Volumetric stability of biphasic hap/β-tcp/collagen implants in malar augmentation: A CBCT-Based case series after orthognathic surgery

Objective: Evaluate volumetric stability and symmetry of Biphasic Hydroxyapatite (HAp)/β-Tricalcium phosphate (β-TCP)/collagen (BCP-collagen) implants in malar augmentation post-orthognathic surgery over one year using Cone-Beam-CT (CBCT) and explore influencing factors. Methods: Retrospective case-series analysis of 45 patients (38 females) who underwent bimaxillary orthognathic surgery with malar augmentation using BCP-collagen implants. CBCT scans were taken at 1 week, 4 months, and 12 months post-surgery. Regression analysis explored potential factors influencing volume loss, including age and sex (p < 0.05). Results: Median patient-age was 26 years (IQR: 22–32). One week postoperatively, median implant-volume was 1356.70 mm³ (SD = 5888.53). By four-months, it decreased to 985.46 mm³ (SD = 4352.47), a 25.4 % reduction (p < 0.001). Afterwards, a 1.3 % volume decrease (p = 0.42). Volume loss varied between 35.1 and 14.7 %. Asymmetry >7 % was observed in 17.7 % of patients. No significant differences in volume loss were found between sexes (p = 0.6) or age groups (p > 0.9). Regression showed no significant associations with age (β = 0.02, 95 %CI: −0.48, 0.53, p > 0.9) or sex (β = 11, 95 %CI: −30, 52, p = 0.6). Conclusion: BCP-collagen implants exhibit early volume loss but stabilise long-term. High variability and asymmetry in volumetric changes challenge standard overcorrection strategies, emphasising the need for early monitoring. CBCT enables precise volumetric assessment and may improve surgical decision-making.