Tooth agenesis is one of the most common developmental anomalies encountered in orthodontic practice, yet its true impact on dentofacial structures remains a subject of debate. The 1997 European Journal of Orthodontics study by Sema Yüksel and Tuba Üçem offers valuable insight by analyzing how the location of missing teeth influences skeletal, dental, and soft tissue relationships.

---

Tooth agenesis, particularly involving the maxillary lateral incisors and mandibular second premolars, creates a discrepancy between tooth size and arch length. Clinically, this imbalance raises important questions:

• Does agenesis significantly alter skeletal growth?
• Should treatment planning be fundamentally modified?
• Are these patients skeletally different or primarily dentoalveolar adaptations?

This study attempts to answer these questions using cephalometric analysis.

Study Design at a Glance

The researchers evaluated 74 patients with tooth agenesis and compared them to a control group of 13 individuals without agenesis.

Patients were categorized into:

• Anterior agenesis group (e.g., missing incisors)
• Posterior agenesis group (e.g., missing premolars)
• Combined anterior + posterior agenesis

Further subdivision included unilateral vs bilateral absence to assess symmetry-related effects.

Key Findings: What Actually Changes?

1. Skeletal Pattern: Surprisingly Stable

One of the most clinically reassuring findings:

• Most patients exhibited a Class I skeletal relationship (normal ANB)
• No major skeletal discrepancies across groups
• Even when differences existed, values remained within normal limits

However, subtle trends were noted:

• Bilateral posterior agenesis showed slightly protrusive maxilla and mandible
• Bilateral anterior agenesis showed a tendency toward forward mandibular rotation (reduced NSGn)

These changes are statistically significant but not clinically dramatic.

2. Dental Compensation: The Real Story

The most consistent adaptation was dentoalveolar:

• Upper incisors were more proclined and protrusive in agenesis groups
• Greater protrusion seen when:
  • Missing posterior teeth
  • Multiple teeth were absent

Why?
Likely due to tongue adaptation—more space allows forward positioning of incisors.

Interestingly:

3. Soft Tissue Profile: Minimal Impact

Despite dental changes:

• No significant differences in lip position
• Soft tissue profile remained relatively stable

This highlights an important clinical point:
👉 Dentofacial compensation often masks underlying dental irregularities.

4. Effect of Location Matters

The study strongly emphasizes that location of missing teeth influences patterns:

• Anterior agenesis
  • More influence on incisor inclination and vertical pattern
• Posterior agenesis
  • More influence on sagittal positioning of jaws and molars
• Bilateral cases
  • Show greater skeletal and dental deviations than unilateral cases

Clinical Implications for Orthodontic Treatment

From a treatment planning perspective, this study reinforces several key principles:

• Do not assume major skeletal discrepancies in hypodontia patients
• Focus more on:
  • Space management
  • Incisor positioning
  • Occlusal relationships
• Expect compensatory incisor proclination, especially in posterior agenesis
• Always evaluate:
  • Unilateral vs bilateral absence
  • Number of missing teeth
  • Functional adaptations (tongue posture)

Example:
A patient with bilateral missing mandibular second premolars may present with:

• Forward-positioned incisors
• Mild skeletal protrusion
  But still fall within normal cephalometric limits—guiding a conservative, dentoalveolar-focused treatment approach.