Evaluating the
Effect of Depth of Cure on Flexural Strength of Intact and Repaired Fiber
Reinforced Experimental Composite Compared to Conventional Bulk-Fill
Composites: An In Vitro Study.
I. Introduction
A. Background and significance of composite materials in dentistry
Composite materials are one of the most essential materials in modern
dentistry due to their aesthetic and mechanical features. These materials have
revolutionized dentistry by offering a unique combination of versatility,
aesthetic appeal, functional strength, biocompatibility and durability (Mittal
et al.,2024). Composites are used in a wide range of dental procedures such as
crowns, veneers, inlays, onlays, etc. catering to both major and minor
restorative work. This widespread use of composites in dentistry is due to
their ability to mimic the physical and optical characteristics of teeth, thus
restoring the dental function, form and appearance.
B. Overview of fiber reinforced
composites and conventional bulk-fill composites
Some of the commonly used composites are fiber-reinforced composites and
conventional bulk-fill composites. Fiber-reinforced composites are created by
combining a polymer matrix with reinforcing fibers like carbon, polyethylene or
glass fibers to enhance their mechanical properties and wear resistance (Sunarintyas
et al., 2013). FRCs, especially those
with continuous unidirectional fiber reinforcements, are known for their high
strength, modulus, biocompatibility, and design flexibility, making them ideal
for applications such as endodontic posts, fixed partial dentures, and
periodontal fiber bands (Hu et al., 2022). In contrast, conventional bulk-fill
composites are formulated by mixing resin with a filler material such as silica
or quartz to increase their strength and durability. Bulk-filled composites are
gaining popularity as they can allow bulk placements in thick increments. This
method significantly reduces clinical time and cost in comparison to the
conventional composite (Wang et al., 2021).
C. Importance of studying depth of
cure and flexural strength-
The two important criteria for
characterization of composite materials used in dentistry are depth of cure and
flexural strength. The thickness of resin monomer that can be polymerized with
light corresponds to the depth of cure, and it is important for ensuring
complete polymerization material (Tsujimoto et al.,2017; Lee et al., 2019). It
is well established that full polymerization of restorative materials into the
body (depth of cure) plays a vital role to ensure longevity and effectiveness
as this directly affects their mechanical properties which includes strength, compressive
modulus etc. ensuring they function collectively in a close replication to its
original form inside the mouth during masticatory forces being exerted upon
them typically on an average about 912 times/day /person or near constant
chewing influence around upper bound (Gul et al.,;Camargo et al,.). Flexural
strength refers to a material’s ability to resist deformation under stress. It
is an important functional property that shows how well the material can bear
occlusal forces and masticatory stresses. Dental restorations using a composite
material with good flexural strength show resistance to fracture and wear,
thereby meeting the necessary longevity criterion (Irie et al., 2021). Factors
that may influence depth of cure and flexural strength include the type, size
(of fillers), composition of monomers present in composites used as well as
light power and curing time utilized for polymerizing composite materials (Gul
et al., 2020; Lee et al., 2019). Alterations in filler content and particle
size are employed to enhance translucency, thus increasing the depth of cure of
bulk-fill composites (Gul et al., 2020). The size and distribution of the
filler particles within the resin matrix also have a key influence on physical
properties like flexural strength, depth cure (Moharam et al., 2017). Changes
in the curing protocol such as alteration of light intensity, the distance of
curing and curing time may also impact the depth of cure and flexural strength (Mohannad
& Baban, 2016; Raafat, 2018). To conclude, the depth of cure and flexural
strength are vital parameters that may affect the durability and longevity of
composites. Hence, understanding these properties is of great importance to
ensure the success of restorations.
II. Conventional Bulk-Fill Composites
A. Composition and structure
These high-viscosity (sculptable) bulk-fill composites, possess increased
depths of cure compared with conventional resin composite materials, allowing
placement and photopolymerization of thick composite layers up to 4–5 mm (Aggarwal
et al.2019). Bulk-fill composites contain a resin matrix, fillers and other
additives as well to impart unique properties. These are available in
compliance with low viscosity flowable and high viscous sculpt- able forms for
easy insertion and adaptation to the cavity preparations (Aggarwal et al.,
2019). Types of resin matrix include a combination of monomers such as Bis-GMA
(Bisphenol A-Glycidyl Methacrylate) for strength and rigidity, UDMA (Urethane
Dimethacrylate) for flexibility or TEGDMA(Triethylene Glycol
dimethylmethacyrate ) to lower the viscosity thereby making it more workable (Nagrale
et al. 2023). Filler particles such as silica, quartz, and glass are added to
improve the mechanical properties of Restoration Giving it strength for
compressive stress resistance wear resistances radiopacity etc.
Hence, a composite requires initiators and accelerators which are
camphorquinone (C) and amine compounds respectively to polymerize when cured
under light. It also contains various modifiers or additives, such as flow
Modifiers, stabilizers, pigments and opacifiers to improve the handling of
composite resin and aesthetic results. Fine radiopaque particles, including
(but not limited to) barium glass or ytterbium trifluoride can be added to the
composite mixture for it to appear radio-opaque and easily discernible from
natural tooth structure on radiographs. These features enable bulk-fill
composites to be easily placed in larger increments, while still delivering the
mechanical properties and esthetic results that are necessary for dental
restorations – essentially combining efficiency with durability.
B. Mechanical properties
Bulk-fill composities are designed to possess certain mechanical
properties that would enable them to perfom effectively in dental restorations.
C. Applications in dental
restorations
III. Fiber Reinforced Composites
A. Composition and structure
B. Mechanical properties
C. Applications in dental restorations
IV. Depth of Cure
A. Definition and
measurement techniques
B. B. Factors affecting depth of cure in
composites
1. Light intensity and wavelength
2. Composite material composition
3. Polymerization time
C. Comparison of depth of cure between fiber reinforced and bulk-fill
composites
V. Flexural Strength
A. Definition and importance in dental materials
B. Factors affecting flexural strength
1. Material composition
2. Polymerization process
C. Comparison of flexural strength between fiber reinforced and bulk-fill
composites
VI. Repairability of Composites
A. Challenges in repairing dental composites
B. Methods for repairing
conventional bulk-fill composites
C. Methods for repairing fiber
reinforced composites
VII. In Vitro Studies on Depth of Cure and Flexural Strength
A. Overview of relevant in vitro studies
B. Key findings on depth of cure
C. Key findings on flexural strength
D. Comparison of intact and repaired composites
VIII. Conclusion
A. Summary/ Takeaway of key findings from the literature
B. Implications for dental
practice
C. Areas for future research (and
discussing why this study is of importance)
Need to write it in the manner I have written for the first few headings, please add references in harvard style as much as possible
