© 2006 J.Bringas, DMD, DDS, MS

Working Length Determination

Presented by:Josef Ma. Karlos S. Bringas, D.M.D., D.D.S., M.S.Department of Endodontics

© 2006 J.Bringas, DMD, DDS, MS

Radiographic Length

• The length of the tooth as it appears on the radiograph.

© 2006 J.Bringas, DMD, DDS, MS

Estimated Working Length

• Radiographic length minus 1mm.

© 2006 J.Bringas, DMD, DDS, MS

Final Working Length

• is determined to be -1 mm from the anatomical apex as measured from the working length (WL) radiograph.

• THIS IS THE LENGTH TO WHICH THE CANAL WILL BE CLEANED & SHAPED AND OBTURATED.

© 2006 J.Bringas, DMD, DDS, MS

Select a Reference Point

© 2006 J.Bringas, DMD, DDS, MS

Take a Preoperative Radiograph

© 2006 J.Bringas, DMD, DDS, MS

Preoperative Radiograph

• Measure the radiographic length.

Reference pt.

Apex

© 2006 J.Bringas, DMD, DDS, MS

Measure the radiographic length

Ex. 22mm

© 2006 J.Bringas, DMD, DDS, MS

Compute for Estimated Length

• Estimated Length is radiographic length minus 1mm.

Ex. 22mm - 1mm = 21mm

© 2006 J.Bringas, DMD, DDS, MS

Treatment Record

© 2006 J.Bringas, DMD, DDS, MS

Treatment Record

Incisal edge

21 mm

© 2006 J.Bringas, DMD, DDS, MS

Set #15 file to Estimated Length

Insert the file into the canal to stopper length and take a radiograph at this time.

© 2006 J.Bringas, DMD, DDS, MS

Working Length Radiograph

• The best case scenario is that there is no radiographic distortion with the preoperative radiograph.

• The working length radiograph should show that the file ends 1mm short of the apex.

© 2006 J.Bringas, DMD, DDS, MS

Working Length Radiograph

• File appears to end 1mm short of the apex.

• No need to adjust the final working length.

© 2006 J.Bringas, DMD, DDS, MS

Working Length Radiograph

• In this case, estimated working length is equal to the final working length.

• EWL = FWL• Record FWL

© 2006 J.Bringas, DMD, DDS, MS

Treatment Record

Incisal edge

21 mm

21 mm

© 2006 J.Bringas, DMD, DDS, MS

Working Length Radiograph

• Sometimes, the radiograph shows that the file extends more apical than the ideal.

• This means that the EWL is long.

• Deduct this discrepancy from your EWL to arrive at the Final Working Length.

© 2006 J.Bringas, DMD, DDS, MS

Working Length Radiograph

© 2006 J.Bringas, DMD, DDS, MS

Working Length Radiograph

• Example: EWL=21mm

• Since radiograph shows that file is 1mm long then…

1mm

© 2006 J.Bringas, DMD, DDS, MS

Working Length Radiograph

• Example:• EWL – 1mm =

FWL

• 21mm – 1mm = 20mm

1mm

© 2006 J.Bringas, DMD, DDS, MS

Working Length Radiograph

• Example:• EWL – 1mm =

FWL

• 21mm – 1mm = 20mm

1mm

© 2006 J.Bringas, DMD, DDS, MS

Treatment Record

Incisal edge

21 mm

20 mm

© 2006 J.Bringas, DMD, DDS, MS

Working Length Radiograph

• Sometimes, the radiograph shows that the file does not reach the ideal length.

• This means that the EWL is short.

• Add this discrepancy to your EWL to arrive at the Final Working Length.

© 2006 J.Bringas, DMD, DDS, MS

Working Length Radiograph

© 2006 J.Bringas, DMD, DDS, MS

Working Length Radiograph

• Example:• EWL=21mm

• Since radiograph shows that file is 0.5mm short then…

0.5mm

© 2006 J.Bringas, DMD, DDS, MS

Working Length Radiograph

• Example:• EWL+0.5

mm=FWL

• 21mm+0.5mm=21.5mm

0.5mm

© 2006 J.Bringas, DMD, DDS, MS

Treatment Record

Incisal edge

21 mm

21.5 mm

© 2006 J.Bringas, DMD, DDS, MS

Working Length Radiograph

• If the radiograph shows that the discrepancy is more than 2mm, then a new radiograph should be taken after computing for the working length.

© 2006 J.Bringas, DMD, DDS, MS

Unacceptable discrepancy