3-dimensional physiologic postural range of the mandible: a computerized-assisted technique-a case study

Abstract

Previous studies demonstrated that while the mandible assumes its resting position in space, antagonistic muscles should assume minimal muscle activity within a spatial range. This zone of mandibular rest has been mapped using physiologic parameters of muscle activity and incisal spatial kinematics. This case study expands on previous research by monitoring incisal and posterior jaw position and includes lateral pterygoid muscle activity, thus allowing for determining the spatial range including additional relevant coordinates and muscle activity. Four positions were evaluated: a maximum physiologic open position, a maximum physiologic closed position, physiologic rest position, and maximum physiologic protrusion position. Within the physiologic zone of rest formed by these 4 positions, the vertical and anterior borders of the envelope of function may be documented for the incisal and posterior mandible in true 3-dimensional fashion to assist the clinician in determining a physiologic interocclusal freeway space and vertical dimension of occlusion. Advantages and limitations are discussed.

Figure 1

Adapted and modified from [, page 9]. SEMG of the temporalis anterior (TA), masseter (MM), temporalis posterior (TP), and suprahyoid (DA) sites in combination with incisal spatial kinematics. “Maximum physiologic opening” or the bottom of the physiologic zone (incisal position 1) was determined when the suprahyoid activity was above what was determined as normal levels. The top of the zone or “maximal physiologic closing” (incisal position 3) was determined when elevator activity increased to greater than what was determined as physiologic normal levels. Physiologic rest (incisal position 2) position after 45–60 minutes of ULF-TENS.

Figure 2

Jaw Motion Analysis system mounted on subject. Courtesy of Zebris Medical GmbH.

Figure 3

SEMG activity of the bilateral temporalis anterior (TA), masseter (MAS) suprahyoid (DIG), and lateral pterygoids (LP) at the initial baseline/postural resting position (Pre-TENS).

Figure 4

Recorded during jaw protrusion against resistance while the teeth are separated. Baseline values of the lateral pterygoids were normalized to this maximal effort.

Figure 5

SEMG activity of the bilateral temporalis anterior (TA), masseter (MAS) suprahyoid (DIG), and lateral pterygoids (RLP/LLPT) after 25 minutes of ULF-TENS. Recording demonstrates that baseline levels from all sites are low and balanced.

Figure 6

Spatial position of the lower jaw combined with bilateral SEMG activity of the temporalis anterior (TA), masseter (MAS), suprahyoid (DIG), and lateral pterygoid (LPT) sites. Coordinates listed are representative of mandibular position relative to centric occlusion and physiologic rest.

Figure 7

Spatial position of the lower jaw combined with bilateral activity of the temporalis anterior (TA), masseter (MAS), suprahyoid (DIG), and lateral pterygoid (LPT) sites. Coordinates listed are representative of mandibular position relative to centric occlusion and physiologic rest and were documented during the “burst” of suprahyoid (DIG) activity, and determined to be “Maximum Physiologic Opening”.

Figure 8

Spatial position of the lower jaw combined with bilateral activity of the temporalis anterior (TA), masseter (MAS), suprahyoid (DIG), and lateral pterygoid (LPT) sites. Coordinates listed are representative of mandibular position relative to centric occlusion and physiologic rest and were documented during the “burst” of LPT activity and determined to be “Maximum Physiologic Closing”.

Figure 9

Spatial position of the lower jaw combined with bilateral activity of the temporalis anterior (TA), masseter (MAS), suprahyoid (DIG), and lateral pterygoid (LPT) sites. Coordinates listed are representative of mandibular position relative to centric occlusion and physiologic rest and were documented during the “burst” of LP activity and determined to be “Maximum Physiologic Protrusion”.

Figure 10

Spatial position of the lower jaw combined with bilateral activity of the temporalis anterior (TA), masseter (MAS), suprahyoid (DIG), and lateral pterygoid (LPT) sites. Coordinates listed are representative of mandibular position relative to centric occlusion and physiologic rest, maximal physiologic opening (position 1), maximal physiologic closing (position 2), and maximal physiologic protrusion (position 3).