Mandibular reconstruction in adults: a review

The use of customized 3D-printed mandibular prostheses with pressure-reducing device: A clinical trial

BACKGROUND

Segmental bone defects of the mandible result in the complete loss of the affected region. We had incorporated the pressure-reducing device (PRD) designs into the customized mandible prostheses (CMP) and conducted a clinical trial to evaluate this approach.

METHODS

Seven patients were enrolled in this study. We examined the association among the history of radiotherapy, the number of CMP regions, the number of chin regions involved, and CMP exposure.

RESULTS

We included five men and two women with an average age of 55 years. We excised tumors with an average weight of 147.8 g and the average weight of the CMP was 68.5 g. No significant difference between the two weights was noted (p = 0.3882). Three patients received temporary dentures and the CMP remained stable in all patients.

CONCLUSION

The use of PRD in CMP may address the previous challenges associated with CMP, but further research is necessary.

Effects of Ibuprofen and Diclofenac Pre-Treatment on Viability and Apoptosis Processes in Human Dental Pulp Stem Cells

Background and Objectives: Stem cell-based regeneration strategies have shown therapeutic efficacy in various fields of regenerative medicine. These include bone healing after bone augmentation, often complicated by pain, which is managed by using nonsteroidal anti-inflammatory drugs (NSAIDs). However, information is limited about how NSAIDs affect the therapeutic potential of stem cells. Materials and Methods: We investigated the effects of ibuprofen and diclofenac on the characteristics, morphology, and immunophenotype of human mesenchymal stromal cells isolated from the dental pulp (DPSCs) and cultured in vitro, as well as their effects on the expression of angiogenic growth factors (VEGFA and HGF) and selected genes in apoptosis signalling pathways (BAX, BAK, CASP3, CASP9, and BCL2). Results: Ibuprofen and diclofenac significantly reduced the viability of DPSCs, while the expression of mesenchymal stem cell surface markers was unaffected. Both ibuprofen and diclofenac treatment significantly upregulated the expression of HGF, while the expression of VEGFA remained unchanged. Ibuprofen significantly altered the expression of several apoptosis-related genes, including the upregulation of CASP9 and BCL2, with decreased CASP3 expression. BAK, CASP3, CASP9, and BCL2 expressions were significantly increased in the diclofenac-treated DPSCs, while no difference was demonstrated in BAX expression. Conclusions: Our results suggest that concomitant use of the NSAIDs ibuprofen or diclofenac with stem cell therapy may negatively impact cell viability and alter the expression of apoptosis-related genes, affecting the efficacy of stem cell therapy.

Study on mechanical properties of dual-channel cryogenic 3D printing scaffold for mandibular defect repair

Mandibular defect repair has always been a clinical challenge, facing technical bottleneck. The new materials directly affect technological breakthroughs in mandibular defect repair field. Our aim is to fabricate a scaffold of advanced biomaterials for repairing of small mandibular defect. Therefore, a novel dual-channel scaffold consisting of silk fibroin/collagen type-I/hydroxyapatite (SCH) and polycaprolactone/hydroxyapatite (PCL/HA) was fabricated by cryogenic 3D printing technology with double nozzles. The mechanical properties and behaviors of the dual-channel scaffold were investigated by performing uniaxial compression, creep, stress relaxation, and ratcheting experiments respectively. The experiments indicated that the dual-channel scaffold was typical non-linear viscoelastic consistent with cancellous tissue; the Young's modulus of this scaffold was 60.1 kPa. Finite element analysis (FEA) was employed performing a numerical simulation to evaluate the implantation effect in mandible. The stress distribution of the contact area between scaffold and defect was uniform, the maximum Mises stress of cortical bone and cancellous bone in defect area were 54.520 MPa and 3.196 MPa, and the maximum displacement of cortical bone and cancellous bone in defect area were 0.1575 mm and 0.1555 mm respectively, which distributed in the incisor region. The peak maximum Mises stress experienced by the implanted scaffold was 3.128 × 10-3 MPa, and the maximum displacement was 6.453 × 10-2 mm distributed near incisor area. The displacement distribution of the scaffold was consistent with that of cortical and cancellous bone. The scaffold recovered well when the force applied on it disappeared. Above all, the dual-channel scaffold had excellent bio-mechanical properties in implanting mandible, which provides a new idea for the reconstruction of irregular bone defects in the mandible and has good clinical development prospects.

Personalized lattice-structured prosthesis as a graftless solution for mandible reconstruction and prosthetic restoration: A finite element analysis

Oral cavity tumors are a prevalent cause of mandible reconstruction surgeries. The mandible is vital for functions like oralization, respiration, mastication, and deglutition. Current mandible reconstruction methods have low success rates due to complications like plate fracture or exposure, infections, and screw loosening. Autogenous bone grafts are commonly used but carry the risk of donor region morbidity. Despite technological advances, an ideal solution for mandible reconstruction remains elusive. Additive manufacturing in medicine offers personalized prosthetics from patient-specific medical images, allowing for the creation of porous structures with tailored mechanical properties that mimic bone properties. This study compared a commercial reconstruction plate with a lattice-structured personalized prosthesis under different biting and osseointegration conditions using Finite Element Analysis. Patient-specific images were obtained from an individual who underwent mandible reconstruction with a commercial plate and suffered from plate fracture by fatigue after 26 months. Compared to the commercial plate, the maximum von Mises equivalent stress was significantly lowered for the personalized prosthesis, hindering a possible fatigue fracture. The equivalent von Mises strains found in bone were within bone maintenance and remodeling intervals. This work introduces a design that doesn't require grafts for large bone defects and allows for dental prosthesis addition without the need for implants.

Computational models and their applications in biomechanical analysis of mandibular reconstruction surgery

Advanced head and neck cancers involving the mandible often require surgical removal of the diseased parts and replacement with donor bone or prosthesis to recreate the form and function of the premorbid mandible. The degree to which this reconstruction successfully replicates key geometric features of the original bone critically affects the cosmetic and functional outcomes of speaking, chewing, and breathing. With advancements in computational power, biomechanical modeling has emerged as a prevalent tool for predicting the functional outcomes of the masticatory system and evaluating the effectiveness of reconstruction procedures in patients undergoing mandibular reconstruction surgery. These models offer cost-effective and patient-specific treatment tailored to the needs of individuals. To underscore the significance of biomechanical modeling, we conducted a review of 66 studies that utilized computational models in the biomechanical analysis of mandibular reconstruction surgery. The majority of these studies employed finite element method (FEM) in their approach; therefore, a detailed investigation of FEM has also been provided. Additionally, we categorized these studies based on the main components analyzed, including bone flaps, plates/screws, and prostheses, as well as their design and material composition.

Deep Circumflex Iliac Artery Flap Reconstruction in Brown Class I Defect of the Mandible Using a Three-Component Surgical Template System

BACKGROUND

Computer-assisted surgery is widely used in mandibular reconstruction, but the process is not well described for cases using the deep circumflex iliac artery flap (DCIA) as the donor site. This study aimed to present a DCIA-based three-component surgical template system (3-STS) in patients with a mandibular Brown class I defect.

METHODS

This retrospective cohort study compared clinical outcomes of mandibular reconstruction with DCIA flap using 3-STS or conventional surgical templates. The primary outcome of the study was the accuracy of reconstruction, and the secondary outcomes included surgical time and bone flap ischemia time. Surgery-related parameters and functional outcomes were also recorded and compared.

RESULTS

Forty-four patients (23 in the 3-STS group and 21 in the control group) between 2015 and 2021 were included. Compared with the control group, the 3-STS group had higher accuracy of reconstruction, indicated by lower deviation in absolute distance (1.45 ± 0.76 mm versus 2.02 ± 0.89 mm; P = 0.034), and less deviation in coronal and sagittal angles (0.86 ± 0.53 degree versus 1.27 ± 0.59 degrees, P = 0.039; and 2.52 ± 1.00 degrees versus 3.25 ± 1.25 versus, P = 0.047) between preoperative and postoperative computed tomographic imaging. Surgical time and bone flap ischemia time were significantly reduced in the 3-STS group compared with the control group (median time, 385 minutes versus 445 minutes and 32 minutes versus 53 minutes, respectively; P < 0.001). In addition, masseter attachment was preserved in the 3-STS group but not in the control group. No differences were found in adverse events or other clinical variables.

CONCLUSION

The 3-STS can improve accuracy, simplify intraoperative procedures to increase surgical efficiency, and preserve functionality in mandibular reconstruction for Brown class I defects.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Use of customized 3-dimensional printed mandibular prostheses with a dental implant pressure-reducing device in mandibular body defect: A finite element study performing multiresponse surface methodology

Background/purpose

Segmental body defects of the mandible result in the complete loss of the affected region. In our previous study, we investigated the clinical applicability of a customized mandible prosthesis (CMP) with a pressure-reducing device (PRD) in an animal study. In this study, we further incorporated dental implants into the CMP and explored the use of dental implant PRD (iPRD) designs.

Materials and methods

By employing a finite element analysis approach, we created 4 types of CMP: CMP, CMP with iPRD, CMP-PRD, and CMP-PRD with iPRD. We developed 2 parameters for the iPRD: cone length (CL) in the upper part and spring pitch (SP) in the lower part. Using the response surface methodology (RSM), we determined the most suitable structural assignment for the iPRD.

Results

Our results indicate that CMP-PRD had the highest von Mises stress value for the entire assembly (1076.26 MPa). For retentive screws and abutments, CMP with iPRD had the highest von Mises stress value (319.97 and 452.78 MPa, respectively). CMP-PRD had the highest principal stress (131.66 MPa) in the anterior mandible. The iPRD reduced principal stress in both the anterior and posterior mandible. Using the RSM, we generated 25 groups for comparison to achieve the most favorable results for the iPRD and we might suggest the CL to 12 mm and the SP to 0.4 mm in the further clinical trials.

Conclusion

Use of the PRD and iPRD in CMP may resolve the challenges associated with CMP, thereby promoting its usage in clinical practice.

Biomechanical feasibility of non-locking system in patient-specific mandibular reconstruction using fibular free flaps

Mandibular reconstruction with free fibular flaps is frequently used to restore segmental defects. The osteosythesis, including locking and non-locking plate/screw systems, is essential to the mandibular reconstruction. Compared with the non-locking system that requires good adaption between plate and bone, the locking system appears to present a better performance by locking the plate to fixation screws. However, it also brings about limitations on screw options, a higher risk of screw failure, and difficulties in screw placement. Furthermore, its superiority is undermined by the advancing of patient-specific implant design and additive manufacturing. A customized plate can be designed and fabricated to accurately match the mandibular contour for patient-specific mandibular reconstruction. Consequently, the non-locking system seems more practicable with such personalized plates, and its biomechanical feasibility ought to be estimated. Finite element analyses of mandibular reconstruction assemblies were conducted for four most common segmental mandibular reconstructions regarding locking and non-locking systems under incisal biting and right molars clenching, during which the influencing factor of muscles' capacity was introduced to simulate the practical loadings after mandibular resection and reconstruction surgeries. Much higher, somewhat lower, and similar maximum von Mises stresses are separately manifested by the patient-specific mandibular reconstruction plate (PSMRP), fixation screws, and reconstructed mandible with the non-locking system than those with the locking system. Equivalent maximum displacements are identified between PSMRPs, fixation screws, and reconstructed mandibles with the non-locking and locking system in all four reconstruction types during two masticatory tasks. Parallel maximum and minimum principal strain distributions are shared by the reconstructed mandibles with the non-locking and locking system in four mandibular reconstructions during both occlusions. Conclusively, it is feasible to use the non-locking system in case of patient-specific mandibular reconstruction with fibular free flaps based on the adequate safety, comparable stability, and analogous mechanobiology it presents compared with the locking system in a more manufacturable and economical way.

Preparation and characterization of 3D hydroxyapatite/collagen scaffolds and its application in bone regeneration with bone morphogenetic protein-2

Desirable bone engineering materials should have a conducive three-dimensional (3D) structure and bioactive mediators for guided bone regeneration. In the present study, hydroxyapatite (HA)/collagen (Col) scaffolds were prepared by an optimized freeze-drying process. The porosity, moisture content, and mechanical properties of the composite have been investigated. The micro-morphology and structure were analyzed with scanning electron microscopy (SEM) and transmission electron microscopy (TEM), confirmed that self-cross-linked HA/Col was evenly distributed and formed a 3D porous scaffold. The physicochemical/mechanical characterization was carried out by Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). Morphological observation and CCK-8 assay of co-culture cells indicated that HA/Col scaffolds were biocompatible. Then HA/Col scaffolds coupled with recombinant human bone morphogenetic proteins 2 (rhBMP-2) were implanted in the mandibular critical size defect in rats, and histological staining was used to evaluate the bone reconstruction. The result showed that HA/Col coupled with rhBMP-2 could significantly improve the formation of new bone and angiogenesis within the scaffolds as well as the proliferation and differentiation of osteoblasts. Thanks to the encouraging osteogenesis effects, the well-defined 3D scaffolds (HA/Col) cooperating with bioactive agents (rhBMP-2) are expected to be a promising candidate for bone tissue engineering applied to regenerative medicine.

Adipose-Derived Stem Cells Enhance Graft Incorporation and Mineralization in a Murine Model of Irradiated Mandibular Nonvascularized Bone Grafting

BACKGROUND

Nonvascularized bone grafting represents a practical method of mandibular reconstruction. However, the destructive effects of radiotherapy on native bone preclude the use of nonvascularized bone grafts in head and neck cancer patients. Adipose-derived stem cells have been shown to enhance bone healing and regeneration in numerous experimental models. The purpose of this study was to determine the impact of adipose-derived stem cells on nonvascularized bone graft incorporation in a murine model of irradiated mandibular reconstruction.

METHODS

Thirty isogenic rats were randomly divided into 3 groups: nonvascularized bone graft (control), radiation with nonvascularized bone graft (XRT), and radiation with nonvascularized bone graft and adipose-derived stem cells (ASC). Excluding the control group, all rats received a human-equivalent dose of radiation. All groups underwent mandibular reconstruction of a critical-sized defect with a nonvascularized bone graft from the contralateral hemimandible. After a 60-day recovery period, graft incorporation and bone mineralization were compared between groups.

RESULTS

Compared with the control group, the XRT group demonstrated significantly decreased graft incorporation (P = 0.011), bone mineral density (P = 0.005), and bone volume fraction (P = 0.001). Compared with the XRT group, the ASC group achieved a significantly increased graft incorporation (P = 0.006), bone mineral density (P = 0.005), and bone volume fraction (P = 0.013). No significant differences were identified between the control and ASC groups.

CONCLUSIONS

Adipose-derived stem cells enhance nonvascularized bone graft incorporation in the setting of human-equivalent radiation.

One-stage reconstruction using a fibula osteocutaneous free flap and an anterolateral thigh free flap for an extensive composite defect after en bloc resection of squamous cell carcinoma on the mouth floor, mandible, and anterior neck: A CARE-compliant case report

RATIONALE

Although regional metastasis to the lymph nodes is common in advanced oral cancer, extensive local invasion into surrounding structures such as the mandible, skin and soft tissue of the neck, and masticator space is relatively rare. Sometimes surgical treatment cannot be performed and only palliative chemotherapy and radiation therapy are offered to preserve the quality of life of patients with advanced oral cancer. Nevertheless, the surgical resection of tumors remains the most effective treatment. This study presents a case of aggressive mouth floor cancer in which extensive composite defects on the mouth floor, oral mucosa, mandible, skin and soft tissue of the neck caused by tumor resection were reconstructed.

PATIENT CONCERNS

A 66-year-old man and a 65-year-old man with no significant personal or family history visited our clinic due to a large and multiple masses on the floor of the mouth and both sides of the neck.

DIAGNOSIS

Histopathological evaluation of the biopsy specimen revealed squamous cell carcinoma.

INTERVENTIONS

A fibula osteocutaneous free flap and customized titanium plate were used for the intraoral lining. Mandibular reconstruction was performed using a 3D-printed bone model, and an anterolateral thigh free flap was used to resurface the anterior of the neck.

OUTCOMES

Reconstruction using this method was successful, and excellent functional and aesthetic outcomes were achieved without cancer recurrence.

LESSONS

This study show that the reconstruction of extensive composite defects of the oral mucosa, mandible, and neck soft tissue following surgical resection of mouth floor cancer can be performed in a single-stage operation. Through a single-stage reconstruction, both excellent functional aspects without cancer recurrence and satisfactory aesthetic outcomes can be obtained.

The Progress in Reconstruction of Mandibular Defect Caused by Osteoradionecrosis

Osteoradionecrosis (ORN) is described as a disease with exposed, nonviable bone that fails to heal spontaneously or by means of conservative treatment after radiotherapy in at least 3 months. Though traditional theories in the early stage including hypoxic-hypocellular-hypovascular and fibro-atrophic in addition to new findings such as ferroptosis were put forward to explain the mechanisms of the osteoradionecrosis, the etiology of ORN is still unclear. With the high rate of occurrence in the head and neck area, especially in the mandible, this disease can disrupt the shape and function of the irradiated area, leading to a clinical presentation ranging from stable small areas of asymptomatic exposed bone to severe progressive necrosis. In severe cases, patients may experience pain, xerostomia, dysphagia, facial fistulas, and even a jaw defect. Consequently, sequence therapy and sometimes extensive surgery and reconstructions are needed to manage these sequelae. Treatment options may include pain medication, antibiotics, the removal of sequesters, hyperbaric oxygen therapy, segmental resection of the mandible, and free flap reconstruction. Microanastomosed free-flaps are considered to be promising choice for ORN reconstruction in recent researches, and new methods including three-dimensional (3-D) printing, pentoxifylline, and amifostine are used nowadays in trying increase the success rates and improve quality of the reconstruction. This review summarizes the main research progress in osteoradionecrosis and reconstruction treatment of osteoradionecrosis with mandibular defect.

An Analysis of the Viability of Nonvascular Iliac and Fibula Grafts in Mandibular Reconstruction in Patients with Circulatory Diseases: A Prospective Randomized Study

Vascularized bone grafts are considered as the gold standard for mandibular reconstruction. However, there are certain limitations of them, such as they are contraindicated in patients with circulatory disturbances. Therefore, Non-vascular bone grafts become the viable option for reconstruction. Our study aims to prospectively compare the long-term viability of avascular iliac and fibula bone grafts in the reconstruction of mandibular defects. Objectives were to evaluate the difficulty in swallowing, mastication, speech problems, infection, wound dehiscence, restricted limb movement, and altered gait among the iliac and fibula group. A total of 14 patients, planned for the reconstruction of mandibular defects from 2016 to 2018 were randomly allocated into two groups; nonvascular iliac and fibula graft groups. Clinical assessment for improvement in function, esthetics, wound healing, pain, and donor site morbidity was done and was followed up for one year. Digital orthopantomogram was taken for radiographic evaluation for up to one year. Difficulty in swallowing, mastication, speech, infection, restricted limb movement, and altered gait was statistically significant and was seen more in the fibula group. Wound dehiscence with graft exposure was found in one subject. The overall success rate was 100% in the iliac group and 85.7% in the fibula group. Considering the long-term complications and success rate, the nonvascular iliac graft was found to be superior and can be used as an alternative to a nonvascular fibula graft for a defect length up to 7 cm.

Iliac crest towards alveolar processes or mandibular inferior margin in mandibular reconstruction with a vascularized iliac bone flap: which is better?

OBJECTIVE

The study aims to compare differences among iliac bone flaps with different iliac crest orientations for the repair of mandibular defects with an aim to analyze their advantages, disadvantages, and effects.

MATERIAL AND METHODS

Clinical data and computed tomography scans of all patients who underwent iliac bone flap repair of the mandible in Peking University School and Hospital of Stomatology from January 2016 to April 2021 were collected. Patients were divided into the iliac crest towards alveolar process (Group A) and the iliac crest towards mandibular inferior margin (Group B). Software was used to measure corresponding indicators. The results obtained for the groups were statistically analyzed.

RESULTS

The study included 78 patients (25 and 53 in groups A and B, respectively). The symmetry of the LC-type defect was better in group A (p < 0.05). The all-bone width of the alveolar process side in group A was greater than 6 mm; in 15 cases of group B, the width was less than 6 mm (p < 0.05). The intermaxillary distance of two sites were higher in group B (p < 0.05). The bone cortical thickness was significantly thicker in group A (p < 0.05).

CONCLUSION

One year after the mandibular body defect was reconstructed with a vascularized iliac bone flap, the iliac crest towards alveolar process group showed better bone symmetry, width, intermaxillary distance, and cortical thickness to meet the planting requirements.

CLINICAL RELEVANCE

The use of an iliac crest towards alveolar process may be a better approach for mandible reconstruction.

Towards Optimum Mandibular Reconstruction for Dental Occlusal Rehabilitation: From Preoperative Virtual Surgery to Autogenous Particulate Cancellous Bone and Marrow Graft with Custom-Made Titanium Mesh-A Retrospective Study

The purpose of this retrospective study was to evaluate computer-assisted virtual surgery and the outcomes of mandibular reconstruction using an autogenous particulate cancellous bone and marrow (PCBM) graft combined with a custom-made titanium mesh (TiMesh) using a three-dimensional (3D) printing model. Eighteen consecutive patients were included, and preoperative virtual simulation surgery was performed using digital data. Segmental bone defects showed deviation of the mandible due to displacement of the condyle and segments, unnatural length of the mandibular body, or poorer intermaxillary relationship compared to the marginal bone defect caused by previous operations. These mandibular disharmonies could be simulated, and virtual surgery was performed on a computer with adjustment of displaced mandibular segments, length of the mandibular body, and dental arch with digital bone augmentation. TiMesh was manually pre-bent using a 3D printing model, and PCBM from the iliac crest was grafted with TiMesh. The short-term clinical results were good; reconstruction of the alveolar crest was prosthetically desirable; and minor complications were observed. In conclusion, virtual reconstruction is crucial for treating complex deviated mandibles. Accurate condylar and dental arch positions with an optimum mandibular length are important for prosthetically satisfactory mandibular reconstruction.

Donor site morbidity after computer assisted surgical reconstruction of the mandible using deep circumflex iliac artery grafts: a cross sectional study

BACKGROUND

Computer Assisted Design and Computer Assisted Manufacturing (CAD/CAM) have revolutionized oncologic surgery of the head and neck. A multitude of benefits of this technique has been described, but there are only few reports of donor site comorbidity following CAD/CAM surgery.

METHODS

This study investigated comorbidity of the hip following deep circumflex iliac artery (DCIA) graft raising using CAD/CAM techniques. A cross-sectional examination was performed to determine range of motion, muscle strength and nerve disturbances. Furthermore, correlations between graft volume and skin incision length with postoperative donor site morbidity were assessed using Spearman's rank correlation, linear regression and analysis of variance (ANOVA).

RESULTS

Fifteen patients with a mean graft volume of 21.2 ± 5.7 cm³ and a mean incision length of 228.0 ± 30.0 mm were included. Patients reported of noticeable physical limitations in daily life activities (12.3 ± 11.9 weeks) and athletic activities (38.4 ± 40.0 weeks in mean) following surgery. Graft volume significantly correlated with the duration of the use of walking aids (R = 0.57; p = 0.033) and impairment in daily life activities (R = 0.65; p = 0.012). The length of the scar of the donor-site showed a statistically significant association with postoperative iliohypogastric nerve deficits (F = 4.4, p = 0.037). Patients with anaesthaesia of a peripheral cutaneous nerve had a larger mean scar length (280 ± 30.0 mm) than subjects with hypaesthesia (245 ± 10.1 mm) or no complaints (216 ± 27.7 mm).

CONCLUSIONS

Despite sophisticated planning options in modern CAD/CAM surgery, comorbidity of the donor site following  iliac graft harvesting is still a problem. This study is the first to investigate comorbidity after DCIA graft raising in a patient group treated exclusively with CAD/CAM techniques. The results indicate that a minimal invasive approach in terms of small graft volumes and small skin incisions could help to reduce postoperative symptomatology. Trial registration Retrospectively registered at the German Clinical Trials Register (DRKS-ID: DRKS00029066); registration date: 23/05/2022.

Use of an occlusal ramp for rehabilitation after a mandibulectomy and its effects on mastication

STATEMENT OF PROBLEM

Patients with a mandibular defect can develop mandibular deviation, resulting in a loss of or reduction in occlusal contact and ultimately loss of function. The occlusal ramp is a prosthesis used to help restore the masticatory function of such patients and is used particularly in the maxillofacial rehabilitation of patients with masticatory dysfunction resulting from mandibular deviation. The occlusal ramp is usually attached to a mandibular denture or worn as an independent device placed on the palate corresponding to the mandible that produces the offset. However, evidence of the effects of its use is sparse.

PURPOSE

The purpose of this clinical study was to investigate the effects of occlusal ramp use in functional rehabilitation.

MATERIALS AND METHODS

This study included 10 patients who had received mandibulectomies (5 men and 5 women; mean age 76.7 years, range 67 to 90 years) with deviation of the mandible. An occlusal ramp was fabricated for each participant as part of their maxillofacial prosthetic treatment. Masticatory performance was evaluated before and after the treatment by measuring glucose extraction while masticating a piece of gummy jelly. The Wilcoxon signed-rank test was used for statistical analysis (α=.05).

RESULTS

The median masticatory performance score, represented as glucose concentration (mg/dL), was 82.45 before treatment and 115.45 after treatment, with an overall improvement of 33.00. Scores differed significantly before and after treatment (P=.005). Masticatory performance for each participant improved in the range of 17.7 to 103.3, highlighting the role that the occlusal ramp played in mastication, although with differing effects in each participant.

CONCLUSIONS

Masticatory performance in participants with mandibular deviation after a mandibulectomy was significantly improved with an occlusal ramp. This suggests the effectiveness of using occlusal ramps in maxillofacial prosthetic treatment for the recovery of masticatory function in patients with mandibular deviation.

Reconstruction of the mandible from partial inputs for virtual surgery planning

Statistical Shape Models (SSMs) and Sparse Prediction Models (SPMs) based on regressions between cephalometric measurements were compared against standard practice in virtual surgery planning for reconstruction of mandibular defects. Emphasis was placed on the ability of the models to reproduce clinically relevant metrics. CT scans of 50 men and 50 women were collected and split into training and testing datasets according to an 80:20 ratio. The scans were segmented, and anatomical landmarks were identified. SPMs were constructed based on direct regressions between measurements derived from the anatomical landmarks. SSMs were developed by establishing correspondence between the segmented meshes, performing alignment, and principal component analysis. Anterior and bilateral defects were simulated by removing sections of the mandibles in the testing set. Measurement errors after reconstruction ranged from 1.07˚ to 2.2˚ and 0.66 mm to 2.02 mm for mirroring, from 0.45˚ to 3.67˚ and 0.66 mm to 2.54 mm for the SSMs, and from 1.74˚ to 5.01˚ and 0.64 mm to 2.89 mm for the SPMs. Surface-to-surface errors ranged from 1.01 mm to 1.29 mm and 1.06 mm to 1.33 mm for mirroring and SSMs, respectively. Based on the results, SSMs are recommended for VSP in the absence of normal patient anatomy.

Primary Reconstruction in Segmental Resection of Mandible-An Outcome Analysis of Different Reconstructive Techniques

Functional and cosmetic defects in the maxillofacial region may result from trauma, inflammatory disease, benign or malignant tumors. There are several well established reconstructive options for restoring mandibular continuity and function. Traditionally, surgeons have used their past experience to determine the best way to perform the osteotomy, graft harvesting, and graft shaping procedures for mandibular reconstruction. Focus has now shifted to optimize functional and aesthetic outcomes in mandible reconstruction. Refinements in surgical techniques continue to improve patient's quality of life. The purpose of this study was to evaluate the outcome of a range of reconstructive techniques in 20 patients who underwent segmental resection of mandible during the period 2004-2017.

Retrospective three-dimensional analysis of bone resorption volumes of free microvascular scapular and fibular grafts

Defects in head and neck regions are standardly treated with microvascular grafts, such as free scapular (SFF) and fibular flaps (FFF), which are subject to a certain amount of bone resorption over time. The aim of this study was the 3-dimensional evaluation of bone resorption volume in both grafts. Over a period of 10 years, computed tomograms (CT) of patients with mandibular reconstructions with SFFs and FFFs were examined. The respective grafts were segmented as well as 3-dimensionally measured. Furthermore, factors such as gender, age, nicotine abuse, previous disease with type 2 diabetes, and adjuvant therapies, were examined for their influence. A total of 211 CT scans from 67 patients (40 SFFs and 27 FFFs) were included in the study. SFFs showed slightly higher median bone volumes (87.60% at 730 days and 86.55% at 1500 days) than FFFs (84.40% at 730 days and 82.10% at 1500 days). When final volumes were considered, FFFs had higher mean volume values (88.22%) than SFFs (83.82%), with significant correlation between resorption volume and time progression (r = 0.357, p = 0.024). All previously mentioned factors had no significant effect on bone resorption. Bone volumes of FFFs showed postoperative volume reductions similar to those of SFFs, with isolated SFFs having markedly lower volume values. The choice of a microvascular graft for reconstruction in the mandible proves difficult regarding bone resorption. The presented results may support decisions about future transplantations.

An innovative additively manufactured implant for mandibular injuries: Design and preparation processes based on simulation model

Objective: For mandibular injury, how to utilize 3D implants with novel structures to promote the reconstruction of large mandibular bone defect is the major focus of clinical and basic research. This study proposed a novel 3D titanium lattice-like implant for mandibular injuries based on simulation model, which is designed and optimized by a biomechanical/mechanobiological approach, and the working framework for optimal design and preparation processes of the implant has been validated to tailored to specific patient biomechanical, physiological and clinical requirements. Methods: This objective has been achieved by matching and assembling different morphologies of a lattice-like implant mimicking cancellous and cortical bone morphologies and properties, namely, an internal spongy trabecular-like structure that can be filled with bone graft materials and an external grid-like structure that can ensure the mechanical bearing capacity. Finite element analysis has been applied to evaluate the stress/strain distribution of the implant and bone graft materials under physiological loading conditions to determine whether and where the implant needs to be optimized. A topological optimization approach was employed to improve biomechanical and mechanobiological properties by adjusting the overall/local structural design of the implant. Results: The computational results demonstrated that, on average, values of the maximum von-Mises stress in the implant model nodes could be decreased by 43.14% and that the percentage of optimal physiological strains in the bone graft materials can be increased from 35.79 to 93.36% since early regeneration stages. Metal additive manufacturing technology was adopted to prepare the 3D lattice-like implant to verify its feasibility for fabrication. Following the working framework proposed in this study, the well-designed customized implants have both excellent biomechanical and mechanobiological properties, avoiding mechanical failure and providing sufficient biomechanical stimuli to promote new bone regeneration. Conclusion: This study is expected to provide a scientific and feasible clinical strategy for repairing large injuries of mandibular bone defects by offering new insights into design criteria for regenerative implants.

Benefits of Patient-Specific Reconstruction Plates in Mandibular Reconstruction Surgical Simulation and Resident Education

Poorly contoured mandibular reconstruction plates are associated with postoperative complications. Recently, a technique emerged whereby preoperative patient-specific reconstructive plates (PSRP) are developed in the hopes of eliminating errors in the plate-bending process. This study’s objective is to determine if reconstructions performed with PSRP are more accurate than manually contoured plates. Ten Otolaryngology residents each performed two ex vivo mandibular reconstructions, first using a PSRP followed by a manually contoured plate. Reconstruction time, CT scans, and accuracy measurements were collected. Paired Student’s t-test was performed. There was a significant difference between reconstructions with PSRP and manually contoured plates in: plate-mandible distance (0.39 ± 0.21 vs. 0.75 ± 0.31 mm, p = 0.0128), inter-fibular segment gap (0.90 ± 0.32 vs. 2.24 ± 1.03 mm, p = 0.0095), mandible-fibula gap (1.02 ± 0.39 vs. 2.87 ± 2.38 mm, p = 0.0260), average reconstruction deviation (1.11 ± 0.32 vs. 1.67 ± 0.47 mm, p = 0.0228), mandibular angle width difference (5.13 ± 4.32 vs. 11.79 ± 4.27 mm, p = 0.0221), and reconstruction time (16.67 ± 4.18 vs. 33.78 ± 8.45 min, p = 0.0006). Lower plate-mandible distance has been demonstrated to correlate with decreased plate extrusion rates. Similarly, improved bony apposition promotes bony union. PSRP appears to provide a more accurate scaffold to guide the surgeons in assembling donor bone segments, which could potentially improve patient outcome and reduce surgical time. Additionally, in-house PSRP can serve as a low-cost surgical simulation tool for resident education.

The role of computer aided design/computer assisted manufacturing (CAD/CAM) and 3- dimensional printing in head and neck oncologic surgery: A review and future directions

Microvascular free flap reconstruction has remained the standard of care in reconstruction of large tissue defects following ablative head and neck oncologic surgery, especially for bony structures. Computer aided design/computer assisted manufacturing (CAD/CAM) and 3-dimensionally (3D) printed models and devices offer novel solutions for reconstruction of bony defects. Conventional free hand techniques have been enhanced using 3D printed anatomic models for reference and pre-bending of titanium reconstructive plates, which has dramatically improved intraoperative and microvascular ischemia times. Improvements led to current state of the art uses which include full virtual planning (VP), 3D printed osteotomy guides, and patient specific reconstructive plates, with advanced options incorporating dental rehabilitation and titanium bone replacements into the primary surgical plan through use of these tools. Limitations such as high costs and delays in device manufacturing may be mitigated with in house software and workflows. Future innovations still in development include printing custom prosthetics, 'bioprinting' of tissue engineered scaffolds, integration of therapeutic implants, and other possibilities as this technology continues to rapidly advance. This review summarizes the literature and serves as a summary guide to the historic, current, advanced, and future possibilities of 3D printing within head and neck oncologic surgery and bony reconstruction. This review serves as a summary guide to the historic, current, advanced, and future roles of CAD/CAM and 3D printing within the field of head and neck oncologic surgery and bony reconstruction.

Influence of Radiotherapy on Ossification of Vascularized Osseous Reconstruction of the Jaw: A Radiological Retrospective Cohort Study Based on Panoramic Radiographs

Background: The aim of this study was to evaluate the impact of irradiation and time of irradiation on the ossification of jaws reconstructed with free bone grafts. Methods: In total, 100 reconstructions of the jaw were retrospectively evaluated for ossification between bone segments by two raters based on postoperative panoramic radiographs (immediate postOP, approximately 6, 12 and 24 months follow-up). Three subgroups were divided according to the time of irradiation: preoperative radiation therapy (n = 41), postoperative radiation therapy (n = 26) and patients without any radiation therapy (n = 33) as the control group. Ossification time and influencing factors were documented. Results: The fastest ossification with a median of 304 ± 37 days was observed (p < 0.001) in the nonirradiated control group. No significant difference (p = 0.087) in ossification was found between the pre- (447 ± 136 days) and postoperative (510 ± 112 days) radiation groups. Ossification between two graft segments (336 ± 38 days) showed significantly (p < 0.001) faster ossification than between the original and grafted bone (448 ± 85 days). Moreover, closer initial contact between the segments resulted in faster ossification (p < 0.001). When analyzing cofactors, tobacco consumption was the only negative factor aggravating ossification (p = 0.006). Conclusion: Head and neck radiation corresponded with the impaired and prolonged ossification of jaw reconstructions with free bone grafts. There was no difference in ossification if radiotherapy was performed before or after reconstructive surgery. A close bony contact was particularly important for ossification between the original and grafted bone.

Semi-automated digital workflow to design and evaluate patient-specific mandibular reconstruction implants

The reconstruction of large mandibular defects with optimal aesthetic and functional outcomes remains a major challenge for maxillofacial surgeons. The aim of this study was to design patient-specific mandibular reconstruction implants through a semi-automated digital workflow and to assess the effects of topology optimization on the biomechanical performance of the designed implants. By using the proposed workflow, a fully porous implant (LA-implant) and a topology-optimized implant (TO-implant) both made of Ti-6Al-4V ELI were designed and additively manufactured using selective laser melting. The mechanical performance of the implants was predicted by performing finite element analysis (FEA) and was experimentally assessed by conducting quasi-static and cyclic biomechanical tests. Digital image correlation (DIC) was used to validate the FE model by comparing the principal strains predicted by the FEM model with the measured distribution of the same type of strain. The numerical predictions were in good agreement with the DIC measurements and the predicted locations of specimen failure matched the actual ones. No statistically significant differences (p < 0.05) in the mean stiffness, mean ultimate load, or mean ultimate displacement were detected between the LA- and TO-implant groups. No implant failures were observed during quasi-static or cyclic testing under masticatory loads that were substantially higher (>1000 N) than the average maximum biting force of healthy individuals. Given its relatively lower weight (16.5%), higher porosity (17.4%), and much shorter design time (633.3%), the LA-implant is preferred for clinical application. This study clearly demonstrates the capability of the proposed workflow to develop patient-specific implants with high precision and superior mechanical performance, which will greatly facilitate cost- and time-effective pre-surgical planning and is expected to improve the surgical outcome.

Surgical Navigation in Mandibular Reconstruction: Accuracy Evaluation of an Innovative Protocol

Aim: the purpose of this work is to present an innovative protocol for virtual planning and surgical navigation in post-oncological mandibular reconstruction through fibula free flap. In order to analyze its applicability, an evaluation of accuracy for the surgical protocol has been performed. Methods: 21 patients surgically treated for mandibular neoplasm have been included in the analysis. The Brainlab Vector Vision 3.0^® software for surgical navigation has been used for preoperative surgical planning and intra-operative navigation. A post-operative accuracy evaluation has been performed matching the position of mandibular landmarks between pre-operative and post-operative CT scans. Results: the maximal discrepancy observed was included between −3.4 mm and +3.2 mm, assuming negative values for under correction and positive values for overcorrection. An average grade of accuracy included between 0.06 ± 0.58 mm and 0.43 ± 0.68 mm has been observed for every mandibular landmark examined, except for mandibular angles that showed a mean discrepancy value included between 1.36 ± 1.73 mm and 1.46 ± 1.02 mm when compared to preoperative measurements. Conclusion: a satisfying level of accuracy has been observed in the protocol presented, which appears to be more versatile if compared to closed custom-made systems. The technique described may represent a valid option for selected patients, but it cannot be considered for routine activity because of the complexity of the method, the mobility of the jaw, the necessity of surgical navigator and the long surgical learning curve that is required.

The Use of Customized Three-Dimensionally Printed Mandible Prostheses with a Pressure-Reducing Device: A Finite Element Analysis in Different Chewing Positions, Biomechanical Testing, and In Vivo Animal Study Using Lanyu Pigs

Segmental bony defects of the mandible constitute a complete loss of the regional part of the mandible. Although several types of customized three-dimension-printed mandible prostheses (CMPs) have been developed, this technique has yet to be widely used. We used CMP with a pressure-reducing device (PRD) to investigate its clinical applicability. First, we used the finite element analysis (FEA). We designed four models of CMP (P1 to P4), and the result showed that CMP with posterior PRD deployment (P4 group) had the maximum total deformation in the protrusion and right excursion positions, and in clenching and left excursion positions, posterior screws had the minimum von Mises stress. Second, the P4 CMP-PRD was produced using LaserCUSING from titanium alloy (Ti-6Al-4V). The fracture test result revealed that the maximum static pressure that could be withstood was 189 N, and a fatigue test was conducted for 5,000,000 cycles. Third, animal study was conducted on five male 4-month-old Lanyu pigs. Four animals completed the experiment. Two animals had CMP exposure in the oral cavity, but there was no significant inflammation, and one animal had a rear wing fracture. According to a CT scan, the lingual cortex of the mandible crawled along the CMP surface, and a bony front-to-back connection was noted in one animal. A histological examination indicated that CMP was significantly less reactive than control materials (p = 0.0170). Adequate PRD deployment in CMP may solve a challenge associated with CMP, thus promoting its use in clinical practice.

Osteosarcoma of the Mandible in an Elderly Patient

Osteosarcoma is a malignant tumor in which the cancerous cells produce an osteoid matrix or mineralized bone. Jaw bones are affected in 6% of all osteosarcomas and are the fourth most common site of origin. Surgical treatment of osteosarcoma in elderly patients is rarely reported. Here, we report successful treatment of osteosarcoma arising in the mandible of a 90-year-old man. The patient was referred to our institution for diagnosis and treatment of an oral lesion. Intraoral examination revealed that a hard mass measuring 35 × 27 mm was located on the floor of the oral cavity, attached to the bone, and its growth displaced the tongue posteriorly. Therefore, he experienced difficulty in speech and swallowing. Biopsy of the mandibular mass was suspicious for chondrosarcoma. Preoperative examination did not detect critical risks for general anesthesia or surgery. Based on a clinical diagnosis of a malignant bone tumor of the mandible, segmental mandibular resection with reconstruction using a titanium plate was performed. Surgical site infection occurred on postoperative day 12, which was resolved by drainage, local irrigation, and administration of antibiotics. There was no delirium or cardiovascular or pulmonary complications. Surgery resolved the patient's difficulties in speech and swallowing. There was no evidence of tumor recurrence or metastasis 4 years after surgery. This case showed that it was not necessary to exclude surgical treatment merely because the patient was 90 years old. Indications for surgery should be determined individually to improve the patient's quality of life.

Spontaneous bone regeneration in resected non-continuous mandible due to medication-related osteonecrosis of the jaw

Few cases of spontaneous bone regeneration after extensive resection of the jaw bone have been reported, but it is more common in young adults or children. In this case, we report spontaneous bone healing in a 73-year-old female patient. On radiological examination, necrotic regions were seen in the right mandible. She was diagnosed with medication-related osteonecrosis of the jaw due to previous bisphosphonate use. After segmental resection, stabilization achieved using a reconstruction plate. The periosteum was preserved during the procedure. Twelve months later, panoramic radiography was taken and bone formation was seen both horizontally and vertically around the plate. If the periosteum is preserved and stabilization is achieved after resection in benign lesions, the bone may regenerate spontaneously regardless of age. Therefore, instead of simultaneous autogenous bone application, such patients may be followed to determine whether spontaneous bone healing will occur. This should improve patient comfort and reduce surgical cost.

How 3D Printing Is Reshaping Translational Research

"Translational Research" has traditionally been defined as taking basic scientific findings and developing new diagnostic tools, drugs, devices and treatment options for patients, that are translated into practice, reach the people and populations for whom they are intended and are implemented correctly. The implication is of a unidirectional flow from "the bench to bedside". The rapidly emergent field of additive manufacturing (3D printing) is contributing to a major shift in translational medical research. This includes the concept of bidirectional or reverse translation, early collaboration between clinicians, bio-engineers and basic scientists, and an increasingly entrepreneurial mindset. This coincides with, and is strongly complemented by, the rise of systems biology. The rapid pace at which this type of translational research can occur brings a variety of potential pitfalls and ethical concerns. Regulation surrounding implantable medical devices is struggling to keep up. 3D printing has opened the way for personalization which can make clinical outcomes hard to assess and risks putting the individual before the community. In some instances, novelty and hype has led to loss of transparency of outcomes with dire consequence. Collaboration with commercial partners has potential for conflict of interest. Nevertheless, 3D printing has dramatically changed the landscape of translational research. With early recognition and management of the potential risks, the benefits of reshaping the approach to translational research are enormous. This impact will extend into many other areas of biomedical research, re-establishing that science is more than a body of research. It is a way of thinking.

Survival of vascularized osseous flaps in mandibular reconstruction: A network meta-analysis

Objective

An evidence regarding which bony flap for reconstruction of mandibular defects following tumour resection is associated with the highest survival rate is still lacking. This network meta-analysis (NMA) aimed to guide surgeons selecting which vascularized osseous flap is associated with the highest survival rate for mandibular reconstruction.

Methods

From inception to March 2021, PubMed, Embase, Scopus, and Cochrane library were searched to identify the eligible studies. The outcome variable was the flap survival rate. The Bayesian NMA accompanied by a random effect model and 95% credible intervals (CrI) was calculated.

Results

Twenty-two studies with a total of 1513 patients, comparing four osseous flaps namely fibula free flap (FFF), deep circumferential iliac artery flap (DCIA), scapula flap, and osteocutaneous radial forearm flap (ORFF) were included. The respective survival rates of FFF, DCIA, Scapula, and ORFF were 94.50%, 93.12%, 97%, and 95.95%. The NMA failed to show a statistically significant difference between all comparators (FFF versus DCIA (Odd ratio, 1.8; CrI, 0.58,5.0); FFF versus ORFF (Odd ratio, 0.57; CrI, 0.077; 2.9); FFF versus scapula flap (Odd ratio, 0.25; CrI, 0.026; 1.5); DCIA versus ORFF (Odd ratio, 0.32; CrI, 0.037; 2.1); DCIA versus scapula flap (Odd ratio, 0.14; CrI, 0.015; 1.1) and ORFF versus scapula flap (Odd ratio, 2.3; CrI, 0.16; 34)).

Conclusion

Within the limitations of the current NMA, FFF, DCIA, Scapula, and ORFF showed a comparable survival rate for mandibular reconstruction. Although the scapula flap reported the highest survival rate compared to other osseous flaps for mandibular reconstruction; however, the decision making when choosing an osseous flap should be based on many factors rather than simply flap survival rate.

A novel loop neurorrhaphy technique to preserve lower lip sensate in mandibular reconstruction using an innervated vascularized iliac bone flap

BACKGROUND

This study aimed to introduce a novel loop neurorrhaphy technique using an innervated vascularized iliac bone flap (VIBF) with vascularized ilioinguinal nerve (IIN) to reconstruct the inferior alveolar nerve (IAN) and preserve lower lip sensation simultaneously with mandibular reconstruction.

METHODS

This study prospectively included patients who underwent mandibular reconstruction using VIBF from May 2018 to April 2020. Subjects were allocated into two groups: (1) Group I; innervated VIBF with loop neurorrhaphy (IIN doubly anastomosed with IAN and mental nerve), (2) Group II (control); conventional VIBF. Evaluation was done with operative time, intraoperative indocyanine green (ICG), lower lip sensory assessment (two-point discrimination [TPD] test and current perception threshold [CPT]), and drooling.

RESULTS

Twelve patients were included; 6 in each group, (7 males and 5 females), age ranging from 18 to 57 years (average: 36.75 years). In all cases, intraoperative perfusion of IIN was confirmed by ICG. Group I showed a statistically significant more flap harvesting time compared with group II (mean difference, 5.67 min; P = 0.0091). There was a significant difference in sensory recovery favoring group I (P < 0.05). The TPD results in group I showed an average of 9.8 ± 6.9 mm and 6.2 ± 5.7 mm on operated and non-operated sides, while Group II showed a poor sensory recovery, and the TPD showed an average of 24.6 ± 6.7 mm and 8.4 ± 2.3 mm on operated and non-operated sides. The CPT results showed a significant difference between both groups. In Group I, the extent of drooling was 3.16 ± 0.75, while in Group II, the score was 1.6 ± 0.81, revealing a significant difference favoring Group I.

CONCLUSIONS

Concurrent mandibular reconstruction using VIBF and loop neurorrhaphy with vascularized IIN to reconstruct IAN successfully restore lower jaw form and preserve lip sensation.

Pharmacological Approaches and Regeneration of Bone Defects with Dental Pulp Stem Cells

Bone defects in the craniomaxillofacial skeleton vary from small periodontal defects to extensive bone loss, which are difficult to restore and can lead to extensive damage of the surrounding structures, deformities, and limited functions. Plenty of surgical regenerative procedures have been developed to reconstruct or prevent alveolar defects, based on guided bone regeneration involving the use of autogenous bone grafts or bone substituents. However, these techniques have limitations in the restoration of morphological and functional reconstruction, thus stopping disease progression but not regenerating lost tissue. Most promising candidates for regenerative therapy of maxillofacial bone defects represent postnatal stem cells, because of their replication potential in the undifferentiated state and their ability to differentiate as well. There is an increased need for using various orofacial sources of stem cells with comparable properties to mesenchymal stem cells because they are more easily available with minimally invasive procedures. In addition to the source of MSCs, another aspect affects the regeneration outcomes. Thermal, mechanical, and chemical stimuli after surgical procedures have the ability to generate pain, usually managed with pharmacological agents, mostly nonsteroidal anti-inflammatory drugs (NSAIDs). Some studies revealed that NSAIDs have no significant cytotoxic effect on bone marrow stem cells from mice, while other studies showed regulation of osteogenic and chondrogenic marker genes in MSC cells by NSAIDs and paracetamol, but no effect was observed in connection with diclofenac use. Therefore, there is a need to focus on such pharmacotherapy, capable of affecting the characteristics and properties of implanted MSCs.

Application of Three-Dimensional Printed Customized Surgical Plates for Mandibular Reconstruction: Report of Consecutive Cases and Long-Term Postoperative Evaluation

ABSTRACT

This study aims to evaluate the use of customized surgical plates in patients with mandibular defects concerning postoperative aesthetics and functional outcomes during the 2-year follow-up. Preoperative virtual surgical plans and patient-specific three-dimensional printed plates were tailored for consecutive patients. Preoperative preparation, surgical produces, postoperative aesthetics, and functional outcomes were described in detail. The average follow-up period was over 2 years. In the presented clinical cases, aesthetic and functional outcomes were reported to be satisfactory.

Distraction Osteogenesis and Customized Temporomandibular Joint Prosthesis in the Reconstruction of a Large Mandibular Defect - A Case Report

The Rationale:

Mandibular resections involve esthetic and functional impairment and impose a challenge during the reconstruction. This case report is a successful reconstruction with distraction osteogenesis (DO) and customized temporomandibular joint (TMJ) prosthesis.

Patient Concerns:

A 51-year-old male patient presented with a complaint of facial asymmetry, mastication, and speech difficulties.

Diagnosis:

As the patient had undergone a hemimandibulectomy procedure 20 years ago, clinical examination showed facial asymmetry. Radiographic examination exhibited the defect and a radiopaque image representing Kirschner's wire.

Treatment:

DO by bone transport was performed, followed by dental implant and TMJ prosthesis placement.

Outcomes:

DO is a viable treatment option in resections, even when the defect was generated by an ancient injury. The follow-up is around 7 years after the osteogenic distraction, with no complaints and functional capacity.

Take-away Lessons:

The major challenge in mandibular reconstructions through DO is to reproduce the curve of the arch.

Mandibular distraction of free iliac crest bone graft as treatment in a patient with a history of gunshot wound. Case Report

Introduction: The combination of non-vascularized iliac crest bone graft and distraction osteogenesis in a second surgical intervention has only been described to achieve alveolar ridge augmentation. This technique is not recommended to treat bone defects of the jaws caused by firearm projectile. Case presentation: 40-year-old woman with a segmental mandibular defect in the mandible body caused by the impact of a firearm projectile at the age of 1 year. The patient developed a severe Class II dentofacial anomaly that required a two-stage treatment; she underwent mandibular reconstruction with free iliac crest bone graft followed by a bilateral mandibular distraction at the level of the iliac crest bone graft. With these interventions, a remarkable improvement of the patient's malformation was achieved. Conclusion: Horizontal distraction of the free iliac crest bone graft is a safe and predictable procedure to treat dentolabial anomalies requiring mandibular reconstruction. This procedure was performed in the patient without complications. Further studies on the effectiveness of this technique are required.

Analysis of hard tissue facial symmetry after unilateral mandibular reconstruction

Background

This study aimed to determine how successful reconstruction of the mandible can recover the symmetry.

Materials and methods

All patients who underwent surgical treatment for unilateral mandibular reconstruction in 4 years were retrospectively examined. Bilateral differences of gonion (GO) positions were measured in 3 dimensions based on immediate postoperative computed tomography. The data collected was analyzed in 3 ways: First, the comparison of bilateral differences of GO in 3 dimensions. Second, the mean Asymmetry Index in control subjects was used to divide all cases into three groups: “Symmetry,” “Asymmetry,” and “Marked asymmetry.” Third, “maximum normal asymmetry” was calculated, and all cases were categorized as below and above maximum normal asymmetry. The difference between two gonial angles was used to determine the amount of asymmetry.

Results

Forty-seven patients and 47 normal adults were enrolled. The mean bilateral GO difference in the control group was higher than in the study group patients, but it was not statistically significant. The mean Asymmetry Index for the control group was not also significantly higher than the study cases. The study group was “Symmetric” in 78.7% of the cases whereas the control group in 91.4%, 19.1% of the study group and 8.5% of controls were “Asymmetric,” and 2.1% of study cases and 0% of controls were “Markedly Asymmetric.” Maximum normal asymmetry was 82.9% in the study group and 97.8% in the control group. The mean differences between the right and left gonial angles were higher in the study group, but it was not significant (P = 0.1).

Conclusions

Our study’s results showed that bilateral symmetry in mandibular reconstruction patients was satisfactory and similar to the normal individuals.

Three-Dimensional Bioprinting Using a Coaxial Needle with Viscous Inks in Bone Tissue Engineering - An In vitro Study

Introduction:

Vascularized autologous tissue grafts are considered “gold standard” for the management of larger bony defects in the craniomaxillofacial area. This modality does however carry limitations, such as the absolute requirement for healthy donor tissues and recipient vessels. In addition, the significant morbidity of large bone graft is deterrent to fibula bone flap use. Therefore, less morbid strategies would be beneficial. The purpose of this study was to develop a printing method to manufacture scaffold structure with viable stem cells.

Materials and Methods:

In total, three different combinations of ground beta tri-calcium phosphate and CELLINK (bioinks) were printed with a nozzle to identify a suitable bioink for three-dimensional printing. Subsequently, a coaxial needle, with three different nozzle gauge combinations, was evaluated for printing of the bioinks. Scaffold structures (grids) were then printed alone and with additional adipose stem cells before being transferred into an active medium and incubated overnight. Following incubation, grid stability was evaluated by assessing the degree of maintained grid outline, and cell viability was determined using the live/dead cell assay.

Results:

Among the three evaluated combinations of bioinks, two resulted in good printability for bioprinting. Adequate printing was obtained with two out of the three nozzle gauge combinations tested. However, due to the smaller total opening, one combination revealed a better stability. Intact grids with maintained stability were obtained using Ink B23 and Ink B42, and approximately 80% of the printed stem cells were viable following 24 hours.

Discussion:

Using a coaxial needle enables printing of a stable scaffold with viable stem cells. Furthermore, cell viability is maintained after the bioprinting process.

Mandibular Reconstruction With Block Iliac Crest: An Institutional Experience

STUDY DESIGN

Mandibular reconstruction is a challenge. Several reconstructive techniques are available, and the individualization of choice for each patient leads to better results and quality of life for the individual.

OBJECTIVE

The aim of this study is to evaluate the characteristics and complications of cases submitted to mandibular reconstruction with autogenous bone graft block of the iliac crest.

METHODS

Records of 45 patients undergoing mandibular reconstruction with autogenous bone graft block of the iliac crest were analyzed from January 2000 to December 2014. The data collected included age, gender, etiology and graft size, surgical approach, complications, comorbidities, and habits and addictions. Analysis of variance, chi-square test, and Fisher exact test were used for analysis of the variables with a significance level of P < .05.

RESULTS

The success rate of the 45 charts analyzed was 75.6%. No statistical differences were found between age and presence of complications, between defect size and presence or absence of complications, and between type of surgical approach and presence or absence of complications.

CONCLUSION

According to our study, medical history may influence postoperative complications and require attention, though further studies should be performed to further elucidate the relationship between diseases and postoperative complications.

Reconstruction of Oromandibular Defect After Tumor Resection by Sternomastoid-clavicular Flap

ABSTRACT

The study aims to evaluate sternocleidomastoid-clavicular osteo-myocutaneous flap (SCM-OMCF) for reconstruction of mandibular defects after tumor resection. In the period between 2010 and 2018, thirteen patients with primary mandibular tumors underwent mandibular resection and reconstruction with SCM-OMCF. Patients were followed up for 10 to 66 months. Hospital was 13 ± 4 days. All patients started fluid in the 2nd day. The mean time to start oral fluid was 7.5 ± 0.8 day. Four (30.8%) patients suffered from complications (infection and salivary leak in 1 case due to partial flap loss, donor wound dehiscence in 1 case, deep venous thrombosis in 1 case and chest infection in 1 case). None of our cases experienced motor disability. Two cases (15.9%) underwent reoperations. The overall aesthetic outcome was found excellent in 5 cases, satisfactory in 5 cases and fair in 3 cases. The functional outcomes were satisfactory. Tumor recurrences were detected in 2 (15.9%) patients. Two patients died during follow up within 2 years after 1st surgery due to local and distant recurrences. SCM-OMCF is a versatile, safe and simple technique for reconstructing mandibular defects less than 11 cm.

One stage microvascular mandible reconstruction by using scapula chimeric flap combined with computer-aided-design and computer-aided-manufacturing plate including bilateral alloplastic TMJ prosthesis: A case report

This report focuses a defect comprising the complete mandible due to osteonecrosis, including both condyles, that required bilateral temporomandibular joint (TMJ) reconstruction with complete mandibular corpus using a computer-aided-design and computer-aided-manufacturing(CAD-CAM) planning to harvest a scapula chimeric free flap combined with plate including bilateral alloplastic TMJ prosthesis. This procedure was realized in one and the same surgery. A 73 year-old-man developed an osteoradionecrosis of the total mandible including both condyles after radiation therapy for a squamous cell carcinoma of the tongue base(cT4aN2bM0G3). A CAD-CAM reconstruction was planned with a plate extended by bilateral individual TMJ prosthesis, individual fossa components and combined with a composite free flap originating from the subscapular vessel system including scapula(circumflex subscapular artery) for reconstruction of the mandibular corpus which was osteotomized in three segments with a resection guide, the parascapular skin paddle (descending branch of circumflex subscapular artery) for compensation of the soft tissue deficiency of the cervical skin and latissimus dorsi muscle(thoracodorsal artery) for the inner mucosal lining and intraoral reconstruction. The subscapular artery was anastomosed to the external carotid artery and two concomitant veins were sutured end-to-side to the internal jugular vein. The patient was discharged without feeding tube and tracheostomy. No complications have been observed after 6 months follow-up. The patient was able to tolerate soft diet and had comprehensible speech. Thus, a total mandibular reconstruction including both condyles using alloplastic and autoplastic reconstruction in one and the same stage is a valid option and may be considered in comparably severe cases.

Evaluation of Effective Condyle Positioning Assisted by 3D Surgical Guide in Mandibular Reconstruction Using Osteocutaneous Free Flap

In the present study, the reproducibility and postoperative stability of a 3D printed surgical guide were evaluated in mandibular reconstruction with an osteocutaneous free flap (OCFF), including a fibular free flap (FFF) and deep circumflex iliac artery free flap (DCIA). Fifteen patients were enrolled, and a 3D surgical guide was fabricated by simulation surgery using preoperative (T0) Computed tomography (CT) images. Mandibular reconstruction was performed with OCFF using the 3D surgical guide. Postoperative CTs were taken immediately, 1 week (T1), and 6 months (T2) after surgery, to evaluate the reproducibility of the 3D surgical guide and condyle stability. Error of the 3D surgical guide ranged from 0.85 to 2.56 mm. There were no differences in reproducibility according to flap type. Condylar error and error at mandible midpoint were significantly different in FFF. However, there was no difference in DCIA error between the condyle and mandible midpoint. Regarding condyle stability 6 months after surgery, condyles moved more than 2 mm (up to 2.85 mm) in FFF, whereas there were no significant movement in DCIA. Careful intraoperative flap fixation and closed postoperative observation should be considered for stable clinical outcome, especially in the case of FFF.

Systematic scoping review of mandibular bone tissue engineering

Tissue engineering is a promising alternative that may facilitate bony regeneration in small defects in compromised host tissue as well as large mandibular defects. This scoping systematic review was therefore designed to assess in vivo research on its use in the reconstruction of mandibular defects in animal models. A total of 4524 articles were initially retrieved using the search algorithm. After screening of the titles and abstracts, 269 full texts were retrieved, and a total of 72 studies included. Just two of the included studies employed osteonecrosis as the model of mandibular injury. All the rest involved the creation of a critical defect. Calcium phosphates, especially tricalcium phosphate and hydroxyapatite, were the scaffolds most widely used. All the studies that used a scaffold reported increased formation of bone when compared with negative controls. When combined with scaffolds, mesenchymal stem cells (MSC) increased the formation of new bone and improved healing. Various growth factors have been studied for their potential use in the regeneration of the maxillofacial complex. Bone morphogenic proteins (BMP) were the most popular, and all subtypes promoted significant formation of bone compared with controls. Whilst the studies published to date suggest a promising future, our review has shown that several shortfalls must be addressed before the findings can be translated into clinical practice. A greater understanding of the underlying cellular and molecular mechanisms is required to identify the optimal combination of components that are needed for predictable and feasible reconstruction or regeneration of mandibular bone. In particular, a greater understanding of the biological aspects of the regenerative triad is needed before we can to work towards widespread translation into clinical practice.

Accuracy of Computer-Aided Design/Computer-Aided Manufacturing-Assisted Mandibular Reconstruction With a Fibula Free Flap

BACKGROUND

The recent increase in computer-aided design and computer-aided manufacturing (CAD/CAM)-assisted surgery has warranted a thorough evaluation of the accuracy of virtual plan execution. Mandibular reconstructions with a fibula free flap were evaluated by comparing the fibular segments postoperatively with the virtual surgical plans.

METHODS

This study included computed tomography data for 20 patients (11 males; mean age 61.3 years, range 47-74) that received a mandibular reconstruction with a fibula free flap. Linear distances (superior and inferior borders) of 41 fibula segments and intercoronoid distances were measured.

RESULTS

The mean difference was 3.11 ± 2.80 mm for superior borders (range 0.02-12.20 mm), and 2.75 ± 2.61 mm for inferior borders (range 0.22-13.58 mm). The mean intercoronoid difference was 3.57 ± 1.80 mm (range 0.91-6.11 mm).

CONCLUSION

This study confirmed the presumed accuracy regarding the use of fibular and mandibular cutting guides. CAD/CAM is an attractive technique which enhances efficiency and assurance during surgery and preoperative planning.