8- rotary instrumentation systems

Why are the 3 parts of the rotary system?

Rotary instruments

Motor- continuous or reciproc

Obturation material 

What 2 techniques to do RCT?

Apicoronal- step back- start in apex

Coronoapical- can use continuous and reciprocal techniques

What are the objectives of access cavity prep?

Remove all caries

Preserve sound structure

Unroof pulp chamber

Remove all coronal pulp tissue

Locate canal orifices

What is the function of Gates Glidden Bur and its characteristics?

Widen coronary thirds

Stainless steel- 6 diff sizes

Tip is only active part- has cutting capacity- can fracture but is rigid

What is ni ti rotary files made of and its characteristics?

Nicker and titanium 

How much is the speed of the electric motor of ni ti rotary files?

150-300rpm

What are characteristics of ni ti rotary files?

Super elastic and flexible

Resist plastic deformation

Fracture resistance

Good cutting and inactive tip- use lateral movements

Use flexible NiTi files in curved canals

Explore coronal 2/3- with K-files 10-20 to create a glide path

Prepare coronal 2/3- with rotary files- continuous rotation

Determine WL- tactile, electronic apex locator, radiograph 

Continue shaping- coronoapically with rotary files

Maintain patency- recapitulate with small K-file (#10) between files

Use pecking motion- advance 1 mm, withdraw 2–3 mm, clean

What types of irrigating solutions are used?

2.5-5% sodium hypochlorite- to dissolve pulp tissue (organic)

15-17% EDTA- treat calcified canals (inorganic) and removes smear layer

0.2% chlorhexidine gluconate- antimicrobial

What may the interaction between Naocl and EDTA cause?

EDTA increases effectiveness of naocl

But too much damages dentin

What other devices can be used to disinfect?

Laser systems

Gaseous ozone

Passive ultrasonic irrigation

Photo activation disinfection

What are advantages of rotary instruments?

Reduces apical transportation, steps and perforations

Centre the duct

Less apical extrusion- so less inflammation and post op pain

What are disadvantages of rotary instruments?

Hard if patient doesn’t open mouth far

Can’t pre curve files

Easy to fracture if pressure forced on

What are the general principles of technique of rotary systems?

Preop x ray

Remove caries

Open canal and only isolate once canal is localised

Root canal permeabilisation to find apex

Conductometry with apex locator and x ray

Root instrumentation and irrigate

Conometry x ray

Obturate canals

Final x ray

How to find apex with files?

PathFile (Dentsply Maillefer) – taper 2% and gauge 13,16,19

ProGlider (Dentsply Maillefer): Newer and just one filePathFile

4 x rays for RCT

Initial

Preop

Conductometry and conometry x ray

Post op

What movements are conducted in root instrumentation?

Progression and relief- not too much pressure, only for 2/3 secs

Rotate on entry and exit

Don’t force

What is the sequence of use of shaping and finishing files of protaper gold?

S- yellow, purple, white, F- yellow, red, blue

What are the features of protaper gold files?

Variable taper

Inactive tip

First line always measures 18mm

1mm diff between each line

In the reciprocal system how many movements complete one full cycle?

3 movements- 150 degree, then goes back 30

What are the 2 types of fractures?

Torsion- part of instrument remains immobilised, rest keeps turning

Flexural- cyclic fatigue- rotates freely in curved duct until max curvature

How do we prevent the fracture of rotary instrument?

Control speed and torque

Progression and relief movements

No pressure

Control number of file uses

Irrigate and lubricate

What anatomical factors contributes to the wear of rotary files?

More curved

Narrow ducts

Confluent ducts

More ducts, more wear