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Foramen Last

eliminates constrictions in the coronal region cleans coronal 2/3’s of canal b/4 apical 1/3 is entered limits the engagement of each file ~ 2-5mm reduces the impact of canal curvature better tactile awareness during apical shaping. Foramen Last.

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Foramen Last

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  1. eliminates constrictions in the coronal region cleans coronal 2/3’s of canal b/4 apical 1/3 is entered limits the engagement of each file ~ 2-5mm reduces the impact of canal curvature better tactile awareness during apical shaping Foramen Last • allows greater volume of irrigant penetration • minimizes transportation, zipping, ledging • less irritants and toxins pushed through the foramen • working length less likely to change • less stress, minimizes breakage

  2. The ‘Apical Control Zone’ is a matrix-like region created in the apical third of the root canal space. The zone demonstrates an exaggerated taper from the clinician defined apical constriction whether this is spatially a linear or point determination. This enhanced taper in the apical control zone provides resistance form against the condensation pressures of obturation and acts to prevent the extrusion of the filling material during obturation. Apical Control Zone

  3. Apical Control Zone

  4. .2 mm taper 0.0 mm 20 0.25 mm 25 0.5 mm 30 0.75 mm 35 1.0 mm 40 2.0 mm 42 3.0 mm 44 4.0 mm 46 David Rosenberg

  5. Distal Root 1 mm from Apex Canal not debrided and shaped to the correct diameter Necrotic Tissue

  6. Distal Root 1 mm from Apex Isthmus Necrotic Tissue and Debris Canals not debrided and shaped to the correct diameter

  7. Median of maxillary canal diameters 1mm from apex Mx. cent. incisor .34mm Lateral incisor .45mm Canine .31mm Premolar .37mm MB1, MB2 (molar) .19mm DB .22mm Palatal .33mm What does the literature say about canal diameters? Wu et al 2000

  8. Median of mandibular canal diameters 1mm from apex Md. central incisor .37mm Lateral incisor .37mm Canine .31mm Premolar .35mm MB (molar) .40mm ML .38mm Distal .46mm What does the literature say about canal diameters? Wu et al 2000

  9. Radiographic Terminus – NOT!! Radiographic terminus alters throughout life – cellular cementum deposition Apical foramen

  10. Electric Foramenal Locators • must turn unit on before attaching probe to unit… “might think in previous tooth” • canals can be wet, but chamber must be dry… no shared fluid between canals • instrument must be free in access opening… no contact with metal In 1962 Sunada determined that the resistance between oral mucosa and periodontal ligament is a constant value 6.5 ohms (40/μAmp)

  11. * Anatomic apex PDL, cementum & bone EAL = 0.0 Bleeding point

  12. Working Length • generic knowledge of root lengths • measure radiograph – • advantage of digital images • foramenal locators • USED REPEATEDLY • final WL determined after coronal debridement – lengths change with shaping foramenal locators USED REPEATEDLY

  13. Guru Conclusions Several trends are increasingly evident: • most NiTi techniques are hybrid rotary file protocols • most operators create tapered apical preparations, ranging from .06 to .2 or more • most use a thermolabile technique • most use patency files all the time • all use foramenal locators as primary length determinant • not all take WL x-rays and some use paper points for length confirmation • presence of an ACZ is dependent on operator’s technique

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