Inter- and intraobserver reproducibility of buccal bone measurements at dental implants with cone beam computed tomography in the esthetic region
© Slagter et al.; licensee Springer. 2015
Received: 24 December 2014
Accepted: 19 February 2015
Published: 18 April 2015
Sufficient buccal bone is important for optimal esthetic results of implant treatment in the anterior region. It can be measured with cone beam computed tomography (CBCT), but background scattering and problems with standardization of the measurements are encountered. The aim was to develop a method for reliable, reproducible measurements on CBCTs.
Using a new method, buccal bone thickness was measured on ten CBCTs at six positions along the implant axis. Inter- and intraobserver reproducibility was assessed by repeated measurements by two examiners.
Mean buccal bone thickness measured by observers 1 and 2 was 2.42 mm (sd: 0.50) and 2.41 mm (sd: 0.47), respectively. Interobserver intraclass correlation coefficient was 0.96 (95% CI 0.93 to 0.98). The mean buccal bone thickness of the first measurement and the second measurement of observer 1 was 2.42 mm (sd: 0.50) and 2.53 mm (sd: 0.49), respectively, with an intraobserver intraclass correlation coefficient of 0.93 (95% CI 0.88 to 0.96). The mean buccal bone thickness of the first measurement and the second measurement of observer 2 was 2.41 mm (sd: 0.47) and 2.52 mm (sd: 0.47), respectively, with an intraobserver intraclass correlation coefficient of 0.96 (95% CI 0.93 to 0.97).
Applying the methods used in this study, CBCTs are suitable for reliable and reproducible measurements of buccal bone thickness at implants.
KeywordsDental implants Esthetic region CBCT Bone thickness
Single-tooth implant placement in the esthetic zone is a highly reliable treatment option for replacing a failing tooth [1-4]. Yet, research interest has shifted from implant survival towards optimal preservation of soft and hard tissues [5-7]. Especially in the esthetic region, buccal bone and its preservation is one of the key factors in esthetic outcome .
Computerized tomography (CT) scans and cone beam CTs (CBCTs) are commonly used for presurgical planning and to predict bone density and potential stability of dental implants . Next to this, CTs and CBCTs also allow for measuring bone at dental implants during follow-up [10,11]. The quality and accuracy of a three-dimensional (3D) model derived from a (CB)CT is dependent on scanner-related factors such as type of scanner, field of view (FoV), artifacts, and voxel size . In addition, patient-related factors such as patient position and metal artifacts  and operator-related factors such as the segmentation process or interpretation of the (CB)CT are of influence . It has been reported that buccal bone thickness at implant sites can be measured with CBCT, but background scattering and problems with standardization of the measurements are frequently encountered . In view of the aforementioned factors, there is need for a reliable, reproducible method to facilitate measurements. The use of 3D image diagnostic and treatment planning software programs in combination with software programs for tracking and registration of the exact position of existing dental implants in radiographs can be of help .
The aim of the current study was to develop a reproducible method based on 3D image diagnostic and treatment planning software programs for buccal bone measurements at implants on CBCTs.
CBCT imaging and software protocol
Continuous variables were expressed as a mean with standard deviation. Interobserver and intraobserver variability was assessed using two-way mixed intraclass correlation coefficient single measures analysis . All analyses were performed using SPSS software (version 20.0).
The mean buccal bone thickness measured by observers 1 and 2 was 2.42 mm (sd: 0.50) and 2.41 mm (sd: 0.47), respectively. Interobserver intraclass correlation coefficient was 0.96 (95% CI 0.93 to 0.98). The mean buccal bone thickness of the first measurement and the second measurement of observer 1 was 2.42 mm (sd: 0.50) and 2.53 mm (sd: 0.49), respectively, with an intraobserver intraclass correlation coefficient of 0.93 (95% CI 0.88 to 0.96). The mean buccal bone thickness of the first measurement and the second measurement of observer two was 2.41 mm (sd: 0.47) and 2.52 mm (sd: 0.47), respectively, with an intraobserver intraclass correlation coefficient of 0.96 (95% CI 0.93 to 0.97).
Intraobserver and interobserver agreement was very high with measurements on CBCTs of bone buccally of dental implants. Apparently, the method is clear and measurements can be performed reproducibly. Moreover, measurements are not observer dependent, meaning that results of different observers in different studies can be compared with each other.
In previous studies, buccal bone thickness was also measured, but the exact position of these measurements at the surface of the implant was not determined by 3D image-based diagnostic and treatment planning software programs [10,11,15]. It is important to perform measurements of bone thickness at the same position at implants to make comparison in time possible. Because of the cylindrical contour of the implant, thickness of bone can vary considerably in the mesio-distal direction. The combination of the software programs MIRIT (for determination and registration of the implant position in Maxilim) and Research Tool in NobelClinician (for alignment of planning implant and registered implant) makes the method reproducible.
Scattering of the titanium dental implant makes it difficult to perform measurements from the bone-to-implant boundary to the buccal outer contour of the bone . The combination of Research Tool in NobelClinician (exact positioning of the planning implant) and Measurement Tool in NobelClinician (for measurements from central axis of the implant) makes it possible to bypass the scattering area. Measurements are corrected by subtraction of the known radius of implant, resulting in the actual thickness of bone.
Measurements are not directly possible in NobelClinician, because the image-recognizing program MIRIT can only be executed in the configuration of Maxilim. It would be desirable if the total procedure could be carried in one program, being NobelClinician.
When applying 3D image-based software programs according to the set-up used in this study, CBCTs are suitable for reliable and reproducible measurements of buccal bone thickness at implants.
cone beam computed tomography
Digital Imaging and Communications in Medicine
field of view
Multimodality Image Registration using Information Theory
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