strength (687 MPa). Therefore, the objective of this study was to determine the effect of the low fusing porcelain veneer on the strength of this all ceramic restoration. Disk shaped specimens of the Procera AllCeram coping material were prepared and the veneering porcelain (AllCeram Porcelain) a low fusing surface porcelain was applied according to manufacturers' specifications. Two specimen configurations were tested: 1) 1.5 mm thick aluminum oxide coping material with 0.5 mm AllCeram Porcelain, and 2) 1.0 mm thick aluminum oxide coping material with 1.0 mm AllCeram Porcelain. Half the samples were tested with the specimens in tension and the other half tested in compression. Five specimens of each group were tested using a biaxial flexural test (similar to ASTM F394-78 and ISO/DIS 6872 tests). The strength is reported as the apparent strength (as compared to the true strength) because the elastic properties are not uniform through the specimen thickness in these two layer samples (which is required by the standard equations). However, the apparent strength represents the effective strength of the veneered coping material. ANOVA and Scheffé tests were used to calculate the significance of differences at p<0.05. The Weibull moduli was calculated to describe the variation in flexural strength. The thickest AllCeram Porcelain (1.0 mm) tested with the veneering porcelain on the tension side showed the lowest apparent strengths (158 MPa) while the thinner AllCeram Porcelain (.5 mm) tested with the veneering porcelain on the compressive side showed much higher strength (415 MPa). The other samples showed intermediate values. The lowest Weibull moduli were observed when the samples were tested with the porcelain in tension.
Conclusions: The Procera AllCeram specimen with a coping thickness of 1.5 mm and 0.5 mm AllCeram Porcelain demonstrated a flexural strength of 415 MPa with the veneering porcelain in compression.

Abstract: The purpose of this investigation was to compared the in vitro fracture resistance of Procera AllCeram crowns fabricated with two different coping thicknesses. A stainless steel master die was milled to the dimensions of a simulated crown preparation for a maxillary premolar according to the requirements for the Procera AllCeram crown. The die was replicated in a material which has a similar modulus of elasticity as dentin. Copings were fabricated for two groups of nine (9) samples which formed the experimental populations. One group received copings of 0.5 mm thickness, while the other group received copings 0.7 mm in thickness. AllCeram Porcelain was added to each coping to create a crown with an overall axial wall thickness of 1.0 mm and an occlusal thickness of 2.5 mm. To simulate a cemented condition the internal surface of each crown was air abraded with 50 µm aluminum oxide under a pressure of 80 psi, silanated and cemented to the tooth replica (die) using a resin cement (Panavia 21, J. Morita USA Inc., Tustin, CA). Each crown specimen was held under a load of 5.0 Kg for 10 minutes while the cement was allowed to set, and the crowns and tooth simulations were stored for 24 hours in 100% humidity prior to being placed in the Instron machine and loaded till fracture at a crosshead speed of 0.5 mm/sec. A mean fracture load for the crowns with a coping thickness of 0.5 mm at 225 Kg was measured, while the 0.7 mm coping fractured under a mean load of 220 Kg.
Conclusions: From the analysis of these data it was concluded that no significant difference in the fracture resistance of Procera AllCeram crowns was found with coping thicknesses of 0.5 mm and 0.7 mm.

Abstract: The objective of this study was to investigate the effect of Kinetic Cavity Preparation (K.C.P.) abrasive on shear bond strength of resin cement to an aluminum oxide coping material used in the manufacturing of the Procera AllCeram crown. Forty (40) aluminum oxide coping material samples were fabricated by Procera Sandvik, Stockholm, Sweden. The samples were divided into four groups of 10 samples each for testing the bond strength under four different surface abrasion treatments: 1) air abrasion with 25 mm aluminum oxide at medium speed (120 psi), 2) air abrasion with 25 mm aluminum oxide at high speed (160 psi), 3) air abrasion with 50 mm aluminum oxide at medium speed (120 psi), and 4) air abrasion with 50 mm aluminum oxide at high speed (160 psi). A 4.0 mm area was isolated on the treated surfaces of each aluminum oxide sample, and a resin cement (Panavia 21) was applied to this area according to the manufacturers instructions. After the cement had set, the samples were kept at 100% humidity for seven (7) days. The samples were subjected to a shear load using the Instron machine at a crosshead speed of 0.5 mm/min. The results were: Treatment 1 (18.27 ± 3.89 MPa),Treatment 2 (21.46 ± 4.28 MPa), Treatment 3 (20.13 ± 4.35 MPa), and Treatment 4 (18.09 ± 5.18 MPa).
Conclusions: A two-way ANOVA indicated no significant difference at p < 0.05 in the shear bond strengths of the resin cement under any of the four treatment conditions tested. More important than the surface treatment method was the high bond strength with the resin cement Panavia 21.

Abstract: The purpose of this study was to examine the shear bond strength of four known luting agents when used with the Procera AllCeram coping to determine if one cement was better than an another for the Procera system. Forty (40) Procera AllCeram aluminum oxide samples (CeraOne blanks) were fabricated by Procera Sandvik in Stockholm, Sweden. The samples were divided into four groups of 10 samples each and the aluminum oxide surface was air abraded (sandblasted) using 50 mm aluminum oxide at 80 psi and the microetcher. Following surface preparation, each group received one of the following four luting agents: 1) IPS Empress (Ivoclar North America, Inc., Amherst, N.Y.), 2) C & B Metabond (Parkel, Farmingdale, NY) 3) Enforce (L.D., Caulk / Dentsply International Inc., Milford, DE.), and 4) Panavia 21 EX (Kurary Co., L.T.D., Osaka, Japan). Each of the samples were bonded according to manufacturers' recommendations and using the recommended silanating agents. After the cement had set, the samples were kept at 100% humidity for seven (7) days. The aluminum oxide samples were then subjected to a shear load using the Instron machine at a crosshead speed of 0.5 mm/min. The results were: Empress (8.84 ± 2.95 MPa), C & B Metabond (10.77 ± 1.55 MPa), Enforce (11.99 ± 3.11 MPa), and Panavia 21 (16.81 ± 4.02 MPa).
Conclusions: The analysis of variance demonstrated a significant difference in bond strength between Panavia 21 and the other resin cements, and no differences were found between the other three cements. Clearly, the resin cement Panavia 21 demonstrated a higher bond strength when cemented to the Procera AllCeram aluminum oxide coping material.

Abstract: The purpose of this project was to determine if the luting agent has any effect on the fracture resistance of the Procera AllCeram restoration. A stainless master model was milled to the dimensions of a porcelain crown preparation for a maxillary premolar. The master model was then replicated to produce twenty-seven (27) dies in a material with a modulus of elasticity similar to dentin. Procera AllCeram copings with a thickness of 0.5 mm were fabricated for the twenty-seven dies. AllCeram Porcelain was added to the copings to produce an axial wall thickness of 1.0 mm and an occlusal thickness of 2.6 mm. The dies and their respective crowns were then divided into three groups of nine each, and the internal surfaces of the crowns were air abraded with 50 mm aluminum oxide particle at 80 psi. The abraded surfaces were then silanated prior to cementation. The three luting agents tested were zinc phosphate, a resin cement (Panavia 21), and a hybrid glass-ionomer cement (Duet). All crowns were cemented according to the manufacturers recommendations and under a load of 5 kg for 10 minutes. After the cement had set, the samples were held in 100% humidity for 24 hours prior to testing, then placed in an Instron machine and loaded until fracture at a crosshead speed of 0.5 mm/sec.
Conclusions: Panavia 21 (225 kg) and Duet (214.6 kg) had significantly higher load to fracture values than the zinc phosphate (153.5 kg) cement. However, all of the values for the different luting agents were clinically acceptable.

Abstract: The marginal adaptation of cemented restorations that range from 25 to 40 µm has been suggested as a clinical goal, however, marginal openings in this range are rarely achieved clinically. The American Dental Association (ADA) Specification No. 8 states that the luting cement film thickness for a crown restoration should be no more than 25 µm when using a Type I luting agent, or 40 µm when the luting agent is Type II. McLean and von Fraunhofer examined 1000 crowns clinically over a period of five years and concluded that a marginal opening of <120 µm was clinically acceptable. 21 Studies of other all-ceramic crown systems have reported mean marginal openings that were often less than 155 µm, but ranged from zero to 313 µm.22,23 It would seem appropriate that a marginal opening between 40 µm and 100 µm would be considered clinically acceptable by most practitioners. The purpose of this study was to determine the precision of fit of a Procera AllCeram crown. Five patient simulation models were created having a maxillary right first premolar and first molar samples for measuring the precision of fit of the Procera AllCeram crown. The tooth preparations were standardized using: (1) a total convergence angle of 10 degrees, (2) chamfer margins 1.3 to 1.5 mm circumferentially, and (3) occlusal reduction of 2.0 mm. Procera AllCeram copings were fabricated and the anatomical features of the tooth were built-up by the ceramic technician using the AllCeram Porcelain. To measure the precision of fit, the crown was cemented to its die using a silicone impression material as the luting agent (Extrude Light-bodied, Kerr Mfg. Co., Romulus, MI). When the silicone had set, the crown was carefully removed from its die leaving the silicone intact on the die. A 12.0 millimeter square area that completely covered the silicone material and die was digitized using a laser digitizer and an x- and y-axis measurement matrix of 100 µm between each data point. When digitizing was completed, the silicone luting agent was removed from the die and the die was again digitized without removal from the digitizer. The database created by this procedure provided measurements of: (1) the physical dimension of the three-dimensional space (luting space) between the crown and the die and (2) the topography of the internal surface of the crown. The marginal opening (MO) and internal adaptation of the crowns were determined from the data base. The mean gap dimension at MO for the molar was 62 µm (SD 49) with lower and upper 95 percent confidence internals (CIs) of 55 and 70 µm, respectively. The premolar mean MO was 55 µm (SD 51) with lower and upper 95 percent CIs of 48 µm and 63 µm, respectively. The MOs for both groups of artificial crowns were well below the 100 µm selected as the standard for a clinically acceptable crown. All other internal measurements between the die and the internal surface of the coping were beneath the 100 µm as well.
Conclusions: Based on this investigation, a Procera AllCeram crown can be treatment planned with confidence knowing that MO will consistently be less than 70 µm.

Abstract: The purpose of this study was to examine the wear of enamel against samples of: 1) Procera AllCeram aluminum oxide coping material veneered with the AllCeram Porcelain, 2) feldspathic porcelain Ceramco (Ceramco, Inc., Burlington NJ), and 3) Olympia gold (JF Jelenko and Co., Armonk, NY). The enamel samples were prepared from recently extracted human teeth as abraders approximately 3.0 mm in diameter. These enamel abraders were polished flat using 600-grit silicon carbide paper, and then attached to the end of a steel rod for positioning in a specially designed wear machine. Once positioned in the wear machine, the enamel sample was further polished flat using 3.0 µm variance silicon carbide paper while the abrader was rotating in the wear machine. A hole was drilled in the center of the enamel abrader that would function as a reference for measurements prior to, and following the wear test and the abraders were ultrasonically cleaned and stored at 100% relative humidity. Disk shaped samples of the Ceramco porcelain and the Olympia gold were prepared by a commercial laboratory familiar with their use, while the Procera AllCeram aluminum oxide samples were prepared by Procera Sandvik and the AllCeram porcelain was applied to the surface of the coping material by a ceramist familiar with this technique. The Procera and Ceramco sample disks were polished flat using 600-grit silicon carbide paper, ultrasonically cleaned and then autoglazed. The Olympia gold disks were polished flat to 1.0 mm variance with a diamond pastes and then cleaned ultrasonically. Each disk was then secured in a plastic well for positioning in the wear machine. The enamel abrader was brought into contact with the material sample under a load of 1.0 pound during 10,000 rotational cycles in human saliva. For wear measurements, impressions were made of the enamel abraders and their reference holes using a polyvinyl siloxane impression material prior to, and following the wear test. These impressions were sectioned along the long axis of the steel rod holding the enamel abrader, and the wear was determined by comparing the depth of the reference holes. All measurements were made with a stereomicroscope (Zeiss, West Germany) at 64x magnification. Measurements were made on the disk samples at four locations on the circular path that the abrader had traveled using a profilometer (Surfanalyzer System 400, Federal Products Corp., Providence, R.I.). Vertical loss was calculated and an average of the four readings was used for data analysis. The wear data were evaluated by analysis of variance (ANOVA) and Scheffe's test (p = 0.001). The mean wear of the enamel abraders when opposed by the Olympia gold (9.0 µm), the AllCeram Porcelain (60 µm), and Ceramco porcelain (230 µm) were significantly different (p < 0.001). Significant differences were also found when the wear of the disk samples were compared. The wear of Olympia gold (0.32 µm) was significantly different than the wear of the AllCeram Porcelain (4.3 µm) and Ceramco porcelain (3.7 µm).
Conclusions: This study showed that feldspathic porcelain was more abrasive to the enamel, while the AllCeram Porcelain was more compatible with the enamel. To know that the Procera AllCeram porcelain occlusal surface will not destroy the opposing natural tooth is reassuring to the clinician. A sacrifice of greater wear of the Procera AllCeram crown is the trade-off for the reduced enamel destruction, however, this tradeoff is a clear benefit to the patient. In vivo research on the wear characteristics of Procera AllCeram crowns is in progress that hopefully will demonstrate this same advantage in the clinical environment.

Abstract: The purpose of this study was to determine the wear of the Procera AllCeram coping material should it becomes exposed to the oral environment. Fifteen human enamel samples 3.0 mm in diameter were polished with 600 grit silicone carbide (SiC) paper, 3.0 µm Sic film, and thoroughly cleaned. A small reference hole to be used in wear measurements was placed within the center of each enamel sample. The fifteen enamel samples were divided into three groups each containing five samples. Fifteen Procera aluminum oxide disks 10.0 mm in diameter were fabricated to form the coping samples. The aluminum oxide disks were also divided into three groups; 5 samples were roughened with a diamond bur to form one group, 5 were roughened and then polished with Dialite polishing points (Braessler), 5 were roughened, polished and then glazed but not polished. All samples were ultrasonically cleaned before being placed in the wear machine. An aluminum oxide disk was aligned opposing a human enamel sample and a load of 453.6 g was applied axially. The enamel sample under load and in contact with the alumina oxide disk was rotated for 10,000 cycles in the wear machine in the presence of human saliva. Wear was determined by measuring the depth of the enamel reference hole prior to, and following the 10,000 wear cycles. The enamel wear when opposed by the aluminum oxide roughened disk ranged from 90-180 µm, while the enamel wear when opposed by the roughened and polished disk ranged from 15-60 µm. When the aluminum oxide disk was glazed and not polished, the enamel wear ranged from 210-313 µm.
Conclusions: From these data it was determined that if the Procera aluminum oxide coping should become exposed in the oral environment, it will not cause excessive wear to opposing enamel if it is polished with suitable porcelain polishing points.

Abstract: The purpose of this study was to determine if the color of the Procera AllCeram restoration will remain stable over time. Twenty (20) Procera aluminum oxide disks, 16.0 mm in diameter and 2.0 mm thick, were used as the substrate to which 2.0 mm of AllCeram Porcelain was added. A colorimeter (Minolta Chroma-Meter CR-321, Minolta Camera Co., LTD Japan) was used to determine the baseline color readings of Yxy and L*a*b* values recorded prior to placement of the discs in the Weather-O-Meter. During the accelerated aging process, the samples were exposed to light, heat, and changes in humidity for 300, 600, 900, and 1200 hours. The total time of 1200 hours was considered equivalent to five (5) years in the oral environment. At each time interval, the samples were removed from the Weather-O-Meter and Yxy and L*a*b* values were recorded using the colorimeter. From the color data a E (or color change) was calculated as a single measure of the color comparison for each sample prior to aging and at the end of each of the four aging test periods. A E value greater than 3.7 has been reported as necessary for observable color changes to be detected by the human eye.
Conclusions: In this study, the E value after 300 hours was 1.41 (sd 1.10) and for 1200 hours of accelerated aging 1.03 (SD 0.62) indicating that no clinically detectable color change was measured for the AllCeram veneering porcelain.

Abstract: The reported density of the Procera AllCeram coping material of 99.7% has raised the question of translucency or the passage of light through the coping to produce an esthetic crown. At the same time a concern for the potential transparency of the coping which would require opaquing the underlying tooth to prevent the show through of any substructures with discoloration. The translucency of the coping can be demonstrated by simply placing a light source inside the coping and seeing the illumination or translucency of the light source showing through the coping. The purpose of this study was to determine the transparency of the coping material and is overall masking ability. Tooth preparation models were milled from white plaster and black graphite, and copings were fabricated for each of these models in varying thicknesses (0.4, 0.6, 0.8, and 1.2 mm). The masking ability of the coping samples was determined by measuring the reflectance from the occlusal surface of the preparation models, and the occlusal surfaces of the copings placed on the models using the colorimeter (Minolta Chroma-Meter CR-321). The data output from the colorimeter was recorded from an area 3.0 mm in diameter on the occlusal surface of both the models, and the models plus the copings as CIE L*a*b* color coordinate values.
Conclusions: The L*a*b* values of the various copings measured on black graphite and white plaster exhibited no significant differences when the wall thickness was increased. From this investigation it was concluded that additional laboratory procedures to eliminate the unwanted influences of any dark underlying materials present beneath a Procera AllCeram crown is unnecessary.

Abstract: The purpose of this investigation was to examine the in-vitro tensile strength of four bonded to dentin all-ceramic systems: IPS-Empress, OPC, In-Ceram and Procera AllCeram using the recommended resin cement. Further to investigate the effects of thermocycling on the tensile strength and to evaluate the mode of fracture of the failed specimens with an Optical Microscopy. Twenty wax patterns were sent to each manufacturer in order to have substrates fabricated for each of the ceramic systems. Dentin surfaces of natural human teeth were prepared for etching and bonding of resin cements and ceramic systems. The specific cement chosen for each ceramic system was determined by the manufacturers recommendation. In the case of Procera the cement chosen was Panavia 21 EX based upon previous studies. After bonding the specimens were placed in a Instron testing machine and subjected to tensile forces until failure. One half of the samples were without thermocycling and one half with thermocycling. The load to failure was computed as was the mechanism of failure of the resin bond.
Conclusions: It was concluded that: 1) No statistically significant difference was found in the tensile bond strengths of Empress, In-Ceram and Procera bonded to dentin, under no thermocycled conditions, 2) The tensile bond strengths of OPC/LUTE-IT to dentin under thermocycling and non-thermocycling conditions, were significantly lower than the bond strengths of the other porcelain systems used in this study, 3) Thermocycling had no effect in the mode of failure of the specimens, and 4) The most likely failure point in the bonding of porcelain to dentin is in the resin cement.