Supervisors info:
Τσιχλάκης Κωνσταντίνος, Καθηγητής, Δοντά Αικατερίνη, Αναπληρώτρια Καθηγήτρια, Γκριτζάλης Παναγιώτης, Επίκουρος Καθηγητής
Summary:
AIM
The aim of this study was to evaluate the dimensions and anatomic
characteristics of the nasopalatine canal and the adjacent buccal osseous plate
of the alveolar process, using Cone-Beam Computed Tomography (CBCT) imaging.
MATERIALS AND METHODS
In the present study -retrospective in design- the subjects enrolled were out
of a series of 124 CBCT examinations of dentulous and edentulous implants’
patients. Patients evidenced with nasopalatine pathology (e. g. nasopalatine
duct cyst) were excluded from the present study. The CBCT images were obtained
using a New Tom VGi CBCT imaging unit (QR Systems, Verona, Italy). Operating
parameters were set at 3.66mA, 110kV and 3.6sec exposure time. The nasopalatine
canal’s dimensions and anatomic characteristics, as well as the dimensions of
the adjacent buccal osseous plate, were assessed on to the reformatted sagittal
and coronal CBCT slices. The reformation of the sagittal slice under evaluation
was orientated perpendicular on the floor of the nasal cavity and hard palate
antero-posteriorly, being also parallel to the course of the nasopalatine
canal. Within this reconstructed slice the canal was clearly depicted. Three
Oral Maxillofacial Radiologists evaluated the scans in a standardized viewing
procedure and performed measurements to determine both the anatomic
characteristics and dimensions of the nasopalatine canal, as well as the
dimensions of the adjacent osseous buccal plate. The parameters under
evaluation were (in mm): The diameter of the incisive foramen, the diameter of
the nasal foramen, the diameter in the middle of the nasopalatine canal, the
length of the nasopalatine canal. The alveolar bone was measured in three
different areas accordingly: Buccal border of the incisive foramen, palatal
border of the incisive foramen, at the middle of the nasopalatine canal. The
anatomic variants of the nasopalatine canal were also recorded and classified
as; A: a single canal, B: two parallel canals, C: variations of the Y-type of
canal with one oral/palatal opening (incisive foramen) and two or more nasal
openings (foramina of Stenson). Data were analyzed using IBM-SPSS v.22 and
Minitab v.16.1. The nasopalatine canal’s anatomical variations were assessed
with the use of MS Excel 2013 and Statistica v.10 Enterprise. The observation
quality control was performed by the use of the Cohen's Kappa, Fleiss' Kappa
and Intra Class Correlation (I.C.C.) statistical tests. The aforementioned data
were subjected to Analysis of Variance (ANOVA one-way), t-test and X2. The
signicance level was set at p0.05 for all statistical tests.
RESULTS
The population studied consisted of 57 men and 67 women (mean age of 48.73
years). The intraobserver coefficients calculated for only the first observer
(Cohen’s Kappa>0.90 and I.C.C.>0.90), suggesting excellent intraobserver
agreement. In general, strong and excellent interobserver agreement was found
(Fleiss Kappa=0.83, p<0.05 and I.C.C. >0.90, p<0.05). The evaluation of the
different anatomic variations of the nasopalatine canal resulted in the
following findings: (A) a single canal was identified in 56.5%; (B) two
separate parallel canals were detected in 25%; (C) variations of the Y type of
canal were seen in 18.5%. An independent additional canal, anterior and
superior to the nasopalatine canal, was found in 4% of the patients. The
dimensions’ analysis of the nasopalatine canal pointed a mean diameter of both
the incisive and nasal foramen these of 6.00mm and 3.10mm respectively. The
mean diameter in the middle aspect of the nasopalatine canal was 2.04mm, while
the mean length was 12.16mm. The dimension of the buccal osseous plate’s width
is increasing proportionally to the crestal, middle and apical position of the
area under evaluation (mean values 6.86mm, 6.86mm and 7.61mm respectively). A
statistically significant correlation was found regarding the dimensions of the
nasopalatine canal and the adjacent buccal osseous plate in male subjects, once
the mean values found were higher among males than females. Edentulous patients
presented a statistically significant correlation regarding the dimensions of
the osseous buccal plate. The types of nasopalatine canal presented a
significant effect on the diameter of the incisive foramen. The mean values
were higher in type C, tracked by the variations of type A and B. The type of
nasopalatine canal had also a significant effect on its length as to the mean
values in type A be presented higher. We also found out that the absence of the
central incisors had a statistically significant effect on the crestal
measurements of the buccal osseous plate. Its width is gradually decreased
throughout the cases of missing central incisors.
DISCUSSION-CONCLUSIONS
Imaging of the nasopalatine canal using CBCT provides important information
about the anatomy of the anterior maxilla. This enables a more precise
preoperative assessment for implant placement, since this anatomical area is
considered as a region presenting high esthetic challenges. We found
statistical significant correlations between the gender and the dimensions of
the nasopalatine canal as well as the adjacent osseous buccal plate. The mean
values were generally higher in male subjects. Statistical significant
correlations were also found in edentulous patients, as the dimensions of the
buccal osseous plate are mostly affected. It has also been shown that the type
of nasopalatine canal had a significant effect both on the length of the
nasopalatine canal, as well as on the diameter of the incisive foramen. The
width of the osseous buccal plate was found to be higher in cases where both
central incisors were present, while it decreased in cases where one or two
central incisors were missing. In conclusion, the accurate interpretation of
the CBCT imaging data, regarding the anterior maxillary area, provides valuable
information upon the preoperative evaluation of the aesthetic zone.
Keywords:
anterior maxilla, cone-beam computed tomography, implants, nasopalatine canal
