Shear rebond strength of Rexillium III to enamel using resin composite cements.

This investigation evaluated the shear rebond strength of Rexillium III to enamel using various resin composite luting systems (Panavia, Imperva Dual, ABC Enhanced, C&B Metabond, Optibond, and Comspan). Cast Rexillium III cylinders (3.9 x 6.0 mm) were bonded to human molar buccal enamel surfaces (n = 8) with each cement type after etching with 37% phosphoric acid for 30 seconds. Bonded specimens were stored in distilled water for 7 days at 37 degrees C +/- 2 degrees C and thermocycled (1,500 cycles) in 5 degrees C and 55 degrees C water baths (1 minute dwell time). Specimens were randomly tested in shear mode on an Instron Testing Machine at a crosshead speed of 0.5 mm per minute. Debonded specimens were then rebonded after appropriate metal conditioning and re-etching the enamel surface for 30 seconds. Analysis of variance (P < 0.001) and the Ryan-Einot-Gabriel-Welsh multiple range test showed significant differences between several of the resin cements (P < 0.05). Panavia exhibited significantly higher shear rebond strength than any of the other cements tested. Only Imperva Dual exhibited a significantly lower shear rebond strength compared to its initial shear bond strength.

Shear bond strength of Rexillium III to enamel using resin composite cements.

This study evaluated the shear bond strength of Rexillium III (Jeneric Pentron, Wallingford, CT) to enamel using various resin composite luting systems. Cast alloy cylinders (3.9 mm X 6.0 mm) were bonded with each cement to human molar buccal enamel surfaces (n = 8). The enamel was etched using a 35% phosphoric acid solution for 30 seconds. Bonded specimens were stored in distilled water for 7 days at 37 degrees C and thermocycled (1,500 cycles) in 5 degrees C and 55 degrees C water baths (1-minute dwell time). Specimens were randomly tested in shear using a crosshead speed of 0.5 mm per minute. Use of a one-way analysis of variance (P < .001) and Ryan-Einot-Gabriel-Welsh multiple range test showed significant differences between several of the resin cements. Panavia exhibited a significantly higher shear bond strength than any of the other cements tested.

Compressive characteristics of an internally threaded post system.

PURPOSE: The effects of oblique compressive forces were evaluated for extracted teeth restored with posts of solid and internally threaded designs. MATERIALS AND METHODS: A group of 25 roots was restored with crowns supported by Para-post dowels and pin-retained composite resin cores, and a second group was restored with gold copings cast to internally threaded stainless steel-post prototypes. Samples were then embedded in epoxy resin and loaded at 45 degrees until failure. Failure force and type were statistically analyzed to determine statistical difference (P < .05) between groups. RESULTS: No statistical difference was shown between groups for either fracture force or type. CONCLUSIONS: The internally threaded post system resisted oblique loading forces similarly to a solid post system.

Histopathologic effects of kinetic cavity preparation for the removal of enamel and dentin. An in vivo animal study.

Recent developments in technology, direct placement restorative materials, and cavity preparation design have renewed interest in kinetic cavity preparation, a term to describe the use of air-abrasion for removal of tooth structure. This study compared the pulpal response of 120 teeth in mixed-breed dogs treated with four kinetic cavity preparation combinations of pressure (80 psi and 160 psi) and aluminum oxide particle sizes (27 microns and 50 microns) to those treated with high-speed rotary burs. Class V buccal preparations were made and restored with an interim material. Teeth were collected 72 hours after surgery, decalcified, sectioned, stained with hematoxylin and eosin, and blindly evaluated by two examiners at the minimal dentin thickness. Samples were graded for extent of displacement, disruption, inflammation, and necrosis of pulpal structures. Differences between groups were analyzed with the use of Bonferroni-adjusted multiple Mann-Whitney-Wilcoxon tests with p < 0.05 being significant. Higher pressures and smaller particles yielded significantly fewer pulpal effects than the high-speed treated teeth whereas lower pressures and larger particles were not significantly different for most effects evaluated. No adverse soft tissue effects were noted when kinetic cavity preparation was directed at attached gingiva.

Scanning electron micrographic effects of air-abrasion cavity preparation on human enamel and dentin.

Recent developments in technology and restorative materials have renewed interest in air abrasion as a means of tooth preparation. The technique, also called kinetic cavity preparation, uses kinetic energy to remove tooth structure. The purpose of this investigation was to use scanning electron microscopy to compare the effects of this technique to those of high-speed burs on extracted human teeth. Class V buccal preparations were made on five teeth with a No. 34 carbide bur used at 400,000 rpm and on 23 teeth with kinetic cavity preparation using differing combinations of aluminum oxide particle sizes and delivery pressures. Features of the specimens prepared at high speed included sharp line angles, chipping of the cavo-surface margin, and striated internal surfaces. Kinetic cavity preparations had rounded cavo-surface margins and internal line angles. The surfaces were microscopically rough and the dentinal tubules were occluded. There was little difference in appearance between specimens treated with various combinations of particle sizes and delivery pressures.

Retentive characteristics of an internally threaded post system.

Internally threaded, stainless steel posts 10 mm in length and 1.82 mm in diameter or stainless-steel Para-Post dowels 1.7 mm in diameter were cemented in extracted human teeth with zinc phosphate cement. Titanium alloy screws 1.5 mm in diameter were placed in the internally threaded posts and tensile force was applied to the screws or Para-Post dowels until dislodgment of the post or fracture. The retention of the Para-Post system was significantly greater than the experimental posts. Although all screws exhibited deformation, there was no breakage or distortion of the internally threaded posts or Para-Post dowels. Retention for both systems exceeded reported forces generated in humans.

A potential MRI hazard: forces on dental magnet keepers.

The objective of this study was to determine the forces on dental prosthetic magnet keepers, with a view to assessing the potential for patient injury during magnetic resonance imaging (MRI). Four pre-formed keepers and one castable keeper alloy were tested. Magnetizations and high field susceptibilities were determined for each of the five specimens using data from a vibrating sample magnetometer. The magnetic field intensity with respect to distance from the main magnet coil was obtained from the manufacturer (1-5 tesla General Electric Signa Imaging System). A plot of force versus distance from the main coil and the maximum force at the magnet portal was determined for each specimen. The maximum forces ranged from 0.12-0.24 N for the pre-formed keepers and 3.67 MNm-3 for the castable alloy. It was concluded that the risk of patient injury by displacement is minimal, if the keepers are properly attached to supporting structures.

Magnetic resonance image degradation from prosthetic magnet keepers.

Eight types of prosthetic magnet keepers were imaged in a water phantom and a living human subject by a 1.5 T magnetic resonance device. Image artifacts were present for all eight samples and ranged from 160 mm to greater than 280 mm in diameter. These artifacts obliterate vital craniocervical areas making their examination by magnetic resonance impossible. Patients with magnetic keepers requiring comprehensive magnetic resonance imaging of the head and neck region must have them removed.

Construction of a ceramometal mandibular repositioning splint.

This article described laboratory and chairside techniques for making a porcelain-bonded-to-metal occlusal overlay repositioning splint and suggests how both dental laboratory technician and dentist can anticipate and overcome some problems commonly encountered during fabrication and seating. A ceramometal occlusal overlay and repositioning splint is often the splint of choice for patients who must wear one at all times during prolonged occlusal splint therapy. Unlike the commonly used acrylic resin splints, the ceramometal splint is durable, provides good esthetics and anatomic functional tooth form, and can be worn at all times including meals.