Research Article :
This study was carried out to study a restorative
technique of 2 mm thickness of composite resin filling material that bonded, by
adhesive (4-META), to MOD cavities (Mesial, Occlusal and Distal surfaces of a
tooth) partially filled with amalgam filling materials in upper premolars on
the fracture resistance when compared to a sound tooth. Forty freshly sound extracted
upper premolars were divided into four groups: the first group of ten sound
premolars is subjected to fracture resistance test, the second group of ten
premolars with a MOD of half intercuspal distance cavities, which was prepared
with long bevel at the cavosurface angle and the teeth were filled with
composite resin following incremental technique. The third group of ten teeth
were prepared with a box form and butt joint of the same MOD cavities dimension
and filled with non-gamma II amalgam. The fourth group of ten premolars with
the same MOD cavities dimension are filled with amalgam, a 2 mm thickness of
amalgam was removed of the occlusal surface after 24 hours, extended proximally
mesially and distally, etch of the exposed enamel, dentin and amalgam was
performed, and 4-META adhesive was applied to amalgam and exposed dentin and
enamel followed by posterior composite bonded to tooth and amalgam, and cured
with light for 40 seconds. The teeth of all groups were tested for fracture
resistance. The group I showed the highest resistance to fracture followed by
group IV followed by group II and lastly, group III. This study concluded that
the use of combined bonded amalgam-composite and tooth structure provided the
best technique for filling than cavity only filled with composite or amalgam. Selection of filling material to
restore large cavities is of prime importance. One criterion is to be
considered for its suitability to restore coronal strength; Difficulties with
restoring class II cavities with posterior composite resin are enumerated, and
the problem is especially when a gingival margin lies close to or apical to the
cement-enamel
junction [1]. The increased demand to restore
teeth with composite resin is to obtain an esthetic restoration [2]. The more
tooth structure is removed; the cusps were weakened and more susceptible to
fracture or cracked when filled with composite resin and consequently may
propagate under stress of mastication to the pulp [3]. Filling materials used to restore
such weakened teeth demonstrated the advantage of the ability of posterior
composites resin to bond such weakened teeth, i.e. improved strength for the
bonded restored tooth over that of conventional unbounded amalgam
restored tooth. On the other hand, the stress will
develop across the bond interface between tooth structure and composite
resulting in changing the intercuspal dimension of premolars and molars
containing mesio-occluso-distal restorations. Etching the enamel and the use of
bonding agent can improve the seal of the resin to tooth and the strength of
that bond, but the appearance of fracture cracks near the margins and parallel
to it are thought to arise from contraction of the composite bonded strongly to
the enamel, shrinkage stress has been associated with postoperative
sensitivity and marginal stain [4]. The incidence
of enamel cracks were found more often in relation to bonding to composite
related to the greater contraction during polymerization and higher coefficient
of thermal expansion [5,6]. Sakshi Singhal, et al. stated
that the potential consequences of polymerization
shrinkage included the enamel fracture, gap
formation between dentine and restoration, cuspal movement, and cracked cusps
causing postoperative pain and micro-leakage [7]. To study the effect of 2 mm
thickness of posterior composite filling material bonded to amalgam and tooth
on fracture resistance of upper premolars. Materials that were used in this
study were: 1.
Extracted maxillary premolars 2.
Filtek supreme composite 3.
Bonding agent 4.
4-Admix Amalgam 5.
4-META adhesives 6.
Instrom testing machine. Forty freshly extracted human
upper premolars were collected from outpatient department, faculty of
dentistry, Alexandria University. The Coronal portions were examined carefully
by a magnifying lens, the teeth that showed caries, cracks, white spots or
developmental anomalies were excluded. The teeth were placed in artificial
saliva with a formula: Dipotassium Hydrogen Phosphate………0.200
gm/litre Calcium Phosphate………………………0.300 gm/litre Potassium Thiocyanate…………………..0.300
gm/litre Sodium Bicarbonate……………………..1.500
gm/litre Potassium Chloride………………………1.200 gm/litre Sodium Chloride…………………………0.700 gm/litre Urea………………………………………0.130 gm/litre Distilled water…….……………………...100.000
cc The teeth were divided into four
groups, 10 teeth each. MOD cavity, with ½ inter-cusp distances was prepared in
the forty teeth using ultra high speed and copious amount of water. The depth
of the cavities was 4 mm starting at the cavosurface margin in dentine. The
proximal boxes extended to the axial line angles keeping ½ intercuspal
distances. The internal line angles were kept rounded. Group
I was constituted of 10 premolars and left sound
without any preparation and act as a control. Group
II was constituted of 10 premolars. The cavosurface
margin finished with long bevel. Incremental
technique was followed to restore with composite resin, with enamel and dentine
bonding agent. Group
III was constituted of 10 premolars. Enamel
Margin Finished with a butt joint and restored with non-gamma II amalgam. Group
IV was constituted of 10 premolars. Enamel margin kept
with 90° butt joint and filled with amalgam, the final contour. This
group was completed in the following manner: The occlusal part of amalgam had
been ground by 2 mm depth and extended to the mesial and distal surfaces (Figure 1). The enamel was cleaned using
prophy powder. A total etch technique was performed with 37% phosphoric acid
gel for 15 seconds (Figure 2). Wash
with water for 10 seconds and dry. A 4-Methacryloyloxyethy
Trimellitate Anhydride (4-META) adhesive was applied on
the amalgam by following manufacturers instructions, where dryness and
degreasing of amalgam was carried out using cavity dries (Methyl-ethyl ketone, ethyl
acetate 99%). This was followed by the application of adhesive primer on the
amalgam to bond any Bis-GMA
(Bisphenol A-Glycidyl Methacrylate) composite resin to amalgam. A layer base
and catalyst mixed 1:1 and applied as a thin layer over amalgam to mask color of
amalgam (Figure 3). Enamel bonding
agent Bis-GMA type is applied on enamel. Composite resin was applied to the
amalgam and furnished on amalgam to bond enamel and dentin (Figures 4 and 5). It was cured with
light for 40 seconds. Figure 2:
Group IV: Total etch of enamel, Dentine and Amalgam. Figure 3: Opaque
had applied to amalgam on occlusal surface. Figure 4:
Group IV: Composite had bonded to amalgam, dentine and enamel by 4-META. Figure 5: Group
IV: Distal surface of combined amalgam composite filling. All the extracted teeth were
mounted in a base of auto polymerizing resin so as to be placed on the lower
plate form of the tensometer (Instrom) (Figure
6). The upper arm allow steel ball to rest against the inclined planes of
buccal and palatal cusps of the premolars. Compressive force was applied at a
cross-head speed of 1 mm/min. the force needed to fracture each specimens of
each group was recorded. Figure 6: Instrom
testing machine. The results can be summarized in Table 1. Fracture resistance of group
(I) premolars ranged between 260 and 210 kg with a mean value of 233 kg and
standard deviation of 19.55. That of group (II) fracture resistance of
premolars was ranged between 185 and 155 kg with a mean value of 169 kg and
standard deviation of 9.37 (Figure 7). Table 1:
Fracture resistance (in kg) of all groups. The line of fracture appeared mesiodistally
and composite resin adhered to both buccal and palatal cusps (Figure 7). Fracture
resistance of group (III) premolars ranged between 120 and 90 kg with a mean
value of 105 kg and standard deviation of 10.8. The line of fracture seen mesiodistally
and amalgam failed down of the tooth and not adhered to tooth structure. Fracture
resistance of group (IV) premolars was ranged between 170 and 220 kg with a
mean value of 194 kg and standard deviation of 16.02 (Figure 8). The line of fracture also passed mesiodistally and cusps
fractured with adhered composite but amalgam failed down by leaving the tooth
surface. Figure 8: Group
IV: Composite amalgam specimen subjected to fracture resistant test. Statistical comparisons between different groups by
applying ANOVA (Analysis of Variance) test were in Table 2. Statistical comparison between group (I) and all other
groups, showed that group (I) had a higher fracture resistance than all other
groups and the difference is statistically significant. Comparison between
groups (II) and (III) showed that group (II) had a higher fracture resistance
than group (III), and the difference is statistically significant at 5% level
of significance. Evaluation of group (IV) statistically showed that it had a
higher fracture resistance than groups (II) and (III) and the difference is
statistically significant at 5% level (f=4.31, L.S.D = 11.7) (Table 1). This study was carried out to
evaluate a technique to restore teeth that susceptible to fracture. MOD
cavities were that type which showed split possibilities or crack propagation
under masticatory
load. The cavities were first filled with
amalgam, a 2 mm thickness was reduced occlusally to mesial and distal surfaces,
a total etch protocol was followed and composite was bonded to enamel, dentin
and bonded to amalgam by 4-META adhesive. The teeth of all groups were
subjected to compressive force until fracture occurred and compared. The result showed that there was
a statistical significant difference between teeth that have no cavities and
all other teeth containing filling. This may be due to the fact that drilling a
cavity and when filled by any technique, showed lower resistance to fracture. This
agreed with Larissa Pottmaier FL who stated that all teeth with preparations
were significantly weaker than intact teeth and as the occlusal isthmus was
widened the teeth become weaker [8]. Teeth filled with composite resin
showed higher fracture resistance than teeth filled with amalgam. This may be
due to the fact that the phenomenon of bonding, that bond composite to tooth is
not in conjunction with amalgam This agreed with Demarco, et al. who stated
that the ability to bond such restorations to tooth surface, either enamel or
dentine, improved strength for the bonded restored tooth over that of
conventional non-bonded
amalgam restored teeth [2]. Also coincides with
Mirzaei, et al. who stated that amalgam does not bond to tooth structure while
posterior composite resin may form a strong bond to enamel and a weaker bond to
dentin [9]. The result showed that in
combined amalgam and composite filling, amalgam failed down after splitting of
teeth leaving the dentine. But composite was bonded well to the buccal
and palatal cusps. This may be due to that amalgam has no adhesive property in
this new technique, and only acts as a rigid base, supporting cusps against
contraction of composite. So no enamel cracks would occur without cusp
deflection, helping marginal adaptation. Coincide with Magne P, et al. and Han,
et al. who stated that contraction forces caused by polymerization shrinkage
developed internal stresses, producing cracks in the enamel [10,11]. This agreed with Boroujeni, et al.
who stated that marginal adaptation is influenced by the following variables
including preparation of cavity, technique of enamel etching, use of bonding
agent, technique of insertion, procedure of finishing, and restorative material
itself [12]. The teeth with combined fillings, composite that bonded to amalgam
and tooth structure showed a higher
fracture resistance than teeth filled with other
fillings. This may be due to the new design; bond to buccal and palatal
surfaces will help in cusp tie through a bonding agent. The set amalgam will act as a
base that supports cusps
and prevent its deformation during shrinkage or curing of the bonded composite
resin and so no cracks would be expected. At the same time, the use of
composite in 2mm thickness will strengthen the composite as more curing will
occur in thin section. Bonding of composite to amalgam through the adhesive
4-META and to the tooth structure would allow both filling materials and tooth
structure to be as one piece. The decreased thickness of
composite in MOD cavity will reduce the squeal of shrinkage and its effects. This
agreed Boroujeni, et al. who stated that adhesive and conventional cavities
showed highly significant results indicating better marginal adaptation. Also
small size cavities may have reduced shrinkage because of decreased cavity
volume and less occluso-gingival
depth that helps complete curing, and coincide with Cramer, et al. who stated
that posterior composite resin placed with an incremental technique produces
greater resistance to Cuspal fracture, and agreed with the findings of Giannini
M who stated that the excellent interface between amalgam and composite
material could be explained by the fact that the bonding penetrates into the
irregularities and porosities of the amalgam surface thus, creating a bond with
the composite material. Also agreed with Souza, et al. who stated that
polymerization shrinkage of the composite resin during curing compromised the
composite resin tooth bond. The volume of composite resin increases with large
restorations so that shrinkage forces prevail, producing marginal openings
despite enamel etching [12-15]. Within the limit of this study it
is concluded that, bonded composite filling strengthens teeth having large
cavities and amalgam with subsequent bonded 2 mm thickness of composite by 4-META
and extended to buccal and palatal
cusps allow composite resin to bond amalgam
and strengthen tooth structure. While the set amalgam at the base of the cavity
and at cervical position helps to prevent cusp deflection and cracks in large
cavities. The decreased amount of composite will reduce the contraction stress
and give more chance for curing. 1.
Patrascu I, Ilici R and Galbinasu
BM. In Vitro Evaluation of the Influence of Contraction Strength in
Polymerization of Restorative Composite on Adhesive Capacity of Adaption
Systems (2018) Romanian J Oral Rehab 10: 6-14. 2.
Demarco FF, Zanchi CH, Bueno M
and Piva E. Composite Veneering of Complex Amalgam Restorations (2007) Oper
Dent 32: 94-98. https://doi.org/10.2341/06-8 3.
Mantri SP and Mantri SS.
Management of shrinkage stresses in direct restorative light-cured composites:
a review (2013) J Esthet Restor Dent 25: 305-313. https://doi.org/10.1111/jerd.12047
4.
Heintze SD and Rousson V.
Clinical effectiveness of direct class II restorations-a meta-analysis (2012) J
Adhes Dent 14: 407-431. https://doi.org/10.3290/j.jad.a28390
5.
Clark DJ, Sheets CG and Paquette
JM. Definitive Diagnosis of Early Enamel and Dentin Cracks Based on Microscopic
Evaluation (2003) J Esthet Restor Dent 15: 391-401. https://doi.org/10.1111/j.1708-8240.2003.tb00963.x
6.
Park J, Chang J, Ferracane J and
Lee IB. How should composite be layered to reduce shrinkage stress: incremental
or bulk filling? (2008) Dent Mater 24: 1501-1505. https://doi.org/10.1016/j.dental.2008.03.013
7.
Singhal S, Gurtu A, Singhal A,
Bansal R and Mohan S. Effect of Different Composite Restorations on the Cuspal
Deflection of Premolars Restored with Different Insertion Techniques-An In
vitro Study (2017) J Clin Diagn Res 11: ZC67-ZC70. https://dx.doi.org/10.7860%2FJCDR%2F2017%2F20159.10440
8.
Pottmaier LF, Linhares LA,
Baratieri LN and Vieira LCC. Evaluation of the fracture resistance of premolars
with extensive and medium cavity preparations restored with direct restoring
systems (2018) Indian J Dent Res 29: 465-469. https://doi.org/10.4103/ijdr.IJDR_602_16
9.
Mirzaei M, Ghavam M and
Rostamzadeh T. Reinforcement of Unsupported Enamel by Restorative Materials and
Dentin Bonding Agents: An In Vitro Study (2010) J Dent (Tehran) 7: 84-88. 10. Magne
P, Silva S, Andrada MD and Maia H. Fatigue resistance and crack propensity of
novel super-closed sandwich composite resin restorations in large MOD defects
(2016) Int J Esthet Dent 11: 82-97. 11. Han
L, Okamoto A, Fukushima M and Okiji T. Enamel Micro-cracks Produced around
Restorations with Flowable Composites (2005) Dent Mater J: 83-91. https://doi.org/10.4012/dmj.24.83
12. Boroujeni
PM, Mousavinasab SM and Hasanli E. Effect of configuration factor on gap
formation in hybrid composite resin, low-shrinkage composite resin and
resin-modified glass ionomer (2015) J Investig Clin Dent 6:156-60. https://doi.org/10.1111/jicd.12082
13. Cramer
NB, Stansbury JW and Bowman CN. Recent advances and developments in composite
dental restorative materials (2011) J Dent Res 90: 402-416. https://doi.org/10.1177%2F0022034510381263
14. Giannini
M, Paulillo L and Ambrosano G. Effect of surface roughness on amalgam repair
using adhesive systems (2002) Braz Dent J 13: 179-183. http://dx.doi.org/10.1590/S0103-64402002000300007
15. Souza-Junior
EJ, de Souza-Régis MR, Alonso RC, de Freitas AP, Sinhoreti MA, et al. Effect of
the Curing Method and Composite Volume on Marginal and Internal Adaptation of
Composite Restoratives (2011) Oper Dent 36: 231-238. https://doi.org/10.2341/10-107-L Samir Koheil,
Professor of Conservative Dentistry and Implant, Faculty of Dentistry,
Alexandria University, Egypt, E-mail: skoheil@yahoo.com Koheil S. A combined amalgam-composite filling technique
to resist cuspal fracture (2019) Dental Res Manag 3: 47-50 Amalgam-composite filling, Cuspal fracture,
Mesio-occluso-distal restorations, Enamel fracture.A Combined Amalgam-Composite Filling Technique to Resist Cuspal Fracture
Samir Koheil
Abstract
Full-Text
Introduction
Aim
of the Work
Materials
and Methods
Grouping
Testing of Samples
Results
Discussion
Conclusions
References
*Corresponding
author
Citation
Keywords
