Construction of tooth positioners with LTV vinyl silicone rubber and some case reports.
In the orthodontic field, attention has recently begun to center on active treatment with tooth positioners, appliances with elasticity made of rubber materials used for orthodontic force in place of conventional metal wires[1-7]. Tooth positioners were contrived by KESLING as retainers to be used after the use of metal wires in active treatment[8,9]. Nowadays, it is used for closing the spaces due to band removal after active treatment, for the minute regulation of the occlusal relationship and for aftercare as a retainer. Not only that, as it is possible to regulate malocclusion by moving teeth with rubberlike elasticity applied in place of metal wires or brackets, it is beginning to draw attention as a new active treatment appliance to be substituted for conventional metal wires. With regard to the materials for tooth positioners to be used as active treatment appliances, various kinds of materials have been applied since KESLING contrived them[10-12], but few materials satisfy the necessary conditions for tooth positioners[10]; 1) easy manipulability, 2) elasticity and hardness, 3) tastelessness and odorlessness in the oral cavity and 4) durability. Polyurethane rubber and heatvulcanized silicone (HTV) rubber which are tasteless, odorless and superior in elasticity, have recently been developed[1,4-7], but these materials require special mold materials and equipment in the preparation process which is also very complicated, so their use has not been widespread as yet. Therefore, for several years the authors have been studying their practical application and trying to develop a material that is easy to manipulate and superior in physical properties[2,3,13]. As a result, the authors have developed a clinically applicable method of tooth positioners with low temperature vulcanized (LTV) vinyl silicone rubber. The following is an outline of its physical properties, the method for its preparation and some case reports.
The philosophy of the tooth positioning appliance
Abstract It is not necessary or desirable to treat every case of malocclusion that is presented. Many, if not most, of these children of 3 to 6 years can be safely put under observation in order that the tendency of growth can be noted. A fair percentage will be seen to improve as Nature seeks to correct some earlier period of retarded growth. Others may require the correction of a habit which is obstructing the normal course of development. Still others, such as the cases shown here, require slight mechanical corrections before normal function can be established and the forces of normal occlusion can exert their influence. Practically all of these cases suffer from low and improperly balanced muscle tone, and myofunctional therapy is used both during treatment and afterward to overcome this deficiency. As the span of attention is short in these younger cases, appointments must be kept brief and appliances simple; however, if these conditions are observed, the preschool children will be found to be among our most cooperative patients.
The crystal structure of stilpnomelane. Part II. The full cell
Summary The structural formula of stilpnomelane averaged from 37 representative literature analyses and based on the determined structure is (Ca,Na,K)4(Ti0·1Al2·3Fe35·5Mn0·8Mg9·3)[Si63Al9](O,OH)216·nH2O. Ferrostilpnomelanes have up to 12 R 3+ cations in the octahedral sheet, ferristilpnomelanes commonly have between 24 and 30 R 3+ cations, rarely up to 37. The two groups can be distinguished by accurate X-ray powder diffraction, ferrostilpnomelanes having d 001 less and a greater than have ferristilpnomelanes. The unit cell is triclinic, a = b∼21·8 Å, γ = 120°, d 001∼12·2 Å, P . Hexagonal groups or ‘islands’ of 24 silicon-oxygen tetrahedra co-ordinate to the octahedral sheet, the centres of the ‘islands’ are displaced by 5a/12, 8b/12 on either side of the octahedral sheet as a result of warping of this sheet to permit articulation with the smaller tetrahedral sheet. The 24-tetrahedra ‘islands’ are linked laterally by 6-member rings of inverted tetrahedra, which in turn link at their apices to like rings connecting the next sheet of ‘islands’. Thus a single tetrahedral layer is 4 tetrahedra thick and has symmetry 6/m. The 6-member rings of tetrahedra act as hinges permitting up to 0·5 Å extension or contraction of the tetrahedral sheet to accommodate variations in the octahedral sheet dimensions with varying R 2+/R 3+ ratio.