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Statement of problem. For clinical investigations of allergic reactions to dental materials, it is necessary to know the type of metal used in restorations in the mouth of the patient. However, an intraoral method of sampling the dental alloy without removing the metal restoration has not yet been established. Purpose. This study attempted to establish a clinically serviceable method for microsampling dental alloy. Material and methods. A piece of silicone sampling tube is held on the surface of the metal restoration. This surface was ground with a carbide bur through the sampling tube, and the ground metal particles were then recovered from the inner surface of the tube. The recovered sample was subjected to energy-dispersive x-ray microanalysis. The percentage recovery of ground alloy by this microsampling method, which was the ratio of the recovered weight of metal to the total weight of the metal ground, was evaluated using 3 mm diameter × 1 mm thick disk-shaped specimens of Ag-Au-Pd and Ni-Cr alloys. Results. Elemental analysis of the retrieved alloys identified the component elements in the alloy compositions. The percentage recovery by this microsampling method was 75.0% for Ag-Au-Pd alloy and 69.9% for Ni-Cr alloy, respectively. Conclusions. The microsampling method demonstrated a relatively high percentage recovery of the ground alloy particles. This microsampling method would be of great benefit clinically to patients who have allergic reactions to dental materials. (J Prosthet Dent 1999;82:221-5.)

Statement of problem. Special technical skills and experiences are required to fabricate a telescopic crown to provide adequate retention with precise frictional retention ("conus friction force") between coping and telescope. It is also difficult to control clinically alterations of retentive forces after prolonged usage. Purpose. This study examined an innovative telescopic crown system for removable partial dentures that can be fabricated without special technical skill or experience and readily adjusted retentive forces. The retention of telescopic crowns was investigated after repeated insertion/separation tests. Material and methods. Ten telescopic crowns were constructed to evaluate retentive forces. Each telescopic crown was adjusted to provide a retentive force of approximately 9.8 N. Each telescopic crown was then subjected to 10,000 insertion/separation cycles, and retentive force of each telescopic crown was recorded initially and after every 1,000 cycles. The retentive force of each telescopic crown was re-adjusted after these measurements to provide a retentive force of approximately 9.8 N. The retentive force was recorded a second time after each 1,000 insertion/separation cycles up to 10,000 cycles. Results. Retention of the telescopic crowns gradually diminished, depending on the number of insertion/separation cycles. The mean retentive force after 10,000 insertion/separation cycles was over 2 N. All 10 telescopic crowns were re-adjusted to exert a retentive force of 9.8 N after the initial 10,000 cycles, and the retentive force also diminished on the second 10,000 cycles. Conclusions. Reduction of retention was dependent on insertion/separation cycles. This new telescopic crown with reduced retention could be easily readjusted. Readjusted retentive forces were at least equivalent to the initial retention. (J Prosthet Dent 1999;81:684-8.)

Statement of problem . The construction of precise fixed prostheses that are harmonious within the stomatognathic function has been regarded as a critical requirement for successful oral rehabilitation. However, techniques for construction have been unsuccessful in producing a prosthesis that can be inserted without intraoral occlusal adjustment. Purpose . In this study, a new method of constructing a precise prosthesis that requires limited occlusal adjustment at the final seating is described. Material and methods . The precision of this method was compared with a conventional method. Fourteen artificial crowns were fabricated on an experimental abutment by using both double-casting and conventional methods. The distances between the cusp tips and occlusal surfaces of the abutments, which were measured on wax/resin patterns and resultant crowns, were recorded to estimate clinical error for each method. Results . Error for the double-casting method was markedly less than the conventional method. This study demonstrated that a new double-casting method was precise and sufficiently reliable for clinical application. (J Prosthet Dent 1998;79:120-24.)

A procedure is described for the fabrication of a record base for an edentulous maxillary arch with severe undercuts in the labial aspect of the anterior residual ridge. The record base is fabricated from autopolymerizing resin without soft lining materials and without blockout of the labial undercut of the stone cast.

Immersion of dental impressions in 2% glutaraldehyde has been shown to be an effective disinfection procedure for viral contamination. This study compared the effect of immersing impression materials on the concentrations of glutaraldehyde. Contamination with saliva slightly affected the concentration of glutaraldehyde. Irreversible hydrocolloid impression material markedly decreased the concentration of glutaraldehyde, whereas the immersion of silicone rubber impression material only slightly affected the concentration of glutaraldehyde. Attention should be paid to the concentration of glutaraldehyde solution when irreversible hydrocolloid impression material is immersed in the disinfectant.

The effect of glutaraldehyde solution, an effective disinfectant for viruses, on the dimensional stability of hydrophilic silicone rubber impression materials was evaluated in this study. Disinfection with 2% glutaraldehyde solution showed a slight expanding effect on the dimensional stability of the hydrophilic silicone rubber impression materials (less than 0.03%). It was revealed that glutaraldehyde can be used for the disinfection of hydrophilic silicone rubber impression materials. Attention should be paid, however, to the conditions for investment or casting to eliminate the expanding effect of this disinfecting procedure.

Statement of problem. Tray adhesive, which is used for the adhesion of elastomer rubber impression materials to a custom resin tray, lowers the retention of the impression materials to the impression modeling plastics, as some ingredients of tray adhesive make the impression modeling plastic soft and tacky. Purpose. The efficacy of tray adhesive, which is used for the adhesion of elastomer rubber impression materials to a custom resin tray, on the adhesion between elastomer rubber impression material and impression modeling plastic was investigated. Material and methods. Four silicone rubber impression materials (two addition reaction types and two condensation reaction types), two polysulfide rubber impression materials, and one impression modeling plastic were used in this study. Tensile strength between elastomer rubber impression material and impression modeling plastic with or without the application of tray adhesive was evaluated. Results. Although tray adhesives for both addition reaction type and both condensation reaction type of silicone impression materials and one tray adhesive for polysulfide rubber impression material increased the tensile strength between the impression material and impression modeling plastic, one tray adhesive for polysulfide rubber impression material decreased the tensile strength when sufficient drying time was not applied. (J Prosthet Dent 1998;79:140-44.) CLINICAL IMPLICATIONS Inaccurate casts would result from lowered adhesive strength. The results of this study revealed that tray adhesive for addition reaction types and condensation reaction types of silicone rubber impression materials were effective regardless of the drying time. It also revealed that polysulfide rubber impression materials caused a contrary effect without sufficient drying time.

reattach the superstructure to the abutments of an implant prosthesis.1,2 Removing the cemented superstructure from the abutment can be difficult; hence, it is always possible to damage the cemented superstructure during removal. To eliminate this problem, prepare a cylindrical guide hole on the lingual surface of the abutment and an access hole on the lingual side of the superstructure (Fig. 1). To remove the superstructure from the abutment, insert a removing driver (Fig. 2) (trial product, Yoshida, Tokyo, Japan) into the guide hole through the access hole (Fig. 3). Turn the removing driver to generate a shear force to raise the superstructure (Fig. 4). The shear force will cause the temporary cement layer to fracture and enable removal of the superstructure from the abutment. This technique is easy and reliable.

Anterior disk displacement without reduction, called "closed locking," is a serious stage of the internal derangement of the temporomandibular joint. Many types of conservative and surgical treatments have been applied to this problem. A new manipulation technique to release "closed locking" of the temporomandibular joint and the clinical results on 35 patients are reported in this study. Voluntary maximal mouth opening of the patients were measured as interincisal distance before and after the application of the manipulation technique. The voluntary maximal mouth opening of 14 of 17 patients (82%) who were younger than 30 years was improved to more than 40 mm after the application of the manipulation technique. Contrariwise, the voluntary maximal mouth opening of only 5 of 18 patients (28%) who were older than 30 years was improved to more than 40 mm.

Chairside scoring of chewing function of complete denture wearers has been difficult. This study presents a table for chairside evaluation of the chewing function of Japanese complete denture wearers. The concept can be effective in other countries and permit international comparisons among complete denture wearers.

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