Irrigating solutions play an important role in the eradication of intracanal microbes and debris dissolution during endodontic treatment. Different combinations of solutions and protocols have been advocated, with sodium hypochlorite (NaOCl), ethylenediamine tetra acetic acid (EDTA), and chlorhexidine (CHX) remaining the most widely used ones by many clinicians. Although these solutions provide efficient inorganic dissolution and antimicrobial capacity, their use has also been reported to cause undesired effects on root dentin composition and mechanical and biomechanical properties, such as microhardness, surface roughness, bond strength, and matrix metalloproteinase (MMP) activity. Several corroborating studies attribute these changes in mechanical properties of dentine to the use of irrigating solutions, and there are limited reports on how the solutions affect the expression of MMPs, which may be a correlating link to understanding the role of these enzymes in dentin collagen and changes in the mechanical properties of dentin. Hence, using the basis of several studies from the literature, the objective is to comprehensively review the influence of individual and combined irrigating solutions on root dentine structure and the activity of the MMPs.

Aim: To compare two flat‐side single‐file rotary instruments with three single‐file reciprocating systems through a multimethod assessment.Methodology: A total of 290 new NiTi single‐file rotary (AF F One Blue 25/0.06 and Platinum V.EU 25/0.06) and reciprocating (One Files Blue R25, Reciproc Blue R25, Reciproc R25) instruments were selected, carefully examined for any major deformations, and evaluated regarding their macroscopic and microscopic design, nickel and titanium elements ratio, phase transformation temperatures, and mechanical performance (time/rotation to fracture, maximum torque, angle of rotation, microhardness, maximum bending, and buckling strengths). One‐way anova post hoc Tukey, T‐test, and nonparametric Mood's median tests were used for statistical comparisons (α = 5%).Results: Tested instruments had identical blade counts and near‐identical helical angles of approximately 24° (rotary instruments) and 151° (reciprocating instruments). The flat‐side analysis revealed a few inconsistencies, such as discontinuity segments, different orientations, and gaps in the homogeneity of the bluish colour. Microscopically, flat‐side instruments exhibited blade discontinuity and an incomplete S‐shaped cross‐section. The surface finish was smoother for One Files Blue and more irregular for both rotary instruments. There were distinct phase transformation temperatures amongst all instruments. All heat‐treated instruments were in R‐phase arrangement, and Reciproc was in R‐phase plus austenite at test temperature (20°C). Compared with the reciprocating instruments, both flat‐side instruments exhibited lower results in the cyclic fatigue tests using two different clockwise kinematics, maximum torque, angle of rotation, and maximum buckling strength (p < .05). The rotary systems also exhibited low flexibility (p < .05). AF F One Blue had the lowest microhardness, whilst Reciproc had the highest value.Conclusion: This multimethod investigation revealed that the flat‐side rotary instruments underperformed the reciprocating instruments regarding cyclic fatigue (with two different clockwise kinematics), maximum torque, angle of rotation, maximum buckling strength, and flexibility. Manufacturing inconsistencies were also observed in some of the flat‐side instruments, including discontinuity segments, different orientations, and in the homogeneity of their bluish colour given by the heat treatment.

The loss of periodontal tissue support and vertical buccal bone loss in apico-marginal defects can often be mistaken for features indicative of vertical root fractures and this study reports thirteen cases with persistent symptomatic apical periodontitis, apico-marginal defects, and large periapical lesions that were managed with endodontic microsurgery in conjunction with bone grafts and barrier placements with a follow-up period of up to 9 years. At the recall sessions, all cases were asymptomatic with radiographical success with only 2 cases exhibiting residual apical radiolucency, but with evident reduction in the lesion size, indicative of healing. This study highlights the potential of utilizing endodontic microsurgery combined with guided tissue regeneration that proved effective in stimulating the regeneration of periodontal tissue in cases of apico-marginal defects that can lead to favourable long-term outcomes.