Electromyography of the Mandibular Postural Position in the Rhesus Monkey (Macaca mulatta)

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68000/2/10.1177_00220345740530043801.pd

An electromyographic study of mastication in the rhesus monkey (Macaca mulatta)

Twenty-eight monkeys (Macaca mulatta) were monitored during 84 electromyographic recording sessions to study the function of certain masticatory and facial muscles during mastication. During the period of closing muscle function, strong activity was noted in the temporal and masseter musculature and in the superior head of the lateral pterygoid muscle. The relative participation of the elevator muscles differed among the four age groups. During the period of opening muscle activity, the suprahyoids and the inferior head of the lateral pterygoid muscle functioned during the depression of the lower jaw. A comparison of the results of this study with the numerous human EMG studies of mastication indicate a basic similarity in muscle function during chewing in the two species, although age-related differences in specific muscle group activities do exist.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22292/1/0000732.pd

Fabrication of the acrylic splint Herbst appliance

This article describes the fabrication of one type of Herbst appliance, a removable or fixed functional appliance that causes the posturing of the mandible in a forward position. The type of Herbst appliance described in this article consists of a wire framework to which are attached the various parts of the Herbst bite-jumping mechanism. The acrylic part of the appliance is fabricated from splint Biocryl or from methylmethacrylate. The steps of the fabrication of the appliance are described in detail.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27439/1/0000478.pd

Electromyography of the oral phase of deglutition in the rhesus monkey (Macaca mulatta)

Patterns of activity of selected muscle groups which function during the oral phase of swallowing were analysed electromyographically in 33 monkeys (Macaco mulatta) during a total of 113 recording sessions. Salivary, water and masticatory swallows were studied. The activity of the suprahyoid muscle group was relatively constant in each animal during all types of swallows. However, three patterns of muscle activity of the other masticatory muscles were identified. In the first pattern (pattern A), the suprahyoids usually fired concurrently with the superior head of the lateral pterygoid muscle with little or no elevator activity evident. In the second pattern (pattern B), the temporal muscle, masseter muscle and superior head of the lateral pterygoid muscle fired concurrently with the suprahyoids. In the third pattern (pattern C), elevator and lateral pterygoid activity preceded the suprahyoid burst. The inferior head of the lateral pterygoid was not active in any swallowing pattern. About 60-70 per cent of the salivary swallows were of pattern A. Most water-swallows were of patterns B and C, while those swallows associated with mastication were entirely of pattern C.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33841/1/0000099.pd

Long-term mandibular adaptations to protrusive function: An experimental study in Macaca mulatta

Twenty-three male juvenile rhesus monkeys ((Macaca mulatta) were used in an experimental study of long-term mandibular adaptations to induced protrusive function. Serial protrusive appliances were placed in 11 experimental animals and mandibular adaptations were monitored cephalornetrically. Twelve animals were used as controls. After 48 weeks significant increases in increments of condylar growth and in overall mandibular length were noted in the treated animals. At the end of the 144-week experimental period, the mandibles of the treated animals were 5 to 6 mm longer than those of the control animals. The results of this study do not support the hypothesis that the mandible has a genetically predetermined length.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26617/1/0000158.pd

Contractile properties of the muscles of mastication of rhesus monkeys (Macaca mulatta) following increase in muscle length

The hypothesis was tested that increasing the resting length of the masseter and temporalis muscles by a bite-opening appliance with or without detachment and re-attachment of the masseter would not affect the contractile properties of these muscles. Appliances opened the bite of 10 adult female monkeys 20mm. Five received the appliance alone (Group A); five received the appliance and in addition the masseter was detached and re-attached (Group ADR). Comparisons were made 48 weeks later. Small bundles of fibres were excised from the masseter and temporalis muscles of experimental animals and from 8 control animals. Isometric and isotonic contractile properties were measured in vitro and fibre classification and fibre areas were determined histochemically. No significant differences were observed within either masseter or temporalis muscles between animals in Groups A and ADR. In both groups, the bundles of fibres from the masseter had prolonged contraction and relaxation times compared to control masseter muscles but no difference was observed in the percentage of Type II fibres. As detachment and re-attachment had no significant effect on morphological or physiological characteristics, other than those due to lengthening, this procedure may be useful in decreasing the passive tension induced when orthognathic surgery increases muscle length. The significant prolongation of the contractile response of the masseter is similar to the adaptation induced by long-term stimulation at low frequency.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24139/1/0000396.pd

The Relationship between Posttreatment Smile Esthetics and the ABO Objective Grading System

ABSTRACT Objective: To evaluate the correlations between the components of the Objective Grading System developed by the American Board of Orthodontics (ABO) and smile esthetics. Materials and Methods: The clinical photographs of 48 orthodontically treated patients were rated by a panel of 25 experienced orthodontists (15 men and 10 women) and 20 parents of orthodontic patients (eight men and 12 women). One of the investigators, a director of the ABO, scored the posttreatment dental casts and panoramic radiographs of all patients according to the guidelines of the Objective Grading System. The relationship between the occlusal outcome and perceived smile attractiveness of the subjects were evaluated by a Pearson product-moment correlation. Logistic regression was used to determine whether the individual component or total combined scores of the ABO Grading System could predict whether a smile would be considered ''attractive'' or ''unattractive'' by the panel of raters. Results: Extremely weak relationships were found among all factors of the ABO Objective Grading System and perceived smile attractiveness (r values ranging from Ϫ0.11 to 0.14; P Ͼ .05). As derived from logistic regression equations, neither total scores nor individual components of the ABO Grading system could predict attractive or unattractive smiles. Conclusions: This study suggests that additional criteria might be incorporated into the assessment of overall orthodontic treatment outcomes, including variables evaluating the smile

Craniofacial adaptation to protrusive function in young rhesus monkeys

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34208/1/0000497.pd

Comparison of two protocols for maxillary protraction: bone anchors versus face mask with rapid maxillary expansion

To test the hypothesis that there is no difference in the active treatment effects for maxillary advancement induced by bone-anchored maxillary protraction (BAMP) and the active treatment effects for face mask in association with rapid maxillary expansion (RME/FM)

Three-dimensional analysis of maxillary changes associated with facemask and rapid maxillary expansion compared with bone anchored maxillary protraction

Our objectives in this study were to evaluate in 3 dimensions the growth and treatment effects on the midface and the maxillary dentition produced by facemask therapy in association with rapid maxillary expansion (RME/FM) compared with bone-anchored maxillary protraction (BAMP)