What Is the Microbial Profile in Persistent Endodontic Infections? A Scoping Review.

INTRODUCTION: This scoping review aimed to map the evidence about the microbiota found in persistent endodontic infections. METHODS: The study protocol was prospectively registered and is available at https://osf.io/3g2cp. The electronic search was performed in MEDLINE via PubMed, Lilacs, BBO, Scopus, Web of Science, Cochrane Library, and Embase. The eligibility criteria were based on the PCC acronym, where P (Population) represents patients with teeth presenting persistent endodontic infection, C (Concept) represents microbial profile, and C (Context) represents undergoing endodontic retreatment. Clinical studies that evaluated the microbial profile of samples collected from root canals of teeth undergoing retreatment, using classical or molecular methods, were included. Studies that did not show a minimum period of 1 year between primary endodontic treatment and retreatment or did not radiographically evaluate the quality of primary root canal filling were excluded. Two reviewers independently selected the articles and collected data. RESULTS: From a total of 957 articles, 161 were read in full, and 32 studies were included. The most prevalent species were Enterococcus faecalis, Parvimonas micra, Porphyromonas endodontalis, Porphyromonas gingivalis, Prevotella intermedia, Dialister invisus, Propionibacterium acnes, Tannerella forsythia, and Treponema denticola. Cases with symptomatology or inadequate root canal filling presented an increase in specific bacterial species compared to those with no symptomatology or adequate filling. A greater number of microorganisms was observed in teeth with inadequate coronal restoration compared to those with adequate restoration. CONCLUSIONS: Persistent endodontic infections have a polymicrobial profile identified by the commonly used methods for bacterial detection/identification and are subject to the limitations present in each of those methods.

Influence of variations in the environmental pH on the solubility and water sorption of a calcium silicate-based root canal sealer.

AIM: To evaluate the influence of pH variation on the solubility and water sorption of a premixed calcium silicate-based root canal sealer (EndoSequence BC Sealer) compared to the gold standard based on epoxy resin (AH Plus Jet) after immersion in distilled water and phosphate-buffered saline (PBS). METHODOLOGY: Solubility and water sorption were evaluated after immersion in distilled water or PBS at several pHs (5, 7 and 12) and the values were calculated as percentages of the original mass after 24 h, 7 and 30 days of immersion. The crystalline structures present in the sealers and surface precipitates were assessed by X-ray diffraction. The Shapiro-Wilk's test revealed that data were normally distributed; thus, statistical analysis was performed using one-way anova and Tukey's tests or independent t-test, assuming a 5% α-error. RESULTS: EndoSequence BC Sealer was associated with significantly greater water sorption and solubility compared to AH Plus Jet in all tested conditions (P < 0.05). The acid environment increased the 24 h solubility of EndoSequence BC Sealer immersed in PBS (P < 0.05) and did not induce significative changes in the water sorption (P > 0.05). Alkaline pH reduced the solubility of EndoSequence BC Sealer and increased that of AH Plus Jet at all experimental times and soaking media (P < 0.05). Alkaline environment also significantly increased the water sorption of AH Plus Jet immersed in PBS (P < 0.05). Immersion in PBS significantly reduced the solubility of EndoSequence BC Sealer and significantly increased that of AH Plus Jet (P < 0.05). Precipitates on the surface of EndoSequence BC Sealer corresponding to hydroxyapatite and calcium carbonate were detected after immersion in PBS at pH 5 and 7 for 30 days. CONCLUSIONS: EndoSequence BC Sealer had significantly greater solubility and water sorption than AH Plus Jet. Although the alkaline pH and soaking media directly influenced the solubility and water sorption of the sealers, the solubility of AH Plus Jet remained within the limits recommended by ISO 6876, whilst the solubility of the EndoSequence BC Sealer did not comply with ISO recommendations in all the conditions tested.

Influence of ultraconservative access cavities on instrumentation efficacy with XP-endo Shaper and Reciproc, filling ability and load capacity of mandibular molars subjected to thermomechanical cycling.

AIM: To evaluate the influence of ultraconservative access cavities (UltraAC) on canal shaping and filling ability and load capacity of mandibular molars after root canal preparation with XP-endo Shaper (XP) or Reciproc (RC), under simulated clinical conditions. Traditional access cavities (TradAC) were used for comparison. METHODOLOGY: Forty extracted mandibular molars were scanned by micro-computed tomographic and, based on similar anatomical features, were divided into four groups (n = 10), according to the type of access cavity and canal instrumentation protocol: TradAC/RC, TradAC/XP, UltraAC/RC and UltraAC/XP. All root canal procedures were performed with the teeth placed in a dental mannequin. Teeth were scanned after root canal instrumentation and filling. Unprepared canal area, dentine removed, accumulated hard tissue debris (AHTD), canal transportation, presence of voids and filling material remnants within the pulp chamber were analysed. After restorative procedures, the teeth were subjected to thermomechanical cycling and to a load capacity test. Statistical analyses were performed using two-way anova test, considering the randomized blocks design (P < 0.05). RESULTS: The percentage of unprepared canal area was significantly lower in TradAC groups when compared to UltraAC groups (P < 0.05), regardless of the instrument used. The UltraAC/XP group had significantly lower percentage of root dentine removed when compared to other groups (P < 0.05). UltraAC/XP and TradAC/XP groups had significantly lower percentages of AHTD than UltraAC/RC and TradAC/RC groups (P < 0.05). Regarding canal transportation, in the MB root canals, the TradAC/XP group had significantly lower values than other groups (P < 0.05). In general, in ML and distal root canals, TradAC/XP and UltraAC/XP groups had significantly lower values of canal transportation when compared to other groups (P < 0.05). Moreover, the UltraAC/RC had the greatest canal transportation values in MB and distal canals. The UltraAC groups had significantly greater percentages of voids and volume of remaining root filling material within the pulp chamber after cleaning procedures than TradAC groups (P < 0.05). There was no difference in the load capacity amongst groups (P < 0.05). CONCLUSION: The UltraAC/XP and UltraAC/RC groups had significantly greater areas of unprepared canal walls, significantly more voids and volume of root filling material remnants within the pulp chamber after canal filling. UltraAC/XP was associated with significantly less root dentine removal and significantly more AHTD whilst TradAC/XP had overall significantly less canal transportation. No differences were observed in the load capacity amongst groups.

Preserving dentine in minimally invasive access cavities does not strength fracture resistance of restored mandibular molars.

AIM: To evaluate the correlation between the volume of dental hard tissues removed and the fracture resistance of mandibular molar teeth with ultraconservative (UltraAC) or traditional (TradAC) access cavity preparations. METHODOLOGY: Sixty recently extracted and intact mandibular first molars were scanned in a microcomputed tomographic (micro-CT) device, anatomically matched and assigned at random to 2 groups (n = 30), according to the access cavity type: UltraAC or TradAC. After access preparation, mesial and distal canals were prepared using Reciproc instruments and a new scan was taken. The volumes of pulp chamber and dental hard tissues in each specimen were measured before and after the experimental procedures, and the percentage volume reduction of hard tissues calculated for the entire tooth and for the crown separately. Teeth were then root filled, restored and subjected to fracture resistance tests in an universal testing machine. The force required to fracture was recorded in Newtons (N). The adherence of the variables to a Gaussian curve was verified using a Shapiro-Wilk test. Skewed data were analysed with nonparametric Wilcoxon signed rank or Spearman correlation tests, whilst the normally distributed data were analysed with a dependent samples Student t-test. Level of significance was set at 5%. RESULTS: Pre-operatively, no difference was observed between groups regarding the volume of pulp canal space or dental hard tissues (P > 0.05). After access preparation, volumes of the removed hard tissues from the entire tooth and from the crown were significantly greater in teeth prepared with TradAC than with UltraAC (P < 0.05). No significant difference was observed in the fracture resistance values between TradAC (902.9 ± 347.8 N) and UltraAC (948.7 ± 405.7 N) groups (P = 0.975). The Spearman test was unable to identify a correlation between fracture resistance and percentage volume of removed dental hard tissues in the entire root (P = 0.525, r = -0.084) or only in the crown (P = 0.152, r = -0.187). CONCLUSION: The volume of hard dental tissues removed, although greater in teeth with TradAC compared to UltraAC, did not correlate with the fracture resistance results, indicating that a minimally invasive access cavity did not increase the resistance of restored mandibular first molars to fracture.

The influence of endodontic access cavity design on the efficacy of canal instrumentation, microbial reduction, root canal filling and fracture resistance in mandibular molars.

AIM: To assess the impact of conservative endodontic access cavities (CEC) and truss access cavities (TAC) during root canal treatment performed on mandibular molars in terms of: ability to shape and fill root canals, microbial reduction in canals, and cleaning of the pulp chamber. In addition, the fracture resistance of the teeth after coronal restoration was assessed. Traditional endodontic cavities (TEC) were used as a reference technique for comparison. METHODOLOGY: Thirty extracted intact mandibular molars were scanned in a microcomputed tomography device (micro-CT), matched based on similar anatomical features and assigned to TEC, CEC or TAC groups (n = 10). The specimens were accessed accordingly, and root canals were contaminated with bacterial suspensions of Enterococcus faecalis (21 days). Subsequently, the first microbial sample was collected from root canals (S1). The canals were initially prepared with Reciproc Blue R25 instrument followed by a second instrumentation using Reciproc Blue R40. Eight mL of 0.5% NaOCl were used as an irrigant for each instrument. A final irrigation protocol was performed with 2 mL of 0.5% NaOCl, 2 mL of 17% EDTA and another 2 mL of 0.5% NaOCl. Microbial samples were collected from root canals after R25 (S2), R40 (S3) and final irrigation (S4). The teeth were rescanned after S4. Then, root canals were filled, rescanned, restored and the teeth subjected to fracture resistance tests. The statistical analysis was performed with type I negative binomial and beta 0-1 inflation regression models for microbiological analysis. Instrumentation, filling and resistance to fracture results were subjected to anova and Tukey tests (P < 0.05). RESULTS: S4 revealed no significant variations in microbial reduction amongst the groups (P > 0.05). TEC had a significantly lower percentage of unprepared surface area than CEC (P < 0.05). No differences were found regarding the percentage of dentine removed, transportation, centring ability and filling voids amongst the groups (P > 0.05). The TEC group had a significantly lower volume of remaining root filling material within the pulp chamber than CEC and TAC groups (P < 0.05). There was no difference regarding fracture resistance amongst the groups (P > 0.05). CONCLUSION: Conservative access cavities did not offer any advantage in comparison with the traditional endodontic cavities in any of the parameters considered. Furthermore, conservative methods were associated with larger percentages of unprepared canal surface area and larger volumes of remaining root filling material within the pulp chamber.

The impact of minimally invasive root canal preparation strategies on the ability to shape root canals of mandibular molars.

AIM: To evaluate the use of a reduced taper endodontic instrument system (Bassi Logic™ .03 taper) and expandable heat-treated system (XP-endo Shaper) on the ability to shape canals in mandibular molars, by means of microcomputed tomography (micro-CT) analysis. The Reciproc system was used as the reference for comparison. METHODOLOGY: Twenty-four mandibular molars were scanned in a micro-CT, matched based on similar anatomical features and sorted into three groups (n = 8 per group), according to root canal preparation system: Bassi Logic™ .03, XP-endo Shaper and Reciproc. The teeth were mounted onto a mannequin and the pulp chambers were accessed with traditional access cavities. In Bassi Logic™ .03 and Reciproc groups, mesial canals were prepared with size 25, .03 taper or R25 (size 25, .08v taper) instruments and the distal root canal with size 25, .03 taper and size 40, .03 taper or R25 and R40 (size 40, .06v taper), respectively. In XP-endo Shaper groups, all root canals were prepared with XP-endo Shaper (size 30, .04v taper). After root canal preparation, the teeth were rescanned. The percentage of untouched canal areas and the percentage of removed dentine were evaluated separately for mesial and distal root canals. The data were analysed using one-way anova and Tukey tests (P < 0.05). RESULTS: The Bassi Logic™ .03 group was associated with a greater percentage of untouched canal areas when compared to XP-endo Shaper and Reciproc groups for mesial and distal root canals (P < 0.05), but no differences were found between XP-endo Shaper and Reciproc groups (P > 0.05). No significant difference was observed in the percentage of dentine removed amongst the groups for mesial and distal root canals (P > 0.05). CONCLUSION: The use of a reduced taper system (Bassi Logic™ .03) during root canal preparation resulted in a greater percentage of untouched canal areas when compared to XP-endo Shaper and Reciproc instruments. No differences were observed amongst the systems regarding the percentage of dentine removed.

A laboratory study of the impact of ultraconservative access cavities and minimal root canal tapers on the ability to shape canals in extracted mandibular molars and their fracture resistance.

AIM: To evaluate the influence of ultraconservative endodontic access cavities (UEC) and the use of instruments with various tapers (.03 or .05) and tip diameters (25 or 40) on the ability to shape canals in mandibular molars and their fracture resistance in comparison with traditional endodontic access cavities (TEC). METHODOLOGY: Thirty-two intact extracted mandibular molars were scanned in a micro-computed tomography device, matched based on similar anatomical features and assigned to UEC or TEC groups and to subgroups according to mechanical canal preparation with Bassi Logic™ rotary NiTi instruments with .03 or .05 taper (n = 8 per group). The teeth were mounted onto a mannequin head, and the pulp chambers were accessed and the root canals subjected to instrumentation. In the first stage, size 25 endodontic instruments were used, with .03 or .05 tapers. The teeth were re-scanned. Subsequently, a second canal instrumentation was performed with the size 40 instruments with .03 or .05 tapers and scanned again. The root canals were filled and then the teeth restored before being subjected to fracture resistance tests. The data on untouched canal areas, canal transportation, centring ability, the percentage of removed dentine and maximum load at fracture were analysed. One-way anova and Tukey's tests were performed for inter-group analysis. The paired-samples t-test was performed on the results between size 25 and size 40 apical preparations for each individual specimen (P < 0.05). RESULTS: No significant difference was observed for the percentage of untouched canal area when comparing UEC and TEC groups or between the .03 and .05 tapers with the same instrument tip size (P > 0.05). There was a significantly lower percentage of untouched canal area after instrumentation with size 40 instruments when compared to size 25 (P < 0.05). No significant difference in the percentage of dentine removed was observed between the access cavities or the different tapers (P > 0.05). Size 40 apical preparations removed significantly more dentine than size 25 preparations (P < 0.05). No significant differences were observed in canal transportation, centring ability and fracture resistance in any of the tested groups (P > 0.05). CONCLUSIONS: Ultraconservative endodontic access cavities did not offer any advantages in comparison with traditional endodontic access cavities on the ability to shape canals, nor the fracture resistance of mandibular molars. No differences were observed in shaping ability and fracture resistance between .03 and .05 taper canal preparations. Apical preparation with larger instruments resulted in significantly less untouched canal area in all groups.