Study design and patient selection
This study was approved by the ethical review board at Nanchang University, China. This study was conducted in the Department of Implantology, Fourth Affiliated Hospital of Nanchang University (Ref No:SFYYXLL-PJ-2021-KY008). The following inclusion criteria were applied to recruit patients for this study [n = 37 (18 males and 19 females)].
- Good state of general health, and no chronic systemic diseases.
- Patients required dental implant treatment in the posterior maxilla.
- Preoperative cone beam computed tomography (CBCT) demonstrated the distance from the antagonist teeth to the implant site bone plane was <7mm, and the height from the antagonist teeth to the mandibular neural tube was >13mm.
- Any patient with a history of temporomandibular joint disease, severe bruxism, oral ulcers, or precancerous lesions was excluded.
In addition, intraoral examination and nonsurgical periodontal treatment were carried out to assure healthy oral condition. The aim of the study was explained to all patients and informed consent was obtained from every patient.
For each patient, preoperative CBCT was performed to ensure that the implant placement space was ≥6mm and the distance from the implant neck to the antagonist teeth was >7mm. The depth of implant placement was recorded. Then, 30 min before the surgical procedure, each patient was premedicated orally with an Ibuprofen sustained-release capsule (100mg) and dexamethasone acetate tablet (2 mg). Chlorhexidine (0.12%) and iodophor were used for oral and skin disinfection, respectively.
The surgical procedures were all performed under the supervision of an experienced oral surgeon and used local anesthesia (4% articaine hydrochloride and 1:100,000 epinephrine; Pierrel, Milan, Italy). The implants were placed immediately or delayed.
Delayed implant placement: A full-thickness mucoperiosteal flap was raised at the alveolar ridge crest. The depth was determined by the preoperative CBCT, and a cavity was drilled using the drilling sequence recommended by the manufacturer. The locking taper implants (Bicon LLC, Boston, MA, USA) were placed. The polyethylene healing plug was trimmed to the level of the ridge top, the harvested bone was placed, and the surgical site was sutured.
Immediate implant placement: According to the preoperative design, the implant hole was prepared following minimally invasive tooth extraction. The locking tapered implants were placed (Bicon LLC, Boston, MA, USA), and the healing plug was trimmed to the level of the alveolar ridge on the buccal side.
In particular, the depth of the implant should be equal to or greater than the planned depth. Patients were prescribed amoxicillin (1500mg tds for 5 days) and 0.12% chlorhexidine mouth rinsing three times a day for 7 days. Patients were recalled after 3 days to evaluate the wound healing. The second-stage surgery was performed after 3 months in the delayed implant placement group, and after 4 months for the immediate implant placement group. Following local infiltration, a crestal incision was made to remove the healing plug. The sulcus former was rotated on the guide pin to remove bone tissues that might affect the prosthesis. Titanium temporary abutment was installed to form the cuff.
The implant level transfer impression was made 2–4 weeks following the abutment installation. The separated single crown and abutment prosthesis was designed as subgingival, semianatomical/nonanatomical cusp, where the height of the abutment body was ≥5mm. The fabricated prosthesis was tested in the mouth to ensure a good position of the abutment–implant and crown–abutment. The crown and abutment were combined using the extraoral cementation technique. The excess adhesive was removed. The patients were recalled biannually for a follow-up examination and nonsurgical periodontal treatment. The clinical and imaging evaluation was performed 1 year postoperatively. Representative images of various clinical procedures are shown in Fig. 1.
All CBCT images were taken at the intercuspal position and used Carestream CS 9300 Select (Carestream Health, Inc, France).
Follow-up and evaluation
Following 1 year of functional loading, evaluation of the prosthesis referred to the definition of implant success, survival, and failure published by Misch . Various clinical indicators, such as modified plaque index (mPI), modified sulcus bleeding index (mSBI), and probing depth (PD) were reviewed and evaluated. All data were measured by the same dentist using a periodontal probe (15 UNC/CP-11.5B Screening Color-Coded Probe, Hu-Friedy, Chicago, IL, USA). In addition, the mechanical complications, such as if the implant or abutment fractured or cracked, the abutment loosened, or the crown cracked were recorded.
The radiographic evaluation was performed using Digimizer Image Analysis Software (V4.5.1, MedCalc Software bvba, Ostend, Belgium). Images were calibrated according to the image length and true length of the implant. The distance from the first thread of the implant to the crest of the alveolar ridge was measured to determine the marginal bone level. The mesial and distal bone heights at the prosthetic insertion were recorded at the time of functional loading as ML(0), DL(0), and the 1-year follow-up as ML(T), DL(T). Average bone resorption was recorded at the mesial marginal bone loss (MBL) = ML(T)–ML(0), and the distal MBL = DL(T)–DL(0);
Average MBL = (Mesial MBL + Distant MBL) 2
The imaging measurement was performed by an assistant blind to the study design. All images were measured once every 2 days, and the average value was taken three times. The satisfaction survey was conducted according to the evaluation method of Pjetursson . The visual analog scale with 0 points (very dissatisfied) and 100 points (very satisfied) was used for statistical analysis.
The SPSS v24 was used to analyze the data. The Kolmogorov–Smirnov test was used to test the normal distribution of the data. Descriptive statistics (mean value, standard deviation, and range) are presented. The predictive variables included patient age, gender, implantation site, bone type, restoration type, smoker or not, whether to implant immediately, implant depth, implant diameter, and implant length. Outcome variables were implant failure and marginal bone resorption. The X2 test was used to analyze the relationship between independent variables and implant failure. Kruskal–Wallis test was used to determine the relationship between implant depth and mPI, mSBI, and PD. A generalized estimation equation was used to analyze the relationship between predictive variables and marginal bone resorption. A significance level of 0.05 was used for all statistical analysis.