Limiting Structures in Dentistry

Study Notes

Limiting Structures

Labial Frenum: A fibrous band similar to the maxillary labial frenum, but unlike it, is active and gets narrower when the mouth opens wide.
Labial Vestibule: The space between the residual alveolar ridge and the lips, important for lip support and denture retention.
Buccal Frenum: Attached to the buccinator muscle fibers, needs relief to prevent denture displacement during function.
Buccal Vestibule: Extends posteriorly from the buccal frenum, bound by residual alveolar ridge and the buccinator muscle.
Lingual Frenum: A fold of mucous membrane that extends along the floor of the mouth, producing a lingual notch in the denture.
Alveololingual Sulcus: Extends from the lingual frenum to the retromylohyoid curtain, divided into three regions:
- Anterior Region: Extends to the premylohyoid fossa where the flange is shorter anteriorly and touches the mucosa of the floor of the mouth when the tongue touches the upper incisors.
- Middle Region: Extends from the premylohyoid fossa to the distal end of the mylohyoid ridge, shallower than other parts of the sulcus.
- Posterior Region: Features the retro-mylohyoid fossa and requires the denture flange to turn laterally to fill the fossa.
Retromolar Pad: Soft elevation of mucosa distal to the third molar, important for support and peripheral seal, requiring the flange to turn laterally to fill the fossa.
External Oblique Ridge: A ridge of dense bone extending from the mental foramen superiorly and distally, sometimes a guide for buccal flange termination.
Mylohyoid Ridge: Irregular bony crest on the lingual surface of the mandible, near the inferior border anteriorly, becoming higher posteriorly.

Supporting Structures

Buccal Shelf Area: Area between the buccal frenum and the anterior border of the masseter, bound by the crest of the ridge, retromolar pad, and external oblique ridge.
Residual Alveolar Ridge: The bony process remaining after tooth loss, varies in size and shape between patients, not ideal for primary stress bearing due to spongy bone.

Relief Areas

Mental Foramen: Located on the external surface of the mandible between the 1st and 2nd premolar area, requires relief to prevent pressure on nerves and blood vessels.
Genial Tubercles: Pair of bony tubercles on the lingual side of the mandible, may become prominent due to resorption, requiring relief.
Torus Mandibularis: Abnormal bony prominence found bilaterally on the lingual side, covered by thin mucosa, may require relief or surgical removal.