Dental Anatomy: Proximal Contact Areas & Embrasures

Proximal Contact Areas

• Proximal contact areas, located on the mesial and distal surfaces of teeth, serve as the point of contact between adjacent teeth.
• They prevent food from packing between teeth, provide support and anchorage, and resist displacement.
• Contact points occur where the occlusal cusp of one tooth touches the occlusal portion of another tooth in the opposing arch.

Cervical Embrasure

• A cervical embrasure is a space between teeth formed due to gingival recession, leaving the interdental papilla and bone not fully filling the interproximal space.
• Larger cervical embrasures are associated with more missing papilla.
• These embrasures can lead to bacterial accumulation, calculus, and food debris, creating potential health concerns.

Embrasures Purpose

• Embrasures facilitate food removal from contact areas, dissipating occlusal trauma forces.
• They also contribute to self-cleaning by the tongue, cheeks, and lips, protecting the gingiva from excess trauma.

Facial and Lingual Contours

• The facial and lingual contours of teeth vary between individuals.
• Generally, the buccal height of contour for both anterior and posterior teeth is located at the cervical third of the tooth.
• The lingual height of contour for anterior teeth is also in the cervical third, while the lingual crest of curvature for posterior teeth is positioned at or near the middle third.
• The crest of curvature represents the widest part of the tooth crown, coinciding with the height of contour.

Curvature of Cementoenamel Junction

• The curvature of the cementoenamel junction (CEJ) is determined by the height of the contact area above the crown cervix and the labiolingual or buccolingual diameter of the crown.

Movements of the Jaw and Larynx

• Mandibular protrusion is facilitated by the lateral pterygoid muscles.
• Mandibular retrusion is achieved by the posterior or horizontal fibers of the temporal muscle and the digastric muscle.
• Lateral excursion of the mandible involves the contraction of a single lateral pterygoid muscle, with the left lateral pterygoid muscle contraction moving the mandible to the right.

Structure of the Temporomandibular Joint – Articulation

• The temporomandibular joint (TMJ) forms the articulation between the temporal bone and the mandible, where one surface moves over the other.
• It functions as a bilateral joint, with the mandible fused at the midline.
• The articular disk, a fibrous pad, resides between the TMJ bones.
• It possesses a concave and convex upper surface, matching the contours of the mandibular fossa (glenoid fossa).
• The disk is thickest at its posterior end (posterior band) and thinnest in the middle (intermediate zone).

Structure of the Temporomandibular Joint – Synovial Cavities

• Two synovial cavities are situated above and below the articular disk, lined by epithelium that secretes synovial fluid.
• Synovial fluid allows the surfaces to rub without irritation.

Structure of the Temporomandibular Joint – Fibrous Capsule

• The TMJ is enclosed by a fibrous capsule.
• The temporomandibular ligament strengthens its lateral aspect, preventing condyle displacement.
• The stylomandibular and sphenomandibular ligaments control medial movement.

Rotational Movement

• As teeth separate, an initial rotational movement occurs in the lower synovial cavity between the disk and the condyle.
• The posterior elastic lamina pulls posteriorly on the disk, causing the disk and condyle to rotate against each other.
• This rotational movement persists as the jaw opens further.
• Additional anterior gliding movement occurs along the posterior slope of the articular eminence.

Gliding Movement

• Gliding movement takes place between the disk and the temporal bone.
• The condyle and disk move forward until slightly anterior to the crest of the articular eminence.

General Rules of Tooth Identification

• The distal surface of a tooth has a CEJ curvature approximately 1 mm less than the mesial surface.
• Tooth roots typically curve distally, especially at the apex.
• The distal incisal edges of anterior teeth are more rounded compared to their mesial counterparts.

Maxillary Lateral Incisors – Right vs. Left

• Exhibit mesioincisal angles that are more square than distoincisal angles.
• The cervical line crest is often displaced distally from the labial or lingual view.
• The mesiocervical line curves more incisally than the distocervical line.

Maxillary First Molars

• The occlusal view displays a prominent oblique ridge, less likely to be crossed by a groove.
• Possess three roots.
• Typically exhibit five cusps.
• May feature a Cusp of Carabelli on the mesiolingual cusp.
• The mesiolingual cusp is larger than the distolingual cusp on the right and left sides.

Papillae – Circumvallate or Vallate

• Form a V-shaped row composed of circular, raised structures.
• Approximately 13 elevations are present.
• Located about two-thirds of the way back on the tongue, with the point of the V facing posteriorly.
• These papillae develop from different pharyngeal arches.
• They rest in troughs surrounded by taste buds along their lateral surfaces.
• Salivary glands known as the glands of von Ebner are located at the bottom of the trough.

Tongue Muscles – Extrinsic Muscles

• Palatoglossus: Runs from the anterior soft palate, extending downward and forward towards the tongue's lateral borders. Elevates the tongue's posterior part and pulls it slightly backward.
• Genioglossus: Originates from the superior genial tubercles and inserts into the tongue's midline, extending from tip to base. Aids in tongue protrusion, retrusion, and depression.

Open Contact and Diastema

• An open contact exists when adjacent teeth don't touch tightly at their contact areas.
• This open space traps food debris.
• A wide open contact is called a diastema.
• Large diastemas might be large enough to prevent food trapping and allow for self-cleaning.

This quiz covers essential concepts related to proximal contact areas and cervical embrasures in dental anatomy. Understand their roles in dental health, food distribution, and the implications of gingival recession. Test your knowledge on how these features interact to maintain oral hygiene.