LETTERS TO THE EDITOR A word of caution To the Editor:
I am writing to present a "Case Report" for all practitioners of dentistry as follows: In a recent orthodontic debanding/debonding procedure, the use of an 1156 carbide bur at high speed produced a "shower of sparks" when inadvertently touched against the residual portion of a ceramic bracket on an adjacent tooth. Normally any portion of the ceramic bracket that will not come off with the usual special instrumentation is taken off with diamond burs at high speed with copious water. Therefore this "shower of sparks" phenomenon had not been noticed before. It would be advisable for practitioners using steel or carbide instruments on a patient with ceramic brackets be most careful to avoid this contact, or consider using only fine diamonds when removing any "flash" or when finishing the,tooth surface after ceramic bracket removal. The consequences for the patient or members of the staff may be serious if occurring in the vicinity of flammable anesthetics or gases and should reinforce the use of copious water to dampen any accidental contact and the use safety glasses for all concerned. Lart3, K. Aagesen, DDS, MS 1000 West University Suite 200 Rochester, M! 48307-1875
Comments on static magnetic fields To the Editor:
I would like to comment on an article that was published in the JOURNAL by Linder-Aronson and Lindskog entitled "A Morphometric Study of Bone Surfaces and Skin Reactions After Stimulation With Static Magnetic Fields in Rats." (AM J ORTHOD DENTOFAC ORTHOP 1991 ;99:44-8) The work reported in this article is difficult to interpret and would certainly not be easy to reproduce. For example, it is not clear whether the effects reported are actually due to the magnetic field. They may, in fact, be more related to mechanical and chemical factors or they may be nonexistent. Consequently, many questions arise to challenge the claims made in this study. Specifically, there is a serious lack of information about the magnet, the field parameters, and its orientation. Which Samarium-Cobalt (SmCo) alloy was used? What is the energy product? The dimensions of the SmCo magnet are given as 2 x 4 mm. What is the third dimension-this is critical, particularly for oral application? Is the 2 x 4 mm dimension the pole face? If so, how was it oriented with respect to the target epithelial and osseous 18A
tissues? The change in the magnetic field geometry as the aluminum rings are adjusted for growth should be described since this changes dosimetry and has a potential impact on the bioeffect. The lack of this information represents a serious deficiency in the article. These factors influence the magnetic field flux density at t h e epithelial and osseous interfaces. Consequently, there certainly is a critically varying dose at these different levels that is not given. Any potent!al bioeffect is certainly dependent on actual magnetic field flux level, particularly within the biologic window. What was the effect of the opposing magnet on this flux density? Did the aluminum rings perturb the field in any way? The experimental design should have included modelling and mapping of the flux density in gauss or tesla units as they varied with the field gradient. Furthermore, this research was inadequately controlled leading to faulty interpretation of the data. For example, sham magnets were not employed! Were the active magnets coated to prevent leach-out products, thereby avoiding potential chemical complications? Indeed, the magnets were probably contacting the skin, as stated on page 44: "to examine the soft tissue in immediate contact with the magnets." Were the magnets therefore positioned between the aluminum ring and the skin? Was there a cutout in the ring to accommodate the magnets? Were the corners of the magnets impinging on the skin? Also, were the legs shaved? Considering these factors, it is not clear whether sham magnets would not have had the same effect on the soft and hard tissue as was observed with the active ones. To further complicate the situation, another dosim-
I am writing to present a "Case Report" for all practitioners of dentistry as follows: In a recent orthodontic debanding/debonding procedure, the use of an 1156 carbide bur at high speed produced a "shower of sparks" when inadvertently touched against the residual portion of a ceramic bracket on an adjacent tooth. Normally any portion of the ceramic bracket that will not come off with the usual special instrumentation is taken off with diamond burs at high speed with copious water. Therefore this "shower of sparks" phenomenon had not been noticed before. It would be advisable for practitioners using steel or carbide instruments on a patient with ceramic brackets be most careful to avoid this contact, or consider using only fine diamonds when removing any "flash" or when finishing the,tooth surface after ceramic bracket removal. The consequences for the patient or members of the staff may be serious if occurring in the vicinity of flammable anesthetics or gases and should reinforce the use of copious water to dampen any accidental contact and the use safety glasses for all concerned. Lart3, K. Aagesen, DDS, MS 1000 West University Suite 200 Rochester, M! 48307-1875
Comments on static magnetic fields To the Editor:
I would like to comment on an article that was published in the JOURNAL by Linder-Aronson and Lindskog entitled "A Morphometric Study of Bone Surfaces and Skin Reactions After Stimulation With Static Magnetic Fields in Rats." (AM J ORTHOD DENTOFAC ORTHOP 1991 ;99:44-8) The work reported in this article is difficult to interpret and would certainly not be easy to reproduce. For example, it is not clear whether the effects reported are actually due to the magnetic field. They may, in fact, be more related to mechanical and chemical factors or they may be nonexistent. Consequently, many questions arise to challenge the claims made in this study. Specifically, there is a serious lack of information about the magnet, the field parameters, and its orientation. Which Samarium-Cobalt (SmCo) alloy was used? What is the energy product? The dimensions of the SmCo magnet are given as 2 x 4 mm. What is the third dimension-this is critical, particularly for oral application? Is the 2 x 4 mm dimension the pole face? If so, how was it oriented with respect to the target epithelial and osseous 18A
tissues? The change in the magnetic field geometry as the aluminum rings are adjusted for growth should be described since this changes dosimetry and has a potential impact on the bioeffect. The lack of this information represents a serious deficiency in the article. These factors influence the magnetic field flux density at t h e epithelial and osseous interfaces. Consequently, there certainly is a critically varying dose at these different levels that is not given. Any potent!al bioeffect is certainly dependent on actual magnetic field flux level, particularly within the biologic window. What was the effect of the opposing magnet on this flux density? Did the aluminum rings perturb the field in any way? The experimental design should have included modelling and mapping of the flux density in gauss or tesla units as they varied with the field gradient. Furthermore, this research was inadequately controlled leading to faulty interpretation of the data. For example, sham magnets were not employed! Were the active magnets coated to prevent leach-out products, thereby avoiding potential chemical complications? Indeed, the magnets were probably contacting the skin, as stated on page 44: "to examine the soft tissue in immediate contact with the magnets." Were the magnets therefore positioned between the aluminum ring and the skin? Was there a cutout in the ring to accommodate the magnets? Were the corners of the magnets impinging on the skin? Also, were the legs shaved? Considering these factors, it is not clear whether sham magnets would not have had the same effect on the soft and hard tissue as was observed with the active ones. To further complicate the situation, another dosim-
