Orthodontic management of a dental anomaly pattern (DAP) including mandibular canine transmigration: A case report: A challenging treatment but worth it!

Orthodontic technology has advanced to the point where management of cases with multiple dental anomalies should be within an orthodontist''s daily armamentarium. A patient with bilateral agenesis of lower second premolars, delayed development, and transmigration of a mandibular canine was treated with the aid of hemisection, indirect/closed exposure, application of continuous force, targeted delivery, and strict attention to keeping the roots as much in bone as possible. This was accomplished without implants or flattening the facial profile, yet with excellent periodontal status and a fully functioning occlusion.     

Prosthetic Rehabilitation of a Hemisected Maxillary Molar: A Rare Entity

Gingival recession beyond grade III and grade IV level involving furcation defects can lead to tooth loss if not intervened at appropriate time. The treatment options include scaling and root planing, Furcation-plasty, Tunnel preparation, Root separation and resection. The chief complaint of the patient was pain in the upper left first molar because of grade III furcation involvement. Since it was a four rooted molar, the treatment of choice was hemisection of the tooth and extraction of the distal half following endodontic treatment. As the second molar was mesially tilted the prosthodontic rehabilitation was done with a hybrid prosthesis involving a full coverage conventional porcelain fused to metal retainer on the hemisected molar and a resin bonded partial coverage retainer on the tilted second molar. The resultant prosthesis is termed as "Hybrid prosthesis".     

Adenosine A1 Receptor Mrna Expression and the Effects of Systemic Theophylline Administration On Respiratory Function 4 Months After C2 Hemisection

Abstract

Background: Previous studies from our laboratory have demonstrated that in an animal model of acute cervical spinal cord injury (SCI), respiratory function can be restored by theophylline. We also have shown that respiratory recovery occurs spontaneously after prolonged postinjury survival periods when a hemidiaphragm is paralyzed by an ipsilateral upper cervical (C2) spinal cord hemisection. Theophylline mediates functional recovery by central nervous system adenosine A1 receptor antagonism; however, it is unclear whether adenosine receptors are altered after prolonged postinjury periods and whether theophylline can further enhance restored respiratory function that occurs spontaneously.

Objective: To assess putative effects of systemic theophylline administration on further enhancing spontaneous respiratory muscle recovery 4 months after C2 hemisection in rats and to determine whether adenosine A1 receptor mRNA expression is altered in these animals.

Methods: Electrophysiologic assessment of respiratory activity in the phrenic nerves was conducted in C2 hemisected rats 4 months after hemisection under standardized conditions. Immediately thereafter, rats were killed and the cervical spinal cords were prepared for adenosine A1 receptor mRNA expression by in situ hybridization.

Results: Spontaneous recovery of respiratory activity in the ipsilateral phrenic nerve was detected in a majority (15/20) of C2 hemisected animals and amounted to 44.06% ± 2.3 8% when expressed as a percentage of activity in the homolateral phrenic nerve in noninjured animals. At the optimal dosage used in the acute studies, theophylline (15 mg/kg) did not enhance, but rather unexpectedly blocked, recovered respiratory activity in 4 out of 5 animals tested. At dosages of 5 mg/kg and 2.5 mg/kg, the drug blocked recovered respiratory activity in 3 out of 4 and 3 out of 5 animals tested, respectively. Quantitative analysis of adenosine A1 receptor mRNA expression did not reveal a significant difference between experimental animals and sham-operated animals.

Conclusion: The blockade or attenuation of spontaneously recovered respiratory activity following theophylline administration cannot be attributed to changes in adenosine A1 receptors because there were no significant differences in adenosine A1 mRNA expression with sham-operated animals. Lack of alteration in A1 mRNA expression 4 months after cervical SCI suggests that A1 receptor plasticity is not activated by chronic injury. Obliteration of spontaneous recovery with theophylline most likely involves a separate unknown mechanism. These findings suggest that there may be a limited therapeutic window for the clinical application of theophylline in SCI patients with respiratory deficits. Theophylline may be more effective clinically in the acute phase of injury rather than in the chronic phase.     

Immediate plasticity in the motor pathways after spinal cord hemisection: implications for transcranial magnetic motor-evoked potentials

The present study evaluates motor functional recovery after C2 spinal cord hemisection with or without contralateral brachial root transection, which causes a condition that is similar to the crossed phrenic phenomenon on rats. 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. Both electrophysiological and neurological facilitations were significantly attenuated by the selective serotonin synthesis inhibitor para-chlorophenylalanine (p-CPA). These results suggest that serotonergic reticulospinal fibers located contralateral to hemisection contribute to the behavioral and electrophysiological improvement that immediately follows spinal cord injury (SCI).     

Serotonin receptors 5-HT<Subscript>1A</Subscript> and 5-HT<Subscript>3</Subscript> reduce hyperexcitability of dorsal horn neurons after chronic spinal cord hemisection injury in rat

Spinal cord injury (SCI) results in abnormal pain syndromes in humans. In a rodent model of SCI, T13 spinal hemisection results in allodynia and hyperalgesia due in part to interruption of descending pathways, including serotonergic (5-HT) systems, that leads to hyperexcitability of dorsal horn neurons. To characterize further the role of 5-HT and 5-HT receptor subtypes 5-HT_1A and 5-HT₃ in neuronal activation after hemisection, we have examined the responsiveness of dorsal horn neurons to a variety of innocuous and noxious peripheral stimuli. Male Sprague-Dawley rats, 150–175 g, were spinally hemisected (n=40) at T13 and allowed 4 weeks for development of mechanical allodynia and thermal hyperalgesia. Animals then underwent electrophysiologic recording and the results were compared with those from sham controls (n=15). Evoked responses of convergent dorsal horn neurons (n=224 total) at L3–L5 to innocuous and noxious peripheral stimuli were characterized after administration of vehicle, 5-HT (25, 50, 100, and 200 μg), 5-HT (100 μg) in conjunction with the selective 5-HT_1A antagonist WAY 100135 (100 μg), the 5-HT₃ antagonist MDL 72222 (100 μg), the selective 5-HT_1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 150 μg), or the 5-HT₃ agonist 2-Me-5HT (75 μg), with or without pretreatment with antagonists; all treatments were delivered topically onto the cord adjacent to the recording electrode. In hemisected animals, increased responsiveness of convergent cells to all peripheral stimuli was observed bilaterally when compared to controls. No changes in ongoing background activity were present. In control animals, only the highest dose of 5-HT (200 μg) was sufficient to reduce evoked activity, whereas in hemisected animals a concentration-dependant decrease in response was observed. In hemisected animals, both 5-HT_1A and 5-HT₃ receptor antagonism reduced the effectiveness of 5-HT, restoring elevated evoked activity by up to 70% at the doses tested. Administration of 5-HT_1A and 5-HT₃ receptor agonists also decreased hyperexcitability, effects prevented by pretreatment with corresponding antagonists. These results demonstrate the development of denervation supersensitivity to 5-HT following SCI, corroborate behavioral studies showing the effectiveness of 5-HT in reducing allodynia and hyperalgesia after SCI, and contribute to a mechanistic understanding of the role of 5-HT receptor subtypes in chronic central pain. Electronic Publication     

大鼠脊髓半横切损伤动物模型的建立与神经功能评价

目的:建立一种稳定可靠、操作简单的脊髓半横切损伤动物模型,并对其神经功能进行初步评价。方法:将18只SD大鼠随机分为正常对照、假手术组和T10段脊髓半切组。术后不同时间点分别采用BBB运动功能评分及足迹法检测其脊髓功能的变化情况,同时检测其运动诱发电位(MEP)和体感诱发电位(SEP),记录N1及P1波潜伏期。结果:损伤组BBB运动功能评分显著低于正常对照及假手术组(P<0.01),且足迹法检测结果也存在统计学意义(P<0.01)。神经电生理检测结果表明,SEP和MEP潜伏期均具有统计学意义(P<0.01)。结论:成功制备了大鼠脊髓半切损伤动物模型,为研究脊髓损伤相关机制及药物治疗奠定了基础。     

牙半切除术后全冠修复的疗效观察

目的　观察牙半切除术后剩余牙体全冠修复的治疗效果。方法　选择隐裂、根折或根分叉病变患者 ,对欲保留牙根进行根管治疗后 ,行半牙切除术。 3～ 6个月后全冠修复剩余牙体。结果　 18例中 ,成功 8例 ,有效 4例 ,失败 6例 ,4例上颌第一磨牙全部失败。失败病例X线片显示根尖无明显阴影或原根尖阴影无明显扩大 ,但牙槽骨吸收明显 ,多已大于 1/ 2 ,牙周间隙显著增宽。结论　严格选择病例 ,合理设计修复体 ,半切术后剩余牙体仍可采用相当于单端固定桥的全冠修复方法。     

Expression of some neurotrophins in the spinal motoneurons after cord hemisection in adult rats

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 3 dpo. Evaluation of hindlimb functions by Basso Beattie Bresnahan (BBB) scoring showed that the hindlimb support and stepping function improved very quickly at 7 dpo. 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.     

An investigation of the cortical control of forepaw gripping after cervical hemisection injuries in rats

Previous studies in mice have demonstrated that forepaw gripping ability, as measured by a grip strength meter (GSM), is dependent on the contralateral sensorimotor cortex, but this dependency changes after hemisection injury at cervical level 4 (C4). Initially, the mouse fails to grip with the forepaw ipsilateral to the hemisection but gripping recovers. Additionally, a mouse's gripping by the contralateral paw becomes independent of the sensorimotor cortex, indicating a reorganization of cortical control of gripping function (Blanco, J.E., Anderson, K.D., Steward, O. 2007. Recovery of forepaw gripping ability and reorganization of cortical motor control following cervical spinal cord injuries in mice. Exp. Neurol. 203, 333-348.). Here we explore whether a similar reorganization occurs after cervical hemisection injuries in rats. We show that as in mice, unilateral lesions of the sensorimotor cortex impair rats' griping by the contralateral paw. We also confirm from previous studies that cervical hemisections impair rats' griping by the ipsilateral paw. In contrast to mice, however there is minimal recovery of gripping after complete lateral hemisections and secondary lesions of the sensorimotor cortex continue to impair rats' gripping by the contralateral paw. Thus, forelimb gripping ability as measured by the GSM is dependent on the contralateral sensorimotor cortex in rats even after a cervical hemisection.     

Postnatal conversion of cross phrenic activity from an active to latent state

Spinal cord hemisection rostral to the phrenic nucleus leads to paralysis of the ipsilateral hemidiaphragm and respiratory insufficiency. Recovery of the paralyzed hemidiaphragm may be induced by activating a latent respiratory motor pathway in adult rats. Although the pathway is latent in adults, it may not be latent in neonatal rats as shown by the spontaneous expression of activity over this pathway in an earlier in vitro study. Activity mediated over the latent pathway is known as “crossed phrenic activity”. Whether crossed phrenic activity following C2 spinal cord hemisection occurs spontaneously in the neonatal rat in vivo is still unknown. We hypothesized that crossed phrenic activity may be spontaneously expressed in neonates in vivo and may be converted from a spontaneously active state to a latent and nonfunctional state during postnatal development. Thus, a time course study was designed to analyze this activity in rat pups at different ages. The functional status of the ipsilateral and contralateral hemidiaphragms was tested by EMG analysis following hemisection. Crossed phrenic activity was expressed in ventral, lateral, and dorsal parts of the ipsilateral hemidiaphragm in P2 and some P3 and P4 neonatal rats. During postnatal development, the activity was observed only in the ventral area of the ipsilateral hemidiaphragm in P7, P14, P21 and P28 animals. Significant decreases in the extent of ventral crossed phrenic activity were observed from P2 to P28. The pathway generating this activity becomes latent by postnatal day 35. The present results suggest that spontaneous crossed phrenic activity occurs in vivo following C2 hemisection and the activity gradually decreases during the first four postnatal weeks.