The accuracy of computer-assisted surgical planning in soft tissue prediction following orthognathic surgery

Accuracy of Dolphin Imaging software in predicting soft tissue changes of Class II Division 1 incisor relationship treated by all first premolar extraction compared with post-treatment lateral cephalogram

BACKGROUND

To quantify the accuracy of Dolphin Imaging software in predicting soft tissue changes of Class II Division 1 incisor relationship treated by all first premolar extraction compared with actual changes.

METHODS

Pretreatment and post-treatment lateral cephalograms of 30 young adult subjects (25 females and 5 males; age range of 16 to 21 years) were imported and traced in Dolphin Imaging software (version 11.95). Tracings of actual treatment results and the Dolphin predicted treatment outcome were superimposed to calculate the prediction errors. The mean difference for the Holdaway soft tissue analysis and at each landmark was measured in both the X and Y axes. Paired t test was used to compare the statistical differences in Holdaway soft tissue analysis parameters.

RESULTS

There were significant differences between the predicted and actual values in three parameters of the Holdaway soft tissue analysis (P < 0.05). The overall accuracy of estimation was better in vertical direction than horizontal. Prediction of upper and lower lip landmarks was overestimated horizontally and underestimated vertically, whereas that belonging to chin was underestimated horizontally and overestimated vertically. Soft tissue nasion and soft tissue A-point were most accurately predicted, whereas the least accuracy was found in soft tissue chin region.

CONCLUSIONS

Dolphin Imaging Software (version 11.95) can be accurate enough for use in patient communication and education but should be used with caution. It is most accurate in predicting soft tissue changes in the nasion and A-point regions, but least accurate in chin region.

Prediction accuracy of Dolphin software for soft-tissue profile in Class I patients undergoing fixed orthodontic treatment

BACKGROUND

Simulation and prediction can facilitate the decision between an extraction versus nonextraction treatment plan. This study aimed to assess the accuracy of Dolphin Imaging software in predicting profile changes in class I borderline cases.

METHODS

In this retrospective study, class I borderline patients (i.e., both extraction and nonextraction treatment plans were possible for them) aged 15-35 years were enrolled. All of the cephalometric analyses were done by Dolphin Imaging software, version 11.8 Premium. The initial cephalograms were superimposed on initial photographs. The final values for the 7 angular and linear landmarks of the upper and lower incisors were extracted from post-treatment cephalograms and inserted in the "Goals" tab of the Dolphin Imaging software. Post-treatment images of patients were simulated. Final post-treatment photographs were superimposed on the simulated pictures. The differences between the real and simulated pictures were calculated in relation to the reference lines. The P value was set at 0.05.

RESULTS

A total of 70 patients (36 with tooth extraction, and 34 without tooth extraction) were included. In the extraction group, the horizontal position of both lips was predicted to be significantly more protruded than it actually was, whereas in the nonextraction group, the only difference between the simulated and actual results was that the vertical position of the lower lip, which was simulated as being more inferior than it actually was.

CONCLUSIONS

Despite the statistically significant differences between the real and simulated pictures, the differences were small and clinically insignificant. Prediction via Dolphin Imaging software can be an appropriate guide in extraction-nonextraction borderline cases.

Analysis of facial features and prediction of lip position in skeletal class III malocclusion adult patients undergoing surgical-orthodontic treatment

OBJECTIVES

This study presents a retrospective study aimed to analyze the facial features at each stage of surgical-orthodontic treatment for skeletal class III malocclusion, and predict the changes in the lips after treatment.

MATERIALS AND METHODS

There were 49 skeletal class III malocclusion patients treated with bimaxillary surgery and orthodontic treatment enrolled in this study. Lateral cephalograms were obtained before treatment (T0), 1 month before surgery (T1), 1 month after surgery (T2), and after debonding (T3) for cephalometric measurements. After the measurement of the required variables, paired t-test, Pearson's correlation analysis, and multiple linear regression were performed using SPSS 19.0.

RESULTS

The main factors associated with changes in the upper lip included ΔUIE-V, ΔA-V, ΔU1A-V, and ΔL1A-V, and those associated with changes in the lower lip included ΔLIE-V, ΔL1A-V, ΔB-V, ΔPog-V, and Δfacial angle. The predicted regression equation for the horizontal change in the upper lip was represented as ΔUL-vertical reference line (VRL) = 9.430 + 0.779 (ΔUIE-VRL) - 0.542(VULT) (P < 0.05) with a mean error of 1.04 mm; the corresponding equation for the lower lip was ΔLL-VRL = -1.670 + 0.530 (ΔB-VRL) + 0.360 (Ls-E) + 0.393 (ΔLIE-VRL) (P < 0.05), with a mean error of 1.51 mm.

CONCLUSIONS

This study explored the relationship between orthognathic surgery and changes in the lips and obtained the predictive equations of lip position after treatment by using multiple linear regression, which likely offers a reference for prediction of soft tissue changes before surgical-orthodontic treatment in patients with skeletal class III malocclusion.

CLINICAL RELEVANCE

The findings can help dentists to rapidly predict the lip changes after surgical-orthodontic treatment in patients with skeletal class III malocclusion. The study has been registered with the Chinese Clinical Trial Registration (No: ChiCTR1800017694).

Accuracy of computer-aided prediction in soft tissue changes after orthodontic treatment

INTRODUCTION

An accurate prediction in the soft tissue changes is of great importance for orthodontic treatment planning. Previous studies on the accuracy of the Dolphin visual treatment objective (VTO) in predicting treatment results were mainly focused on orthognathic treatment. The accuracy of Dolphin VTO prediction for orthodontic treatment is, however, poorly understood. The aim of this study was to evaluate the accuracy of Dolphin VTO prediction in soft tissue changes after orthodontic treatment by comparing the changes between predicted and actual values.

METHODS

A total of 157 patients were screened for eligibility, and 34 young adult patients (8 males, 26 females; mean age 24.8 ± 3.9 years) were finally included in the study based on the inclusion and exclusion criteria. The landmarks and parameters of the Holdaway soft tissue analysis were used for the cephalometric analyses. The cephalometric tracings of the actual treatment result and the Dolphin predicted treatment outcome were superimposed to calculate the prediction errors. Paired t test was used to compare the statistical differences between the predicted and actual treatment outcomes of the parameters used in the Holdaway soft tissue analysis.

RESULTS

There were significant differences between the predicted and actual values in parameters of the Holdaway soft tissue analysis (P < 0.05). The prediction of the landmarks in the lips region (ie, subnasale, soft tissue A-point, upper lip, lower lip, and soft tissue B-point) was inclined to be overestimated horizontally and underestimated vertically, whereas the prediction of the landmarks belonging to the chin region (ie, soft tissue pogonion, soft tissue gnathion, and soft tissue menton) was inclined to be underestimated horizontally and overestimated vertically. The most accurate prediction was found in the soft tissue A-point, whereas the least accurate one was found in the soft tissue in the chin region. The prediction was relatively more accurate in the vertical direction than in the horizontal direction.

CONCLUSIONS

The Dolphin VTO prediction in soft tissue changes after the orthodontic treatment in patients with bimaxillary protrusion is the most accurate for the soft tissue A-point and the least accurate for the soft tissue chin region.

Nasolabial Changes Following Double Jaw Surgery

BACKGROUND

This study aimed to analyze 3-dimensional nasolabial soft tissue changes following double jaw surgery with Le Fort I maxillary advancement and relate them to underlying surgical movements.

METHODS

Pre- and post-surgical cone-beam computed tomography images of 37 maxillomandibular surgery patients with ≥2 mm of advancement at A-point were analyzed. Lateral cephalograms were constructed to determine horizontal and vertical surgical movements and 3-dimensional facial images were created from the CBCTs to calculate linear and angular changes.

RESULTS

Alar base width increased 1.9 mm, nasal tip protrusion decreased 0.74 mm, the upper lip flattened 7.71 degree and increased 0.9 mm in length, nasal tip was displaced 2.47 mm superiorly causing an increased concavity of 5.52 degree for the overall dorsal surface and 3.99 degree at the supratip break angle (SBA), nasal tip angle decreased 2.16 degree and nasolabial angle decreased 7.37 degree. Correlations were found between underlying surgical movements and nasal tip protrusion, SBA, nasolabial angle (NLA), and nasal tip elevation (NTE). Multiple linear regression equations were calculated to predict changes in SBA from horizontal change at A-point, NLA from horizontal change at B-point, and NTE from the change at A-point horizontally and U1-tip vertically.

CONCLUSION

Double jaw surgery with maxillary advancement has significant effects on nasolabial anatomy.

3D Soft-Tissue Prediction Methodologies for Orthognathic Surgery—A Literature Review

Three-dimensional technologies have had a wide diffusion in several fields of application throughout the last decades; medicine is no exception and the interest in their introduction in clinical applications has grown with the refinement of such technologies. We focus on the application of 3D methodologies in maxillofacial surgery, where they can give concrete support in surgical planning and in the prediction of involuntary facial soft-tissue changes after planned bony repositioning. The purpose of this literature review is to offer a panorama of the existing prediction methods and software with a comparison of their reliability and to propose a series of still pending issues. Various software are available for surgical planning and for the prediction of tissue displacements, but their reliability is still an unknown variable in respect of the accuracy needed by surgeons. Maxilim, Dolphin and other common planning software provide a realistic result, but with some inaccuracies in specific areas of the face; it also is not totally clear how the prediction is obtained by the software and what is the theoretical model they are based on.

How accurate is the soft tissue prediction of Dolphin Imaging for orthognathic surgery?

PURPOSE

The purpose of this retrospective study is to evaluate the accuracy of soft tissue prediction models with Dolphin Imaging.

MATERIALS AND METHODS

Preoperative and 1-year postoperative Lateral cephalograms (LCG) of patients undergoing Le Fort I, bilateral sagittal split osteotomy (BSSO) or bimaxillary osteotomy (Bimax) between 2006 and 2009 were retrospectively collected. A hard tissue virtual surgery was performed on the preoperative LCG to match the hard tissue of the 1-year postoperative LCG. The soft tissue changes were then modelled by Dolphin Imaging (version 11.5b) and the differences in x- and y-coordinates of 11 hard tissue and 14 soft tissue landmarks between the predicted model and 1-year postoperative LCG were determined. Statistical analyses were performed using a one-tailed, one-sample t-test for both soft- and hard tissue differences, and a Bland-Altman plot for interobserver bias.

RESULTS

A total of 108 patients were included, the mean age was 30 years and 23% were male. The virtual treatment was considered accurate; all hard tissue landmark differences were less than 1mm. The soft tissue model by Dolphin Imaging showed significant differences of more than 2mm for several landmarks, including the vertical positioning of Stomion Inferius (P=0.007), Lower lip (P=0.005) and Pogonion (P=0.03) in the Bimax group and horizontal positioning of Stomion Inferius (P<0.001) in the BSSO group.

CONCLUSIONS

Dolphin Imaging gives reasonable predictions of postoperative outcome. There is, however, room for improvement, especially regarding the vertical prediction in the lower lip region.

Comparison of the Accuracy of Manual and Digital Cephalometric Prediction Methods in Orthognathic Surgical Planning: A Pilot Study

Objective

To compare and evaluate the reliability of manual and digital cephalometric prediction methods in orthognathic surgical planning.

Methods

Ten adults (5 females and 5 males) with skeletal class III malocclusion were included. The mean patient age was 21.97 years. Pre- to postoperative changes were evaluated using paired t-test. Manual surgical predictions made by tracing on acetate paper and digital predictions made using computer software were compared with actual postoperative values using intraclass correlation coefficient and root mean square.

Results

Statistically significant changes were observed in SNA, SNB, ANB, U1i-FH, and Nperp-A following bimaxillary orthognathic surgery (p<0.001). Postoperative changes in Co-A and Nperp-Pg were statistically significant (p<0.05). Comparison of manual and digital surgical predictions with actual postoperative values revealed that overbite and overjet showed the lowest agreements. Manual predictions were less accurate for points that were difficult to distinguish (Co and U6). Skeletal predictions were more accurate than dental predictions.

Conclusion

Parameters with low reproducibility (Co and U6) decrease the reliability of predictions. Dental predictions were inaccurate in both methods due to the effects of intermaxillary elastics, but both methods yielded similar predictions for skeletal parameters. The impact of applying strong elastics for postoperative intermaxillary fixation should be considered when making surgical predictions.

Virtual Planning of a Complex Three-Part Bimaxillary Osteotomy

In maxillofacial surgery, every patient presents special problems requiring careful evaluation. Conventional methods to study the deformities are still reliable, but the advent of tridimensional (3D) imaging, especially computed tomography (CT) scan and laser scanning of casts, created the opportunity to better understanding the skeletal support and the soft tissue structures. Nowadays, virtual technologies are increasingly employed in maxillofacial surgery and demonstrated precision and reliability. However, in complex surgical procedures, these new technologies are still controversial. Especially in the less frequent cases of three-part maxillary surgery, the experience is limited, and scientific literature cannot give a clear support. This paper presents the case of a young patient affected by a complex long face dentofacial deformity treated by a bimaxillary surgery with three-part segmentation of the maxilla. The operator performed the surgical study completely with a virtual workflow. Pre- and postoperative CT scan and optical scanning of plaster models were collected and compared. Every postoperatory maxillary piece was superimposed with the presurgical one, and the differences were examined in a color-coded map. Only mild differences were found near the osteotomy lines, when the bony surface and the teeth demonstrated an excellent coincidence.

Achieved chin position after genioplasty follows the planned horizontal change better than the planned vertical change

PURPOSE

The soft-tissue pogonion closely follows changes of the bony pogonion, but it is unknown how often an augmented bony pogonion reaches the intended position. Here we assessed the agreement between planned surgical changes and achieved results in chin surgery.

MATERIALS AND METHODS

Surgical treatment was planned based on clinical examination, cast model analysis, and cephalometric image analysis. The mobile chin segment was stabilized using one chin plate. Preoperative and postoperative cephalometric X-ray images were digitized, and cephalometric tracing was performed. We calculated and analyzed the changes between the preoperative and postoperative images as well as between planned genioplasty movements and actual surgical changes in the horizontal and vertical directions.

RESULTS

This study included 36 patients. In 34 patients, the absolute mean horizontal difference was less than 2 mm. We found a higher range of absolute error in vertical (0.00-5.60) compared to horizontal (0.01-3.64) movement. There was no significant difference between the mean planned chin movement and the mean achieved position with regard to the horizontal and vertical movement (p = 0.97 and 0.79, respectively).

CONCLUSIONS

The mean values for linear difference in both the horizontal and vertical directions were in line with the acceptable mean of ≤2 mm proposed in the literature.

Cone-beam evaluation of pharyngeal airway space in class I, II, and III patients

OBJECTIVES

The purpose of this study is to make a 3-dimensional (3-D) evaluation of the pharyngeal airway space (PAS) in patients with class I, II, and III malocclusion.

STUDY DESIGN

Sixty patients were evaluated. The patients were divided in 3 groups according to their occlusion classification. The volume and area of PAS were evaluated using the software Dolphin 3-D Imaging in the preoperative period for orthognathic surgery.

RESULTS

PAS volume and area were influenced by different patterns of malocclusion. The mean volume and area for class III patients were statistically bigger than for classes I and II patients (P < .001). There was also a significant difference for volume values between class I and II patients, being the bigger volume for the class I patients (P < .05).

CONCLUSIONS

It was possible to conclude that the class III patients presented a bigger PAS compared with classes I and II patients.

Evaluation of the soft tissue treatment simulation module of a computerized cephalometric program

Objective:

The purpose of this study is to compare the accuracy of the treatment simulation module of Quick Ceph Studio (QCS) program to the actual treatment results in Class II Division 1 patients.

Design:

Retrospective study.

Materials and Methods:

Twenty-six skeletal Class II patients treated with functional appliances were included. T0 and T1 lateral cephalograms were digitized using QCS. Before applying treatment simulation to the digitized cephalograms, the actual T0-T1 difference was calculated for the SNA, SNB, ANB angles, maxillary incisor inclination, and protrusion and mandibular incisor inclination and protrusion values. Next, using the treatment simulation module, the aforementioned values for the T0 cephalograms were manually entered to match the actual T1 values taking into account the T0-T1 differences. Paired sample t-test were applied to determine the difference between actual and treatment simulation measurements.

Results:

No significant differences were found for the anteroposterior location of the landmarks. Upper lip, soft tissue A point, soft tissue pogonion, and soft tissue B point measurements showed statistically significant difference between actual and treatment simulation in the vertical plane.

Conclusion:

Quick Ceph program was reliable in terms of reflecting the sagittal changes that would probably occur with treatment and growth. However, vertical positions of the upper lip, soft tissue pogonion, soft tissue A point, and soft tissue B point were statistically different from actual results.

Comparison of soft-tissue profiles in Le Fort I osteotomy patients with Dolphin and Maxilim softwares

INTRODUCTION

To correct dentofacial deformities, a combination of orthodontic treatment and orthognathic surgery is needed. Prediction software packages are beneficial in treatment planning and achieving improved outcomes, but before using any software, its reliability and reproducibility must be assessed. The aim of this study was to evaluate the accuracy of 2-dimensional Dolphin (version 10; Dolphin Imaging & Management Solutions, Chatsworth, Calif) and 3-dimensional Maxilim (Medicim, Sint-Niklaas, Belgium) softwares in predicting the soft-tissue profiles of patients who had Le Fort I osteotomies.

METHODS

The presurgical and postsurgical cone-beam computed tomography synthesized lateral cephalograms of 13 patients were collected. Using the Dolphin and Maxilim softwares, the postsurgical profiles were predicted. The positions of the soft-tissue landmarks in profile views were compared with landmarks in the postsurgical photographs. The data were analyzed with the coefficient of reliability and paired-sample t tests.

RESULTS

The alpha values of the interclass correlations for each landmark in the x and y planes were between 0.96 and 0.99, except for stomion superior in Maxilim (0.83). The 95% confidence interval and the absolute mean of the error showed that errors in the Dolphin software were greater than those in the Maxilim software, but the differences were not significant (P >0.05), except for soft-tissue A-point. The greatest errors were seen in the chin region. The prediction errors of the nasolabial and mentolabial angles were greater; the prediction error in the Dolphin software was 9°, which has clinical significance.

CONCLUSIONS

The Dolphin and Maxilim softwares are both appropriate for clinical use. Their inaccuracies in the prediction of the chin region should be considered in complicated surgical planning.

Reliability of a novel CBCT-based 3D classification system for maxillary canine impactions in orthodontics: the KPG index

The aim of this study was to evaluate both intra- and interoperator reliability of a radiological three-dimensional classification system (KPG index) for the assessment of degree of difficulty for orthodontic treatment of maxillary canine impactions. Cone beam computed tomography (CBCT) scans of fifty impacted canines, obtained using three different scanners (NewTom, Kodak, and Planmeca), were classified using the KPG index by three independent orthodontists. Measurements were repeated one month later. Based on these two sessions, several recommendations on KPG Index scoring were elaborated. After a joint calibration session, these recommendations were explained to nine orthodontists and the two measurement sessions were repeated. There was a moderate intrarater agreement in the precalibration measurement sessions. After the calibration session, both intra- and interrater agreement were almost perfect. Indexes assessed with Kodak Dental Imaging 3D module software showed a better reliability in z-axis values, whereas indexes assessed with Planmeca Romexis software showed a better reliability in x- and y-axis values. No differences were found between the CBCT scanners used. Taken together, these findings indicate that the application of the instructions elaborated during this study improved KPG index reliability, which was nevertheless variously influenced by the use of different software for images evaluation.

Cephalometric evaluation of the predictability of bimaxillary surgical-orthodontic treatment outcomes in long face pattern patients: a retrospective study

OBJECTIVE: The aim of this study was to compare by means of McNamara as well as Legan and Burstone's cephalometric analyses, both manual and digitized (by Dentofacial Planner Plus and Dolphin Image software) prediction tracings to post-surgical results. METHODS: Pre and post-surgical teleradiographs (6 months) of 25 long face patients subjected to combined orthognathic surgery were selected. Manual and computerized prediction tracings of each patient were performed and cephalometrically compared to post-surgical outcomes. This protocol was repeated in order to evaluate the method error and statistical evaluation was conducted by means of analysis of variance and Tukey's test. RESULTS: A higher frequency of cephalometric variables, which were not statistically different from the actual post-surgical results for the manual method, was observed. It was followed by DFPlus and Dolphin software; in which similar cephalometric values for most variables were observed. CONCLUSION: It was concluded that the manual method seemed more reliable, although the predictability of the evaluated methods (computerized and manual) proved to be reasonably satisfactory and similar.

Rapid prototyping in craniofacial surgery: using a positioning guide after zygomatic osteotomy - A case report

INTRODUCTION

The management of post-traumatic deformity in the midface region poses challenges for the maxillofacial surgeon. Ensuring symmetry after zygomatic osteotomy can be difficult and precise positioning of the osteotomised bony fragments requires careful treatment planning. It may be necessary to use a coronal flap to allow the surgeon to compare the contralateral zygomatic bone to allow symmetrical reduction. The authors present a new technique for the positioning of osteotomised zygomatic bones using a combination of computer assisted surgical simulation and rapid prototyping.

METHOD

A patient presented to our unit with a post-traumatic zygomatic deformity. Using surgical simulation software the displaced zygomatic bone was osteotomised and placed in the idéal position on a three-dimensional computed tomography scan (3D CT). The position was determined by reference to the contralateral zygoma. In addition the repositioning of the soft tissues was simulated. A surgical guide which allowed intraoperative positioning of the osteotomised zygoma was manufactured by a rapid prototyping process. Use of the guide allowed a minimally invasive approach to the affected zygoma. The post-operative results were compared to the predicted outcome.

RESULTS

The post-operative appearance was satisfactory and corresponded well with the predicted result. There was a significant reduction in operative time compared to the previous management of similar cases.

Immediate postoperative outcome of orthognathic surgical planning, and prediction of positional changes in hard and soft tissue, independently of the extent and direction of the surgical corrections required

Our purpose was to evaluate the immediate postoperative outcome of preoperatively planned and predicted positional changes in hard and soft tissue in 100 prospectively and consecutively planned and treated patients; all had various dentofacial deformities that required single or double jaw orthognathic correction using the computerised, cephalometric, orthognathic, surgical planning system (TIOPS). Preoperative cephalograms were analysed and treatment plans and prediction tracings produced by computerised interactive simulation. The planned changes were transferred to models and finally to operation. Five to 6 weeks postoperatively, the changes in profile actually obtained in the hard and soft tissue were cephalometrically assessed. The mean accuracy was relatively high. At the cephalometric reference points where significant differences between planned or predicted, and actually obtained, positional changes in hard and soft tissue were apparent and the inaccuracies were, except for the predicted horizontal position of the lower lip, relatively small. However, the variability of the predicted outcome in individual hard and soft tissues was relatively high. Using the TIOPS planning system with the presently included soft tissue algorithms, the current study shows relatively high mean predictability of the immediately postoperative hard and soft tissue outcome, independent of the extent and direction of required orthognathic correction. Because of the relatively high individual variability, caution is required when presenting the planned and predicted positional changes in the hard and soft tissue preoperatively in individual patients.

Comparison of actual surgical outcomes and 3-dimensional surgical simulations

PURPOSE

The advent of imaging software programs has proved to be useful for diagnosis, treatment planning, and outcome measurement, but precision of 3-dimensional (3D) surgical simulation still needs to be tested. This study was conducted to determine whether the virtual surgery performed on 3D models constructed from cone-beam computed tomography (CBCT) can correctly simulate the actual surgical outcome and to validate the ability of this emerging technology to recreate the orthognathic surgery hard tissue movements in 3 translational and 3 rotational planes of space.

MATERIALS AND METHODS

Construction of pre- and postsurgery 3D models from CBCTs of 14 patients who had combined maxillary advancement and mandibular setback surgery and 6 patients who had 1-piece maxillary advancement surgery was performed. The postsurgery and virtually simulated surgery 3D models were registered at the cranial base to quantify differences between simulated and actual surgery models. Hotelling t tests were used to assess the differences between simulated and actual surgical outcomes.

RESULTS

For all anatomic regions of interest, there was no statistically significant difference between the simulated and the actual surgical models. The right lateral ramus was the only region that showed a statistically significant, but small difference when comparing 2- and 1-jaw surgeries.

CONCLUSIONS

Virtual surgical methods were reliably reproduced. Oral surgery residents could benefit from virtual surgical training. Computer simulation has the potential to increase predictability in the operating room.