THE EFFECT OF ENVIRONMENTAL PRESSURE CHANGES DURING DIVING ON THE RETENTIVE STRENGTH OF DIFFERENT LUTING AGENTS FOR FULL CAST CROWNS

Statement of problem. The effect of pressure cycling on the bond stren gth of cement luting agents is largely unknown. Purpose. This study in vestigated the effect of pressure cycling on the retention of full cas t crowns to extracted teeth. Material and methods. Sixty extracted sin gle-rooted premolar teeth had full cast cron ns cemented, 20 with a zi nc phosphate cement, 20 with a glass ionomer, and 20 with a resin ceme nt. After 7 days of storage, each of the teeth in the experimental gro ups was pressure cycled 15 times from 0 to 3 atmospheres (304 KPa), af ter which the force required to dislodge the crowns was tested in an I nstron testing machine. Results. A significant difference was found (S tudents t test; p > 0.01) between the force required to remove the cro wns in the zinc phosphate control (142.10 +/- 36.42 N) and experimenta l (15.93 +/- 11.13 N) groups and the glass ionomer cemented control (1 86.33 +/- 24.33 N) and experimental (91.50 +/- 33.07 N) groups; no dif ference was found between the resin cemented control (291.15 +/- 78.48 N) and experimental (281.32 +/- 85.43 N) groups. Conclusion. This stu dy showed that the retention of full cast crowns to extracted teeth is reduced after pressure cycling if the crowns are cemented with either zinc phosphate cement or glass ionomer cement. Dentists should consid er using a resin cement when cementing crowns and fixed partial dentur es for patients, such as divers, who are likely to be exposed to press ure cycling.