A Study on Fracture Resistance of Class IV Cavities Treated with Pins

Тhе use of pins in restoration of large cavities with esthetic resin materials appear in the dental literature after 1970 and there are less than 20 publications, focused around restorations of class IV cavities. The aim of the present study is to test the role of pins in the fracture resistance in class IV restorations with resin materials. Materials and methods: 68 matured human upper and lower sound front teeth are included in the study. The groups are upper incisors, lower incisors, canines with or without pins. All cavities are filled with the same resin material, technology and Prime bond NT. Termocycling: 30 days in 30ºС, 100% humidity, 60 days in 100% humidity 2Х12 hours at 35ºС and 40ºС and 100 dry cycles, 20 seconds each in the following order - 45ºС ± 3ºС, room temperature, 5ºС, room temperature, two series, 50 each with two days between in Cultura incubator of Viva Dent 55ºС and ice. Machine for vertical load testing ZD 10/90, load in Newtons (N), from 20 N to 1275 N, speed 0.5 mm/ min, displacement from 0.1 to 1.2 mm. Type of fractures observed: adhesive, cohesive in dentine and in resin material, mixed. Results: The highest proportion of fractures observed was in front teeth with large cavities and with pins, low loading (493-503N). Front teeth with large cavities without pins have better resistance and lower proportion of fractures (488-526N). Canines are more resistible with pins and less without. Lowest resistance is found in lower front teeth when pins are present. Conclusion: In class IV restorations when tissue loses are less than 2/3 of the incisal ridge pins can decrease the fracture resistance of the teeth.