Please activate JavaScript!
Please install Adobe Flash Player, click here for download

Journal of Oral Science & Rehabilitation No. 3, 2016

Journal of Oral Science & Rehabilitation Volume 2 | Issue 3/2016 43 A x i a l p l a n e i n c o m p u t e d t o m o g r a p h y Introduction Edentulous patients seeking dental treatment to restore function and esthetics have tradition- allyreceived removable complete orpartial den- tures. However, the use of removable dentures may give the patient a sense of insecurity, re- duced masticatory function and taste capacity, as well as low self-esteem.1 For these reasons, approaches to treatment have turned toward dental implants, which produce marked im- provements in patients’ quality of life and high treatment success rates.2, 3 An adequate radiographictechniquethatwill provide a sufficientlyaccurate assessment ofthe bone dimensions is of great help when planning the surgical intervention. Intra-oral and pano- ramicradiographsgiveinformationintwodimen- sions, visualizing bone morphology in a bucco- lingual direction, but lack the third dimension. Both techniques are only useful for a primary preoperative evaluation to obtain preliminary information about the available bone height.4 Three-dimensionalinformation is obtained using computed tomography (CT). In edentulous mandibles, the location and course of the mandibular canal remain relatively unchanged in the cranial and caudal borders of the mandible, although some atrophy at the lin- gual and buccal external borders may occur.5 Recently, some anatomicalstructures inthe jaw- bone, which are difficult to detect using conven- tional radiography, have been explored using CT.6–9 Investigations of mandibular accessory foramina and canals have drawn attention to anatomical variations of perimandibular neuro- vascularization.10–13 Although there is a wide range of dental CT equipment marketed as providing exact bone data at a 1:1 scale, several studies have shown discrepancies between radiographic CT meas- urements and clinical measurements taken di- rectly from the bone.4, 14–16 Furthermore, depen- dingonthepositioningofthepatientwhentheCT measurements are taken, these discrepancies between radiographic measurement and measu- rements taken from real bone can increase even further.17, 18 In 2008, Cucchiarelli et al. compared the discrepancies between radiographic measu- rementswithCTandmeasurementstakendirec- tlyfrom 15 edentulous maxillae, using two diffe- rent axial reference planes.19 The study showed distortions with regard to the real bone measu- rements, and these discrepancies were different for each of the two axial reference planes used. The aims of the present ex vivo study were to assess the accuracy of dental CT scans and to comparethe discrepancies obtainedwhen either the occlusalplane orthe basalplanewas used as the axial reference plane. Materials and methods M a n d i b l e s Atotalof39normalanddrymandiblesfromadult cadavers aged 35–83 (mean age of 50) were examined following state regulations, the study protocol having been approved by the Murcia (Spain) City Hall Health Service. Thirty of these mandibles were edentulous and the other nine retainedteeth. In orderto homogenizethe study, multiple exodontias were performed on the nine mandibles that retained teeth. M a r k i n g t h e o c c l u s a l p l a n e The occlusalplanewas marked onthe nine man- dibles that retained teeth before the exodontias were performed.Thiswas done bymarking a line parallel to the teeth from the incisal edge of the central incisorto the vestibular cusps ofthe sec- ond molar (Fig. 1a). Once the occlusal plane had been marked, the teeth were extracted. For the 30 edentulous mandibles, the occlu- sal plane was established in the anterior region by measuring a height of 1 cm (the usual height ofthe mandibularincisal crowns) and inthe pos- terior region by dividing the retromolar trigone into three parts: upper, middle and lower.There- after, a meeting point between the upper third andthe middle partwaschosen;thispointusual- ly measured 1 cm in height (Fig. 1b).20 Once the occlusal planes of the mandibles had been established, a Moyco wax piece (ThompsonDentalManufacturing,Montgomery- ville, Pa., U.S.) was molded to follow the previ- ously established plane. After placing the wax simulationoftheocclusalplane (Fig.1c),thiswas divided into 18 parts using 2 mm lead strips. Thesestripswereplaced6mmapartsothatthey corresponded to the 18 tomographic slices per- formed for each mandible (Fig. 1d). Lastly, Fox planes were attached to the wax on each of the 39 mandibles (to be used as a guidefordelimitingtheocclusalplaneradiograph- ically) and each assembly was placed into a po- lymethylmethacrylate(PMMA)boxforradiogra- phic study. Volume 2 | Issue 3/201643

Pages Overview