Non-ionizing real-time ultrasonography in implant and oral surgery: A feasibility study

Abstract

Purpose: Ultrasound imaging has potential to complement radiographic imaging modalities in implant and oral surgery given that it is non-ionizing and provides instantaneous images of anatomical structures. For application in oral and dental imaging, its qualities are dependent on its ability to accurately capture these complex structures. Therefore, the aim of this feasibility study was to investigate ultrasound to image soft tissue, hard tissue surface topography and specific vital structures.

Material and methods: A clinical ultrasound scanner, paired with two 14-MHz transducers of different sizes (one for extraoral and the other for intraoral scans), was used to scan the following structures on a fresh cadaver: (i) the facial bone surface and soft tissue of maxillary anterior teeth, (ii) the greater palatine foramen; (iii) the mental foramen and (iv) the lingual nerve. Multiple measurements relevant to these structures were made on the ultrasound images and compared to those on cone-beam computed tomography (CBCT) scans and/or direct measurements.

Results: Ultrasound imaging could delineate hard tissue surfaces, including enamel, root dentin and bone as well as soft tissue with high resolution (110 μm wavelength). The greater palatine foramen, mental foramen and lingual nerve were clearly shown in ultrasound images. Merging ultrasound and CBCT images demonstrated overall spatial accuracy of ultrasound images, which was corroborated by data gathered from direct measurements.

Conclusion: For the first time, this study provides proof-of-concept evidence that ultrasound can be a real-time and non-invasive alternative for the evaluation of oral and dental anatomical structures relevant for implant and oral surgery.

Keywords: alveolar ridge; anatomy; bone regeneration; cone-beam computed tomography; dental implants; ultrasonography.

Figure 1:

Frontal view of the maxillary anterior teeth before and after full-thickness flap elevation. The buccal plate is thin. The distance between CEJ to the bone crest is 4.1±0.9 mm. The mucosal thickness at 5 mm apical to the CEJ is 0.3±0.1 mm.

Figure 2:

Intraoral and extraoral ultrasound scans of maxillary anterior teeth. The colored and windowed ultrasound image is to highlight hard tissue surfaces that are hyperechoic. A merged image is to show match of the spatial relationship of dental anatomy. On the ultrasound image, the surfaces of enamel, root dentin and alveolar bone are clearly delineated. Additionally, the soft tissue layer, including alveolar mucosa, submucosa and muscle layers can be seen. On the extraoral ultrasound image, the surfaces of enamel, root dentin and alveolar bone are also clearly delineated. The labial concavity apical to the root apex can be seen with this extraoral scan. Additionally, the soft tissue layer, including the lip, alveolar mucosa, submucosa and muscle layers can be seen. (CEJ: cementoenamel junction) (Scale bar= 5 mm)

Figure 3:

An image composite including images of the greater palatine foramen, the mental foramen, and the lingual nerve. The greater palatine foramen and the mental foramen are shown on the ultrasound image as a discontinuity of the bone surface. The ultrasound image including the mental foramen also presents a clear delineation of the surface of enamel, root dentin, alveolar bone and the mucosal layer. The merged images demonstrate an overall spatial registration of ultrasound and CT image, suggesting the accuracy of ultrasound images for mapping the surface topography of oral anatomy. The lingual nerve (asterisk) is shown as a hyperechoic structure lying next to the lingual side of the mandible, shown as a hyperechoic line. (CEJ: cementoenamel junction; NA: not available) (Scale bar= 5 mm)