Clinical evaluation of the bulk fill composite

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Available online at www.sciencedirect.com

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Clinical evaluation of the bulk fill composite QuiXfil in molar class I and II cavities: 10-year results of a RCT Katrin Heck ∗ , Juergen Manhart, Reinhard Hickel, Christian Diegritz Department of Conservative Dentistry and Periodontology, University Hospital, Ludwig-Maximilians-University Munich, Goethestr. 70, 80336 Munich, Germany

a r t i c l e

i n f o

a b s t r a c t

Article history:

Objective. The objective of this RCT was to compare the 10-year clinical performance of

Received 24 May 2017

QuiXfil with that of Tetric Ceram in posterior single- or multi-surface cavities.

Received in revised form

Methods. 46 QuiXfil (Xeno III) and 50 Tetric Ceram (Syntac classic) composite restorations

20 October 2017

were placed in 14 stress bearing class I and 82 class II cavities in first or second molars.

Accepted 23 March 2018

Clinical evaluation was performed at baseline and after up to 10 years by using modified

Available online xxx

US Public Health Service criteria. At the last recall period, 26 QuiXfil and 30 Tetric Ceram restorations in 11 stress bearing class I and 45 class II cavities, were assessed.

Keywords:

Results. Ten failed restorations were observed during the follow-up period, four Tetric Ceram

Composite

restorations failed due to secondary caries (2), tooth fracture (1) and bulk fracture combined

Molars

with secondary caries (1) whereas six QuiXfil restorations failed due to secondary caries (1),

Clinical study

tooth fracture (2), secondary caries combined with restoration fracture (1), restoration frac-

Longevity

ture (1) and postoperative sensitivity (1). Fisher’s exact test yielded no significant difference

USPHS criteria

between both materials (p = 0.487).

Significance. Both materials, bulk fill QuiXfil restorations and Tetric Ceram restorations, showed highly clinical effectiveness during the 10-year follow-up. © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

1.

Introduction

Direct composite materials are used ubiquitous for the restoration of class I and II lesions in posterior teeth. Main advantages of these restorations are conservative cavity preparations without the need for macro-mechanical retention areas and maximum preservation of healthy tooth structure and adhesive reinforcement of weak cusps. Furthermore, good esthetics in less treatment appointments are

accomplished while costs are kept to a minimum compared to indirect restorative techniques [1,2]. When used within the indications and handled in accordance to the instructions of the manufactures’, posterior composite restorations exhibit also an excellent clinical longevity [3–7].

Conventional hybrid composite materials are usually processed in an incremental layering technique with a layer thickness of 2 mm to overcome the problems of polymerization stress and limited depth of cure [8]. Each increment is light cured separately for 10–40 s, depending on the intensity

∗

Corresponding author.

E-mail address: kheck@dent.med.uni-muenchen.de (K. Heck). https://doi.org/10.1016/j.dental.2018.03.023 0109-5641/© 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

Please cite this article in press as: Heck K, et al. Clinical evaluation of the bulk fill composite QuiXfil in molar class I and II cavities: 10-year results of a RCT. Dent Mater (2018), https://doi.org/10.1016/j.dental.2018.03.023

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of the curing device, formulation and shade/translucency of the composite material [9]. This results in a time-consuming application procedure of resin based composites that requires, for economic reasons, an adequate fee to cover the expenses [10].

At the end of the 1990s, highly-filled packable composites were introduced into the market with the expectations to render the direct adhesive technique less complicated and more cost-effective [11]. Meanwhile, packable composites do not play a relevant role anymore, as the expectations, which were linked to this special group of composite materials, such as easier achievement of tight physiological proximal contacts, increase of polymerization depth and sculptability could either not be fulfilled or technical handling and material properties were comparable to regular hybrid composites [12].

However, easier and faster placement of resin based composites is still highly demanded by general dental practitioners. The group of bulk fill composites, most of them introduced in the recent years, seems to meet the expectations from dental practitioners to provide a direct adhesive restorative material that can be manipulated faster and more convenient in the cavity [13] compared to conventional hybrid composites while still maintaining good mechanical properties – such as marginal adaptation, sealing properties, fracture strength, wear resistance – and long-term clinical success. These composites can be placed into the cavities in increments of 4 mm without prolonged curing time or using a curing device with increased irradiance [8,14]. Bulk fill composites are provided in two different viscosities [15].

High-viscosity bulk fill composites can be used to completely fill the cavities up to the occlusal surface with only one material, whereas low-viscosity bulk fill composites require a final capping layer of 2 mm by a regular hybrid composite material because of inferior mechanical properties (e.g. E-modulus and wear) due to their reduced filler load and filler composition [16–18].

QuiXfil (Dentsply DeTrey, Konstanz, Germany) was the first bulk fill composite marketed already in 2003. This highviscosity bulk fill composite has a filler load of 86 wt.%/66 vol.% and is available in one translucent shade that allows to cure 4 mm increments in 10 s using a polymerization light of minimum 800 mW/cm2 intensity [14]. The bimodal filler technology shows a particle distribution with two distinct peaks at 0.8 mm and 10 ␮m, shrinkage is claimed 1.7 vol.% by the manufacturer [19].

The aim of this longitudinal randomized controlled clinical study on two adhesive restorative systems (composite and respective bonding agent) was to provide a survey on the clinical results of QuiXfil/Xeno III restorations in permanent molars up to 10 years compared to restorations placed with Tetric Ceram/Syntac Classic (Vivadent, Schaan, Liechtenstein). Furthermore it should be determined whether the bulk fill composite QuiXfil combined with a single-step self-etch adhesive showed a clinical acceptance rate comparable to a traditional hybrid composite material combined with a three-step etch-and-rinse adhesive using the modified USPHS scoring system.

2.

Method and materials

2.1.

Study design and participants

The methods of restoration placement and clinical evaluation have already been published [20]. Forty-six QuiXfil (Dentsply DeTrey, Konstanz, Germany) composite restorations in combination with the self-etching adhesive Xeno III (Dentsply DeTrey, Konstanz, Germany) and fifty Tetric Ceram (Vivadent, Schaan, Liechtenstein) composite restorations bonded with the etch-and-rinse adhesive Syntac classic (Vivadent, Schaan, Liechtenstein) were randomized placed by three well trained dentists according to manufacturers’ instructions.

Table 1 shows details on material composition. Each patient gave written consent to participate in the study before treatment. Ethical approval was granted by an ethics committee (Approval Number 2001-D-8473).

Patients in need of more than one restoration received at least 1 restoration with the testing material QuiXfil and one with the control material Tetric Ceram and a maximum of 2 restorations of each type. A random design was used to allocate the restorative materials to the teeth [20,21]. Eleven stress bearing class I and forty-five class II cavities could be included in the 10 year recall. Fillings had been placed either due to presence of primary caries or because of the replacement of failed restorations, in first or second molars with existing antagonistic and at least one neighboring tooth. Further inclusion and exclusion criteria for patients or teeth are shown in Table 2.

2.2.

Clinical procedure

All patients received local anesthesia during treatment. Teeth were cleaned with fluoride-free prophylaxis paste and a rubber cup. To preserve a maximum of sound tooth structure, preparation was limited to the removal of caries or old insufficient restorations followed by rounding the internal line and point angles and preparation of the enamel margins with butt joint margins. Cavity preparation was carried out with 80 ␮m grit diamond burs and finished with 25 ␮m grit diamond burs (Intensiv, Viganello-Lugano, Switzerland). Cases requiring direct pulp capping were excluded. No liners or bases were used. Isolation and contamination control were carried out with suction device and cotton rolls. Rubber-dam was used in cases, where this was not considered sufficient. Metal matrix bands and wooden wedges were used when appropriate.

The self-etching adhesive Xeno III was used for QuiXfil restorations. Liquid A and B were dispensed in a dappen dish, mixed with a microbrush for 5 s and applied on enamel and dentin for 20 s. Thereafter the solvent was vaporized with oil-free compressed air and light cured for 10 s. The QuiXfil composite was incrementally applied, in layers up to 4 mm thick, according to manufacturers’ recommendations. In cavities with more than 4 mm depth, a second increment was placed. Each layer was light cured for 10 s (800 mW/cm2 ).

As control Tetric Ceram combined with the etch-and-rinse system Syntac classic was used to restore cavities. According to the directions of the manufacturer, enamel was etched

Please cite this article in press as: Heck K, et al. Clinical evaluation of the bulk fill composite QuiXfil in molar class I and II cavities: 10-year results of a RCT. Dent Mater (2018), https://doi.org/10.1016/j.dental.2018.03.023

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Table 1 – Materials, manufacturer and composition.

Material

Type

Manufacturer

Composition resin matrix

Filler

QuiXfil

Posterior bulk fill composite material

Dentsply DeTrey

• Urethane dimethacrylate (UDMA) • Triethyleneglycol dimethacrylate (TEGDMA) • Di- and trimethacrylate resins • Carboxylic acid modified dimethacrylate resin

Silanated strontium aluminum sodium fluoride phosphate silicate glass (86 wt.% or 66 vol%)

Tetric Ceram

Hybrid composite material

Ivoclar Vivadent

• Bis-GMA • Urethane dimethacrylate (UDMA) • Triethyleneglycol dimethacrylate (TEGDMA)

Barium glass, ytterbium trifluoride, Ba-Al-fluorosilicate glass, highly dispersed silicon dioxide, and spheroid mixed oxide (79 wt.% or 60 vol%)

Xeno III

Single step self-etching adhesive

Dentsply DeTrey

Liquid A • 2-hydroxyethyl methacrylate (HEMA) • Purified water • Ethanol • Butylated hydroxy toluene (BHT) • Highly dispersed silicon dioxide Liquid B • Phosphoric acid modified methacrylate (Pyro-EMA) • Mono fluoro phosphazene modified methacrylate (PEM-F) • Urethane dimethacrylate • Butylated hydroxy toluene (BHT) • Camphorquinone • Ethyl-4-dimethylaminobenzoate

Syntac Classic

Etch&Rinse multi-step adhesive

Ivoclar Vivadent

Primer Polyethylene glycol dimethacrylate, maleic acid, and ketone in an aqueous solution Adhesive Polyethylene glycol dimethacrylate and glutaraldehyde in an aqueous solution.

Heliobond Bis-GMA 60 wt.% Triethylene glycol dimethacrylate 40 wt.%

Table 2 – Inclusion and exclusion criteria.

Inclusion criteria

Exclusion criteria

Population

• Age ≥ 18 years • Patients with a high level of oral hygiene

• Age < 18 years • Patients suffering from allergies or severe systemic diseases

Teeth

• Vital first or second molars with positive reaction to cold thermal stimulus • Treated cavities with an isthmus size of at least 1/3 of the intercuspal distance

• Teeth with periodontal problems • Non-vital teeth • Teeth with identifiable pulpal inflammation or pain before treatment • Teeth formerly or now subjected to direct pulp capping • Teeth with initial defects only

with 37% phosphoric acid for 30 s and dentin for 15 s, thoroughly rinsed with water spray, followed by slightly drying the cavities with oil-free compressed air. Syntac Primer was applied in a thin layer for 15 s, then excess solvent was dispersed with oil-free compressed air, followed by application of Syntac Adhesive for 10 s and thinning with oil-free compressed air. Heliobond was then applied in a thin layer and polymerized for 20 s. Placement of Tetric Ceram followed the incremental technique (2 mm thick layer) and each increment was light cured for 20 s (800 mW/cm2 ).

Finishing and polishing of all restorations was done under water cooling with fine-grit diamond burs, polishing discs and strips (Sof-Lex, 3 M, St. Paul, MN, US) and a composite polishing kit (Enhance, Dentsply, Milford, DE, USA). High-gloss polishing was achieved with Prismagloss composite polishing paste (Dentsply) applied with a foam cup.

2.3.

Evaluation of restorations

Restorations were assessed at baseline (14 days after treatment), after 3 months, 6 months, 18 months, 3 years, 4 years Please cite this article in press as: Heck K, et al. Clinical evaluation of the bulk fill composite QuiXfil in molar class I and II cavities: 10-year results of a RCT. Dent Mater (2018), https://doi.org/10.1016/j.dental.2018.03.023

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Table 3 – Outcome variables and methods for the direct evaluation of the restorations.

Criterion

Methods of evaluation

Surface texture Color match/change of restoration color Anatomic form of the complete surface Anatomic form at the marginal step Marginal integrity Discoloration of the margin and secondary caries Integrity of the tooth Integrity of the restoration Occlusion

Visual and probe Visual

Testing of sensitivity Postoperative symptoms Patients’ acceptance

3.

Results

Visual and probe Visual and probe Visual and probe Visual Visual and probe Visual and probe Visual (articulating paper) Thermal testing (CO2 ice) Interviewing the patient Interviewing the patient

and 10 years. At the 10-year recall the restorations were evaluated by one experienced dentist. Each restoration was rated using mirror and probe (outcome variables are listed in Table 3) and scored using the modified USPHS criteria for the direct evaluation of the adhesive technique [22–24].

This assessment resulted in ordinally structured data for the outcome variables (alfa = excellent result; bravo = acceptable result; charlie = replacement of the restoration for prevention; delta = unacceptable, replacement immediately necessary) [25].

At the 10-year recall 26 QuiXfil and 30 Tetric Ceram restorations could be evaluated (Table 4). Failed and removed restorations up to the 4-year recall (four QuiXfil, one Tetric Ceram) are included in the number of 56 rated restorations [20,26,27].

2.4.

rank test for comparison between the test materials was used.

For survival analysis, data was censored after 10 years followup.

Statistical analysis

Data management and analysis were performed using SPSS software (Version 23.0, SPSS, Chicago, IL, USA). Descriptive statistics were used to describe the frequency distributions of the evaluated criteria and the reasons for failure. Nonparametric statistical procedures (˛ = 0.05) were used due to ordinally structured data for the assessment of the restorations. The Mann-Whitney U-test was used to explore significant differences of the 10-year results between both types of direct composite restorations. The same test was used to detect differences between baseline and 10-year results within the restoration materials for the criteria listed in Table 3 and to analyze performances between small and large cavities.

Therefore a classification of cavity size for each material, QuiXfil or Tetric Ceram, was made: 1- or 2-surfaces (“small cavity” group) and 3 or more surfaces (“large cavity” group).

2 × 2 tables were generated and Fisher’s exact test was used to analyze the clinical failure (alpha- and bravo-scored vs. charlie-and-delta-scored restorations). To generate survival curves up to 10 years, the Kaplan–Meier method and the log-

The results of the clinical evaluation comparing 26 QuiXfil and 30 Tetric Ceram direct composite restorations at baseline and the 10-year follow up are reported in Table 5. A Mann Whitney U-test was conducted to exhibit the differences in the clinical criteria listed in Table 3 between the test materials Tetric Ceram and QuiXfil after 10 years. The results indicate, that anatomic form at the marginal step was better for Tetric Ceram than for QuiXfil (p = 0.006) and that integrity of the restoration was superior for Tetric Ceram compared to QuiXfil (p = 0.003) as well. Large Tetric Ceram restorations exhibited significantly lower marginal integrity (p = 0.003) and higher discoloration of the margin (p = 0.044) than small Tetric Ceram restorations. For QuiXfil poorer values in larger cavities compared to smaller ones could also be found for discoloration of the margin (p = 0.036) and integrity of the restoration (p = 0.002). No significant differences between class I and class II cavities restored either with Tetric Ceram or QuiXfil could be found. However, QuiXfil restorations in class II cavities performed significantly poorer at integrity of the restoration (p = 0.002) and anatomic form at the marginal step (p = 0.042) compared to class II Tetric Ceram restorations.

Statistical comparison with the MWU-test between the results at baseline and after 10 years of clinical service yielded for QuiXfil restorations a significant deterioration in anatomic form at the marginal step (p < 0.001), of the marginal integrity (p < 0.001), of the marginal discoloration (p < 0.001), of tooth integrity (p = 0.002) and restoration integrity (p < 0.001).

Class I QuiXfil restorations showed no significant differences, while class II restorations after 10 years revealed significantly poorer values in surface texture (p = 0.049), anatomic form at the marginal step (p = 0.008), marginal integrity (p < 0.001), integrity of the tooth (p = 0.005) and restoration integrity (p < 0.001). Tetric Ceram restorations showed a significant increase in marginal discoloration (p < 0.001), marginal integrity (p < 0.001) and a significant deterioration of tooth integrity (p = 0.024). After 10 years class I Tetric Ceram restorations showed no significant difference compared to baseline, whereas class II restorations yielded poorer values for marginal integrity (p < 0.001), marginal discoloration (p < 0.001) and tooth integrity (p = 0.020). However, it must be mentioned that these effects are mainly results of alfa-bravoshifts, meaning that the majority of the restorations remained clinical acceptable and functional.

One class I and five class II QuiXfil restorations and four class II Tetric Ceram restorations failed in up to 10 years clinical service and were scored delta (Table 6). All restorations were replaced at the respective follow up-time. Fisher’s exact test revealed no significant difference between composite materials (p = 0.487) concerning the failure rate. However, “large cavities” failed statistically significant more often than “small cavities” (p = 0.025), but no significant difference was found between class I and class II restorations (p = 0.667).

Please cite this article in press as: Heck K, et al. Clinical evaluation of the bulk fill composite QuiXfil in molar class I and II cavities: 10-year results of a RCT. Dent Mater (2018), https://doi.org/10.1016/j.dental.2018.03.023

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Fig. 1 – Kaplan–Meier survival curves for QuiXfil and Tetric Ceram composite restorations (log-rank p = 0.287).

Fig. 2 – Kaplan–Meier survival curves for class II cavities treated with QuiXfil and Tetric Ceram composite restorations (log-rank p = 0.397).

Please cite this article in press as: Heck K, et al. Clinical evaluation of the bulk fill composite QuiXfil in molar class I and II cavities: 10-year results of a RCT. Dent Mater (2018), https://doi.org/10.1016/j.dental.2018.03.023

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Table 4 – Number (n), restoration recall rate percentages in parentheses and size of evaluated direct composite restorations at the 10-year recall.

QuiXfil Tetric Ceram

n (%)

1-surface restorations

2-surface restorations

3-surface restorations

4-surface restorations

Class I

Class II

26 (56.52) 30 (60.00)

6 5

10 15

6 5

4 5

6 5

20 25

Table 5 – QuiXfil and Tetric Ceram direct composite restorations: Results of the clinical evaluation [%] at baseline and 10-year follow-up.

QuiXfil direct composite restorations Modified USPHS scores (%)

10 years

Baseline Alfa

Surface texture Color match Anatomic form of the complete surface Anatomic form at the marginal step Marginal integrity Discoloration of the margin and secondary caries Integrity of the tooth Integrity of the restoration Occlusion Testing of sensitivity Postoperative symptoms Patient’s acceptance

Bravo

100 100 97.8 97.8 100 100 100 100 95.7 100 100 95.7

2.2 2.2

4.3

4.3

Alfa

Bravo

92.3 96.2 96.2 69.2 53.8 46.2 80.8 73.1 92.3 100 92.3 96.2

7.7 3.8 3.8 30.8 46.2 46.2 11.5 19.2 7.7

Charlie

Delta

7.6 7.7 7.7

3.8 3.8

3.8

Tetric Ceram direct composite restorations Modified USPHS scores (%)

Baseline Alfa

Surface texture Color match Anatomic form of the complete surface Anatomic form at the marginal step Marginal integrity Discoloration of the margin and secondary caries Integrity of the tooth Integrity of the restoration Occlusion Testing of sensitivity Postoperative symptoms Patient’s acceptance

100 96 100 100 100 100 100 100 100 100 100 100

Bravo 4

10 years Alfa

Bravo

96.7 100 100 96.7 73.3 66.7 90.0 100 100 100 100 100

3.3

3.3 23.3 23.3 6.7

Charlie

Delta

3.3 10.0 3.3

Table 6 – Reason and time of failure of Quixfil/Xeno III and Tetric Ceram/Syntac classic restorations.

Material

Tooth (FDI notation)

Restoration surfaces

Months after baseline

USPHS score

Failure type

QuiXfil Tetric Ceram QuiXfil QuiXfil QuiXfil QuiXfil

36 26 36 36 36 36

mod modb mo mo o modv

18 36 36 36 48 120

QuiXfil Tetric Ceram Tetric Ceram Tetric Ceram

27 36 37 16

modp mod modl mop

120 120 120 120

Delta Delta Delta Delta Delta Delta Charlie Charlie Charlie Charlie Delta Charlie

Restoration fracture Tooth fracture Tooth fracture Postoperative sensitivity Tooth fracture Restoration fracture Secondary caries Secondary caries Secondary caries Secondary caries Marginal integrity Secondary caries

In Fig. 1, the Kaplan–Meier survival graph indicate no significant difference between QuiXfil and Tetric Ceram restorations (log-rank p = 0.287). At ten years, there was a cumulative

survival of 88.9% for Tetric Ceram restorations and 86.8% for QuiXfil restorations. Survival curves for “small cavities” showed a significant better clinical performance for Tetric

Please cite this article in press as: Heck K, et al. Clinical evaluation of the bulk fill composite QuiXfil in molar class I and II cavities: 10-year results of a RCT. Dent Mater (2018), https://doi.org/10.1016/j.dental.2018.03.023

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Ceram than QuiXfil (log-rank p = 0.048) with a cumulative survival probability of 94.0% for QuiXfil compared to 100% for Tetric Ceram. There was no statistical significant difference between survival curves for Tetric Ceram and QuiXfil in “large cavities” (QuiXfil 76.2%, Tetric Ceram 65.1%, log-rank p = 0.754), class I cavities (QuiXfil 91.7%, Tetric Ceram 100%, log rank p = 0.338) or class II cavities (QuiXfil 85.2%, Tetric Ceram 86.7%, log rank p = 0.397) (Fig. 2).

4.

Discussion

The present longitudinal randomized controlled clinical study investigated the performance of the posterior bulk fill composite QuiXfil compared to the well-established hybrid composite Tetric Ceram at an observation time of 10 years.

Developments in resin composite technology and regular introduction of new products have been so rapid in the last decades, that long-term clinical data over 10 years are rarely available and currently non-existent for bulk fill composite resin materials. Meanwhile available long-term studies observe a different failure rate during aging of composite restorations and indicate the need of longer observation periods [6,28–30]. This is also confirmed by our results. QuiXfil showed a failure rate of 7.5% after 3 years, 10.8% after 4 years and 23% after 10 years. For Tetric Ceram the failure rates are 2.2%, 2.2% and 13.3%, respectively. This corresponds to a quite stable annual failure rate (AFR) of 2.5% after 3 years, 2.7% after 4 years and 2.3% after 10 years with QuiXfil and an excellent initial AFR of 0.7% after 3 years, 0.6% after 4 years and a still very good AFR of 1.3% at 10 years for Tetric Ceram.

As the numbers of failure in both material groups were very low (6 and 4 failures respectively) the differences are not significant. Opdam et al. found a decreased annual failure rate for composite restorations over time compared to amalgam but admittedly not in high-risk caries groups [3]. A weakness in analysis of long-term prospective clinical studies is the often poor recall rate. Clinical trials require a lot of time to be concluded while patients are moving or losing interest in returning for recall [31]. Therefore, our restoration recall rate of 58% at 10 years is certainly not uncommon. Brunthaler et al. found a significant negative correlation between recall rate and observation period. However, no correlation between recall and failure rates could be found [29]. In contrast to that, Beck et al. found a decreased failure rate when the recall rate increases [32].

In 2007, revised in 2010, new recommendations by the FDI for conducting clinical studies of dental restorative materials were published along with sophisticated assessment criteria by a group of experienced international clinical researchers to update the methodology and scoring system that has been introduced by Cvar and Ryge in 1971 known as the USPHS criteria [21,33–35]. It was considered necessary to adapt the study designs and scoring principles of the early 1970s to the needs, questions and problems when studying the clinical performance of today’s restorative materials that are primarily adhesively bonded to tooth structures and require a system which is able to evaluate these materials on a more discriminative scale [21,34,35]. The relatively new FDI criteria are continuously gaining in importance and are meanwhile

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used in many clinical studies [4,36]. However, the present study started before the introduction of the FDI criteria, thus employing a modified USPHS scoring system that was still used for rating at the 10-year recall. The scores of the 4-step USPHS evaluation system [33] have direct clinical implications and a built-in definition of clinically acceptable restorations [37]. It needs to be mentioned that restorations scored with alfa and bravo are considered “clinically acceptable”. Therefore, differences between alfa and bravo scores are only in degree and not in essence. Restorations rated with charlie or delta scores however had experienced an essential change.

Composite resins are indicated for the restoration of posterior load-bearing cavities [4,38,39]. They show acceptable wear rates when manipulated and light-cured correctly [40].

However, until recently, layering techniques with 2 mm increments and separate light curing have been considered the gold standard for the placement of direct composite restorations in posterior cavities [15,41]. This application procedure was used to reduce the negative effects of polymerization shrinkage and polymerization contraction stress, such as poor marginal integrity, insufficient adherence to the cavity walls, postoperative symptoms or cusp deflections and to improve the ratio of bonded to unbonded composite surfaces (C-factor) [42,43].

The introduction of bulk fill composite materials changed the application procedure in placing thicker increments up to 4 mm due to improvements in depth of cure (DOC). This can alleviate the restorative process for the dental team, reduces the risk of entrapping air voids between subsequent increments with negative effects on mechanical strength, is time-saving and renders the treatment procedure more economic [13]. The bulk fill composites are classified in low- and high-viscosity materials [15]. The low-viscosity variants need a 2 mm capping layer of a regular composite due to their inferior mechanical properties whereas the high-viscosity bulk fill composites can be extended to the occlusal surface [17,18].

The increased DOC of bulk fill composites is the result of larger filler particles, a reduced filler load in flowable bulk fill composites, an adjustment of refractive index of filler particles and organic matrix, and initiator systems that are more sensitive to polymerization light [15,44,45].

In up to 10-years of clinical service, ten restorations (six QuiXfil and four Tetric Ceram) failed. The main reasons for failure were secondary caries and marginal discoloration, followed by tooth fracture, restoration fracture, postoperative sensitivity and deterioration of the marginal integrity.

The results agree with the classification of failures according to Hickel et al., since secondary caries, tooth fracture and restoration fracture occur mainly as a late failure after more than 2 years [21,34,35]. Statistical analysis detected no difference between the materials concerning the failure rate or type of failure; however, “large cavities” suffered statistically more failure than “small cavities”, regardless of the material. No statistically difference was found between QuiXfil and Tetric Ceram restorations in large cavities. Higher failure rates in large cavities have been described in many studies [4,29,38,46–48]. Opdam et al. found that the risk of failure increases by 40% per surface [47].

Secondary caries was the main reason for failure in this study. Demarco et al. also stated that the main reason for failure in long-term studies are secondary caries and frac-

Please cite this article in press as: Heck K, et al. Clinical evaluation of the bulk fill composite QuiXfil in molar class I and II cavities: 10-year results of a RCT. Dent Mater (2018), https://doi.org/10.1016/j.dental.2018.03.023

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ture, a meta-analysis by Heintze and Rousson confirmed that marginal caries occurred no earlier than at 2 years and Astvaldsdottir found that more than 75% of secondary caries occurred after 3 years, pointing out the necessity of an adequate follow-up time [5,28,30]. Since only patients with good oral hygiene have been included in this study, secondary caries may be related to the effectiveness of the bonding systems or physical parameters of the restoration material.

Two large QuiXfil restorations fractured, one after 18 months and another one after 120 months, none of the Tetric Ceram restoration showed deterioration of the restoration integrity. Mahmoud et al. also described fractures of restoration as the main cause of failure for QuiXfil restorations after 3 years [49]. Reasons for the fracture of restorations have been described in correlation with the flexural strength, fracture toughness and fatigue resistance of restoration materials and also with patient related variables like bruxism and parafunctions [39,50]. Since patients were not categorized according to bruxism at the time of patient recruitment, no additional multivariate analysis was possible. Indeed all restoration fractures occurred in the QuiXfil-group, although the flexural strength and fracture toughness of QuiXfil is comparable to Tetric Ceram and the flexural fatigue limit is significantly lower for Tetric Ceram [19,51,52].

Three teeth fractured during the observation period. One tooth with a large Tetric Ceram restoration after 36 months, one with a small QuiXfil restoration also after 36 months and another one with a small QuiXfil restoration after 48 months.

A possible cause for this could be parafunctions like bruxism, since several studies demonstrated a correlation between patients with bruxism and tooth fracture and patients with bruxism were not excluded in this study [53,54]. Since the restoration materials were used with their respective adhesive systems, the failures of the small QuiXfil restorations might also be attributed to the adhesive. Siso et al. found a higher fracture resistance in premolars cups of endodontically treated teeth when using total-etch two-step adhesive compared to a single-step adhesive [55].

For QuiXfil restorations a significant increase of marginal discoloration (46.2% bravo, 3.8% charlie and 3.8% delta) and lower marginal integrity (46.2% bravo) were found after 10 years compared to baseline. Similarly, Tetric Ceram restorations showed significant more marginal discoloration (23.3% bravo and 10% delta) and deterioration of marginal integrity (23.3% bravo and 3.3% charlie) after 10 years. Loss of marginal integrity at baseline could be caused by shrinkage stress, the effect of cavity geometry on C-factor or faulty adaption of the restorative material to the cavity walls [20,56,57]. Hickel et al. described the deterioration of margins to usually occur over a medium service time [21]. One possible cause for the worsening of marginal adaptation and marginal discoloration over time may be the hydrolysis of the adhesive. Water, and also chemicals, could be absorbed by the monomers of the adhesive material and could lead to chemical and physical processes which can result in disintegration of the adhesive bond [58–60].

In this study, like in other clinical trials that were started 10–15 years ago, the restoration materials were mostly combined with the recommended adhesive of the same manufacturer. We wanted to compare the company suggested

“fast track solution” consisting of self-etch adhesive and bulk fill material on the one side with the gold standard at that time (hybrid composite with etch & rinse) on the other side.

Nowadays, frequently a study design with only one material variable, either a different restorative composite or different adhesive system, is being preferred to reduce number of parameters, since some differences between the restorative groups can also be attributed to the adhesive systems. In vitro test and clinical non-carious cervical lesion (NCCL) studies showed the best results for three-step etch and rinse systems compared to different self-etch systems [61,62]. A systematic review from Brunthaler et al. found no statistically significant influence of the adhesive system in long term class II trials [29]. van Dijken et al. also observed after 8 years a non-significant 1.69% failure rate for Ceram X restorations bonded with the one step self-etch adhesive Xeno III compared to 1.63% for the two step etch and rinse adhesive Excite [63]. The contradicting results can possibly be explained by the differences in the dentin of class V non-carious lesions and the substrate in class II cavities, which are influenced by caries or amalgam [63].

Material-, patient- and dentist-related factors affect the longevity of restorations [32]. It must be distinguished between early failures, failures after a medium time period (6- to 24 months) and late failures after 2 or more years of clinical service [21]. Late failures are often caused by tooth or restoration fractures, secondary caries and wear or deterioration of the material [7].

5.

Conclusion

The overall success rate of this long term study indicate that the posterior bulk fill material QuiXfil (76.9%) and the hybrid composite Tetric Ceram (86.7%) perform with no significant difference quite well. Both materials clinically perform acceptable over 10 years, however large restorations failed significantly more often than small restorations, regardless of the material (p = 0.025). In larger class II cavities (three and more surfaces) the annual failure rate (AFR) was 3% with QuiXfil and 4% with Tetric Ceram whereas the overall AFR in all class II cavities was 2.5% with QuiXfil and 1.6% with Tetric Ceram.

Funding This study was sponsored in part by Dentsply DeTrey, Konstanz, Germany.

Acknowledgments The author would like to express their gratitude to Dr. Lidka Thiele, Dr. Petra Neuerer and Dr. Birgit Jaensch for the participation in the clinical study.

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