Masticatory performance, muscle activity, and occlusal force in preorthognathic surgery patients

Previous studies have indicated that patients scheduled for orthognathic surgery tend to have lower maximum bite forces and exert lower forces during mastication. The effect of these deficits on masticatory performance have not been previously assessed. Masticatory performance was analyzed in four groups: male and female orthognathic surgery patients prior to presurgical orthodontics (n = 12 and 23), and male and female controls (n = 27 and 31). Mastication performance was analyzed by having the subjects chew 5-g pieces of carrot for 20 cycles and measuring the resulting median particle size with a standard sieve method. Masticatory performance showed the same trends as maximum bite force and masticatory forces: male controls had the best and patients the poorest masticatory performance. There was a weak correlation between masticatory performance and maximum bite force at the molar positions. Masticatory performance also weakly correlated to electromyographic signals during mastication of a constant bolus (gummy bears) for all muscles except the left posterior temporalis. Correlations were generally not present or were very weak between masticatory performance, estimated masticatory forces, and muscle efficiency, suggesting that muscle efficiency and forces generated during mastication are not the primary factors that determine masticatory performance. Other factors contributing to a person's ability to chew food might include occlusal relationships and mechanical advantage.

Small, blue collar work site hypertension screening: a cost-effectiveness study

This study determined the cost-effectiveness of one- versus two-stage hypertension screening at small to medium-sized blue collar, multicultural work sites using voluntary health organization and public health unit personnel. Workers with diastolic blood pressure (DBP) > or = 90 mm Hg were randomly allocated to one- or two-stage screening with differing physician referral protocols based on blood pressure level and treatment status. At first screening of 7856 workers, 12.5% had DBP > or = 90 mm Hg or < 90 and on medication with 64% aware of having hypertension, 42% on medication and 30% controlled (DBP < 90 mm Hg). One year later, there were no significant differences in effects or cost-effectiveness between groups. Both had significant DBP decrease (8.5 mm Hg), 54% had seen a physician within the recommended time, and 50% were controlled on medication or any treatment. One-stage screening, being easier to implement, is the preferred option.

Estimated masticatory forces in patients before orthognathic surgery

There has been relatively little study of masticatory forces in dentofacial deformity patients before orthognathic surgery. This study used a mathematical equation based on electromyographic activity (EMG) during mastication and forces obtained during isometric bites to estimate masticatory forces in 55 control subjects and 48 patients. Subjects chewed on a constant bolus while EMG recordings were made bilaterally from the superficial masseter, anterior temporalis, and posterior temporalis muscles. Unilateral isometric bite forces in the first molar position and simultaneous EMGs were recorded in these same subjects. Superficial masseter muscle activity and isometric bite forces were strongly correlated. The slope of masseter EMG versus isometric force was used to estimate the masticatory forces. Males were found to have significantly higher estimated masticatory forces than females.

Use of homologous bone in maxillofacial surgery

Homologous bone grafts were used in 135 maxillofacial surgical procedures, including acute midfacial fracture repair (n = 77), elective osteotomies of the facial bones (n = 35), secondary correction of traumatic deformities (n = 6), mandibular reconstruction (n = 10), facial bone augmentation (n = 5), and reconstruction of maxillary tumor defects (n = 2). Postsurgical complications occurred in five of the patients. This article reviews the rationale for using homologous bone grafts, their immune response, how they heal, and the risk of transmission of disease.

Repeat administration of high dose melphalan in relapsed myeloma

At a median time of 20 months following high dose melphalan for myeloma, 29 patients relapsed and were treated with induction chemotherapy to maximum response followed by a second course of high dose melphalan. The majority (90%) of patients received 200 mg m-2 with an autologous bone marrow transplant. Sixteen (55%) patients achieved complete remission and 11 (38%) a partial response. The median duration of remission was 17 (4-42) months. The median survival has not been reached, with 50% of patients alive at 58+ months after presentation. The period of neutropenia was similar during both first and second high dose procedures, but the duration of thrombocytopenia was longer in patients receiving melphalan for a second time (median 22 (16-56) days and 41 (18-69) days respectively). There was one treatment-related death due to thrombocytopenic haemorrhage. Repeated administration of high dose melphalan is a feasible approach for patients with relapsed myeloma.

Treatment of mandibular angle fractures using two 2.4-mm dynamic compression plates

Sixty-five consecutive patients with fractures of the mandibular angle were treated by open reduction and internal fixation using two dynamic compression plates placed through a transoral incision using transbuccal trochar instrumentation and 2.4-mm screws. In the first 20 cases, the screws were inserted without tapping the drill holes. In the remaining 45 cases, the drill holes were tapped. No patient was placed into postsurgical maxillomandibular fixation or training elastics. Overall, 21 fractures (32%) developed infections requiring secondary surgical intervention. The infection rate was higher in those fractures where the holes were not tapped (40%) than those cases when the holes were tapped (29%). Of the 21 fractures that required hardware removal, 9 fractures were healed and required no further treatment; 12 had no firm bony union and required postsurgical maxillomandibular fixation. Only one case resulted in a malunion with resulting malocclusion. The use of two dynamic compression plates was found to be relatively easy, but resulted in an unacceptable rate of infection.

Tuberculosis in Canada: a focal disease requiring distinct control strategies for different risk groups

Cases of new or reactivated tuberculosis (TB) reported in Canadian residents during 1985-1987 (1984-1988 in the province of Quebec) were analyzed by geographic region relative to the geographic distribution of groups known to be at high risk. The crude incidence rate (per 100,000 population) of TB was calculated by census division (or Région socio-sanitaire in Quebec). Rates of TB by census division ranged from 0 to over 200 per 100,000 population; the average rate for Canada was 8.3 per 100,000. Census divisions with very high rates (over 20 per 100,000) were concentrated in the northern regions, with 80% or more of TB cases occurring among aboriginal persons. Census divisions with moderately high TB rates of 10-19 per 100,000 were located either in northerly regions or in major metropolitan areas; reported TB cases in these areas occurred disproportionately in the aboriginal or immigrant populations. Tuberculosis continues to become more geographically focused and limited to aboriginal Canadians, immigrants and the urban poor. Priority must be given to full implementation of effective prevention and control methods in geographic areas with higher incidence rates. Different methods will be required for different areas depending upon the risk groups present.

The second Chalmers J. Lyons Academy study of fractures of the edentulous mandible

A review of 167 fractures in 104 edentulous mandibles treated by several surgeons using a variety of methods was undertaken. Most patients (81.5%) had open reduction and internal fixation using bone plates. Problems in healing, either delayed or fibrous union, occurred in 21 of 167 fractures (12.6%) in 16 of 104 patients (15%). One fourth of patients treated by closed reduction techniques had problems with union, whereas extraoral open reduction with bone plate fixation produced very good results. The factors involved in treating these challenging fractures is discussed and comparisons are made with the previous Chalmers J. Lyons Academy study.

Rigid fixation of mandibular condyle fractures

This article reviews the anatomy and surgical approaches for treating fractures of the mandibular condyle with plate and screw fixation. Advantages and disadvantages of the preauricular, submandibular, intraoral, retromandibular, and rhytidectomy approaches are presented.

Sequencing treatment for naso-orbito-ethmoid fractures

This article presents a strategy for treating naso-orbito-ethmoid fractures. Eight steps for the management of such injuries are presented: surgical exposure, identification of the medial canthal tendon/tendon-bearing bone fragment, reduction/reconstruction of medial orbital rim, reconstruction of the medial orbital wall, transnasal canthopexy, reduction of septal fractures, nasal dorsum reconstruction/augmentation, and soft tissue adaptation. Following these steps can make treatment outcomes more predictable.

Complications of nonrigid fixation of mandibular angle fractures

This retrospective study analyzed complications in 96 patients with 99 mandibular angle fractures treated during a 3-year period with either closed reduction or nonrigid means of fixation combined with maxillomandibular fixation. An overall complication rate of 17% occurred. Infection was the most common complication, occurring in 17 fractures. Thirteen fractures had infection as the only complication; in the remaining four patients, infection was combined with malunion/malocclusion. The results of this study show that mandibular angle fractures in an inner-city population are associated with a high incidence of postsurgical complications.

Treatment of mandibular angle fractures using the AO reconstruction plate

Fifty-two patients with fracture of the mandibular angle were treated by extraoral open reduction and internal fixation using the AO reconstruction bone plate (Synthes, Paoli, PA). None were placed into postsurgical maxillomandibular fixation. Four patients developed early infections requiring incision and drainage (7.5%). One patient required removal of the hardware after the fracture had healed. The use of the AO reconstruction bone plate for fractures of the mandibular angle was found to be very predictable and was associated with a low rate of complications.

Rigid skeletal fixation of fractures

Rigid skeletal fixation of facial fractures has evolved from the principles established in orthopedics. It has taken a long time to develop rigid internal fixation devices that provide stability combined with safety. The application of rigid skeletal fixation to the facial skeleton requires the surgeon to pay strict attention to detail, which may add a small time increment to the procedure. However, the benefits to patients of having early use of the jaws and exact placement of bony segments seem to outweigh the disadvantages. The future of this constantly developing field will almost certainly center around technologic innovations that will make the application of fixation devices easier. It is likely that future research will provide devices that are more biocompatible, and perhaps just over the horizon, devices that are bioresorbable.

Relationship of substance abuse to complications with mandibular fractures

This retrospective study analyzed the relationship between complications and substance abuse following mandibular fracture. Over a 2-year period, the records of 352 patients with 589 mandibular fractures were reviewed for methods of treatment and other variables, including chronic abuse of drugs. An overall complication rate of 18.5% was found. Positive associations between complications and chronic abuse of alcohol and nonintravenous and intravenous drugs were found. Intravenous drug abusers had a 30%, nonintravenous drug abusers had a 19%, and chronic alcohol abusers had a 15.5% incidence of complications. Those individuals who did not use any drug chronically had a 6.2% complication rate. The results of this study show that chronic substance abuse can significantly affect treatment outcomes for management of mandibular fractures.

A preliminary study of maximum voluntary bite force and jaw muscle efficiency in pre-orthognathic surgery patients

The functional state of dentofacial deformity patients before orthognathic surgery has received relatively little study. In this study, the ability to generate occlusal force was compared between 84 patients before treatment for various dentofacial deformities and 57 controls. Maximal and submaximal bite forces were measured at the incisor and right and left first molar bite positions. Electromyographic activity (EMG) was recorded bilaterally from the anterior temporalis, posterior temporalis, and masseter muscles during each bite. An efficiency ratio was calculated for the jaw muscles by dividing the level of EMG by the occlusal force. There was a reduced ability to generate occlusal forces in the patients before surgery, especially among female patients. The reductions in maximal occlusal force were correlated with reduced efficiency of the jaw muscles.

Growth of the mandible following replacement of the mandibular condyle with the sternal end of the clavicle: an experimental investigation in Macaca mulatta

This study was designed to investigate the long-term effects of transplanted clavicles to the temporomandibular joint (TMJ) in juvenile monkeys. Sixteen juvenile female monkeys (Macaca mulatta) were used in this experiment. Eight animals were used as controls and were allowed to grow undisturbed for an 18-month period (group control). Eight animals were divided into two groups and underwent bilateral condylar excision via extraoral vertical ramus osteotomies. Four of these animals had their condylar segments removed and immediately replaced to serve as surgical controls (group condyle). The other four underwent condylar replacement with the sternal end of their clavicles (group SCJ). Standardized lateral cephalometric radiographs with the aid of tantalum bone markers were used to evaluate maxillary and mandibular growth. One-way analysis of variance (ANOVA) was used to determine the significance of differences between groups. All animals showed good mandibular function and a class I molar relationship following an 18-month evaluation period. Statistical analysis showed there was no significant difference in maxillary or mandibular growth between any of the three groups. The results of this investigation show that the sternal end of the clavicle may be a viable option in mandibular condylar transplant surgery.

Validation of respiratory inductance plethysmography ("Respitrace") for the measurement of tidal breathing parameters in newborns

INTRODUCTION

The ratio of the time to reach peak (maximum) tidal expiratory flow (Tme) to total expiratory time (Te) is smaller in infants who later develop lower respiratory tract disease. In previous studies infants have been sedated and flow measured using a pneumotachograph with face-mask. These methodological factors are known to affect tidal breathing, and the frequent need for sedation limits the use of the technique to relatively small studies. The aim of this study was to validate uncalibrated respiratory inductance plethysmography (Respitrace) to measure Tme/Te in unsedated newborns.

METHODS

Nineteen normal term infants were studied during quiet sleep. Agreement between Tme/Te measured directly using a pneumotachograph and with Respitrace was assessed in 15 infants. Repeatability of the Respitrace technique was assessed in 10 infants.

RESULTS

The mean Tme/Te for the 19 infants using Respitrace was 0.46 (S.D. 0.14). The mean difference between Tme/Te obtained using Respitrace and that measured with a pneumotachograph was 0.014; 95% of Respitrace readings were between -0.042 and 0.070 of the pneumotachograph values. The mean difference between repeat Respitrace values was 0.02 with 95% of the second measurements within 0.066 of the first.

CONCLUSIONS

These results indicate that Respitrace can be used to determine Tme/Te accurately.

Bone strain following application of a rigid bone plate: an in vitro study in human mandibles

This study evaluated the effect of a bone plate on mandibular bone strain patterns during static loading. A stainless steel bone plate was unilaterally attached to five human mandibles, which were then subjected to static loads of 60 kiloponds. Four strain gauges attached to the cortical bone were used to measure the strain patterns within the mandible both before and after the bone plate was attached. The results showed that statistically significant alterations in the strain patterns occurred following plating of the mandible. The mandible with the plate attached became more stiff, presumably due to the difference in modulus of elasticity between the plate and the bone. However, this increase in stiffness was relatively small when compared with both total strain under load and strain produced by tightening of the bone screws.

Major psychological disorders in chronic TMD patients: implications for successful management

The authors assessed psychological disorders in 50 chronic TMD patients. These disorders appear to be a major concomitant factor in chronic TMD, and may need to be treated for successful outcomes.

Treatment of mandibular angle fractures using two mini dynamic compression plates

Thirty patients with 31 fractures of the mandibular angle were treated by open reduction and internal fixation using two mini dynamic compression plates with self-threading screws placed through a transoral incision with transbuccal trochar instrumentation. None of the patients were placed into postsurgical maxillomandibular fixation (MMF) or training elastics. Complications requiring secondary surgical intervention occurred in nine fractures (29%). Three were early infections requiring incision and drainage, removal of the hardware, and postoperative MMF. One was a nonunion with malocclusion requiring application of a more rigid bone plate. Five fractures developed late chronic swelling and low-grade infection requiring plate removal. Osseous union had occurred in these cases and no MMF was necessary. The use of two mini dynamic compression plates in the manner done in this study was found to be a relatively easy but unpredictable treatment for fractures of the mandibular angle.

Reproducibility of mandibular motion and muscle activity levels using a commercial computer recording system

A commercial computer recording system (BioPak) was tested for its accuracy and reproducibility in recording mandibular motion and muscle activity levels (EMG). Accuracy of measurements of mandibular motion was tested using sliding calipers. Accuracy of muscle activity levels was checked with a sine-wave calibration signal of known amplitude and frequency. Reproducibility of motion and of EMG was made using five control subjects each tested on 3 separate days. Computer measurements of motion were found to require correction for nonlinearity at openings beyond 45 mm. Most maximum voluntary excursions were found to be more reproducible than motions during mastication. However, lateral deviation during opening was strongly affected by magnet orientation and varied greatly between trials. Electromyographic recordings were distorted by improper treatment of high-frequency components of the signal and also varied greatly between trials. This study suggests that the BioPak system may indicate changes in some measures of mandibular motion and EMG levels in patients for whom no changes have occurred.

The effects of zygomatic complex fracture on masseteric muscle force

The masseter muscle often has been implicated as a primary cause of postreduction displacement of the fractured zygomatic complex. However, this contention has never been proved. This study compared masseter muscle force in 10 male controls with that in 10 male patients who had sustained unilateral zygomaticomaxillary complex (ZMC) fractures. Calculation of muscle force was based on measured bite force, electromyogram, and radiographic determination of muscle vectors. It was found that the masseter muscle in patients with ZMC fractures developed significantly less force than masseter muscle in controls. Following fracture, the masseter force slowly increased, but at 4 weeks following surgery the majority of patients were still well below control levels. The results of this study cast uncertainty on the role of the masseter muscle in postreduction displacement of the fractured ZMC.