Fracture strength of weakened human premolars restored with amalgam with and without cusp coverage

Purpose: To determine the effect of cusp coverage with amalgam restorations on the fracture strength of weakened human maxillary premolars. Materials and Methods: 30 extracted human maxillary premolars were divided into three groups; Group A (control): uncut teeth, Group B: wide MOD cavities prepared and the pulp chamber's roof removed. The teeth were restored with amalgam without cusp coverage, Group C: same as Group B plus cusp reduction and restored with amalgam. The teeth were included in metal rings with self-curing polystyrene resin and stored in water for 24 hrs. The restorations were refined with rubber points, polished and further stored in water for 24 hrs before being subjected to a compressive axial load in a Universal testing machine at 0.5 mm/min. Results: The mean fracture strength obtained was: Group A: 173.3 Kgf, Group B: 47.3 Kgf and Group C: 127.7 Kgf. All values were statistically significantly different (P< 0.05). The amalgam restoration of weakened human premolars with cusp coverage amalgam significantly increased the fracture strength of the teeth (63 %) as compared to teeth restored without cusp coverage. The results showed that cusp coverage with amalgam might be an option for restoring weakened endodontically-treated teeth.