Combined anatomical variations: The mylohyoid bridge, retromolar canal and accessory palatine canals branched from the canalis sinuosus

Assessment of Canalis Sinuosus located in maxillary anterior region by using cone beam computed tomography: a retrospective study

Background

The aim of the study is to determine the distribution, location, diameter, and distance measurements of Canalis Sinusosus (CS) in relation with age and sex.

Methods

300 Cone-Beam Computed Tomography (CBCT) images were evaluated. The distance between CS and nasal cavity floor (NCF), buccal cortical bone margin (BCM), alveolar ridge (AR), respectively.The presence of CS smaller than 1 mm, and the diameter of CS larger than 1 mm were determined. Accessory canals (AC) were classified according to their position relative to the teeth.

Results

435 CS with a diameter of at least 1 mm and 142 CS < 1 mm were identified. The most frequently observed location of CS was the region of the right central incisors. The mean diameter of the canals ( CS ≥ 1) was 1.31 ± 0.19 on the right side and 1.29 ± 0.17 on the left side. No gender differences were found in canal diameter were observed (p > 0.05). There was no significant difference between men and women in the distance between CS and the NCF on the right side, and a significant difference was found in the distance of CS-NCF on the left side (p = 0.047). There were no significant differences between age groups in all parameters.

Conclusion

CBCT is a useful tool for identifying CS. Location and diameter of ACs could not be associated with a specific age group or sex.

Anatomical variations and accessory structures in the maxilla in relation to implantological procedures: an observational retrospective study of 212 cases using cone-bean computed tomography

PURPOSE

This study used cone-beam computed tomography (CBCT) to analyze the prevalence of several maxillary anatomical/accessory structures, as well as variations within each type, assessing how accurate diagnosis can minimize the risk of intraoperative complications during implantological procedures in the oral cavity.

METHODS

212 CBCT scans of the maxilla were analyzed, captured over a period of 18 months for surgical planning purposes. The prevalence of posterior superior alveolar arteries (PSAA), maxillary sinus septa (MSS), and branches of the canalis sinuosus (CS) were evaluated, as were the diameter and location of each anatomical structure in horizontal and vertical planes. P < 0.05 was considered statistically significant.

RESULTS

PSAAs were observed in 99.1% of cases, the intrasinus type being the most frequent; MSS were noted in 15.6% of the sample, mainly in the posterior region with sagittal orientation; CS branches were observed in 50% of patients, mainly in relation to the incisors and significantly more prevalent among males.

CONCLUSIONS

The use of CBCT significantly increases the possibility of clearly identifying these anatomical structures. The differences found between patients highlight the importance of carrying out an exhaustive radiological study of the individual to prevent complications, such as Schneiderian membrane perforation, neurovascular damage or bleeding during surgery.

An Anatomic Predisposition to Mandibular Angle Fractures

PURPOSE

To investigate a predisposition to mandibular angle fractures, a retrospective study was performed in which fractured mandibles were compared with healthy mandibles with no history of fracture. Other investigations of angle fracture risk have exclusively studied patients with existing fractures. In addition, the risk has not been comprehensively explained in conjunction with the specific features of mandibular anatomy. We sought to characterize any anatomic variations between the jaws that had fractured and those that had never fractured.

MATERIALS AND METHODS

Healthy mandibles with no history of fracture were physically measured at the William M. Bass Skeletal Collection at the University of Tennessee, Knoxville and compared with fractured mandibles from computed tomography (CT) scans at the Dartmouth Hitchcock Medical Center. A total of 52 healthy mandibles and 44 CT scans were evaluated. MATLAB machine learning algorithms (MathWorks, Natick, MA) were used to compare the study populations and isolate those anatomic features that differed between healthy and fractured mandibles.

RESULTS

Machine learning classifiers were able to differentiate between male and female jaws, with the condylion-gnathion distance the most distinguishing feature. The 6 most common anatomic features that differed between healthy and fractured mandibles were the 1) retromolar space, 2) perimeter of the cross-section just proximal to the second molar, 3) breadth of the ramal cross-section, 4) thickness of the oblique ridge, 5) transgonial angle, and 6) location of the ipsilateral mental foramen. The presence of third molars was also related to fracture risk, with third molars present in 72.7% of the fractured mandibles versus 26.9% of unfractured mandibles. Of the fractured mandibles with third molars present, 87.5% had the fracture running directly through the tooth or its socket.

CONCLUSIONS

The results from the present study have provided evidence that anatomic differences exist between mandibles that sustain angle fractures and those that do not. Although much of the morphology was found to be interdependent, the fracture risk could be accurately predicted using 6 anatomic features. Understanding these mandibular variations and identifying patients vulnerable to mandibular fracture could provide clinicians with additional objective information. Furthermore, using the methods demonstrated in our study, future research could focus on developing an algorithm that includes these unique anatomic features in the hope of assisting surgeons in providing tailored treatment for mandibular angle fractures according to patient-specific morphology.

The unusually lower position of the mandibular foramen and the canal of the neck of mandible

BACKGROUND

The inferior alveolar nerve (IAN) courses through the mandibular foramen (MF) to enter the first segment of the mandibular canal (MC) in the mandibular ramus, to further supply with trigeminal fibers the lower teeth of that hemimandible. As the IAN also supplies the mylohyoid nerve, it is a mixed nerve.

METHODS

Unusual morphologies of the mandibular ramus were encountered during a retrospective study of archived CBCT files.

RESULTS

A previously unreported anatomic variation was found bilaterally in an edentulous mandible, consisting of a lowered position of the MF, with seemingly compensatory lengthening and enlargement of the sulcus colli, thus shortened MCs. Also, a rare neurovascular canal of the neck of the mandible was incidentally found unilaterally in another case and is reported here.

CONCLUSIONS

Such possibilities of variation could justify the individual effect of the IAN block.

Canalis sinuosus: anatomical variation or structure?

PURPOSE

The main goal of the present study was to verify the presence, spatial location, the end of the canalis sinuosus (CS) trajectory and size of CS using cone beam computed tomography (CBCT) to characterise it as either a structure or an anatomical variation.

METHODS

A trained examiner specialist in dental radiology and imagenology selected 200 CBCT images of the maxilla from 107 (53.5%) female and 93 (46.5%) male individuals aged between 18 and 85 years.

RESULTS

A total of 133 (66.5%) patients had CS, being 61 (45.86%) unilateral and 72 (54.14%) bilateral. A higher frequency of CS was observed in males (P < 0.05) and no relationship was found between its presence and age. The end of the CS trajectory was more frequent in the regions of central incisor (n = 91; 44.39%), followed by lateral incisor (n = 45; 21.95%) and canine (n = 29; 14.15%). In our sample, the majority of these canals had a diameter of up to 1 mm (n = 198/205; 96.6%). No statistically significant relationship between diameter and the end of the CS trajectory, with location (i.e. bilateral or unilateral) was found. Gender and age had no influence on diameter, spatial location and the end of the CS trajectory (P > 0.05%).

CONCLUSION

As CS was frequently found in our sample, it can be considered an anatomical structure, and as such, it is fundamental that the dentist requests a CBCT examination before performing any invasive procedure in the maxillary region to preserve this important structure.

A rare anatomic variation: Triple mental foramina

Multiple mental foramina (MF) are rarely found in the human mandible. We report on the case, as documented using cone beam computed tomography (CBCT), of the triple MF that were identified on the right hemimandible of a 28-year-old female patient. The distal foramen was located on the mandible between the apices of the second premolar root and the first molar mesiovestibular root, being reached by a thin canal that left the mandibular canal. A pair of mesial foramina were identified between the apices of the premolar teeth. Thus, the three foramina corresponded to a surface area of 23.49mm² of the mandible. On the opposite side, a single mental foramen had a surface area of just 13.25mm². On each side, retromolar canals that opened into the retromolar fossae were also found. The anatomic possibility of multiple MF increases the surface area at risk during surgical procedures, increases the risk of neurovascular damage and obscures the common tooth-related location of the mental foramen. Practitioners should, therefore, consider a personalised and imaging-documented approach so as to avoid treatment failure.

The dentomaxillary apparatus from molecular biology to variational anatomy-Underpinning interdisciplinary research

Over the past decades, the research environment in anatomy has dramatically changed. Studies have become more interdisciplinary and complex, with many components required, from basic to clinical research. Within this framework, this special issue was designed to create a link between fundamental fields such as developmental and molecular biology, dental materials, anatomy, histology, and their applications in the clinical research of the dentomaxillary apparatus.

Agger Nasi Cells Versus Lacrimal Cells and Uncinate Bullae in Cone-Beam Computed Tomography

The maxillary bone's frontal process, lacrimal bone, and ethmoidal labyrinth's uncinate process can each harbor pneumatizations, referred to as agger nasi cells (ANCs), lacrimal cells (LCs), and uncinate bullae (UBs), respectively. Different studies have failed to differentiate ANCs from LCs. We aimed at studying these 3 anatomic sites to establish the anatomical patterns that could be encountered. We performed a retrospective study on cone-beam computed tomography scans of 36 patients (72 sides); the anatomic identification was supported by bidimensional multiplanar reconstructions (MPRs) in all 3 planes and 3-dimensional volume renderings. We established 6 patterns of pneumatization as follows: (1) type I: single LCs (47%), (2) type II: distinctive adjacent LCs and ANCs (8%), (3) type III: LCs expanded as UBs (6%), (4) type IV: ANCs adjacent to LCs expanded with UBs (1%), (5) type V: ANCs expanded as LCs (27%), and (6) type VI: ANCs expanded as LCs and further expanded as UBs (11%). In a type I pattern case, we found a cell-in-cell aspect on sagittal MPRs, which was further demonstrated as being an anterolateral recess of the middle nasal meatus projected in front of an LC. Such an "agger nasi recess" of the middle meatus was not previously described. For an accurate anatomical diagnosis, computed tomography studies should use complementary MPRs in all anatomical planes, as well as 3-dimensional models, to avoid confusing ANCs with LCs and better document the drainage pathways.

Vertical and sagittal combinations of concha bullosa media and paradoxical middle turbinate

Common anatomic variants of the middle nasal turbinate include its pneumatization (i.e. concha bullosa media) and its paradoxical curvature. We report here two cases of differently combined variations of the middle turbinate which were documented in cone beam computed tomography (CBCT). The first report presents the vertical combination of a double or septated lamellar concha bullosa with the paradoxical curvature of middle turbinate. This combined variant associated (coincidental findings): ipsilateral paradoxical superior turbinate and contralateral paradoxical middle turbinate, concha bullosa superior and concha bullosa suprema. In the second case was found the sagittal combination of successive anterior concha bullosa media and posterior paradoxical curvature of the middle turbinate. An ethmoidal sinolith was found embedded in lamella basalis. The contralateral superior turbinate was pneumatized. These rare findings demonstrate that sound knowledge of possible anatomical variations, supported by a complete use of the tools available for the CBCT documentation of cases, is able to enrich the picture of human anatomic variations, with a direct impact on clinical and surgical practice. The septa-containing lamellar concha bullosa and paradoxical middle concha combination is a variation that affects surgical practice.