Intraoral Ultrasonography for Mid‐Buccal Probing Depth Assessment: A Proof‐of‐Concept Clinical Agreement Study

AIM: To evaluate the agreement between ultrasound-derived gingival sulcus depth (uGSD) and clinical probing depth (PD) at standardised mid-buccal sites as a proof-of-concept study. MATERIALS AND METHODS: Mid-buccal measurements were obtained from 963 sites in 69 participants (767 anterior, 127 premolars, 69 first molars) using an 18-MHz ultrasound transducer and a UNC-15 probe. uGSD was measured on B-mode images; reliability was assessed by two trained examiners. Agreement was evaluated using intra-class correlation coefficient (ICC), Bland-Altman analysis and mean absolute error (MAE). Generalised estimating equations and clustered ICCs accounted for within-patient clustering. Subgroups included PD strata, bleeding, tooth type, calculus, restorations (prosthetic crowns/orthodontic attachments) and smoking. RESULTS: Ultrasound measurements showed high reliability (ICCs > 0.90). Agreement between uGSD and clinical PD was strong (ICC = 0.942; 95% CI: 0.935-0.949), with negligible mean difference (+0.023 mm) and low MAE (0.29 ± 0.32 mm). Subgroup ICCs ranged from 0.786 to 0.952; 85.0% of sites differed by ≤ 0.50 mm and 96.7% by ≤ 1.00 mm. Molar sites showed the highest MAE (0.38 mm) and slight underestimation (-0.123 mm). CONCLUSION: Intraoral ultrasonography showed high agreement with clinical PD at standardised mid-buccal sites in anterior teeth, premolars and first molars. It may serve as a non-invasive adjunct to conventional probing; however, broader studies are needed across complex sites and examiner experience levels.