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Double Bite Trays: Reality or Panacea?

 
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Double Bite Trays: Reality or Panacea?
By Lloyd A. Kwok, D.D.S.

Not all Double Bite Trays are created equal. There have been several negative reports from lab technicians and some well known clinicians regarding their use and misuse. On the other hand, many excellent clinicians have used them routinely with terrific results. I concur wholeheartedly with one of the top clinicians in the U.S. who stated he would prefer to have a single crown placed in his own mouth utilzing the double arch impression as opposed to a full arch impression.

It is a fact that a double arch impression gives a dynamic functional impression in centric occlusion with the teeth under occluding loading forces. However, all other criteria such as correct anatomical contour of the tray, buccal lingual width, peripheral height, non absorbent thin mesh, and posterior crossbar have to be satisfied to obtain optimum results. Over 80% of all Crown and Bridge work constitutes the single unit, two crowns and/or a three unit bridge. For this reason, the double arch impression is widely used, and is gaining more acceptance among dentists who use them correctly.

I strongly advocate the use of a full half arch tray that captures the cuspid, canine, lateral and central. This impression will simulate a full arch impression in centric occlusion. When mounted properly on the articulator without removing the models from the impression, it will give the most optimum interocclusal record. The articulated models will provide canine rise and incisal guidance to determine the presence of any disclusion or laterotrusive interferences.

Full arch impressions for a single unit or two crowns are not as accurate as a double bite impression. You are taking the prepared side of the impression in an open (mouth) position with pressure applied to the periodontal ligaments. The opposing impression is taken in the same manner, usually with alginate, which if not poured up immediately or soon thereafter shrinks. Usually bubbles in the impression create blotches on the occlusal surfaces of the molar and bicuspid areas which have to be removed to provide good occlusion.

The final step involves taking a bite registration in a closed position, which in most cases do not fit the models exactly. They either have to be adjusted or hand articulated to place the models in occlusion. To make matters worse, what if the full arch impression does not have a full complement of teeth and free end saddles are present? How does one obtain a correct bite registration on a free end saddle case involving moveable tissue? A double bite on the other hand captures the bite registration in centric occlusion provided there are enough teeth on the opposite side of the arch that interdigitate.

Dr. Lloyd Kwok is a graduate of the University of Illinois Dental School, class of 1963. He practiced general dentistry in San Francisco where he has done over 15,000 units utilizing the double bite impression tray technique and has lectured in the United States and many foreign countries. He is a member of several professional organizations, including the CDA, ADA, AGD, FDI and a Fellow of the Academy of Dentistry International.