PubMed · 3268994
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G Guénin. 1988. [Shape memory and associated phenomena].. https://pubmed.ncbi.nlm.nih.gov/3268994/
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The purpose of this article is to comprehensively investigate the sources of variation in the expression of torque in preadjusted appliances. Variables related to properties of materials were systematically analyzed, including (1) the inability to fill the slot because of the size difference of archwires and bracket slot, (2) irregularities from the manufacturing process of brackets precluding proper engagement, (3) differences in the stiffness of wire alloys engaged to the bracket slot, (4) variations between actual and reported bracket torque values, and (5) ligation modes, all of which might account for increased third-order clearance or bracket-archwire "play." The effect of these variations on the expression of torque is discussed, and the net buccolingual inclinations are provided as a function of wire size and composition for common bracket slot-archwire combinations. Most reports published on this issue indicate a loss of torque control as high as 100% of the prescribed value. Furthermore, the fallacy of transferring the ideal crown inclination to the torque prescribed in the bracket is illustrated, along with the underestimation of the prescribed torque relative to the proper tooth crown. The realistically required torque is analyzed to its constituent components, involving tooth inclination, compensation for the slot-wire play, and incomplete ligation with elastomeric ligatures. Based on the evidence available, it is proposed that a high-torque prescription should be selected to account for the lack of full expression of the prescribed torque that occurs clinically.
The advent of nonsurgical ultrasonic tips has opened up a new horizon in endodontic treatment. There are a number of nonsurgical endodontic ultrasonic systems currently available in the market and it is difficult to renew all of them. Based on similarities among different instrument systems, and attempt has been made to classify instruments into broad categories. This article describes the utility of each type of ultrasonic tip and the principles behind its usage. These instruments may be area specific or use specific, but can be used in an area other than the one for which they are specifically designed if the general principles regarding ultrasonic tips are understood and applied.
This article describes the use of an innovative, engine-driven, rotary, root canal preparation instrument. The geometric design of this nickel-titanium instrument is totally different from currently marketed manual or engine-driven stainless steel or nickel-titanium instruments. The thin, taperless, noncutting shafts of LightSpeed instruments maximize the flexibility of the nickel-titanium alloy, particularly in the larger sizes. The three different methods for using the LightSpeed cutting heads and three different methods for using the LightSpeed system are described. LightSpeed instruments enable larger apical preparations in curved canals with less coronal flaring than is possible with most other techniques.