Tooth deformation patterns in molars after composite restoration.

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Restorative Dentistry

Background:

• Polymerization shrinkage of composite restorations induces residual stresses, potentially leading to tooth deformation.
• This deformation can manifest as debonding, enamel cracks, and post-operative sensitivity.
• Previous measurements of shrinkage-induced deformation were limited to discrete points.

Purpose of the Study:

• To analyze the cuspal deformation pattern in the occlusal portion of molars.
• To investigate deformation across various cavity types and sizes after light-cured composite restoration.

Main Methods:

• Five extracted human molars were prepared with Class I, Class II OM, large Class II OM, and large Class II MOD cavities.
• Cavities were restored using a light-curing composite and dentin adhesive system.
• A profilometer and Cumulus software were used to digitize and analyze cuspal contour changes, visualized via color contour maps.

Main Results:

• Cuspal deformation was observed as a reduction in buccal and lingual contour perpendicular to the tooth surface.
• Large Class II MOD cavities showed the most significant cuspal deformation.
• Large Class II OM restorations exhibited less deformation than large MOD cavities, while Class I and small Class II OM restorations showed minimal, non-significant differences.

Conclusions:

• Composite restoration curing leads to tooth deformation due to polymerization shrinkage.
• Cavity preparation type and size significantly influence the extent and pattern of inward cuspal movement.
• This study successfully quantified and visualized the complex patterns of cuspal deformation caused by composite shrinkage.