Qualitative SEM analysis of fracture surfaces for dental ceramics and polymers broken by flexural strength testing and crown compression.

Purpose: To perform qualitative analysis using scanning electron microscopy (SEM) of fracture surfaces for ceramic and polymeric dental materials broken via standardized flexural and crunch-the-crown (CTC) tests.

Materials And Methods: Zirconia, glass-ceramic, and polymeric (Trilor; TRI, Juvora; JUV, Pekkton; PEK) materials were loaded using crowns for CTC tests, discs (zirconia and glass-ceramics) for piston-on-3 ball tests, bars (polymer) for 3-point bend tests, and bars (zirconia, glass-ceramics) for 4-point bend tests. SEM was used to characterize the fracture surfaces and identify fracture surface features (e.

An experimental study of flexural strength and hardness of zirconia and their relation to crown failure loads.

Statement Of Problem: Dental zirconia is often marketed and selected for restorative use based upon the biaxial flexural strength of prefabricated specimens (disks) without considering other mechanical and physical properties.

Purpose: The purpose of this in vitro study was to test whether 4-point flexural strength, biaxial flexural strength, and/or hardness may correlate with failure loads for crowns made of different zirconia materials.

Material And Methods: Three brands of zirconia (BruxZir, Cercon, and Katana) were used to fabricate anatomically contoured crowns, rectangular bars, and circular disks.

Effect of liner and porcelain application on zirconia surface structure and composition.

The purpose of this study was to determine if there is an effect of liner and porcelain application (layering and pressing techniques) on the surface of yttria-stabilized tetragonal zirconia polycrystals (Y-TZP), which were exposed to permutations of liner, layered porcelain, and pressed porcelain. Scanning electron microscope (SEM)/energy dispersive spectroscope (EDS) was used to identify changes in composition and microstructure after removing liner and porcelain with hydrofluoric acid. Simulated aging was also conducted to determine the effect of liner and porcelain on low-temperature degradation.

Correlation of flexural strength of coupons versus strength of crowns fabricated with different zirconia materials with and without aging.

Background: The purpose of this study was to determine the presence of a correlation between flexural strength and simulated crown strength; a correlation between crown strength and mode of fracture; an effect of aging on the flexural strength; and an effect of aging on the crown strength.

Methods: Two hundred forty zirconia specimens were fabricated with 2 different designs, fully contoured crown shape specimens (n = 120) and rectangular coupons (n = 120), to provide 10 specimens each of 6 brands of zirconia (Lava Plus High Translucency [3M ESPE], Argen HT [Argen Corp], Zirlux [Ardent], BruxZir [Glidewell Laboratories], ZenoStar [Wieland Dental], and DDBioZX(2) [Dental Direkt]). One-half of each sample type was given a severe, simulated low-temperature aging treatment.

Effect of grain size on the monoclinic transformation, hardness, roughness, and modulus of aged partially stabilized zirconia.

Objective: Low-temperature-degradation (LTD) has been reported to cause property changes in yttria-tetragonal zirconia polycrystals (Y-TZP). The current study measured monoclinic phase transformation of Y-TZP with different grain sizes and corresponding property changes due to artificial aging.

Null Hypothesis: the grain size of aged Y-TZP will not influence its transformation, roughness, hardness or modulus of elasticity.

Evaluation of zirconia-porcelain interface using X-ray diffraction.

The aim of this study was to determine if accelerated aging of porcelain veneering had an effect on the surface properties specific to a tetragonal-to-monoclinic transformation (TMT) of zirconia restorations. Thirty-six zirconia samples were milled and sintered to simulate core fabrication followed by exposure to various combinations of surface treatments including as-received (control), hydrofluoric acid (HF), application of liner plus firings, application of porcelain by manual layering and pressing with firing, plus accelerated aging. The quantity of transformed tetragonal to monoclinic phases was analyzed utilized an X-ray diffractometer and one-way analysis of variance was used to analyze data.

Effect of imaging powder and CAD/CAM stone types on the marginal gap of zirconia crowns.

Objective: To compare the marginal gap using different types of die stones and titanium dies with and without powders for imaging.

Methods: A melamine tooth was prepared and scanned using a laboratory 3-shape scanner to mill a polyurethane die, which was duplicated into different stones (Jade, Lean, CEREC) and titanium. Each die was sprayed with imaging powders (NP, IPS, Optispray, Vita) to form 15 groups.

Phase transformation of dental zirconia following artificial aging.

Aims: Low-temperature degradation (LTD) of yttria-stabilized zirconia can produce increased surface roughness with a concomitant decrease in strength. This study determined the effectiveness of artificial aging (prolonged boiling/autoclaving) to induce LTD of Y-TZP (yttria-tetragonal zirconia-polycrystals) and used artificial aging for transformation depth progression analyses. The null hypothesis is aging techniques tested produce the same amount of transformation, transformation is not time/temperature dependent and LTD causes a constant transformation throughout the Y-TZP samples.

The failure load of CAD/CAM generated zirconia and glass-ceramic laminate veneers with different preparation designs.

Statement Of Problem: Fracture of feldspathic porcelain laminate veneers represents a significant mode of clinical failure. Therefore, ceramic materials that withstand a higher load to fracture, especially for patients with parafunctional habits, are needed.

Purpose: The purpose of this study was to examine the correlation of material (zirconia, TZP, glass-ceramic, IEC, and feldspathic porcelain, FP) design (incisal overlapped preparation, IOP, and three-quarter preparation, TQP), and fracture mode to failure load for veneers supported by composite resin abutments.

Recent advances in the development of GTR/GBR membranes for periodontal regeneration--a materials perspective.

Unlabelled: Periodontitis is a major chronic inflammatory disorder that can lead to the destruction of the periodontal tissues and, ultimately, tooth loss. To date, flap debridement and/or flap curettage and periodontal regenerative therapy with membranes and bone grafting materials have been employed with distinct levels of clinical success. Current resorbable and non-resorbable membranes act as a physical barrier to avoid connective and epithelial tissue down-growth into the defect, favoring the regeneration of periodontal tissues.

Evaluation of the optical properties of CAD-CAM generated yttria-stabilized zirconia and glass-ceramic laminate veneers.

Statement Of Problem: When feldspathic porcelain (FP) laminate veneers are used to mask tooth discoloration that extends into the dentin, significant tooth reduction is needed to provide space for the opaque layer and optimize the bonding of the restoration.

Purpose: The purpose of this study was to investigate the color effect of trial insertion paste (TP), composite resin abutment (CRA), and veneer regions on the optical properties of feldspathic porcelain (FP), yttria-stabilized zirconia (Y-TZP), and IPS e.max CAD HT (IEC) veneers.

Influence of low-temperature environmental exposure on the mechanical properties and structural stability of dental zirconia.

Purpose: The effect of dental fabrication procedures of zirconia monolithic restorations and changes in properties during low-temperature exposure in the oral environment is not completely understood. The purpose of this study was to investigate the effect of procedures for fabrication of dental restorations by low-temperature simulation and relative changes of flexural strength, nanoindentation hardness, Young's modulus, surface roughness, and structural stability of yttria-stabilized zirconia.

Materials And Methods: A total of 64 zirconia specimens were prepared to simulate dental practice.

Acellular dermal matrix graft: synergistic effect of rehydration and natural crosslinking on mechanical properties.

This investigation studied how the incorporation of a natural crosslinking agent, genipin (Gp), into the AlloDerm® (AD) rehydration protocol affects the biomechanical properties and the stability of the collagenous matrix. AD is a minimally processed, noncrosslinked, freeze-dried collagen-based graft. Samples were immersed in a saline solution for 5 min and then randomly assigned for further rehydration (30 min) into three groups, according to the crosslinking agent: G1-control (saline), G2-1 wt % genipin, and G3-1 wt % glutaraldehyde.

A novel spatially designed and functionally graded electrospun membrane for periodontal regeneration.

A periodontal membrane with a graded structure allows tailoring of the layer properties to design a material system that will retain its physical, chemical and mechanical characteristics for a period long enough to optimize periodontal regeneration. In this work a novel functionally graded membrane (FGM) was designed and fabricated via sequential multilayer electrospinning. The FGM consists of a core layer (CL) and two functional surface layers (SLs) interfacing with bone (nano-hydroxyapatite, n-HAp) and epithelial (metronidazole, MET) tissues.

Freeze-dried acellular dermal matrix graft: effects of rehydration on physical, chemical, and mechanical properties.

Objectives: To test the effect of rehydration time over the range prescribed in the manufacturer's protocol on (1) the biomechanical properties and on (2) the recovery and stabilization of the collagenous matrix of AlloDerm.

Methods: A sterile dish containing warm saline solution was prepared, and samples rehydrated for 5 min. Subsequently, three other dishes with the solution were prepared and samples assigned into three groups according to the total rehydration time: 10 min (G1), 20 min (G2), and 40 min (G3).