24A
Letters to the editor
2. Tallents RH, Macher DJ, Rivoli P, Puzas JE, Scapino RP, Katzberg RW. An animal model for disk displacement. J Craniomandib Disord Facial Oral Pain 1990;4:233-40. 3. Schellhas KP, Piper MA, Omlie MR. Facial skeletal remodeling due to temporomandibular joint degeneration: an imaging study of 1130patients. AINR (Am J Neuroradiology) 1990;11:541-51. 4. Schellhas KP. Internal derangement of the temporomandibular joint: radiologic staging with clinical, surgical, and pathol~ic correlation. Magn Reson Imaging 1989;7:495-515. 5. Ricketts RM. Lamin~raphy in the diagnosis of temporomandibular disorders. J Am Dent Assoc 1953;46:620. 6. Sanchez-Woodworth R, Katzberg RW, TaUents RH, Guay JA. Radiographic assessment of temporomandibular joint pain and dysfunction in the pediatric age group. J Dent Child 1988;55:27881.
C o m m e n t on differential tooth movement To the Editor:
I would congratulate Richard Parkhouse for the excellent treatment results on the three cases described in his article "Differential Tooth Movement In Uphill Cases," June 1992, AJO-DO. However, attention should be directed to the pretreatment and posttreatment reactions of the anterior portion of the palate as shown by the superimposed tracings of the palate on all three cases (pp. 495,497,500). These palatal tracings seem to show the anteroposterior dimension of the anterior palate apparently unaltered after rather extensive orthodontic (not orthopedic) movement of the maxillary incisor teeth in a lingual (posterior) direction. In other words, the tracings would indicate that the incisor teeth remained in approximately the same anterior/posterior position within the anterior portion of the palate after they were orthodontically retracted, and that the anterior palate actually moved lingually with the incisor teeth (presumably by concomitant osteoclastic activity on the labial cortical bone and osteoblastic reaction on the palatal cortex). Thus, the anterior portion of the palate would appear to move posteriorly along with the retracted incisor teeth, instead of the teeth moving through the anterior palatal bone. Unfortunately, previous bone implant and laminographic studies '.2 have rather conclusively shown that such a response of the anterior palate to orthodontic forces is just not possible physiologically or anatomically. I am confident that if Dr. Parkhouse would retrace the before/after treatment results on the palate (giving par-
Am. J, Orthod. Dentofac. Orthop. October 1992
ticular attention to superimposing the maxillae using anatomic landmarks, especially the inferior border of the palate), he will find that the orthodontically retracted incisor teeth have been moved through the alveolar bone of the anterior palate. Once the apical portion of the teeth have contacted the palatal cortex no further posterior movement is possible and the roots will remain against the palatal cortical bone. In summary, the anterior portion of the palate will not move lingually as orthodontic forces move the incisor teeth lingually. Although the alveolar bone directly supporting the teeth can be moved lingually (and elongated), it does not appear possible to move the apices of the roots more lingually than the pretreatment position of the palate. Thus, there appears to be an anatomic limitation to the lingual movement of maxillary incisor teeth. This letter is not intended to in any way diminish the excellent article by Parkhouse, but solely to draw attention to the reaction of the anterior palate during orthodontic retraction of the maxillary incisorsmthe three tracings in the published article would tend to give the erroneous impression that with adequate orthodontic forces the maxillary incisors could be retracted without limit--a theory which has been shown to be anatomically incorrect. John G. Edwards, DDS, MS 7400 Baltusrol Ln. Charlotte, NC 28210 REFERENCES 1. Edwards JG. A study of the anterior portion of the palate as it relates to orthodontictherapy. AM J ORT~tOD1976;69:249-73. 2. Ten Hoeve A, Mulie RM. The effect of antero-postero incisor repositioningOn the palatal cortex as studies with laminagraphy. J Clin Orthod 1976;10:12-36.
Th a n k you A word of thanks to Barry Mollenhauer for his guest editorial "Chaos Theory and Fractors," reprinted from the Australian Orthodontic Journal, which appeared in the August issue of the AJO-DO.
Letters to the editor
2. Tallents RH, Macher DJ, Rivoli P, Puzas JE, Scapino RP, Katzberg RW. An animal model for disk displacement. J Craniomandib Disord Facial Oral Pain 1990;4:233-40. 3. Schellhas KP, Piper MA, Omlie MR. Facial skeletal remodeling due to temporomandibular joint degeneration: an imaging study of 1130patients. AINR (Am J Neuroradiology) 1990;11:541-51. 4. Schellhas KP. Internal derangement of the temporomandibular joint: radiologic staging with clinical, surgical, and pathol~ic correlation. Magn Reson Imaging 1989;7:495-515. 5. Ricketts RM. Lamin~raphy in the diagnosis of temporomandibular disorders. J Am Dent Assoc 1953;46:620. 6. Sanchez-Woodworth R, Katzberg RW, TaUents RH, Guay JA. Radiographic assessment of temporomandibular joint pain and dysfunction in the pediatric age group. J Dent Child 1988;55:27881.
C o m m e n t on differential tooth movement To the Editor:
I would congratulate Richard Parkhouse for the excellent treatment results on the three cases described in his article "Differential Tooth Movement In Uphill Cases," June 1992, AJO-DO. However, attention should be directed to the pretreatment and posttreatment reactions of the anterior portion of the palate as shown by the superimposed tracings of the palate on all three cases (pp. 495,497,500). These palatal tracings seem to show the anteroposterior dimension of the anterior palate apparently unaltered after rather extensive orthodontic (not orthopedic) movement of the maxillary incisor teeth in a lingual (posterior) direction. In other words, the tracings would indicate that the incisor teeth remained in approximately the same anterior/posterior position within the anterior portion of the palate after they were orthodontically retracted, and that the anterior palate actually moved lingually with the incisor teeth (presumably by concomitant osteoclastic activity on the labial cortical bone and osteoblastic reaction on the palatal cortex). Thus, the anterior portion of the palate would appear to move posteriorly along with the retracted incisor teeth, instead of the teeth moving through the anterior palatal bone. Unfortunately, previous bone implant and laminographic studies '.2 have rather conclusively shown that such a response of the anterior palate to orthodontic forces is just not possible physiologically or anatomically. I am confident that if Dr. Parkhouse would retrace the before/after treatment results on the palate (giving par-
Am. J, Orthod. Dentofac. Orthop. October 1992
ticular attention to superimposing the maxillae using anatomic landmarks, especially the inferior border of the palate), he will find that the orthodontically retracted incisor teeth have been moved through the alveolar bone of the anterior palate. Once the apical portion of the teeth have contacted the palatal cortex no further posterior movement is possible and the roots will remain against the palatal cortical bone. In summary, the anterior portion of the palate will not move lingually as orthodontic forces move the incisor teeth lingually. Although the alveolar bone directly supporting the teeth can be moved lingually (and elongated), it does not appear possible to move the apices of the roots more lingually than the pretreatment position of the palate. Thus, there appears to be an anatomic limitation to the lingual movement of maxillary incisor teeth. This letter is not intended to in any way diminish the excellent article by Parkhouse, but solely to draw attention to the reaction of the anterior palate during orthodontic retraction of the maxillary incisorsmthe three tracings in the published article would tend to give the erroneous impression that with adequate orthodontic forces the maxillary incisors could be retracted without limit--a theory which has been shown to be anatomically incorrect. John G. Edwards, DDS, MS 7400 Baltusrol Ln. Charlotte, NC 28210 REFERENCES 1. Edwards JG. A study of the anterior portion of the palate as it relates to orthodontictherapy. AM J ORT~tOD1976;69:249-73. 2. Ten Hoeve A, Mulie RM. The effect of antero-postero incisor repositioningOn the palatal cortex as studies with laminagraphy. J Clin Orthod 1976;10:12-36.
Th a n k you A word of thanks to Barry Mollenhauer for his guest editorial "Chaos Theory and Fractors," reprinted from the Australian Orthodontic Journal, which appeared in the August issue of the AJO-DO.
