(60) In-vitro Study of Laser-Assisted Prefabricated Ceramic Crown debonding as compared to Traditional Rotary Instrument Removal

Introduction: This in-vitro study aimed to compare the laser-assisted and rotary retrieval of prefabricated zirconia crowns cemented with resin modified glass ionomer in primary anterior teeth and permanent posterior teeth and to assess the retrieval time required and procedure-associated temperature changes.

Methods: Extracted primary anterior (n=18) and permanent posterior (n=13) teeth were prepared for prefabricated zirconia crowns which were cemented with resin-modified glass-ionomer cement. Specimens were stored in the humidor for at least 48 hours prior to undergoing crown removal procedures either by an air-rotary handpiece and diamond bur; or erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser with Turbo MX handpiece, 5W, 20Hz settings. Intra-pulpal temperature was measured using a microthermal couple element and recorded in 30-second intervals.. Following crown removal, selected specimens from each group were examined using scanning electron microscopy (SEM).

Results: The average crown removal time for rotary handpiece and laser methods were 80.9±19.36 sec; and 353.3±110.6 sec, respectively for anterior primary teeth. The average crown removal time for rotary handpiece and laser methods were 114.2±32.1 sec and 288.5±76.1 sec, respectively for posterior teeth. The removal time of the laser group was significantly longer than the rotary group, 272.4 sec on average (95% CI: 216.8-328.0, p< 0.001) for primary anterior teeth and 174.2 sec on average (95% CI: 127.0-221.5, p< 0.001) for posterior teeth. The maximum observed temperature for anterior teeth for the rotary group was 22.2±8.5°C compared to 27.7±1.6°C for the laser group, thus laser exhibited 5.5°C on average (95% CI: 4.6-6.4) higher than the rotary group (p < 0.001). The maximum observed temperature for posterior teeth for the rotary group was 21.8±0.77°C compared to 25.8±0.85°C for the laser group, thus laser was associated with a change in temperature 2.33°C on average (95% CI: 1.36-3.30) higher than with the rotary group (p-value < 0.001). SEM analyses revealed more open dentinal tubule in the rotary group compared to the laser group suggesting the laser group may induce less pulpal irritation and postoperative sensitivity.

Conclusions: For a prefabricated zirconia crown used in pediatric patients for anterior primary and posterior permanent teeth, the rotary handpiece removal method appears to be efficient compared to the Er,Cr:YSGG laser. However, the Er,Cr:YSGG laser can be safely used to retrieve the crown with minimal damage to the crown and possibly to the abutment tooth.

Lead Author's Contributions to the Research Project. : The Lead Author was responsible for data collection and assisted in composition of the abstract.