These are the average diameters of maxillary teeth one millimeter from the apex, ranging from .19 mm in the MB root of the molar to .45 mm in the lateral incisor.
And in the mandibular teeth, there was no canal diameter smaller than a size 30 file. As the data suggests, instrumenting these canals with a small apical file size with a highly tapered instrument won’t adequately clean and shape the apical portion of these canals.
Foramen Last eliminates constrictions in the coronal region allows greater volume of irrigant penetration cleans coronal 2/3’s of canal b/4 apical 1/3 is entered minimizes transportation, zipping, ledging limitsirritants and toxins pushed through the foramen less the engagement of each file ~ 2-5mm reduces the impact of canal curvature working length less likely to change better tactileminimizes breakage less stress, awareness during apical shaping
Apical Control ZoneThe ‘Apical Control Zone’ is a matrix-like region created inthe apical third of the root canal space. The zonedemonstrates an exaggerated taper from the cliniciandefined apical constriction whether this is spatially a linearor point determination. This enhanced taper in the apicalcontrol zone provides resistance form against thecondensation pressures of obturation and acts to preventthe extrusion of the filling material during obturation.
0.0 mm 200.25 mm 250.5 mm 300.75 mm 351.0 mm 402.0 mm 423.0 mm 444.0 mm 46 DavidRosenberg
Apical Gauging Avoid apical parallelismObjective - linear or point apical control zone
Distal Root1 mm from Apex Canal not debrided and shaped to the correct diameter Necrotic Tissue
Distal Root 1 mm from Apex Necrotic TissueCanals not debrided and shaped to the correct diameter and Debris
What does the literature say about canal diameters?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 Wu et al 2000
What does the literature say about canal diameters?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 Wu et al 2000
Radiographic Terminus – NOT!! Radiographic terminus alters throughout life – cellular cementum deposition Apical foramen
Electric Foramenal Locators In 1962 Sunada determined that the must turn unit on before attaching resistance between oral mucosa probe to unit… and periodontal ligament is a “might think in previous tooth” constant value 6.5 ohms (40/μAmp) 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
Working Length generic knowledge of root lengths measure radiograph – advantage of digital images foramenal locators foramenal locators USED REPEATEDLY USED REPEATEDLY final WL determined after coronal debridement – lengths change with shaping
Guru ConclusionsSeveral 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