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primary anterior teeth are the most commonly affected teeth due to early childhood caries and trauma . according to huber et al . , they are called the social six as they are the most prominent teeth in a smile .
loss of primary anterior teeth leads to mastication problems , speech disorders such as difficulty in pronunciation , development of parafunctional habits , hesitation to play among the peer groups due to esthetic concerns , and also reduction in vertical facial height .
intracanal post and core system were used to regain the lost tooth structure and bring back the original smile of the patient .
different kinds of materials have been used for intracanal reinforcement in primary teeth such as short composite posts , short wire posts , ni - cr coil spring posts , glass fiber posts , polyethylene fiber post / ribbond , and metal screw posts .
the crown anatomy can be restored by direct composite buildup by incremental method or using celluloid strip crowns . in this study , three post systems were used , namely , omega loop , glass fiber post , and ribbond .
the use of omega loop as an intracanal retainer was introduced by mortada and king in 2004 for primary teeth .
the introduction of fiber posts in the 1960s provided the dental profession an alternative treatment modality to cast / prefabricated posts , pins , and orthodontic wires .
glass fiber posts are commonly used in pediatric dentistry , thereby used as one of the post materials in our study .
polyethylene fibers , a recently developed material ( ribbond ) , reported to have clinical advantage over the traditional intracanal post material .
these fibers improve the impact strength , modulus of elasticity , and flexural strength of composite materials .
all the materials used as intracanal posts have their own advantages and disadvantages . despite numerous clinical reports on primary teeth restoration
, there is no enough information about the physical and mechanical properties of the post - supported restorations . in our study , the traditional materials and the recent materials were compared for their fracture resistance leaving behind the cost and technique sensitivity .
the aim of this in vitro study was to compare the compressive strength among three different intracanal post materials in primary anterior teeth .
the study was performed in the department of pedodontics and preventive dentistry , srm dental college , ramapuram , chennai , tamil nadu , india .
a total of sixty single - rooted primary anterior teeth ( central incisors , lateral incisors , and canines were included in the study ) with initial physiological resorption not more than 2/3 of the root were collected and included in the study .
teeth with more than 2/3 of the roots resorbed and teeth with any evidence of crack or fracture were excluded .
the central incisors , canines , and lateral incisors were equally distributed in three groups .
the samples were cleaned with 2% sodium hypochlorite and stored in physiological saline till the preparation .
the samples were decoronated 1 mm coronal to cementoenamel junction using a diamond disc in a micro motor with saline as a coolant .
pulpectomy was done and obturated with zinc oxide eugenol paste leaving 4 mm of the canal space for post .
one millimeter thickness glass ionomer cement ( gic ) base was given to separate the obturating material from the post space .
care was taken to avoid smearing zinc oxide eugenol remnants on the walls of the post space .
all the samples were numbered from 1 to 60 and divided into three groups containing twenty samples each : 
 group i : polyethylene fiber reinforced composite ( ribbond)group ii : omega loop  0.7 mm orthodontic wiregroup
group i : polyethylene fiber reinforced composite ( ribbond ) group ii : omega loop 
for all the groups , canals were etched with 37% phosphoric acid ( ivoclar vivadent ) and monobond
it is suitable for all types of indirect restorative materials , easy storage , can be used along with glass and oxide ceramics , metal composites , frc 's according to manufacturer instructions ( multilink speed , ivoclar vivadent ) .
dual - cure composite material was placed inside the post space ; polyethylene fiber ( everstic , gc corporation , japan ) was condensed into the space such that it extended 2 mm outside the canal and cured for 60 s [ figure 1 ] . ribbond post luted with dual cure composite
a 1.5 cm length of 0.7 mm round orthodontic stainless steel wire was bent using number 130 orthodontic pliers , into an omega - shaped loop according to mortada and king .
dual - cure composite material was placed inside the post space , and the omega loop was inserted and cured for 60 s. this wire comprised pulpal end and an incisal end .
the pulpal ends of the wire were compressed together using a needle holder , and inserted into the canal .
the pulpal end extended approximately 3 mm into the root canal so as to increase the overall retention of the wire ; the incisal end projected 23 mm above the remaining structure ; this provided better mechanical retention and support for restorative material [ figure 2 ] .
omega loop post luted with dual cure composite the canals were etched , and bonding agent was applied .
the post space was filled with dual - cure composite , 5 mm of prefabricated glass fiber post ( dentsply , germany ) was inserted , and post was luted extending 2 mm outside the canal [ figure 3 ] .
core buildup was done for all the sixty samples by incremental method using resin composite ( dentsply , germany ) .
the specimens were stored in 37c sterile water solution for 72 h till subjected to testing .
the acrylic resin block mounted with tooth was subjected to compressive load at the angulation of 148 at the speed of 0.5 mm / min .
fracture at any point of the sample was recorded as failure of the post system [ figure 4 ] .
glass fiber post luted with dual cure composite the acrylic block loaded in universal testing machine at 148 angulation data were subjected to statistical analysis using spss software ( version 19 , spss inc . ,
the samples were cleaned with 2% sodium hypochlorite and stored in physiological saline till the preparation .
the samples were decoronated 1 mm coronal to cementoenamel junction using a diamond disc in a micro motor with saline as a coolant .
pulpectomy was done and obturated with zinc oxide eugenol paste leaving 4 mm of the canal space for post .
one millimeter thickness glass ionomer cement ( gic ) base was given to separate the obturating material from the post space .
care was taken to avoid smearing zinc oxide eugenol remnants on the walls of the post space .
all the samples were numbered from 1 to 60 and divided into three groups containing twenty samples each : 
 group i : polyethylene fiber reinforced composite ( ribbond)group ii : omega loop  0.7 mm orthodontic wiregroup iii : prefabricated glass fiber - reinforced composite post . 
 
group i : polyethylene fiber reinforced composite ( ribbond ) group ii : omega loop 
for all the groups , canals were etched with 37% phosphoric acid ( ivoclar vivadent ) and monobond n is a ivaclor vivadent product .
it is suitable for all types of indirect restorative materials , easy storage , can be used along with glass and oxide ceramics , metal composites , frc 's according to manufacturer instructions ( multilink speed , ivoclar vivadent ) .
dual - cure composite material was placed inside the post space ; polyethylene fiber ( everstic , gc corporation , japan ) was condensed into the space such that it extended 2 mm outside the canal and cured for 60 s [ figure 1 ] .
a 1.5 cm length of 0.7 mm round orthodontic stainless steel wire was bent using number 130 orthodontic pliers , into an omega - shaped loop according to mortada and king .
dual - cure composite material was placed inside the post space , and the omega loop was inserted and cured for 60 s. this wire comprised pulpal end and an incisal end .
the pulpal ends of the wire were compressed together using a needle holder , and inserted into the canal .
the pulpal end extended approximately 3 mm into the root canal so as to increase the overall retention of the wire ; the incisal end projected 23 mm above the remaining structure ; this provided better mechanical retention and support for restorative material [ figure 2 ] .
the canals were etched , and bonding agent was applied . the post space was filled with dual - cure composite , 5 mm of prefabricated glass fiber post ( dentsply , germany ) was inserted , and post was luted extending 2 mm outside the canal [ figure 3 ] .
core buildup was done for all the sixty samples by incremental method using resin composite ( dentsply , germany ) .
the specimens were stored in 37c sterile water solution for 72 h till subjected to testing .
the acrylic resin block mounted with tooth was subjected to compressive load at the angulation of 148 at the speed of 0.5 mm / min .
fracture at any point of the sample was recorded as failure of the post system [ figure 4 ] .
glass fiber post luted with dual cure composite the acrylic block loaded in universal testing machine at 148 angulation
data were subjected to statistical analysis using spss software ( version 19 , spss inc . ,
table 1 shows the mean compressive strength values of group 1 , group ii , and group iii as 83.25 n , 61.60 n , and 75.55 n , respectively .
comparison of compressive strength between three groups ( one - way analysis of variance ) group i ( ribbond ) shows the highest fracture resistance , followed by group iii ( glass fiber post ) and group ii ( omega loop ) . in group
i ( ribbond ) , the compressive strength values ranged between 35 n and 275 n. in group ii ( omega loop ) , the values ranged between 28 n and 144 n. in group iii ( glass fiber post ) , the values ranged between 38 n and 158 n. table 1 shows the one - way anova which was done for the intergroup comparison .
since p value is not significant , anova is not followed by post hoc test .
the main advantage of a post and core system is to provide retention and stability for the crown .
the advantages and disadvantages of all the three post systems are shown in table 2 .
the material used as a post can affect the fracture resistance of the post and core system .
a simpler and effective method to use an omega loop was introduced by mortada and king .
the greatest advantage is that the wire does not cause any internal stress in the root canal .
comparison of advantages and disadvantages of three post systems glass fiber reinforced composite resin posts can be used as an alternative to the other post systems .
the properties of fiber post depend on the nature of the fibers , interface strength , and geometry of reinforcement . in glass fiber post and composite core system , modulus of elasticity is similar to dentin , thereby improves the stress distribution between posts and dentin , thus resulting in better flexibility when load is applied .
this property reduces the risk of root fracture . in our study , ribbond showed the highest fracture resistance .
the patented leno weave pattern is the characteristic feature of ribbond fiber designed with a lock stitch feature that effectively transfers forces throughout the weave without stress transfer back into the resin .
as the fibers of ribbond has no memory , it adapts to the contours of the teeth and dental arch easily .
it is translucent , practically colorless and disappears within the composite posts or acrylic offering excellent esthetics . in the present study ,
the tooth was decoronated 1 mm above the cementoenamel junction , to simulate a clinical condition of reduced amount of tooth structure .
zinc oxide eugenol was the material of choice for obturation as it is the most common material .
alves and vieira rde and viera and ribeiro have concluded that the type of obturation material used for endodontic treatment does not interfere with mechanical properties of the post system .
the post space was carefully separated from zinc oxide eugenol giving 1 mm gic base .
this was done by many authors for better bonding of the post material . according to pithan
, the minimum post length should be 23 mm to give more support and retention to the crown .
in primary teeth , it should not interfere with root resorption and the physiological eruption of permanent teeth .
hence , the length of the post was restricted to 3 mm . the present in vitro study
has yielded the fracture resistance values between 28 n and 275 n. in contrast , permanent teeth studies have shown higher fracture resistance ranging from 400 n to 935 n. the high value was due to larger diameter of the permanent teeth .
the authors have insisted that the diameter of the tooth is one of the factors affecting fracture resistance .
the authors have suggested that increase in diameter proportionately enhances the strength . according to mountain et al . in 2010 ,
the levels of bite force in primary anterior teeth ranged between 6.87 n to 140.09 n. this range is similar to our compressive strength values which ranged between 28 n to 275 n. in contrast , seraj et al . have quoted higher values in cementum - extended composite post system which was 601 n. the authors explained that the higher value was due to ferrule effect .
the wide range in fracture resistance values in our study was due to variation in sample sizes ( incisors and canines were of different length and diameter ) .
future studies with similar samples ( e.g. only central incisors ) are needed to substantiate our results .
group i ( ribbond ) showed the highest fracture resistance values among the three test groupsgroup ii ( omega loop ) showed the least fracture resistance values among the three test groupsthe order of fracture resistance values was decreasing from group i ( ribbond ) followed by group iii ( glass fiber post ) and group ii ( omega loop)although there is difference in mean values among the three groups , p value was nonsignificant ( 0.220)in vivo studies with 1 year follow - up are needed to justify our results . 
 
group i ( ribbond ) showed the highest fracture resistance values among the three test groups group ii ( omega loop ) showed the least fracture resistance values among the three test groups the order of fracture resistance values was decreasing from group i ( ribbond ) followed by group iii ( glass fiber post ) and group ii ( omega loop ) although there is difference in mean values among the three groups , p value was nonsignificant ( 0.220 ) in vivo studies with 1 year follow - up are needed to justify our results .
objective : the objective of our study was to compare the fracture resistance and the mode of failure among three different post materials in primary anterior teeth.materials and methods : a total of sixty extracted primary anterior teeth were selected for the study . 
 the samples were divided into three groups of twenty teeth each : group i ( ribbond ) , group ii ( omega loop ) , and group iii ( glass fiber post ) . 
 pulp therapy was followed by intracanal post and crown buildup . 
 the samples were mounted in self - cure acrylic and subjected to compressive strength test using universal testing machine ( instron ) . 
 the maximum force at which the tooth fractured was recorded.results:the values were subjected to one - way analysis of variance . 
 the mean compressive strength values of ribbond , omega loop , and glass fiber post were found to be 83.25 n , 61.60 n , and 75.55 n , respectively . 
 the p value was found to be 0.220.conclusion:group i ( ribbond ) showed the highest fracture resistance values followed by group iii ( glass fiber post ) and group ii ( omega loop ) . 
 although there is difference in mean values , they were nonsignificant .