A comparison of frontal radiographs obtained from cone beam CT scans and conventional frontal radiographs of human skulls

Alveolar bone changes after tooth-borne surgically assisted rapid maxillary expansion: A three-dimensional study

INTRODUCTION

Surgically assisted rapid maxillary expansion (SARME) with a dental-anchorage appliance can induce dental and skeletal complications adjacent to the teeth supporting the device. The purpose of this study was to quantify the dentoskeletal changes observed after SARME using a tooth-borne device.

MATERIALS AND METHODS

Cone beam CT images from 39 patients were compared between the preoperative (T1) and the postoperative period (T2). The mean time to complete the second imaging was 13.8 ± 6.9 months after the SARME. Dental and bone parameters were assessed: the vestibular bone height (BH), the bone thickness (BT), the existence of fenestrations, and the root resorption at the level of first upper premolar (P1) and the first upper molar (M1). The maxillary expansion parameters were also collected.

RESULTS

Both vertical and horizontal vestibular bone loss were observed mainly in the first upper molar sectors: The BT decreased from 0.93 ± 0.50 mm to 0.53 ± 0.51 mm (p < 0.0001) and the BH decreased from 1.84 ± 1.05 mm to 0.93 ± 1.02 mm (p < 0.0001) for tooth #16. The bone loss also affected the first upper premolars but in a more limited manner. Significant fenestrations were observed at the apex of the mesio-vestibular root of teeth #16 and #26. We noted significant root resorption affecting the mesio-, disto-vestibular and palatal roots of tooth #16 (mean reductions of 0.32, 0.35, and 0.55 mm, respectively; p < 0.05), and the palatal root of tooth # 26 (loss of 0.58 mm; p = 0.004). The mean bone expansion was 3.76 mm and 1.41 mm at the premolar and molar levels, respectively (p < 0.0001), while a mean 6.24 mm and 4.23 mm inter-cuspid expansion was noted at the P1 and M1 levels (p < 0.0001).

CONCLUSION

Our results document the vestibular bone changes and low root resorption, mostly in the molar sectors, associated with SARME using dental-anchorage devices.

A comparative study of the reproducibility of landmark identification on posteroanterior and anteroposterior cephalograms generated from cone-beam computed tomography scans

Objective

This in-vivo study aimed to compare landmark identification errors in anteroposterior (AP) and posteroanterior (PA) cephalograms generated from cone-beam computed tomography (CBCT) scan data in order to examine the feasibility of using AP cephalograms in clinical settings.

Methods

AP and PA cephalograms were generated from CBCT scans obtained from 25 adults. Four experienced and four inexperienced examiners were selected depending on their experience levels in analyzing frontal cephalograms. They identified six cephalometric landmarks on AP and PA cephalograms. The errors incurred in positioning the cephalometric landmarks on the AP and PA cephalograms were calculated by using the straight-line distance and the horizontal and vertical components as parameters.

Results

Comparison of the landmark identification errors in CBCT-generated frontal cephalograms revealed that landmark-dependent differences were greater than experience- or projection-dependent differences. Comparisons of landmark identification errors in the horizontal and vertical directions revealed larger errors in identification of the crista galli and anterior nasal spine in the vertical direction and the menton in the horizontal direction, in comparison with the other landmarks. Comparison of landmark identification errors between the AP and PA projections in CBCT-generated images revealed a slightly higher error rate in the AP projections, with no inter-examiner differences. Statistical testing of the differences in landmark identification errors between AP and PA cephalograms showed no statistically significant differences for all landmarks.

Conclusions

The reproducibility of CBCT-generated AP cephalograms is comparable to that of PA cephalograms; therefore, AP cephalograms can be generated reliably from CBCT scan data in clinical settings.

Mandibular Midline Distraction Osteogenesis with a Bone-borne, Tooth-borne or Hybrid Distraction Appliance: a Systematic Review

Objectives

The objective of the present systematic review was to assess the transverse skeletal and dental arch expansion and relapse after mandibular midline distraction osteogenesis with a bone-borne, tooth-borne or hybrid distraction appliance.

Material and Methods

A MEDLINE (PubMed), Embase and Cochrane library search in combination with a hand-search of relevant journals was conducted. Human studies published in English until the 3^rd of July, 2018 were included.

Results

Two comparative and seven non-comparative studies characterized by high risk of bias fulfilled the inclusion criteria. Transverse mandibular widening was achieved with the different types of distraction appliance displaying a horizontal V-shaped opening with larger anterior transverse expansion declining progressively towards the posterior part of the mandible. Bone-borne and hybrid appliance facilitate more skeletal expansion compared with tooth-borne appliance, whereas comparable dental arch expansion was achieved with the different types of distraction appliance. Skeletal and dental arch relapse with the different type of appliance was limited and comparable. However, frequency of complications was higher with bone-borne appliance compared with tooth-borne or hybrid appliance.

Conclusions

Mandibular midline distraction osteogenesis with bone-borne, tooth-borne or hybrid distraction appliance is an effective treatment modality to correct severe transverse mandibular discrepancies, although the skeletal and dental arch expansion pattern was dissimilar with the different types of appliance. However, dissimilar evaluation methods, different outcome measures, various methodological confounding factors posed serious restrictions reviewing the literature in a quantitative systematic manner. Hence, well-designed long-term randomized controlled trials applying three-dimensional technology, patient-related outcome measures and an economic perspective are needed before definite conclusions can be provided.

Evaluation of three-dimensional superimposition technique on parietal bone of the puberty beagle dogs

OBJECTIVES

This study aimed to (a) evaluate the stability of the parietal bone of 6-9 months old beagles and (b) examine whether parietal regional superimposition can provide an atraumatic and effective solution for further maxillary expansion study.

MATERIALS AND METHODS

Six prepubertal 6-month-old male beagles were included. Six miniscrew markers were inserted into the left and right sides of the parietal bone, and two of them were placed bilaterally near the palatal suture. The subjects were scanned with cone beam computed tomography (CBCT) at three time points of T₀ (6 months old), T₁ (7.5 months old) and T₂ (9 months old), respectively. All skull models were analyzed by both the miniscrew superimposition and the parietal regional superimposition.

RESULTS

The two superimposition methods had no significant difference (p > 0.05) in displacements of miniscrew markers between left and right first premolars (PM1). The maxillary superimposition between T₀ and T₂ indicated that the length and width of the maxillary as well as the width of the zygoma root increased significantly (p < 0.05), while the height of maxillary had no significant difference (p > 0.05) over the 3 months.

CONCLUSIONS

The parietal bone is relatively stable for beagles from 6 months old to 9 months old and thus can be used as a reference region for 3D skull model superimposition of the beagle dog.

Effect of changing the head position on accuracy of transverse measurements of the maxillofacial region made on cone beam computed tomography and conventional posterior-anterior cephalograms

OBJECTIVES

This study aimed to assess the effect of head position on the accuracy of transverse measurements of the maxillofacial region on CBCT and conventional posteroanterior (PA) cephalograms. The second objective of this study was to find skull positions with the greatest and smallest effect on transverse measurements in the maxillofacial region.

METHODS

PA cephalograms and CBCT scans were obtained from 10 dry human skulls in 7 positions, namely the central position, 10° and 20° rotations, 10° and 20° tilts and 10° and 20° tips. The CBCT scans were converted to PA cephalograms on which distances from six landmarks, namely the nasal cavity, zygomatic arch, jugale, antegonion, condylion and zygomaticofrontal suture to the mid-sagittal plane, were measured on both sides using Dolphin two-dimensional software. The paired t-test was used to compare the mean values separately in each position (for each landmark) with the gold standard (central skull position). The interclass correlation coefficient and the Bland-Altman plot were used to compare the mean values measured by two observers.

RESULTS

The mean values of the distances measured on CBCT PA cephalograms were greater than those measured on conventional PA cephalograms; this difference was statistically significant for some landmarks (p < 0.005). The rotated position (as compared with the central position) caused the greatest change in values for most landmarks on both sides (p < 0.005).

CONCLUSIONS

The CBCT PA cephalogram was more accurate than the conventional PA cephalogram, and landmarks farther from the midline exhibited greater changes on cephalograms compared with those closer to the midline. Patients are at risk of improper positioning when undergoing extraoral radiography such as PA cephalograms. Changes in head position may affect the transverse measurements and thus the treatment plan.

New three-dimensional cephalometric analyses among adults with a skeletal Class I pattern and normal occlusion

Objective

The purpose of this study was to assess new three-dimensional (3D) cephalometric variables, and to evaluate the relationships among skeletal and dentoalveolar variables through 3D cephalometric analysis.

Methods

Cone-beam computed tomography (CBCT) scans were acquired from 38 young adults (18 men and 20 women; 22.6 ± 3.2 years) with normal occlusion. Thirty-five landmarks were digitized on the 3D-rendered views. Several measurements were obtained for selected landmarks. Correlations among different variables were calculated by means of Pearson's correlation coefficient values.

Results

The body of the mandible had a longer curve length in men (102.3 ± 4.4 mm) than in women (94.5 ± 4.7 mm) (p < 0.001), but there was no significant difference in the maxillary basal curve length. Men had significantly larger facial dimensions, whereas women had a larger gonial angle (117.0 ± 4.0 vs. 113.8 ± 3.3; p < 0.001). Strong-to-moderate correlation values were found among the vertical and transverse variables (r = 0.71 to 0.51).

Conclusions

The normative values of new 3D cephalometric parameters, including the maxillary and mandibular curve length, were obtained. Strong-to-moderate correlation values were found among several vertical and transverse variables through 3D cephalometric analysis. This method of cephalometric analyses can be useful in diagnosis and treatment planning for patients with dentofacial deformities.

Nasolabial aesthetics correlates poorly with skeletal symmetry in unilateral cleft lip and palate

OBJECTIVE

To evaluate the correlation between symmetry of the craniofacial skeleton and aesthetics of the nose and upper lip in children with complete unilateral cleft lip and palate (CUCLP).

MATERIAL AND METHODS

Craniofacial symmetry was evaluated on postero-anterior (PA) cephalograms of 54 children (37 boys and 17 girls; mean age = 11.0 years, SD 1.6) with CUCLP repaired with a one-stage closure (Cleft group). Treated subjects were age- and gender-matched with 54 untreated subjects taken from the University of Michigan Growth Study (Control group). Fourteen coefficients of asymmetry (CAs) were calculated and four angles were measured. Four raters assessed the nasolabial appearance on cropped facial and profile photographs with the 5-grade aesthetic index of Asher-McDade (grade 1 means the most aesthetic and grade 5 the least aesthetical outcome) in the Cleft group only. Independent t-tests were used to evaluate the inter-group differences for CAs. Pearson's correlation coefficients were calculated to examine a relationship between particular components of the aesthetical index and CAs. Multiple regression analyses were carried out to explain the nasolabial aesthetics on the basis of craniofacial symmetry.

RESULTS

In the Cleft group, most cephalometric variables demonstrated asymmetry not exceeding 10%. The Cleft and Control groups differed regarding three angular measurements (Se, Ism, and ANS) and 1 CA (Mo-V). Three of the four nasolabial components demonstrated correlation with some cephalometric variables. However, the correlation coefficients were low (range: -0.309 to 0.305).

CONCLUSIONS

There is a weak correlation between craniofacial skeletal symmetry and aesthetics of the nose and upper lip in children with CUCLP.

Conventional frontal radiographs compared with frontal radiographs obtained from cone beam computed tomography

AIM

To test the hypothesis that there is no difference between measurements performed on conventional frontal radiographs (FRs) and those performed on FRs obtained from cone beam computed tomography (CBCT) scans.

MATERIALS AND METHODS

This study consisted of conventional FRs and CBCT-constructed FRs obtained from 30 young adult patients. Twenty-three landmarks were identified on both types of cephalometric radiographs. Twenty-one widely used cephalometric variables (14 linear distances, 4 angles, and 3 ratios) were calculated. Paired t-tests were performed to compare the means of corresponding measurements on two cephalometric radiographs of the same patient.

RESULTS

Reproducibility of measurements ranged from 0.85 to 0.99 for CBCT-constructed FRs, and from 0.78 to 0.96 for conventional FRs. A statistically significant difference was observed between conventional FRs and CBCT-constructed FRs for all linear measurements (eurR-eurL, loR-loL, moR-moL, zygR-zygL, lapR-lapL, mxR-mxL, maR-maL, umR-umL, lmR-lmL, agR-agL, me-ans) (P < .05), except for the ans-cr measurement (P > .05). However, no statistically significant differences were noted between conventional FRs and CBCT-constructed FRs for ratios and angular measurements (P > .05).

CONCLUSIONS

The hypothesis was rejected. A difference has been noted between measurements performed on conventional FRs and those performed on CBCT-constructed FRs, particularly in terms of linear measurements.

The reliability of cone-beam computed tomography (CBCT) - generated frontal cephalograms

BACKGROUND

The purpose of this study was to evaluate the reliability of measurements from cone-beam computed tomography (CBCT)-generated frontal cephalogram.

MATERIALS AND METHODS

CBCT and conventional posteroanterior (PA) cephalograms were taken from 30 adult patients. CBCT image was set according to the Frankfurt-Horizontal (FH) plane as the horizontal plane and the midsagittal reference (MSR) plane. The CBCT frontal cephalograms were generated using the orthogonal Raycast method (group CT(raycast)), the orthogonal maximum intensity projection (MIP) method (group CT(MIP)) after the head reorientation according to the reference planes, and the generator tool provided by the employed 3-dimensional (3D) imaging software (group CT(generator)), respectively. The differences between the CBCT-generated frontal cephalograms and conventional PA cephalograms (group PA(ceph)) were compared by paired t-test (p<0.05).

RESULTS

The significant differences were shown in two measurements for group CT(raycast), in 12 measurements for group CT(MIP), and in eight measurements for group CT(generator). It was confirmed that the CBCT frontal cephalograms, generated by means of the Raycast method (Group CT(raycast)), were more comparable to the conventional PA cephalograms in their measurements than were the others (Groups CT(MIP), CT(generator)).

CONCLUSION

This study may well suggest that frontal cephalograms derived by 3D CBCT reorientation can be effectively employed in clinical applications.

Evaluating craniofacial asymmetry with digital cephalometric images and cone-beam computed tomography

INTRODUCTION

The aim of this study was to evaluate craniofacial asymmetry by using 2-dimensional (2D) posteroanterior cephalometric images, 3-dimensional cone-beam computed tomography (CBCT), and physical measurements (gold standard).

METHODS

Ten dry human skulls were assessed, and radiopaque markers were placed on 17 skeletal landmarks. Twenty linear measurements were taken on each side to compare the right and left sides and to compare these measurements with the physical measurements made with a digital caliper. To acquire the 2D posteroanterior radiographs, an Extraoral Phosphor Storage Plate (Air Techniques, Chicago, Ill) was used as the image receptor with a Eureka x-ray-Duocon Machlett unit (Machlett Laboratores, Chicago, Ill). Three-dimensional imaging data were acquired from a CB MercuRay (Hitachi Medical, Tokyo, Japan).

RESULTS

On average, the right side was larger than the left for most of the 20 distances evaluated in the digital 2D and the CBCT images, and there was poor agreement between the digital 2D images and the physical measurements (kappa = 0.0609) and almost perfect agreement (kappa = 0.92) between the CBCT and physical measurements when individual measurements were considered.

CONCLUSIONS

Human skulls, with no apparent asymmetry, had some differences between the right and left sides, with dominance for the right side but with no clinical significance. CBCT can better evaluate craniofacial morphology when compared with digital 2D images.

Cephalometric measurements from 3D reconstructed images compared with conventional 2D images

OBJECTIVE

To assess whether the values of different measurements taken on three-dimensional (3D) reconstructions from cone-beam computed tomography (CBCT) are comparable with those taken on two-dimensional (2D) images from conventional lateral cephalometric radiographs (LCRs) and to examine if there are differences between the different types of CBCT software when taking those measurements.

MATERIAL AND METHODS

Eight patients were selected who had both an LRC and a CBCT. The 3D reconstructions of each patient in the CBCT were evaluated using two different software packages, NemoCeph 3D and InVivo5. An observer took 10 angular and 3 linear measurements on each of the three types of record on two different occasions.

RESULTS

Intraobserver reliability was high except for the mandibular plane and facial cone (from the LCR), the Na-Ans distance (using NemoCeph 3D), and facial cone and the Ans-Me distance (using InVivo5). No statistically significant differences were found for the angular and linear measurements between the LCRs and the CBCTs for any measurement, and the correlation levels were high for all measurements.

CONCLUSION

No statistically significant differences were found between the angular and linear measurements taken with the LCR and those taken with the CBCT. Neither were there any statistically significant differences between the angular or linear measurements using the two CBCT software packages.

Measurements on 3D models of human skulls derived from two different cone beam CT scanners

The aims of this study were to compare measurements on three-dimensional (3D) models of human skulls derived from two different cone beam CT scanners (CBCT) and to evaluate if the used hardware can influence the performed measurements. CBCT scans of 40 dry human skulls with both the i-CAT and the Iluma cone beam CT scanners were made. From the CBCT scans, 3D models were constructed. One operator identified 19 landmarks five times on both types of 3D models with a time interval of 1 week. Intra-observer reliability was high for most measurements. There was a statistically significant and clinically relevant difference for some measurements between constructed 3D models of the same skull from the two different CBCT devices. Used hardware for scanning might influence the measurements performed. This means that care should be taken when interpreting measurements made on CBCT 3D models derived from different CBCT devices.