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