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Biomedical subjects

W J Thrash

Publications and source records attributed to W J Thrash.

At least 19 recordsLinked to original sources
PubMed1998

Condylar resorption after bicortical screw fixation of mandibular advancement.

PURPOSE: This study evaluated long-term condylar resorption after mandibular advancements stabilized with bicortical screws. PATIENTS AND METHODS: One hundred mandibular deficiency patients who underwent bilateral sagittal split osteotomies (BSSO) fixed with three bicortical screws per side, and who were followed for a minimum of 1 year with complete radiographic records, were evaluated. Preoperative panoramic radiographs were traced and superimposed as a best fit over long-term panoramic radiographs. Cephalometric tracings were available on all patients preoperatively, immediately after surgery, 6 to 8 weeks after surgery, and at long term after surgery. These tracings were used to show the amount of the initial advancement and any changes that occurred between 6 to 8 weeks and long term in those patients who exhibited 10% or greater changes in their condylar height. Preoperative temporomandibular joint signs and symptoms were recorded on all patients before surgery and at 6 months after surgery. RESULTS: There were 10 patients who had 10% or greater vertical change in their condyles; all changes were unilateral. Large advancement (P > .009) and preoperative temporomandibular joint symptoms (P > .01) statistically correlated with long-term postoperative condylar resorption. There was not a direct correlation between the amount of vertical change in the condyle and the amount of relapse. There was an improvement in temporomandibular joint symptoms for the group as a whole and in the group with condylar resorption. CONCLUSIONS: Patients with large advancements and preoperative temporomandibular joint symptoms appear to be at risk for condylar resorption. These results are similar to those from other studies in which rigid fixation or miniplates were used for cases of mandibular advancement.

Adolescent↗
PubMed1994

The effect of stannous fluoride on dentinal hypersensitivity.

Many agents have shown varying degrees of effectiveness on pain resulting from exposed dentine. One which has shown some promising results is stannous fluoride (SnF2). The purpose of the following paper is twofold: to review and summarise the clinical literature pertaining to the relative effectiveness of solutions or gels containing SnF2 in controlling pain associated with dentinal hypersensitivity; and to statistically re-evaluate these studies in combination, in order to develop recommendations for the optimal use of SnF2 for hypersensitivity. Seven blinded clinical studies were identified and reviewed. Five of these compared 0.4 per cent SnF2 gel solution to an identical placebo. One compared a 0.4 per cent SnF2 gel solution and a 0.717 per cent F solution to an aqueous placebo. The final study compared a 0.717 per cent F solution to an aqueous placebo. Statistical power analysis and a combined meta-analysis were used to ensure adequate internal consistency and to contribute to an overall consensus of the efficacy across time. It was concluded that the 0.717 per cent F solution provides a virtually immediate and definable effect, which seems to continue for several months. This effect was present in all subjects used in the study. This solution was applied directly to the sensitive area for one minute and allowed to remain for 3-5 minutes. An additional one minute application was applied if needed. The effect of the 0.4 per cent SnF2 gel appears to be more gradual, perhaps involving a different mechanism of action. This solution requires approximately two to four weeks of continuous treatment to be effective. It was concluded that an effective strategy involving the use of stannous fluoride gel includes the application of the 0.717 per cent F solution in the office, effectively providing immediate relief. The patient would then use the 0.4 per cent SnF2 gel at home in order to achieve the long-term effect. In order to control episodic pain while the gel is developing its effect, a small amount of the 0.717 per cent F solution could be given to the patient for occasional symptomatic application.

Dentin Sensitivity↗
PubMed1992

Electrophysiological assessment of human inferior alveolar nerve function.

This study describes a technique for making electrophysiological recordings from the inferior alveolar nerve of conscious human subjects. Recordings were obtained from 6 of 10 subjects, with consistent waveform latencies and amplitudes across subjects. The neurogenic origin of the responses was verified by blocking the nerve with 2% xylocaine, resulting in a loss of the waveform. The method is relatively simple, tolerated well by patients, and yields consistent electrophysiological information. Proposed refinements of the technique could result in a clinically useful method of objectively assessing the functional state of the inferior alveolar nerve following injury or surgical intervention.

Action Potentials↗
PubMed1992

Effect of a fluoride solution on dentinal hypersensitivity.

This two-phase experiment assessed the effects over time of a solution containing 1.09% sodium fluoride, .40% stannous fluoride, and .14% hydrogen fluoride (.717% fluoride solution, DentinBloc) on pain associated with dentinal hypersensitivity. During phase I, 30 subjects demonstrating dentinal hypersensitivity to a blast of cool air were divided into three double blind experimental groups. After baseline data were collected for all subjects, one group was instructed to apply the .717% fluoride solution twice a day. A second group was instructed to apply a gel containing .04% stannous fluoride (Gel-Kam) twice a day. A third group was instructed to apply distilled water. Each subject was assessed at 2, 4, 8, and 16 weeks utilizing the "method of limits" with a standardized, repeatable cold thermal stimulus. The results of a two factor repeated ANOVA indicated that those subjects who applied the .717% fluoride solution reported significantly less sensitivity at the 2-week period than the other groups (P < .05). In addition, those subjects whose solution contained the 0.4% stannous fluoride reported significantly less sensitivity at the 4- to 8-week periods (P < .05). Phase II of the study assessed the .717% fluoride solution on a more precise time course. These included: immediately, 15 minute, 1 day, 1 week and 2 weeks. A one factor repeated ANOVA revealed that this effect presented 15-minute post application (P < .05) and continued throughout the testing periods. It was concluded that the fully active 0.717% fluoride solution was an effective agent in the control of dentinal hypersensitivity after two 1-minute applications.

Analysis of Variance↗
PubMed1991

Evaluation of postoperative diflunisal for periodontal surgery pain.

This study evaluated the efficacy of diflunisal as an analgesic to reduce postoperative pain when administered immediately following periodontal surgery. It was a continuation of a previous investigation which tested the effectiveness of diflunisal, administered preoperatively, in reducing periodontal surgical pain. Twenty-four patients were divided into two groups in a double-blind, random manner. Group 1 received postoperative therapeutic doses of diflunisal equal to the preoperative doses administered in the first study, and Group 2 received postoperative placebos. The postoperative diflunisal group reported significantly less pain (P less than or equal to 0.05) than the postoperative placebo group, and used rescue medication significantly less often (P less than or equal to 0.05). There was no significant difference in postsurgical discomfort between diflunisal administered postoperatively in this study and equal dosages of diflunisal administered preoperatively as previously reported.

Adult↗
PubMed1990

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).

Analysis of Variance↗
PubMed1989

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.

Adult↗
PubMed1989

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.

Adolescent↗
PubMed1989

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.

Cephalometry↗
PubMed1989

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.

Adult↗
PubMed1989

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).

Adult↗
PubMed1988

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.

Bone Screws↗
PubMed1988

Evaluation of preoperative diflunisal for postoperative pain following periodontal surgery.

The effectiveness of diflunisal as a preoperative medication to reduce pain following periodontal surgery was evaluated. Fifty patients were divided into two groups in a double-blind random manner: Group one received preoperative difunisal and Group two received preoperative placebo. The preoperative diflunisal group reported significantly less discomfort (P less than 0.05) than the preoperative placebo group and used rescue medication significantly less often (P less than 0.01). Therapeutic doses of diflunisal, given presurgically, are significantly more effective than placebo in limiting postoperative pain associated with periodontal surgery.

Adolescent↗
PubMed1986

Incidence of maxillary sinusitis following Le Fort I maxillary osteotomy.

Twenty adult patients with maxillofacial discrepancies most amenable to correction by Le Fort I osteotomy were evaluated for the incidence of postoperative maxillary sinusitis. Before surgery, each patient was evaluated both radiographically, by Waters' projection technique, and subjectively, according to a brief questionnaire pertaining to sinus symptoms. Identical evaluations were carried out at three- and six-month intervals following surgery. The results show no increase in the incidence of maxillary sinusitis following Le Fort I osteotomy.

Adolescent↗
PubMed1986

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.

Adult↗
PubMed1986

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.

Bone Screws↗