Influence of luting agents on time required for cast post removal by ultrasound: an in vitro study

Abstract

Objective:This in vitro study evaluated the influence of luting agents on ultrasonic vibration time for intraradicular cast post removal.Material and Methods:After endodontic treatment, 30 roots of extracted human canines were embedded in resin cylinders. The post-holes were prepared at 10 mm depth and their impressions were taken using autopolymerizing acrylic resin. After casting procedures using a nickel-chromium alloy, the posts were randomly distributed into 3 groups (n=10) according to the luting material: G1- zinc phosphate (SS White) (control group), G2 - glass ionomer cement (Vidrion C; SS White), and G3- resin cement (C&B; Bisco). In G3, the adhesive procedure was performed before post cementation. After 24 h, the cement line was removed at the post/tooth interface using a fine diamond bur, and the ST-09 tip of an Enac ultrasound unit was applied at maximum power on all surfaces surrounding the posts. The application time was recorded with a chronometer until the post was completely dislodged and data were analyzed by ANOVA and Tukey's test (p<0.05).Results:The roots were removed from the acrylic resin and inspected to detect cracks and/or fractures. The means for G1, G2, and G3 were 168.5, 59.5, and 285 s, respectively, with statistically significant differences among them. Two G3 posts resisted removal, one of which developed a vertical fracture line.Conclusions:Therefore, the cement type had a direct influence on the time required for ultrasonic post removal. Compared to the zinc phosphate and glass ionomer cements, the resin cement required a longer ultrasonic vibration time.

Effect of the action of diamond burs with high speed on the tensile strength of cores cemented with zinc phosphate at different preparation times

“…In the case of zinc phosphate, it would be wise to wait a while after cementation, until the setting reaction is completed, and then use the diamond burs for the core preparation, thus avoiding damages to the cementing film and ensuring the prosthesis success 7,[11][12] .…”

“…Through these mechanical waves, intense mechanical vibrations reach the cement layer between the metal post and the root canal wall, and may result in retention loss of cemented cores. Therefore, some authors recommend that the preparation is not performed immediately after the cementing of intraradicular retainers 3,7,[11][12] .…”

“…According to the records of Craig 10 , Berbet et al 4 , Contin 12 , Van Noort 13 , Al-Ali et al 11 , Anusavice 2 , and Soares et al 7 , the zinc phosphate cement is considered friable. It is recommended, therefore, to wait a while to start the nucleus re-preparation after cementation.…”

“…Several authors claim that ultrasonic vibration decreases the retention of cores fixed with conventional cements [4][5][6][7] .…”

Comparison of Different Ultrasonic Tip Angulations on Time Required for Cast Post Removal

“…5 Therefore, endodontically treated teeth often require post-and-core restorations for retention purposes because of extensive structural defects resulting from caries and access cavity preparation. [7][8] Cast posts have good resistance and adaptation to root canals, resulting in a uniform thickness of cement. 9 However, post removal can be necessary, when the length or diameter of the post is unsatisfactory, or when the apical seal of the root filling is inadequate, requiring a nonsurgical reintervention.…”