Effect of surface treatment on the dislocation resistance of prefabricated esthetic fiber posts bonded with self-adhesive resin cement: A systematic review and meta-analysis.

BACKGROUND: This systematic review aimed to determine the presence of any in vitro proof to validate the utilization of surface treatments to advance the bond strength of fiber posts to intraradicular dentin with self-adhesive resin cements.
METHODOLOGY: Laboratory studies that assessed the push-out or pull-out bond strength of the prefabricated esthetic posts whose surface was treated with either chemical or physical treatment or a combination and bonded using self-adhesive resin cement within root canal model were included for this systematic review. The review began after obtaining the registration number from the International Prospective Register of Systematic Reviews (PROSPERO ID-CRD42020165009). Study reporting was performed following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Relevant articles were identified using a literature database search in Web of Science, Scopus, PubMed, and EBSCO. Besides this, handsearch was also done to ensure complete capture of the articles.
RESULTS: Fifteen articles were then selected and included in this study, out of which four were excluded for meta-analysis due to usage of the artificial substrate. It was shown that an additional step of surface treatment of esthetic fiber post did not result in significant improvement in dislocation resistance. Assessment of risk of bias categorized the available research into high risk and medium risk. The results showed heterogeneity.
CONCLUSION: The use of additional steps such as chemical, mechanical, or a combination of post surface treatment does not have any added benefit. However, the results must be interpreted with caution due to methodological shortcomings. Copyright:

INTRODUCTION

Root canal-treated teeth lacking enough crown structure require a post to retain core for definitive restoration.[12] Fiber posts with their similar elastic modulus to that of dentin produce favorable stress distribution, leading to low occurrences of root fractures.[23] Along with this, these colored fiber posts have several other advantages such as improved light dispersion through the root and gingival tissues, suppression of the corrosive reactions that happen with metal alloy prefabricated posts, and simple removal in case of endodontic retreatment.[4] Even though numerous studies have been performed to evaluate the adhesion of cements and fiber posts, debonding of posts remain the main reason for the failure.[567]

Present-day fiber posts are made up of resin matrix-embedded unidirectional fibers (carbon, quartz, or glass). The resin matrix is responsible for the resistance to compression, whereas the fibers provide the resistance against flexure and also form the surface onto which the functional monomers confined in the adhesive cements will interact.[8] Carbon fiber posts and preformed metallic posts are not indicated in the anterior region as these have shown unacceptable esthetics, hence the emergence of esthetic fiber posts usage.[9]

Resin cements are widely used for luting of indirect restorations, but their bond strength is significantly influenced by the technique used for cementation.[1011] For the past few years, self-adhesive resin cements have been tried for cementing fiber posts into intraradicular dentin to provide easier clinical application compared to the regular resin cements which are more technique sensitive.[312] Their use eliminates etching of the post space or adhesive system usage. They are dual polymerized and used for adhesive bonding of all indirect restorations including fiber posts.[13]

To improve the bond strength between the post and the resin cements, several surface pretreatments of glass fiber posts (GFP) have been tried out, which can be classified into (1) physical or chemical means for exposing the inorganic glass fibers and creating surface irregularities such as silanization and sandblasting and (2) chemical treatments for increasing the micromechanical and chemical post attachments such as hydrogen peroxide (H2O2) and hydrofluoric acid (HF).[5141516] In a study by Monticelli et al., it was seen that surface conditioning improved fiber post bonding.[17] Even though silanization has the advantage of being a convenient chairside operation, its effect on bond strength was questionable.[18]

Sandblasting makes the glass fibers accessible for chemical interaction by the removal of the top layer of resin. Naturally, sandblasting also roughens the surface, thereby significantly increasing the surface area and energy.[8] Other techniques of surface treatments such as aluminum oxide particle air abrasion and hydrofluoric acid etching have been previously tested with self-adhesive resin cement for bond strength improvements. These have helped improve the surface roughness (adhesive area), increase the surface free energy, and expose resin composite filler components. Similarly, hydrogen peroxide was also found to escalate the surface roughness.[19]

Despite the number of in vitro studies, it is unclear whether different surface treatments on fiber posts can improve its retention of using self-adhesive resin cements. Hence, the current study aimed to systematically establish the presence of any in vitro data to validate the use of surface treatments to advance the bond strength of fiber posts to intraradicular dentin using self-adhesive resin cements.

METHODOLOGY

This systematic review was conducted to verify whether there is in vitro evidence to justify the application of surface treatments to increase the bond strength of the prefabricated esthetic posts using self-adhesive resin cement to intraradicular dentin. Study reporting was performed following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The protocol was registered on the International Prospective Register of Systematic Reviews (PROSPERO) before commencing (Registration number CRD42020165009).

Search strategy

Relevant articles were identified using a literature database search in Web of Science, Scopus, PubMed, and EBSCO. Besides this, handsearch was also done by checking the bibliography of identified documents to ensure complete capture of the articles. The literature review in various databases was conducted using specific keywords and subject headings derived after scoping searches. For example, the search string used for literature review in PubMed database was ((((((((((((tooth color*) OR (translucent)) OR (glass fiber)) OR (quartz fiber)) OR (zirconia)) OR (non metal*)) OR (non-metal*)) OR (esthetic)) AND ((post) OR (dowel))) AND (((((silan*) OR (air abrasi*)) OR (etch*)) OR (adhesi*)) OR (surface treatment))) AND ((((((((self adhesive luting resin) OR (self-adhesive luting resin)) OR (self adhesive resin)) OR (self-adhesive resin)) OR (self adhesive cement)) OR (self-adhesive cement)) OR (self-adhesive luting cement)) OR (self adhesive luting cement))) AND ((((((((push out bond strength) OR (push-out bond strength)) OR (pull out bond strength))) OR (pull-out bond strength)) OR (bond strength)) OR (retenti*)) OR (dislocation resistance))) AND ((((teeth) OR (root canal)) OR (post space)) OR (dentin)) [Supplementary Table 1].

Supplementary Table 1

Details of PubMed search conducted on June 3, 2021, though search string developed by combining keywords and subject terms

Search number	Query	Search details	Results
1	Tooth color*	(“teeth s”[All Fields] OR “teeths”[All Fields] OR “tooth”[MeSH Terms] OR “tooth”[All Fields] OR “teeth”[All Fields] OR “tooth s”[All Fields] OR “tooths”[All Fields]) AND “color*”[All Fields]	8258
2	Translucent	“translucence”[All Fields] OR “translucencies”[All Fields] OR “translucency”[All Fields] OR “translucent”[All Fields]	7667
3	Glass fiber	(“eyeglasses”[MeSH Terms] OR “eyeglasses”[All Fields] OR “glasses”[All Fields] OR “glass”[MeSH Terms] OR “glass”[All Fields]) AND (“dietary fiber”[MeSH Terms] OR (“dietary”[All Fields] AND “fiber”[All Fields]) OR “dietary fiber”[All Fields] OR “fiber”[All Fields] OR “fibre”[All Fields] OR “fiber s”[All Fields] OR “fiberized”[All Fields] OR “fibers”[All Fields] OR “fibre s”[All Fields] OR “fibres”[All Fields])	9123
4	Nonmetal*	“non”[All Fields] AND “metal*”[All Fields]	52,706
5	Nonmetal*	“nonmetal*”[All Fields]	1756
6	Esthetic	“aesthetical”[All Fields] OR “aesthetically”[All Fields] OR “esthetical”[All Fields] OR “esthetically”[All Fields] OR “esthetics”[MeSH Terms] OR “esthetics”[All Fields] OR “aesthetic”[All Fields] OR “aesthetics”[All Fields] OR “esthetic”[All Fields]	74,804
7	Quartz fiber	(“quartz”[MeSH Terms] OR “quartz”[All Fields] OR “quartzes”[All Fields]) AND (“dietary fiber”[MeSH Terms] OR (“dietary”[All Fields] AND “fiber”[All Fields]) OR “dietary fiber”[All Fields] OR “fiber”[All Fields] OR “fibre”[All Fields] OR “fiber s”[All Fields] OR “fiberized”[All Fields] OR “fibers”[All Fields] OR “fibre s”[All Fields] OR “fibres”[All Fields])	1361
8	Zirconia	“zirconia s”[All Fields] OR “zirconias”[All Fields] OR “zirconium oxide”[Supplementary Concept] OR “zirconium oxide”[All Fields] OR “zirconia”[All Fields]	9076
9	(((((((tooth color*) OR (translucent)) OR (glass fiber)) OR (nonmetal*)) OR (nonmetal*)) OR (esthetic)) OR (quartz fiber)) OR (zirconia)	((“teeth s”[All Fields] OR “teeths”[All Fields] OR “tooth”[MeSH Terms] OR “tooth”[All Fields] OR “teeth”[All Fields] OR “tooth s”[All Fields] OR “tooths”[All Fields]) AND “color*”[All Fields]) OR (“translucence”[All Fields] OR “translucencies”[All Fields] OR “translucency”[All Fields] OR “translucent”[All Fields]) OR ((“eyeglasses”[MeSH Terms] OR “eyeglasses”[All Fields] OR “glasses”[All Fields] OR “glass”[MeSH Terms] OR “glass”[All Fields]) AND (“dietary fiber”[MeSH Terms] OR (“dietary”[All Fields] AND “fiber”[All Fields]) OR “dietary fiber”[All Fields] OR “fiber”[All Fields] OR “fibre”[All Fields] OR “fiber s”[All Fields] OR “fiberized”[All Fields] OR “fibers”[All Fields] OR “fibre s”[All Fields] OR “fibres”[All Fields])) OR (“non”[All Fields] AND “metal*”[All Fields]) OR “nonmetal*”[All Fields] OR (“aesthetical”[All Fields] OR “aesthetically”[All Fields] OR “esthetical”[All Fields] OR “esthetically”[All Fields] OR “esthetics”[MeSH Terms] OR “esthetics”[All Fields] OR “aesthetic”[All Fields] OR “aesthetics”[All Fields] OR “esthetic”[All Fields]) OR ((“quartz”[MeSH Terms] OR “quartz”[All Fields] OR “quartzes”[All Fields]) AND (“dietary fiber”[MeSH Terms] OR (“dietary”[All Fields] AND “fiber”[All Fields]) OR “dietary fiber”[All Fields] OR “fiber”[All Fields] OR “fibre”[All Fields] OR “fiber s”[All Fields] OR “fiberized”[All Fields] OR “fibers”[All Fields] OR “fibre s”[All Fields] OR “fibres”[All Fields])) OR (“zirconia s”[All Fields] OR “zirconias”[All Fields] OR “zirconium oxide”[Supplementary Concept] OR “zirconium oxide”[All Fields] OR “zirconia”[All Fields])	158,350
10	Post	“post”[All Fields]	959,546
11	Dowel	“dowel”[All Fields] OR “dowels”[All Fields]	991
12	(post) OR (dowel)	“post”[All Fields] OR “dowel”[All Fields] OR “dowels”[All Fields]	960,176
13	Silan*	“silan*”[All Fields]	16,360
14	Air abrasi*	(“air”[MeSH Terms] OR “air”[All Fields]) AND “abrasi*”[All Fields]	1805
15	Etch*	“etch*”[All Fields]	35,176
16	Adhesi*	“adhesi*”[All Fields]	366,492
17	Surface treatment	(“surface”[All Fields] OR “surface s”[All Fields] OR “surfaced”[All Fields] OR “surfaces”[All Fields] OR “surfacing”[All Fields] OR “surfacings”[All Fields]) AND (“therapeutics”[MeSH Terms] OR “therapeutics”[All Fields] OR “treatments”[All Fields] OR “therapy”[MeSH Subheading] OR “therapy”[All Fields] OR “treatment”[All Fields] OR “treatment s”[All Fields])	351,195
18	((((Silan*) OR (Air abrasi*)) OR (Etch*)) OR (Adhesi*)) OR (Surface treatment)	“silan*”[All Fields] OR ((“air”[MeSH Terms] OR “air”[All Fields]) AND “abrasi*”[All Fields]) OR “etch*”[All Fields] OR “adhesi*”[All Fields] OR ((“surface”[All Fields] OR “surface s”[All Fields] OR “surfaced”[All Fields] OR “surfaces”[All Fields] OR “surfacing”[All Fields] OR “surfacings”[All Fields]) AND (“therapeutics”[MeSH Terms] OR “therapeutics”[All Fields] OR “treatments”[All Fields] OR “therapy”[MeSH Subheading] OR “therapy”[All Fields] OR “treatment”[All Fields] OR “treatment s”[All Fields]))	728,431
19	Self-adhesive luting resin	(“ego”[MeSH Terms] OR “ego”[All Fields] OR “self”[All Fields]) AND (“adhese”[All Fields] OR “adhesion”[All Fields] OR “adhesions”[All Fields] OR “adhesive s”[All Fields] OR “adhesively”[All Fields] OR “adhesiveness”[MeSH Terms] OR “adhesiveness”[All Fields] OR “adhesivenesses”[All Fields] OR “adhesives”[Pharmacological Action] OR “adhesives”[MeSH Terms] OR “adhesives”[All Fields] OR “adhesive”[All Fields] OR “adhesivities”[All Fields] OR “adhesivity”[All Fields]) AND (“luted”[All Fields] OR “luting”[All Fields]) AND (“resin s”[All Fields] OR “resinous”[All Fields] OR “resins, plant”[MeSH Terms] OR (“resins”[All Fields] AND “plant”[All Fields]) OR “plant resins”[All Fields] OR “resin”[All Fields] OR “resins”[All Fields])	591
20	Self-adhesive luting resin	“self-adhesive”[All Fields] AND (“luted”[All Fields] OR “luting”[All Fields]) AND (“resin s”[All Fields] OR “resinous”[All Fields] OR “resins, plant”[MeSH Terms] OR (“resins”[All Fields] AND “plant”[All Fields]) OR “plant resins”[All Fields] OR “resin”[All Fields] OR “resins”[All Fields])	437
21	Self-adhesive resin	(“ego”[MeSH Terms] OR “ego”[All Fields] OR “self”[All Fields]) AND (“adhese”[All Fields] OR “adhesion”[All Fields] OR “adhesions”[All Fields] OR “adhesive s”[All Fields] OR “adhesively”[All Fields] OR “adhesiveness”[MeSH Terms] OR “adhesiveness”[All Fields] OR “adhesivenesses”[All Fields] OR “adhesives”[Pharmacological Action] OR “adhesives”[MeSH Terms] OR “adhesives”[All Fields] OR “adhesive”[All Fields] OR “adhesivities”[All Fields] OR “adhesivity”[All Fields]) AND (“resin s”[All Fields] OR “resinous”[All Fields] OR “resins, plant”[MeSH Terms] OR (“resins”[All Fields] AND “plant”[All Fields]) OR “plant resins”[All Fields] OR “resin”[All Fields] OR “resins”[All Fields])	4028
22	Self-adhesive resin	“self-adhesive”[All Fields] AND (“resin s”[All Fields] OR “resinous”[All Fields] OR “resins, plant”[MeSH Terms] OR (“resins”[All Fields] AND “plant”[All Fields]) OR “plant resins”[All Fields] OR “resin”[All Fields] OR “resins”[All Fields])	1020
23	Self-adhesive cement	(“ego”[MeSH Terms] OR “ego”[All Fields] OR “self”[All Fields]) AND (“adhesive cement”[Supplementary Concept] OR “adhesive cement”[All Fields] OR “adhesive cement”[All Fields])	216
24	Self-adhesive cement	“self-adhesive”[All Fields] AND (“cement s”[All Fields] OR “cementable”[All Fields] OR “cementation”[MeSH Terms] OR “cementation”[All Fields] OR “cementations”[All Fields] OR “cementing”[All Fields] OR “dental cementum”[MeSH Terms] OR (“dental”[All Fields] AND “cementum”[All Fields]) OR “dental cementum”[All Fields] OR “cement”[All Fields] OR “dental cements”[MeSH Terms] OR (“dental”[All Fields] AND “cements”[All Fields]) OR “dental cements”[All Fields] OR “cemented”[All Fields] OR “cements”[All Fields])	999
25	Self-adhesive luting cement	“self-adhesive”[All Fields] AND (“luted”[All Fields] OR “luting”[All Fields]) AND (“cement s”[All Fields] OR “cementable”[All Fields] OR “cementation”[MeSH Terms] OR “cementation”[All Fields] OR “cementations”[All Fields] OR “cementing”[All Fields] OR “dental cementum”[MeSH Terms] OR (“dental”[All Fields] AND “cementum”[All Fields]) OR “dental cementum”[All Fields] OR “cement”[All Fields] OR “dental cements”[MeSH Terms] OR (“dental”[All Fields] AND “cements”[All Fields]) OR “dental cements”[All Fields] OR “cemented”[All Fields] OR “cements”[All Fields])	442
26	Self-adhesive luting cement	(“ego”[MeSH Terms] OR “ego”[All Fields] OR “self”[All Fields]) AND (“adhese”[All Fields] OR “adhesion”[All Fields] OR “adhesions”[All Fields] OR “adhesive s”[All Fields] OR “adhesively”[All Fields] OR “adhesiveness”[MeSH Terms] OR “adhesiveness”[All Fields] OR “adhesivenesses”[All Fields] OR “adhesives”[Pharmacological Action] OR “adhesives”[MeSH Terms] OR “adhesives”[All Fields] OR “adhesive”[All Fields] OR “adhesivities”[All Fields] OR “adhesivity”[All Fields]) AND (“luted”[All Fields] OR “luting”[All Fields]) AND (“cement s”[All Fields] OR “cementable”[All Fields] OR “cementation”[MeSH Terms] OR “cementation”[All Fields] OR “cementations”[All Fields] OR “cementing”[All Fields] OR “dental cementum”[MeSH Terms] OR (“dental”[All Fields] AND “cementum”[All Fields]) OR “dental cementum”[All Fields] OR “cement”[All Fields] OR “dental cements”[MeSH Terms] OR (“dental”[All Fields] AND “cements”[All Fields]) OR “dental cements”[All Fields] OR “cemented”[All Fields] OR “cements”[All Fields])	595
27	(((((((self adhesive luting resin) OR (self-adhesive luting resin)) OR (self adhesive resin)) OR (self-adhesive resin)) OR (self adhesive cement)) OR (self-adhesive cement)) OR (self-adhesive luting cement)) OR (self adhesive luting cement)	((“ego”[MeSH Terms] OR “ego”[All Fields] OR “self”[All Fields]) AND (“adhese”[All Fields] OR “adhesion”[All Fields] OR “adhesions”[All Fields] OR “adhesive s”[All Fields] OR “adhesively”[All Fields] OR “adhesiveness”[MeSH Terms] OR “adhesiveness”[All Fields] OR “adhesivenesses”[All Fields] OR “adhesives”[Pharmacological Action] OR “adhesives”[MeSH Terms] OR “adhesives”[All Fields] OR “adhesive”[All Fields] OR “adhesivities”[All Fields] OR “adhesivity”[All Fields]) AND (“luted”[All Fields] OR “luting”[All Fields]) AND (“resin s”[All Fields] OR “resinous”[All Fields] OR “resins, plant”[MeSH Terms] OR (“resins”[All Fields] AND “plant”[All Fields]) OR “plant resins”[All Fields] OR “resin”[All Fields] OR “resins”[All Fields])) OR (“self-adhesive”[All Fields] AND (“luted”[All Fields] OR “luting”[All Fields]) AND (“resin s”[All Fields] OR “resinous”[All Fields] OR “resins, plant”[MeSH Terms] OR (“resins”[All Fields] AND “plant”[All Fields]) OR “plant resins”[All Fields] OR “resin”[All Fields] OR “resins”[All Fields])) OR ((“ego”[MeSH Terms] OR “ego”[All Fields] OR “self”[All Fields]) AND (“adhese”[All Fields] OR “adhesion”[All Fields] OR “adhesions”[All Fields] OR “adhesive s”[All Fields] OR “adhesively”[All Fields] OR “adhesiveness”[MeSH Terms] OR “adhesiveness”[All Fields] OR “adhesivenesses”[All Fields] OR “adhesives”[Pharmacological Action] OR “adhesives”[MeSH Terms] OR “adhesives”[All Fields] OR “adhesive”[All Fields] OR “adhesivities”[All Fields] OR “adhesivity”[All Fields]) AND (“resin s”[All Fields] OR “resinous”[All Fields] OR “resins, plant”[MeSH Terms] OR (“resins”[All Fields] AND “plant”[All Fields]) OR “plant resins”[All Fields] OR “resin”[All Fields] OR “resins”[All Fields])) OR (“self-adhesive”[All Fields] AND (“resin s”[All Fields] OR “resinous”[All Fields] OR “resins, plant”[MeSH Terms] OR (“resins”[All Fields] AND “plant”[All Fields]) OR “plant resins”[All Fields] OR “resin”[All Fields] OR “resins”[All Fields])) OR ((“ego”[MeSH Terms] OR “ego”[All Fields] OR “self”[All Fields]) AND (“adhesive cement”[Supplementary Concept] OR “adhesive cement”[All Fields] OR “adhesive cement”[All Fields])) OR (“self-adhesive”[All Fields] AND (“cement s”[All Fields] OR “cementable”[All Fields] OR “cementation”[MeSH Terms] OR “cementation”[All Fields] OR “cementations”[All Fields] OR “cementing”[All Fields] OR “dental cementum”[MeSH Terms] OR (“dental”[All Fields] AND “cementum”[All Fields]) OR “dental cementum”[All Fields] OR “cement”[All Fields] OR “dental cements”[MeSH Terms] OR (“dental”[All Fields] AND “cements”[All Fields]) OR “dental cements”[All Fields] OR “cemented”[All Fields] OR “cements” [All Fields])) OR (“self-adhesive” [All Fields] AND (“luted”	4059
		[All Fields] OR “luting”[All Fields]) AND (“cement s”[All Fields] OR “cementable”[All Fields] OR “cementation”[MeSH Terms] OR “cementation”[All Fields] OR “cementations”[All Fields] OR “cementing”[All Fields] OR “dental cementum”[MeSH Terms] OR (“dental”[All Fields] AND “cementum”[All Fields]) OR “dental cementum”[All Fields] OR “cement”[All Fields] OR “dental cements”[MeSH Terms] OR (“dental”[All Fields] AND “cements”[All Fields]) OR “dental cements”[All Fields] OR “cemented”[All Fields] OR “cements”[All Fields])) OR ((“ego”[MeSH Terms] OR “ego”[All Fields] OR “self”[All Fields]) AND (“adhese”[All Fields] OR “adhesion”[All Fields] OR “adhesions”[All Fields] OR “adhesive s”[All Fields] OR “adhesively”[All Fields] OR “adhesiveness”[MeSH Terms] OR “adhesiveness”[All Fields] OR “adhesivenesses”[All Fields] OR “adhesives”[Pharmacological Action] OR “adhesives”[MeSH Terms] OR “adhesives”[All Fields] OR “adhesive”[All Fields] OR “adhesivities”[All Fields] OR “adhesivity”[All Fields]) AND (“luted”[All Fields] OR “luting”[All Fields]) AND (“cement s”[All Fields] OR “cementable”[All Fields] OR “cementation”[MeSH Terms] OR “cementation”[All Fields] OR “cementations”[All Fields] OR “cementing”[All Fields] OR “dental cementum”[MeSH Terms] OR (“dental”[All Fields] AND “cementum”[All Fields]) OR “dental cementum”[All Fields] OR “cement”[All Fields] OR “dental cements”[MeSH Terms] OR (“dental”[All Fields] AND “cements”[All Fields]) OR “dental cements”[All Fields] OR “cemented”[All Fields] OR “cements”[All Fields]))
28	Push-out bond strength	“push”[All Fields] AND “out”[All Fields] AND “bond”[All Fields] AND (“strength”[All Fields] OR “strengths”[All Fields])	868
29	Push-out bond strength	“push-out”[All Fields] AND “bond”[All Fields] AND (“strength”[All Fields] OR “strengths”[All Fields])	863
30	Pull-out bond strength	“pull”[All Fields] AND “out”[All Fields] AND “bond”[All Fields] AND (“strength”[All Fields] OR “strengths”[All Fields])	122
31	Pull-out bond strength	“pull-out”[All Fields] AND “bond”[All Fields] AND (“strength”[All Fields] OR “strengths”[All Fields])	117
32	Dislocation resistance	(“dislocate”[All Fields] OR “dislocates”[All Fields] OR “dislocating”[All Fields] OR “dislocator”[All Fields] OR “dislocators”[All Fields] OR “joint dislocations”[MeSH Terms] OR (“joint”[All Fields] AND “dislocations”[All Fields]) OR “joint dislocations”[All Fields] OR “dislocated”[All Fields] OR “dislocation”[All Fields] OR “dislocations”[All Fields]) AND (“resist”[All Fields] OR “resistance”[All Fields] OR “resistances”[All Fields] OR “resistant”[All Fields] OR “resistants”[All Fields] OR “resisted”[All Fields] OR “resistence”[All Fields] OR “resistences”[All Fields] OR “resistent”[All Fields] OR “resistibility”[All Fields] OR “resisting”[All Fields] OR “resistive”[All Fields] OR “resistively”[All Fields] OR “resistivities”[All Fields] OR “resistivity”[All Fields] OR “resists”[All Fields])	863
33	Bond strength	“bond”[All Fields] AND (“strength”[All Fields] OR “strengths”[All Fields])	19,493
34	Retenti*	“retenti*”[All Fields]	203,624
35	((((((push out bond strength) OR (push-out bond strength)) OR (pull out bond strength)) OR (pull-out bond strength)) OR (dislocation resistance)) OR (bond strength)) OR (retenti*)	(“push”[All Fields] AND “out”[All Fields] AND “bond”[All Fields] AND (“strength”[All Fields] OR “strengths”[All Fields])) OR (“push-out”[All Fields] AND “bond”[All Fields] AND (“strength”[All Fields] OR “strengths”[All Fields])) OR (“pull”[All Fields] AND “out”[All Fields] AND “bond”[All Fields] AND (“strength”[All Fields] OR “strengths”[All Fields])) OR (“pull-out”[All Fields] AND “bond”[All Fields] AND (“strength”[All Fields] OR “strengths”[All Fields])) OR ((“dislocate”[All Fields] OR “dislocates”[All Fields] OR “dislocating”[All Fields] OR “dislocator”[All Fields] OR “dislocators”[All Fields] OR “joint dislocations”[MeSH Terms] OR (“joint”[All Fields] AND “dislocations”[All Fields]) OR “joint dislocations”[All Fields] OR “dislocated”[All Fields] OR “dislocation”[All Fields] OR “dislocations”[All Fields]) AND (“resist”[All Fields] OR “resistance”[All Fields] OR “resistances”[All Fields] OR “resistant”[All Fields] OR “resistants”[All Fields] OR “resisted”[All Fields] OR “resistence”[All Fields] OR “resistences”[All Fields] OR “resistent”[All Fields] OR “resistibility”[All Fields] OR “resisting”[All Fields] OR “resistive”[All Fields] OR “resistively”[All Fields] OR “resistivities”[All Fields] OR “resistivity”[All Fields] OR “resists”[All Fields])) OR (“bond”[All Fields] AND (“strength”[All Fields] OR “strengths”[All Fields])) OR “retenti*”[All Fields]	223,137
36	Teeth	“teeth s”[All Fields] OR “teeths”[All Fields] OR “tooth”[MeSH Terms] OR “tooth”[All Fields] OR “teeth”[All Fields] OR “tooth s”[All Fields] OR “tooths”[All Fields]	248,516
37	Root canal	“dental pulp cavity”[MeSH Terms] OR (“dental”[All Fields] AND “pulp”[All Fields] AND “cavity”[All Fields]) OR “dental pulp cavity”[All Fields] OR (“root”[All Fields] AND “canal”[All Fields]) OR “root canal”[All Fields]	37,789
38	Post space	“post”[All Fields] AND (“space”[All Fields] OR “space s”[All Fields] OR “spaces”[All Fields])	15,050
39	Dentin	“dentin”[MeSH Terms] OR “dentin”[All Fields] OR “dentine”[All Fields] OR “dentines”[All Fields] OR “dentins”[All Fields] OR “dentin s”[All Fields] OR “dentinal”[All Fields]	39,802
40	(((Teeth) OR (root canal)) OR (post space)) OR (dentin)	“teeth s”[All Fields] OR “teeths”[All Fields] OR “tooth”[MeSH Terms] OR “tooth”[All Fields] OR “teeth”[All Fields] OR “tooth s”[All Fields] OR “tooths”[All Fields] OR (“dental pulp cavity”[MeSH Terms] OR (“dental”[All Fields] AND “pulp”[All Fields] AND “cavity”[All Fields]) OR “dental pulp cavity”[All Fields] OR (“root”[All Fields] AND “canal”[All Fields]) OR “root canal”[All Fields]) OR (“post”[All Fields] AND (“space”[All Fields] OR “space s”[All Fields] OR “spaces”[All Fields])) OR (“dentin”[MeSH Terms] OR “dentin”[All Fields] OR “dentine”[All Fields] OR “dentines”[All Fields] OR “dentins”[All Fields] OR “dentin s”[All Fields] OR “dentinal”[All Fields])	290,039
41	((((((((((((tooth color*) OR (translucent)) OR (glass fiber)) OR (nonmetal*)) OR (nonmetal*)) OR (esthetic)) OR (quartz fiber)) OR (zirconia)) AND ((post) OR (dowel))) AND (((((Silan*) OR	(((“teeth s”[All Fields] OR “teeths”[All Fields] OR “tooth”[MeSH Terms] OR “tooth”[All Fields] OR “teeth”[All Fields] OR “tooth s”[All Fields] OR “tooths”[All Fields]) AND “color*”[All Fields]) OR (“translucence”[All Fields] OR “translucencies”[All Fields] OR “translucency”[All Fields] OR “translucent”[All Fields]) OR ((“eyeglasses”[MeSH Terms] OR “eyeglasses”[All Fields] OR “glasses”[All Fields] OR “glass”[MeSH Terms] OR “glass”[All Fields]) AND (“dietary fiber”[MeSH Terms] OR (“dietary”[All Fields] AND “fiber”[All Fields]) OR “dietary fiber”[All Fields] OR “fiber”[All Fields] OR “fibre”[All Fields] OR “fiber s”[All Fields] OR “fiberized”[All Fields] OR “fibers”[All Fields] OR “fibre s”[All Fields] OR “fibres”[All Fields])) OR (“non”[All Fields] AND “metal*”[All Fields]) OR “nonmetal*”[All Fields] OR (“aesthetical”[All Fields] OR “aesthetically”[All Fields] OR “esthetical”[All Fields] OR “esthetically”[All Fields] OR “esthetics”[MeSH Terms] OR “esthetics”[All Fields] OR “aesthetic”[All Fields] OR “aesthetics”[All Fields] OR “esthetic”[All Fields]) OR ((“quartz”[MeSH Terms] OR “quartz”[All Fields] OR “quartzes”[All Fields]) AND (“dietary fiber”[MeSH Terms] OR (“dietary”[All Fields] AND “fiber”[All Fields]) OR “dietary fiber”[All Fields] OR “fiber”[All Fields] OR “fibre”[All Fields] OR “fiber s”[All Fields] OR “fiberized”[All Fields] OR “fibers”[All Fields] OR “fibre s”[All Fields] OR “fibres”[All Fields])) OR (“zirconia s”[All Fields] OR “zirconias”[All Fields] OR “zirconium oxide”[Supplementary Concept] OR “zirconium oxide”[All Fields] OR “zirconia”[All Fields])) AND (“post”[All Fields] OR (“dowel”[All Fields] OR “dowels”[All Fields])) AND (“silan*”[All Fields]	174
	(Air abrasi*)) OR (Etch*)) OR (Adhesi*)) OR (Surface treatment))) AND ((((((((self adhesive luting resin) OR (self-adhesive luting resin)) OR (self adhesive resin)) OR (self-adhesive resin)) OR (self adhesive cement)) OR (self-adhesive cement)) OR (self-adhesive luting cement)) OR (self adhesive luting cement)))	OR ((“air”[MeSH Terms] OR “air”[All Fields]) AND “abrasi*”[All Fields]) OR “etch*”[All Fields] OR “adhesi*”[All Fields] OR ((“surface”[All Fields] OR “surface s”[All Fields] OR “surfaced”[All Fields] OR “surfaces”[All Fields] OR “surfacing”[All Fields] OR “surfacings”[All Fields]) AND (“therapeutics”[MeSH Terms] OR “therapeutics”[All Fields] OR “treatments”[All Fields] OR “therapy”[MeSH Subheading] OR “therapy”[All Fields] OR “treatment”[All Fields] OR “treatment s”[All Fields]))) AND (((“ego”[MeSH Terms] OR “ego”[All Fields] OR “self”[All Fields]) AND (“adhese”[All Fields] OR “adhesion”[All Fields] OR “adhesions”[All Fields] OR “adhesive s”[All Fields] OR “adhesively”[All Fields] OR “adhesiveness”[MeSH Terms] OR “adhesiveness”[All Fields] OR “adhesivenesses”[All Fields] OR “adhesives”[Pharmacological Action] OR “adhesives”[MeSH Terms] OR “adhesives”[All Fields] OR “adhesive”[All Fields] OR “adhesivities”[All Fields] OR “adhesivity”[All Fields]) AND (“luted”[All Fields] OR “luting”[All Fields]) AND (“resin s”[All Fields] OR “resinous”[All Fields] OR “resins, plant”[MeSH Terms] OR (“resins”[All Fields] AND “plant”[All Fields]) OR “plant resins”[All Fields] OR “resin”[All Fields] OR “resins”[All Fields])) OR (“self-adhesive”[All Fields] AND (“luted”[All Fields] OR “luting”[All Fields]) AND (“resin s”[All Fields] OR “resinous”[All Fields] OR “resins, plant”[MeSH Terms] OR (“resins”[All Fields] AND “plant”[All Fields]) OR “plant resins”[All Fields] OR “resin”[All Fields] OR “resins”[All Fields])) OR ((“ego”[MeSH Terms] OR “ego”[All Fields] OR “self”[All Fields]) AND (“adhese”[All Fields] OR “adhesion”[All Fields] OR “adhesions”[All Fields] OR “adhesive s”[All Fields] OR “adhesively”[All Fields] OR “adhesiveness”[MeSH Terms] OR “adhesiveness”[All Fields] OR “adhesivenesses”[All Fields] OR “adhesives”[Pharmacological Action] OR “adhesives”[MeSH Terms] OR “adhesives”[All Fields] OR “adhesive”[All Fields] OR “adhesivities”[All Fields] OR “adhesivity”[All Fields]) AND (“resin s”[All Fields] OR “resinous”[All Fields] OR “resins, plant”[MeSH Terms] OR (“resins”[All Fields] AND “plant”[All Fields]) OR “plant resins”[All Fields] OR “resin”[All Fields] OR “resins”[All Fields])) OR (“self-adhesive”[All Fields] AND (“resin s”[All Fields] OR “resinous”[All Fields] OR “resins, plant”[MeSH Terms] OR (“resins”[All Fields] AND “plant”[All Fields]) OR “plant resins”[All Fields] OR “resin”[All Fields] OR “resins”[All Fields])) OR ((“ego”[MeSH Terms] OR “ego”[All Fields] OR “self”[All Fields]) AND
	AND (((((((push out bond strength) OR (push-out bond strength)) OR (pull out bond strength)) OR (pull-out bond strength)) OR (dislocation resistance)) OR (bond strength)) OR (retenti*))) AND ((((Teeth) OR (root canal)) OR (post space)) OR (dentin))	(“adhesive cement”[Supplementary Concept] OR “adhesive cement”[All Fields] OR “adhesive cement”[All Fields])) OR (“self-adhesive”[All Fields] AND (“cement s”[All Fields] OR “cementable”[All Fields] OR “cementation”[MeSH Terms] OR “cementation”[All Fields] OR “cementations”[All Fields] OR “cementing”[All Fields] OR “dental cementum”[MeSH Terms] OR (“dental”[All Fields] AND “cementum”[All Fields]) OR “dental cementum”[All Fields] OR “cement”[All Fields] OR “dental cements”[MeSH Terms] OR (“dental”[All Fields] AND “cements”[All Fields]) OR “dental cements”[All Fields] OR “cemented”[All Fields] OR “cements”[All Fields])) OR (“self-adhesive”[All Fields] AND (“luted”[All Fields] OR “luting”[All Fields]) AND (“cement s”[All Fields] OR “cementable”[All Fields] OR “cementation”[MeSH Terms] OR “cementation”[All Fields] OR “cementations”[All Fields] OR “cementing”[All Fields] OR “dental cementum”[MeSH Terms] OR (“dental”[All Fields] AND “cementum”[All Fields]) OR “dental cementum”[All Fields] OR “cement”[All Fields] OR “dental cements”[MeSH Terms] OR (“dental”[All Fields] AND “cements”[All Fields]) OR “dental cements”[All Fields] OR “cemented”[All Fields] OR “cements”[All Fields])) OR ((“ego”[MeSH Terms] OR “ego”[All Fields] OR “self”[All Fields]) AND (“adhese”[All Fields] OR “adhesion”[All Fields] OR “adhesions”[All Fields] OR “adhesive s”[All Fields] OR “adhesively”[All Fields] OR “adhesiveness”[MeSH Terms] OR “adhesiveness”[All Fields] OR “adhesivenesses”[All Fields] OR “adhesives”[Pharmacological Action] OR “adhesives”[MeSH Terms] OR “adhesives”[All Fields] OR “adhesive”[All Fields] OR “adhesivities”[All Fields] OR “adhesivity”[All Fields]) AND (“luted”[All Fields] OR “luting”[All Fields]) AND (“cement s”[All Fields] OR “cementable”[All Fields] OR “cementation”[MeSH Terms] OR “cementation”[All Fields] OR “cementations”[All Fields] OR “cementing”[All Fields] OR “dental cementum”[MeSH Terms] OR (“dental”[All Fields] AND “cementum”[All Fields]) OR “dental cementum”[All Fields] OR “cement”[All Fields] OR “dental cements”[MeSH Terms] OR (“dental”[All Fields] AND “cements”[All Fields]) OR “dental cements”[All Fields] OR “cemented”[All Fields] OR “cements”[All Fields]))) AND ((“push”[All Fields] AND “out”[All Fields] AND “bond”[All Fields] AND (“strength”[All Fields] OR “strengths”[All Fields])) OR (“push-out”[All Fields] AND “bond”[All Fields] AND (“strength”[All Fields] OR “strengths”[All Fields])) OR (“pull”[All Fields] AND “out”[All Fields] AND “bond”[All Fields] AND (“strength”[All Fields] OR “strengths”[All Fields])) OR (“pull-out”[All Fields] AND “bond”[All Fields] AND (“strength”[All Fields] OR “strengths”[All Fields])) OR ((“dislocate”[All Fields] OR “dislocates”[All Fields] OR “dislocating”[All Fields] OR “dislocator”[All Fields] OR “dislocators”[All Fields] OR “joint dislocations”[MeSH Terms] OR (“joint”[All Fields] AND “dislocations”[All Fields]) OR “joint dislocations”[All Fields] OR “dislocated”[All Fields] OR “dislocation”[All Fields] OR “dislocations”[All Fields]) AND (“resist”[All Fields] OR “resistance”[All Fields] OR “resistances”[All Fields] OR “resistant”[All Fields] OR “resistants”[All Fields] OR “resisted”[All Fields] OR “resistence”[All Fields] OR “resistences”[All Fields] OR “resistent”[All Fields] OR “resistibility”[All Fields] OR “resisting”[All Fields] OR “resistive”[All Fields] OR “resistively”[All Fields] OR “resistivities”[All Fields] OR “resistivity”[All Fields] OR “resists”[All Fields])) OR (“bond”[All Fields] AND (“strength”[All Fields] OR “strengths”[All Fields])) OR “retenti*”[All Fields]) AND (“teeth s”[All Fields] OR “teeths”[All Fields] OR “tooth”[MeSH Terms] OR “tooth”[All Fields] OR “teeth”[All Fields] OR “tooth s”[All Fields] OR “tooths”[All Fields] OR (“dental pulp cavity”[MeSH Terms] OR (“dental”[All Fields] AND “pulp” [All Fields] AND “cavity”[All Fields]) OR “dental pulp cavity”[All Fields] OR (“root”[All Fields] AND “canal”[All Fields]) OR “root canal” [All Fields]) OR (“post”[All Fields] AND (“space”[All Fields] OR “space s”[All Fields] OR “spaces”[All Fields])) OR (“dentin”[MeSH Terms] OR “dentin” [All Fields] OR “dentine” [All Fields] OR “dentines” [All Fields] OR “dentins” [All Fields] OR “dentin s” [All Fields] OR “dentinal” [All Fields]))

Screening and selection

In vitro studies that assessed the push-out or pull-out bond strength of the prefabricated esthetic posts whose surface was treated with a chemical, mechanical, or combined means and bonded using self-adhesive resin cement within natural or artificial substrate were included for this study. Only published articles in the English language after 2001 (year of introduction of self-adhesive resin cement) were considered.

Studies which include other posts than prefabricated esthetic posts, studies where no surface treatment of the post was carried out, studies which do not have a control group, experiments were other modes of testing than dislocation resistance was used, and those whose data were unavailable despite requesting the authors were all excluded. Title and abstract screening were done by two reviewers, and full-text screening of the articles was carried out by three reviewers. Any sort of disagreement was settled by the subject expert.

Data collection

A data extraction sheet was prepared in MS Excel, to easily identify the variables in the articles. The research team made groups to categorize the variables under the type of the prefabricated esthetic posts, surface pretreatment of the post, substrate to which post is bonded, and the push-out/pull-out bond strength values (the arithmetic average of the values of the thirds was used). All the bond strength values were expressed in megapascal. From the articles, even other relevant information such as the size and nature of the post, root canal preparation, mode of cement application, storage of samples, and a mode of failure was extracted considering the inclusion criteria.

Assessment of risk of bias

Assessment of the quality of the articles was done following Sarkis-Onofre et al. and Moraes et al. that classifies potential risk of bias as being high, moderate, and low risk.[35] The quality assessment was based on (a) intact human or bovine teeth, (b) similar canal size of the specimen, (c) sample size calculation, (d) randomization of the samples, (e) size of post and post space and cleansing step, (f) treatment by single operator, (g) manufacturer's instruction followed, (h) aging done, and (i) blinding of the operator. Letter “Y” (yes) was denoted when the parameter was present in the article and if not then “N” (no) was denoted under the parameter which was prepared for the risk of bias assessment. The total number of Y for each article determines the grading of risk of bias and was performed by four reviewers. Grading was done as follows: 1–3, high risk of bias; 4–6, moderate risk of bias; and 7–9, low risk of bias.

Statistical analysis

Review Manager (RevMan, Australian Cochrane Centre, 2008) Version 5.3 was used to perform the meta-analysis. Subgroup analysis was performed by type of prefabricated esthetic posts used as well as the type of post surface treatment performed (chemical treatment, physical treatment, or a combination). We have calculated the weighted average, heterogeneity, and confidence interval for the mean difference between groups by applying the random-effects model. Statistical heterogeneity between surface treatments among the included studies was assessed using the I2 statistic. Based on Z-test, P < 0.05 was considered statistically significant.

RESULTS

Results from the literature search, screening, and selection

The results from the above search terms obtained are as follows: PubMed, 174; Scopus, 83; Web of Science, 56; EBSCO, 32; and handsearch, 29 articles. Articles that appeared in more than one database were removed as duplication, resulting in 199 articles. From this, 165 were excluded after abstract screening, bringing the number to 34 studies [Figure 1].

Figure 1

Flow diagram for reporting articles for systematic review methodology following PRISMA guidelines

Characteristics of the excluded studies

Few of the studies had adhesive applied to post spaces instead of the post surface.[202122232425] In others, cements other than self-adhesive cements were used.[262728] A study by Faria-e-Silva et al. did not have any surface treatments done on the post, whereas some had no control group.[27293031323334] Few of them displayed incomplete datasets.[823242535] Hence, a total of 19 were excluded from our study.

Characteristics of included articles

RelyX Unicem (3M ESPE) was the most used self-adhesive resin cement. Among the various posts used such as GFP and quartz fiber posts (QFP) (transparent and opaque), surface pretreatment done with silane did not demonstrate a statistically significant difference between treated and non-treated groups.[3637383940] Among other studies, sandblasting or sandblasting combined with silanization showed significantly higher bond strength.[818194142] Most of the failures demonstrated were adhesive in nature between the post and the root dentin.

Risk of bias

Out of all the evaluated studies, nine of them showed a high risk of bias Table 1.[183637404142434445] None of the studies had blinding of the operator and a few of them were conducted by multiple operators.[43819] Strict adherence to the manufacturer's instructions was followed by all except in a few studies.[18414445] It was also found out that only two articles showed sample size calculation.[1947]

Table 1

Risk of bias of the included studies

Author and year	Intact teeth	Similar canal size of the specimens	Sample size calculation	Randomization	Size of post and post space, cleansing step mentioned	Treatment by single operator	Manufacturer’s instruction followed	Aging done	Blinding of testing operator	Risk of bias
Khoroushi et al., 2014[46]	Yes	No	No	Yes	Yes	No	Yes	Yes	No	Moderate
Rathke et al., 2009[36]	Yes	No	No	No	Yes	No	Yes	No	No	High
Mazzitelli et al., 2012[37]	Yes	No	No	No	Yes	No	Yes	No	No	High
Elnaghy and Elsaka 2016[4]	Yes	No	No	Yes	No	Yes	Yes	No	No	Moderate
Leme et al., 2013[38]	No	No	No	Yes	Yes	Yes	Yes	No	No	Moderate
Chen et al., 2014[43]	Yes	No	No	Yes	No	No	Yes	No	No	High
Majeti et al., 2014[44]	Yes	No	No	No	Yes	No	No	No	No	High
Tian et al., 2012[39]	Yes	No	No	Yes	Yes	No	Yes	No	No	Moderate
Liu et al., 2014[18]	Yes	No	No	Yes	No	No	No	No	No	High
Schmage et al., 2009[41]	Yes	No	No	No	Yes	No	No	Yes	No	High
Machry et al., 2020[19]	No	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Moderate
Graiff et al., 2014[47]	No	Yes	Yes	Yes	Yes	No	Yes	No	No	Moderate
Prado M et al., 2017[45]	No	Yes	No	No	No	No	No	No	No	High
Wrbas et al., 2007[40]	No	No	No	No	Yes	No	Yes	No	No	High
Costa Dantas et al., 2012[42]	No	Yes	No	No	No	No	Yes	No	No	High

Meta-analysis results

Meta-analysis was carried out by combining 11 in vitro studies to assess the effect of surface treatment on the dislocation resistance of prefabricated esthetic posts bonded with self-adhesive resin cement. Only studies carried out on natural teeth were included for meta-analysis. The features of all the studies included are summarized in Table 2. As shown in the forest plot, there was no significant difference in the dislocation resistance of silanated and nonsilanated GFP [Figure 2a] as well as QFP [Figure 2b] when bonded with self-adhesive resin cement. Even air abrasion with and without silanization showed no significant increase in dislocation resistance as compared to the control group [Figure 2c and d]. As for the GFP, none of the other chemical post- and pretreatments also proved better than the untreated posts [Figure 3]. This was substantiated with P > 0.05 for the Z test. However, since the I2 >50% in almost all the forest plots, the pooled statistics need to be interpreted with caution because of the presence of significant statistical heterogeneity.

Table 2

Characteristics of the included studies

Author and year	Substrate	Root canal preparation	Esthetic post used	Self- adhesive resin cement used	Surface treatment	Aging	Sample size	Test used	Bond strength (mean ± SD) in MPa*	Failure types (%)
Khoroushi et al., 2014[46]	Human teeth	Cold lateral condensation done using ProTaper gutta percha points and AH26 sealer Post space was prepared using drills	GFP	BisCem	PT1: Control	37°C, 100% humidity for 24 h (1000 thermocycles), 5°C-55°C, 30 s (dwell time)	n = 16	Push-out bond strength test	7.2 ± 3.1a	AP-16.6, AD-8.4, M-75
					PT2: HPS				7.9 ± 4.3a, b	AP-33.4, M-58.2
					PT3: HPSO (hesperidin)				10.79 ± 5.26b, c	AP-16.6, CC-8.4, M-75
					PT4: HPSO (rosmarinic acid)				15.28 ± 4.61c	AP-8.4, AD-8.4, CC-16.6, M-66.6
					PT5: HPSO (sodium ascorbate)				11.37 ± 3.04b, c	AP-12, CC-8.4, M-66.6
Rathke et al., 2009[36]	Human teeth	Obturation not done Post space was prepared using canal drills	Opaque QFP	RelyX Unicem	PT1: Control	24 h at 37°C	n = 5	Push-out bond strength test	18.80 ± 4.21a	No S - AP-62, AD-17, M-21 S - AP-55, AD-25, M-20
					PT2: S				23.29 ± 4.70b
			Translucent QFP		PT1: Control				23.37 ± 2.03b
					PT2: S				28.99 ± 7.09b
			GFP		PT1: Control				24.68 ± 6.41b
					PT2: S				23.06 ± 7.23b
Mazzitelli et al., 2012[37]	Human teeth	Lateral condensation done using gutta percha and AH Plus Sealer Post space prepared using universal drills	QFP	RelyX Unicem	PT1: Control	1 month at 37°C and 100% humidity	n~25	Push-out bond strength test	9.30 ± 2.6a	AD-69, AP-19, M-6, CC-6
					PT2: S				7.24 ± 2.4a	AD-100
					PT3: HP				7.25 ± 2.4a	AD-100
					PT4: A				7.02 ± 3.1a	AD-100
					PT5: Industrially S				6.25 ± 2.5a	AD-100
				MaxCem	PT1: Control		n~25		3.86 ± 2.9b	AD-85, CC-15
					PT2: S				4.79 ± 2.1c	AD-83, CC-17
					PT3: HP				1.63 ± 1.2b	AD-58, AP-38, M-2, CC-2
					PT4: A				1.15 ± 1.1b	AD-48, AP-44, M-5, CC-3
					PT5: Industrially S				1.83 ± 1.9b	AD-66, CC-34
Elnaghy and Elsaka 2016[4]	Human teeth	Gutta percha and AH Plus Sealer used Post space prepared using preshaped drills and postdrills	GFP	RelyX Unicem	PT1: Control	37°C, 100% humidity for 1 week	n = 90	Micro push-out bond strength test	7.64 ± 3.24a	AP-7, AD-50, CC-5, M-38
					PT2: S				6.60 ± 3.31a	AP-10, AD-54, CC-7, M-29
					PT3: A				5.55 ± 2.79b	AP-10, AD-52, CC-9, M-29
					PT4: HF				3.87 ± 1.63b	AP-5, AD-41, CC-7, M-48
					PT5: O (CH2Cl2)				11.49 ± 5.18c	AP-2, AD-43, CC-5, M-50
Leme et al., 2013[38]	Bovine teeth	Lateral condensation done using gutta percha and sealer 26 Post space prepared using posthole drills	GFP	RelyX Unicem	PT1: Control	37°C, 100% humidity for 24 h	n = 30	Pull out bond strength test	2.69 ± 0.27b	AP-29, AD-32, M-39
					PT2: S				5.93 ± 3.21a	AP-7, AD-62, M-31
					PT3: SO (Solobond)				6.72 ± 3.92a	AP-26, AD-45, M-29
					PT4: SO (Scotchbond)				7.43 ± 3.31a	AP-24, AD-42, M-34
					PT5: SO (excite)				6.65 ± 2.40a	AP-18, AD-51, M-31
Chen et al., 2014[43]	Human teeth	Lateral condensation using gutta percha and sealer Post space prepared using number 1-2 Peeso Reamer and enlarged with standard drill system	GFP	RelyX Unicem	PT1: Control	Distilled water for 7 days	n = 60	Micro push-out bond strength test	4.7 ± 2.1a	AD-80, CC-15, M-5
					PT2: Polydopamine conditioning				8.2 ± 2.8b	AD-90, CC-5, M-5
Majeti et al., 2014[44]	Human teeth	Lateral condensation done using gutta percha and AH Plus sealer Post space prepared using number 3 drill	GFP	RelyX Unicem	PT1: Distilled water	37°C in distilled water for 24 h	n = 60	Push-out bond strength test	15 s: 8.22 ± 3.57a	AP-26.6, AD-41.6, CC-31.6
									30 s: 8.24 ± 3.63a	AP-28.3, AD-43.3, CC-28.3
									60 s: 8.17 ± 3.61a	AP-26.6, AD-41.6, CC-31.6
					PT2: O (H3PO4)				15 s: 11.06 ± 4.19#	AP-18.3, AD-46.6, CC-35
									30 s: 9.43 ± 3.41$	AP-21.6, AD-45, CC-33.3
									60 s: 8.95 ± 3.38$	AP-26.6, AD-41.6, CC-31.6
					PT3: HP				15 s: 8.20 ± 3.50A	AP-28.3, AD-43.3, CC-28.3
									30 s: 8.59 ± 2.96A	AP-26.6, AD-41.6, CC-31.6
									60 s: 10.95 ± 4.34B	AP-16.6, AD-48.3, CC-35
Tian et al., 2012[39]	Human teeth	Thermoplastic zed gutta percha and AH Plus sealer done Post space prepared using twist drill number 4	GFP	RelyX Unicem	PT1: Control	37°C in saline solution for 24 h	n = 4	Pull out bond strength test	5.21 ± 1.16a	Mainly AD
					PT2: S		n = 8		5.42 ± 1.01a
Liu et al., 2014[18]	Human teeth	Gutta percha points and sealer Post space preparation using Peeso Reamer, glass fiber special burs	GFP	RelyX Unicem	PT1: Control	37°C in distilled water for 24 h	n = 60	Micro push-out bond strength test	14.77 ± 2.77a	Mainly CD
					PT2: A				16.89 ± 3.88a
					PT3: S				15.29 ± 3.08a
					PT4: AS				15.33 ± 4.77a
Schmage et al., 2009[41]	Human teeth	Obturation not mentioned Post space prepared using number 2 drills	GFP	RelyX Unicem	PT1: Control	37°C in distilled water for 24 h (thermocycling 5000 cycles, 5°C-55°C, 30 s dwell time)	n = 10	Pull-out bond strength test	15.54 ± 2.29a, c	AP-50, CC/M-50
					PT2: S				13.21 ± 4.31a, b	AP-20, CC/M-80
					PT3: HFS				9.75 ± 2.88b	AP-30, CC/M-70
					PT4: A (Cojet) S				18.52 ± 4.45c	AP 30, CC/M-70
Machry et al., 2020[19]	Bovine teeth	Cold lateral condensation done using gutta percha and AH Plus sealer Post space prepared using diamond burs	GFP	RelyX U200	PT1: Control	24 h at 37°C	n = 40	Push-out bond strength test	2.76 ± 1.8a	AD-67.5, AP-12.5, CP-17.5
					PT2: Control S				2.0 ± 1.4a	AD-80, AP-7.5, CP-12.5
					PT3: HF				2.5 ± 1.4a	AD-67.5, AP-12.5, CP-20
					PT4: HFS				2.2 ± 1.0a	AD-52.5, AP-17.5, CP-30
					PT5: HP				2.6 ± 2.7a	AD-25, AP-37.5, CP-37.5
					PT6: HPS				1.6 ± 0.3a	AD-67.5, AP-20, CP-12.5
					PT7: A				2.2a	AD-55, AP-5, CP-40
					PT8: AS				2.0 ± 0.5a	AD-65, AP-15, CP-20
Graiff et al., 2014[47]	Simulated root canal (plexiglass mold)	Obturation not mentioned Artificially tapered post space	GFP	RelyX Unicem	PT1: Control	Not mentioned	n = 10	Pull out bond strength test	26.18 ± 7.17b	M-100
					PT2: O (Pretreated with MMA)				29.55 ± 5.74a	M-100
					PT3: AO (MMA and Cojet)				25.25 ± 4.53b	M-100
Prado et al., 2017[45]	Silicone matrix	Obturation and post space preparation not mentioned	GFP	RelyX U200	PT1: Control	Not mentioned	n = 40	Push-out bond strength test	9.65 ± 3.64b	CM-100
					PT2: S				15.94 ± 6.53a	CM-100
					PT3: HP				9.40 ± 3.98b	CM-100
					PT4: A				13.13 ± 3.58a	CM-98, M-1, CC-1
					PT5: O (Ammonia plasma)				14.44 ± 4.04a	CM-70, M-30
					PT6: O (Hexamethyldisiloxane plasma)				13.24 ± 5.28a	CM-59, M-40, AP-1
Wrbas et al., 2007[40]	Bovine teeth	Obturation not mentioned Post space prepared using postdrill system	QFP	RelyX Unicem	PT1: Control	1 week in humid temperature	n = 10	Pull out bond strength test	4.79 ± 0.58a	Covered bonding surface percentage = 20 ± 11.3
					PT2: S				4.74 ± 0.88a	Covered bonding surface percentage = 25 ± 13.1
Costa Dantas et al., 2012[42]	Composite core with central hole of 1.8 mm	Obturation not mentioned Post space prepared with a central hole	GFP	RelyX Unicem	PT1: Control	Stored for 24 h	n = 8	Push-out bond strength test	13.9 ± 1.4a	AP
					PT2: S				11.7 ± 3.1a	AP
					PT3: HF				10.9 ± 5.3a	AP
				PT4: HFS				12.3 ± 5.4a	AP
					PT5: O (argon plasma polymerization)				12.4 ± 2.0a	AP
					PT6: O (ethylenediamine plasma)				17.3 ± 2.7b	Cohesive in composite core

*Different letters/symbols indicate significant difference as per the data extracted from each of the study. GFP: Glass fiber post, QFP: Quartz fiber post, ZP: Zirconia post, PT: Post surface treatment, S: Silane, A: Air abrasion, AS: A and S, HF: Hydrofluoric acid, HFS: HF and S; HP: Hydrogen peroxide, HPS: HP and S, O: Others, HPSO: HP, S and O, AO: A and O, AP: Adhesive failure of post to cement, AD: Adhesive failure of cement to dentin, CC: Cohesive failure of cement, CD: Cohesive failure of dentin, CP: Cohesive failure of post, CM: Cohesive failure of post and cement, M: Mixed failure, SD: Standard deviation

Figure 2

Forest plot that assessed the dislocation resistance of (a) glass fiber post with no treatment (control) and silane treatment, (b) quartz fiber post with and without silanization, and (c) bond strength of glass fiber posts with no treatment to those treated with air abrasion as well as (d) comparison between control and glass fiber posts subjected to air abrasion followed by silane treatment

Figure 3

Forest plot that compared the dislocation resistance of glass fiber post with no treatment (control) (a) to those treated with hydrogen peroxide, (b) to those treated with hydrogen peroxide followed by silane treatment, (c) glass fiber posts treated with hydrofluoric acid, and (d) those treated with hydrofluoric acid followed by silanization

DISCUSSION

Due to the growing demand for esthetics, metallic posts have been replaced by tooth-colored metal-free post systems such as GFP, zirconia posts, and QFP, out of which GFP are most used in this study. Even though metal posts are rigid and strong, their main shortcomings include discoloration, chances of the post and root fracture, and risk of corrosion.[48] Prefabricated GFP help in uniform stress distribution across the root due to its low modulus of elasticity and flexibility.[22] One of the major disadvantages shown by the prefabricated fiber posts is the highly cross-linked less reactive polymer matrix of the post material, making bonding to resin luting agents and tooth difficult.[49] Among the different posts used, GFP were commonly used. This is due to their excellent esthetic property, great strength, stiffness, elastic modulus comparable to dentin, and weaker fracture resistance.[29]

Self-adhesive cements are the latest addition to the resin category. They are dual cured and show a greater bond to dentin surfaces. Unlike other resin cements, a separate adhesive bonding agent is not needed, thus time-saving and shortening the procedure.[12] RelyX Unicem, commonly used cement in this study, along with its multifunctional monomers and phosphoric acid groups demineralizes and infiltrates enamel and dentin creating micromechanical retention and chemical bonding to hydroxyapatite.[313] This chemical interaction is due to calcium ion chelation by the acidic groups of self-adhesive cements.[22] Therefore, the bonding mechanism is mainly due to chemical adhesion and micromechanical retention. Additional benefits include long-term stability, high moisture tolerance, and reduced risk of postoperative sensitivity.

To increase the retentive strength of the post, pretreatments are done such as chemo/mechanical conditioning, which eliminates or dissolves the epoxy matrix of posts, exposing the fibers that get activated and react with resinous cement.[37] Silanization is, without doubt, the most common treatment done on fiber post surface. Silane solutions are organic–inorganic hybrid compounds that cause adhesion between different matrices.[35] Silane agents provide retention of the fiber posts by a chemical reaction between silicon oxide present on the surface layer and the adhesive matrix.[39] On the application of H2O2, spaces are created between the fibers which favor the micromechanical interlocking between the post and cement.[46] Sandblasting with aluminum oxide particles leads to plastic deformation and improved surface roughness of the fiber post, leading to an increased surface area for bonding. This helps in increasing the contact angle of the polymer surface.[37] Hydrofluoric acid etching demonstrates fractured fibers and exposes the resin matrix helping in micromechanical retention.[18] The effect of silanization on the retention of posts by the bond between the resin cement and the post surface has been widely debated. Even though many studies show no change in bond strength after silanization, Aksornmuang et al. and Goracci et al. in their studies demonstrated increased bonding after silanization to surfaces of quartz and GFP.[5051] However, this study shows that there is not much significant difference seen in post retention in any of the above-mentioned surface treatment on fiber post surface.

Retention of the post to root structure is most measured using push-out bond strength test, which produces shear stress at post cement interface similar to clinical conditions.[44] Various factors influencing the bond strength are length, diameter, shape, surface treatment of post as well as root dentin, canal regions, type of posts, and luting agents used.[18] Micro push-out bond strength test demonstrates bond strength at coronal, middle, and apical levels of the root dentin. Higher bond strength is seen in the coronal third compared to the middle and apical thirds. This can be due to decreased penetration of the curing light till apex, difficulties in moisture control in the apical third, incomplete infiltration and distribution of resin cement leading to the formation of bubbles and voids in the apical region, and formation of a thick smear layer throughout the post space.[444] Pull-out tests have shown to be more advantageous than push-out tests as they efficiently measure simultaneously shear as well as tensile bond strength. They also eliminate the chance of a fractured post segment being left behind in the root canal.[39]

Adhesive failures occurring between root dentin and resin cement are frequently seen. The flexural strength property of fiber posts is used to evaluate the fracture resistance. Posts demonstrating higher values of flexural strength are more resistant to fracture than those showing the least value.[4] Mode of failures is not influenced by silane or other surface treatments as the stresses were distributed uniformly and post surface area revealing exposed glass/quartz fibers were limited.[36] A higher percentage of cohesive failures (i.e. failures within the cement itself), was seen in self-adhesive cements as they showed higher bond strengths.[18]

Most of the studies investigated here show a high risk of bias, leading to high heterogeneity. This is because the variables that could influence this result were not controlled by the researchers. Even though the studies simulated clinical conditions, being in vitro does not wholly replicate oral conditions. For better clinical results, randomized control trial with longer follow-up periods or in vitro studies with a robust experimental design are required to get a better insight into the influence of post surface treatment and bond strength. Furthermore, further studies are to be conducted to evaluate the effect of sealers and obturation, the technique of post space preparation, and canal cleansing strategy on the bonding of self-adhesive resin cement.

CONCLUSION

GFP are the commonly tested prefabricated esthetic fiber post. Among the various treatments on the surface of different prefabricated posts, silane treatment was the commonly researched modality. However, analysis of included in vitro studies demonstrated no significant improvement in bond strength of self-adhesive resin cement to fiber post subjected to surface treatment, when compared to the nontreated posts. Thus, the use of an additional step to assist in improving the adhesion could be a futile exercise. Nonetheless the results of this systematic review should be interpreted with caution as most of the considered studies were having a high risk of bias. Therefore, further studies with a low risk of bias are required to further validate the results.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.