Effects of citric acid and EDTA conditioning on exposed root dentin: An immunohistochemical analysis of collagen and proteoglycans

The effect of different conditioning agents on dentin roughness and collagen structure

OBJECTIVES

To assess the impact of various organic and inorganic acids on the roughness, demineralization, and collagen secondary structures of human dentin and to compare these effects with those of traditional agents, specifically phosphoric acid (PA) and ethylenediaminetetraacetic acid (EDTA).

METHODS

Coronal dentin discs (n = 10) were examined by optical profilometry (roughness) and ATR-FTIR before and after conditioning with 32 % PA, 3 % nitric acid (NA), 20 % citric acid (CA), 20 % phytic acid (IP6) or 17 % EDTA. Spectra data were processed to quantify dentin demineralization (DM%) and percentage area of amide I curve-fitted components of β-turns, 310-helix, α-helix, random coils, β-sheets, and collagen maturation index. Statistical analysis was performed by one-way ANOVA or Kruskal-Wallis for DM% and roughness parameters, and paired t-test/Wilcoxon test for amide I components at significance level set at α = 0.05.

RESULTS

All treatments resulted in increased roughness parameters, with the most significant changes occurring primarily with PA, while EDTA exhibited the least changes. DM% was NA>PA>IP6>CA>EDTA in a descending order. Regarding amide I components, NA demonstrated a significant reduction in β-turns, 310-helices, and α-helices and it increased β-sheets and random coils. PA resulted in reduction in β-turns and α-helices while it increased β-sheets. CA and EDTA did not cause significant changes. The collagen maturation index significantly increased only after IP6 treatment.

CONCLUSIONS

The effect on dentin roughness parameters, demineralization, and collagen secondary structures varied based on the type of dentin surface treatment.

CLINICAL SIGNIFICANCE

Understanding the impact of acids on the intrinsic properties of dentin is clinically essential for gaining insights into how these effects influence adhesion to dentin, the long-term stability of resin-based restorations, and the success of remineralization therapies.

Effect of experimental dentin etchants on dentin bond strength, metalloproteinase inhibition, and antibiofilm activity

OBJECTIVE

this study evaluated dentin microtensile bond strength (µTBS) and failure modes (at 24 h and one year), bonding interface regarding hybridization, surface morphology regarding demineralization, in situ metalloproteinase (MMP) activity, and antibacterial effect of three dentin etchants compared to 35% phosphoric acid (PA).

MATERIALS AND METHODS

The Adper Single Bond 2 adhesive (3 M Oral Care) was applied on moist dentin etched with PA (control) or on air-dried dentin etched with 3% aluminum nitrate + 2% oxalic acid (AN), 6.8% ferric oxalate + 10% citric acid (FO), or 10% citric acid (CA). The µTBS test used 40 human teeth (n = 10). Failure modes and surface morphology were analyzed by scanning electron microscopy (n = 3), while bonding interface morphology and MMP activity were evaluated by laser scanning confocal microscopy (n = 3). Antibacterial activity was evaluated against S. Mutans biofilm by means of viable cells count (CFU/mL).

RESULTS

PA presented the highest bond strengths regardless of aging time. PA, AN, and CA showed stable bond strengths after one year of storage. Adhesive and mixed failures were predominant in all groups. Thin hybrid layers with short resin tags were observed for the experimental etchants. The AN-based etchant was able to inhibit MMP activity. All tested etchants presented antibacterial activity against S. Mutans biofilm.

SIGNIFICANCE

This study suggests different dentin etchants capable of inhibiting MMP activity while also acting as cavity disinfectants.

Approaches to minimize tooth staining associated with silver diamine fluoride: A systematic review

OBJECTIVE

To the effectiveness of different strategies to overcome silver diamine fluoride (SDF)-mediated tooth staining.

MATERIALS AND METHODS

Four online databases (PubMed, ScienceDirect, Scopus, and Web of Science) were searched using different MeSH terms and Boolean Operators to retrieve the articles (until June 2021), followed by a hand-search of the reference list of the included articles. All full-text, original studies in English that evaluated SDF staining and at least one SDF modification/alternative were included.

RESULTS

Among the assessed studies, nine studies explored the stain-minimization effect of potassium iodide (KI) post-application following SDF treatment. Among these, eight concluded that KI application after SDF treatment significantly reduced tooth staining, while one showed marginal staining following glass ionomer restoration of the SDF-treated dentine. Additionally, one study applied potassium fluoride (KF) and silver nitrate (AgNO₃ ) concurrently to mitigate SDF-mediated staining. One study compared SDF staining with polyethylene glycol (PEG)-coated nanoparticles containing sodium fluoride (NaF), and another used nanosilver fluoride (NSF) for staining comparison with SDF.

CONCLUSIONS

Within the limitations of this study, the addition of different materials to SDF has proven to be a beneficial strategy for overcoming tooth staining associated with SDF. Future studies are warranted, particularly clinical trials, to validate these findings.

CLINICAL SIGNIFICANCE

SDF-mediated tooth staining is a serious concern that limits its clinical use. A review of various strategies to overcome this problem will help clinicians enhance its clinical use and patient acceptance.

Combined Surgical and Restorative Procedures to Treat Maxillary Canine with Gingival Recession and Cervical Wear

Introduction

Gingival recession (GR) with cervical tooth wear is a major concern for patients on the prominent maxillary canines, from both esthetic and dentine hypersensitivity points of view. Hypersensitivity could be treated nonsurgically; however, esthetics remain the major patients' concern that mostly requires surgical intervention for covering the denuded root surface. Several surgical procedures are applied successfully for covering single and multiple gingival recession; however, these procedures are sensitive procedures and not always predictable. Semilunar coronally repositioned flap (SCRF) is a very simple procedure that found to be very predictable for covering a single recession in presence of sufficient keratinized gingiva apical to the recession. The procedure provides better clinical outcome by involving less adjacent papillary tissue that maintains greater blood supply and achieves maximum flap stability with mattress sutures with minimal postoperative complications. Therefore, this case report is aimed at explaining the simplicity of this surgical procedure in the presence of wide keratinized tissue around the recession and starting the restorative procedure after a sufficient soft tissue healing period. Case Presentation. 42-year-old systemically healthy female patient referred with a single wide gingival type 1 (RT1) and cervical wear around tooth #43. A semilunar coronally repositioned flap was released and advanced coronally to cover the denuded root totally; then, the flap stabilized by three mattress sutures, and complete root coverage was achieved. Six months later, the cervical lesion was restored with composite filling material. Sixteen-month and 32-month postoperative follow-up revealed full coverage of the denuded root surface with firm stable gingiva; later, the gingiva in the area looked stable and healthy.

Conclusion

Using SCRF in treating RT1 recession in the presence of wide keratinized gingiva is very promising surgical intervention for receded root coverage that requires less technical skill.

Evaluation of antimicrobial photodynamic therapy with acidic methylene blue for the treatment of experimental periodontitis

OBJECTIVE

To investigate the security and effectiveness of antimicrobial photodynamic therapy (aPDT) with a citric acid-based methylene blue (MB) on the periodontal repair following the treatment of ligature-induced experimental periodontitis (EP) in rats.

MATERIAL AND METHODS

Were used 120 male rats, randomly divided into 4 experimental groups (n = 30): no treatment (NT), SRP alone (SRP), SRP plus aPDT using conventional MB pH 7.0 (aPDT-pH7), SRP plus aPDT using acidic MB pH 1.0 (aPDT-pH1). EP was induced at day 0 by the placement of a ligature around the mandibular left first molars. Ten animals per group/period were euthanized at 14, 22 and 37 days. Histopathological, histometric (percentage of bone in the furcation [PBF]) and immunohistochemical (for tartrate-resistant acid phosphatase [TRAP] and osteocalcin [OCN]) analyses were performed. Data were statistically analyzed.

RESULTS

aPDT-pH1 showed the highest PBF as compared with the other treatments. Collectively, tissues' reaction to both dyes were controlled and healthy for the periodontium. Both aPDT protocols reduced the extent and intensity of the local inflammatory response, reduced the alveolar bone resorption, and promoted a better structural arrangement of the connective tissue as compared with SRP. TRAP expression was downregulated while OCN expression was upregulated by aPDT as compared with SRP alone.

CONCLUSION

Our data implicate that the novel MB pH 1.0 is as safe as the conventional MB for use in aPDT and raises its additional benefit of increasing the amount of alveolar bone in the furcation.

Blood clot stabilization after different mechanical and chemical root treatments: a morphological evaluation using SEM

Purpose

This in vitro study was conducted to evaluate the effects of different debridement techniques and conditioning procedures on root surface morphology and blood clot stabilization.

Methods

Two debridement techniques (curette [CU] vs. high-speed ultrasound [US]) and 2 conditioning procedures (ethylenediaminetetraacetic acid [EDTA] and phosphoric acid [PA]) were used for the study. Seven experimental groups were tested on root surfaces: 1) no treatment (C); 2) CU; 3) US; 4) CU+EDTA; 5) US+EDTA; 6) CU+PA; and 7) US+PA. Three specimens per group were observed under scanning electron microscopy (SEM) for surface characterization. Additional root slices received a blood drop, and clot formation was graded according to the blood element adhesion index by a single operator. Data were statistically analyzed, using a threshold of P<0.05 for statistical significance.

Results

The C group displayed the most irregular surface among the tested groups with the complete absence of blood traces. The highest frequency of blood component adhesion was shown in the CU+EDTA group (P<0.05), while no differences were detected between the CU, US+EDTA, and CU+PA groups (P<0.05), which performed better than the US and US+PA groups (P<0.05).

Conclusions

In this SEM analysis, EDTA and conventional manual scaling were the most efficient procedures for enhancing smear layer removal, collagen fiber exposure, and clot stabilization on the root surface. This technique is imperative in periodontal healing and regenerative procedures.

The concentration of citric acid as dental root conditioner influences the behavior of fibroblasts from human periodontal ligament

OBJECTIVE

This study investigated the behavior of fibroblasts from human periodontal ligament (hPLF) cultured on dental roots subjected to different protocols of citric acid conditioning.

MATERIALS AND METHODS

32 human teeth extracted due to advanced periodontal disease provided 63 radicular fragments, which were randomly divided in groups according to the treatment given to the surface: rinsing with saline solution for 90 s (C), 10 % citric acid (CA10), or 50 % citric acid (CA50). The treatments were applied during 90 s, 120 s and 180 s (n = 9). hPLF were cultured for 24, 48 and 72 h (n = 3) on the treated samples and analyzed by scanning electron microscopy (SEM) for surface area covered by cells and dentinal tubules widening.

RESULTS

Excepting group C, all the other groups showed almost complete coverage of root surface by hPLF with time. At 24 h of cell culture, the largest area of coverage was seen in the samples treated with CA10-90 (98 ± 0.89 %) at 24 h of cell culture and this difference was significant (p < 0.05) in comparison to CA10-180 (84.04 ± 5.01 %), CA50-90 (63.28 ± 12.46 %), CA50-180 (56.59 ± 8.76 %) and C (0.06 ± 0.11 %). In all the other comparisons, there was no statistically significant differences between CA10 and CA50 (p > 0.05). Cells grown on surfaces treated with CA10 were more spread and flatten than in the CA50 specimens.

CONCLUSIONS

Periodontally compromised roots surfaces conditioned with 10 % citric acid for 90 s resulted in better substrate for hPLF proliferation, in initial periods of culture than 50 % citric acid. The enlargement of the dentinal tubules did not seem to be influenced by the acid concentration.

Role of proteoglycans on the biochemical and biomechanical properties of dentin organic matrix

OBJECTIVE

Proteoglycans (PGs) are multifunctional biomacromolecules of the extracellular matrix of collagen-based tissues. In teeth, besides a pivotal regulatory role on dentin biomineralization, PGs provide mechanical support to the mineralized tissue and compressive strength to the biosystem. This study assessed enzymatic protocols for selective PGs removal from demineralized dentin to determine the roles of these biomacromolecules in the bulk mechanical properties and biostability of type I collagen.

METHODS

Selective removal of glycosaminoglycans chains (GAGs) and PGs from demineralized dentin was carried out by enzymatic digestion protocols using chondroitinase ABC (c-ABC) and trypsin (Try). A comprehensive study design included assessment of dentin matrix mass loss, biodegradability of the PGs/GAGs-depleted dentin matrix, ultimate tensile strength (UTS) and energy to fracture tests. Quantitative data was statistically analyzed by two-way and one-way ANOVA followed by the appropriate post hoc tests (α=0.05).

RESULTS

Transmission electron microscopy images show effective GAGs removal by c-ABC and Try and both enzymatic methods released statistically similar amounts of GAGs from the demineralized dentin. Try digestion resulted in about 25% dentin matrix mass loss and increased susceptibility to collagenolytic digestion when compared to c-ABC (p=0.0224) and control (p=0.0901). Moreover, PGs digestion by Try decreased the tensile strengths of dentin. Statistically lower energy to fracture was observed in c-ABC-treated dentin matrix.

CONCLUSIONS

GAGs plays a pivotal role on tissue mechanics and anisotropy, while the core protein of PGs have a protective role on matrix biostability.

Bone demineralization with citric acid enhances adhesion and spreading of preosteoblasts

BACKGROUND

Previous studies have demonstrated that bone demineralization can improve consolidation in bone grafts. The biologic mechanisms underlying this phenomenon remain unclear.

METHODS

Twelve adult male guinea pigs were used in this experiment. Forty-five bone samples removed from the calvaria of nine animals were divided in groups (n = 9) according to the time of demineralization with citric acid (50%, pH 1): 15, 30, 90, and 180 seconds and non-demineralized samples (control). Preosteoblasts (MC3T3-E1) were cultured on the bone samples for 24, 48, and 72 hours (n = 3). Fifteen samples removed from the remaining three animals were analyzed by scanning electron microscopy/energy dispersive spectrometry (SEM/EDS) after demineralization (n = 3).

RESULTS

The number of preosteoblasts increased significantly with time in all groups. The bone surface area covered by these cells increased with time, except in the control group. Intragroup differences occurred between 24 and 72 hours (P < 0.05). Samples demineralized for 30 seconds showed greater area covered by preosteoblast cells than for the other times of demineralization in all periods of cell culture (P < 0.05) without a statistically significant difference compared with 15 seconds. SEM/EDS showed diminished content of calcium (Ca) after 15 seconds of demineralization, but the Ca content increased after 180 seconds of demineralization (P < 0.05). The phosphorus (P) amount increased significantly only after 30 seconds of demineralization (P < 0.5). The sulfur (S) content was increased in demineralized samples in relation to non-demineralized ones, reaching the highest level after 90 seconds, when the difference became significant in relation to all the other times of demineralization (P < 0.05). Magnesium (Mg) content did not differ significantly between demineralized and non-demineralized samples.

CONCLUSIONS

Bone surfaces demineralized for 30 seconds increased the spreading of preosteoblasts as well as the surface area covered by these cells. Bone demineralization deserves to be studied in periodontal and maxillofacial regenerative procedures.

The effect of MTAD, an endodontic irrigant, on fibroblast attachment to periodontally affected root surfaces: A SEM analysis

BACKGROUND

Root surface debridement (RSD) is necessary to create an environment suitable for reattachment of the periodontium. Root surface conditioning may aid the formation of a biocompatible surface suitable for cell reattachment. BioPure™ MTAD (mixture of Doxycycline, citric acid and a detergent) is an endodontic irrigant with antibacterial properties and the ability to remove smear layer. It was hypothesized that MTAD may be useful for root surface conditioning. The efficacy of MTAD as a conditioner was measured by examining fibroblast attachment to root surfaces.

MATERIALS AND METHODS

Thirty-two specimens of human teeth with advanced periodontal disease were used. The surfaces were root planed until smooth. Half of the specimens were treated with 0.9% saline and the other samples with Biopure MTAD. As a negative control group, five further samples were left unscaled with surface calculus. Human gingival fibroblast cells HGF1-PI1 were cultured and poured over the tooth specimens and incubated. After fixation, the samples were sputter-coated with gold and examined with a SEM. The morphology and number of attached, fixed viable cells were examined. The data was analysed using the Mann-Whitney-U statistical test.

RESULTS

There was no significant difference between the numbers of attached cells in the experimental group treated with MTAD and the control group treated with saline. Little or no attached cells were seen in the negative control group.

CONCLUSION

RSD created an environment suitable for cell growth and attachment in a laboratory setting. The use of MTAD did not promote the attachment and growth of cells on the surface of human roots following RSD.

Influence of concentration, time and method of application of citric acid and sodium citrate in root conditioning

Objective

The aim of this study was to establish the parameters of concentration, time and mode of application of citric acid and sodium citrate in relation to root conditioning.

Material and Methods

A total of 495 samples were obtained and equally distributed among 11 groups (5 for testing different concentrations of citric acid, 5 for testing different concentrations of sodium citrate and 1 control group). After laboratorial processing, the samples were analyzed under scanning electron microscopy. A previously calibrated and blind examiner evaluated micrographs of the samples. Non-parametric statistical analysis was performed to analyze the data obtained.

Results

Brushing 25% citric acid for 3 min, promoted greater exposure of collagen fibers in comparison with the brushing of 1% citric acid for 1 minute and its topical application at 1% for 3 min. Sodium citrate exposed collagen fibers in a few number of samples.

Conclusion

Despite the lack of statistical significance, better results for collagen exposure were obtained with brushing application of 25% citric acid for 3 min than with other application parameter. Sodium citrate produced a few number of samples with collagen exposure, so it is not indicated for root conditioning.

Effects of citric acid and EDTA on periodontally involved root surfaces: a SEM study

AIM

Root debridement by scaling and root planing may not completely remove contaminated cementum particularly in more apical areas. The smear layer formed during root planing inhibits cell migration and attachment leading to impaired marginal periodontal healing. The present study was done to compare the morphological effects of root surface demineralization using citric acid and EDTA as root-conditioning agents.

MATERIALS AND METHODS

Thirty fragments of human dental roots previously exposed to periodontal disease were scaled and randomly divided into the following groups of treatment: Group I: Hand instrumentation and conditioning with normal saline for 5 minutes as control; group II: Hand instrumentation and conditioning with citric acid (pH 1) for 5 minutes and group III: Hand instrumentation and conditioning with EDTA (pH-7.4) for 5 minutes. Scanning electron microscopy was used to check for the presence of residual smear layer and for measuring the number and area of exposed dentin tubules.

RESULTS

The mean efficacy of smear layer removal was compared between groups I and II, groups I and III and groups II and III, it was found to be statistically significant at 5%. When the mean diameter of the dentinal tubules and mean total surface area occupied by the dentinal tubule orifices was compared between groups II and III it was found to be statistically significant at 1% level of significance.

CONCLUSION

Citric acid causes greater degree of morphological alterations than EDTA and is considered to be a better root-conditioning agent. However, the use of EDTA cannot be ruled out.

CLINICAL SIGNIFICANCE

This study supports the hypothesis that demineralizing agents can be used as an adjunct to the periodontal treatment aiming at restoring the biocompatibility of roots and helps in choosing an appropriate agent for root conditioning.

Comparison among four commonly used demineralizing agents for root conditioning: a scanning electron microscopy

Dental roots that have been exposed to the oral cavity and periodontal pocket environment present superficial changes, which can prevent connective tissue reattachment. Demineralizing agents have been used as an adjunct to the periodontal treatment aiming at restoring the biocompatibility of roots.

OBJECTIVE

This study compared four commonly used demineralizing agents for their capacity of removing smear layer and opening dentin tubules.

METHODS

Fifty fragments of human dental roots previously exposed to periodontal disease were scaled and randomly divided into the following groups of treatment: 1) CA: demineralization with citric acid for 3 min; 2) TC-HCl: demineralization with tetracycline-HCl for 3 min; 3) EDTA: demineralization with EDTA for 3 min; 4) PA: demineralization with 37% phosphoric acid for 3 min; 5) CONTROL: rubbing of saline solution for 3 min. Scanning electron microscopy was used to check for the presence of residual smear layer and for measuring the number and area of exposed dentin tubules.

RESULTS

Smear layer was present in 100% of the specimens from the groups PA and control; in 80% from EDTA group; in 33.3% from TC-HCl group and 0% from CA group. The mean numbers of exposed dentin tubules in a standardized area were: TC-HCl=43.8±25.2; CA=39.3±37; PA=12.1±16.3; EDTA=4.4±7.5 and CONTROL=2.3±5.7. The comparison showed significant differences between the following pairs of groups: TC-HCl and CONTROL; TC-HCl and EDTA; CA and CONTROL; and CA and EDTA. The mean percentages of area occupied by exposed dentin tubules were: CA=0.12±0.17%; TC-HCl=0.08±0.06%; PA=0.03±0.05%; EDTA=0.01±0.01% and CONTROL=0±0%. The CA group differed significantly from the others except for the TC-HCl group.

CONCLUSION

There was a decreasing ability for smear layer removal and dentin tubule widening as follows: AC>TC-HCl>PA>EDTA. This information can be of value as an extra parameter for choosing one of them for root conditioning.

Ultramorphology of the root surface subsequent to hand-ultrasonic simultaneous instrumentation during non-surgical periodontal treatments: an in vitro study

Objective

The purpose of this study was to investigate the ultramorphology of the root surfaces induced by mechanical instrumentation performed using conventional curettes or piezoelectric scalers when used single-handedly or with a combined technique.

Material and Methods

Thirty single-rooted teeth were selected and divided into 3 groups: Group A, instrumentation with curettes; Group B instrumentation with titanium nitride coated periodontal tip mounted in a piezoelectric handpiece; Group C, combined technique with curette/ultrasonic piezoelectric instrumentation. The specimens were processed and analyzed using confocal and scanning electron microscopy. Differences between the different groups of instrumentation were determined using Pearson’s χ ² with significance predetermined at α=0.001.

Results

Periodontal scaling and root planing performed with curettes, ultrasonic or combined instrumentation induced several morphological changes on the root surface. The curettes produced a compact and thick multilayered smear layer, while the morphology of the root surfaces after ultrasonic scaler treatment appeared irregular with few grooves and a thin smear layer. The combination of curette/ultrasonic instrumentation showed exposed root dentin tubules with a surface morphology characterized by the presence of very few grooves and slender remnants of smear layer which only partially covered the root dentin. In some cases, it was also possible to observe areas with exposed collagen fibrils.

Conclusion

The curette-ultrasonic simultaneous instrumentation may combine the beneficial effects of each instrument in a single technique creating a root surface relatively free from the physical barrier of smear layer and dentin tubules orifices partial occlusion.

Initial fibroblast attachment to Erbium:YAG laser-irradiated dentine

AIMS

To evaluate the effects of Erbium (Er):YAG laser irradiation on the morphology of resected dentine surfaces, and to investigate fibroblast attachment to laser-irradiated dentine surfaces.

METHODOLOGY

Dentine blocks obtained from single-rooted human teeth were divided into the following groups after sterilization in an autoclave: (i) Laser group treated with Er:YAG laser irradiation (30 mJ per pulse, 10 pps, 60 s); (ii) L-MTAD group treated with laser irradiation as in (i) plus a mixture of doxycycline, tetracycline isomer and citric acid; (iii) RC-Prep group treated with EDTA gel or cream (RC-Prep) and (iv) Control group left untreated. After each treatment, the dentine blocks were incubated with NIH/3T3 fibroblasts cultured to subconfluency in Dulbecco's modified Eagle's medium supplemented with 10% foetal bovine serum and antibiotics. The number of attached cells amongst the groups was analysed statistically at the 5% significance level. The dentine surface morphologies and cell attachments were evaluated by counting assays, histological observations and scanning electron microscopy (SEM).

RESULTS

The number of attached cells was significantly higher (P < 0.05) in the Laser group than in the RC-Prep and Control groups at 16 h. Dendritic cell extension of the fibroblasts was only observed in the Laser group at 8 h by SEM. In the histological analyses, significantly more attached cells were found on the dentine surfaces treated with laser irradiation.

CONCLUSIONS

Er:YAG laser irradiation induced morphological alterations in dentine surfaces, which may improve the attachment of fibroblasts to dentine.

A scanning electron microscopy study of diseased root surfaces conditioned with EDTA gel plus Cetavlon after scaling and root planing

In the present investigation, a scanning electron microscopy analysis was performed to evaluate the effects of the topical application of ethylenediaminetetraacetic acid (EDTA) gel associated with Cetavlon (EDTAC) in removing the smear layer and exposing collagen fibers following root surface instrumentation. Twenty-eight teeth from adult humans, single rooted and scheduled for extraction due to periodontal reasons, were selected. Each tooth was submitted to manual (scaling and root planing) instrumentation alone or combined with ultrasonic instruments, with or without etching using a 24% EDTAC gel. Following extraction, specimens were processed and examined under a scanning electron microscope. A comparative morphological semi-quantitative analysis was performed; the intensity of the smear layer and the decalcification of cementum and dentinal surfaces were graded in 12 sets using an arbitrary scale ranging from 1 (area covered by a smear layer) to 4 (no smear layer). Root debridement with hand instruments alone or combined with ultrasonic instruments resulted in a similar smear layer covering the root surfaces. The smear layer was successfully removed from the surfaces treated with EDTAC, which exhibited numerous exposed dentinal tubules and collagen fibers. This study supports the hypothesis that manual instrumentation alone or instrumentation combined with ultrasonic instrumentation is unable to remove the smear layer, whereas the subsequent topical application of EDTAC gel effectively removes the smear layer, uncovers dentinal openings and exposes collagen fibers.

Can interaction of materials with the dentin-pulp complex contribute to dentin regeneration?

Understanding outcomes of the interaction between a dental material and tooth tissue is important in terms not only of biocompatibility but also of the potential for the material to modulate the response of the tissue. This interaction is influenced by many factors, including the chemistry of the material and any of its eluted components or degradation products, and the manner in which the tissue responds to these agents. Past studies of this interaction have primarily been aimed at identifying cytotoxic effects. More recently, investigations have focused on specific cellular responses, and in particular, on understanding how the materials themselves actually may contribute to regenerative processes in the tooth. Recent work has demonstrated the solubilization of proteins from dentin exposed to certain materials, such as calcium hydroxide, mineral trioxide aggregate, and acidic solutions that relate to those used in dentin bonding agents, with the subsequent modulation by these proteins of gene expression in odontoblast-like cells. This work suggests that dentin bridge formation under such materials may be stimulated through this process. Thus, there is much merit in examining both how new dental materials can be developed and how more traditional ones can be modified to preferentially stimulate regenerative processes when preferred. This review summarizes current knowledge about the potential beneficial effects derived from the interaction of dental materials with the dentin-pulp complex, as well as potential future developments in this exciting field.

Immunohistochemical and biochemical assay of versican in human sound predentine/dentine matrix

Aim of this study was to investigate the distribution of versican proteoglycan within the human dentine organic matrix by means of a correlative immunohistochemical analysis with field emission in-lens scanning electron microscope (FEI-SEM), transmission electron microscope (TEM), fluorescence microscope (FM) and biochemical assay. Specimens containing dentine and predentine were obtained from non carious human teeth and divided in three groups: 1) FEI-SEM group: sections were exposed to a pre-embedding immunohistochemical procedure; 2) TEM group: specimens were fixed, demineralised, embedded and submitted to a post-embedding immunohistochemical procedure; 3) FM group: sections mineralised and submitted to a pre-embedding immunohistochemical procedure with fluorescence labelling. Specimens were exposed to two different antibodies to assay distribution of versican fragments and whole versican molecule. Western Blotting analysis of dentine and pulp extracts was also performed. The correlative FEI-SEM,TEM and FM analysis revealed positive immunoreaction for versican fragments both in predentine and dentine, while few gold particles identifying the whole versican molecule were found in predentine only under TEM. No labelling of versican whole molecule was detected by FEI-SEM and FM analysis. The immunoblotting analysis confirmed the morphological findings. This study suggests that in fully developed human teeth versican fragments are significant constituents of the human dentine and predentine organic matrix, while versican whole molecule can be visualised in scarce amount within predentine only. The role of versican fragments within human dentine organic matrix should be further elucidated.

Dentin treatment with MMPs inhibitors does not alter bond strengths to caries-affected dentin

OBJECTIVES

This study aimed to investigate if the use of protease inhibitors (EDTA and chlorhexidine) may influence microtensile bond strength (MTBS) of an etch-and-rinse adhesive system to caries-affected human dentin.

METHODS

Flat middle coronal dentin surfaces with a central region of caries-affected dentin surrounded by sound dentin were bonded with Adper Scotchbond 1 after: (1) etching with 35% H3PO4; (2) etching with 0.1M EDTA and (3) 35% H3PO4-etching followed by 5% chlorhexidine application. Resin composite build-ups were constructed incrementally and trimmed to yield hourglass specimens (0.8mm2 bonded area) that contained sound or caries-affected dentin (confirmed after debonding by microhardness measurements - KHN). Bonded specimens were tensioned at 0.5mm/min. Data were analyzed by ANOVA and multiple comparisons tests (p<0.05). Failure mode analysis was performed by scanning electron microscopy (SEM).

RESULTS

H(3)PO(4), EDTA and chlorhexidine pre-treatments yielded similar MTBS values, in both dentin substrates. Bond strength to sound dentin was significantly higher than that to caries-affected dentin after H3PO4-etching. Caries-affected dentin exhibited lower KHN than sound dentin.

CONCLUSIONS

Conditioning of caries-affected dentin with EDTA or a combined use with H3PO4 and chlorhexidine may be proposed as these protease inhibitors do not reduce MTBS to caries-affected dentin if compared to conventional H3PO4 treatment.