Modification of the restoration protocol for resin-based composite (RBC) restoratives (conventional and bulk fill) on cuspal movement and microleakage score in molar teeth

DENTAL-3164; No. of Pages 7

ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 8 ) xxx–xxx

Available online at www.sciencedirect.com

ScienceDirect journal homepage: www.intl.elsevierhealth.com/journals/dema

Modification of the restoration protocol for resin-based composite (RBC) restoratives (conventional and bulk fill) on cuspal movement and microleakage score in molar teeth I. Politi a , L.E.J. McHugh a , R.S. Al-Fodeh b , G.J.P. Fleming a,∗ a b

Materials Science Unit, Dublin Dental University Hospital, Trinity College Dublin, Lincoln Place, Dublin 2, Ireland Department of Prosthodontics, Jordan University of Science and Technology, Irbid 22110, Jordan

a r t i c l e

i n f o

a b s t r a c t

Article history:

Objective. To modify the resin-based composite (RBC) restoration protocol for standard-

Received 13 February 2018

ised Class II cavities in third molar teeth restored using conventional RBCs or their bulk

Received in revised form

fill restorative counterparts. Employing cuspal deflection using a twin channel deflection

20 April 2018

measuring gauge (during) and microleakage to determine marginal integrity (following)

Accepted 9 May 2018

RBC restoration, the modified restoration protocol results were compared with traditional

Available online xxx

(oblique) restoration of Class II cavities.

Keywords:

subjected to standardised Class II cavity preparations and randomly allocated to four groups.

Cuspal movement

Restorations were placed in conjunction with a universal bonding system and resin restora-

Methods. Thirty-two sound third molar teeth, standardised by size and morphology, were

Microleakage score

tive materials were irradiated with a light-emitting-diode light-curing-unit. The cumulative

Resin-based composite

buccal and palatal cuspal movements from a twin channel deflection measuring gauge were

Bulk fill and conventional

summed, the restored teeth fatigued thermally prior to immersion in 0.2% basic fuchsin dye

restorative material

for 24 h, before sectioning and examination for microleakage. Results. Teeth restored using conventional RBC materials had significantly higher mean total cuspal movement values compared with bulk fill resin restorative restoration (all p < 0.0001). Teeth restored with Admira Fusion and Admira Fusion x-tra had significantly the lowest microleakage scores (all p < 0.001) compared with Tetric EvoCeram and Tetric EvoCeram Bulk Fill restored teeth. The microleakage scores for the range of RBC materials tested were significantly reduced (all p < 0.001) when the modified RBC restoration protocol was employed compared with the traditional Class II restoration technique. Significance. Modification of the RBC restoration protocol of some conventional RBCs and bulk fill resin restoratives significantly improve bond integrity and could be translated as a validation of the limited clinical studies available on bulk fill materials in the dental literature where Class II cavities perform less well than Class I cavities following extended follow-up. Clinical significance. The results of the current study add further weight to experimental protocols employing cuspal movement (during) and cervical microleakage (following) RBC

∗

Corresponding author. E-mail address: [email protected] (G.J.P. Fleming). https://doi.org/10.1016/j.dental.2018.05.010 0109-5641/© 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

Please cite this article in press as: Politi I, et al. Modification of the restoration protocol for resin-based composite (RBC) restoratives (conventional and bulk fill) on cuspal movement and microleakage score in molar teeth. Dent Mater (2018), https://doi.org/10.1016/j.dental.2018.05.010

DENTAL-3164; No. of Pages 7

2

ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 8 ) xxx–xxx

restoration of standardised cavities in natural dentition to provide an indication of polymerization shrinkage stress at the tooth/RBC restoration interface in a ‘clinically meaningful context’. © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

1.

Introduction

There is no doubt that dental amalgam restorations have little place today in the world of aesthetic restorative dentistry [1,2] owing to their silvery/grey appearance notwithstanding the issues around the Minimata convention [3] and environmental efforts to ban mercury-based materials [4]. However, despite the increased teaching [1,3,5] and usage [2] of resin-based restoratives, dental amalgam has significant advantages in terms of longevity as a posterior restorative material [6,7]. While resin-based composite (RBC) materials meet patient demand for the delivery of aesthetic restorative dentistry [8], even for experienced clinical operators, RBC materials are technique sensitive [5] and can take two and a half times longer than an equivalent dental amalgam restoration to place [9]. Today there is an abundance of RBC materials available to the dental practitioner and recent bulk fill variants of RBC materials have been marketed with placement increments of ≤5 mm which significantly reduce RBC restoration placement times [10]. Bulk fill RBC materials have been classified as low viscosity bulk fill flowable base materials or high viscosity bulk fill restorative materials [10]. The employment of low viscosity bulk fill flowable base materials necessitates the addition of a capping material, namely a conventional RBC (traditional, hybrid, micro-hybrid or nano-hybrid depending on the practitioner preference), since conventional RBCs have increased wear resistance and mechanical properties [10] compared with the low viscosity bulk fill flowable base materials. However, it should be noted that while bulk fill RBCs have some innovative adjustments made to reduce shrinkage stress for higher volume curing these materials are predominantly just more translucent. Surefil (Dentsply Caulk, Milford, DE, USA) and Alert (Pentron, Orange, CA, USA) in 1999, with Quixfil (Dentsply Caulk, Milford, DE, USA) and X-tra Fil (Voco GmbH, Cuxhaven, Germany) launched in 2003, were historically among the first bulk fill RBCs introduced to the dental market [11]. The noteworthy four-year randomized controlled clinical evaluation in 2010 by Manhart et al. [12] highlighted no clinical contraindications for Quixfil restorations in Class I and Class II cavities. As a result, numerous dental materials manufacturers have recently introduced bulk fill RBC materials to the market. Clinical evaluations of bulk fill RBC materials are limited in the dental literature with the exception of the van Dijken and Pallesen [13–16] randomized controlled three[13,14], five- [15] and six-year [16] studies on SDR (Dentsply Caulk, Milford, DE, USA) — a low viscosity bulk fill flowable base material. The studies [13–16] corroborated the Manhart et al. [12] findings for Quixfil, although it should be noted that there are currently no randomized controlled clinical evaluations on high viscosity bulk fill restorative materials or low

viscosity bulk fill flowable base materials (other than SDR) in the dental literature. Further examination of the van Dijken and Pallesen [13–16] results highlighted lower annual failure rates for Class I cavities restored with the SDR (capped with Ceram X mono (Dentsply Caulk, Milford, DE, USA)) compared with the Class II restored cavities at five- [15] and six- [16] years. In the absence of controlled clinical studies on bulk fill RBCs, investigators have focused on in-vitro shrinkage testing methodologies which provide limited information of clinical performance. Therefore the dental community needs to assess how the measurement of polymerization shrinkage stress in-vivo at the tooth/RBC interface could be performed in a ‘clinically meaningful context’ [17]. Employing experimental protocols for cuspal deflection (during) and cervical microleakage (following) RBC restoration of standardised Class II cavities in maxillary premolar [10,18] or third molar [19] teeth has been shown to provide an indication of polymerization shrinkage stress at the tooth/RBC restoration interface. The scope of the cuspal deflection and cervical microleakage experimental protocols has recently been extended to determine the adhesive potential of universal [20] and three-, two- and one-step [21] bonding systems. The studies highlighted the usefulness of the in-vitro measurements of bond integrity at the tooth/RBC interface which provided a ‘clinically meaningful context’ [17] to RBC materials performance in-vivo not least because the authors employ natural dentition as the substrate. In one study [19], ® Futurabond DC SingleDose (Ref 1574, Lot 1547600; Voco, Cuxhaven, Germany) — a one-step ‘mild self-etch’ adhesive, was selected since ‘mild self-etch’ adhesives [10,18–21] do not ‘underperform at dentin’ [22,23]. The restoration technique for Class II cavities necessitated the use of eight oblique increments of a conventional RBC material compared with two increments for the bulk fill restorative RBC materials [19]. The total cuspal movement for Tetric EvoCeram (6.0 (2.0) ␮m) and Admira Fusion (6.4 (2.8) ␮m) were not significantly different (p = 0.997). When the bulk fill resin restoratives were employed [19] there were no significant differences (p = 1.000) in total cuspal movement for Tetric EvoCeram Bulk Fill Restorative (3.3 (0.8) ␮m) and Admira Fusion x-tra (3.4 (0.9) ␮m). In terms of cervical microleakage, third molar teeth restored with Admira Fusion and Admira Fusion x-tra had significantly the lowest microleakage scores (all p < 0.001) compared with the Tetric EvoCeram and Tetric EvoCeram Bulk Fill restored teeth. The poor microleakage performance of Tetric EvoCeram and Tetric EvoCeram Bulk Fill were unexpected. To further investigate the finding the authors considered if modifying the RBC restoration protocol for a Class II cavity configuration (previously employed [19]) to a Class I configuration, would reflect the five[15] and six- [16] year results of the randomized controlled studies of van Dijken and Pallesen.

Please cite this article in press as: Politi I, et al. Modification of the restoration protocol for resin-based composite (RBC) restoratives (conventional and bulk fill) on cuspal movement and microleakage score in molar teeth. Dent Mater (2018), https://doi.org/10.1016/j.dental.2018.05.010

DENTAL-3164; No. of Pages 7

ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 8 ) xxx–xxx

The aims of the current study therefore were to assess the cuspal movement using a twin channel deflection measuring gauge and the cervical microleakage scores following thermocycling to determine the marginal integrity of the restored teeth following modification of the RBC restoration protocol with the conventional RBCs or their bulk fill resin restorative counterparts previously used [19]. The hypotheses proposed were that modification of the RBC restoration protocol would result in a decrease in total cuspal movement and concomitant decrease in cervical microleakage scores for all resin-based restorative materials examined.

2.

Materials and methods

Human third molar teeth, extracted for atypical facial pain, pericoronitis or periodontal disease were collected in accordance with the ethical guidelines of the Trinity College Faculty Research Ethics Committee. All teeth were cariesfree, hypoplastic defect-free and crack-free with a maximum bucco-palatal-width (BPW) of 10.25–10.75 mm. Additional tooth morphology inclusion criteria were that the maxillary and mandibular third molar teeth had four cusps (two buccal and two lingual) to further reduce the possibility of increased anatomical variances between teeth [24]. Following tooth selection, hand-scaling was employed (if necessary) to eliminate calculus deposits and the teeth were randomly distributed into four groups (Groups A–D) with eight teeth in ® each group (n = 8). A cold cure denture base material (ProBase Cold, Ivoclar Vivadent, Schaan, Lichtenstein) was used to fix the individual teeth into a stainless steel mould, crown uppermost with the long axis of the tooth vertical. When the cold cure denture base material had set, the teeth were stored in high purity double distilled water (23 ± 1 ◦ C). Under copious water irrigation, standardised Class II cavities were prepared such that the width of the approximal box was two-thirds the BPW, the occlusal isthmus was half the BPW, the cavity at the occlusal isthmus was standardised to 3.5 mm from the tip of the highest cusp [19]. In addition, all cavosurface margins were prepared at 90◦ with rounded internal line angles [19] and all cavity dimensions were checked with a digital micrometre calliper gauge (Mitutoyo Corp., Kawasaki, Japan) reading to 0.01 mm. Unless moisture isolation was required for aspects of the experimental protocol, the teeth were stored in high purity double distilled water at 23 ± 1 ◦ C. All preparations were cleaned with copious amounts of high purity double distilled water, prior to air-drying for 30 s ® [25] and bonding with Futurabond U SingleDose (Ref 1574, Lot 1547600). In accordance with the manufacturers instructions ® for Futurabond U SingleDose, following blister activation, a homogeneous adhesive mixture was produced by continuous stirring with the supplied Single Tim applicator (Voco GmbH) and rubbed into the enamel and dentine surfaces for 20 s using the applicator brush [25]. The homogeneous adhesive mixture was air-dried for 5 s and light irradiated for 10 s at an intensity of 1130 ± 35 mW/cm2 (determined with the NIST spectrophotometer contained within a MARC patient simulator (BlueLight Analytics Inc., Halifax, Canada)) using a ® bluephase style (Ivoclar Vivadent) light emitting diode (LED) polywave technology light curing unit (LCU) measured to be

3

operating with a spectral range of between 320–520 nm. The adhesively treated teeth were restored using a horizontal incremental technique with conventional RBCs, namely Tetric EvoCeram (Shade A3, Lot T04946: Ref. 590314WW; Ivoclar Vivadent) [26] for Group A teeth and Admira Fusion (Shade A3, Lot 1545568; Voco GmbH) [27] for Group B teeth. The horizontal incremental technique involved the placement of four horizontal increments (∼2.0 mm thickness), two each for the mesial and distal approximal boxes which crossed the mesiodistal width of the tooth and two central increments. The ® Futurabond U SingleDose adhesively treated teeth in Groups C and D were restored using bulk fill restorative materials (Group E: Tetric EvoCeram Bulk Fill (Shade IVA, Lot T02443, Ref 638244WW; Ivoclar Vivadent) [28] and Group F: Admira Fusion x-tra (Shade U, Lot 1537600; Voco GmbH) [29]). For the bulk fill restoratives, the restoration technique involved the placement of two horizontal increments (∼4.0 mm thickness) one each for the mesial and distal approximal boxes that again crossed the mesio-distal width of the tooth and one occlusal (central) increment.

2.1.

Cuspal movement

A twin channel deflection measuring gauge (Mercer 122L Twin Channel Analogue Gauge Unit, Engineering & Gauge Ltd.) employing two Mercer 490 probes (Engineering & Gauge Ltd., St. Alban’s, Hertfordshire, UK) was used to determine the cuspal movement by placing the probe receptors in contact with the buccal and palatal cusps of the third molar teeth [19]. To mimic the clinical scenario, a Tofflemire matrix band was shaped and placed around each third molar tooth prior to RBC placement. Special attention and care had to be taken when shaping the matrix band to enable the Mercer 490 probes receptors free-contact with the buccal and palatal cusps of the teeth. To enable consistency in cuspal movement determination between individual teeth and groups, all baseline cuspal movement measurements for each of the 32 third molar teeth were evaluated by placing the palatal probe receptor 2.5 mm from the cusp tip and calibrating the measurement gauge to zero. Individual RBC increments were light irradiated for 20 s with the LED LCU tip maintained ∼2 mm from the cusp tips. Following the initiation of light irradiation, buccal and palatal cuspal movement measurements were recorded up to 180 s, at time intervals of 30, 60, 90 and 180 s, since no cuspal recoil occurs beyond 180 s post light irradiation [19]. Buccal and palatal cusp movements measurements were summed and the mean total cuspal movement measurement was calculated for each tooth and for the respective groups. A one-way analyses of variance (ANOVA) with Independent Samples ttest and post-hoc Tukey’s tests were determined [30] with SPSS Statistics V22.0 software (SPSS Inc., Chicago, IL, USA) to identify statistically significant differences in mean total cuspal movement measurements between groups (p < 0.05).

2.2.

Cervical microleakage assessment

The RBC restored teeth had root apices sealed with sticky wax and all tooth surfaces were also sealed with nail varnish (Rimmel 60 Seconds, London, UK) with the exception of a 1 mm band around the margins of each restoration. Follow-

Please cite this article in press as: Politi I, et al. Modification of the restoration protocol for resin-based composite (RBC) restoratives (conventional and bulk fill) on cuspal movement and microleakage score in molar teeth. Dent Mater (2018), https://doi.org/10.1016/j.dental.2018.05.010

DENTAL-3164; No. of Pages 7

ARTICLE IN PRESS

4

d e n t a l m a t e r i a l s x x x ( 2 0 1 8 ) xxx–xxx

ing tooth sealing, thermocycling was performed between two water-baths maintained at 4 ± 1 ◦ C and 65 ± 1 ◦ C [31] where each thermal cycle involved submerging the restored teeth for 10 s in each water-bath, with a 25 s transfer between waterbaths for 500 cycles [32,33] before 24 h immersion in 0.2% basic fuchsin dye. On removal from the immersion solution the teeth were cleaned with copious amounts of high purity double distilled water, a ceramic cutting disc (Struers, Glasgow, Scotland) was employed at 125 rpm under a weight of 100 g to section the RBC restored teeth mid-sagitally in the mesio-distal direction. Cervical microleakage assessment of the sectioned restored third molar teeth was performed under a Stemi 305 stereo-microscope (Zeiss MicroImaging GmbH, Jena, Germany) at ×25 magnification. The extent of the cervical microleakage was recorded using a semi-quantitative non-parametric scale where ‘0’ was no evidence of dye penetration; ‘1’ was superficial dye penetration not beyond the amelo-dentinal junction (ADJ); ‘2’ was dye penetration along the gingival floor and up to the axial wall; ‘3’ was dye penetration along the axial wall and across the pulpal floor and ‘4’ was dye penetration into the pulp chamber [10,18–21,34–41]. To statistically analyse the cervical microleakage scores, given the semi-quantitative non-parametric scale employed, a Kruskal–Wallis test followed by paired group comparisons using Mann–Whitney U tests [30] were conducted (p < 0.05) using the SPSS software (V22.0).

3.

Results

3.1.

Cuspal movement

When tested using Levene statistics, the variances of the total cuspal movement values (Table 1) for the restored teeth in Groups A–D were homogeneous (p > 0.593). A one-way ANOVA of the mean total cuspal movement measurements highlighted statistically significant differences (p < 0.0001) between the groups tested. For the teeth restored with the conventional RBCs using the horizontal incremental placement technique (six increments), the mean total cuspal movement for Tetric EvoCeram was 6.0 (1.7) ␮m (Group A) and Admira Fusion was 6.1 (1.8) ␮m (Group B) and the values were not significantly different (p = 0.998). When the bulk fill resin restoratives were employed to restore the teeth using the horizontal incremental technique (three increments), the total cuspal movement for Tetric EvoCeram Bulk Fill Restorative was 4.0 (0.8) ␮m (Group C) and Admira Fusion x-tra was 3.9 (1.2) ␮m (Group F) and the values were not significantly different (p = 1.000). The conventional RBC materials had significantly higher mean total cuspal movement values (all p < 0.048) compared with their bulk fill resin counterpart materials when the one-way ANOVA of the mean total cuspal deflection measurements were assessed.

Fig. 1 – The cervical microleakage scores recorded for the conventional RBCs (Tetric EvoCeram and Admira Fusion) and the bulk fill restorative RBCs (Tetric EvoCeram Bulk Fill and Admira Fusion x-tra) placed using a modified RBC restoration protocol in conjunction with the 1-step bonding system are presented using a box and whisker plot (Fig. 1). Median cervical microleakage scores are indicated by the bold black line across the box, the highest and lowest cervical microleakage scores recorded are represented by the whiskers, while the box contain the inter-quartile range.

cervical microleakage score was evident between Groups A–D (p < 0.001) when the Kruskal–Wallis non-parametric test was employed. For the conventional RBCs, the Mann–Whitney U tests reported a significant increase in microleakage score (p < 0.001) for Tetric EvoCeram (Group A) compared with Admira Fusion (Group C) restored teeth. For the bulk fill restorative RBCs, a significant increase in microleakage score (p < 0.001) was evident for Tetric EvoCeram Bulk Fill (Group C) compared with the Admira Fusion x-tra (Group F) restored teeth. Additionally, the conventional RBC materials had significantly lower microleakage scores compared with their bulk fill resin counterpart materials (all p < 0.036) when the Kruskal–Wallis test followed by paired group comparisons using Mann–Whitney U tests were assessed.

4. 3.2.

Discussion

Cervical microleakage assessment

The box and whisker plot (Fig. 1) presents the cervical microleakage scores recorded for the conventional RBCs and their bulk fill resin counterpart RBCs, in conjunction with the 1-step adhesive system. Statistically significant differences in

In-vitro testing methodologies routinely employed to determine the polymerization shrinkage of RBC materials focus on shrinkage strain and/or shrinkage stress measurements during and following light irradiation [42] with the most popular techniques used being the linometer [43] and ‘bonded-disk’

Please cite this article in press as: Politi I, et al. Modification of the restoration protocol for resin-based composite (RBC) restoratives (conventional and bulk fill) on cuspal movement and microleakage score in molar teeth. Dent Mater (2018), https://doi.org/10.1016/j.dental.2018.05.010

DENTAL-3164; No. of Pages 7

ARTICLE IN PRESS 5

d e n t a l m a t e r i a l s x x x ( 2 0 1 8 ) xxx–xxx

Table 1 – Mean total cuspal movements (␮m) with associated standard deviations for the appropriate RBC investigated (at 180 s following light irradiation) using (a) the modified restoration protocol and (b) the traditional Class II restoration protocol [19], when restoring the third molar teeth (same size and morphology inclusion criteria as Ref. [19]). Groups linked with the same superscript letter are not significantly different using one-way analyses of variance and post-hoc Tukey’s tests. (a) RBC material

Number of increments

Cuspal movement (␮m)

Tetric EvoCeram Admira Fusion Tetric EvoCeram Bulk Fill Admira Fusion x-tra Bulk Fill

2,2,2 (6 in total) 2,2,2 (6 in total) 1,1,1 (3 in total) 1,1,1 (3 in total)

6.0 (1.7)a 6.1 (1.8)a 4.0 (0.8)b 3.9 (1.2)b

(b) RBC material [19]

Number of increments

Cuspal movement (␮m)

Tetric EvoCeram Admira Fusion Tetric EvoCeram Bulk Fill Admira Fusion x-tra Bulk Fill

3,3,2 (8 in total) 3,3,2 (8 in total) 1,1 (2 in total) 1,1 (2 in total)

6.1 (2.0)a 6.4 (2.8)a 3.3 (0.8)b 3.4 (0.9)b

[44] methods. However, no bench-top laboratory shrinkage testing protocol provides a prediction of clinical performance [17,45]. Clinically, Class II RBC restorations most frequently fail by marginal leakage [46] when the synergism of the tooth/RBC interface, mediated by the adhesive bond, is compromised [47,48]. In the current study, human maxillary and mandibular third molar teeth were employed, where the inclusion criteria accommodated for size variance [24] by selecting the BPW of the teeth to vary between 10.25–10.75 mm. Additionally, to reduce the morphology variances reported among third molar teeth in the literature [24], only third molar teeth with four cusps (two buccal and two lingual) were included [19]. The preparation of an extensive amalgam replacement Class II cavity in a tooth is known to result in a marked reduction in cuspal stiffness [49] owing to the loss of marginal ridge integrity [50]. In an ‘ideal world’ the RBC material would compensate for the reduction in cuspal stiffness [49] by restoring the marginal ridge integrity [50]. In the current ® study, the Futurabond DC SingleDose treated teeth (same size and morphology inclusion criteria as [19]) were restored with the conventional RBC restoration protocols being modified, namely, six RBC increments (four horizontal increments that crossed the mesio-distal width of the tooth (two each for the mesial and distal approximal boxes) and two central increments). Similarly, for the bulk fill restoratives, the RBC placement technique was modified and involved three increments, namely, one horizontal increment each for the mesial and distal approximal boxes that crossed the mesiodistal width of the tooth and one central increment. Mean total cuspal movements of 6.0 (1.7) ␮m (Group A) and 6.1 (1.8) ␮m (Group B) were achieved for the conventional RBCs and 4.0 (0.8) ␮m (Group C) and 3.9 (1.2) ␮m (Group D) for the adhesively treated teeth restored using the bulk fill restorative materials. It is noteworthy that regardless of the restoration protocol for Tetric EvoCeram and Admira Fusion RBCs (eight oblique increments for a Class II cavity [19] or four horizontal (two central) increments for the modified RBC restoration protocol) the total cuspal movements did not vary significantly (all p > 0.05) between RBC materials or restoration protocol (Table 1). Additionally, for the Tetric EvoCeram Bulk Fill and Admira Fusion x-tra restored teeth, the total cuspal move-

ments also did not vary significantly (all p > 0.05), regardless of the bulk fill restorative or the RBC restoration protocol. As a result, the hypotheses proposed that modification of the RBC restoration protocol would result in a decrease in total cuspal movement was rejected. Third molar teeth have significantly reduced ‘anatomic crown’ length and a wider surface area [24] compared with anterior dentition such that standardised Class II cavities prepared in third molar teeth have shorter and thicker cusps. The application of simple cantilever beam theory to the experimental set-up informs that deformation would be proportional to the cubed power of the cuspal length [51–53]. The possibility of cuspal movement, for standardised short and thick cusps where cuspal movement measurements were evaluated by placing the palatal probe receptor 2.5 mm from the cusp tip, between the different RBC restoration protocols would therefore perhaps not have been unexpected. However, the reduced movement for the bulk fill resin restorative RBCs over their conventional RBC counterparts for conventional Class II restoration protocol was expected since the oblique incremental restoration technique [19] involved RBC contact with a maximum of one cusp at a time with no constraints on the system [54–57]. ‘Microleakage’ as quantified in the current study provides a measurement of dye ingress (along bonded interfaces and/or dye permeation through the ‘mild self-etch’ adhesive) and is not a predictor for microbial ingress [58] owing to the semi-quantitative non-parametric scale employed. For the conventional RBCs and bulk fill resin restoratives investigated, third molar teeth restored with Admira Fusion and Admira Fusion x-tra had significantly the lowest microleakage scores (all p < 0.001) compared with Tetric EvoCeram and Tetric EvoCeram Bulk Fill restored teeth. Interestingly, the microleakage scores for the range of RBC materials tested were significantly reduced (all p < 0.001) when the modified RBC restoration protocol was employed compared with the traditional restoration technique for a Class II cavity. The poor microleakage performance of Class II cavities in third molar teeth restored with Tetric EvoCeram and Tetric EvoCeram Bulk Fill reported previously [19] was significantly improved by modifying the RBC restoration protocol. Polymerisation kinetics [59] reported

Please cite this article in press as: Politi I, et al. Modification of the restoration protocol for resin-based composite (RBC) restoratives (conventional and bulk fill) on cuspal movement and microleakage score in molar teeth. Dent Mater (2018), https://doi.org/10.1016/j.dental.2018.05.010

DENTAL-3164; No. of Pages 7

6

ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 8 ) xxx–xxx

reduced penetration on light irradiation for Tetric EvoCeram Bulk Fill compared with Admira Fusion x-tra, when employ® ing the bluephase 20i (Ivoclar Vivadent) light emitting diode (LED) polywave technology LCU. It would appear that this finding has merit given the reduced volume of RBC material necessary to be irradiated for the modified RBC restoration protocol which would account for the significant reduction in microleakage for the Tetric EvoCeram and Tetric EvoCeram Bulk Fill RBCs. While the compatibility of the adhesive system (Futurabond U SingleDose) with the Admira resin restoratives was suggested as an explanation for the increased cervical microleakage scores for Tetric EvoCeram resin restoratives previously [19], it is interesting that lower micrleakage scores are also evident for the Admira Fusion and Admira Fusion x-tra RBCs. The hypothesis that modification of the RBC restoration protocol would result in a decrease in cervical microleakage scores for all resin-based restorative materials examined was therefore accepted.

5.

Conclusion

It would appear that modification of the RBC restoration protocol of some conventional RBCs or bulk fill resin restoratives may significantly improve bond integrity and could be translated as a validation of the limited clinical studies available on bulk fill materials in the dental literature where Class II cavities perform less well than Class I cavities following five- and six-year follow-up. These results add further weight to experimental protocols employing cuspal deflection (during) and cervical microleakage (following) RBC restoration of standardised cavities in natural dentition to provide an indication of polymerization shrinkage stress at the tooth/RBC restoration interface in a ‘clinically meaningful context’.

references

[1] Roeters FJ, Opdam NJ, Loomans BA. The amalgam-free dental school. J Dent 2004;32:371–7. [2] Opdam NJ, Loomans BA, Roeters FJ, Bronkhorst EM. Five-year clinical performance of posterior resin composite restorations placed by dental students. J Dent 2004;32:379–83. [3] Burke FJT. Amalgam to tooth-coloured materials–implications for clinical practice and dental education: governmental restrictions and amalgam-usage survey results. J Dent 2004;32:343–50. [4] Lynch CD, Opdam NJ, Hickel R, Brunton PA, Gurgan S, Kakaboura A, et al. Academy of operative dentistry European section: Guidance on the use of resin composites for direct restoration of posterior teeth. J Dent 2014;42:377–83. [5] Lynch CD, Wilson NH. The teaching of posterior resin composites: planning for the future based on 25 years of research. J Dent 2014;42:645–52. [6] Lucarotti PS, Holder RL, Burke FJT. Outcome of direct restorations placed within the general dental services in England and Wales (Part 1): variation by type of restoration and re-intervention. J Dent 2005;33:805–15. [7] Moraschini V, Fai CK, Alto RM, Dos Santos GO. Amalgam and resin composite longevity of posterior restorations: a systematic review and meta-analysis. J Dent 2015;43:1043–50.

[8] Burke FJT. Patient acceptance of posterior composite restorations. Dent Update 1989;16:114–20. [9] Dilley DC, Vann Jr WF, Oldenburg TR, Crisp RM. Time required for placement of composite versus amalgam restorations. J Dent Child 1990;57:177–83. [10] Tomaszewska IM, Kearns JO, Ilie N, Fleming GJP. Bulk fill restoratives: to cap or not to cap—that is the question? J Dent 2015;43:309–16. [11] Ilie N, Keßler A, Durner J. Shining a light on high volume photocurable materials. Dent Mater 2018;34:695–710. [12] Manhart J, Chen HY, Hickel R. Clinical evaluation of the posterior composite Quixfil in class I and II cavities: 4-year follow-up of a randomized controlled trial. J Adhes Dent 2010;12:237–43. [13] van Dijken JW, Pallesen U. A randomized controlled three year evaluation of “bulk-filled” posterior resin restorations based on stress decreasing resin technology. Dent Mater 2014;30:e245–51. [14] van Dijken JW, Pallesen U. Randomized 3-year clinical evaluation of Class I and II posterior resin restorations placed with a bulk-fill resin composite and a one-step self-etching adhesive. J Adhes Dent 2015;17:81–8. [15] van Dijken JW, Pallesen U. Posterior bulk-filled resin composite restorations: a 5-year randomized controlled clinical study. J Dent 2016;51:29–35. [16] van Dijken JWV, Pallesen U. Bulk-filled posterior resin restorations based on stress-decreasing resin technology: a randomized, controlled 6-year evaluation. Eur J Oral Sci 2017;125:303–9. [17] Bouillaguet S, Gamba J, Forchelet J, Krejci I, Wataha JC. Dynamics of composite polymerization mediates the development of cuspal strain. Dent Mater 2006;22:896–902. [18] Moorthy A, Hogg CH, Dowling AH, Grufferty BF, Benetti AR, Fleming GJP. Cuspal deflection and microleakage in premolar teeth restored with bulk-fill flowable resin-based composite base materials. J Dent 2012;40:500–5. [19] McHugh LEJ, Politi I, Al-Fodeh RS, Fleming GJP. Implications of resin-based composite (RBC) restoration on cuspal deflection and microleakage score in molar teeth: placement protocol and restorative material. Dent Mater 2017;33:e329–35. [20] Kearns JO, Barry JG, Fleming GJP. Cuspal deflection and cervical microleakage scores to determine the adhesive potential of universal bonding systems. J Dent 2014;42:970–6. [21] Sultan A, Moorthy A, Fleming GJP. The adhesive potential of dentin bonding systems assessed using cuspal deflection measurements and cervical microleakage scores. Dent Mater 2014;30:1154–60. [22] Yoshida Y, Van Meerbeek B, Nakayama Y, Yoshioka M, Snauwaert J, Abe Y, et al. Adhesion to and decalcification of hydroxyapatite by carboxylic acids. J Dent Res 2001;80:1565–9. [23] Yoshioka M, Yoshida Y, Inoue S, Lambrechts P, Vanherle G, Nomura Y, et al. Adhesion/decalcification mechanisms of acid interactions with human hard tissues. J Biomed Mater Res 2002;59:56–62. [24] Fennis WMM, Kuijs RH, Kreulen CM, Roeters FJM, Creugers NHJ, Burgerdijk RCW. A survey of cusp fractures in a population of general dental practices. Int J Prosthodont 2003;15:559–63. [25] Product specification for Futurabond Universal Adhesive (Voco GmbH, Cuxhaven, Germany). [26] Product specification for Tetric EvoCeram RBC (Ivoclar Vivadent, Schaan, Lichtenstein). [27] Product specification for Admira Fusion (Voco, Cuxhaven, Germany). [28] Product specification for Tetric EvoCeram Bulk Fill (Ivoclar Vivadent, Schaan, Lichtenstein).

Please cite this article in press as: Politi I, et al. Modification of the restoration protocol for resin-based composite (RBC) restoratives (conventional and bulk fill) on cuspal movement and microleakage score in molar teeth. Dent Mater (2018), https://doi.org/10.1016/j.dental.2018.05.010

DENTAL-3164; No. of Pages 7

ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 8 ) xxx–xxx

[29] Product specification for Admira Fusion x-tra (Voco, Cuxhaven, Germany). [30] Hannigan A, Lynch CD. Statistical methodology in oral and dental research: pitfalls and recommendations. J Dent 2013;41:385–92. [31] Gale MS, Darvell BW. Thermal cycling procedures for laboratory testing of dental restorations. J Dent 1999;27:89–99. [32] ISO. Dental materials—testing of adhesion to tooth structure. Technical specification no. 11405; 2003. [33] ISO. Dental materials—guidance on testing of adhesion to tooth structure. Technical specification no. 11405; 2004. [34] Abbas G, Fleming GJP, Harrington E, Shortall ACC, Burke FJT. Cuspal movement in premolar teeth restored with a packable composite cured in bulk or incrementally. J Dent 2003;31:437–44. [35] Fleming GJP, Hall D, Shortall ACC, Burke FJT. Cuspal movement and microleakage in premolar teeth restored with posterior filling materials of varying reported volumetric shrinkage values. J Dent 2005;33:139–46. [36] Palin WM, Fleming GJP, Nathwani H, Burke FJT, Randall RC. In vitro cuspal deflection and microleakage of maxillary premolars restored with novel low-shrink dental composites. Dent Mater 2005;21:324–35. [37] Fleming GJP, Khan S, Afzal O, Palin WM, Burke FJT. Investigation of polymeristaion shrinkage strain, associated cuspal movement and microleakage of MOD cavities restored incrementally with resin-based composite using an LED light curing unit. J Dent 2007;35:97–103. [38] Fleming GJP, Cara RR, Palin WM, Burke FJT. Cuspal movement and microleakage in premolar teeth restored with resin-based filling materials cured using a ‘soft-start’ polymerisation protocol. Dent Mater 2007;23:637–43. [39] Cara RR, Fleming GJP, Palin WM, Walmsley AD, Burke FJT. Cuspal deflection and microleakage in premolar teeth restored with resin-based composites with and without an intermediary flowable layer. J Dent 2007;35:482–9. [40] El-Helali R, Dowling AH, McGinley EL, Duncan HF, Fleming GJP. Influence of resin-based composite restoration technique and endodontic access on cuspal deflection and cervical microleakage scores. J Dent 2013;41:216–22. [41] Palin WM, Hadis MA, Leprince JG, Leloup G, Boland L, Fleming GJP, et al. Reduced polymerization stress of MAPO-containing resin composites with increased curing speed, degree of conversion and mechanical properties. Dent Mater 2014;30:507–16. [42] Watts DC, Marouf AS, Al-Hindi AM. Photo-polymerization shrinkage-stress kinetics in resin-composites: methods development. Dent Mater 2003;19:1–11. [43] DeGee AJ, Feilzer AJ, Davidson CL. True linear polymerization shrinkage of unfilled resins and composites determined with a linometer. Dent Mater 1993;19:11–4. [44] Watts DC, Cash AJ. Determination of polymerization kinetics in visible-light cured materials: methods development. Dent Mater 1991;7:281–7.

7

[45] Heintze SD, Rousson V, Mahn E. Bond strength tests of dental adhesive systems and their correlation with clinical results—a meta-analysis. Dent Mater 2015;31:423–34. [46] Davidson CL, DeGee AJ, Feilzer AJ. The competition between the composite-dentin bond strength and the polymerisation contraction stress. J Dent Res 1984;63:1396–9. [47] Van Meerbeek B, Peumans M, Poitevin A, Mine A, Van Ende A, Never A, et al. Relationship between bond-strength tests and clinical outcomes. Dent Mater 2010;26:e100–21. [48] Van Meerbeek B, Yoshihara K, Yoshida Y, Mine A, De Munck J, Van Landuyt KL. State of the art of self-etch adhesives. Dent Mater 2011;27:17–28. [49] Reeh ES, Messer HH, Douglas WH. Reduction in tooth stiffness as a result of endodontic and restorative procedures. J Endod 1989;15:512–6. [50] Reeh ES, Douglas WH, Messer HH. Stiffness of endodontically-treated teeth related to restoration technique. J Dent Res 1989;68:1540–4. [51] Hood JA. Biomechanics of the intact, prepared and restored tooth: some clinical implications. Int Dent J 1991;41:25–32. [52] Lee MR, Cho BH, Son HH, Um CM, Lee IB. Influence of cavity dimension and restoration methods on the cusp deflection of premolars in composite restoration. Dent Mater 2007;23:288–95. [53] Chuang SF, Chang CH, Chen TYF. Spatially resolved assessment of composite shrinkage in MOD restorations using a digital-image-correlation technique. Dent Mater 2011;27:134–43. [54] Sakaguchi RL, Douglas WH, Peters MC. Curing light performance and polymerization of composite restorative materials. J Dent 1992;20:183–8. [55] Versluis A, Tantbirojn D, Pintado MR, DeLong R, Douglas WH. Residual shrinkage stress distributions in molars after composite restoration. Dent Mater 2004;20:554–64. [56] Versluis A, Douglas WH, Cross M, Sakaguchi RL. Does an incremental filling technique reduce polymerization shrinkage stresses? J Dent Res 1996;75:871–8. [57] Braga RR, Boaro LC, Kuroe T, Azevedo CL, Singer JM. Influence of cavity dimensions and their derivatives (volume and ‘C’ factor) on shrinkage stress development and microleakage of composite restorations. Dent Mater 2006;22:818–23. [58] Heintze SD. Systematic reviews. I. The correlation between laboratory tests on marginal quality and bond strength. II. The outcome between marginal quality and clinical outcome. J Adhes Dent 2007;9:77–106. [59] Ilie N, Fleming GJP. In vitro comparison of polymerisation kinetics and the micro-mechanical properties of low and high viscosity giomers and RBC materials. J Dent 2015;43:814–22.

Please cite this article in press as: Politi I, et al. Modification of the restoration protocol for resin-based composite (RBC) restoratives (conventional and bulk fill) on cuspal movement and microleakage score in molar teeth. Dent Mater (2018), https://doi.org/10.1016/j.dental.2018.05.010