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gested adding 10% more water to the regular irreversible hydrocolloid powder/water (P/W) ratio” (p 412). 2. “Appleby et a1.3stated that it is more important to choose the reversible hydrocolloid with the lowest mean bond strength. However, the low bond strengths demonstrated in Ca-W and P-W combinations suggested that for a successful impression, it is also crucial to choose a compatible irreversible hydrocolloid for the agar” (p 416). The words speak for themselves. There was no criticism of his work or any accusation of “failing. . . .” To requote our research: “However, the low bond strengths demonstrated in CaW and P-W combinations suggested that for a successful impression, it is also crucial to choose a compatible irreversible hydrocolloid for the agar” (p 416). ISRAELLEWINSTEIN, D.M.D.,PH.D. HEBREW UNIVERSITY-HADASSAH SCHOOL OF DENTALMEDICINE P.O. Box 1172, JERUSALEM ISRAEL REFERENCE 1. Lewinstein I. CraigRG.Theeffectof powder/water ratioof irreversible bydrocolloidonthebondstrengthof irreversiblehydrocolloidandagar J PROSTHET DENT 1989;62:412-6. combinations.

Drs. Elledge and Schorr (J PROSTHETDENT 1990;63:541-4), it was mentioned that “Clasp-bearing zones that are to remain on porcelain-veneered surfaces will require laboratory procedures that necessitate having the RPD for construction of the crown in an indirect technique.” However, I would like to explain that in such instances, the resin shell may be built by the dentist to touch all internal surfaces of the clasp assembly and be sent to the laboratory with the final impression, interocclusal record, and the opposing model. In the laboratory, the shell is seated on the trimmed die and the margins are rewaxed. An index is constructed to touch and surround the shell except for the occlusal surface and about 1 mm occlusocervically. The index may be made from any elastomeric putty impression material. The index is sectioned by use of a scalpel and the shell is removed. The die is waxed for the porcelain metal in the usual way and, of course, clear from the index. The pattern is cast and seated on the die for porcelain buildup, with the index as a guide. A porcelain try-in in the patient’s mouth is recommended to perform the necessary adjustments before final glazing. Accordingly, the new PFM crown will be totally in touch with the clasp assembly of the existing RPD. M.S.ELATTAR

To THE EDITOR: In regard to the article “A provisional and new crown to fit. into a clasp of an existing removable partial denture” by

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Back issues of the JOURNALOFPROSTHETICDENTISTRYare available for purchase from the publisher, Mosby-Year Book, Inc., at a cost of $6.50 per issue. (Foreign postage is not included.) The following quantity discounts are available: 25% off on quantities of 12 to 23, and one third off on quantities of 24 or more. Please write to the Mosby-Year Book, Inc., Circulation Department, 11830 Westline Industrial Drive, St. Louis, MO 63146-3318, or call (314)872-8370, ext. 7351 for information on availability of particular issues for that period from 1978 to 1989. If unavailable from the publisher, photocopies of complete issues are available from University Microforms International, 300 N. Zeeb Rd., Ann Arbor, MI 48106, (313)761-4700.

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A provisional and new crown to fit into a clasp of an existing removable partial denture.

READERS’ ROUND TABLE gested adding 10% more water to the regular irreversible hydrocolloid powder/water (P/W) ratio” (p 412). 2. “Appleby et a1.3st...
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