Modeling stability post zygomatic fracture reconstruction.

Zygomaticomaxillary complex (ZMC) fracture repair is one of the most common surgical procedures performed in craniomaxillofacial trauma management. Miniplates and screws are used to stabilize the fractured bone using small local incisions, however, these procedures are not infrequently associated with hardware-related post-operative complications. The amount of fixation hardware utilized varies depending on the fracture pattern and surgical judgment, with three-point fixation being the conventionally accepted treatment. However, limited experimental testing and clinical studies have suggested that ZMC stabilization may be achieved with less than three-point fixation. In this study, we utilized a previously developed finite element modeling approach that allows for detailed bone and muscle representation to study the mechanical behavior of the fractured craniomaxillofacial skeleton (CMFS) under one, two, or three-point fixation of the ZMC. Results suggest that using a miniplate along the infraorbital rim in three-point fixation increases the amount of strain and load transfer to this region, rather than offloading the bone. Two-point (zygomaticomaxillary and zygomaticofrontal) fixation yielded strain patterns most similar to the intact CMFS. One-point (zygomaticofrontal) fixation resulted in higher tensile and compressive strains in the zygomaticofrontal region and the zygomatic arch, along with a higher tensile strain on the zygomatic body. These modeling results provide biomechanical evidence for the concept of over-engineering in the stabilization of facial fractures. Furthermore, they support previous suggestions that less than three-point fixation of ZMC fractures may be adequate to achieve uneventful healing.

Comparison of stress distribution around all-on-four implants of different angulations and zygoma implants: a 7-model finite element analysis.

BACKGROUND: In recent years, zygomatic implants and the all-on-four treatment concept have been increasingly preferred for rehabilitation of atrophic maxillae. However, debate continues regarding the optimal configuration and angulation of the implants. The aim of this study was to analyze the biomechanical stress in implants and peri-implant bone in an edentulous maxilla with zygomatic implants and the all-on-four concept, using multiple implant configurations. METHODS: A total of 7 models consisting different combinations of 4-tilted dental implants and zygomatic implants were included in the study. In each model, a total of 200 N perpendicular to the posterior teeth and 50 N with 45° to the lateral tooth were applied. A finite element analysis was performed for determination of stress distribution on implants and peri-implant bone for each model. RESULTS: Higher stress values were observed in both cortical and trabecular bone around the 45°-tilted posterior implants in all-on-four models when compared to zygomatic implants. In cortical bone, the highest stress was established in an all-on-four model including 45°-tilted posterior implant with 4,346 megapascal (MPa), while the lowest stress was determined in the model including anterior dental implant combined with zygomatic implants with 0.817 MPa. In trabecular bone, the highest stress was determined in an all-on-four model including 30°-tilted posterior implant with 0.872 MPa while the lowest stress was observed in quad-zygoma model with 0.119 MPa. Regarding von Mises values, the highest stress among anterior implants was observed in an all-on-four model including 17° buccally tilted anterior implant with 38.141 MPa, while the lowest was in the including anterior dental implant combined with zygomatic implants with 20,446 MPa. Among posterior implants, the highest von Mises value was observed in the all-on-four model including 30°-tilted posterior implant with 97.002 MPa and the lowest stress was in quad zygoma model with 35.802 MPa. CONCLUSIONS: Within the limits of the present study, the use of zygoma implants may provide benefit in decreasing biomechanical stress around both dental and zygoma implants. Regarding the all-on-four concept, a 17° buccal angulation of anterior implants may not cause a significant stress increase while tilting the posterior implant from 30° to 45° may cause an increase in the stress around these implants.

Rotation of a Part of the Composite Flap for Simultaneous Gonion Reduction and Malar Augmentation During Rhytidectomy in Asians.

BACKGROUND: The desired facial shape that Asians aim to achieve through plastic surgery differs from that of westerners. OBJECTIVES: The author facilitates facial volume deflation by using the rotation of a part of the composite flap to the malar area resulting in volumetric augmentation during rhytidectomy; simultaneously, a volumetric reduction was implemented in the gonion. METHODS: Extended deep plane rhytidectomy with the rotation of a part of the composite flap was performed in 49 patients, whereas extended deep plane rhytidectomy without the rotation of a part of the composite flap was performed in 20 patients. For the results, the satisfaction survey of the surgery was conducted in all patients and by 2 surgeons during a follow-up visit 12 months later. To assess the surgical outcome objectively, the author used the Allergan photometric midface volume deficit scale to measure the midface volume. The midface contour and degree of projection were analyzed using lateral view photographs of the patients. The measurement of segment CM (distance between the lateral canthus and mouth corner) and segment MA (distance from segment CM to the most protruding malar area) was performed. RESULTS: The patients who underwent extended deep plane rhytidectomy with the rotation of a part of the composite flap reported higher overall satisfaction and achieved more favorable results, as evaluated by the 2 aesthetic surgeons (P < 0.05). The scores on the Allergan photometric midface volume deficit scale showed a significant increase before and after the surgery in both groups (P < 0.05), also as evaluated by the 2 aesthetic surgeons. However, the change in scores was found to be higher in the extended deep plane rhytidectomy with the rotation of a part of the composite flap group. The midface contour and degree of projection showed an increase of 20.6% on the right face and 22.7% on the left face, respectively (P < 0.001). CONCLUSION: Using the rotation of a part of the composite flap during rhytidectomy resulted in overall satisfactory outcomes for all patients. Based on these findings, it can be concluded that the use of this surgical method is beneficial and effective.

The Spatial Relationship Between Coronoid Process and Zygomatic Complex After Reduction Malarplasty.

BACKGROUND: Reduction malarplasty presents challenges in terms of postoperative complications, particularly limited mouth opening. Excessive inward displacement of the zygomatic complex can impinge on the coronoid process resulting in restricted mouth opening. This study aimed to assess the spatial relationship between the coronoid process and the zygomatic complex after reduction malarplasty. METHODS: A retrospective study was conducted, including consecutive patients underwent reduction malarplasty. Radiological measurements were performed before surgery and during the final follow-up, including the coronoid-condylar index, distance between the coronoid process and zygomatic complex, and thickness and density of the temporal and masseter muscles. Clinical and radiographic data were recorded and analyzed. RESULTS: A total of 159 female patients were included with an average age of 28.1 years and a mean follow-up of 6.7 months. The mean coronoid-condylar index was 1:1.4, ranging from 1:0.6 to 1:2.6. Following surgery, the distances between the coronoid process and the anterior zygoma decreased by approximately 1 mm. Additionally, the postoperative distance between the highest point of the coronoid process and the zygomatic arch decreased by around 4 mm horizontally and changed approximately 1 mm vertically. No significant changes were observed in the thickness and density of the temporal and masseter muscles after surgery. CONCLUSIONS: Reduction malarplasty led to a slight decrease in the distance between the coronoid process and the zygoma. The operation generally resulted in proximity between the highest point of the coronoid process and the zygomatic arch. However, we believe that common reduction malarplasty rarely leads to osseous impingement. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

The accuracy of virtual surgical planning assisted management for L-shaped reduction malarplasty: A retrospective study.

This study aims to evaluate the accuracy of L-shaped reduction malarplasty with bone setback or resection on the zygoma and the mortice and tenon joint structure on the zygomatic arch under the guidance of virtual surgical planning (VSP). Adult patients with zygomatic protrusion or hypertrophy were enrolled and divided. L-shaped reduction malarplasty with or without bone resection and with the mortice and tenon joint structure on the zygomatic arch was conducted either by digital procedures comprising VSP and three-dimensional (3D) printing titanium templates (Group I) or by conventional methods (Group II). Positions of representative landmarks and superimposition models were analyzed by 3D cephalometry. Satisfaction rate and incidences of clinical complications were compared as well. Satisfactory reduction of zygomatic protrusion or hypertrophy was recognized among all 78 patients. Improved symmetry and great surgical accuracy were observed according to the cephalometry analyses. The bone segment movement of virtual plans and actual results in Group I were measured and showed no obvious difference for the inward movement (5.42 ± 0.98 mm vs. 5.33± 0.93 mm, P = 0.6906) and the sagittal overlap (4.77 ± 1.32 mm vs. 4.87± 1.21 mm, P = 0.7386) at the zygoma roots, along with the step length at the long-arm of the L-shaped osteotomy line (2.43 ± 1.11 mm vs. 2.39± 0.89 mm, P = 0.8665). The high resemblance between virtual plans and actual results was depicted via superimposition models. Meanwhile, a higher satisfaction rate (28 in 36, 78% vs. 20 in 42, 48%) and a lower incidence rate of complications (11 in 36, 31% vs. 21 in 42, 50%) were found in Group I. Within the limitations of the study it seems that the application of VSP in reduction malarplasty could significantly contribute to better surgical accuracy and reduced difficulties in the operation, which would be beneficial to patients with zygoma hypertrophy or prominence.

Novel Clinical Anatomical Consideration of the Superficial and Deep Layers of the Deep Temporal Fascia.

BACKGROUND: The deep temporal fascia provides anchoring during thread lifting, which is a minimally invasive face-lifting procedure. However, anatomical studies involving the deep temporal fascia in addition to effective and safe thread-lifting procedures are scarce. The authors clarified the anatomy of the superficial layer of the deep temporal fascia and its surrounding structure using ultrasonography, histologic sections, and cadaveric dissection to propose an effective thread-lifting procedure guideline. METHODS: The authors included 20 healthy young participants from the Republic of Korea. Real-time, two-dimensional, B-mode ultrasonography was performed. Longitudinal scanning was performed along three vertical lines: the line passing through the jugale, the anterior margin of the condylar process of the mandible, and the midpoint between the jugale and anterior margin of the condylar process. Histologic samples from three fresh adult cadavers were harvested from 2.5 cm above and below the zygomatic arch. Eighteen fresh adult hemifaces of cadavers from the Republic of Korea (six men and three women, aged 67.3 ± 7.2 years) were used to confirm the morphology of the deep temporal fascia. RESULTS: The superficial layer of the deep temporal fascia crossed the zygomatic arch and was connected to the origin of the zygomaticus major muscle at the line passing through the jugale. The superficial layer continued inferiorly to the parotidomasseteric fascia at the line passing through the midpoint and condylar process of the mandible. CONCLUSION: This study yielded the novel anatomy of the superficial layer of the deep temporal fascia, and this anatomical structure may be used for an ideal thread-lifting procedure.

Long-term survival and complications of Quad Zygoma Protocol with Anatomy-Guided Approach in severely atrophic maxilla: A retrospective follow-up analysis of up to 17 years.

INTRODUCTION: The objective of the study was to provide long-term clinical outcomes and complications in the severely atrophic edentulous maxillae treated by means of the quad zygoma protocol (QZP) using the Anatomy-Guided Approach (AGA). METHODS: This was a retrospective cohort study of all consecutive patients with severely atrophic edentulous maxilla and insufficient bone height and width in the anterior and posterior regions bilaterally, who underwent rehabilitation with the QZP between May 2006 and December 2021. All patients were followed for at least 1 year. All zygomatic implants (ZIs) were placed by the same surgeon. The primary endpoint of the study was the implant survival rate. Secondary endpoints were implant success rate, prosthesis success rate, complications, and Oral Health-Related Quality of Life using the OHIP-14 questionnaire. RESULTS: A total of 56 patients (men 16, women 40) with 224 ZIs (Nobel Biocare, n = 204; Straumann, n = 16; Southern Implant, n = 4) placement were included with a mean follow-up period 8.8 ± 3.9 years (range, 1.2-17.0). The survival (success) rate was 97.7%. Five ZIs in four patients failed. The mean time between implant placement and failure was 8.6 years (range, 0.5-13.3). All patients received immediate loading with acrylic prosthesis. The successful rates for the definitive prosthesis were 98.2%. Forty-two patients received posterior cantilever for rehabilitation of fixed definitive prosthesis. Local orofacial inflammation (35.7%) and Sinusitis (12.5%) were the most common complications, occurring at a mean follow-up of 10.0 (range, 4.2-14.9) and 10.3 (range, 4.3-16.2) years, respectively. In 48 patients, the mean score of the OHIP-14 questionnaire was 1.7 ± 2.6 with the follow-up period of 9.0 ± 4.1 years. CONCLUSIONS: The rehabilitation of severely atrophic edentulous maxilla using the QZP has shown a predictable and high survival rate in the long term. The implementation of an immediate loading protocol offers potential benefits in stabilizing ZIs with cross-arch stabilization. Moreover, the use of a posterior cantilever in reconstruction can effectively establish functional occlusion through well-distributed ZIs, eliminating the need for additional implant placement.

Successful Reduction of Unilateral Zygoma Fracture Following Bilateral Malar Reduction Surgery.

Malar reduction surgery can increase its susceptibility to fractures in case of trauma. Patients who had malar reduction surgery and sustained a zygoma fracture pose unique challenges for treatment and management. This is a case of a 28-year-old female patient who presented with a unilateral zygoma fracture following bilateral malar reduction and augmentation rhinoplasty 6 years ago. Physical examination revealed a clicking sound when opening the mouth at the right zygomatic buttress and a depressed preauricular area, suggesting arch fracture. Computed tomography imaging demonstrated a loosened screw at the right zygomatic buttress and a depressed arch fracture. She wanted to remove all plates and treat her right fractured zygoma with absorbable materials. Through the bilateral intraoral incisions, the authors removed the plates and screws and reduced the depression with the Langenbeck elevator through the same right intraoral incision without fixation. The reduction was well-maintained without complications based on postoperative plain x-rays 1 month after surgery. She reported that the pain was mostly gone and that she did not hear any abnormal sounds when opening her mouth after the surgery. In this case, if the zygomaticomaxillary buttress is minimally displaced, but the zygomatic arch fracture is significantly depressed, the authors believe that fracture reduction with only an intraoral incision would be enough to achieve an optimal outcome. If the plates and screws used in the previous malar reduction are not well maintained, it may be necessary to remove them.

Volume Redistribution of the Buccal Fat Pad After Reduction Malarplasty.

BACKGROUND: During reduction malarplasty, cheek bulging could be found immediately after zygomatic complex is moved inwards, backwards and upwards. As patient is in the supine position during surgery, the effect of gravity is eliminated, so the only reason for the bulge is the redistribution of the soft tissue in the deep facial spaces. The buccal fat pad, with its main body behind the zygomatic arch and buccal extension in the cheek area, is most likely to be responsible for the bulge. METHODS: 3D buccal extension models were reconstructed from preoperative and long-term follow-up CT images and the volume measured. By comparing the pre- and postoperative 3D models, the shape deviation of the buccal extension and facial soft tissue can be identified. RESULTS: Eleven patients (22 buccal extensions) met the inclusion criteria. Compared with the preoperative buccal extension volume, the postoperative volume increased significantly. By comparing the reconstructed models, the buccal extension volume increase with anteroinferior protrusion can be visually detected, and cheek bulging was clearly identified on the lower face. The bulging area coincided with the projection of the buccal extension on the skin surface. CONCLUSIONS: Reduction malarplasty may cause volume redistribution of the buccal fat pad. Therefore, preoperative assessment of the size of the buccal fat pad based on CT images is recommended. The buccal extension volume increase with anteroinferior protrusion is an important cause of postoperative cheek bulging and should be considered during treatment. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Peri-zygomatic complications on zygomatic implants with or without penetrating the external surface of zygoma: A 2-year retrospective study.

OBJECTIVES: The main purpose of this retrospective study was to assess the difference in the incidence of peri-zygomatic complications (PZCs) when zygomatic implants (ZIs) penetrate or do not penetrate the external surface of zygoma. MATERIALS AND METHODS: This study included 32 patients with edentulous maxillae or potentially edentulous maxillae undergo zygomatic implantation. The patients were divided into the penetration group (P-group) and the non-penetration group (N-group) according to whether the apex of implants penetrated the external surface of zygoma in postoperative CBCT. The extension length, the penetration section of the implants, and the skin thickness at the corresponding position were simultaneously measured. Clinical follow-up was conducted regularly until 2 years after surgery. The occurrence of PZCs (including peri-zygomatic infection, skin numbness, non-infectious pain, and foreign body sensation) was recorded. A mixed effect logistic model was used to compare the difference of complication rate between the P-group and the N-group, and odds ratio (OR) was calculated. Then identify the impact of the extension length, penetration section and skin thickness in P-group with the same model. RESULTS: A total of 71 ZIs were implanted in 32 patients, including 37 implants in the P-group and 34 implants in the N-group. During the 2-year follow-up, a total of 13 implants occurred PZCs, with an overall complication rate of 18.3%. Thereinto, the incidence rate was 29.7% in the P-group, and 5.9% in the N-group (OR = 6.77). In P-group, there was a significant difference in complication rate of different extension lengths, while the penetration section and skin thickness had no statistical significance on the complication rate. CONCLUSION: Under the limitation of this study, to minimize the risk of PZCs, ZI should be placed in a manner that avoids the apex penetrating the external surface of the zygoma.

Combining Patient-specific Implant With Malar Reduction to Repair Mid-facial Asymmetry Caused by Craniofacial Fractures in Asians.

Mid-facial asymmetry caused by bone defect or deformation resulted from craniofacial fracture was a common secondary complication needed to repair. Patient-specific implant (PSI) designed with the unaffected side as a template is a good choice to repair this kind of facial asymmetry. However, in Asians, the broad and prominent zygomatic bone in unaffected side is not an optimal template, because the oval facial shape was considered as a more attractive appearance in Asian esthetic concept. To repair the mid-facial asymmetry and to improve the facial contour, the authors combined PSI implantation with malar reduction in one-stage surgery. The authors referred the facial proportion index (the optimal ratio of mid and lower face was 1.27) as a basis for preoperative precise design to determine the ideal facial shape of unaffected side, and used mirror image overlay technique with the ideal shape of unaffected side as a template to design the PSI. With this surgical strategy, patients not only can repair facial asymmetry but also can get a more attractive appearance.

Anti-sagging Method in Reduction Malarplasty: Application of the Bracing System with the Preservation of the Zygomaticus Major Muscle Bony Attachment.

BACKGROUND: Cheek drooping after reduction malarplasty remains a concern for patients. OBJECTIVES: To evaluate the anti-drooping effectiveness of the bracing system technique with the preservation of the zygomaticus major muscle (ZMj) bony attachment and to determine the role of ZMj in anti-drooping. METHODS: A retrospective analysis was conducted of patients who accepted this method in our department from February 2016 to May 2021. Patients' subjective evaluation and two plastic surgeons' objective assessment of photographs were performed. The pre- and postoperative three-dimensional (3D) ZMj models were reconstructed and compared. ZMj length and tortuosity were also measured from 3D models. RESULTS: Twenty-two patients (44 ZMjs) met the inclusion criteria. Most patients (21/22, 95.45%) were satisfied with the postoperative appearance without ageing after reduction malarplasty, except for one feeling slightly older after the operation. The objective scoring results showed no deepening of the nasolabial fold in the majority (20/22, 90.91%) of patients. Two patients were one-grade worse, from score 1 to 2. Upward movement of the postoperative ZMj bony attachment was clearly observed compared with the preoperative 3D model. The significantly reduced ZMj tortuosity (p < 0.001) and the slightly increased ZMj length (not significant) after surgery supported the straightening of the ZMj which was also seen in the 3D comparison. CONCLUSIONS: The bracing system technique with preservation of the bony attachment of the ZMj is an effective and cost-effective anti-sagging method for reduction malarplasty. The ZMj was lifted and straightened after reduction malarplasty, which helped to prevent sagging. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Surgical and health related quality of life outcomes following treatment with zygomatic implant perforated (ZIP) flaps.

BACKGROUND: The zygomatic implant perforated (ZIP) flap is a novel approach to the challenge of reconstructing the maxilla. We report on our experience using the ZIP flap technique for patients undergoing infrastructure maxillectomy at Chris O'Brien Lifehouse, Sydney, Australia. METHODS: Thirteen patients who underwent a ZIP flap reconstruction between August 2019 and August 2021 were identified. Demographic, surgical, and histopathological information was collected. Health Related Quality of Life (HRQOL) was assessed using the FACE-Q Head and Neck Cancer module, the M.D. Anderson Dysphagia Inventory, and the Speech Handicap Index. RESULTS: A total of 44 zygomatic implants were placed, of which 42 (95%) survived. The median time from surgery to dental rehabilitation was 35 days. HRQOL data was available for nine patients over 24 months, demonstrating improved speech and swallowing outcomes over the follow up period. CONCLUSIONS: The ZIP flap is a reproducible surgical technique that facilitates rapid dental rehabilitation post infrastructure maxillectomy.

Technique-Related Survival Rate and Complications of Zygomatic Implant Placement: A Systematic Review and Meta-Analysis.

PURPOSE: To assess the survival rate (SR) and probability of postoperative complications at both the implant and patient level for each of the four surgical techniques for zygomatic implant (ZI) placement: Brånemark, sinus slot, extrasinus, and extramaxillary. MATERIALS AND METHODS: A systematic literature review and meta-analysis of clinical studies that reported the survival rate and postoperative ZI complications for the rehabilitation of atrophic edentulous maxillae was conducted based on PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) recommendations. Two independent reviewers consulted four databases during the literature search: MEDLINE (PubMed), Google Scholar, Clinicaltrials.gov, and LILACS. Duplicate articles were eliminated. RESULTS: A total of 35 studies were included in the meta-analysis. Subgroup analysis showed that study design (prospective vs retrospective) had no significant impact (P = .10) on the outcomes. The SR was highest for the Brånemark and extrasinus techniques (100%) and lowest for the sinus slot technique (94%; 95% CI = 86% to 102%). The extramaxillary (38%; 95% CI = 1% to 3%) and the Brånemark (29%; 95% CI = 15% to 44%) techniques resulted in the highest occurrence of patient-level complications. Moreover, the extramaxillary technique showed the highest percentage of prothesis-related complications (44%; 95% CI = 27% to 62%). CONCLUSIONS: ZI placement was demonstrated to be a reliable technique for the rehabilitation of severely atrophic maxillae, irrespective of the surgical technique evaluated. Accurate case and surgical protocol selection is of paramount importance to reduce technique-related postoperative complications.

Role of Intraoperative Imaging in Improving Closed Reduction of Zygomatic Arch Fractures: A Systematic Review and Meta-analysis.

PURPOSE: The use of intraoperative imaging (IOI) to improve the reduction adequacy of zygomatic arch (ZMA) fractures has been reported, but few systematic reviews have examined this topic. The aim of this review was to investigate and compare the value of IOI with conventional methods without IOI (N-IOI) for the closed reduction of ZMA fractures. METHODS: Electronic retrieval of MEDLINE, Embase, Cochrane Library, Web of Science, Scopus, and citation search until December 2, 2022, was used to identify controlled clinical trials that employed IOI for improving adequacy in closed reduction of ZMA fractures. The predictor variable was the use of IOI-yes/no (IOI vs N-IOI). The covariates included imaging technique (ultrasound, C-arm, and cone beam computed tomography) and ZMA fracture type (M-shape fracture, mechanistic force in 1 direction; variable fracture, mechanistic force in 2 directions). The primary outcome variables were the reduction adequacy of ZMA fractures (the remaining cortical step and dislocation angle) compared with the ideal mirrored position. Weighted or mean differences, risk ratios, and corresponding 95% confidence intervals were calculated, where P >.05 and I2＜50% fixed effect model was adopted, and a vice versa random effect model was adopted. RESULTS: A total of 1250 studies were identified, of which 6 studies with 259 participants were included. The meta-analysis results indicated that compared with N-IOI, IOI yielded fewer cortical steps (-1.76 [-2.42, 1.10], P ＜.00001, fixed model) and dislocation angles (-5.60 [-8.08, 3.12], P＜.00001, fixed model) in patients with variable ZMA fractures, while no significant difference was detected in the M-shape ZMA fracture (-0.72, [-2.93, 1.48], P = .52; -1.48, [-3.51, 0.55], P = .15). Although there was no significant difference in postoperative correction (0.35, [0.06, 2.01] P = .24, fixed model), all secondary revision cases occurred in the N-IOI group. Descriptive analysis showed that IOI yielded better symmetry and appearance satisfaction. CONCLUSION: IOI improved the adequacy of the procedure and led to a better postoperative appearance, especially for patients with variable ZMA fractures. Furthermore, the use of IOI avoided the risk of secondary surgery. In future studies, researchers should standardize the scale and outcomes to facilitate the intuitive evaluation of reduction adequacy.

Stress distribution and displacement with four different types of MARPE on craniofacial complex: A three-dimensional finite element analysis.

BACKGROUND: Various designs of mini-implants assisted rapid palatal expander (MARPE) appliances can impact treatment effectiveness through their biomechanical effects. The purpose of the study was to study the stress distribution and displacement with four different designs of the MARPE appliance on the craniofacial complex. METHODS: A 3D finite element model of the craniofacial complex was created from CBCT DICOM data, comprising four distinct groups. Each group consisted of one 4-hole expansion screw positioned between the second premolar and first molar in all models. Group 1 used four single-cortical mini-implants (1.5×8mm) engaging only the palatal cortex. Group 2 employed four mini-implants (1.5×11mm) engaging both the palatal and nasal cortices. Group 3 had monocortical implants on the palatal slopes, while Group 4 was similar to group 3 with implants in the acrylic wings. Comparisons between groups were made for anchorage (groups 1 and 2), mini-implant position (groups 1 and 3) and surface effect (groups 3 and 4). Von Mises stresses and displacements at various skeletal and dental points were evaluated using ANSYS software. RESULTS: The highest stresses were observed in the maxillary, pterygoid and zygomatic bones, as well as in the mid- palatal suture in all four groups. Downward and forward rotation of the craniofacial complex was noted. Group 2 showed greater skeletal expansion than group 1. Among groups 1 and 3, group 3 showed a better stress distribution. Group 4 showed less dentoalveolar rotation than group 3. CONCLUSIONS: The MARPE appliances had an impact on the craniofacial complex with stresses on the mid-palatal suture, maxillary bone, pterygoid bones and anterior teeth. Clockwise rotation of the maxilla, zygomatic bones and dentition was noted, while the pterygoid bones and pterygoid suture were displaced backwards. MARPE with bicortical anchorage produces better skeletal expansion. Placing implants on the palatal slopes with acrylic wings results in better skeletal expansion with less clockwise rotation of the dentition.

The Value of Intraoperative Computed Tomography in the Treatment of Zygomatic Complex Fractures.

BACKGROUND: Due to the complex anatomical morphology and lack of anatomic markers on the surface of zygomatic complex (ZMC), the treatment results of ZMC fractures are often suboptimal. PURPOSE: The study aimed to evaluate the effectiveness of intraoperative computed tomography (ICT) in the treatment of unilateral ZMC fractures, and further study the feasibility of ICT to replace early postoperative Computed Tomography (CT). STUDY DESIGN, SETTING, AND SAMPLE: The investigators designed a retrospective cohort study. Adult patients who underwent surgery with unilateral ZMC fractures were enrolled. PREDICTOR VARIABLE: According to whether intraoperative CT was used, the subjects were divided into the ICT group and the control group (without ICT). MAIN OUTCOME VARIABLES: Five distances and 3 angles representing bilateral ZMC symmetry were main outcome variables. The differences of outcome variables were compared between the 2 groups and the indices of ICT group were further compared with their postoperative indices. COVARIATES: Demographics (eg age), etiology (eg traffic injury), dysfunction (eg diplopia), and surgical approach (eg vestibular incision) were collected as covariates while we conducted clinical investigation, examination, and implementation. ANALYSES: The data were analyzed using independent-samples t test, paired-samples t test, Mann-Whitney U test, and χ2 test. P value < .05 was considered statistically significant. RESULTS: A total of 60 patients (18 to 59 years) were enrolled in this study. All median values of the measurements in the ICT group were smaller than those in the control group, and the differences of horizontal displacement distance (0.56 vs 1.02 mm), anteroposterior displacement distance (1.69 vs 2.34 mm, 0.90 vs 2.35 mm), horizontal angle of bilateral zygomatic arch (2.31 vs 4.19°), and horizontal angle of bilateral zygomatic process (1.77 vs 2.94°) were significantly different between the 2 groups with P value < .05. Moreover, there was no statistically significant difference in all indices between the intraoperatively and postoperatively injured sides in the ICT group. CONCLUSIONS: ICT can improve the treatment outcomes of ZMC fractures by evaluating the fracture reduction adequacy during surgery. Moreover, ICT can replace early postoperative CT.