Harry C. Lundeen

Occlusal forces during chewing and swallowing as measured by sound transmission

Forces during the phase of occlusal contact during chewing and swallowing are surprisingly high (36.2% and 41%), about 40% of the subjects maximum biting force. Previous studies using transducers in fixed partial dentures measured only a portion of the total force and have given the impression that chewing forces are much less than the data reported in this study. The importance of occlusal stability in the intercuspal position is of utmost clinical significance. Steep anterior guidance does not appear to expose the teeth to extreme lateral forces. The gliding contacts of the teeth while entering and leaving the intercuspal position have been shown to be of short duration and low magnitude when compared with the forces generated in the intercuspal position. During chewing, the peak occlusal force occurred well after the peak EMG activity. EMG activity by itself does not directly correlate with the force generated during chewing. The sound transmission method for measuring interjaw force during chewing, which was developed as part of this project, proved to be practical for research purposes. No intraoral devices are required, and the time relationship to force is accurate to within 15 ms.

Limits of human bite strength

lhe greatest human bite strength in the early literature was reported more than 300 years ago by Borelli of Rome, Italy, in 1681.’ He attached weights to a cord, which passed over the molar teeth of the open mandible, and with closing of the jaw, up to 440 lbs (200 kg) were raised.’ In recent times, the greatest reported bite strength was 348 lbs (158 kg) in the Alaskan Eskimo.2 Bite strength records have been limited by instrumentation. Black,3 for example, reported that at least one of his subjects could have exceeded the 275 lb (125 kg) limit of his gnathodynamometer. Furthermore, his subjects were biting unilaterally and, as in many other studies, did not have the advantage of bilateral support. An improved gnathodynamometer was needed if increased bite strengths were to be measured. Today’s soft diet cannot compare with the hard, frozen diet of the Eskimos for strengthening the mandibular muscles.4 However, many people today undergo jaw muscle-strengthening through clenching and bruxing habits that may be considerably more rigorous than even the chewing demands of the Eskimo. Our hypothesis was that human bite strength of the bruxer-clencher has been underestimated, and some individuals can exceed the bite strength of the Eskimo.

Centric relation records: The effect of muscle action

Abstract A comparison of condylar positions was made by means of the Buhnergraph system with articulator-mounted casts. Three types of positional records were made and compared on eight subjects. Either heavy or light muscle contraction by the patient or electrically stimulated muscle contraction was used to position the condyles while the records were being formed.

An evaluation of mandibular border movements: Their character and significance

1. A comparison of protrusive and lateral condylar border movement pathways of 163 subjects revealed considerable similarity when the frequency of 80% of the pathways was compared with the average pathway. 2. A description of the pathways of posterior cusps during lateral contact gliding movement must consider three simultaneously acting guidance factors: (1) the nonworking condyle pathway, (2) the amount of Bennett movement or the working-side condyle displacement, and (3) the anterior guidance or working-side tooth contacts. 3. A Bennett movement of 2.5 to 3.5 mm caused a dramatic flattening of lateral movement pathways of the molar cusp as seen in the frontal plane. The steepness of neither the anterior guidance nor the nonworking condylar pathway had much influence on the molar cusp pathway in the presence of this excessive Bennett movement. 4. Viewed in the horizontal plane, excessive Bennett movement contributed to the greatest potential for collisions of molar cusps during lateral movements. This phenomenon was more pronounced on the nonworking side. 5. When the Bennett movement was 0.75 mm or less the tracing in the frontal plane showed that the 40-degree anterior guidance became the dominant influence over molar cusp lateral movement pathways.

Chewing Patterns in Normal Children

Chewing patterns are precisely plotted in deciduous, mixed and permanent dentitions. These show a progression from a large component in the opening movement with a more medial closing path in the deciduous dentition, to a more vertical overall pattern with the closing path lateral to the opening path in the early permanent dentition.

Simplified Condylar Movement Recorders for Analyzing TMJ Derangements

AbstractThis article describes three simplified condylar movement (SCM) recorders: the WhipMix Quick Set Recorder, the Panadent Quick Analyzer and the SAM Axiograph. The authors explain how these systems may be used to record condylar movements associated with temporomandibular joint internal derangements. Examples of the recordings that may be produced are shown from four patients. The diagnostic information obtained from SCM recorders may become a permanent part of the patients record.