Mandibular Stability Research Articles

Mandibular osteotomies for access to select parapharyngeal space neoplasms

Tumors involving the parapharyngeal space present a challenge of surgical access. We reviewed all parapharyngeal space tumors resected at the University of California, San Francisco, between 2003 and 2006 and identified 14 patients who had a mandibular osteotomy to enhance surgical access to the parapharyngeal space. The surgical approach for the 14 patients who had a mandibulotomy was accomplished via either 1 or 2 mandibular osteotomies. A single paramedian osteotomy between the canine and the first premolar was used in 4 cases, whereas a combination of a horizontal osteotomy above the lingula and a paramedian osteotomy between the canine and first premolar was employed in 8 cases. A lingual dental splint and rigid fixation were used to achieve mandibular stabilization and fixation. We found that the single and double mandibular osteotomies provided excellent surgical access allowing for total tumor removal with few sequelae.

Mandibular stability after SSRO with or without postoperative maxillo-mandibular fixation for class III malocclusion

The objective of this study was to assess the usefulness of maxillo-mandibular fixation (MMF) from a viewpoint of skeletal and occlusal stability and to investigate the complications after surgery with and without MMF. Twenty-seven patients who underwent surgical correction of class III malocclusion were analyzed. The surgical procedure in all cases consisted of a bilateral sagittal splitting ramus osteotomy (SSRO). The segments were then fixed rigidly with titanium screws. A postoperative MMF was performed in 13 patients within 1 day of the SSRO. The MMF lasted for 1 week. The other 14 patients were free to move their jaw on the day of the surgery and received occlusal guidance with elastics starting from the third postoperative day. Cephalograms were taken preoperatively, at 1 day postoperatively and at 1, 3, 6, 12, and 24 months after surgery. Skeletal and occlusal stabilities along with postoperative complications were then assessed. Discomfort of the pharynx and postoperative pain was more severe in the MMF group. Even without MMF, occlusion was guided to the ideal position by an average of 5.3 days after surgery. Occlusal and skeletal stability was satisfactory in both groups, and there was no correlation between the surgical results and postoperative MMF. MMF may not be necessary after a rigid fixation SSRO, considering the risks of airway problems.

Postoperative Stability After Sagittal Split Ramus Osteotomies for a Mandibular Setback With Monocortical Plate Fixation or Bicortical Screw Fixation

This comparative study was performed to analyze mandibular stability after bilateral sagittal split ramus osteotomies for a mandibular setback with a monocortical plate fixation or bicortical screw fixation. A total of 60 patients with a skeletal Class III malocclusion who underwent sagittal split osteotomies and mandibular setback were included in the present study. Among the patients, 30 were osteosynthesized monocortically with a titanium plate, while the other 30 were osteosynthesized bicortically with positioning screws. This retrospective study used cephalometric radiographs taken preoperatively (T0), and at 1 week (T1), 3 months (T2), and 1 year (T3) postoperatively. The linear and angular changes of the cephalometric landmarks of the chin region were measured at each time period, and the changes of each cephalometric landmark were determined for 4 different time intervals: T0 to T1 (Delta T1), T1 to T2 (Delta T2), T2 to T3 (Delta T3), and T0 to T3 (Delta T4). Postoperative changes in mandibular shape were analyzed using a paired t test to determine the stability of fixation methods. The surgical changes (Delta T1) could be characterized as posterior movements of the mandibular body and posterosuperior movements of the chin landmark. The results of the cephalometric analysis at 3 and 12 months postsurgery (Delta T2 and Delta T3) could be characterized as anterosuperior movements of the mandible. In both treatment groups, surgical changes were relatively well maintained. Likewise, analysis of the horizontal and vertical movements of the chin landmarks indicated a similar tendency in both groups. There were no statistically significant differences between the measurements of postoperative changes at each time period after surgery. The findings of our study suggest that there were no significant differences in postoperative changes in mandibular shape in both the monocortical and bicortical fixation groups after sagittal split ramus osteotomy. We concluded that monocortical osteosynthesis using a miniplate could be used to obtain stable postoperative changes after mandibular setback.

Iatrogenic Traumatic Brain Injury

Traumatic penetrations of foreign objects into the craniocerebral cavity are often encountered in the department of emergency and traumatology. A 5-year-old child was brought to the department of pediatric neurosurgery with a severe headache and fatigue. On admission, the patient had initial neurologic examinations and radiologic scans. The consciousness assessment by Glasgow Coma Scale was 13. Neuroradiologic studies revealed a long hyperdense object extending from the extracranial cavity into the middle cranial fossa. A thorough history was obtained with attention to how and when the injury was sustained. Two weeks before the incident, the child had a blunt trauma of mandibular fractures with dislocation of the temporomandibular joint. Maxillomandibular surgery was performed with a Kirschner's knitting needle to fixate the temporomandibular articulation and simple interdental ligatures for mandibular fracture stabilization. The present radiologic film suggested that the mandibular fracture was not properly fixated allowing the mobilization of Kirschner's needle moving either externally or internally. A standard pterional access with frontotemporosphenoidal approach was performed according to the method of Yasargil and Oikawa-Miyazawa followed by an extradural approach method of Dolenc to the middle cranial structure at the skull base. Several stages of hemostasis were carried out with electrohemocoagulation on the penetrated Kirschner's needle during the needle extracting process at the extradural space of the middle cranial fossa. Two weeks postoperatively, computed tomography scan revealed the supratentorial and middle craniocerebral structures were in symmetric localization. The patient was free of neurologic deficits with no signs of excessive cerebrospinal fluid volume formation. In conclusion, the method of fixation requires appropriate application techniques to ensure adequate fracture fixation during the healing cascade. The neurosurgical approach also requires a specific measure on its management and rehabilitation for the maintenance of such a patient.

Postoperative Stability After Sagittal Split Ramus Osteotomies for Mandibular Setback With Monocortical Plate Fixation or Biocortical Screw Fixation

Statement of the Problem: This comparative study was an analysis of a mandibular stability following bilateral sagittal split ramus osteotomies for mandibular setback with monocortical titanuim plate fixation or bicortical screw fixation.

An In Vitro Biomechanical Evaluation of Fixation Techniques for Sagittal Split Ramus Osteotomy: Mandibular Advancement and Setback

Statement of the Problem: This comparative study was an analysis of a mandibular stability following bilateral sagittal split ramus osteotomies for mandibular setback with monocortical titanuim plate fixation or bicortical screw fixation. Materials and Methods: A total of 57 patients with skeletal Class III malocclusion who underwent sagittal split osteotomies and mandibular setback were included in this study. Of these patients, 29 patients were osteosynthesized monocortically with titanium plate, and 28 patients were osteosynthesized bicortically with positioning screws. Method of Data Analysis: This retrospective study utilized cephalometric radiographs, which were taken preoperatively, and 1 week, and 1 year postoperatively. Cephalometric parameters – gonial angle (GA), mandiblular plane angle (MPA), SNB, upper facial height ratio (U/F) were measured. Postoperative changes in the mandibular shape were analyzed by Wilcoxon signed-rank test to determine the stability of fixation methods. Results: The postoperative changes in gonial angle and mandibular plane angle tended to increase in both monocortical (changes in GA: 2.20, MPA: 1.19) and bicortical fixation group (changes in GA: 2.18, MPA: 1.17). In addition, the upper facial height ratio showed decrease in both monocortical ( 0.64) and bicortical fixation group ( 0.25). However, SNB showed decrease in monocortical fixation group ( 0.62), and increase in bicortical fixation group (0.30). In statistical analysis, there was no significant difference in postoperative changes in gonial angle, mandibular plane angle, SNB, upper facial height ratio in both patient groups. Conclusion: These findings suggested there was no significant difference in postoperative changes in mandibular shape in both monocortical and bicortical fixation group after sagittal split ramus osteotomy. It was concluded that monocortical osteosysnthesis using miniplate could be used to obtain stable postoperative changes after mandibular setback.

Alignment stability in Class II malocclusion treated with 2- and 4-premolar extraction protocols

The purpose of this study was to compare the postretention stability of the correction of mandibular anterior-tooth irregularity in patients with Class II malocclusions whose orthodontic treatments included extraction of 2 or 4 premolars. A total of 66 patients were selected who initially had at least one-half-cusp Class II malocclusions. Nineteen patients (9 male, 10 female) with an initial mean age of 14.04 years were treated with extraction of 2 premolars (group 1); 47 patients (20 male, 27 female) with an initial mean age of 13.03 years were treated with extraction of 4 premolars (group 2). A subgroup of group 2, with a similar amount of initial anterior-tooth irregularity as group 1, was also compared with group 1. Little's irregularity index was used to evaluate anterior tooth irregularity in dental casts obtained from each patient before treatment, after treatment, and 5 years after active treatment. Initial cephalometric variables, initial treatment priority index, pretreatment age, treatment time, and posttreatment time of the groups were compared with t tests. Similarly, Little's irregularity index values at prettreament, posttreatment, and postretention were also compared with the t test. Cephalometric treatment changes within groups were evaluated with dependent t tests. There were no statistically significant differences in posttretention anterior-tooth irregularity between groups 1 and 2 or the subgroup. Treatment of Class II malocclusion with extraction of either 2 maxillary premolars or 4 premolars provides the same mandibular anterior-tooth alignment stability.

Evaluation of transitional implant stabilized overdentures: a case series report

Transitional implants (TI) can immediately improve the stability and retention of existing unstable mandibular complete dentures. This study evaluated the improvement of mandibular complete denture stability and retention with the use of TI. Three TIs were placed in the intraforaminal region of the edentulous mandible of seven patients (three men, four women; mean age 69.7 years). The patients' existing mandibular complete dentures were immediately modified to TI-stabilized overdentures. Their masticatory movements (mandibular movements during mastication) were measured using a commercially available tracking device (BioPACK, Bioresearch, Japan), both before TI placement and about 1 month after delivery of the TI-stabilized overdentures. The mean time of each chewing phase (opening, closing, and occluding) and coefficients of variation were calculated. The patients also completed a questionnaire about the foods they could chew and indicated on a 100 mm Visual Analog Scale (VAS) their personal levels of comfort, ease of chewing, speech, and stability. For masticatory movements, there were no significant differences (P > 0.05) between the TI-stabilized overdentures and existing complete dentures. However, the number of foods that could be chewed increased, and the stability and comfort were reported as improved with the TI-stabilized overdentures. Using TIs, the stability and comfort of the existing mandibular complete dentures studied in this report could be immediately improved.

Five-Year Experience Comparing Resorbable to Titanium Miniplate Osteosynthesis in Cleft Lip and Palate Orthognathic Surgery

To evaluate 5-year outcome stability and complications in orthognathic surgery using resorbable versus titanium osteofixation. Twenty-two cleft lip and palate maxillary retrognathia cases were operated on using either poly (70L-lactide-co-30DL-lactide) or titanium miniplate osteofixation. All had two-piece Le Fort I maxillary advancement osteotomy, 11 had simultaneous mandibular setback, and 13 had alveolar bone grafts. Average operative movement and postoperative instability recorded for maxillary horizontal movement (A-point-Nasion) were 2.5 mm and 2.1 mm for the study group, compared with 6.3 mm and 1.9 mm for the control group. For maxillary vertical movement (ANS-Nasion), measured values were 4.9 and 1.3 mm for the study group and 2.3 and 0.9 mm for the controls. For mandibular horizontal movement, measured values were 10.7 mm and 2.8 mm for the study group and 1.9 mm and 0.8 mm for the controls. Gonial angle measures were 7.1 degrees and 3.5 degrees for the study group and 6.7 degrees and 3.1 degrees for the controls. Foreign body granuloma and fistulation occurred in 1 (9%) member of the study group, but was treated successfully with debridement; implant palpability subsided after 24 months. Three (27%) controls required plate removal, but the remaining plates were palpable. In the study group, horizontal maxillary stability appeared inferior to vertical stability, but mandibular stability was more reliable. Because groups were not matched for magnitude or direction of movement, the results of this study are preliminary and should be interpreted cautiously.

A Custom-Made Distraction Device for Experimental Mandibular Distraction Osteogenesis

Distraction osteogenesis has recently become popular in craniofacial reconstruction, after it was first described for long bones. Despite the widespread clinical use of this technique, currently, lack of an ideal experimental model for small animals hampers investigations focused on its molecular basis, which warrants further elucidation. The authors developed a new device for distraction of the rat mandible and, to asses its effectiveness, practiced on 30 animals assigned to either an acute 3-mm distraction group (n = 7) or a gradual distraction group (0.25 mm twice a day for 6 days; n = 23). The authors applied the devices to a localization that allowed them to perform the ostomies posterior to the molar teeth. Because of a U-shaped plate that the authors used for posterior pin fixation, their device maintained its stability until the end of the study, despite the delicate anatomy of the bone at the posterior part of the mandible. Additionally, the authors described a practical and easy method of transient mandibular stabilization method that facilitates the manipulations while the mouth is open for safer airway control during surgery. This new nutrition technique with enteral feeding solution solved the problem of progressive weight loss after surgery. Application of the device was easy and practical, without demanding complex manipulations. The authors did not observe any device dislodgement or a high rate of accidental fractures during the manipulations. They demonstrated that the device works properly and is able to create ossified regenerate bones that fill the entire distraction gap, which can be used for various investigations during distraction osteogenesis.

Poster 7: mandibular stability following sagittal split osteotomy using poly-l-lactic acid straight mini-plates and screws for osteosynthesis in the prognathism patients

Poster 7: mandibular stability following sagittal split osteotomy using poly-l-lactic acid straight mini-plates and screws for osteosynthesis in the prognathism patients

Maximizing mandibular prosthesis stability utilizing linear occlusion, occlusal plane selection, and centric recording.

The stability of mandibular complete dentures may be improved by reducing the transverse forces on the denture base through linear (noninterceptive) occlusion, selecting an occlusal plane that reduces horizontal vectors of force at occlusal contact, and utilizing a central bearing intraoral gothic arch tracing to record jaw relations. This article is intended to acquaint the reader with one technique for providing stable complete denture prostheses using the aforementioned materials, devices, and procedures.

Stability after distraction osteogenesis to lengthen the mandible: results in 50 patients

Purpose The purpose of this study was to investigate mandibular stability after lengthening the mandible by means of distraction. Materials and Methods Fifty patients (mean age, 14.7 years; range, 11.2 to 37.3 years) with Angle Class II mandibular hypoplasia were treated by bilateral distraction osteogenesis to lengthen the mandible. Patients were divided into a high-angle group, with a high mandibular angle (sella/nasion-mandibular plane [SN-MP] >38°), and a normal-to-low mandibular angle group (SN-MP ≤38°). Clinical measurements and standardized cephalometric radiographs were taken just before operation; postdistraction at time of removal of the distraction devices, and 6 months and 1 year postoperatively. Analysis was performed by means of angle measurements: sella/nasion-maxilla point A (SNA), sella/nasion-mandibular point B (SNB), and SN-MP. Results Eight of 14 high-angle patients showed a degree of relapse (57%), and only 3 of 36 patients showed relapse in the low/normal-angle group (8.3%). Conclusion It can be concluded that high-angle patients are still at risk of relapsing and that distraction osteogenesis cannot prevent relapse in cases with a high mandibular plane angle. For low-angle patients, however, distraction is a safe and predictable procedure.

下顎枝矢状分割術を施行した顎変形症患者における術前・術後の下顎頭の位置と下顎骨の安定性―ＰＬＬＡ製スクリュー，チタン製スクリュー，ワイヤーを用いた各種骨片固定法の比較―

In this study, to investigate the involvement of changes in the condylar position on mandibular stability after a sagittal split ramus osteotomy (SSRO) for mandibular prognathism, the condylar position and mandibular movement in 32 patients who underwent SSRO were radiographically examined using standard tomographs and lateral cephalometric radiographs. Subjects were separated into three groups: 8 patients who received titanium fixation, 9 patients who received poly-L-lactic acid (PLLA) fixation, and 15 patients who received wire fixation. Cephalometric analysis was evaluated preoperatively (T1), immediately after surgery (T2), and at one year after surgery (T3). Changes in condylar position were determined using tomographs at the times of T1 and T3, measuring on the right and left sides independently. The results of cephalometric analysis showed that a significant forward movement of mandible (point B) at the time of T3 was observed in the wire fixation group compared with the PLLA and titanium fixation groups, while no differences in the other cephalometric variables were indicated. Regarding changes in condylar position, no significant differences were found in the three fixation groups at the times of T1 and T3, showing similar patterns of the position changes in the three fixation groups. These results suggest that mandibular stability after SSRO is not associated with changes in condylar position or method of bone fixation.

Ultrasound: assessment of the distraction osteogenesis wound in patients undergoing mandibular lengthening

Purpose: Common methods of assessment of the clinical distraction osteogenesis (DO) wound consist of serial physical examinations, plain radiographs, and computed tomography (CT). Ultrasound (US) is an inexpensive and efficient method of imaging that provides detailed assessment of bone formation across a defect. It has proved to be useful for the evaluation of long bone DO healing. The purpose of this study was to determine the efficacy of US for evaluation of bone formation in the mandibular distraction wound. Patients and Methods: Ten patients underwent mandibular expansion (18 sides) with semiburied, unidirectional distraction devices. The wounds were assessed with plain radiographs and US immediately before device removal. Estimates of bone formation, using a semiquantitative bone fill score, were made for plain radiographs and US. US beam penetration depth, in millimeters, was also measured. During removal of the distraction device, bone formation and mandibular stability were assessed by the surgeon and graded on a semiquantitative scale. Results: US bone fill scores correlated with intraoperative assessment of bone formation and stability ( r = 0.758, P = .0018) at all 18 mandibular sites. Plain radiographic scores also correlated with bone formation ( r = 0.592). However, in 14 of 18 sides, plain radiographs underestimated bone formation compared with US and operative findings. Conclusion: The results of this study indicate that US is an accurate noninvasive technique that may prove to be useful in assessing the mandibular DO regenerate in patients.

Analysis of feeding function and jaw stability in bedridden elderly.

The purpose of this study was to analyze the relationship between jaw stability and the feeding function of 53 bedridden elderly dysphagic patients. Investigations included a questionnaire on daily life activities and meals, oral examinations, functional tests for feeding ability, and assessments of feeding function during the meal. The results of intraoral examination of this patient population for jaw stability revealed that 34.0% of individuals had posterior support for occlusion regardless of whether they had natural teeth or dentures. Thus, the number classified as having mandibular stability (ST) was 18 and that with no mandibular stability (NST) was 35. In a Repetitive Saliva Swallowing Test (RSST), 83.3% of the NST group and 40.0% of the ST group were unable to swallow more than 3 times within 30 seconds. In a water swallowing test, 91.4% of the NST of group was unable to swallow 15 mL of water by a single swallow, while 40.0% of ST group was capable. The results suggest that jaw stabilization by occlusion with the posterior teeth or dental prosthetics is important to feeding function, particularly swallowing.

Is adjustability advantageous in mandibular advancement appliances in the treatment of sleep-disordered breathing?

Mandibular advancement appliances (MAD) that can adjust the amount of mandibular protrusion in response to treatment results are becoming popular with dentists who treat sleep-disorder breathing. Clinicians commonly assume that they are more efficacious and more comfortable to wear than monoblock appliances. An adjustable MAD was compared with one that stabilized the mandible at 70% of the protrusive path. There was not a significant difference in their overall efficacy. The adjustable MAD appeared to be more effective in the more severe cases, presumably due to the greater mandibular advancement; the nonadjustable MAD appeared to be more effective in the less severe cases, presumably due to the greater mandibular stabilization. Existing research was examined and biomechanical principles were considered. Insufficient research exists to definitely evaluate the pros and cons of adjustability vs. stability. There does not appear to be sufficient evidence to support the assumption that adjustable MADs are more efficacious or more comfortable to wear than monoblock appliances.

Comparative Study of Mandibular Stability After Sagittal Split Osteotomies: Biocortical Versus Monocortical Osteosynthesis

Abstract Objective: A comparative study of clinical mandibular stability following bilateral sagittal split osteotomies by means of monocortical versus bicortical osteosynthesis was undertaken. Design: This retrospective study utilized cephalometric radiographs, which were taken at 1 week and 6 months postoperatively. Setting: The research was carried out at the Department of Plastic and Reconstructive Surgery of the Nagasaki University School of Medicine. Patients: A total of 32 patients who underwent only sagittal split osteotomies and mandibular set back in our unit was included in this study. Of these patients, 17 patients were osteosynthesized monocortically, and 15 patients were osteosynthesized bicortically. Main Outcome Measures: Four measurements—gonial angle (GA), mandibular plane (MP), SNB, and percentage of upper face to total face height (percent upper to total face)—were completed to evaluate postoperative mandibular movement. Result: Statistical analyses of cephalometric measurements (GA, M...

Effects of wire and miniplate fixation on mandibular stability and TMJ symptoms following orthognathic surgery

The effects of wire and miniplate fixations on mandibular stability and temporomandibular joint (TMJ) symptoms were analyzed in 145 patients in whom mandibular prognathism had been corrected by the bilateral sagittal split osteotomy (BSSO). The subjects were divided into two groups based on the method of fixation. Group I consisted of 105 patients treated with intraosseous wiring and group II consisted of 40 patients treated with titanium miniplates. The mean maxillomandibular fixation periods for groups I and II were 48 days and 23 days, respectively. Lateral cephalograms were taken immediately before surgery, within a week after surgery, and at least a year after surgery. Changes in the positions of the incisal edge of the lower central incisors, point B, pogonion, and menton were examined. TMJs were examined clinically for pain, sounds, movements, and limitations before treatment and at least a year after surgery. In both groups, the mean of the horizontal relapses was correlated to the magnitude of their surgical movements. In group II, the mean horizontal relapse was smaller, but not significantly more than that of group I. There was no statistical difference in the pre- and postoperative incidence of TMJ signs and symptoms between the two groups. It can be concluded that miniplate fixation for the BSSO procedure has the advantages of shortening the maxillomandibular fixation period and maintaining the postoperative stability of the mandible without causing adverse effects on the TMJ.

Transverse lag screw fixation in midline mandibulotomy. A case series.

Vertical midline mandibulotomy has provided a relatively simple and efficient means of obtaining access to intraoral tumors that are too large or too posterior to be removed transorally. Midline mandibulotomy has had the advantage of nerve and muscle preservation and places the osteotomy outside the typical field of radiotherapy, in contrast to lateral and paramedian osteotomies. Plate and screw fixation has been the usual means of osteosynthesis for these mandibulotomies; however, plate contouring over the symphyseal surface has been a time-consuming process. Unless the plate was contoured exactly, mandibular malalignment and malocclusion in dentulous patients has occurred. Use of parallel transverse lag screws has become a popular method of osteosynthesis for parasymphyseal fractures, and we have extended their use for mandibulotomy fixation. This paper reports our clinical experience with transverse lag screw fixation of midline mandibulotomies in 9 patients from 1994 to 1997. There were 7 men and 2 women with a mean age of 56 (range 35 to 71 years). The pathological diagnosis in all patients was squamous cell carcinoma; 8 cases were primary, and 1 patient presented with recurrent tumor. No tumors involved the mandibular periosteum. One patient had had previous radiotherapy, and 3 patients underwent postoperative radiotherapy. The mean follow-up has been 17 months (range 9 to 27). There was 1 minor complication and 1 major complication related to our technique. The major complication was a delayed nonunion of the mandibulotomy. This occurred because the 2 parallel screws were placed too close to one another, and this placement resulted in a delayed sagittal fracture of the anterior cortex and subsequent nonunion. Transverse lag screw fixation has not affected occlusion in our dentulous patients. Speech and diet were normal in the majority of our patients. Transverse lag screw fixation of the midline mandibulotomy has been a relatively safe, rapid, and reliable method for tumor access and postextirpation mandibular stabilization and has significant advantages over other current methods of mandibulotomy and fixation.