Introduction clinical concern that can result in secondary

Introduction

The longevity of restorations is dependent upon many factors,
including operator skill, the materials and techniques used, the criteria for
replacement, patient compliance with oral hygiene advice, the oral environment
and its contribution to the patient’s susceptibility to caries, and possibly,
the means by which the treatment is funded.1

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Ideal restorative materials must have the ability to protect
exposed dentine from bacteria and their toxins. 2The interface between restoration and
the dental substrate is an area of
clinical concern that can result in secondary decay, marginal discoloration,
and pulpits.3 For that reason, perfect sealing
should be the plan of each clinical performance.4

Marginal discoloration

As a result of colored molecules infiltration at the
tooth-restoration interface, marginal staining will occur. Macroleakage and marginal staining are the end result of adherence breakdown after
microleakage begins at the marginal surface. 5

Causes of marginal discoloration

Presence of excess filling material, a deficit of filling
material at the margin and the formation of gaps can be considered as the
primary factors of marginal discoloration. 6, 7

Several factors can cause defects at the tooth-restoration
interface and lead to marginal
discoloration, such as unsatisfactory restoration placement and finishing
technique, or by inadequate bonding and stress fatigue.  Resin based
composites shrink on polymerization and can generate high stresses at bonded
surfaces in confined cavity preparations.8  Failure at the tooth-restoration interface can
happen if the forces of polymerization contraction exceeded adhesive bond
strength.

Diagnosis of marginal staining

To control the quality of restorations, the most commonly
used direct method is the United States Public Health Service (USPHS)
evaluation system.9

When the USPHS criteria were used to evaluate bulk
discoloration and cavosurface marginal
discoloration, interexaminer agreements were relatively poor varying between
68% to 78% and 54% to 72% respectively. 10

 

Color transparencies were
used to evaluate bulk and covosurface
marginal discoloration indirectly, due to the need to develop standardized
indirect techniques. The results of Color transparencies were compared to those
obtained with the USPHS direct technique. The results indicated poor coloration
between the two methods, and the USPHS was considered as the least sensitive.   11

However, several factors can influence the results of the indirect evaluation. Such as the differences in reflectance spectra between
restorative materials and tooth structure.12 As well as surface morphology and
specimen thickness.13, 14

Furthermore, the differences in light scattering properties
between microfilled and macrofilled composite resins can affect the
results of reflectance spectra. 15

Due to the difficulty of
performing the indirect method in vivo, the
USPHS criteria for direct evaluation remains the preferred system for
evaluating important characteristics of dental restorations like color
matching, secondary caries, cavosurface margin discoloration and postoperative
sensitivity.16

Predicted outcomes from marginal staining

Marginal staining can lead to poor aesthetic, penetration of
bacteria as a result of gap presence which can cause sensitivity and secondary
caries. 17

Every plaque retention site is a possible site for secondary
caries to occur.18

The stability of tooth-restoration adhesive interface can be compromised as a result of
fluids along the interface, which can cause hydrolytic breakdown of the
adhesive resin and the collagen within hybrid layer.19

Kidd et al. 20 Examined 56 cavity margins, and they
found that caries lesions are more likely to be present in the outer enamel and
enamel of the cavity wall where the margin was stained. Thus, marginal staining
of restorations is likely indicating caries at the cavity walls.

Differential diagnosis in regards to marginal
discoloration

Tooth colored restorations usually exhibits marginal staining
in different appearance and each has different causes behind it. For example;
White line: usually cause by a crack or fissure in the enamel. A white margin
can be also a void in the interface space between the bond and the enamel (a
brown line is formed after staining of this type void). Gray line: Typically, this discoloration is due to the background
being visible through the bonding layer due to a too thick application of the
bonding agent. And brown line: staining of the bond layer usually due to excess
film thickness. A brown line can also result from micro-leakage at the
interface between uncut enamel and the composite restoration where the
composite “laps” over the margin.  21

Because of the importance traditionally attributed to
microleakage for the occurrence of secondary caries,22 stains at the margins of tooth-colored
restorations are prone to be misdiagnosed as recurrent carious lesions,23 leading to replacement of the
restoration as preventive measure. However, a correlation between the width of
a marginal discrepancy and the presence of recurrent caries only exists when
frankly cavitated lesions are detected at the restoration margins.24, 25 As secondary carious lesions are
known to be localized and delineated defects, a reconsideration of the
conventional treatment approach has been recently recommended. In deciding
whether to repair or to replace a defective restoration, a “minimal treatment”
should be preferred. Simple re-contouring and re-polishing of small marginal
defects should be performed as a first option,23 mainly in patients with a low
caries-risk status.26 Conversely, if any clinical doubt
exists in areas prone to plaque accumulation, in presence of larger defects and
higher caries risk, an exploratory preparation into the composite material at
the tooth/resin composite interface may help in diagnosing the existence and
the size of the lesion.23, 27 Being localized in nature, it rarely
progress along the tooth/resin composite interface.25 When sound tooth tissue is exposed,
the exploratory cavity may be repaired using a conventional restorative
technique. 28

Comparison of different materials regarding
marginal discoloration

Packable composite has higher filler content in comparison to
hybrid composite, which is essential in reducing shrinkage of the composite
during polymerization. Theoretically, the high filler percentage will lead to
minimal marginal defect and discoloration. 29

In contrast to this theory, a study done by  L Shi et al, 30 compared TPH Spectrum/XenoIII (TS)
restorations and the Synergy Compact/One Coat (SC) restorations in regards to
marginal discoloration, and found no difference in the results between the two
groups. Which is in agreement with another study that compared TPH Spectrum and
SureFil (Dentsply). 31

To evaluate the efficiency of simplified bonding system, a
study was conducted to evaluate the initial clinical performance of conventional
hybrid resin composite (SpectrumTPH, Dentsply DeTrey GmbH), and packable
composite (SureFil, Dentsply DeTrey GmbH, Konstanz, Germany), using a resin
adhesive (Non-Rinse Conditioner and Prime & Bond NT, both manufactured by
Dentsply DeTrey GmbH).  Restorations were
evaluated using U.S. Public Health Service-Ryge modified criteria and by using
color transparencies and die stone replicas. The results showed Alfa rating (90
percent or higher) for both composites in regards to marginal discoloration,
anatomical form, surface texture and surface staining. 32

That was in agreement with another study, where Alfa rating
(80 percent or higher) was reported for both packable (SureFil, Dentsply DeTrey
GmbH, Konstanz, Germany) and a conventional (SpectrumTPH, Dentsply DeTrey GmbH)
resin-based composite. 33

The two-year performance of SureFil (Dentsply DeTrey GmbH,
Konstanz, Germany) packable posterior resin-based composite in Class I and II
restorations was studied by Turkun
et al. there were five
Bravos for surface staining and three for marginal adaptation. One restoration
had marginal discoloration at the one-year recall period and four others had
marginal discoloration at the two-year recall period (P