172 Reviews and abstracts

axillary Mouthguard: A ary Report of Use in

Aust. Went. .I. 1986;31:200-6

Stock mouthguards designed for the protection of

The bimaxillary mouthguard, according to the au-

teeth during contact sport can be bought at most sporting goods stores. Such mouthguards are generally loose

thor, provides the maximum possible protection be-

fitting and easily displaced by an impact force. Indi- vidually fitted custom mouthguards, unfitted stock type,

cause (1) protection is provided for the lower teeth, (2)

and self-fitted mouth-formed mouthguards were devel- oped to overcsome this problem. Since teeth have to be

the mandible is stabilized to the head, and (3) the cra-

clenched to maintain the mouthguard in position, there is almost an elimination of oral airflow. This is likely

niomandibular relationship reduces mandibulocranial

to present a problem in that during strenuous physical exertion, the respiratory minute volume (RMV) in-

force transmission. The method of constructing the

creases until approximately two thirds of breathing oc- curs through the mouth. To overcome this deficiency,

mouthguard is described in detail. Preliminary reports

the author developed a bimaxillary mouthguard, which in essence comprises upper and lower polyvinylacetate-

on its use appear promising.

polyethylene polymer vacuum-formed mouthguards (approximately 3 mm thick over the anterior teeth) joined together on either side with the jaws parted about 7 to 10 mm. The remaining aperture in the incisor region permits optimum oral airflow.

Alex Jacobson

Thesis abstracts

lysis of the Time-Dependent Force Loss of Orthodontic Wires David Jaekwan Jo Loma Linda University, I985

The purpa’se of this study was to measure the force loss of five brands of orthodontic wire subjected to a variety of stress modes.

A total of 126 samples of 0.016 x 0.016 Blue El- giloy, Yellow Elgiloy, Permachrome Standard, Multi- phase, and Azura wire were tested in a simple cantilever spring configuration. Force loss during a 72-hour period was compared to (1) wire type, (2) type of bends (45”

and 90”), (3) direction of force (winding and unwind- ing), (4) amount of force, and (5) heat treatment.

Force loss ranged from least to greatest in the fol- lowing order: Permachrome Standard, Yellow Elgiloy, Multiphase, Azura, and Blue Elgiloy. Placement of a 45” or a 90” sharp bend made no significant difference in force loss over time. Force applied to ~~~~~~ a loop produced force losses from 180% to 350% above the loss that occurred when force was applied to wind a loop. The amount of time-dependent force loss in- creased when the magnitude of force increased. Heat treatment significantly reduced force loss in all wires.

Heat treatment and forces that wind a loop during activation were shown to be the most significant factors in reducing force loss over time in the five orthodontic wires tested.

Stability in Mechanica Maxilla With Surgical/ Expansion of the Man Adult Baboon Robert D. Mitchell Loma Linda University, 1985

An adult baboon received simultaneous palatal ex- pansion and mandibular surgical/mecha~~c~ expansion to evaluate the stability of basal bone and the dentoal- veolar arch. Surgical expansion of the mandible in hu-

A young adult baboon with full den&ion and normal

mans with severe constriction has not been performed;

occlusion had expansion appliances inserted at the time of mandibular osteotomy. The symphysis was sectioned

thus, the purpose of this study was to evaluate the fea-

to within 5 mm of the crestal alveolar bone between the central incisors. Both appliances were activated

sibility of mandibular expansion in the baboon with

every other day until 10 mm of dental expansion and 5 mm of basal bone expansion was achieved. The ap- pliances were left in place for 3% months to retain

future application to humans.

expansion and then removed to allow relapse to take place for 2 months. Expansion was evaluated using photographs, models, cephalograms, and tetracycline bone labels.

The dentition and alveolar processes relapsed 18% to 30% from maximal expansion; however, the basal bone demonstrated virtually no relapse. The tetracy- cline labels indicated new bone formalion at the sym- physis midline. There were no complications associated with the mandibular osteotomy and there was no evi- dence of temporomandibular joint dysfunction.