Cleaning, Shaping, and Obturation

Lecture given 8/25/2025, this was kind of a repeat lecture so I picked out the emphasized points

the root canal system must be…

cleaned of its organic remnants and shaped to facilitate the cleaning action via irrigation and receive a 3D filling that will seal off the entire root canal space

what are the biologic objectives of a root canal?

to completely debride the pulp space of pulpal tissue, bacteria and microorganisms, and endotoxins

what are schilder’s 5 mechanical objectives of a root canal treatment?

continuously tapering funnel

canal narrower apically

prepare in multiple planes (flow concept)

maintain original position of apical foramen

apical foramen as small as practical

how can you estimate the working length using a radiograph?

measure from the incisal edge (or cusp tip) to the readiographic terminus

this length should be used for preparing the initial gliding path

glide path

a smooth, paved, reproducible pathway of endodontic files to the apical foramen

t/f the saliva in a canal is enough, you can work in a canal without hydrating it

false- never work in a dry canal

why is it important to pre-curve a file?

because using a straight file can result in apical perforation, ledge formation, or apical blockage

how should you precurve files?

use cotton pliers or a piece of gauze wetted with alcohol

when creating the gliding path, what is a good rule of thumb to follow before proceeding to the next larger file?

do at least 20 strokes

what should you do if you are unable to negotiate a #10 file to the estimated working length?

do not use force, switch to a smaller file, then return to a #10 file or larger

where can gates glidden burs be used?

only in the coronal one third of the canal

how should gates glidden burs be used/how is coronal flaring created?

brushing towards the wall to avoid damaging the furcation

what are the rules that should be followed when using gates gliddden burs?

use a size that fits passively and loosely in the canal

should be used while rotating

place it into the canal at the point where it begins to bind, withdraw slightly, and then start the drill

the master apical file should be at least size…

25

master apical file

largest binding file at the working length

why must flutes be cleaned of dentinal shavings between each insertion using alcohol wet gauze?

to avoid clogging the canal, allows the file to work better, and allows you to see if the file is winding or unwinding

how long can rotary instruments be used at working length?

no more than one second!

t/f rotary instruments can be used beyond working length just for a second if you need to unclog the canal

false- rotary instruments are not to be taken beyond working length

crown down technique

instrumentation of the root canal system from the coronal aspect toward the apex

larger rotary instruments are used first followed by the next smaller size

t/f you can use rotary instruments before hand instruments if the canal is totally calcified

false- never use rotary instruments without hand instruments first

when is cleaning and shaping complete?

when you have prepared the apex to at least size 25 file

when you have performed step back to at least a size 50

when you have used rotary instruments to working length

when you have achieved all of schilder’s 5 mechanical objectives

and when you can fit the gutta percha cone to the working length

what is the correct cone fit of gutta percha?

0.5 mm short of working length

0.5 mm short of RT (unsure on that, slide86)

a good tug back at the apical portion of the canal

which plugger has the largest diameter, and which has the smallest?

largest- #12

smallest- #8