- Email: [email protected]
Correlating TMJ symptoms with condylar position following rigid fixation of sagital splits
Ml6 Zuniga, DMD, MS. University
of Dentistry, KM)
of North Carolina School Chapel Hill, NC 27514 (Joseph SA, Knigge
The inhalation of nitrous oxide in concentrations below those required for anesthesia produces analgesia in man and animals in a dose-dependent manner. Nitrous oxide increased P-endorphin concentration along the Proopiomelanocortin (POMC) neuronal system in rats and stimulated l3-endorphin secretory activity in vitro in previous studies. A reinvestigation of the analgesic properties of nitrous oxide and the reversal potential of a narcotic antagonist was made in a series of behavioral studies in the rat. Finally, the contribution of the P-endorphin mediated analgesia system in terminal fields in the periaqueductal grey (PAG). Thirty male Sprague-Dawley rats weighing between 350 and 450 gms were used. Every rat was entered into three experiments, and analgesia testing was performed by the radiant heat tail flick and electrical evoked foot flick tests. Analgesia was calculated as percentage of the maximal possible effect (per cent MPE) before and after exposures to 30, 60, and 80% nitrous oxide, while exposures to air served as control. The involvement of opioid elements in nitrous oxide analgesia was studied by comparing the effects of naloxone (10 mg/kg s.c.) and saline on air and 80% nitrous oxide in a double-blind manner. The effects of lesioning the PAG on nitrous oxide analgesia were examined next. All the animals that participated in experiment one and two were anesthetized and fixed to a stereotaxic apparatus. Trephine bur holes were drilled into the skull and kainic acid (OS pg, n = 18) or saline (0.09%, n = 9) was bilaterally injected into the PAG. Ten days postoperatively, the animals were exposed to either air or 80% nitrous oxide. Analgesia was similarly tested in a blind manner. Localization of lesions were verified by histology. In Friedman’s two-way analysis of variance rats, exposed to 80% and 60% nitrous oxide expressed statistically significant elevations of per cent MPE. Rats exposed to 30% nitrous oxide showed no significant difference in per cent MPE but had an increase in coefficient of variance. Pretreatment with naloxone produced a significant decrease in per cent MPE (P = 0.005) and an increase in variance of response. Kainic acid lesions of the PAG reversed analgesia produced by 80% nitrous oxide (P = 0.001). Nitrous oxide produced a concentration-dependent analgesia in rats in which higher concentrations of nitrous oxide produce a more reproducable and relatively stable analgesia. Nitrous oxide analgesia was partially antagonized by naloxone, which may be due in part to an increase in variance of response by naloxone. P-Endorphin terminal fields of the AG appear to be critically involved in the production of analgesia by nitrous oxide. In conclusion, it is probable that the P-endorphin mediated analgesia system described by other evidence is responsible for analgesia following stimulation of POMC-producing neurons by nitrous oxide. ABSTRACT SESSION IV ON ORTHOGNATHIC AND PREPROSTHETIC SURGERY
SUNDAY, SEPTEMBER~~, 10:00AMTO 1:00 PM MODERATOR: BRIAN ALPERT, DDS
REACTOR PANEL: RAYMOND J. FONSECA, DMD, AND MYER S. LEONARD, DDS, MD Relapse Following Mandibular Advancement Using Dental Plus Skeletal Maxillomandibular Fixation-An Experimental Investigation. Kathleen H. Mayo, DDS. University of Michigan, Department of OMS, Ann Arbor, MI 48109 (Ellis E) Investigators have found that the majority of skeletal relapse occurs during the period of maxillomandibular fixation. All such reports utilized the dentition to hold the mandible in its new position. An unproven method that has gained popularity is the combined use of dental and skeletal fixation. This mode of fixation bypasses the dentition and directly secures the skeletal elements with wires. The purpose of this investigation was to evaluate the short-term effectiveness of dental plus skeletal maxillomandibular fixation in holding the mandible in its new position following mandibular advancement surgery. Twenty-four adult female Macaca mulatta were used in this experiment. All animals underwent a sagittal ramus advancement osteotomy of two molar cusps (approximately 7 mm). Each of the 24 animals was randomly assigned to one of two groups based upon the type of postsurgical maxillomandibular fixation used. Group DF (dental fixation) had the upper and lower teeth bonded together for six weeks with orthodontic composite resin. Group SF (skeletal fixation), in addition to this regimen, had bilateral circummandibular wires attached to pyriform aperture wires. Cephalometric radiographs were used to statistically analyze changes up to six weeks postsurgically with the use of tantalum bone markers placed throughout the craniofacial complex. The results showed the following: 1) Group DF animals underwent a significant amount of horizontal relapse during the period of maxillomandibular fixation (P < 0.01). Group SF showed complete horizontal stability of the surgical result. 2) Group DF animals underwent significant changes in the vertical position of the mandibular symphysis during the period of maxillomandibular fixation (P < O.OS), with a mean inferior repositioning of 1.3 mm. Group SF animals underwent no such increase in anterior facial height and showed almost complete vertical stability of the surgical result. The authors conclude that skeletal wires in addition to dental maxillomandibular fixation can significantly improve postsurgical stability following mandibular advancement osteotomy. This study was supported by NIH-NIDR grant DE06874. Correlating TMJ Symptoms With Condylar Position Following Rigid Fixation of Sagittal Splits. David I? Timmis, DDS, and C. C. Chilcoat. University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78284 (Skoczylas LJ, Van Sickels JE). A prospective study of 18 patients (17 women, one man), with a mean age of 25.7 years was performed to evaluate pre- and postoperative (six months) condylar position, MIO, and TMJ symptomatology after rigid fixation of bilateral ramus sagittal split osteotomies. Nine patients received mandibular advancements and concomitant maxillary LFI osteotomies. Five received mandibular advancements only. Three patients had mandibular setbacks and LFI, while one underwent an isolated man-
Ml7
dibular setback. Tomograms of both TMJs were taken with a Quint Sectograph-200 after obtaining a preoperative submental vertex radiograph to allow subsequent reproducible positioning. The anatomic detail of the condyle and fossa was traced by a single examiner at Tl (immediately preoperatively), T2 (immediately postoperatively), and T4 (six months postoperatively). Three lines were drawn on the Tl radiograph. The first was from a point designating the squamotympanic fissure to the height of the articular eminence. Perpendicular to this, a second line was scribed through the center of the condyle, and a third line was drawn connecting an arbitrary point on the condylar neck to the center point. These Tl reference lines were transferred to subsequent radiographs. Anterior-posterior, superior-inferior, and rotational movements of the condyle were noted for the intervals Tl -T2 and Tl-T4. In addition, preoperative and six-month postoperative maximal interincisal opening (MIO) and TMJ clicking were noted. Condylar movement was statistically similar after mandibular advancement and setback, either alone or with LFI. Mean movements during the Tl-T2 interval was posterior (-.46 mm; range - 3.5 to 1) and inferior ( - .22 mm: range - 2 to 2) for mandibular advancement and anterior (. 19 mm; range 1.5 to - 1) and inferior ( - .69 mm; range -4 to 5) for mandibular posterior repositioning. Proximal segment rotation was counterclockwise (mean -3.4 degrees) with advancement and clockwise (mean 1.6 degrees) with mandibular setback. Tl-T4 analysis revealed a trend toward normalization. Short-term F/U revealed a significant (P < 0.01) decrease in MI0 (mean 12%). MI0 per cent decrease was highly correlated with total bilateral proximal segment rotation (P < 0.01). while statistically unrelated to condylar bodily movement. A trend of MI0 reduction was noted with anterior-superior ( - 18.9%). posterior-superior (- 18.15%), posterior-inferior (- 13.66%), and anterior-inferior (- 8.78%) condylar movement. TMJ clicking incidence was similar pre- and postoperatively. Three clicking joints resolved, two new clicks emerged and four remained unchanged. Clicking incidence was unrelated to condylar movement or segment rotation, although no clicks were observed in nondisplaced condyles.
averaged, and stored for mathematical calculation. Since the distance from the center of rotation to each pre- and postoperative anterior skeletal landmark is unchanged by surgery and each of the pins autorotate through the same angle between pre- and postoperative tracings, the change in anterior point position theoretically can be used to solve simultaneous equations and derive the X-Y coordinates of the actual center of rotation. Dental landmarks were not used since positional changes occur rapidly during fixation and would introduce error. Data for each patient were calculated and analyzed by superimposing on sella nasion at sella. Using pairs of points, the mean X and Y coordinates for the mathematical center of rotation were computed and compared to the actual mean postoperative change in the cephalometric condylar center. The mean differences between coordinate values for the computed center and cephalometric center of rotation were X = 40.5 mm (SD = 29.4) and Y = 48.1 mm (SD = 45.1), indicating that the computed center is considerably anterior and inferior to the condyle. The actual mean change in condylar center as determined by preand postoperative digitized tracing was X = 3.41 mm (SD = 4.1) and Y = 0.6 mm (SD = 2.74). Although, in theory, the center of mandibular rotation can be mathematically determined, small errors in reliably identifying anterior skeletal landmarks create large errors in the location of the computed center. The change in condylar center seen on digitized pre- and postoperative tracings suggests rotation about the superior anterior aspect of the condylar head. Mathematical methods for determining the center of mandibular rotation are extremely sensitive to errors in landmark identification and are of questionable reliability. The actual center of rotation as determined by digitized pre- and postoperative tracings appears to be about the anterior/superior aspect of the condylar head. This study was supported by NIH grant DE05215.
The Center of Mandibular Rotation in Maxillary Impaction Surgery. Arabelfa Malone-Trahey. Departments of Orthodontics and OMS, University of North Carolina, Chapel Hill, NC 27514 (Conover M, Thomas P)
Textured surface dense HA (TDH) blocks were created by waffling the surface of the HA block to provide 0.5mm deep depressions. The histologic response to these TDH blocks was assessed in a dog model. Fourteen TDH blocks (15 x 15 x 3 mm) were placed as onlays or interpositional grafts on the angle regions of the dog. Through an extraoral dissection, the angle was exposed keeping the muscular attachment intact at the inferior border. An osteotomy approximately 1.5 cm in length and 1 cm in width allowed a downgraft of the inferior border. A TOH block was placed as an interpositional graft, stabilized with a 26-gauge stainless steel wire. After the interpositional graft was performed, a subperiosteal tunnel was created along the ramus, and a TDH block was placed on the mid-ramus cortical bone and stabilized with a 26gauge stainless steel wire. The dogs received one dose of intramuscular penicillin immediately postoperatively. Clinically, the inlays were immobile at four weeks and the onlay blocks immobile by six weeks. All tissues healed uneventfully. Radiographic signs of bone bridging the osteotomy segments were present by four weeks. The implants were removed at six weeks and nine months for
The premise that the mandible rotates around the cephalometrically determined center of the condyle during LeFort maxillary impaction surgery is unsupported by research data. Some investigators have attempted to mathematically determine the center of rotation and suggest that it does not coincide with the condylar center. Differences between assumed and actual centers of rotation can lead to errors in surgical positioning and A-P discrepancies in the course of finishing orthodontics. Since current treatment planning techniques and, ultimately, the surgery are based on this hypothesis, it is appropriate to submit it to statistical analysis. Thirty adult patients undergoing LeFort I maxillary impaction without a mandibular ramus procedure were studied. The immediate pre- and postoperative cephalometric radiographs were traced and a 25-point model was digitized for each tracing. Each point was digitized twice, computer
Histologic Response to Textured Dense Hydroxylapatite Blocks in Dogs. Michael S. Block, DMD, and Daniel Spagnoli. Louisiana State University School of Dentistry, 1100 Florida Avenue, New Orleans, LA 70119 (Kent JN)
of Dentistry, KM)
of North Carolina School Chapel Hill, NC 27514 (Joseph SA, Knigge
The inhalation of nitrous oxide in concentrations below those required for anesthesia produces analgesia in man and animals in a dose-dependent manner. Nitrous oxide increased P-endorphin concentration along the Proopiomelanocortin (POMC) neuronal system in rats and stimulated l3-endorphin secretory activity in vitro in previous studies. A reinvestigation of the analgesic properties of nitrous oxide and the reversal potential of a narcotic antagonist was made in a series of behavioral studies in the rat. Finally, the contribution of the P-endorphin mediated analgesia system in terminal fields in the periaqueductal grey (PAG). Thirty male Sprague-Dawley rats weighing between 350 and 450 gms were used. Every rat was entered into three experiments, and analgesia testing was performed by the radiant heat tail flick and electrical evoked foot flick tests. Analgesia was calculated as percentage of the maximal possible effect (per cent MPE) before and after exposures to 30, 60, and 80% nitrous oxide, while exposures to air served as control. The involvement of opioid elements in nitrous oxide analgesia was studied by comparing the effects of naloxone (10 mg/kg s.c.) and saline on air and 80% nitrous oxide in a double-blind manner. The effects of lesioning the PAG on nitrous oxide analgesia were examined next. All the animals that participated in experiment one and two were anesthetized and fixed to a stereotaxic apparatus. Trephine bur holes were drilled into the skull and kainic acid (OS pg, n = 18) or saline (0.09%, n = 9) was bilaterally injected into the PAG. Ten days postoperatively, the animals were exposed to either air or 80% nitrous oxide. Analgesia was similarly tested in a blind manner. Localization of lesions were verified by histology. In Friedman’s two-way analysis of variance rats, exposed to 80% and 60% nitrous oxide expressed statistically significant elevations of per cent MPE. Rats exposed to 30% nitrous oxide showed no significant difference in per cent MPE but had an increase in coefficient of variance. Pretreatment with naloxone produced a significant decrease in per cent MPE (P = 0.005) and an increase in variance of response. Kainic acid lesions of the PAG reversed analgesia produced by 80% nitrous oxide (P = 0.001). Nitrous oxide produced a concentration-dependent analgesia in rats in which higher concentrations of nitrous oxide produce a more reproducable and relatively stable analgesia. Nitrous oxide analgesia was partially antagonized by naloxone, which may be due in part to an increase in variance of response by naloxone. P-Endorphin terminal fields of the AG appear to be critically involved in the production of analgesia by nitrous oxide. In conclusion, it is probable that the P-endorphin mediated analgesia system described by other evidence is responsible for analgesia following stimulation of POMC-producing neurons by nitrous oxide. ABSTRACT SESSION IV ON ORTHOGNATHIC AND PREPROSTHETIC SURGERY
SUNDAY, SEPTEMBER~~, 10:00AMTO 1:00 PM MODERATOR: BRIAN ALPERT, DDS
REACTOR PANEL: RAYMOND J. FONSECA, DMD, AND MYER S. LEONARD, DDS, MD Relapse Following Mandibular Advancement Using Dental Plus Skeletal Maxillomandibular Fixation-An Experimental Investigation. Kathleen H. Mayo, DDS. University of Michigan, Department of OMS, Ann Arbor, MI 48109 (Ellis E) Investigators have found that the majority of skeletal relapse occurs during the period of maxillomandibular fixation. All such reports utilized the dentition to hold the mandible in its new position. An unproven method that has gained popularity is the combined use of dental and skeletal fixation. This mode of fixation bypasses the dentition and directly secures the skeletal elements with wires. The purpose of this investigation was to evaluate the short-term effectiveness of dental plus skeletal maxillomandibular fixation in holding the mandible in its new position following mandibular advancement surgery. Twenty-four adult female Macaca mulatta were used in this experiment. All animals underwent a sagittal ramus advancement osteotomy of two molar cusps (approximately 7 mm). Each of the 24 animals was randomly assigned to one of two groups based upon the type of postsurgical maxillomandibular fixation used. Group DF (dental fixation) had the upper and lower teeth bonded together for six weeks with orthodontic composite resin. Group SF (skeletal fixation), in addition to this regimen, had bilateral circummandibular wires attached to pyriform aperture wires. Cephalometric radiographs were used to statistically analyze changes up to six weeks postsurgically with the use of tantalum bone markers placed throughout the craniofacial complex. The results showed the following: 1) Group DF animals underwent a significant amount of horizontal relapse during the period of maxillomandibular fixation (P < 0.01). Group SF showed complete horizontal stability of the surgical result. 2) Group DF animals underwent significant changes in the vertical position of the mandibular symphysis during the period of maxillomandibular fixation (P < O.OS), with a mean inferior repositioning of 1.3 mm. Group SF animals underwent no such increase in anterior facial height and showed almost complete vertical stability of the surgical result. The authors conclude that skeletal wires in addition to dental maxillomandibular fixation can significantly improve postsurgical stability following mandibular advancement osteotomy. This study was supported by NIH-NIDR grant DE06874. Correlating TMJ Symptoms With Condylar Position Following Rigid Fixation of Sagittal Splits. David I? Timmis, DDS, and C. C. Chilcoat. University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78284 (Skoczylas LJ, Van Sickels JE). A prospective study of 18 patients (17 women, one man), with a mean age of 25.7 years was performed to evaluate pre- and postoperative (six months) condylar position, MIO, and TMJ symptomatology after rigid fixation of bilateral ramus sagittal split osteotomies. Nine patients received mandibular advancements and concomitant maxillary LFI osteotomies. Five received mandibular advancements only. Three patients had mandibular setbacks and LFI, while one underwent an isolated man-
Ml7
dibular setback. Tomograms of both TMJs were taken with a Quint Sectograph-200 after obtaining a preoperative submental vertex radiograph to allow subsequent reproducible positioning. The anatomic detail of the condyle and fossa was traced by a single examiner at Tl (immediately preoperatively), T2 (immediately postoperatively), and T4 (six months postoperatively). Three lines were drawn on the Tl radiograph. The first was from a point designating the squamotympanic fissure to the height of the articular eminence. Perpendicular to this, a second line was scribed through the center of the condyle, and a third line was drawn connecting an arbitrary point on the condylar neck to the center point. These Tl reference lines were transferred to subsequent radiographs. Anterior-posterior, superior-inferior, and rotational movements of the condyle were noted for the intervals Tl -T2 and Tl-T4. In addition, preoperative and six-month postoperative maximal interincisal opening (MIO) and TMJ clicking were noted. Condylar movement was statistically similar after mandibular advancement and setback, either alone or with LFI. Mean movements during the Tl-T2 interval was posterior (-.46 mm; range - 3.5 to 1) and inferior ( - .22 mm: range - 2 to 2) for mandibular advancement and anterior (. 19 mm; range 1.5 to - 1) and inferior ( - .69 mm; range -4 to 5) for mandibular posterior repositioning. Proximal segment rotation was counterclockwise (mean -3.4 degrees) with advancement and clockwise (mean 1.6 degrees) with mandibular setback. Tl-T4 analysis revealed a trend toward normalization. Short-term F/U revealed a significant (P < 0.01) decrease in MI0 (mean 12%). MI0 per cent decrease was highly correlated with total bilateral proximal segment rotation (P < 0.01). while statistically unrelated to condylar bodily movement. A trend of MI0 reduction was noted with anterior-superior ( - 18.9%). posterior-superior (- 18.15%), posterior-inferior (- 13.66%), and anterior-inferior (- 8.78%) condylar movement. TMJ clicking incidence was similar pre- and postoperatively. Three clicking joints resolved, two new clicks emerged and four remained unchanged. Clicking incidence was unrelated to condylar movement or segment rotation, although no clicks were observed in nondisplaced condyles.
averaged, and stored for mathematical calculation. Since the distance from the center of rotation to each pre- and postoperative anterior skeletal landmark is unchanged by surgery and each of the pins autorotate through the same angle between pre- and postoperative tracings, the change in anterior point position theoretically can be used to solve simultaneous equations and derive the X-Y coordinates of the actual center of rotation. Dental landmarks were not used since positional changes occur rapidly during fixation and would introduce error. Data for each patient were calculated and analyzed by superimposing on sella nasion at sella. Using pairs of points, the mean X and Y coordinates for the mathematical center of rotation were computed and compared to the actual mean postoperative change in the cephalometric condylar center. The mean differences between coordinate values for the computed center and cephalometric center of rotation were X = 40.5 mm (SD = 29.4) and Y = 48.1 mm (SD = 45.1), indicating that the computed center is considerably anterior and inferior to the condyle. The actual mean change in condylar center as determined by preand postoperative digitized tracing was X = 3.41 mm (SD = 4.1) and Y = 0.6 mm (SD = 2.74). Although, in theory, the center of mandibular rotation can be mathematically determined, small errors in reliably identifying anterior skeletal landmarks create large errors in the location of the computed center. The change in condylar center seen on digitized pre- and postoperative tracings suggests rotation about the superior anterior aspect of the condylar head. Mathematical methods for determining the center of mandibular rotation are extremely sensitive to errors in landmark identification and are of questionable reliability. The actual center of rotation as determined by digitized pre- and postoperative tracings appears to be about the anterior/superior aspect of the condylar head. This study was supported by NIH grant DE05215.
The Center of Mandibular Rotation in Maxillary Impaction Surgery. Arabelfa Malone-Trahey. Departments of Orthodontics and OMS, University of North Carolina, Chapel Hill, NC 27514 (Conover M, Thomas P)
Textured surface dense HA (TDH) blocks were created by waffling the surface of the HA block to provide 0.5mm deep depressions. The histologic response to these TDH blocks was assessed in a dog model. Fourteen TDH blocks (15 x 15 x 3 mm) were placed as onlays or interpositional grafts on the angle regions of the dog. Through an extraoral dissection, the angle was exposed keeping the muscular attachment intact at the inferior border. An osteotomy approximately 1.5 cm in length and 1 cm in width allowed a downgraft of the inferior border. A TOH block was placed as an interpositional graft, stabilized with a 26-gauge stainless steel wire. After the interpositional graft was performed, a subperiosteal tunnel was created along the ramus, and a TDH block was placed on the mid-ramus cortical bone and stabilized with a 26gauge stainless steel wire. The dogs received one dose of intramuscular penicillin immediately postoperatively. Clinically, the inlays were immobile at four weeks and the onlay blocks immobile by six weeks. All tissues healed uneventfully. Radiographic signs of bone bridging the osteotomy segments were present by four weeks. The implants were removed at six weeks and nine months for
The premise that the mandible rotates around the cephalometrically determined center of the condyle during LeFort maxillary impaction surgery is unsupported by research data. Some investigators have attempted to mathematically determine the center of rotation and suggest that it does not coincide with the condylar center. Differences between assumed and actual centers of rotation can lead to errors in surgical positioning and A-P discrepancies in the course of finishing orthodontics. Since current treatment planning techniques and, ultimately, the surgery are based on this hypothesis, it is appropriate to submit it to statistical analysis. Thirty adult patients undergoing LeFort I maxillary impaction without a mandibular ramus procedure were studied. The immediate pre- and postoperative cephalometric radiographs were traced and a 25-point model was digitized for each tracing. Each point was digitized twice, computer
Histologic Response to Textured Dense Hydroxylapatite Blocks in Dogs. Michael S. Block, DMD, and Daniel Spagnoli. Louisiana State University School of Dentistry, 1100 Florida Avenue, New Orleans, LA 70119 (Kent JN)