Q:In the most recent issue, Vol 2 No 6, you were asked "Are there any harmful side effects from the routine use of X-ray by dentists to examine teeth for cavities or from lamps used to harden non amalgam fillings?" You dealt with the first half of this question very ably and interestingly, but as far as I could see, you did not address yourself to the second half of the question at all. I wonder if you would be kind enough to do so in your next issue. M.M. G., Pershore.

A:We asked dentist Jack Levenson, our resident expert on amalgam and other dental poisons, to comment. His views:"The lamps, which employ ultraviolet light, are no more dangerous (or safe) than any other form of ultraviolet light, whether it derives naturally from the sun or artificially, from such devices as sunbeds.

"There have been no anecdotal reports or studies showing any extensive harm from these lamps, so I think that very occasional exposure does no possible lasting harm.

"The single exception is a published paper alleging that when composite dental materials are used with ultraviolet light, formaldehyde is given off. Patients sensitive to formaldehyde would suffer severe reactions over 10 days, which recede over the next 11 days.

"Nevertheless, in practice I have not found this to be so, and this paper has never been followed up by any others.

"If I suspect that a patient is highly sensitive and may react to one of the composite materials (and this would go for the composites plus the lamp) I have a blood test done beforehand, place a single filling with the material, then do a full blood test two days afterward. If we see changes in the white blood corpuscles, we know the patient is reacting to the substance. We then wait and try different materials. On the few instances where patients cannot tolerate any composite materials, they have to consider gold, porcelain or having the tooth removed."