Image fusion-based low-dose CBCT enhancement method for visualizing miniscrew insertion in the infrazygomatic crest.

Digital dental technology covers oral cone-beam computed tomography (CBCT) image processing and low-dose CBCT dental applications. A low-dose CBCT image enhancement method based on image fusion is proposed to address the need for subzygomatic small screw insertion. Specifically, firstly, a sharpening correction module is proposed, where the CBCT image is sharpened to compensate for the loss of details in the underexposed/over-exposed region. Secondly, a visibility restoration module based on type II fuzzy sets is designed, and a contrast enhancement module using curve transformation is designed. In addition to this, we propose a perceptual fusion module that fuses visibility and contrast of oral CBCT images. As a result, the problems of overexposure/underexposure, low visibility, and low contrast that occur in oral CBCT images can be effectively addressed with consistent interpretability. The proposed algorithm was analyzed in comparison experiments with a variety of algorithms, as well as ablation experiments. After analysis, compared with advanced enhancement algorithms, this algorithm achieved excellent results in low-dose CBCT enhancement and effective observation of subzygomatic small screw implantation. Compared with the best performing method, the evaluation metric is 0.07-2 higher on both datasets. The project can be found at: https://github.com/sunpeipei2024/low-dose-CBCT .

Consideration of the diameter of superficial temporal arteries related to filler injections in the temporal region.

BACKGROUND: The concavity of the temple due to adipose tissue atrophy from aging accentuates the zygomatic arch and lateral orbital rim, leading to an aged appearance. The use of hyaluronic acid filler in the temporal region has gained popularity due to its procedural simplicity and consistent outcomes. OBJECTIVE: To evaluate the safety of administering hyaluronic acid filler in the temporal region concerning the frontal branch of the superficial temporal artery, which is at risk of injury. METHODS: Empirical observations were conducted on the internal diameter of the frontal branch of the superficial temporal artery, a critical anatomical site for potential injury. RESULTS: A significant proportion of the artery segments exhibited an internal diameter below 1 mm. Given that the outer diameter of an 18-gauge cannula is 1.27 mm, this method can be considered a relatively secure approach for enhancing the temporal region. CONCLUSION: The use of an 18-gauge cannula for hyaluronic acid filler administration in the temporal region appears to be a safe and effective method, with the potential risk to the frontal branch of the superficial temporal artery being minimal.

Post-Treatment Displacement of Facial Soft Tissue Fillers-A Retrospective Ultrasound-based Investigation of 382 Zygomatic Regions.

BACKGROUND: Clinical and ultrasound experience has revealed that after soft tissue injections of the lateral cheek, the filler may displace from the zygoma to the caudal temporal area. OBJECTIVE: To obtain more data to provide insight into product distribution when soft tissue fillers are injected in the zygomatic region. METHODS: Two hundred patients were examined with facial ultrasound imaging of the zygomatic and temporal region. Inclusion criteria were simply a positive response on the screening questionnaire as to whether or not they had filler injections placed in their lateral cheek. Control injections were also performed to the zygomatic regions of a body donor and in 10 patients ultrasound-guided. RESULTS: A correlation was found between the layers in which filler was detected on the zygoma and where it was ultimately found in the temples. Four different redistribution patterns were observed: (1) migration of filler within the superficial muscular aponeurotic system (SMAS) on the zygoma into the superficial temporal fascia. Migration of filler from the lateral suborbicularis oculi fat to (2) the deep interfacial plane of the temple or (3) to the superficial temporal fat pad; (4) migration from the supraperiosteal layer of the zygoma to the superficial temporal fat pad. Body donor and patients: filler deposits injected on the zygoma were witnessed to shift during injection into the caudal part of the temple. CONCLUSION: Soft tissue filler aliquots may be redistributed into the temples after injections of the lateral side of the zygomatic arch. The displacement follows a distinct pattern depending on the initial layer of injection.

Zygomatic Anterolateral Temporal Approach for P1/P2 segment complex posterior cerebral aneurysm: a single-center retrospective study.

Treating complex posterior cerebral artery (PCA) aneurysms, such as fusiform, giant, and dissecting aneurysms, poses significant challenges. Parent artery occlusion carries a risk of ischemic stroke and fails to alleviate mass effects. This study aims to analyze the technical nuances and patient outcomes of treating complex PCA aneurysms, ranging from the P1 to P2P segments, using a Zygomatic Anterolateral Temporal Approach(ZATA) combined with flow reconstruction. This study was a retrospective study. Surgical treatment was performed on twelve patients with complex PCA aneurysms located in the P1 to P2P segments. Ten patients underwent flow reconstruction including Superficial Temporal Artery(STA)-Middle Cerebral Artery(MCA),Internal Maxillary Artery(IMA)-Radial Artery(RA)-MCA,STA-PCA(P2), and IMA-RA-PCA(P2). The aneurysm occlusion rate, surgical complications, and patient prognosis, including stroke occurrence/ modified Rankin Scale(mRS), were recorded and analyzed. Using the ZATA, all twelve complex PCA aneurysms were successfully clipped/resected/trapped. This included two high-position aneurysms (> 3 mm above the posterior clinoid process) at the P1/P2 junction and three P2P aneurysms. The mass effects of six large or giant aneurysms were resolved or alleviated. Postoperative and follow-up CTA/DSA confirmed the patency of the bypass vessels. Four patients experienced strokes in the perioperative period, with three ischemic and one hemorrhagic. The median follow-up period was 28.5 months. At the last follow-up, the good prognosis rate (mRS ≤ 2) was 83.3%, and one patient had died. Clipping/resection/trapping of aneurysms via the ZATA, combined with flow reconstruction, is a feasible option for treating complex PCA aneurysms from the P1 to P2P segments. This approach helps maintain or improve cerebral perfusion in the affected vascular territory.

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.

Orthodontic maxillary molar movement-induced zygomatic pillar remodeling and its consequences on occlusal characteristics and stress distribution.

OBJECTIVE: We aimed to evaluate changes in the zygomatic pillar during orthodontic treatment involving premolar extraction, analyze the effects of maxillary first molar movement on zygomatic pillar remodeling, and examine occlusal characteristics and stress distribution after remodeling. METHODS: Twenty-five patients who underwent premolar extraction were included in the study. The zygomatic pillar measurement range was defined, and cross-sectional areas, surface landmark coordinates, alveolar and cortical bone thicknesses, and density changes were assessed using Mimics software based on the cone-beam computed tomography scans taken before (T0) and after the treatment (T1). Multiple linear regression analysis was performed to determine the correlation between changes in the zygomatic pillar and maxillary first molar three-dimensional (3D) movement and rotation. Additionally, the correlation between pillar remodeling and occlusal characteristics was analyzed by Teetester. Pre- and post-reconstruction 3D finite element models were constructed and loaded with an average occlusal force of two periods. RESULTS: The morphological and structural remodeling of the zygomatic pillar after orthodontic treatment involving premolar extraction showed a decreased cross-sectional area of the lower segment of the zygomatic pillar. The zygomatic process point moved inward and backward, whereas the zygomatico-maxillary suture point moved backward. The thicknesses of the zygomatic pillar alveolar and cortical bones were thinner, and reduced alveolar bone density was observed. Simultaneously, the movement and angle change of the maxillary first molar could predict zygomatic pillar reconstruction to a certain extent. With decreasing the total occlusal force and the occlusal force of the first molar, occlusal force distribution was more uniform. With zygomatic pillar remodeling, occlusal stress distribution in the zygomatic alveolar ridge decreased, and occlusal stress was concentrated at the junction of the vertical and horizontal parts of the zygomatic bone and the posterior part of the zygomatic arch. CONCLUSIONS: Orthodontic treatment involving premolar extraction led to zygomatic pillar remodeling, making it more fragile than before and reducing the occlusal force of the maxillary first molar and the entire dentition with stress concentrated in weak areas. CLINICAL RELEVANCE: No other study has focused on the effects of orthodontics on pillar structures. The present study indicates that the mesial movement of the maxillary first molar weakened the zygomatic pillar and reduced occlusal function, thereby providing insights for inserting anchorage screws and facial esthetics.

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.

Three-dimensional Measurement of the Zygomatic-maxillary Complex in the Class III Malocclusion Patients with Maxillary Retrusion.

This study investigated the anatomic features of the zygomatic-maxillary complex in patients with maxillary retrusion without clefts. Individuals were grouped, and craniofacial measurements were performed for 21 individuals with skeletal Class III malocclusion with maxillary retrusion (CIII) and 48 individuals from the control group (CG). We evaluated the predetermined hard-tissue and soft-tissue points of the facial profile in each group. Independent sample t -tests were performed to determine the differences between groups (significance set at P <0.05). Multiple points on the midface, including the most posterior point on the contour of the maxillary alveolar process, lowest point of the zygomaticomaxillary suture, furthest point to the zygomatic self-base plane, superior point in the infraorbital foramen, and lowest point of the inferior margin of the orbit to the coronal plane were smaller in CIII than in CG (all P <0.05). The soft tissue thickness in these regions was significantly increased compared with that in the normal group. In summary, for class III malocclusion patients with maxillary retrusion, the deficiency in the midface gradually decreased going upward, with the deficiency at the maxillary alveolar level being the most serious. To some extent, soft tissues compensate for the deficiencies in the facial skeleton, and standard Le Fort I osteotomy advancement was sufficient to achieve a harmonious appearance.

Transmalar Kirshner Wire Fixation Under Ultrasound Scanning is Useful for Unstable Zygomatic Arch Fracture Combined With Zygomatic Body Fracture.

Plate fixation to zygomatic arch fractures carries the risk of facial nerve palsy and scarring of the cheek; however, without plate fixation, bone deviation or displacement may reoccur after surgery. Furthermore, zygomatic arch fractures combined with zygomatic body fractures are more postoperatively unstable than single zygomatic arch fractures. Few reports have focused on this combined fracture type, and no consensus has been reached regarding treatment. Because plate fixation for slight deviation of the zygomatic body has little advantage for stabilization, the authors, usually opt for transmalar pinning alone instead of plate fixation at the hospital. This study is a retrospective case series of 7 patients, among 100 zygomatic fractures excluding isolated zygomatic arch fractures, treated using transmalar pinning under ultrasound scanning. The reduction was performed through the oral and temporal incision as a surgical procedure. Under ultrasound observation, a Kirshner wire was inserted into the zygomatic body from the unaffected side while maintaining the reduced position. The wire was removed at an outpatient visit 2 to 3 months following surgery. In all cases, the zygomatic body was of the laterally rotated type, and postoperative morphologic evaluation showed improvement without postoperative complications. Scores were higher in middle-aged and older than in young people. Correction of zygomatic rotation also scored higher than zygomatic arch morphology. Transmalar Kirshner wire fixation under ultrasound observation is a simple and minimally invasive method for zygomatic arch fractures, which avoids the possible complications related to plate fixation.

Evaluation of Bone Thickness and Density Values in Resistance Regions in Rapid Maxillary Expansion Using Computed Tomography.

OBJECTIVES: This study used computed tomography (CT) to compare the bone thickness and density values around the zygomaticomaxillary, zygomaticotemporal, and pterygomaxillary sutures that are resistant to rapid maxillary expansion (RME) treatment according to age, sex, and cervical vertebrae maturation (CVM) stage. METHODS: The study included 200 paranasal sinus records obtained for medical diagnosis and examination in a radiology clinic. The records provided data on 110 males and 90 females aged between 4 and 28 years. Bone thickness and density values around the zygomaticomaxillary, zygomaticotemporal, and pterygomaxillary sutures were measured using CT imaging. The correlations of bone thickness and density values with the variables of age, sex, and CVM stage were evaluated. RESULTS: No statistically significant difference was revealed between the bone thickness values around the zygomaticomaxillary and zygomaticotemporal sutures and age, sex, CVM stage, and the right and left regions of the same individual ( P >0.05). A strong correlation was identified between Hounsfield units (Hu) values on bone density in all 3 regions and age and sex ( P <0.001). No correlation was found between the CVM stage and density values around the zygomaticomaxillary, zygomaticotemporal, and pterygomaxillary sutures ( P >0.05). CONCLUSIONS: The Hu values of the records from females were higher than those of males in all age groups. It was observed that with increasing age, bone density values increased in all 3 regions, and thus circummaxillary region's Hu value increased.

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 .

Evaluation of Different Fixation Methods Combinations After L-Shaped Osteotomy Reduction Malarplasty: An In Vitro Biomechanical Study.

BACKGROUND: This in vitro study compared the stability of different fixation method combinations for the zygomatic complex after simulated L-shaped osteotomy reduction malarplasty, a common facial contouring surgery in East Asia with high postoperative complications due to poor fixation methods. MATERIALS AND METHODS: The study used 108 zygoma replicas with various fixation methods combinations in the zygomatic body (L-shaped plate with short wing on zygoma and on the maxilla, two bicortical screws, one bicortical screw with L-shaped plate, square plate, and rectangular plate) and zygomatic arch (Mortise-Tenon structure, 3-hole plate, and Mortise-Tenon structure plus short screw). The failure force under incremental load was applied through the Instron tensile machine to a well-stabilized model using a rubber band simulating the masseter muscle and recorded the increasing force digitally. ANOVA test was used for comparison between recorded values (P < 0.05). RESULTS: The results showed that the most stable combination was a six-hole rectangular plate and a Mortise-Tenon structure plus one short screw (358.55 ± 51.64 N/mm2). The results also indicated that the placement vector of the fixation methods around the L-shaped osteotomy and the use of the two-bridge fixation method were important factors in enhancing the stability of the zygomatic complex. CONCLUSION: The study suggested that surgeons should choose appropriate fixation methods based on these factors to reduce postoperative complications and improve surgical outcomes. NO LEVEL ASSIGNED: This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. 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 .

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 .

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.

Investigating the Contraction Pattern of the Zygomaticus Major Muscle and its Clinical Relevance: A Functional MRI Study.

BACKGROUND: Our understanding of facial anatomy has significantly evolved, yet the detailed contraction patterns of facial muscles and their presentation during clinical imaging remain largely unexplored. Understanding the contraction patterns and visual presentation of these muscles, particularly the zygomaticus major could enhance pre-surgical facial assessments and the development of new treatment strategies. METHODS: A total of 34 healthy young individuals (17 female, 17 male) with a mean age of 23.6 (2.4) years [range: 20-30] were investigated regarding the length, thickness, width, and angle of the zygomaticus major muscle in five different facial expressions (i.e., repose, anger, joy, surprise, and sadness) utilizing MR imaging. RESULTS: Joyful expressions caused a reduction in muscle length to 85.6% of its original length and an increase in width (103.4%), thickness (108.4%), and facial angle (2.72°) when compared to that in repose, suggesting isotonic contraction. Conversely, expressions of anger, surprise, and sadness generally led to muscle stretching, seen through changes in length (98.9%, 104.3%, and 102.7%, respectively), width (98.8%, 96.5%, and 99.4%, respectively), and thickness (91.2%, 91.0%, and 102.7%, respectively), with variable alterations in facial angle (0.55°, 1.85°, and 1.00°, respectively) depending on the specific expression. CONCLUSION: This MRI-based study indicates that the zygomaticus major muscle experiences isotonic contraction, characterized by decreased length and increased width and thickness. The findings underline the importance of muscle thickness as a reliable parameter in assessing facial muscle function and offer valuable guidance for practitioners in accurately evaluating muscle performance during different facial expressions. NO LEVEL ASSIGNED: This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. 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 .

Learning curve of dynamic navigation-assisted zygomatic implant surgery: An in vitro study.

STATEMENT OF PROBLEM: Dynamic computer-assisted zygomatic implant surgery (dCAZIS) has been reported to provide clinical efficacy with high accuracy and low risk of complications. However, the learning curve before performing dCAZIS effectively is unknown. PURPOSE: The purpose of this in vitro study was to explore the learning curve of dCAZIS in dentists with different levels of experience in implant dentistry and navigation surgery. MATERIAL AND METHODS: Six senior dental students were randomly divided into 3 groups for initial training (FH-CI group: pretraining on freehand conventional implant surgery; FH-ZI group: pretraining on freehand ZI surgery; DN-CI group: pretraining on conventional implant surgery under dynamic navigation). Then, every operator conducted 6 repeated dCAZIS training sessions on edentulous 3-dimensional (3D) printed skull models and was asked to complete a self-report questionnaire after each training session. A total of 36 postoperative cone beam computed tomography (CBCT) scans with 144 ZI osteotomy site preparations were obtained and superimposed over the preoperative design for accuracy measurements. The operation time, 3D deviations, and results of the self-reports were recorded. Comparisons among groups were analyzed with independent-sample Kruskal-Wallis tests (α=.05), and correlations between study outcomes and the number of practices were calculated. RESULTS: Operator experience and increased practice times did not significantly affect the accuracy of dCAZIS (P>.05). However, the operation time varied among groups (P<.001), and significantly shortened with more practice, reaching 11.51 ±1.68 minutes at the fifth attempt in the FH-CI group (P<.001 compared with the first practice), 14.48 ±3.07 minutes at the third attempt in the FH-ZI group (P=.038), and 8.68 ±0.58 minutes at the sixth attempt in the DN-CI group (P<.001). All groups reached their own learning curve plateau stage within 6 practice sessions. As the number of practice sessions increased, the results from the self-report questionnaires gradually improved. CONCLUSIONS: Among dentists with different levels of experience in implant dentistry and navigation surgery, dCAZIS was found to have a learning curve with respect to operation time but not implant accuracy. Experience in ZI surgery had little impact on the learning curve of dCAZIS, but experience in navigation surgery was a key factor.

Long-term evaluation of soft-tissue changes after miniscrew-assisted and conventional rapid palatal expansion using voxel-based superimposition of cone-beam computed tomography scans.

INTRODUCTION: This study aimed to evaluate the soft-tissue changes in the long-term after miniscrew-assisted rapid palatal expansion (MARPE) and conventional rapid palatal expansion (RPE) appliances compared with a matched control group using voxel-based superimposition of cone-beam computed tomography (CBCT) scans. METHODS: A total of 180 CBCTs for 60 patients at 3-time points were evaluated: pretreatment (T1), postexpansion (T2), and posttreatment (T3) for 3 groups: (1) MARPE, (2) RPE, and (3) controls (time-period T1 to T3: MARPE, 2 years 8 months; RPE, 2 years 9 months; control, 2 years 7 months). The voxel-based superimposition technique was used to superimpose the CBCT scans, after which the soft-tissue surfaces were extracted from the superimposed T1-CBCT, T2-CBCT, and T3-CBCT scans. Nine landmarks were identified on the CBCT scans: nasion, A-point, pogonion, right and left alar base, right and left zygoma, and right and left gonion. The coordinates of the 9 parameters were obtained in the x-axis, y-axis, and z-axis for the CBCT scans and subjected to statistical analyses. The changes in the soft-tissue surfaces were also evaluated by color-coded maps for short-term (T2) and long-term (T3) changes. The mean changes from T1 to T2 and T1 to T3 were tested against no change within the groups by paired t test, and the mean changes among the 3 groups were compared with analysis of variance F test with Tukey's Honest significant difference used for adjusting P values for multiple testing. RESULTS: In the short term, both MARPE and RPE led to a significant downward movement of pogonion, left gonion, and lateral movement of the right and left alar base compared with controls at T2 (P <0.05). In addition, MARPE led to a significant downward movement of right gonion than controls at T2 (P <0.05). Moreover, RPE led to a significant downward and forward movement of A-point and downward movement of the right and left alar base than controls at T2 (P <0.05). However, in the long-term, there were no significant differences in the soft-tissue changes among the MARPE, RPE, and control groups. CONCLUSIONS: MARPE and RPE do not lead to significant soft-tissue changes in the long term when compared with controls.

Assessing the frequency and variability of accessory zygomatic sutures in dry skulls: clinical insights and potential implications.

PURPOSE: This study aimed to determine the presence and incidence of accessory sutures and bipartite zygomatic bone types, and their effects on population affinity and clinical significance. METHODS: We examined 120 dry skulls and 50 zygomatic bones to evaluate the presence, frequency, and location of accessory zygomatic sutures as well as subtypes of bipartite zygomatic bones. Morphometric analysis included measuring the total width and length of the zygomatic bone with accessory sutures (ASs), the total length of the AS, and the shortest distance between the AS and various anatomical landmarks. RESULTS: Bipartite zygomatic bone was observed in 14 of 120 dry skulls (11.6%) and 1 of 50 zygomatic bones (2%), indicating an overall incidence of 16 occurrences (8.82%). The ASs were predominantly located posterolaterally in 11 cases (six males, five females), anteromedially in two cases (one male, one female), superiorly in one case (male), and superolaterally in one case (male). Significant differences were noted in the distribution of the ASs (p < 0.001). Notably, a vertical inferior bipartite zygomatic type, which has not been reported in the literature, was identified. Correlations were observed between the various anatomical landmarks. Among females, the length of AS was significantly different (p = 0.038). Significant differences were also noted in the shortest distance between the AS and the zygomaticofacial foramen (ZFF) based on the body side (p = 0.034). CONCLUSIONS: Our study suggests that the bipartite zygomatic bone is not a common occurrence, indicating its significance as a morphological variation present in certain individuals. The type VII bipartite zygomatic bone exhibited the highest incidence rate, suggesting potential ethnic-specific differences in the prevalence of certain subtypes. The consistent pattern of suture distribution, along with the asymmetry and variability in suture patterns, emphasizes its potential clinical relevance.

Anatomical variations of the zygomaticofacial foramen and its related canal through the zygomatico-orbital and zygomaticotemporal foramina in dry human skulls.

PURPOSE: The aim of this study is to reveal the location of the zygomaticofacial foramina, the variations of their numbers, and their connections between the zygomatico-orbital and zygomaticotemporal foramina. METHODS: Ethics committee approval of our study was received by the Istanbul Medical Faculty Clinical Research Ethics Committee (date:30.07.2021, number:358356). 171 zygomatic bones of unknown gender from the Department of Anatomy, Istanbul University, were included in this study. The number of zygomaticofacial foramina and their connections with the zygomatico-orbital foramen and the zygomaticotemporal foramina were examined. Also, the morphometric distances between the zygomaticofacial foramen were calculated. Evaluation of the data was done with SPPS v.21. RESULTS: The number of zygomaticofacial foramina was found as 299. It was found single, double, three, four, five and six foramina, in 52 (30.4%), 52 (30.4%), 24 (14.03%), 10 (5.85%), 5 (2.93%), 1 (0.58%) zygomatic bone, respectively. Zygomaticofacial foramen was absent in 27 (15.8%) bones. Of these 299 foramina, 129 were found to be connected with zygomatico-orbital foramen and 23 with zygomaticotemporal foramen. It was noted that 147 zygomaticofacial foramina had no connection with any foramina. The distances between the zygomaticofacial foramen and the frontozygomatic suture, temporal process, maxillary process, the lowest point of the zygomatic bone, and orbital rim were found as 25.30 ± 2.81mm, 18.74 ± 3.56mm, 21.56 ± 4.16mm, 18.72 ± 2.57mm, 6.67 ± 3.27mm, respectively. CONCLUSION: Consequently, the location and variations of ZFF are of great importance for maxillofacial surgery and regional block anesthesia. Knowing its location and variations will help prevent complications during any surgical intervention in this region.