Evaluating the risk of post-extraction inferior alveolar nerve injury through the relative position of the lower third molar root and inferior alveolar canal

The aim of this study was to introduce a method to evaluate the risk of inferior alveolar nerve (IAN) injury following the extraction of impacted lower third molars. Two hundred impacted lower third molars adjacent to the IAN were evaluated. These were divided into four classification groups according to preoperative cone beam computed tomography (CBCT) findings: AR, apical region; LT, lateral region of the tapered root; LE, lateral region of the enlarged root; AE, adjacent to the enlarged root. All teeth were dislocated along the long axis or arc of the root by tooth sectioning technique and extracted by a single surgeon. The primary outcome variable was postoperative neurosensory impairment of the IAN. The χ² test was used to evaluate differences in postoperative IAN injury between the classifications. Logistic regression analysis was used to evaluate the risk factors for postoperative IAN injury. The overall incidence of postoperative IAN injury was 7%. Specifically, most injuries involved classification AE (AE 36%, LE 8.6%, LT 3.6%, AR 0%), and the difference was statistically significant (P <  0.05). Logistic regression showed that classification AE was the only risk factor for postoperative IAN injury (P <  0.001). According to preoperative CBCT, the risk of postoperative IAN injury is higher when the IAN is adjacent to the enlarged part of the root.     

Complications associated with inferior alveolar nerve repositioning for dental implant placement: a systematic review

Inferior alveolar nerve (IAN) repositioning has been used widely in recent years as an alternative approach for dental implant placement in the atrophic posterior mandible. The aim of this study was to answer the question: What are the complications associated with IAN repositioning? A systematic literature review performed in accordance with the PRISMA statement, using the PubMed (MEDLINE), Cochrane Library, and Scopus databases, identified a total of 116 articles related to this technique. Of those articles, 24 were included in the final review. Lateralization was the chosen technique in seven studies, transposition in 15 studies, and two studies reported both techniques. The longest follow-up period was 49.1 months and the shortest 6 months. Of the patients who underwent lateralization, 95.9% initially showed a neurosensory disturbance, and the condition remained at the end of the study for 3.4% of those patients. With regard to the patients who underwent transposition, neurosensory alterations were observed in 58.9% of patients initially, and the condition remained for 22.1% of those affected at the end of the study. Only one study found no neurosensory disturbance at any time. More data consolidation is necessary to determine scientifically if, which, and when the IAN repositioning technique can be recommended.     

Damage to the inferior alveolar nerve as the result of root canal therapy

BackgroundEndodontic treatment of mandibular molar teeth has the potential to damage the inferior alveolar nerve via direct trauma, pressure or neurotoxicity.MethodsThe author reviewed all cases of involvement of the inferior alveolar nerve resulting from root canal therapy in patients seen in a tertiary referral center during an eight-year period (1998 through 2005). The author had encouraged practitioners to refer patients immediately to a university clinic.ResultsThe author saw 61 patients during the eight-year period. Eight patients were asymptomatic and received no treatment. Forty-two patients exhibited only mild symptoms or were seen more than three months after undergoing root canal therapy, and they received no surgical treatment. Only 10 percent of these patients experienced any resolution of symptoms. Eleven patients underwent surgical exploration. Five of these patients underwent exploration and received treatment within 48 hours, and all recovered completely. The remaining six patients underwent surgical exploration and received treatment between 10 days and three months after receiving endodontic therapy. Of these patients, four experienced partial recovery and two experienced no recovery at all.ConclusionsEarly surgical exploration and débridement may reverse the side effects of endodontic treatment on the inferior alveolar nerve.Clinical ImplicationsIf the radiograph obtained after endodontic therapy shows sealant in the inferior alveolar canal, then immediate referral to an oral and maxillofacial surgeon is indicated if the patient has continued symptoms of paresthesia or pain once the local anesthetic should have worn off. Immediate surgical exploration and débridement may provide satisfactory results.     

Clinical and electrophysiological assessment of inferior alveolar nerve function after lateral nerve transposition

Inferior alveolar nerve (IAN) transposition surgery may cause some degree of sensory impairment. Accurate and reproducible tests are mandatory to assess IAN conduction capacity following nerve transposition. In this study subjective (heat, pain and tactile-discriminative tests) and objective (electrophysiological) assessments were performed in 10 patients receiving IAN transposition (bilaterally in 8 cases) in order to evaluate any impairment of the involved nerves one year post-operatively. All patients reported a tingling, well-tolerated sensation in the areas supplied by the mental nerve with no anaesthesia or burning paresthesia. Tactile discrimination was affected the most (all but 1 patient). No action potential was recorded in 4 patients' sides (23.5%); 12 sides showed a decreased nerve conduction velocity (NCV) (70.5%) and 1 side normal NCV values (6%). There was no significant difference in NCV decrease between partial and total transposition sides, if examined separately. Nerve conduction findings were related 2-point discrimination scores, but not to changes in pain and heat sensitivity. These findings show that lateral nerve transposition, though resulting in a high percentage of minor IAN injuries, as determined by electrophysiological testing, provides a viable surgical procedure to allow implant placement in the posterior mandible without causing severe sensory complaints. Considering ethical and forensic implications, patients should be fully informed that a certain degree of nerve injury might be expected to occur from the procedure. Electrophysiological evaluation is a reliable way to assess the degree of IAN dysfunction, especially if combined with a clinical examination. Intraoperative monitoring of IAN conduction might help identify the pathogenetic mechanisms of nerve injury and the surgical steps that are most likely to harm nerve integrity.     

种植体挤压致骨折片突入下牙槽神经管内后无不适1例

牙种植体或骨折片进入下牙槽神经管往往会导致患者出现暂时或长期的下唇麻木、疼痛不适等症状,最终需拔除种植体。本文所报道的病例为种植体挤压骨折片突入下牙槽神经管,术后患者均未出现异常疼痛及麻木感;术后3个月锥形束CT显示突入的骨折片已改建吸收,种植体获得较好的骨结合,术后3．5个月完成修复负重,随访2年,患者未诉不适。适当地减少植入种植体的长度及正确的操作可大大降低这一风险的发生。     

Inferior alveolar canal course: a radiographic study

Objectives: To describe the morphology and course of the inferior alveolar canal (IAC) as it appears in digital panoramic radiographs.
Materials and methods: Three hundred and eighty-six digital rotational panoramic radiographs (OPG) were studied using the Clinview Software (6.1.3.7 version, Instrumentarium). Among the 386 radiographs, 86 radiographs with 5-mm steel balls were used to calculate the magnification.
Results: The average magnification of radiographs in this study was 7.24±7.55%. The course of IAC as seen in the panoramic radiograph may be classified into four types: (1) linear curve, 12.75%, (2) spoon-shaped curve, 29.25%, (3) elliptic-arc curve, 48.5%, and (4) turning curve, 9.5%. On panoramic radiographs, the IAC appeared closest to the inferior border of the mandible in the region of the first molar. In relation to the teeth, on panoramic radiographs, the IAC appeared closest to the distal root tip of the third molar and furthest from the mesial root tip of the first molar.
Conclusion: In the OPG, there are four types of IAC: linear, spoon shape, elliptic-arc, and turning curve. The data found in the study may be useful for dental implant, mandibule surgery, and dental anesthesia. The limitations of the panoramic radiograph in depicting the true three-dimensional (3D) morphology of the IAC are recognized, computed tomography (CT) and cone beam (CB)3D imaging being more precise.     

下牙槽神经阻滞麻醉误注次氯酸钠意外

次氯酸钠（NaClO）是一种高效快速的广谱抗菌剂,使用不当可引起一系列不良反应。本文报道1例误将1%NaClO作为麻醉药进行下牙槽神经阻滞麻醉时引发的医疗意外。     

Vertical splitting of the mandibular body as an alternative to inferior alveolar nerve lateralization

The aim of this study was to present and evaluate a modified technique to inferior alveolar nerve lateralization (IANL) that allows the placement of longer implants in the posterior mandibular region. One hundred and forty-three consecutive patients were enrolled in this study; these patients had between 1.8 and 8 mm residual crestal height above the mandibular canal. Vertical splitting of the mandibular body was performed using piezoelectric surgery followed by bone expansion and insertion of special conical implants of 10 and/or 12 mm in length. Two hundred and sixty-nine osteotomies were performed and 636 implants were inserted, with a survival rate of 99% at the end of 12 months. Immediately postoperative there was an alteration of sensation in the lip/chin area in 8.5% of cases; 4.1% regained full sensation within 10–14 days, 2.6% after 8 weeks, and 0.7% had persistent paresthesia that did not affect their daily activities. Progressively increasing pain and numbness was present in 1.1%; the implants were removed 6 months postoperatively. This is a relatively simple procedure that has no limitations in clinical situations with minimal bone height. It allows for greater implant stability, and the risk of neurological disturbance is minimal.     

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根管闭锁（pulp canal obliteration,PCO）是牙外伤后常见的并发症之一,通常发生于青少年,多见于年轻恒牙。PCO的发生机制尚不明确,可能是外伤后受损的牙髓出现血管再生和（或）神经再生的结果,也可能是由于外伤本身或者复位固定外伤牙后牙髓血液流量的改变导致。对于牙外伤后出现PCO的患牙,一些学者认为根管治疗不仅可以避免出现根尖周炎症,而且有利于患牙的美容修复。大多数学者则认为可对患牙进行长期的随访观察,只有伴有PCO的外伤牙出现牙髓坏死或者发展为根尖周炎时才考虑根管治疗,而且根管治疗对PCO的患牙是一项挑战,在技术上是复杂的。总之,为了及时检测到PCO的发生,对外伤牙定期随访和密切观察是十分必要的。     

颏管的应用解剖学研究

目的 :研究国人颏管的形态及颏管与下颌管、切牙神经管的位置关系 ,为口腔牙种植等颏区手术提供解剖学数据。方法 :磨开 13例 ( 2 6侧 )甲醛溶液固定的湿下颌骨标本的下颌管前段、颏管和切牙神经管始段 ,直接观察测量。另取 2 1侧经过脱钙处理的下颌骨标本 ,解剖并显露下颌管、颏管和切牙神经管进行观测。结果 :下颌管前端分成 2个管 :颏管和切牙神经管。大多数颏管行向后上外开口于颏孔 ,颏管长为 :( 5 .61±1.0 7)mm ,管径为 :( 2 .5 3± 0 .47)mm ,颏孔前缘至下颌管前端的水平距离为 :( 2 .82± 1.2 9)mm ,颏孔下缘到下颌管上缘的垂直距离为 ( 3 .83± 1.43 )mm ,颏管与下颌管之间的角度为 ( 63 .5 7± 13 .71)° ,颏管内有颏神经和颏血管行走。结论 :下颌管向后上外方续为颏管再通向颏孔 ,并非以往认为的下颌管自后上内向前下外方向直接开口于颏孔。     

应用锥形束CT影像对颏管的三维定量测量及临床意义

目的:应用锥形束CT(CBCT conebeam computed tomography)影像对颏管三维结构、走向及毗邻关系进行定量测量,为确保颏孔区域牙种植手术的安全提供依据。方法:对我院门诊口腔科80例患者的160侧下颌骨CBCT影像进行回顾性分析,对颏管的曲面、矢状位、冠状位、水平位及3D影像进行测量分析。结果:曲面和矢状位影像可对下颌管进行全面的观察。水平位影像显示下颌管在下颌骨体部靠近舌侧与下颌骨体平行走行,之后,以23°±5°角偏离舌侧转向颊侧走行,下颌管向颊侧走行与颏管形成的角度为101.76°±18.27°,最终分成切牙管与颏管。冠状位影像测量颏管的长度为8.09±1.06mm,直径为1.68±0.52mm,与下颌骨体下缘所呈的倾斜角为36.48°±8.43°。颏管起始处至牙槽嵴顶的距离16.10±4.29mm。3D侧位影像可清晰显示颏孔位置。结论:CBCT影像可清晰显示颏管的三维结构、走向及毗邻关系,明确了此区域神经、血管的分布及骨组织的状况,为牙种植钉及手术入路的选择提供可靠依据。     

Perforation of the inferior alveolar nerve by the maxillary artery: An anatomical study

The infratemporal fossa is a clinically important anatomical area for the delivery of local anaesthetic agents in dentistry and maxillofacial surgery. We studied the infratemporal fossas in white cadavers, and in particular the topographical relations of the inferior alveolar nerve and the maxillary artery. In 3 of the 50 fossas dissected the maxillary artery passed through the inferior alveolar nerve, splitting it into superficial and deep divisions. Entrapment of the maxillary artery may cause numbness or headache and may interfere with injection of local anaesthetics into the infratemporal fossa.     

Articaine buccal infiltration enhances the effectiveness of lidocaine inferior alveolar nerve block

Aim  To compare mandibular tooth pulpal anaesthesia and reported discomfort following lidocaine inferior alveolar nerve block (IANB) with and without supplementary articaine buccal infiltration.
Methodology  In this prospective randomized double-blind cross-over study, thirty-six healthy adult volunteers received two IANB injections of 2 mL lidocaine 2% with epinephrine 1 : 80 000 over two visits. At one visit, an infiltration of 2 mL of articaine 4% with epinephrine 1 : 100 000 was administered in the mucobuccal fold opposite a mandibular first molar. At the other visit, a dummy injection was performed. Injection discomfort was recorded on 100 mm visual analogue scales. Pulpal anaesthesia of first molar, premolar, and lateral incisor teeth was assessed with an electronic pulp tester until 45 min post-injection. A successful outcome was recorded in the absence of sensation on two or more consecutive maximal pulp tester stimulations. Data were analysed using McNemar and Student's t -tests.
Results  The IANB with supplementary articaine infiltration produced more success than IANB alone in first molars (33 volunteers vs. 20 volunteers respectively, P  < 0.001), premolars (32 volunteers vs. 24 volunteers respectively, P  = 0.021) and lateral incisors (28 volunteers vs. 7 volunteers respectively, P  < 0.001). Buccal infiltration with articaine or dummy injection produced less discomfort than IANB injection ( t  = 4.1, P  < 0.001; t  = 3.0, P  = 0.005 respectively).
Conclusions  The IANB injection supplemented with articaine buccal infiltration was more successful than IANB alone for pulpal anaesthesia in mandibular teeth. Articaine buccal infiltration or dummy buccal infiltration was more comfortable than IANB.     

牙颌CT对上颌磨牙近中颊侧第二根管的影像学研究

目的：利用牙颌CT（PROMAX3D）研究活体上颌磨牙近中颊侧第二根管（MB2）口、髓腔形态及其解剖位置关系影像,为临床根管治疗提供可靠的影像学依据。方法：对上颌磨牙根管治疗的患者,使用牙颌CT进行扫描,感兴趣区重建完成之后在颊舌向、水平位以及3D影像上针对上颌磨牙根管数目、牙髓形态影像分析研究。结果：牙颌CT能够在水平位和3D影像上清晰地显示上颌磨牙近中颊侧第二根管的数目、根管口的形态,在颊舌向影像上清楚地显示MB2髓腔的形态及走向。结论：牙颌CT利用不同方向的影像,真实地显示了上颌磨牙近中颊侧第二根管口的形态和髓腔的走向,为临床根管治疗提供可靠的影像学依据,有效地指导了临床医师的治疗工作。     

A prospective, randomized single-blind study of the anesthetic efficacy of frequency-dependent conduction blockade of the inferior alveolar nerve

Introduction

The purpose of this prospective, randomized single-blind study was to evaluate the degree of pulpal anesthesia obtained with frequency-dependent conduction blockade of the inferior alveolar nerve (IAN).

Methods

Eighty adult volunteers randomly received two IAN blocks: an IAN block followed by continuous electrical stimulation for 3 minutes of the first molar or lateral incisor for six cycles over a time period of 64 minutes; an IAN block followed by mock electrical stimulation using the same cycles. The IAN blocks were administered at two separate appointments spaced at least 1 week apart in a crossover design. An electric pulp tester was used to test for anesthesia of the first molar and lateral incisor. Anesthesia was considered successful when two consecutive 80 readings were obtained within 15 minutes, and the 80 reading was recorded through the 60th minute.

Results

The anesthetic success rate for the stimulated IAN block was 35% and 48% for the lateral incisor and first molar, respectively. For the mock stimulated IAN, success was 18% for the lateral incisor and 62% for the first molar. There was no significant difference between the two IAN block techniques.

Conclusions

We concluded that the stimulation of nerves in the presence of local anesthesia (frequency-dependent nerve block) did not statistically increase the success rate of pulpal anesthesia for an IAN block.