READERS’
ROUND
TABLE
To THE EDITOR: The article, “Anteroposterior Position of ‘Myo-Monitor Centric’,” by Warden H. Nobel, D.D.S., M.S. (J. PROSTHET. DENT. 33: 398-402, 1975)) cannot go without comment. Having worked with the instrument daily on a clinical basis for several years and having taken no less than five courses in the proper use of the Myo-Monitor, I must conclude that Dr. Nobel’s test contained several serious errors which led him to obtain incorrect data and, therefore, to draw incorrect conclusions. It would be very easy to acquire different points of “myo-centric” if one did not understand the true meaning of the term. As a matter of fact, one would expect this if an initial reading is taken upon application of the Myo-Monitor and another is taken sometime afterward. The reason for this is the existence of spasm in the musculature. When spasm is present during an initial reading, this position will probably not coincide with the position obtained once the Myo-Monitor has had a chance to trigger the release of the high-energy phosphate bonds in the muscle in spasm, breaking down adenosine triphosphate to adenosine diphosphate and allowing the muscle to return to its normally relaxed state in rest position. Muscles in spasm have to be relaxed before a recording is made, otherwise the positions will be different. The recording medium used in the Noble tests was a wax-foil combination which is completely inadequate for registration using the Myo-Monitor. We merely want to stimulate nerves and the muscles they innervate without any external forces, whether from the dentist, patient, or recording medium. While Dr. Noble reportedly followed the Myo-Monitor instruction manual, he apparently failed to incorporate an understanding of muscle and nerve physiology. It is important, to say the least, that the breakdown of high-energy phosphate bonds in muscle be understood to even begin to understand the Myo-Monitor and to use it properly. One assumes when preparing a technique manual for someone who has taken courses in the use of the Myo-Monitor that the reader will be reminded of, or will have acquired, the information from the courses given, prior to obtaining the instrument or the manual. To obtain a scientific instrument (in this case a Myo-Monitor) and to run tests without thoroughly understanding the basis for and the physiology behind it is to abuse the scientific basis for the test; to, in fact, be led to improper conclusions; to mislead our profession in reporting erroneous findings; and to devastatingly slow up the always too-slow educational process. Very detailed research has been done by Myo-Tronics Research Inc. to develop the mandibular Kinesiograph. Using this machine, we have the ability to trace mandibular movements and excursions and also to pinpoint centric relation, centric occlusion, and myo-centric. We can trace the movements, we can record them, and we can return to them. Using the Kinesiograph, we can repeatedly show that, by using the Myo-Monitor and by doing warm-up recordings, the position for any one patient in a relaxed state, with no muscle spasm present, is always the same. Therefore, rather than building to pre-existing positions of malocclusion, based on muscle in spasm, the spasm can be made to relax and reconstruction can be done to attain a proper physiologic position. It is interesting to note that with the Kinesiograph one can record centric relation, yet the centric relation is not within the functional envelope of motion and patients do not function from it. Obviously, if it is so important to return to a position not within the functional envelope, then certainly we do not have to establish a free centric slide (noninterferring pathway) from centric occlusion to centric relation; rather, we must place the patient in the exact functional position which, as shown by the Kinesiograph, is the position repeatedly returned to by the Myo-Monitor. This is not to say that other means of arriving at centric occlusion might not give accurate positions, but that there is now a method of obtaining this position regardless of factors individual to the dentist or patient.
591
592
Readers’
round
table
A clinician who is familiar with the Myo-Monitor and understands its use can arrive at the same position time after time. There is no question that the study done by Dr. Noble was done without being fully familiar with the instrument in a clinical sense, and that he based his references on articles written by men who were also unschooled in the use and understanding of the machine. This falls far short of the objectivity needed when evaluating new or old procedures. ROBERT M. SALISBURY, D.M.D. B~vn. 544 JOHN RINGLINC SLR.~S~TA, FLA. 33577
To
THE
EDITOR:
Position of I thank Dr. Sahsbury for his interest in my study entitled “Anteroposterior but J do not understand many of the comments in his letter. ‘Myo-Monitor Centric’,” First, as was stated in the article, the instruction manual for the Myo-Monitor was carefully followed, and the instrument was used on the patient for several minutes before recordings were taken. Therefore, we assumed that the muscles were relaxed and not in spasm. The wax-metal interocclusal recording medium was used because we experienced less variation with the wax than with the acrylic resin interocclusal records. A dentist who has used the Myo-Monitor for several years made these records and was surprised at the high variability when using the acrylic resin recording medium. I appreciate Dr. Salisbury’s comments about the recording made with the mandibular Kinesograph. Careful reading of the article, however, will show that I did not propose or criticize a particular centric occlusion position. In fact, I made the statement that “. there is still the unsolved problem of exactly where and how the maxillomandibular relationship should be recorded.” Dr. Salisbury provides no information to change this viewpoint. With regard to the objectivity with which this study was conducted, it is an accepted fact that any researcher must base his knowledge on published data. In 1973, I wrote to MyoTronics Research Inc. and specifically requested any new or unpublished material which I could use for my article. The reply J received was that this data was not available. Therefore, as of this date, euer>j published report shows that “Myo-Monitor centric” is a variable and unstable position. There is no published research to contradict this theory, although I would certainly welcome additional information on this subject. WARDEN IL NOBLE, D.D.S.? MS. 450 SCTTER ST. SAN FRANCISCO, CALIP. 94108
ROUND
TABLE
To THE EDITOR: The article, “Anteroposterior Position of ‘Myo-Monitor Centric’,” by Warden H. Nobel, D.D.S., M.S. (J. PROSTHET. DENT. 33: 398-402, 1975)) cannot go without comment. Having worked with the instrument daily on a clinical basis for several years and having taken no less than five courses in the proper use of the Myo-Monitor, I must conclude that Dr. Nobel’s test contained several serious errors which led him to obtain incorrect data and, therefore, to draw incorrect conclusions. It would be very easy to acquire different points of “myo-centric” if one did not understand the true meaning of the term. As a matter of fact, one would expect this if an initial reading is taken upon application of the Myo-Monitor and another is taken sometime afterward. The reason for this is the existence of spasm in the musculature. When spasm is present during an initial reading, this position will probably not coincide with the position obtained once the Myo-Monitor has had a chance to trigger the release of the high-energy phosphate bonds in the muscle in spasm, breaking down adenosine triphosphate to adenosine diphosphate and allowing the muscle to return to its normally relaxed state in rest position. Muscles in spasm have to be relaxed before a recording is made, otherwise the positions will be different. The recording medium used in the Noble tests was a wax-foil combination which is completely inadequate for registration using the Myo-Monitor. We merely want to stimulate nerves and the muscles they innervate without any external forces, whether from the dentist, patient, or recording medium. While Dr. Noble reportedly followed the Myo-Monitor instruction manual, he apparently failed to incorporate an understanding of muscle and nerve physiology. It is important, to say the least, that the breakdown of high-energy phosphate bonds in muscle be understood to even begin to understand the Myo-Monitor and to use it properly. One assumes when preparing a technique manual for someone who has taken courses in the use of the Myo-Monitor that the reader will be reminded of, or will have acquired, the information from the courses given, prior to obtaining the instrument or the manual. To obtain a scientific instrument (in this case a Myo-Monitor) and to run tests without thoroughly understanding the basis for and the physiology behind it is to abuse the scientific basis for the test; to, in fact, be led to improper conclusions; to mislead our profession in reporting erroneous findings; and to devastatingly slow up the always too-slow educational process. Very detailed research has been done by Myo-Tronics Research Inc. to develop the mandibular Kinesiograph. Using this machine, we have the ability to trace mandibular movements and excursions and also to pinpoint centric relation, centric occlusion, and myo-centric. We can trace the movements, we can record them, and we can return to them. Using the Kinesiograph, we can repeatedly show that, by using the Myo-Monitor and by doing warm-up recordings, the position for any one patient in a relaxed state, with no muscle spasm present, is always the same. Therefore, rather than building to pre-existing positions of malocclusion, based on muscle in spasm, the spasm can be made to relax and reconstruction can be done to attain a proper physiologic position. It is interesting to note that with the Kinesiograph one can record centric relation, yet the centric relation is not within the functional envelope of motion and patients do not function from it. Obviously, if it is so important to return to a position not within the functional envelope, then certainly we do not have to establish a free centric slide (noninterferring pathway) from centric occlusion to centric relation; rather, we must place the patient in the exact functional position which, as shown by the Kinesiograph, is the position repeatedly returned to by the Myo-Monitor. This is not to say that other means of arriving at centric occlusion might not give accurate positions, but that there is now a method of obtaining this position regardless of factors individual to the dentist or patient.
591
592
Readers’
round
table
A clinician who is familiar with the Myo-Monitor and understands its use can arrive at the same position time after time. There is no question that the study done by Dr. Noble was done without being fully familiar with the instrument in a clinical sense, and that he based his references on articles written by men who were also unschooled in the use and understanding of the machine. This falls far short of the objectivity needed when evaluating new or old procedures. ROBERT M. SALISBURY, D.M.D. B~vn. 544 JOHN RINGLINC SLR.~S~TA, FLA. 33577
To
THE
EDITOR:
Position of I thank Dr. Sahsbury for his interest in my study entitled “Anteroposterior but J do not understand many of the comments in his letter. ‘Myo-Monitor Centric’,” First, as was stated in the article, the instruction manual for the Myo-Monitor was carefully followed, and the instrument was used on the patient for several minutes before recordings were taken. Therefore, we assumed that the muscles were relaxed and not in spasm. The wax-metal interocclusal recording medium was used because we experienced less variation with the wax than with the acrylic resin interocclusal records. A dentist who has used the Myo-Monitor for several years made these records and was surprised at the high variability when using the acrylic resin recording medium. I appreciate Dr. Salisbury’s comments about the recording made with the mandibular Kinesograph. Careful reading of the article, however, will show that I did not propose or criticize a particular centric occlusion position. In fact, I made the statement that “. there is still the unsolved problem of exactly where and how the maxillomandibular relationship should be recorded.” Dr. Salisbury provides no information to change this viewpoint. With regard to the objectivity with which this study was conducted, it is an accepted fact that any researcher must base his knowledge on published data. In 1973, I wrote to MyoTronics Research Inc. and specifically requested any new or unpublished material which I could use for my article. The reply J received was that this data was not available. Therefore, as of this date, euer>j published report shows that “Myo-Monitor centric” is a variable and unstable position. There is no published research to contradict this theory, although I would certainly welcome additional information on this subject. WARDEN IL NOBLE, D.D.S.? MS. 450 SCTTER ST. SAN FRANCISCO, CALIP. 94108
