William J. Thrash

Relapse after rigid fixation of mandibular advancement

In 19 subjects rigid fixation of bilateral sagittal split osteotomies was used for mandibular advancement. Five angles and four linear measurements were determined cephalometrically for two time intervals: before surgery to immediately after surgery (T1-T2), and immediately after surgery to six months to one year after surgery (T2-TL). A multiple regression analysis with a backward stepping procedure was used to determine relationships between relapse, as defined by the position of pogonion at T2-TL (PgT2) and B point during this same time interval (BT2). The only significant predictor of PgT2 was PgT1 (P less than 0.001) (amount of advancement of pogonion during the time interval T1-T2). When BT2 was examined, both the change in position of B point at T1-T2 (P less than 0.001) and the change in anterior facial height at T1-T2 (P less than 0.02) were significant predictors of relapse. There were no other predictors of relapse. Advancements of 6 to 7 mm or greater as measured at B or Pg deserve special attention as they were more predisposed to relapse. Methods for preventing relapse are discussed.

Factors Contributing to Relapse in Rigidly Fixed Mandibular Setbacks

The incidence of, and factors accounting for, relapse in 25 subjects who underwent mandibular setbacks via a bilateral sagittal split osteotomy with rigid fixation were studied. Fourteen had single-jaw operations, and the remaining 11 had concomitant maxillary procedures. Cephalometric radiographs were reviewed preoperatively, immediately postoperatively, and 6 months to 3 years after surgery. Relapse was defined as forward movement of pogonion during the postoperative period. No difference in the movement of the mandible in one- or two-jaw cases was noted. Even with excellent occlusal results, there was a tendency for the mandible (chin point) to rotate forward. In the one-jaw cases 43.7% relapse was noted, whereas 53.4% was seen in the two-jaw cases. A regression analysis showed that the magnitude of setback was the single factor that significantly predicted relapse in one-jaw cases, whereas alteration of the proximal segment accounted for relapse in two-jaw procedures. These results seem interrelated when considering alterations in the spatial arrangement of the muscular tissues and their attachments.

Causes, location, and timing of relapse following rigid fixation after mandibular advancement

The purpose of this study was to evaluate two different groups of patients who underwent bilateral sagittal split osteotomy for mandibular advancement. One group demonstrated no relapse, whereas a second group had documented relapse. The following questions were asked: 1) What factors contribute to relapse? 2) At what site in the mandible is movement seen? and 3) During what period does movement occur? A retrospective lateral cephalometric serial analysis was performed on 50 patients at multiple time intervals. Criteria for a candidate include 1) mandibular advancement surgery with rigid fixation, with or without genioplasty, 2) no maxillary surgery, and 3) relapse of 25% or more of the advancement. Of the 50 patients analyzed, 13 (26%) showed relapse of 25% or more and served as the relapse group. Twelve patients showed no relapse and served as the comparison group. Multiple-regression analysis for the relapse group showed that magnitude of advancement, increasing gonial arc and changing mandibular plane significantly accounted for 84.9% of the variance observed in relapse (P less than .001). Repeated-measures ANOVA showed that the majority of relapse occurred in the first 6 weeks after surgery (68%, P less than .05). Results of a paired t test showed that a significant change occurred in all the linear and angular measures except SN-AR-GO (P less than .05).

Arthroscopic TMJ surgery: effects on signs, symptoms, and disc position.

Nineteen subjects with documented intra-articular pathology refractory to nonsurgical therapies underwent temporomandibular joint (TMJ) arthroscopy involving lysis and lavage in the superior joint space. Following surgery, subjects were evaluated for 6 to 12 months by clinical examinations and questionnaires at designated time periods and by postsurgical joint imaging. Significant improvement was noted in pain, mandibular movement, and diet. No improvement was noted in the incidence of joint sounds, and disc position was unchanged in 80% of the joints. The findings suggest that disc repositioning may not be needed to achieve clinical success.

A retrospective study of relapse in rigidly fixated sagittal split osteotomies: Contributing factors

Fifty-one patients who underwent mandibular advancements with or without genioplasties were rigidly fixated with three, 2-mm bicortical screws per side. Radiographs were digitized preoperatively, immediately postoperatively, at 6 weeks, at 6 months, and at a subsequent long-term follow-up period. Location of the cephalometric landmarks, referenced to a vertical reference line (in millimeters), was used as the dependent variable. An overall inspection of the data shows that rigidly fixated mandibular advancements were very stable. The average case showed further advancement of pogonion from 6 weeks to the long-term follow-up period. However, relapse was noted in several cases. Factors that could be used as predictors of relapse were examined. Results indicated that magnitude of advancement was the only factor that successfully predicted relapse, accounting for 37.9% of the variance in the sample. Anatomic changes found to accompany such advancement are as follows: (1) when pogonion comes forward, anterior facial height and mandibular plane decrease while the proximal segment rotates forward, and (2) the maxillary central incisors flare and the mandibular incisors upright during this time period. A small degree of relapse as assessed at pogonion occurred during the first 6 weeks, followed by an advancement from 6 weeks to the longest time interval after the surgical procedure. However, these directional movements were not statistically significant.

Effect of transcutaneous electrical nerve stimulation for controlling pain associated with orthodontic tooth movement

Transcutaneous electrical nerve stimulation (TENS) was assessed for its effect on periodontal pain associated with orthodontic separation. Forty-five adult subjects were randomly assigned to a TENS group, a placebo TENS group, and a control group. They were further subdivided into intraoral and extraoral electrode placement, and 1-, 2-, and 3-day treatment duration groups. In each patient orthodontic separators were placed mesial and distal to the upper first molars, bilaterally. Subjects were asked to rate their discomfort every 12 hours for 4 days with a 10 cm visual analogue scale. The results showed a significant decrease in reported pain for those subjects in the TENS group at the 24-, 36-, and 48-hour assessment periods as compared to either the placebo or control group. In the control group postseparation discomfort continued through the 60-hour assessment period. The present study suggests that TENS is an effective nonpharmacologic method of controlling postadjustment tooth pain.

Postsurgical maxillary movement: A comparison study of bone plate and screw versus wire osseous fixation

This study was designed to examine amounts of postoperative maxillary movement in patients who received Lefort I osteotomies, comparing bone plate and screw fixation with conventional transosseous wire fixation. Cephalograms of 17 patients whose maxillae were fixated with wire osseous fixation and 13 patients whose maxillae were fixed with bone plates and screws were compared at four different time periods throughout the first postoperative year. Millimeters of movement of five maxillary assessment points were assessed in the horizontal and vertical planes of space by use of a line constructed 7 degrees to sella-nasion at nasion as the horizontal reference. Results indicate that the amount of maxillary movement was similar for the two groups during the two time periods subsequent to the surgical procedure. However, it appears that the maxillae fixated with bone plates and screws were more stable than those with wire osteosynthesis during the last postoperative period (6 months to 1 year) and during the overall postoperative time interval (2 days to 1 year).

A lateral cephalometric analysis of nasal morphology following Le Fort I osteotomy applying photometric analysis techniques

Fifty patients who had undergone Le Fort I maxillary osteotomies were studied. Cephalograms were available preoperatively and at least 6 months postoperatively. Soft-tissue analysis of the nasal profile was done employing three angles commonly used in the photometric analysis performed for rhinoplasty: nasal tip projection angle, columellar angle, and supratip break angle. Maxillary movement was assessed in two ways: 1) horizontal and vertical component vectors of A-point movement were calculated, and 2) maxillary rotation, defined as the change in the angle of a line drawn from the anterior nasal spine to the posterior nasal spine relative to the anterior cranial base, was calculated. The component vectors of A-point movement and maxillary rotation were then used as predictor variables for change in the soft-tissue angles in a multiple-regression analysis. A weak correlation was found between A-point movement in both the horizontal and vertical dimensions and the nasal tip projection angle. When A-point was moved in an anterior and superior direction, the nasal tip rotated up. The converse was true with movement in the posterior and inferior direction. Only A-point movement in the horizontal dimension had a significant relationship with columellar angle. When A-point was moved in an anterior direction, columellar angle increased. This study shows that prediction of the soft-tissue profile of the nose following maxillary surgery is difficult.

A comparative study of normal sensibility of the inferior alveolar nerve and the infraorbital nerve

In order to assess the degree of similarity of the infraorbital nerve and inferior alveolar nerve, thirty subjects with no history of sensory injury were examined by a battery of neurosensory tests including: light touch, brush stroke direction, two-point discrimination, and thermal disk temperature assessment. In a matched sample experimental design, the sensibility of the inferior alveolar nerve (lower lip) was compared to the inferior orbital nerve (upper lip). The product moment correlations revealed a significant relationship (degree of sameness) between the upper and lower lip. The comparison of the upper and lower lip appear to be acceptable for retrospective tests for detection of neurosensory injury of the inferior alveolar nerve. Of these tests, light touch appears to be the most consistent while remaining sensitive to individual variation. The thermal disk assessment was least sensitive in that no individual variation could be demonstrated. In addition, there appear to be greater variations in men than in women.