Virtual occlusion in orthognathic surgery

Does Maxillomandibular Fixation Technique Affect Occlusion Quality in Segmental LeFort I Osteotomy?

BACKGROUND

Segmental maxillary osteotomies require precise occlusal control due to variability in individual segment positioning. The role of maxillomandibular fixation (MMF) technique on occlusal control has not been validated.

PURPOSE

The purpose is to measure and compare the accuracy of occlusal positioning among MMF techniques.

STUDY DESIGN, SETTING, SAMPLE

This was a double-blinded in vitro study on experiment models to simulate a 3-piece LeFort I osteotomy. The models were constricted posteriorly and expanded using 3 different MMF techniques and compared to the unaltered baseline occlusion. Based on sample size calculation, 32 separate attempts were made for each MMF technique.

PREDICTOR VARIABLE

The predictor variable was MMF technique (brackets, MMF screws, and embrasure wires).

MAIN OUTCOME VARIABLES

The primary outcome variable was the visual occlusal analysis score, a 1.00 to 4.00 continuous scale measuring the similarity of the achieved occlusion to the planned (control) occlusion assessed by an oral and maxillofacial surgeon and an orthodontist. High visual occlusal analysis score indicated greater occlusal accuracy, with 3.50 defined as the threshold for accuracy. The secondary outcome variable was the linear error of the achieved occlusion at the canine and first molar teeth, with lower error indicating greater accuracy. An a priori accuracy threshold of 0.5 mm was set for this variable.

COVARIATES

None.

ANALYSES

Kruskal-Wallis test with post hoc testing was used to analyze the difference in the outcome variables of interest. P value < .05 was considered statistically significant.

RESULTS

Thirty-two attempts for each technique showed that brackets had higher VAOS than MMF screws and embrasure wires (median differences 1.49 and 0.48, P < .001), and had lower linear occlusal error (median differences 0.35 to 0.99 mm, P < .001).

CONCLUSION AND RELEVANCE

MMF technique influences the quality of occlusal control, with greater visual rating scores and lower linear errors seen with brackets than with embrasure wires or MMF screws.

A New Approach to Virtual Occlusion in Orthognathic Surgery Planning Using Mixed Reality-A Technical Note and Review of the Literature

Orthognathic surgery plays a vital role in correcting various skeletal discrepancies of the maxillofacial region. Achieving optimal occlusion is a fundamental aspect of orthognathic surgery planning, as it directly influences postoperative outcomes and patient satisfaction. Traditional methods for setting final occlusion involve the use of dental casts which are time-consuming, prone to errors and cannot be easily shared among collaborating specialties. In recent years, advancements in digital technology have introduced innovative approaches, such as virtual occlusion, which may offer enhanced accuracy and efficiency in orthognathic surgery planning. Furthermore, the emergence of mixed reality devices and their 3D visualization capabilities have brought about novel benefits in the medical field, particularly in computer-assisted planning. This paper presents for the first time a prototype tool for setting virtual occlusion during orthognathic surgery planning using mixed reality technology. A complete walkthrough of the workflow is presented including an explanation of the implicit advantages of this novel tool. The new approach to defining virtual occlusion is set into context with other published methods of virtual occlusion setting, discussing advantages and limitations as well as concepts of surgical occlusion for orthognathic surgery.

Reproducibility and reliability of digital occlusal planning for orthognathic surgery

The digital articulation of dental models is gradually replacing the conventional physical approach for occlusal prediction planning. This study was performed to compare the accuracy and reproducibility of free-hand articulation of two groups of digital and physical dental models, 12 Class I (group 1) and 12 Class III (group 2). The models were scanned using an intraoral scanner. The physical and digital models were independently articulated 2 weeks apart by three orthodontists to achieve the maximum inter-digitation, with coincident midlines and a positive overjet and overbite. The occlusal contacts provided by the software color-coded maps were assessed and the differences in the pitch, roll, and yaw were measured. The reproducibility of the achieved occlusion of both the physical and digital articulation was excellent. The z-axis displayed the smallest absolute mean differences of 0.10 ± 0.08 mm and 0.27 ± 0.24 mm in the repeated physical and repeated digital articulations, respectively, both in group 2. The largest discrepancies between the two methods of articulation were in the y-axis (0.76 ± 0.60 mm, P = 0.010) and in roll (1.83° ± 1.72°, P = 0.005). The overall measured differences were< 0.8 mm and< 2°. Despite the steep learning curve, digital occlusal planning is accurate enough for clinical applications.

Contemporary management of complex craniofacial trauma: virtual planning, navigation and the novel thermoformed cage splints in a strategic, sequential, computer-guided protocol

INTRODUCTION

It was the aim of the study to assess if computerized simulation and the use of thermoformed cage splints are useful to plan cases of complex craniofacial trauma.

MATERIALS AND METHODS

patients with fractures in any of the thirds of the craniofacial skeleton and occlusion impairment. Virtual surgical planning with digital reduction of fractures, navigated planning, thermoformed cage splints were used in all cases. Surgical outcomes were evaluated by computing the surface deviation and occlusograms between planned and postoperative models.

RESULTS

13 patients were enrolled in this study. Accuracy of bone repositioning was evaluated compared with the surgical planning. For the mandible, mean Root Mean Square Error (RMSE) was of 1.67 with a standard deviation (SD) of ±0.75 mm (p < 0.001); for the maxilla, average RMSE was of 0.88 with SD of ±0.52 mm (p < 0.001); and for midfacial and upper third bone segments, average RMSE was of 0.59 with SD of ±0.47 mm (p < 0.001) CONCLUSIONS: Within the limitations of the study it seems that thermoformed cage splints might be a promising alternative to other well-established approaches for accurate occlusal restoration and can be fully integrated within the digital workflow.

Static mandibular condyle positions studied by MRI and condylar position indicator

We compared mandibular condyle positions as determined by magnetic resonance imaging (MRI) and a mechanical device, the condylar position indicator (CPI). Both methods assessed 3 mandibular positions in 10 asymptomatic males and 10 asymptomatic females, aged 23 to 37 years, free from temporomandibular disorders: maximum intercuspation, bimanually manipulated centric relation, and the unguided neuromuscular position. Bite registrations were obtained for bimanual operator guidance and neuromuscular position. 3 T MRI scans of both temporomandibular joints produced 3D data of the most superior condylar points in all 3 mandibular positions. Using mounted plaster casts and the same bite registrations, an electronic CPI displayed 3D data of its condylar spheres in these positions. The results showed interclass correlation coefficients ranging from 0.03 to 0.66 (95% confidence intervals from 0 to 0.8) and significantly different condyle positions between both methods (p = 0.0012, p < 0.001). The implications of the study emphasize that condyle position is unpredictable and variable. Its exact knowledge requires radiological imaging and should not rely on CPI assessments.

A Full Computerized Workflow for Planning Surgically Assisted Rapid Palatal Expansion and Orthognathic Surgery in a Skeletal Class III Patient

In the present case report, we present and discuss the digital workflow involved in the orthodontic/orthognathic combined treatment of a skeletal malocclusion correction in a 17-year-old male patient affected by a skeletal class III, facial asymmetry, sagittal and transversal deficiency of the medium third of the skull, dental crowding, and bilateral cross-bite. The first stage of the treatment involved surgically assisted rapid palatal expansion and occlusal decompensation, using fixed self-ligating appliance. An orthodontic software package (i.e., Dolphin 3D Surgery module) was used to perform virtual treatment objective evaluation by integrating data from cone beam computer tomography acquisition, intraoral scan, and extraoral photographs. The software allowed a comprehensive evaluation of skeletal, dento-alveolar, and soft-tissue disharmonies, qualitative and quantitative simulation of surgical procedure according to skeletal and aesthetic objectives, and, consequently, the treatment of the malocclusion. Using a specific function of the software, the surgical splint was designed according to the pre-programmed skeletal movements, and subsequently, the physical splint was generated with a three-dimensional (3D) printing technology. Once a proper occlusal decompensation was reached, a Le Fort I osteotomy of the maxilla and a bilateral sagittal surgical osteotomy of the mandible were executed to restore proper skeletal relations. The whole treatment time was 8 months. The orthodontic/orthognathic combined treatment allowed to correct the skeletal and the dental imbalance, as well as the improvement of facial aesthetics. Accordingly, the treatment objectives planned in the virtual environment were achieved. Virtual planning offers new possibilities for visualizing the relationship between dental arches and surrounding bone and soft structures in a single virtual 3D model, allowing the specialists to simulate different surgical and orthodontic procedures to achieve the best possible result for the patient and providing an accurate and predictable outcome in the treatment of challenging malocclusions.

Annual review of selected scientific literature: A report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

The Scientific Investigation Committee of the American Academy of Restorative Dentistry offers this review of the 2021 dental literature in restorative dentistry to inform busy dentists regarding noteworthy scientific and clinical progress over the past year. Each member of the committee brings discipline-specific expertise to coverage of this broad topical area. Specific subject areas addressed, in order of the appearance in this report, include COVID-19 and the dental profession (new); prosthodontics; periodontics, alveolar bone, and peri-implant tissues; implant dentistry; dental materials and therapeutics; occlusion and temporomandibular disorders; sleep-related breathing disorders; oral medicine and oral and maxillofacial surgery; and dental caries and cariology. The authors focused their efforts on reporting information likely to influence daily dental treatment decisions with an emphasis on future trends in dentistry. With the tremendous volume of dentistry and related literature being published daily, this review cannot possibly be comprehensive. Rather, its purpose is to update interested readers and provide important resource material for those interested in pursuing greater details on their own. It remains our intent to assist colleagues in negotiating the extensive volume of important information being published annually. It is our hope that readers find this work useful in successfully managing the patients and dental problems they encounter.

Plaster Casts vs. Intraoral Scans: Do Different Methods of Determining the Final Occlusion Affect the Simulated Outcome in Orthognathic Surgery?

A virtual occlusal adjustment in orthognathic surgery has many advantages; however, the haptic information offered by plaster casts is missing when using intraoral scans. Feeling the interferences may be helpful in defining the best possible occlusion. Whether the use of a virtual occlusal adjustment instead of the conventional approach has a significant effect on the postsurgical position of the jaws is a question that remains unanswered. This study compares a virtual method to the conventional method of defining the final occlusion. Twenty-five orthognathic patients were included. Bimaxillary and single-jaw orthognathic surgery (mandible only) was simulated. The two methods were compared regarding discrepancies in the simulated postsurgical position of the mandible, measured three-dimensionally using MeshLab (MeshLab 2020.12 3D). An analysis using SPSS revealed no significant differences between the tested methods (p-values: 0.580 to 0.713). The mean absolute discrepancies ranged from 0.14 mm to 0.72 mm, laying within the scope of the clinically acceptable inaccuracies of an osteosynthesis in orthognathic surgery. The lack of haptic information in virtual planning had no relevant influence on the definition of the final occlusion and the simulated postsurgical outcome. However, in individual cases, plaster models might still be helpful in finding the adequate occlusion, especially in the sagittal dimension and in cases of patients with an anterior open bite, but this remains to be tested.