Abstract: The modulus of elasticity and yield strength of a rigid core rod are set within predetermined limits as to limit the elastic deformation and prevent plastic deformation of a dental tray during multiple impression taking, bite registration and subsequent handling. The tray is formed with a frame which provides a positive recovery force when it is flexed. The cross section of the core rod may be optimized to further limit deflection in a predetermined plane. Various preferred materials including nonwoven spun-bonded filaments are selected for supporting impression material on the tray while minimizing the likelihood of obstructing a patient's teeth during full occlusion.

Abstract: An anchoring pin for retention of a dental restoration onto a tooth stub, the pin including an upper retention portion on which a restoration is to be formed, a lower anchoring threaded portion self-threadable in a bore pre-drilled in the tooth stub and a stop collar interconnected between the retention portion and the anchoring portion. A stepped dental drill having two coaxial drill bits of different diameters is provided, which in addition to forming the bore makes a counterbore at the mount of the bore at the exposed excavated surface of the tooth. The counterbore receives the stop collar of the anchoring pin as the latter is driven into the tooth bore thereby preventing bottoming out of the pin so as to avoid concentrated stress at the tip of the pin and also providing distribution of stress as the wider collar abuts the bottom of the counterbore.

Abstract: A vibration cancellation device is provided for an air motor with a reciprocating drive piston. The device consists of an anti-phase piston which is axially aligned with the drive piston and reciprocates in the opposite direction of the drive piston. In one embodiment, the stroke of the anti-phase piston is adjustable to permit optimizing its vibration cancellation characteristics.

Abstract: A dental post for retention a dental restoration onto a prepared tooth stub, includes an elongated cylindrical portion insertable into the tooth stub and a head portion extending from the surface of the tooth stub for securement within the dental restoration. The head portion of the post is anatomically shaped to conform to the shape of the dental restoration.

Abstract: A dental post for retaining a dental restoration onto a tooth stub and a method for making dental post. The dental post includes a cylindrical body portion and a head portion which extends outwardly from the body portion. The body portion is inserted in a bore in the tooth and secured therein by cement. To improve cement retaining capacity of the dental post, there are provided on the body portion non-continuous raised portions, spaced by wide open gaps to retain large segments of thick segments of cement. The overall portion of the gap area surface is greater than that of the land area surface.

Abstract: A self-threading dental anchor for insertion into a blind channel extending from an excavated surface of a tooth, the channel having a tapered seat portion of predetermined degrees, the dental anchor including an upper retention section to provide retention of a superstructure formed on the tooth, and a lower anchoring section connected thereto for engagement in the tooth channel to threadingly anchor the dental anchor to the tooth, the anchoring section having a helical buttress-type thread thereon. The buttress-type thread has a substantially planar lower surface facing towards a distal insertion end of the anchoring section, and an angled upper surface tapering inwardly towards the upper retention section to provide a crest therebetween, the crest having a knife-like cutting edge. The distal insertion end of the anchoring section is tapered to provide a slope thereon equal to the predetermined degrees of the tapered seat portion of the tooth channel to provide a mating angled configuration therebetween.

Abstract: A probe unit for an electro-surgical device to apply high level frequency voltage to an operating area, the probe unit including an operative end portion provided with a forward cutting tip, and a rear housing connector portion provided with a ferrule rotatably connected to the remaining body portion thereof, a rear end of the operative end portion being threadingly engaged with the ferrule for rotation therewith and for easy removal thereof so that the operative end portion can be sterilized and then re-engaged onto the ferrule of the rear housing connector portion. The operative end portion has an elongated length considerably longer than the rear housing connector portion to prevent cross-contamination of a user and/or patient when the probe unit is being used. The body of the operative end portion is tapered with a rear enlarged portion thereof being provided with laterally extending fins thereabout to provide for uniform curing and a uniform cross-section thereof.

Abstract: A casting machine including a control circuit which automatically controls ts operation. The casting machine includes a casting chamber which supports an alloy filled open-ended container whose open end faces the sprue hole of an investment casting ring. The control circuit couples a vacuum to the casting chamber while maintaining the casting chamber in its initial upright position. After a first timing interval, the chamber is inverted and the vacuum is decoupled from the casting chamber, and compressed air is applied to the casting chamber. After a second subsequent time interval the casting chamber is automatically returned to its initial upright position, the action of which causes the casting chamber to be automatically vented to the atmosphere.