Journal of the Korean Academy of Pediatric Dentistry 2010;37(2):226-232.
Published online May 31, 2010.
Doo Young Lee1, Je Seon Song2, Jae-Ho Lee Lee2, Byung-Jai Choi2, Seong Oh Kim2
1Department of Pediatric Dentistry, College of Dentistry, Yonsei University
2Department of Pediatric Dentistry and Oral Science Research Center, College of Dentistry, Yonsei University 
Correspondence:  Seong Oh Kim,  Tel: 02-2228-3171, Email:
Received: 5 January 2010   • Accepted: 22 March 2010
ncidence of tooth impaction varies from 5.6 to 18.8% of the population. Failure of eruption of the first and second permanent molars is rare; the prevalence in the normal population is 0.01% in case of the first permanent molar, and 0.06% in case of the second permanent molar. Permanent molars are particularly important for providing sufficient occlusal support and co-ordinating facial growth. Failure of eruption of permanent molars may result in various complications such as decrease in vertical dimension, posterior open bite, extrusion of antagonistic teeth, resorption and inclination of adjacent teeth, formation of cyst and so on. Treatment options of impacted teeth are periodic observation, surgical exposure, surgical exposure with subluxation, orthodontic relocation, and surgical extraction before prosthetic treatment. Early diagnosis and treatment are important, because delayed treatment induces various problems such as decreased spontaneous eruptive force, decreased successful percentage, increased treatment period, increased various complications. Prevalence of the failure of mandibular first molars is rare but eruptive guidance before extraction of impacted teeth is necessary due to importance of permanent molars. We reported two cases of surgical exposure of impacted mandibular first molar. In these cases, we could observe different result of the impacted mandibular first molar after surgical exposure.
Key Words: Mandibular first molar, Failure of eruption, Surgical exposure, Spontaneous eruption

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