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Three-dimensional (3D)-printed guides have been used in endodontics to prepare a conservative access, locate calcified or missing canals, and perform precisive osteotomy in apicoectomy. Here, we present the treatment of a fusion tooth by combining 3D printing technology and endodontic intervention in a 10-year-old patient. The bifid crown of a maxillary right lateral incisor #7 had caused esthetic concerns and malocclusion. Clinical and radiographic examinations showed that #7 is fused with a supernumerary tooth with 2 independent root canals. The fusion involved the entire crown and the coronal and middle roots. Because of financial constraints, a multidisciplinary approach involving endodontic, orthodontic, and prosthodontic treatment was excluded. We hemisectioned the tooth intraorally with a 3D-printed guide, extracted the supernumerary tooth, and transplanted tooth #7 to a position with improved esthetics and occlusion. A 3D-printed tooth replica was used to prepare the recipient site for autotransplantation. At the 6-month follow-up, tooth #7 was diagnosed with pulp necrosis and asymptomatic apical periodontitis. Root canal treatment of tooth #7 was completed, and osseous healing was observed 8 months later. The patient had no clinical symptoms and was satisfied with the outcome 14 months after hemisection and transplantation. The open space between teeth #7 and #8 was closed without orthodontic treatment. We present an alternative option to treat a fusion tooth in young patients who do not opt for other treatment options because of their stage of development or for socio-economic reasons. Techniques in modern endodontics, such as cone-beam computed tomographic imaging and 3D printing, should be adapted when it is beneficial to patients. [ABSTRACT FROM AUTHOR]

The respiratory rhythm is generated by the parafacial respiratory group, Bötzinger complex, and pre-Bötzinger complex and relayed to pre-motor neurons, which in turn project to and control respiratory motor outputs in the brainstem and spinal cord. The phrenic nucleus is one such target, containing phrenic motoneurons (PhMNs), which supply the diaphragm, the primary inspiratory muscle in mammals. While some investigators have demonstrated both ipsi- and contralateral bulbophrenic projections, there exists controversy regarding the relative physiological contribution of each to phasic and tonic drive to PhMNs and at which levels decussations occur. Following C1- or C2 spinal cord hemisection-induced silencing of the ipsilateral phrenic/diaphragm activity, respiratory stressor-induced, as well as spontaneous, recovery of crossed phrenic activity is observed, suggesting an important contribution of pathways crossing below the level of injury in driving phrenic motor output. The precise mechanisms underlying this recovery are debated. In this review, we seek to present a comprehensive discussion of the organization of the bulbospinal network controlling PhMNs, a thorough appreciation of which is necessary for understanding neural respiratory control, accurate interpretation of studies investigating respiratory recovery following spinal cord injury, and targeted development of therapies for respiratory neurorehabilitation in patients sustaining high cervical cord injury. [ABSTRACT FROM AUTHOR]

Mandibular first molars are the major standpoint for occlusion, and also have a wide peri-cemental area. Under specific conditions, hemisection of the tooth is indicated after an endodontic treatment. The following case report presents the hemisection of grossly carious, endodontically treated mandibular first molar, in a 23 year old female, followed by replacement of the mesial root with a single piece immediate loaded BCS (Bi-Cortical Screw) implant and a single unit porcelain fused to metal crown for the prosthetic rehabilitation of the remaining tooth structure, with the BCS implant providing strength and support to the weakened tooth structure. This procedure is an innovation in prosthetic rehabilitation of tooth structure left after hemisection and enhances the predictability of success rate of hemisection. [ABSTRACT FROM AUTHOR]

The aim of the present study has been to analyze the influence of residual root number and bone density on the loading distribution of restorations combining implant and residual tooth after tooth hemisection using finite element analysis. Based on the image data of two patients, one has one distal root and the other has two distal roots in the mandibular right first molar, eight models were created (four models for each patient): a single crown was placed on the implant and residual tooth in two different bone densities; two separate crowns for the implant and residual tooth in two different bone densities. Vertical force of 100-N was applied on the crowns. The results show that the increase in number of residual roots decreased the magnitude of all biomechanical parameters. Higher values were observed in models with low bone density, especially in one distal root models. The maximum values of strains in spongious bone with the model (one distal root, low spongious bone density, a single crown was placed on the implant and residual tooth) even reached 9000 μstrain. From a biomechanical point of view, when two residual roots exist, a single crown placed on the implant and distal half of the molar or two separate crowns for them seem to be an acceptable treatment option, regardless of the bone density. If there is one residual root and the bone density is low, the prosthesis which combines implant with the root might not be used. [ABSTRACT FROM AUTHOR]

Tooth hemisection preserves partial tooth structure and reduces the resorption of alveolar bone. The aim of this study was to analyze the feasibility of preserving a molar after hemisection and inserting a dental implant with different prosthetic superstructures by means of finite element analysis. First, the distance between the root of the mandibular second premolar and the distal root of the first molar were measured in 80 cone beam computed tomography (CBCT) data sets. Based on these data, the lower right posterior jaw segment was reconstructed and the geometries of the appropriate implant were imported. Four models were created: (1) Hemi-1: An implant (3.7 × 9 mm) replaced the mesial root of the molar, and a single crown was placed on the implant and residual tooth. (2) Hemi-2: Two separate crowns were generated for the implant and the residual tooth. (3) Single: An implant (5.5 × 9 mm) with crown replaced the whole molar. (4) FPD: A 3-unit fixed partial denture combined the distal residual part of the molar and premolar. The results indicated that stresses in the cortical bone and strains in the majority region of the spongious bone were below the physiological upper limits. There were higher stresses in implant with the Hemi-1 and Single models, which had the same maximum values of 45.0 MPa. The FPD models represented the higher values of stresses in the teeth and strains in PDL compared to other models. From a biomechanical point of view, it can be concluded that a combination of an implant and residual molar after tooth hemisection is an acceptable treatment option. [ABSTRACT FROM AUTHOR]

Primates are an important and unique animal resource. We have developed a nonhuman primate model of spinal cord injury (SCI) to expand our knowledge of normal primate motor function, to assess the impact of disease and injury on sensory and motor function, and to test candidate therapies before they are applied to human patients. The lesion model consists of a lateral spinal cord hemisection at the C7 spinal level with subsequent examination of behavioral, electrophysiological, and anatomical outcomes. Results to date have revealed significant neuroanatomical and functional differences between rodents and primates that impact the development of candidate therapies. Moreover, these findings suggest the importance of testing some therapeutic approaches in nonhuman primates prior to the use of invasive approaches in human clinical trials. Our primate model is intended to: 1) lend greater positive predictive value to human translatable therapies, 2) develop appropriate methods for human translation, 3) lead to basic discoveries that might not be identified in rodent models and are relevant to human translation, and 4) identify new avenues of basic research to 'reverse-translate' important questions back to rodent models. [ABSTRACT FROM AUTHOR]

Abstract: Progressive changes in the muscle tone and stretch reflex after spinal cord injury (SCI) provide insight into the time-course development of spasticity. This study quantified the time-course changes of hypertonia for rats following SCI of T8 hemisection. A miniature manual stretching device measured the reactive torque via a pair of pressure sensing balloons; the angular displacement was measured via an optoelectronic device. Various stretching frequencies were tested, specifically 1/3, 1/2, 1, 3/2 and 2 Hz. The reactive torque and angular displacement were used to derive the viscous and elastic components representing the viscosity and stiffness of the rat''s ankle joint. The enhanced velocity-dependent properties of spasticity were observed in the SCI hemisection rats (n=9) but not in the controls (n=9). Time-course measurements from pre-surgery to 56 days following SCI showed that the muscle tone of the hemisection rats dropped immediately after spinal shock and then gradually increased to reach a peak around 21 days postinjury (P<0.01). The muscle tone remained at least 75% of the peak value up to the end of an 8 week observation period (P<0.05). The changes of muscle tone can also be verified from the electrophysiological evaluations of electromyography (EMG) (P<0.05). In addition to conventional BBB motor behavior score, our results provided time-course quantification of the biomechanical and electrophysiological properties of muscle tone from the onset of SCI. Such data are useful for investigating progressive recovery of spinal damage in animal model and for future objective assessment of improved treatment for SCI human subjects. [Copyright &y& Elsevier]

Abstract: Consequences of spinal cord injury (SCI) depend on the level and extent of injury. Cervical SCI often results in a compromised respiratory system. Primary treatment of SCI patients with respiratory insufficiency continues to be with mechanical ventilatory support. In an animal model of SCI, an upper cervical spinal cord hemisection paralyzes the hemidiaphragm ipsilateral to the side of injury. However, a latent respiratory motor pathway can be activated to restore respiratory function after injury. In this review, restoration of respiratory activity following systemic administration of theophylline, a respiratory stimulant will be discussed. Pharmacologically, theophylline is a non-specific adenosine receptor antagonist, a phosphodiesterase inhibitor and a bronchodilator. It has been used in the treatment of asthma and other respiratory-related diseases such as chronic obstructive pulmonary disease (COPD) and in treatment of apnea in premature infants. However, the clinical use of theophylline to improve respiration in SCI patients with respiratory deficits is a more recent approach. This review will focus on the use of theophylline to restore respiratory activity in an animal model of SCI. In this model, a C2 hemisection (C2HS) interrupts the major descending respiratory pathways and paralyzes the ipsilateral hemidiaphragm. The review also highlights involvement of central and peripheral adenosine receptors in functional restitution. Biochemical binding assays that highlight changes in adenosine receptors after chronic theophylline administration are discussed as they pertain to understanding adenosine receptor-mediation in functional recovery. Finally, the clinical application of theophylline in SCI patients with respiratory deficits in particular is discussed. [Copyright &y& Elsevier]

Abstract: Cervical spinal cord hemisection at C2 leads to paralysis of the ipsilateral hemidiaphragm in rats. Respiratory function of the paralyzed hemidiaphragm can be restored by activating a latent respiratory motor pathway in adult rats. This pathway is called the crossed phrenic pathway and the restored activity in the paralyzed hemidiaphragm is referred to as crossed phrenic activity. The latent neural pathway is not latent in neonatal rats as shown by the spontaneous expression of crossed phrenic activity. However, the anatomy of the pathway in neonatal rats is still unknown. In the present study, we hypothesized that the crossed phrenic pathway may be different anatomically in neonatal and adult rats. To delineate this neural pathway in neonates, we injected wheat germ agglutinin conjugated to horseradish peroxidase (WGA–HRP), a retrograde transsynaptic tracer, into the phrenic nerve ipsilateral to hemisection. We also injected cholera toxin subunit B–horseradish peroxidase (BHRP) into the ipsilateral hemidiaphragm following hemisection in other animals to determine if there are midline-crossing phrenic dendrites involved in the crossed phrenic pathway in neonatal rats. The WGA–HRP labeling was observed only in the ipsilateral phrenic nucleus and ipsilateral rostral ventral respiratory group (rVRG) in the postnatal day (P) 2, P7, and P28 hemisected rats. Bilateral labeling of rVRG neurons was shown in P35 rats. The BHRP study showed that many phrenic dendrites cross the midline in P2 neonatal rats at both rostral and caudal parts of the phrenic nucleus. There was a marked reduction of crossing dendrites observed in P7 and P28 animals and no crossing dendrites observed in P35 rats. The present results suggest that the crossed phrenic pathway in neonatal rats involves the parent axons from ipsilateral rVRG premotor neurons that cross at the level of obex as well as decussating axon collaterals that cross over the spinal cord midline to innervate ipsilateral phrenic motoneurons following C2 hemisection. In addition, midline-crossing dendrites of the ipsilateral phrenic motoneurons may also contribute to the crossed phrenic pathway in neonates. [Copyright &y& Elsevier]

Abstract: It is well known that some growth factors can not only rescue neurons from death, but also improve motor functions following spinal cord injury. However, their cellular distribution in situ and temporal expressions following spinal cord injury have not been determined, especially in primates. This study investigated the temporal changes in the expression of two growth factors—epidermal growth factor (EGF) and transforming growth factor-beta 1 (TGF-β1) in the injured motoneurons of the spinal cord and the associated precentral gyrus in adult Rhesus monkeys subjected to spinal cord hemisection. Animals were allowed to survive 7, 14, 30 and 90 days post operation (dpo). Functional recovery of the hindlimbs was assessed using Tarlov scale. The immunohistological expressions of EGF and TGF-β1 in the ventral horn motoneurons decreased sharply at 7 dpo in the cord segments caudal to the lesion site, which was followed by an increase and a peak between 14 and 30 dpo for EGF and at 90 dpo for TGF-β1. Changes in the expression of EGF in the precentral gyrus were similar to that in the spinal cord. No TGF-β1 immunoreactive neurons were detected in the precentral gyrus. In the spinal segments rostral to the lesion, the expressions of EGF and TGF-β1 peaked at 30 dpo. The mRNA of EGF was detected in both spinal motoneurons and the precentral gyrus, while that of TGF-β1, only in the spinal motoneuons, suggesting that the spinal motoneurons themselves could synthesize both the growth factors. Partial locomotor recovery in hindlimbs was seen, especially after 14 dpo. It was concluded that a possible association existed between the modulation of EGF and TGF-β1 and the recovery of locomotor function, and their roles differed somewhat in the neuroplasticity observed after spinal cord injury in primates. [Copyright &y& Elsevier]

Abstract: Measurement of spinal cord evoked potentials (SCEPs) is proposed as a means of predicting locomotion outcome in the rat spinal cord injury (SCI) model. Using 55 rats, three reproducible peak waves (waves I, II and III) were observed during stimulation at the C7 level with recording at the L1 epidural space. Hemisection at the T13 level showed three wave loss patterns: wave III loss only, loss of both wave II and III, and loss of all three waves. Defining an ideal SCI model as establishment of stable monoparesis or paraparesis, all animals in the wave II–III loss group showed favorable results. Histological data and electrophysiological properties allowed reasonable assumptions of wave origin: wave I from extrapyramidal tracts, wave II from the ventral corticospinal tract, and wave III from the dorsal corticospinal tract. Complete destruction of pyramidal tracts in both dorsal and ventral fibers was essential for long-term impairment of locomotion. [Copyright &y& Elsevier]

Abstract: There are numerous studies reporting on the crucial roles of neurotrophins (NTFs) in neuronal survival and sprouting after spinal cord injury (SCI). But studies on endogenous changes of neurotrophins after SCI are few. In this study we explored by means of immunohistochemistry the localization of NGF, BDNF and NT-3 in the normal adult spinal cord (SC) and the changes in the expression of these chemicals in the ventral horn after right cord hemisection at T9-10. The results showed an obvious increase in the numbers of NGF, BDNF and NT-3-immunoreactive neurons in the ventral horn and also an increase in their intracellular optical density (O.D.) at 3, 7 and 21 days after cord hemisection, when compared with sham-operated rats. The expression of NGF peaked at 7 days postoperation (dpo), while BDNF and NT-3 expressions peaked at 3dpo. Evaluation of hindlimb functions by Basso Beattie Bresnahan (BBB) scoring showed that the hindlimb support and stepping function improved very quickly at 7dpo. This study indicated that NGF, BDNF and NT-3 could play important but different roles in the mechanisms of spinal neuroplasticity at different times after SCI. [Copyright &y& Elsevier]

Abstract: The present study evaluates the motor functional recovery after C2 spinal cord hemisection combined with contralateral brachial root transection, which causes a condition that is similar to the crossed phrenic phenomenon (CPP). Descending motor pathways, including the reticulospinal extrapyramidal tract and corticospinal pyramidal tracts, were evaluated by transcranial magnetic motor-evoked potentials (mMEPs) and direct cortical electrical motor-evoked potentials (eMEP), respectively. All MEPs recorded from the left forelimb were abolished immediately after the left C2 hemisection. Left mMEPs recovered dramatically immediately after contralateral right brachial root transection. Corticospinal eMEPs never recovered, regardless of transection. The facilitation of mMEPs in animals that had undergone combined contralateral root transection was well correlated with open-field behavioral motor performance. [Copyright &y& Elsevier]

We tested the effect of age at the time of spinal cord injury (SCI) on locomotor recovery, in open field tests, and mechanical hyperalgesia, using paw withdrawal frequency (PWF) in response to noxious mechanical stimuli, in male Sprague–Dawley rats after spinal hemisection at T13 in young (40 days), adult (60 days) and middle-age (1 year) groups. Behavioral outcomes were measured weekly for 4 weeks in both SCI and sham groups. Following SCI, the young and adult groups recovered significantly more locomotor function, at a more rapid rate, than did the middle-age group. The PWF of the young group was significantly increased, the adult group was significantly decreased, and the middle-age group showed no significant change in fore- and hindlimbs when compared to other age groups, pre-injury and sham controls. These results support age-dependent behavioral outcomes after SCI. [Copyright &y& Elsevier]

We hypothesized that pretreatment with chronic cervical dorsal rhizotomy (CDR; C3–C6) would reveal ineffective crossed spinal pathways to phrenic motoneurons. Anesthetized CDR (1 week post-rhizotomy) and control rats were spinally hemisected at C2, and phrenic potentials were evoked by stimulating the ventrolateral funiculus contralateral and rostral to hemisection. Phrenic potentials contralateral to the stimulating electrode were evoked at lower stimulus currents (CDR=640±46 μA; control=900±50 μA; P<0.05) and potential amplitude was significantly greater in CDR versus control rats (P<0.05). The serotonin receptor antagonist methysergide (4 mg/kg, i.v.) had no effect on the crossed phrenic potential amplitude (91±17% of control at 800 μA; P>0.05). Thus, CDR enhances crossed phrenic pathways but serotonin receptor activation is not necessary to maintain this effect. [Copyright &y& Elsevier]