Ultrasonic Assessment of Mucosal Thickness around Implants: Validity, Reproducibility, and Stability of Connective Tissue Grafts at the Buccal Aspect

Purpose: (1) To assess validity and reproducibility of mucosal thickness (MT) registration by means of an ultrasonic device and (2) to determine the MT stability of connective tissue grafts (CTGs) when applied at the buccal aspect of single implants demonstrating alveolar process deficiency. Materials and Methods: For the validity assessment, four human cadaver edentulous maxillae were used to determine MT at 100 different sites. Soft tissue thickness as recorded with the ultrasonic device was compared with MT as registered with Micro-CT (UGent, Ghent, Belgium), taking the latter as gold standard. For the reproducibility assessment, 50 duplicate ultrasonic registrations were used. For the clinical part, 10 non-smoking patients with a single implant were included. All demonstrated alveolar process deficiency and had been provided with a provisional screw-retained crown at the time of inclusion. Following an intrasulcular incision at the buccal aspect, a CTG was inserted to thicken soft tissues. MT was assessed at t0 (before CTG), t1 (immediately after CTG), t2 (suture removal), t3 (permanent crown installation), and t4 (9 months after CTG). Results: There was a strong correlation between ultrasonic and Micro-CT measurements (r=0.89, p<.001). However, the former significantly underrated MT by 0.13mm (p=030). There was a strong correlation between duplicate ultrasonic recordings (r=0.99, p<.001). Seven females and three males were included in the clinical study with a mean age of 52. MT significantly increased by 0.92mm between t0 and t1 (p=005). Between t3 and t4, there was a slight, yet significant decrease of 0.15mm (p=047). Conclusion: The ultrasonic device can be used as a non-invasive, reliable, and reproducible method to evaluate MT. Using this technology around single implants demonstrated that CTG may substantially thicken the peri-implant mucosa with acceptable stability over a 9-month period.