|Year : 2016 | Volume
| Issue : 1 | Page : 17-22
Two-year clinical performance of four adhesive strategies
Salah Hasab Mahmoud1, Tamer Mohamed Elshehawy2, Naglaa Rizk Elkholany1, Essam Elsaad Al-wakeel3
1 Department of Operative Dentistry, Faculty of Dentistry, Mansoura University, Mansoura, Egypt
2 Department of Operative Dentistry; Department of Biomaterials, Faculty of Dentistry, Mansoura University, Mansoura, Egypt
3 Department of Biomaterials, Faculty of Dentistry, Mansoura University, Mansoura, Egypt
|Date of Web Publication||12-Apr-2016|
Tamer Mohamed Elshehawy
Department of Operative Dentistry; Department of Biomaterials, Faculty of Dentistry, Mansoura University, Mansoura
Source of Support: None, Conflict of Interest: None
Objective: To assess the clinical performance of four adhesive strategies; 3-step etch-and-rinse Adper Scotchbond Multi-Purpose (SM), 2-step etch-and-rinse (Adper Single Bond-2 [S2]), 2-step self-etch Adper Scotchbond SE (SE) and 1-step self-etch (Adper Single Bond Universal [SU]). Materials and Methods: Eighty cervical cavities exhibiting dentin carious lesions were used. Four adhesives from the same manufacturer (3M ESPE, St. Paul, MN, USA) representing different bonding strategies were used; SM (3-step etch-and-rinse), Adper S2 (2-step etch-and-rinse), SE (2-step self-etch) and SU (1-step self-etch). Cavities were restored with a nanohybrid composite resin (Z-350XT - 3M ESPE, St. Paul, MN, USA), and clinically followed up for 24 months using the modified United States Public Health Service criteria. Results: The outcome of Wilcoxon signed rank test showed no significant difference among the groups for each adhesive material at different evaluation periods (P > 0.05). Furthermore, the Friedman test revealed that there was no significant difference between all materials in all evaluation criteria, except for marginal discoloration at 24-month evaluation period. At 24-month evaluation period, teeth restored with self-etch adhesives showed more marginal staining. Conclusions: The four bonding strategies used in the current study showed an acceptable 2-year clinical performance.
Keywords: Adhesive, clinical, etch-and-rinse, self-etch
|How to cite this article:|
Mahmoud SH, Elshehawy TM, Elkholany NR, Al-wakeel EE. Two-year clinical performance of four adhesive strategies. J Dent Res Rev 2016;3:17-22
|How to cite this URL:|
Mahmoud SH, Elshehawy TM, Elkholany NR, Al-wakeel EE. Two-year clinical performance of four adhesive strategies. J Dent Res Rev [serial online] 2016 [cited 2020 Jun 5];3:17-22. Available from: http://www.jdrr.org/text.asp?2016/3/1/17/180111
| Introduction|| |
The first successful attempt for bonding resin adhesives to enamel was performed by Buonocore in 1955.  Enamel adhesion considered a nonproblematic process due to the homogenisity of its structure, it composed of 95 wt% inorganic structure; mainly hydroxyapatite (HAp). However, bonding to dentin was more challenging due to its heterogeneous structure and high water content.  Dentinal tubules fluid represents another challenge for dentin-adhesion. Moreover, the smear layer and smear plug can act as obstacles to prevent resin infiltration into dentin. ,,
According to recent minimally invasive concepts, caries excavation must be restricted to caries-infected dentin, whereas caries-affected dentin should be preserved.  Bonding to dentin is a technique sensitive procedure that often has multiple clinical steps. Hence, the creation of successful tooth-colored restorations mainly depends on the correct application of adhesives following their manufacturers' instructions.  Many attempts have been made to simplify the bonding procedures, for example, combining primer and adhesive into one bottle (2-step etch-and-rinse adhesives), as well as, using of acidic primers in self-etch adhesives to replace the traditional etching step.
The current 2-step adhesives are classified into two groups. The first group referred to as 2-step etch-and-rinse adhesives, in which the primer and adhesive are provided in the same bottle. Etching the dentin with phosphoric acid gels should precede the application of these adhesives. The second group is the 2-step self-etch adhesives, where acidulated primers are used to etch the dentin surface, and then a separate bonding agent is applied. To simplify the clinical application procedure and save time, 1-step self-etch adhesives were introduced. This bonding agent category contains all the adhesive components in one bottle. Thus it is referred to as an "all-in-one" system. ,,,
This study evaluated the clinical performance of a nanohybrid resin composite bonded with four different adhesive strategies (3-step etch-and-rinse, 2-step etch-and-rinse, 2-step self-etch, and 1-step self-etch) to carious cervical lesions. This study was designed to test the null hypothesis that there are no differences in the clinical performance of nanohybrid resin composite restorations bonded with the above-mentioned adhesive strategies when applied to carious cervical cavities.
| Materials and Methods|| |
Four commercially available brands of adhesive systems from the same manufacturer (3M ESPE, St. Paul, MN, USA) representing four different adhesive strategies were used. The materials used in this study are listed in [Table 1].
Adult patients attending the Dental Clinic at Faculty of Dentistry, Mansoura University who needed, at least, one tooth Class V restoration were asked to participate in the follow-up. Female patients who were pregnant or nursing were excluded. All patients were informed of the background of the study, which was approved by the Ethics Committee of the University of Mansoura. Only those who demonstrated good oral hygiene and complete normal occlusion were selected to join this study. Reasons for placement the restorations were primary carious lesions. Fifty-six patients participated, 18 men and 38 women with a mean age of thirty. All selected patients were received oral hygiene instructions before operative treatment. The selected patients had no complaints or just slight pain with cold. Only carious lesions that confined to the cervical third of the crown and do not need underlying liner were selected. Randomization had done by the order of patient attendance, which means that there was no bias in selecting a certain patient to a certain group.
The prepared cavities were divided into four equal groups from (n = 20). The restoration protocol was summarized in [Table 2]. Each cavity was prepared using a round diamond bur (Komet Brasseler GMbH and Co. KG, Lemgo, Germany). The parallelism between occlusal and gingival surfaces was done by fissure bur to avoid any mean of macro-mechanical retention. The occlusal enamel margin of the cavity was beveled by a flame-shaped diamond point from the same bur manufacture. Under rubber dam isolation each adhesive was applied following the manufacturers' instructions as follow:
Adper Scotchbond Multi-Purpose (SM); dentin surface was etched with phosphoric acid gel for 15 s, rinsed for 15 s and air-dried. A layer of primer was applied on the etched surface and gently air-dried for 5 s, then adhesive was applied and light-cured for 10 s using a light emitting diode (LEDition, Ivoclar Vivadent, Germany) with a curing light output of 600 mW/cm. 
Adper Single Bond-2; the primer/adhesive layer was applied on the etched enamel and dentin surface with agitation for 10 s then light-cured for 10 s.
Adper Scotchbond SE (SE); the self-etching primer, provided in a separate bottle, was applied on the surface then a layer of adhesive were applied, air-dried for 10 s and cured for 10 s. An additional coat of the adhesives was applied, air dried again then light-cured for 10 s.
Single Bond Universal (SU); the all in one adhesive was applied with agitation for 10 s, air-dried for 2 s then light-cured for 10 s.
The prepared cavities were restored with a resin composite (Z-350 XT) in two increments and light-cured for 40 s for each increment. Each restoration was finished with a tapered-shape finishing stone then polished using Sof-lex disc system (3M ESPE, St. Paul, MN, USA).
Clinical evaluation procedures
Each restoration was clinically evaluated immediately after placement of resin restoration (baseline). Furthermore, it was followed-up for 6, 12, and 24 months by two independent examiners. A kappa test was performed to ensure inter-examiner reliability. Restorations were evaluated using modified United States Public Health Service criteria for retention, marginal discoloration (interfacial staining), recurrent caries, and marginal adaptation/integrity, in addition to postoperative sensitivity [Table 3].
|Table 3: Modified United States Public Health Service criteria for the direct clinical evaluation of the restorations|
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The data were collected and statistically analyzed using SPSS software program (SPSS version 22, IBM, Chicago, IL, USA). Wilcoxon signed rank test was used to compare the results of each material with its baseline results. Friedman test was used for comparing the different study groups. The level of significance was set at P = 0.05.
| Results|| |
There was no missed case in the study. The outcome of the clinical evaluation is shown in [Table 4]. The outcome of the Wilcoxon signed rank test showed no significant difference within the same adhesive group at different evaluation periods (P > 0.05).
|Table 4: The results of clinical evaluation of the four used strategies at different time intervals|
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The clinical evaluation in this study includes the following aspects; retention, marginal discoloration, recurrent caries, marginal adaptation, and postoperative sensitivity. The results of Friedman test showed that all restorations were retained after 24 months. Furthermore, there was no significant difference in marginal discoloration of restorations among the different time intervals within the same group (P > 0.05). Although SE results showed a little deviation from the baseline, this change failed to be statistically different (Wilcoxon signed rank test). However, there was a significant difference of marginal discoloration between all groups at 24 months (P < 0.05); at 24-month evaluation period, teeth restored with self-etch adhesives showed more marginal staining. The results showed that there was no recurrent caries at 24 months. Furthermore, there was no significant difference in marginal adaptation among different time intervals and restorative material (P > 0.05). Only eight restorations exhibited postoperative sensitivity (four restorations with SM, two with SE and two with SU). The sensitivity disappeared within few days.
| Discussion|| |
Laboratory tests such as; tensile or shear bond strength and microleakage tests were designed to evaluate the performance of adhesives under occlusal loading to simulate the "real" condition. However, due to the variability and lack of standardization among these studies, it is difficult to generalize their conclusions.  Furthermore, most of these studies were conducted in "ideal" laboratory conditions, which do not simulate the multi-factorial clinical scenario. Therefore, the clinical follow-up remains the ultimate proof of effectiveness. ,
Cervical cavities were used, in this study, as they considered the gold standard cavities to test clinical effectiveness of adhesives. This is attributed to the absence of the macro-mechanical undercuts. Furthermore, they are widely available, more accessible as they usually found in anterior teeth or premolars. , It has been reported that bonding to sclerotic dentin (which is mainly associated with noncarious lesions) is less reliable compared with young 'sound' dentin. 
Yoshiyama et al.  showed that the microtensile bond strength of dentin adhesive to the cervical sclerotic dentin was significantly lower than that of sound dentin. Moreover, the hybrid layer is thinner in sclerotic dentin compared with sound dentin. , This is due to the inability of acid conditioners to demineralize the more mineralized sclerotic dentin.  Conversely, caries-affected dentin exhibits a different ultra-morphological structure in comparison with caries-infected dentin; apposition of peri-tubular dentin, precipitation of mineral crystals (whitlockite) in the tubules, as well as, marked reduction in dentin permeability. The mode of adhesion to sclerotic dentin is like to that of etched enamel, based on the creation of a highly energetic surface together with an increased bonding area and surface roughness, and not on resin-impregnation of the intertubular dentin. The removal of the outer surface of the sclerotic dentin by roughening with a diamond bur has been recommended to create a better and homogeneous hybrid layer.  So, in this study carious cervical lesion was used to facilitate the procedures and ensure better prognosis from one side and from the other side to deal with caries, noticing the effect of bacteria and the different histological layer of caries.
According to the ADA guidelines, the acceptable retention rates after 2 years must be <5% to be accepted.  The four adhesives in this study fulfilled these guidelines. The null hypothesis of the current study was accepted as the 24-month retention rate of the four different adhesive strategies showed no significant difference at any recall time. This may be attributed to the presence of 10-mehacryloxy decyl dihydrogenphosphate (10-MDP) monomer present in SU "multi-mode adhesive," which played a great role in the stability of the adhesive/dentin interface. MDP can chemically bond to HAp crystals of dentin. The MDP monomer bonds to the Ca 2+ ions of HAp crystals via the formation of electrostatic inter-action ionic bonds. The continuation of this reaction leads to the deposition of successive coats (nearly 4 nm thick) of MDP-Ca salts on the outer surface of HAp. This process was referred to as (nano-layering). Furthermore, the phosphate group of MDP can bond to the phosphate group of HAp via covalent bonds. These nano-coats are acid/base resistant, thus, it can decrease the solubility of HAp against the acidic attacks from pathogenic oral biofilms.  Moreover, it was established that long-term follow-up of both etch-and-rinse adhesives and self-etch ones exhibited satisfactory clinical success in spite of the differences of hybrid layer thickness. ,,
Among contemporary adhesives, self-etch adhesives have become popular, especially because of their user-friendliness and short application time.  SU similar to many other 1-step self-etch adhesives, contains phosphoric acid ester methacrylates as functional monomers. Whereas SE is a "strong" self-etch adhesive with a pH = 1, SU is considered an "ultra-mild" self-etch adhesive because its pH is relatively high pH > 2. This high pH may explain the significant deterioration of marginal adaptation from baseline to 18-month for SU. Self-etch adhesives do not etch enamel to the same depth as phosphoric acid.  Both SE and SU self-etch adhesives in this study resulted in a significant increase in staining around enamel margins from baseline to 24-month. This was in a agreement with several previous studies which explained the presence of the interfacial staining by a poor ability of self-etch adhesives to etch the dentin surface, , even though with using "strong" self-etch adhesives (pH = 1), such as SE. 
One of the drawbacks of the acidic monomers in self-etch adhesives is their instability in water.  SE is not a conventional 2-step self-etch adhesive, its two separate bottles and technique of application prevent water from remaining inside the dentin-resin interface. In this study, the quality of the enamel margins, specifically interfacial staining, decreased significantly for the two self-etch adhesives at 18-month. In spite of the presence of interfacial staining, the two self-etch adhesives resulted in similar retention rates compared with the two etch-and-rinse adhesives.
Marginal adaptation of resin composite restoration is dependent on several factors including polymerization shrinkage, hygroscopic properties, bonding between restoration material and the cavity walls, the coefficient of thermal expansion of the material and the finishing methods. Bonding of resin-based composite to dentin is mainly based on micromechanical retention (formation of intratubular resin tags with anastomoses between the tubules) and on the formation of a hybrid layer or "resin-dentin interdiffusion zone" which is an admixture of demineralized collagen with the monomers of the primer and the adhesive. ,
Postoperative sensitivity has been attributed to several factors including; operative trauma, dentin etching, desiccation, leakage, and bacterial penetration to the pulp. Obliteration of the exposed dentin tubules by a dental adhesive should eliminate possible thermal and mechanical oral stimuli.  The absence of postoperative sensitivity at 24-month in this study was related to using sharp cutting bur under abundant irrigation with cold water spray, careful drying of the cavity, and incremental placement of dental composite resin. In addition, the restorations made in this study were in shallow and medium depth-cavities showed significantly lower postoperative sensitivity than those made in deep cavities.
The outcome of this study was in full agreement Perdigão et al.  who reported that, although 18-month retention was similar for the different adhesion strategies, enamel marginal deficiencies were more prevalent for the self-etch adhesives. Furthermore, it agreed with the studies by Swift et al.  and Abdalla and Garcia-Godoy  who concluded that there were no significant differences between different adhesives used. The only manifested difference was in margin adaptation and interfacial staining.
Conversely, the result of this study disagreed with the study by Tuncer et al.  who concluded that, cervical restorations placed with an etch-and-rinse adhesive showed higher retention than SE self-etch adhesive. Furthermore, Kim et al.  who concluded that, 3-step etch-and-rinse adhesive was found to have significantly superior marginal adaptation compared with 1-step self-etch adhesive. This disagreement may be due to the difference in the follow-up period, the number of cases and different adhesives composition.
One of the limitations of this clinical investigation is that 24 months that may be a short period for substantial changes to become noticeable regarding the clinical performance of dentin adhesives. More long-term randomized clinical trials are needed to reflect the differences among the four adhesion strategies evaluated in this study.
| Conclusions|| |
Based on the results and within the limitations of this study, it was concluded that there was no significant effect of time on the clinical performance of adhesives used in the current study.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]