Sensory Changes Related to Dental Implant Placement: A Scoping Review

Abstract

Aims:

To perform a scoping review of the literature to elucidate the occurrence of nerve damage related to dental implant placement and the factors causing the sensory changes.

Methods:

An extensive electronic search was conducted using the Cochrane Library, Medline via Ovid, PubMed, Wiley Online, Science Direct, CINAHL, and the Google Scholar databases from the year 1950 to 2020.

Results:

The search resulted in 1,067 articles, out of which 76 were selected for this review. The articles were categorized as literature review articles, retrospective studies, prospective studies, and case series/case reports. Altogether, 2,526 subjects were assessed retrospectively, with 5.27% transient and 1.39% persistent sensory changes, and a cohort of 2,750 subjects were followed prospectively, with 6.22% transient and 1.31% persistent sensory changes. A total of 336 subjects were enrolled in various case reports and case series, with 5.95% transient sensory changes and 84.52% persistent neurosensory changes. The articles included were not of high quality and have variations in their study designs and reporting procedures, with limited sensory change data to include in this study.

Conclusion:

After surgical placement of dental implants in 5,612 patients, the incidence of transient sensory changes was 5.63%, and the incidence of persistent sensory changes was 6.33%. Factors affecting the incidence were: mandibular location of the implant, with the inferior alveolar nerve as the most commonly affected nerve. The common symptoms reported were paresthesia and dysesthesia. Age and gender were among other factors, for which data were not available in all the articles. J Oral Facial Pain Headache 2022;36:165–186. doi: 10.11607/ofph.3027

Dental implants have become a common mode of treatment for the replacement of missing dentition.^1,2 Though the clinical restorative success rate is very good,³ the neurologic complications associated with dental implant placement have not been clearly described in the literature.⁴ Goodacre et al⁵ performed a systematic review analysis with 217 articles from 1981 to 2001. After collecting clinical data on the success and failure rates of dental implants and listing the associated complications, the review concluded that, among the most acute complications associated with the surgical placement of dental implants, neurosensory disturbances rated as high as 39% and as low as 0.6%, with a mean of 6.1% after one-stage implant surgery.⁶ Berglundh et al⁷ published a systematic review in 2002 including articles with a 5-year follow-up period and found that, in the studies included, the incidence of sensory disturbance was 41%. In 1% to 2% of cases, these disturbances persisted for more than a year after dental implant surgery. In 2008, Greenstein et al⁸ detailed the surgical complications while placing dental implants and recommended steps to avoid and manage them. Lamas Pelayo et al⁹ performed a Medline search in 2008 for intraoperative complications during dental implant placement and found that nerve damage was the second most common acute complication after hemorrhage, which can become persistent if left untreated. Most of the literature available previously does not delineate between painful and nonpainful transient and persistent sensory changes.¹⁰

There is a wide discrepancy and inconsistent data on the incidence and characterization of sensory changes and pain caused due to surgical placement of dental implants in the literature.⁴ During the surgical placement of dental implants, nerve injury can occur at any stage; ie, while administering the local anesthetic, during or after implant surgery, or during insertion of the implant. Neural damage can either occur due to direct mechanical injury to the nerve (ie, during the osteotomy or implant placement) or indirectly due to the inflammatory response in surrounding tissues following the surgery.¹¹ Crush-type injuries can occur or compartment syndrome can affect the inferior alveolar nerve due to the nature of the nerve’s anatomy.¹² Perineural inflammation along the nerve trunk with no frank axonal damage is sufficient to induce pain in an organ innervated by the affected nerves.¹³ Depending on the degree of nerve damage, altered sensations and/or pain can occur.¹² These sensory changes can vary from being transient to permanent. Nonpainful sensory changes may present with signs such as paresthesia and/or anesthesia, whereas painful sensory changes may pre-sent with signs such as allodynia and hyperalgesia in addition to the signs of nonpainful sensory changes.¹¹ The literature reports 4% to 8% incidence of residual long-term neurosensory disturbances, such as inferior alveolar nerve paresthesia.^14,15 In many instances, there is a reduction in these symptoms as time progresses. According to a retrospective review by Goodacre et al,⁶ neurosensory impairments reduced from 7% to 1–2% after the elapse of the first year. However, a few other prospective studies^16–18 provide a range from 0% to 13% for the incidence of long-term neurosensory alterations. This wide-ranged discrepancy may be due to numerous factors, including variability in surgical techniques, the type of surgery performed, the proximity to the nerve canal, the psychologic status of the patient, and most important, lack of documentation and skill in evaluating neurosensory function.¹⁹

This study aims to perform a scoping review of the literature to elucidate the incidence of and factors affecting the transient and persistent sensory changes after dental implant placement in order to map the research done in this area and to identify any existing gaps in knowledge, which will pave the way for future systematic reviews on this topic.²⁰

Materials and Methods

The inclusion criteria were as follows: articles published from 1950 to 2020, with no language restrictions, only human studies, and any study design, including meta-analysis, systematic review, non/randomized clinical trial, cohort, case-control, prospective, retrospective, literature review, case report, and case series.

Although the present study is not a systematic review, the PRISMA-ScR methodology was followed (see checklist Fig 1) to conduct this scoping review.^20,21 A scoping review is a newer approach for gathering evidence and is different from a systematic review. A scoping review is a useful tool to identify research gaps and summarize the qualitative findings of the available research.^22–25 Assessment of risk of bias is required for a systematic review but is not mandatory for a scoping review. A scoping review is less rigorous and can be a prerequisite to doing a systematic review. A scoping review informs us what the gap in knowledge is and whether it is necessary to do a systematic review on the subject.

Fig 1.

PRISMA-Scr protocol.

The use of the present scoping review protocol was attempted in the Cochrane Library; however, its strict guidelines failed to identify any articles. Extensive electronic searches of the Cochrane Library, Medline, PubMed, and Science Direct, Springer link, Wiley online library, CINAHL (Cumulative Index to Nursing and Allied Health Literature), and Google Scholar databases were conducted with no language barrier from the years 1950 to 2020. The Boolean search method was used for the following keywords: dental implants; sensory changes; altered sensations; paresthesia; neurosensory disturbances; neuropathy; and trigeminal neuropathy.

Introduction

With the limited and conflicting data available, an attempt was made to perform a critical overview of available publications and research to reach valid conclusions on the incidence of transient (less than 3 months) and persistently altered (3 or more months) sensations following surgical placement of dental implants. This is the cutoff point used in the literature to demarcate the transition between acute and chronic pain,²⁶ and the authors decided to use the same cutoff point for the demarcation between transient and persistent sensory changes, though a recent meta-analysis reported short-term sensory changes lasting up to 10 days following implant placement, intermediate altered sensations lasting from 3 to 6 months, and persistent sensory changes 1 year after implant placement.²⁷

The exclusion criteria were as follows: animal studies, articles reporting neurosensory disturbances following any other invasive surgical procedures, and articles reporting sensory disturbances due to prostheses following dental implant placement. If information was available on chronic pain (3 or more months) after dental implant placement, it was included.

For the data collection process, the preliminary search included literature on any database or internet source with the key terms and without any language restrictions. Research articles, literature reviews, case reports, scientific posters, and published chapters in books, dissertations, and websites were reviewed.

The online searches resulted in: sensory changes with dental implants (29,100 results); dental implant neuropathy (19,900 results); paresthesia with dental implants (7,510 results); pain with dental implants (120,000 results); neurosensory disturbances after dental implant (10,700 results); and trigeminal neuropathy (51,100 results).

An overview of the entire search provided 1,067 articles. Around 55 duplicates were found, and the remaining 1,012 abstracts were screened. Of these, 814 articles were excluded, resulting in 198 articles with abstracts and full texts. After a further thorough reading of the full-text articles, 126 articles were excluded because of lack of exclusivity of transient or persistent sensory changes after dental implant placement in patients. Finally, 72 articles were included in this study. The PRISMA flow diagram was used to obtain the information through the different phases of this scoping review (Fig 2).

Fig 2.

Flowchart showing study inclusion process.

The literature review articles reveal that numerous reviews have been performed in the past; however, none provide an accurate report on the incidence of long-term sensory alterations after dental implant placement with predefined inclusion criteria. Therefore, out of the 72 articles included in this scoping review, further categorization was based on the study design: 30 literature reviews (Table 1); 7 retrospective studies (Table 2); 12 prospective studies (Table 3); and 23 case reports and case series (Table 4).

Table 1.

Literature Review Articles

Author	Year	Journal	Methods, Results, and Conclusions
Padmanabhan et al37	2020	Journal of Indian Prosthodontic Society	The aim of this systematic review and meta-analysis was to evaluate the incidence, distribution, and recovery rate of neurosensory disturbance This study concluded that mandibular implant placement is associated with a considerable risk of neurosensory disturbance More randomized controlled trials are required to quantify the effect of factors leading to altered sensation during implant placement.
Carter et al42	2016	British Dental Journal	This article is both a case series and a review of patients presenting with trigeminal neuropathy in eight years to a specialist trigeminal neuropathy dental service. It is highlighted that the majority of these neuropathies are iatrogenic in nature and rarely caused by neoplasia or other medical conditions. Authors found that 68 out of 372 (18.28%) patients had mandibular trigeminal neuropathy due to dental implants.
Lin et al27	2016	PLoS One	This is a meta-analysis of 26 articles published between 1990 to 2016. The meta-analysis revealed that the short-term (ie, 10 days after implant placement) altered sensation was 13% and the long-term (ie, 1 year after implant placement) altered sensation was 3%.
Al-Sabbagh et al19	2015	Dental Clinics of North America	The article lists multiple risk factors for neuropathic pain, reviews literature on the incidence of neurosensory disturbances, and emphasizes that the published studies have not always differentiated between painful and nonpainful disturbances.
Jacobs et al43	2014	Periodontology 2000	The aim was to review neurovascular challenges in the jawbone and potential risks. Articles, case reports, micro- and macro-anatomical studies, and radiographic studies were included.
Dannan44	2013	The Internet Journal of Dental Science	No accurate search criteria for articles listed. Articles with traumatic injury to inferior alveolar nerve after dental implant surgery were only included. Methods that could be used to diagnose sensory deficiency were emphasized. No research question; poor study design.
Juodzbalys et al45	2013	Clinical Oral Implants Research	The purpose was to analyze reasons for nerve injury and propose guidelines for managing inferior alveolar nerve injuries.
Renton46	2013	British Dental Journal	Discusses complications related to all surgical interventions. Suggests managing techniques. Nerve injury/damage was included.
Tinastepe and Oral47	2013	Ağri	Posttraumatic peripheral pain neuropathies are seen after dental treatments are discussed.
Greenwood and Corbett48	2012	Chapter in: Dental Emergencies	Chapter in a book highlighting neurosensory disturbances after implant placement and management.
Palma-Carrió et al49	2011	Medicina Oral, Patologia Oral, y Cirugia Bucal	Only PubMed search engine used. Articles from 2000 to 2010 included. No inclusion/exclusion criteria. Sensory disturbances caused by direct placement of implants included. No graphs, tables. No predefined criteria for complications, as in all were included under sensory changes—eg, postoperative pain, sensory deficits, peri-implantitis, neurogenic pain.
Juodzbalys et al30	2011	Journal of Oral & Maxillofacial Research	Articles from 1972 to 2010. Language limited to English in the search. Keywords limited to inferior alveolar nerve – injuries, paresthesia, repair. The purpose was to review etiologic factors, mechanisms, clinical symptoms, diagnostic methods, and to create guidelines for the management of the inferior alveolar nerve injury during implant placement.
Siqueira and Siqueira50	2011	Revista Dor	The aim was to review dental implant loss, especially related to trigeminal sensory abnormalities, nerve injury, or persistent pain related to implant procedures. Suggested protocol with topics to be investigated during clinical assessment.
Sánchez Garcés et al51	2011	Chapter in: Implant Dentistry. The Most Promising Discipline of Dentistry	Talks about neurosensory impairment as one of the complications of implant dentistry.
Kim52	2011	Chapter in: Implant Dentistry. A Rapidly Evolving Practice	The chapter contains surgical complications associated with dental implant surgery and management. Neurosensory disturbance as one of the complications.
Alhassani and AlGhamdi53	2010	Journal of Oral Implantology	Discusses the cause of inferior alveolar nerve injury and its diagnosis, prevention, and management.
Moore and Haas54	2010	Dental Clinics of North America	Article reviews extend complications like paresthesia and assess the incidence of paresthesia in surgical procedures of dental implants, which were as high as 37%.
Renton55	2010	Dental Update	Reviews the etiology and prevention of IAN injuries in relation to dental procedures.
Lamas Pelayo et al9	2008	Medicina Oral, Patologia Oral, y Cirugia Bucal	The aim was to study the intraoperative complications in implant surgery, carrying out a review of articles appearing in Medline over the last 10 years. Nerve damage was listed as one of the complications.
Misch and Wang56	2008	Implant Dentistry	The aim of this review was to highlight the challenges of treatment plan–related, anatomy-related, and procedure-related surgical complications, as well as to discuss the etiology, management, and treatment options to achieve a satisfactory treatment outcome. Nerve injury was listed as an anatomy-related complication.
Greenstein et al8	2008	Journal of Periodontology	Addresses surgical complications associated with dental implant placement and discusses how to avoid and manage them. Nerve injury as one of the complications that may occur due to intrusion into the inferior alveolar, lingual, or mental nerve. It can also result due to bone compression on the nerve. Describes various symptoms and the clinical test to differentiate them and manage such conditions.
Peñarrocha et al57	2007	Oral Diseases	Conditions leading to trigeminal sensory deficits have been listed along with their etiologies. Dental implantology is one of the causes of trigeminal neuropathy.
Greenstein and Tarnow58	2006	Journal of Periodontology	Articles address position, number, and size of the mental foramen, mental nerve anatomy, and consequences of nerve damage were evaluated for information pertinent to clinicians performing implant dentistry. Guidelines were developed to avoid nerve injury during surgery in the foramina area.
Hegedus and Diecidue59	2006	International Journal of Oral & Maxillofacial Implants	The article reviews different nerve injuries, symptoms, and diagnoses and provides information for clinicians to manage patients with neurosensory disturbances.
Worthington60	2004	International Journal of Oral Maxillofacial Implants	Focuses on problems of nerve damage associated with implant placement in the posterior mandible, as well as the causes and recommendations to help practitioners avoid this complication.
Goodacre et al5	2003	Journal of Prosthetic Dentistry	The article identifies types of complications that have been reported with implants and associated implant prostheses. A Medline and an extensive hand search were performed on English-language publications beginning in 1981 to 2001. The search focused on publications that contained clinical data regarding success/failure/complications; The neurosensory disturbance was found to be 7% (among 2,142 patients, 151 showed the incidence).
Mraiwa et al61	2003	Clinical Implant Dentistry & Related Research	The review was based on scientific evidence on the anatomical, histologic, physiologic, and clinical aspects of the neurovascularization of the anterior mandible. Neurovascular disturbances associated with different nerves, along with the reported incidence, have been reviewed.
Gregg14	2000	Annals of the Royal Australasian College of Dental Surgeons	The review reports a permanent neurosensory disorder of 8% resulting from injuries to the trigeminal nerve. The importance of differentiating between different sensory disturbances is mentioned.
Dao and Mellor12	1998	International Journal of Prosthodontics	Literature review with retrospective studies, patient surveys, and few prospective psychologic studies on sensory disorders following dental implant surgeries.
Vallerand62	1992	New York State Dental Journal	Review of surgical procedures and protocols to avoid, diagnose, and manage nerve injuries.

Table 2.

Retrospective Research Articles

Author	Year	Title	Journal	Study design	Enrolled subjects for dental implant surgeries	Gender/age	Location	Subjects with altered sensation	Tests performed	Symptoms	Duration of symptoms
Vázquez-Delgado et al10	2018	Prevalence of neuropathic pain and sensory alterations after dental implant placement in a university-based oral surgery department: A retrospective cohort study	Gerodontology	Retrospective cohort study; clinical files from patients submitted to dental implant placement between February 2004 and September 2014 in the Oral Surgery and Implantology Master degree program of the Faculty of Dentistry of the University of Barcelona (Spain)	1,156 patients, of which 1,012 met the study inclusion criteria	417 men (41.2%) and 595 women (58.8%) Mean age 60.7 y (16–90 y)	Maxilla, mandible, and intermental implant placements	3 patients were diagnosed as having PPTN, which corresponds to a prevalence of 0.3% (95% CI: 0%–0.6%). Additionally, 5 patients (0.5%; 95% CI: 0%–1.07%) presented TNWP. The combined prevalence of both disorders was 0.8% (95% CI: 0.02%–1.3%).	Sensory alterations were assessed according to the Guidelines of the International Taskforce on Somatosensory Testing of the IASP SIG-OFP (IASP): pinprick testing of the affected zone, thermal stimulation, von Frey filaments evaluation, directional discrimination, two-point discrimination, and finally subjective evaluation by the patient.	Patients with the diagnosis of painful PTTN according to diagnostic criteria of the ICHD-3 beta; paresthesias, hypoesthesia	Follow-up appointments lasted until the medical condition resolved or until it was considered stable in time (ie, permanent paraesthesia after a 12- to 14-month follow-up period).
Scarano et al63	2017	Neurosensory disturbance of the inferior alveolar nerve after 3,025 implant placements	Implant Dentistry	Retrospective study; patients enrolled between February 2004 and July 2015.	1,065 patients	No gender prevalence mentioned in the study; mean age 58.9 y	Patients with partial or complete mandibular edentulism were selected to receive dental implants for oral rehabilitation.	Only 23 (2.2%) of the 1,065 patients presented with sensitivity disturbances 1 month after implant placement, and only 2 (0.19%) after 6 months, though a complete recovery was observed in these patients within 13 months.	Sensitivity (thermal, tactile, pain) was evaluated on the first recall, and patients with IAN sensory disturbances were recalled at intervals of 1, 3, and 6 months after implant placement.	Sensitivity disturbances	10 days after implant surgery and repeated at intervals of 1, 3, and 6 months up to 13 months
Deppe et al64	2015	Trigeminal nerve injuries after mandibular oral surgery in a university outpatient setting—A retrospective analysis of 1,559 cases	Clinical Oral Investigation	Retrospective analysis from January 2000 to December 2009	48 patients had dental implant surgery	NA	Mandibular post-canine region	2 patients (4.1%); alveolar nerve injuries	Clinical tests performed with 3 months of follow-up	Hypoesthesia Anesthesia	Not significant after a year
KÜtÜk et al65	2013	Anterior mandibular zone safe for implants	Journal of Craniofacial Surgery	Retrospective clinical study 2007 to 2012	55	9 women, 1 man	Mandibular canine region	1,019 dental implants were placed	Dental volumetric CT scans; mechano-receptive test to determine neurosensory changes	Tingling, burning in 8 patients (80%); throbbing in 2 patients (20%); continuous pain in all patients: unilateral (90%), bilateral (10%)	1 mo in 50%; 6 mo in 10%; 24 mo in 10%; continued in 30%
Kwon et al66	2004	The prevalence of sensory disturbance after implant surgery—Retrospective survey of implant practitioners	Journal of the Korean Association of Oral and Maxillofacial Surgeons	Retrospective	47	NA	N/A	Inferior alveolar nerve damage was seen in 45%; 21 cases (61%) were found with a sensory disturbance, which recovered in 6 months, except for 2 cases where sensory disturbance persisted	NA	Dysesthesia Anesthesia Hyperesthesia Hypoesthesia	Sensory disturbance recovered in 6 mo, except for 2 cases where sensory disturbance persisted.
Ellies and Hawker17	1993	The prevalence of altered sensation associated with implant surgery	International Journal of Oral & Maxillofacial Implants	Retrospective questionnaire analysis	112	64 women, 36 men; mean age 57 y	Mandible	Altered sensation was reported by 36%, with 23% of them having transient changes and 13% experiencing permanent changes	Restrospective questionnaire	Numbness/ paresthesia was the most common complaint in almost all patients.	5-year data collected
Ellies16	1992	Altered sensation following mandibular implant surgery: A retrospective study	Journal of Prosthetic Dentistry	Retrospective questionnaire study	226	NA	Mandible	37% reported altered sensations, with 28% having transient sensory changes and 8% reporting long-term sensory changes; higher changes were reported in women.	Questionnaire study; 80% responded	NA	27 (13%) patients experienced altered sensation within 3 mo, and 17 (8%) patients experienced persistent changes more than 3 mo

IASP = International Association for the Study of Pain; ICHD = International Classification of Headache Disorders; PTTN = painful posttraumatic neuropathy; SIG-OFP = Special Interest Group of Orofacial Pain; TNWP = trigeminal neuropathy without pain.

Table 3.

Prospective Research Articles

Author	Year	Title	Journal	Study design	Enrolled subjects for dental implant surgeries/implants, n	Gender/age	Location	Subjects with altered sensation	Test(s) performed	Symptoms	Duration of symptoms
Hartmann et al67	2017	Neurophysiological changes associated with implant placement	Clinical Oral Implants Research	Prospective with follow-up of 9 y	33/NA	17 men, 16 women; median 58 y (28–80 y)	Maxilla, mandible	1	Mechanical and thermal QST on implant vs control side at chin and lower lip	Abnormal sensory responses to touch coexisting with numbness and temperature algesia	Followed up for 9 y; 1 patient presented late for initial evaluation; loss in MDT and VDT, with a gain in sensitization for pain were experienced by 1 patient for 9 y
Vazquez et al38	2008	Efficacy of panoramic radiographs in the preoperative planning of posterior mandibular implants: A prospective clinical study of 1,527 consecutively treated patients	Clinical Oral Implants Research	Prospective clinical study of 1,527 consecutively treated patients	1,527/2,584 consecutively placed	890 women and 637 men; aged from 17 to 86 y (mean age 53 y)	Posterior segment of the completely edentulous mandible	2	A panoramic radiograph was the only preoperative imaging technique used to determine the incidence of altered mental nerve sensation after implant placement in the posterior segment of the mandible.	Temporary paresthesia	Lasted 3 and 6 wk; resolved spontaneously
Abarca et al69	2006	Neurosensory disturbances after immediate loading of implants in the anterior mandible: An initial questionnaire approach followed by a psychophysical assessment	Clinical Oral Investigations	Prospective study to assess past and present neurosensory disturbances using a questionnaire and a psychophysical approach in patients treated with three immediate loaded implants in edentulous anterior mandible	65/NA	30 women, 35 men/30–84 y	Anterior mandible; all of them treated with 3 immediately loaded implants	58 completed the questionnaire; 19 (33%) reported neurosensory disturbance after surgery; of these, 11 patients had less than 3 mo of disturbance, and the remaining 8 still complained of neurosensory disturbance	Questionnaire and psychophysical testing: 2-point discrimination test, light touch, thermal sensitivity	Most common sites affected: inferior lip, gingiva, chin Symptoms: numbness (9 patients), followed by cutting, beating, itching (2 patients)	Sensory disturbance lasted for 8 and 21 mo for the 8 patients.
Kubilius et al70	2004	Traumatic damage to the inferior alveolar nerve sustained in course of dental implantation. Possibility of prevention	Stomatologija	Prospective; tactile and pain sensitivity thresholds determined during first 2 d of implantation, then 7, 14, 28, 45, 60, 90 d, followed by 1 to 2 y	383/11,152	137 women, 246 men	Mandible	68 (17.755%) suffered from inferior alveolar nerve damage after dental implant placement	Sensographic method used to detect tactile and pain sensitivity thresholds	38 (9.92%) with mild IAN transient damage had predominant paresthesia; 27 (7.05%) with moderate IAN transient damage exhibited paresthesia; 3 (0.78%) with severe persistent IAN damage experienced hyperesthesia	Follow-up to 45 d postoperation and follow-up to 2 y
El-Sheikh et al71	2003	Changes in passive tactile sensibility associated with dental implants following their placement	International Journal of Oral & Maxillofacial Implants	Prospective study to investigate the changes in passive tactile sensibility for a period of 3 mo following implant surgery	5/10 (2 each)	2 women, 3 men/56–78 y	Anterior mandible	NA	Measurement of force applied with a custom device	Significant increase in passive tactile sensitivity during 3 mo in subjects treated with immediate loading of implants	Follow-up to 3 mo after surgery
Walton72	2000	Altered sensation associated with implants in the anterior mandible: A prospective study	Journal of Prosthetic Dentistry	Prospective study; objective and subjective tests performed before implant surgery and at planned intervals for 12 mo following surgery	75/NA	47 women, 28 men/40–87 y	Anterior mandible	24% reported altered sensation in anterior mandible in the short term; with only 1% reporting changes 1 y after surgery	Objective and subjective tests	Numbness and tingling of lower lip	Follow-up to 12 mo after surgery
Bartling et al18	1999	The incidence of altered sensation of the mental nerve after mandibular implant placement	Journal of Oral & Maxillofacial Surgery	Prospective study to determine the incidence of altered sensation; neurologic testing followed up until 6 mo, or later until the altered sensation resolved after the implant surgery	94/405	43 women, 51 men	Mandible	8 patients (8.5%) reported altered sensation in the postoperative visit	Subjective assessment and neurologic testing	Paresthesia, anesthesia Most of these patients had a large number of implants placed, but the altered sensations returned to normal in all of them by 121 d following implant placement.	Follow-up to 6 mo after surgery
Wismeijer et al73	1997	Patients’ perception of sensory disturbances of the mental nerve before and after implant surgery: A prospective study of 110 patients	British Journal of Oral & Maxillofacial Surgery	Prospective randomized controlled clinical trial: Patient perception of sensation of lower lip before surgery, 10 d later, and 16 mo after implant surgery	110/NA	76 women, 34 men; 30–80 y	Mandible	Considering a 3-mm safety margin around the mental foramen, the study still showed 7% sensory disturbance in the lower lip	Questionnaire	26 (25%) had altered sensation of lower lip before surgical procedure; 11 (11%) at 10 d, and 10 (10%) had altered sensation of lower lip 16 mo following surgery	Follow -to 16 mo postsurgery
Higuchi et al15	1995	Implant survival rates in partially edentulous patients: A 3-year prospective multicenter study	Journal of Oral and Maxillofacial Surgery	Prospective study	139/460	NA/15–80 y	Maxilla, mandible	NA	Questionnaire, 80% responded	4% paresthesia of inferior alveolar nerve was reported	Follow-up to 5 y
Johns et al74	1992	A multicenter study of overdentures supported by Brånemark implants	The International Journal of Oral & Maxillofacial Implants	Prospective study with 9 clinical centers with 1-y follow-up	133/117 in maxilla, 393 in mandible	59 women, 74 men/ 32–75 y	Maxilla, mandible	NA	Multicenter study involving 9 clinical centers, clinical and radiologic exams	19 patients suffered from paresthesia after mandibular implant surgery; 16 of these recovered by the time of prosthesis placement	In 1 patient, paresthesia still existed 1 y later.
Kiyak et al76	1990	The psychological impact of osseointegrated dental implants	The International Journal of Oral & Maxillofacial Implants	Prospective longitudinal questionnaire study; assessed before and after until 18 mo after surgery	39, but a total of 27 completed the study/NA	79.5% women, 19.5% men; 36–78 y	NA	4.3% experienced facial paresthesia at first-stage surgery; later, 43.5% reported experience at second stage, but none reported persistent sensory changes	Questionnaire	Paresthesia	Follow-up to 14–18 mo
van Steenberge et al77	1990	The applicability of osseointegrated oral implants in the rehabilitation of partial edentulism: A prospective multicenter study on 558 fixtures	The International Journal of Oral & Maxillofacial Implants	Prospective study with 9 clinical centers; with follow-up visits after 1 wk, 1 mo, 6 mo, and 12 mo; patients will be evaluated after 24, 36, 48, and 60 mo following prosthesis placement	154/558; 68 in maxilla, 91 in mandible (521 completed the study)	NA/15–80 y	Maxilla, mandible	16 patients complained of transient paresthesia of lower lip; 1 year after prosthesis placement, 6 patients still complained of persistent paresthesia	Clinical exam	Paresthesia of the lower lip	Follow-up to 12 mo; then later to 60 mo after prosthesis placement

QST = quantitative sensory testing; IAN = inferior alveolar nerve; MDT = mechanical detection threshold; VDT = vibration detection threshold.

Table 4.

Case Reports and Case Series

Author	Year	Title	Journal	Enrolled subjects for dental implant surgeries	Gender	Age	Tooth number(s) restored, (number of implants)	Symptoms	Duration post injury	Pain level (0–10 VAS)
Politis et al40	2017	Report of neuropathic pain after dental implant placement: A case series	International Journal of Oral & Maxillofacial Implants	26	NA	NA	Mandibles of 18 patients, 6 received regular implants and 2 received a zygomatic implant in the maxilla	17 developed pain due to implant placement, 9 developed pain with unknown cause	12 mo	NA
Devine et al41	2016	Chronic post-surgical pain following the placement of dental implants in the maxilla: A case series	European Journal of Oral Implantology	10	9 women, 1 man	Average 55.4 y	6 patients had single implants placed, 4 had multiple implants	Onset of pain was immediate in 9 patients with constant pain	NA	Pain intensity ranged from 2 to 9 (average 5.6)
Du Toit et al78	2015	Implant injury case series and review of the literature part 1: Inferior alveolar nerve injury	Journal of Oral Implantology	4	Woman Woman Woman Man	42 yr 33 y 27 y 43 y	29, 30 (2) 29, 30 (2) 29, 30 (2) 29, 30 (2)	Paresthesia Anesthesia Paresthesia Paresthesia	8 wk NA 3 mo 12 mo	NA
Givol et al79	2013	Inferior alveolar neurosensory deficiency associated with placement of dental implants	Journal of Periodontology	92	58 women	27–89 y	NA	NA	More than 5 y	Pain level not available
Mourào et al80	2013	Role of homeopathy in post-surgical dental implants paresthesia–A case report	Journal of Case Studies in Homeopathy	1	Man	63 y	18, 24, 25 (3)	Paresthesia	12 mo	3
Wright81	2011	Persistent dysesthesia following dental implant placement: A treatment report of 2 cases	Implant Dentistry	2	Man Woman	56 y 66 y	14 (1) 24 (4)	Dysesthesia Dysesthesia	28 mo 36 mo	3 7
Stamatin et al82	2011	Post-implant neurological complications in the horizontal mandibular arch	International Journal of Medical Dentistry	27	Woman Woman	54 y 44 y	21 (1) 21 (1)	Paresthesia Paresthesia	NA	Disappeared after 6 wk Disappeared after 3 wk
Al-Ouf and Salti83	2011	Post-insertion pain in region of mandibular dental implants: A case report	Implant Dentistry	1	Woman	27 y	19, 20 (2)	Dysesthesia	NA	Implant removal reduced pain
Yoon et al84	2010	Use of botulinum toxin type A injection for neuropathic pain after trigeminal nerve injury	Pain Medicine	1	Woman	62 y	23, 24, 25, 26 (4)	Dysesthesia, allodynia, paresthesia	2 mo	NA
Rodriguez-Lozano et al85	2010	Neuropathic orofacial pain after dental implant placement: Review of the literature and case report	Oral Surgery, Oral Medicine, Oral Pathology Oral Radiology, & Endodontics	1	Woman	62 y	Maxilla (8)	Dysesthesia, allodynia	8 mo	NA
Leckel et al86	2009	Neuropathic pain resulting from implant placement: Case report and diagnostic conclusions	Journal of Oral Rehabilitation	1	Man	56 y	19, 20 (2)	Dysesthesia	17 mo	Pain free after removal of one implant
Khawaja and Renton87	2009	Case studies on implant removal influencing the resolution of inferior alveolar nerve injury	British Dental Journal	4	Woman Woman Woman Woman	55 y 56 y 46 y 39 y	30 (2) Mandibular quadrant of partial denture 19 (1) Mandibular left and right quadrants for a mandiblar implant partial denture 20 (1) 29 (1)	Paresthesia of lower lip and chin Paresthesia Paresthesia, mechanical allodynia, dysesthesia Paresthesia, mechanical allodynia Paresthesia of right lower lip	Numbness immediately after surgery until implant was removed 18 h after surgery; one of the implants was removed 24 h postsurgery; implant removed 2 days later; implant removed 4 days later	Decrease in symptoms 3 mo later Decrease in symptoms at 2-mo follow-up No improvement in symptoms at 3-mo follow-up No improvement
Liang et al88	2008	Neurovascular disturbance associated with implant placement in the anterior mandible and its surgical implications: Literature review including report of a case	Chinese Journal of Dental Research	1	Woman	61 y	Mandibular arch (4)	Paresthesia, dysesthesia	NA	NA
Elian et al89	2005	Unexpected return of sensation following 4.5 years of paresthesia: Case report	Implant Dentistry	1	Man	34 y	19, 20, 29, 30 (4)	Paresthesia	NA	Pain reduced after implant removal
Flanagan90	2002	Delayed onset of altered sensation following dental implant placement and mental block local anesthesia: A case report	Implant Dentistry	1	Woman	45 y	20 (1)	Paresthesia	Pain started 4 mo after surgery	Pain free 17 mo later
Gregg14	2000	Neuropathic complications of mandibular implant surgery: Review and case presentation	Annals of the Royal Australasian College of Dental Surgeons	2	Woman Man	45 y 50 y	Right mandibular body (2) Mandible	Paresthesia Dysesthesia, mechanical allodynia, hyperalgesia	3 mo to more than 1 y 1 y	NA
*Kim et al91	2013	Clinical outcome of conservative treatment of injured inferior alveolar nerve during dental implant placement	Journal of the Korean Association of Oral and Maxillofacial Surgeons	64	35 women 29 men	NA	Posterior mandible	6 anesthesia 28 hypoesthesia and paresthesia 17 hypoesthesia 13 dysesthesia	3 had transient sensory changes, whereas 54 had persistent sensory changes	NA
*Juodzbalys et al45	2013	Inferior alveolar nerve injury associated with implant surgery	Clinical Oral Implants Research	16	8 women 8 men	36–65 y	Right and left premolar, molar region in the mandible	5 hyperalgesia 11 hypoalgesia	More than 3 mo for 11 subjects	NA
*Renton et al39	2012	Post-implant neuropathy of the trigeminal nerve. A case series	British Dental Journal	30	20 women 10 men	26–80 y	Mandibular second premolar, molar	Paresthesia in 47% of cases; mechanical/,thermal allodynia 30%; anesthesia 40% Functional disabilities: Kissing 54%, speech 46%, eating, drinking, brushing teeth due to pain 30% Recurrent lip biting 23% Dribbling 33% Psychologic problems 30%	NA	NA
*Tay and Zuniga94	2007	Clinical characteristics of trigeminal nerve injury referrals to a university center	The International Journal of Oral & Maxillofacial Surgery	59 patients included in the study, but only 7 (11%) were related to implant procedures	5 women, 2 men	17–27 y	NA	7 patients had at least one functionality problem; 3 mild sensory impairment; 2 moderate; 2 with no deficit	NA	NA
*Libersa et al95	2007	Neurosensory disturbances of the inferior alveolar nerve: A retrospective study of complaints in 10 years	Journal of Oral & Maxillofacial Surgery	382 subjects were included, and 12 were related to dental implant placement	Prospective longitudinal questionnaire study; assessed before, after up to 18 mo after surgery	NA	IAN	3 (1%) were transient; 9 (12%) with permanent neurosensory disturbances	NA	NA
*Hillerup96	2007	Iatrogenic injury to oral branches of the trigeminal nerve: Records of 449 cases	Clinical Oral Investigations	449	NA	16–83 y	Implant surgery, 16 out of 449 iatrogenic injuries (3.6%) included in the study	Paresthesia Allodynia	NA	NA
*Chaushu et al98	2002	Medicolegal aspects of altered sensation following implant placement in the mandible	The International Journal of Oral & Maxillofacial Implants	16	12 women, 4 men	28–67 y	Mandibular: 2 premolar, 1 molar	Lip and chin; all 16 patients had persistent sensory changes	NA	NA

IAN = inferior alveolar nerve; VAS = visual analog scale.

Data Analysis

Variable and poor reporting of data is seen in the diverse group of included articles. Any variability among studies in a review is termed heterogeneity.²⁸ The considerable variation in results due to inconsistent methodology may be misleading. However, the following were performed:

• Counts and rates calculation of counting the number of symptoms that each individual experienced

• Time-to-event data that analyzes the time until an event occurs

• Quantitative data analysis by data tabulation

• Narrative assessment of results

Results

The quantitative results of retrospective articles (n = 7) are described in Table 5. Transient sensory changes were symptoms noticed immediately or within a week of implant placement. Persistent sensory changes lasted for more than 3 months. Common characteristics observed in retrospective studies were:

Table 5.

Retrospective Articles Analysis Results

Study	Enrolled subjects for dental implant surgeries, n	Transient sensory changes, n (%)	Persistent sensory changes, n (%)
Vázquez-Delgado et al10	1,012	0 (0)	5 (0.49)
Scarano et al63	1,065	23 (2.16)	2 (0.19)
Deppe et al64	48	2 (4.16)	0 (0)
KÜtÜk et al65	55	10 (18.18)	5 (9.09)
Kwon et al66	47	21 (44.68)	2 (4.26)
Ellies16	212	61 (28.77)	17 (8.02)
Ellies and Hawker17	87	16 (18.39)	4 (4.60)
Total	2,526	133 (5.27)	35 (1.39)

• The most common location of the implant was the posterior mandible (n = 5), followed by the anterior region, from canine to canine (n = 1).

• The nerve most damaged was the inferior alveolar nerve (n = 4), followed by the mandibular incisive nerve (n = 1).

• There was a female sex predominance, although no data were available on the male to female ratio. Age data were also not available.

• The most common symptoms reported were paresthesia and dysesthesia, though the percentage was not available.

Out of the 7 articles, the study design of 3 was questionnaire-type research with yes or no responses or multiple choices, and 2 were clinical tests with subjective and objective evaluations to assess the neurosensory function. The clinical exam included tests to evaluate the detection threshold, detection perception, thermal detection, pinprick, and two-point discrimination. One of them also included radiographic assessment using CT scans.

The quantitative results of prospective articles (n = 13) are described in Table 6. Common characteristics of subjects in the prospective articles were:

Table 6.

Prospective Articles Analysis Results

Study	Enrolled subjects for dental implant surgeries, n	Transient sensory changes, n (%)	Persistent sensory changes, n (%)
Hartmann et al67	33	0 (0)	1 (3.03)
Vazquez et al38	1,527	2 (0.13)	0 (0)
Abarca et al69	58	11 (18.97)	8 (13.79)
Kubilius et al70	383	65 (16.97)	3 (0.78)
El-Sheikh et al71	5	5 (100)	0 (0)
Walton72	75	18 (24)	1 (1.33)
Bartling et al18	94	8 (8.51)	0 (0)
Wismeijer et al73	110	11 (10)	10 (9.09)
Higuchi et al15	139	6 (4.32)	6 (4.32)
Johns et al74	133	19 (14.28)	1 (0.75)
Kiyak et al76	39	2 (5.12)	0 (0)
van Steenberghe et al77	154	16 (10.39)	6 (3.90)
Total	2,750	163 (5.93)	36 (1.31)

• The most common location was the posterior mandible, and the inferior alveolar nerve was the most common nerve damaged. Three articles reported sensory changes after placement of implants in the anterior mandible (138 subjects), with the mandibular incisor nerve being the most commonly damaged.

• The sex and age data of patients who developed neuropathy were not available.

• The most common symptoms reported were paresthesia and hyperesthesia, but the percentages were not available. Additionally, the sensory changes were not listed in all articles.

• The common sites where neuropathy was reported were the inferior lip, gingiva, and chin.

Sensory changes in case reports and case series (n = 20) are reported in Table 7. Common characteristics observed in these 336 patients (8 patients described individually, and 328 described as part of a case series) were:

Table 7.

Case Series and Case Reports Analysis Results

Study	Enrolled subjects for dental implant surgeries, n	Transient sensory changes, n (%)	Persistent sensory changes, n (%)
Politis et al40	26	2 (7.69)	24 (92.30)
Devine et al41	10	0 (0)	10 (100)
Du Toit et al78	4	0 (0)	4 (100)
Givol et al79	92	0 (0)	92 (100)
Mourào et al80	1	0 (0)	1 (100)
Wright81	2	0 (0)	2 (100)
Stamatin et al82	27	2 (7.40)	0 (0)
Al-Ouf and Salti83	1	1 (100)	0 (0)
Yoon et al84	1	0 (0)	1 (100)
Rodriguez-Lozano et al85	1	0 (0)	1 (100)
Leckel et al86	1	0 (0)	1 (100)
Khawaja and Renton87	4	1 (25)	3 (75)
Liang et al88	1	0 (0)	1 (100)
Elian et al89	1	0 (0)	1 (100)
Flanagan90	1	0 (0)	1 (100)
Gregg14	2	0 (0)	2 (100)
Kim et al91	64	3 (5.26)	54 (94.74)
Juodzbalys et al45	16	5 (31.25)	11 (68.75)
Renton et al39	30	3 (10)	27 (90)
Tay and Zuniga94	7	0 (0)	7 (100)
Libersa et al95	12	3 (25)	9 (75)
Hillerup96	16	0 (0)	16 (100)
Chaushu et al98	16	0 (0)	16 (100)
Total	336	20 (5.95)	284 (84.52)

• The most affected region was the mandibular posterior region. The inferior alveolar nerve (IAN) was the most affected.

• Women (70.83%) were primarily affected, with an age range from 17 to 83 years (mean 58 years).

• The most common symptom was paresthesia (75%).

• Immediate removal of implants within 24 hours led to improvement in symptoms when compared to delay in removal or treatment.

An association was found between pain and number of implants, but the evaluation was only at the 1-week postoperative follow-up. The pain was present but insignificant in a 2-year follow-up study. The study design of the prospective articles included questionnaire-type (n = 5), pain scale (visual analog scale [VAS], n = 1) and clinical examination (neurosensory testing, n = 7). A few articles with questionnaires also had clinical test evaluations as part of their examinations. Therefore, the data of both retrospective and prospective studies were combined to assess the incidence of sensory changes after dental implant placement (Table 8).

Table 8.

Sensory Changes in Subjects Due to Implant Placement

Study design	Enrolled subjects for dental implant surgeries, n	Transient sensory changes, n (%)	Persistent sensory changes, n (%)
Retrospective	2,526	133 (5.27)	35 (1.39)
Prospective	2,750	163 (5.93)	36 (1.31)
Case reports and case series	336	20 (5.95)	284 (84.52)
Total	5,612	316 (5.63)	355 (6.33)

Discussion

There are many articles in the literature related to pain following dental implant placement in patients, but there are very few that specifically mention sensory changes such as paresthesia, hypoesthesia, dysesthesia, numbness, tingling, etc. These sensory changes could be either transient or persistent.^11,19,29

The present scoping review identified a total of 72 articles, of which 30 were literature reviews, 7 were retrospective, 12 were prospective, and 23 were case reports and case series on sensory changes after dental implant placement in patients. Of the 30 literature reviews, the included articles were on sensory changes related to dental implant placement and on risk factors, complications, and techniques to manage and avoid them.

Iatrogenic mishaps may occur, as with any other surgical procedures. Clinicians should be cautious, and a better understanding of the anatomy of vital structures around implants is necessary. Ultimately, it is prudent not to use specific locations that have high potential risks for nerve injury.

Mastering technical and safety (eg, implant drill stops) procedures for placing implants are important.³⁰ Pain due to local anesthetic, direct impingement of the implant on the nerves, overdrilling the osteotomy site, and partial or complete nerve transaction are iatrogenic mishaps that can be avoided with drill stops, experience, and training.³¹ Moreover, treatment planning with radiographs or cone beam tomograms should be recommended to ensure nerves are completely separated from the dental implant using the smallest field of view necessary so that the radiation exposure is minimal.^32,33 If the mandibular canal cannot be seen on a panoramic radiograph, a cone beam tomogram should be taken to verify its location. However, if such scenarios occur, it was observed that early treatment interventions, either by removal of implant or medications, lead to a better prognosis. Also, most sensory alterations found in this review with the prospective and retrospective articles were reported prior to 2005. Since then, many technologic advancements have been implemented in the field of dental implantology, such as implant placement with the help of computer guidance or augmented reality.^34,35 Hence, iatrogenic failures and nerve damage can be limited.

To manage nerve damage successfully, it is vital to be able to evaluate the extent of nerve damage and the risk factors associated with it as early as possible. Clinicians performing surgical procedures should familiarize themselves with a neurosensory examination that requires no special equipment. Follow-up radiographs and evaluations are mandatory to detect any changes, as early treatment intervention is helpful to resolve neurosensory disturbances after dental implant placement.^30,36

Timely and early referral to an orofacial pain specialist for noninvasive management is the responsibility of a clinician treating neurosensory trauma cases after implant placement. It is reported that delayed reporting of pain and/or sensory alterations by patients, the poorer the chances for the sensations to return to normal. A better prognosis was observed in a group of patients with early visits to the clinic and with implants placed with a safety margin of at least 2 mm from the IAN.^37,38 The factors that influence the final results are the distance from the implant to the IAN canal and the surgeon’s immediate management, such as implant removal, decompression, and medication.³⁰ These steps ensure the quality of life of the patient is maintained.

In this review, the incidence of transient neurosensory changes was observed in 5.27% and persistent neurosensory changes in 1.39% of the subjects in retrospective studies; moreover, the incidence of transient neurosensory changes was observed in 5.93% and persistent neurosensory changes in 1.31% of the subjects in prospective cohort studies. The incidence of transient neurosensory changes was observed in 5.95% and persistent neurosensory changes in 84.52% of the subjects enrolled in case reports and case series (Table 8). Including the case series and case reports in calculating the incidence could skew the average percentage, as these cases were chosen for publication due to the presence of sensory disturbances after implant surgery, but it was decided to include them in this scoping review, as this information was available in the literature. It is also important to note that, in this scoping review, it was not possible to distinguish between sensory changes related to frank axonal damage and sensory changes following implant placement without evidence of neural damage, and this should be addressed in future studies.

It was found that the mandibular premolar and molar regions were commonly affected areas due to the complex anatomy in this region, which is similar to the findings of Renton et al³⁹ on common implant positions associated with inferior alveolar nerve injury. In addition, more implants were placed in the mandible than in the maxilla, which is in accordance with the previous literature.^39,40 In this review, women more commonly developed sensory alterations when compared to men, possibly due to various reasons, such as: women visit their health care providers more than men; the prevalence of chronic pain disorders is greater in women than in men; and there could be complex interactions of factors, such as the influence of sex hormones, differences in coping strategies, etc.^39,41

The present results are based on low-quality research. Most of the research articles included were questionnaire-based and are thus solely dependent on the patients’ subjective responses, so the results may not be accurate, especially as patients may be incapable of differentiating and describing the exact symptoms. The report of incidence numbers is based on a diverse group of studies; therefore, the reported incidence is likely biased in many ways and should be interpreted with caution.

In the prospective research articles, follow-up evaluations with neurosensory testing and clinical examinations were limited, mainly for a week or two. Long-term evaluation is necessary for accurate results. Furthermore, data were not available in most of the studies regarding number of implants placed, gender distribution, or specific symptoms of patients.

As can be seen, there was no standardized methodology used, which illustrates wide heterogeneity. The data for persistent pain were insufficient, and cohort studies examining persistent pain after dental implant placement could not be found.

This scoping review reports the incidence of transient and persistent sensory changes related to dental implant placement. As this review has identified gaps in knowledge, it is hoped that the results may assist in informed decision-making for health care providers (clinicians), researchers, and patients.

Conclusions

Even though the results are based on research that is not of particularly high quality, this study found that the incidence of transient (less than 3 months) sensory changes after dental implant placement is approximately 5.63%, and the incidence of persistent (more than 3 months) sensory changes after dental implant placement is approximately 6.33%.

Nerve injuries in relation to dental implants are impactful, can be persistent, and are often life-changing for patients. Dental implant treatment is, by nature, an elective procedure, and thus these injuries are avoidable if proper treatment planning is followed and if referral to the respective specialist to manage these injuries is timely. The present authors suggest more prospective controlled trials with surgical control and a long-term follow-up to assess persistent pain and neurosensory testing (preferably quantitative sensory testing) on every visit.

Key Findings

• The incidence of transient sensory changes after dental implant placement is approximately 5.63%.

• The incidence of persistent sensory changes after dental implant placement is approximately 6.33%.

• These injuries may be avoidable if proper treatment planning is followed and referral to the respective specialist to manage these injuries is timely.

Funding Statement

This study presents independent research funded by the Center for Temporomandibular Disorders and Orofacial Pain, Department of Diagnostic Sciences at Rutgers School of Dental Medicine. The views and opinions expressed by authors in this manuscript are those of the authors and do not necessarily reflect those of the funding source.