(86) Healing Pattern of Guided Bone Regeneration Evaluated by Ultrasonography

Introduction: Guided bone regeneration (GBR), especially horizontal bone augmentation, has been proved to be a predictable treatment modality to reconstruct edentulous ridge. Numerous techniques and materials have been developed to achieve optimal outcomes. Conventionally, the GBR outcomes were evaluated by clinical assessment, CBCT, or volumetric analysis. However, the longitudinal changes of tissue maturation, especially at the early stage of healing, were poorly understood. The purpose of this case series was to assess real-time changes of ridge morphology and tissue perfusion using non-invasive, non-ionizing ultrasonography evaluating the healing pattern of GBR.

Methods: 11 patients who had received GBR surgeries to augment bone deficiency, mainly at the horizontal direction, were included. The surgeries were conducted in a University setting using a similar surgical protocol, including full-thickness flap elevation, decortication, grafting with allogenous bone particles and collagen membranes, and primary closure. The edentulous ridges were evaluated preoperatively (baseline) and post-operatively at 1-, 2-, 4-, and 6-weeks, 3, and 6 months using dental ultrasonography. A high-frequency scanning protocol was implemented using a commercial ultrasound device (ZS3, Mindray, Mountain View, CA) coupled with a mini-sized transducer. Occlusal, facial, and lingual surfaces of the edentulous ridges were scanned to obtain cross-sectional images. B-mode still images and color-flow cine-loops using color Doppler were obtained to evaluate ridge dimension and tissue perfusion. Longitudinal scans were collected to measure linear anatomical changes, including crestal bone width, crestal soft tissue thickness, and facial/lingual soft tissue thickness using open-source software (Horos, Annapolis, MD). Blood flow velocity within the region of interest (ROI) at the coronal part of the ridge was quantified using programming software (MATLAB, Natick, MA). The apical limit of ROI was defined as 4 and 6 mm below the top of the ridge at the occlusal and facial/lingual scans, respectively.

Results: All patients experienced uneventful healing at two weeks post-operatively. Mild wound dehiscence had occurred at one surgical site and eventually healed without complication. The average horizontal bone gain was 2.4 mm at four months. A homogenous pixel density within soft tissue was appreciated at four months with a continuous hyperechoic line indicating a mature cortical bone plate. Different collagen membranes materials exhibited various absorption times detected on the ultrasound scans. Blood flow velocity representing the tissue perfusion showed a pattern significantly increased at two weeks, peaked approximately at 4-6 weeks, and returned to the baseline level at 3-4 months post-operatively.

Conclusions: Ultrasonography provided a unique advantage in monitoring the healing pattern longitudinally, including early wound opening, blood perfusion changes, and maturation of bone graft particles of the guided bone regeneration procedure.

Lead Author's Contributions to the Research Project. : The Lead Author was responsible for the data collection, performing the data analysis and the composition of the abstract