Comparison of Antimicrobial Substantivity of Six Root Canal Irrigants against Enterococcus Faecalis

Palazzi F, Del Fabbro M, Taschieri S, Mohammadi Z, Asgary S, Bukiet F.

Iran Endod J 2018;13(3): 293-298.

(ABSTRACT) Introduction: The antimicrobial substantivity of MTAD, Tetraclean, Tetraclean NA, Q-Mix, 2% CHX and Octenisept was assessed in human root dentine blocks infected with Enterococcus (E.) faecalis. Methods and Materials: A total of 170 dentine tubes were prepared from human maxillary incisors. After crown and apical third removal, cementum was abraded. The remaining center-holed pieces were cut into 4-mm blocks, infected with E. faecalis in BHI broth for 28 days, then randomly divided into 6 experimental groups (n=25) and 2 controls (n=10). At 0, 7, 14, 21 and 28 days, dentine chips were removed from the canals, with sequential round burs with increasing diameters, and collected into freshly prepared BHI broth. After culturing, growing colonies were counted as colony forming units (CFU). Conventional non-parametric tests (Kruskal-Wallis and Mann-Whitney tests) were used to assess intra-group (at different time frames) and inter-group (at each experimental time) differences (P=0.05). Results: Tetraclean yielded the lowest CFU counts (P<0.001) at each observation time. Tetraclean NA and Q-Mix showed better (P<0.001) substantivity than 2% CHX and MTAD (except for Q-Mix versus MTAD at 14 days, P=0.21). Conclusions: In this in vitro study, Tetraclean NA and Q-Mix displayed the best antimicrobial substantivity against E. faecalis after Tetraclean in infected human root dentine. Considering the findings of our study and potential drawbacks of antibiotic-based irrigants, free-antibiotic irrigants may represent viable alternative for final rinse in root canal treatment.

Keywords: Antimicrobial Substantivity; Enterococcus faecalis; MTAD; Qmix; Tetraclean

 Recent Advances in Root Canal Disinfection: A Review

 Mohammadi Z, Jafarzadeh H, Shalavi S, Palazzi F.

 Iran Endod J. 2017 Fall;12(4):402-406.

(ABSTRACT) The microbial biofilm is an important factor for human infection. Finding effective antimicrobial strategies should be considered for decreasing antimicrobial resistance and controlling the infectious diseases. Treatment of infected canal systems may not be able to remove all bacteria and so bacterial persistence after treatment may occur. Application of antibacterial nanoparticles may be a potential strategy to improve the elimination of bacteria from the canal. Furthermore, mechanism of action and applications of photodynamic therapy and Photon-induced photoacoustic streaming (PIPS) and GentleWave system was reviewed.

Keywords: GentleWave Irrigation; Nano-Particles; Nano-Technology; Photodynamic Therapy; Photon-Induced Photo Acoustic Streaming; Root Canal Disinfection.

Root Canal Irrigants and Dentin Bonding: An Update  

Mohammadi Z, Yaripour S, Shalavi S, Palazzi F, Asgary S.

Iran Endod J. 2017 Spring;12(2):131-136.

(ABSTRACT) The purpose of the review was to assess the effect of root canal irrigants on dentin bonding. A PubMed-based search was conducted on the articles published from 1980 to 2016. A brief overview and reviewing the effect on dentin bonding of common root canal irrigation solutions such as sodium hypochlorite (NaOCl), chlorhexidine (CHX), ethylenediaminetetraacetic acid (EDTA), mixture of a tetracycline, acid and a detergent (MTAD) and ozone was conducted. Findings showed that, depending on the type of dentin bonding, using NaOCl may decrease, increase or not affect the bond strength. In addition, due to its broad-spectrum matrix metalloproteinase-inhibitory effect, CHX as well as MTAD can significantly improve the resin-dentin bond stability. However, the effect of ozone therapy on bond strength was controversial.

Keywords: Bond Strength; Chlorhexidine; EDTA; MTAD; Ozone; Sodium Hypochlorite

Effect of Surfactants on the Efficacy of Root Canal Irrigants: A Review

Mohammadi Z, Shalavi S, Giardino L, Palazzi F. 

N Y State Dent J 83(3):37-42.

(ABSTRACT) The mechanical debridement of the root canal system fails to completely remove debris from the root canal walls. So, one or more irrigants must be used for complete disinfection of the root canal system (RCS). One possible way to improve the bactericidal efficacy of the disinfecting solutions is to incorporate different detergents as surface active agents to help reduce the surface tension and increase the wettability of the solutions. Surfactants have been added to various root canal irrigation solutions. The purpose of this paper is to review the effects of adding surfactants to established root canal irrigants and new surfactant-containing root canal irrigants.

Penetration of  hypochlorites with lowered surface tension into dentine tubules

Palazzi F, Sadile G, Mohammadi Z, Del Fabbro M, Riccitiello F.
Minerva Stomatol. 2016 Dec;65(6):368-377.

(ABSTRACT) Background: the purpose of the present study was to assess the effect of concentration and temperature of sodium hypochlorite (NaOCl) with added surfactants and time of exposure on its penetration into human dentine. Methods: Seventy-five extracted permanent maxillary anterior teeth with single canals were shaped by using Protaper SX hand-operated instruments. Then teeth were sectioned perpendicular to their long axis. The crowns and apical thirds of all the teeth were removed. the remaining roots were processed into 4-mm-long blocks and stained overnight in crystal violet. One hundred fifty stained blocks were further split into halves and treated by six NaOCl-based solutions from different brands: three solutions added with surfactants (Hypoclean, H6, Chlor-Xtra) and their regular counterparts (5.25%, 6%, <%6NaOCl). The dentine blocks were exposed to the solutions for 2, 5, and 20 minutes at 20° C, 37° C, and 45° C, respectively. The depth of penetration of NaOCl was determined by bleaching of the stain and measured by light microscopy at magnifications of 20x and 40x. Statistical analysis was made by using two way ANOVA and by comparing groups two by two with t-test. Results: the shortest penetration (130.80±1.92μm) was measured after incubation with 5.25%NaOCl for 2 minutes at 20° C; the highest penetration (375.40±3.05μm) was obtained with Chlor-Xtra for 20 minutes at 45° C. Temperature and exposure time had a significant direct relationship with penetration of sodium hypochlorites with lowered surface tension into dentinal tubules. Conclusions: the exposure time and temperature of sodium hypochlorite as well as the addition of surfactants may influence the penetration depth of irrigants into dentinal tubules.

Key words: Sodium hypochlorite, surface tension, surface-active agents, wettability.

Penetration of sodium hypochlorite modified with surfactants into root canal dentin

Palazzi F, Blasi A, Mohammadi Z, Del Fabbro M, Estrela C.
Braz Dent J. 2016 Mar-Apr; 27(2):208-16.

(ABSTRACT) The aim of this study was to evaluate the effect of concentration, exposure time and temperature of sodium hypochlorite (NaOCl) added with surfactants on its penetration into dentinal tubules. Sixty-five extracted human permanent maxillary anterior teeth with single canals were prepared by ProTaper rotary instruments. The teeth were then sectioned perpendicular to the long axis. The crowns and apical thirds of all the teeth were removed. The remaining roots were processed into 4-mm-long blocks and stained overnight in crystal violet. One hundred and thirty stained blocks were further split into halves and treated by nine different types of NaOCl-based solutions. Three solutions were added with surfactants (Hypoclean, H6, Chlor-Xtra) and the others were regular hypochlorites at increasing concentrations (1%, 2%, 4%, 5.25%, <6%, 6% NaOCl) from different brands. The dentin blocks were exposed to the solutions for 2, 5, and 20 min at 20 °C, 37 °C and 45 °C, respectively. The depth of NaOCl penetration was determined by bleaching of the stain and measured by light microscopy at 20X and 40X. Statistical comparisons were made by using a generalized linear model with Bonferroni’s post- hoc correction. The shortest penetration (81±6.6 μm) was obtained after incubation in 1%NaOCl for 2 min at 20 °C; the highest penetration (376.3±3.8 μm) was obtained with Chlor-Xtra for 20 min at 45 °C. Varying NaOCl concentration produced a minimal effect while temperature and exposure time had a significant direct relationship with NaOCl penetration into dentinal tubules, especially those with lowered surface tension. The exposure time and temperature of sodium hypochlorite as well as the addition of surfactants may influence the penetration depth of irrigants into dentinal tubules.

Keywords: sodium hypochlorite, surfactant, penetration, temperature, time.

Management of Root Resorption Using Chemical Agents: A Review

Mohammadi Z, Cehreli Z, Shalavi S, Giardino L, Palazzi F, Asgary S.

Iran Endod J. 2016 Winter;11(1):1-7.

(ABSTRACT) Root resorption (RR) is defined as the loss of dental hard tissues because of clastic activity inside or outside of tooth the root. In the permanent dentition, RR is a pathologic event; if untreated, it might result in the premature loss of the affected tooth. Several hypotheses have been suggested as the mechanisms of root resorption such as absence of the remnants of Hertwig’s epithelial root sheath (HERS) and the absence of some intrinsic factors in cementum and predentin such as amelogenin or osteoprotegerin (OPG). It seems that a barrier is formed by the less-calcified intermediate cementum or the cemento-dentin junction that prevents external RR. There are several chemical strategies to manage root resorption. The purpose of this paper was to review several chemical agents to manage RR such as tetracycline, sodium hypochlorite, acids (citric acid, phosphoric acid, ascorbic acid and hydrochloric acid), acetazolamide, calcitonin, alendronate, fluoride, Ledermix and Emdogain.

Keywords: Alendronate; Calcitonin; Citric Acid; Emdogain; Fluoride; Osteoclast; Root Resorption; Tetracycline

Impact of Ultrasonic Activation on the Effectiveness of Sodium Hypochlorite: A Review

Mohammadi Z, Shalavi S, Giardino L, Palazzi F, Asgary S.
Iran Endod J. 2015 Fall;10(4):216-20.

(ABSTRACT) Using ultrasonic devices in endodontics can enhance the antibacterial and tissue dissolving ability of different root canal irrigants such as sodium hypochlorite (NaOCl) which is the most common irrigant with excellent antibacterial and tissue dissolving abilities. However, due to its high surface tension, its penetration into the irregularities of the root canal system is a challenge. The purpose of this paper was to review the different ultrasonic devices, different types of ultrasonic irrigation, the effect(s) of ultrasonic activation on the antibacterial and biofilm-removal abilities of NaOCl as well as the effect of ultrasonic activation on the smear layer removal ability of NaOCl.

Keywords: Antibacterial Activity; Biofilm; Root Canal Irrigants; Smear Layer; Sodium Hypochlorite; Ultrasonic Activation

Agonistic and Antagonistic Interactions between Chlorhexidine and Other Endodontic Agents: A Critical Review
Mohammadi Z, Giardino L, Palazzi F, Asgary S.

Iran Endod J 2015;10(1): 1-5

(ABSTRACT) Root canal irrigants play a significant role in elimination of the microorganisms, tissue remnants, and removal of the debris and smear layer. No single solution is able to fulfill all these actions completely; therefore, a combination of irrigants may be required. The aim of this investigation was to review the agonistic and antagonistic interactions between chlorhexidine (CHX) and other irrigants and medicaments. An English-limited Medline search was performed for articles published from 2002 to 2014. The searched keywords included: chlorhexidine and sodium hypochlorite/ethylenediaminetetraacetic acid/calcium hydroxide/mineral trioxide aggregate. Subsequently, a hand search was carried out on the references of result articles to find more matching papers. Findings showed that the combination of CHX and sodium hypochlorite (NaOCl) causes color changes and the formation of a neutral and insoluble precipitate; CHX forms a salt with ethylenediaminetetraacetic acid (EDTA). In addition, it has been demonstrated that the alkalinity of calcium hydroxide (CH) remained unchanged after mixing with CHX. Furthermore, mixing CHX with CH may enhance its antimicrobial activity; also mixing mineral trioxide aggregate (MTA) powder with CHX increases its antimicrobial activity but this may negatively affect its mechanical properties.

Keywords: Calcium Hydroxide; Chlorhexidine; Ethylenediaminetetraacetic Acid; Interaction; Mineral Trioxide Aggregate; Sodium Hypochlorite

Antibacterial power of sodium hypochlorite combined with surfactants and acetic acid

Giardino L, Estrela C, Mohammadi Z, Palazzi F.
Braz Dent J. 2014;25(4):289-94.

(ABSTRACT) The aim of this ex vivo study was to compare the antibacterial power of 1%NaOCl with 1% acetic acid, 5.25%NaOCl and two commercially available NaOCl modified with surfactants in bovine root dentin. A total of 120 dentin tubes prepared from intact bovine incisors were infected for 21 days with Enterococcus faecalis and randomly divided into six groups as follows: 5.25%NaOCl; Hypoclean; Chlor-Xtra; 1%NaOCl with 1% acetic acid; infected dentin tubes (positive control); and sterile dentin tubes (negative control). At experimental times of 0, 7, 14, 21 and 28 days, dentin chips were collected using sequential round burs with increasing diameters in separate test tubes containing 3 mL of freshly prepared BHI. Statistical analysis were performed using parametric methods (one-way ANOVA, and Bonferroni’s multiple comparisons test, α=0.01). After culturing, the number of colony-forming units (CFU) was counted. All the NaOCl solutions showed small number of CFU over 28 days. ChlorXtra and Hypoclean had the smallest number of CFU at all times with greater antimicrobial efficacy than 5.25% NaOCl and 1% NaOCl solution with 1% acetic acid.

Key Words: sodium hypochlorite, acetic acid, surfactant, Enterococcus faecalis, irrigant.

Determining the minimum inhibitory concentration of Tetraclean against Candida albicans

Qyasian A, Mohammadi Z, Giardino L, Palazzi F, Shalavi S, Sabbaghi S, Khoshbin E.
Niger J Med. 2014 Jul-Sep;23(3):201-6.

(ABSTRACT) The purpose of the present study was to determine the minimum inhibitory concentration (MIC) of Tetraclean, chlorhexidine, hydrogen peroxide, and sodium hypochlorite against Candida albicans. Amphotericin B was used as positive control and RPMI plus 1 ml Candida suspension was used as negative control. Serial dilution method was used to determine MIC of the irrigants. Findings showed that all positive controls demonstrated complete inhibition of C. albicans at concentration of 0.78 μg mL^-1. On the other hand, all negative controls were positive for fungal growth which confirms the methodology of the study. Findings

showed that the MIC of CHX was significantly lesser than other tested irrigants (p<0.05). The MICs of other groups in an ascending order were as follows: Tetraclean, NaOCl, and H₂O₂. However, the difference between Tetraclean and NaOCl was not significant (p>0.05). It can be concluded that MIC of CHX was significantly lower than other irrigations solutions which confirms its strong antifungal activity.

Keywords: Candida albicans, chlorhexidine, hydrogen peroxide, sodium hypochlorite, Tetraclean

Effect of irrigation with Tetraclean on bacterial leakage of obturated root canals

Mohammadi Z, Shalavi S, Giardino L, Palazzi F.

NY State Dent J 2014 Apr;80(3):39-43

(ABSTRACT) The purpose of the study presented here was to evaluate the effect of Tetraclean, Hypoclean, Chlor-Xtra, 2% Chlorexidine and 6% sodium hypochlorite/17% EDTA as a final irrigant on bacterial leakage of the root canal. One hundred and fifty-five extracted human maxillary central incisors were randomly divided into five experimental groups of 25 teeth each and two control groups of 15 teeth each. The root canals in group 5 were irrigated with 5 ml of 17% EDTA at the end of root canal preparation. The teeth in each group were obturated with gutta-percha and AH-26 sealer. Positive control teeth were obturated with a single gutta-percha cone without sealer, and negative controls were obturated in the same way as experimental groups. The coronal portion of each root was placed in contact with inoculum of Enterococcus faecalis in Brain Heart Infusion (BHI) culture media. Findings showed that the mean number of days for bacterial penetration in the Tetraclean group was greater than for other experimental groups. On the other hand, the Chlor-Xtra group showed the fewest mean number of days for bacterial leakage.

Microbial biofilms in endodontic infections: an update review

Mohammadi Z, Palazzi F, Giardino L, Shalavi S.

Biomed J 2013 Mar-Apr;36(2):59-70.

(ABSTRACT) Biofilms and microbial aggregates are the common mechanisms for the survival of bacteria in nature. In other words, the ability to form biofilms has been regarded as a virulence factor. Microbial biofilms play an essential role in several infectious diseases such as pulp and periradicular pathosis. The aim of this article was to review the adaptation mechanisms of biofilms, their roles in pulpal and periapical pathosis, factors influencing biofilm formation, mechanisms of their antimicrobial resistance, models developed to create biofilms, observation techniques of endodontic biofilms, and the effects of root canal irrigants and medicaments as well as lasers on endodontic biofilms. The search was performed from 1982 to December 2010, and was limited to papers in English language. The keywords searched on Medline were “biofilms and endodontics,” “biofilms and root canal irrigation,” “biofilms and intra‐canal medicament,” and “biofilms and lasers.” The reference section of each article was manually searched to find other suitable sources of information.

Keywords: biofilm, intracanal medicaments, periapical infections, pulpal infections, root canal irrigation

Evaluation of the antifungal activity of four solutions used as a final rinse in vitro

Mohammadi Z, Giardino L, Palazzi F. 

Aust Endod J 2013 Apr;39(1):31-4.

(ABSTRACT) The aim of the study was to compare the antifungal activity of 1.3% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), MTAD and Tetraclean as a final rinse against Candida albicans in a human tooth model in vitro. Ninety extracted human maxillary central and lateral incisor teeth were randomly divided into four groups each with 20 teeth, a positive and a negative control each with five teeth. After preparing the root canals, teeth were inoculated with Candida albicans (ATCC 10261) and incubated for 72 h. Teeth were divided into four experimental groups according to the irrigation solution as follows: NaOCl, CHX, MTAD and Tetraclean. After culturing aliquots from the experimental teeth on Sabouraud 4% dextrose agar, colony-forming units were counted. The results showed that 1.3% NaOCl and 2% CHX were equally effective and significantly superior to MTAD and Tetraclean (P < 0.05). Furthermore, antifungal efficacy of Tetraclean was significantly superior to MTAD (P < 0.05).

Keywords:  Candida albicans, chlorhexidine, MTAD, sodium hypochlorite, Tetraclean.

Effect of initial irrigation with sodium hypochlorite on residual antibacterial activity of Tetraclean Mohammadi Z, Giardino L, Palazzi F, Shahriari S.

N Y State Dent J 2013 Jan;79(1):32-6.

(ABSTRACT) The purpose of this study was to assess the effect of dentin pretreatment with sodium hypochlorite (NaOCl) on the antibacterial substantivity of Tetraclean in bovine root dentin in vitro. One hundred and forty dentin tubes prepared from bovine incisor teeth were infected with Enterococcus faecalis for 14 days. The specimens were divided into five groups as follows: Tetraclean; 5.25% NaOCl/Tetraclean; 2% chlorhexidine (CHX); infected dentin tubes (positive control); and sterile dentin tubes (negative control). Round burs were used to collect dentin chips into tryptic soy broth. After culturing, the number of colony-forming units (CFU) was counted. In all experimental groups, the number of CFU was minimal in the first cultures. And the results obtained were significantly different from each other at any time period (p < 0.05). The Tetraclean group showed the most effective antibacterial action at all five experimental periods (p < 0.05). The NaOCl/Tetraclean group showed lesser antibacterial substantivity than Tetraclean at all time periods (p< 0.05). The chlorhexidine group showed the least antibacterial activity at all time periods. In conclusion, the residual antibacterial activity of Tetraclean was significantly decreased in dentin samples pretreated with NaOCl.

Substantivity of three concentrations of Tetraclean in bovine root dentin

Mohammadi Z, Giardino L, Palazzi F, Shalavi S, Farahani MF.

Chonnam Med J 2012 Dec;48(3):155-8.

 (ABSTRACT) In the present study, the residual antibacterial activity, or substantivity, of three con- centrations of Tetraclean (Ogna Laboratori Farmaceutici, Muggiò, Italy) was assessed in bovine root dentin in vitro. One hundred ten dentin tubes prepared from bovine in- cisor teeth were infected in vitro for 14 days with

Enterococcus faecalis. Thereafter, the specimens were divided into five groups as follows: 100% Tetraclean, 10% Tetraclean, 1% Tetraclean, sterile dentin tubes (negative control), and infected dentin tubes (positive control). Dentin chips were collected with round burs into tryptic soy broth and, after culturing, the number of colony-forming units (CFU) was counted. The num- ber of CFU was minimal in the first cultures in all experimental groups, and the results obtained were significantly different in the different groups at all time periods (p<0.05). At all five experimental periods, the 100% Tetraclean group showed the most effective antibacterial action (p<0.05). In each group, the number of CFU increased significantly with time (p<0.05). There was a direct relationship between the concen- tration of Tetraclean and its substantivity. In conclusion, under the conditions of the study presented here, the substantivity of 100% Tetraclean was significantly higher than that of lower concentrations.

Key Words: Tetraclean; Enterococcus faecalis; Dentin

Antimicrobial effect of three new and two established root canal irrigation solutions

Mohammadi Z, Shalavi S, Giardino L, Palazzi F, Mashouf RY, Soltanian A.

Gen Dent 2012 Nov-Dec;60(6):534-7.

(ABSTRACT) This study sought to assess the efficacy of two established and three relatively new root canal irrigants against five different microorganisms using the agar diffusion method. Sodium hypochlorite (NaOCl) -based irrigants demonstrated the most effective antimicrobial activity.

The effect of ascorbic Acid on the substantivity of Tetraclean in sodium hypochlorite-treated bovine dentin.

Mohammadi Z, Giardino L, Palazzi F, Shalavi S.

J Dent (Tehran). 2012 Summer; 9(3):230-6. Epub 2012 Sep 30.

(ABSTRACT) Objective: The purpose of this study was to assess the in vitro effect of ascorbic acid on the antibacterial substantivity of Tetraclean in bovine root dentin pre- treated with sodium hypochlorite (NaOCl). Materials and Methods: Eighty dentin tubes prepared from bovine incisor teeth were infected with Enterococcus faecalis for 14 days. The specimens were di- vided into five groups as follows: Tetraclean; 5.25% NaOCl/Tetraclean; 5.25% NaOCl/ascorbic acid/Tetraclean; infected dentin tubes (positive control); and ste- rile dentin tubes (negative control). At experimental times of 0, 7, 14, 21 and 28 days, dentin chips were removed from the canals by sequential sterile low-speed round burs with increasing diameters of 025, 027, 029, 031 and 033 ISO sizes, respectively. After culturing, the number of colony-forming units (CFU) was counted. Results: In all experimental groups, the number of CFU was minimum in the first cultures and the results obtained were significantly different at any time period (p < 0.05). The Tetraclean group showed the most effective antibacterial action at all five experimental periods (p < 0.05). NaOCl/Tetraclean group showed the least antibacterial activity at all time periods. The NaOCl/ascorbic acid/Tetraclean group showed similar antibacterial substantivity to the Tetraclean group at all time periods (p> 0.05). Conclusion: Ascorbic acid prevents the decrease of residual antibacterial activity of Tetraclean in dentin samples pretreated with NaOCl.

Keywords: Ascorbic Acid; Enterococcus Faecalis; Pretreatment; Sodium Hypochlorite; Substantivity; Tetraclean

Debridement effectiveness of two different techniques using negative pressure irrigation system

Efficacia nella detersione di due differenti tecniche d’irrigazione a pressione negativa.

Palazzi F, Giardino L, Mohammadi Z, Rengo S, Riccitiello F.

G. It. Endod Nov 2012;26(3)117–127.

(ABSTRACT) Objectives: To evaluate the cleaning efficacy of two apical negative pressure irrigation tech- niques compared to needle irrigation. Materials and Methods: Eighty extracted human single canal teeth were shaped and assigned to 3 experimental groups (n = 20) according to the irrigation technique performed and two negative control groups (n = 10) as follows: 1) NI (Max-I-Probe side-vented needle irrigation); 2) EV (EndoVac system); 3) EVM (EndoVac-modified technique); 4) EV-C (EndoVac-negative control); 5) NI-C (needle irrigation-negative control). A scanning electron microscopic evaluation was performed. The presence of debris and smear layer at all levels (coronal, middle, apical) was evaluated. Results and conclusions: A new

irrigation protocol, using EndoVac System resulted in better removal of the smear layer at all levels.

Keywords: Closed system model; EndoVac; Needle irrigation; Negative pressure irrigation; Smear layer.

Comparative wettability of different sodium hypochlorite solutions

Analisi comparativa della bagnabilità di diverse soluzioni di ipoclorito di sodio.

Giardino L, Morra M, Becce C, Pappen FG, Mohammadi Z, Palazzi F.

G It Endod Sept 2012;26(2):57–62.

Objectives: To evaluate the cleaning efficacy of two apical negative pressure irrigation tech- niques compared to needle irrigation. Materials and Methods: Eighty extracted human single canal teeth were shaped and assigned to 3 experimental groups (n = 20) according to the irrigation technique performed and two negative control groups (n = 10) as follows: 1) NI (Max-I-Probe side-vented needle irrigation); 2) EV (EndoVac system); 3) EVM (EndoVac-modified technique); 4) EV-C (EndoVac-negative control); 5) NI-C (needle irrigation-negative control). A scanning electron microscopic evaluation was performed. The presence of debris and smear layer at all levels (coronal, middle, apical) was evaluated. Results and conclusions: A new irrigation protocol, using EndoVac System resulted in better removal of the smear layer at all levels.

Keywords Surfactants; Wettability; Sodium hypochlorite; Contact angle; Surface tension.

Antibacterial activity of a new mineral trioxide aggregate-based root canal sealer

Mohammadi Z, Giardino L, Palazzi F, Shalavi S.
Int Dent J 2012 Apr;62(2):70-3.

Objectives: To compare the antibacterial effect of AH-26, white-coloured mineral trioxide aggregate (WMTA) and CPM sealer against Staphylococcus aureus and Streptococcus mutans after 24 h and 1 week. Materials and methods: All materials were prepared according to the manufacturers’ directions immediately before testing. The antibacterial effect of each agent was determined by measuring the diameter of the zone of inhibition in millimetres after incubation at 37 °C for 24 h and 7 days in a humid atmosphere. Each test was repeated three times. Results: In the 24-h and 7-day samples, the antibacterial activity of AH-26 was significantly greater than that of the two other materials tested against both bacteria (P < 0.05). The antibacterial activities of CPM sealer and WMTA against S. aureus were not significantly different (P > 0.05) in 24-h or 7- day samples, but CPM sealer demonstrated a significantly greater effect than WMTA against S. mutans (P < 0.05). Conclusion: All products studied exhibited antibacterial activity. However, in 24-h and 7-day samples, AH-26 exerted the greatest activity against both organisms tested.

Key words: Agar diffusion test, AH-26 sealer, CPM sealer, MTA, Staphylococcus aureus, Streptococcus mutans.

Comparison of the surface tension of 5.25% sodium hypochlorite solution with three new sodium hypochlorite-based endodontic irrigants

Palazzi F, Morra M, Mohammadi Z, Grandini S, Giardino L.

Int Endod J 2012 Feb;45(2):129-35.

Aim To investigate the surface tension characteristics of 5.25% sodium hypochlorite and three recently introduced sodium hypochlorite solutions, which had been modified to reduce their surface tension: Chlor- Xtra, Hypoclean A and Hypoclean B. Methodology Freshly produced MilliQ water was used as a reference liquid. All measurements of surface tension were taken by the Wilhelmy plate technique, using a Cahn DCA-322 Dynamic Contact Angle Analyzer at the temperature of 22 °C. A glow-dis-charge cleaned glass slide was immersed in 5 mL of the test liquid in a beaker cleaned with hot chromic acid, rinsed with MilliQ water and finally air plasma-cleaned in a glow-discharge reactor. The force on the glass slide was recorded continuously by the instrument software as the beaker was raised and withdrawn at the constant speed of 40 micron/s, until at least 1 cm of the glass slide was immersed. The typical accuracy was 0.5 mJ m^-2. For each sample, fifteen measurements were taken, and mean values were calculated. A Kruskal–Wallis anova analysis, followed by Mann–Whitney’s U rank sum test for pair-wise comparisons, was used to compare surface tension values. Statistical significance was set at a = 0.05. Results MilliQ water (72.13 mJ m^-2) and 5.25% sodium hypochlorite (48.90 mJ m^-2) had the highest surface tension values (P < 0.01) compared to Chlor- Xtra (33.14 mJ m^-2), Hypoclean B (30.00 mJ m^-2) and Hypoclean A (29.13 mJ m^-2). Hypoclean A had the lowest surface tension (P < 0.01). Conclusions The new 5.25% sodium hypochlorite solutions modified with surfactants, Hypoclean A and Hypoclean B, had surface tension values that were significantly lower (P < 0.01) than Chlor-Xtra and 5.25% NaOCl. Because of their low surface tension and increased contact with dentinal walls, these new irrigants have the potential to penetrate more readily into uninstrumented areas of root canal system as well as allow a more rapid exchange with fresh solution, enabling greater antimicrobial effectiveness and enhanced pulp tissue dissolution ability.

Keywords: chlor-Xtra, hypoclean, irrigants, sodium hypochlorite, surface tension, tetraclean.

Laser application in tooth bleaching: an update review

Mohammadi Z, Palazzi F, Giardino L.

Minerva Stomatol 2011 Apr;60(4):167-78. Review

Since the development of laser, a variety of potential applications for lasers in endodontics such as pulp diagnosis, disinfection of the root canal system, canal shaping, obturation of the root canal, apicoectomy, treatment of dentin hypersensitivity, and tooth bleaching have been proposed. The aim of this paper was to review the benefits and drawbacks of laser tooth bleaching.

Key words: Laser therapy – Tooth bleaching – Endodontics.