Effect of Nail Biting Habit on Mandibular Bone Structure: A Retrospective Radiological Study

Nail biting (onychophagia) is classified as a body-focused repetitive behavior and represents a common parafunctional habit, particularly among children and adolescents. Continuous repetitive mechanical forces generated during nail biting may affect the stomatognathic system; however, the possible effects of this habit on mandibular bone structure have not been sufficiently investigated.

Fractal analysis is a radiological assessment method used to evaluate trabecular bone architecture by quantifying structural complexity. Higher fractal dimension values indicate increased complexity of bone patterns. In addition, panoramic morphometric indices such as mandibular cortical width, panoramic mandibular index, and Klemetti index provide information regarding cortical bone quality and quantity.

In this retrospective case-control study, existing panoramic radiographs of individuals with and without nail biting habits will be evaluated. Radiological parameters including fractal dimension, mandibular cortical width, panoramic mandibular index, and Klemetti index will be compared between groups. This study aims to determine whether nail biting habit is associated with measurable changes in mandibular trabecular and cortical bone characteristics.

Inclusion criteria

• Children aged 8-10 years who were examined at the Department of Pediatric Dentistry, Faculty of Dentistry, Recep Tayyip Erdoğan University.
• Systemically healthy participants.
• Participants with available diagnostic-quality panoramic radiographs obtained during routine dental examinations.
• Participants with and without a history of nail biting habit.
• Panoramic radiographs with sufficient image quality for fractal dimension analysis and mandibular morphometric measurements.
• Radiographs without periapical pathology in teeth adjacent to the regions of interest (ROI) used for fractal analysis.
• Participants with at least 20 existing teeth.
• Radiographic records with available parental radiographic information and consent documentation.

Exclusion criteria

• Participants with systemic diseases or conditions that may affect bone metabolism, including diabetes mellitus, osteoporosis, osteomalacia, renal diseases, hypothyroidism, or hyperparathyroidism.
• Participants using medications that may influence bone density or bone metabolism.
• Participants with temporomandibular joint disorders affecting the subcondylar region.
• Participants with mandibular pathological conditions, including cysts, tumors, or other lesions affecting mandibular bone structure.
• Participants with periapical pathology adjacent to the regions selected for fractal analysis.
• Participants with fewer than 20 teeth.
• Panoramic radiographs with insufficient diagnostic quality or image artifacts that prevent reliable measurements.
• Radiographs that do not allow accurate evaluation of mandibular cortical and trabecular bone parameters.