Dental Anatomy: Shapes and Contact Areas

Shapes of Teeth

• Facial and Lingual surfaces are trapezoidal
• Proximal surfaces are also trapezoidal
• Anterior Teeth are Trapezoidal
• Max. Posterior teeth are trapezoidal
• Mand. Posterior teeth are trapezoidal

Proximal Contact Areas

• Contact areas exist where teeth touch in the arch
• They must be small enough to prevent food and bacteria build-up
• They must be large enough to prevent food impaction
• They provide support and anchorage for teeth

Contact Areas: 5 General Rules

• Contact areas become more cervically located from anterior to posterior
• The distal contact area is more cervically located than the mesial
• This is because the crown length decreases from anterior to posterior
• The size of the contact area increases from anterior to posterior
• This is because posterior teeth are wider than anterior teeth
• Anterior contact areas are centered in the faciolingual direction
• Posterior contact areas are located just facial to the center

Why Understand The General Rules?

• They provide the foundation for good form and function
• They are a benchmark to use when examining variations
• They allow you to identify discrepancies and dysfunction in the dentition
• They correlate contacts to the health of the periodontium
• They help understand the importance of proper contacts in restorative dentistry
• They show the challenges associated with abnormal contacts

Interproximal Spaces

• This is the space between the proximal surfaces of two teeth
• In a healthy mouth, the gingiva fills the interproximal space

Interdental Papilla

• This is the gingiva located in the interproximal space
• It should be wider cervically and narrower coronally
• This shape depends on proper contact and alignment

Embrasures

• The spaces formed by the interproximal contours of adjacent teeth
• They are named for their position in relation to the contact area
• There are 4 embrasures for each tooth:
  • Facial
  • Lingual
  • Occlusal/Incisal
  • Cervical/Gingival

Embrasures: Facial/Lingual View

• Occlusal/Incisal Embrasure: Located coronally to the contact area
• Cervical/Gingival Embrasure: Located cervically to the contact area

Embrasures: Occlusal/Incisal View

• Facial Embrasure: Located facially to the contact area
• Lingual/Palatal Embrasure: Located lingually to the contact area

Embrasures: 5 General Rules

• Occlusal/Incisal embrasures increase in size from anterior to posterior
• Cervical/Gingival embrasures decrease in size from anterior to posterior
• Facial and lingual embrasures are equal in size in anterior teeth
• Lingual embrasures are larger than facial on posterior teeth
• Embrasures are symmetrical

Cervical Line Curvature

• The cervical line is also known as the Cemento-Enamel Junction (CEJ)

Cervical Line Curvatures: 5 General Rules

• The direction of curvature changes:
  • Facial and lingual are curved apically
  • Proximal surfaces are curved incisally or occlusally
• The depth of curvature on the proximal surface depends on the height of the contact area and the diameter of the crown
• The depth of curvature on the proximal surface is greater on anterior teeth than posterior teeth
• Cervical lines on the proximal surface are more pronounced on the mesial than the distal
• Variations in cervical line curvature are linked to the degree of proximal contacts, axial inclination, and tooth shape

This quiz covers the shapes of teeth, specifically focusing on the trapezoidal aspects of different teeth types and their contact areas. It includes the general rules regarding how these contact areas are positioned and sized within the dental arch. Perfect for dental students looking to test their knowledge on dental anatomy.