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ePaper created 2014-10-07, 09:31:41 | version 1.30.01
I opinion _ CBCT in orthodontics A discrepancy between tooth size and arch length is one of the most common problems in clinical orthodontics. This can be resolved by means ofextractions,interproximalenamelreduction,dis- talisationoftheposteriorteeth,orexpansionofthe dental arches. In orthodontics, where non-extrac- tion is becoming increasingly popular, the use of CBCThasbecomemandatory.Expansionoftheden- tal arches is very often associated with root resorp- tion and causes significant buccal tipping of the teeth. It is known that tipping of the teeth is associ- ated with root resorption and buccal cortical bone dehiscences. CBCT allows the clinician to evaluate the volume of the cancellous alveolar bone and the position of the root in relation to the cortical plates (Fig. 2). This information helps the orthodontist establishthelimitationsintoothmovement,sothat the treatment will not induce root resorption or the decline of the periodontal system.3 _Periodontal bone level The periodontal status of the patient should always be verified prior to orthodontic treatment. This should be done on a regular basis for patients diagnosed with periodontal disease, as well as for all adult patients and young people over the age of 18 years (in accordance with the American Board of Orthodontics’ requirements) who are about to undergo orthodontic treatment. Usually, periodon- tal status is checked using a panoramic radiograph or a full-mouth series of radiographs. With CBCT, this kind of radiograph is no longer necessary, because the information can be extracted from the 3-D volume. In addition, CBCT images have the advantage of being 3-D, allowing the clinician to observe and quantify the exact amount of bone surrounding each surface of the tooth, lingual and buccal,aswellasinterproximaldefects(Figs.3&4).1 _The state and condition of the TMJ Clinical examination alone is usually not able to establish the condition of the TMJ or diagnose temporomandibular joint dysfunction syndrome. For this reason, images of the TMJ are essential for evaluating the condyle–fossa relationship (Fig. 5) and the functional joint spaces (Fig. 6) to determi- nate the morphological changes in the osseous structures of the joint and to assess their severity. The morphological changes associated with tem- poromandibular joint dysfunction syndrome in- clude wear, loss of cortical bone, flattening of the articular surfaces (Fig. 6) and osteophytes (Fig. 7).1,4 Recent studies recommend CBCT as the most appropriate radiographic investigation tool for evaluation of TMJ morphological changes.5 _Cephalometric analysis Cephalograms can be extracted from CBCT images (Fig. 8) and the measurements performed on CBCT synthetic cephalograms have proved to be on average similar to those on conventional cephalograms.2 _Transversal discrepancy between the maxillae and mandible Owing to the accuracy with which the land- marks representing the widths of the maxillae and mandible can be identified on CBCT images, it is far Fig. 11_Odontoma causing the impaction of a premolar. Fig. 12_External root resorption of a crowded central incisor. 18 I cone beam3_2014 Fig. 11 Fig. 12 CBE0314_16-20_Iacob 30.09.14 14:14 Seite 3