378
J. Dent.
1992;
20:
No. 6
transducer resonance. Other sensors such as microphones may have similar problems, and unless the sampling rate is at least twice this resonant frequency, high frequency ‘noise’ will be aliased and will appear in the captured envelope as a spurious low frequency signal. If suitable precautions are not taken against this, or are not stated in published work, low frequency components in captured sounds may again be open to doubt. In addition, we have investigated the effect of changing the sensor position, and have found the most satisfactory place to be at the glabella, just above and between the eyes, where the sounds of occlusion are carried up the maxillary buttresses with least interference from other routes of sound conduction. We have also considered the interpretation of gnathosonic data. Prolonged sliding contact between teeth should produce a correspondingly long signal, and signal length has been used by various researchers as a diagnostic index. There is a basic problem, however, in that long but quiet signals will appear to decay to background in a relatively short time. They might then be mistaken for short signals. For example, gnathosonics has historically used analogue equipment such as chart recorders, where signal attenuation can be adjusted so that quiet and loud noises have similar amplitudes for ‘comparison’. However, an enlarged quiet recording from a patient in pain might then appear to have a long duration. A subsequent reduced loud signal when the patient is pain free might in the same way appear to be of short duration. This would give the expected appearance of the tooth sound becoming crisper as treatment progressed, whereas this might not be the case at all. We have not yet properly solved this problem, even for digitized waveforms, and other workers should be aware of this capacity for inadvertent signal manipulation. On occasions we have also observed that inadvertent earth loops, which arise when the chassis potential of different components of electronic equipment are not the same, can introduce spurious extra components into a captured signal. These are usually of low frequency, further complicating what may already be an aliased signal with false low frequencies. Further, we have examined gnathosonic sounds by recording them on cassette tape, and have encountered a problem with automatic gain control which attenuates any high signal amplitude. The problem for gnathosonics is that the initial signal is indeed of high amplitude which then decays. Attenuation of the initial peak has been found to give a false shape to the sound envelope, not least because the attenuation persists into subsequent vibrations. The simple answer is to keep the signal below the age threshold, and users of such recorders should be aware of the problem. A second problem with tape recorders, and indeed hard copy devices such as chart recorders, is that the frequency response must be uniform across the desired frequency range. Workers should therefore check that sound envelopes have not been distorted in this way. We believe that these sources of error are sufficiently serious as to cast doubt on gnathosonic data unless a research report includes the means of their control. What appears to be lacking from gnathosonics is an agreed standard against which all work can be judged, and it is our opinion that the most pressing need at present is the setting of such a standard. This therefore is a major goal of our current research. In the meantime, researchers in this field should be aware of the pitfalls, particularly aliasing, and ensure that
any research publications include full specifications of the apparatus used and the methods by which the problems highlighted here have been addressed. FL D. Bagnall K. W. Tyson Edinburgh Dental School
Periodontics:
A Practical Approach
Dear Sir,
While wishing to extend my thanks to Dr Caffesse for reviewing my book Periodontics: A Practical Approach (J. Dent. 199 1; 19, 368). I cannot let some of his comments pass unchallenged. I am surprised that the innovative separation of the treatment philosophy, principles and methods, comprising Part II, from that of the corroborative research findings presented in Part III, should have come across so adversely and moreover, stated to have led to minor inconsistencies. The purpose of this format was to facilitate an unimpeded examination and understanding of the practical aspects of periodontics, whilst maintaining a close link with the readily accessible documentary support for this approach in the separate review of the scientific basis of therapy, as stated clearly in the preface, and reinforced by Sture Nyman in the foreword to the book. A further and closer examination of the book will, I am confident, make the merits of this layout more evident and in turn clarify any apparent inconsistencies. Should however any such inconsistencies still persist, a note thereof for rectification in subsequent editions would be appreciated. The statements that the author’s ‘personal views comprise approximately 75 per cent of the book’ and ‘are unsupported by references or resources for further reading’ are astonishing and cannot be sustained and, indeed, are countermanded by the later statements that ‘Part III presents a review of current research findings to support the clinical approach recommended.. . and that these chapters present extensive reviews of pertinent topics and are supported by excellent citations’. Furthermore, the fact that the major part of the book does, by design, not incorporate the supportive references in their conventional juxtapositioning to the text, cannot be construed as rendering the content as unsubstantiated personal opinion. These statements are therefore not considered to be justified. Finally, the classification and nomenclature of surgical procedures is viewed somewhat critically. The purpose of this simplified approach to surgery of only three basic techniques is to avoid the conventional treatment planning difficulties in which, as stated in the preface, the appropriate techniques must be selected from the bewildering array currently available to cater for the varying degrees of breakdown present in any one case. In addition, the terms given are, with the exception of ‘surgical reattachment’, not unique and describe precisely and unequivocally the objective of the exercise, unlike that of, for example, the ‘Modified Widman flap’ used elsewhere. It is of further interest in this context, that no
Letters to the Editor
mention is made of the terms, introduced in the section on disease management, of ‘phased instrumentation’, the ‘gingival response’ and ‘gingival and periodontal pocket therapy’. These are unique, and designed to avoid traditional terminology relating to non-surgical treatment that imply a surgical component is forthcoming, and in turn, de-emphasizes the fundamental role of the management of the cause of disease in favour of that directed at its effects.
379
The comments regarding the sequence of Parts II and III of the text are noted and will be given consideration in the next edition. J. B. Kieser Institute of Dental Surgery Eastman Dental Hospital London
ANNOUNCEMENT FROM THE EDITOR The JoumuZ of Dentistryis an established forum for the publication of papers reporting recent research in the field of dental science, and explains the relevance of these innovations to the contemporary practice of clinical dentistry. As an enhanced service to its readers the Journd of Dentistrywill expand its coverage of the following sections: 0
Letters to the Editor - expressing views of interest and relevance, and as a means of stimulating debate
0
Short Communications - presenting preliminary results of a study. Guaranteed rapid publication
0
Review Articles - overviews of established and emerging areas for research in dental science
Authors are encouraged to submit their contributions to: The Editor, Journal of Dentistry, c/o Department of Restorative Dentistry, University Dental Hospital of Manchester, Higher Cambridge Street, Manchester MI5 6F’H, UK Naim Wilson Editor
J. Dent.
1992;
20:
No. 6
transducer resonance. Other sensors such as microphones may have similar problems, and unless the sampling rate is at least twice this resonant frequency, high frequency ‘noise’ will be aliased and will appear in the captured envelope as a spurious low frequency signal. If suitable precautions are not taken against this, or are not stated in published work, low frequency components in captured sounds may again be open to doubt. In addition, we have investigated the effect of changing the sensor position, and have found the most satisfactory place to be at the glabella, just above and between the eyes, where the sounds of occlusion are carried up the maxillary buttresses with least interference from other routes of sound conduction. We have also considered the interpretation of gnathosonic data. Prolonged sliding contact between teeth should produce a correspondingly long signal, and signal length has been used by various researchers as a diagnostic index. There is a basic problem, however, in that long but quiet signals will appear to decay to background in a relatively short time. They might then be mistaken for short signals. For example, gnathosonics has historically used analogue equipment such as chart recorders, where signal attenuation can be adjusted so that quiet and loud noises have similar amplitudes for ‘comparison’. However, an enlarged quiet recording from a patient in pain might then appear to have a long duration. A subsequent reduced loud signal when the patient is pain free might in the same way appear to be of short duration. This would give the expected appearance of the tooth sound becoming crisper as treatment progressed, whereas this might not be the case at all. We have not yet properly solved this problem, even for digitized waveforms, and other workers should be aware of this capacity for inadvertent signal manipulation. On occasions we have also observed that inadvertent earth loops, which arise when the chassis potential of different components of electronic equipment are not the same, can introduce spurious extra components into a captured signal. These are usually of low frequency, further complicating what may already be an aliased signal with false low frequencies. Further, we have examined gnathosonic sounds by recording them on cassette tape, and have encountered a problem with automatic gain control which attenuates any high signal amplitude. The problem for gnathosonics is that the initial signal is indeed of high amplitude which then decays. Attenuation of the initial peak has been found to give a false shape to the sound envelope, not least because the attenuation persists into subsequent vibrations. The simple answer is to keep the signal below the age threshold, and users of such recorders should be aware of the problem. A second problem with tape recorders, and indeed hard copy devices such as chart recorders, is that the frequency response must be uniform across the desired frequency range. Workers should therefore check that sound envelopes have not been distorted in this way. We believe that these sources of error are sufficiently serious as to cast doubt on gnathosonic data unless a research report includes the means of their control. What appears to be lacking from gnathosonics is an agreed standard against which all work can be judged, and it is our opinion that the most pressing need at present is the setting of such a standard. This therefore is a major goal of our current research. In the meantime, researchers in this field should be aware of the pitfalls, particularly aliasing, and ensure that
any research publications include full specifications of the apparatus used and the methods by which the problems highlighted here have been addressed. FL D. Bagnall K. W. Tyson Edinburgh Dental School
Periodontics:
A Practical Approach
Dear Sir,
While wishing to extend my thanks to Dr Caffesse for reviewing my book Periodontics: A Practical Approach (J. Dent. 199 1; 19, 368). I cannot let some of his comments pass unchallenged. I am surprised that the innovative separation of the treatment philosophy, principles and methods, comprising Part II, from that of the corroborative research findings presented in Part III, should have come across so adversely and moreover, stated to have led to minor inconsistencies. The purpose of this format was to facilitate an unimpeded examination and understanding of the practical aspects of periodontics, whilst maintaining a close link with the readily accessible documentary support for this approach in the separate review of the scientific basis of therapy, as stated clearly in the preface, and reinforced by Sture Nyman in the foreword to the book. A further and closer examination of the book will, I am confident, make the merits of this layout more evident and in turn clarify any apparent inconsistencies. Should however any such inconsistencies still persist, a note thereof for rectification in subsequent editions would be appreciated. The statements that the author’s ‘personal views comprise approximately 75 per cent of the book’ and ‘are unsupported by references or resources for further reading’ are astonishing and cannot be sustained and, indeed, are countermanded by the later statements that ‘Part III presents a review of current research findings to support the clinical approach recommended.. . and that these chapters present extensive reviews of pertinent topics and are supported by excellent citations’. Furthermore, the fact that the major part of the book does, by design, not incorporate the supportive references in their conventional juxtapositioning to the text, cannot be construed as rendering the content as unsubstantiated personal opinion. These statements are therefore not considered to be justified. Finally, the classification and nomenclature of surgical procedures is viewed somewhat critically. The purpose of this simplified approach to surgery of only three basic techniques is to avoid the conventional treatment planning difficulties in which, as stated in the preface, the appropriate techniques must be selected from the bewildering array currently available to cater for the varying degrees of breakdown present in any one case. In addition, the terms given are, with the exception of ‘surgical reattachment’, not unique and describe precisely and unequivocally the objective of the exercise, unlike that of, for example, the ‘Modified Widman flap’ used elsewhere. It is of further interest in this context, that no
Letters to the Editor
mention is made of the terms, introduced in the section on disease management, of ‘phased instrumentation’, the ‘gingival response’ and ‘gingival and periodontal pocket therapy’. These are unique, and designed to avoid traditional terminology relating to non-surgical treatment that imply a surgical component is forthcoming, and in turn, de-emphasizes the fundamental role of the management of the cause of disease in favour of that directed at its effects.
379
The comments regarding the sequence of Parts II and III of the text are noted and will be given consideration in the next edition. J. B. Kieser Institute of Dental Surgery Eastman Dental Hospital London
ANNOUNCEMENT FROM THE EDITOR The JoumuZ of Dentistryis an established forum for the publication of papers reporting recent research in the field of dental science, and explains the relevance of these innovations to the contemporary practice of clinical dentistry. As an enhanced service to its readers the Journd of Dentistrywill expand its coverage of the following sections: 0
Letters to the Editor - expressing views of interest and relevance, and as a means of stimulating debate
0
Short Communications - presenting preliminary results of a study. Guaranteed rapid publication
0
Review Articles - overviews of established and emerging areas for research in dental science
Authors are encouraged to submit their contributions to: The Editor, Journal of Dentistry, c/o Department of Restorative Dentistry, University Dental Hospital of Manchester, Higher Cambridge Street, Manchester MI5 6F’H, UK Naim Wilson Editor
