'Bone map' for a safe placement of miniscrews generated by computed tomography.

OBJECTIVES: The aim of this manuscript is to provide a bone map that can be used as a general guide to determine the areas where miniscrews can be safely anchored. MATERIALS AND METHODS: Twenty-one computed tomographies (CTs) of maxilla and mandible were taken by the imaging centre ORTOSCAN and two measures were taken: --first, the interradicular space in the mesiodistal plane of the maxillary and mandible teeth with slices taken at 3, 6, and 9 mm from the alveolar crest, in the palatine and vestibular slices, --second, the interradicular space in the vestibular-lingual direction. RESULTS: We can see that the greatest amount of mesiodistal bone is between the first and second inferior molars on the vestibular side and between the second and first inferior molars on the lingual side, whereas the least amount of bone on the mesiodistal plane is between the inferior incisors on the vestibular side. To determine the length of the miniscrew, we must take into account that the greatest amount of vestibular-lingual bone is between the first and second inferior molar, whereas the least amount is between the central and lateral inferior incisors. CONCLUSIONS: Mesiodistal values in vestibular are those that must be considered when inserting the microscrew so as not to damage the dental tissue. Mesiodistal measurements taken in palatal-lingual do not present problems when inserting microscrews.

Initial stress differences between tipping and torque movements. A three-dimensional finite element analysis.

The aim of this study was to analyse the distribution of the stress on dental and periodontal structures when a simple tipping dental movement or torque movement is produced. A tridimensional computer model based on finite element techniques was used for this purpose. The model of the lower canine was constructed on the average anatomical morphology and 396 isoparametric elements were considered. The three principal stresses (maximum, minimum and intermediate) and Von Mises stress were determined at the root, alveolar bone and periodontal ligament (PDL). It was observed how the distribution of stress is not the same for the three structures studied. In all loading cases for bucco-lingually directed forces, the three principal stresses were very similar in the PDL. The dental apex and bony alveolar crest zones are the areas that suffer the greatest stress when these kind of movements are produced.