Three-dimensional maxillary and mandibular regional superimposition using cone beam computed tomography: a validation study

Hard and soft tissue alterations using dual-zone concept versus connective tissue graft at maxillary immediate implant placement: A 1-year randomized clinical and volumetric trial

OBJECTIVES

To evaluate the esthetic outcome, as well as clinical, radiographic, and volumetric tissue alterations 1 year after immediate implant placement (IIP) with connective tissue grafting (CTG) versus dual-zone concept (DZ) at sites with thin labial bone in the esthetic zone.

MATERIALS AND METHODS

This randomized clinical trial included 30 patients treated with IIP simultaneous with either CTG or DZ (n = 15 each). Pink esthetic score (PES) was assessed 6 months after crown placement as the primary outcome. Amount of bone labial to the implant, labio-palatal ridge reduction, and crestal bone changes were measured via CBCT after 1 year. Volumetric analysis of linear labial soft tissue contour, interdental, and mid-facial soft tissue level changes, and total volume loss (mm3) were measured after 1 year.

RESULTS

Similar PES was observed in the CTG (12.53 ± 1.13) and DZ (12.13 ± 1.55) groups, with no significant difference (p = 0.42). Likewise, there were no statistically significant differences found between the two groups in labio-palatal bone reduction (mm&%), interdental papillae, and mid-facial gingival levels (p > 0.05). However, the mean vertical crestal bone changes in the CTG and DZ groups were -1.1 ± 0.6 mm and 0.2 ± 1.0 mm, respectively, with a statistically significant difference (p = 0.0002). Moreover, CTG revealed less linear and total volume (mm3) loss in the labial soft tissue which was statistically significant compared to DZ (p = 0.007).

CONCLUSION

Both groups demonstrated the same PES, nevertheless, volumetric analysis revealed twice total labial volume loss in DZ compared to CTG. It might be concluded that the use of CTG with IIP caused less horizontal reduction in the supra-implant complex compared to the DZ.

Validation of a fully automatic three-dimensional assessment of orthognathic surgery

The aim of the present study was to propose and validate FAST3D: a fully automatic three-dimensional (3D) assessment of the surgical accuracy and the long-term skeletal stability of orthognathic surgery. To validate FAST3D, the agreement between FAST3D and a validated state-of-the-art semi-automatic method was calculated by intra-class correlation coefficients (ICC) at a 95 % confidence interval. A one-sided hypothesis test was performed to evaluate whether the absolute discrepancy between the measurements produced by the two methods was statistically significantly below a clinically relevant error margin of 0.5 mm. Ten subjects (six male, four female; mean age 24.4 years), class II and III, who underwent a combined three-piece Le Fort I osteotomy, bilateral sagittal split osteotomy and genioplasty, were included in the validation study. The agreement between the two methods was excellent for all measurements, ICC range (0.85-1.00), and fair for the rotational stability of the chin, ICC = 0.54. The absolute discrepancy for all measurements was statistically significantly lower than the clinical relevant error margin (p < 0.008). Within the limitations of the present validation study, FAST3D demonstrated to be reliable and may be adopted whenever appropriate in order to reduce the work load of the medical staff.

Maxillary cortical bone remodeling characteristics in extraction patients: A cone-beam computed tomography study

INTRODUCTION

This study aimed to evaluate labial and palatal cortical bone remodeling (BR) characteristics and related aspects of maxillary incisors after retraction, as these aspects are still controversial among orthodontists.

METHODS

Cortical BR and incisor movement of 44 patients (aged 26.18 ± 4.71 years) who underwent maxillary first premolar extraction and incisor retraction were analyzed using superimposed cone-beam computed tomography images. Labial BR/tooth movement (BT) ratios at the crestal, midroot (S2), and apical (S3) levels were compared using the Friedman test and pairwise comparisons. Multivariate linear regressions were used to explore the relationships between the labial BT ratio and several factors, including age, ANB angle, mandibular plane angle, and incisor movement patterns. According to the type of palatal cortical BR observed, the patients were divided into 3 groups: type I (no BR without root penetration of the original palatal border [RPB]), type II (BR with RPB), and type III (no BR with RPB). Student's t test was used to compare the type II and III groups.

RESULTS

The mean labial BT ratios at all levels were <1.00 (0.68-0.89). This value at the S3 level was significantly smaller than that at the crestal and S2 levels (P <0.01). Multivariate linear regression indicated that the tooth movement pattern negatively correlates with the BT ratio at S2 and S3 levels (P <0.01). Type I was noted in 40.9% of the patients, and similar proportions exhibited type II (29.5%, 25.0%) or type III remodeling (29.5%, 34.1%). The retraction distance of the incisors in type III patients was significantly larger than in type II patients (P <0.05).

CONCLUSIONS

The amount of cortical BR secondary to maxillary incisor retraction is less than the tooth movement. Bodily retraction may lead to lower labial BT ratios at the S3 and S2 levels. Roots penetrating the original border of the cortical plate are necessary for palatal cortical BR initiation.

An application framework of 3D assessment image registration accuracy and untouched surface area in canal instrumentation laboratory research with micro-computed tomography

OBJECTIVES

The purpose of this study was to develop a customized framework for evaluating the registration accuracy of four registration techniques and measuring the untouched surface area of canal instrumentation by visually inspecting and calculating the overlapping area of the surfaces.

METHODS

Twenty-one mandibular incisors were scanned by micro-computed tomography before and after instrumentation. Elastix registration, surface registration, manual registration, and DataViewer registration techniques were used to align the pre- and post-operative datasets. The customized MeVisLab framework was created to investigate the registration accuracy by visual inspection and calculating overlapping areas. The canal surfaces were imported into the same framework to measure the untouched surface area and the consistence test was validated. The correlation between registration accuracy and untouched surface area was analyzed.

RESULTS

There is a statistically significant difference between manual registration and automatic registration (P < 0.05). There is no statistical difference between the two untouched surface measure methods (P > 0.05). The partial correlation coefficients for the untouched surface area and registration accuracy were 0.45 (P < 0.05).

CONCLUSIONS

This application framework based on free customizable software, allows a new method to measure registration accuracy and untouched surface area in an efficient and sensitive way. The application of a precise registration method would improve the quality of micro-CT canal instrumentation studies.

CLINICAL RELEVANCE

This study developed a customized framework based on free software for evaluating the registration accuracy of different registration techniques and measuring the untouched surface area of canal instrumentation could help researchers to improve the quality of micro-CT studies of canal instrumentation.

Bone dimensional changes after flapless immediate implant placement with and without bone grafting: Randomized clinical trial

INTRODUCTION

Immediate implant in postextraction sockets requires managing the postextraction alveolar resorption. This randomized clinical trial examined vertical and horizontal changes 1-year following flapless immediate implant with and without xenograft at sites with thin labial plate.

METHODS

Forty patients with hopeless teeth in maxillary esthetic zone were randomly assigned to receiving either one immediate implant without bone graft (control) or with bone graft (intervention). Cone beam computed tomography (CBCT) scans were obtained pre-extraction and 1-year postoperatively to measure thickness and dimensional changes of the labial bone.

RESULTS

Cone beam computed tomography measurements revealed that a xenograft, when compared to no xenograft, led to 0.2 mm increased fill of the horizontal gap (95% confidence interval (CI): -1.1, 0.7). In both groups, there was a significant reduction in the labio-palatal bone width after 1 year compared to baseline (P ≤ 0.05). There was no significant difference (P > 0.05) between the xenograft when compared to no xenograft regarding the labio-palatal bone collapse % at 0 mm (-0.2, 95% CI: -4.8, 4.5) and 2 mm apical to the labial crest (1.9, 95% CI: -1.8, 5.6). While at 5 mm the ridge was significantly reduced (P ≤ 0.05) in the no xenograft when compared to xenograft (4.5, 95% CI: 0.7, 8.2). The xenograft when compared to no xenograft, led to 1.1 mm less vertical bone changes (95% CI: 0.4, 1.9). Both groups revealed significant positive correlation between labio-palatal socket dimension and bone formed labial to the implant (P ≤ 0.05). [Correction added on 7 February 2023, after first online publication: In the 8th line of this section, the word "collapse" was changed to "ridge" in this version.] CONCLUSION: This investigation suggested that immediate implants with or without grafting the labial gap preserved alveolar bone dimension and that bone formation labial to the implant was related to initial labio-palatal socket dimension.

Comparison of two 3-dimensional user-friendly voxel-based maxillary and 2-dimensional superimposition methods

INTRODUCTION

Cephalometric superimpositions have many uses in orthodontics, including growth evaluation and outcome assessment. However, 2-dimensional (2D) cephalograms can be distorted and yield incomplete 2D data. Cone-beam computed tomography (CBCT) imaging provides a 3-dimensional (3D), undistorted, and more complete patient analysis. CBCT imaging provides many unique advantages to the orthodontic practice and can influence how treatment outcomes are assessed. This study aimed to investigate the validity of 3D maxillary voxel-based superimpositions compared with the 2D method recommended by the American Board of Orthodontists.

METHODS

This retrospective study included pretreatment and posttreatment CBCT images of 30 adolescent patients. The images were superimposed using the 3D voxel-based tools in Dolphin Imaging software (Dolphin Imaging and Management Solutions, Chatsworth, Calif). Two different 3D anatomic registration areas (3DA-3DB) were tested for the validity and reproducibility of the 3D maxillary superimpositions as compared with the 2D method. Linear and angular measurements were used to evaluate the dental changes of the maxillary right central incisor and first molar. Data distribution was normal by the Shapiro-Wilk W test. A mixed model analysis of variance test was done to compare the 3 superimposition types within each subject, followed by pairwise Tukey-Kramer comparisons when indicated.

RESULTS

After applying the Benjamini-Hochberg procedure to control the false discovery rate at 0.05 with multiple testing, the U1 vertical difference was statistically significant (P <0.0001) for the superimposition method, though the mean differences were clinically nonsignificant (0.52 mm, 0.76 mm). The U1 angular and U6 vertical differences were not statistically significant for the superimposition method (P = 0.3636 and P = 0.1863, respectively).

CONCLUSIONS

The 3D voxel-based maxillary superimpositions showed similar results to conventional 2D superimpositions recommended by the American Board of Orthodontists.

Changing clear aligners every 10 days or 14 days ? A randomised controlled trial

Objectives:

To compare 10-day and 14-day change regimens to achieve orthodontic tooth movement (OTM) in patients wearing clear aligners and to determine their subsequent pain perception.

Material and methods:

A total of 175 clear aligner patients were assessed for eligibility. Seventy-two patients were randomly assigned to a 10-day group (N = 36) and a 14-day group (N = 36) and were instructed to change the appliances every 10 or 14 days, respectively. OTM efficacy and OTM variation between the actual and predicted OTM digital models measured by shell-to-shell deviation, as well as pain perception determined by a visual analog scale (VAS), were assessed at T0 (baseline, before the placement of the aligners), T1 (stage 8, after completion of aligners #8), and T2 (stage 16, after completion of aligners #16).

Results:

The 10-day and 14-day groups showed similar OTM efficacy at both T1 and T2 for all types of tooth movements (p > 0.09 for all) and similar OTM shell-to-shell deviation at T1 (p = 0.06) and T2 (p = 0.22). The two groups also had similar VAS scores of pain perception throughout the study (p > 0.05 for all).

Conclusion:

The 10-day and 14-day groups showed similar tooth movement and pain perception, suggesting that the clear aligners may be changed every 10 days without a significant compromise in the clinical efficacy of OTM and patient comfort.

Trial registration:

ChiCTR, ChiCTR-IOR-15007532. Registered 17 November 2015, https://www.chictr.org.cn/showproj.aspx?proj=12500

Pilot study of factors contributing to canine impaction after secondary alveolar bone grafting in unilateral cleft lip and palate patients

Alveolar bone grafting (ABG) is broadly performed for cleft lip and palate patients. The rate of canine impaction post-ABG is much higher than the prevalence of canine impaction in non-cleft patients. This pilot study was designed to investigate factors involved in canine eruption failure after ABG and to predict the possibility of canine impaction in unilateral cleft lip and palate (UCLP) patients. This retrospective observational study examined 45 patients with UCLP (mean age 7.9 years) classified into an impacted group (n = 9) and a spontaneously erupted group (n = 36). From 3D images, we measured lateral incisor presence or absence, lateral incisor position on the cleft side, canine position, movement change, cleft volume, and canine and first premolar overlap-area. Multivariate logistic regression analysis using independent variables indicated significant differences in results, selecting highly relevant items. Multivariate analysis indicated a significant association between the overlap-area between the canine and the first premolar at pre-ABG (p = 0.038) and the distance between the cleft side cusp tips of canine and the lateral cleft margin of pre-ABG (p = 0.005). Results suggest that canine impaction is predictable at an early stage in pre-ABG and show the possibility of comprehensive diagnosis of canine impaction using computed tomography.

Computed tomography imaging superimposition protocols to assess outcomes in orthognathic surgery: a systematic review with comprehensive recommendations

OBJECTIVES

A systematic review was performed to analyze the current evidence on three-dimensional (3D) computed tomography (CT) superimposition protocols used to assess dentomaxillofacial changes after orthognathic and orthofacial surgery. Accuracy, reproducibility, and efficiency were evaluated.

METHODS

The search was divided into Main Search (PubMed, EMBASE, Cochrane Library, LILACS, and SciELO), Grey Literature search (Google Scholar and Open Grey), and Manual search. Thirteen studies were included. Of these, 10 reported data on accuracy, 10 on reproducibility and five on efficiency. Seven proposed or evaluated methods of voxel-based superimposition, three focused on the surface-based technique, one compared surface- and voxel-based superimposition protocols, one used the maximum mutual information algorithm, and one described a landmark-based superimposition method. Cone-beam computed tomography (CBCT) was the most common imaging technique, being used in 10 studies.

RESULTS

The accuracy of most methods was high, showing mean differences smaller than voxels' dimensions, ranging between 0.05 and 1.76 mm for translational accuracy, and 0.10-1.09° for rotational accuracy. The overall reproducibility was considered good as demonstrated by the small mean error (range: 0.01-0.26 mm) and high correlation coefficients (range: 0.53-1.00). Timing to complete virtual superimposition techniques ranged between a few seconds up to 40 min.

CONCLUSIONS

Voxel-based superimposition protocols presented the highest accuracy and reproducibility. Moreover, superimposition protocols that used automated processes and involved only one software were the most efficient.

A semi-automatic approach for longitudinal 3D upper airway analysis using voxel-based registration

OBJECTIVES

To propose and validate a reliable semi-automatic approach for three-dimensional (3D) analysis of the upper airway (UA) based on voxel-based registration (VBR).

METHODS

Post-operative cone beam computed tomography (CBCT) scans of 10 orthognathic surgery patients were superimposed to the pre-operative CBCT scans by VBR using the anterior cranial base as reference. Anatomic landmarks were used to automatically cut the UA and calculate volumes and cross-sectional areas (CSA). The 3D analysis was performed by two observers twice, at an interval of two weeks. Intraclass correlations and Bland-Altman plots were used to quantify the measurement error and reliability of the method. The relative Dahlberg error was calculated and compared with a similar method based on landmark re-identification and manual measurements.

RESULTS

Intraclass correlation coefficient (ICC) showed excellent intra- and inter-observer reliability (ICC ≥ 0.995). Bland-Altman plots showed good observer agreement, low bias and no systematic errors. The relative Dahlberg error ranged between 0.51 and 4.30% for volume and 0.24 and 2.90% for CSA. This was lower when compared with a similar, manual method. Voxel-based registration introduced 0.05-1.44% method error.

CONCLUSIONS

The proposed method was shown to have excellent reliability and high observer agreement. The method is feasible for longitudinal clinical trials on large cohorts due to being semi-automatic.

Comparison of surface- and voxel-based registration on the mandibular ramus for long-term three-dimensional assessment of condylar remodelling following orthognathic surgery

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.

Evaluating the Relationship between Mandibular Third Molar and Mandibular Canal with Semiautomatic Segmentation: A Pilot Study on CBCT Datasets

Inferior alveolar nerve injury is the main complication in mandibular third molar surgery. In this context, cone-beam computed tomography (CBCT) has become of crucial importance in evaluating the relationship between mandibular third molar and inferior alveolar nerve. Due to the growing interest in preoperative planning in oral surgery, several post-processing techniques have been implemented to obtain three-dimensional reconstructions of a volume of interest. In the present study, segmentation techniques were retrospectively applied to CBCT images in order to evaluate whether post-processing could offer better visualization of the structures of interest. Forty CBCT examinations performed for inferior third molar impaction were analyzed. Segmentation and volumetric reconstructions were performed. A dataset composed of multiplanar reconstructions for each study case, including segmented images, was submitted for evaluation to two oral surgeons, two general practitioners and four residents in oral surgery. The visualization of root morphology, canal course, and the relationship with mandibular cortical bone on both native CBCT and segmented images were assessed. Inter-rater agreement showed values of intraclass correlation coefficient (ICC) above 0.8 for all the examined parameters. Oral surgeons presented higher ICC values (p < 0.05). Segmented images can improve preoperative evaluation of the third molar and its relationship with the surrounding anatomical structures compared to native CBCT images. Further evaluation is needed to validate these preliminary results.

Navigation-assisted maxillofacial reconstruction: accuracy and predictability

The aim of this study was to evaluate the accuracy of navigation-assisted maxillofacial reconstruction and to identify the predictors of the clinical outcomes. A total of 112 patients who underwent navigation-assisted maxillofacial reconstruction with free flaps between 2014 and 2019, performed by a single surgical team, were assessed. Accuracy was evaluated by superimposing the postoperative computed tomography data with the preoperative virtual surgical plan. Predictors of the clinical outcomes affecting the accuracy were identified and analysed. The mean deviation and root mean square (RMS) estimate of the orbital, maxillary, and mandibular reconstructions were 0.88 ± 3.25 mm and 3.38 ± 0.73 mm, 0.77 ± 3.44 mm and 3.69 ± 0.82 mm, and 1.07 ± 4.16 mm and 4.67 ± 3.95 mm, respectively (P < 0.05). There was no significant difference in orbital volume or projection between the preoperative, postoperative, and healthy orbits (P = 0.093 and P = 0.225, respectively). Multivariate linear regression analysis confirmed significant associations between the accuracy of navigation-assisted mandibular reconstruction and preservation of the condyle, type of reconstruction, type of osteosynthesis plate, and number of bony segments. Navigation-assisted midface reconstruction yielded a higher level of accuracy in the final surgical outcome when compared to mandibular reconstruction. Computer-assisted techniques and intraoperative navigation can be an alternative or adjunct to current surgical techniques to improve the final surgical outcome, especially in more complex maxillofacial reconstructions.

Virtual Analysis of Segmental Bimaxillary Surgery: A Validation Study

PURPOSE

Three-dimensional (3D) assessment of orthognathic surgery is often time consuming, relies on manual re-identification of anatomical landmarks or is limited to non-segmental osteotomies. The purpose of the present study was to propose and validate an automated approach for 3D assessment of the accuracy and postoperative outcome of segmental bimaxillary surgery.

METHODS

A semi-automatic approach was developed and validated for virtual surgical analysis (VSA) of segmental bimaxillary surgery using a pair of pre- and postoperative (2 weeks) cone-beam computerized tomography (CBCT) scans. The output of the VSA, the accuracy of the surgical outcome, was calculated as 3D translational and rotational differences between the planned and postoperative movements of the individual bone segments. To evaluate the reliability of the proposed VSA, intra-class correlation coefficients (ICC) were calculated at a 95% confidence interval on measurements of 2 observers. The VSA was deemed reliable if the ICC was excellent (> 0.80) and the absolute difference of the repeated intra- and inter-observer translational and rotational measurements were significantly lower (p < 0.05) than a hypothesized clinical relevant threshold of 1 voxel (0.45 mm) and 1 degree, respectively.

RESULTS

A total of 10 subjects (6 male; 4 women; mean age 24.4 years) with skeletal class 2 and 3, who underwent segmental bimaxillary surgery, 3-piece Le Fort I, bilateral sagittal split osteotomy and genioplasty, were recruited. The intra- and inter-observer reliability was excellent, ICC range [0.96 - 1.00]. The range of the mean absolute difference of the repeated intra- and inter-observer translational and rotational measurements were [0.07 mm (0.05) - 0.20 mm (0.19)] and [0.11˚ (0.08) - 0.63˚ (0.42)], respectively. This was significantly lower than the hypothesized clinical relevant thresholds (P < .001).

CONCLUSION

The validation showed that the VSA has excellent reliability for quantitative assessment of the postoperative outcome and accuracy of segmental bimaxillary surgery.

A comparison of voxel- and surface-based cone-beam computed tomography mandibular superimposition in adult orthodontic patients

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 superimpositions were performed using the mandibular basal bone as a reference. The accuracy of the two methods was evaluated using the absolute mean distance measured. The time that was required to perform the measurements using these methods was also compared. Statistical differences were determined using paired t-tests, and inter-observer reliability was assessed by intraclass correlation coefficients (ICCs).

RESULTS

The absolute mean distance on seven mandible surface areas between voxel- and surface-based registrations was similar but not significantly different. ICC values of the surface-based registration were 0.918 to 0.990, which were slightly lower than those of voxel-based registration that ranged from 0.984 to 0.996. The time required for voxel-based registration and surface-based registration was 44.6 ± 2.5 s and 252.3 ± 7.1 s, respectively.

CONCLUSIONS

Both methods are accurate and reliable and not significantly different from each other. However, voxel-based registration is more efficient than surface-based registration for CBCT mandibular superimposition.

The Evolution of the Cephalometric Superimposition Techniques from the Beginning to the Digital Era: A Brief Descriptive Review

Superimposition of craniofacial structures from radiographic examination has been always used for assessing changes in the maxilla-mandibular complexes, especially for the evaluation of potential changes occurring during growth as well as after orthodontic treatment and/or maxillofacial surgery. However, the availability of cone beam computed tomography (CBCT) and the recent advancement in 3D imaging have allowed the development of specific techniques for the registration and superimposition of virtual three-dimensional anatomical structures, improving the diagnosis and treatment plan strategies. In the present paper, it will be discussed the evolution of superimposition techniques from the beginning (2D) to the newest 3D approach, describing the most used methods and their main advantages and disadvantages, focusing primarily on accuracy and reproducibility of each technique.

Voxel-based superimposition of Cone Beam CT scans for orthodontic and craniofacial follow-up: Overview and clinical implementation

INTRODUCTION

The increasing use of three-dimensional (3D) imaging in orthodontics has led to the development of 3D superimposition techniques. These techniques use stable anatomic structures as references in order to compare Cone Beam CT (CBCT) scans of the same subject at different time-points. Three methods have been described in the literature: landmark-based, surface-based and voxel-based 3D superimpositions.

OBJECTIVE

This article focuses on the voxel-based approach, which is the most described and the only one that can be fully automatized. The aim of this paper is to offer clinicians a practical tutorial on craniofacial voxel-based 3D superimposition.

MATERIAL AND METHODS

We provide an updated overview of the available implementation methods, describing their methodology, validations, main steps, advantages and drawbacks. The historical open-source method is the most widespread for research purposes, but takes around three hours to achieve for an experienced operator. Several commercially-available software perform superimpositions in a few minutes.

RESULTS

We used two of the available methods to conduct the superimposition process with three representative clinical cases in order to illustrate the different types of results that can be obtained.

CONCLUSIONS

Commercially-available software provide user-friendly and fully automatized superimposition methods, allowing clinicians to perform it easily and helping to reduce human error in image analysis. Still, quantitative evaluation of the results remains the main challenge of this technique.

Micro-osteoperforation effectiveness on tooth movement rate and impact on oral health related quality of life

OBJECTIVES

To investigate the effect of micro-osteoperforation (MOP) on the rate of tooth movement (RTM), space closure duration, and oral health-related quality of life (OHRQoL) during completion of anterior retraction in patients undergoing combined orthodontic-surgical treatment after premolar extraction and decompensation with sliding mechanics.

MATERIALS AND METHODS

Twenty-four participants with indications for premolar extractions were randomly allocated to treatment with conventional sliding mechanics (control group; CG) or with to treatment in which three MOPs were performed every activation (experimental group; EG). Dental impressions were taken monthly until space closure was completed and dental casts were converted to three-dimensional models. After the anterior retraction procedure, Oral Health Impact Profile (OHIP-14) questionnaires were filled out at 4 and 72 hours.

RESULTS

Eighteen patients (7 men and 11 women) remained in the trial until space closure was completed (mean follow-up period = 247 days). For full space closure RTM, no significant difference (P = .492) was found between groups (0.614 mm/month for the CG; 0.672 mm/month for the EG). The RTM for different time points, groups, time frames and their interaction were statistically different (P < .05). In multiple correlation analysis, the RTM significantly decreased over time for both groups (P < .05). The OHRQoL scores were significantly higher (worse) for the EG. The psychological, physical and social disabilities, and handicap domains displayed significant differences between the two groups.

CONCLUSION

Use of MOPs did not change the full space closure RTM, while it had a negative impact on OHRQoL.

Accuracy and reliability of voxel-based dentoalveolar registration (VDAR) in orthognathic surgical patients: a pilot study with two years' follow-up

The purpose of this study was to validate the applicability of using maxillary voxel-based dentoalveolar registration (VDAR) at long-term follow up in orthognathic surgical patients. A retrospective sample of 25 patients (skeletal class II or III) who underwent bimaxillary orthognathic surgery was recruited and divided into two groups. Group A included 15 patients (seven females, eight males, mean (SD) age 25.8 (14.4) years) with unrestored dentition and group B involved 10 patients (five females, five males, mean (SD) age: 26.2 (11.9) years) with dental restorative treatment. Postoperative cone-beam computed tomography (CBCT) scans were acquired at four time-points, one to six weeks (T1), six months (T2), one year (T3) and two years (T4). Voxel- based registration was applied using the cranial base and then complete dental segment with part of the alveolar bone at T1-T2, T1-T3 and T1-T4 time-intervals. The translational and rotational accuracy and reproducibility of the registered maxillary segment was evaluated at these three intervals by analysing the transformation matrix using singular value decomposition. All translational and rotational measurements showed excellent reliability in both groups without any significant difference. The combined translational and rotational difference was found to be within the clinically acceptable range of 2mm and 4°. The VDAR was found to be accurate and reliable to be utilised for a long-term skeletal follow-up in orthognathic surgical patients.

Assessment of methods used for 3-dimensional superimposition of craniofacial skeletal structures: a systematic review

Background

So far, several techniques have been recommended for the assessment of craniofacial changes through skeletal tissue superimposition, but the evidence that supports them remains unexplored. The purpose of the present study is to assess the available literature on skeletal-tissue superimpositions of serial craniofacial CT or CBCT images used to detect morphological changes.

Materials and Methods

Medline (via Pubmed), EMBASE, Google Scholar, Cochrane Library, Open Grey and Grey Literature Report were searched (last search: 17.11.2019) using specific terms that fulfilled the requirements of each database in the context of the study aim. Hand searches were also performed. The outcomes of interest were the accuracy, precision, or agreement between skeletal-tissue superimposition techniques to assess changes in the morphology of craniofacial structures. Studies of any design with sample size ≥3 were assessed by two authors independently. The study protocol was registered in PROSPERO (ID: CRD42019143356).

Results

Out of 832 studies, fifteen met the eligibility criteria. From the 15 included studies, 12 have shown high total risk of bias, one low risk of bias, and two studies have shown unclear risk of bias. Thirteen out of the 15 studies showed high applicability concerns, two unclear and no study had low applicability concerns. There was high heterogeneity among studies regarding the type of participants, sample size, growth status, machines, acquisition parameters, superimposition techniques, assessment techniques and outcomes measured. Fourteen of them were performed on Cone Beam Computed Tomography (CBCT) and one on Computed Tomography (CT) derived 3D models. Most of the studies (eleven) used voxel-based registration, one landmark-based registration and three studies compared different registration techniques, which include the surface-based registration. Concerning the area of interest, nine studies focused on the anterior cranial base and certain facial structures, four on maxillary structures and four on mandibular structures. Non-growing participants were included in six studies, growing in eight, whereas one study had both.

Conclusion

Most of the available studies had methodological shortcomings and high applicability concerns. At the moment, certain voxel-based and surface-based superimpositions seem to work properly and to be superior to landmark-based superimposition. However, further research in the field is required to develop and properly validate these techniques on different samples, through high quality studies with low applicability concerns.

kVp, mA, and voxel size effect on 3D voxel-based superimposition

OBJECTIVES

To evaluate the effect of changing kVp, mA, and voxel size on the accuracy of voxel-based superimposition on the anterior cranial base.

MATERIALS AND METHODS

Cone beam computed tomography (CBCT) scans were taken on a phantom skull using different kVp, mA, and voxel size combinations. CBCT scans were superimposed using commercially available software. Two separate open-source software programs were used to generate a three-dimensional (3D) color map objective assessment of the differences in seven different regions: Nasion, Point A, Zygomatic (right and left), Point B, and Gonial (right and left). Each region had around 200 points that were used to calculate the mean differences between the superimpositions.

RESULTS

Intraclass correlation showed excellent reliability (0.95). Lowering the kVp made the biggest difference, showing an average discrepancy of 0.7 ± 0.3 mm, and a high mean of 1.4 ± 0.3 in the Right Gonial region. Lowering the mA showed less of a discrepancy, with an average of 0.373 ± 0.2 mm, and the highest discrepancy, also on the Right Gonial Area, of 0.7 ± 0.1 mm. The voxel size had the least impact on the accuracy of registered volumes, with mean discrepancy values of less than 0.2 mm.

CONCLUSIONS

Using different CBCT settings can affect the accuracy of the voxel-based superimposition method. This is particularly the case when using low kVp values, while changes in mA or voxel sizes did not significantly interfere with the superimposition outcome.

In-vitro assessment of the accuracy and reliability of mandibular dental model superimposition based on voxel-based cone-beam computed tomography registration

Objective

This study was performed to evaluate the accuracy and reliability of a newly designed method to achieve mandibular dental model superimposition, using voxel-based cone-beam computed tomography (CBCT) registration.

Methods

Fourteen dry cadaveric mandibles and six teeth extracted from patients with severe periodontitis were used to establish 14 orthodontic tooth-movement models. The protocol consisted of two steps: in the first step, voxel-based CBCT mandible superimposition was performed; the reference comprised the external portion of the symphysis, extending to the first molar. The laser-scanned dental model image was then integrated with the CBCT image to achieve mandibular dental model superimposition. The entire process required approximately 10 minutes. Six landmarks were assigned to the teeth to measure tooth displacement, using tooth displacement on the superimposed laser-scanned mandibles as the reference standard. Accuracy was evaluated by comparing differences in tooth displacement based on the method and the reference standard. Two observers performed superimposition to evaluate reliability.

Results

For three-dimensional tooth displacements, the differences between the method and the reference standard were not significant in the molar, premolar, or incisor groups (p > 0.05). The intraclass correlation coefficients for the inter- and intra-observer reliabilities of all measurements were > 0.92.

Conclusions

Our method of mandibular dental model superimposition based on voxel registration is accurate, reliable, and can be performed within a reasonable period of time in vitro, demonstrating a potential for use in orthodontic patients.

Accuracy between virtual surgical planning and actual outcomes in orthognathic surgery by iterative closest point algorithm and color maps: A retrospective cohort study

BACKGROUND

To evaluate the accuracy between actual outcomes and virtual surgical planning (VSP) in orthognathic surgery regarding the use of three-dimensional (3D) surface models for registration using iterative closest point (ICP) algorithm and generated color maps.

MATERIAL AND METHODS

Construction of planning and postoperative 3D models in STL files format (M0 and M1, respectively) from CBCT of 25 subjects who had been submitted to bimaxillary orthognathic surgery was performed. M0 and M1 were sent to Geomagic software in semi-automatic alignment surface mesh order of M0 and M1 for registration using ICP algorithm to calculate mean deviation (MD, MD+, MD-, SD) and root mean square (RMS - 3D Error). Color maps were generated to assess qualitative congruence between M0 and M1. From deviation analysis, 3D Error was defined as accuracy measurement. To assess the reproducibility, the workflow was performed by two evaluators multiple times. t-tests were used to assess whether all means of MD, MD+, MD-, SD and 3D Error values would be ≤ - 2 mm and ≥ 2 mm.

RESULTS

High intra and inter evaluators correlation were found, supporting the reproducibility of the workflow. t-tests proved that all MDs and 3D Error values were > - 2 mm and < 2 mm.

CONCLUSIONS

3D error mean was within the standards of clinical success lower than 2 mm. ICP algorithm provided a reproducible method of alignment between 3D models and generated color maps to evaluate 3D congruence but did not answer all methodological parameters regarding the assessment of accuracy in orthognathic surgery.

Efficacy of Alveolar Ridge Preservation after Maxillary Molar Extraction in Reducing Crestal Bone Resorption and Sinus Pneumatization: A Multicenter Prospective Case-Control Study

Aim

To evaluate, with three-dimensional analysis, the effectiveness of alveolar ridge preservation (ARP) after maxillary molar extraction in reducing alveolar bone resorption and maxillary sinus pneumatization when compared to unassisted socket healing.

Methods

Patients were included in the study following inclusion criteria and underwent minimally traumatic maxillary molar extraction followed by ARP using synthetic nanohydroxyapatite (Fisiograft Bone, Ghimas, Italy) (test group) or unassisted socket healing (control group). Cone-beam computerized tomographies (CBCT) were performed immediately after tooth extraction (T0) and 6 months postoperatively (T1). CBCTs were superimposed by using a specific software (Amira, Thermo Fisher Scientific, USA) and the following items were analyzed in both groups: (i) postextractive maxillary sinus floor expansion in coronal direction and (ii) postextractive alveolar bone dimensional changes (both vertical and horizontal). All data were tested for normality and equality of variance and subsequently analyzed by independent samples T-test and Mann–Whitney test.

Results

Thirty patients were treated by three centers and twenty-six (test n=13; control n=13) were included in the final analysis. Mean sinus pneumatization at T1 was 0.69±0.48 mm in the test group and 1.04±0.67 mm in the control group (p=0.15). Mean vertical reduction of the alveolar bone at T1 was 1.62±0.49 mm in the test group and 2.01±0.84 mm in the control group (p=0.08). Mean horizontal resorption of crestal bone at T1 was 2.73±1.68 mm in test group and 3.63±2.24 mm in control group (p=0.24).

Conclusions

It could be suggested that ARP performed after maxillary molar extraction may reduce the entity of sinus pneumatization and alveolar bone resorption, compared to unassisted socket healing. This technique could decrease the necessity of advanced regenerative procedures prior to dental implant placement in posterior maxilla.

Computer-guided implant removal: A clinical report

Occasionally, osseointegrated dental implants must be removed because of complications such as malpositioning or screw fracture. This is most often accomplished with a surgical handpiece and trephine. However, a flap is often required to access and visualize the implants. This paper presents a treatment in which computer planning and a 3-dimensional-printed, custom fabricated, surgical guide was used to assist in implant removal. This technique simplified the procedure, allowed conservative removal of peri-implant bone, and permitted subsequent immediate implant replacement.

Replacement of the Distorted Dentition of the Cone-Beam Computed Tomography Scans for Orthognathic Surgery Planning

PURPOSE

Cone-beam computed tomography (CBCT) does not record dental morphology accurately because of the scattering produced by metallic restorations and the reported magnification of the dentition. The aim of this study was the development and evaluation of a new method for the replacement of the distorted dentition of CBCT scans with a 3-dimensional (3D) dental image captured by a digital intraoral camera.

MATERIALS AND METHODS

Six dried skulls with orthodontic brackets fixed on the teeth were used in this study. Three intraoral markers made of dental stone were constructed and attached to orthodontic brackets. The skulls were scanned by CBCT and the occlusal surfaces were captured using the TRIOS 3D intraoral scanner. The digital intraoral scan (IOS) was fused into the CBCT models. This produced a new composite digital model of the skull and the dentition. The skulls were scanned again using the commercially accurate Faro laser arm to produce the 3D model the skull and teeth gold standard for the assessment of the accuracy of the developed method. This was assessed by measuring the distance between the occlusal surfaces of the new composite model and the gold standard 3D laser produced model.

RESULTS

The results showed the errors related to the superimposition of the intraoral image on the CBCT to replace the distorted dentition were 0.11 to 0.20 mm.

CONCLUSION

The results of this novel method suggest that the dentition on the CBCT scan can be accurately replaced with the digital IOS image captured by an intraoral scanner to create a composite model that will improve the accuracy of digital orthognathic surgical planning and the fabrication of the guiding occlusal wafer.

Accuracy and reliability of landmark-based, surface-based and voxel-based 3D cone-beam computed tomography superimposition methods

OBJECTIVES

To evaluate and compare the accuracy and reliability of 3 different methods of three-dimensional cone-beam computed tomography scans (3D CBCTs) superimpositions: landmark-based, surface-based and voxel-based.

MATERIALS AND METHODS

Pre- and post-orthodontic treatment CBCTs (T1 and T2) of 20 subjects with a mean age of 11 years were obtained. Seven points on the zygomatic arch and supraorbital region were selected to perform landmark-based superimposition. Surface-based and voxel-based superimpositions were performed using the anterior cranial base as a reference. Each superimposition method of T1 and T2 scans was repeated twice to assess the reliability. Accuracy of each technique was tested by superimposing duplicated sets of T1 scans. A total of 11 landmarks on the anterior cranial base, maxilla and mandible were located, and deviations of these landmarks on superimposed data were quantified to assess reliability and accuracy of all superimpositions.

RESULTS

There were no significant differences from zero when duplicated sets of T1 scans were superimposed using surface-based and voxel-based methods. Statistical significant differences were detected in several parameters when evaluating the accuracy of the landmark superimposition. Superimposition of T1 and T2 scans for testing the reliability revealed intraclass correlation coefficients greater than 0.90 for all measurements except for ACP-x and PNS-y of landmark-based method as well as ANS-x of voxel-based method.

CONCLUSIONS

Surface-based and voxel-based superimposition methods using the anterior cranial base as a reference structure were accurate and reliable in detecting changes in landmark positions when superimposing. Landmark-based superimposition method was reliable but less accurate than the other methods.

Rapid 3D mandibular superimposition for growing patients

OBJECTIVE

To evaluate the precision and reproducibility of a protocol to perform rapid voxel-based superimposition of the mandible in growing patients using CBCT.

MATERIALS AND METHODS

The sample comprised two cone-beam computed tomography scans taken at least 1 year apart from each of 24 growing patients. Voxel-based superimposition was performed by two examiners independently. The internal part of the symphysis extending to the first molar was used as the reference. The superimposition process took approximately 5 minutes. Once the mandibles were superimposed, surface models were created and root mean square (RMS) changes were obtained by means of iterative closest point. To evaluate precision, differences in three areas were measured between time point 1 (T1) and time point 2 (T2) superimposed. To evaluate reproducibility between different examiners, the distances between T2 superimposed by each operator were measured in five different areas. Descriptive statistics were used to evaluate the precision of the superimposition and the interexaminer reproducibility measurements for each case were reported individually.

RESULTS

The superimposition mean error between T1 and T2 for the right and left sides of the mandible and chin were 0.23 mm, 0.25 mm, and 0.33 mm, respectively. Interexaminer reproducibility error was ≤0.3 mm in 20 of 24 cases for measurements near the registration area. In the ramus area, two cases had errors >1 mm (1 mm-1.3 mm).

CONCLUSION

The rapid superimposition was precise for assessing dentoalveolar changes and structures close to the registration area. However, evaluation of the condyles and ramus area had limitations and needs improvement.

3D Mandibular Superimposition: Comparison of Regions of Reference for Voxel-Based Registration

Introduction

The aim was to evaluate three regions of reference (Björk, Modified Björk and mandibular Body) for mandibular registration testing them in a patients’ CBCT sample.

Methods

Mandibular 3D volumetric label maps were built from CBCTs taken before (T1) and after treatment (T2) in a sample of 16 growing subjects and labeled with eight landmarks. Registrations of T1 and T2 images relative to the different regions of reference were performed, and 3D surface models were generated. Seven mandibular dimensions were measured separately for each time-point (T1 and T2) in relation to a stable reference structure (lingual cortical of symphysis), and the T2-T1 differences were calculated. These differences were compared to differences measured between the superimposed T2 (generated from different regions of reference: Björk, Modified Björk and Mandibular Body) over T1 surface models. ICC and the Bland-Altman method tested the agreement of the changes obtained by nonsuperimposition measurements from the patients’ sample, and changes between the overlapped surfaces after registration using the different regions of reference.

Results

The Björk region of reference (or mask) did work properly only in 2 of 16 patients. Evaluating the two other masks (Modified Björk and Mandibular body) on patients’ scans registration, the concordance and agreement of the changes obtained from superimpositions (registered T2 over T1) compared to results obtained from non superimposed T1 and T2 separately, indicated that Mandibular Body mask displayed more consistent results.

Conclusions

The mandibular body mask (mandible without teeth, alveolar bone, rami and condyles) is a reliable reference for 3D regional registration.