Morphology of the greater palatine grooves of the hard palate: A CBCTstudy

Background: There is increasing frequency of dentoalveolar and palatal implants placed in the posterior maxilla for prosthodontic and orthodontic purposes. The purpose of this study is to provide information on the location and morphology of the greater palatine grooves (GPG) in the hard palate and to promote awareness of this structure. A cc ep te d A rt ic le This article is protected by copyright. All rights reserved. Materials and methods: Eighty-nine Cone Beam CT (CBCT) scans were analysed for the presence of a groove, crest or bridging. Results: This study on the morphology of the GPG in the maxillary first and second molar regions showed three distinct appearances: i, no palatal groove, ii, one palatal groove, iii, two palatal grooves. The detection frequency of no palatal groove in the first molar region was 60%, 34% had one groove and 6% having two grooves. The detection frequency of no palatal groove in the second molar region was 72%, 26% had one groove and 2% had two grooves. The number of crests in the first and second molar regions ranged from 0-3. Conclusion: The present study demonstrates a great variation in morphology of the GPG of the hard palate. Knowledge of the GPG will decrease possible complications of implant surgery, particularly palatal implant surgery and to not confuse the GPG with pathology. INTRODUCTION Cone beam computed tomography (CBCT) is now used extensively for pre-implant assessment of the jaws. One of the most important functions of CBCT is the identification of vital structures prior to implant placement. There is now a growing use of palatal implants (temporary anchorage devices) for orthodontic purposes. The GPG is a significant structure in the hard palate that should be considered when placing implants in the upper molar regions, but there is very little in the literature regarding this structure. The greater palatine nerve and vessels pass inferiorly in the pterygopalatine fossa and exit via the greater palatine foramen onto the hard palate. They pass in a groove in the hard palate to supply the mucous membrane of the hard palate, including the palatal glands and the palatal gingiva. The greater palatine nerve supplies the mucosa of the hard palate as far anteriorly as the maxillary canines. 2 A cc ep te d A rt ic le This article is protected by copyright. All rights reserved. Frequently, there are bony ridges and protuberances forming grooves in the hard palate in the second and first molar regions adjacent to the course of the greater palatine neurovascular bundle. A study by Hassanali and Mwaniki identified the presence of crests and bridges along the borders of the palatine grooves. These features were also studied by Zivanovic and were found to be present in ancient skulls. The morphological variation of the greater palatine foramen and groove may be significant when administering local anaesthesia or performing palatal surgery. These grooves and crests should also not be mistaken for the presence of disease. The purpose of this study is to provide information on the location and morphology of the GPGs in the hard palate and to promote awareness of this structure, particularly with more implant surgery occurring in this region. MATERIAL AND METHODS The study group comprised of 89 scans which included the maxilla (55 femaleand 34 male) with an average age of 31.5 years (range 6-78 years). The scans which included the maxilla, were selected randomly from a database from a private maxillofacial radiology practice and ethics approval was obtained for this study. Cone beam scans where the first molar and second maxillary molars were missing were excluded. Patients with local pathology and exostoses in the first and second maxillary molar regions were also excluded. The CBCT studies were acquired with an i-CAT cone beam CT (Imaging Sciences International) using 120 kV and 3-7 mA. The software Xoran-CAT was used for the analysis of the datasets. Orientation of the three planes was achieved by lining up the infraorbital margins, anterior and posterior nasal spines, and orientating the hard palate parallel to the axial plane. A cc ep te d A rt ic le This article is protected by copyright. All rights reserved. The scans were reviewed by a registered oral and maxillofacial radiologist. The second and first molar regions bilaterally were analysed for the presence of a groove, crest or bridging. The distance of the groove from the greater palatine foramen in the first and second molar positions were also measured. The presence or absence of torus palatinus was also recorded. RESULTS The assessed patient pool of 89 cases provided 178 sites. This study on the morphology of the GPG in the maxillary first and second molar regions showed three distinct morphologies (Fig 1-3). In the first molar region, 107 sites had no signs of a groove, 61 sites had one groove while 10 sites had two grooves. In 29 cases, the grooves in the first molar region were bilateral while in 20 cases, the groove was unilateral. In the second molar region, 128 sites had no signs of a groove, 46 sites had one groove and 4 sites had two grooves. In 13 cases, the grooves in the second molar region were bilateral while in 10 cases, the groove was unilateral. The number of crests at each site varied from 0 to 3. In the first molar region, 84 sites had no crests, 82 had one crest, 11 had two crests and 1 had three crests. In the second molar region, 113 sites had no crests, 50 sites had one crest, 14 sites had two crests and 1 site had three crests. The average distance of the groove in the first molar region from the greater palatal foramen is 11.8 mm (range 6-18.5mm). The average distance of the groove in the second molar region from the greater palatal foramen is 9.6 mm (range 5-14.5mm). Torus palatinus was present in 8 cases (9%).