Purpose: To investigate the effect of lateral sinus floor elevation (LSFE) on sinus membrane

(SM) thickness and sinus health in mucosa thickness less and more than 5 mm. Materials and

Methods: LSFE was performed in a prospective controlled clinical trial on two groups with less

than and more than 5 mm (group A & B) SM thickness and followed for 6 months. Using

preoperative and 6-month postoperative CBCT and clinical evaluation, SM thickness changes

(primary outcome variable), sinus health, augmented bone height, and length (augmentation

adequacy), membrane–related variables, and operation time were measured. Results: Forty

unilateral sinus augmentations (A:20, B:20) with simultaneous installation of 52 fixtures were

performed on 40 subjects (72.5% males, mean age of 48.8±7.6). The mean preoperative and 6-

month SM thicknesses in group A and group B were 1.4±0.9 and 1.3±0.6 mm, and 6.8±1.0 and

3.4±1.7 mm, respectively. The mean postoperative SM thickness significantly decreased

(P<0.001) only in group B. The mean SM thickness changes also revealed a noticeable

difference between the two groups (P<0.001). Augmentation adequacy and membrane

perforation rate were similar in both groups. Clinical and radiographic rhinosinusitis was not

detected in any of the patients. Bleeding during separation and resistance to elevation in group B

were significantly higher than in group A (P=0.003, P=0.001). Surgical time in group B (12.08 ±

8.26 minutes) was longer than in group A (8.64 ± 3.70 minutes), without reaching a significant

level (P=0.097). Conclusions: LSFE in thickened mucosa (≤10 mm) and thinner mucosa (≤5

mm) does not cause abnormal changes in the sinus membrane and sinus health. LSFE in

thickened mucosa results in adequate sinus augmentation. Thickened SM also shows a

significant thickness reduction. The thickened membrane does not appear to be a

contraindication to SFE.