Tooth extraction is the most common surgical procedure and is associated with changes to the supporting structures. The aim of this review was to assess the magnitude of dimensional change of both the hard and soft tissues of the alveolar ridges after tooth extraction.

The Medline and Cochrane Central databases were searched and a selection of dental journals hand searched for English language randomised controlled trials and prospective cohort studies that monitored changes to the hard and soft tissues of the alveolar ridge. The outcome had  to be assessed in the form of changes in the clinical or radiographic alveolar bone dimensions, as well as dimensional soft tissue changes. Only studies reporting on undisturbed post-extraction dimensional changes relative to a fixed reference point over a clearly stated time period were included.  Identification and data extraction was performed independently by two reviewers.

20 studies met the inclusion criteria and they found that

•  In human hard tissue,
• horizontal dimensional reduction (3.79 ± 0.23 mm) was more than vertical reduction (1.24 ± 0.11 mm on
• buccal, 0.84 ± 0.62 mm on mesial and 0.80 ± 0.71 mm on distal sites) at 6 months.
• Percentage vertical dimensional change was 11–22% at 6 months.
• Percentage horizontal dimensional change was 32% at 3 months, and 29–63% at 6–7 months.
• Soft tissue changes demonstrated 0.4–0.5 mm gain of thickness at 6 months on the buccal and lingual aspects.
• Horizontal dimensional changes of hard and soft tissue (loss of 0.1–6.1 mm) was more substantial than vertical change (loss 0.9 mm to gain 0.4 mm) during observation periods of up to 12 months, when study casts were utilized as a means of documenting the changes.

The authors  concluded

 Human re-entry studies showed horizontal bone loss of 29–63% and vertical bone loss of 11–22% after 6 months following tooth extraction. These studies demonstrated rapid reductions in the first 3–6 months that was followed by gradual reductions in dimensions thereafter.

Tan WL, Wong TL, Wong MC, Lang NP. A systematic review of post-extractional alveolar hard and soft tissue dimensional changes in humans. Clin Oral Implants Res. 2012 Feb;23 Suppl 5:1-21. doi: 10.1111/j.1600-0501.2011.02375.x. PubMed PMID: 22211303