Does incisor inclination change during orthodontic treatment affect gingival thickness and the width of keratinized gingiva? A prospective controlled study.

Objective: This prospective controlled study aimed to assess whether changes in mandibular incisor inclination during orthodontic treatment with fixed appliances affect gingival thickness (GT) and the width of keratinized gingiva (WKG), and having as reference an untreated group of participants.

Materials and methods: Forty consecutively recruited adult orthodontic patients and 40 untreated volunteers, matched for age and gender and selected from the same background population serving as controls, were included. Mandibular incisor inclination was measured in lateral cephalograms before treatment commencement (T0) and 1 month before fixed appliances' removal (T1). Gingival thickness was measured using an Ultrasound Device (US) and width of keratinized gingiva (WKG) using a standard periodontal probe within the frames of a full periodontal examination at T0, T1, and 1 year after bracket removal (T2), that is, at about 30 months from T1.

Results: Nineteen females and 21 males in each group [mean age in years (range): intervention group 23.1 (16.8-43.3); control: 21.85 (18.2-43.9)] were analysed. Overall, change in incisor proclination [mean change in Incisor Mandibular Angle Plane-IMPA (ΔIMPA) was 6.35° (SD 5.08°)] was not associated with any significant change in soft tissue thickness and with alterations in WKG. The group receiving fixed appliances did not exhibit thickening or thinning of GT in comparison to the control group; the WKG was reduced in the intervention group in comparison to the untreated group, where it essentially remained unchanged (#41: coeff.: -0.29, P value: .1, 95% CIs: -0.65, 0.06; #31: coeff.: -0.51, P value: .01, 95% CIs: -0.88, -0.14).

Conclusions: Lower incisor proclination during orthodontic treatment does not appear to significantly alter GT and WKG, but orthodontic treatment, overall, leads to reduction of the WKG.