Mean CWb and GT values were comparable in both groups and amounted to 4.53 ± 1.54 mm (median 4.50; 95% CI 3.68, 5.38) and 5.66 ± 1.75 mm (median 5.0; 95% CI 4.69, 6.64) in the TR group and 5.26 ± 1.25 mm (median 5.00; 95% CI 4.57, 5.95) and 4.96 ± 1.75 mm (median 5.0; 95% CI 4.24, 5.68) in the AB group, respectively. Between-group differences did not reach statistical significance.

Mean SA26 values were 12.42 ± 10.11 mm² (median 11.36; 95% CI 6.82, 18.02) in the AB group and amounted to 22.07 ± 12.98 mm² (median 18.83; 95% CI 14.88, 29.26) at the TR-treated sites. The resulting differences between both groups were statistically significant (p = 0.031).

Mean BI26 values amounted to 79.67 ± 15.66% (median 78.85; 95% CI 70.99, 88.34) in the AB group and tended to be lower at the TR-treated sites, revealing a mean value of 69.26 ± 26.01% (median 72.44; 95% CI 53.85, 82.66) (Fig. 3). These differences, however, failed to reach statistical significance (p = 0.157) (Table 2).

In both groups investigated, the linear regression analysis failed to reveal any significant correlations between BI26 and CWb (TR: Coef. 1.106; R² = 0.003; p = 0.851; AB: Coef. − 0.410; R² = 0.002; p = 0.886) or BI26 and SA26 (TR: Coef. 0.619; R² = 0.058; p = 0.387; AB: Coef. 0.311; R² = 0.066; p = 0.354) values, respectively (Fig. 4).