R. Liberman

Effect of sodium hypochlorite on dentin microhardness.

This study was designed to evaluate the effect on root dentin microhardness of 2.5% and 6% sodium hypochlorite solutions for various irrigation periods. Forty-two bovine roots were divided into seven groups. The control group was irrigated with saline. The experimental samples were continuously irrigated with 2.5% or 6% NaOCl for 5, 10, or 20 min. Microhardness was measured at depths of 500 mum, 1000 mum, and 1500 mum from the lumen. A decrease in microhardness was found at 500 mum between the control and samples irrigated with 6% NaOCl and 2.5% NaOCl (p = 0.352, p = 0.084 respectively) at all irrigation periods. There also was a significant difference in groups irrigated for 10 or 20 min (p = 0.001, p < 0.001 respectively). At all distances, the decrease in microhardness was more marked after irrigation with 6% NaOCl than 2.5% NaOCl.

Effect of retention grooves on tooth-denture base bond

The bond strength of acrylic resin teeth with and without retention grooves processed onto standard and high-impact denture base resin was investigated. A shear compressive force was applied at an angle of 130 degrees to the lingual surface of the teeth until fracture occurred. The values were subjected to a two-way analysis of variance with repeated measures. Canine teeth bonded better than central or lateral incisors (p less than 0.01). A significantly greater force was required to fracture teeth from high-impact resin (p less than 0.01). Vertical retention grooves enhanced bond strength (p less than 0.01).

The effect of retention grooves in acrylic resin teeth on tooth denture-base bond

A progressive shear compressive load was applied at an angle to the lingual surface of acrylic resin teeth bonded to denture base acrylic resin. No statistically significant advantage was derived by preparing retention grooves of different shapes in the ridge lap surface of the denture teeth.

The control of marginal microleakage in amalgam restorations using a dentin adhesive: a pilot study.

Abstract A pilot study showed that marginal microleakage in fresh amalgam restorations was eliminated at both the enamel and dentin/cementum margins of Class V restorations in an in vitro study using Scotchbond Dental Adhesive applications to the cavity margins prior to the condensation of a spherical high-copper amalgam alloy.

The Effect of Instrumentation with Two Different File Types, Each with 2.5% NaOCl Irrigation on the Microhardness of Root Dentin

The aim of this study was to measure root-dentin microhardness after instrumentation with two types of files and using irrigation with 2.5% sodium hypochlorite. Thirty roots were instrumented with irrigation: 10 roots had the pulp extirpated only; 10 roots were instrumented with stainless steel files, and 10 roots were instrumented with rotary nickel-titanium (NiTi) files. Additionally, five roots were extirpated only without irrigation and served as a control. The roots were sliced and root-dentin microhardness was determined at depths of 500 microm and 1000 microm from the pulp-dentin interface. Significant differences were found between the microhardness at 500 microm and 1000 microm (p < 0.001) in all groups. Instrumentation with NiTi rotary files affected dentin microhardness significantly to a lesser extent.

Marginal microleakage: the effect of the number of cavity-varnish layers and the type of amalgam used

Abstract Microleakage of Class V amalgam restorations was studied, using 3 different types of alloy and varying numbers of application of cavity varnish. Significantly less microleakage was recorded by applying 2 layers of cavity varnish and using Tytin or Silmet amalgam alloys. Permite C alloy showed no statistical difference irrespective of the number of varnish applications.

A combined amalgam and composite resin restoration

Difficulties with restoring class II cavities with posterior composite resin are enumerated. The problem is especially acute when a gingival margin lies close to or apical to the cementoenamel junction. A technique is described whereby the proximal portion of class II cavities is restored with amalgam to the contact area and composite resin inserted in the remainder of the cavity. Microleakage was studied by dye penetration tests. At the composite resin/cementum interface microleakage was significantly greater than at the amalgam/cementum and amalgam/composite resin interfaces (p less than 0.001). No statistically significant difference was observed in microleakage between the amalgam/cementum and amalgam/composite resin interfaces.

Restoration of posterior pulpless teeth: Amalgam overlay versus cast gold onlay restoration

I n the restoration of posterior endodontically treated teeth, a number of principles must be considered. Pulpless teeth, being brittle, have a tendency to fracture.lm3 Causes may be either mechanical, such as loss of the occlusal portion of the pulp chamber, which is resistant to pressure and stress,4 or biologic (for example, pulpless teeth show a 9% reduction in moisture content of their calcified tissues).5 Restoration of such teeth should provide adequate resistance to horizontal and vertical forces. The cast onlay restoration provides cusp protection against vertical forces, whereas a sufficient width of dentin is necessary to withstand horizontal forces.6 Preparation and restoration of teeth with amalgam overlays (N = 48)

Retention of prefabricated posts with dental adhesive and composite

Sixty-three No. 4 Dentatus threaded posts were cemented in extracted teeth and tested for tensile strength. The cementing medium was Silar composite alone or in combination with a conventional bonding agent or Scotchbond dental adhesive, or both. Results indicate that: Retention was greater when the posts were cemented with the Silar composite preceded with the application of Scotchbond. Retention was less with Silar composite alone or combined with a conventional bonding agent. Scotchbond is suggested for use as a bonding agent when cementing Dentatus posts with composites.

The Effect of CO2 Laser on the Microhardness of Human Dental Hard Tissues Compared with That of the High-Speed Drill

OBJECTIVE The purpose of this study was to examine the effect of 9.6-microm CO(2) laser energy on the microhardness of human dental hard tissues compared with that of high-speed drill cavity preparation, and to determine the applicability of this laser in clinical treatment. MATERIALS AND METHODS A total of 10 caries-free human single-rooted teeth were used for this study. The crowns were resected and the roots were longitudinally sectioned into two halves. In each slice one half of the enamel and the dentin were treated with 9.6-microm CO(2) laser irradiation, and in the other half the enamel and dentin were treated with a high speed drill, each half for 3 s. Following treatment, the samples were polished and tested for microhardness. The results were compared using analysis of variance. RESULTS Statistically significant differences in dentin microhardness were found between specimens treated with 9.6-microm CO(2) laser energy as compared with specimens treated with the high-speed drill (p = 0.0156). There were no statistically significant differences in enamel microhardness between specimens treated with 9.6-microm CO(2) laser energy and specimens treated with the high-speed drill. CONCLUSION The clinical use of 9.6-microm CO(2) laser energy for cavity preparation should be further analyzed, and compared with different types of lasers used in dentistry, such as 10.6-microm CO(2) or Er-YAG.