Minimally invasive techniques for lateral maxillary sinus floor elevation: small lateral window and one-stage surgery-a 2-5-year retrospective study

Abstract

This study aimed to introduce a minimally invasive technique for maxillary sinus floor elevation using the lateral approach (lSFE) and to determine the factors that influence the stability of the grafted area in the sinus cavity. Thirty patients (30 implants) treated with lSFE using minimally invasive techniques from 2015 to 2019 were included in the study. Five aspects of the implant (central, mesial, distal, buccal, and palatal bone heights [BHs]) were measured using cone-beam computed tomography (CBCT) before implant surgery, immediately after surgery (T0), 6 months after surgery (T1), and at the last follow-up visit (T2). Patients' characteristics were collected. A small bone window (height, (4.40 ± 0.74) mm; length, (6.26 ± 1.03) mm) was prepared. No implant failed during the follow-up period (3.67 ± 1.75) years. Three of the 30 implants exhibited perforations. Changes in BH of the five aspects of implants showed strong correlations with each other and BH decreased dramatically before second-stage surgery. Residual bone height (RBH) did not significantly influence BH changes, whereas smoking status and type of bone graft materials were the potentially influential factors. During the approximate three-year observation period, lSFE with a minimally invasive technique demonstrated high implant survival rate and limited bone reduction in grafted area. In conclusion, lSFE using minimally invasive techniques was a viable treatment option. Patients who were nonsmokers and whose sinus cavity was filled with deproteinized bovine bone mineral (DBBM) had significantly limited bone resorption in grafted area.

Fig. 1

Schematic diagram of the retrospective study

Fig. 2

Radiographic assessment. Lower end of the line represents implant platform, upper end of the line represents uppermost level of the grafted sinus floor. T0: immediately after implant surgery; T1: before second-stage surgery; T2: at the last follow-up visit. BH_T0, BH_T1, BH_T2: BH was measured at T0, T1 and T2 respectively. BH was measured at five aspects of each implant: central (BHC), mesial (BHM), and distal (BHD), buccal (BHB), and palatal (BHP) aspects

Fig. 3

Representative images of the small lateral bone window prepared in our study

Fig. 4

Bone window dimensions and bone height of five aspects of implants. a Bone window dimensions. b–f Bone height and analysis at T0, T1 and T2. *** P < 0.01, ** P < 0.05. T0, immediately after bone grafting; T1, before second-stage surgery; T2, last follow-up visit. BH, distance between implant platform and uppermost level of bone graft within sinus cavity. BH was measured at five aspects of each implant: central (BHC), mesial (BHM), and distal (BHD), buccal (BHB), and palatal (BHP) aspects

Fig. 5

The scatter plots with fitted value lines of the relationship between RBH and ΔBHT0–T1. a–e Linear regression line of RBH and ΔBHC_T0–T1, ΔBHM_T0–T1, ΔBHD_T0–T1, ΔBHB_T0–T1, and ΔBHP_T0–T1, respectively. ΔBH_T0–T1 represents the bone height changes from T0–T1. RBH represents residual bone height

Fig. 6

Surgery procedures of lSFE with minimally invasive technique and implant placement. a After raising full-thickness flap, small lateral bone window was prepared. b The Schneiderian membrane was then gently elevated. c, d The dimensions of bone window were measured. e An implant was placed immediately. f The space between sinus floor and sinus membrane were grafted with bone graft materials. g Absorbable collagen membrane was used to cover bone window and implant. h Mucosal flaps were carefully sutured