This prospective clinical study aims to evaluate the effects of fixed lingual retainers placed after orthodontic treatment on periodontal soft and hard tissue parameters using ultrasonographic imaging. A total of 53 participants (636 anterior teeth) who had completed fixed orthodontic therapy were examined at baseline, 3 months, and 6 months after retainer placement. Ultrasonographic assessments were performed to measure gingival thickness, marginal bone level, and gingival level. Periodontal clinical parameters, including plaque index, gingival index, probing depth, bleeding on probing, and clinical attachment loss, were also recorded. The study seeks to determine whether fixed retainers induce measurable alterations in periodontal structures and to explore potential correlations between gingival phenotype and ultrasonographic findings.

Orthodontic retention is a critical phase following active treatment, aiming to maintain the corrected tooth positions and ensure long-term stability. Fixed lingual retainers are widely used due to their minimal patient compliance requirements and aesthetic advantages. However, the long-term presence of fixed retainers may influence periodontal health by altering plaque accumulation patterns and modifying soft and hard tissue dynamics. The literature remains inconclusive regarding whether these appliances cause clinically significant periodontal changes.

This prospective observational clinical study was conducted to evaluate the ultrasonographic and clinical periodontal changes that occur following the placement of fixed lingual retainers in orthodontically treated individuals. Fifty-three participants (aged 16-24 years) who had completed fixed orthodontic treatment were enrolled. All participants received fixed stainless-steel lingual retainers bonded to the anterior teeth (canine-to-canine) in both maxillary and mandibular arches. Participants were divided into four subgroups according to post-treatment incisor inclination changes determined by cephalometric analysis: Maxillary Retroclination, Maxillary Proclination, Mandibular Retroclination, and Mandibular Proclination groups.

Ultrasonographic imaging was performed using a high-frequency intraoral probe with a custom-designed silicone stabilizing cap to ensure consistent contact with the gingival tissue. Measurements were taken perpendicular to the tooth surface at three time points: immediately after retainer placement (T0), three months (T1), and six months (T2). The following ultrasonographic parameters were recorded:

Gingival thickness (GT)

Marginal bone level (MBL)

Gingival level (GL)

Conventional periodontal indices were also assessed at each visit, including the Plaque Index (PI), Gingival Index (GI), Probing Depth (PD), Bleeding on Probing (BOP), and Clinical Attachment Loss (CAL). Gingival phenotype classification was determined based on gingival thickness and keratinized tissue width.

The main objective of this study is to determine whether fixed lingual retainers induce measurable changes in gingival or bone morphology as assessed by ultrasonography and to evaluate the relationship between periodontal phenotypes and ultrasonographic findings. The study also aims to contribute to the validation of ultrasonography as a noninvasive, radiation-free diagnostic method for longitudinal monitoring of periodontal tissue dynamics following orthodontic retention.

Inclusion Criteria:

• Inclusion Criteria:
• Patients who have completed comprehensive orthodontic treatment with fixed appliances.
• Patients with a fixed mandibular or maxillary lingual retainer in place for at least 6 months.
• Age between 18 and 40 years.
• Good general health with no systemic conditions affecting periodontal tissues.
• Non-smokers or light smokers (<5 cigarettes/day).
• Presence of all anterior teeth without significant restorations or prosthetic crowns.

Exclusion Criteria:

• History of periodontal surgery or advanced periodontitis prior to orthodontic treatment.
• Systemic diseases or medications affecting periodontal health (e.g., diabetes, immunosuppressive therapy).
• Pregnancy or lactation.
• Poor oral hygiene or non-compliance with oral hygiene instructions.
• Teeth with caries, large restorations, or endodontic treatment in the area of interest.
• Patients with removable retainers or interrupted use of fixed retainers.

The study population consisted of individuals who had completed fixed orthodontic treatment at the Department of Orthodontics, Selçuk University Faculty of Dentistry. All participants were systemically healthy, non-smoking young adults aged between 16 and 24 years, with good oral hygiene and no active periodontal disease. Each subject had maxillary and/or mandibular anterior teeth bonded with fixed retainers in passive condition. A total of 53 individuals (636 anterior teeth) were evaluated and categorized into four subgroups according to the inclination of anterior teeth: maxillary retroclination, maxillary proclination, mandibular retroclination, and mandibular proclination.