Preclinical Prosthetic Dentistry · MU Plovdiv

27. Biomechanics of the masticatory articulation. Articulation cycles – opening and closing.

Inside: 5 sections · 2 labelled pictures · 2 tables · 13 flashcards · 3 min

Topic 27 of 96 in the MU Plovdiv syllabus for Preclinical Prosthetic Dentistry (Dental Medicine, Year 2). The free AceMed note covers it in 5 sections, about 368 words (3 min of reading), with 13 flashcards.

In this note

  1. Introduction
  2. Vertical movement: opening and closing
  3. Horizontal movement: forward and sideways
  4. Recording the horizontal border movements
  5. What controls the movement

Introduction

The mandible moves in three dimensions, but any movement can be broken into two simple parts:

  • Rotation: every point turns around an axis.
  • Translation: every point moves the same way at the same time.

It is easiest to describe them as projections onto the three planes (sagittal, horizontal and frontal), each with its own axis of rotation.

Vertical movement: opening and closing

  1. From the intercuspal position to the rest position the condyles mostly rotate around the terminal hinge axis.
  2. Pure rotation lasts for about the first 12 mm of incisor opening. Then the TMJ ligaments and muscles force the condyles to translate: the lateral pterygoid pulls the condyle-disc assembly forward down the back slope of the eminence.
  3. At maximum opening the movement is pure translation.
  4. Closing reverses the sequence; the shape of the teeth decides the last part of the path.

The rotation happens between condyle and disc (lower compartment); the translation between disc and eminence (upper compartment).

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