Prevalence of hypodontia and associated factors: a systematic review and meta-analysis

Objectives: To determine the prevalence and factors associated with hypotonia. Design: Systematic review and meta-analysis. Data source: A search strategy was developed along with inclusion criteria and run in MEDLINE and EMBASE (published from 2002 to August 2012) databases to reveal all studies on the prevalence of hypodontia or associated factors. A hand search of reference lists and a Google search aimed to improve the sensitivity of the literature search. Selection criteria: All studies on the prevalence of hypodontia or associated factors published from 2002 onwards were included. Abstracts of non-English papers were also analyzed. Data selection and extraction: All potential articles were checked against the inclusion criteria independently, and in duplicate by two investigators. A checklist was used to assess the quality of selected studies. Main outcome: Prevalence of hypodontia, excluding third molars. Results: The overall prevalence of hypodontia was found to be 6.4% (95% CI: 5.7, 7.2). There was a statistically significant difference in the prevalence of hypodontia by continent (Q=34.18, P<0.001). Prevalence of hypodontia was the highest in Africa: 13.4% (95% CI: 9.7, 18.0), followed by Europe (7% CI: 6.0-8.0%), Asia (6.3% CI: 4.4, 9.1) and Australia (6.3% CI: 5.3, 7.4) with a lower prevalence in North America (5.0% CI: 4.1-5.9) and Latin America and Caribbean (4.4% CI: 3.2-6.1). Females were found to have a higher prevalence than males (combined OR 1.22; 95% CI: 1.14, 1.30). The most commonly affected teeth were mandibular second premolars followed by maxillary lateral incisors and maxillary second premolars. The prevalence of mild, moderate and severe hypodontia was found to be 81.6, 14.3 and 3.1% respectively. Conclusions: There was a high variation in the prevalence of hypodontia between the studies. African populations were found to have a higher risk for tooth agenesis and there was an increased risk for females to have hypodontia than males.