A comprehensive review of the literature and data analysis on hypo-hyperdontia

The objectives of this study were i) to conduct a comprehensive review of the literature on hypo-hyperdontia, and ii) to categorize the reported cases based on occurrence. An extensive search of the literature covering the period from January 1966 to January 2014 was conducted using the Embase, Google Scholar, Medline, and PubMed databases. The key words used in the search strategy were "concomitant", "agenesis", "hypodontia", "hyperdontia", "supernumerary teeth", "syndromes", and "hypohyperdontia" in various combinations. The retrieved data were analyzed based on gender, occurrence, and occurrence of both hypodontia and hyperdontia. Descriptive statistics were carried out using the chi-squared test. For hypo-hyperdontia overall, seven case studies and 40 cases involving 103 patients were reported. Our comprehensive review revealed that hypo-hyperdontia occurs most commonly in males (P < 0.05), and the bimaxillary type (65%) was reported most commonly in comparison with the maxillary, pre-maxillary and mandibular types (P < 0.001). Twenty syndromic cases and two case studies on familial occurrence of hypohyperdontia were reported. Almost 57% of cases affected the anterior region, whereas 43% of cases affected the anteroposterior region. The anterior region was most commonly affected by hyperdontia whereas the posterior region was most commonly affected by hypodontia. Hypo-hyperdontia is commonly seen in males, and the most common type is bimaxillary occurrence. G/BBB syndrome is commonly associated with hypo-hyperdontia, being relatively frequent in the anterior region, where mesiodens is frequently seen, and second premolars are the most commonly missing teeth.