Assessment of the risk of perforation of the mandibular canal by implant drill using density and thickness parameters

Inferior alveolar nerve injury resulting from different implant rotary instruments: An ex vivo comparative study in human cadaveric mandibles

The present study aimed to evaluate the degree of nerve injury on inferior alveolar nerve (IAN) by different implant drills resulting from direct canal intrusion into inferior alveolar canal (IAC). A cadaveric study involving 7 human mandibles was performed to evaluate mechanical injury of canal enclosed IAN resulting from different drills. In group 1, osteotomies were created using different drills with 1 mm of intracanal intrusion, simulating accidental drill intrusion into canal. In group 2, drilling was stopped when the tip has breached into IAC, limited by tactile feedback of operator. The depth and width of nerve defects were assessed using optical coherence tomography. A significant difference in defect depth was found (p < 0.001) in group 1. A sinus lift reamer inflicted the least damage (0.068 ± 0.022 mm). It was also found that the mean defect depth was significantly different when a twist drill was used (p = 0.016). Sinus lift reamer can be used safely for osteotomy preparation in mandible when bone height is limited or when radiographic visualization of canal is poor. Bone corticalization around IAC does not provide adequate protection for IAN in the event of accidental intracanal intrusion.

Accuracy of on-site teleoperated milling with haptic assistance

PURPOSE

In bone surgery specialties, like orthopedics, neurosurgery, and oral and maxillofacial surgery patient safety and treatment success depends on the accurate implementation of computer-based surgical plans. Unintentional plan deviations can result in long-term functional damage to the patient. With on-site teleoperation, the surgeon operates a slave robot with a physically-decoupled master device, while being directly present at the operation site. This allows the surgeon to perform surgical tasks with robotic accuracy, while always remaining in the control loop.

METHODS

In this study the master- and slave-side accuracy of an on-site teleoperated miniature cooperative robot (minaroHD) is evaluated. Master-side accuracy is investigated in a user study regarding scale factor, target feed rate, movement direction and haptic guidance stiffness. Scale factors are chosen to correspond to primarily finger, hand, and arm movements. Slave-side accuracy is investigated in autonomous milling trials regarding stepover, feed rate, movement direction, and material density.

RESULTS

Master-side user input errors increase with increasing target feed rate and scale factor, and decrease with increasing haptic guidance stiffness. Resulting slave-side errors decrease with increasing scale factor and are < 0.07 mm for optimal guidance parameters. Slave-side robot position errors correlate with the feed rate but show little correlation with stepover distance. For optimal milling parameters, the 95th percentile of tracked slave-side position error is 0.086 mm with a maximal error of 0.16 mm.

CONCLUSION

For optimal guidance and milling parameters, the combined error of 0.23 mm is in the range of the dura mater thickness (< 0.27 mm) or mandibular canal wall (~ 0.85 mm). This corresponds to safety margins in high-demand surgical procedures like craniotomies, laminectomies, or decortication of the jaw. However, for further clinical translation, the performance and usability of on-site teleoperated milling must be further evaluated for real-life clinical application examples with consideration of all error sources in a computer-assisted surgery workflow.

Evaluation of Cortical Thicknesses and Bone Density Values of Mandibular Canal Borders and Coronal Site of Alveolar Crest

Objectives

The objectives of this retrospective study are to measure the amount of the alveolar crest cortication and cortication around the mandibular canal, and to evaluate bone density values of alveolar crest, cortication around mandibular canal, and possible implant placement area for edentulous sites.

Material and Methods

Six hundred forty-two cone-beam computed tomography scans from 642 subjects were evaluated in four centers. Cortical thicknesses of alveolar crest and mandibular canal cortical borders (buccal, lingual, apical, and coronal) in each mandibular posterior teeth region were measured. Bone density of alveolar crest and mandibular canal cortical borders (buccal, lingual, apical, and coronal) in each mandibular posterior teeth region were recorded. The correlations between numeric variables were investigated using Pearson's correlation test.

Results

The largest cortical border of the canal was measured 1.1 (SD 0.71) mm at the left second molar area and in coronal side of the mandibular canal (MC). Left and right first premolar regions showed higher bone density values compared to the other sites in all bone density values evaluations. The buccal side of the canal at the right first premolar region showed the highest bone density values (832.32 [SD 350.01]) while the coronal side of the canal at the left second molar region showed the lowest (508.75 [SD 225.47]). The bone density of possible implant placement area at the both left (692.25 [SD 238.25]) and right (604.43 [SD 240.92]) edentulous first premolar showed the highest values. Positive correlations between the bone density values of alveolar crest and the coronal side of MC were found in molar and left second premolar regions (P < 0.05).

Conclusions

Results may provide information about the amount of cortication and bone densities tooth by tooth for posterior mandible to surgeons for planning the treatment precisely.

The nature of malpractice claims related to nerve damage after dental implants insertion in Israel during 2005-2020: A descriptive study

INTRODUCTION

Dental implant placement is a routine practice in dentistry, with a possible uncommon risk of neurosensory injury. The present study analyzed all dental implant claims involving sensory nerve disturbances between 2005 and 2020 in Israel. The study was conducted to understand implant risk management better and improve the patient's safety.

MATERIALS AND METHODS

All legal claims registered by Medical Consultant International (MCI) involving nerve damage claims between 2005 and 2020 were included in the study. The data included demographic details such as age, sex, event date, claim delivery date, and treatment settings. Information on the nerve damage included the damaged nerve, side of injury, and the number of implants performed in the same surgery.

RESULTS

There were 218 claims regarding nerve damage out of 1154 claims for dental implant therapy. The mean age for nerve damage claims was 54.1 ± 11 years. There were more female than male claims (p = 0.02), with 87% of cases concerning damage to the inferior alveolar nerve (p < 0.0001), out of those molar areas being more frequently involved in nerve damage (64.3%, p < 0.0001). The left side was 1.4 times more frequent than the right side (p = 0.043). The risk for nerve injury was 7.4 times higher when placing multiple implants compared to single dental implant (p < 0.0001).

CONCLUSIONS

Clinicians should be aware that placement of multiple implants, left-side implant placement, and patient gender may increase risk for a malpractice claim for neurosensory disturbances.

The Radiological Evaluation of Mandibular Canal Related Variables in Mandibular Third Molar Region: a Retrospective Multicenter Study

OBJECTIVES

The aim of this retrospective study was to investigate anatomical structure of mandibular canal and the factors those increase the possibility of inferior alveolar nerve damage in mandibular third molar region of Turkish population.

MATERIAL AND METHODS

Overall 320 participants with 436 mandibular third molars were included from four different study centers. Following variables were measured: type and depth of third molar impaction, position of mandibular canal in relation to third molars, morphology of mandibular canal, cortication status of mandibular canal, possible contact between the third molars and mandibular canal, thickness and density of superior, buccal, and lingual mandibular canal wall, bucco-lingual and apico-coronal mandibular canal diameters on cone-beam computed tomography scans.

RESULTS

Lingual mandibular canal wall density and thickness were decreased significantly as the impaction depth of mandibular third molar was increased (P = 0.045, P = 0.001 respectively). Highest buccal mandibular canal wall density and thickness were observed in lingual position of mandibular canal in relation to mandibular third molar (P = 0.021, P = 0.034 respectively). Mandibular canal with oval/round morphology had higher apico-coronal diameter in comparison to tear drop and dumbbell morphologies (P = 0.018). Additionally, mandibular canals with observed cortication border and no contact with mandibular third molar had denser and thicker lingual mandibular canal wall (P = 0.003, P = 0.001 respectively).

CONCLUSIONS

Buccal and lingual mandibular canal wall density, thickness and mandibular canal diameter may be related with high-risk indicators of inferior alveolar nerve injury.

Anatomy of the mandibular canal and surrounding structures: Part I: Morphology of the superior wall of the mandibular canal

INTRODUCTION

Previous studies of the mandibular canal (MC) have raised questions about the structure of its superior wall that have not been answered. The goal of this anatomical and radiological study was to investigate how CBCT imaging could predict the structure of the superior wall of the MC.

METHODS

Twenty sides from ten dry mandibles derived from six females and four males were used for this study. The mandibles were examined with CBCT. The specimens were then prepared by the methods of our previous study and observed inferiorly. The inferior views were classified into four groups by gross observation of the surface of the superior wall of the MC: class I (trabecular pattern), class II (osteoporotic pattern), class III (dense/irregular pattern), and class IV (smooth pattern). Coronal section CBCT images were classed according to whether the superior wall of the MC was visible.

RESULTS

Class I was most common in dentulous sections in both genders, and class IV was most common class in edentulous sections in both genders. The superior wall was visible in 59.1% in dentulous and 84.9% in edentulous sections, and non-visible in the remainder.

CONCLUSION

Tooth presence and sex are important factors influencing the superior wall of the MC. When the superior wall cannot be seen on CBCT, it is more likely to belong to class II (osteoporotic) than other classes.

Diagnostic Potential of Panoramic Radiography and CBCT in Detecting Implant-Related Ex Vivo Injuries of the Inferior Alveolar Canal Border

The aim of this ex vivo study was to compare the diagnostic performances of panoramic radiography and cone beam computerized tomography (CBCT) in detecting implant-related injuries of the inferior alveolar canal. Monocortical bone windows were created in 60 fresh sheep hemimandibles, the inferior alveolar canals were revealed and 120 dental implants were inserted. Three types of injuries, described as pilot drill damage (PDRILL), collapsing of the superior border of the canal (COLL), penetration of the implant tip into the canal (PENET) and one control group, were simulated. Standard (PANO) and dentition mode panoramic (PANO-DENT) images as well as CBCT data presented as multiplanar reconstruction (MPR) and cross-sectional (CROSS) views were evaluated by 6 observers who had also expressed their level of confidence to their final diagnosis. Intra- and interobserver agreement scores were rated good. The area under the curve (AUC) values and the confidence scores for CROSS and multiplanar reformation (MPR) views were both significantly higher than those of PANO and PANO-DENT (P < .05 for each) in PDRILL group. In COLL group, observers showed less confidence to PANO and PANO-DENT compared to CROSS and MPR techniques (P < .05 for each). No other significant differences were found. Within the limits of this experimental study, it can be suggested that the standard and dentition modes of panoramic radiography can be as effective as CBCT in the detection of penetrating and collapsing injuries, but multiplanar and cross-sectional views of the CBCT are more accurate than panoramic radiography in the detection of pilot drill injuries in sheep mandible.

Incidence of neurosensory disturbance in mandibular implant surgery - A meta-analysis

Aim

Implantology has been widely accepted as the mainstay treatment for rehabilitating complete and partial edentulism. However, it is associated with some failures and complications, the most concerning being neurosensory disturbance. Although neurosensory disturbance has been extensively studied, the incidence and cause remains largely variable. Thus, the aim of this systematic review and meta-analysis was to evaluate the incidence, distribution, and recovery rate of neurosensory disturbance.

Settings and Design

This systematic review was conducted as per the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement. A structured literature review was conducted using the following databases: PubMed, Science Direct, Cochrane, Ovid, and Google Scholar for reports related to neurosensory disturbance experienced after implant placement in the mandible.

Statistical Analysis Used

Incidence and recovery rate for 100 person-years was calculated using the Poisson regression model. The risk difference of incidence between anterior and posterior implants was calculated with a random effects model.

Results

Electronic database search yielded 1589 articles; a total of nine articles were selected for the meta-analysis. The risk of neurosensory disturbance was estimated at 13.50/100 person-years (95% confidence interval (CI): 10.98-16.03), with a greater risk with anteriorly placed implants: -0.02 (95% CI: -0.21-0.16) (P = 0.05). The overall recovery rate was estimated at 51.30/100 person-years (95% CI: 31.2-71.4).

Conclusions

Within the limitations of the study, it can be concluded that mandibular implant placement is associated with a considerable risk of neurosensory disturbance. A large proportion of these patients present with spontaneous recovery; however, clinicians must take necessary precautions to avoid such complications. More randomized controlled trials are required to quantify the effect of factors leading to altered sensation during implant placement.

Microsurgical Anatomy of the Superior Wall of the Mandibular Canal and Surrounding Structures: Suggestion for New Classifications for Dental Implantology

Our goal was to clarify the relationship between the superior wall of the mandibular canal and the presence of teeth. We also sought to study the structural changes of the mandibular canal after tooth loss. Twenty sides from 10 dry mandibles derived from six males and four females were used for this study. The age of the specimens at the time of death ranged from 57 to 91 years. The mandibles were cut in the midline resulting in 20 hemi-mandibles. The presence of teeth (from the second premolar to the third molar) was recorded for each hemi-mandible. The mandibular canal in the body of the mandible was divided into four areas, that is, Areas 1-4. The superior wall of the mandibular canal and a cancellous bone pattern above the mandibular canal were observed. Next, the mandibular canal was horizontally cut at its center and the superior wall of the mandibular canal observed inferiorly. A total of 75 areas (20 dentulous areas and 55 edentulous areas) were produced. The distal view was classified into three groups, Type I (trabecular pattern), Type II (osteoporotic pattern), and Type III (dense/irregular pattern). The Type I pattern was found in 60.0% (12/20) of the dentulous areas and 32.7% of the edentulous areas. While the Type II pattern was found in 15.0% (23/55) of the dentulous areas and 41.8% of the edentulous areas. The inferior view was classified into four groups depending on the surface of the superior wall of the mandibular canal, that is, Class I (trabecular pattern), Class II (osteoporotic pattern), Class III (dense/irregular pattern), and Class IV (smooth).The Class I pattern was seen most frequently (55.0%) in dentulous areas and the Class IV pattern (45.5%) most frequently in edentulous areas. Based on these results, we conclude that the superior wall of the mandibular canal could change following tooth loss. Clin. Anat. 33:223-231, 2020. © 2019 Wiley Periodicals, Inc.

The Anatomical Nature of Dental Paresthesia: A Quick Review

Dental paresthesia is loss of sensation caused by maxillary or mandibular anesthetic administration before dental treatment. This review examines inferior alveolar block paresthesia symptoms, side effect and complications. Understanding the anatomy of the pterygomandibular fossa will help in understanding the nature and causes of the dental paresthesia. In this review, we review the anatomy of the region surrounding inferior alveolar injections, anesthetic agents and also will look also into the histology and injury process of the inferior alveolar nerve.

Nerve regeneration techniques respecting the special characteristics of the inferior alveolar nerve

PURPOSE

The aim of this study was to examine the in situ regeneration of the inferior alveolar nerve (IAN) in its bony channel, using autologous tissue in combination with a recombinant human nerve growth factor (rhNGF).

MATERIALS AND METHODS

A total of 20 New Zealand rabbits were randomly divided into five groups. Following dissection of the IAN, the animals underwent reconstruction either with muscle tissue (groups 1 and 2) or with fat tissue (groups 3 and 4). In group 5 (control), the dissected nerve was resected and reconstructed by placement of the reversed autologous segment. After 2 and 4 weeks, 1 mL rhNGF was locally injected in groups 1 and 3. Nerve function was monitored by measuring the jaw-opening reflex using electromyography for a period of 24 weeks.

RESULTS

Regeneration of the nerve was achieved in all groups, but preoperative threshold values were not achieved. Comparing the experimental groups to the control, there was a significant difference in favor of the autologous nerve reconstruction. Differences between the experimental groups remained statistically not significant.

CONCLUSION

Regeneration of the IAN with autologous tissue is possible, but without achieving preoperative thresholds. Additional injection of a growth factor seems to improve the speed of regeneration for fat and muscle grafts.

Persistent pain and neurosensory disturbance after dental implant surgery: prevention and treatment

Nerve trauma caused by dental implant placement is associated with altered sensation and chronic pain. Complete or partial loss of sensation is often reported by patients who have experienced nerve trauma during implant surgery. Some patients report persistent pain and neurosurgery disturbance long after the normal healing time has passed. In addition, neuropathic pain is reported after implant surgery. Practitioners who place dental implants must be familiar with the differential diagnosis, prevention, and management of neuropathic pain. This article provides insights into the prevention and management of neurosensory deficits and chronic persistent neuropathic pain and considerations for patient referral.

In vitro correlation of the level of inferior alveolar canal with CBCT imaging

PURPOSE

The aim was to correlate the level of the inferior alveolar canal on cadaver specimens and as evaluated with three-dimensional radiographic cone-beam computed tomography (CBCT) imaging.

METHODS

Twenty-one skulls with intact mandibles (42 inferior alveolar canals) were imaged with an I-CAT Cone-Beam 3D Imaging System and multi-planar reformatted images obtained were scored to assess the level of the canal (Level I, Level II, and Level III). The mandibles were later dissected and level of the canal was directly visualized, scored, and further correlated with results from CBCT imaging.

RESULTS

There was no difference in the level of the inferior alveolar canal between the dissected cadaver specimen and CBCT images. Also, there was no statistically significant difference in the level of the canal among the gender assigned to the specimens and corresponding CBCT images. There were no statistical differences in the level of the canal (cadaver specimen vs. CBCT) between the left and right sides of the specimens, as studied individually.

CONCLUSION

Our study indicates that there is close correlation of the level of the inferior alveolar canal between cadaver specimens and CBCT images. Well-designed studies would be required to further validate the findings in this study.

Radiographic evaluation of the course and visibility of the mandibular canal

Purpose

This study was performed to investigate the course of the mandibular canal on panoramic radiography and the visibility of this canal on both panoramic radiography and cone-beam computed tomography (CBCT).

Materials and Methods

The study consisted of panoramic radiographs and CBCT images from 262 patients. The course of the mandibular canal, as seen in panoramic radiographs, was classified into four types: linear, elliptical, spoon-shaped, and turning curves. The visibility of this canal from the first to the third molar region was evaluated by visually determining whether the mandibular canal was clearly visible, probably visible, or invisible. The visibihlity of the canal on panoramic radiographs was compared with that on CBCT images.

Results

Elliptical curves were most frequently observed along the course of the mandibular canal. The percentage of clearly visible mandibular canals was the highest among the spoon-shaped curves and the lowest among the linear curves. On panoramic radiographs, invisible mandibular canals were found in 22.7% of the examined sites in the first molar region, 11.8% in the second molar region, and 1.3% in the third molar region. On CBCT cross-sectional images, the mandibular canal was invisible in 8.2% of the examined sites in the first molar region, 5.7% in the second molar region, and 0.2% in the third molar region.

Conclusion

The visibility of this canal was lower in the first molar region than in the third molar region. The mandibular canal presented better visibility on CBCT images than on panoramic radiographs.

Risk assessment of inferior alveolar nerve injury for immediate implant placement in the posterior mandible: a virtual implant placement study

OBJECTIVES

To investigate the prevalence and morphological parameters of lingual concavity, and whether these factors are related to a higher risk of inferior alveolar nerve (IAN) injury when performing an immediate implant surgery in posterior mandible region.

METHODS

The CBCT images from 237 subjects (1008 teeth) were analysed the shape of the mandibles (C, P, U type), dimensional parameters of lingual concavity (angle, height, depth), and its relation to inferior alveolar canal (IAC) (A, B, C zone), RAC (distance from root apex to IAC) and probability of IAN injury. Multiple logistic regression modelling to determine the odds ratio of variables that made an important contribution to the probability of IAN injury and to adjust for confounding variables.

RESULTS

The U type ridge (46.7%) and the most concave point located at C zone (48.8%) are most prevalent in this region. The mandibular second molar presents highest risk for IAN injury than other tooth type (p<0.001), which were 3.82 times to occur IAN injury than the mandibular second premolar. The concave point located at A zone and B zone were 7.82 and 3.52 times than C zone to have IAN damage, respectively. The probability of IAN injury will reduce 26% for every 1mm increase in RAC (p<0.001).

CONCLUSIONS

The tooth type, morphological features of lingual concavities, and RAC are associated with risks of IAN injury during immediate implant placement.

CLINICAL SIGNIFICANCE

Pre-surgical mapping of the IAC and identification of its proximity relative to the lingual concavity in the posterior mandible regions may avoid unpleasant complications, specifically when performing immediate implant procedures.

Clinical and radiological classification of the jawbone anatomy in endosseous dental implant treatment

Objectives

The purpose of present article was to review the classifications suggested for assessment of the jawbone anatomy, to evaluate the diagnostic possibilities of mandibular canal identification and risk of inferior alveolar nerve injury, aesthetic considerations in aesthetic zone, as well as to suggest new classification system of the jawbone anatomy in endosseous dental implant treatment.

Material and Methods

Literature was selected through a search of PubMed, Embase and Cochrane electronic databases. The keywords used for search were mandible; mandibular canal; alveolar nerve, inferior; anatomy, cross-sectional; dental implants; classification. The search was restricted to English language articles, published from 1972 to March 2013. Additionally, a manual search in the major anatomy and oral surgery books were performed. The publications there selected by including clinical and human anatomy studies.

Results

In total 109 literature sources were obtained and reviewed. The classifications suggested for assessment of the jawbone anatomy, diagnostic possibilities of mandibular canal identification and risk of inferior alveolar nerve injury, aesthetic considerations in aesthetic zone were discussed. New classification system of the jawbone anatomy in endosseous dental implant treatment based on anatomical and radiologic findings and literature review results was suggested.

Conclusions

The classification system proposed here based on anatomical and radiological jawbone quantity and quality evaluation is a helpful tool for planning of treatment strategy and collaboration among specialists. Further clinical studies should be conducted for new classification validation and reliability evaluation.

A histomorphometric analysis of the nature of the mandibular canal in the anterior molar region

OBJECTIVES

Knowledge of the position and configuration of the mandibular canal is a basic requirement before implant placement in the mandible. Radiological studies suggest a positive correlation between alveolar trabecular bone quality and mandibular canal corticalization. The aim of this study was to test this assumption histomorphometrically in the anterior molar region, which is one of the most frequent places for implantation.

MATERIALS AND METHODS

Fifty thin ground sections (from 28 male and 22 female cadavers) of the first molar region were investigated for trabecular bone volume and thickness and the presence of a mandibular canal wall.

RESULTS

Trabecular bone volume was significantly higher in males (p = 0.009). Further, it correlated significantly with the presence of a canal wall (rho = 0.585, p < 0.001), indicating that a reduced trabecular bone volume is associated with a reduced amount of bone surrounding the alveolar nerve. The cranial aspects of the canal wall were present at a significantly lower frequency (64.64 %) than the buccal, lingual, or caudal sides (p < 0.006).

CONCLUSION

The present study demonstrated that low trabecular bone volume correlates with only a fragmentarily present mandibular canal wall. This suggests that bone surrounding the alveolar nerve is of trabecular, not cortical, origin and possibly affected by reduction of the trabecular bone.

CLINICAL RELEVANCE

These results imply that oral surgeons should pay particular attention to implant placement in patients with low alveolar bone quality. The cranial aspects of the mandibular canal might be only fragmentarily or even completely missing. Consequently, they hardly present resistance during implant site preparation, and the risk for nerve injury, e.g., due to post-surgery hematoma, could be increased.

Injury of the Inferior Alveolar Nerve during Implant Placement: a Literature Review

Objectives

The purpose of present article was to review aetiological factors, mechanism, clinical symptoms, and diagnostic methods as well as to create treatment guidelines for the management of inferior alveolar nerve injury during dental implant placement.

Material and Methods

Literature was selected through a search of PubMed, Embase and Cochrane electronic databases. The keywords used for search were inferior alveolar nerve injury, inferior alveolar nerve injuries, inferior alveolar nerve injury implant, inferior alveolar nerve damage, inferior alveolar nerve paresthesia and inferior alveolar nerve repair. The search was restricted to English language articles, published from 1972 to November 2010. Additionally, a manual search in the major anatomy, dental implant, periodontal and oral surgery journals and books were performed. The publications there selected by including clinical, human anatomy and physiology studies.

Results

In total 136 literature sources were obtained and reviewed. Aetiological factors of inferior alveolar nerve injury, risk factors, mechanism, clinical sensory nerve examination methods, clinical symptoms and treatment were discussed. Guidelines were created to illustrate the methods used to prevent and manage inferior alveolar nerve injury before or after dental implant placement.

Conclusions

The damage of inferior alveolar nerve during the dental implant placement can be a serious complication. Clinician should recognise and exclude aetiological factors leading to nerve injury. Proper presurgery planning, timely diagnosis and treatment are the key to avoid nerve sensory disturbances management.