No abstract

During the period of the study, in general, referral letters to the TMD clinic concerned contained insufficient information. The introduction of a referral pro forma, produced by the TMD clinic, and guidelines might improve the quality of referrals.

Statement of problem: Geometrically, to best resist occlusal forces, the mandibular incisor presents generally an orthogonal inclination (approximately 90 ) to the radius of rotation during the closing movement of the mandible, the centre of rotation being the condyles.Purpose: The objective of this study was to confirm the application of this geometrical principle, named "tangent law", to the inclination of the mandibular canine. If the tangent law is applicable to the mandibular canine, the mean angle between the long axis inclination of the mandibular canine is orthogonal to the condylo-occlusal line.Material and methods: Measurements were taken from sixty lateral cephalometric radiographs in a strict sagittal plane to analyze the incisors, and in the canine plane to analyze the canines.Results: The measurements, close to 90 , confirmed the tangent law for the mandibular incisor (mean: 89.38 AE1.77), and also confirmed our hypothesis about the inclination of the mandibular canine, which was found to follow the same principle (mean: 90.98 AE1.13). A significant smaller variance for the mandibular canine inclination than for the mandibular incisor suggests that the canine may play a key role in occlusal stability.Conclusion: The orthogonal principle of the "tangent law" could constitute a reference value for the inclination of the mandibular canine when planning orthodontic, prosthodontic or implantology procedures.

Many authors agree on the importance of placing dental implants, like other prosthetic restorations, so that the occlusal forces are, ideally, directed along the long axis of the implant body. This helps to preserve the osseointegration and ensures even force distribution over the various supporting screw threads.The authors propose an innovative tool that allows the production of surgical templates, which can optimise the placement of mandibular dental implants, whilst also respecting established geometric and biomechanical concepts.