Papers by Gaylord Throckmorton
Journal of Oral and Maxillofacial Surgery, Jan 4, 2000
This study examined bite force and occlusal contact area in prognathic patients before and after ... more This study examined bite force and occlusal contact area in prognathic patients before and after bilateral sagittal split ramus osteotomy of the mandible using a newly developed pressure-sensitive sheet (Dental-Prescale, Fuji Photo Film Co, Tokyo, Japan). Twenty-five prognathic patients were examined. Bite force and occlusal contact area were measured preoperatively, at 2, 4, and 8 weeks, and at 3 and 6 months after surgery. The bite force and occlusal contact area of 20 healthy subjects were also measured. Both bite force and occlusal contact area of the patients were the lowest 2 weeks after surgery and recovered to the preoperative level between 8 weeks and 3 months. Subsequently, they increased slowly and exceeded the preoperative level at 6 months after surgery. However, even at 6 months, both the bite force and the occlusal contact area of the patients were still only about half or less than that of healthy subjects. This pressure-sensitive device can be used as a simple indicator of postoperative recovery and occlusal improvement in patients following orthognathic surgery.
Journal of Oral Rehabilitation, 2009
Although measurement of maximum voluntary biting force is an important indicator of health of the... more Although measurement of maximum voluntary biting force is an important indicator of health of the masticatory system, few commercially available transducers have been validated for routine clinical use. The T-Scan III Ò system records distribution of relative forces around the tooth row during clenching, but not absolute forces. This study assesses the reliability of T-Scan Ò sensors with and without protection materials and develops calibration curves that allow measurement of absolute forces with the T-Scan III Ò .
Journal of Oral and Maxillofacial Surgery, 1996
Purpose: This study evaluated mandibular motion and bite force in patients with temporomandibular... more Purpose: This study evaluated mandibular motion and bite force in patients with temporomandibular joint disorders after joint surgery.
Journal of Oral and Maxillofacial Surgery, 1992
This study evaluated the effect of a bone plate on mandibular bone strain patterns during static ... more 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.
Journal of Forensic Sciences, 2004
We report the development of an ultrasonic facial scanning technique that allows for the visualiz... more We report the development of an ultrasonic facial scanning technique that allows for the visualization of continuous contours without deforming surface tissues. Adhesive markers are placed on the face to enable measurement of facial tissue thicknesses at specific landmarks. The subject immerses the face in a clear plastic box filled with water for about 20 seconds while the researcher moves the transducer along the bottom of the box, guiding transducer movement by watching the facial image in a mirror placed below. 3D Echotech software (1) builds the images from sequentially acquired 2D frames. Reliability of repeat measurements at landmarks is good, and individual tissues (skin, subcutaneous, muscle) can be distinguished. The method is simple, reliable, less expensive and less time consuming than alternatives such as magnetic resonance imaging (MRI). It is applicable in both research and clinical contexts.
Journal of Forensic Sciences, 2006
As a second step in our three-dimensional (3D) ultrasound research on facial tissues, orthodontic... more As a second step in our three-dimensional (3D) ultrasound research on facial tissues, orthodontic patients with available lateral cephalographs (radiographs) allowing measurements of tissues along the midline of the face were recruited for ultrasound scanning. Comparison of three points on the upper lip (A-point), chin (B-point), and nose (nasion) produced differences of varying magnitude between radiographic and ultrasound measurements, with the B-point measurement being clearly affected by head orientation. Concordance was better for A-point and best for nasion. Although extension of two-dimensional (2D) ultrasound scanning of facial tissues to 3D scanning for forensic and surgical reconstructive purposes remains a worthy goal, it must be recognized that because of the differences in technique, measurements obtained from the different visualization modalities at present vary in their comparability.
Journal of Biomechanics, 1990
Archives of Oral Biology, 1994
Mathematical analyses of mandibular biomechanics often assume a close relation between the relati... more Mathematical analyses of mandibular biomechanics often assume a close relation between the relative activity levels of the jaw-adductor muscles and their mechanical advantage. However, this relation has not been clearly demonstrated. This study examined the relation between muscle activity levels, force generation, and mechanical advantage in 48 (23 male, 25 female) normal subjects. Mechanical advantage in the sagittal plane was calculated from standard lateral cephalograms. Activity for the anterior and posterior temporalis and masseter muscles was recorded from surface electrodes during incisor and molar bites. Muscle activity was standardized by calculating a least-squares regression for electromyographic versus occlusal force. At each bite position the more efficient muscles were recruited at higher rates but muscle size was more important in determining efficiency than was mechanical advantage. Differences in jaw-muscle recruitment rates between males and females were also best explained by differences in muscle size. Decreased muscle recruitment rates at molar bite positions matched increased mechanical advantage for the anterior temporalis and masseter. However, posterior temporalis recruitment patterns seemed to reflect jaw position more closely than mechanical advantage.
Archives of Oral Biology, 1994
Journal of Oral and Maxillofacial Surgery, Jan 7, 1994
Voluntary bite forces were recorded at varying periods in 35 males treated with rigid internal fi... more Voluntary bite forces were recorded at varying periods in 35 males treated with rigid internal fixation for fractures of the mandibular angle. Bite forces were also obtained in 29 male controls for comparison. It was found that molar bite forces in patients were significantly less than in controls for several weeks after surgery. Further, molar bite forces on the side of the fracture were significantly less than on the nonfractured side. The results of this study indicate that recommendations for the amount of fixation required for a given fracture may be reduced.
Http Dx Doi Org 10 2319 061109 333 1, Nov 11, 2009
To compare chewing cycle kinematics of subjects with better and poorer masticatory performance. A... more To compare chewing cycle kinematics of subjects with better and poorer masticatory performance. A cross-sectional study compared masticatory performance, based on the breakdown of the artificial test food Cuttersil, in 30 subjects with Class I occlusion. Individuals with median particle sizes greater and lesser than the median value for the entire sample were categorized as poorer (15) and better (15) performers, respectively. While chewing Cuttersil, three-dimensional jaw movements of subjects were tracked with an optoelectric computer system. Multilevel linear modeling was used to evaluate differences in estimated cycle shape, cycle duration, and maximum excursions, as well as within-subject variation between the two groups. Poorer performers had a significantly longer opening duration (0.274 +/- 0.225 sec vs 0.325 +/- 0.270 sec) than better performers. Poorer and better performers also showed significant differences in cycle shape, including a less horizontal path of closure and more posterior jaw movement in the poorer performers. In addition, poorer performers exhibited significantly more cycle-to-cycle (within-subject) variability in chewing cycle duration, excursive movements, and lateral velocity than did better performers. Poorer performers lacked consistency in their chewing cycles, and their cycle shape differs from that of better performers.
Journal of oral surgery (American Dental Association: 1965)
A two-dimensional model is presented that allows calculation of mechanical advantage for the huma... more A two-dimensional model is presented that allows calculation of mechanical advantage for the human masseter and temporalis muscles. Ten patients with high-angle mandibular deficiency and vertical maxillary excess had greatly reduced mechanical advantages with an anticipated elevated muscle activity. Superior repositioning of the maxilla with mandibular advancement, however, increased the overall mechanical efficiency of the masticatory system. When compared with mandibular advancement alone, the bimaxillary procedure resulted in a 13% increase in the mechanical advantage of the temporalis muscle and a 21% increase for the masseter muscle. This model suggests that various surgical procedures designed to correct facial disharmonies may have either desirable or undesirable effects on jaw biomechanics and long-term stability. Biomechanical influences are important considerations for the clinician in planning surgical procedures to correct dentofacial deformities.
Cranio: the journal of craniomandibular practice
Treatment of adults with vertical maxillary deficiency (short faces) has continually been an intr... more Treatment of adults with vertical maxillary deficiency (short faces) has continually been an intriguing challenge for surgeons and orthodontists. For this category of patients, the introduction of simultaneous bone grafting and Le Fort I osteotomy has opened the door for improved treatment. However, despite the improved surgical techniques, surgeons have been reluctant to increase the vertical dimension of the maxilla by Le Fort I osteotomy with interpositional bone grafts because of inconsistent and variable stability after surgery. This study examines structural and functional adaptation of the adult temporomandibular joint and stability in a primate model following surgical lengthening of the maxilla in the vertical dimension. Results suggest that maxillary surgery and autorotation can alter condylar stress within physiologic ranges. However, further studies are indicated to clarify the surgery's long-term effect.
The International journal of adult orthodontics and orthognathic surgery
The purposes of this investigation were to compare functional performance between controls and a ... more The purposes of this investigation were to compare functional performance between controls and a sample of patients with skeletal anterior open bite prior to surgical correction and to examine how the patients' oral motor function adapted after treatment. Five female patients with skeletal open bite malocclusion were treated with Le Fort I osteotomy and compared to sex-, size-, and age-matched controls. Measurements of skeletal morphology, mandibular range of motion, occlusal force, and muscle efficiency were taken on all subjects over time. Prior to surgery, all patients had lower occlusal forces than did controls at all bite positions. After surgery, occlusal forces at several occlusal positions increased significantly from the presurgical recordings but remained below the level of controls. The mechanical advantages of the muscles of mastication were not significantly different between controls and patients either before or after surgery. The results of this study suggest tha...
American Journal of Orthodontics and Dentofacial Orthopedics
International journal of oral and maxillofacial surgery, 2000
The purpose of this study was to determine the rate of recovery of mandibular motion in patients ... more The purpose of this study was to determine the rate of recovery of mandibular motion in patients treated for fractures of the mandibular condylar process. One hundred and thirty-six patients (111 men, 25 women), 74 treated by closed and 62 by open methods, were included. They underwent testing of mandibular and condyle mobility at 6 weeks, 6 months, and 1, 2, and 3 years post surgery. Their ranges of motion were compared to those of 52 controls (26 men and 26 women). A jaw-tracking device was used to assess mandibular motion. Multilevel statistical models were used to assess differences between groups, and to estimate rate of recovery in the fracture patients. In general, patients with unilateral fractures of the condylar process had maximum excursions that returned to normal values within 3 years after fracture, regardless of treatment. Patients treated open exhibited a faster rate of improvement in maximum interincisal opening than patients treated closed (0.43 mm/month vs 0.15 mm...
Oral surgery, oral medicine, and oral pathology, 1992
Controlled studies of the reproducibility of data from electronic pulp testing instruments are li... more Controlled studies of the reproducibility of data from electronic pulp testing instruments are limited and contain few statistical analyses. The reproducibility of these readings is important if the instrument is to be used for determining differences in sensitivity. Twenty human subjects (16 male) were used in this study. One incisor, one premolar, one molar tooth with small or no restorations, and two gingival soft tissue positions from each upper and lower arch of each subject were stimulated with the Analytic Technology vitality scanner. This procedure was repeated twice with a 5-minute rest between each trial, for a total of three trials. Each subject was then seen again after a period of at least 3 days, at which time the trials were repeated. The collected data were grouped by trial, tooth position, and day. Paired t test analysis of both the absolute difference between any two trials on the same day and the average of the absolute differences between corresponding trials on ...
Journal of oral and maxillofacial surgery : official journal of the American Association of Oral and Maxillofacial Surgeons, 2004
We sought to compare mandibular motion during mastication in patients treated in either an open o... more We sought to compare mandibular motion during mastication in patients treated in either an open or a closed fashion for unilateral fractures of the mandibular condylar process. Eighty-one male patients with unilateral condylar process fractures were treated either with (n = 37) or without (n = 44) surgical reduction and rigid fixation of their condylar process fractures. At 6 weeks, 6 months, 1 year, and 2 years after treatment, the subjects' chewing cycles were recorded using a magnetic sensor array (Sirognathograph; Siemens Corp, Bensheim, Germany) while chewing Gummi-Bears (HARIBO, Bonn, Germany) unilaterally on the same side as the fracture and on the opposite side. The chewing cycles were analyzed using a custom computer program, and the duration, excursive ranges, and 3-dimensional cycle shape were compared between the 2 treatment groups at each time interval using multilevel linear modeling statistics. The 2 treatment groups did not differ significantly for any measure of...
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Papers by Gaylord Throckmorton