Following ethical approval from the Bioethics Committee of Sichuan University (Reference No: WCCSIRB-D-2014-010), nine health male adult beagle dogs (weight 14–17 kg, age 12–14 months) with completely sound oral condition were recruited by following the ARRIVE guidelines (25) for preclinical animal studies (Supplementary file). All animals were provided by Laboratory Animal Center of Sichuan University. An identical housing and feeding condition was required for all the animals at the Experimental Animal Center of Laboratory of Biotherapy. With injecting general anesthesia with Sumianxin (0.1 ml/kg xylazine hydrochloride, Changchun Military Academy of Medical Sciences, Changchun, China) and local anesthesia (2–4 ml lidocaine 2% epinephrine, Tianjin Pharmaceutical Co. Ltd, Tianjin, China) at the surgical sites, a total of 54 screw-type titanium dental implant with plasma-sprayed hydroxyapatite (HA) coating (3.3 mm Ø × 8 mm, cylindrical, non-submerged healing, BLB, China) were inserted in the mandibular region of each dog (n = 6 per dog). The sample size was calculated based on a prior power analysis in G*power 3.1 at a power of 80% (26). Following crown preparation and attachment, each implant was followed-up for a period of at least 1 months. The surgical procedure has been explained in a prior publication (27, 28). Thereafter, all animals were euthanized using an overdose of xylazine hydrochloride (intravenous injection) and immediate perfusion of 4% paraformaldehyde and 0.0125% glutaraldehyde in 0.1 M phosphate buffer (pH 7.4). All dogs were healthy with clinically stable implants before sacrifice. The mandible blocks with implants were harvested and IO, CBCT and micro-CT images were acquired for each sample, where micro-CT acted as the gold standard. Table 1 describes the details of the acquisition devices and scanning parameters. Following image acquisition, 16 samples were found to have bone defects and were included in the study. The marginal bone level around the implant lower than the first screw loop of the implant from the top was judged as the bone defect; otherwise, the others were excluded. All the images were manually reoriented along implants long axis with DataViewer (ver. 1.5.1.2, Bruker). Following orientation, three types of bone defects were recognized and diagnosed using micro-CT, which included dehiscence (n = 5), infrabony defect (n = 3) and crater-like defect (n = 8) (Fig. 1). The diagnosis was carried out by a consultant oral and maxillofacial radiologist with an experience of over 20 years. Later, two dentists were recruited as observers with an experience of at least 5 years in dental imaging. Following training and calibration of the observers, all the samples marked by the implant site were renumbered and randomized by the method of random sort in Excel. The observers were asked to detect the location of the defect (mesial, distal, buccal, lingual) and the shape of the defect (dehiscence, horizontal defect, vertical defect, carter-like defect). If a vertical defect existed than the observers were additionally asked to classify based on the number of remained walls i.e. 1-walled, 2-walled, 3-walled or combined. All evaluations were performed with both IO and CBCT images.
Table 1
Details of the protocols for each acquisition device and scanning parameter.
|
Intraoral radiography
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Cone-beam computed tomography
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Micro-CT
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System
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Dentsply Sirona
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NewTom GiANO CBCT
|
Quantum FX
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System’s origin
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Sirona Dental Systems GmbH, Bensheim, Germany
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NewTom, Verona, ltaly
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Caliper, Life Sciences, Perkin Elmer
|
Tube current (mA)
|
7
|
5
|
0.16
|
Tube voltage (kV)
|
60
|
90
|
90
|
Voxel size (mm)
|
-
|
0.1
|
0.02
|
Field of view (cm)
|
3.3 x 4.3
|
5 x 5
|
10 x 10
|
Exposure time (S)
|
0.12
|
14.8
|
180
|
Following diagnosis, both observers measured the defect depth and width on IO, CBCT and micro-CT images at each side of peri-implant bone defect via CT-analyzer software (version 1.16.1.0, Skyscan1272, Bruker MicroCT, Kontich, Belgium). The slices in 3D images were standardized to that of the 2D image. A mesio-distal and bucco-lingual slice was selected from the sagittal and coronal view individually on the 3D images and were oriented parallel to the long axis of implant. The width and depth of the defects were measured as shown in Fig. 2. The observers performed both diagnosis and measurement tasks at a two weak interval with randomization of the data for assessing the observer reliability.
Statistical Analysis
Data were analyzed using SPSS software (Version 22, IBM, New York, USA). The diagnostic accuracy of IO and CBCT images for the defect detection and classification was assessed by calculating the sensitivity and intra- and inter‐rater reliability (Cohen's and Fleiss's Kappa) of each method and observer. The interpretation of Kappa values was carried out as suggested by Landis and Koch (29). Intra-correlation coefficient (ICC) was utilized for calculating the absolute inter-protocol, intra-rater, and inter-rater agreement for defects depth and width measurements. Kruskal-Wallis one-way ANOVA test was performed to compare the depth and width of the infrabony defect with that of the crater-like defect. A p value of < 0.05 was considered as statistically significant.