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.
Properties of LTV vinyl silicone rubber-based resilient denture base liner and directions for use.
The authors have developed a new type of resilient denture liner which consists of LTV vinyl silicone rubber as a principal component. The product's features include good resilience against mucosal supporting tissues and excellent properties of adhesion to the denture base resin. A further advantage is that it does not deteriorate, even after years of use. This article describes the properties of the material, the directions for its use, and several clinical examples. Introduction In daily clinical practice, denture-wearing patients often complain of oral mucosal pain during mastication. In such cases, the practitioner grinds the base of the denture or attempts occlusal adjustments to relieve the pain. However, in many instances, neither of these treatments alleviates the pain. The following conditions often result in oral mucosal pain due to friction with the rigid resin denture base during mastication. 1) Extreme resorption of the lower alveolar process. 2) An alveolar ridge with a sharp knife-like bone margin. 3) An alveolar ridge which is covered with thin and non-resilient soft tissue. 4) An alveolar ridge with a bulging projection or osteoma. Traditionally, dentists have treated these difficult cases by lining the resin denture base with a rubber-like, flexible and resilient material which serves as a cushion. An ideal resilient denture lining material requires the following properties: 1) longevity without deterioration of physical properties, i.e., no change in flexibility or resilience; 2) stable and strong adhesion to the denture base resin; 3) biological stability with no detrimental effect on the oral mucosa; 4) high resistance to wear; 5) easy processing. On the other hand, denture base liners that were marketed in the past did not show longevity in the oral environment due to problems such as deterioration, discoloration, peeling off from the resin base, and failure to provide * 西 山 實 : Department of Dental Materials, Nihon University School of Dentistry, 1-8-13 KandaSurugadai, Chiyoda-ku, Tokyo 101, Japan ** 加藤 武彦 : Kato Dental Office, 975-2 Hiyoshihonchou, Kouhoku-ku, Yokohama-shi, Kanagawa 223, Japan
APPLICATION OF THE FINITE ELEMENT METHOD TO ROTARY-WING AEROELASTICITY.
Recent research in rotary-wing aeroelasticity has indicated that all fundamental problems in this area are inherently nonlinear. The non-linearities in this problem are due to the inclusion of finite slopes, due to moderate deflections, in the structural, inertia and aerodynamic operators associated with this aeroelastic problem. In this paper the equations of motion, which are both time and space dependent, for the aeroelastic problem are first formulated in P.D.E. form. Next the equations are linearized about a suitable equilibrium position. The spatial dependence in these equations is discretized using a local Galerkin method of weighted residuals resulting in a finite element formulation of the aeroelastic problem. As an illustration the method is applied to the coupled flap-lag problem of a helicopter rotor blade in hover. Comparison of the solutions with previously published solutions establishes the convergence properties of the method. It is concluded that this formulation is a practical tool for solving rotary-wing aeroelastic stability or response problems.