Date Published: February 8, 2017
Publisher: Public Library of Science
Author(s): Hsun-Liang Chan, Khaled Sinjab, Ming-Pang Chung, Yi-Chen Chiang, Hom-Lay Wang, William V. Giannobile, Oliver D. Kripfgans, Sompop Bencharit.
Facial crestal bone level and dimension determine function and esthetics of dentition and dental implants. We have previously demonstrated that ultrasound can identify bony and soft tissue structures in the oral cavity. The aim of this study is to evaluate the accuracy of using ultrasound to measure facial crestal bone level and thickness.
A commercially available medical ultrasound scanner, paired with a 14 MHz imaging probe was used to scan dental and periodontal tissues at the mid-facial site of each tooth on 6 fresh cadavers. The alveolar crest level in relation to the cemento-enamel junction and its thickness on ultrasound images were measured and compared to those on cone-beam computed tomography (CBCT) scans and/or direct measurements on a total of 144 teeth.
The mean crestal bone level measured by means of ultrasound, CBCT and direct measures was 2.66 ± 0.86 mm, 2.51 ± 0.82 mm, and 2.71 ± 1.04 mm, respectively. The mean crestal bone thickness was 0.71 ± 0.44 mm and 0.74 ± 0.34 mm, measured by means of ultrasound and CBCT, respectively. The correlations of the ultrasound readings to the other two methods were between 0.78 and 0.88. The mean absolute differences in crestal bone height and thickness between ultrasound and CBCT were 0.09 mm (-1.20 to 1.00 mm, p = 0.06) and 0.03 mm (-0.48 to 0.54 mm, p = 0.03), respectively.
Ultrasound was as accurate in determining alveolar bone level and its thickness as CBCT and direct measurements. Clinical trials will be required to further validate this non-ionizing and non-invasive method for determining facial crestal bone position and dimension.
The thickness and level of the facial alveolar bone are important prognostic parameters for functional and esthetic outcomes of periodontal and dental implant therapy. For instance, gingival recession is commonly accompanied with thin facial bone and/or bony dehiscence . Sockets with a thin buccal plate have approximately two times more horizontal and vertical bone resorption after immediate implant placement . Extraction sockets with thin buccal bone (≤1 mm), a majority (71%) have significant horizontal and vertical buccal bone resorption during the healing period. Therefore, it is critical to diagnose the dimension and location of the facial plate before performing these procedures.
Six cadaver heads, 3 males and 3 females with a mean age of 75.2 (range: 66 to 89) years were studied. A total number of 144 teeth were measured with the CBCT method, including 67 anterior teeth, 37 premolars and 40 molars in both maxillae and mandiblae. Of those teeth, five teeth (three 2nd molars and 2 canines) were excluded for ultrasound due to suboptimal image quality (Table 1). Fig 1 illustrates the ultrasound images of different tooth types. The landmarks, including the CEJ and facial alveolar crest were clearly demarcated and correlated with those on the cadaver specimens. Additionally, the tooth and bone surface contours as well as gingiva/mucosa were identifiable. The mean crestal bone level measured from ultrasound images, CBCT images and cadavers directly was 2.66 ± 0.86 mm, 2.51 ± 0.82 mm, and 2.71 ± 1.04 mm, respectively (Table 2). Likewise, the mean crestal bone thickness was 0.71 ± 0.44 mm and 0.74 ± 0.34 mm, measured from ultrasound and CBCT images, respectively (Table 1). Statistically significant correlations were found for bone height readings between ultrasound and direct methods (r = 0.88, p<0.001), between ultrasound and CBCT methods (r = 0.78, p<0.001), and direct and CBCT methods (r = 0.70, p<0.001) (Table 3 and Fig 2). A statistically significant correlation was also found for bone thickness measurements obtained between ultrasound imaging and CBCT scans (r = 0.81, p<0.001) (Table 3 and Fig 2). The mean absolute difference (95% CI) in bone level between ultrasound and direct, ultrasound and CBCT, CBCT and direct was 0.09 mm (-0.98 to 0.80 mm, p = 0.03), 0.09 mm (-1.20 to 1.00 mm, p = 0.06), 0.20 mm (-1.70 to 1.30 mm, p = 0.018), respectively (Table 3 and Fig 3). The mean absolute difference (95% CI) in bone thickness between ultrasound and CBCT was 0.03 mm (-0.48 to 0.54 mm, p = 0.03) (Table 3 and Fig 3). Tissue biotype is considered an important determinant of treatment outcomes in the management of periodontal diseases [15, 16], in bone regenerative procedures , and in implant therapy [18–20]. While significant efforts have been placed in developing methods to evaluate soft tissue biotypes [21, 22], it is undeniable that the underlying hard tissue influences the overlying tissue biotype . It has been suggested that a moderate correlation exists between facial gingival thickness and underlying bone thickness . Ultrasound has proven a suitable tool for evaluating soft tissue, e.g., gingival/mucosal thickness [12, 13, 24]. Although ultrasound has been used for evaluating bone surface topography in orthopedics, it is the first time to apply this technology to quantify the alveolar bone dimension and correlate the readings with radiographic and direct measurements on human cadavers. Further improvement of ultrasound accuracy by increasing spatial resolution could make this novel technique a clinical reality. Facial alveolar bone dimension was assessed with a commercially available medical ultrasound scanner and compared to those measured directly on specimens and by cone beam computed tomography. Strong correlations (r>0.80) and agreements (mean differences< 0.1 mm) of ultrasound readings to the other two methods hold promise for clinical use of ultrasound for evaluating crestal bone level as well as the thickness. Source: http://doi.org/10.1371/journal.pone.0171237