Management of mandibular nerve injuries from dental implants

Treatment of the patient who has sustained a nerve injury from dental implant procedures involves prompt recognition of this complication, evaluation of sensory dysfunction, the position of the nerve vis-à-vis the implant, and timely management of the injured nerve. In some patients, removal or repositioning of the implant and surgical exploration and repair of the injured nerve will maximize the implant patient's potential for a successful recovery from nerve injury.     

口腔种植中下颌神经损伤的评估、处理与预后

下颌神经损伤是下颌后牙区种植手术中较为严重的并发症，一旦发生，对医患双方都会造成不小的困扰。本文就口腔种植手术过程中下颌神经损伤的评估手段、非手术治疗措施及预后的影响因素做一综述，旨在为遇到该问题的临床医生提供参考。     

罹患牙周牙髓联合病变下颌磨牙拔除后运用牙槽嵴保存术提高种植治疗安全性的效果观察（附1例3年随访报告）

种植治疗作为修复牙列缺损的重要方式,充足的软硬组织条件是种植修复成功的必要条件。下颌磨牙区与下颌管关系紧密,种植治疗时种植体最根方与下颌管间应保持一定的安全距离,避免神经损伤。罹患重度牙周病变的下颌磨牙自然愈合后常常骨量不足,要实现以修复为导向的种植治疗的难度与风险大大增加。牙槽嵴保存术能够阻止或减缓牙槽骨宽度及高度的丧失,为种植治疗创造良好的骨量条件。文章展示了1例因牙周牙髓联合病变保留无望的下颌第二磨牙行微创拔牙同期牙槽嵴保存术后6个月实施种植修复治疗的过程,提高了种植治疗的安全性并取得了良好的治疗效果,积累了针对此类病例的临床经验。     

Trigeminal nerve injuries after mandibular implant placement--practical knowledge for clinicians

Endosseous mandibular implant placement can result in injuries to the peripheral branches of the trigeminal nerve even with the most careful preoperative planning and intraoperative technique. In the past, many patients have been discouraged from seeking repair for such injuries because of the unreliability of the techniques for correcting the injury. It is now possible to perform microneurosurgical repair of such injuries. If the repair is done in a timely fashion, sensation can be improved or restored and painful nerve dysesthesia can be relieved. This article reviews the different types of nerve injuries, their symptoms and diagnosis, and provides information for clinicians to manage their implant patients with neurosensory disturbance.     

Is there an association between the use of antidepressants and complications involving dental implants? A systematic review and meta-analysis

The aim of this systematic review was to evaluate published evidence on the association between the use of antidepressants and complications involving dental implants. Two reviewers independently performed electronic searches of the MEDLINE/PubMed, Cochrane Library, and Scopus databases for relevant articles published up to May 30, 2019. This review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The Newcastle–Ottawa Scale was used for the appraisal of the methodological quality of the studies included. A meta-analysis was performed to determine the risk of dental implant failure in individuals taking antidepressants. Five comparative observational studies were selected for this review; these included a total of 2056 participants with 5302 implants. The results suggest a risk ratio of 3.73 (95% confidence interval 1.85–7.52, P = 0.0002) for implant failure in antidepressant users submitted to oral rehabilitation when compared to non-users. However, these studies did not present methodological rigour or standardize the drugs used. Thus, there is insufficient evidence for an association between antidepressant use and dental implant complications.     

Iatrogenic trigeminal post-traumatic neuropathy: a retrospective two-year cohort study

With the growing demand for dental work, trigeminal nerve injuries are increasingly common. This retrospective cohort study examined 53 cases of iatrogenic trigeminal nerve injury seen at the Department of Oral and Maxillofacial Surgery, University Hospitals of Leuven between 2013 and 2014 (0.6% among 8845 new patient visits). Patient records were screened for post-traumatic trigeminal nerve neuropathy caused by nerve injury incurred during implant surgery, endodontic treatment, local anaesthesia, tooth extraction, or specifically third molar removal. The patients ranged in age from 15 to 80 years (mean age 42.1 years) and 68% were female. The referral delay ranged from 1 day to 6.5 years (average 10 months). The inferior alveolar nerve (IAN) was most frequently injured (28 cases), followed by the lingual nerve (LN) (21 cases). Most nerve injuries were caused during third molar removal (24 cases), followed by implant placement (nine cases) and local anaesthesia injuries (nine cases). Pain symptoms were experienced by 54% of patients suffering IAN injury, compared to 10% of patients with LN injury. Persistent neurosensory disturbances were identified in 60% of patients. While prevention remains the key issue, timely referral seems to be a critical factor for the successful treatment of post-traumatic neuropathy.     

微创拔除压迫下牙槽神经的第三磨牙方法分析

目的: 应用牵引拔牙、截冠和超声骨刀微创拔牙技术拔除压迫下牙槽神经的第三磨牙,观察术后产生下唇麻木等并发症的发生情况。方法: 选择60例全景片和锥形束CT（CBCT）显示下颌第三磨牙牙根压迫下牙槽神经的患者,分别采用3种方法拔牙各20例,术后检查下唇麻木情况。结果: 应用牵引拔牙技术和截冠方法拔除压迫下牙槽神经的第三磨牙,术后无人发生下唇麻木,而应用超声骨刀微创拔牙的患者中有1例出现轻微的下唇麻木症状,经用药1个月后好转。结论: 牵引拔牙技术、截冠和超声骨刀3种方法均可有效避免智牙拔除后下唇麻木的并发症。     

Evaluation of factors predictive of lingual nerve injury in third molar surgery

The aim of this study was to investigate risk factors for temporary and permanent lingual nerve injury after extraction of mandibular third molars. It was based on a 4-year prospective study of 2134 consecutive mandibular third molar operations in 1384 consecutive day case patients. During the study period (1994-1998) data were collected prospectively on patient, dental and surgical factors and correlated with lingual nerve injury using Student's t test, xi(2) and multiple logistic regression analysis. The incidence of temporary and permanent lingual nerve injury was 1 and 0.3%, respectively, per tooth. Factors that predicted temporary and permanent lingual nerve injury by univariate analysis were age, depth of application, difficulty of operation, surgeon and surgical technique used. Independent risk factors identified by multivariate analysis for temporary lingual nerve injury were perforation of the lingual plate, exposure of the nerve and increased difficulty of operation. The predictors for permanent lingual nerve injury in order of importance were perforation of the lingual plate, surgeon, increased difficulty of operation, exposure of the nerve and increased age of the patient. Surgical factors are the main contributors to lingual nerve injury during third molar extraction, but patient and dental factors are also involved.     

Evaluation of risk of injury to the inferior alveolar nerve with classical sagittal split osteotomy technique and proposed alternative surgical techniques using computer-assisted surgery

Neurosensory disturbance after sagittal split osteotomy is a common complication. This study evaluated the course of the mandibular canal at three positions using computed tomography (CT), assessed the risk of injury to the inferior alveolar nerve in classical sagittal split osteotomy, based on the proximity of the mandibular canal to the external cortical bone, and proposed alternative surgical techniques using computer-assisted surgery. CT data from 102 mandibular rami were evaluated. At each position, the distance between the mandibular canal and the inner surface of the cortical bone was measured; if less than 1mm or if the canal contacted the external cortical bone it was registered as a possible neurosensory compromising proximity. The course of each mandibular canal was allocated to a neurosensory risk or a non-neurosensory risk group. The mandibular canal was in contact with, or within 1mm of, the lingual cortex in most positions along its course. Neurosensory compromising proximity of the mandibular canal was observed in about 60% of sagittal split ramus osteotomy sites examined. For this group, modified classic osteotomy or complete individualized osteotomy is proposed, depending on the position at which the mandibular canal was at risk; they may be accomplished with computer-assisted navigation.     

Long term success of 6 implants supporting a mandibular screw-retained fixed dental prosthesis: a clinical report

Dental implant therapy has become successful with improved surgical and prosthodontic techniques. However, most clinical trials, even though well controlled, are limited in longevity. There are few clinical reports that show long-term results with dental implants. Although there are many similarities among criteria for success in these studies, these criteria may vary from what the individual patient reports as a success. This clinical report describes the 28-year successful clinical outcome of a 62-year-old woman with dental implants supporting a mandibular screw-retained fixed dental prosthesis.     

Immediate placement of bone level Sraumann implants: a case series

Endosseous dental implants have revolutionized the methods clinicians use to treat edentulous and partially edentulous patients. Traditional implant protocol specifies a healing period of several months after tooth extraction, as well as an unloaded healing period prior to restoration. Over the last decade, numerous studies have documented successful immediate placement of endosseous dental implants in fresh extraction sites and have found positive results with early functional loading. The purpose of this article is to present a clinical treatment protocol for the immediate placement and early loading of dental implants and to report the clinical and radiographic outcomes of the SLActive surface Straumann Bone Level implant placed in either maxillary or mandibular fresh extraction sockets.     

下磨牙区种植体尖端与下颌管间安全距离的探讨

目的:探讨下颌磨牙区植入的种植体尖端与下牙槽神经管上缘之间的安全距离。方法:用游标卡尺测量23例患者全景片中的30颗下颌磨牙区种植体长度,除以对应的种植体实际长度,计算全景片中下颌磨牙区垂直放大率(vertical magnification factor,MF);选择种植体尖端至下牙槽神经管上缘间距离小于2mm的8例患者的全景片,测量片中12颗种植体尖端至下牙槽神经管上缘间的距离,除以对应种植体的垂直放大率,计算其实际距离;记录该8例患者有无下唇和(或)颏部感觉异常。结果:①全景片中下颌磨牙区垂直放大率为1.27±0.02;②12颗种植体尖端距下牙槽神经管上缘之间的距离为(1.19±0.33)mm(0.69～1.89mm);③8例接受种植体植入的患者,无一例出现下唇或颏部感觉异常。结论:下颌磨牙区植入种植体的尖端与下颌管上缘之间保存完整的骨壁,是防止损伤下牙槽神经的最关键因素之一。     

跨下颌神经管种植在萎缩下颌后牙区的应用

目的：探讨在下颌后牙缺失骨高度严重不足时,采用超声上颌窦内提升骨刀制备种植窝,进行偏颊侧跨下牙槽神经种植的可行性。方法：11例下颌后牙缺失患者,牙槽嵴顶至下颌神经管上缘距离3.2-5.5mm,按照手术导板偏颊侧倾斜角度,常规制备种植窝至下颌神经管上端1mm处,再用超声内提升骨刀头从已备种植床中央向下方跨过下牙槽神经继续备洞至植入长度,共植入种植体25颗;术中及术后当天密切观察种植床出血及下唇感觉,负载后1、3、6、9、12个月定期复查。结果：术中均未损伤下牙槽神经;观察期间种植体稳固无一脱落,种植体周围牙龈组织健康,种植体周围未见骨低密度影,负载后12月种植体边缘骨高度与刚负载时边缘骨高度差异无统计学上意义;咀嚼功能恢复满意。结论：应用超声上颌窦内提升骨刀,进行跨下颌神经管种植是一种安全、简单、可靠的修复下颌后牙缺失骨高度严重不足的方法,可避免使用传统的外置法植骨、牵张成骨术、下牙槽神经移位术。     

Neuropathic pain resulting from implant placement: case report and diagnostic conclusions

Summary  Temporary or persisting dysesthesia of the nervus alveolaris inferior has often been described as a complication of implant surgery of the lower mandible. In most cases, lesion of the nerve results in anaesthesia of the innervated region, a symptom clearly indicative of correct diagnosis. In our case report, however, a minor perforation of the roof of the mandibular canal during implant placement apparently provoked discrete irritation of the nerve, resulting in persistent neuropathic pain without concomitant hypesthesia or dysesthesia. Because the canal could not be detected in conventional dental radiographs, this uncharacteristic situation made correct diagnosis difficult and led to unnecessary surgical procedures including extraction of adjacent teeth. Medical imaging [computed tomography (CT)] finally revealed the close proximity of the apex of the implant and the bony structure of the mandibular canal. The effect on the nervus alveolaris inferior was also demonstrated using an innovative high-resolution dental magnetic-resonance-imaging technique reflecting vascular reactions of the neurovascular bundle after potentially damaging surgical intervention. After removal of the causative implant, the pain gradually faded over a period of a year.     

Risk Assessment Before Extraction for Immediate Implant Placement in the Posterior Mandible: A Computerized Tomographic Scan Study

Background: Controversy exists in treatment planning relative to the attempt of saving a tooth with unfavorable prognosis or extracting it and placing an immediate or delayed implant. Preextraction radiographic assessments of teeth are traditionally performed using two‐dimensional periapical and panoramic radiographs. These can reveal bone loss around a tooth, but have limited use in assessing implant risk before tooth extraction. Three‐dimensional radiographs or cone‐beam (CB) or computerized tomographic (CT) scans are often taken after tooth extraction and socket healing to assess the healed ridge as a potential implant site. However, when treatment planning for an immediate implant in the posterior mandible, a CT scan taken before tooth extraction can be of value in assessing the available bone and anatomy of the area. This allows the clinician and patient to consider alternative options, such as treating and maintaining the tooth or using a delayed implant protocol, when the site presents a high risk for immediate implant placement (IIP). The purpose of the present study is to assess the prevalence of sites associated with the mandibular second premolar, mandibular first molar, and mandibular second molar teeth that present high risk for IIP using a preextraction CT scan to assess the available apical bone and the anatomy of the posterior mandible in the area of the anticipated extraction site. Methods: One hundred consecutive CT scans were obtained and screened from the New York University College of Dentistry, Office of Quality Assurance–Approved Implant Dentistry Database. Forty‐one of these CT scans were further assessed because they included the presence of ≥2 of the following tooth types: mandibular second premolars, mandibular first molars, and mandibular second molars. Measurements were obtained on the axial sections of the selected teeth to evaluate the amount of bone available apical to the root apices to determine the frequency of sites where an IIP protocol presented a high risk for inferior alveolar nerve injury or lingual plate perforation. Results: Of the 135 teeth assessed from 41 CT scans, 65% of the mandibular second premolars, 53% of the mandibular first molars, and 73% of mandibular second molars had <6 mm of bone available for IIP, presenting high risk for inferior alveolar nerve injury. Of the sites in which the inferior alveolar canal did not limit available bone for IIP, 7% of the second premolars, 9% of the first molars, and 31% of the second molars presented high risk for lingual plate perforation. Conclusions: Preextraction CT scans may present a useful diagnostic aid to assess the risk of inferior alveolar nerve injury and lingual plate perforation for IIP in the posterior mandible. This information may be used for assessing risk when deciding whether to retain a questionable tooth or replace it with an implant with either an IIP or delayed protocol.     

Elimination of permanent injuries to the inferior alveolar nerve following surgical intervention of the “high risk” third molar

We aimed to find out whether improved preoperative assessment and surgical planning with cone beam computed tomography (CT) could reduce damage to the inferior alveolar nerve when high risk impacted mandibular third molars are extracted. We recorded the presence or absence of postoperative neuropathy after extraction of 200 lower third molars in 185 patients (where cone beam CT had shown contact between the nerve and root) after treatment in the oral surgery department of King's College Hospital. All patients had had cone beam CT of the teeth after panoramic radiography had indicated increased risk of injury to the nerve during extraction. Experienced oral surgeons did all the operations and postoperative reviews. Patients reported temporary alteration of sensation after operation in 12% of teeth but it resolved in all cases and no patient reported permanent loss of sensation. Permanent sensory disturbance in the distribution of the inferior alveolar nerve after third molars have been removed can be eliminated in high risk cases if operations are planned carefully (including cone beam CT), and the procedure is done by a skilled surgeon who has an appreciation of the anatomy of the nerve and roots, and an insight into the mechanical effect of their surgical manipulation. The incidence of permanent neurosensory dysfunction in this study was zero even though all teeth were intimately related to the inferior alveolar canal.     

Nerve injury caused by mandibular block analgesia

Fifty-four injection injuries in 52 patients were caused by mandibular block analgesia affecting the lingual nerve (n=42) and/or the inferior alveolar nerve (n=12). All patients were examined with a standardized test of neurosensory functions. The perception of the following stimuli was assessed: feather light touch, pinprick, sharp/dull discrimination, warm, cold, point location, brush stroke direction, 2-point discrimination and pain perception. Gustation was tested for recognition of sweet, salt, sour and bitter. Mandibular block analgesia causes lingual nerve injury more frequently than inferior alveolar nerve injury. All grades of loss of neurosensory and gustatory functions were found, and a range of persisting neurogenic malfunctions was reported. Subjective complaints and neurosensory function tests indicate that lingual nerve lesions are more incapacitating than inferior alveolar nerve lesions. Unlike most mechanical injuries after surgery, injection injuries were not followed by a course of spontaneous improvement of neurosensory and/or gustatory function. This may indicate neurotoxicity as a central aetiological factor. Fifty-four percent of the nerve injuries were associated with Articaine 4%, and a substantial increase in the number of injection injuries followed its introduction to the Danish market.     

Inferior alveolar nerve repositioning

Nerve repositioning is a viable alternative for patients with an atrophic edentulous posterior mandible. Patients, however, should be informed of the potential risks of neurosensory disturbance. Documentation of the patient's baseline neurosensory function should be performed with a two-point discrimination test or directional brush stroke test preoperatively and postoperatively. Recovery of nerve function should be expected in 3 to 6 months. The potential for mandibular fracture when combining nerve repositioning with implant placement also should be discussed with the patient. This can be avoided by minimizing the amount of buccal cortical plate removal during localization of the nerve and maintaining the integrity of the inferior cortex of the mandible. Additionally, avoid overseating the implant, thus avoiding stress along the inferior border of the mandible. The procedure does allow for the placement of longer implants, which should improve implant longevity. Patients undergoing this procedure have expressed overall satisfaction with the results. Nerve repositioning also can be used to preserve the inferior alveolar nerve during resection of benign tumors or cysts of the mandible. This procedure allows the surgeon to maintain nerve function in situations in which the nerve would otherwise have to be resected.     

伴下颌神经管变异的种植修复1例

下颌神经管的位置是下颌后牙种植手术考虑的重要因素,下颌神经管变异的病例在临床上极为少见。本文报道了1例C1、C2、C5、C6及D1、D4-D6缺失伴C5、C6牙下方神经管变异,且对验为烤瓷桥修复的患者,并结合临床和文献资料,对其种植方案、上部修复效果进行讨论。