Chipping Resistance Research Articles

UDDEHOLM CALDIE

Abstract Uddeholm Caldie is a high-carbon, chromium-molybdenum-vanadium alloy cold-work tool steel that is produced using the electroslag remelting (ESR) process. It is suitable for short and medium run tooling in applications where a combination of very high chipping resistance and compressive strength is required. This datasheet provides information on composition, physical properties, hardness, and elasticity. It also includes information on wear resistance. Filing Code: TS-785. Producer or source: Uddeholms AB (a voestalpine company).

Effect of Aging and Pre-sintering Surface Treatment of Zirconia Cores on Chipping of Veneered Zirconia Crowns

Abstract Aim: This study was conducted to study the effect of surface treatment of zirconia cores by nanosilica before sintering on veneers chipping and to evaluate the effect of aging in terms of thermocycling and cyclic loading on veneer chipping before and after surface treatment. Method: Model acrylic tooth was prepared for zirconia crown, twenty silicon impressions were recorded and epoxy resin dies were produced. Twenty zirconia cores were fabricated by CAD/ CAM system and divided into 2 groups (n=10) group I was the control which veneered with porcelain by hand layering technique while group II was subjected to treatment by nanosilica slurry before sintering then veneered and fired to produce crowns. The crowns were cemented by resin cement on their epoxy dies and they were subjected to 10000 thermocycles and 10000 cyclic loads. All crowns were loaded till chipping of veneer layer then the chipped surfaces were examined by SEM/EDX. Results: There was no significant difference in chipping resistance between group I and group II. Conclusions: Treatment of zirconia cores by nanosilica before sintering has no effect on chipping resistance of the veneer layer after subjecting to aging process (thermocycling and cyclic loading).

Altering of optical and mechanical properties in high-translucent CAD-CAM resin composites during aging

ObjectivesThis study was aimed to monitor the alteration of the optical and mechanical properties of high-translucent CAD-CAM resin composites (HTRCs) during aging. Corrections for the measured transmitted irradiance are proposed. MethodsIndividual sets (n = 6) of plane-parallel test specimens (0.5-, 2- and 4-mm) of seven HTRCs were prepared. The optical properties (absorbance, transmittance, reflectance, linear absorption coefficient, and transmitted irradiance) were assessed by regular spectrometric testing methodologies and were corrected to account for light reflection. Several edge chipping resistance parameters (edge force at different edge distances, edge chip resistance), as well as mechanical parameters obtained from depth-sensing indentation (Vickers hardness, indentation modulus, creep, elastic and plastic indentation work), were considered. Aging involved storage for two weeks in artificial saliva at 37 °C, followed by thermal aging (10,000 thermocycles, 5 °C–55 °C) and storage in alcohol/water solution, employing non-aged specimens as a reference. Filler size and shape were analyzed by scanning electron microscopy. ResultsReflectance varied from 11% to 27% and was altered during aging. Linear absorption coefficients of 0.281 mm−1 to 0.369 mm−1 were obtained for non-aged specimens, with very low changes during aging. A difference between the true and measured irradiance was identified to decrease exponentially with the specimen’s thickness. The impact of HTRC was stronger than the impact of aging. ConclusionsReflectance determined by spectrometric analysis was identified as a possible criterion to estimate surface degradation during aging. Corrections for thin and translucent specimens are needed when determining transmitted irradiance through restorations. Depth-sensing indentation was evidenced as the most discriminatory testing methodology for aging, but the results do not correlate with the edge chipping resistance parameters.

General regularities of edge chipping tests for ceramics in the case of conical indenters with different rounding tip

The results of a combined numerical and experimental research of mechanical properties of ceramics by the edge chipping test of specimens are presented. The edge chipping tests were carried out by means of conic diamond indenters with spherical tip radii of 100 μm, 200 μm and 400 μm. The numerical analysis of the fracture resistance of ceramic materials has been performed by means of finite element modeling (on the basis of ANSYS software) of the contact interaction between the indenter and the specimen. The principle of the geometric similarity has been employed to establish the correct parameters of the basic distances for the edge chipping tests (upper and lower limits) as well as to construct a unified curve of the edge chipping resistance for indenters with various tip radii. The unified curve of the edge chipping resistance is assumed to be a mechanical characteristic of brittle materials. This curve gives the possibility to compare the results of edge chipping tests of ceramic materials obtained using indenters with different tip radii.

Influence of residual thermal stresses on the edge chipping resistance of PFM and veneered zirconia structures: Experimental and FEA study

ObjectiveChipping fractures of the veneering porcelain are frequently reported for veneered all-ceramic crowns. In the present study, the edge chipping test is used to measure the toughness and the edge chipping resistance of veneered zirconia and porcelain-fused-to-metal (PFM). The aim is to describe an edge chipping method developed with the use of a universal testing machine and to verify the accuracy of this method to determine the influence of residual thermal stresses on the chipping fracture resistance of veneering porcelain. A finite element analysis (FEA) was used to study the residual stress profiles within the veneering porcelain. MethodsVeneered zirconia and PFM bar specimens were subjected to either a fast or a slow cooling protocol. The chipping resistances were measured using the edge chipping method. The load was applied in two different directions, in which the Vickers indenter was placed in the veneering porcelain either parallel or perpendicular to the veneer/framework interface. The mean edge chipping resistance (ReA) and fracture toughness (KC) values were analysed. ReA was calculated by dividing the critical force to cause the chip by the edge distance. KC was given by a fracture analysis that correlates the critical chipping load (FC) regarding edge distance (d) and material toughness via KC=FC/(βd1.5). ResultsThe ReA revealed similar values (p>0.005) of chipping resistance for loads applied in the parallel direction regardless of framework material and cooling protocol. For loads applied in the perpendicular direction to the veneer/framework interface, the most chip resistant materials were slow cooled veneered zirconia (251.0N/mm) and the PFM fast cooled (190.1N/mm). KC values are similar to that for monolithic porcelain (0.9MPa.√m), with slightly higher values (1.2MPa.√m) for thermally stressed PFM fast cooled and veneered zirconia slow cooled groups. SignificanceThe developed and reported edge chipping method allows for the precise alignment of the indenter in any predetermined distance from the edge. The edge chipping method could be useful in determining the different states of residual thermal stresses on the veneering porcelain.

Edge chipping resistance of ceramics bonded to a dentine analogue

ObjectiveTo evaluate the edge chip resistance (ReA) of two CAD/CAM monolithic ceramics (GC- IPS e.max CAD and YZ- Zenostar Zr Translucent) bonded to a dentine analogue substrate (G10- NEMA G10). MethodsPlate-shaped specimens were prepared from GC and YZ ceramics and were either bonded (B) to G10 or attached (NB) to a universal testing machine for edge chipping test. Samples from all groups (GC-B, GC-NB, YZ-B and YZ-NB) were indented (n = 25) at different edge distances (d = 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 mm) to produce chips. Force (F, in N) and d values were recorded and ReA (in N/mm) were calculated. Data were statistically analyzed using Pearson´s correlation, Student t, ANOVA and Tukey tests (α = 0.05). ResultsA strong correlation (R ≥ 0.98) was found between F and d values for all groups. ReA values increased with increasing d, irrespective of ceramic type (GC and YZ) or fixation method (B and NB). Significant differences (p < 0.05) in mean ReA values were found between B and NB ceramics at lower d (0.1–0.3 mm) that did not persist (p > 0.05) at greater d (0.5 and 0.6 mm), meaning, bonding (B) to G10 protected both materials against chipping close to the edge. ConclusionsThe larger the distance from the occlusal contact to the restoration edge, the greater the chance to avoid ceramic chipping in monolithic restorations. For d ≤ 0.3 mm, such F vs d relation is less critical for edge resistance of YZ and for resin bonded monolithic ceramics.

Maturation of restorative glass ionomers with simplified application procedure

ObjectivesRecent developments in glass ionomers (GI), including improved mechanical properties, allow the application of a filling without using a varnish to protect the initial setting reaction. Thus, this study aims to monitor the mechanical behavior of these new developments in comparison to traditional and clinically established GIs within one year of maturation by using generally accepted testing methodology along with a new test for determining chipping resistance. Materials and methodsFour GIs were characterized by assessing the variation in edge strength (ES), compressive strength (CS), Vickers hardness (HV) and indentation modulus (YHU). A special jig was constructed to examine ES, allowing a standardized positioning of the specimen during measurement to simulate clinical chipping, which is a commonly observed failure in brittle restoratives. ResultsThe properties analyzed herein progressively enhanced with maturation, but each properties followed different patterns. All applied tests were able to discriminate between different GI products and maturation stages. Depth-sensing indentation was evidenced as the most discriminatory testing methodology. Differences in chemical composition were better reflected by YHU, while the effect of maturation by HV. HV correlates moderate with CS (0.669) and ES (0.468). The correlation of YHU with the same parameters was lower (0.550 and 0.369). A very good correlation was identified between HV and YHU (0.843). ConclusionsThe new developed test was identified as reliable, sensitive to changes in the chemical composition of GIs and during maturation, easy-to-implement and may be used for ascertaining chipping resistance. The claimed improvement in mechanical properties in the absence of a protective varnish was generally confirmed.

3D Printing of Resin Material for Denture Artificial Teeth: Chipping and Indirect Tensile Fracture Resistance.

3D printing of denture artificial teeth with resin materials is worthy of study in a novel way. This study evaluated chipping and indirect tensile fracture resistance of 3D printing resin material (Dentca 3D printing denture teeth resin) compared with conventionally prefabricated resin denture teeth (Premium-8, Surpass, SR-Orthosit-PE, and Preference). One hundred tooth specimens were prepared for testing. The 3D printed tooth specimens were printed at a 50 µm layer thickness with methacrylate-based photopolymerized resin by stereolithography 3D printing. Chipping and indirect tensile fracture tests were conducted at a speed of 1 mm/min until fracture. The indirect tensile fracture loads of the 3D printed resin teeth were higher than those of Premium-8, Surpass, and SR-Orthosit-PE, and lower than those of Preference teeth. Regarding chipping resistance, the 3D printed resin teeth were not different from Surpass and SR-Orthosit-PE, and were lower than Premium-8 and Preference teeth. The 3D printed resin teeth exhibited vertical fracture of the loaded cusp without deformation in chipping. The 3D printed resin teeth showed simultaneous fracture of two cusps in indirect tensile fracture, unlike other teeth. The results of this study suggest that 3D printing technology using resin materials provides adequate fracture resistance for denture artificial tooth use.

Influence of crown design and material on chipping-resistance of all-ceramic molar crowns: An in vitro study.

All-ceramic restorations have become popular and the trend is ongoing. However, the incidence of chipping within the veneering layer has been a commonly reported failure in clinical practice. The aim of this in vitro study was to evaluate the effect of ceramic crown design (monolithic vs bi-layered) and material on the chipping resistance of molar crowns submitted to compressive cyclic loading. Fifty identical epoxy resin replicas of a mandibular first molar with crown preparation were divided into 5 groups (n = 10) as follows: the MLD group - monolithic CAD/CAM lithium-disilicate glass-ceramic (LDGC) crowns; 30 zirconia cores were veneered with either feldspathic porcelain by hand-layering technique (ZHL) or by heat-pressing technique (ZVP), or with milled LDGC veneers and subsequently fused to the cores (ZLD); 10 porcelain-fused-to-metal (PFM) crowns acted as a control group. All crowns were cemented using Panavia® F2.0 resin cement (Kuraray Dental, Tokyo, Japan). After storage in water at 37°C for 1 week, the specimens were subjected to compressive cyclic loading at the mesiobuccal cusp which was tilted at 30°. A load cycle of 50-450 N was used and specimens were maintained in an aqueous environment throughout 500,000 cycles in a universal testing machine (Instron, Norwood, USA). The data was statistically analyzed at 5% significant level with Fisher's exact test and Kaplan-Meier survival analysis. Significant differences in survival rates of the specimens used in the groups (p < 0.001) were found. Specimens of the PFM, ZHL and ZVP groups underwent failures at different stages of the 500,000 fatigue cycles, while specimens of the MLD and ZLD groups survived the entire fatigue test. ZHL and ZVP crowns had the worst chipping-resistance, while PFM crowns performed slightly better. The Kaplan-Meier test revealed significantly higher survival rates for the MLD and ZLD specimens compared to the other 3 groups. The use of LDGC as a monolithic molar crown and as a veneer over a zirconia core resulted in superior resistance to cuspal chipping.

Comparison of dimensional stability of die stone and die silicone: An In Vitro comparative study

Background: Die silicone is used for making dies for chair side fabrication of inlays and onlays. Die silicone material is user friendly and fast setting but undergoes shrinkage. Aim: To compare the dimensional stability between Die stone and Die Silicone. Methods: A metal die with known dimensions is made. Impressions of the metal die are made with Polyether impression material. Dies are made out of Die Stone and Die Silicone. The Dimensions of the reproduced details are measured and compared. Results: Both Die Stone and Die Silicone produce comparable results. Conclusion: As Die Silicone is made of Polymer, its dimensional stability is a query. But in the study it was found that, they had similar results. With the advantages of fast setting, chipping and abrasion resistance, it would make Die Silicone a more user friendly material of choice for die making.

Cutting performance of tools made of different materials in the machining of 42CrMo4 high-strength steel: a comparative study

This research conducted a comparative study on the wear mechanisms and cutting performance of the YT15 cemented carbide tool, KY1615 ceramic tool, and Ti(C,N)-based cermet tools including T1500A, self-made TMWNC, and TMWC in the machining of 42CrMo4 high-strength steel. The results indicated that the cemented carbide tool presented severe notch wear and chipping accompanied by adhesive wear, as a result of the continuous impact from chips and workpiece burrs and the bigger friction force with the workpiece. The ceramic tool exhibited serious abrasive wear and adhesive wear with obvious crater wear on the rake face and furrow-like scratches on the flank face, due to the bigger cutting force, higher cutting temperature, and the lack of binder phase in the tool material. The wear mechanism of Ti(C,N)-based cermet tools was mainly abrasive wear with crater wear and flank wear in virtue of the smaller affinity with the workpiece material, smaller friction coefficient against steels, and better oxidation resistance. At the different cutting speeds, the comprehensive cutting performance of cermet tools was better than that of cemented carbide tools and ceramic tools, indicating the advantage of cermet tools in the machining of 42CrMo4 high-strength steel. Meanwhile, when the cutting speed was lower at 150 m/min, the comprehensive cutting performance of self-made cermet tools with better edge chipping resistance and notch wear resistance was better than that of the commercially available cermet tool.

Unified curve of the edge chipping resistance in connection with the rounding radius indenter

The results of a combined computational and experimental research into the fracture resistance of ceramic materials by specimen edge chipping are provided. The chipping was performed with conic diamond indenters that had spherical tip radii of 100, 200 and 400μm. The computational analysis was conducted on the basis of finite element modeling by means of ANSYS software. The parameters of the basic distances in an analysis of the stress, strain, and displacement fields in the chipping zone for the tests (upper and lower limit) have been established for the above-mentioned indenters in order to ensure the correct comparative assessment of the materials under research. Unified curves of edge chipping resistance of the ceramic materials have been obtained for the indenters with various spherical tip radii.

Fabrication and cutting performance of Ti(C,N)-based cermet tools used for machining of high-strength steels

Two kinds of Ti(C,N)-based cermet tools, namely TMWNC and TMWC, were fabricated for the machining of high-strength steels. This research investigated the cutting performances of both tools in terms of chip morphology, cutting force, cutting temperature, and tool wear and failure mechanisms. The results reveal that at the same cutting speed, the life of TMWC tool is longer than that of TMWNC tool with lower cutting force and higher cutting temperature than those of TMWNC tool. For TMWNC tool, at a lower cutting speed of 150m/min, the tool failure is caused by abrasive wear. And when the cutting speed increases further, the surface flaking and nose breakage occur due to the comprehensive effects of adhesive wear, abrasive wear and thermal-mechanical fatigue. While for TMWC tool, the tool wear is severe with chipping, as a result of adhesive wear and abrasive wear. The research has proven the application feasibility of TMWNC and TMWC tools in the machining of high-strength steels. The TMWNC tool with higher fracture toughness presents better edge chipping resistance, and the TMWC tool with higher hardness and hot hardness exhibits better resistance against breakage.

Effect of cycloaliphatic structure of polyester on the formability and stone-chip resistance for automotive pre-coated metals

Abstract Four types of cycloaliphatic structure of polyester were synthesized, using 1,4-cyclohexanedicarboxylic acid (1,4-CHDA). Those resins were formulated to make polyester/melamine coatings to control the formability, and to have good stone-chip resistance. The characteristics, viscoelastic behavior and flexibility of those resins were measured by DMA and tensile test. Cycloaliphatic structure of polyester coatings were coated on the cold roll steel sheets to verify formability, using a deep drawing test and stone-chip resistance was measured by the chipping resistance test at the −20 °C. Results showed that storage modulus decreased, and glass transition temperatures shifted to lower temperatures with increasing contents of cycloaliphatic structure. So, cycloaliphatic structure of 1,4-CHDA provides lower stiffness and higher softness to the polyester coating and has better elasticity than aromatic structure of IPA. To analyze the formability, we calculated F U (the forming coefficient based on strain energy) and F e (the forming coefficient based on strain). When F U and F e are both larger than 1, the polyester coatings have good formability. Also, BCHDA-20 had 0.44% of removed area by the chipping resistance test and it means that cyclic structure of 1,4-CHDA has better elasticity than aromatic structure, and can give better impact resistance From those tests, BCHDA-20 which had 20 mol of 1,4-CHDA had good formability and also showed good stone-chip resistance. So, cycloaliphatic structure provides lower stiffness and higher softness to the polyester coating for automotive pre-coated metals.

Edge chipping resistance and flexural strength of polymer infiltrated ceramic network and resin nanoceramic restorative materials

Statement of problemTwo novel restorative materials, a polymer infiltrated ceramic network (PICN) and a resin nanoceramic (RNC), for computer-assisted design and computer-assisted manufacturing (CAD-CAM) applications have recently become commercially available. Little independent evidence regarding their mechanical properties exists to facilitate material selection. PurposeThe purpose of this in vitro study was to measure the edge chipping resistance and flexural strength of the PICN and RNC materials and compare them with 2 commonly used feldspathic ceramic (FC) and leucite reinforced glass-ceramic (LRGC) CAD-CAM materials that share the same clinical indications. Material and methodsPICN, RNC, FC, and LRGC material specimens were obtained by sectioning commercially available CAD-CAM blocks. Edge chipping test specimens (n=20/material) were adhesively attached to a resin substrate before testing. Edge chips were produced using a 120-degree, sharp, conical diamond indenter mounted on a universal testing machine and positioned 0.1 to 0.7 mm horizontally from the specimen’s edge. The chipping force was plotted against distance to the edge, and the data were fitted to linear and quadratic equations. One-way ANOVA determined intergroup differences (α=.05) in edge chipping toughness. Beam specimens (n=22/material) were tested for determining flexural strength using a 3-point bend test. Weibull statistics determined intergroup differences (α=.05). Flexural modulus and work of fracture were also calculated, and 1-way ANOVA determined intergroup differences (α=.05) ResultsSignificant (P<.05) differences were found among the 4 CAD-CAM materials for the 4 mechanical properties. Specifically, the material rankings were edge chipping toughness: RNC>LRGC=FC>PICN; flexural strength: RNC=LRGC>PICN>FC; flexural modulus: RNC<PICN<LRGC<FC; and work of fracture: RNC>LRGC=PICN>FC. ConclusionsThe RNC material demonstrated superior performance for the mechanical properties tested compared with the other 3 materials.

1,3-Butadiene polymerization using binary, ternary and quaternary cobalt catalysts for high 1,4-transpolybutadiene

Binary, ternary, and quaternary cobalt catalysts for 1,4-transpolybutadiene were prepared, and their reactivity and microstructure were studied. A novel binary catalytic system composed of cobalt adduct (2-PhC6H4O)3Al·Co(OAc)2/AlR3, a ternary system of Co(2-ethylhexanoate)2/AlEt(OPh)2/AlEt3, where OPh is p-dodecyl phenolate, and a quaternary system of cobalt carboxylate·(dialkyl phosphite)/AlR3/(HOPh, p-dodecyl phenol), for high 1,4-transpolybutadiene were compared in polymerization. The binary molecular catalyst, (2-PhC6H4O)3Al·Co(OAc)2/AlR3, was designed as cobalt and aluminum bimetallic form of an intermediate structure in the active site of 1,3-butadiene polymerization for high trans configuration. The bulky ligand, 2-PhC6H4O-, promotes the syn conformation in the active site in favor of trans configuration in polybutadiene. The catalytic activity was reached to 215 kg/(Co mol h) in the quaternary catalytic system. The microstructure consisted of ca. 91% trans, 2% cis and 7% vinyl. Molecular weight was able to be controlled to ca. 700,000 with MWD ca. 2.0. Catalytic reactivity in 1,3-butadiene polymerization was in the order of quaternary > binary > ternary. Diethyl phosphite and triethyl phosphate remarkably reduce molecular weight with high reactivity. The transpolybutadiene prepared by the quaternary catalyst had the glass transition temperature of ca. −80 °C, the melting point of ca. 30 °C, and possessed a low level of crystallinity at room temperature. In the carbon black composite, transpolybutadiene showed superior abrasion resistance, tear strength and chipping resistance to natural rubber, but exhibited high compound Mooney viscosity and low moduli.

On edge chipping testing and some personal perspectives on the state of the art of mechanical testing

ObjectiveThe edge chipping test is used to measure the fracture resistance of dental restoration ceramics and resin composites. This paper focuses on the progress of evaluating chipping resistance of these materials and also on the progress of standardization of this test method. This paper also makes observations about the state of the art of mechanical testing of ceramic and composite restorative materials in general. Interlaboratory comparative studies (“round robins”) are recommended. MethodsAn edge chipping machine was used to evaluate dozens of materials including porcelains, glass ceramics, aluminas, zirconias, filled resin-composites, new hybrid ceramic-resin composites, laminated composite ceramics, and even polymethyl methacrylate based denture materials. Force versus distance data was collected over a broad range with different indenters. Several chipping resistance parameters were quantified. ResultsOlder restorative materials such as feldspathic porcelains and veneering materials had limited chipping resistance, but more modern ceramics and filled composites show significant improvements. A yttria-partially stabilized zirconia had the greatest resistance to chipping. Much of the early work on edge chipping resistance of brittle materials emphasized linear force versus distance trends obtained with relatively blunt Rockwell C indenters. More recently, trends for dental restorative materials with alternative sharper indenters have been nonlinear. A new phenomenological model with a simple quadratic function fits all data exceptionally well. It is loosely based on an energy balance between indenter work and fracture and deformation energies in the chipped material. SignificanceAlthough a direct comparison of our laboratory scale tests on idealized simple geometries to clinical outcomes has not yet been done, anecdotal evidence suggests the procedure does produce clinically relevant rankings and outcomes. Despite the variations in the trends and indenters, comparisons between materials can easily be made by chipping convenient block-shaped specimens with sharp conical 120°, Vickers, or Rockwell C indenters at a defined edge distance of 0.5mm. Broad distance ranges are recommended for trend evaluation. This work has provided important information for standardization.

The impact of luting agents and stiffness of implant-abutments on marginal adaptation, chipping, and fracture resistance of zirconia crowns

ObjectivesThis in vitro study evaluated the impact of cements and implant analogs with different e-moduli on marginal adaptation, chipping, and the fracture resistance of zirconia crowns. Methods80 crowns (Cercon, DeguDent) were manufactured for 40 polyoxymethylene (POM) and 40 titanium (Ti) one-piece implant analogs and divided into 10 groups: A, zinc oxide phosphate (Hoffmann׳s Cement, Richter&Hoffmann, Berlin, D); B, zinc oxide eugenol (Temp Bond, KerrHawe, Bioggio, CH); C, resin (Variolink II, Ivoclar-Vivadent, Schaan, FL); D, zinc oxide without eugenol (Temp Bond NE, KerrHawe, Bioggio, CH); E, glass ionomer (Ketac Cem, 3M ESPE, Seefeld, D). All samples were thermally mechanically loaded (1.2×10(6)×50N; 3000×5°C/55°C). Marginal adaptation was semiquantitatively evaluated before and after ageing with a scanning electron microscope. After ageing, intact samples underwent a fracture resistance test. ResultsThe best sealed margins before ageing were achieved with resin and zinc oxide cement and with resin after ageing. Zinc oxide samples showed the most discontinuously sealed margins after ageing and the difference between POM and Ti samples was significant only for zinc oxide. The numbers of samples failing during TCML were as follows: A(Ti − POM)=0−1; B(Ti − POM)=0−5; C(Ti − POM)=1/1; D(Ti − POM)=2−2; E (Ti − POM)=0−2. Fracture resistance test [N]: A(Ti − POM)=1181−801; B(Ti − POM)=1469−1517; C(Ti − POM)=1704−1408; D(Ti − POM)=1992−883; E (Ti − POM)=2750−1015. ConclusionsTCML reduced the number of perfectly sealed samples and increased the number of chipped samples cemented onto POM implants with zinc oxide. This study could not show any significant impact on the fracture resistance of zirconia when different cements and implant analogs were used.

Chipping fracture resistance of dental CAD/CAM restorative materials: Part I – Procedures and results

ObjectiveThe edge chipping test was used to measure the fracture resistance of CAD/CAM dental restoration ceramics and resin composites. MethodsAn edge chipping machine was used to evaluate six materials including one feldspathic porcelain, two glass ceramics, a filled resin-composite, a yttria-stabilized zirconia, and a new ceramic-resin composite material. Force versus edge distance data were collected over a broad range of forces and distances. Data were analyzed by several approaches and several chipping resistance parameters were evaluated. The effects of using different indenter types were explored. ResultsThe force versus distance trends were usually nonlinear with good fits to a power law equation with exponents usually ranging from 1.2 to 1.9. The order of chipping resistance (from least to greatest) was: feldspathic porcelain and a leucite glass ceramic (which were similar), followed by the lithium disilicate glass ceramic and the two resin composites (which were similar), and finally the zirconia which had the greatest resistance to chipping. Chipping with a Vickers indenter required 28–45% more force than with the sharp conical 120° indenter. The two indenters rank materials approximately the same way. The power law exponents were very similar for the two indenters for a particular material, but the exponents varied with material. The Rockwell C indenter gives different power law trends and rankings. SignificanceDespite the variations in the trends and indenters, simple comparisons between materials can be made by chipping with sharp conical 120° or Vickers indenters at 0.50mm. Broad distance ranges are recommended for trend evaluation.

Chipping fracture resistance of dental CAD/CAM restorative materials: Part 2. Phenomenological model and the effect of indenter type

The edge chipping resistances of six CAD/CAM dental restoration materials are analyzed and correlated to other mechanical properties. A new quadratic relationship that is based on a phenomenological model is presented. ObjectiveThe purpose of this study was to further analyze the edge chipping resistance of the brittle materials evaluated in Part 1. One objective was to determine why some force-distance trends were linear and others were nonlinear. A second objective was to account for differences in chipping resistance with indenter type. MethodsEdge chipping experiments were conducted with different indenters, including some custom-made sharp conical indenters. A new force – distance quadratic expression was correlated to the data and compared to the linear and power law trends. ResultsThe new quadratic function was an excellent fit in every instance. It can account for why some materials can be fit by a linear trend, while others can be fit by the power law trend. The effects of indenter type are accounted for variations in crack initiation and by the wedging stresses once an indentation hole is created. SignificanceThe new quadratic force – edge distance function can be used with edge chipping data for all brittle materials, not just those evaluated in this study. The data trends vary from linear to nonlinear depending upon the material's hardness, fracture toughness, and elastic modulus.