The Muscle Engram: The Reflex That Limits Conventional Occlusal Treatment

Abstract

The engram (the masticatory "muscle memory") is shown to be a conditionable reflex whose muscle conditioning lasts less than two minutes, far shorter than previously thought. This reflex, reinforced and stored in the masticatory muscles at every swallow, adjusts masticatory muscle activity to guide the lower arch unerringly into its ICP. These muscle adjustments compensate for the continually changing intemal and external factors that affect the mandible's entry into the ICP. A simple quick experiment described in this article isolates the engram, enabling the reader to see its action clearly for the first time. It is urged that every reader perform this experiment. This experiment shows how the engram, by hiding the masticatory muscles' reaction (the hit-and-slide), limits the success of the therapist in achieving occlusion-muscle compatibility. This finding has major clinical implications. It means that, as regards the muscle aspect of treating occlusion, the dentist treating occlusion conventionally is working blind, a situation the neuromuscular school of occlusal thought seeks to correct. The controversy over occlusion continues.

Selection of test bites records as part of a forensic bite mark analysis protocol

“…In order to avoid modifying the subject's natural bite pattern, each subject was asked to try to contact all of his/her posterior teeth in the same biting act. The mandible was not manipulated in any way to allow the natural design of the engram during the arc of closure and to avoid overwhelming (Lerman 2011). The wafers were removed from the mouth while they were still warm and in a single movement to avoid deformations.…”

“…There are millions of possible mandibular placements for occlusion's intercuspal position (considering the mandible's placement in all three dimensions of space) and the range of motion is influenced by a high number of factors. The neuromuscular system adapts easily to these factors determining an "engram" (the socalled "muscle memory"), which cannot be interpreted as a simple mechanical abstraction of motion in a single plane (Lerman 2011). The goal of this research was to establish if differences exist between three wax test bites (Webster's type 3 bites in which teeth biting right through or almost through the bitten material, typical of the bite found in cheese) (Webster 1982) taken from the same subjects, to corroborate if the first test bite was of superior quality, and to discuss the value of having more test bites to dynamically interpret the bite action.…”

Applying neuromuscular techniques in the orthodontic setting

“…Head posture is also adjusted to facilitate a mandibular trajectory free from premature occlusal contacts as the mandible moves to CO. 29 Although the CNS elaborates a habitual rest position that will reduce functional demands, it remains an accommodative response. 24,25 After obtaining detailed information about habitual function, the next step is to determine the mandibular posture and path of closure without occlusal conditioning. To do this, the periodontal afferent inputs to the CNS are interrupted, allowing relaxation of the mandibular postural muscles.…”

“…An Aqualizer (Jumar Corp., Prescott, AZ, USA), which is a temporary diagnostic splint, is useful for producing a rapid relaxation of the masseter and temporalis muscles, and was used on the patient discussed in this case report. 24,25 The TENS application lasts at least 45 minutes when the muscles are relaxed; as assessed using surface electromyography. The TENS device is then switched off, and the muscles are assessed using surface electromyography to ensure that the output is below normal limits.…”

“…This "muscle memory" is the result of the physiologic demands of dental occlusion, and the implications it has on our social and biological function. 24,25 Analysis entails performing mandibular tracking during opening and closing of the lower jaw and during swallowing. Surface electromyography is then performed during mandibular rest, clenching, and movement.…”