Resident: Swan
Article Title: Aberrant Root Formation: Review of Root Genesis and Three Case Reports
Author: Saini et al.
Journal: Pediatric Dentistry
Volume (Number): 26:3 (2004)
Major Topic: Root Development/Tooth Eruption
Type of Article: Case Report
Main Purpose: Present 3 cases of unerupted teeth with root dysmorphology and discuss root development and tooth eruption briefly.
Findings:
Root Genesis: Root formation follows the completion of the crown formation, resulting from interactions between dental epithelial and mesenchymal tissues. Root formation can be affected by chemo and radiation therapy, trauma, and hereditary factors (dentin dysplasia and others).
-- After crown formation, inner and outer epithelial cells (enamel organ) join together at the cervical end to form Hertwig’s Epithelial root sheath. IEE directs transformation of peripheral dental papilla cells into odontoblasts. The odontoblasts proliferate and secrete predentin. When the predentin mineralizes, the root sheath cells uncouple from the dentinal surface and move a distance to form the epithelial rests of Malassez. This creates holes in the root sheath. Mesenchymal cells of the dental follicle migrate through these holes to contact the dentinal surface, transforming into cementoblasts. There you have cementum.
Eruption: Eruption is mediated largely by the dental follicle (thin, dense ectomesenchymal tissue surrounding the crown). After root formation begins, the dental follicle lays down an eruption pathway for the tooth to follow. The follicle has specialized cells that can propagate selective bone turnover (resorption occlusally and apposition apically to the developing tooth). As the tooth moves coronally, more root growth occurs, filling the space passively. Every tooth has a specific time during which eruption is capable. If this eruption pathway is compromised during this time, ankylosis may occur.
Case 1: 14 yo f presents with a retained carious/nonrestorable max. right primary second molar and an impacted maxillary right second premolar with completed crown formation. The tooth was located close to the sinus, showed no pulpal obliteration or internal resorption, and no root formation. No history of trauma or significant medical history, and the other 3 premolars had erupted with complete root formation. At one year follow up, no root formation was noted and the pt was advised to have a fixed s.m. placed. She didn’t. 2 years later, root trunk had begun to form, but the tooth hadn’t erupted an farther. At this time the maxillary first molar was tipped and in contact with the first permanent premolar. The authors postulate that this premolar either formed its crown completely with subsequent delay of root genesis, or that possibly this was a supernumerary tooth and the normal series 2nd premolar never formed. (Supernum. Premolars often have severely delayed root formation.) The authors concluded in hindsight that the premolar should have been extracted with subsequent s.m.
Case 2: 30 yo m with similar situation as case 1—impacted maxillary right second premolar. No sig med history or trauma. X-ray showed the crown to be undergoing resorption. The mesially tipped first permanent molar was in contact with the first premolar. The impacted crown was palpable clinically near the vestibule as a bony hard swelling. These teeth usually undergo replacement resorption and become ankylosed (dental and osseous structures become difficult to distinguish) Due to the resorptive stage and age of the patient ext was not recommended.
Interestingly, evidence supports the eruption of rootless teeth. This means that unerupted teeth with no roots can still have an intact follicle/eruption pathway mechanism.
Case 3: 14 yo f complained of a broken filling in a mandibular 1st permanent molar. Examination revealed multiple missing premolars and a retained, impacted primary second molar. Extraction was not recommended as it already showed signs of internal resorption. Some may argue that proximity to the sinus floor might have inhibited root formation, but root formation is not an active growth process in an apical direction. Rootless teeth are seen in dentin dysplasia, but you should see other things with this condition: pulp obliteration, normal eruption, apical radiolucencies, early exfoliation.
Key Points/Summary: We don’t know the exact mechanism behind tooth eruption and root formation, but we do know that the enamel organ and dental follicle play a critical role. If all the steps don’t synchronize, eruption complications can result. In cases like this it’s impossible to determine the exact cause of their failed eruption.
Assessment of Article: Good to review this information. The only “clinical” help I take from the article is the ability to amaze and confuse parents when they ask about their kid’s unerupted teeth.