Repair Bond Strength of Aged Silorane-based Composite Using Intermediate Adhesive Systems Based on Different Monomers Ayman M. El-Amina / Lamia E. Daifallab / Mohamed H. Zaazouc / Hussein A. F. Gomaad / Enas H. Mobarake

Purpose: To investigate the effect of pre-repair aging periods and intermediate adhesive systems based on different monomers on the repair bond strength of silorane-based resin composite. Materials and Methods: A total of 32 Filtek P90 (3M ESPE) substrate specimens (4 mm diameter and 4 mm height) were made. Substrate specimens were grouped according to the pre-repair time periods into four groups (n = 8/group): 15 to 30 min, 24 h, 1 month, and 3 months. All substrate specimens were ground flat using a diamond stone and were etched using Scotchbond phosphoric acid etchant (3M ESPE). The specimens of each pre-repair time period were equally distributed among the two repair groups, using either silorane-based (P90 System Adhesive) or acrylamide-based (AdheSE One F, Ivoclar Vivadent) intermediate adhesive systems. Specimens of P90 System adhesive received Filtek P90 as the repair resin composite, and Tetric N-Ceram (Ivoclar Vivadent) was used with AdheSE One F specimens. Additional specimens were made from the repair resin composite materials to study the cohesive strength. Specimens were sliced into sticks (0.6 ± 0.01 mm2) for microtensile bond strength testing (μTBS). Modes of failure were determined. Results: Two-way ANOVA with repeated measures revealed no significant effect for the pre-repair aging periods, intermediate adhesive systems based on different monomers, or their interaction on repair bond strength of silorane-based resin composite. Conclusion: Up to 3 months of pre-aging the repaired silorane-based resin composite had no negative effect on its repair bond strength, even when an intermediate adhesive system based on a different monomer (acrylamide) was used. Keywords: adhesive systems, microtensile bond strength, pre-repair aging, repair, silorane-based resin composite. J Adhes Dent 2015; 17: 163–168. doi: 10.3290/j.jad.a33971


olymerization shrinkage of resin composite restorative materials still remains one of the major limitations that affects the longevity of such materials.4,16


Associate Lecturer, Restorative Dentistry Department, Oral and Dental Research Division, National Research Center, Cairo, Egypt. Performed the main practical part of the experiment.


Lecturer, Restorative Dentistry Department, Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt. Conducted the study, wrote the manuscript.


Associate Professor, Restorative Dentistry Department, Oral and Dental Research Division, National Research Center, Cairo, Egypt. Proofread the manuscript.


Professor, Restorative Dentistry Department, Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt. Proofread the manuscript.


Professor, Restorative Dentistry Department, Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt. Idea, hypothesis, experimental design, constructed the molds, contributed substantially to discussion, proofread the manuscript.

Correspondence: Professor Enas H. Mobarak, Cairo University, PO Box 12311, 14 ElZahra St, Dokki, Giza, Egypt. Tel: +20-22-2206-6203 or +20-0147-069-439, Fax: +20-22-3338-5775. e-mail: [email protected]

Vol 17, No 2, 2015

Submitted for publication: 14.01.14; accepted for publication: 18.02.15

In 2007, as an attempt to decrease the polymerization shrinkage of resin composite restorations, new cationic ring-opening silorane-based monomer systems were introduced.13 However, instances of their failure have also been found in clinical practice. Consistent with the philosophy of minimum Intervention,42 repair of failed restorations is a more conservative alternative than total replacement, especially when the tooth/restoration interface is free of staining or secondary caries.17 However, the repair procedure can compromise the strength of the restoration.35 Additionally, resin composite restorations routinely undergo a kind of biodegradation after being exposed to complex oral environmental factors, which may also jeopardize the repair bond strength.37 Many studies have addressed the repair of resin composite restorations in order to establish efficient and durable interfacial bonds between fresh and aged restorations. These repair modalities include both chemical and mechanical methods.26,31,40 Hydrofluoric or phosphoric acid31 were used for chemical conditioning. Silane9 and adhesive appli163

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cation35 were found to enhance surface wetting and chemical bonding.35,41 Surface grinding with diamond burs,26 silicon paper, carborundum stones,5 finishing disks,9 sandblasting,5,6 and air abrasion with silica or alumina3 have also been tested. None of these surface treatments can be universally recommended as an applicable repair technique for the different sorts of composites.15 Accordingly, regardless of the repair protocol used, adequate interfacial bonding between pre-existing and fresh resin composite restorations is required for successful repair. It is also important to guarantee the compatibility between the substrate and repair materials, especially if their monomer compositions differ. At the same time, a variety of single-step self-etching adhesive systems with modified monomers were also introduced on the market, aiming to enhance the bonding effectiveness and durability.22 A unique advantage of these bis-acrylamide–based self-etching adhesives is their hydrolytic stability33 because of the lower reactivity of the carbonyl group. In addition, they exhibit high purity as well as exceptional solubility in liquids with different polarity.21 Bis-acrylamide–based adhesives showed a similar reactivity when compared to dimethacrylates and can therefore be used in water-based self-etching adhesives instead of the conventional dimethacrylate products.33 However, no study to date has been done to examine the possible efficacy of self-etching adhesive systems with modified monomers in the repair of silorane-based resin composite. The null hypothesis was that there is no difference in the repair bond strength of the fresh or pre-aged silorane-based composite regardless of whether a silorane- or acrylamide-monomer–based intermediate adhesive system was used for repair.

MATERIALS AND METHODS Two resin composite restorative materials as well as two intermediate adhesive systems were used in the present study. Their brand names, manufacturers, description, chemical composition, mode of application, and batch numbers are listed in Table 1. Preparation of Substrate Specimens A total of 32 specimens were made from Filtek P90 resin composite using a specially constructed split Teflon mold (substrate mold). The mold (30 mm in diameter and 4 mm in thickness) was enclosed in a metal ring, and it had a central 4-mm-diameter hole in which the substrate resin composite was packed using a plastic instrument (Carl Martin; Solingen, Germany). The substrate mold was placed on top of a celluloid strip matrix (Dental Technologies; Lincoln Wood, IL, USA) on a glass slab. Another celluloid strip (50 μm thickness) and a glass slab were pressed onto the top surface of the substrate specimen. The glass slab was then removed and each specimen was light cured from the top and the bottom surfaces using an LED light-curing unit (Blue Phase C5, Ivoclar Vivadent; Schaan, Lechtenstein) for 40 s. Afterwards, the specimen was removed from 164

the mold and cured from both sides for another 40 s. During the whole procedure, the light intensity of the curing unit was verified to be ≥ 500 mw/cm2 using a radiometer (Kerr Dental Specialties; Orange, CA, USA). The remaining fine flashes were carefully removed using a sharp lancet (Wuxi Xinda; Shanghai, China). A magnifying lens was used to check specimens for any defects, which led to them being discarded and replaced. The bottom of each specimen was marked with either a black or red indelible marker (Sharpie; Oak Brook, IL, USA) for the repair resin composite buildup materials Filtek P90 and Tetric N-Ceram, respectively. Specimens were then stored in artificial saliva28 for the proposed pre-repair time periods (n = 8) of 15 to 30 min, 24 h, 1 month or 3 months at 37ºC in a thermal incubator. The artificial saliva was replaced weekly.19 Surface Treatment of Substrate Specimens Each specimen was removed from the artificial saliva and thoroughly rinsed for 30 s, then blotted dry with a tissue. The surface of each specimen was ground flat using a diamond wheel stone. Each specimen height was checked using a digital caliper (Mitutoyo; Kawasaki, Japan) to ensure that only 150 to 200 μm was removed. The specimens were then washed for 30 s and blotted dry. Then, the surface was etched using Scotchbond phosphoric acid etchant (3M ESPE; St Paul, MN, USA) for 30 s, rinsed for 15 s, and dried with air for 5 s from a distance of 1 cm. Application of Repair Restorative Materials Each treated substrate specimen was placed in the repair mold while performing the repair procedures. The repair mold was composed of a polyvinylchloride (PVC) tube enclosing three split Teflon disks. The base disk (20 mm external diameter, 3.5 mm thick) had a hole with an internal diameter of 4 mm to hold the substrate specimen during adhesive system application. The substrate specimens of each pre-repair time period received silorane-based (P90 System Adhesive, 3M ESPE; Seefeld, Germany) or acrylamide-based (AdheSE One F, Ivoclar Vivadent; Schaan, Liechtenstein) intermediate adhesives prior to the application of the respective resin composite buildup material, Filtek P90 resin composite (3M ESPE; St Paul, MN, USA) or Tetric N-Ceram (Ivoclar Vivadent). Each intermediate adhesive system was applied and light cured according to the manufacturer’s instructions (Table 1). Then, the repair material was built up in two increments (1 mm and 2 mm) using the other two split Teflon disks (Fig 1) placed on top of the base disk. A Teflon pusher was designed to ease the removal of the repaired specimen out of the disk. Specimens were stored in artificial saliva for 24 h before being prepared for microtensile bond strength testing. For studying the cohesive behavior of both resin composite materials, additional specimens were made to serve as controls. Disks (n = 8/group) from the same materials (Filtek P90 and Tetric N-Ceram) were prepared with the same dimensions (4 mm diameter and 7 mm height) and pre-aged in a similar manner to those designed for microtensile repair bond strength testing. The Journal of Adhesive Dentistry

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Table 1 Material brand names/manufacturers, description/chemical composition, application mode, batch numbers Brand name/ Description/chemical composition manufacturer

Application mode

Batch #

Filtek P90 Visible light-activated low shrinkage microhybrid silorane(3M ESPE; St based resin composite containing: Paul, MN, USA) Organic resin: Silorane ECHCPMS, camphorquinone, stabilizers and pigments; Inorganic fillers: Silanized quartz, yttrium fluoride (76 wt%) with average particle size of 0.47 μm.

40-s light curing of one increment (4 mm thickness) for the substrate material. 40-s light curing of two increments (1st 1 mm thick, 2nd 2 mm thick) for the repair material.


Tetric N-Ceram (Ivoclar Vivadent; Schaan, Liechtenstein)

Visible light-activated nanohybrid methacrylate-based resin composite containing: Matrix (19 to 20 wt%): bis-GMA, UDMA, TEG-DMA, bis-EMA; Fillers: Barium glass, ytterbium trifluoride, mixed oxide and copolymers (80 to 81 wt%, mean particle size 0.7 μm); Additional contents: additives, catalysts, stabilizers, pigments (< 1 wt%).

40-s light curing of two increments (1st 1 mm thick, 2nd 2mm thick) for the repair material.


P90 System Adhesive (3M ESPE; Seefeld, Germany)

Two-step self-etching adhesive system. Primer: phosphoric acid methacryloxy-hexylester mixture, 1,6 hexanedioldimethacylate, copolymer of acrylic and itaconic acid, phosphine oxide, (dimethylamino) ethyl methacrylate, bis-GMA, HEMA, water, ethanol, silane-treated silica filler with primary particle size ca 7 nm; fillers 8 to 12 wt%, camphorquinone. Bond: TEG-DMA, phosphoric acid methacryloxyhexylesters, 1,6-hexanediol dimethacylate, camphorquinone, silanetreated silica fillers (fillers 5 to 10 wt%).

Primer: Shake bottle briefly, apply with microbrush on the substrate surface, rub for 15 s, disperse gently with air for 15 s, light cure for 10 s.


AdheSE One F (Ivoclar Vivadent)

Self-etching, light-curing, nano-filled, single-component adhesive with fluoride release, containing derivatives of bisacrylamide, water, alcohol, bis-methacryl amide dihydrogen phosphate, amino acid acrylamide, hydroxyl alkyl methacrylamides, alkyl sulphonic acid acrylamide, silicon dioxide, initiators, stabilizers, potassium fluoride.

Scotchbond Etchant gel: 35% phosphoric acid by weight, 60% water, 5% (3M ESPE; St synthetic amorphous silica as thickening agent. Paul, MN, USA)

8AY Bond: Agitate bottle, apply the adhesive with a microbrush, gently disperse with air for 10 s, light cure for 10 s. Remove the VivaPen cap and snap on the brush cannula until the yellow color of the bond becomes visible on the brush. Apply until the entire surface is thoroughly coated. Brush the bonding agent for 30 s, disperse excess with a strong stream of air for 10 s until a glossy immobile liquid film is evident. Light cure for 10 s.


Apply for 15 s, rinse with oil-free air-water syringe for 15 s, dry with air for 5 s.


ECHCPMS: bis-3,4-epoxycyclohexylethyl-phenyl-methylsilane; HEMA: 2-hydroxyethyl-methacrylate; bis-GMA: bisphenol-A-glycidyl-dimethacrylate; TEG-DMA: triethylene glycol dimethacrylate; bis-EMA: bisphenol A-ethoxylated dimethacrylate.

Microtensile Bond Strength Assessment Each specimen was fixed to the cutting machine (Isomet low-speed saw; Lake Bluff, IL, USA) to be serially sectioned into multiple beam-shaped sticks. The crosssectional area (0.6 mm2 ± 0.01 mm) was confirmed with a digital caliper (Mitutoyo). From each specimen (control or repaired), six sticks were tested. For microtensile bond strength measurement, each stick was fixed vertically on a specially designed attachment jig20 using a cyanoacrylate adhesive (Rocket, Dental Ventures of America; Corona, CA, USA). The attachment was mounted on a computer-controlled universal testing machine (Model LRX, Lloyd Instruments; Fareham, UK) stressed in tension at a crosshead speed of 0.5 mm/min until failure. The results were recorded from the machine’s computer software (Nexygen-MT, Lloyd Instruments). The maximum load required for debonding was recorded in Newtons (N) and converted to MPa by dividing it by the bonded cross sectional area of the material in mm2. Vol 17, No 2, 2015

Fig 1 The split Teflon mold used for the application of repair materials.

Statistical Analysis Two-way ANOVA with repeated measures was used to statistically test the effect of the pre-repair aging periods and the intermediate adhesive systems based on different monomers as well as their interaction on the recorded repair bond strength values of silorane-based resin composite. One-way ANOVA was used to test the 165

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Table 2 periods

Mean (SD) microtensile strength in MPa of the control and repaired groups over different pre-repair aging

Pre-repair aging period

15 to 30 min 24 h 1 month 3 months

Tested groups


P90 System Adhesive repair group

AdheSE One F repair group

Cohesive strength, Filtek P90

Cohesive strength, Tetric N-Ceram

35.1 (10.5)a

32.2 (10.5)a

51.6 (12.9)b

54.0 (16.1)b

Repair Bond Strength of Aged Silorane-based Composite Using Intermediate Adhesive Systems Based on Different Monomers.

To investigate the effect of pre-repair aging periods and intermediate adhesive systems based on different monomers on the repair bond strength of sil...
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