Orthodontic treatment is often focused on tooth movement, but what happens to the supporting alveolar bone? Alveolar bone dehiscences (ABDs) and fenestrations (ABFs) are critical yet often overlooked risks in orthodontics. With the increasing use of clear aligner therapy (CAT) and expansion mechanics, understanding these defects is crucial for treatment planning and long-term periodontal health.
What Are ABDs and ABFs?
• Alveolar Bone Dehiscences (ABDs): A vertical bone defect where the root surface is exposed beyond the normal alveolar crest (Wennström et al., 1987).
• Alveolar Bone Fenestrations (ABFs): A defect where the root is exposed through the cortical plate, but the alveolar crest remains intact (Evangelista et al., 2015).
Both conditions are associated with orthodontic mechanics that move teeth beyond their alveolar boundaries, leading to bone loss, recession, and compromised periodontal stability.
How Orthodontics Contributes to ABDs and ABFs
Several factors increase the risk of these defects:
✅ Thin Buccal Bone: Naturally thin cortical plates, especially in the lower incisors and maxillary canines, are predisposed to ABDs (Wilcko et al., 2009).
✅ Excessive Labial/Buccal Tooth Movement: Proclination of incisors in non-extraction cases frequently leads to dehiscences (Wennström et al., 1987).
✅ Uncontrolled Expansion: Rapid palatal expansion and uncontrolled transverse movements can cause fenestrations, particularly in posterior teeth (Vanarsdall, 1994).
✅ High Orthodontic Forces: Heavy forces increase bone resorption and disrupt remodelling (Reitan, 1964).
Recent Evidence: Do ABDs Remodel Over Time?
A 2025 study by Kumar et al. investigated ABDs and ABFs in adults treated with non-extraction CAT and Class II elastics. Their key findings:
🔹 ABDs increased significantly post-treatment (OR: 2.69) and remained elevated even two years into retention (OR: 2.46).
🔹 ABFs were not significantly affected by CAT.
🔹 No evidence of alveolar bone remodelling or defect resolution during retention, indicating that once ABDs form, they may persist long-term.
Clinical Implications: How to Minimise Risk
💡 Possible use of CBCT as Pre-Treatment Assessment tools – Traditional 2D radiographs often miss buccal and lingual bone defects.
💡 Control Proclination and Expansion – Limit labial movement of incisors, especially in non-extraction cases.
💡 Apply Light, Continuous Forces – High-force mechanics increase the risk of irreversible bone loss.
💡 Consider Surgical Adjuncts – PAOO (Wilckodontics) and guided bone regeneration can mitigate alveolar bone limitations (Wilcko et al., 2009).
Takeaway
ABDs and ABFs are not just transient side effects of orthodontic movement—they may persist long after treatment ends. Careful treatment planning, CBCT-based risk assessment, and conservative mechanics are essential to prevent irreversible periodontal damage.
Opmerkingen