Objectives:

To compare in vitro static failure loads and -modes of resin composite crowns with two fibre-reinforced composite (FRC)-posts.

 

Methods:

Clinical crowns of single-rooted upper premolars were cut off at the cemento-enamel junction. The canals were prepared with gates glidden drills up to size 4. No post-space preparations were made. Roots were embedded in acrylic and canal entrances were standardised (depth 2 mm, diameter 1.75 mm). Before resin composite crowns (Filtek Z250) were made (using an anatomical mould), three groups of 14 samples were treated as follows: (1) custom-made unidirectional glass-FRC post (EverStickPost®); fibres 5 mm of depth in the canal, (2) similar post-system as (1) with an occlusally placed veil-woven hybrid glass-FRC layer (experimental), (3) no fibre-reinforcement (control). The posts were cemented with a resin-cement (Panavia F). Static load was applied using a standard loading device with a cylindrical bar (diameter2 mm, crosshead speed 5 mm/min). Site of loading was the central fissure of the occlusal surface under an angle of 60 degrees with the tooth long-axis, in the direction of the buccal cusp. Two operators assessed failure modes independently. Favourable failures were defined as reparable failures. Unfavourable were non-reparable (root)fractures. 

 

Results:

Group	Mean Maximum Failure Load (N)	Sd (N)	Favourable Failures	Unfavourable Failures
1: FRC-post	1695	481	0	14
2: FRC-post + veil-woven	1580	272	6	8
3: No FRC (control)	1764	495	0	14

No statistical significant difference was found between the failure loads (ANOVA, p=0.83). Favourable failures (intra-observer agreement: k=0.76) occurred significantly more often in Group 2 than in the other groups (Fisher's Exact Test, p=0.002).

 

Conclusion:

These results showed no difference in maximum static failure loads between complete resin composite crowns with or without fibre-reinforcement, in endodontically treated premolars. However, composite crowns with FRC-posts and occlusal fibre-reinforcement failed more favourable.