External oblique ridge

  • Continuation of anterior border of mandibular ramus.
  • Arises lateral to alveolar process from 3rd molar to 1st molar area.
  • Thick in posterior areas, thinner anteriorly.
  • Appears as linear radiopaque structure running obliquely downward and forward from 3rd molar area.
  • Internal oblique ridge: attachment of mylohyoid muscle, which supports the floor of oral cavity – it is LOWER (like a floor).
  • External oblique ridge: arises on the ascending ramus, so it is HIGHER (ascending).