10.59987/ads/2015.1.10-14
The main purpose of a post-endodontic restoration with posts is to guarantee the retention of the restorative material. The aim of the study was to examine, through the push-out test, how bond strength between the post and the dentin varied with etching time with 37% orthophosphoric acid, before cementation of a glass fiber post. Moreover, it has been examined if over-etching (application time of the acid: 2 minutes) was an effective technique to improve the adhesion to the endodontic substrate, after highlighting the problems of adhesion concerning its anatomical characteristics and the changes after the endodontic treatment. Highest bond strength values were found by etching the substrate for 30 sec., while over-etching didn’t improve bond strength to the endodontic substrate.
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Annali di stomatologia
glass fiber posts
Evaluation of over-etching technique in the endodontically treated tooth restoration
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Original Article
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2022-08-12
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2023-12-04
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G. Pompa
2015
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Evaluation of over-etching technique in the endodontically treated tooth restoration
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                                                                                                     Original article



    Evaluation of over-etching technique
    in the endodontically treated tooth restoration




                                                                                                       i
                                                                                                     al
                                                                                                  on
    Guido Migliau, MD, DDS, PhD                              Enamel, dentin and cementum represent different ad-
    Luca Piccoli, DDS, PhD                                   hesive surfaces due to the composition, morphology
    Laith Konstantinos Besharat, DDS, MSc, PhD               and biomechanical characteristics (1, 2). Adhesion ob-
    Stefano Di Carlo, MD, DDS                                tained through adhesive systems is both chemical and
    Giorgio Pompa, MD, DDS                                   micro-mechanical, with the formation of the hybrid layer




                                                                                        zi
                                                             (3) and resin tags achieved through etching which in-
                                                             creases the available surface contact with the resin (4).
    Department of Oral and Maxillo Facial Sciences,          In endodontically treated teeth, the substrate with




                                                                          na
    School of Dentistry, “Sapienza” University of Rome,      which adhesion is obtained is the dentin, pulp cham-
    Italy                                                    ber and root canal (5, 6).
                                                             The presence of contaminants (intermediate medica-
                                                             tions, cements, gutta-percha) (7-9) the passage of irrigat-
    Corresponding author:




                                                               er
                                                             ing solutions which destroy collagen fibers (10-12), the
    Laith Konstantinos Besharat                              loss of the intrinsic humidity (13), the presence of a
    Department of Oral and Maxillo Facial Sciences,          smear layer produced by the endodontic instruments (14)
    School of Dentistry, “Sapienza” University of Rome       and other factors related to the endodontic treatment are
    Viale Regina Elena, 287/A


                                                        t    an obstacle to adhesion of the post. An endodontically
    Via Caserta, 6
    00161 Rome, Italy
                                                     In      treated tooth is far weaker than a vital tooth, because of
                                                             the loss of the dental substance (15) so the post is a key
    E-mail: besharatlk84@yahoo.it                            element in the post-endodontic restoration (16-18).
                                                             Adhesion problems are accentuated by the “C factor”,
                                                             which is very high in the post-space, like a first-class
                                        ni
    Summary                                                  conservative cavity. The cavity shape is deeper than
                                                             broader, with a consequent polymerization shrinkage
    The main purpose of a post-endodontic restora-           stress of composite cements (19, 20), and is charac-
                                io

    tion with posts is to guarantee the retention of the     terized by a lower accessibility and visibility of the
    restorative material. The aim of the study was to        area, which makes it difficult for correct execution of
    examine, through the push-out test, how bond             the adhesive protocols.
    strength between the post and the dentin varied          The principal aim of the study was to evaluate and
                       iz



    with etching time with 37% orthophosphoric acid,         compare the bond strength values obtained during the
    before cementation of a glass fiber post. More-          cementation of the glass fiber posts with etching-time.
    over, it has been examined if over-etching (appli-
         Ed




    cation time of the acid: 2 minutes) was an effec-
    tive technique to improve the adhesion to the en-        Materials and methods
    dodontic substrate, after highlighting the prob-
    lems of adhesion concerning its anatomical char-         Forty dental monoradicular elements, with no decay
    acteristics and the changes after the endodontic         and extracted for periodontal reasons, kept in bal-
    treatment. Highest bond strength values were             anced salt solution. Crown of all teeth was removed
IC




    found by etching the substrate for 30 sec., while        using a diamond cylindrical bur under water cooling
    over-etching didn’t improve bond strength to the         at cemento-enamel junction, plumb to the tooth axis.
    endodontic substrate.                                    Roots were treated endodontically with simultaneous
                                                             technique using nickel-titanium (NiTi) instruments “Mt-
C




    Key words: endodontic substrate, etching time,           wo” (Sweden & Martina), following the manufactures in-
    dental bonding, glass fiber posts.                       structions, namely 10/.04 taper - 15/.05 taper - 20/.06 ta-
                                                             per- 25/.06 taper. The irrigation protocol used 5% sodi-
                                                             um hypochlorite (Niclor 5, Ogna), during the preparation,
    Introduction
©




                                                             with a final irrigation for 2 minutes with 5% sodium
                                                             hypochlorite warmed to 37°C. EDTA was used at the
    The development of the materials and techniques in       end of preparation in order to remove smear layer. Root
    dentistry has recently took steps forward and suc-       canal filling was carried out with the lateral condensation
    ceed in preserving teeth instead of extracting them.     technique with ISO standardized gutta-percha points
    Most of these improvements were evident in conserv-      and cement containing epoxy resin Top Seal (Dentsply,
    ative dentistry and in particular, adhesive dentistry.   Maillefer). Then the experimental protocol established

    10                                                                           Annali di Stomatologia 2015; VI (1): 10-14
    Evaluation of over-etching technique in the endodontically treated tooth restoration


    the preparation of the post space, realized with Largo 1
    and 2 burs at a length of 10 mm for each sample.
    The samples were divided into four groups and re-
    stored, as following:
    - Group A (10 samples): etching for 15 seconds




                                                                                                               i
        using 37% orthophosphoric acid (Superlux –




                                                                                                             al
        Thixo etch – DMG), using a 3 steps dual-curing
        adhesive system (Luxabond – Total etch – DMG),
        dual-cured resin-composite cement (LuxaCore –




                                                                                                          on
        DMG) and glass fiber posts (LuxaPost – DMG).
    - Group B (10 samples): etching for 30 seconds
        using 37% orthophosphoric acid (Superlux –
        Thixo etch – DMG), using a 3 steps dual-curing
        adhesive system (Luxabond – Total etch – DMG),




                                                                                                zi
        dual-cured resin-composite cement (LuxaCore –
        DMG) and glass fiber posts (LuxaPost – DMG).
    - Group C (10 samples): etching for 2 minutes us-




                                                                                  na
        ing 37% orthophosphoric acid (Superlux – Thixo
        etch – DMG), using a 3 steps dual-curing adhe-
        sive system (Luxabond – Total etch – DMG),                  Figure 1. Slices of samples after the push-out test.
        dual-cured resin-composite cement (LuxaCore –




                                                                       er
        DMG) and glass fiber posts (LuxaPost – DMG).
    - Group D or control group (10 samples): without                an optical microscope (Zeiss laser scan). We used for
        the etching time step, using a 3 steps dual-curing          each picture the same angle of view and enlargement
        adhesive system (Luxabond – Total etch – DMG),              (50x) after the push-out test (Fig. 1).
        dual-cured resin-composite cement (LuxaCore –


                                                            t       Similarly, we took a picture of a marked size (1 mm).
        DMG) and glass fiber posts (LuxaPost – DMG).
                                                         In         Image processing software provided with the optical
                                                                    microscope-Zeiss laser scan was used to analyze the
                                                                    pictures after calibrating the space using the marked
    Preparation of the samples for the mechanical                   size. The visible circumference size was found, fol-
    tests                                                           lowing the line of the fracture.
                                                 ni
                                                                    Knowing the thickness of the sample (1 mm) and the
    The portion of each roots corresponding to the bond-            taper of the apical surface of the post, we calculated
    ed fiber post was transversally sectioned into 1 mm-            the lateral surface area of a truncated cone which is
                                     io

    thick serial slices, using a microtome, the Micromet            the bonded surface area through the formula:
    (Remet) posting a low-speed saw (Norton – Dia                   SL = π (R + r)[(h2 + (R – r)2]0,5, where R is the coronal
    Wheel), 0.2 mm thick, under water-cooling operating             post radius, r the apical post radius, and h the thick-
    at 2.240 spins per minute.                                      ness of the slice.
                           iz



    The sections, were realized in apical-coronal direc-            Each section was submitted to the same procedure.
    tion and each section was marked on the apical sur-             Statistical analysis was performed using SPSS Inc,
    face to put it exactly under the punch of the machine           ver. 13.0, Chicago, IL, USA. Chi-squared test was
           Ed




    for the push-out test. A number was assigned to each            used for statistical evaluation of proportions. In cas-
    root and a progressive alphabetical letter to each              es with more than 2 independent means we used
    slice from the apical surface to the coronal one.               the ANOVA test. A p-value of less than 0.05 was
                                                                    considered significant. A 95% CI was used in all
                                                                    analysis. In order to assure data reliability data were
    The push-out test                                               entered in two different personal computers by the
IC




                                                                    two examiners, the two data files were compared in
    Push-out load was applied using a universal testing             order to detect entry errors. The two files resulted
    machine Galdabini- Sun 500 at a crosshead speed of              identical.
    0.5 mm/min to obtain the extrusion of the post.
C




    The punch was positioned to touch the post only,
    without stressing the surrounding dentinal walls. The           Results
    load was applied on the apical surface of the slice in
    apical-coronal direction, with the purpose of prevent-          For each analyzed section we obtained the bond
©




    ing the conical shape of the canal from withstanding            strength between the post and the dentin (MPa).
    the dislodgement of the post.                                   Then, the average values, between the section of
    Push-out strength data was in Newtons (N) which                 every single root, between the roots of the same
    was converted to MegaPascals (MPa) by dividing the              group were calculated to follow up the variations of
    load by the bonded surface area.                                the bond strengths of the different groups. There are
    In order to obtain the bonded surface area of each              the results obtained in Table 1.
    sample, we took pictures of the apical surface using            Results were analyzed using the ANOVA test.

    Annali di Stomatologia 2015; VI (1): 10-14                                                                             11
    G. Migliau et al.


    Table 1. Results of the bond strength between the post and the dentin.

    Group A                  Samples           MPa                  Group B                Samples             MPa
    A1                       3                 9,24                 B1                     4                   18,73
    A2                       5                 18,8                 B2                     5                   9,98




                                                                                                             i
    A3                       5                 6,854                B3                     5                   15,01




                                                                                                           al
    A4                       6                 7,861                B4                     5                   9,47
    A5                       6                 6,08                 B5                     5                   6,25
    A6                       6                 6,743                B6                     5                   10,14




                                                                                                        on
    A7                       5                 11,08                B7                     3                   16,5
    A8                       5                 7,8298               B8                     5                   17,23
    A9                       4                 8,52                 B9                     3                   11,33
    A10                      7                 14,81                B10                    4                   11,2
                                               Average 7,026                                                   Average 12,584




                                                                                               zi
    Group C                  Samples           MPa                  Group D                Samples             MPa
    C1                       5                 5,01                 D1                     5                   5,54




                                                                                 na
    C2                       4                 12,36                D2                     4                   9,58
    C3                       4                 13,87                D3                     4                   5,55
    C4                       4                 10,812               D4                     5                   10,6
    C5                       5                 6,05                 D5                     4                   11,07
    C6                       4                 11,49                D6                     5                   5,753




                                                                       er
    C7                       4                 11,85                D7                     4                   4,43
    C8                       5                 18,87                D8                     5                   4,45
    C9                       4                 14,78                D9                     5                   4,41
    C10                      4                 8,33                 D10                    5                   3,91
                                               Average 11,34


                                                            t                                                  Average 6,52
                                                         In
    Table 2. Descriptives.

                                                         Descriptives Mpa
                                             ni
              N         Mean       Std.          Std. Error             95% Confidence               Minimum         Maximum
                                   Deviation                           Interval for Mean
                                                                 Lower Bound     Upper Bound
                                   io


    A         10        9.7638     4.08128       1.29061         6.8442          12.6834             6.08            18.80
    B         10        12.5840    4.03647       1.27644         9.6965          15.4715             6.25            18.73
    C         10        11.3512    4.14027       1.30927         8.3894          14.3130             5.01            18.87
                             iz



    D         10        6.4753     2.68710       .84974          4.5531          8.3975              3.91            11.07
    Total     40        10.0436    4.31323       .68198          8.6641          11.4230             3.91            18.87
            Ed




    Discussion and conclusions                                      Yet, results cannot support the hypothesis of over-
                                                                    etching time as an effective technique to improve the
    After the experimental study, the results (Tabs. 1, 2,          adhesion to the endodontic substrate or, at least, not
    Fig. 2) show that etching time is crucial in the cemen-         considering the times of application of the acid for 2
    tation of the posts. The lowest bond strength values            minutes.
IC




    were found in Group D, where the etching step was               Literature is still very controversial about this issue
    not performed.                                                  because, even though acid etching allows to look for
    As far as the time of application of the orthophosphoric        the collagen fibers which were destroyed during the
    acid, comparing Groups A (15 seconds), B (30 sec-               endodontic treatment but which are necessary for the
C




    onds), and C (2 minutes), highest bond strength values          adhesion, over etching could be counter-productive
    obtained result in the group B. Differences that are sta-       and lead to losing the normal structure of the dentinal
    tistically significant occur between Group B and D and          tubules (21-27).
    between C and D, therefore etching for 15s or eliminate         Further studies are required to be carried out on this
©




    the etching step with the acid ortophosphoric doesn’t           issue, taking into account the substrate, its character-
    guarantee a satisfying bond strength. On the other              istics to enable to provide for its deficiencies. By ap-
    hand etching for at least 30s guarantees a better bond          plying the proper operating procedures and valuing
    strength, an over-etching doesn’t improve or diminish           the state of the dental element, we should be able to
    bond strength. As a result, it would be interesting to an-      choose the appropriate direct or indirect restoration,
    alyze how the bond strength varies between 30 sec-              which could assure the most reliable guarantees of a
    onds and 2 minutes of application of the acid.                  long-term prognosis.

    12                                                                                 Annali di Stomatologia 2015; VI (1): 10-14
    Evaluation of over-etching technique in the endodontically treated tooth restoration


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    14                                                                                      Annali di Stomatologia 2015; VI (1): 10-14
