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A reconstruction of the central mandible is described using a single carved segment of iliac bone. The design of the graft takes into account the forces acting upon the remaining mandibular remnants and the need to provide absolutely rigid fixation until bony union is achieved.
A method of reconstruction of the zygoma, temporo-mandibular joint and hemi-mandible utilising a segment of the outer table of the sternum, sterno-costal joint and rib vascularised by an ipsilateral pectoralis major muscle flap is described. The mobility of an isolated sterno-coastal joint is compared with movements of the temporo-mandibular joint.
We describe the reconstruction of the mandible using the spine of the scapula pedicled upon trapezius in a woman who had undergone previous mandibular irradiation and surgery. We show how the vascular supply to the trapezius scapular spine compound flap can be approached posteriorly and the spine of the scapula used to provide good length and contour for replacement of a wide mandibular defect.
This paper reports experimental measurements which show that canine mandibular bone tissue is elastically isotropic. Earlier work has established that human, canine and bovine cortical bone tissue of the femur, tibia and skull are elastically anisotropic and therefore the reported isotropy of mandibular tissue was unexpected. The isotropic elastic moduli of the canine mandible are represented by a Young's modulus of 7.5 GPa and a Poisson's ratio of 0.4. Earlier work gave the three orthotropic Young's moduli of the cortical one of the canine femur as 12.8 GPa, 15.6 GPa and 20.1 GPa. The experimental technique employed is elastic wave propagation at ultrasonic frequencies.
Three-dimensional finite element models of a partially edentulated human mandible were generated to calculate the mechanical response to simulated isometric biting and mastication loads. The level of mesh refinement was established via a convergence test and showed that a model with over 30,000 degrees of freedom was required to obtain analysis accuracy. The functional loading cases included muscle loading based on an algorithm that assigns muscle forces in accordance with muscle cross-sectional area, while maintaining static equilibrium. Results were found for isometric application of unilateral and bilateral bite and mastication loading, and two different sets of displacement boundary conditions were imposed at the condyles. The mechanical response is shown in terms of displacements, principal strains, and a new measure called the 'mechanical intensity scalar'. For each load case studied, there was substantial bending in the molar region of the corpus and high tensile strains in the anterior portion of the ramus.
A female infant presented with a midline cleft of the mandible and a midline dermoid in the neck. Midline clefts are rare craniofacial clefts. Midline mandibular clefts can be associated with midline cleft of upper lip and a dermoid of nose. But a midline mandibular cleft with a midline dermoid in the neck has not been reported before.
A model to quantify muscle response to occlusal contacts is useful in developing an understanding of the mechanism by which the occlusion programs muscle function. A knowledge of how the occlusion programs muscle function enables the dentist to develop manipulative skills of the mandible which are necessary for diagnosis and effective occlusal treatment. This article presents complicated neuromuscular responses (reflexes) to occlusal contacts in an oversimplified way and with analogies so that the clinical significance of these neuromuscular reflexes in diagnosis and treatment can be more easily understood.
A method has been described for determining the location of the physiologic equilibrium point of the mandible. The clinical implications of this equilibrium point were discussed. Further studies relating the equilibrium point to different growth and development patterns, functional excursions, and radiographic studies were outlined.
The Selspot system has been developed to record mandibular movements with LED. The aim has been to make a system that is easy to manipulate and permits chewing performance with only minimal mechanical interferences. This study was performed to obtain information on the suitability of the Selspot system for collecting data on the cranial position of the mandible during chewing and swallowing. The results coincided with reports by others using different methods, and the suitability of the system was regarded as good for studying occlusal position during function. The following conclusions could be drawn from the results: 1. In the sagittal plane the chewing activity was performed in a more anterior position than the swallowing contact position. 2. The lateral and vertical cranial position is unstable in the beginning of the chewing period but stabilizes to the occlusal position in the latter half of the chewing period. 3. The occlusal position during chewing does not seem to be a single position but rather a three-dimensional occlusal zone.
Mandibular movements were recorded with the Selspot system in 16 complete denture patients, before and after treatment with mandibular OIFD. The general chewing pattern underwent only minor changes. However, some chewing cycle parameters showed obvious alterations. Increased mandibular velocity and displacement, especially in the opening phase, were registered. The cycle duration showed a tendency to decrease due to a significant shortening of the occlusion phase. This can be attributed to the stabilization of the occlusion provided by the fixed denture in the mandible.
While autogenous bone augmentations for atrophic edentulous mandibles are not the ideal solution for this problem, we do not share the pessimism of other investigators. The average loss of bone over the 92-month observation period was 60% for this small sample of eight patients. However, there was an 81% gain in bone height in the premolar-molar regions when compared with presurgical measurements. Seven of the eight patients believed these procedures were beneficial.
Twenty-five edentulous patients with established hyperparathyroidism were evaluated to establish a possible relation between extreme reduction of the height of the mandible and systemic bone loss. As an important parameter of the severity of the systemic bone loss, the level of the intact biologically active molecule of the parathormone was used. In this study no relation between hyperparathyroidism and reduction of the residual alveolar ridge could be established. In only two patients the reduction could be classified as "severe." Furthermore the level of the active, intact, circulating parathormone or the duration of the hyperparathyroidism could not be identified as an important factor in relation to the local phenomenon of reduction of the alveolar ridges.
Mechanical analyses supporting various and prevailing stomatognathic concepts of occlusal function are sparse. This study, using a mechanical model, simulates a system in function and provides a vectorial analysis based on a static equilibrium of forces generated in a mandible at 10 different positions. The positions analyzed were one in centric occlusion and nine in eccentric positions. Four eccentric positions were in a balanced occlusal relationship and five were in group function. Among other conclusions that were drawn, the most relevant seems to be the finding that cusp inclines and condylar path inclination have a profound influence on the forces acting within the joints and dentition.
This study measured the amount of positional change in the terminal transverse horizontal axis of the mandible that results from altering undesirable neuromuscular influence. Centric relation records were made on 19 healthy subjects before and after deprogramming. The axis was located with a computerized axiograph, and the centric relation records were compared in vivo at the axis location. The positional change of the axis was quantified in three dimensions at an accuracy of +/- 0.05 mm. The net amount of positional change was compared to scores from the temporomandibular joint scale to test for correlation with the potential for developing a temporomandibular disorder. The findings showed that the amount of positional change in the terminal transverse horizontal axis in 18 of 19 healthy patients after 12 hours of deprogramming was less than 0.5 mm and did not correlate with scores from the TMJ Scale.
A successful implant restoration is dependent on proper implant position. Correct implant placement is more predictable when a surgical stent is used. This article describes the fabrication of a surgical stent for the edentulous mandible using a denture with acceptable adaptation and tooth arrangement as a given.
The purpose of this study was to evaluate the effects of a change in the lateral anterior guidance pathway on the lateral border movement pathway of mandible. The results showed that altered occlusal guidance reproducibly and reversibly changed (increased) the lateral border movement area in two subjects who had unilaterally restricted lateral border movements.
In a previous article we reported on our development of a biomechanical analog of the human mandible and a simple support model was introduced. The model has been further developed to calculate the relative degree of load on the working and balancing sides of the temporomandibular joint during unilateral clench. The relative load on each joint is a function of the biting force, the geometric setting (subject's anatomy, points of application of the biting force on the dental arch and of the resultant of the forces of the masticatory muscles), and the value of the electromyographic asymmetry (relative contribution of working-versus balancing-side muscles) and activity indexes (relative contribution of masseter versus anterior temporal muscle of both sides). The proposed biomechanical model showed that the reaction forces that act on the temporomandibular joint during unilateral clench do not always load the balancing-side joint more than the working-side joint. Modifications of the asymmetry index changed the relative load between the two joints, and a higher temporal muscle activity increased the joint load on both the working and the balancing sides.
Aggressive juvenile fibromatosis involving the facial bones is rare, difficult to diagnose clinically, histologically confusing, and requires aggressive surgical treatment. Only four cases involving the mandible have been previously reported. A review of the literature is presented here in conjunction with a case report of this rare tumor.