Abnormal immobility, union or fusion May occur between two bones at their articulation (i e , TMJ) or between teeth and alveolar bone In such a case, the periodontal ligament is obliterated by a 'bony bridge' and the tooth root is fused to the alveolar bone Dental ankylosis prevents both eruption and orthodontic movement In a growing child, an ankylosed tooth appears to 'submerge' as adjacent unaffected teeth continue their normal pattern of eruption