To THE EDITOR: In the October

1991 issue of THE JOURKAL OF PROSTHETIC DENTISTRY, I was misquoted in the article, “Stresses at the dentinoenamel junction of human teeth-a finite element investigation,” by Goel, Khera, Ralston, and Chang. This article demonstrates the relationship between stress concentrations focused at the dentoenamel junction (DEJ) and cervical lesions. In the discussion, the article states that the demonstrable high stresses in the area of the DEJ could contribute to the development of V-shaped notches in the cervical area by mechanical abrasion as suggested by McCoy. This is erroneous. In my article, I implied that what we are actually seeing are classic examples of hard tissue fatigue due to compression failure. The tooth brush has very little to do with this phenomenon. The authors state that compressive occlusal stresses in enamel and dentin are high, but have limited clinical significance. I strongly disagree. In my opinion, high stress at the DEJ is a major etiological factor in the initiation of dental compression syndrome or bruxim. DR. GENE MCCOY IMPLANT AND RECONSTRUCTIVE SUITE 226, Fox PLAZA SAN FRANCISCO, CA 94102



6. On the longevity

of teeth. J Oral Implantology


Reply To THE EDITOR: Our most sincere thank you to Dr. Gene McCoy for his generously kind words regarding our article, “Stresses at the dentinoenamel junction of human teeth-a finite element investigation.” It was not the intent of the authors to misquote Dr. McCoy. In reality, our own findings and discussion regarding the chipping of cervical enamel due to stress distribution fully concur with his contention. The entire second paragraph of the discussion section is in total agreement with his concept, except that we believe that once the enamel is chipped away, exposing the “soft” dentin, tooth brushing will contribute to the development of the cervical abrasion lesions. With regard to the sentence where Dr. McCoy’s article is referred to, perhaps, a differently worded sentence (“This in turn could expose the softer dentin, which could be mechanically abraded at an accelerated rate by tooth bushing into V-shaped notches in the cervical area such as those observed by Lee and Eakle’O and McCoy.i’“) would have been more appropriate. We regret our poor sentence structure and the impiied misquoting of Dr. McCoy’s article. As regards to the high compressive stresses on the occlusal enamel and dentin and the limited clinical significance, those stresses are at least functional if not physiologic or normal. In addition, there is no evidence that the


stresses at the DEJ are the “major etiologic factor in the initiation of dental compression syndrome or bruxism.” SATISH C. K~ERA, BDS, DDS, MS College

of Dentistry

University of Iowa Iowa


IA 52242

To THE EDITOR: Bravo! to Kenneth E. Bloodworth and Philip J. Render for their article calling for the development of radiopaque acrylic resins for prostheses (J PROSTHET DENT 1992; 67:121-3). Although rare, inhalation or ingestion of fragments of acrylic resin can be life-threatening since they have the same radiodensity as soft tissues. One resilient denture liner (Novus, Hygenic Corp., Akron, Ohio) uses barium sulfates as the filler to produce a different radiodensity. Unfortunately, dentists and laboratory technicians do not seem to be adequately concerned when informed of the potential for these materials to be seen on radiographs in emergency situations. It is good that Bloodworth and Render have pointed out the magnitude of the situation. In recent years, the National Institute of Dental Research has funded two institutions to develop innovative approaches to the problem (Rawls HR et al. Dent Mater 1990;6:250-55; and Rawls HR et al. J Dent Res 1990; 69(1865):342) using triphenyl bismuth, a soluble nontoxic heavy metal additive. Such developments may help solve this persistent problem. LAWRENCE GETTLEMAN, DMD, MSD UNIVERSITY OF LOUISVILLE SCHOOL OF DENTISTRY DEPARTMENT OF PROSTHODONTICS LOUISVILLE. KY 40292


To THE EDITOR: Having recently read the article “Pattern of tooth contacts in eccentric mandibular position in young adults” by Ingervall, Hahner, and Kessi (J PROSTHET DENT 1991;66: 169-76), I am prompted to respond. It is always intriguing to have input from another dental speciality involved with occlusion. Several ideas mentioned prompted questions. In their discussion of the literature, the authors note that most studies have been recorded to an edge-to-edge position of the canines approximately 3 mm lateral to the intercuspal position. They state that: “An eccentric position of this magnitude is probably rarely used during natural function (chewing).” Certainly most clinicans would agree with this, but what about parafunction? Why are many canines faceted? If “on laterotrusion most subjects had group function on the functional side,” then isn’t this contact (probably parafunctional rather than functional) even more significant? It was also interesting that men were selected for this study, based in part on “the fact that no sex differences in tooth contacts have been reported.” It is my clinical experience, and I believe is supported by the literature, that young women have the highest incidence of acute TMJ







Development of radiopaque acrylic resins for prostheses.

To THE EDITOR: In the October 1991 issue of THE JOURKAL OF PROSTHETIC DENTISTRY, I was misquoted in the article, “Stresses at the dentinoenamel junct...
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