ah plus root canal sealer – an updated literature review

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REVIEW ARTICLE

Key words adhesion, AH Plus, biocompatibility, physicochemical properties, root canal sealer

Ansgar Hergt, Annette Wiegand, Michael Hülsmann, Tina Rödig

AH Plus root canal sealer – an updated literature review

Aim: To review the literature over the last 10 years on AH Plus, focusing on physicochemical prop-erties, penetration of dentinal tubules, influence on the resistance to vertical root fracture, adhesion, antibacterial effect, biocompatibility, tooth discolouration, retreatability and the effect of increased temperature.Methodology: An electronic search in the database PubMed for 2005 to 2014 was performed using the search term ‘AH Plus’. Only original research publications were selected; reviews, case reports, studies not focusing on sealers and studies dealing with sealing ability or where leakage of sealers was investigated were excluded.Results: 610 publications were found from which 180 were selected for this review. There was great variance in the results of these studies. Concerning penetration into dentinal tubules, adhesion to the root canal wall, antibacterial effects, biocompatibility, removal during retreatment, effect of increased temperature, AH Plus performed equal or even superior compared to other sealers. Setting time and dimensional change did not completely fulfill the requirements of the ISO 6876 and ANSI/ADA No. 57 specifications in all studies. Discolouration may appear after application of AH Plus into the pulp chamber.Conclusion: Most of the studies confirmed that AH Plus fulfills the requirements of a root canal filling material as defined by the specifications for root canal filling materials and the guidelines of the European Society of Endodontology (ESE).

Ansgar Hergt

Prof. Dr. Annette Wiegand

Prof. Dr. Michael Hülsmann

PD Dr. Tina Rödig

All at:Department of Preventive Dentistry, Periodontology and CariologyUniversity of GöttingenRobert-Koch-Str. 4037075 Göttingen,Germany

Correspondence to:PD Dr. Tina Rödig,Department of Preventive Dentistry, Periodontology and CariologyUniversity of GöttingenRobert-Koch-Str. 4037075 Göttingen,Germany.Tel: +49 551 3922877Fax: +49 551 3922037Email: [email protected]

Introduction

A new era of root canal sealers started as André Schroeder developed the prototype of the first resin based sealer AH 26 (Dentsply DeTrey, Konstanz, Germany) in 1955. Until then, the majority of seal-ers were composed of zinc oxide-eugenol, calcium hydroxide or contained medicaments or pharma-ceuticals such as formaldehyde or corticosteroids. Although still available on the market, the sealer was replaced by AH Plus (Dentsply DeTrey) in 1995 (Fig 1). Twenty years later, AH Plus most likely rep-resents the gold standard in clinical practice and the

reference material for other types of sealers in la-boratory and clinical research1-8. Although it showed a similar composition to AH 26, the addition and exchange of components made AH Plus a new seal-ing material requiring new studies to determine its properties and its clinical performance.

The aim of root canal treatment is prevention or healing of apical periodontitis by preparation, disin-fection and complete obturation of the root canal system. Gutta-percha is still the most commonly used core material for root canal filling and is ap-plied in combination with a sealer. The function of a sealer is to compensate for irregularities between

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core material and the root canal wall to prevent the passage of microorganisms and fluid along the root canal system by blocking the apical foramen, dentinal tubules and accessory canals9. Louis Gross-man was the first to define requirements for an ideal root canal filling material which are still valid today. Adopting Grossman’s requirements and according to the guidelines of the European Society of Endo-dontology (ESE)9, a root canal sealer should show a number of desirable properties (Table 1).

The literature is replete with studies on the prop-erties of different sealers. In 2005, Rödig et al10 published a review of the literature (1995 to 2005) about epoxy-resin-based root canal sealers (AH 26 and AH Plus) and a silicone-based root canal sealer ( RoekoSeal, Coltène/Whaledent, Langenau, Ger-many). The aim of the following paper is to present a structured and updated review of the studies pub-lished during the last 10 years evaluating the prop-erties, benefits and limitations of AH Plus.

Review design

This review aimed to systematically present the liter-ature about AH Plus over the last 10 years. An elec-tronic search in the database PubMed was performed in October 2014 using the search term ‘AH Plus’ with filters set from 01/01/2005 to 31/10/2014.

Two authors (AH and TR) independently re-viewed the titles and abstracts of the articles found. After abstracts were screened, the remaining articles were ordered in full text. Language was restricted to English.

The systematic search resulted in 610 abstracts, of which 430 were excluded due to the following reasons: literature review; case report; study not fo-cusing on AH Plus or sealers, e.g. examination of

irrigation solution or root canal preparation; study dealing with sealing ability or leakage of sealers; study published for the second time. Studies on seal-ing ability or leakage were excluded since Rechen-berg et al11 detected potential systematic errors in in vitro experiments on microbial leakage through root canal-filled teeth.

Finally, 180 articles were considered relevant, and categorised as follows: physicochemical prop-erties (n = 306,12-40), penetration (n = 107,41-49), resistance to vertical root fracture (n = 138,50-61), adhesion (n = 441,62-104), antibacterial effect (n = 2213, 105-125), biocompatibility (n = 412,126-165), discolouration (n = 44,166-168), removal during re-treatment (n = 135,169-180) and the effect of in-creased temperature (n = 53,45,181-183).

Compositions and properties

According to the manufacturer’s information, AH Plus represents a paste-paste system which contains epoxide paste and amine paste. The components of AH Plus are given in Table 2.

Physicochemical properties

Thirty studies examined the physicochemical prop-erties of AH Plus. Almost all studies investigated the physicochemical characteristics according to the specifications no. 57 ANSI/ADA184 and ISO 6876185, which allows reproducibility and compari-son amongst studies. Mostly, the physicochemical properties under investigation were setting time, radiopacity, flow ability, dimensional change, film thickness and solubility. A summary of all relevant studies is presented in Table 3.

Setting Time

An appropriate setting time of a root canal sealer is essential to allow adequate time for obturation of one or more root canals6. Setting time is dependent on temperature, particle size and constituent com-ponents and humidity23. However, Duarte et al16 found that setting time is not altered by moisture16. In some of the studies, assessment of setting time was

Fig 1 In 1995, AH Plus was introduced as a new endodontic sealer; AH 26 is a powder/ liquid sealer and AH plus is a paste/paste sealer.

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based on visual inspection only6. To allow an objec-tive assessment, most studies used a Gilmore needle with a head weight of 200 g to examine setting time according to ISO 6876. The high range of data for setting time can be explained by different time points of measurements, e.g. evaluation of initial or final setting time. Setting time for AH Plus varies between 492 min and 1440 min6,17,18,20,21,23-28. The addition of nanoparticles is responsible for extending setting time by 5 min13. Most of the studies concluded that the setting time of other sealers is according to the data provided by the manufacturers17.

Radiopacity

The degree of radiopacity is important for control of homogeneity of a root canal filling, but what also should be taken into consideration is that an extreme degree of contrast could imply a false impression of a dense and homogeneous root canal obturation21,23. AH Plus showed a high radiopacity as reported in several studies17,21,23,24. The values for radiopacity of a sealer, as recommended by the ISO and ANSI/ADA, should not be lower than 3 mm thickness of 1 mm aluminium6. Most of the other sealers tested also fulfilled these standards14,24.

Table 1 Desirable properties of sealers as suggested by the

ESE9.

A sealer should be:

Biocompatible

Dimensionally stable

Able to seal

Unaffected by tissue fluids and insoluble

Nonsupportive of bacterial growth

Radiopaque

Not stain dental hard tissues

Removable from the root canal if retreatment is necessary

Table 2 Composition of AH Plus according to the manufacturer.

Epoxide paste Amine paste

Diepoxide

Calcium tungstate

Zirconium oxide

Aerosil

Pigment

1-adamantane amine

N,N’-dibenzyl-5-oxa-non-

andiamine-1,9

TCD-diamine

Calcium tungstate

Zirconium oxide

Aerosil

Silicone oil

Table 3 Summary of the studies investigating the physicochemical properties of AH Plus.

Study Setting time(min)

Radiopacity(mm Al)

Flow(mm)

Dimensional change (%)

Film thickness(μm)

Solubility(%)

Versiani et al26 (2006) 492 – 508 - 38.6 ± 3.9 1.28 10.60 ± 0.54 0.21

Resende et al23 (2009) 494 ± 7.03 6.1 ± 0.2 38.4 ± 3.0 1.4 ± 0.3 - 0.41 ± 0.29

Marin-Bauza et al21 (2010) 579 ± 4.95 5.97 ± 0.24 36.8 ± 3.0 1.7 ± 0.3 - 0.74 ± 0.41

Garrido et al18 (2010) 783 ± 12.20 211 ± 1.17 40.3 ± 0.4 0.2 ± 0 10 ± 10 -1.12 ± 0.19

Flores et al17 (2011) 580 ± 3.05 6.00 ± 0.12 - 1.3 ± 0.2 - 0.36 ± 0.14

Marciano et al20 (2011) 711.3 ± 95.0 14.50 ± 1.69 39.2 ± 3.9 - 43.7 ± 0.5 0.30 ± 0.02

Schäfer et al24 (2013) 630 6.3 ± 0.4 - - - 0.36 ± 0.29

Vitti et al27 (2013) 610.8 – 1086.6 - 38.0 ± 0.6 - - -0.84 ± 0.03

Zhou et al28 (2013) 690 ± 45 - 21.2 ± 0.3 -0.034 ± 0 16.1 ± 4.5 0.06 ± 0.04

Borges et al14 (2014) - 193.80 ± 7.82 - - - 0.56 ± 0.48

Sonntag et al25 (2014) 1440 53.3 18.0 ± 1.0 -2.2 ± 2.1 8 ± 1.0 0.1 ± 0.1

Viapiana et al6 (2014) 1345 ± 16 15.74 ± 0.25 23 0.6 ± 0.4 85 ± 8.0 -0.25 ± 0.10


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flow depends on features like the internal diameter of the root canal, temperature, time, particle size, rate of shear and speed of insertion18. A high flow is associated with an increased risk of apical extrusion (Figs 2a to 2c), which can compromise apical healing and induce inflammatory reactions of the periapical tissues39. Actual studies demonstrate an adequate flow for AH Plus according to the ANSI/ADA stand-ards6,20,23,27,28. Also, all other sealers under investi-gation fulfilled these requirements.

Dimensional change

Dimensional changes of a root canal sealer should not exceed 0.1% expansion or 1.0% shrinkage during setting. Most of the studies concluded that AH Plus and the majority of the available sealers do not fulfill these standards17,22,23,26. In most of the studies, an expansion during setting of AH Plus was found, which is likely to be due to water absorp-tion17,18,21,23,26.

Film thickness

A low film thickness is recommended for a uniform distribution of the sealer on the root canal wall and into anatomical irregularities6,20. This prop-erty depends on the same features as flow ability. ISO 6876185 requests a maximum film thickness of 50 μm. For AH Plus, most studies18,20,25,26,28 except one6 reported a film thickness of 8.0 to 43.65 μm. Acroseal (Septodont, Niederkassel, Germany), Adseal (MetaBiomed, Chungbuk, Korea) and AH 26 have a higher film thickness than recommended18,20. EasySeal (Komet, Lemgo, Germany)25, Epiphany (SybronEndo, California, USA)26, Endosequence BC Sealer (Brasseler, Georgia, USA), MTA Fillapex (An-gelus, Londrina, Paraná, Brazil), ThermaSeal (Dents-ply Tulsa Dental, Oklahoma, USA) and Pulp Canal Sealer (Kerr Corporation, California, USA)28 fulfill these requirements.

Solubility and water sorption

Besides good biocompatibility, low solubility40 and high dimensional stability32 are important proper-ties of a root canal filling material. High solubility of the sealer may result in small gaps and micro-

a

b

c

Fig 2 Periapical radiographs of tooth 25 with a necrotic pulp and a radiolucency at the distal aspect of the root: a)the postoperative radiograph after warm vertical compaction showed a lateral canal disclosed by filling material extrud-ing into the periradicular tissues; b) after 4 months, a partial resorption of the extruded material occurred; c) 5-year follow-up showing complete osseous repair but the sealer was not completely resorbed.

Flow

The ANSI/ADA184 and ISO 6876185 specifica-tions require a sealer to have a minimum flow of 20 mm/10 min or 17 mm/10 min, respectively. The


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leakages along the filling material, which promotes ingress of bacteria. Dissolution of the sealer also may release components responsible for irritation and subsequent inflammation of the periapical tissues. The requirements for root canal sealing materials have been defined by the ISO Standard 6876185: after storage in deionized distilled water for 24 h, the maximum loss of dry mass should be less than 3%. In a study by Donnelly et al33, AH Plus (1.07 %) and GuttaFlow (Coltène/Whaledent) (0.38%) demonstrated a low water sorption. The lowest water sorption (0.28%) was recorded for Kerr EWT (Kerr Corporation) but this sealer showed a high solubility (3.95%), which was significantly higher than the solubility of AH Plus and Gutta-Flow. Methacrylate resin-based sealers (Epiphany), InnoEndo (Heraeus Kulzer, Hanau, Germany) and EndoREZ (Ultradent Products, Utah, USA), and a glass-ionomer based sealer (Ketac Endo, 3M ESPE, Seefeld, Germany) showed a significantly higher water absorption and solubility (4.23% to 12.04%) than AH Plus. Only AH Plus and GuttaFlow, Seal-Apex (Kerr Dental, Rastatt, Germany), MTA Fill-apex6,14 and RealSeal (SybronEndo)24 fulfilled the ISO Standard 6876, which consisted of a maximum mass loss of 3%. In a study by Borges et al29, the weight loss of AH Plus (0.28%) and four different calcium silicate-containing sealers was tested after 24 h storage in distilled water. AH Plus (0.28%) and Angelus MTA (Angelus) were in the range of 3% weight loss. For Angelus MTA, an increase in weight of 1.28% was reported29. Further studies confirmed these findings31,33,34,38.

Influence of calcium hydroxide on physical properties

Calcium hydroxide (Ca(OH)2) exerts influence on some physical properties of a sealer such as solu-bility, flowability and film thickness16. Calcium hy-droxide has been widely accepted as the most fre-quently used intracanal medicament35. Remnants of calcium hydroxide may interfere with the filling material15,19,37, which may result in increased ap-ical leakage15,36 or in potential reduction of sealer adaptation30 and alteration of physical properties.

Duarte et al16 reported that a mixture of AH Plus with 10 % calcium hydroxide was significantly

more soluble and showed a higher film thickness compared with AH Plus without calcium hydroxide. Moreover, the flowability was significantly lower for AH Plus with 10% calcium hydroxide16.

Influence of location inside the tube

Setting time and flow showed higher values if taken from near the opening of the tubes. Radiopacity was lower at the opening of the tubes compared with a portion of sealer collected from the bottom of the tubes. These findings may be related to an unequal mixture between the inorganic and the organic phases of the sealer inside the tubes12.

It can be concluded that AH Plus fulfills the guidelines published in ISO 6876 and ANSI/ADA specifications on the maximum loss of weight, de-fined as being less than 3% of the initial mass. Re-quirements concerning flow, film thickness and ra-diopacity are also fulfilled by AH Plus. Setting time and dimensional change did not completely meet the requirements of the ISO 6876 and ANSI/ADA guidelines in all studies. Calcium hydroxide exerts influence on some physical properties of AH Plus, namely solubility, flowability and film thickness.

Penetration into dentinal tubules

Usually, root canal obturation is performed using a core material, e. g. gutta-percha and a sealer, which should seal irregularities between the core material and root canal dentine resulting from the physical inability of gutta-percha to adapt tightly to canal walls48.

The flow properties of a sealer are influenced by the viscosity of the material, temperature and hu-midity45. The effect of temperature (25°C/37°C) on viscosity was tested on Apexit (Ivoclar Vivadent, Ell-wangen, Germany), Tubuliseal EWT (Sybron Endo), Grossman’s sealer (Guy’s and St Thomas NHS Trust, London, UK), Ketac Endo and AH Plus, demonstrat-ing that AH Plus was the only sealer showing no temperature dependent change in viscosity45. More-over, Ravindranath et al46 stated that penetration of AH Plus into the dentinal tubules was independent of the obturation technique46.


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Penetration compared to other types of sealers

Balguerie et al41 obturated root canals of extracted teeth, which were transversely sectioned at 2, 5, and 8 mm from the working length and inspected under the scanning electron microscope (SEM) at a magnification between 500x and1,500x. They con-cluded that AH Plus showed the best tubular pene-tration when compared to Acroseal (Septodont), Endobtur (Septodont), Ketac-Endo (3M ESPE) and RoekoSeal Automix (Coltène/Whaledent), with a majority of sections showing no gaps between sealer and dentine. Another ex vivo study reported similar results demonstrating a superior perfor-mance for AH Plus compared to Resino Seal (Am-rit Chemicals and Mineral Agency, Punjab, India) and a zinc oxide eugenol sealer (Vishal Dentocare, Ahmedabad, India)49.

Resilon (Pentron Clinical Technologies, Connect-icut, USA) is a synthetic, polyester polymer-based core material developed to improve the seal be-tween filling material and root dentine47, and is used in combination with a resin-based sealer (RealSeal or Epiphany). The penetration of these sealers into dentinal tubules has been shown to be significantly better than AH Plus in the coronal (RealSeal) and middle third (Epiphany) of the root canal44,48. In contrast, Epiphany SE (a self-etch version of Epiph-any) did not perform superiorly when compared to AH Plus48.

Chandra et al44 and Chadha et al43 compared the penetration ability of Endo REZ and AH Plus with conflicting results. Depending on the fact that the root canal was left moist or dried prior to sealer ap-plication, penetration ability of Endo REZ was better or worse compared to AH Plus43,44.

Primary treatment and retreatment

In an ex vivo study, Kok et al7 compared dentine penetration of AH Plus and MTA Fillapex after root canal treatment and subsequent retreatment. They found no significant difference between both types of sealers after the primary treatment (instrumenta-tion and obturation). Interestingly, after retreatment, neither MTA Fillapex or AH Plus were able to pen-etrate into dentinal tubules7.

Influence of activated irrigation on penetration

Bolles et al42 examined the effect of two different sonic irrigation systems (EndoActivator [Dentsply Tulsa] and Vibringe [Vibringe, Amsterdam, Nether-lands]), when activating ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite (NaOCl), on sealer penetration into dentinal tubules by using confocal laser scanning microscopy. They concluded that the use of EndoActivator or Vibringe did not improve penetration of AH Plus when compared to manual irrigation42.

AH Plus shows good penetration into dentinal tubules which is similar or superior to other types of sealers. Comparison of AH Plus with adhesive root canal filling materials with regard to penetration ability resulted in conflicting findings.

Influence on tooth resistance to vertical root fracture

Vertical root fracture is a common risk for root canal-treated teeth and one of the most serious complica-tions making tooth extraction necessary in the majority of the cases61. Usually, fracture resistance is meas-ured using a universal testing machine with a steel tip, which is driven downwards into the root canal or onto the filling material until fracture occurs50,51,53,55. The results of several recent studies are conflicting. Ersev et al50 examined root canal fillings with AH Plus or MetaSEAL (Parkell Inc, New York, USA), performed with a single cone or a lateral compaction technique. The load until root fracture was significantly lower in the instrumented but unfilled teeth, compared to those filled with AH Plus or MetaSEAL, in combination with gutta-percha using the single cone technique. In contrast, no significant difference between the lateral compaction groups and the unfilled specimens was observed. Moreover, no significant difference in root fracture resistance between lateral compaction and single cone technique was detected50. Ribeiro et al58 investigated the influence of different filling materials on root fracture susceptibility in mandibular incisors58. Gutta-percha or Resilon in combination with different sealers (AH Plus, AH 26, Epiphany, Endofill [Dentsply/Maillefer]) did not significantly increase root fracture


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resistance compared to the unfilled control group58. Jainaen et al51,52 found similar results and demon-strated no significant difference in fracture susceptibil-ity between sound and prepared root canal dentine51. Moreover, Ulusoy et al60 concluded that root canal fillings with gutta-percha and AH Plus did not in-crease fracture resistance compared to instrumented and unfilled specimens. Root canal filled specimens were significantly more susceptible to fracture than the positive controls (untreated teeth).

It was suggested that adhesive root canal fillings (RealSeal) or glass ionomer sealers (ActiV GP + gutta-percha) may exhibit better adhesion to root canal dentine, thereby increasing the resistance against vertical root fracture. Only one study evaluated the fracture resistance of a glass ionomer sealer (ActiV GP) compared to AH Plus53. The fracture values were significantly higher than those of instrumented but unfilled teeth but not superior to AH Plus and gutta-percha53. Monteiro et al56 concluded that teeth filled with Resilon and RealSeal were significantly more resistant to fracture than teeth obturated with gutta-percha and AH Plus. Similar results were reported for the RealSeal system54 and Epiphany SE Sealer57. In contrast, fracture resistance of roots filled with gutta-percha/AH Plus and gutta-percha/RealSeal was significantly higher than of those filled using the RealSeal system and RealSeal cone/AH Plus55. The authors concluded that the lower fracture resistance of roots filled with RealSeal may be due to more ef-ficient transmission of forces within the canal rather than due to a direct effect of the material itself.

Calcium silicate-based sealers, e.g. Endo Sequence BC sealer, demonstrated no significant differences compared to AH Plus, regarding fracture resistance, but both sealers performed significantly better than the mineral trioxide aggregate-based sealers Tech Biosealer (Tech Biosealer Endo, Isasan SRL, Revello Porro, Italy) and Fillapex (Angelus, Londrina, Paraná, Brazil)8,59.

Obturation technique (single cone/lateral com-paction) does not influence fracture resistance of root canal fillings with gutta-percha and AH Plus. Stud-ies on ‘adhesive’ root canal filling materials report inconsistent results with regard to fracture resistance compared to AH Plus. Limited information suggests that calcium silicate-based sealers may show a frac-ture resistance comparable to that of AH Plus.

Adhesion

Three-dimensional obturation of the root canal is an essential part of endodontic treatment. Ideally, the sealer should adhere to the root canal wall and to gutta-percha as well. There are no standardised recommendations for the adhesion strength of root canal sealers to dentine. Some studies examined the shear bond strength (MPa) of the sealer with a uni-versal testing machine using push-out tests104. The final irrigation solution might have an influence on the adhesion of the sealer81,82,94,101.

The influence of irrigants on smear layer removal and adhesion

Vilanova et al98 examined the influence of irrigation solutions on the bond strength of AH Plus and Epiph-any to the root canal wall. Following preparation, root canals were irrigated with 1% NaOCl, 1% NaOCl + 17% EDTA, 17% EDTA, 24% EDTA gel or 2% chlorhexidine (CHX) gel. AH Plus achieved sig-nificantly higher bond strengths (8.74 ± 2.75 MPa) than Epiphany (6.74 ± 3.97 MPa), with removal of the smear layer increasing the bond strength of AH Plus to root canal dentine98. Eldeniz et al72 and de Assis et al69 confirmed these results. In contrast, Shokouhinejad et al90 showed that the presence or absence of smear layer did not influence the bond strength of AH Plus to root dentine.

Nunes et al83 concluded that AH Plus had a sig-nificantly greater adhesion to dentine than Epiphany and that bond strength could be improved by a final irrigation with NaOCl and EDTA. Neelakantan et al81 examined the impact of dentine conditioning using different sequences of solutions (3% NaOCl, 17% EDTA, 7% maleic acid and 2% CHX) and its influ-ence on the sealing ability and dentine bond strength of AH Plus. Final irrigation with a decalcifying agent decreased leakage and increased push-out bond strengths. This effect was abolished when NaOCl was used as a final irrigant. Moreover, these authors stated that continuous chelation with a 1:1 mixture of 18% etidronic acid (HEBP), with 5% NaOCl during instrumentation, resulted in significantly higher bond strengths of AH Plus than irrigation with NaOCl and EDTA82. The wettability of AH Plus improved after smear layer removal and a final irrigation with CHX,


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because it decreases the contact angle between AH Plus and the dentine surface69.

CHX in combination with EDTA improved the bond strength of AH Plus101. An alternative may be smear layer removal with NaOCl in combi-nation with 37% phosphoric acid in order to in-crease bond strengths101. Ravikumar et al85 ex-amined the adhesion of AH Plus to root dentine after final irrigation with NaOCl and a decalcify-ing agent (maleic acid, citric acid or MTAD). Fi-nal irrigation with NaOCl + maleic acid resulted in superior bond strengths (6.54 ± 1.12 MPa) than NaOCl + EDTA (5.43 ± 1.02 MPa), NaOCl + citric acid (4.14 ± 0.46 MPa) and NaOCl + MTAD (an irrigant composed of tetracycline, citric acid and a detergent; 1.10 ± 0.45 MPa). It was speculated that MTAD may have a negative influence on the adhesive ability of AH Plus85. Do Prado et al103 showed that final irrigation with NaOCl after smear layer removal was associated with the highest val-ues of adhesion force in the AH Plus groups. How-ever, Rocha et al86 concluded that 2.5% NaOCl adversely affected bond strength of AH Plus com-pared to 2.0% CHX.

Scelza et al88 demonstrated that different ir-rigating solutions (10.0% citric acid, 17.0% EDTA or 2.5% NaOCl) did not affect resistance to the displacement of AH Plus using a push-out test. Several studies investigated the effect of a final rinse of MTAD on the adhesion of AH Plus and concluded that bond strengths of gutta-percha/AH Plus to root dentine is adversely affected by this solution75,78,85.

Activated irrigation

Ultrasonic activation of 3% NaOCl and 17% EDTA also improved the adhesion of AH Plus in the coronal and middle part of the root canal94. In the apical part, manual dynamic activation with a gutta-percha cone resulted in the highest bond strengths94.

Adhesion properties compared to other types of root canal sealers

Compared with other root canal sealers, AH Plus was found to be superior with regard to adhesion to root dentine when a standardised irrigation pro-

tocol (NaOCl + EDTA) was used before obtura-tion70,73,89,92,95,96. Fisher et al73 compared Kerr EWT, AH Plus, Resilon, ActiV GP and Endo REZ and concluded that AH Plus had significantly higher bond strength than all other groups. Ersahan and Aydin99 found similar results. They concluded that AH Plus showed a significantly higher bond strength to root canal dentine than EndoREZ and Sealapex99. AH Plus in combination with gutta-percha showed higher values for bond strength when compared to sev-eral so-called ‘adhesive’ root canal filling materials such as Resilon/Epiphany92, Resilon/Epiphany SE70 or EndoREZ89. Moreover, Ungor et al95 and Ure-yen Kaya et al96 reported similar results. However, Mahdi et al79 concluded that the sealer/core material (epoxy-resin-based, methacrylate-resin-based and resin-coated) did not influence the push-out bond strength values (RealSeal, AH Plus and EndoREZ).

Bioceramic root canal sealers such as iRoot SP (Innovative BioCeramix Inc, Vancouver, Canada) or EndoSequence BC Sealer showed a similar adhesion to root canal dentine compared with AH Plus using push-out tests87,90.

MTA (ProRoot MTA, Dentsply Maillefer) and a MTA-based sealer (Endo-CPM, EGEO SRL, Buenos Aires, Argentina) might be superior concerning ad-hesion to root canal walls65,91. Sun et al93 demon-strated superior bond strength to root canal dentine for MetaSEAL compared to AH Plus. However, Law-son et al100 concluded that the push-out strength of AH Plus is significantly higher than MetaSEAL for single-cone technique and warm vertical compac-tion.

Gesi et al74 analysed failure modes of root slices after push-out testing. AH Plus/gutta-percha slices failed along the gutta-percha/sealer interface while Resilon/Epiphany failed predominantly along the sealer/dentine interface.

Overall, smear layer removal with chelating agents such as EDTA or citric acid in combination with NaOCl resulted in improved adhesion of AH Plus to root canal dentine62,72,98,101. An interesting result was reported by de Assis et al102. They con-cluded that disinfection of gutta-percha with 2% CHX improved adhesion force between root canal sealer (AH Plus) and gutta-percha, compared with 5.25% NaOCl and distilled water102.


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Laser irradiation

An alternative method to increase adhesion of a root canal sealer may be laser irradiation of the dentine surface62,63,66,77. Laser irradiation causes morphological alteration of the dentinal tissue re-sulting in irregularities and increased surface area of the root canal walls77, which subsequently might improve adhesion of the sealer66. The best values for adhesion were obtained after pretreatment of the root canal with Er:YAG irradiation or EDTA as a final flush. Ayranci and Koseoglu66 evaluated the effect of Nd:YAG or Er:YAG laser irradiation or an irrigation with EDTA on the adhesion of AH Plus to root dentine. After these pretreatments, root canal filling was performed with AH Plus and gutta-percha. In the apical and middle part of the root canal, laser irradiation did not improve adhesion of AH Plus compared with EDTA. Only in the coronal part, pretreatment of the dentinal surface with an Er:YAG laser resulted in significantly better AH Plus adhesion than a final irrigation with EDTA66. How-ever, pretreatment of dentine with 15% citric acid increased shear bond strength significantly when compared with Er:YAG laser irradiation62. This find-ing may be due to incomplete removal of the smear layer by laser irradiation62. Alfredo et al63 found that irradiation of root dentine with a gallium-alu-minium arsenide (GaAlAs) semiconductor 980 nm diode laser (SIROlaser 2.2; SIRONA Dental, Ben-sheim, Germany) significantly increased adhesion of AH Plus (8.69 ± 2.44 MPa) compared to non-irradiated controls (3.86 ± 0.60 MPa), which were irrigated with 2 mL 1% NaOCl (5 min), 2 mL 17% EDTA (5 min) and rinsed again with distilled water for 1 min.

Gutta-percha solvents

Gutta-percha solvents used during endodontic re-treatment were shown to decrease bond strength of AH Plus1,80. Chloroform, xylene and Endosolv (Septodont, Niederkassel, Germany)80 had an ad-verse effect on the bond strength of AH Plus. Euca-lyptol and orange oil did not decrease adhesion of AH Plus to root canal dentine1.

Influence of AH Plus on fibre post insertion

Several studies examined the influence of root canal sealers on the bond strength of fibre posts to root canal dentine68,71,84. In all studies, extracted human teeth were randomly divided into experimental groups followed by root canal preparation to sizes 35 to 45 and irrigation with NaOCl. Subsequently, ob-turation with gutta-percha without sealer or gutta-percha with different sealers was performed. After post space preparation, all fibre posts were inserted with Panavia 2.0 (Kuraray Dental, Hatters heim am Main, Germany)71, RelyX Unicem (3M ESPE)68 or Clearfil SA Cement (Kuraray Dental)84. AH Plus, AH 26, iRoot SP and Epiphany did not interfere with bond strengths of fibre posts cemented with self-adhesive resin cements (RelyX Unicem, Clearfil SA Cement) when root canals were irrigated with dis-tilled water or CHX after post space preparation. However, Endofill (Dentsply Maillefer, Dentsply, Petrópolis, Brazil) and Endomethasone (Septodont) showed significantly lower bond strengths68,84. When no irrigation was performed, adhesion of fibre posts cemented with Panavia F 2.0 was significantly decreased, independent of the sealer type71.

Influence of calcium hydroxide on adhesion properties of AH Plus

Calcium hydroxide did not interfere with the push-out bond strength of AH Plus when the intracanal medicament was removed, e.g. by NaOCl irrigation, NiTi files, passive ultrasonic irrigation or distilled water, prior to root canal filling64,67,97. However, Guiotti et al76 concluded that intracanal dressings with Ca(OH)2 reduced bond strength of AH Plus in all root canal thirds. In this study, all specimens were only immersed in NaOCl and shaken for 3 min to remove Ca(OH)2, resulting in incomplete removal of the intracanal medicament76. It can be assumed that remnants of calcium hydroxide influenced adhesion of AH Plus negatively.

The push-out bond strength of AH Plus is im-proved by removing the smear layer with decalcify-ing agents like EDTA or phosphoric acid. Activation of the final irrigant, e.g. by ultrasonic activation, improves adhesion properties. The bond strength of


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gutta-percha/AH Plus to root dentine is adversely affected by MTAD. Adhesive root canal filling ma-terials or bioceramic sealers, except MTA-based sealers, are not superior to AH Plus with respect to bond strength. Er:YAG laser irradiation improves adhesion only in the coronal part of the root canal. AH Plus did not interfere with the bond strength of fibre posts cemented with self-adhesive resin ce-ments, and calcium hydroxide did not interfere with the push-out bond strength of AH Plus when the intracanal medicament was completely removed.

Antibacterial effect

Common tests to examine the antibacterial activ-ity of root canal sealers are the agar diffusion test (ADT) or the direct contact test (DCT)109-111,115,119. Most of the studies tested antibacterial effects of root canal sealers in vitro, while only few tested an-tibacterial effects ex vivo on extracted human or bovine teeth117,118,120,121.

The ADT is commonly used to evaluate the anti-bacterial effectiveness of a sealer in its freshly mixed and its set state. A bacterial suspension, e. g. E. fae-calis, is placed on Schaedler agar plates. The mixed sealer is applied to sterile cellulose plates, which are placed in direct contact with the agar plates and cul-tivated at 37°C for 48 h under anaerobic conditions. Finally, inhibition zones can be measured111.

Moreover, the antibacterial effect of a root canal sealer may also be determined with a DCT109,111,119, in which bacterial species are cultivated in brain heart diffusion solution or Schaedler liquid medium before application on well cell culture plates. The sealer111 or specimens with sealer (e.g. dentine blocks)109 are applied on these culture plates following in-cubation under anaerobic conditions at 37°C. For determination of the antibacterial effect, bacterial growth, correlating with optical density of the sus-pension, is measured and compared with the control group109,111.

Antibacterial effect against E. faecalis and C. albicans

AH Plus displayed a good antibacterial effect against E. faecalis when freshly mixed112, but there was

no or only a minimal effect after a setting time of 48 h110,111,117. Pizzo et al119 showed that freshly mixed AH Plus completely inhibited bacterial growth (E. faecalis) but 24-h-old samples showed no anti-bacterial effect. Using DCT, Zhang et al125 reported that AH Plus killed all bacteria (E. faecalis) after 5 min, but no antibacterial effect was detected after the sealer had set for 1, 3 and 7 days.

In an ex vivo study, Wang et al123 evaluated the antimicrobial effects of root canal sealers (AH Plus, EndoSequence BC sealer, Kerr Pulp Canal sealer EWT) on E. faecalis biofilms in dentinal tubules. They placed the different sealers on the root canal wall for 1, 7, and 30 days and determined the propor-tions of dead and live bacteria inside the dentinal tu-bules using confocal laser scanning microscopy. For AH Plus, significantly more dead bacteria in dentine were found after 30 days than after 1 or 7 days. This finding may be due to a release of antibacterial com-pounds from the sealers into the dentinal tubules, prolonging the long-term action of the antibacterial effect123. Ozcan et al117 investigated different obtu-ration techniques (Thermafil, continuous wave, lat-eral compaction, matched taper single gutta-percha cone and laterally compacted matched taper gutta-percha cone) in combination with AH Plus, ex vivo, on teeth which were infected with E. faecalis, when specimens were placed into a bacterial suspension. The study group examined the reduction of E. fae-calis by determining remaining colony-forming units (CFU). AH Plus was effective in killing E. faecalis, with the exception of the Thermafil group, in which the bacteria were completely killed only in 2 out of 10 specimens117. This may be due to the fact that in the Thermafil group, sealer was placed only at the orifice of the root canal to prevent sealer extrusion.

Yasuda et al124 found the highest antimicrobial activity for AH Plus when compared to SuperBond Sealer (Sun Medical, Shiga, Japan), Sealapex, Roe-koSeal Automix, Canals N (Showa Yakuhin Kako, Tokyo, Japan) and ProRoot MTA. Sedgley121 tested the intracanal survival of E. faecalis after obturation with gutta-percha and AH Plus in extracted human canines. After 8 months of incubation, viable bacte-ria were detected in 8 out of 20 root canals (40%).

However, Slutzky-Goldberg et al122 and Neela-kantan and Subbarao116 reported that AH Plus was completely ineffective against E. faecalis and C. al-


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bicans when freshly mixed, as well as 1, 2, 7 and 14 days later. In contrast, Ozcan et al118 and Miyagak et al114 concluded that AH Plus showed a very potent antifungal activity against C. albicans.

Antibacterial effects of AH Plus when mixed with CHX, cetrimide (CTR), amoxicillin or nanoparticles

CHX was shown to be an effective antimicrobial irrigant, and CTR is a cationic surfactant that has demonstrated its ability to eradicate a E. faecalis biofilm106. CTR in combination with AH Plus had concentration-dependent antimicrobial activity. E. faecalis biofilm formation was inhibited by AH Plus + CTR at a concentration of 0.2%, whereas 2.0% CHX mixed with AH Plus exhibited a lower antimicrobial activity106. In a molecular-based and culture-based comparison, root canal irrigation with 2% CHX for 10 min, before obturation with gutta-percha and AH Plus was more effective in removing E. faecalis than immediate obturation108. Freshly mixed and set samples (1, 3 and 7 days) of AH Plus mixed with amoxicillin completely inhibited cell growth of E. faecalis. The differences were statistically signifi-cant when compared to fresh and set sealer samples without amoxicillin105.

Moreover, nanoparticles were used to improve the antibacterial effect of AH Plus against E. faecalis. Kesler Shvero et al113 and Barros et al13, 107 exam-ined samples of AH Plus and AH Plus incorporating quarternary ammonium polyethylenimine (QPEI) nanoparticles. These studies demonstrated a posi-tive effect of incorporated nanoparticles for all tested sealers (AH Plus, Pulp Canal Sealer and GuttaFlow)

in a dose-dependent manner113. Nevertheless, ad-dition of QPEI did not result in a significant increase in the antibacterial effects of AH Plus after ageing13.

AH Plus shows an antibacterial effect against E. faecalis and C. albicans when freshly mixed. This effect cannot be demonstrated for older sam-ples. Compared to other types of sealer (e.g. Endo-Sequence BC sealer, Pulp Canal Sealer, SuperBond Sealer, Sealapex, RoekoSeal Automix, Canals N and ProRoot MTA), AH Plus exerts a superior antibacterial effect. Obturation technique does not influence anti-bacterial properties. Incorporated nanoparticles and AH Plus mixed with CTR or amoxicillin have a posi-tive influence on the antibacterial effect of AH Plus.

Biocompatibility

Biocompatibility of a root canal sealer is very im-portant because of its close contact to the periapical tissues (Figs 3a to 3b). Extrusion of filling material may induce periapical inflammation, delayed heal-ing and also affect the outcome of root canal treat-ment. Biocompatibility is assessed according to ISO 10993-5186.

In vitro studies

In vitro studies often used mouse, hamster or human fibroblasts as test materials126,128,130,132,134,137,

139,142,148,153,155-157,162,164,165. Moreover, cytotoxic-ity of sealers was examined using human138,147,163 and mouse osteoblasts149. Table 4 gives an overview about the in vitro studies on the biocompatibility of AH Plus. Most of these investigations confirmed a

Fig 3a and b As the sealer may come into close contact with periradicular tissues as a result of extrusion via the apical foramen, good bio-compatibility is mandatory. a b


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Table 4 In vitro studies on biocompatibility of AH Plus, sorted according to test material.

Study Test material Technique Non-toxic after specific period of time

Overall period

Bouillaguet et al129 (2006) Mouse fibroblasts Cell viability Still toxic after 3 days 3 days

Brackett et al132 (2008) Mouse fibroblasts Cell viability Still persistent mild inflammatory response after 3 weeks

6 weeks

Lodiene et al148 (2008) Mouse fibroblasts Cell viability Non-toxic after 24 h 24 h

Valois and Azevedo161 (2008) Mouse fibroblasts Cell cycle,cell viability Cytotoxic after 24 h 24 h

Al-Hiyasat et al126 (2010) Mouse fibroblasts Cell viability Cytotoxic after 48 h 48 h

Zhang et al164 (2010) Mouse fibroblasts Cell viability Toxic after 24 h 24 h

Karapinar-Kazandag et al146 (2011) Mouse fibroblasts Cell viability Toxic after 7 days (undiluted and diluted eluates)

7 days

Zoufan et al165 (2011) Mouse fibroblasts Cell viability Cytotoxic after 3 days 3 days

Garza et al142 (2012) Mouse fibroblasts Cell viability Cytotoxic after 24 h 24 h

Silva et al156 (2013) Mouse fibroblasts Cell viability Non-cytotoxic after 2 weeks 4 weeks

Silva et al157 (2013) Mouse fibroblasts Cell viability Non-cytotoxic after 2 weeks 5 weeks

Cotti et al137 (2014) Mouse fibroblasts Cell viability Still toxic after 3 days 3 days

Brackett et al134 (2010) Mouse fibroblastsMouse osteoblastsRat osteoblasts

Cell viability Toxic after 12 weeksToxic after 12 weeksNon-toxic after 12 weeks

12 weeks

Bin et al128 (2012) Hamster fibroblasts Cell viability, number of micronuclei

Genotoxic/cytotoxic after 3 days 3 days

Willershausen et al162 (2011) Human fibroblasts Cell viability Cytotoxic after 4 days 4 days

Silva et al155 (2012) Human fibroblasts Cell viability Cytotoxic after 24 h 24 h

Miletic et al150 (2005) Human cervical carcinoma, mouse fibroblasts

Cell viability Still toxic after period of 4 weeks 4 weeks

Kim and Shin147 (2014) Human gingival fibroblasts, human osteosarcoma cells

Cell viability Cytotoxic after 7 days 7 days

Eldeniz et al139 (2007) Human gingival fibroblasts Mouse fibroblasts

Cell viability Non-cytotoxic Still cytotoxic after 7 days

7 days

Hakki et al145 (2013) Immortalized murine cemento-blast cell line

Cell viability Diluted sealer (1:2) and 1:4) non-toxic after 30 h

90 h

Pinna et al152 (2008) Rat osteosarcoma Cell viability Non-toxic after 3 weeks 5 weeks

Brackett et al131 (2011) Human monocytes Mitochondrial response Cytokine secretion over 3 days 3 days

Xu et al163 (2010) Human osteoblasts Cell viability Toxic after 3 days 3 days

Loushine et al149 (2011) Mouse osteoblast Cell viability Non-toxic after 3 weeks 6 weeks

Brackett et al130 (2012) Mouse osteoblasts Mitochondrial response Still cytotoxic after 52 weeks 52 weeks

Brackett et al133 (2009) Human monocytes Mitochondrial response No cytokine secretion at any time 12 weeks

Brackett et al131 (2011) Human monocytes Mitochondrial response Cytokine secretion over 3 days 3 days

Gandolfi et al141 (2008) Human osteosarcoma cells Cell viability Still toxic after 3 days 3 days

Ehsani et al138 (2012) Human osteosarcoma cell line Cell viability Cytotoxic after 3 days 3 days

Camargo et al136 (2009) Hamster fibroblasts, human pulp cells

Cell cycle, formation of micronuclei

Still toxic after 24 h 24 h

Bryan et al135 (2010) Preosteoblast cell line derived from mouse calvaria

Cell viability Non-toxic after 3 weeks 5 weeks

Guven et al144 (2013) Human tooth germ stem cells Cell viability Cytotoxic after 14 days 14 days


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severe or moderate cytotoxicity for freshly mixed AH Plus, which decreased to mild cytotoxic reactions after 1 week and was categorised as non-cytotoxic after 2 or 3 weeks149,156. The initial cytotoxicity was attributed to a minimum release of formaldehyde from the epoxy resin component or the amines added to accelerate epoxy polymerisation146. Al- Hiyasat et al126 showed that cell viability of fibroblasts was re-duced by AH Plus after 48 h but compared to the other test materials AH Plus was the significantly least cytotoxic sealer followed by EndoRez, Epiphany and MetaSEAL, which was the most cytotoxic. Cell viability of MetaSEAL was reduced to 11%126.

Some authors evaluated cell viability by dimeth-ylthiazol diphenyltetrazolium bromide (MTT) assay at different time intervals126,128,129,132-135,137,139,

148,152,163-165, others determined cell viability using the tryptan blue exclusion assay155, Alamar Blue Assay141,162 or MTS Assay146 (Table 4). Brackett et al134 demonstrated the longest time period for cyto-toxic reactions for AH Plus compared to other stud-ies. In this in vitro study, AH Plus was placed in direct contact with three different cell lines (fibroblasts and osteoblasts) and the sealer was found to be severely cytotoxic over a period of 8 weeks134. It is assumed that human fibroblasts and rat osteoblasts are not as sensitive as mouse or hamster fibroblasts/osteo-blasts134,139. AH Plus was severely cytotoxic in the freshly mixed state and slightly cytotoxic after 7 days on mouse fibroblasts but did not exert any cytotox-icity to human gingival fibroblasts (fresh and aged samples)139.

Three out of 31 studies examined cytotoxicity of root canal sealers by measuring their effect on cytokine production130,131,133 (Table 4). Brackett et al133 found no cytokine secretion after 12 weeks. Se-cretion of tumor necrosis factor (TNF ) was meas-ured 6 h after mixing but disappeared completely in aged samples after 1 year, whereas cell viability only increased by 60%130.

Two studies evaluated the cytotoxic effects of root canal sealers on the cell cycle of mouse fibro-blasts by flow cytometry136,161,163. Cell proliferation of human osteoblasts was inhibited because flow cy-tometry accumulated in the G1 phase of the cell cycle. An MTT assay confirmed these findings163. Camargo et al136 found that AH Plus did not interrupt the cell cycle of hamster fibroblasts but increased the num-

ber of micronuclei, which is indicative of genotoxicity and changes of the cell cycle. These findings may be due to damage to the DNA-containing structures136. Valois and Azevedo161 found that AH Plus inhibited cell growth in a dose-dependent manner161.

Al-Hiyasat et al126 showed that diluted AH Plus (1:10) increased cell viability from 74% to 95% compared to the undiluted specimens. Karapinar-Kazandag et al146 and Zoufan et al165 found similar results. If a root canal sealer is extruded into the periapical tissues, the extruded material is diluted by body fluids. It can be concluded from the afore-mentioned studies that the degree of dilution of the eluates usually reduced the cytotoxic effect of a root canal sealer126,146,165.

Eight out of 28 studies confirmed good biocom-patibility for AH Plus. However, testing periods were very short in the remaining studies in which AH Plus was classified as not being biocompatible.

Table 4 summarises all relevant in vitro studies on the biocompatibility of AH Plus.

In vivo studies

Only a few in vivo studies evaluated the subcutane-ous tissue reaction of endodontic sealers in rats127,

140,143,153,154,158,160. In these studies, subcutaneous pockets in Wistar rats were prepared and polyethyl-ene tubes filled with freshly mixed endodontic sealer were implanted into these pockets. Tissue reactions were evaluated after 3, 7, 15, 30 and 60 days. All studies showed a moderate inflammatory response that was still present after 7 days143, 30 days127,158 and 60 days140,153,154 (Table 5). No difference be-tween AH Plus and the control group was noted after 60 days160. In the study by Scarparo et al153, the cyto-toxicity of AH Plus diminished over a period of 60 days but macrophages were still present after this time153.

Another option to determine the degree of cyto-toxicity is placement of intraosseous implants filled with mixed sealer. Sousa et al159 found that the in-flammatory response to AH Plus in mandibular sym-physis of guinea pigs, decreased from severe (after 4 weeks) to moderate (after 12 weeks), whereas the inflammatory response in specimens filled with EndoREZ were still severe after 12 weeks. Implants filled with Epiphany resulted in a slight inflammatory response after the end of the test period159.


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Mutoh et al151 examined the periapical tissue re-action in 40 Wistar rats after coating the root apices of freshly extracted teeth with two resin-based root canal sealers (Epiphany, AH Plus) and one eugenol-based sealer (Canals, Showa Yakuhin Kako, Tokyo, Japan), followed by immediate replantation. Histo-logical evaluation demonstrated mild inflammation after 7 days. After 14 days, the inflammatory lesions which were induced by all tested sealers had healed and been replaced by fibrous connective tissue151.

With the exception of one study151, all studies detected inflammatory responses against AH Plus at the end of the test period (Figs 4a to 4b).

Table 4 summarises all in vitro studies on the bio-compatibility of AH Plus.

Most of the in vivo studies attest that AH Plus has a lower cytotoxicity than methacrylate resin-based sealers (e.g. EndoREZ) or resin-based sealers (e.g. Epiphany). AH Plus seems to be more cytotoxic than silicone-based sealers (GuttaFlow and Roeko-Seal) or bioceramic sealers (e.g. EndoSequence BC Sealer) and MTA. Although MTA Fillapex contains MTA powder, this sealer performs inferiorly with regard to biocompatibility, in comparison to AH Plus. Most in vivo/ex vivo studies concluded that every sealer induces inflammatory responses. It is important to note that a 12-week analysis of bio-

logical behaviour of these materials is a short time interval when compared to the time the sealer is expected to remain inside the root canal134.

Discolouration induced by AH Plus

Four studies examined the discolouration effect of AH Plus compared to other sealers4,166-168. How-ever one study investigated the darkening effect of the sealer placed into the root canal168, and three studies applied the sealer in the pulp chamber to simulate root canal sealer remnants after obtura-tion4,166,167. The colour change caused by AH Plus was significantly different to the controls (tooth be-fore preparation, tooth filled with distilled water or tooth filled with gutta-percha only) and increased over time4,166,168. Darkening of coronal dentine was more obvious when AH Plus was placed in the pulp chamber compared to specimens with sealer limited to the root canal.

Compared to MTA, AH 26 and Endomethasone, AH Plus induced less discolouration4,167,168.

It can be concluded that AH Plus induces colour changes in dentine.

Table 5 In vivo studies on the biocompatibility of AH Plus, sorted according to test material.

Study Test material Technique Non-toxic after specific period of time

Overall period

Batista et al127 (2007) Rat connective tissue Microscopically Still inflammatory response observed after 30 days

30 days

Gomes-Filho et al143 (2007) Rat connective tissue Microscopically Still inflammatory response observed after 30 days

30 days

Scarparo et al153 (2009) Rat connective tissue Microscopically Still inflammatory response observed after 60 days

60 days

Scarparo et al154 (2010) Rat connective tissue Microscopically Still toxic after 60 days 60 days

Farhad et al140 (2011) Rat connective tissue Histological analysis Cytotoxic after 60 days 60 days

Mutoh et al151 (2013) Rat connective tissue Histological evalu-ation

No inflammatory response after 14 days

14 days

Tavares et al160 (2014) Rat connective tissue reaction

Histological analysis Non-cytotoxic after 60 days 60 days

Sousa et al159 (2006) Intraosseous implants in guinea pigs

Histological exam-ination

Still inflammatory response after 12 weeks

12 weeks

Silveira et al158 (2011) Mouse connective tissue Microscopically Mild inflammatory reaction after 30 days

30 days


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Removal of AH Plus during retreatment

Removal of root canal filling material is necessary to allow thorough disinfection and obturation in re-treatment cases. Therefore, gutta-percha and sealer must be completely removed from the root canal system, since bacterial biofilm may be located in any unfilled spaces, between sealer and gutta-percha as well as between sealer and the root canal wall. The sealer also can (incompletely) block the apical foramen and if not removed, can prevent sufficient disinfection of the most apical part of the root canal. As a consequence, one of the requirements for a sealer should be that it can be removed easily and predictably during endodontic retreatment allowing access to the apical foramen and to establish patency of the root canal172, 176. So far, only few studies have addressed the removal of AH Plus from root canals during retreatment. Due to the good attachment of the sealer to root dentine, it should be expected that complete removal may be difficult to achieve.

Basic techniques for removal of filling materials include the use of endodontic instruments, solvents or ultrasonics. When exposed for 1 or 2 min to differ-ent solvents (xylene and Endosolv-R [Septodont]), the Vicker’s microhardness of AH Plus decreased sig-nificantly178. Endosolv-R was more efficient than xy-lene in short-term softening of AH Plus and the other sealers. No significant difference was found between AH Plus and Adseal, whereas both solvents were less effective against AH 26178. Using Endosolv-R, Vicker’s microhardness of AH Plus decreased from

163 to 63 after 1 min (xylene: 157 to 21), and to 9.2 after 2 min of exposure which was a 94% reduction. The reduction of Vicker´s microhardness decreased from 157 to 21 after 1 min using xylene and to 17.3, which was a 89.1% reduction, after 2 min of expo-sure178. AH Plus and Epiphany sealer demonstrated higher solubility in terms of weight loss after 2 or 5 min of exposure to chloroform than to eucalyp-tol169. For chloroform, the mean weight loss after 2, 5 and 10 min was 6.0%, 6.5% and 7.6%, respect-ively and for eucalyptol 4.8%, 5.3%, and 6.5%, re-spectively169. Whitworth and Boursin180 confirmed that AH Plus showed high solubility in volatile sol-vents such as chloroform and halothane. In another study, AH Plus specimens showed a higher mean weight loss after 10 min of immersion in xylene than in refined orange oil or tetrachloroethylene177.

Removal of AH Plus with four different irrigation techniques in a lateral groove model, as described by van der Sluis et al179, was significantly more ef-fective with passive ultrasonic irrigation than syr-inge irrigation, RinsEndo or EndoActivator174. None of the investigated techniques were able to remove the sealer completely from the lateral groove. In a literature review, Duncan and Chong172 also sug-gested the use of ultrasonic activated irrigation for sealer removal.

Gutta-percha and AH Plus could be removed more effectively than a bioceramic sealer (BC Sealer, Brasseler) using several different techniques (heat, chloroform, rotary and hand instruments)175. Pa-tency was regained in 100% of the specimens175. In contrast, significantly less remnants remained

a b c

Fig 4 a) Periapical radiographs of tooth 37 with a large apical radiolucency. Immediately after root canal filling, a minimal amount of extruded filling material was visible at the mesiolingual and distal apices. b) At 7-month follow-up, a reduction of the periapical lesion was evident although the extruded material was not yet resorbed. c) Thirteen months after treatment, periapical healing occurred and the extruded material was resorbed almost completely.


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after removal of Resilon and RealSeal compared to gutta-percha and AH Plus using chloroform, irriga-tion with 2.5% NaOCl and hand instruments171. Working time did not differ significantly between groups171. Bodrumlu et al170 compared the efficacy of three techniques for removing Resilon/Epiphany or gutta-percha/AH Plus from straight and curved root canals. Removal techniques included the use of a Gates-Glidden drill, a Gates-Glidden drill and chloroform or the System B heating device. Root canals obturated with gutta-percha/AH Plus showed significantly more remnants than canals filled with Resilon/Epiphany, irrespective of the removal tech-nique. Also, significantly more time was required for retreatment170.

In another in vitro study, removal of three seal-ers (MTA Fillapex, MTA Plus and AH Plus) using NiTi retreatment files (ProTaper Universal Retreat-ment, Dentsply) was assessed5. The AH Plus group showed the significantly highest amount of re-maining material and the longest working time5. Erdemir et al173 evaluated the dissolving effect of halothane and chloroform on different root canal sealers. AH Plus adhered tightly to the wall of glass tubes and neither files nor solvents (chloroform and halothane) were able to remove the sealer173. It must be noted that glass capillary tubes were used instead of extracted teeth with a questionable clin-ical relevance.

In summary, removal of AH Plus seems to be more difficult and time-consuming than removal of other sealers. Passive ultrasonic irrigation can be recommended for removal, and the use of a solvent seems to be helpful. Complete removal of AH Plus cannot be achieved with either technique. Never-theless, none of the existing root canal filling mater-ials can be completely removed due to the complex-ity of the root canal system.

The effect of increased temperature on AH Plus

If a temperature difference arises inside a solid ma-terial, heat is transferred from areas of higher tem-perature to those of lower temperature by heat conduction182. The thermal conductivity of several sealers (Sealapex, AH Plus, AH 26, Endomethasone

and RoekoSeal) was compared by Keles et al182. The conductivity coefficient of AH Plus was found to be significantly higher than those of the other materi-als, which means the heat produced in the heated section can be transferred easily to the cold end182.

Increasing the temperature from 25°C to 37°C, viscosity of AH Plus did not change significantly com-pared to Apexit, TubliSeal EWT, Grossman’s Sealer and KetacEndo45. The authors concluded that AH Plus may be the sealer of choice for filling techniques that take more time. When used in combination with a thermoplastic obturation technique at 200°C, AH Plus showed disintegration and chemical changes in the sealer with yet unknown effects on the sealer’s properties compared to MTA and two experimental tricalcium-silicate sealers3. Fourier transform infrared (FTIR) spectroscopy demonstrated stretching of the N-H group, resulting from heat application3. Camill-eri181 confirmed these results and stated that setting time of AH Plus was reduced considerably while film thickness and flow properties increased after subject-ing the sealer to a temperature of 100°C for 1 min to simulate a warm compaction technique. Viapiana et al183 concluded that physical and chemical prop-erties of AH Plus were negatively affected by tem-perature changes.

Heat conductivity for AH Plus is better, com-pared to other sealers. Physicochemical properties like setting time, film thickness and flow properties might be influenced by heat, e.g. when using warm obturation techniques.

Summary

In summary, it can be concluded that AH Plus:• fulfills the guidelines published in ISO 6876 and

ANSI/ADA specifications concerning the max-imum loss of weight, flow, film thickness and ra-diopacity, whereas setting time and dimensional change did not completely meet the require-ments in all studies;

• shows good penetration into dentinal tubules;• shows a good push-out strength, which can be

negatively influenced by calcium hydroxide med-ication;

• exerts some antibacterial effect at least for a short time following obturation;


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• shows cytotoxic effects during a short time period during setting of the sealer;

• can induce minor colour changes in dentine;• is difficult to remove completely during endo-

dontic retreatment;• undergoes changes in setting time, film thickness

and flow properties, when used in conjunction with a warm thermoplastic obturation technique;

• most of the studies confirmed that AH Plus fulfills the requirements of a root canal filling material as defined by the specifications for root canal fill-ing materials and the guidelines of the European Society of Endodontology (ESE)9.

Despite these minor limitations AH Plus performs equally or even superior to other differently com-posed sealers in the majority of comparative studies. AH Plus can be recommended as a sealer for endo-dontic treatment.

Acknowledgements

This study was supported by a grant from the DENTSPLY/DeTrey.

References

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ah plus root canal sealer – an updated literature review

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