Analysis of the hard and soft tissue following immediate and early implant placement in the anterior area of maxilla

Objective: To compare the difference of soft and hard tissue changes between immediate implant and early implant placement in maxillary anterior region, so as to provide the basis for the selection of implant timing and surgical method for patients in clinical maxillary anterior dental esthetic zone. Methods: From January 2016 to January 2019, 89 patients [48 males and 41 females, aged (38.0±13.3) years] with dentition defect and single tooth implant restoration in the Department of Oral Implantology, Dalian Stomatological Hospital were retrospectively collected. The patients were divided into three groups according to different implant timing and operation methods: immediate implant flapless group (26 cases), immediate implant flap group (30 cases) and early implant group (33 cases, early implant 4-8 weeks after tooth extraction). The operation time, intraoperative and postoperative complications were compared among the three groups. Cone-beam CT was taken before operation, immediately after operation and 6 months after operation. The bone plate thickness immediately after implantation, bone plate thickness at 6 months after operation and absorption amount of bone plate thickness at labial side (immediately after operation minus 6 months after operation) were measured, and the absorption rate of labial bone plate was calculated. Three dimensional quantitative analysis was performed on the lip bone increment, residual bone volume (6 months after operation minus preoperative), and bone volume absorption rate of the three groups immediately after operation by using GuideMia, PlastyCAD and Geomagic engineering software. The pink and white esthetic indexes of the three groups were evaluated at 9 months and 15 months after implant placement. The implant stability quotient (ISQ) value was measured at 6 months after implantation, and the patients' satisfaction with the whole treatment process was investigated at 6 months after implantation. Results: The operation time of immediate implant flapless group was the shortest, the median (lower quartile, upper quartile) was 36.5 (33.3, 38.5) min. At 9 months after operation, PES was relatively high [8.5 (8.0, 9.0)], and the final patient satisfaction was 8.0 (7.3, 8.8), and the difference was statistically significant compared with the other two groups (P 0.05). At 6 months after operation, the thickness of labial bone plate in early group was 3.09 (3.00, 3.25) mm, which was greater than that in the immediate non flap group [1.90 (1.72, 2.33) mm] and that in the immediate implant flap group [2.39 (2.05, 3.06) mm], and the difference was statistically significant (P 0.05). Conclusions: Immediate implant can reduce the treatment time with equal esthetic outcome of implant supported restoration of anterior teeth, and patients prefer it more. The bone volume of lip side was not significantly increased after immediate flap operation, and the bone absorption was less after immediate flap operation. Early implant placement can better maintain the three-dimensional bone mass, and the three groups can obtain good clinical results in the short term, but the long-term effect needs further follow-up study.