Mandibular Research Articles

Biomechanical analysis of partial mandibular implants with various lattice designs of different material properties: In vitro study and finite element analysis

For patients with mandibular bone defects, although reconstruction plates can be used for repair, achieving both occlusal function and facial aesthetics is challenging. In the present study, in vitro experiments and finite element analysis (FEA) were conducted to determine the biomechanical characteristics of multiple porous lattice structures of varying shapes and diameters that were used for mandibular implants. Additionally, an abutment designed to carry occlusal forces was added to the top of the implants. The stress distribution of four lattice designs (tetrahedron, quad-diametral-cross, hex-star, and hex-vase) of three sizes (2.5, 3.0, and 3.5 mm) in cubic porous models were analyzed by FEA. Subsequently, two optimal designs for 3D-printed titanium alloy were selected. These designs, featuring different lattice diameters (0.5, 0.7, and 0.9 mm), were tested to determine their elastic modulus, which was used in another FEA of a mandibular implant designed for a patient with a malignant tumor in the right mandible. This model, which included an abutment design, was subjected to a vertical force of 100 N and muscle forces generated by biting. This analysis was conducted to determine the elastic modulus of the implant and the values of stress and strain on the implant and surrounding bone. The lattice designs of quad-diametral-cross and hex-vase exhibited smaller high-stress regions than those of tetrahedron and hex-star. In vitro tests revealed that the elastic modulus of the lattices increased with the rod diameter. When these values were applied to mandibular implants, Young’s modulus decreased, which in turn increased the frictional stress observed at the interface between the abutment and the implant. However, the implant’s maximum stress remained below its yield strength (910 MPa), and the strain on the surrounding bone varied between 1500 and 3000 μstrain. As indicated by Frost’s theory, these implants are unlikely to damage the surrounding bone tissue and are likely to support bone growth.  

Axolotl mandible regeneration occurs through mechanical gap closure and a shared regenerative program with the limb.

The mandible plays an essential part in human life and, thus, defects in this structure can dramatically impair the quality of life in patients. Axolotls, unlike humans, are capable of regenerating their lower jaws; however, the underlying mechanisms and their similarities to those in limb regeneration are unknown. In this work, we used morphological, histological and transcriptomic approaches to analyze the regeneration of lateral resection defects in the axolotl mandible. We found that this structure can regenerate all missing tissues in 90 days through gap minimization, blastema formation and, finally, tissue growth, differentiation and integration. Moreover, transcriptomic comparisons of regenerating mandibles and limbs showed that they share molecular phases of regeneration, that these similarities peak during blastema stages and that mandible regeneration occurs at a slower pace. Altogether, our study demonstrates the existence of a shared regenerative program used in two different regenerating body structures with different embryonic origins in the axolotl and contributes to our understanding of the minimum requirements for a successful regeneration in vertebrates, bringing us closer to understand similar lesions in human mandibles.

An Osteoimmunomodulatory Biopatch Potentiates Stem Cell Therapies for Bone Regeneration by Simultaneously Regulating IL-17/Ferroptosis Signaling Pathways.

Currently, there are still great challenges in promoting bone defect healing, a common health problem affecting millions of people. Herein an osteoimmunity-regulating biopatch capable of promoting stem cell-based therapies for bone regeneration is developed. A totally biodegradable conjugate is first synthesized, which can self-assemble into bioactive nano micelles (PPT NMs). This nanotherapy effectively improves the osteogenesis of periodontal ligament stem cells (PDLSCs) under pathological conditions, by simultaneously regulating IL-17 signaling and ferroptosis pathways. Incorporation of PPT NMs into biodegradable electrospun nanofibers affords a bioactive patch, which notably improves bone formation in two rat bone defect models. A Janus bio patch is then engineered by integrating the bioactive patch with a stem cell sheet of PDLSCs. The obtained biopatch shows additionally potentiated bone regeneration capacity, by synergistically regulating osteoimmune microenvironment and facilitating stem cell differentiation. Further surface functionalization of the biopatch with tannic acid considerably increases its adhesion to the bone defect, prolongs local retention, and sustains bioactivities, thereby offering much better repair effects in rats with mandibular or cranial bone defects. Moreover, the engineered bioactive patches display good safety. Besides bone defects, this osteoimmunity-regulating biopatch strategy can be applied to promote stem cell therapies for spinal cord injury, wound healing, and skin burns.

Cephalometric differences in grades II and IV adenoid hypertrophy: A cross-sectional study.

This study aims to determine whether there were cephalometric changes between grades II and IV adenoid hypertrophy. A cross-sectional study was conducted on 120 6-12-year-old patients selected from the ear, nose, and throat department at Imam Al-Hussein Medical City in Karbala. Patients were classified into three groups (each = 40) based on endoscopic findings: control, grade II, and grade IV. The findings were confirmed with cephalometric radiographs. Specific cephalometric points were identified to measure sella-nasion-point A (SNA), sella-nasion-point B (SNB), point A-nasion-point B (ANB), sella-nasion-pogonion (SNPog), sella nasion plane-palatal plane (SNPP), palatal plane-mandibular plane (PPMP), sella nasion plane-mandibular plane (SNMP), saddle, articular, gonial angles, and the y-axis. Additionally, superior-posterior airway space (SPAS), posterior air way space (PAS), mandibular plane-hyoid bone (MP-H), third cervical vertebra-hyoid bone (C3-H), total anterior facial height (TAFH), total posterior facial height (TPFH), upper anterior facial height (UAFH), lower anterior facial height (LAFH), and the Jarabak ratio were measured. Analysis of variance (ANOVA) and Welch tests indicated statistically significant differences (P < 0.05) among the three groups in SNA, SNB, SNPog, PPMP, SNMP, gonial angle, y-axis, SPAS, PAS, MP-H, and the Jarabak ratio. Tukey's honestly significant difference (HSD) and Games-Howell tests indicated a statistically significant difference between grade II and grade IV in SNA, SNMP, y-axis, SPAS, PAS, MP-H, and Jarabak ratio. The present study demonstrated that craniofacial changes start to occur at the moderate adenoid enlargement throughout the downward backward mandibular rotation. More changes would become evident at the severe stage; therefore, an urgent medical intervention and the establishment of nasal breathing by orthodontic treatment with breathing activity would be needed.

Uncovering similarities in the process of lower jaw and limb regeneration within axolotls

Uncovering similarities in the process of lower jaw and limb regeneration within axolotls

Validated 3D finite-element model of the Risso’s dolphin (Grampus griseus) head anatomy demonstrates gular sound reception and channelling through the mandibular fats

Like other odontocetes, Risso's dolphins actively emit clicks and passively listen to the echoes during echolocation. However, the head anatomy of Risso's dolphins differs from that of other odontocetes by a unique vertical cleft along the anterior surface of the forehead and a differently-shaped lower jaw. In this study, 3D finite-element sound reception and production models were constructed based on computed tomography (CT) data of a deceased Risso's dolphin. Our results were verified by finding good agreement with experimental measurements of hearing sensitivity. Moreover, the acoustic pathway for sounds to travel from the seawater into the dolphin's tympanoperiotic complexes (TPCs) was computed. The gular reception mechanism, previously discovered inDelphinus delphisandZiphius cavirostris, was also found in this species. The received sound pressure levels and relative displacement at TPC surfaces were compared between the cases with and without the mandibular fats or mandible. The results demonstrate a pronounced wave-guiding role of the mandibular fats and a limited bone-conductor role of the mandible. For sound production modelling, we digitally filled the cleft with neighbouring soft tissues, creating a hypothetical 'cleftless' head. Comparison between sound travelling through a 'cleftless' head vs. an original head indicates that the distinctive cleft plays a limited role in biosonar sound propagation.

Assessing biological invasion predatory impacts through interaction strengths and morphological trophic profiling

AbstractBiological invasions are a major stressor on ecosystems worldwide, but tools to predict their predatory impact remain limited. Here, we quantified invader impacts using two complementary approaches: functional responses (to reveal per capita and multiple predator interaction strengths) and ecomorphology (to reveal trophic profiles and competitive overlap). We compared Mozambique tilapia Oreochromis mossambicus, a native southern African cichlid, and a near-trophically analogous invasive congener, the Nile tilapia Oreochromis niloticus. Both Nile tilapia and Mozambique tilapia exhibited a potentially prey population destabilizing Type II functional response. In both single and multiple predator pairings, invasive Nile tilapia had significantly greater prey consumption rates than native Mozambique tilapia, and thereby a greater predatory impact than its native congeneric. Attack rates were greater for Nile tilapia than Mozambique tilapia, with both species showing more similar handling times and maximum feeding rates. No evidence for multiple predator effects was detected within or between these species, and therefore impacts of both species increased additively in the presence of conspecific or heterospecific competitors. Morphological trait analyses found general differences between these two species, with the invasive Nile tilapia having distinctively larger lower jaw closing force, gill resistance and gill raker length, which facilitated greater feeding capacities over the native species. Trophic profiles predicted using morphological trait differences showed high dietary overlap and served as evidence for potential exploitative competition between the two species. These results reveal superior interaction strengths and ecomorphological trait profiles of an invasive over native species which could influence impact and native species replacement dynamics. Novel applications of functional response and ecomorphology provide complementary insights into predatory and competitive impacts from invasive species, aiding impact prediction across environmental contexts.

Assessment of Diagnosis of Apical Root Fractures During Tooth Extraction Using Different Radiographic Techniques: An Ex-vivo Study

Objective: This study aimed to examine the diagnostic ability of different imaging techniques for apical root fractures that occur during tooth extraction by specialist dentists in different branches. Methods: Dry human mandibles used for education at Faculty of Dentistry and teeth extracted for routine treatment were used. After the root lengths were measured using a periodontal probe, the samples were adjusted to different lengths. These specimens were placed on a dry human mandible, and images were obtained and recorded using a periapical device, panoramic device, and computed tomography. Radiographs and recordings were performed by an oral and maxillofacial radiologist. The evaluation process was performed by an oral and maxillofacial radiologist, periodontologist, and oral and maxillofacial surgeon. Results: The diagnosis of 1 mm root presence and absence on periapical radiographs showed significant agreement among all observers. In the presence of 2 mm and 3 mm roots, all observers stated that the roots were present. On the panoramic radiographs, moderate agreement was observed in teeth with a 1 mm root. However, poor agreement between observers was observed for teeth with 2 mm and 3 mm roots. Cone-beam computed tomography (CBCT) was effective for the diagnosis of all observers. Conclusion: Consistent with the literature, the present study showed a higher interobserver agreement in CBCT. However, considering the patient's anxiety during the procedure, the duration of local anesthesia, and the surgeon's fatigue, two-dimensional radiographs are generally preferred over CBCT, which has a longer image processing time. Diagnosis using periapical radiographs was more effective than that using panoramic radiographs.

Biomechanical Evaluation of the Osseointegration Levels of Implants Placed Simultaneously With Tibia, Femur, and Jaw Allogeneic Bone Grafts.

In implant-supported prosthetic treatments, the jaw bones may not always have enough bone to accommodate implants. Allogeneic grafts can also be preferred as an alternative to autogenous grafts in cases of vertical and horizontal bone deficiencies. The aim of this study is to evaluate the osseointegration levels of lathe-faced titanium implants placed together with allogeneic bone tissue transplants obtained from tibia, femur, and mandible bones using a biomechanical method. Twenty-eight female Sprague Dawley rats were included in the study. The subjects were divided into groups where bone transplantations were performed together with implant placement from the tibia (n=7), femur (n=7), and lower jaw (n=7) regions. Four rats (left and right) were used as donors. Grafts, along with implants, were surgically placed in the corticocancellous part of the metaphyseal parts of the tibia bones of rats. At the end of the 2-week experimental setup, all rats were killed, and the implants and surrounding bone tissues were subjected to biomechanical reverse torque analysis (N/cm), no statistical difference was detected in terms of bone-implant fusion between the groups in which the femur and tibia bones were transplanted (P>0.05), while the bone-implant fusion value in the group in which the lower jaw bone was transplanted was found to be statistically higher than the femur and tibia bones (P<0.05). Based on the limited results of this study, it can be thought that the lower jaw allogeneic jawbone has a higher osseointegration potential than allogeneic grafts obtained from the femur and tibia.

Evaluating the Feasibility of Short Dental Implants as Alternatives to Long Dental Implants in Mandibular Bone: A Finite Element Study.

This study uses finite element analysis to investigate the potential application of shorter dental implants as a substitute for longer implants in the lower jaw (mandible). FEA allows the evaluation of the stress patterns around the implant-bone interface, a critical factor for successful osseointegration. Ten models were generated, encompassing five long (L1-L5) and five short implant models (S1-S5) with variations in diameter and length. Hypermesh software was utilized to meticulously prepare the FEA models, ensuring accurate mesh generation. The FEA simulations were conducted under four distinct loading scenarios (100 N occlusal load, 40 N lateral load, 100 N oblique at 30°, and 100 N oblique at 45°) to realistically mimic the forces exerted during biting, using an ABAQUS CAE solver. The results revealed that the von Mises stress generated within the short implant models was demonstrably lower compared to their long implants. Additionally, a significant drop in stress was observed with increasing the diameter of the short implants, to a certain diameter range. These findings suggest the potential for successful substitution of long implant model L4 with short implant model S4 due to the demonstrably lower stress values achieved. Furthermore, the data indicates the possibility of utilizing short implant models S3 and S5 as alternatives to long implant models L3 and L5, respectively. These observations hold significant promise for evaluating the feasibility of replacing long implants with shorter variants, potentially leading to a reduction in implant-related failures.

A Novel Technique for Repairing Alveolar Clefts: Computer-Assisted Design With Posterior of Mandible Block Bone Grafts

Objective: Iliac cancellous bone graft is the gold standard for the treatment of alveolar clefts. However, the resorption rate of iliac cancellous bone is generally high. In this study, the authors propose a new method for repairing alveolar clefts using block bone grafts in the posterior region of the mandibular molar and the anterior margin of the ascending branch. Methods: Ten patients with a diagnosis of unilateral or bilateral alveolar cleft were collected. Block bone grafting between the posterior mandibular molar region and the inner and outer oblique lines of the anterior margin of the ascending branch was used to treat the alveolar synostosis. Preoperative, 1-week postoperative, and 6-month postoperative multislice spiral computed tomography scans of the patients were collected and analyzed for preoperative design and postoperative graft bone morphology using computer-assisted software tools, which were also required to measure the changes in the bone tissue density in the posterior mandibular bone extraction area. Results: At 6 months postoperatively, the mean bone resorption rate of the posterior mandibular bone grafts for cleft alveolar processes was 33.96% ± 11.23%. Bone tissue density in the posterior mandibular bone grafting area recovered to near preoperative levels at 6 months postoperatively. Conclusion: The novel method of bone grafting for the cleft alveolar process used in this paper is really effective. Postoperative posterior mandibular bone extraction did not cause sequelae such as mandibular bone defects or poor morphology in the patients. Computer-assisted design and three-dimensional printing technology helped to improve intraoperative bone grafting accuracy and postoperative assessment.

Multimaterial additive manufacturing of poly-L-lactic acid– hydroxylapatite/graphene oxide scaffold fabricated via vat photopolymerization: experimental investigation, analysis and cell study

PurposeThis study aims to design and implement a multimaterial system for printing multifunctional specimens suitable for various sectors, with a particular focus on biomedical applications such as addressing mandibular bone loss.Design/methodology/approachTo enhance both the mechanical and biological properties of scaffolds, an automatic multimaterial setup using vat photopolymerization was developed. This setup features a linear system with two resin vats and one ultrasonic cleaning tank, facilitating the integration of diverse materials and structures to optimize scaffold composition. Such versatility allows for the simultaneous achievement of various characteristics in scaffold design.FindingsThe printed multimaterial scaffolds, featuring 20 Wt.% hydroxylapatite (HA) on the interior and poly-L-lactic acid (PLLA) with 1 Wt.% graphene oxide (GO) on the exterior, exhibited favorable mechanical and biological properties at the optimum postcuring and heat-treatment time. Using an edited triply periodic minimal surface (TPMS) lattice structure further enhanced these properties. Various multimaterial specimens were successfully printed and evaluated, showcasing the capability of the setup to ensure functionality, cleanliness and adequate interface bonding. Additionally, a novel Gyroid TPMS scaffold with a nominal porosity of 50% was developed and experimentally validated.Originality/valueThis study demonstrates the successful fabrication of multimaterial components with minimal contaminations and suitable mechanical and biological properties. By combining PLLA-HA and PLLA-GO, this innovative technique holds significant promise for enhancing the effectiveness of regenerative procedures, particularly in the realm of dentistry.

Facial asymmetry outcome of orthognathic surgery in mild craniofacial microsomia compared to non-syndromic class II asymmetry

ObjectivesTo compare the facial asymmetry after bimaxillary surgery between mild craniofacial microsomia (CFM) and non-syndromic class II asymmetry.Materials and methodsCone-beam computed tomography scans of adults with Pruzansky-Kaban types I and IIA CFM (CFM groups, n = 20), non-syndromic skeletal class II asymmetry (Class II group, n = 20), and normal controls (control group, n = 20) were compared. The area asymmetry of lower face and jaw bones was quantified. Landmark-based method was used to evaluate the lower facial asymmetry regarding midline, cants, and contour.ResultsThere were no significant postoperative differences in the hemi-facial and hemi-jaw area asymmetry between CFM and Class II groups, both of which were significantly larger than the control group. No significant difference was found in the midline deviation and lip and occlusal cants between CFM and Class II groups. The vertical contour asymmetry in CFM group became significantly larger than Class II group. Compared to the control group, the deviation of pronasale, subnasale, and soft-tissue menton, lip and occlusal cants, and sagittal and vertical contour asymmetry in CFM group were significantly larger, as were the deviation of subnasale and soft-tissue menton and vertical contour asymmetry in Class II group.ConclusionsThe vertical contour asymmetry of mild CFM was significantly larger than non-CFM class II after surgery, while the area asymmetry, midline deviation, cants, and sagittal contour asymmetry of lower face showed no significant difference.Clinical relevanceBe aware that correcting vertical asymmetry of contour, lip, and dentition in CFM is still challenging.

Kinematics of mandibular advancement devices (MADs): Why do some MADs move the lower jaw backward during mouth opening?

Mandibular advancement devices (MADs) are widely used treatments for obstructive sleep apnea. MADs function by advancing the lower jaw to open the upper airway. To increase patient comfort, most patients allow the mouth to be opened. However, not all systems maintain the lower jaw in a forward position during mouth opening, which results in the production of a retrusion that favors the collapse of the upper airway. Furthermore, the kinematic behavior of the mechanism formed by the mandible-device assembly depends on jaw morphology. This means that, during mouth opening, some devices cause lower jaw protrusion in some patients, but cause its retraction in others. In this study, we report the behavior of well-known devices currently on the market. To do so, we developed a kinematic model of the lower jaw device assembly. This model was validated for all devices analyzed using a high-resolution camera system. Our results show that some of the devices analyzed here did not produce the correct behavior during patient mouth opening.Graphic abstract

Evaluation of mandibular trabecular bone by fractal analysis in pediatric patients with hypodontia of the mandibular second premolar tooth

BackgroundIt is still unclear whether the trabecular structure of the jaw is different in individuals with hypodontia than in those without hypodontia; this is important for clinicians. The aim was to determine whether the mandibular trabecular bone structure of children and adolescents with hypodontia differs from the control group by using the fractal analysis (FA) method in this study.MethodsA total of 138 panoramic radiographs of 69 cases and 69 control subjects (mean age 13.2 ± 10.1) were evaluated. The age and gender of subjects in the case and control groups were matched. Three regions of interest (ROIs) were selected from the panoramic radiographs. ROI1 refers to the center of the ramus rising above the mandibular foramen. ROI2 refers to the area between the apical level of the mandibular molar and the upper border of the mandibular canal. ROI3, the missing tooth region, refers to the apical third of the mesial side of the erupting or fully erupted permanent mandibular first molar. Mann-Whitney U and Wilcoxon tests were used. p < 0.05 was accepted for the significance value.ResultsThe mean fractal dimension (FD) values of ROI1, ROI2, and ROI3 were 1,25, 1,20, and 1,13, respectively. The means FD values obtained from the ramus region were higher than the other regions (p < 0.05). The FD values did not differ significantly according to gender and age (p > 0.05). The FD values of the case group were lower than the control group for ROI3 (p < 0.05).ConclusionThe results of this study showed that the mandibular trabecular bone quality of pediatric patients with one missing tooth was different from the healthy group. The difference in the mean FD values from the ROIs indicates that the ramus has a denser structure than the mandibular corpus. Clinicians should factor this into their dental treatment planning process.

The anatomy of mastication in a toothless mammal: Morphological characteristics of the temporomandibular joint in the platypus (Ornithorhynchus anatinus)

AbstractThe temporomandibular joint (TMJ) is a distinguishing feature of mammals, and in most mammals includes an articular disc that buffers the loads placed on it by mastication. The disc is well developed in mammals with significant lateral masticatory jaw movements but is absent in toothless mammals, including extant monotremes, although histological studies of developing monotremes have shown rudimentary discs that fail to mature. Platypus (Ornithorhynchus anatinus) grind their food between keratinous pads in the maxillae and lower jaws and are the only edentulate mammals that masticate their food. In this study, we characterize the anatomy of the TMJ of the adult platypus to see if we can reconcile the anatomy, including the absence of the articular disc, with the mandibular movements observed in video recordings. We studied the gross anatomy of the maxillofacial region and the microstructure using microcomputed tomography (micro‐CT) and histological examination. Platypuses had well‐developed masticatory muscles but lacked an articular disc between the mandibular condyle and glenoid fossa. The surface of the glenoid fossa was slightly concave than that of the condylar head was correspondingly slightly convex. The pre‐ and postglenoid processes were not well developed. Micro‐CT showed dense trabecular bone in the anterior part of the condyle, where the lateral pterygoid muscle attached. Histological analysis showed that the surfaces of the condyle and glenoid fossa consisted of dense, avascular and thickened fibrous connective tissue. In addition, well‐developed synovial folds were present. These anatomical characteristics are consistent with both anterior and lateral movements of the mandible, while the thick layer of connective tissue substitutes for a disc by absorbing the mechanical stresses associated with mastication. The failure of the disc primordium to develop cannot be attributed to a lack of muscle development, but the distribution of stresses in the toothless platypus jaw is likely to be different from those in a masticating eutherian.

Are different screw lengths associated with osteosynthesis quality in the region of the mental foramen?

AbstractIntroductionThe use of two monocortical malleable 04‐hole miniplates, placed above and below the mental foramen, has been indicated to prevent the adverse effects of tension and torsion forces on fracture healing. To obtain good fixation in the mandible's outer cortex screws, 5–8 mm long have been recommended. However, studies have shown thicknesses in the mental foramen region of up to 3 mm, meaning the length of the screw could be a risk to nerve or tooth root damage. The purpose of this study is to identify the influence of screw length on osteosynthesis quality in the region of the mental foramen.Materials and Methods10 synthetic polyurethane human lower jaw replicas were subjected to a linear loading test to evaluate fixation techniques with 5 and 10 mm of displacement. In the photoelastic analysis, 02 lower jaw models were made of photoelastic resin and subjected to linear loading in the fixation technique with 10 mm of displacement. Two 04‐hole miniplates in the region of the mental foramen either fixed completely with 4 mm screws (group 1) or with 5 mm screws in the tension zone and 8 mm screws in the compression zone (group 2). The variables were registered for peak load and peak displacement, and final load and final displacement. One‐way analysis of variance (ANOVA) was applied, followed by the Tukey test, with a significance of 5% (p = 0.05) for the comparisons between the means.ResultsConsidering 95% confidence intervals, the mechanical test showed no statistical differences in peak load between the fixations groups. In the photoelastic analysis, the fringes were concentrated on the distal segment of the fracture in both groups.ConclusionDue to the lack of statistical difference in the biomechanical and photoelastic tests, considering the methodologic limitation, our study indicates a tendency of advantage toward the treatment of fractures with two 04‐hole plates, fixed with 4 mm screws, to minimize complications like tooth or nerve damage. In vivo studies are needed to verify the convergence of the results of in vitro studies to evaluate the resistance and stability in real masticatory forces.

Three-dimensional analysis of posttreatment tooth movements despite bonded retainers: partI-upper jaw.

Adverse side effects of fixed retainers in terms of unwanted tooth movements have been described for both the upper and lower jaw, but data about the extent and movement patterns for the maxilla are scarce. The purpose of the present retrospective case-control study was to analyze the amount and direction of unwanted tooth movements despite upper bonded retainers as well as to analyze possible predisposing pretreatment- and treatment-related factors. Plaster casts of 1026 patients who completed orthodontic treatment and asubsequent retention phase of 2years were screened for unintentional tooth movements. The study group comprised 57patients with visually obvious tooth movements in the upper jaw, while 57randomly selected patients without visible tooth movements served as control group. For all patients, plaster casts after debonding of multibracket appliance (T1) and after supervised retention (T2) were digitized, and superimposed digitally using astable palatal reference area. Thereafter, translational and rotational movements were measured in all three planes of space. Pretreatment- and treatment-related factors of the study and control groups were compared by χ2 test, exact Fisher test, Mann-Whitney U test, and the T‑test for independent samples. The mean translational movements ranged between 0 and 0.6 mm and the average rotational movements between 0 and 1.3°. Large individual movements up to 2.7 mm translation and 15.9° rotation were seen. Amovement pattern around the Y‑ and Z‑axis with an opposite rotational peak at the canines ("upper twist effect") was identified. Compared to the control group, patients of the study group showed asignificantly smaller intercanine width pretreatment. Also, study group patients presented alarger intercanine expansion and aslightly larger overjet reduction during treatment, and were more often affected by retainer bonding site detachments and wire fractures, but without reaching statistically significance. Upper bonded retainers show asimilar unwanted movement pattern ("twist effect") like the one described for mandibular retainers.

Tissues response and bone-forming capacity of zinc oxide–eugenol sealer following the addition of nanohydroxyapatite-tyrosine amino acid: An in vivo animal study

Abstract Introduction: The zinc oxide–eugenol (ZOE) sealer is used till now in many private dental clinics although many sealers have been developed. The current study aimed to compare the biocompatibility and remineralizing capacity of ZOE sealer following the addition of nanohydroxyapatite-tyrosine amino acid. Materials and Methods: Twenty rabbits were used in this investigation, and they were divided into four groups based on the test observation period (3, 7, 21, and 28 days) following surgical implantation. General anesthesia was given for each rabbit with a subcutaneous incision of about 1 cm ± 0.5 cm made along the symphyseal area of the mandible of each rabbit. Each rabbit had four bone cavities generated in the interdental space of the lower jaw between the central and molar teeth, with one longitudinal subcutaneous incision. The ZOE sealers were mixed and directly inserted within the cavities as follows: ZOE alone on the central area of the right side of the jaw (Group A), 10% nHAp and Tyrosine mixed ZOE at the molar area (Group B), empty cavity (−ve control) located at the central area of the left side of the jaw (Group C) and 20%/nHAp and Tyrosine mixed ZOE located at the molar area on the left side of the jaw (Group D). Animals were scarified and bone biopsy samples from the tested parts were collected. Histological analysis was performed using a low-power light microscope and immunohistochemistry using runt-related transcription factor 2 (Runx2) antibody. Data were statistically analyzed utilizing the SPSS software. One-way analysis of variance was used and the post hoc test Duncan’s test was utilized to measure the significance among various groups at P ≤ 0.01. Results: The inflammatory process decreased over time for all experimental groups, associated with an increase in granulation tissue formation which was gradually decreasing over time to permit an increase in new blood vessels and new bone formation for all experimental groups that increased with time. Group D displayed the highest levels of new bone formation. Runx2 antibody expression declined progressively, particularly in Group D on 28 days. Conclusion: Superior new bone formation and biocompatible properties were demonstrated by the 20% nHAp and tyrosine mixed ZOE sealer.

Positions of the Mandibular Foramen and Canal in Different Skeletal Classes and Implications for Bilateral Sagittal Split Osteotomy.

To evaluate the positions of the mandibular foramen (MF) and mandibular canal (MC) between different skeletal classes to highlight the implications for bilateral sagittal split osteotomy (BSSO). A cross-sectional study was performed using cone-beam computed tomography on 90 patients classified into classes I, II and III. Linear measurements were performed on multiplanar reconstructions as follows: from the MF to the edge of the mandibular ramus (1), to the mandibular notch (2), to the ramus width (3) and to the occlusal plane (4); and from the MC to the alveolar crest (A), to the lower border of the mandible (B) and to the mandibular buccal cortical bone (C). Mandibular thickness (D), width (E) and height (F) of the MC were measured. Intra-class correlation coefficient (ICC) checked the reliability. Two-way ANOVA and Tukey's test were used to compare measurements and classes. Linear measurements 2 presented a statistically significant difference between classes I and II. There was no statistically significant difference between the classes and measurements B, C, D, E and F. Linear measurements A were shorter in class III than in class II. Although most measurements suggest that the BSSO technique does not need to be modified for each skeletal class, measurements from the MF to the mandibular notch in class II and from the MC to the alveolar crest on distal of the second molars in class III could help surgeons to recognize critical regions.