Investigation of the Effects of Different Finish Line Geometries on the Fracture Resistance and Microleakage Potential of Occlusal Veneers Using Scintigraphy

Project no. 32788 · Status: Kapanmış (Yayın bekleniyor) · 2025

Summary

<p><strong>Objective:</strong>&nbsp;The&nbsp;aim&nbsp;of&nbsp;this&nbsp;in&nbsp;vitro&nbsp;study&nbsp;was&nbsp;to&nbsp;evaluate&nbsp;the&nbsp;effect&nbsp;of&nbsp;different&nbsp;finish&nbsp;line&nbsp;designs&nbsp;on&nbsp;the&nbsp;fracture&nbsp;load,&nbsp;marginal&nbsp;microleakage,&nbsp;and&nbsp;failure&nbsp;mode&nbsp;distribution&nbsp;of&nbsp;lithium&nbsp;disilicate&nbsp;occlusal&nbsp;veneers&nbsp;using&nbsp;a&nbsp;scintigraphic&nbsp;method.</p><p><strong>Materials&nbsp;and&nbsp;Methods:</strong>&nbsp;Fifty&nbsp;extracted&nbsp;human&nbsp;mandibular&nbsp;molars&nbsp;were&nbsp;randomly&nbsp;allocated&nbsp;into&nbsp;five&nbsp;groups&nbsp;(n&nbsp;=&nbsp;10)&nbsp;as&nbsp;non-prepared&nbsp;control,&nbsp;chamfer,&nbsp;knife-edge,&nbsp;shoulder,&nbsp;and&nbsp;butt-joint.&nbsp;Occlusal&nbsp;veneers&nbsp;were&nbsp;designed&nbsp;digitally&nbsp;and&nbsp;fabricated&nbsp;from&nbsp;lithium&nbsp;disilicate&nbsp;glass-ceramic&nbsp;using&nbsp;the&nbsp;heat-press&nbsp;technique,&nbsp;and&nbsp;were&nbsp;adhesively&nbsp;cemented&nbsp;following&nbsp;standardized&nbsp;surface&nbsp;treatment&nbsp;and&nbsp;cementation&nbsp;protocols.&nbsp;All&nbsp;specimens&nbsp;underwent&nbsp;thermocycling&nbsp;(10,000&nbsp;cycles,&nbsp;5–55&nbsp;°C).&nbsp;Marginal&nbsp;microleakage&nbsp;was&nbsp;quantitatively&nbsp;assessed&nbsp;using&nbsp;technetium-99m–based&nbsp;uptake&nbsp;system&nbsp;and&nbsp;expressed&nbsp;as&nbsp;counts&nbsp;per&nbsp;minute&nbsp;(CPM).&nbsp;Afterwards,&nbsp;they&nbsp;were&nbsp;loaded&nbsp;to&nbsp;fracture&nbsp;by&nbsp;using&nbsp;a&nbsp;universal&nbsp;testing&nbsp;machine&nbsp;under&nbsp;oblique&nbsp;loading&nbsp;at&nbsp;45°.&nbsp;Failure&nbsp;modes&nbsp;were&nbsp;evaluated&nbsp;under&nbsp;stereomicroscopy&nbsp;and&nbsp;SEM&nbsp;and&nbsp;classified&nbsp;as&nbsp;adhesive,&nbsp;cohesive,&nbsp;or&nbsp;mixed.&nbsp;Data&nbsp;were&nbsp;analyzed&nbsp;using&nbsp;one-way&nbsp;ANOVA&nbsp;and&nbsp;chi-square&nbsp;tests&nbsp;(α&nbsp;=&nbsp;0.05).</p><p><strong>Results:</strong>&nbsp;No&nbsp;statistically&nbsp;significant&nbsp;differences&nbsp;were&nbsp;found&nbsp;among&nbsp;preparation&nbsp;designs&nbsp;for&nbsp;marginal&nbsp;microleakage&nbsp;(p&nbsp;=&nbsp;0.359)&nbsp;or&nbsp;fracture&nbsp;load&nbsp;(p&nbsp;=&nbsp;0.249).&nbsp;Numerically,&nbsp;the&nbsp;shoulder&nbsp;group&nbsp;exhibited&nbsp;the&nbsp;lowest&nbsp;mean&nbsp;microleakage&nbsp;values,&nbsp;while&nbsp;the&nbsp;butt-joint&nbsp;group&nbsp;showed&nbsp;the&nbsp;highest.&nbsp;Knife-edge&nbsp;preparations&nbsp;demonstrated&nbsp;the&nbsp;highest&nbsp;mean&nbsp;fracture&nbsp;load,&nbsp;whereas&nbsp;chamfer&nbsp;preparations&nbsp;showed&nbsp;the&nbsp;lowest.&nbsp;Cohesive&nbsp;and&nbsp;mixed&nbsp;failures&nbsp;predominated&nbsp;across&nbsp;all&nbsp;groups.&nbsp;When&nbsp;failure&nbsp;modes&nbsp;were&nbsp;regrouped&nbsp;into&nbsp;three&nbsp;main&nbsp;categories,&nbsp;no&nbsp;significant&nbsp;association&nbsp;was&nbsp;observed&nbsp;between&nbsp;preparation&nbsp;design&nbsp;and&nbsp;failure&nbsp;mode&nbsp;distribution&nbsp;(p&nbsp;=&nbsp;0.167).&nbsp;<strong>Conclusion:</strong>&nbsp;Within&nbsp;the&nbsp;limitations&nbsp;of&nbsp;this&nbsp;<em>in&nbsp;vitro</em>&nbsp;study,&nbsp;finish&nbsp;line&nbsp;design&nbsp;did&nbsp;not&nbsp;significantly&nbsp;influence&nbsp;the&nbsp;fracture&nbsp;resistance&nbsp;or&nbsp;marginal&nbsp;microleakage&nbsp;of&nbsp;lithium&nbsp;disilicate&nbsp;occlusal&nbsp;veneers.&nbsp;Conservative,&nbsp;morphology-guided&nbsp;preparation&nbsp;designs&nbsp;may&nbsp;therefore&nbsp;be&nbsp;clinically&nbsp;preferable&nbsp;when&nbsp;adequate&nbsp;adhesive&nbsp;protocols&nbsp;are&nbsp;applied.</p><p><strong>Keywords:</strong>&nbsp;occlusal&nbsp;veneer;&nbsp;lithium&nbsp;disilicate;&nbsp;finish&nbsp;line&nbsp;design;&nbsp;fracture&nbsp;resistance;&nbsp;microleakage;&nbsp;scintigraphy.</p>

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