A study on the changes in attractive force of magnetic attachments for overdenture
PURPOSE Although magnetic attachment is used frequently for overdenture, it is reported that attractive force can be decreased by abrasion and corrosion. The purpose of this study was to establish the clinical basis about considerations and long term prognosis of overdenture using magnetic attachments by investigating the change in attractive force of magnetic attachment applied to the patients. MATERIALS AND METHODS Among the patients treated with overdenture using magnetic attachments in Dankook University Dental Hospital, attractive force records of 61 magnetic attachments of 20 subjects who re-visited from July 2013 to June 2014 were analyzed. Dental magnet tester (Aichi Micro Intelligent Co., Aichi, Japan) was used for measurement. The magnetic attachments used in this study were Magfit IP-B Flat, Magfit DX400, Magfit DX600 and Magfit DX800 (Aichi Steel Co., Aichi, Japan) filled with Neodymium (NdFeB), a rare-earth magnet. RESULTS Reduction ratio of attractive force had no significant correlation with conditional variables to which attachments were applied, and was higher when the maintenance period was longer (P<.05, r=.361). Reduction ratio of attractive force was significantly higher in the subject group in which attachments were used over 9 years than within 9 years (P<.05). Furthermore, 16.39% of total magnetic attachments showed detachment of keeper or assembly. CONCLUSION Attractive force of magnetic attachment is maintained regardless of conditional variables and reduction ratio increased as the maintenance period became longer. Further study on adhesive material, attachment method and design improvement to prevent detachment of magnetic attachment is needed.
An attachment for overlay dentures.
lh’ is article presents an approach which utilizes the last few teeth remaining in a ravaged dentition. We are attempting to transfer some of the occlusal forces from an overlay denture through the periodontal ligament to the bone and, at the same time, provide a reasonable amount of retention for the overlay denture. Retention is often a problem for the overlay dentures over simple copings when only two teeth remain. Often, one cuspid or bicuspid is left on each side of the arch. This is particularly a problem when treating the mandibular arch, which has a more limited basal seat area. If the resorption pattern suggests an unfavorable prognosis for a complete denture, preservation of the remaining teeth for the longest period of time should be the goal. Attached gingiva all around each tooth and reasonably good bone should be present to warrant this approach. First, periodontal treatment is performed, eliminating pockets and excess soft tissue to provide a sulcus depth of 2 to 3 mm. if at all possible (Fig. 1, A). The patient is given a proper home-care regimen and watched for several months, since the ultimate success of the treatment is dependent upon how well the soft tissues are maintained. There is usually an unfavorable crown: root ratio present. In order to significantly alter this, endodontic treatment is next performed. The canal enlargement is kept conservative to maintain as much root structure as possible. Since many mandibular cuspids and bicuspids present a constriction of the root in cross section, the diameter of the post should be kept within safe limits. The initial post preparation can be accomplished by the endodontist following obturation of the canal. With the use of a Gates-Glidden bur, which approximates the diameter of the cervical portion of the canal, an enlargement is made to about 40 per cent of the depth of the embedded root. Cotton is then placed in the canal, and the opening is obturated with cement. Once the endodontist feels that the teeth are ready, proceed with the prepara-
New Alumosilicate Fillers Based on Sedimentary Rocks for Asphalt Concrete
Asphalt concrete is the most common material for highway and motorway construction. The quality of asphalt is determined, to a large extent, by properties of asphalt binder. Fillers, which are mineral powders from carbonate rocks and aggregates fines, such as limestone and dolomite, are often used in the composition of bitumen mastics affecting the performance of asphalt. This article explores the feasibility of using the fines of aluminosilicate sedimentary rocks as fillers. These materials are composed of clay minerals, which change their properties upon the contact with water. Normally, the use of such fillers is restricted because of poor water resistance and swelling of asphalt concrete. In order to improve the performance of these fillers, the thermal modification at moderate temperatures of 500–600 C has been proposed. Such treatment provides sufficient structural stability of obtained materials and results in the reduction of water absorption of asphalt, improved water resistance (up to 2.5 times) and also, in reduced swelling (up to 9 times). It has been demonstrated that improvement in the filler performance can be achieved by a heat treatment. Such treatment induces changes in the mineral composition and converts the structure of clay minerals into the frame structure of zeolite, as confirmed by X-ray diffraction and infrared spectroscopy. Due to thermal treatment, there is a change in the acid-base properties of the surface of the filler, which is reflected in the profiles of the main adsorption centers. As a result, due to chemisorption, the modified aluminosilicate fillers are able to interact with bitumen. The application of new filler materials in asphalt concrete enables to enhance the performance.