Purificación Varela-Patiño

Alternating versus Continuous Rotation: A Comparative Study of the Effect on Instrument Life

INTRODUCTION Rotary nickel-titanium instruments have multiple advantages but with the risk of more fractures because of flexure or torsion. Alternating rotation appears to be an alternative to continuous rotary movement. The objective of this study was to determine the influence of the type of instrument rotation on the frequency of fractures or deformation. METHODS Instrumentation was performed on 120 molar root canals with an angle of curvature greater than 30 degrees using alternating rotation (group A: 60 degrees clockwise, 45 degrees counterclockwise) and continuous rotation (group B). RESULTS The results indicate that instruments used with alternating rotation have a higher mean number of uses (13.0) compared with the continuous rotation group (10.05); this difference was statistically significant (p < 0.05). CONCLUSIONS The ProTaper shaping instruments (S1 and S2) are those that achieved the greatest difference in use with alternating rotation, with S2 being the most resistant to fracture or deformation with the two types of movement used.

In vitro comparison of passive and continuous ultrasonic irrigation in simulated lateral canals of extracted teeth

INTRODUCTION Complete endodontic system disinfection requires the removal of vital and necrotic pulp tissue, microorganisms, and toxins. The purpose of this study was to compare the effects of 2 ultrasonic irrigation techniques on the penetration of sodium hypochlorite into the main canal and simulated lateral canals of extracted teeth. METHODS Two simulated lateral canals each were created 2, 4, and 6 mm from the working length in 60 single-rooted teeth (6 canals/tooth, n = 360). To resemble the clinical situation, a closed system was created in each tooth. The teeth were randomly assigned to 3 experimental irrigation groups: group 1 (n = 20), positive pressure irrigation (PPI); group 2 (n = 20), passive ultrasonic irrigation (PUI); and group 3 (n = 20), continuous ultrasonic irrigation (CUI). Samples were evaluated by direct observation of still images recorded under a dental operating microscope. To examine irrigating solution penetration, 20% Chinese ink (Sanford Rotring GmbH, Hamburg, Germany) was added to a 5% sodium hypochlorite solution and delivered into the root canals. RESULTS The results showed a significantly higher (P < .05) penetration of irrigant into the lateral canals in the CUI group. PUI and CUI did not differ significantly in solution penetration into the apical thirds of the main canals. The PPI group showed a significantly lower penetration of sodium hypochlorite into the main and lateral canals compared with the CUI and PUI groups. CONCLUSIONS CUI as a final rinse significantly increased the penetration of irrigating solution into simulated lateral canals.

Colorimeter and scanning electron microscopy analysis of teeth submitted to internal bleaching.

INTRODUCTION This in vitro study compared the tooth color and the ultrastructure of internal dental tissues before and after internal bleaching. METHODS Sodium perborate was placed in the pulp chamber of endodontically treated molars and sealed with intermediate restorative material. The test samples were stored in a physiologic solution, and the bleaching agent was replaced every 7 days. A control group was used. After 1 month, the colors of the test and control samples were measured with a colorimeter, and the internal surfaces were observed under field emission scanning electron microscopy (FESEM). RESULTS Statistically significant differences were found between the test and control sample colors. The FESEM ultrastructure analysis of the internal enamel and dentin surfaces did not show any changes after the internal bleaching. CONCLUSIONS The results of the present study show that sodium perborate is effective in bleaching nonvital teeth and does not produce ultrastructural changes in the dental tissues.

Combined Endodontic-Periodontal Treatment of a Palatogingival Groove.

A palatogingival groove is a developmental anomaly that predisposes the involved tooth to develop a severe periodontal lesion. These grooves often present a clinical challenge because diagnosis and treatment planning require an interdisciplinary approach. This case report describes the successful management of a right maxillary lateral incisor with a deep palatogingival groove in combination with an extensive periodontal pocket and pulp necrosis of the involved tooth. Collaborative management used a combination of endodontic treatment, periodontal therapy, odontoplasty, and a periodontal regenerative procedure using protein complex derived from enamel matrix (Emdogain; Straumann, Basel, Switzerland). Despite a predicted poor prognosis, the tooth lesion healed. This report also discusses the rationale behind the treatment modalities.

Ultramicroscopic study of the interface and sealing ability of four root canal obturation methods: Resilon versus gutta‐percha

Recently, filling materials have been introduced based on the dentine adhesion technologies used in conservative dentistry in an attempt to seal the root canal more effectively. The purpose of this study was to investigate the interface between the canal and root-filling material. Sealing ability of four root canal obturation methods was analysed by means of scanning electron microscopy. Extracted single-rooted teeth were endodontically treated and filled with gutta-percha/Pulp Canal Sealer using the Thermafil (TH) technique, gutta-percha/Pulp Canal Sealer using the System B (SB) technique, Resilon points/RealSeal (RS) and RealSeal 1/RealSeal (RS1). Specimen interfaces were analysed using field-emission scanning electron microscopy. The adhesive groups RS and RS1, formed hybrid layers but showed areas of separation (gaps) similar to those in the conventional obturation groups. The RS and RS1 groups showed less separation in the coronal third, but the separation was similar to that in the TH and SB groups in the middle and apical thirds. The sealing ability of Resilon is not superior to that of existing materials.

Management of large class II lesions in molars: how to restore and when to perform surgical crown lengthening?

The restoration of endodontic tooth is always a challenge for the clinician, not only due to excessive loss of tooth structure but also invasion of the biological width due to large decayed lesions. In this paper, the 7 most common clinical scenarios in molars with class II lesions ever deeper were examined. This includes both the type of restoration (direct or indirect) and the management of the cavity margin, such as the need for deep margin elevation (DME) or crown lengthening. It is necessary to have the DME when the healthy tooth remnant is in the sulcus or at the epithelium level. For caries that reaches the connective tissue or the bone crest, crown lengthening is required. Endocrowns are a good treatment option in the endodontically treated tooth when the loss of structure is advanced.

In vitro comparison of passive and continuous ultrasonic irrigation in curved root canals

Background The efficacy of endodontic irrigation procedures can be compromised by the complexity of the root canal system. Delivering irrigants to the apical third of curved canals presents a particular challenge to endodontists. This study compared the effects of two ultrasonic irrigation techniques on the penetration of sodium hypochlorite into the main canal and simulated lateral canals of curved roots in extracted teeth. Material and Methods Two sets of simulated lateral canals were created at 2, 4, and 6 mm from the working length in 60 single-rooted teeth (6 canals/tooth, n = 360 canals). The teeth were randomly divided into three experimental irrigation groups: group 1 (n = 20), positive pressure irrigation (PPI); group 2 (n = 20), passive ultrasonic irrigation (PUI); and group 3 (n = 20), continuous ultrasonic irrigation (CUI). To assess the irrigation solution penetration, 20% Chinese ink (Sanford Rotring GmbH, Hamburg, Germany) was added to a 5% sodium hypochlorite solution and delivered into the curved root canals. The penetration of contrast solution into the simulated lateral canals was scored by counting the number of lateral canals (0-2) penetrated to at least 50% of the total length. Results The CUI group showed significantly higher (P < 0.05) irrigant penetration into the lateral canals and into the apical third of the main canals. The PPI group showed significantly lower sodium hypochlorite penetration (P < 0.001) into the main and lateral canals compared with that in the CUI and PUI groups. Significantly higher irrigant penetration was observed in the PUI group than the PPI group. Conclusions Using CUI as the final rinse significantly increased the penetration of irrigant solution into the simulated lateral canals and apical third of curved roots. Key words:Continuous ultrasonic irrigation, curved root canals, passive ultrasonic irrigation, positive pressure irrigation, root canal irrigation.

Alternating versus continuous rotation: Root canal transportation and centering ratio with the ProTaper Next

Background: The technique of alternating rotation has been used with NiTi rotary instruments to increase the resistance to fracture compared with conventional continuous rotation. However, it is still not clear what type of instrumentation could provide better results in the preservation of the original canal anatomy. Aim: The aim of this study is to determine the influence of the type of rotation on canal transportation and centering ability using cone-beam computed tomography (CBCT) imaging. Materials and Methods: In total, 50 mesial canals of mandibular molars with curvatures between 30° and 60° were divided into two experimental groups (n = 25 each) according to the type of movement employed with the ProTaper Next (PTN) instruments: Group A (alternating rotation) and Group B (continuous rotation). Canals were scanned before and after instrumentation using a CBCT scanner to evaluate root canal transportation and the centering ratio at 3, 5, and 7 mm from the apex. Data were analyzed statistically using Students t-test; the significance level was set at P < 0.05. Results: There was no significant difference between the groups in canal transportation or the centering ratio at any of the three studied cross sections (3, 5, and 7 mm). Conclusions: PTN instruments promoted minimal apical transportation and remained relatively centered within the root canal, with no significant difference between alternating and continuous rotation.

Continuous Apical Negative-Pressure Ultrasonic Irrigation (CANUI): a new concept for activating irrigants

Background: Irrigation of the root canal system is an essential step in the endodontic treatment. The aim of this article is to introduce continuous apical negative-pressure ultrasonic irrigation (CANUI), a new irrigation concept, and compare the characteristics of this new technique with current devices for activating the irrigant. Material and Methods: CANUI is designed for cleaning and disinfecting the root canal system. The device consists of a tube inside another tube that allows the continuous ultrasonic exchange of fresh irrigant, as the irrigant is simultaneously aspirated apically. The coronal and apical tubes are 0.75 and 0.3 mm in diameter, respectively. It is composed of a nickel-titanium microcannula suitable for the working length of curved canals. Results: The CANUI technique has the advantages of apical negative pressure (to avoid apical extrusion of the irrigant) and continuous ultrasonic irrigation (continuous refreshment of the irrigant and forced introduction into the canal ramifications). Conclusions: The CANUI technique could improve the irrigation technique of dentists to reach more disinfection in endodontic treatments. Key words:Apical negative pressure, continuous ultrasonic irrigation, irrigation in curved canals, irrigation systems.

Vertical Root Fracture initiation in curved roots after root canal preparation: A dentinal micro-crack analysis with LED transillumination

Background One of the causative factors of root defects is the increased friction produced by rotary instrumentation. A high canal curvature may increase stress, making the tooth more susceptible to dentinal cracks. The purpose of this study was to evaluate dentinal micro-crack formation with the ProTaper NEXT and ProTaper Universal systems using LED transillumination, and to analyze the micro-crack generated at the point of maximum canal curvature. Material and Methods 60 human mandibular premolars with curvatures between 30–49° and radii between 2–4 mm were used. The root canals were instrumented using the Protaper Universal® and Protaper NEXT® systems, with the aid of the Proglider® system. The obtained samples were sectioned transversely before subsequent analysis with LED transillumination at 2 mm and 8 mm from the apex and at the point of maximum canal curvature. Defects were scored: 0 for no defects; and 1 for micro-cracks. Results Root defects were not observed in the control group. The ProTaper NEXT system caused fewer defects (16.7%) than the ProTaper Universal system (40%) (P<0.05). The ProTaper Universal system caused significantly more micro-cracks at the point of maximum canal curvature than the ProTaper NEXT system (P<0.05). Conclusions Rotary instrumentation systems often generate root defects, but the ProTaper NEXT system generated fewer dentinal defects than the ProTaper Universal system. A higher prevalence of defects was found at the point of maximum curvature in the ProTaper Universal group. Key words:Curved root, Micro-crack, point of maximum canal curvature, ProTaper NEXT, ProTaper Universal, Vertical root fracture.