The mandibular buccal frenum is defined as a fold of mucous membrane at the posterior labial vestibule and attaches the lips and the cheeks to the alveolar mucosa, gingiva, and underlying periosteum. The buccal frenum becomes a problem when its attachment is too close to the marginal gingiva. It may then pull on healthy gingiva, encourage plaque formation and interfere with tooth brushing. Especially, heavy buccal frenum mucogingivally results in insufficent attached gingiva, inadequate vestibular depth and high frenum attachment and also difficulty in eruption of mandibular premolar. Frenotomy, frenectomy and mucogingival surgery are used in treating heavy buccal frenum. Frenotomy with autogenous free gingival graft has been used popularly because of its stable result. But, it is difficult in younger children because of inadequate donor site, difficulty in making recipient site and behavior management. Frenotomy with apically positioned flap is considered as more efficient way for a very young child with heavy buccal frenum. Additionally, modified deep sedation with $N_2O-O_2$ can be used as an adjunct for the effective treatment outcome. Decrease in muscle pull, adequate width of attached gingiva and increased vestibular depth can be expected from this treatment approach.