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Relationship between anterior mandibular bone thicknessand the angulation of incisors and caninesa CBCT study

Agnieszka Srebrzyska-Witek1 & Rafa Koszowski2 & Ingrid Ryo-Kalinowska3

Received: 9 January 2017 /Accepted: 11 October 2017 /Published online: 23 October 2017# The Author(s) 2017. This article is an open access publication

AbstractObjectives The morphology of the maxillary and mandibularalveolar cortex plays an important role in the planning oforthodontic treatment. Cone-beam computed tomography(CBCT) provides a precise demonstration of anatomical struc-tures. Therefore, the aim of this paper was to evaluate whatinfluence the position of incisors and canines have on thedimensions of the cortical and spongious bone of the anteriormandibular alveolar process.Materials and methods The material consisted of 100 CBCTvolumes (61 females and 39 males, aged 1871 years) obtain-ed by means of a Gendex GXCB-500 machine and analysedusing i-CAT Vision and CorelDRAW 9 software. Several lin-ear and angular measurements were taken of cortical andspongious mandibular, vestibular and lingual alveolar bone.Results The thickness of the vestibular spongious bone in-creased around lateral incisors and canines together with den-tal axis inclination, as did the thickness of the lingualspongious bone around central incisors and canines withgreater angles of vestibular cortex curvature. In all teeth, thethickness of lingual cancellous bone decreased along withincrease of the angle of tooth inclination. In the case of almostall groups of teeth, the thickness of lingual cancellous bone

around teeth declined as the angle of curvature of the corticalbone decreased. The rotation of mandibular incisors and ca-nines did not affect the thickness of the surrounding bone.Conclusions The position of teeth has little influence on ves-tibular bone thickness and is only significant around centralincisors. In the case of almost all groups of teeth, the thicknessof lingual spongious bone around teeth declined as the angleof curvature of the cortical bone decreased.Clinical relevance CBCT is a diagnostic tool that providesdetailed information on the dimensions of the anterior dentatemandibular alveolar process.

Keywords Cone-beam computed tomography . Imaging,three-dimensional . Mandible . Alveolar process


Due to its specific anatomy, the anterior mandible is an areathat poses considerable diagnostic and therapeutic problems.This is due to the relatively small dimensions of teeth as wellas the small distances between them, and these difficultiesmay be further intensified by frequent dental crowding[13]. The vestibular cortical bone of the mandibular alveolarprocess is of utmost importance as its dimensions influencethe aesthetics of the patients smile. This structure is prone toresorption, e.g. during the course of periodontal bone diseaseas well as during orthodontic or implantological treatment.Moreover, the profile of the periodontal bone, mainly the ves-tibular cortical bone, affects the healing of post-extractionwounds. Bone remodelling occurs after any dental extractionthat leads to atrophy, mainly in the transsectal plane, andwhich is more advanced on the vestibular side of the jaw.This hampers or even makes it impossible to manufacture

* Ingrid

1 Private Practice, Kossak-Szczuckiej Street 7/1,40-578 Katowice, Poland

2 Academic Center of Dentistry and Specialized Medicine, Pl.Akademicki 17, 41-902 Bytom, Poland

3 Independent Unit of Propedeutics of Dentomaxillofacial Radiology,Medical University of Lublin, Karmelicka Street 7,20-081 Lublin, Poland

Clin Oral Invest (2018) 22:15671578


fixed prosthetic appliances, either conventional devices orthose based on dental implants [4, 5].

Provided the anatomy of the recipient site is thoroughlyassessed by the dentist, the latter is able to choose a suitableimplant with the desired shape and dimensions, plan its finalposition and decide whether further augmentation is neces-sary. Correct preoperative diagnostics also make it possibleto predict potential bone resorption. Immediate implant place-ment combined with simultaneous bone augmentation is be-coming increasingly common. The status and thickness of thevestibular mandibular cortex is of key importance whenchoosing the correct treatment options [6].

The morphology of the maxillary and mandibular alveolarcortex plays an important role in the planning of orthodontictreatment, especially in cases where there is a considerablediscrepancy between the volume of teeth and the amount ofspace available in the dental arches. The movement and incli-nation of teeth towards the oral vestibule often results in re-duced thickness of the external cortex or in its discontinuity inthe form of fenestrations and/or dehiscences. Orthodonticforces applied during this kind of treatment increase tissuestrain and result in reduced keratinized gingiva thickness. Asa result, it may become too thin for the progenitor cells re-sponsible for bone formation. Gingival recessions may devel-op, and this complication is more common aroundmandibularincisors [7].

When the maxillary and mandibular alveolar cortex is thin,periodontal surgery is recommended so as to increase its thick-ness before embarking on any orthodontic expansion of thedental arch. Such surgery is based on transplanting the hardpalate mucosa or subepithelial connective tissue [810].

The recent development of radiological imaging in theform of cone-beam computed tomography (CBCT) providesa more precise demonstration of anatomical structures and thedetection of pathological lesions. CBCT has proved extremelyuseful in dentistry due to its relatively low exposure dose(when compared with medical CT) and high resolution [6].CBCT scanning is frequently used in the planning ofimplantological and orthodontic treatment. We thus assumedthat application of CBCT may supply crucial information onthe relationships between the morphology of the dentate ante-rior mandible and the position of teeth. Therefore, the aim ofthis paper is to evaluate what influence the position of inferiorincisors and canines have on the dimensions of the corticaland spongious bone of the anterior mandibular alveolarprocess.

Material and methods

The material consisted of cone-beam computed tomographyvolumes obtained from the Radiological Lab of the JomadentHealth Center in Dbrowa Grnicza (Poland) from 2010 to

2012. The study was approved by the local bioethical com-mittee (KNW/0022/KB/190/13). All the CBCT examinationswere performed due to clinical indications and not for thepurpose of this study. The selection criteria for patients wereas follows: age over 18 years and all upper and lower incisors,canines, premolars and at least the first molars present in thedental arches. The exclusion criteria were as follows: ortho-dontic treatment (current or previous), prosthetic crowns onmandibular incisors and canines, the presence of any lesion(e.g. a tumour, cyst, periapical lesion, supernumerary tooth),foreign bodies in the anterior mandible, previous surgery onthe anterior mandible as well as CBCT volumes of inferiorquality (artefacts, incomplete coverage of the anterior mandi-ble, patient movement, incorrect exposure settings, low reso-lution) and medication intake affecting bone metabolism(such as bisphosfonates, calcium).

Eventually, 100 CBCT volumes from 61 females and 39males aged from 18 to 71 years (mean age 41.34 years,43.95 years in males and 39.67 years in females) qualifiedfor the retrospective analysis. Statistical analysis was per-formed in two age groupsbetween 18 and 49 years of age(70 CBCT volumes taken in 45 women and 25 men) andbetween 50 and 71 years of age (the remaining 30 volumesincluding 16 women and 14 men). All the CBCTs were ob-tained with a Gendex GXCB-500 machine, and the followingexposure parameters were applied: 120 kV, 5 mA, exposuretime between 6 and 8 s and voxel size 0.3 mm. The region ofinterest included upper and lower dental arches within a cy-lindrical field of view of 8 8 cm. The slices obtained in thisway were analysed using specially designed i-CAT Visionsoftware, which was unable to perform all the planned linearand angular measurements. Therefore, the authors developedtheir own method so as to transfer selected slices from i-CATVision software to CorelDRAW 9 software (serial numberDX9XR6840J50620) by means of IrfanView software (byIrfan Skiljan).

Image analysis consisted of measurements taken in themandible in the area of teeth 43, 42, 41, 31, 32 and 33. Inthe first step, an axial slice at the cervix level of the mandibularanterior teeth was formed with i-CAT Vision software. Then,lines were drawn at each tooth and these lines crossed at twopoints: the first was located at the maximum convexity of thevestibular outline of the tooth and the second similarly atmaximum lingual tooth convexity. The line was always drawnin the middle of the cross section of the root canal (Fig. 1).These cross-sectional images were then exported toCorelDRAW 9. To maintain measurement accuracy, two cal-ibrating lines of known length, perpendicular one to another,were drawn using IrfanView software (Fig. 1). Before pro-ceeding with further measurements in CorelDRAW 9, the cor-rect size of the exported image was set using theabovementioned calibration lines so as to ensure a highly ac-curate linear and angular measurement.

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The following parameters were measured on cross-sectional slices of six anterior mandibular teeth:

1. The thickne