Micro-CT evaluation of sonically and ultrasonically activated irrigation on the removal of hard-tissue debris from isthmus-containing mesial root canal systems of mandibular molars

AIM

To evaluate the efficacy of sonically and ultrasonically activated irrigation on removal of accumulated hard-tissue debris (AHTD) in mesial root canal systems of mandibular molars using micro-computed tomographic (micro-CT) analysis.

METHODOLOGY

Forty mesial roots of mandibular molars with two independent canals joined apically by an isthmus (Vertucci type II) were selected. The root canals were instrumented using Reciproc R25 instruments, and specimens were scanned at a resolution of 10.5 μm. Subsequently, n = 10 roots were assigned to each of the four final irrigation groups such that the group means and variances were almost identical: sonically activated irrigation with EndoActivator (EA) or EDDY (ED), ultrasonically activated irrigation (UAI) and manual irrigation without activation (MI). The final irrigation procedures were performed using a total of 5 mL 1% NaOCl and 5 mL 15% EDTA per canal over 5 min with activation time of 4 × 20 s. Reconstructed data sets were coregistered, and the mean percentage reduction of AHTD after final irrigation was compared statistically between groups using analysis of variance at a significance level set at 5%.

RESULTS

A significant reduction of AHTD was achieved after final irrigation in all groups (P < 0.05), ranging from 44.1% to 66.8%. The vol% of debris after irrigation was 3.7 ± 1.9% for EA, 3.3 ± 2.3% for ED, 2.1 ± 1.6% for UAI and 4.4 ± 2.3% for MI, with no significant difference between groups (P > 0.05).

CONCLUSIONS

None of the final irrigation protocols completely removed AHTD from mesial root canal systems in extracted human mandibular molars. Sonically and ultrasonically activated irrigation performed no better compared to manual irrigation.

Efficacy of the ProTaper retreatment system in removing Thermafil, GuttaCore or vertically compacted gutta-percha from curved root canals assessed by micro-CT

AIM

To evaluate ex vivo the efficacy of ProTaper Universal Retreatment files (Dentsply Sirona, Ballaigues, Switzerland) in removing Thermafil, GuttaCore (both Dentsply Sirona) or vertically compacted gutta-percha from curved root canals using micro-CT.

METHODOLOGY

Sixty curved molar roots with the same mean canal curvatures and radii in two directions were prepared using ProFile instruments (Dentsply Sirona) to size 30 with .04 taper and obturated with either Thermafil, GuttaCore or vertically compacted gutta-percha and AH Plus (n = 20). Specimens were retreated using the ProTaper Universal Retreatment files D1, D2 and D3 to working length, and root canal preparation was completed with ProTaper Next (Dentsply Sirona) to size ×4. Percentages of residual filling material and dentine removal were assessed using micro-CT imaging. Working time and procedural errors were recorded. Statistical analysis was performed using Kruskal-Wallis and Wilcoxon tests.

RESULTS

No significant differences between carrier-based and warm vertical compaction regarding residual filling material (14.2-19.3%) and dentine removal (2.7-3.2 mm³ ) were detected (P > 0.05). Time to reach working length was significantly faster for canals filled with GuttaCore than that observed for Thermafil and warm vertical compaction (P < 0.05). Five lateral perforations with the D3 file occurred during retreatment, one in the Thermafil and four in the vertical compaction group.

CONCLUSIONS

Remaining filling material and dentine removal were similar for all canal filling techniques. Regaining working length was significantly faster for GuttaCore compared with Thermafil and vertically compacted gutta-percha. Procedural errors occurred during retreatment of severely curved root canals with the ProTaper Universal Retreatment files in 5 of 60 canals (8%).

Comparison of hand and rotary instrumentation for removing gutta-percha from previously treated curved root canals: a microcomputed tomography study

AIM

To compare the efficacy of hand and rotary nickel-titanium (NiTi) instruments in removing filling material from curved root canals of root filled teeth with unknown preparation parameters.

METHODOLOGY

Ninety mandibular molars with root fillings in curved root canals and homogenous root canal filling extending to 0-2 mm short of the radiographic apex were selected. Root canal curvatures and radii were measured in two directions and microcomputed tomography (micro-CT) scans were used to determine preoperative volumes of the filling material. Subsequently, the teeth were assigned to two identical groups (n = 14). The root fillings were removed with Hedström files or FlexMaster NiTi rotary instruments. Postoperative micro-CT imaging was used to assess the percentage of residual filling material as well as the amount of dentine removal. Working time and procedural errors were recorded. Data were compared using analysis of covariance and analysis of variance procedures.

RESULTS

Root canals retreated with Hedström files were associated with less remaining filling material compared with FlexMaster instruments (P < 0.05). Both retreatment techniques removed similar amounts of dentine with no significant differences (P > 0.05). FlexMaster instruments were significantly faster than Hedström files (P < 0.05). No procedural errors were detected in the Hedström group, whilst three instruments fractured in the FlexMaster group.

CONCLUSIONS

Hand instrumentation resulted in significantly less residual filling material than retreatment with rotary NiTi instruments. Dentine removal was not significantly different for both techniques. FlexMaster NiTi rotary files were significantly faster than Hedström files, but were associated with a higher risk of instrument fracture.

Efficacy of Two Different CHX-Containing Desensitizers: A Controlled Double-Blind Study

CHX-containing desensitizers are used for treatment of hypersensitive teeth. This positive effect shows a durability of 3-month.

Efficacy of D-RaCe and ProTaper Universal Retreatment NiTi instruments and hand files in removing gutta-percha from curved root canals - a micro-computed tomography study

AIM

To compare the efficacy of two rotary NiTi retreatment systems and Hedström files in removing filling material from curved root canals.

METHODOLOGY

Curved root canals of 57 extracted teeth were prepared using FlexMaster instruments and filled with gutta-percha and AH Plus. After determination of root canal curvatures and radii in two directions, the teeth were assigned to three identical groups (n = 19). The root fillings were removed with D-RaCe instruments, ProTaper Universal Retreatment instruments or Hedström files. Pre- and postoperative micro-CT imaging was used to assess the percentage of residual filling material as well as the amount of dentine removal. Working time and procedural errors were recorded. Data were analysed using analysis of covariance and analysis of variance procedures.

RESULTS

D-RaCe instruments were significantly more effective than ProTaper Universal Retreatment instruments and Hedström files (P < 0.05). Hedström files removed significantly less dentine than the rotary NiTi systems (P < 0.0001). D-RaCe instruments were significantly faster compared to both other groups (P < 0.05). No procedural errors such as instrument fracture, blockage, ledging or perforation were detected in the Hedström group. In the ProTaper group, four instrument fractures and one lateral perforation were observed. Five instrument fractures were recorded for D-RaCe.

CONCLUSIONS

D-RaCe instruments were associated with significantly less residual filling material than ProTaper Universal Retreatment instruments and hand files. Hedström files removed significantly less dentine than both rotary NiTi systems. Retreatment with rotary NiTi systems resulted in a high incidence of procedural errors.

Comparison of root canal preparation with two rotary NiTi instruments: ProFile .04 and GT Rotary

AIM

To compare root canal preparation using ProFile .04 and GT Rotary nickel-titanium instruments (both Dentsply Maillefer, Ballaigues, Switzerland).

METHODOLOGY

Fifty extracted mandibular molars with mesial root canal curvatures between 20 and 40 degrees were randomly divided into two groups and embedded in a muffle system. All root canals were prepared to size 45 using ProFile .04 or GT rotary instruments. The following parameters were evaluated: straightening of root canal curvature, postoperative root canal cross-section, cleaning ability, safety issues and working time.

RESULTS

Both NiTi systems maintained curvature well; the mean degree of straightening was <1 degrees . The majority of the root canals prepared with ProFile .04 (80.8%) and GT (84.0%) postoperatively showed a round or oval cross-section. For debris, ProFile .04 and GT rotary achieved 67.1% and 71.6% scores of 1 and 2, respectively. Concerning the coronal region statistical analysis showed a better result for GT than for ProFile .04. For the middle and apical thirds of the root canals, results did not differ significantly. None of the two systems completely removed smear layer. Ten procedural incidents occurred with ProFile .04 compared with five with GT. Mean working time was shorter for ProFile .04 (131.8 s) than for GT (143.7 s); the difference was not significant.

CONCLUSIONS

Both systems respected original root canal curvature well and were safe to use. Smear layer removal was not satisfactory with either systems.

Diagnosis and root canal treatment of a mandibular second premolar with three root canals

AIM

To present a case of a mandibular second premolar with three root canals.

SUMMARY

An accurate diagnosis of the morphology of the root canal system is a prerequisite for successful root canal treatment. A review of the literature reveals a low incidence of all types of premolars with three root canals. Diagnostic means such as preoperative radiographs and examination of the pulp chamber floor aid the location of root canal orifices. The diagnostic and therapeutic problems concerning premolars with unusual anatomy are described on the basis of a clinical example. A case report describes the successful treatment of a mandibular second premolar with three root canals.

KEY LEARNING POINTS

Clinicians should be aware of unusual root canal anatomy in mandibular premolars. Radiographs exposed at two different horizontal angles and their careful interpretation facilitate the search of additional root canals. The use of magnification and additional lighting are recommended for the clinical examination of the pulpal floor.

Quality of preparation of oval distal root canals in mandibular molars using nickel-titanium instruments

AIM

The aim of this study was to compare the preparation of oval distal root canals in mandibular molars using three different nickel-titanium (NiTi) instruments: Lightspeed (Lightspeed Inc., San Antonio, TX, USA). ProFile .04 (Maillefer Ballaigues. Switzerland) and Quantec SC (Tycom, Irvine, CA, USA).

METHODOLOGY

Three groups of 20 extracted mandibular molars with oval distal root canals were embedded in a muffle system as described by Bramante et al. (1987) and modified by Hülsmann et al. (1999). Preparation of the root canals was performed with particular emphasis on the buccal and lingual extensions of the oval shape. The following parameters were evaluated: comparison of pre- and postoperative photographs with regard to the buccal and lingual extensions of the preparation, safety issues (file fractures, perforations, apical blockages, loss of working length), cleaning ability (SEM investigated using a 5-score system for remaining debris and smear layer) and working time.

RESULTS

Superimposition of pre- and postoperative cross-sections in the majority of specimens revealed uninstrumented or incompletely instrumented buccal or lingual extensions (Lightspeed and Quantec SC, 56.7%; ProFile .04, 55%) For debris removal, Quantec SC achieved the best results (54.2% scores 1 and 2), followed by ProFile .04 (52.5%) and Lightspeed (46.7%). Preparation resulted in substantial smear layer covering the canal walls for every system (ProFile .04, 38.3%; Quantec SC, 36.6%; Lightspeed, 28.3%). Differences between the three systems were not significant for any of the parameters investigated. Preparation with Lightspeed resulted in two fractured instruments; with Quantec SC. two apical blockages occurred. With ProFile .04, no complications were noticed. Mean working time was shorter for ProFile .04 (261.2 s) than for Quantec SC (272.4 s) and Lightspeed (338.9 s); the differences were not significant.

CONCLUSIONS

The flexibility of the NiTi instruments investigated in this study did not allow controlled preparation of the buccal and lingual extensions of oval root canals. The instruments frequently produced a circular bulge in the canal whilst the buccal and lingual extensions remained unprepared, leaving smear layer and debris.

Dose reduction by direct-digital cephalometric radiography

Patient radiation exposure was determined for conventional and direct-digital cephalometric radiography. An anthropomorphic phantom was positioned to expose lateral cephalographs from the patient's left side. The conventional radiographs were exposed with a Siemens Orthophos C unit (77 kV, 14 mA, 0.5 s) and a film-screen system of a relative speed of 400. The direct-digital radiographs were exposed with a Siemens Orthophos DS Ceph (73 kV, 15 mA, 15.8 s). A set of 108 thermoluminescence detectors (TLDs; Bicron STI/Harshaw, Solon, Ohio) was used for dose measurements. For each measurement, 84 TLDs were placed at the surface of the head and neck, as well as inside the phantom, at anatomically relevant positions. The remaining detectors were employed for calibration purposes and quality control. The highest absorbed doses were recorded for the conventional technique at the skin of the left parotid region (132 microGy), in the left parotid gland (103 microGy), and in the ocular lens of the left eye (81 microGy). Digital cephalometry resulted in an absorbed dose about 2 times lower than the dose received by the conventional technique. The effective doses had the same relation (conventional 2.3 microSv; digital 1.1 microSv). The results demonstrate that direct-digital cephalometric radiography cuts the patient's dose in half compared with the conventional screen-film technique. Direct-digital cephalometry is more advantageous than the conventional technique from the perspective of radiation protection.