The aim of this study is to determine the clinical success of short implants (6mm) alone and standard implants (10mm) combined with sinus floor elevation in atrophic maxilla.

Implant treatment in posterior maxilla is commonly faced with great challenges due to the limited residual bone height and poor bone quality. Efforts have been made to allow successful implant treatment in atrophic posterior maxillae.Osteotome sinus floor elevation (OSFE) has been proven to be a predictable surgical procedure to vertically increase the bone volume in atrophic maxilla.On the other hand, short implants (intra-bony length of 8mm or less) are being increasingly used in extremely resorbed maxilla to avoid additional surgical trauma and expense.However, still limited randomized controlled trials have compared the clinical success of short implants and standard implants combined with OSFE.

This study is designed as a prospective randomized controlled clinical study. We plan to enroll 180 patients in need of dental implant treatment in posterior maxilla. All patients will sign the informed consent form before treatment. The study is approval by the Ethics Committee of Shanghai Ninth People Hospital, China. The clinical component of the study will be initiated in May 2015 at the Department of Oral and Maxillofacial Implantology, Shanghai Ninth People Hospital, Shanghai Jiao-Tong University, China.

A block randomization sequence will be used to assign eligible patients to three groups: Group 1: short implants (6mm) alone; Group 2: standard implants (10mm) combined with OSFE. The assignment will be concealed from the clinical operators until the beginning of implant surgery. The outcome examiners and patients will be kept blinded to the assignment.

The required sample size is calculated based on the primary outcome parameter, implant survival rate. A recent study (Rossi et al. 2016) compared survival rate of short implants and standard implants (Survival rate: 86.7% VS 96.7%). If α=0.05, and 1-β =0.8, a sample size of n=116 per group is required. Assuming a drop-out rate of 10%, 125 patients per group will be required. The total required sample size will thus be n=250.

Inclusion Criteria:

The following inclusion criteria are applied:

• age≧18 years, partial edentulism in posterior maxilla for at least three months from tooth loss,
• residual bone height range from 6-8mm,
• sufficient bone width in edentulous region.

Exclusion Criteria:

The patients will be excluded on the basis of:

• heavy smoker (>10 cigarettes per days),
• uncontrolled diabetes mellitus or other systemic diseases,
• uncontrolled periodontal infection,
• insufficient bone quality to achieve implant stability and
• previous implant installation or bone grafting at surgical site.