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Voxel-based registration (a–c) Reconstruction of the CBCT image in coronal (a), sagittal (b), and axial (c) views. The red frame indicates the registration reference area. (d) Image of voxel-based CBCT mandible superimposition. CBCT, cone-beam computed tomography.
Source publication
Objective
To evaluate the accuracy, reliability, and efficiency of voxel- and surface-based registrations for cone-beam computed tomography (CBCT) mandibular superimposition in adult orthodontic patients.
Methods
Pre- and post-orthodontic treatment CBCT scans of 27 adult patients were obtained. Voxel- and surface-based CBCT mandibular superimposit...
Similar publications
Cephalometry is a standard diagnostic tool in orthodontic and orthognathic surgery fields. However, built-in magnification from the cephalometric machine produces double images from left- and right-side craniofacial structures on the film, which poses difficulty for accurate cephalometric tracing and measurements. The cone-beam computed tomography...
Citations
... Voxel-based registration (VBR) aligns two CBCT images using maximization of mutual information of the voxels, and surface-based registration (SBR) aligns two surfaces, e.g. using the iterative closest point algorithm. Voxel-and surface-based registration have previously been compared for 3D assessment of orthognathic surgery, including single-piece Le Fort I osteotomy [15], orthodontic treatment [16], and for evaluation of growing subjects [17] and mandibular condyle remodelling [18]. In most of the comparative studies the two registration techniques were proven to be accurate and reliable with statistically insignificant differences, unlikely to be of clinical significance [15][16][17]. ...
... Voxel-and surface-based registration have previously been compared for 3D assessment of orthognathic surgery, including single-piece Le Fort I osteotomy [15], orthodontic treatment [16], and for evaluation of growing subjects [17] and mandibular condyle remodelling [18]. In most of the comparative studies the two registration techniques were proven to be accurate and reliable with statistically insignificant differences, unlikely to be of clinical significance [15][16][17]. However, the performance of the two registration techniques has not been compared for assessment of segmental bimaxillary surgery, such as combined multi-piece Le Fort I osteotomy, bilateral sagittal split osteotomy and genioplasty. ...
... The present study found statistically significant differences between VBR and SBR. Previous comparative studies also found that SBR had higher variability than VBR [15,16]. However, the difference were statistically insignificant. ...
The purpose of the present study was to compare the precision and reliability of voxel- and surface-based registration for computer-assisted assessment of the surgical accuracy and postoperative stability of segmental bimaxillary surgery. Three-dimensional translational and rotational measurements were performed by two observers using voxel- and surface-based registration. The precision and reliability of the measurements were calculated by the mean absolute differences (MAD) and intraclass correlation coefficients (ICC) at 95 % confidence intervals. A paired t-test or the non-parametric equivalent, Wilcoxon signed-rank test, was applied to statistically evaluate whether the precision of voxel- and surface-based registration was statistically significantly different (p < 0.05). Voxel-based registration had high precision (MAD <0.44 mm/0.92°) and excellent reliability, ICC [0.82–1.00]. The precision of surface-based registration was lower (MAD <0.56 mm/1.45°) and the reliability ranged from poor to excellent for the different bone segments, ICC [0.33–1.00]. Both registration techniques had high precision and excellent reliability for the assessment of the surgical accuracy, and the error margin of both techniques was clinical irrelevant. However, the increased precision of voxel-based registration was statistically significant (p < 0.05) for the maxillary segments and the chin, and the stability measurement error (ranging up to 1.58 mm and 4.46°) introduced by surface-based registration may be considered clinical relevant for these bone segments. Within the limitations of the present comparative study, voxel-based registration generally exhibited higher precision and reliability than surface-based registration for the surgical accuracy and postoperative stability assessment of segmental bimaxillary surgery.
... Out of the lack of stable structures, some authors even superimposed based on the teeth that appeared relatively stable [23], but collateral effects on other teeth could not be ignored. Thus, the present study evaluated the efficacy for torque control using CBCT combined with Dolphin voxel-based superimpositions, which was reported to be precise, reliable and user friendly [24,25]. According to method analysis, the average method errors of angular and linear values were 0.5° and 0.2 mm respectively, lower than the range reported by Huanca et al. [26] and Tepedino et al. [27]. ...
Objectives
The objectives of this retrospective clinical study were to evaluate the efficacy of clear aligners on upper-incisor torque control, with the expectation of providing guidance for clinics.
Materials and methods
Pretreatment (T0) and posttreatment (T1) cone-beam computed tomography (CBCT) scans of 47 patients with a nonextraction treatment using clear aligners were obtained and 120 upper-incisors with torque ≥5° were selected. Voxel-based superimpositions were performed using Dolphin imaging software and achieved movements were then measured. Difference between achieved and predicted movement (DAPM) and the efficiency for upper-incisor torque were used to evaluate the torque control efficacy.
Results
The achieved torque movement with clear aligners was lower than predicted significantly, as the mean efficiency was 46.81±33.95%. Additionally, the achieved incisor movement of the crown and root differed significantly from the predicted movement, especially root movement.
Conclusions
Clear aligners struggle to control upper-incisor torque, particularly root movement. In that case, overcorrection is necessary to prevent torque loss.
Clinical relevance
Clear aligners remain a limitation on torque control and overcorrection should be considered.
... Voxel-based registration (VBR) [13,14] uses the grayscale of the voxels to align two 3D volumetric images to the best superimposition [15]. It is today's method of choice [12,[16][17][18] and is considered more reliable than landmark-based cephalometric analysis [16]. Alignment by VBR, validated with the anterior cranial base as a reference, shows high accuracy [19], and is considered to be more consistent than SBR [12,19]. ...
... However, it was concluded that the performance of the registration on the mandibular ramus may have been compromised by inappropriate reference structures proposed in the literature, which seem to alter due to remodeling, and may have influenced the registration [20]. Related studies comparing the performance of VBR and SBR for assessment of the outcome of orthognathic surgery [12] and in adult orthodontic subjects [18] found the two registration methods to be accurate and reliable. Voxel-based registration was associated with less variability [12] and was more efficient than SBR [18]. ...
... Related studies comparing the performance of VBR and SBR for assessment of the outcome of orthognathic surgery [12] and in adult orthodontic subjects [18] found the two registration methods to be accurate and reliable. Voxel-based registration was associated with less variability [12] and was more efficient than SBR [18]. However, the statistical differences between the two registration methods were insignificant and were unlikely to have any clinical significance [12,18]. ...
The literature lacks a reliable holistic approach for the three-dimensional (3D) assessment of the temporomandibular joint (TMJ) including all three adaptive processes, which are believed to contribute to the position of the mandible: (1) adaptive condylar changes, (2) glenoid fossa changes, and (3) condylar positional changes within the fossa. Hence, the purpose of the present study was to propose and assess the reliability of a semi-automatic approach for a 3D assessment of the TMJ from cone-beam computed tomography (CBCT) following orthognathic surgery. The TMJs were 3D reconstructed from a pair of superimposed pre- and postoperative (two years) CBCT scans, and spatially divided into sub-regions. The changes in the TMJ were calculated and quantified by morphovolumetrical measurements. To evaluate the reliability, intra-class correlation coefficients (ICC) were calculated at a 95% confidence interval on the measurements of two observers. The approach was deemed reliable if the ICC was good (>0.60). Pre- and postoperative CBCT scans of ten subjects (nine female; one male; mean age 25.6 years) with class II malocclusion and maxillomandibular retrognathia, who underwent bimaxillary surgery, were assessed. The inter-observer reliability of the measurements on the sample of the twenty TMJs was good to excellent, ICC range (0.71–1.00). The range of the mean absolute difference of the repeated inter-observer condylar volumetric and distance measurements, glenoid fossa surface distance measurements, and change in minimum joint space distance measurements were (1.68% (1.58)–5.01% (3.85)), (0.09 mm (0.12)–0.25 mm (0.46)), (0.05 mm (0.05)–0.08 mm (0.06)) and (0.12 mm (0.09)–0.19 mm (0.18)), respectively. The proposed semi-automatic approach demonstrated good to excellent reliability for the holistic 3D assessment of the TMJ including all three adaptive processes.
... Surface-based registration aligns two 3D surfaces using the iterative closest point algorithm [49], and SBR has been shown to be a reproducible method [50,51]. Both registration methods have been found to be reliable and accurate [52][53][54]. Although VBR has been shown to be more consistent and efficient than SBR, the differences between the two methods were statistically insignificant [52][53][54]. ...
... Both registration methods have been found to be reliable and accurate [52][53][54]. Although VBR has been shown to be more consistent and efficient than SBR, the differences between the two methods were statistically insignificant [52][53][54]. Another comparative study proved that SBR was more accurate and reliable than VBR on the mandibular ramus for the long-term 3D assessment of condylar remodeling following orthognathic surgery [55]. ...
This systematic review aimed to determine the accuracy/stability of patient-specific osteosynthesis (PSI) in orthognathic surgery according to three-dimensional (3D) outcome analysis and in comparison to conventional osteosynthesis and computer-aided designed and manufactured (CAD/CAM) splints or wafers. The PRISMA guidelines were followed and six academic databases and Google Scholar were searched. Records reporting 3D accuracy/stability measurements of bony segments fixated with PSI were included. Of 485 initial records, 21 met the eligibility (566 subjects), nine of which also qualified for a meta-analysis (164 subjects). Six studies had a high risk of bias (29%), and the rest were of low or moderate risk. Procedures comprised either single-piece or segmental Le Fort I and/or mandibular osteotomy and/or genioplasty. A stratified meta-analysis including 115 subjects with single-piece Le Fort I PSI showed that the largest absolute mean deviations were 0.5 mm antero-posteriorly and 0.65° in pitch. PSIs were up to 0.85 mm and 2.35° more accurate than conventional osteosynthesis with CAD/CAM splint or wafer (p < 0.0001). However, the clinical relevance of the improved accuracy has not been shown. The literature on PSI for multi-piece Le Fort I, mandibular osteotomies and genioplasty procedure is characterized by high methodological heterogeneity and a lack of randomized controlled trials. The literature is lacking on the 3D stability of bony segments fixated with PSI.
... Regarding the accuracy of both matching procedures, the literature states that VBR displays less variability than SBR. However, differences between both methods were found to be non-significant [5,17]. This indicates that determinations in 3D models by means of SBR and in scans by means of VBR can be compared with each other. ...
(1) Background: For years, Cone-Beam Computed Tomography’s (CBCT) have been the golden standard to evaluate implant placement accuracy. By validating Intraoral Scans (IOS) as an alternative to determine implant placement accuracy, a second CBCT could be avoided. (2) Methods: Using dynamic guided implant surgery, 23 implants were placed in 16 partially edentate patients. Preoperatively, both CBCT and IOS (Trios® 3) were obtained and subsequently imported into DTX Studio™ planning software to determine the ideal implant location. A CBCT scan and an IOS including scan abutments were acquired immediately after placement. Both postoperative CBCT and postoperative IOS were used to compare the achieved implant position with the planned implant position and were projected and analyzed using the Implant Position Orthogonal Projection (IPOP) method. (3) Results: Mean differences between the CBCT and IOS methods on the mesio–distal plane were 0.09 mm (p = 0.419) at the tip, 0.01 mm (p = 0.910) at the shoulder, −0.55° (p = 0.273) in angulation, and 0.2 mm (p = 0.280) in implant depth. Mean differences between both methods on the bucco-lingual/bucco-palatal plane were 0.25 mm (p = 0.000) at the tip, 0.12 mm (p = 0.011) at the shoulder, −0.81° (p = 0.002) in angulation, and 0.17 mm (p = 0.372) in implant depth. A statistical analysis was performed using a paired t-test. All mesiodistal deviations between the two methods showed no significant differences (p > 0.05). Buccolingual/buccopalatal deviations showed no significant difference in implant depth deviation. However, significant differences were found at the tip, shoulder, and angulation (p < 0.05). These values are of minimal clinical significance. (4) Conclusions: This study supports the hypothesis that a postoperative IOS is a valid alternative for determining implant placement accuracy.
... Regarding the accuracy of both matching procedures, the literature states that VBR displays less variability than SBR. However, differences between both methods were found to be non-significant [5,17]. This indicates that determinations in 3D models by means of SBR and in scans by means of VBR can be compared with each other. ...
... 17 Voxel-based method was used for skeletal superimposition because of the higher efficiency, elimination of segmentation errors in 3D surface models, and greater ease of assessing inner structures that allows the superimposed structures to be viewed in multiplanar slices. 18,19 The average overjet decreased insignificantly from 4.53 AE 1.52 mm to 2.81 AE 1.1 mm after treatment ( Table 1). The largest overjet in our patients was 7.1 mm and the molar relationship was half-cusp Class II. ...
Background/purpose
The treatment effects of Invisalign® are still obscure due to methodological limitations of previous studies. We introduced a method to comprehensively evaluate the dental and skeletal changes of Class II malocclusion treated non-extraction with Invisalign® and compare with the virtual simulation of ClinCheck® using digital models integrated into maxillofacial cone-beam computed tomography (CBCT).
Materials and methods
The pretreatment (T1) and posttreatment (T2) scanned digital images of actual dentitions were integrated into maxillofacial CBCT images. To evaluate three-dimensional movement of maxillary teeth and change of mandible position, T1 and T2 digital model-integrated maxillofacial CBCT images were superimposed using voxel-based registrations of stable cranial base structures. To evaluate movement of mandibular teeth, model-integrated mandibular CBCT superimposition was registered on mandibular basal bone. To compare achieved and predicted tooth movements, the actual dental images and the virtual digital models created by ClinCheck® were registered on the T1 dentitions.
Results
For simulated upper first molar (U6) distalization of more than 1 mm, treatment accuracy ranged from 31.1% to 40.1%, which was significantly less than virtual planning and previous reports. In unilateral Class II subjects, the amount of U6 distalization on the Class II side was not significantly different from contralateral side, indicating efficacy of sequential distalization was questionable. Those with favorable overjet correction showed evidence of condylar distraction.
Conclusion
Digital model-integrated CBCT superimpositions reflected the actual treatment changes in comparison with the virtual simulation, and showed that ideal occlusion was not achieved in mild to moderate Class II adult patients treated non-extraction with Invisalign®.
... Intensity-based registration using histogram-matched images replaced the inaccurate manual registration using several reference points ( Figure 3) [19,20]. Therefore, 3D CBCT images were superimposed using intensity-based registration, which shows high accuracy [19,21] (Figure 4). ...
... Intensity-based registration using histogram-matched images replaced the inaccurate manual registration using several reference points (Figure 3) [19,20]. Therefore, 3D CBCT images were superimposed using intensity-based registration, which shows high accuracy [19,21] (Figure 4). ...
This study aimed to evaluate the bone volume change at donor sites in patients who received mandibular body bone block grafts using intensity-based automatic image registration. A retrospective study was conducted with 32 patients who received mandibular bone block grafts between 2017 and 2019 at the Pusan National University Dental Hospital. Cone-beam computed tomography (CBCT) images were obtained before surgery (T0), 1 day after surgery (T1), and 4 months after surgery (T2). Scattered artefacts were removed by manual segmentation. The T0 image was used as the reference image for registration of T1 and T2 images using intensity-based registration. A total of 32 donor sites were analyzed three-dimensionally. The volume and pixel value of the bones were measured and analyzed. The mean regenerated bone volume rate on follow-up images (T2) was 34.87% ± 17.11%. However, no statistically significant differences of regenerated bone volume were noted among the four areas of the donor site (upper anterior, upper posterior, lower anterior, and lower posterior). The mean pixel value rate of the follow-up images (T2) was 78.99% ± 16.9% compared with that of T1, which was statistically significant (p < 0.05). Intensity-based registration with histogram matching showed that newly generated bone is generally qualitatively and quantitatively poorer than the original bone, thus revealing the feasibility of pixel value to evaluate bone quality in CBCT images. Considering the bone mass recovered in this study, 4 months may not be sufficient for a second harvesting, and a longer period of follow-up is required.
... 19,20 Voxel-based registration uses the grayscale of the voxels to align two 3D volumetric images to the best superimposition. 21,22 Surface-and voxel-based registration have previously been validated for different purposes 19,20,[23][24][25] and were compared for 3D assessment of surgical outcome in adult orthodontic subjects, 26 following orthognathic surgery 27 and for evaluation of growing subjects. 18 The two registration methods were found to be reliable and accurate. ...
... 18 The two registration methods were found to be reliable and accurate. 18,26,27 Differences between the two registration methods were statistically insignificant and were unlikely to have any clinical importance. 18,26,27 However, the performance of the registration methods has not been compared for evaluation of condylar remodelling. ...
... 18,26,27 Differences between the two registration methods were statistically insignificant and were unlikely to have any clinical importance. 18,26,27 However, the performance of the registration methods has not been compared for evaluation of condylar remodelling. These methods are dependent on the reference structure, the region or volume of interest, which is an important observerdependent input parameter. ...
Objectives
The purpose of the present study was to validate and compare the accuracy and reliability of surface- and voxel-based registration on the mandibular rami for long-term three-dimensional (3D) evaluation of condylar remodelling following Orthognathic Surgery.
Methods
The mandible was 3D reconstructed from a pair of superimposed pre- and postoperative (two years) cone-beam computerized tomography scans and divided into the condyle, and 21 ramal regions. The accuracy of surface- and voxel-based registration was measured by the absolute mean surface distance of each region after alignment of the pre- and postoperative rami. To evaluate the reliability, mean absolute differences and intra class correlation coefficients (ICC) were calculated at a 95% confidence interval on volumetric and surface distance measurements of two observers. Paired t-tests were applied to statistically evaluate whether the accuracy and reliability of surface- and voxel-based registration were significantly different (p < 0.05).
Results
A total of twenty subjects (sixteen female; four male; mean age 27.6 years) with class II malocclusion and maxillomandibular retrognathia, who underwent bimaxillary surgery, were included. Surface-based registration was more accurate and reliable than voxel-based registration on the mandibular ramus two years post-surgery (p < 0.05). The inter observer reliability of using surface-based registration was excellent, ICC range [0.82–1.00]. For voxel-based registration, the inter observer reliability ranged from poor to excellent [0.00–0.98]. The measurement error introduced by applying surface-based registration for assessment of condylar remodelling was considered clinical irrelevant (1.83% and 0.18 mm), while the measurement error introduced by voxel-based registration was considered clinical relevant (5.44% and 0.52 mm).
Conclusions
Surface-based registration was proven more accurate and reliable compared to voxel-based registration on the mandibular ramus for long-term 3D assessment of condylar remodelling following Orthognathic Surgery. However, importantly, the performance difference may be caused by an inappropriate reference structure, proposed in the literature, and applied in this study.
The three-dimensional (3D) imaging is being widely used in all dental fields. In orthodontics one of its uses is for 3D superimposition methods. There are three methods to compare Cone Beam Computed Tomography (CBCT) scans of the same patient taken at different treatment time-points. They are landmark-based, surface-based and voxel-based methods. The superimposition allows us to analyze and compare the dental, skeletal and soft tissue changes during orthodontic treatment. Thus, allowing us to evaluate the efficiency of the treatment method and the effects of the orthodontic appliance. By using landmark-based CBCT superimposition software we aim to create clinical protocol for comparing the transversal (dental, skeletal and soft tissue) changes after using Rapid Maxillary Expansion (RME) in growing patients. Consecutive CBCT scan of the patients were made-one at the beginning of the treatment (at the stage of orthodontic treatment planning) and one after the rapid maxillary expansion had finished. Each of the CBCTs were analyzed and the obtained values and measurements were put in a table by order. The same reference bone points and planes were used. Then the superimposition method was done using the software. This superimposition method relies on localizing the landmarks on stable anatomical structures. The software offers manual placement of the landmarks using fitting tool where the user places 3 landmarks sequentially on the initial and on the final CBCT scan. It starts by placing the first landmark on the final CBCT and finishes with placing the last on the initial CBCT. For better accuracy the software allows adjusting the bone density thresholds for both CBCT scans so that the bone surface can be displayed equally. If there are any mismatches, they can be corrected by manually rotating or moving the final volume. After superimposing the volumes, the dental, skeletal and soft tissues changes can be evaluated by using different measurement tools. The landmark-based method requires knowledge of the anatomical structures and well-trained eye of the user in order to get good superimposition. The used software provides user-friendly and fast superimposition method, allowing the clinicians to perform it easily. The landmark-based method is reliable but less accurate method compared to the surface-based and voxel-based superimposition methods. It gives credible and reproducible results for the purpose of the clinical protocol and the research. The results obtained from the superimpositions are commensurable and corresponding to the difference in the measurements obtained from separate measurements made on the initial and final CBCTs. The CBCT software analysis allows the assessment of the airway volume changes with different orthodontic treatments and appliances. A disadvantage of the software is that it does not allow comparing and superimposing of the segmented jaws taken from the CBCT.
