QUESTIONS AND ANSWERS R eaders a re invited to send questions to TH E JOU RN A L ab o u t any aspect of dental practice or practice m anagem ent. T h eir questions w ill be answered by com petent authorities in the vari ous aspects o f dentistry. Q uestions m ust be signed when subm itted but may appear in this col um n with initials only, if the qu estio ner w ishes to rem ain anonym ous.
activity in this well-protected area. A ccuracy o f tooth form ation charts ■ A well-built male Caucasian bom Jan 25, 1958 came to my office March 23,1970 requesting relief from a vague pain in his upper right molar-premolar area. Clinical and X-ray examination revealed an exceptionally deep cari ous lesion in the lower right second molar, which was treated. The pa tient was advised that there was no ap parent reason for the pain in the upper region, that it might be referred from the lower carious tooth, and to return if the pain persisted. The patient did return, Aug 22, 1974, requesting routine dental care. A complete clinical examination in cluding full-series X rays revealed many carious lesions, two bilateral mandibular clusters o f (three each) overlapping, poorly developed super numerary teeth resembling premolars, and a supernumerary premolar devel oping in the area between the mesial root o f the upper right first molar and distal to the root of the upper right sec ond premolar, which did not show on X rays taken 4'A years before. This raises the question o f the ac curacy of the commonly accepted charts o f chronological tooth forma tion which approximate hard tissue formation for this area as follows: for mation begins about 2 years o f age; crown is completed about 6 to 7 years; root is completed about 12 years. This patient at age 12 showed no signs of this development except possibly (on hindsight) the pain that originally brought him into the office. A t age 16Vi he shows a partially calcified crown with an active growth area apically. I am at a loss to explain the origin o f the ameloblasts and odontoblasts, their dormant state, and their delayed
SOL A. GROSS, DDS KEW GARDENS, NY
■ In my experience, I have discov ered late-developing supernumerary teeth in premolar regions in two pa tients. Earlier radiographs of these patients did not reveal the supernum erary teeth. In both instances the pa tients were 12 years of age when the teeth became radiographically evi dent; they were undetectable at age 10 years. N oy es, Schour, and N o y es state that remnants o f the dental lamina may persist as epithelial pearls and differentiate into supernumerary teeth. The strands o f cells that arise from the dental lamina, according to Diamond, are not always limited to a single proliferation for each tooth but often include accessory strands. If these strands penetrate to a region where they may develop, an enamel organ arises and subsequently a su pernumerary tooth is formed. This would explain the origin o f the ameloblasts, odontoblasts, and the supernumerary teeth. I am unable to explain why they develop so late in som e patients. Graber has said “ there is no definite time when supernumerary teeth may de velop” ; therefore, w e should be alert to the possibility that they may appear long after the permanent teeth in the area have erupted and their roots cal cified. It would seem that there is a greater likelihood of finding latedeveloping supernumerary teeth in the premolar area than in other dental areas. FAUSTIN N. WEBER, DDS PROFESSOR AND CHAIRMAN DEPARTMENT OF GRADUATE ORTHODONTICS, UNIVERSITY OF TENNESSEE, COLLEGE OF DENTISTRY, MEMPHIS
Cyanoacrylate ce m e n tsprecautions? m What precautions should be taken with the intraoral use o f cyanoacryl ate cements to avoid possible harm to patients? LYNN HARNER, DDS DODGE CITY, KAN
■ The Council on D ental Materials and D evices published in the D ecem ber issue of The Journal o f the A m er ican D en tal A ssociation (page 1386) a status report on cyanoacrylate ce ments used in dentistry. The Council believes that at the present time cy anoacrylates cannot be recommend ed for routine use in dentistry. The cyanoacrylate polymers undergo degradation in the biologic system and may form cyanoacetate and pos sibly formaldehyde, both o f which may give rise to local irritation. The most severe responses are to the methyl 2-cyanoacrylate, which breaks down most rapidly. At least one ethyl 2-cyanoacrylate is marketed at the present time (C yano-D ent, Ellman Dental Manufacturing C o.). Studies using this material indicate that it is less retentive for cementing pins than zinc phosphate or carboxylate cem ents. If a decision is made to use the ethyl 2-cyanoacrylate cem ent to cement retentive pins, the pin holes must match the pins in size, the den tin should be dried without desicca tion, and the pins should be held in place under pressure until the bond is set. A lso, care must be exercised so that the liquid cem ent does not contact the skin because the hardened film is difficult to remove. JOHN W. STANFORD, PHD SECRETARY, COUNCIL ON DENTAL MATERIALS AND DEVICES JADA, V ol. 90, April 1975 ■ 727