Instrumentation Time Efficiency and Histologically the Debriding Efficacy.

Patient selection was based on the following criteria:

• the aims and requirements of the study were freely accepted by the parents;
• primary molars with at least 11.0 ± 1.0 mm of working length
• Treatment was limited to patients in good health;
• All teeth had vital and non-vital pulps without a sinus tract;
• Excess of bleeding during a pulpotomy; 6) Presence of enough coronal tooth and root structure;
• No prior pulpectomy treatment on the involved tooth,
• absence of perforation in the internal and/or external furcation area and
• No analgesics or antibiotics were used before the clinical procedures began. Exclusion criteria were patients without inclusion requirements or failure to obtain parent´s authorization, and were excluded if they were older than 7 years old, had a positive history of antibiotic use within the past month, diabetic, hemophilic or if the tooth had root resorption or been previously accessed and initiated a pulpectomy.

Once eligibility was confirmed, the parents were informed of the study design, the clinical procedure involved, and the associated risks. Patients aged 4-7 years of age were enrolled in this study, forty-five teeth (19 maxillaries and 26 mandibular teeth), which had a total of 102 canals and completely formed apices and of minimum 10 mm root length were selected. All selected teeth had mature apexes with no radiographic sign of root resorption.

Of the 45 treated primary molars, 31 teeth were diagnosed as having chronic pulpitis, and 14 as having pulp necrosis that responded negative to hot and cold tests; and, clinically, all pulps were confirmed to be necrotic on entrance into the pulp chamber. Informed consent was obtained and written by the parents from each patient in accordance with the approval of the study by the ethical board of the Universidad Autónoma de Baja California, Facultad de Odontología Tijuana, México. All clinical procedures and measurements were conducted by the author.

A #0 periapical radiograph was taken for each tooth in buccolingual projection to allow proper selection. The selected teeth included 7 second maxillary molars (three canals each), 9 first maxillary molars (2 canals each), 3 central incisors (one canal each), 18 first mandibular molars (2 canals each), 8 second mandibular molars (three canals each) for a total of 45 teeth with 102 canals.

A standard session time recommended by the pedodontists was approximately 20-35 minutes in length to allow for acceptable time for completion of treatment. All treatment was performed by the author. As a novel treatment in Pedodontics, were included electronic apex locator (EAL), EndoVac system and two rotary systems: LightSpeed LSX instruments and ProTaper Next.

The teeth were randomly divided into 3 groups (each tooth was considered as an experimental unit): Control Group (n= 15): the root canals were prepared manually with K-files (Dentsply-Maillefer, Ballaigues, Switzerland) and "step back technique" up to size #35.

Group 1 (n= 15): the root canals were instrumented with rotary LightSpeed LSX instruments (Discus Dental, Culver City, CA, USA). They were used to complete the canal preparation to a size #50 for the anteriors and molar teeth to size #40.

Group 2 (n= 15): root canals were instrumented with ProTaper Next (Dentsply Maillefer, Ballaigues, Switzerland) using X1, X2 to X3. 0.5% NaOCl was used for irrigation. The instrumentation time was measured for all the procedures and the results were analyzed with student's t-test. All statistical procedures were computed with SPSS 21.0 (SPSS Inc., Chicago, IL, USA). The Student t test was used to compare data whether there were statistically significant differences between the results obtained clinically. Significance was set at p < 0.05.

Pilot study. All the procedures were done in extracted primary teeth, they were prepared and disinfected before using the instgruments. After the debridement of the canals, the teeth were sectioned longitudinally and observed under microscope.

Clinical Protocol. After local anesthesia by 2% lidocaine with 1:100,000 epinephrine (58 Rue du Pont de Creteil, Saint - Maur des Fossés F-94100, France) and rubber dam isolation the tooth was disinfected with 2.5% NaOCl (Ultra bleach, Bentonville, AR, USA).

All caries was removed and endodontic access cavities made with sterile high speed carbide # 331 (SS White. Lakewood, NJ). The cervical third of each canal was flared with a SX ProTaper file (Maillefer, Ballaigues, Switzerland).

Each canal was irrigated consequently with 2.0 cc 0.5% sodium hypochlorite. The final rinse was aspirated but no attempt was made to dry the canals. Working length was established with the Root ZX Electronic Apex Locator (J Morita, Irvine, CA) and confirmed radiographically. The canals were negotiated and enlarged with K-files hand instruments (Dentsply-Maillefer, Ballaigues, Switzerland) until reaching an ISO #20 at the working length.

The Root ZX was used in accordance with the manufacturer's instructions. The buccal clip was attached to the patient's lip, and the probe was connected to a stainless steel 15 K-file. The file was advanced within the root canal to a point just beyond the major foramen, as indicated by the flashing APEX bar on the liquid crystal display of the EAL.

When the file was in position the LCD display showed a flashing bar between APEX and 1. Measurements were considered to be correct if the instrument remained constant for at least 4-5 seconds. A digital photograph was taken and stored in Adobe Photoshop 5.5 (Adobe Systems Inc., San Jose, CA, USA). The position of the file tip for each root canal were evaluated by two examiners, if the two examiners disagreed a third previously calibrated researcher was asked to make the final decision. The final WL was established to be 1 mm coronal to the major foramen (12).

For the control group the root canals were prepared manually with K-files and "step back technique" up to size #35. For the Group 1, LightSpeed LSX rotary instruments (Discus Dental, Culver City, CA, USA) were used to complete the canal preparation to a size #50 for the anteriors and molars to size #40.

For the group 2 the root canals were instrumented with ProTaper files using X1, X2 (21mm) to X3 (21mm). 0.5% NaOCl was used for irrigation, the original protocol suggested by ProTaper for permanent teeth was simplified for this study.

After completion of canal instrumentation, all canals were irrigated with distilled water for 30 seconds using the EndoVac irrigation system (Discus Dental, Culver City, CA, USA).

The EndoVac system is able to apply the irrigant to working length and evacuate it using apical negative pressure. The negative pressure avoids forcing the irrigant beyond the apex into the periapical tissues.

The canals were dried with sterile paper points and obturated at the same appointment using calcium hydroxide and iodoform paste (Pearson Dental, Sylmar CA) by using pluggers or syringes (Messing Root Canal Gun, PD, Vevey, Switzerland). Access cavities of anterior teeth were etched and restored with Fuji IX (GC Corp, Tokyo, Japan). For posterior teeth, a buildup restoration was placed by using the same etching technique and Fuji IX or temporary metallic crown.

A stopwatch with alarm (http://stopwatch.onlineclock.net/) was used to record instrumentation time for each group.

Children were recalled for clinical and radiographic examinations were evaluated, based on the criteria of Coll and Sadrian at 6-month intervals for a follow-up period of 2 years. Teeth that exhibited no symptoms of pain, tenderness to percussion, swelling, sinus tract, or pathological mobility were judged clinically successful (42 teeth).

Teeth that showed no evidence of periradicular or interradicular radiolucency, internal or external root resorption, or periodontal ligament space widening were judged raiographically successful. Radiographic evidence of pulp canal obliteration was noted, but it was not regarded as failure.