Dental Versus Zygomatic Implants in the Treatment of Maxillectomy: A Finite Element Analysis.

This study analyzed the stress distributions on zygomatic and dental implants placed in the zygomatic bone, supporting bones, and superstructures under occlusal loads after maxillary reconstruction with obturator prostheses. A total of 12 scenarios of 3-dimensional finite element models were constructed based on computerized tomography scans of a hemimaxillectomy patient. Two obturator prostheses were analyzed for each model. A total force of 600 N was applied from the palatal to buccal bones at an angle of 45°. The maximum and minimum principal stress values for bone and von Mises stress values for dental implants and prostheses were calculated. When zygomatic implants were applied to the defect area, the maximum principal stresses were similar in intensity to the other models; however, the minimum principal stress values were higher than in scenarios without zygomatic implants. In models that used zygomatic implants in the defect area, von Mises stress levels were significantly higher in zygomatic implants than in dental implants. In scenarios where the prosthesis was supported by tissue in the nondefect area, the maximum and minimum principal stress values on cortical bone were higher than in scenarios where implants were applied to defect and nondefect areas. In patients who lack an alveolar crest after maxillectomy, a custom bar-retained prosthesis placed on the dental implant should reduce stress on the zygomatic bone. The stress was higher on zygomatic implants without alveolar crest support than on dental implants.

Effectiveness of zygomatic-implant fixed rehabilitation for the atrophic edentulous maxilla: protocol for a systematic review and network meta-analysis.

BACKGROUND: Atrophic edentulous maxilla is a debilitating condition caused by the progressive and irreversible bone resorption following loss of teeth, that results in bone of inadequate volume and density. This makes conventional implant therapy extremely challenging without complex reconstructive procedures. Several techniques such as sinus augmentation, short implants, and tilted implants have been used for the rehabilitation of the atrophic maxilla. In recent years, zygomatic implants have emerged as a graftless rehabilitation technique. However, few studies compare zygomatic-implant fixed rehabilitation with other fixed rehabilitation techniques. The existing body of evidence on zygomatic implants is largely based on clinical and disease-oriented outcomes. METHODS: A network meta-analysis (NMA) will be conducted in order to compare the effectiveness of zygomatic-implant fixed rehabilitation with the other rehabilitation techniques. Experimental and observational studies comparing different implant-assisted fixed rehabilitation in adults with atrophic maxilla will be included. The primary and secondary outcomes will be patient's satisfaction and quality of life respectively. Additional outcomes include the implant's survival/success, and biological and prosthetic complications. An electronic search will be performed through various databases for articles in English and French, without time limits. Risk of bias will be assessed using the Revised Cochrane Risk-of-Bias tool for randomized controlled trials, and ROBINS-I for non-randomized and observational studies. Two independent reviewers will screen the titles and abstracts and extract data. Any discrepancy between reviewers will be discussed and resolved through consensus or with the help of a third reviewer. Pairwise meta-analyses will be performed using a random effects model. I2, τ2, transitivity, subgroup/meta-regression analyses will assess and explain heterogeneity and distribution of effect modifiers. A network plot will be created to connect the different interventions directly and indirectly. Interventions will be ranked using the surface under cumulative ranking curve. Confidence in the results of the NMA will be assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE). DISCUSSION: This study will be the first to assess the effectiveness of zygomatic-implant fixed rehabilitation for the atrophic maxilla using NMA. The evidence obtained will aid clinical decision-making and will advance the knowledge of the rehabilitation techniques for the atrophic maxilla. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42023353303.

Prosthetic rehabilitation of patients with maxillary oncology defects using zygomatic implants.

PURPOSE: Prosthetics for patients after oncological resection of the upper jaw is a complex problem associated with the physiological and anatomical separation of the oral cavity and the nasal/paranasal region. This study reports the clinical results of the use of the zygomatic implants for prosthetic rehabilitation in patients with maxillectomy due to upper jaw tumors. MATERIALS AND METHODS: The study included 16 patients who underwent prosthetic rehabilitation using a zygomatic implant after maxillectomy period from 2021 to 2023. After the tumor was removed, immediate surgical obturators were placed. Main prosthetic rehabilitation was performed 6-12 months after tumor removal, but before that, a temporary obturator was made and used. Six-twelve months after tumor resection, 1-4 zygomatic implants were inserted into the zygomatic bone unilaterally or bilaterally. A total of 42 zygomatic implants were installed, 2 of which were unsuccessful and were removed in 1 patient. The implants were placed using the surgical guide, which was planned and prepared digitally. RESULTS: No postsurgical complications were seen, and the patients were discharged from the hospital after 7-10 days. The patients were able to return to a normal diet (hard food) after just 7 days following surgery, with no further complaints regarding function or pain, apart from the residual edema caused by the intervention. CONCLUSIONS: The use of prostheses fixed on zygomatic implants in patients with maxillary defects is an effective method of prosthodontic rehabilitation in complex clinical cases after maxillectomy.

Round and flat zygomatic implants: effectiveness after a 3­year follow­up non­interventional 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.

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.

The 'Manchester' method of minimal access fixation of the zygomatic arch in zygomatic complex fractures: a case series.

We have introduced a minimally invasive approach for the fixation of the zygomatic arch during the surgical management of zygomatic complex fractures. Access for this technique is provided by a preauricular approach and eyelid incisions with the addition of transcutaneous stab incisions overlying the arch. These stab incisions allow transcutaneous drilling and screw placement through a size CH 20 (5.0 mm) paediatric nasopharyngeal airway (NPA). We present a case series of seven patients. In all patients the arch component was successfully reduced and fixed, and no intraoperative or postoperative complications were observed. The use of an NPA is novel. It functions as a flexible self-irrigating sleeve and protects the skin from mechanical and thermal damage. The technique uses readily available equipment, is easy to learn, and simplifies surgery to the zygomatic arch.

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.

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.

Displacement of Zygomatic Implant in Infratemporal Region in a Case of COVID-19-Associated Mucormycosis.

Reconstruction of maxillary defects can be carried out using a variety of treatment modalities. The choice of modality depends on numerous factors, including the size and extent of the defect, patient characteristics, and existing comorbidities. One of the various options is reconstruction and rehabilitation using a fixed prosthesis supported over a zygomatic implant. In maxillectomy cases, a zygomatic implant can be used to improve the retention of the obturator prosthesis, as the loss of alveolar bone makes it impossible to use conventional endosseous implants. Although zygomatic implants are reported to have high success rates, they are not free of complication. We hereby present a rare complication associated with the placement of a zygomatic implant in a patient with COVID-19-associated mucormycosis who underwent operation. This rare complication has never been reported before. This case report also highlights on the management of complications involving displacement of a zygomatic implant in the infratemporal region.

1-Piece Versus 2-Piece Fronto-Temporo-Orbito-Zygomatic Craniotomy: A Narrative Overview of Evolution.

BACKGROUND: The fronto-temporo-orbito-zygomatic (FTOZ) craniotomy is a commonly utilized surgical approach for many complex skull base lesions, especially lesions traversing skull base compartments. This craniotomy has evolved over multiple stages, originating from the classic pterional craniotomy and many variations that have emerged over time. METHODS: Few clinical and anatomic studies have both shaped these craniotomies as well as provided immense information about instances in which they are most useful. We review the origin and history of the one-piece and two-piece fronto-temporo-orbito-zygomatic craniotomy and deliberate their advantages and disadvantages. RESULTS: The FTOZ craniotomy provides access to the orbit as well as to multiple compartments in the cranium (anterior, middle and upper third posterior cranial fossae); thus, offering a multi-corridor approach to complex skull base lesions. The one-piece and two-piece fronto-temporo-orbitozygomatic craniotomies are two particularly notable variations that have stood the test of time. Selection between the two variations is mostly surgeon preference and comfort with the technique; however, there are certain indications that specifically suit each approach. Additionally, a pictorial review has been crafted to clearly illustrate the cuts to be made in both methods. CONCLUSION: Understanding the evolution of this craniotomy and surgical approach provides an insight into accessing complex skull base pathologies with minimal brain retraction via safe and viable corridors.

All-on-4 Concept With Use Of Zygoma Implants for Rehabilitation in the Severely Atrophied Maxilla With a Definitive Immediate Restoration.

This case report of a 45-year-old patient at initial presentation shows an illustration of the limitations of periodontal maintenance therapy and subsequent implant prosthetic therapy. In close consultation with the patient, treatment strategies were adopted to maximize the preservation of prognostically questionable teeth. Eight years later, the patient had a highly atrophied maxilla that could be successfully restored with implants. This was achieved with 2 zygoma implants and 2 anterior conventional implants, which were immediately loaded according to the All-on-4 concept and immediately provided with a definitive prosthetic restoration. The case report demonstrates to the general practitioner that using zygoma implants in such constellations may offer a solution to achieve a fixed, rapid, and financially acceptable prosthetic rehabilitation.

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.

Guided placement of zygomatic implants in head and neck cancer patients: implant survival and patient outcomes at 1-3 years of follow-up.

Zygomatic implants (ZI) are a valuable option for supporting an obturator prosthesis after maxillary resection. This study was performed to assess the clinical outcomes of a digitally validated guided technique for ZI placement, followed by immediate prosthetic obturation. The primary objective was to evaluate implant survival, while the secondary objective was to assess patient-reported quality of life post-rehabilitation. Twelve patients treated for head and neck cancer received a total of 36 ZI after ablative surgery. The mean duration of ZI follow-up was 30.1 months. The survival rate of ZI placed in non-irradiated patients was 100%, while it was 85% in irradiated patients. Patient-reported outcomes were evaluated using the Liverpool Oral Rehabilitation Questionnaire (LORQv3) and the University of Washington Quality of Life Questionnaire (UW-QOL v4). Most patients reported satisfactory outcomes in the oral function domain of the LORQv3 (mean score 17.7 ± 4.5; possible range 12-48, with lower scores indicating better outcomes). Regarding the UW-QOL v4, the swallowing and chewing domains had the highest scores (mean 97.5 ± 8.7 and 95.8 ± 14.4, respectively; maximum possible score of 100). In conclusion, this treatment approach improves function and quality of life after maxillary ablative surgery. However, irradiated patients showed a noticeable trend of higher implant failure, and this was influenced by tumour position and size impacting the radiation dose to the zygomatic bone.

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.

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.

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.

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.