For information about abnormal tooth morphology, refer to the following:

• Definition
• Common Issues
• Solutions

Definition

Although ‘normal’ tooth morphology, i.e. the shape of the crown and root of the tooth, varies extensively from person to person, or between various ethnic groups, there are deviations from the ‘normal’ that all dentists must be able to recognize. Extremely large or small crowns, “peg” or “conical” shaped crowns, adjacent crowns fuzed together (concrescence ), dental restorations that do not conform to the ‘normal’, etc. Abnormal tooth morphology can sometimes cause issues when treating patients with clear aligners.

Common issues

Common abnormal tooth morphologies that cause issues are the following:

• Small, peg-shaped teeth and small or short clinical crowns
  • The small surface area of these teeth reduces the aligner’s ability to grasp or adapt to the tooth. This reduced ‘fit’ affects the effectiveness of the aligner to move the tooth.

• Large, bulbous teeth with excessive undercuts
  • Excessive undercuts on bulbous teeth can ‘over-retain an aligner making it difficult to remove, difficult to fabricate requiring excessive trimming of the margin of the aligner, and difficult to seat.
• Shovel-shaped incisors
  • Commonly cause black triangles

Solutions

Following are some troubleshooting options for abnormal tooth morphology:

• Anticipate future restorations to restore a more ‘normal’ morphology
• Short clinical crowns:
  • Consider pre-aligner acrylic temporary crowns
  • Request engagers on the first or second premolars for better aligner retention when submitting the case. Direct placing the engagers during Step 1
  • Use dimples to create retention points
  • Consider not moving those teeth with treatment