Sensory nerve conduction study of the mental nerve

The Effect of Mandibular Angulation on Preoperative Assessment of Dental Implant Insertion at Premolar Region: CBCT Study

Backgrounds

This study investigated the effect of mandibular angulation on the perioperative evaluation of the implant placement at the premolar region on panoramic reconstructed images using cone beam computed tomography (CBCT).

Methods

A total of six dried anonymous human mandibles was included. Two implants were inserted in the left and right first premolar region. CBCT scans were obtained from each mandible at the standard position, +20° extension, and -20° flexion. The distance of the implant from the anterior loop of the inferior alveolar nerve and mental foramen was measured. Mean absolute error (MAE) of the distance of the implant from both anatomical landmarks was measured. The Wilcoxon matched-pair signed-rank test was used for the comparison of the measurements. All data were analyzed with the Stata program (version 15.1).

Results

No statistically significant differences were found between the distance of the implant from the mental foramen and the anterior loop of the inferior alveolar nerve up to 20° extension and flexion at both sides of the mandible. (All p > 0.1) However, a variable range of MAE (SD) in the distance of the implant from different anatomical landmarks was found (0.9 ± 0.7 to 3.3 ± 2.1).

Conclusions

We found no statistical difference in measurements of the distance of the implant from two anatomical landmarks at different head positions up to 20° extension and flexion. However, clinically, variable range in the distance of the implant from anatomical landmarks should be considered. Our findings could alert dentists of the possibility of error up to 20° extension and flexion on the perioperative evaluation of dental implant placement.

Accuracy in the Diagnosis of the Mental Nerve Loop. A Comparative Study Between Panoramic Radiography and Cone Beam Computed Tomography

Dental implant and chin osteotomy are executed on the mandible body and the mental nerve is an important anatomical limit. The aim of this research was to know the position of the mental nerve loop comparing result in panoramic radiography and cone beam computed tomography. We analyzed 94 hemimandibles and the patient sample comprised female and male subjects of ages ranging from 18 to 52 years (mean age, 35 years) selected randomly from the database of patients at the Division of Oral Radiology at Piracicaba Dental School State University of Campinas; the anterior loop (AL) of the mental nerve was evaluated regarding the presence or absence, which was classified as rectilinear or curvilinear and measurement of its length was obtained. The observations were made in the digital panoramic radiography (PR) and the cone beam computed tomography (CBCT) according to a routine technique. The frequencies of the AL identified through PR and CBCT were different: in PR the loop was identified in 42.6% of cases, and only 12.8% were bilateral. In contrast, the AL was detected in 29.8% of the samples using CBCT, with 6.4% being bilateral; Statistical comparison between PR and CBCT showed that the PR led to false-positive diagnosis of the AL in this sample. According to the results of this study, the frequency of AL is low. Thus, it can be assumed that it is not a common condition in this population.

Neurophysiological assessment of trigeminal nerve reflexes in disorders of central and peripheral nervous system

The trigeminal nerve and nuclei (the trigeminal complex) are unique in the human body with regard to their anatomical and physiological characteristics. They are also special regarding the lesions in which they are involved, both at the peripheral level because of the susceptibility of some terminal branches, and at the nuclei because of their large size and the large amount of connections with other centers. Conventional magnetic resonance imaging studies are often not sufficiently informative to demonstrate very tiny lesions that could be responsible for an important damage in the brainstem. Therefore, clinical neurophysiology and specifically, the techniques used in the study of the trigeminal functions, remain as convenient diagnostic and research tools to document clinically evident lesions or uncover subclinical abnormalities. This review is focussed on the clinical applicability of the study of trigeminal reflexes, including methods employed in the documentation of focal lesions of peripheral branches, trigeminal involvement of peripheral neuropathies, specific lesions of the trigeminal ganglia, central nervous dysfunctions causing abnormalities in the excitability of trigeminal neurons, and the possible use of trigeminal nerve reflexes in the study of facial pain syndromes and headache.

Morphometric Analysis of Implant-Related Anatomy in Caucasian Skulls

BACKGROUND

Sequelae related to implant placement/advanced bone grafting procedures are a result of injury to surrounding anatomic structures. Damage may not necessarily lead to implant failure; however, it is the most common cause of legal action against the practitioner. This study aimed to describe morphological aspects and variations of the anatomy directly related to implant treatment.

METHODS

Morphometric analyses were performed in 22 Caucasian skulls. Measurements of the mental foramen (MF) included height (MF-H), width (MF-W), and location in relation to other known anatomical landmarks. Presence or absence of anterior loops (AL) of the inferior alveolar nerve (IAN) was determined, and the mesial extent of the loop was measured. Additional measurements included height (G-H), width (G-W), thickness (G-T), and volume (G-V) of monocortical onlay grafts harvested from the mandibular symphysis area, and thickness of the lateral wall (T-LW) of the maxillary sinus. The independent samples t test, and a two-tailed t test with equal variance were utilized to determine statistical significance to a level of P < 0.05. Multiple regression analyses were performed to determine if each one of these measurements was affected by age and gender.

RESULTS

The most common location of the MF in relation to teeth was found to be below the apices of mandibular premolars. The mean MF-H was 3.47 +/- 0.71 mm and the mean MF-W was 3.59 +/- 0.8 mm. The mean distance from the MF to other anatomical landmarks were: MF-CEJ = 15.52 +/- 2.37 mm, MF to the most apical portion of the lower cortex of the mandible = 12.0 +/- 1.67 mm, MF to the midline = 27.61+/- 2.29 mm, and MF-MF = 55.23 +/- 5.34 mm. A high prevalence of AL was found (88%); symmetric occurrence was a common finding (76.2%), with a mean length of 4.13 +/- 2.04 mm. The mean size of symphyseal grafts was: G-H = 9.45 +/- 1.08 mm, G-W = 14.5 +/- 3.0 mm, and G-T = 6.15 +/- 1.04 mm, with an average G-V of 857.55 +/- 283.97 mm3 (range: 352 to 1,200 mm3). The mean T-LW of the maxillary sinus was 0.91 +/- 0.43 mm.

CONCLUSION

Implant-related anatomy must be carefully evaluated before treatment due to considerable variations among individuals, in order to prevent injury to surrounding anatomical structures and possible damage.