Wear of a dental composite in an artificial oral environment: A clinical correlation.

The study objective was to correlate wear between an in vitro method for simulating wear and in vivo wear of a posterior dental composite. Ten subjects (12 restorations) were selected from a five-year clinical study (University of North Carolina, School of Dentistry) that assessed wear of SureFil composite (Caulk, Dentsply). Subject casts were digitized and changes in volume and mean depth with time were calculated from the 3D digital models for contact and contact-free wear.

Modification of hydroxyapatite/gelatin nanocomposite using polyacrylamide.

A hydroxyapatite (HAp)/gelatin (GEL) nanocomposite was mixed with mineralized polyacrylamide (PAM) to produce a macrocomposite. The mineralization of PAM was carried out by solution-precipitation using Ca(OH)(2) and H(3)PO(4). The crystal growth of HAp in PAM was moderately changed from amorphous-like nanocrystalline to crystalline with the increase of PAM.

Quantification of all-ceramic crown margin surface profile from try-in to 1-week post-cementation.

Objectives: To use profilometry to assess the margin surface profile of all-ceramic crowns (ACC's) at try-in and 1-week after cementation with dual-cured resin (DC, RelyX ARC, 3M ESPE, St. Paul, MN, USA), self-adhesive dual-cured resin (SADC, RelyX Unicem, 3M ESPE), light-cured resin (LC, RelyX Veneer, 3M ESPE) or chemically cured resin-modified glass ionomer (RMGI, RelyX Luting Plus, 3M ESPE) luting cement.

Methods: Forty, sound, extracted, human, premolar teeth underwent a standardised preparation for ACC's.

Cross-linkage of hydroxyapatite/gelatin nanocomposite using imide-based zero-length cross-linker.

Hydroxyapatite [HAp]/Gelatin [GEL] nanocomposite was prepared at 37 and 48 degrees C through coprecipitation process. The HAp/GEL nanocomposite slurries were cross-linked by imide-based zero-length cross-linking agent such as N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide (EDC) and N-hydroxysuccinimide (NHS). The chemical bond formation and microstructure in HAp/GEL nanocomposite was investigated as a function of cross-linking agents and temperature.

Organic-inorganic interaction and the growth mechanism of hydroxyapatite crystals in gelatin matrices between 37 and 80 degrees C.

The crystal development of hydroxyapatite[HAp] phase in gelatin[GEL] matrices was investigated in the temperature range 37 to 80 degrees C by using X-ray diffraction, scanning electron microscopy(SEM), thermoanalytical measurement(DT/TGA), Fourier-Transformed Infra-Red(FT-IR) spectroscopy, and transmission electron microscopy(TEM) with electron diffraction(ED). It was found that during the coprecipitation of apatite phase in GEL matrices and the next aging process the crystallites were formed and developed through the two reaction mechanisms of organic-inorganic interaction between apatite phase and GEL molecules, and thermodynamic reaction for the crystal growing. The analytical evidences showed that there was a definite competition between these two mechanisms with the reaction temperature.

Fatigue and plaque rupture in myocardial infarction.

Plaque rupture plays a role in the majority of acute coronary syndromes. Rupture has been associated with stress concentrations, which are affected by tissue properties and anatomy. In this study rupture was not approached as an acute syndrome, but rather as the culmination of a chronic injury or fatigue process.

Evaluation of sub-critical fatigue crack propagation in a restorative composite.

Objectives: Fracture is a major reason for clinical failure of dental restorations. Many clinical fractures are likely to be preceded by a slow sub-critical crack propagation. The purpose of this study was to determine slow crack propagation in a restorative composite.

Residual shrinkage stress distributions in molars after composite restoration.

Objective: Experimental measurements on various restoration configurations have shown that restored teeth deform under the influence of polymerization shrinkage, but actual residual stresses could not be determined. The purpose of this study was to calculate and validate shrinkage stresses associated with the reported tooth deformations.

Methods: Three different restoration configurations were applied in a finite element model of a molar.

Distribution of transient properties during polymerization of a light-initiated restorative composite.

Objectives: To assess residual shrinkage stress, transient properties must be defined that describe the composite transformation during polymerization. The purpose of this study was to determine the development and distribution of properties that affect the creation of residual stresses in a light-initiated restorative composite.

Methods: Microhardness and shrinkage strain were experimentally measured during and/or after light-initiated polymerization.

Tooth deformation patterns in molars after composite restoration.

Objective: Residual stresses from polymerization shrinkage in composite restorations deform a tooth. This may cause debonding, enamel crack propagation, and post-operative sensitivity. Deformation due to shrinkage has been measured previously at a few discrete points.

Measurement of band displacement: a methodology to determine composite packability.

Objective: A posterior composite should be able to maintain its shape when packed against a matrix band. The objective of this study was to develop an in vitro methodology to determine composite packability by measuring the displacement of a matrix band.

Method And Materials: The experimental setup consisted of a sectional matrix system secured for the restoration of an occlusodistal cavity preparation.

Conformational change of hydroxyapatite/gelatin nanocomposite by glutaraldehyde.

The hydroxyapatite (HAp)/gelatin (GEL) nanocomposite was prepared through the coprecipitation and then cross-linked by using glutaraldehyde (GA). From FT-IR measurement the spectral features for amide bands and phosphate bands were severely modified by the cross-linkage and the organic content increased with the degree of cross-linkage. From Transmission Electron Microscopy (TEM) and electron diffraction analyses we could confirm the preferentially directional growth of needle-like HAp particles, which were embedded in GEL by the mineralization.

Preparation of hydroxyapatite-gelatin nanocomposite.

A nanocomposite of gelatin[GEL]-hydroxyapatite[HAp] was prepared using the biomimetic process. The hydroxyapatite nanocrystals were precipitated in aqueous solution of gelatin at pH 8 and 38 degrees C. The chemical bonding between calcium ions of HAp and carboxyl ions of GEL molecules induced a red-shift of the 1339 cm(-1) band of GEL in FT-IR analysis.

Iatrogenic tooth abrasion comparisons among composite materials and finishing techniques.

Statement Of Problem: Many different rotary instruments are available for shaping composite restorations. Whether use of these instruments causes undesirable iatrogenic abrasion of either the tooth surface or the composite restorative material is unknown. Assuming that damage occurs, which technique is least damaging is unknown.

An intra-oral hydraulic system for controlled loading of dental implants.

This study reports a method for controlling loads on an in vivo dental implant and its application for the investigation of early loading versus delayed loading of dental implants. The method was developed for the purpose of studying an ongoing hypothesis that amounts to bone loss around dental implants are related to mechanical-mediated adaptation of the alveolar bone. Using a customized intra-oral hydraulic system, the daily loading over a dental implant has been completed and recorded for six Sinclair swine.