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PubMed1977

An experimental study of increased vertical dimension in the growing face.

Five juvenile rhesus monkeys were used in an experiment designed to study the structural adaptations in the craniofacial complex that resulted from increases in vertical dimension. The bite was opened 2,3,10, or 15 mm. by means of cast bite splints cemented on the maxillary arch. Adaptations were monitored in these animals by means of serial cephalometric radiography with metallic implants. The results of this study indicate that any change in the vertical dimension of the face results in specific structural adaptations throughout the craniofacial complex. The most significant adaptation occurred in the maxillary region, in which the normal downward displacement of this region was decrease and the anterior displacement was increased. Adaptation were less evident in the mandible, except in those animals in which a severe bite opening was produced; resorption in the region of the gonial angle was evident. Dentitional adaptations were of secondary importance. This study demonstrates that the maxillary complex is a very plastic structure which responds to changes in bite opening and altered muscle length. The clinician should be aware of the changes that result from various alterations of vertical dimension to make sure that these changes are not antagonistic to his over-all treatment goal. He may also take advantage of these changes when designing treatment strategies for certain clinical cases.

Animals↗
PubMed1995

Biomechanical implications of lateral pterygoid contribution to biting and jaw opening in humans.

The contributions of the lateral pterygoid muscle to a variety of different tasks were analysed by a linear programming mode based on the equations for static equilibrium in three dimensions and containing 12 muscles. The model was used to study lateral pterygoid activity at maximum bite force (MBF) for changes in (i) the direction and point of application of the bite force, (ii) the orientation of the masseter and medial pterygoid muscles and (iii) the slope of the articular eminence (glenoid slope). The effects on MBF of removing one or both lateral pterygoids were also examined. Lateral pterygoid provided a very important indirect contribution to some clenching forces. Under some conditions removing one lateral pterygoid muscle (simulating guarding an injured muscle) halved the MBF. Its activity at MBF was reduced as masseter was tilted more forward, the glenoid slope was made more horizontal and the bite force was made more vertical. The muscle helped to oppose (balance) the horizontal reaction forces at the bite point and joints, which potentially pushed the condyle backward. A balancing muscle is now defined as one (like lateral pterygoid) whose activity increases the output force by far more than its direct contribution to that force. In a larger model containing 16 muscles, every muscle was most active when its line of action was parallel to the output force. Finally, in a model which divided lateral pterygoid into superior and inferior heads, activity suddenly switched from the superior head to the inferior head when the angle of opening changed from 120 degrees (forward from the vertical) to 140 degrees.

Biomechanical Phenomena↗
PubMed2002

Reproducibility of characteristics assessing the occlusion of young adults.

The aim of the present investigation was to analyze the reproducibility in the assessment of six morphological and three functional characteristics included in a new method evaluating the occlusion in young adults. These characteristics comprised coincidence of midlines, overjet, overbite, canine relationship, crossbite, scissors bite, recurrent deviation on opening, guided lateral excursions, and discrepancy between the centric relation and the intercuspal position. The study was conducted in three stages: (1) five observers assessed the occlusions of five volunteers, (2) seven observers assessed nine volunteers, and (3) five observers assessed nine volunteers. Two calibrated orthodontists were used as references. For numerical variables, the nonparametric method for repeated measurements (Friedman's test) was used to test the significance of differences, while the proportion of agreement was calculated for categorical assessments. The results were analyzed using two precision levels: within a measurement unit/the same category and an acceptable/nonacceptable dichotomy. The magnitude of systematic differences was small and of minor clinical importance except in measurements of recurrent deviation on opening. The proportional agreement for acceptance was good in the assessment of overjet, coincidence of midlines, crossbite, scissors bite, open bite, and discrepancy between the centric relation and the intercuspal position. Moderate agreement was achieved in the assessment of overbite, canine relationship, recurrent deviation on opening, and guided lateral excursions. Among the nonacceptable cases, the agreement ranged from poor to good. The results indicated that noncalibrated observers assess categorical characteristics inconsistently.

Adolescent↗
PubMed1983

Temporomandibular joint involvement and dental occlusion in a group of adults with rheumatoid arthritis.

The temporomandibular joint (TMJ) and dental occlusion were investigated clinically and radiographically in 59 patients aged 23-83 (mean, 58) years with general joint disease. Forty-nine had rheumatoid arthritis (RA), mostly of long duration. The patients were divided into four groups by type of dentition. Radiographic TMJ abnormality was found in about 4 of 5 patients with RA, in both the dentate and the edentulous group. The abnormality was mainly destructive with productive signs, but in the edentulous group erosive and asymmetrical changes occurred more often. Almost complete restriction of the condylar translation and severely restricted mouth opening (less than or equal to 30 mm) rarely occurred, although the translatory motion was restricted in several patients. Many of these had a satisfactory mouth opening (greater than 40 mm). Occlusal changes-various degrees of anterior bite opening-were reported by about one fourth of both the dentate patients and the complete denture wearers. One patient had occlusal contact on the second molars only. Anterior bite opening occurred only in patients with radiographic TMJ abnormality, including 5 of the 6 patients with complete mandibular head destruction.

Adult↗
PubMed1991

Mandibular function in children with a lateral forced bite.

Open-close-clench cycles have been studied in 12 children with a lateral forced bite in order to investigate how the neuromuscular system of the mandible adapts itself in the presence of occlusal interferences. The mandibular movements were registered in a frontal plane at the central incisors with an opto-electronic registration technique. Series of 35 cycles were recorded to intercuspal position, against flat occlusal splints constructed in intercuspal raised and retruded positions, and against splints with occlusal stops in a retruded position. Average lateral displacements of the mandible during cycle series against flat occlusal splints were measured relative to cycle series to intercuspal position and relative to series against splints with occlusal stops in the retruded position. The lateral mandibular displacements were registered at maximal tooth-tooth or tooth-splint contact and at 7, 14, and 21 mm mouth-opening. It was found that the mandible in the subjects investigated is displaced to the forced bite side both during cycle series into intercuspal position as well as when occlusal contacts are eliminated by the use of flat occlusal splints.

Child↗
PubMed1997

[Treatment of open fractures due to dog bite].

2 patients aged 12 and 19, respectively, sustained open fractures of the wrists due to dog bites. Both were bitten on a wrist by Rotweiller dogs, but with different magnitudes of injury to bone and soft tissue. Treatment, clinical course and recovery are described, together with recommendations for dealing with open fractures due to animal bites. In the presence of considerable injury to soft tissue and bone, and of exposure to canine oral flora, open fractures due to dog bites should be dealt with as high grade open fractures.

Adolescent↗
PubMed1997

Impact velocities of the teeth after a sudden unloading at various initial bite forces, degrees of mouth opening, and distances of travel.

A potentially dangerous situation arises when an individual bites on hard and brittle food which suddenly breaks, since the impact velocity of the lower teeth onto the upper teeth after the food is broken can be high and may cause dental damage. The present experiments were designed to study the magnitude of the impact velocity after a sudden unloading at various initial bite forces, degrees of mouth opening, and distances of travel. Subjects were asked to perform a static biting task during which the resistance to the bite was suddenly removed. The upward mandible movement was arrested after a certain distance. The velocity of the lower teeth at impact was calculated just before the mandible came to a standstill in combinations of 4 different bite forces (100, 80, 60, and 40 N), 4 different initial degrees of mouth opening (33.5, 30.5, 27.5, and 24.5 mm), and 3 different distances of travel of the mandible (4.5, 3.0, and 1.5 mm). We found that the bite force rapidly declined after the unloading, resulting in a small impact velocity of the lower front teeth. This impact velocity largely depended on the magnitude of the initial bite force and the distance traveled; it was barely sensitive to variations in degree of initial mouth opening. The maximal velocity of the lower teeth was 0.43 m/s (at an initial bite force of 100 N). This maximum was reached after a distance of travel of about 4 mm in 12 ms. The data suggest that the rapid decline in bite force coupled with a limitation of impact velocity is due to the force-velocity properties of the active jaw muscles and is not caused by neural control.

Biomechanical Phenomena↗
PubMed2004

Joint tenderness, jaw opening, chewing velocity, and bite force in patients with temporomandibular joint pain and matched healthy control subjects.

AIMS: To evaluate the effect of temporomandibular arthralgia on mandibular mobility, chewing, and bite force. METHODS: Twenty female patients (ages 19 to 45 years) with unilateral temporomandibular joint (TMJ) pain during chewing (49 +/- 27 mm on a 100-mm visual analog scale) and provocation, as well as TMJ tenderness, were studied. The TMJ conditions were classified as disc derangement disorders (n = 9), osteoarthritis (n = 7), and inflammatory disorders (n = 4). The patients were compared with matched healthy volunteers without orofacial pain or tenderness. Exclusion criteria were the presence of fewer than 24 teeth or malocclusion. The methods used were (1) algometric assessment of the pressure pain threshold (PPT) over the TMJ; (2) clinical recordings of maximum jaw opening; (3) computerized kinematic assessment of maximum vertical distance, velocity, and cycle duration during chewing of soft gum; and (4) measurement of unilateral molar bite force. RESULTS: The mean (+/- SD) PPT in the patients' painful side (69 +/- 20 kPa; P = .000001) was significantly lower than in the control subjects (107 +/- 22 kPa). Jaw opening was also significantly less (P = .00003) in the patients (42 +/- 9 mm) than in the controls (52 +/- 4 mm). Chewing cycle duration and maximum closing velocity were significantly different (P < or = .03) in the patients (948 +/- 185 milliseconds and 142 +/- 46 mm/s, respectively) versus the controls (765 +/- 102 milliseconds and 173 +/- 43 mm/s, respectively), and bite force was significantly lower (P = .000003) in the patients (238 +/- 99 N) than in the controls (394 +/- 80 N). Both bite force and jaw opening in patients were significantly correlated (P < or = .02) with PPT (r = 0.53 and 0.63, respectively). CONCLUSION: These systematic findings supplement results from acute pain experiments and confirm indications from unspecified patient groups that the clinical presence of long-standing TMJ pain is associated with marked functional impairment. This impairment might be a result of reflex adaptation and long-term hypoactivity of the jaw muscles.

Adult↗
PubMed2004

The overbite and intraoral mandibular distraction osteogenesis.

PURPOSE: The purpose of this study was to quantify the overbite reduction in skeletal Angle Class II malocclusions and discuss the management of the overbite during and after intraoral distraction of the mandible, and during orthodontic treatment with fixed appliances. MATERIAL AND METHODS: Cephalograms of 26 patients with an Angle Class II malocclusion and orthodontic appliances and distraction osteogenesis of the horizontal part of the mandible before (T0) and at least 1 year after treatment (T1) were evaluated. Mean age of the patients at the time of distraction was 14.6 years (range 12.8-15.9 years) and at the final registration 17.3 years (range 14.6-20.4 years). RESULTS: The overbite decreased significantly and the SpP/MP value increased significantly. The increase in the value of the Y-axis and the MP/SN angle before and after treatment was statistically insignificant. CONCLUSION: Opening of the bite during distraction of the mandible can be expected. The use of the 'floating bone' technique did not correct the overbite permanently. The patients in whom an open bite has already been treated are not ideal for mandibular lengthening by means of distraction osteogenesis.

Adolescent↗
PubMed1985

Cephalometric analysis of condylar adaptations to altered mandibular position in adult rhesus monkeys, Macaca mulatta.

Morphological adaptation to altered position of the mandible was investigated in 19 young adult rhesus monkeys (n = 10 experiment and 9 control). The experimental animals had a bite-splint cemented to the maxillary dentition which opened the bite interincisally by 15 mm and was worn continuously for 48 weeks. Lateral radiographic cephalograms were taken prior to the experiment and at 12-week intervals thereafter. Computerized cephalometry, facilitated by the use of radio-opaque bone markers, was used to assess changes in mandibular position and morphology. An immediate effect of the bite-splint was the clockwise rotation (opening) of the mandible and anterior translation of the condyle on the articular eminence, much as occurs normally during jaw depression. During the next 48 weeks, the mandible (1) rotated anti-clockwise (closed) due mainly to antero-superior displacement of the maxilla and intrusion of the mandibular dentition and (2) underwent a significant increase in length (p less than 0.05). These findings indicate that the mandibular condyle of young adult monkeys is capable of small, but biologically significant, compensatory growth after displacement.

Adaptation, Physiological↗
PubMed1986

The bacteriology of dog bite wounds on initial presentation.

Four hundred twenty patients with open dog bite wounds on initial presentation to the emergency department had Gram stains, aerobic and anaerobic cultures, and antibiotic sensitivities of the bacterial isolates of each wound. Forty-eight percent of the wounds evidenced no bacterial growth. Staphylococcus epidermidis was the most common isolate (20.5%). Multiple bacteria were isolated in 15.5% of patients. Fifty percent of clinically infected wounds showed multiple pathogenic organisms, on both culture and Gram stain. The predominant pathogenic bacteria in clinically infected wounds were, in order, Enterobacteria, Pseudomonas, Staphylococcus aureus, Bacillus subtilis, and beta-Streptococcus. Gram stains were useful in determining specific antibiotic therapy in only 6% of infected cases and in 2% of uninfected cases. Statistical differences appeared between initially clinically infected and uninfected dog bite wounds, in both the types of bacteria and frequency of occurrence. Clinical infections were treated effectively with cephradine in more than 95% of cases. Infected wounds growing multiple pathogenic bacteria and/or Gram stains that showed multiple bacterial types were covered by a cephalosporin or penicillinase-resistant penicillin. Six percent of isolates could require an aminoglycoside for treatment.

Animals↗
PubMed1989

Circumpubertal growth spurt related to vertical dysplasia.

A longitudinal study of 32 individuals representing male and female open and deep bite was examined to determine the relationship between subjects who are characterized by proportionately large and small lower anterior face heights and adolescent facial growth spurts. Open bite individuals matured earlier than deep bite individuals. Morphologic differences between the groups were maintained during the adolescent growth spurt. Further studies are needed to examine the relationships between adolescent growth spurt to stature and somatotype.

Adolescent↗
PubMed1978

Midpalatal suture opening during functional posterior cross-bite correction.

The purpose of this study was to determine whether opening of the midpalatal suture occurs during treatment of posterior cross-bites by means of a Porter or W appliance. In eight of the ten cases treated there was radiographic evidence of midpalatal suture opening. Posterior cross-bite correction with a Porter of W appliance may occur either by a combination of midpalatal suture opening and buccal tipping of posterior teeth or by buccal tipping alone.

Activator Appliances↗
PubMed1989

A longitudinal cephalometric study of incisor supra-eruption in young and adult rhesus monkeys (Macaca mulatta).

Supra-eruption was examined in 28 adult (N = 19 experimental and 9 control) and 12 juvenile monkeys (N = 7 experimental and 5 control). The experimental animals had a bite splint cemented to the posterior maxillary teeth which opened the bite inter-incisally by 15 mm and was worn continuously for 48 weeks. Lateral cephalograms were taken prior to the cementation and at 12-week intervals thereafter. Radio-opaque bone implants placed in the basal bone of the jaws served as fixed reference points from which to assess the vertical and horizontal components of central incisor movement. Significantly greater movement of both upper and lower incisors towards the occlusal plane occurred in the experimental animals of both age groups over the 48 weeks when compared to the same aged controls (p less than 0.01). Mean vertical movement ranged from 4 mm (about 40% of crown length) in the juvenile upper incisors to 1.5 mm (15%) in the adult lower incisors. The overall pattern of movement of upper and lower incisors in the experimental juveniles differed from that in the controls only in the vertical component (p less than 0.01), indicating that the supra-eruptive response was superimposed on the antero-occlusally directed tooth movement and alveolar growth that normally occurs in rhesus monkeys of this age. In contrast to the more evenly distributed response found in the juveniles, the majority of the supra-eruptive response occurred during the first 12 weeks in the experimental adults.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗