Mechanical Failure of Dental Implant Nos

1. Research background NobelBiocare manufacture put forward a new abutment called on1. This concept is based on a two-stage abutment in which the on1 abutment is placed directly on the implant during surgery and will not be disconnected since then. At present, there are very a few clinical prospective studies about clinical effect of Nobelparallel CC implant combined with on1 abutment. 2. Research objective This study will evaluate the clinical efficacy of Nobel parallel with on1 abutment compared to traditional healing cap in posterior teeth in a short term(one year) and long trem (five year) follow-up. 3. Study design and methods: Design type: prospective clinical study. Study duration: 5 years Start time: From the date of adoption of ethics. End time: 2026. Follow up examination: Panoramic images will be taken at all times to measure the marginal bone level of the implant. Clinical examination and questionnaire survey will be conducted to obtain the implant conditions and patients' satisfaction. Periodontal indexes such as keratinized gingival width, plaque index, gingival index, bleeding on probe, probing depth of peri-implant tissue will be evaluate.