About 40 people will participate in the study, which will be conducted at Southern Medical University Southern Hospital. All subjects need to sign an informed consent form before screening, and successful subjects can enter the study. Experimental and control subjects were treated according to the protocol. Treatment was held until the participant entered a follow-up period, or until any of the withdrawal criteria were met. According to conventional clinical practice, the study needs to evaluate the patient's subjective perception and soft and hard tissue changes at 3 months, 6 months, and 1 year after successful implant placement. The specific process is divided into: 1. Screening period: All subjects need to complete the relevant examinations of the screening period before enrollment, and screen according to the admission criteria. (1) Sign informed consent; (2) Record demographic data: date of birth, gender, initials; (3) Medical history and physical examination: collection includes understanding of any current or past diseases, medications, drug allergy history, surgical history, radiotherapy and chemotherapy history, ethnic background, smoking history, whether alcoholism, oral hygiene habits and oral examination, etc.; (4) Among them, oral examination includes the whole oral health before and after surgery and oral and maxillofacial CBCT imaging examination; 2. Treatment period: the control group underwent transalveolar crest parietal maxillary sinus floor lift immediately after implants; The experimental group underwent implant implantation after 6 months of transalveolar crest parietal maxillary sinus floor lift. 3. Follow-up period: The study needs to evaluate the subjective feelings and soft and hard tissue changes of patients at 3 months, 6 months and 1 year after implant placement.

Inclusion Criteria:

1. Age≥ 18 years old
2. If the posterior maxillary tooth is missing for ≥ 3 months, the patient requires implant restoration and the preoperative examination meets the indications for intramaxillary sinus lift
3. Can be scanned with radiology equipment before and after surgery
4. RBH ≤ 5mm, alveolar ridge width ≥5mm, each implant site is measured on CBCT
5. During implant healing, there is no removable restoration at the implant site
6. No history of acute or chronic sinusitis disease, no history of maxillary sinus disease, and no history of previous maxillary sinus surgery
7. Be willing to sign informed consent and authorization form, and be able to return to the clinic on time

Exclusion Criteria:

1. Heavy smokers (10 cigarettes smoked ≥ day)
2. Uncontrolled diabetes (glycated hemoglobin >7%), metabolic bone disease, autoimmune disease or other systemic diseases, the body can hardly withstand implant surgery
3. Mentally unable, pregnant or pregnant women
4. Any history of contraindications or significant impact on dental implant placement, such as bisphosphonate drug use, chemotherapy or immunosuppressants, head and neck radiotherapy, autoimmune disease, and hypertension
5. Untreated periodontal disease, endodontics, or other oral diseases
6. Bruxism patients
7. Previous implant implant failure at the surgical site
8. Anatomical changes in the maxillary sinus, such as maxillary sinus septum or mucosal swelling (defined as the mean thickness of the Schneider membrane at the base of the maxillary sinus > 2 mm)