History of development of reciprocating system

The greatest No. of commercially available files utilized to

shape root canals are manufactured from NiTi and are

mechanically driven in continuous rotation.

On the other hand, reciprocation, defined as any repetitive

back-and-forth motion, has been clinically utilized to drive

stainless steel files since 1958.

Initially, all reciprocating motors and related handpieces

rotated files in large equal angles of 90 clockwise (CW) and

counterclockwise (CCW) rotation.

Over time, virtually all reciprocating systems in the

marketplace began to utilize smaller, yet equal, angles of

CW/CCW rotation. The M4, Endo-Eze, and Endo-Express are

examples of reciprocating systems that utilize small, equal 30

angles of CW/CCW rotation. Further, these systems have

recognized limitations, including decreased cutting efficiency,

more required inward pressure, and a limited capacity to

auger debris out of a canal.

In about 1998, Dr. Ben Johnson and Professor Pierre Machtou

co-discovered the unmistakable advantages of reciprocating

NiTi files utilizing unequal bidirectional movements.

After that, Machtou and his endodontic residents extensively

analyzed this novel unequal reciprocating movement using the

entire series of not-yet-to market PT files.

Dr. Ghassan Yared, a former student of Professor Machtou,

performed exhaustive work to identify the precise unequal

CW/CCW angles that would enable a single reciprocating

25/.08 PT file to optimally shape virtually any canal.

In 2008, a team of 8 international clinicians including Drs. Ben

Johnson, Sergio Kuttler, Pierre Machtou, Wilhelm Pertot, Julian

Webber, John West, Ghassan Yared, and Ruddle, in

collaboration with Dentsply International, began the serious

work of developing both a new reciprocating file and motor for

shaping canals.

In 2011, following 4 years of research and development, both

WaveOne (Dentsply Tulsa Dental Specialties and Dentsply

Maillefer) and RECIPROC (VDW) were internationally

launched as single-file shaping techniques.

Rotation and Reciprocation

Compared to reciprocation, continuous rotation utilizing well-

designed active NiTi files requires less inward pressure and

improves hauling capacity auguring debris out of a canal.

On the other hand, a mechanical reciprocating movement has

merit because it somewhat mimics manual movement and

reduces the various risks associated with continuously rotating

a file through canal curvatures.

Reciprocation of Ni-Ti instruments have the following

advantages over continuous rotation:

1. Binding of the instruments into the root canal dentine walls is

less frequent, reducing torsional stress.

2. The reduction of the number of cycles within the root canal

during preparation results in less flexural stress on the

instrument.

3. There is decreased risk of instrument fracture.

RECIPROC file and WaveOne file are able to completely

prepare root canals with only one instrument.

These files are made of a special nickeltitanium alloy called

M-wire that is created by an innovative thermal treatment

process. The benefits of this M-wire alloy are increased

flexibility and improved resistance to cyclic fatigue of the

instruments.

The RECIPROC and WaveOne files are used in a reciprocal

motion that requires special automated device (motor).

These files are single use to avoid stress and wear on the active

portion of the files and to prevent potential for cross-

contamination between and among patients.

Reciprocating files

WaveOne file system

It is a new single-instrument mechanized shaping system

(DENTSPLY Maillefer, Ballaigues, Switzerland). In most

instances, the WaveOne concept provides a single file shaping

technique, regardless of the length, diameter, or curvature of

any given canal.

In fact, it has been shown that a single file reciprocating

shaping technique utilizing unequal CW/CCW angles is over 4

times safer and almost 3 times faster than using multiple

rotary files to achieve the same final shape.

Strategically, only 1 file is generally utilized to fully shape

virtually any given canal. However, there are 3 WaveOne files

available to effectively address a wide range of endodontic

anatomy commonly encountered in everyday practice.

1. WaveOne Small file: is used in

fine canals. The tip size is ISO 21

with a continuous taper of 6%.

2. WaveOne Primary file: is used in

the majority of canals. The tip size

is ISO 25 with an apical taper of

8% that reduces towards the

coronal end.

3. WaveOne Large file: is used in

large canals. The tip size is ISO 40

with an apical taper of 8% that

reduces towards the coronal end.

Design features of WaveOne files system The WaveOne files have changing pitch and helical angle along their

active portions, and 2 distinct cross-sections along the length of their

active portions. From D1-D8, the WaveOne files have a modified

convex triangular cross-section, whereas from D9-D16, these files

have a convex triangular cross-section.

The WaveOne files have noncutting modified

guiding tips which enable these files to safely

progress through virtually any secured canal.

Together, these design features enhance safety

and efficiency when shaping canals that have a

confirmed, smooth, and reproducible glide path.

Reciprocation movement & WaveOne motor

The e3 motors (Dentsply Tulsa Dental Specialties) is specially

engineered and programmed to drive the new WaveOne

reciprocating files. The WaveOne motor is rechargeable battery

operated with a 6:1 reducing handpiece.

This motor produces a feature-specific, unequal bidirectional file

movement. Because of the reverse helix design, the CCW engaging

angle is 5 times the CW disengaging angle. Additionally, it should be

noted, this motor can drive any market version file system in full CW

rotation at the desired speed and torque.

File selection

If a # 10 K-file is very resistant to movement, useWaveOne Small file.

If a # 10 K-file moves to length easily, is loose or very loose, use

WaveOne Primary file.

If a # 20 K-file or larger goes to length, useWaveOne Large file.

Clinical guidelines for the use of WaveOne file

Create straight line access.

Negotiate canals to patency and create a reproducible glide path.

Select the correctWaveOne file.

Clean the cutting flutes of the instrument after each cutting cycle.

Irrigate and recapitulate the root canal system after each cutting cycle, and

lubricated canal before using file.

Faster preparation time requires

longer irrigation times preferably

with activation of irrigation

solution. Because of the reduced

preparation time, the tissue in

uninstrumented parts of the root

canal system have generally been

exposed for a shorter period of

time to the irrigation solution of

choice.

A WaveOne file was used in a reciprocating motion according to the

manufacturers instructions using (WaveOneTM endo motor). The silicon

stopper was set on the WaveOne file at 2/3 of WL.

Then, the file was introduced in the canal with a slow in (light apical directed

force) and out (circumferential brushing) motion without pulling the

instrument completely out of canal.

After 3 in-and-out movements, the WaveOne file

was pulled out of the canal to clean the flutes, and

the canal was irrigated.

The WaveOne file was used until it had

reached 2/3 of the WL as indicated by stopper

on the file. Then the file was reused in the

same manner until the WL had been reached.

Shaping technique of WaveOne

RECIPROC file system

It is a new system for single file reciprocation without prior use of

hand files. It was developed as single-file shaping techniques (VDW).

The system includes three instruments (R25, R40 and R50) Only one

RECIPROC instrument is used for the canal preparation depending

on the initial size of the canal. The three instruments have regressive

taper, which are:

1. R25 has a diameter of 0.25mm at the tip and an

8% taper over the first 3mm from the tip. The

diameter at D16 is 1.05mm.

2. R40 has a diameter of 0.40mm at the tip and a 6%

taper over the first 3mm from the tip. The

diameter at D16 is 1.10mm.

3. R50 has a diameter of 0.50mm at the tip and a 5%

taper over the first 3mm from the tip. The

diameter at D16 is 1.17mm.

Design features of RECIPROC file system

These instruments are made from an M-wire NiTi. The three

instruments have non-cutting tips. They have an S shaped cross-

section.

VDW. SILVERS RECIPROC is battery operated motor used with

RECIPROC system. The battery is rechargeable and the motor can be

used while the battery is charging.

There are preprogrammed settings for reciprocating system The

instruments are used at 10 cycles of reciprocation per second.

Reciprocation movement & RECIPROC motor

When the instrument rotates in the cutting

direction it will advance in the canal and

engage dentine to cut it. When it rotates in

the opposite direction (smaller rotation)

the instrument will be immediately

disengaged.

File selection

Shaping technique of RECIPROC file

Clinical guidelines for the use of RECIPROC file

Same as inWaveOne file

Studies on reciprocating instruments

The reciprocating movement induced less cyclic fatigue and

promoted an extended life of the ProTaper F2 instruments in

comparison with conventional rotation.

RECIPROC instruments were associated with a significantly higher

cyclic fatigue resistance than theWaveOne instruments.

The authors speculated that this could be attributed to the possible

difference in the cross-sectional designs of the two instruments.

1. Cyclic fatigue

The use of Reciproc and WaveOne instruments resulted in less debris

removal compared with canal shaping performed with ProTaper

instruments.

The studies showed that pecking motion could lead to debris

compaction while a brushing motion leads to debris removal.

3. Debris extrusion

2. Debris removal

Filing with Reciproc showed more apical debris extrusion compared

with that seen withWaveOne and also with rotation ProTaper.

A probable explanation for this finding is that rotary motion tends to

pull dentinal debris into the flutes of the file and directs it toward the

coronal aspect of the canal. Also, continuous rotation compared to

reciprocation, requires less inward pressure and improves capacity

to auger the debris out of a canal.

Many researchers found that instrumentation techniques produce

some debris extrusion and this can induce inflammation within the

periapical area; therefore, instrumentation technique that causes

less extrusion of debris is more desirable.

The presence of bacteria is the main cause of the development of

periodontal infection and apical periodontitis. The aim of

chemomechanical root canal preparation is to eradicate residual

vital and non-vital pulp tissue and reduce the number of pathogenic

organisms. Mechanical instrumentation can disrupt the bacterial

biofilm and has the potential to reduce the presence of bacteria in the

main root canal.

Reciprocating systems resulted in similar bacterial reductions to

those obtained with rotary systems or with the manual

instrumentation technique.

4. Bacterial reduction

5. Maintenance of root canal anatomy

Reciproc and WaveOne instruments were found to maintain the

original canal contour.

In curved canals, Its better instrumented with reciprocating files

than with rotary, which tend to transport the outer canal wall of the

curve in the apical part of the canal.

Reciprocating systems showed good ability and suitable for shaping

curved canals with only one instrument.

A recent study compared the incidence of dentinal defects after root

canal preparation with reciprocating (WaveOne 40/08 and Reciproc

R40) and with rotary instrumentation (Mtwo and Pro- Taper

Universal) on extracted human central lower incisors:

The study concluded that all four systems caused dentinal

defects, but both reciprocating systems caused significantly

more incomplete cracks in the apical (3mm) portion of the root

canals.

RECIPROC was associated with more complete cracks compared

with the full sequence rotary systems.

6. Dentinal defects/cracks

Reciprocating files were faster than rotating files.

The primary WaveOne files were significantly faster for canal

preparation compared to the Reciproc R25 files.

According to the authors with the study the difference can be

attributed to the fact that WaveOne instruments have three cutting

blades and might have better cutting efficacy than the two-bladed

Reciproc properties of the instruments.

7. Clinical efficiency

8. Centric ability WaveOne and Reciproc instruments obtained better centering ability

at all levels especially at the end point of preparation comparing with

Protaper and Mtwo instruments.

The clinical technique in which reciprocating instruments like

WaveOne and RECIPROC are used can play a vital role in the

successful outcome of the cleaning and preparation phase of

endodontic treatment. Most studies agree that the reciprocating

movement can reduce torsional (binding to dentine is reduced) and

flexural stresses (number of rotation cycles are reduced) on

endodontic instruments.

These instruments, also maintain the original canal anatomy and

demonstrate reduced time for canal preparation compared with full

rotary systems.

However, there are conflicting results in the literature regarding the

efficacy of debris removal and bacterial reduction and there remains

the possibility of debris extrusion and dentinal crack formation

during root canal preparation with reciprocating instruments.

Conclusions