Abstract:
OBJECTIVES : To investigate and compare, in vitro, the fracture
behaviours of three types of cusp-replacing posterior
composite resin restorations.
METHODS : Standard preparations for posterior composite
restoration of the mesio-lingual cusp were cut on seventy-
five extracted lower left first and second molars and
restorations placed. Group A (control, n =25) with a conventional
posterior composite resin, Group B (n=25): resin
reinforced with nano-scale electrospun glass fibres Group
C (n=25) :resin reinforced with a fibre substructure. Specimens
were thermocycled for 500 cycles between 5°C and
55°C with a dwell time of 30 seconds, then embedded
in plastic cylinders in acrylic resin. The specimens were
loaded in a universal testing machine at a 30° angle to
the long axis of the tooth until fracture occurred. Fracture
patterns were highlighted by staining, studied under
a microscope and classified as favourable (restorable) or
unfavourable (non-restorable). Sub-classification included
adhesive and cohesive failures.
RESULTS : Group C exhibited significantly more “restorable”
fractures. Group B displayed significantly more “nonrestorable”
fractures. Fracture patterns differed significantly
between the two fibre-strengthening techniques. (Fisher’s
Exact Test p = 0.05)
CLINICAL SIGNIFICANCE : Resin restorations reinforced with
glass-fibre substructures are more readily repaired after fracture, saving tooth structure, and reducing costs to the
patient.
