Inlay Preparation Research Articles

有髄歯切削後におけるタンニン・フッ化物合剤の効果 とくに過敏症状に対する効果について

Tannin-fluoride preparations were applied on to the dentin surface exposed by the preparation of the vital teeth for artificial crowns or inlays and the decrease in the sensibility of the dentin was observed clinically. The results obtained were as follows: 1) In the case of the crown preparation, tannin-fluoride preparations were markedly effective in reducing the dentin hyperesthesia in 50.0% of the cases, effective in 31. 3% and not effective in 18.7%. In the cases of the inlay preparation, the preparations were markedly effective in 57.1% of the cases, effective in 32.8% and not effective in 10.1%. 2) The effect of tannin-fluoride preparations on the hypoesthesia of the dentin was more distinct to the mechanical stimulation than to the thermal stimulation 3) Reapplication of the tannin-fluoride preparations showed a considerable hypoesthetic effect on the non-effective cases of the first application of the mixture. 4) There was no significant difference between the two tannin-fluoride preparations mixed with water and with glycerin.

The Finger Contamination of Dentists and an Examination of Current Sterilization Methods

There is a great deal of literaturature on the sterilization of fingers of physicians and dentists beginning with the pioneer effort of Furbringer and the development of various sterilizers, sterilization methods and length of sterilization time.This is particularly true of clinical dentistry where the dentists come in contact with their patients with naked hands, this situation leading to a possibility of bacterial contamination from dentist to patients or from patients to dentist. For this reason, the present study was undertaken with questionnaires to investigate the finger contamination of dentists and, at the same time, to examine the sterilization methods currently in use in dental clinics.2 obtained the following results.1. The sterilization effects after 5 minutes were 98.5% for 0.1% benzalkonium chloride, 97.8% for Hibisclub, 95.4% for 0.02% chlorhexidine, and 90.5% for 2% creosol.2. Regarding daily variations in bacterial colonies, on the days when the number of outpatients was relatively small, there was a tendency toward increased bacterial colonies. When the fingers were not washed with soap before a dental treatment, a positive reaction was seen in DHL media. When stained by the Gram's method, there were some Gram-negative lactobacilli and Gram-positive streptococci.3. As regards finger contamination in terms of different dental treatments, it was 15.6times in crown preparation 13.9 times in the enlargement of pulp cavity, 12.8 times in scaling, 10.0 times in the installation of crowns, 9.4 times in inlay preparation, and 9.2 times in dental extraction.4. The questionnaires concerning finger contamination sent to practising dentists gave the following responses.(1) The majority of them used cresol for sterilizing purposes followed by benzalkonium chloride, chlorhexidine, and benzethonium chloride. There were some dentists who used soap alone.(2) As for the length of sterilization, 41.7% immersed their fingers in a disinfectant for about 5 seconds, and the rest for about 2 seconds, 15 seconds, or longer than 30 seconds.

A theoretical and clinical investigation into the taper achieved on crown and inlay preparations.

The minimum angles of taper that can in theory be formed to various preparations were established for representative dental preparations and operating distances. These values were compared with the taper of dental preparations formed both under laboratory conditions and in clinical practice, the latter by measurement of taper on the dies of clinically successful crowns and inlays. A possible explanation for the discrepancy noted between recommended degrees of taper and the tapers produced under clinical conditions was considered to be due to the requirement by a dental surgeon to avoid forming undercuts to the line of withdrawal of a cast intracoronal or extracoronal retainer.

Effects of design on stress distribution of intracoronal gold restorations

Eight intracoronal and extracoronal designs for gold restorations with different tapers to the lateral walls were investigated to determine the most efficient design in distributing occlusal stresses. It was found that the occulusal wall of an inlay cavity with a 7 degree taper and no bevel resulted in a better stress distribution than a cavity preparation with a greater taper or a long bevel. It was shown further that a wide inlay preparation resulted in less stress if the cusps were protected by gold.

Photoelastic analysis of inlay and onlay preparations

S i n c e the advent of the cast gold restoration in dentistry, many uses have been made of this method for restoring posterior teeth with proximal lesions. The restorations have ranged (rom simple intracoronal inlays to gold veneer crowns of various types. Of the designs that have been used, some have been based on scientific principles, while others have been rooted in empiricism and tradition. One of the more enduring of the cast restorations has been the Class II inlay? This restoration has been used extensively for 50 years, with many dentists attributing to it advantages which may, in fact, not exist. Cast gold has certain properties which make it superior to silver amalgam,, another material commonly used for Class II restorations. However, many clinicians and researchers have come to realize that, while gold may be stronger and harder, these assets alone do not assure a superior means of restoring Class II lesions. The material itself does not strengthen the remaining tooth structure in a Glass II restoration, that type of restoration being purely intracoronal. Modifications must be made in the design of the preparation to take advantage of the desirable physical properties of the material and to protect the tooth from further breakdown. °-, :~ The purpose of this investigation was to determine the stresses induced at certain critical areas of the tooth by various designs of cast gold restorations when subjected

Scanning analysis of a dual-alloy restoration

1 wo previous reports have described the technique and merit of restoring deep subgingival carious lesions with dental amalgam to create a suitable gingival wall for cast gold restorations. ‘. 2 During the years of service, clinical observations delineated the advantages of the restorations which transcended the minor complications attributed to dissimilar metals. The merits of the method have thus been clinically established. The technique involves restoring the deep gingival part of the proximal portion of Class II cast gold inlay preparations with dental amalgam. The completed gingival restoration is then treated as tooth tissue, and a more occlusal gingival wall is created in the amalgam (Fig. 1) . Extensive gingival caries presents a problem, particularly where a developmental groove is pronounced. Undercuts, inadequate access or visibility, problems in establishing parallelism, and gingival management complicate the procedure. Restoring the deep gingival part with dental amalgam facilitates inlay construction. Since the technique employs dissimilar metals with the associated electrolytic action, a more detailed and accurate investigation of the technique became possible following the extraction of a tooth which had been similarly restored and in service for 13 years. The results confirm the effectiveness of the method.