Round and flat zygomatic implants: effectiveness after a 3‑year follow‑up non‑interventional study

PURPOSE

This non-interventional study investigates variations in the type and frequency of late complications linked to novel zygomatic implant designs, installed adhering to the Zygoma Anatomy-Guided Approach (ZAGA) concept, over an extended follow-up period of at least 3 years.

METHODS

Consecutive patients presenting indications for treatment with ZIs were treated according to ZAGA recommendations. Implants were immediately loaded. The ORIS success criteria for prosthetic offset, stability, sinus changes and soft-tissue status were used to evaluate the outcome.

RESULTS

Twenty patients were treated. Ten patients received two ZIs and regular implants; one received three ZIs plus regular implants, and nine received four ZIs. Fifty-nine ZIs were placed: thirty-six (61%) Straumann ZAGA-Flat implants and twenty-three (39%) Straumann ZAGA-Round implants. Four patients (20%) presented earlier sinus floor discontinuities. Fifteen patients (75%) had prior sinus opacities. Nineteen patients were followed for between 38 and 53 months (mean 46.5 months). One patient dropped out after 20 months. When comparing pre-surgical CBCT with post-surgical CBCT, 84.7% of the sites presented identical or less sinus opacity; nine locations (15%) showed decreased, and another nine increased (15%) post-surgical sinus opacity. Fifty-three ZIs (89.8%) maintained stable soft tissue. Six ZIs had recessions with no signs of infection. ZIs and prosthesis survival rate was 100%.

CONCLUSIONS

The study highlights the effectiveness of ZAGA-based zygomatic implant rehabilitations using Round and Flat designs. Despite patient number constraints, minimal changes in the frequency of late complications from the 1-year follow-up were observed. 100% implant and prosthesis survival rate over a mean follow-up of 46.5 months is reported.

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.

Retrospective comparison of two different miniscrew-supported molar distalization methods applied in the buccal and palatal regions

BACKGROUND

To compare dentofacial effects of distalization with miniscrew-supported pendulum and infrazygomatic crest miniscrews.

METHODS

The study included 36 patients whose lateral cephalometric radiographs were obtained before (T0) and after (T1) distalization. Patients were divided into two groups according to the treatment methods: 1) distalization with miniscrew-supported pendulum (MSP) (n = 19; 14 girls and 5 boys; mean age 16.9 ± 1.46 years) and 2) distalization with infrazygomatic crest (IZC) miniscrews (n = 17; 8 girls and 9 boys; mean age 17.0 ± 1.68 years). Dental, skeletal and soft tissue measurements were performed on lateral cephalograms taken from individuals.

RESULTS

A significant molar distalization was achieved both in the MSP group (3.52 ± 0.76 mm at 8.71 ± 2.02 months) and the IZC group (3.5 ± 0.74 mm at 9.7 ± 2.5 months) (P < 0.001 for both). Premolar distalization was significantly lower in the MSP group (1.73 ± 1.09 mm) than in the IZC group (2.81 ± 0.79 mm) (P < 0.01). Significant molar tipping was observed in both groups (P < 0.001), while no significant difference was found between the groups (P > 0.05). Retrusion of maxillary incisors were significantly higher in the IZC group (2.75 mm) than in the MSP group (0.98 mm) (P < 0.01). A significant difference was found between the two groups with regard to the changes in overjet and overbite (P < 0.05).

CONCLUSIONS

Both distalization methods were found to be effective in achieving a Class I molar relationship in patients with Class II malocclusion.

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.

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 .

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.

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 .

Temporary Anchorage Device Misplaced into Infratemporal Space - A Case Report

INTRODUCTION

During orthodontic treatment, temporary anchoring devices (TADs) are used to restrain tooth movement. They are a relatively recent addition to the dental toolkit.

AIM

As TADs have limitations, Dr. Eric Lieu of Taiwan developed Infra Zygomatic Crest (IZC) screws which are placed between the maxillary second premolar at the bony crest.

TREATMENT PLANNING

The goal of this case study is to emphasize the value of anatomy, site selection, and IZC retrieval in the event of an accident. Cone beam computed tomography was used as a diagnostic tool for the precise location of the displaced IZC and immediate surgical retrieval was done under local anesthesia from the infratemporal space to prevent further complications.

TAKEAWAY LESSONS

Orthodontists knowledge of soft tissue and hard tissue anatomy and precise positioning is crucial for successful TAD implantation.

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 radiographic assessment of different fixation methods stability after l-shaped osteotomy reduction malarplasty: A comparative retrospective study

BACKGROUND

Reduction malarplasty (RM) is a common facial contouring procedure among Orientals. Currently, fixation methods selection and placement vectors are controversial. Therefore, this study aimed to evaluate the effect of different zygomatic complex fixation methods on surgical outcomes stability after RM.

MATERIALS AND METHODS

In this retrospective study, 60 consented patients (120 operated zygoma) who met inclusion criteria were included. ITK-SNAP and 3D Slicer software were used to measure the displacement of the zygomatic complex using postoperative CTs (T1: one week and T2: six months). The region of interest included zygomatic body fixation methods (ZBFm), namely: two bicortical screws (2LS); an l-shaped plate with one bicortical screw (LPLS); an l-shaped plate with short-wing on the zygoma (LPwZ) and on the maxilla (LPwM), combined with zygomatic arch fixation methods (ZAFm), including Mortice-Tenon (MT); 3-hole plate (3HP); and short screw (SS). ANOVA test was used to compare the displacement values among ZBFm/ZAFm combinations.

RESULTS

The 2LS and LPLS groups showed lower displacement than the single l-shaped plate (P< 0.001, P = 0.001), which performed better when the short-wing was fixated on the maxilla (0.9 ± 0.4 mm and 1.2 ± 0.6 mm respectively).

CONCLUSION

After RM, the two-bridge fixation methods (2LS and LPLS) provide better stability than the single l-shaped plate. All ZAF methods showed similar stability when combined with 2LS or LPLS as zygomatic body fixation methods.

Longitudinal reactions of maxillary sinus in patients treated with multiple zygomatic implants: A modified radiographic evaluation with clinical follow-up

OBJECTIVES

To investigate the effects of zygomatic implant placement on the maxillary sinus using radiographic and clinical indicators.

METHODS

Patients with an atrophic maxilla who underwent zygomatic implant placement were included. The thickness and morphology of the Schneiderian membrane (SM), infundibular obstruction, and posterior bone wall of the maxillary sinus were analyzed. The generalized estimating equation and chi-square tests were performed to compare the measurements.

RESULTS

Fifty patients with 100 maxillary sinuses were included. In total, 148 zygomatic implants and 105 regular implants were placed in the maxilla. Overall, the mean pre- and postoperative SM thickness was 2.79 ± 3.26 mm and 3.97 ± 5.45 mm, respectively (p = 0.063). In sinuses with two zygomatic implants, the SM thickness increased significantly from 2.12 ± 2.14 mm preoperatively to 4.07 ± 6.14 mm postoperatively (p = 0.026). The number of sinuses with type IV morphology (fully radiopaque) increased from zero preoperatively to six (13%) postoperatively. Sinuses with a single zygomatic implant showed no difference in the pre- and postoperative SM thickness. Postoperatively, six sinuses had infundibulum obstructions. Postoperative osteitis of the bilateral sinuses was found in two patients.

CONCLUSIONS

We have proposed a new imaging evaluation method and system for evaluating the maxillary sinus response. Preoperative infundibulum obstruction combined with mucosal thickening and double zygomatic implant placement are more likely to induce postoperative maxillary sinus mucositis and osteitis.

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.

Treatment of Sagittal Fracture of the Zygomatic Arch Root

A sagittal fracture at the temporal root of the zygomatic arch (ZAR) often occurs as a component of zygomaticomaxillary complex (ZMC) fractures. However, this area is difficult to access, and anchorage is limited due to the unstable structure around it. Therefore, a preauricular approach using single-screw fixation is proposed, and this study reports its results and usefulness. Forty-four patients with sagittal fractures of ZAR occurring with ZMC fractures were evaluated from 2012 to 2021. Open reduction and internal fixation were performed on all patients with ZMC fractures. Closed reduction using Dingman incision and external finger pressure in group A (indirect approach; 30 patients) and single-screw fixation using a preauricular approach in group B (direct approach; 14 patients) were performed to address sagittal fractures in ZAR. For single-screw fixation, the additional mean operation time was 11.34±3.25 minutes. On postoperative 3-dimensional computed tomography and plain radiographs, group B showed more accurate reduction and less deformity and trismus ( P <0.05). Moreover, a normal diet was initiated more quickly in group B than in group A ( P <0.05). Some cases in group A showed nonunion or malunion. This study revealed that a direct approach (group B) toward sagittal fractures of ZAR is recommended due to more accurate results and fewer complications than those observed with the indirect approach (group A). Moreover, the total operation time and complications may be lesser than those with the bicoronal approach.

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.

Quantitative assessment of image artifacts from zygoma implants on CBCT scans using different exposure parameters

This study was aimed at quantifying artifacts from zygoma implants in cone-beam computed tomography (CBCT) images using different exposure parameters. Two cadaver heads, one with two zygoma implants on each side and the other for control, were scanned using 18 different exposure parameters. Quantitative analysis was performed to evaluate the hypodense and hyperdense artifact percentages calculated as the percentage of the area. Hyperdense artifacts and hypodense artifacts were detected, followed by the calculation of the hyperdense and hypodense artifact percentages in the image. In the qualitative analysis of the artifacts, the scores used were as follows: absence (0), moderate presence (1), or high presence (2) for hypodense halos, thin hypodense lines, and hyperdense lines. Artifact analysis was performed qualitatively and quantitatively using the post-hoc Tukey and Two-way ANOVA tests. As a result, in the qualitative analyses, zygoma implants showed a significant difference compared to the control group with regard to hyperdense and hypodense artifacts (p < 0.05). There was a significant difference between the means according to the FOV size arithmetic averages (p < 0.05). In terms of voxel size, the difference was found to be significant, where 400 microns showed the highest hypodense artifact while 200 microns showed the lowest hypodense artifact. In conclusion, hypodense and hyperdense artifacts were significantly higher in cadavers with zygoma implants than in controls. As FOV and voxel size increase, more hypodense artifacts are produced by zygoma implants so smaller FOV and voxel sizes should be used to prevent poor image quality of adjacent teeth.

Precise Coronoidectomy and Zygomatic Arch Reduction for Unilateral Hyperplasia of the Coronoid Process (Jacob's Disease) via Computer-aided Design and Manufacture

Jacob disease is the new formation of a pseudo-joint between both of enlarged coronoid process and even zygomatic arch. A 23-year-old female patient with facial asymmetry and limited mouth opening was reported. Computed tomography images showed the classic symptom of Jacob disease with a mushroom-shaped tumor mass from the coronoid process a pseudoarthrosis joint with zygomatic arch. Coronoidectomy and zygomatic arch reduction were planned to operate based on computer-aided design/computer-aided manufacturing. During the actual operation, the excision of coronoid process and reconstruction of zygomatic arch were all navigated by 3-dimensional-printed surgical templates as designed through an intraoral approach. As a result, the enlarged coronoid process was smoothly removed without sequela and mouth opening along with facial symmetry were successfully improved. The authors suggested that computer-aided design/computer-aided manufacturing should be considered as an auxiliary technique to shorten operation time and enhance surgical accuracy.

Intraosseous venous malformation of the zygoma: Case report and pooled analysis

The objective of this study is to provide a comprehensive summary of the clinical and radiological features of zygomatic intraosseous venous malformations (IVM), as well as its treatment strategies. The aim is to establish preoperative diagnostic bases that will aid in the identification of zygomatic IVM and facilitate the implementation of effective treatment. Four cases of pathologically diagnosed zygomatic IVM with typical clinical and radiological features were reported. They exhibited comparable clinical and radiological features, and the En bloc excision and reconstruction yielded satisfactory outcome. Pooled data analysis was performed with additional 74 cases collected from 63 previous studies. The results revealed a higher incidence of zygomatic IVMs in middle-aged females, with swelling, pain and ocular dysfunction being the typical clinical manifestations. The characteristic radiological features of these lesions were well-defined, round bony structures with specific internal trabecular patterns. A diagnostic flow-chart assisting the differential diagnosis of IVM was established. En bloc excision was deemed the most advantageous treatment option, as it presented minimal risk of haemorrhaging and no instances of recurrence. The decision to pursue reconstruction was contingent upon the extent of the defect. Alloplastic material has emerged as the most frequently employed reconstruction material in recent reports. The summarized characteristics of zygomatic IVM and the proposed diagnostic and treatment strategies, derived from the pooled analysis of reported cases, may help to improve diagnosis and management in further clinical practice.

A novel technique to quantify bone-to-implant contact of zygomatic implants: a radiographic analysis based on three-dimensional image registration and segmentation

OBJECTIVES

The purpose of this study is to establish a novel, reproducible technique to obtain the BIC area (BICA) between zygomatic implants and zygomatic bone based on post-operative cone-beam computed tomography (CBCT) images. Three-dimensional (3D) image registration and segmentation were used to eliminate the effect of metal-induced artifacts of zygomatic implants.

METHODS

An ex-vivo study was included to verify the feasibility of the new method. Then, the radiographic bone-to-implant contact (rBIC) of 143 implants was measured in a total of 50 patients. To obtain the BICA of zygomatic implants and the zygomatic bone, several steps were necessary, including image preprocessing of CBCT scans, identification of the position of zygomatic implants, registration, and segmentation of pre- and post-operative CBCT images, and 3D reconstruction of models. The conventional two-dimensional (2D) linear rBIC (rBICc) measurement method with post-operative CBCT images was chosen as a comparison.

RESULTS

The mean values of rBIC and rBICc were 15.08 ± 5.92 mm and 14.77 ± 5.14 mm, respectively. A statistically significant correlation was observed between rBIC and rBICc values ([Formula: see text]=0.86, p < 0.0001).

CONCLUSIONS

This study proposed a standardized, repeatable, noninvasive technique to quantify the rBIC of post-operative zygomatic implants in 3D terms. This technique is comparable to conventional 2D linear measurements and seems to be more reliable than these conventional measurements; thus, this method could serve as a valuable tool in the performance of clinical research protocols.

Application of Computer-Aided Design and Individualized Templates for Bilateral Zygomaticomaxillary Complex Fractures

PURPOSE

Reduction of the bilateral zygomaticomaxillary complex (ZMC) fracture with individualized templates based on computer- aided surgical simulation system. To evaluate the practicality and accuracy of this approach in the treatment of bilateral ZMC fracture.

METHODS

Sixteen patients with bilateral ZMC fractures were collected to create a study model. The authors reconstruct the ZMC on one side via the three-dimensional (3D) model, and then mirrored to the opposite side. Multiple individualized templates were made based on the 3D model, and used as intraoperative guidance to reduce fractures. After surgery, the facial symmetry and the position of zygoma were observed. The mouth opening, pupil level, and sensation of infraorbital nerve were evaluated. Some mark points on zygoma were measured and the postoperative horizontal asymmetry rate (H) was calculated. Besides, orbital height and width were measured.

RESULTS

For all patients, the position of bilateral ZMC was basically restored. The patients with restriction of mouth opening all recovered to normal. The H values were less than 3.0% at all mark points. There was almost no difference in bilateral orbital width and height. Meanwhile, there was no significant difference between the preoperative measurements of the ideal virtual 3D model and the postoperative measurements of patients.

CONCLUSIONS

The study proves that application of computer-aided design and individualized templates can accurately guide the reduction operation of ZMC fracture, restore the ideal shape of ZMC, and obtain good facial symmetry.

Intramuscular lipoma of the temporalis muscle extending to the infratemporal fossa: surgical pitfalls and short literature review

Lipomas are benign tumours of mesenchymal origin, representing one of the most common tumours of the body. They are often observed between the fourth and the sixth decade of life and in 13% of the cases they occur in the head and neck region. In case of symptoms, surgical removal is the treatment of choice; when the formation involves the temporal region, the surgical approach is often challenging due to the presence of the neurovascular structures, such as the temporalis branch of the facial nerve and their potential extension to the nearby structures under the zygomatic arch to either the infratemporal fossa or the buccal region. Recurrence can occur frequently only if there is incomplete removal of lipoma. In this paper, the authors discuss surgical pitfalls of a very rare case of a large-sized symptomatic lipoma extended to the infratemporal and pterygomaxillary fossa, surgically removed via trans-zygomatic hemicoronal approach.

Quantitative Morphologic Analysis of Cranial Vault in Twist1+/- Mice: Implications in Craniosynostosis

BACKGROUND

The haploinsufficiency in the TWIST1 gene encoding a basic helix-loop-helix transcription factor is a cause of one of the craniosynostosis syndromes, Saethre-Chotzen syndrome. Patients with craniosynostosis usually require operative release of affected sutures, which makes it difficult to observe the long-term consequence of suture fusion on craniofacial growth.

METHODS

In this study, we performed quantitative analysis of morphologic changes of the skull in Twist1 heterozygously-deleted mice (Twist1+/-) with micro-computed tomographic images.

RESULTS

In Twist1+/- mice, fusion of the coronal suture began before postnatal day 14 and progressed until postnatal day 56, during which morphologic changes occurred. The growth of the skull was not achieved by a constant increase in the measured distances in wild type mice; some distances in the top-basal axis were decreased during the observation period. In the Twist1+/- mouse, growth in the top-basal axis was accelerated and that of the frontal cranium was reduced. In the unicoronal suture fusion mouse, the length of the zygomatic arch of affected side was shorter in the Twist1+/- mouse. In one postnatal day 56 Twist1+/- mouse with bilateral coronal suture fusion, asymmetric zygomatic arch length was identified.

CONCLUSION

The authors'results suggest that measuring the length of the left and right zygomatic arches may be useful for early diagnosis of coronal suture fusion and for estimation of the timing of synostosis, and that more detailed study on the growth pattern of the normal and the synostosed skull could provide prediction of the risk of resynostosis.

CLINICAL RELEVANCE STATEMENT

The data from this study can be useful to better understand the cranial growth pattern in patients with craniosynostosis.

Digital localization of osteotomy position in prominent zygomatic arch

The study aimed at introducing a digital method of locating the osteotomy position of the zygomatic arch during surgery and analyze the accuracy of this method. Patients with a prominent zygomatic bone who underwent zygomatic arch osteotomy and reduction in the orthognathic surgery department of our hospital were selected. Preoperative and postoperative computed tomography (CT) data of the patients were imported into modeling and analysis software Mimics 23.0 in DICOM format to construct 3D models of the zygomatic bone and zygomatic arch region. The data were obtained by locating the simulated osteotomy position of the zygomatic arch before the surgery, applying the digitally modeled osteotomy position of the zygomatic arch during the surgery, and locating the actual osteotomy position of the zygomatic arch after the surgery. The accuracy of the experimental method was verified by matching the preoperative simulation data with the postoperative osteotomy data. A Wilcoxon rank sum test was performed to compare the 20 cases' osteotomy positions obtained by preoperative simulation with the actual postoperative position. There was no significant difference in zygomatic arch osteotomy position between the preoperative simulation and the real postoperative position (Z=-1.867, P=0.062). The digital method to locate the zygomatic arch osteotomy seems to show an acceptable accuracy to achieve the proper osteotomy position and, therefore, should adopted whenever appropriate.

"Digital Simulation of Osteotomy Reduction of a Prominent Zygomatic Arch"

OBJECTIVE

To analyze the value of simulated surgery in predicting the outcome of individualized surgical reduction of a prominent zygomatic arch.

METHODS

Computed tomography data were obtained from the electronic records of 15 patients who underwent surgery at Tianjin Stomatological Hospital for prominent zygoma. The data were imported into Mimics 23.0. Left and right three-dimensional (3D) zygoma models were created through standard procedures. In the 3D models, a wedge-shaped cut of the zygomatic bone was pushed inward, and the osteotomy position of the zygomatic arch was taken as a variable to simulate the reduction malarplasty. The reduction effect was calculated from the simulated movement of the fracture end of the zygomatic arch from internal pushing forces. Stable versus high-efficiency internal pushing areas were defined based on the amount of movement. Mean values with 95% confidence intervals (CI) were calculated for the areas data.

RESULTS

The anterior edge of the stable internal pushing osteotomy area was located in front of the articular tubercle point (95% CI: 10.64-11.89 mm). The posterior edge of the stable internal pushing area was located in front of the articular tubercle point (95% CI: 7.8-9.13 mm). The posterior edge of the high-efficiency internal pushing area was located in front of the articular tubercle point (95% CI: 4.7-5.73 mm).

CONCLUSION

Stable and high-efficiency internal pushing areas were detected above the zygomatic arch. The simulation showed that osteotomy in these areas can provide different degrees of zygomatic arch reduction.

Identification of the Pathway and Appropriate Use of Four Zygomatic Implants in the Atrophic Maxilla: A Cross-Sectional Study

PURPOSE

This cross-sectional study aimed to identify and characterize the pathway for appropriate placement of four zygomatic implants in the severely atrophic maxilla and to group the anatomical variations of the osteotomy trajectory for anterior zygomatic implants.

MATERIALS AND METHODS

CBCT images of patients presenting indications for the use of four zygomatic implants to withstand a maxillary rehabilitation were reviewed. Cross-sectional planes corresponding to the implant trajectories, designed according to a zygoma anatomy-guided approach for implants placed in the anterior and posterior maxilla, were assessed separately. The relationship of the implant osteotomy trajectory with the correlated residual alveolar bone, nasal and sinus cavities, maxillary wall, and zygomatic bone anatomies was established.

RESULTS

The study population included 122 globally recruited patients, with 488 zygomatic implants, 244 of which had their starting point on the anterior incisor-canine area and 244 on the posterior premolar-molar area. The anatomy of the osteotomy path designed for the anterior implants ("A") was named and grouped into five assemblies from zygomatic anatomy-guided ZAGA A-0 to A-4, representing 2.9%, 4.5%, 19.7%, 55.7%, and 17.2% of the studied sites. Percentages for posterior implant ("P") trajectories of the osteotomy were grouped and named as ZAGA P-0 to P-4, representing 5.7%, 10.2%, 8.2%, 18.4%, and 57.4% of the sites, respectively. Approximately 70% of the population presented anatomical intra-individual differences.

CONCLUSION

The trajectory of the zygomatic implant followed different anatomical pathways depending on its coronal point being anteriorly or posteriorly located, which justifies a new zygoma anatomy-guided approach classification for anteriorly placed zygomatic implants. Topographic characteristics of the anatomical structures that are cut by an anterior oblique plane joining the lateral incisor-canine area to the zygomatic bone, representing the planned anterior osteotomy path in a quadruple-zygoma indication, have not been previously reported. Adaptation of surgical procedures and implant sections/designs to individual patients' anatomical characteristics is essential to reduce early and long-term complications.