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The results of these tests demonstrated that aspiration through 30-gauge needles is possible, but since the flow rate is so diminished its clinical application is questionable. The evaluation of the physical properties of these needles proved them to be tough, durable, and suprisingly resistant to breakage, even under the most extreme manipulations and stresses. The insertion of needles into the plastic material clearly showed that the needles are always deflected toward the side without the bevel (the side that contains the point). Finally, the deposition patterns of the injected fluid in tissue have no relationship to the bevel.

Pin channel preparations with twist drills have the potential to produce a temperature increase in the pulp chamber. This temperature increase is related to twist drill diameter, length (depth of channel preparation), and rotational speed.

A liquid solution of an oxalate bonding system containing NTG-GMA and PMDM has become commercially available. The bond strength of this oxalate adhesive (Tenure Solution) to dentin was determined by bonding composite resin cylinders to extracted teeth. The bond strengths obtained in this study are compared to the bond strengths obtained in earlier studies with the first and second generation oxalate adhesives whose components were supplied as powders and required mixing. The oxalate solutions developed significantly higher bond strengths than the original powder type systems.

The problem of glass breakage in the local anesthetic cartridge system was evaluated under laboratory conditions with a mechanical testing machine. The anticipated breakage of the glass did not occur with any frequency, as the rubber stopper produced more uniform failures of the system. The glass cartridge appeared to be quite reliable and resistant to breakage.Local anesthetics have been used for many years to provide patients temporary freedom from pain. Local anesthetic solutions are in wide use in both dentistry and medicine and are the most frequently used drugs in dentistry. Various estimates place the number of injections at approximately one half million daily or 125 million injections per year.These drugs and the armamentarium necessary to administer them have proven to be safe and reliable. Only rarely are there reports of sensitivity to the anesthetic solution or breakage of needles.. Sterility of the solutions has not been a problem as they are carefully processed and evaluated at the factory. Although there are sporadic reports of loss of sterility, this has been attributed to the reuse of the anesthetic cartridges on more than one patient. Monheim states "The success of the cartridge system in dentistry has been due to the sincerity, honesty, and high standards of the manufacturers in giving the profession a near-perfect product." However, on occassion a glass cartridge will break or shatter when inserting the harpoon into the rubber stopper or even during injection. Cooley et al reported on eye injuries occurring in the dental office, one of which was due to glass from a local anesthetic cartridge that exploded and propelled particles into the patient's eye. Forrest evaluated syringes, needles, and cartridges and reported that one brand (made in Britain) fractured more often than any other, but that the fracture rate was too low to be of any consequence.It is apparent that glass cartridges will fracture or burst from time to time. This study evaluates the cartridge system with carefully controlled laboratory procedures. The cartridges were tested under various pressures and conditions in an attempt to determine the causes of failure and when such failure may be anticipated.

Three composite resins were subjected to applications of sodium bicarbonate with an air-powder abrasive instrument. Materials tested were a microfilled, a conventional, and a light-cured composite resin. Samples were tested for surface roughness before and during applications. The applications produced significant increases in roughness. It was concluded that the light-cured composite resin should be the material used for patients undergoing a recall maintenance program in which the instrument is used.

Formaldehyde has been identified as a potential occupational carcinogen and is a component of chemical solutions used in chemical vapor sterilizers. This study evaluated room air for formaldehyde in rooms where chemical vapor sterilizers were in use.

Five microfilled resin restorative materials were evaluated for ease of polish and surface finish. Ease of finish was evaluated subjectively; surface smoothness with a profilometer. In addition, scanning electron microscope examinations were conducted to evaluate the structural composition of the microfills. No difference was found in ease of finish, but surface smoothness varied among the five products. The SEM evaluation revealed that four of the products had a heterogeneous composition while the fifth appeared to be a homogeneous microfill.

The findings in three children with severe asthma are presented. Following intensive round-the-clock therapy with theophylline (the dosage of which maintained serum levels of theophylline between 10 microgram/ml and 20 microgram/ml) and therapy with prednisone (20 mg twice daily for three weeks or more), there were improvements in spirometric and body plethysmographic measurements. Despite this therapy, abnormalities in the forced expiratory volume in one second, the maximal midexpiratory flow, the residual volume, and specific airway conductance remained. These cases represent a subgroup of asthmatic children with reactive airways who have an irreversible component to their disease.

This laboratory study determined the depth reached by self-shearing pins in dentin pin channels. Pin channels were prepared with the self-limiting shoulder twist drill for each of the four systems tested. Mean channel depth reached for the various pin systems was: Stabilok (small), 2.31 mm; Stabilok (medium), 1.78 mm; Reten Pin, 1.40 mm; and TMS (Regular), 2.04 mm. A coparison was also made by calculating the mean percent of penetration in relation to the depth of prepared pin channel: Stabilok (small), 92.50%; Stabilok (medium), 63.62%; Reten Pin, 66.67%; and TMS (Regular) 81.75%.