Types of Resin Composite and Filling Techniques: How They Affect Internal Void Volume and Compressive Strength

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Restorative Dentistry

Background:

• Dental restorations require precise material placement to ensure longevity and prevent secondary caries.
• Internal voids within resin composite restorations can compromise mechanical properties and clinical performance.
• Evaluating void formation and its impact on strength is crucial for optimizing restorative techniques.

Purpose of the Study:

• To compare the void volume percentage and compressive strength of dental restorations fabricated using different resin composite materials and placement techniques.
• To investigate the influence of single-layer versus multilayer incremental techniques on void formation.
• To assess the relationship between void content and the mechanical integrity of the final restoration.

Main Methods:

• Five experimental groups were established using Filtek™ Z350XT and Filtek™ One Bulk Fill resin composites with varying placement strategies (single layer, horizontal, oblique increments).
• Specimens were prepared to specific dimensions (4 mm height, 5 mm diameter) and analyzed for internal void volume using micro-computed tomography (micro-CT).
• Compressive strength testing was performed on all specimens, with data analyzed using ANOVA and Tukey's post hoc tests.

Main Results:

• The bulk fill and flowable composite combination (BF) exhibited the highest void volume percentage (0.5501 ± 0.2031%).
• Single-layer techniques (ZS and BS) demonstrated the lowest void percentages (0.0366 ± 0.0279% and 0.1991 ± 0.1463%, respectively).
• Restorations using Filtek™ Z350XT with single (ZS) and horizontal (ZH) increments showed significantly higher compressive strength (200.18 ± 16.32 MPa and 192.18 ± 17.23 MPa) compared to BS and BF groups.

Conclusions:

• Multilayer incremental filling techniques result in significantly higher internal void percentages compared to single-layer placement.
• Certain resin composite materials may inherently contain voids, irrespective of the placement technique.
• Despite increased void formation with multilayer techniques, these voids do not appear to directly compromise the compressive strength of the evaluated dental restorations.