تکامل تاخیری پره مولر دوم فک پایین با اختلاف قابل توجه از زمان تکامل طبیعی آن در یک دختر 12 ساله

The dentists evaluate dental development according to radiographic records and developmental tables. if a tooth is not visible in radiograph, while expected to be traced in ,mostly is diagnosed as congenital tooth missing. although more than 99% of teeth develop in expected range of time presented in developmental tables ,sometimes this process takes long more than normal and if the dentist  hesitate in treating the problem by closing the space a catastrophic situation might happen because the tooth may develop so later than normal and if the dentist try to  close the space as treatment plan, impacted tooth may resorb the adjacent roots. This report has presented a 12 years old girl with several years delay in eruption of lower left second mandibular premolar. Key words: Dental  development,mandible ,second premolar