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Post Space preparation and Apical seal
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Irrigants and bond strength of resin cement

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When?
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How?
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Which material?

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In most cases, it is best that the clinician who performs the root-canal treatment also prepares the post space, because that person is intimately familiar with the canal anatomy. Guttapercha can be removed with the aid of heat or chemicals, but most often the easiest and most efficient method is with rotary instruments. The classic literature generally states that the timing of the post-space preparation does not matter. A more recent article showed that immediate post preparation was better, whereas another showed no difference.

significantly more dye leakage occurred when the post space was prepared 1 week after obturation, relative to preparation immediately after obturation. The authors of that study hypothesized that when post space preparation is delayed, the sealer sets completely, such that removal of the filling mass later on causes movement that disrupts the bond at the sealer interface.

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Abstract: The aim of this study was to evaluate the seal of a 4-mm
Mineral Trioxide Aggregate (MTA) filling after post space preparation.
Forty single-rooted premolar teeth without curved root anatomy and fractures were selected. The root length was standardized to 12 mm by removing excess from theapical end. The roots were instrumented to a 50 K-file by the step-back technique. The roots were randomly divided into groups A and B, of fifteen each. In group A, the canals were obturated with 7 mm of white MTA. After 24 h, 3 mm of MTA was removed to simulate post space preparation using a long shank diamond round bur. In group B, the canals were filled with 4 mm of white MTA. All samples were attached to a fluid filtration device.
Measurements (μl min-1 cm H2O-1) were taken every 2 min, for 10 min and data were analyzed by an independent t-test (P > 0.05). Fluid transport averaged in groups A and B at 9.2 × 10-4, and 11.8 × 10-
4μl min-1 cm H2O-1, respectively. Independent t-test showed no significant difference between the groups (P < 0.05). Removing set
MTA using a round bur for post space preparation does not affect its sealing ability, when 4 mm of MTA remains. (J Oral Sci 52, 567-570,
2010)

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Another study....
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Teeth treated by vertical compaction and injectable thermoplasticized gutta-percha techniques showed less leakage than those treated by lateral compaction. The least amount of dye leakage existed when the post space preparation was made on day 7 after root canal obturation.
Reference:
Effect of immediate and delayed post space preparation on apical leakage using three root canal obturation techniques after rotary instrumentation.
Chen G , Chang YC .
J Formos Med Assoc.
2011 Jul;110(7):454-9. doi: 10.1016/S0929-6646(11)60067-3.

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Another study...
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Cold lateral condensation (Group I), SimpliFill
(Group II), Thermafil (Group III) and warm vertical compaction (Group IV).
After obturation Peeso Reamers were used to create a post space for Group I, while Groups
2, 3 and 4 incorporated the post space in the obturation (sectional technique) and did not require making a post space after obturation.
Reference:
Aust Endod J.
2006 Dec;32(3):95-100.
Coronal sealing ability of three sectional obturation techniques--SimpliFill, Thermafil and warm vertical compaction--compared with cold lateral condensation and post space preparation.
Gopikrishna V , Parameswaren A .

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Statistical analysis showed that Group I (cold lateral condensation followed by post space made with Peeso Reamers) leaked significantly more (P < 0.05) than the remaining three sectional obturation groups.
It was concluded that stresses generated during post space preparation might be detrimental to the seal obtained by the obturation. Sectional obturations with their superior sealing ability offer a viable alternative.
Reference:
Aust Endod J.
2006 Dec;32(3):95-100.
Coronal sealing ability of three sectional obturation techniques--SimpliFill, Thermafil and warm vertical compaction--compared with cold lateral condensation and post space preparation.
Gopikrishna V , Parameswaren A .

Another study....
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Group A was filled with gutta-percha and sealer using lateral compaction, and post space was prepared immediately using a heated instrument.
Specimens in Group B were filled with the same materials as Group A and post space was prepared after 1 week with Gates-Glidden drills.
Group C was filled with MTA as an apical 5-mm filling. In all groups, materials were left in the root canals at the apical 5-mm level
Reference:
The evaluation of the influence of using MTA in teeth with post indication on the apical sealing ability.
Yildirim T , Taşdemir T , Orucoglu H .
Source :Department of Restorative Dentistry, Faculty of
Dentistry, Karadeniz Technical University, Trabzon, Turkey.

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RESULTS:
The MTA (Group C) showed less microleakage than immediate and delayed post space preparation methods (Group A, B) in 1 month, and this difference was found to be statistically significant (P < .005).
Additionally, no statistically significant difference was determined between Group A and Group B (P > .05).
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CONCLUSION:
These results suggest that MTA can be used in the root canals as apical filling material in teeth with post-core indication.
Reference:
The evaluation of the influence of using MTA in teeth with post indication on the apical sealing ability.
Yildirim T , Taşdemir T , Orucoglu H .
Source :Department of Restorative Dentistry, Faculty of
Dentistry, Karadeniz Technical University, Trabzon, Turkey.

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Yildirim et al. measured sealing ability of MTA in teeth with post indication and compared it with canals filled with gutta-percha and AH-
Plus sealer. They found that a 5-mm MTA filling had less microleakage than 5-mm gutta percha and AH-Plus sealer in teeth with closed apices suggesting that the superior sealing properties of MTA should be valued and considered for obturation in teeth that need post preparation and build-up, as well
Reference:
Yildirim T, Ta¸sdemir T, Orucoglu H (2009) The evaluation of the influence of using MTA in teeth with post indication on the apical sealing ability. Oral Surg Oral Med Oral Pathol Oral Radiol Endod
108,471-474.

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Yildirim et al. reported that the sealing ability of
MTA was superior when the smear layer was present
The smear layer might act as a “coupling agent” enhancing the bond between the MTA and root canal dentin. MTA is a type of hydraulic cement that can set in the presence of water. The moist environment caused by the smear layer might have a positive effect on the adaptation of MTA to the root canal wall.
Reference:
Yildirim T, Oruço˘glu H, Cobankara FK (2008) Long-term evaluation of the influence of smear layer on the apical sealing ability of MTA. J
Endod 34, 1537-1540.

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Another study....
AIM: The effects of immediate versus delayed post space preparation on the apical seal using resin and zinc oxide eugenol (ZOE) sealers were compared by a bacterial leakage model.
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CONCLUSION: According to the results of this study and despite type of sealer, immediate post space preparation did not achieve better sealing than delayed post space preparation. Resin AH26 showed the least leaking teeth in 45 days, but it made no difference in 70 days.
Reference:
J Mass Dent Soc.
2010 Summer;59(2):34-7. Bacterial microleakage and post space timing for two endodontic sealers: an in vitro study.
Jalalzadeh SM , Mamavi A , Abedi H , Mashouf RY ,
Modaresi A , Karapanou V

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Another study....
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Regardless of the obturation technique and sealers used, significantly better (P < 0.001) sealing was achieved at the apical ends using delayed post space preparation than with immediate post preparation. The obturation techniques tested did not significantly affect leakage values. The following statistical ranking of fluid filtration values was obtained for the obturation materials:
Epiphany/Resilon > Sealite Ultra/gutta percha > AH plus/gutta-percha (P < 0.001).
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Conclusion :To reduce apical leakage, clinicians should use
AH plus together with any of the obturation techniques after
7 days of obturation.

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Another study....
The teeth filled with thermoplasticized gutta-percha and
AH Plus endodontic sealer
 the post space was prepared either immediately after obturation or 7 days later using LA Axxess burs (groups
1 and 2), heated pluggers (groups 3 and 4) or solvent delivered with a hand file (groups 5 and 6)
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RESULTS:
Throughout the experimental period, there was no significant difference (p = 0.094) among the preparation techniques, either immediate or delayed
Reference:
Effect of timing and method of post space preparation on sealing ability of remaining root filling material: in vitro microbiological study.
Grecca FS , Rosa AR , Gomes MS , Parolo
CF , Bemfica JR , Frasca LC , Maltz M

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Reference:
Effect of timing and method of post space preparation on sealing ability of remaining root filling material: in vitro microbiological study.
Grecca FS , Rosa AR , Gomes MS , Parolo
CF , Bemfica JR , Frasca LC , Maltz M

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Chlorhexidine
 sodium hypochlorite
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EDTA

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The purpose of this study was to investigate the effects of chlorhexidine (CHX) digluconate at 0.2% and 2% on dentin bonding durability
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CXH digluconate at 2% was able to diminish loss of microtensile bond strength over time
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It is possible that the smear layer cannot be completely infiltrated by CHX 0.2%

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With chlorhexidine, significant reduction of adhesive failures towards dentin cohesive or mixed failures was observed with all posts/cements

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CONCLUSION: According to the results shown in this study, in teeth which are planned to be restored post endodontically with adhesive post and core systems, chlorhexidine may be an appropriate irrigant during root canal treatment resulting in increased bond strength to root canal dentin.

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MMPs play an important role in degradation of the incompletely infiltrated collagen fibrils within hybrid layers.
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MMP inhibitors have been shown to be effec tive in arresting the degradation of hybrid layers.
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Chlorhexidine, an antimicrobial agent, possesses anti-MMP activities against MMP-
2, -8, and -9. It has been shown to effectively inhibit collagen degradation

 although chlorhexidine possesses substantivity, it is water soluble and may eventually leach from hybrid layers.
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Thus, it remains to be determined whether the MMP-inhibiting activity of chlorhexidine is provisional or permanent
(ie, delaying instead of arresting hybrid layer degradation)

 apart from MMPs, cysteine cathepsins that are capable of collagen degradation are present
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These proteases are not amenable to inhibit ion by MMP inhibitors.

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Finally, even when the hybrid layer may be prevented from degradation by MMPs and cathepsins, a zone of resin-sparse, demineralized dentin invariably remains that is potentially susceptible to cyclic fatigue after prolonged intraoral function.
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Thus, the long-term clinical effectiveness of the use of MMP inhibitors in preventing the degradation of hybrid layers has to be further evaluated.

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The effect of different post space irrigants on smear layer removal and dentin bond strength was evaluated
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The teeth of these groups were irrigated for 1 min with 17% ethylenediaminetetracetic acid
(EDTA) (group 1), 5.25% sodium hypochlorite
(NaOCl) (group2)
Reference:
Eur J Oral Sci.
Does endodontic post space irrigation affect smear layer removal and bonding effectiveness? Gu XH , Mao CY , Liang C , Wang HM , Kern M .

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EDTA removed the smear layer extremely effectively and, as a result, improved the bond strength at each region (apical, middle, and coronal) of the roots
Reference:
Eur J Oral Sci.
Does endodontic post space irrigation affect smear layer removal and bonding effectiveness? Gu XH , Mao CY , Liang C , Wang HM , Kern M .

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When sodium hypochlorite is applied onto dentin, it results in strong oxidation and removal of predentin and collagen present on the dentinal surface.
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Hydrogen peroxide, on contact with the dentinal surface, produces oxidation of the surface collagen and other components of the dentinal matrix

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PURPOSE: To analyze the effect of NaOCl treatment on bond adhesion and tensile strength
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CONCLUSION: Within the limitations of this study, NaOCl treatment did not significantly alter tensile bond strength
Reference:
J Prosthet Dent.
2003 Feb;89(2):146-53. In vitro study of endodontic post cementation protocols that use resin cements. Varela SG , Rábade
LB , Lombardero PR , Sixto JM , Bahillo JD , Park SA .

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 etching with 35% phosphoric acid for 30 s;
17% EDTA followed by 5.25% sodium hypochlorite (NaOCl); and ultrasonic agitation associated with 17%
EDTA and 5.25% NaOCl irrigating solutions
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Both 35% phosphoric acid etching and ultrasonic agitation in combination with
EDTA/NaOCl irrigation improved the apical push-out strength of the fiber post
Reference:
Eur J Oral Sci.
2008 Jun;116(3):280-6. Effect of post-space treatment on retention of fiber posts in different root regions using two selfetching systems. Zhang L , Huang L , Xiong Y , Fang M , Chen JH , Ferrari
M

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Smear layer removal facilitates penetration of sealers into the dentinal tubules. It also enhances disinfection of the root canal wall and deeper layers of dentin. Both EDTA and citric acid can effectively remove the smear layer when used together with NaOCl.
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Ingle 2008

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Sodium hypochlorite breaks down to sodium chloride and oxygen whereas hydrogen peroxide breaks down to water and oxygen.
Oxygen from such irrigants cause strong inhibition of the interfacial polymerization of resin bonding materials. The generation of oxygen bubbles may also interface with resin infiltration into the tubules and intertubular dentin
Reference:
Hale Ari, Erdem Yasar, Sema Belli .Effects of NaOCI on bond strengths of Resin cements to root canal dentin.Journal of Endodontics 2003;
29(4): 248-251

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The oxidizing action of these irrigants may also result in oxidation of collagen or other matrix components, thereby interfering with interfacial polymerization
Reference:
Mitzi D.Morris, Kwang-Won lee, Kelli A.Agee, Serge Bouillaguet,
Pashley D.H.Effects of NaOCI and RC-prep on Bond strengths of
Resin cement to endodontic surfaces.Journal of Endodontics 2001;
27(12): 756-757

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