Elastic modulus of a triple-stranded stainless steel arch wire via three- and four-point bending.

The modulus of elasticity (E) was determined in simple three- and four-point bending for an 0.0175" (3 X 0.008") stainless steel arch wire. Using variable light loads (10-160 g) to limit the elastic deflection of a wire to less than 5% of its beam length, the force-deflection profiles were determined for three nominal span lengths (L = 0.35", 0.75", and 1.00") in three-point bending and three nominal inner span lengths (L2 = 0.17", 0.40", and 0.50") in four-point bending (single outer span length, L = 1.00"). By assuming that each wire could be considered as a bundle of frictionless, tightly wound helical springs (i.e., strands), in which both the Young's modulus (E) and the shear modulus (G) contribute to the overall stiffness, values for E equaled 28.6 +/- 0.6 X 10(6) and 29.6 +/- 0.9 X 10(6) psi in three- and four-point bending, respectively. In addition, by using simple beam theory, the values of E for the 0.010" and 0.018" single-stranded wires were measured and equaled 27.2 +/- 0.3 X 10(6) and 27.8 +/- 0.7 X 10(6) psi in three-point bending, and 27.9 +/- 0.7 and 27.8 +/- 1.2 X 10(6) psi in four-point bending, respectively. Despite the fact that the elastic moduli of all three wires were significantly different (p less than 0.001), the results corroborated the metallurgical literature in which E spanned 27.8-30.2 X 10(6) psi. This was in contrast to the dental literature, in which a broader range of values has been reported, i.e., 18.3-38.0 X 10(6) psi.

Acquisition of psychomotor skills in tooth preparation using self-paced instruction.

Self-paced instruction whereby students are provided with learning resources and allowed to learn at their own rate--with or without assistance from instructors--is increasingly being used in dental education. The wide diversity of entering dental student experience with psychomotor tasks suggests that preclinical psychomotor skill development should adapt well to self-paced learning. This study compared self-paced instruction to traditional preclinical teaching of psychomotor skills in cavity preparation. Performance by the self-paced class was significantly better than that of the traditional class on two procedures. There were no significant differences among the other procedures tested.

Elastic property ratios of a triple-stranded stainless steel arch wire.

The general elastic property ratio equations for nth-stranded wires are derived and then specified for the case of a triple-stranded arch wire. Several parameters are defined, including the modulus of elasticity (E) and the helical spring (kappa) and bending plane (lambda) shape factors. Thereafter, the elastic property ratios of a wide range of compositional/configurational combinations are determined, using a representative triple-stranded 0.0175 inch (3 X 0.008 inch) stainless steel wire as the base line. These results show that the particular 3 X 0.008 inch wire studied possesses the stiffness of an 0.010 inch stainless steel wire but has at least 20% more strength and range. Furthermore, the stiffness of the 3 X 0.008 inch multistranded wire is similar to an 0.016 inch nickel-titanium wire but only 40% that of an 0.016 inch beta titanium wire. When these elastic property ratios are compared with the previous results reported by Thurow, Burstone, and Kusy, differences are noted which can be explained on the basis of the mechanical property values and/or the geometric modeling assumed.

Prolonged nursing habit: a profile of patients and their families.

No association of the prolonged nursing-habit with the family background was found with the exception of predominantly lower socioeconomic conditions. All subjects demonstrated prolonged bottle-feeding or breast-feeding. Milk was reported to be the liquid most often used in the bottle. Parents reported that they did not know when weaning should occur, and when oral hygiene should be instituted. The nearly symmetrical caries pattern, the teeth most often affected and the order in which they are attacked and destroyed are conditions which are similar to those described in earlier studies.

Multiple simultaneous synthesis of phenolic libraries.

A series of analogous arrays of small, non-peptidyl, non-oligomeric compounds were synthesized on polystyrene resin. With the aid of a functionally differentiated phenolic scaffold, the batch preparation of unique benzamide and urea resins was accomplished, which were further derivatized in modified 96-well plates. An efficient cleavage reaction of the phenyl benzoate link enabled the isolation of more than 600 phenolic compounds in milligram quantities that were suitable for direct biological screening. The technology described herein represents a facile, economical approach to non-peptidyl chemical diversity.

The design and synthesis of substituted biphenyl libraries.

A novel scaffold system for the generation of diversity libraries has been designed which allows for rapid modification not only of functional groups, but their spatial arrangements as well. The biphenyl scaffold allows for display of three or four diverse functional groups in a wide variety of spatial arrangements depending on the substitution pattern selected. The libraries are generated by a combination of solution and solid-phase chemistries and are cleaved off the solid-support for screening.