Periapical biomechanics and the role of cyclic biting force in apical retrograde fluid movement

Sphericity of periapical lesion and its relation to the novel CBCT periapical volume index

BACKGROUND

The purpose of this study was to assess the sphericity of periapical lesions and its relation to the cone beam computed tomography periapical volume index (CBCTPAVI).

METHODS

261 periapical lesions were assessed using cone beam computed tomography images from InteleViewer^TM. Three-dimensional analysis of the lesions was conducted using analytical imaging software Mimics Research^TM. Lesion volume and surface area measurements were determined using the semi-automatic segmentation technique and these measurements were then used to determine lesion sphericity and CBCTPAVI score. One-way analysis of variance with post-hoc Tuckey test was used to assess for differences in sphericity among CBCTPAVI groups.

RESULTS

The mean sphericity of periapical lesions was 62%. Periapical lesions with larger CBCTPAVI scores were significantly less spherical than lesions with smaller CBCTPAVI scores.

CONCLUSIONS

Periapical lesions of endodontic origin are mostly semi-spherical in their spread and as CBCTPAVI score increases, sphericity decreases, indicating that larger lesions expand less uniformly compared with smaller lesions. Clinicians should be aware that lesions of increased volume, have less sphericity, and are thus elongated or stretched in one or more anatomical plane. This information will assist clinicians in planning and performing periapical surgery and may aid in differential diagnosis of radiolucent jaw lesions.

Efficacy of different irrigation activation systems on bacterial extrusion

The purpose of this study was to evaluate the quantity of extruded bacteria following with EndoVac, EDDY, EndoActivator (EA) and standard needle irrigation (SNI). Ninety teeth with a single root and canal were included in this study. Fifteen teeth were selected as the negative control group to confirm sterilization. Seventy-five teeth were contaminated with Enterococcus faecalis (E. faecalis) for 4 weeks. Teeth were prepared and divided into five groups (n:15): EndoVac, EDDY, EA, SNI and positive control groups. The extruded bacteria were cultured for bacterial quantification. The counts of extruded bacteria were lower in the EndoVac group compared to the EDDY group (P˂ 0.05). The counts of extrusion bacteria were not different in EA and SNI groups compared to EDDY and EndoVac groups (P > 0.05). Within the limits of this study, EndoVac was found to be more reliable irrigation systems than EDDY in terms of the bacterial extrusion.

Effect of human, dentin, albumin and lipopolysaccharide on the antibacteerial activity of endodontic activity of endodontic irrigants

Context

Human dentin powder (HD), bovine serum albumin (BSA) and endotoxin (LPS) may affect the antimicrobial activity of irrigating solutions.

Aim

To evaluate the inhibitory effect of HD powder, BSA, and LPS on the antibacterial activity of 0.5%, 1%, 2.5%, and 5% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX) gel, BioPure mixture of tetracycline, citric acid, and detergent (MTAD), and QMix.

Methods

The direct contact test against Enterococcus faecalis (ATCC 29212) for 2-min, 30-min and 6-h was used. Sterile pyrogen-free water was the negative control. After experimental periods, a neutralizing agent was used. Colony-forming units were determined by 10-fold serial dilutions and culture on agar plates. Data were analyzed by Kruskal-Wallis and Dunn's test (α = 5%).

Results

In the absence of inhibitors, all irrigants eliminated E. faecalis. In contact with HD, all solutions eliminated E. faecalis within 2-min, with the exception of MTAD. In the presence of BSA, only 5% NaOCl killed E. faecalis within 2-min. LPS did not affect the antibacterial effect of any irrigant. At 30-min and at 6-h, all substances eliminated E. faecalis.

Conclusions

In the presence of albumin, irrigants needed >2-min to eliminate E. faecalis, except for 5% NaOCl. The same was observed in the presence of dentin when E. faecalis was exposed to MTAD.

The biomechanical role of periodontal ligament in bonded and replanted vertically fractured teeth under cyclic biting forces

After teeth are replanted, there are two possible healing responses: periodontal ligament healing or ankylosis with subsequent replacement resorption. The purpose of this study was to compare the fatigue resistance of vertically fractured teeth after bonding the fragments under conditions simulating both healing modes. Thirty-two human premolars were vertically fractured and the fragments were bonded together with Super-Bond C&B. They were then randomly distributed into four groups (BP, CP, CA, BA). The BP and CP groups were used to investigate the periodontal ligament healing mode whilst the BA and CA groups simulated ankylosis. All teeth had root canal treatment performed. Metal crowns were constructed for the CP and CA groups. The BP and BA groups only had composite resin restorations in the access cavities. All specimens were subjected to a 260 N load at 4 Hz until failure of the bond or until 2×10⁶ cycles had been reached if no fracture occurred. Cracks were detected by stereomicroscope imaging and also assessed via dye penetration tests. Finally, interfaces of the resin luting agent were examined by scanning electron microscope. The results confirmed that the fatigue resistance was higher in the groups with simulated periodontal ligament healing. Periodontal reattachment showed important biomechanical role in bonded and replanted vertically fractured teeth.

Antibacterial efficacy of photosensitizer functionalized biopolymeric nanoparticles in the presence of tissue inhibitors in root canal

INTRODUCTION

Application of antibacterial nanoparticles to improve root canal disinfection has received strong interest recently. The current study aims to assess the antibacterial effect of a novel photosensitizer (rose bengal functionalized chitosan nanoparticles [CSRBnp]) to eliminate bacteria in the presence of various root canal constituents that are known to inhibit the antibacterial efficacy of root canal disinfectants.

METHODS

The synthesized CSRBnp were evaluated for size, charge, and singlet oxygen release. The antibacterial effect of CSRBnp was tested on planktonic Enterococcus faecalis with or without pretreatment by using different inhibiting agents such as dentin, dentin-matrix, pulp tissue, bacterial lipopolysaccharides, and bovine serum albumin (BSA). Bacterial survival was assessed in a time-dependent manner. The antibacterial effects after photodynamic activation on CSRBnp, a cationic photosensitizer (methylene blue), and an anionic photosensitizer (rose bengal [RB]) in the presence of inhibitors were also evaluated.

RESULTS

CSRBnp were 60 ± 20 nm in size and showed reduced rate of singlet oxygen release as compared with methylene blue and RB. Pulp and BSA inhibited the antibacterial effect of CSRBnp (without photoactivation) significantly (P < .05) even after 24 hours of interaction. In case of photodynamic therapy, the pulp and BSA significantly inhibited the antibacterial activity of all 3 photosensitizers. CSRBnp showed residual effect and completely eliminated the bacteria after 24 hours of interaction after photodynamic therapy.

CONCLUSIONS

The inherent antibacterial activity of polycationic chitosan nanoparticles and the singlet oxygen released after photoactivation of RB synergistically provided CSRBnp the potential to achieve significant antibacterial efficacy even in the presence of tissue inhibitors within root canals.

Apically extruded debris and irrigant with two Ni-Ti systems and hand files when removing root fillings: a laboratory study

AIM

To compare the amount of apically extruded debris and irrigant produced by two Ni-Ti instruments and hand files when removing root fillings, and to compare two experimental models.

METHODOLOGY

Sixty single straight root canals in human mandibular premolars were prepared with K-files and filled with gutta-percha and AH Plus sealer. The teeth were randomly divided into three groups of 20 for removal of the root filling material with Reciproc files (Group 1, RP), Mtwo retreatment files (Group 2, MR) or hand files (Group 3, H). Each group was then equally divided into experimental subgroups: A, with 1.5% agar gel model (AG); B, with empty tube model (ET). Apically extruded debris and irrigant was quantified by subtracting the initial weight of the test apparatus without a tooth from its weight after the root canal retreatment. Comparative analysis of the amount of apically extruded debris and irrigant for each of the instruments and the experimental models was performed. Time for gutta-percha removal was recorded. Data were statistically analysed using one-way analysis of variance.

RESULTS

Removal of root fillings with two Ni-Ti instruments produced less apically extruded debris and irrigant than hand files in both experimental models (P < 0.05). More apically extruded debris and irrigant was produced with Reciproc files than Mtwo retreatment files using the 1.5% agar gel model (P > 0.05). Significantly more apically extruded debris and irrigant was produced with Reciproc files than Mtwo retreatment files using the empty tube model (P < 0.05). The time required to remove the root fillings followed Reciproc<Mtwo R<hand files (P < 0.05).

CONCLUSIONS

All the instruments produced apically extruded debris and irrigant. The two Ni-Ti instruments produced less apically extruded debris and irrigant than hand files. A 1.5% agar gel can provide resistance to apically extruded debris and irrigant and may represent the clinical situation better than the empty tube model.

Retrograde peri-implantitis

Retrograde peri-implantitis constitutes an important cause for implant failure. Retrograde peri-implantitis may sometimes prove difficult to identify and hence institution of early treatment may not be possible. This paper presents a report of four cases of (the implant placed developing to) retrograde peri-implantitis. Three of these implants were successfully restored to their fully functional state while one was lost due to extensive damage. The paper highlights the importance of recognizing the etiopathogenic mechanisms, preoperative assessment, and a strong postoperative maintenance protocol to avoid retrograde peri-implant inflammation.

An investigation of a potential confounder in ex vivo microbiological studies--the bulk flow of fluid through apical foramina during tooth extraction

AIMS

To investigate the factors affecting bulk flow of dye and bacterial suspensions into and out of apical foramina during simulated tooth extraction, using an ex vivo model.

METHODOLOGY

Sixty extracted, single-rooted, human teeth were accessed, root canals located and in 50 the pulps dissolved; 10 teeth with attached periapical lesions were preserved. The size of apical foramina was determined digitally. The teeth were mounted in vials with polyvinylsiloxane impression material. Part 1: different dyes were inoculated in the coronal half of root canals or cervical 'gingival' margin, respectively, in separate experiments using the same teeth. Tooth extraction movements were simulated and apical penetration of the dye solutions with and without coronal restorations were examined in each case (20 teeth re-used 4 × ). Part 2: the same procedures were repeated on 30 more teeth but using a standard inoculum of Acidovorax sp. Part 3: 10 teeth with attached periapical lesions were inoculated with Acidovorax sp. in the absence of coronal restorations. Bacterial leakage into the periapical lesions was assessed.

RESULTS

Coronal restorations significantly reduced the flow of dyes (P=0.002) or bacterial suspension (P=0.001) out of the canals and bacterial suspension into (P=0.02) the canals during simulated tooth extraction. The 'size of apical foramina' were positively correlated with passage of bacterial suspension out of the canal (P=0.04) and from the gingival trough into the canal (P=0.008), in the presence of a coronal restoration.

CONCLUSIONS

The presence of coronal restorations, the size of apical foramina and presence of native canal contents with attached periapical lesions, all influenced fluid flow into and out of canals during simulated tooth extraction movements.

Enterococcus faecalis-mediated biomineralized biofilm formation on root canal dentinein vitro

Enterococcus faecalis is the most predominant bacteria in teeth with failed root canal therapy and is found to survive harsh conditions prevailing in the root canals of endodontically treated teeth. This study aims to investigate the interaction between E. faecalis and root canal dentine substrate. Towards this end, tooth specimens were prepared and divided into two groups. The tooth specimens in group 1 were incubated with E. faecalis for periods of 2-, 4-, and 6-week intervals and the chemical composition of the biofilm was determined using X-ray diffraction and Fourier transform infrared (FTIR) spectroscopy. The tooth specimens in group 2 were incubated with E. faecalis for a period of 6 weeks and the topography and ultrastructure of the biofilm were examined using scanning electron microscopy (SEM), light microscopy, and laser confocal scanning microscopy. The sediments formed from the bacterial interaction on the dentine (in group 1) were also examined by SEM and FTIR. These experiments highlighted different stages in the interaction of E. faecalis with root canal dentine. Further, a bacterial-induced apatite reprecipitation on mature biofilm was also observed. This ability of E. faecalis to form such calcified biofilm on root canal dentine may be a factor that contributes to their persistence after endodontic treatment.

What We Leave Behind In Root Canals After Endodontic Treatment: Some Issues and Concerns

The benefits of using sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) as endodontic irrigants, and calcium hydroxide as an inter-appointment medicament, are well known to dentists. Many steps undertaken during endodontic treatment and retreatment are rather mechanical in nature, and less attention is committed to understanding the biological issues underlying endodontic treatment and retreatment. It should be noted that dentine is the fundamental substrate in endodontic treatment, and its properties and characteristics are the key determinant of nearly all disease and post-disease processes in the teeth. In this article the effects and counter-effects of NaOCl and EDTA on root canal dentine, and some other related issues are reviewed. This information will enable clinicians to use the beneficial effects of these chemicals, while necessary steps are considered to reduce their harmful effects on dentine substrate.