A Novel Approach to Monitoring Graft Neovascularization in the Human Gingiva

Laser Speckle Contrast Imaging, or LSCI, can help monitor long-term changes in human gingival microcirculation in the clinic to track individual disease progression and wound healing. The main advantages of this technique are that it is non-invasive and it assesses the blood perfusion of the gingiva with a good repeatability and reproducibility. This method doesn't require any special tools for the measurement head localization and the post-operative wound healing can be followed within a surgical site of up to six square centimeters.

For laser speckle contrast imaging set-up, switch on the computer and peripherals and switch on the laser speckle contrast imaging instrument. After the instrument has warmed up for at least five minutes, open the software and seat the patient in a comfortable supine position in a dental chair. Place a cuff around the patient's arm and a vacuum pillow under the patient's head.

Then let the patient rest, undisturbed, for 15 minutes before any measurements are taken. Meanwhile, in the Tools menu, select and click Project Editor. A new window will open in which the commonly used settings can be saved.

In the Projects box, click New to create a new project. Enter the Vestibulum and click OK.In the Sites box click New to create a new site. Enter Tooth 14 and click OK.Under the Contents of:Tooth 14 panel, add 10 centimeters as the required distance for the working distance.

And enter a width of three centimeters and a height of two centimeters in the measurement boxes. Set the Point density resolution to Normal and the Frame rate to 16 images per second and select Time from the Duration drop down menu to set the recording duration to 30 seconds. Select Record with no averaging and set the color photo capture rate to one per second.

Then, click Apply and OK to save the project perimeters. In the File menu, select and click New Recording. A new image window will open and the set up panel will be displayed.

Under Recording Setup, select Vestibulum for the Project and Tooth 14 for the Site. Open the Subject dropdown menu, click New in the Select subject dialog box, and enter the name of the patient. Click OK and enter a name for the recording in the Rec Name field and the name of the operator in the Operator field.

Before beginning the microcirculation image measurement, measure the patient's blood pressure and pulse. And evacuate the air from the pillow to adjust the position of the patient's head as necessary. Have the patient open their mouth and use two dental mirrors to gently retract the lips.

Adjust the head of the instrument so that it is parallel to the measured area of the gingiva. Using the built-in 650 nanometer indicator laser to facilitate the positioning of the imager relative to the patient's mouth. Move the instrument in relation to the tissue to achieve a working distance of 10 centimeters.

Instruct the patient to remain still for the duration of the measurement. And click record to start the recording. The color of the image window will change to red, indicating the recording's in progress and the set-up panel will be replaced by the Recording panel.

The recording will stop automatically after 30 seconds, at which point the color of the image window will change to blue and the recording panel will be replaced by the Review panel. Remove the dental mirrors and allow the patient to close their mouth and to swallow. Then click Resume recording to switch back to the live image.

And repeat the procedure two more times. After the last measurement, close the file. To analyze the laser speckle contrast images, go to the split view in the instrument's software and define the regions of interest.

In the region of interest tools palette, select the desired region of interest shape and click on the apply option to Apply on entire recording. Click and hold the mouse button in the intensity image to draw the region of interest and drag the ROI out to the desired size. Adjust, resize, or rotate the region as necessary.

When all of the regions of interest have been defined, select the Add time of interest tool button to define time periods of interest. Then click and hold the graph at the position at which the time of interest should begin and drag the cursor to the desired end position. According to anatomical and surgical conditions of this representative study, the regions of interest were classified into logical zones, depending on their distance from the center of the implanted graft.

In these images, areas of high perfusion are shown in red, while areas of low perfusion are shown in blue. During the first post-operative week, the blood perfusion images revealed ischemia within the operated region that improved daily and hyperemia within the peri-regions. From day 14, the operated area was clinically erythematous in parallel with the severe hyperemia, observed within the blood profusion images.

By the third month, the wound had healed and the gingival perfusion was measured at close to pre-operative circulation levels. Daily plotting of the blood flow values of the wound edge zones allows tracking of the changes in the blood flow, within the different color coded zones within the graft and within the peri-regions of the wound. For example, the blood flow values were similar in all of the regions of interest within the Apical region of the graft, starting with an ischemic phase on day nine that was follow by a four month hyperemic phase.

The LSCI technique allows non-contact and real time recording of the gingival blood flow, making it a suitable method for studying postoperative microcirculation, over an extended period of time, within a human subject. The vascular anatomy of the gingiva is heterogeneous and variance in the wound healing are common. The high reliability of this method allows the sensitive detection of individual variations, which can be particularly important in personalized therapies during micro plastic surgery.

A strict implementation of each step of the protocol is critical to assess in the blood perfusion of the gingiva with a good reproducibility.