Twenty-nine CBCT images (11 females and 18 males) were included in this study. All the implants placed in these included cases survived, representing a 100% implant survival rate. With regards to measurements of mucosal thickening, the intra-examiner reproducibility revealed an exact intra-examiner correlation of 99%, with a p value of 0.40 for a t test for independent samples, indicating a high reproducibility and intra-examiner agreement for the radiographic measurements. The study data for the 29 analyzed CBCT scans are presented in Table 1. The mean follow-up time after implant placement was 3.3 ± 2.2 (range 1 to 7) years.

Percentage and amount of mucosal thickening

Among the subjects, 93.1% of patients had maxillary sinus mucosal/tissue thickening. Specifically, 6.9% of cases exhibited no thickening (≤1 mm), 6.9% had minimal thickening (>1 mm but ≤2 mm), 20.7% of cases had moderate thickening (>2 mm but ≤5 mm), and 65.5% had severe thickening (>5 mm). However, only 45.9% of designated implant sites presented sinus mucosal thickening. The average amount of mucosal thickening in the anterior section (point E1 to floor of the sinus) was 4.63 ± 4.95 mm, in the middle section (point C1 to floor of the sinus) it was 4.87 ± 5.10 mm, and in the posterior section (point D1 to floor of the sinus) it was 3.46 ± 3.17 mm. The average mucosal thickening (point F to floor of the sinus) was 8.34 ± 5.70 mm, and it ranged from 1.55 to 22.81 mm.

Factors associated with mucosal thickening

A significantly higher amount of mucosal thickening was associated with patients with a history of periodontal diseases (p = 0.004). Other factors, such as gender (p = 0.054), and systemic factors, including respiratory diseases (p = 0.313), cardiovascular diseases (p = 0.438), diabetes (p = 0.209), or smoking (p = 0.541), were not significantly associated with mucosal thickening.

In terms of dental history, the presence of tooth restorations (p = 0.056), endodontic treatment (p = 0.379), orthodontic treatment (p = 0.125), edentulism (p = 0.718), and underlying alveolar ridge height (point G to H, p = 0.889) were not associated with mucosal thickening. The results of the statistical analyses after inter-variable adjustment are presented in Table 2.