To track the initiating and developing process of one case diagnosed as chronic periodontitis accompanied with malformed lingual groove in maxillary lateral incisor and report the long-term prognosis to the periodontal conservative and supportive therapy. The patient was diagnosed with mild chronic periodontitis 6 years ago and accepted routine periodontal scaling and root planning（SRP） plus supportive periodontal therapy（SPT） one time. Two years later the periodontal condition deteriorated by deep pockets in molars and severe bone destruction around the maxillary lateral incisor with malformed lingual groove. After SRP in sites which pocket depth more than 4mm plus root canal therapy and lingual groove plasty of maxillary right lateral incisor, the SPT regularly proceeded at 3rd, 6th and 12th month. At present the whole periodontal tissue was healthy, the bone lesion around maxillary lateral incisor recoveredwell, the tooth had no mobile, the cosmetic effect and tooth function was in good state, and the patient was verysatisfied.
