Two-Years Clinical Performance of Bulk-Fill High Viscosity Ormocer Versus Methacrylate-Based Resin Composite Restorative Systems: The Effect of Bulk-Fill Low-viscosity Resin Composite Liners in Class II Restorations.
Phase: NA
Conditions: Dental Caries Class II
Sponsor: Mansoura University

 
 
 
 
A two-year Clinical Impact of Bulk-fill Low-
viscosity Resin Composite Liners in Class II 
Restorations 
 
 
Local ethics committee approval number: M 11120520 
Study Start: January 15, 2020 [Actual] 
Primary Completion: April 27, 2022 [Actual] 
Study Completion: June 17, 2023 [Actual] 
 
 
 
By 
 
Mustafa Ahmed Alsharkawy, B. Dent, MSCD 
Assistant Lecturer, Operative Dentistry Department 
Faculty of Dentistry Mansoura University 
Mansoura University
 
Faculty of Dentistry 
 
Operative Dentistry 

Protocol: 
Introduction 
Patients' increasing desire for aesthetic restorations has led to the use of direct 
resin composites as the most versatile restoration for both anterior and posterior 
teeth, with evidence for their success.1-5 However, polymerization shrinkage and 
indeed the strains it generates are still one of the main reasons for resin composite 
restoration failures. This is because it applies tension to the tooth-restoration 
interface over time, endangering the bonding integrity.6 Furthermore, these stresses 
negatively affect cavity margins with leakage and subsequent carious lesion 
development.7  
These stresses are widely recognized to be affected by the placement 
techniques.8 The standard method for avoiding the clinical effects of polymerization 
stress is incremental layering.9-13 The drawbacks of this technique are the 
possibilities of voids or contaminants inclusion between layers, and difficulties in 
filling conservative cavities.14-16 In addition to, a need for restorative procedures that 
effectively shorten restoration time. In this regard, bulk-fill high-viscosity(regular), 
and low-viscosity (flowable) methacrylate-based resin composites had been 
evolved.17-21  
 Different viscosities are due to filler content that has direct relation with 
material modulus of elasticity.22  Bulk-fill low-viscosity resin composites (BLRC) 
are indicated as liners and stress absorbers in class I and class II cavities, requiring 
an additional layer high-viscosity type.23 10, 24-26 While high viscosity (BHRC) types 
can be inserted up to 5 mm increment, without the need of a veneering layer. 27-30 
The increased curing depth were attributed to monomers which act as modulators in 
the polymerization reaction, resulting in reduced shrinkage.31-35 

 Scientific evidence has shown that bulk-fill resin composites have 
comparable polymerization shrinkage and stress, depth of cure, physic mechanical 
properties, and marginal adaptation when compared to conventional composites.15, 
34-41 Other studies have revealed greater values for shrinkage vectors and a higher 
tendency for debonding.42 In relation to their clinical performance, data investigating 
the high-viscosity methacrylate based types had a heterogeneous behaviour and 
depended mainly in their chemical composition. 43-45 46, 47 Most of the studies have 
reported similar results related to marginal degradation when compared to 
conventional resin composites.46, 48  
Bulk-fill low-viscosity resin composites (BLRC) as liners demonstrated a 
stress reduction ability in posterior resin composite restorations, thereby exhibiting 
a high level of clinical efficacy over three years evaluation.23, 49-54 Besides, their low 
elastic modulus may provide a certain stress-absorbing layer, thus relieving the 
polymerization stress of the veneering regular viscosity composites.55-58, 14 
Moreover, subsequent layer of higher modulus resin composites can be absorbed by 
an elastic intermediary layer, lowering stress at the tooth-restoration interface. In a 
RCT one of the restorative systems that used BLRC liner showed the lowest surface 
staining.54 
 Despite, contradictory evidence had reported decreased adaption and higher 
polymerization shrinkage stress than the high-viscosity counterpart and other study 
found no improvement in the clinical performance of a class II restoration .59, 60 It is 
unknown, nevertheless, whether low viscosity bulk-fill composites would be 
susceptible to proximal contact defects comparable to those reported in glass 
ionomer restoratives.61, 62  

Resin matrix plays an important role on the shrinkage behaviour of resin 
composite restorations.63 The high molecular weight bis-GMA (bisphenol A-
glycidyl methacrylate) has been the main monomer used in methacrylate-based resin 
composites since their development.64 Due to the high viscosity of this monomer, 
low molecular weight monomers (diluents) were added to the final blend to get a 
suitable formulation for clinical use and to allow filler inclusion.65 These diluent 
monomers were supposed to increase the polymerization shrinkage of resin 
composites.66  
To reduce the clinical problems associated with the conventional methacrylate 
based resin composites, Ormocers were developed.67-71 They claimed to lower 
polymerization stress due to their reduced amount of organic resin.67, 69, 72-76  On the 
other hand, their first launched generations did not make any clear progress over the 
methacrylate-based resin composites.77 A probable explanation of the attained 
findings was the inclusion of  methacrylate monomers beside ormocer molecule that 
served as diluents.78 A pure ormocer resin composite was then introduced to the 
market and it was placed by incremental layering .75, 76, 79 
In addition to layering method, the pure material had been implemented for 
bulk-filling with two viscosities like methacrylates (high viscosity, low viscosity). 
In comparison with methacrylate resin composites, the pure ormocer material were 
supposed to lower polymerization shrinkage.75, 76 Bulk-fill high-viscosity ormocer-
based resin composites(BHORC) may be superior alternative to the standard 
layering method, given similar clinical performance after 24 months, with the 
advantage of simplified procedures.80 In addition, a RCT utilized the pure layered 
ormocer material (Admira-fusion) and found non-significant differences over the 
compared methacrylate based resin composites after 24 months in class II 
restorations.79 

As regard lining ormocer-based resin composites, the data is scarce. Torres et 
al81 reported in a one randomized clinical trial to have no influence in their clinical 
performance. So that the aim of this randomized, split-mouth clinical trial was to 
evaluate the clinical performance of class II restorations made with the use of 
BHORC versus BHMRC composites either placed alone or with the effect of BLRC 
liner of the same type after 2 years follow up.  
The null hypotheses in the study were as follows: (1) Different types of matrix 
structures (ormocer vs. methacrylate) have no effect on the clinical performance of 
restorations; (2) A layer of bulk-fill resin composite liner of the same category would 
not affect clinical parameters evaluated. 
Aim of the study 
The current study was intended to evaluate the effect of flowable lining resin 
composites on 2-year clinical performance of bulk-fill ormocer versus methacrylate-
based restorative systems in class Ⅱ cavities according to FDI criteria.  
Null hypothesis  
The null hypothesis that will be tested in this project is that there would be no 
significant difference among the four tested restorative strategies at different clinical 
evaluation periods.  
 
 
 
 
 
 

Materials and Methods 
Materials  
Bulk-fill high viscosity methacrylate-based resin composite (BHMRC) (XTra-fill 
Voco, Germany), Bulk-fill high-viscosity ormocer-based resin composite (BHORC) 
(Admira-Fusion-Xtra Voco, Germany), Bulk-fill low-viscosity methacrylate-based 
resin composite (XTra-Base Voco, Germany) (BLMRC) and bulk-fill low-viscosity 
ormocer-based resin composite (BLORC) (Admira-Fusion-Base Voco, Germany). All 
restorations were performed using the universal adhesive (Futura U bond Voco, 
Germany). 
Methods 
Clinical trial design 
This clinical trial will be conducted according to CONSORT guidelines for 
Randomized Clinical Trials (RCTs).45 It will be carried out after gaining approval 
from Medical Ethics Committee of Mansoura University.  
Recruitment 
Patients enrolled in this study were from the Outpatient Clinic at Mansoura 
University, Faculty of Dentistry. Patients were informed on the background of the 
study and who accepted the study condition signed a consent form. The consent form 
was approved by the ethical committee at faculty of dentistry, Mansoura University. 
Eligibility criteria 
Participants were examined to form a group with 30 patients that justify the 
inclusion and exclusion criteria. Patients were required to have good general health, 
be older than 18 years old. Patients with extremely poor oral hygiene, severe or 
chronic periodontitis, or heavy bruxism habits will be excluded from the study. 

Patients had to present at least four teeth with class II cavities to be restored (molars 
or premolar). Also, unsatisfactory class Ⅱ restorations that are moderately deep with 
an adjacent tooth was involved. 
Randomization 
Randomization was applied by noting each tooth to be restored (FDI 2- digit 
code) on one paper and type of restorative strategy on a second. First, a tooth number 
was drawn blindly. Subsequently a restorative protocol was allocated to this tooth 
by blind drawing. This procedure was repeated if more than three restorations must 
be placed. 
  Interventions: Restorative procedures 
A split-mouth design was used in this study. For ormocer- based resin 
composite restorative system, it will be placed without resin flowable liner in one 
side, while it will be lined in the other side. The same protocol will be applied for 
methacrylate-based resin composite restorative system. Hence, each patient will 
receive four restorations with different strategies. All restorative procedures will be 
carried out by a single operator.  
After administration of local anesthetic, rubber dam will be placed. The cavity 
preparation was then carried out with an outline limited to caries progression. The 
cavities depth in mm will be measured by a periodontal probe to give an idea about 
the thickness of the flowable composite liner (when used) and preserve 2 mm depth 
for the overlying resin. Restorative systems were then be applied according to the 
instructions recommended by their manufactures. Sectional pre-contoured matrix 
with ring, and wave like contour plastic wedges was used to restore the shape of the 
proximal walls. Adhesive and resin composites was cured using a LED (light 

emitting diode) curing unit in the standard application mode and an output of 650 
mW/cm2.   
Clinical evaluation 
 All restorations were clinically evaluated using FDI criteria.46 This evaluation 
was done at the baseline, then after 12-month and finally at 24-months. 
Statistical analysis: 
The Chi-Square test was used for comparison between the four groups within every 
follow up period, while marginal homogeneity test was used to compare the changes 
within each group per time. 
 
 
 
 
 
 
 
 
 
 
 
 

Results: 
 
Table: Scores of all tested criteria and results of Chi-Square and Marginal homogeneity tests 
 
category 
score 
Baseline 
(n=30) 
 
# 
6 Months 
(n=30) 
 
# 
12 Months 
(n=30) 
 
# 
18 Months 
(n=30) 
 
# 
24 Months 
(n=30) 
 
# 
XF $ 
XB $ 
AFX $ 
 
AFB $ 
XF XB AFX AFB 
XF XB AFX AFB 
XF XB AFX AFB 
XF XB AFX AFB 
XF XB AFX AFB 
Marginal staining 
1 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
p1=1.0 
p1=1.0 
p1=1.0 
p1=1.0 
2 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p2=1.0 
p2=1.0 
p2=1.0 
p2=1.0 
3 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p3=1.0 
p3=1.0 
p3=1.0 
p3=1.0 
4 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p4=1.0 
p4=1.0 
p4=1.0 
p4=1.0 
5 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
 
 
 
 
Color match and translucency 
1 
28 
29 
30 
30 
p=0.288 
28 
29 
30 
30 
p=0.288 
28 
29 
30 
30 
p=0.288 
28 
29 
30 
30 
p=0.288 
28 
29 
30 
30 
p=0.288 
p1=1.0 
p1=1.0 
p1=1.0 
p1=1.0 
2 
2 
1 
0 
0 
2 
1 
0 
0 
2 
1 
0 
0 
2 
1 
0 
0 
2 
1 
0 
0 
p2=1.0 
p2=1.0 
p2=1.0 
p2=1.0 
3 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p3=1.0 
p3=1.0 
p3=1.0 
p3=1.0 
4 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p4=1.0 
p4=1.0 
p4=1.0 
p4=1.0 
5 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
 
 
 
 
Fracture of material and 
retention 
1 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
p1=1.0 
p1=1.0 
p1=1.0 
p1=1.0 
2 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p2=1.0 
p2=1.0 
p2=1.0 
p2=1.0 
3 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p3=1.0 
p3=1.0 
p3=1.0 
p3=1.0 
4 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p4=1.0 
p4=1.0 
p4=1.0 
p4=1.0 
5 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
 
 
 
 
Marginal adaptation 
1 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
p1=1.0 
p1=1.0 
p1=1.0 
p1=1.0 
2 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p2=1.0 
p2=1.0 
p2=1.0 
p2=1.0 
3 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p3=1.0 
p3=1.0 
p3=1.0 
p3=1.0 
4 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p4=1.0 
p4=1.0 
p4=1.0 
p4=1.0 
5 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
 
 
 
 
Radiographic examination 
1 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
p1=1.0 
p1=1.0 
p1=1.0 
p1=1.0 
2 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p2=1.0 
p2=1.0 
p2=1.0 
p2=1.0 
3 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p3=1.0 
p3=1.0 
p3=1.0 
p3=1.0 
4 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p4=1.0 
p4=1.0 
p4=1.0 
p4=1.0 
5 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
 
 
 
 
Interproximal contact 
1 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
29 
28 
27 
28 
p=0.784 
p1=0.317 p1=0.317 p1=0.317 p1=0.317 
2 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
1 
2 
3 
2 
p2=0.157 p2=0.157 p2=0.157 p2=0.157 
3 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p3=0.083 p3=0.083 p3=0.083 p3=0.083 
4 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p4=0.157 p4=0.157 p4=0.157 p4=0.157 
5 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
 
 
 
 
Postoperative (hyper-) 
sensitivity and tooth vitality 
1 
29 
30 
28 
30 
p=0.288 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
p1=0.317 p1=0.157 p1=0.083 p1=1.0 
2 
1 
0 
2 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p2=1.0 
p2=1.0 
p2=1.0 
p2=1.0 
3 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p3=0.157 p3=0.157 p3=0.157 p3=0.157 
4 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p4=1.0 
p4=1.0 
p4=1.0 
p4=1.0 
5 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
 
 
 
 
Recurrent caries 
1 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
p1=1.0 
p1=1.0 
p1=1.0 
p1=1.0 
2 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p2=1.0 
p2=1.0 
p2=1.0 
p2=1.0 
3 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p3=1.0 
p3=1.0 
p3=1.0 
p3=1.0 

4 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p4=1.0 
p4=1.0 
p4=1.0 
p4=1.0 
5 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
 
 
 
 
Tooth integrity (enamel 
cracks and tooth fractures) 
1 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
30 
30 
30 
30 
p=1.0 
p1=1.0 
p1=1.0 
p1=1.0 
p1=1.0 
2 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p2=1.0 
p2=1.0 
p2=1.0 
p2=1.0 
3 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p3=1.0 
p3=1.0 
p3=1.0 
p3=1.0 
4 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
p4=1.0 
p4=1.0 
p4=1.0 
p4=1.0 
5 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
 
 
 
 
 
 
#USED test: Chi-Square test for comparing between groups (EXF, SDR and TNFBF) $USED test: Marginal Homogeneity test for comparing 
between different follow up times as compared to baseline value

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