Dental composite biodeterioration in the presence of oral Streptococci and extracellular metabolic products.

Objective: Secondary caries is a primary cause of early restoration failure. While primary dental caries has been extensively researched, our knowledge about the impact of secondary caries on dental restorations is relatively limited. In this study, we examined how different clinically relevant microbially-influenced environments impact the degradation of nano-filled (FIL) and micro-hybrid (AEL) dental composites.

Relationships between composite roughness and Streptococcus mutans biofilm depth under shear in vitro.

Objective: To investigate the effect of substrate, surface roughness, and hydraulic residence time (HRT) on Streptococcus mutans biofilms growing on dental composites under conditions relevant to the oral cavity.

Methods: Dental composites were prepared with varying amounts of polishing and incubated in a CDC bioreactor with an approximate shear of 0.4 Pa.

Logistic Regression Analysis of LC-MS/MS Data of Monomers Eluted from Aged Dental Composites: A Supervised Machine-Learning Approach.

Compound identification by database searching that matches experimental with library mass spectra is commonly used in mass spectrometric (MS) data analysis. Vendor software often outputs scores that represent the quality of each spectral match for the identified compounds. However, software-generated identification results can differ drastically depending on the initial search parameters.

Stoichiometric models of sucrose and glucose fermentation by oral streptococci: Implications for free acid formation and enamel demineralization.

Objectives: The objective of this study is to develop stoichiometric models of sugar fermentation and cell biosynthesis for model cariogenic Streptococcus mutans and non-cariogenic Streptococcus sanguinis to better understand and predict metabolic product formation.

Methods: Streptococcus mutans (strain UA159) and Streptococcus sanguinis (strain DSS-10) were grown separately in bioreactors fed brain heart infusion broth supplemented with either sucrose or glucose at 37 °C. Cell mass concentration and fermentation products were measured at different hydraulic residence times (HRT) to determine cell growth yield.

The impact of long-term aging in artificial saliva media on resin-based dental composite strength.

Although salivary liquid can degrade constituents in resin-based dental composites in short-term incubations, there is a knowledge gap on how longer-term aging impacts their bulk strength. We address this through extended aging studies with resin-based dental composites in different environments. Two commercial composites (FIL and AEL) were aged aseptically at 37°C in air (A, control), artificial saliva (AS), and esterase enzyme amended AS (EAS).

The effect of esterase enzyme on aging dental composites.

We measured the push-out and diametral tensile strength of dental restorative composites following aging under environmental conditions relevant to the oral cavity; air (A), artificial saliva (AS), acidified (50 mM CH COOH, pH = 4.7) artificial saliva (AS + HAc), and AS with esterase enzyme (AS + ENZ). Cylindrical test specimens (6.

Factors affecting the internal brain drain of Saudi healthcare professionals.

Objective: To investigate factors affecting the internal brain drain of healthcare professionals in the Kingdom of Saudi Arabia.

Methods: A cross-sectional study was conducted using an anonymous self-administered online questionnaire sent to all Saudi students enrolled in healthcare profession programs in North America. The data was collected between January and March 2008 at the University of Illinois at Chicago, Chicago, Illinois, United States of America.

The effects of environment and cyclic fatigue on the mechanical properties of an indirect composite.

Objectives: The purpose of this study was to examine the flexure strength (σ) and fracture toughness (K(IC)) of three indirect dental composites (dentin, body, and incisal) with respect to loading (static and cyclic), testing environments (air and water) and ageing (0 (controls) and 6 months in air and water).

Methods: The specimens were 3 mm × 3 mm × 25 mm bars with the fracture toughness specimens having a 0.75 mm notch machined in the midspan.

Aeration prevents methyl mercury production in dental wastewater.

Although research has demonstrated that Hg is methylated in the reducing conditions of the dental clinic wastewater collection system, studies are inconclusive as to whether further methylation occurs in the aeration basin of activated sludge wastewater treatment plant (WWTP) which typically treats this waste. Given the high levels of methyl Hg reported in dental wastewater (DWW), it is important to determine whether additional methylation occurs once it enters the WWTP. To achieve this objective, we incubated DWW under conditions designed to mimic the oxidized conditions of the activated sludge aeration basin in a WWTP.

In vitro evaluation of self-etch bonding in orthodontics using cyclic fatigue.

Objective: To evaluate the bond strength of a self-etch bonding system using static loading and cyclic fatigue with shear testing. This is a two-part evaluation; the first part will evaluate shear testing, the second part tensile testing.

Materials And Methods: Bovine teeth (n = 82) were randomly distributed to either a self-etch (Transbond Plus) or total-etch (37% phosphoric-acid + Transbond XT) group.

Cyclic loading of notched dental composite specimens.

Objective: The purpose of this study was to examine the fracture toughness (K(IC)) of three direct dental composites and one indirect dental composite subject to cyclic loading.

Methods: The composites were a micro-filled (Micronew, Bisco INC., Schaumburg, IL, USA), a hybrid (Renew, Bisco INC.

Reliability of the adhesive remnant index score system with different magnifications.

Objective: To test the hypothesis that adhesive remnant index (ARI) scores show no differences when examined under different magnifications.

Materials And Methods: The study included 80 upper human premolars. Stainless steel brackets were bonded to the specimens with Transbond XT light cure adhesive and Transbond Plus Self Etch Primer (3M Unitek, Monrovia, Calif, USA).

The use of collagen cross-linking agents to enhance dentin bond strength.

Unlabelled: Type I collagen is a major component of the hybrid layer, and improvement of its mechanical properties may be advantageous during bonding procedures.

Objective: To investigate the effect of three different cross-linking agents (Glutaraldehyde [GD], Grape seed extract [GSE], and Genipin [GE]) on the tensile bond strength (TBS) of resin-dentin bonds.

Materials And Methods: Sixty-four sound human molars were collected and their occlusal surfaces were ground flat to expose dentin.

Fatigue behaviour of dental composite materials.

Objective: The intent of the project was to evaluate the fatigue behavior of particle and fiber filled dental composites that are fabricated either directly or indirectly using a notched specimen with respect to the number of cycles until failure.

Methods: The materials were five dental composites, three normally cured in the oral cavity (Restolux, Renew and Filtek Supreme), direct processing, and two laboratory produced (BelleGlass, and Tescera), indirect processing. The specimens were 3mmx3mmx25mm bars with a 0.

Multiaxial analysis of dental composite materials.

Dental composites are subjected to extreme chemical and mechanical conditions in the oral environment, contributing to the degradation and ultimate failure of the material in vivo. The objective of this study is to validate an alternative method of mechanically loading dental composite materials. Confined compression testing more closely represents the complex loading that dental restorations experience in the oral cavity.

Characterization of methyl mercury in dental wastewater and correlation with sulfate-reducing bacterial DNA.

Dental wastewater (DWW) was collected over two months from a 12-chair clinic and a single-chair office to identify conditions that may affect Hg methylation. DWW was settled for 24 h and samples were collected from the top and bottom of the supernatant to simulate a range of particles that may escape in-line traps. Total Hg spanned 5 orders of magnitude (0.

Rebonding of orthodontic brackets. Part II, an XPS and SEM study.

Objective: The hypothesis of this two-part study is that adhesive systems for bonding orthodontic brackets (ie, two self-etch primers [Transbond and M-Bond] and a conventional phosphoric acid etch [Rely-a-Bond]) would show a difference with respect to rebonded enamel surface morphology and chemical composition.

Materials And Methods: This study examined the enamel surface before and after debonding with scanning electron microscopy and the enamel surface chemical composition for the elements Ca, P, O, F, Si, and C using x-ray photoelectron spectroscopy.

Results: The etching of the two self-etch groups is less aggressive and less uniform than that of phosphoric acid.

Rebonding of orthodontic brackets. Part I, a laboratory and clinical study.

Objective: To compare rebonding of orthodontic brackets based on the hypothesis that no difference would be found between the adhesive systems with respect to shear bond strength, mode of failure, and clinical failure rates.

Materials And Methods: The three adhesive systems included two self-etch primers (Transbond and M-Bond) and a conventional phosphoric acid etch (Rely-a-Bond). The sample size was 20 premolars for each adhesive system.

Bond strength analysis of custom base variables in indirect bonding techniques.

Introduction: Various methods are used to prepare the cured composite-adhesive interface for orthodontic indirect bonding. The intent of this study was to determine the effect on the shear bond strength of the following variables: use of a filled flowable composite resin as an adhesive, light air-abrasion of the cured composite bracket pad, and wetting the cured composite bracket pad with an unfilled resin.

Methods: The sample of 240 brackets was divided into 2 groups of 120 each.

Changes in stiffness of demineralized dentin following application of collagen crosslinkers.

It is thought that increasing the strength of the dentin matrix using crosslinking agents may improve both the strength and the durability of resin-dentin bonds. The purpose of this study was to evaluate the effect of two collagen crosslinking agents (glutaraldehyde, GD and grape seed extract, GSE) on the modulus of elasticity of demineralized dentin. Sound molar fragments were fully demineralized and divided into five groups according to the type and concentration of crosslinking agents: 2.

In-vitro evaluation of frictional resistance between brackets with passive-ligation designs.

Introduction: The lower frictional resistance produced by passive self-ligating brackets can be helpful during orthodontic sliding mechanics. The aims of this study were to evaluate the frictional resistance of brackets with passive ligation and to compare these values with corresponding controls.

Methods: Two passive self-ligating brackets (Damon SL II, Sybron Dental Specialties/Ormco, Orange, Calif; SmartClip, 3M Unitek, Monrovia, Calif) and 1 novel bracket with passive elastic ligation (Synergy, Rocky Mountain Orthodontics, Denver, Colo) were used.

Flexure strength evaluation of a laboratory-processed fiber-reinforced composite resin.

Statement Of Problem: A fiber-reinforced composite resin system has been introduced for posterior restorations; however, little information is known regarding possible degradation of its flexure strength with respect to aging and cyclic loading.

Purpose: The aim of this in vitro study was to determine whether the fiber reinforcement improved the flexure strength of an indirect composite resin aged in air and water for 3 months and then subjected to static and cyclic loading.

Material And Methods: The materials tested in this study, non-fiber-reinforced composite resin (n=160) (Tescera Dentin) and fiber-reinforced composite resin (n=160) (Tescera U-beam and Rod), were fabricated as bars, 25.

7.87 eV laser desorption postionization mass spectrometry of adsorbed and covalently bound bisphenol A diglycidyl methacrylate.

Bisphenol A diglycidyl methacrylate (Bis-GMA) was adsorbed onto or covalently bound to a porous silicon oxide surface. Laser desorption 10.5 eV postionization mass spectrometry (LDPI-MS) was previously demonstrated for surface analysis of adsorbed and surface bound Bis-GMA, but signal to noise levels were low and ion fragmentation was extensive.

Magnetic strength and corrosion of rare earth magnets.

Introduction: Rare earth magnets have been used in orthodontics, but their corrosion tendency in the oral cavity limits long-term clinical application. The aim of this project was to evaluate several; magnet coatings and their effects on magnetic flux density.

Methods: A total of 60 neodymium-iron-boron magnets divided into 6 equal groups--polytetrafluoroethylene-coated (PTFE), parylene-coated, and noncoated--were subjected to 4 weeks of aging in saline solution, ball milling, and corrosion testing.