Evaluation of the effects of different groove length and thickness of the retainers on the retention of maxillary anterior base metal resin bonded retainers ' an in vitro study

摘要

Objectives: The resin-bonded fixed partial dentures have gained immense popularity in recent years as they aremore conservative, esthetic, economic and easily fabricated. However debonding is considered the most commoncause of failure of resin bonded prosthesis. The objective of the study were to compare the effects of different groovelengths and thickness of retainers on retention of maxillary anterior base metal resin bonded retainers.Study Design: Twenty five metal dies of maxillary central incisor duplicated from pure typhodont teeth (maxillaryleft central incisors) prepared to receive retainer for resin bonded fixed partial denture having different test designswere made. Five test groups were made with each group having five specimens. Two groups were having preparationdepth of 0.5mm and retention groove lengths of 3mm and 5mm. Two groups had preparation depths of 0.3and 0.7mm with no groove preparation with retainer thickness of 0.3 and 0.7mm respectively. Fifth group with nogroove preparation and preparation depth of 0.5mm was kept as control for all the groups. All the specimens werecemented using calibra (Dentsply) resin cement. Each specimen was subjected to tensile loading in vertical directionon universal testing machine (Instron 5569) at a crosshead speed of 1mm/min. \Results: Groups with 5mm and 3mm groove length recorded higher mean vertical forces when compared to thegroup with no groove preparation. Group with 5mm groove length showed highest mean vertical forces. The groupwith 0.7mm retainer recorded higher mean vertical force values when compared to groups with 0.5mm and 0.3mmretainer thickness. Group with 0.3mm retainer thickness recorded the least mean vertical force value.Conclusion: Placement of the grooves increased the retention values almost 2 ½ times than the grooveless preparationand as the thickness of the retainers increased retention values also increased. Retention value was directlyproportional to the groove length and retainer thickness.