A comparison of 3 methods of face-bow transfer recording: implications for orthognathic surgery

Virtual Versus Conventional Planning in Orthognathic Surgery: A Systematic Review and Meta-analysis

Objectives

The purpose of this study was to compare the accuracy of hard tissues movements planned to result of the maxillary and mandibular positions between conventional surgical planning (CSP) and virtual surgical planning (VSP) in patients undergoing orthognathic surgery.

Methods

A systematic electronic search was carried out in six databases and gray literature with no restriction of publication date and language. Clinical observational studies that compared accuracy of maxillary position between CSP and VSP were included. Linear measurements of the mandible in the transverse plane and linear measurements of the maxilla in the vertical, horizontal and transverse planes were considered for analysis, comparing planned to postoperative outcomes of CSP and VSP. Cochrane tool was used to assess bias risk. A meta-analysis was performed to summarize similar results by using the Review Manager 5.3 software. Significance level was set at 5%.

Results

Six studies (2 RCT and 4 retrospective cohorts) were included according to inclusion and eligibility criteria, involving 255 patients. The inter-rater reliability of selection and eligibility was excellent (k = 0.8315 and k = 0.9329, respectively). Two studies presented that VSP seemed to have better results than CSP regarding linear measurements of the mandible in the transverse plane. Results from CSP and VSP were similar in accuracy for hard tissue in vertical plane of maxillary position (I2 = 0%; p = 0.17), although VSP was more accurate in horizontal plane (I2 = 0%; p = 0.02).

Conclusion

VSP presented better accuracy for transverse movements in mandible of asymmetric patients. VSP showed to be more accurate for movements in the horizontal plane, and qualitative analysis seemed to be more effective for transverse movements.

Surgical Accuracy of 3D Virtual Surgery and CAD/CAM-Assisted Orthognathic Surgery for Skeletal Class III Patients

Orthognathic surgery is an effective surgical method to achieve functionality and facial esthetics for mandibular prognathism. If surgery is performed with a conventional method, errors may occur in the surgical preparation process and the surgical procedures, and there is a limitation in that the accuracy of surgery is determined according to the surgeon's experience and tactual sense. However, with the recent development of three-dimensional (3D) virtual planning and CAD/CAM technology, more 3D and predictable surgical planning and more accurate and time-saving surgery have become possible. The purpose of this study is to evaluate the surgical accuracy of 3D Virtual Surgery, CAD/CAM-Assisted Orthognathic surgery for Skeletal Class III Patients. The study included 18 patients who had undergone orthognathic surgery for skeletal class III malocclusion from January 2020 to December 2021. To evaluate the accuracy of the virtual planning, 3D facial cone-beam computed tomography taken immediately after surgery (T1) and virtual surgery data (Tv) were superimposed in each patient. Landmarks were set on each of the maxillary segment, mandibular distal segment, and left and right mandibular proximal segment, and the difference between T1 and Tv was compared 3D on the x , y , and z -axis. (ΔT: T1-Tv). As a result, the average distance between Tv and T1 at each landmark, all landmarks except for the posterior nasal spine of the maxillary segment showed <1 mm. In particular, the differences across the x and z -axis were very small, while the difference across the y -axis tend to be large. The comparison of the position of each segment in virtual surgery and actual surgery was as follows. It can be seen that all segments were located slightly downward, and the medial pole of the mandibular proximal segment was located posterolateral and the lateral pole was located anteromedial after the actual surgery compared with the virtual planning. It means that the proximal segment was slightly rotated, but the difference was within 1 mm, so it can be considered that the surgery was accurate. Base on this study, orthognathic surgery using 3D virtual surgery planning and CAD/CAM technologies was very accurate. By applying these cutting-edge technologies to clinical practice, it was possible not only to increase the predictability of surgery but also to improve the convenience of surgery. Therefore, it is thought that it will be important for clinicians to make continuous efforts to applicate cutting-edge technologies to be developed in the future to patient diagnosis and surgery.

The untold history of planning in orthognathic surgery: a narrative review from the beginning to virtual surgical simulation

We aimed to produce a narrative review of planning orthognathic surgery, chronologically. Also, to present flaws of methods and the future of orthognathic surgery planning. The search was carried out mainly in PubMed, SCOPUS, Embase, and Cochrane databases. Also was complemented by manual search in reference lists from identified studies and in grey literature. The first orthognathic surgery was reported in 1849, and it took more than a century for the development of the traditional orthognathic 2D planning. Besides the advances, surgeons observed failures and lacks on 2D method in representing with reliability the facial and maxillary tridimensional structure (3D). With technological developments in 90s and 2000s, methodological improvements were granted, and the 3D protocol was created. The CASS and Charlotte protocols were the earliest 3D planning protocols conceived. Since then, some steps were simplified, and new technologies are being developed and added to create a more reliable and precise way of planning orthognathic surgery.

Determining the occlusal plane: a literature review

Objective: The purpose of the present review was to demonstrate the utility of articulator systems and link instrumentation in determining the occlusal plane. The impact of the natural head position and anatomical landmarks on the occlusal plane location has been reported in the literature. Properly chosen instrumentation and management methods eliminate errors in determining the occlusal plane.Methods: The PubMed and the Dentistry & Oral Sciences Source (through EbscoHost) databases were searched for ways to minimize the occurrence of errors when registering and determining the occlusal plane location, with or without the use of face-bows. A hand search and citation mining supplemented the results.Results: Overall, 11 original approaches to occlusal plane determination were identified.Discussion: Identified methods of occlusal plane transfer are based on real or virtual solutions. Owing to the large variety of devices, additional comparative studies are needed.

Surgical Accuracy of Positioning the Maxilla in Patients With Skeletal Class II Malocclusion Using Computer-Aided Design and Computer-Aided Manufacturing-Assisted Orthognathic Surgery

OBJECTIVE

To evaluate the surgical accuracy of positioning the maxilla in patients with skeletal class II malocclusion using computer-aided design and computer-aided manufacturing (CAD/CAM)-assisted orthognathic surgery.

MATERIALS AND METHODS

The samples consisted of 10 patients with skeletal class II malocclusion, whose cone-beam computed tomographys taken before and immediately after surgery were available and who underwent bimaxillary orthognathic surgery by a single surgeon using Le Fort I osteotomy and bilateral sagittal split ramus osteotomy at the Department of Oral and Maxillofacial Surgery, Seoul National University Dental Hospital, Seoul, South Korea between January 2018 and December 2019. After virtual surgical planning was performed using the FACEGIDE system (Korea), surgical cutting guides, intermediate splints, and custom-made titanium mini-plates were fabricated using CAD/CAM technique. Using 8 landmarks (anterior nasal spine, point A, #16, #13, contact point between #11 and #21, #23, #26, posterior nasal spine), the mean differences between the virtually planned (Virtual) and actual postsurgical position of the maxilla (Actual) in the three-dimensional coordinates (ΔActual-Virtual) and their mean absolute deviations were investigated.

RESULTS

The mean differences of 8 landmarks were 0.42 mm left side movement in the transverse coordinate, 0.15 mm forward movement in the sagittal coordinate and 0.10 mm downward movement in the vertical coordinate. Their mean absolute deviations were 0.98, 0.67, and 0.62 mm in the sagittal, vertical, and transverse coordinates, respectively.

CONCLUSIONS

Since the mean difference was less than 0.5 mm and the range of error was less than 1.0 mm, CAD/CAM-assisted orthognathic surgery might have a high degree of surgical accuracy and clinical relevance in the positioning of the maxilla.

Accuracy of virtual surgical planning in segmental osteotomy in combination with bimaxillary orthognathic surgery with surgery first approach

Background

This study aimed to assess the accuracy of virtual surgical planning (VSP) in segmental osteotomy in combination with bimaxillary orthognathic surgery with surgery first approach (SFA) by means of three-dimensional (3D) measuring and superimposition, so as to promote the application of digital technology in combined orthodontic-orthognathic treatment.

Methods

20 patients treated with segmental osteotomy in combination with bimaxillary orthognathic surgery with SFA from 2018 to 2020 were included. All of them acquired VSP performed by ProPlan CMF 3.0 software (Materialise Corporation, Belgium). The preoperative (T0) 3D model of VSP and the postoperative (T1) 3D model, reconstructed by the cone-beam computed tomography (CBCT) data acquired one week after surgery, were compared by measuring the 3D coordinates of the landmarks as well as 3D model superimposition for deviation analysis. The deviation analysis was achieved by Geomagic Studio 2013 (3D Systems Corporation, USA). The differences which represented the accuracy of VSP were evaluated by the root mean square deviation (RMSD) and the Bland–Altman method.

Results

There was no statistically significant difference between the 3D coordinates of T1 and T0 (P > 0.05), and the mean overall RMSD was 1.37 mm, within the clinical relevance of 2 mm. The RMSD of sagittal direction (1.76 mm) was greater than that of coronal and vertical directions (1.09 mm and 1.24 mm), and the RMSD of maxillary and mandibular aspects were basically equal (1.30 mm and 1.45 mm). The Bland–Altman method showed the T0 and T1 measurements were in good agreement. The mean RMSD obtained from the deviation analysis was 1.85 mm, within the clinical relevance.

Conclusions

VSP in segmental osteotomy in combination with bimaxillary orthognathic surgery with SFA proved to acquire accurate outcome in this study.

Comparison of actual amount of movement with surgical treatment objective in the orthognathic maxillary repositioning

OBJECTIVE

To compare the postoperative position of the maxilla with the surgical treatment objectives (STO) in bimaxillary orthognathic surgery for evaluating the surgical accuracy and investigating the pattern and cause of the discrepancy.

METHODS

Patients undergoing conventional bimaxillary orthognathic surgery by a single oral and maxillofacial surgeon were enrolled. Utilizing the superimposition of preoperative and postoperative computed tomography images, the actual amounts of positional change of both the maxillary central incisor and first molars were compared with those of STO. All the patients were divided into two groups according to the actual discrepancy between STO and the postoperative position and factors that may affect surgical accuracy were analyzed.

RESULTS

In 62 cases, the absolute mean value of the positional difference between STO and the actual outcome was 2.20 mm (X-axis, 0.93 mm; Y-axis, 1.31 mm; and Z-axis, 1.09 mm) in the maxillary central incisor. The signed mean value of the central incisor was -0.07 mm, 0.79 mm, and -0.57 mm in the X-, Y-, and Z-axes, respectively, and the value in the Y- and Z-axes showed a statistically significant difference in comparison with STO (P<0.01). Age, sex, skeletal Angle classification, maxillary and mandibular profile, use of 3D virtual surgery, facial asymmetry, and yawing correction did not show a statistically significant correlation with surgical accuracy at the central incisor.

CONCLUSION

There was an acceptable range of discrepancy between postoperative maxillary position and STO after orthognathic surgery; however, there was a tendency for posterior and downward movement in the maxillary anterior teeth.

Assessment of maxillary canting on cone beam computed tomography and digital models: A retrospective study and proposal of a method

OBJECTIVES

The mounting of the plaster casts on articulator procedure is routinely performed in orthognathic surgery to assess canting of the maxillary occlusal plane, but the currently used protocols and reference plane could be source of errors which affect reliability. Nowadays the assessment of canting of the maxillary occlusal plane could be also performed with an entirely digital protocol. Aim of the study was to propose a method to evaluate canting in patients affected by Unilateral Condylar Hyperplasia, comparing the measurements performed on digital models matched on CBCT with those made on traditional articulator.

MATERIALS AND METHODS

A retrospective cross-sectional study was designed on 20 patients affected by vertical Unilateral Condylar Hyperplasia treated in the Units of Orthodontics and Maxillo-Facial Surgery. The canting of the maxillary occlusal plane was measured on plaster casts mounted on the conventional articulator and the measures were compared with those made on digital models matched on CBCT, according the protocol developed in our Unit. Molar, canine and basal difference were measured. To compare the two protocols and to test the agreement, we performed descriptive statistics, comparison between means and Bland Altman analysis. P value was set at 0.05.

RESULTS

Statistic comparison demonstrated agreement between measurements performed with the digital protocol and conventional physical method.

CONCLUSION

Measurements of canting with digital protocol are comparable to the physical standard method. A total digital protocol allows faster availability and storage of patient's data and better communication between orthodontist and maxillo-facial surgeon, especially in patients affected by three-dimensional malocclusions.

Comparison of the postoperative and follow-up accuracy of articulator model surgery and virtual surgical planning in skeletal class III patients

The aim of this study was to evaluate the postoperative and follow-up accuracy of using an intermediate occlusal splint between articulator model surgery (AMS) and virtual surgical planning (VSP) in double-jaw operations. Thirty skeletal class III patients were randomly allocated to have AMS or VSP. In the AMS group surgical planning was done through conventional articulator model surgery, and an intermediate occlusal splint made of acrylic resin was used. In the VSP group the surgical simulation was done virtually, and the same intermediate splint was used in the software and then fabricated using rapid prototyping technology. Preoperatively, one week postoperatively, and 1∼2-years later we obtained follow-up cone-beam computed tomographic (CT) images of each patient. Absolute linear differences between planned and actual outcomes, as well as planned and follow-up outcomes, were evaluated. There was no significant difference in either postoperative accuracy or follow-up accuracy between the methods, and there was no significant difference in the rate of skeletal relapse. Planning transfer by intermediate splint might therefore be the dominant factor in the final inaccuracies. The potentially greater accuracy of VSP may be realised with the help of new positioning devices instead of an intermediate splint.

Current status of surgery-first approach (part III): the use of 3D technology and the implication in obstructive sleep apnea

Considering psychosocial needs of patients, it is not surprising that surgery-first approach (SFA) is becoming more popular than ever. Although the concept of SFA was introduced a few decades ago, the limitation of analysis method based on two-dimensional images makes surgeons reluctant to choose SFA. Recently, the advancement of three-dimensional technology allows us to perform SFA even without minimal pre-surgical orthodontic treatment, and the prediction of surgical outcome became more accurate, especially in obstructive sleep apnea (OSA) patients to whom the advantages of SFA should be more significant. Here, we describe the current trend of SFA and its implication in OSA patients.

The accuracy of maxillary positioning using digital model planning and 3D printed wafers in bimaxillary orthognathic surgery

OBJECTIVE

Orthognathic wafers may be made using digital model movements and CAD-CAM technology. This paper analysed the accuracy of maxillary movements using this new process.

DESIGN

Retrospective study of pre and post-operative cephalograms.

PARTICIPANTS

Thirty consecutive orthognathic patients undergoing bimaxillary osteotomies in a UK hospital.

METHODS

Jaw movements were planned using cephalometric and Orthoanalyzer™ software. The resultant intermediate and final wafer occlusal relationships were used for wafer fabrication by 3D printing of the inter-occlusal space. Pre- and post-operative lateral cephalograms were compared in terms of maxillary antero-posterior and vertical movements. Statistical analyses including the paired t-test, two-sample t-test and Fisher's exact test.

RESULTS

Wide individual variation was observed between the planned and actual movements. Thirteen cases (43%) had a 2 mm discrepancy in at least one variable. Statistically significant differences between the planned and actual maxillary vertical movements were observed for the molar (U6y: p < 0.0001) and anterior maxillary (Ay: p < 0.01) differences. Analysis of a subgroup with primarily impaction movements demonstrated a statistically significant bias towards excessive maxillary advancement (U1x: p < 0.01) and incisor impaction (U1y: p < 0.01) in this group.

CONCLUSIONS

This new digital surgical wafer technique achieves a similar level of accuracy to the conventional facebow and model surgery process.

Accuracy of virtual surgical planning of orthognathic surgery with aid of CAD/CAM fabricated surgical splint-A novel 3D analyzing algorithm

The benefit of computer-assisted planning in orthognathic surgery has been extensively documented over the last decade. This study aims to evaluate the accuracy of a virtual orthognathic surgical plan by a novel three dimensional (3D) analysis method. Ten patients who required orthognathic surgery were included in this study. A virtual surgical plan was achieved by the combination of a 3D skull model acquired from computed tomography (CT) and surface scanning of the upper and lower dental arch respectively and final occlusal position. Osteotomies and movement of maxilla and mandible were simulated by Dolphin Imaging 11.8 Premium^® (Dolphin Imaging and Management Solutions, Chatsworth, CA). The surgical plan was transferred to surgical splints fabricated by means of Computer Aided Design/Computer Aided Manufacturing (CAD/CAM). Differences of three dimensional measurements between the virtual surgical plan and postoperative results were evaluated. The results from all parameters showed that the virtual surgical plans were successfully transferred by the assistance of CAD/CAM fabricated surgical splint. Wilcoxon's signed rank test showed that no statistically significant deviation between surgical plan and post-operational result could be detected. However, deviation of angle U1 axis-HP and distance of A-CP could not fulfill the clinical success criteria. Virtual surgical planning and CAD/CAM fabricated surgical splint are proven to facilitate treatment planning and offer an accurate surgical result in orthognathic surgery.

"Modified Oblique Le Fort III Osteotomy" New Concepts

INTRODUCTION

The purpose of this study is to demonstrate the surgical technique for the correction of midfacial deformities; vertical excess and posteroanterior hypoplasia. This situation obligates the need to move the whole osseous structure in an oblique posteroanterior movement that should correct both midfacial deformities. This should also correct the lip incompetence while improving the malar projection on a profile view of the patient. We also present a mathematical formula that gives the angulation needed for moving the midface complex in a simultaneous vertical and posteroanterior direction. Once given the correct angulation for the desired oblique movement, the surgeon can reproduce this angulation with custom made surgical guides over the stereolithographic model, that can then be used during surgery to achieve the desired movement accurately. This technique exemplified on this paper will give maxillofacial surgeons a new and affordable tool for the correction of midfacial deformities in an accurate and easily reproducible manner and amplifying the surgical repertoire.

MATERIALS AND METHODS

Patients seen in the specialty hospital "Dr. Bernardo Sepulveda" National Medical Center XXI Century, IMSS, during the period from February 2013 to November 2014 with Modified Oblique Le Fort III osteotomies, with the application of two trigonometric formulas for the accuracy of the technique.

CONCLUSIONS

The application of the formulas give accurate results as well as the enlargement of the upper airway and esthetic results.

How accurate are rapid prototyped (RP) final orthognathic surgical wafers? A pilot study

Computer packages have been introduced to simulate the movements of the jaw in three dimensions to facilitate planning of treatment. After final 3-dimensional virtual planning, a rapid prototype wafer can be manufactured and used in theatre. Our aim was to assess the accuracy of rapid prototyping of virtual wafers derived from laser scanned dental models using CAD/CAM software. Upper and lower plaster models from 10 orthognathic patients, the articulated models, and the conventional wafers were scanned. The virtual wafers were made from CAD/CAM software, and printed on a stereolithographic printer. We also scanned the articulated models with rapid prototype wafers in place. The validity of the final rapid prototype wafer was measured by the accuracy with which upper and lower models related to one another. The absolute mean error of the rapid prototype wafer when aligned with the dental models was 0.94 (0.09) mm. The absolute distance of the 2 models articulated by conventional and rapid prototype wafers ranged from 0.04 - 1.73mm. The rapid prototype wafers were able to orientate the upper and lower dental models with an absolute mean error of 0.94 (0.09) mm, but it ranged from 0.04-1.73mm.

Digital model planning and computerized fabrication of orthognathic surgery wafers

Conventional orthognathic wafers are made by a process involving manual movement of stone dental models and acrylic laboratory fabrication. In addition, a facebow record and semi-adjustable articulator system are required for maxillary osteotomy cases. This paper introduces a novel process of producing both intermediate and final orthognathic surgical wafers using a combination of computerized digital model simulation and three-dimensional print fabrication, without the need for either a facebow record or the additional ionizing radiation exposure associated with cone beam computerized tomography.

Evaluation of the inclination of maxillary occlusal plane on mounted casts using a fixed value and customized nasion indicator in artex articulator: Facebow system - An in-vivo comparative study

Aim:

To evaluate and compare the variations in the inclination of occlusal plane of casts mounted on Artex articulator using a facebow with a fixed value and customized nasion indicator.

Materials and Methods:

Twenty two subjects were selected for this investigation. Two maxillary impressions were made, and casts poured. For each of the twenty two subjects, the facebow records were made with, Artex face-bow using a fixed value nasion indicator and customized nasion indicator and mounted. The angle between the occlusal plane of upper cast and the upper articulator arm was measured with a Universal bevel protractor and compared with the gold standard cephalometric value.

Results:

It shows that, when angle was measured between maxillary occlusal plane and upper member of the articulator, on the mounted cast using a customized nasion indicator and fixed value nasion indicator against the gold standard cephalometric value as a whole, it was found to be not significant. But, if each patient were evaluated individually, there found to be the difference in the angle.

Discussion and Conclusion:

Variation in occlusal plane was very minimal and close to the cephalometric value when using customized nasion indicator compared to fixed value nasion indicator on the Artex.

Importance of occlusal plane reproduction on the semi-adjustable articulator in planning maxillary impactions for orthognathic surgery

INTRODUCTION

The aim of this study was to evaluate whether a 6° counterclockwise change in occlusal plane inclination would produce significant modifications on the final result of a maxillary impaction and mandible advancement model surgery.

MATERIALS AND METHODS

Four groups were used in this study, with ten identical maxillary casts and one mandibular cast mounted on the same semi-adjustable articulator, with the same malocclusion. The occlusal plane of the two control and study groups had an inclination of 13° and 7°, respectively. Preoperative and postoperative measures were performed using the Erickson platform and impactions of 6 and 10 mm were tested. To control these movements during model surgery, two splints were fabricated using another two maxillary and mandibular casts mounted with occlusal plane of 13°, simulating the proposed movement.

RESULTS

The results were compared using the t test. Only the antero-posterior movement of the upper incisor was statistically significant for both study groups (p < 0.05), with a mean of 0.48 and 0.94 mm in the 10 and 6 mm impaction groups, respectively.

DISCUSSION

This information means that if an error in the occlusal plane transference occur, it will not be clinically significant, because differences smaller than 1 mm does not have influence on soft and hard tissue final result.

Accuracy of a computer-aided surgical simulation protocol for orthognathic surgery: a prospective multicenter study

PURPOSE

The purpose of this prospective multicenter study was to assess the accuracy of a computer-aided surgical simulation (CASS) protocol for orthognathic surgery.

MATERIALS AND METHODS

The accuracy of the CASS protocol was assessed by comparing planned outcomes with postoperative outcomes of 65 consecutive patients enrolled from 3 centers. Computer-generated surgical splints were used for all patients. For the genioplasty, 1 center used computer-generated chin templates to reposition the chin segment only for patients with asymmetry. Standard intraoperative measurements were used without the chin templates for the remaining patients. The primary outcome measurements were the linear and angular differences for the maxilla, mandible, and chin when the planned and postoperative models were registered at the cranium. The secondary outcome measurements were the maxillary dental midline difference between the planned and postoperative positions and the linear and angular differences of the chin segment between the groups with and without the use of the template. The latter were measured when the planned and postoperative models were registered at the mandibular body. Statistical analyses were performed, and the accuracy was reported using root mean square deviation (RMSD) and the Bland-Altman method for assessing measurement agreement.

RESULTS

In the primary outcome measurements, there was no statistically significant difference among the 3 centers for the maxilla and mandible. The largest RMSDs were 1.0 mm and 1.5° for the maxilla and 1.1 mm and 1.8° for the mandible. For the chin, there was a statistically significant difference between the groups with and without the use of the chin template. The chin template group showed excellent accuracy, with the largest positional RMSD of 1.0 mm and the largest orientation RMSD of 2.2°. However, larger variances were observed in the group not using the chin template. This was significant in the anteroposterior and superoinferior directions and the in pitch and yaw orientations. In the secondary outcome measurements, the RMSD of the maxillary dental midline positions was 0.9 mm. When registered at the body of the mandible, the linear and angular differences of the chin segment between the groups with and without the use of the chin template were consistent with the results found in the primary outcome measurements.

CONCLUSIONS

Using this computer-aided surgical simulation protocol, the computerized plan can be transferred accurately and consistently to the patient to position the maxilla and mandible at the time of surgery. The computer-generated chin template provides greater accuracy in repositioning the chin segment than the intraoperative measurements.

New Methods to Evaluate Craniofacial Deformity and to Plan Surgical Correction

The success of cranio-maxillofacial (CMF) surgery depends not only on surgical techniques, but also upon an accurate surgical plan. Unfortunately, traditional planning methods are often inadequate for planning complex cranio-maxillofacial deformities. To this end, we developed 3D computer-aided surgical simulation (CASS) technique. Using our CASS method, we are able to treat patients with significant asymmetries in a single operation which in the past was usually completed in two stages. The purpose of this article is to introduce our CASS method in evaluating craniofacial deformities and planning surgical correction. In addition, we discuss the problems associated with the traditional surgical planning methods. Finally, we discuss the strength and pitfalls of using three-dimensional measurements to evaluate craniofacial deformity.

In vitro evaluation of new approach to digital dental model articulation

PURPOSE

The purpose of the present study was to evaluate the accuracy of our newly developed approach to digital dental model articulation.

MATERIALS AND METHODS

Twelve sets of stone dental models from patients with craniomaxillofacial deformities were used for validation. All the models had stable occlusion and no evidence of early contact. The stone models were hand articulated to the maximal intercuspation (MI) position and scanned using a 3-dimensional surface laser scanner. These digital dental models at the MI position served as the control group. To establish an experimental group, each mandibular dental model was disarticulated from its original MI position to 80 initial positions. Using a regular office personal computer, they were digitally articulated to the MI position using our newly developed approach. These rearticulated mandibular models served as the experimental group. Finally, the translational, rotational, and surface deviations in the mandibular position were calculated between the experimental and control groups, and statistical analyses were performed.

RESULTS

All the digital dental models were successfully articulated. Between the control and experimental groups, the largest translational difference in mandibular position was within 0.2 mm ± 0.6 mm. The largest rotational difference was within 0.1° ± 1.1°. The averaged surface deviation was 0.08 ± 0.07. The results of the Bland and Altman method of assessing measurement agreement showed tight limits for the translational, rotational, and surface deviations. In addition, the final positions of the mandibular articulated from the 80 initial positions were absolutely agreed on.

CONCLUSION

The results of our study have demonstrated that using our approach, the digital dental models can be accurately and effectively articulated to the MI position. In addition, the 3-dimensional surface geometry of the mandibular teeth played a more important role in digital dental articulation than the initial position of the mandibular teeth.

Comparative study between 2 methods of mounting models in semiadjustable articulator for orthognathic surgery

PURPOSE

Compare the traditional method of mounting dental casts on a semiadjustable articulator and the new method suggested by Wolford and Galiano, 1 analyzing the inclination of maxillary occlusal plane in relation to FHP.

MATERIALS AND METHODS

Two casts of 10 patients were obtained. One of them was used for mounting of models on a traditional articulator, by using a face bow transfer system and the other one was used to mounting models at Occlusal Plane Indicator platform (OPI), using the SAM articulator. After that, na analysis of the accuracy of mounting models was performed. The angle made by de occlusal plane and FHP on the cephalogram should be equal the angle between the occlusal plane and the upper member of the articulator.

RESULTS

The measures were tabulated in Microsoft Excell(®) and calculated using a 1-way analysis variance. Statistically, the results did not reveal significant differences among the measures.

CONCLUSION

OPI and face bow presents similar results but more studies are needed to verify its accuracy relative to the maxillary cant in OPI or develop new techniques able to solve the disadvantages of each technique.

How accurate is model planning for orthognathic surgery?

The purpose of this study was to evaluate the accuracy of model surgery prediction after orthognathic surgery and to identify possible errors associated with the prediction process. The study included 46 patients who had undergone orthognathic surgical procedures; 22 in Group A who had had a Le Fort I osteotomy; and 24 in Group B who had had a Le Fort I osteotomy and mandibular setback surgery. The immediate postoperative and preoperative lateral cephalograms were analysed to calculate surgical changes; these were compared with those obtained from model surgery prediction and a statistical analysis was undertaken. The maxilla was more under-advanced and over-impacted anteriorly than predicted by model surgery. The amount of mandibular setback was more than that predicted by model surgery. None of the differences between prediction planning and actual surgical changes was statistically significant at p<0.05. Inaccuracy with the face bow recording, the intermediate wafer, and auto-rotation of the mandible in the supine or anaesthetized patient would appear to be the principal reasons for errors. Inaccuracies are associated with the transfer of prediction planning to model surgery planning and prediction, which should be eliminated to improve the accuracy and predictability of orthognathic surgery.

Towards an integrated system for planning and assisting maxillofacial orthognathic surgery

Computer-assisted maxillofacial orthognathic surgery is an emerging and interdisciplinary field linking orthognathic surgery, remote signal engineering and three-dimensional (3D) medical imaging. Most of the computational solutions already developed make use of different specialized systems which introduce difficulties both in the information transfer from one stage to the others and in the use of such systems by surgeons. Trying to address such issue, in this work we present a common computer-based system that integrates proposed modules for planning and assisting the maxillofacial surgery. With that we propose to replace the current standard orthognathic preoperative planning, and to bring information from a virtual planning to the real operative field. The system prototype, including three-dimensional cephalometric analysis, static and dynamic virtual orthognathic planning, and mixed reality transfer of information to the operation room, is described and the first results obtained are presented.

Accuracy of a fixed value nasion relator in facebow design

PURPOSE

This study examined whether a fixed value nasion relator accurately locates the orbitale in a patient population.

MATERIALS AND METHODS

The mean value for the vertical distance between soft tissue nasion and orbitale was determined through the analysis of cephalometric radiographs of 114 adult patients. This value was then compared to a facebow design, which uses a fixed value of 25.4 mm.

RESULTS

In this study, the mean distance between the orbitale and nasion was found to be 26.8 mm. The values ranged from 15.9 to 39.4 mm with a standard deviation of 3.87 mm.

CONCLUSION

The difference between the calculated mean and the 25.4 mm fixed value was less than 2.0 mm and presumed to be clinically irrelevant; however, an accumulation of design errors combined with the variation within the patient population was asserted to be clinically relevant and makes the use of a fixed value nasion relator impractical.