Assessment of the prevalence and length of the anterior and caudal loops of the mental nerve as anatomical variants of exiting the mandible at the mental foramen using cone-beam computed tomography: a systematic review and meta-analysis

OBJECTIVES

This systematic review aimed to identify the studies that performed cone-beam computed tomography analysis of the prevalence and length of the anterior loop (AL) and caudal loop (CL) of the mental nerve.

MATERIALS AND METHODS

An electronic database search was performed across PubMed, EMBASE, Web of Science, Scopus, the Cochrane library, and Google Scholar. Original studies reporting the frequency and length of the AL and CL were selected. Qualitative synthesis and meta-analysis were then conducted to assess the prevalence and length of the AL and CL and their associations with age, gender, sides, and dentition status.

RESULTS

A total of 21 studies were included in this review. The pooled prevalence of the AL (95% confidence interval) of the mental nerve at the patient and side level was 51% (31-71%) and 53% (37-69%) while the mean anterior loop length was 2.08 (1.46-2.70) mm. The pooled prevalence of the CL and mean caudal loop length were 100% and 4.73 (3.44-6.01) mm. No significant associations were found between the prevalence and length of the AL and CL and age, gender, sides, and dentition status.

CONCLUSIONS

Overall, the pooled prevalence and mean length of AL of the mental nerve varied among different populations while CL seems to be a constant anatomical landmark with a longer CL than AL.

CLINICAL RELEVANCE

Surgeons performing inter-foraminal oral surgeries like dental implant placement and genioplasty should be aware of the possible distance of the AL and CL to avoid iatrogenic mental nerve injury.

Inferior alveolar nerve injury following dental implant placement: A medicolegal analysis of French liability lawsuits

AIMS

This study thus aimed to review and analyze liability lawsuits resulting from implant surgery-related inferior alveolar nerve (IAN) injury over a twenty-year period in France.

MATERIALS AND METHODS

A retrospective descriptive study was performed to analyze judicial decisions pertaining to IAN injury from a legal database between 2000 and 2020. Inclusion criteria comprised all closed malpractice cases that involved an oral and maxillofacial surgeon or a dentist who performed a mandibular implant surgery resulting in IAN injury. The following data were recorded: judicial decision reference (including jurisdiction and date of final court ruling), timing between the incident and final court ruling, number of involved practitioners, patient's age and gender, practitioner's age and gender, implant type, number of implants, location of iatrogenic implant(s), allegation of IAN injury, alleged cause of injury, justification(s) for conviction, compensation amount and legal costs.

RESULTS

Twelve judicial decisions from high civil courts relating to ten closed cases of liability lawsuits were included and analyzed. All of involved practitioners were dentists or oral surgeons, working in the private sector. Eventually, 85% of them were convicted. Mean indemnification was 17,340€ and highest indemnification was 42,828€ (inflation-adjusted in 2020 euros). Mean interval between the incident and final ruling was 87,1 ± 34,2 months.

CONCLUSIONS

Permanent nerve injury following dental implant placement can result in legal action. In the event of lawsuit, the risk of being convicted is high. Practitioners performing oral implantology procedures should practice effective risk management to avoid time-consuming unwanted litigations and administrative proceedings.

A CBCT Based Three-Dimensional Assessment of Mandibular Posterior Region for Evaluating the Possibility of Bypassing the Inferior Alveolar Nerve While Placing Dental Implants

A high rate of nerve injury and related consequences are seen during implant placement in the posterior mandibular arch. An approach has been proposed to avoid nerve injury by dodging the inferior alveolar nerve (IAN) while placing an implant. A prospective study with a total of 240 CBCT (cone beam computed tomography) images of patients with three dentate statuses, namely, edentulous (group I), partially edentulous (group II) and dentate (group III) were included in the study. The nerve path tracing was done on CBCT images with On-demand 3D software. The three dimensions, i.e., the linear distance from the outer buccal cortical plate to the inferior alveolar nerve (BCPN), linear distance from the outer lingual cortical plate to the inferior alveolar nerve (LCPN) and linear distance from the midpoint of the alveolar crest to the inferior alveolar nerve (ACN) were assessed. The data were presented and analyzed between variables using one-way ANOVA and independent t-test in SPSS version 21.LCPN of the right 1st premolar region (p < 0.05) was significantly different among the groups with edentulous subjects recorded with the minimum value (6.50 ± 1.20 mm). Females were found to have significantly (p < 0.05) less available bone (6.03 ± 1.46 mm) on the right side of the mandibular jaw compared to males in edentulous group of patients. On comparing age groups for partially edentulous subjects, LCPN of the right 1st premolar region had significantly (p < 0.05) less available bone (6.03 ± 0.38 mm) in subjects with age ≥54 years. The IAN follows a lingual course in the molar region and later flips to the buccal side in the premolar region. The LCPN dimension in the 1st and 2nd premolar region was found to be more than 6 mm irrespective of age, gender and side of the jaw. Thus, it can be considered as a suitable site for placing implants while bypassing the IAN with CBCT assessment remaining as the mainstay in the pre-surgical phase.

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.

Location of the Mandibular Incisive Canal Related to the Placement of Dental Implants: A Case Report

Cone-beam computerized tomography (CBCT) can show an uncommon mandibular incisive canal that cannot be detected by panoramic radiography, which is used preoperatively to form the initial plan of the size and length of an implant fixture for surgical placement in the mandibular interforaminal area. Determination of the position and anatomical configuration of the mandibular incisive canal is challenging. The purpose of this case report is to discuss anatomical variations in the mandibular incisive canal and the mental canal by reviewing previous studies. Furthermore, we propose that the anterior loop length of the mental canal near the mental foramen, as well as the diameter of the mandibular incisive canal, should be verified by CBCT prior to performing implant surgery in the anterior mandibular area to prevent possible nerve damage.

Risks of angled implant placement on posterior mandible buccal/lingual plated perforation: A virtual immediate implant placement study using CBCT

Background/purpose

Immediate implant placement has been considered to be a successful treatment procedure. The bone plate perforation (BPP) may be one of severe complication and potentially life-threatening situation. The aim of this virtual study is to evaluate the influences of angled implant insertion on BPP during immediate implant installation in the posterior mandible.

Materials and methods

Cone beam computed tomography images of 488 posterior teeth from 61 patients were selected. Virtual immediate implant placement (VIIP) was performed at each posterior tooth following the appropriate axis with the prosthetic-driven planning and different deviation angles of 3-, 6-, or 9-degree. BPP was then examined from cross-sectional images obtained. Furthermore, the relation of lingual bony morphology and BPP were also determined.

Results

The incidence of buccal and lingual BPP increased as the deviation angle increased in posterior mandible area. Incidence of lingual BPP was significantly influenced by angular deviation and type of lingual bony morphology after adjusting for age, gender, tooth type, and right/left side. An increase in incidence odds of over 6-fold (OR = 6.583) was noted for placements angled by 9° compared with placements made without angulation, and an increase in incidence odds of over 3-fold (OR = 3.622) was noted for teeth with the undercut-type lingual morphology compared with the other types.

Conclusion

The present Results indicate that accurate selection of the implant insertion angle and full awareness of the bony anatomy at the implant recipient site are essential to prevent BPP in the posterior mandible.

Shape Optimization of Bone-Bonding Subperiosteal Devices with Finite Element Analysis

Subperiosteal bone-bonding devices have been proposed for less invasive treatments in orthodontics. The device is osseointegrated onto a bone surface without fixation screws and is expected to rapidly attain a bone-bonding strength that successfully meets clinical performance. Hence, the device's optimum shape for rapid and strong bone bonding was examined in this study by finite element analyses. First, a stress analysis was performed for a circular rod device with an orthodontic force parallel to the bone surface, and the estimate of the bone-bonding strength based on the bone fracture criterion was verified with the results of an animal experiment. In total, four cross-sectional rod geometries were investigated: circular (Cr), elliptical (El), semicircular (Sc), and rectangular (Rc). By changing the height of the newly formed bone to mimic the progression of new bone formation, the estimation of the bone-bonding strength was repeated for each geometry. The rod with the Rc cross section exhibited the best performance, followed by those with the Sc, El, and Cr cross sections, from the aspects of the rapid acquisition of strength and the strength itself. Thus, the rectangular cross section is the best for rod-like subperiosteal devices for rapid bone bonding.