Shear Bond Strength, Bonding Time and Adhesive Remnant Index of Adhesive Precoated Flash Free Adhesive System vs Conventional Adhesive System using Metal Brackets: An In-vitro Study
Correspondence Address :
Hrishikesh Madan Borgikar,
Haripriya, Vidyanagar, Jath. Sangli, Maharashtra, India.
E-mail: borgikarhrishikesh@gmail.com
Introduction: With advances in materials for bonding in orthodontics, errors regarding amount of adhesive to be used can be controlled. Adhesive Precoated (APC™) Brackets were introduced to reduce the step of applying conventional adhesive on base of the bracket. Moreover, APC™ Flash Free Adhesive System (FFAS) eliminated the step of removing excessive adhesive around the brackets.
Aim: To compare Shear Bond Strength (SBS), Bonding Time (BT) and Adhesive Remnant Index (ARI) between Conventional Adhesive System (CAS) and APC™ FFAS using metal brackets.
Materials and Methods: This in-vitro study was carried out in the Department of Orthodontics and Dentofacial Orthopaedics at Bharati Vidyapeeth (Deemed to be University) Dental College and Hospital, Sangli, Maharashtra, India. A total of 78 teeth with metal braces were split into two groups, with 39 samples each receiving treatment with the CAS and the APCTM FFAS. Shear bond forces were applied to each sample using a universal testing machine and recorded in Megapascals (MPa) to provide an indication of SBS. Both Groups’ BT was quantified in terms of seconds. The stereomicroscope indexes of Artun J and Bergland S were used to determine ARI. Microsoft Excel was used for data entry, while Statistical Package for Social Sciences (SPSS) version 24.0 was used for analysis. The normality of the data was tested using two different t-tests. Descriptive statistics were represented in terms of mean and standard deviation. A significant level of 0.05 was used.
Results: The SBS values were 10.35±3.55 MPa and 11.23±3.82 MPa in CAS and FFAS respectively. No significant difference was found among the two groups (p≤0.29) in SBS. BT was significantly (p≤0.001) less in FFAS (95.54±8.72 seconds) compared to CAS (140.85±16.62 seconds). ARI was significantly (p≤0.002) less in FFAS (1.79±0.80) in comparison with CAS (1.23±0.74).
Conclusion: FFAS brackets perform better in comparison to CAS in case of BT and ARI. Both groups show no significant difference in SBS.
Excess adhesive, Orthodontic bracket, Stereomicroscopy
In order to achieve successful orthodontic bonding, it is necessary to take into account the tooth’s surface, including its morphology and enamel preparation, the base of the individual orthodontic attachment, including its mechanical and material properties, and the bonding material, including its good SBS and material composition. The orthodontist has several different cements and resins from which to select (1).
Basic steps in direct bonding are enamel conditioning, priming the tooth surface and bonding the attachment. The bonding step consists of transfer of the bracket, positioning, fitting, removal of excess adhesive and curing. Introduction of Acid-etch technique in 1951 to bond dental restorations to teeth was an important step in history of orthodontic bonding (2). When directly bonding brackets, most orthodontists utilise either a precoated bracket system in which the base of the bracket already has orthodontic glue applied to it, or they manually apply orthodontic adhesive to the base of the bracket. Excess glue surrounding the bracket, which physicians sometimes fail to remove entirely (3) after insertion, is a prime location for the development of mature plaque (4),(5),(6).
A little amount of adhesive around the bracket surface area is still required to guarantee that the glue will be buttered into the bracket backing during the fitting process, even if surplus adhesive (Flash) has to be removed after bracket insertion (7). The innovative APCTM FFAS from 3MTM Unitek (Monrovia, Calif.) eliminates the requirement for flash removal during bracket placement or composite curing. The success of a bond depends heavily on the etching technique used, the adhesive’s mechanical qualities, and the clinician’s expertise. SBS values between 6 and 10 MPa are necessary for strong adhesion (8). Etching time, priming time, and curing time following bracket placement make up BT. ARI was used to measure the quantity of adhesive still present on enamel after debonding, as reported by Artun J and Bergland S (9). Ceramic brackets have been the primary focus of FFAS research in previous studies (10),(11),(12),(13). Only SBS, ARI, and/or BT have been evaluated independently using FFAS in metal brackets (14). This research set out to compare FFAS with CAS in metal brackets with regards to SBS, BT, and ARI.
This in-vitro study was carried out in the Department of Orthodontics and Dentofacial Orthopaedics at Bharati Vidyapeeth (Deemed to be University) Dental College and Hospital, Sangli, Maharashtra, India. On December 13, 2019, the Institutional Ethical Committee approved the study {Letter no. BV(DU)MC&H/IEC/Sangli/Dissertation2019-20/D-33}. Study was delayed because of COVID-19 pandemic. The procedure of study was followed in conformity with the Institute’s ethical standards from September 2020 to March 2021.
Teeth were obtained from a patient undergoing extraction at the Dental College and Hospital of the Bharati Vidyapeeth (Deemed to be University), Sangli, Maharashtra, India. Those utilising the 3MTM Unitek TransbondTM XT CAS for their 3MTM Unitek Victory Series low profile metal brackets served as the control group, while those using the 3MTM Unitek APCTM FFAS served as the experimental group.
Inclusion criteria: Newly extracted human premolars with intact and non carious buccal enamel surface.
Exclusion criteria: Pretreated teeth with bleaching, flurosis, restored teeth, teeth with cracks and previously orthodontically treated teeth.
Sample size calculation: Based on an alpha significance level of 0.05 and power of 80%, 78 samples were assessed according to Grünheid T and Larson BE (15). This in-vitro study was done using 39 human premolars in each group.
Study Procedure
The teeth were thoroughly cleansed of any remaining tissue tags. When the tooth’s root was firmly lodged, each tooth was placed vertically in self-cure orthodontic acrylic blocks. Oil, fluoride-free fine pumice, water, and a slow-speed handpiece were used to clean and polish the teeth’s buccal surfaces before being rinsed and dried. Bonding procedure was done in four steps. Etching was done using 37% orthophosphoric acid for 15 seconds. Etched surface was painted with with 3M™ Unitek Transbond™ XT primer.
In the CAS group, a 3MTM Victory series low profile bracket system was coated with TransbondTM XT light cure adhesive paste (3MTM Unitek) and then selected at random. After applying a steady force to bond the bracket to the tooth, any extra adhesive glue or flash was scraped off with an explorer, as seen in (Table/Fig 1). The APCTM Flash-Free Adhesive Coated Bracket was removed from its container and placed on the tooth in the FFAS group, as illustrated in (Table/Fig 2). Light-emitting Diodes (LED) curing light at 1200-1500 mW/cm2 was used for 20 seconds of curing. Occluso-gingival and mesio-distal bracket placement was optimised to the greatest extent feasible.
The SBS was measured at a crosshead speed of 1 mm/min on a universal testing equipment. To evaluate the SBS, a knife edge shaped equipment was positioned at the enamel-resin contact. By measuring the surface area of the bracket, we were able to convert the maximal force needed to de-bond it from Newtons to Megapascals (1 MPa=1N/mm2) (10). BT was arrived at by adding etching time comprising of priming and etching, to BT, which incorporated bracket placement and curing. An outsider used a stopwatch to time BT and report the results in seconds. To determine the kind of fracture, ARI was measured using a stereoelectronic microscope. The ARI provided by Artun J and Bergland S was used to assess the quantity of adhesive remaining on the tooth after de-bracketing (Table/Fig 3) (9). The following are some of the criteria used in the index: Adhesive removed from tooth=0. One means there is less than half the amount of glue on the tooth. More than half of the glue is still on the tooth if the number is two. Three remaining traces of glue on teeth.
Statistical Analysis
Pilot study was done using 10 samples that were not included in the study. Power was calculated to be 80%. This in-vitro study was done using 39 human premolars in each group. Statistical analysis was performed using SPSS 24.0 (IBM Corp., USA) for Microsoft Windows. Contrasts were analysed using T-tests for each group separately. If the probability value is less than 0.05, then the result is statistically significant.
In the present study, 78 samples were divided equally into two groups as shown in (Table/Fig 4). All three parameters SBS (MPa), BT (seconds) and ARI (0-3) for 39 samples in each group are displayed in (Table/Fig 5).
Measurement and comparison of SBS: CAS exhibited SBS 10.35±3.55 (Mean±SD) MPa compared with FFAS having 11.23±3.82. Although the SBS of the CAS was non significant compared to the FFAS numerically but greater than 10 MPa (15), which is sufficient for orthodontic purposes. The measurements of SBS values from CAS and FFAS were statistically non-significant as shown in (Table/Fig 6).
Measurement and comparison of BT: The BT was significantly different between CAS (140.85±16.62) and FFAS (95.54±8.72) in seconds as shown in (Table/Fig 7).
Measurement and comparison of ARI: The FFAS exhibited less ARI 1.23±0.74 compared with CAS I having 1.79±0.80. Use of flash free bracket prevents extra adhesive to be distributed compared to conventional adhesive resulting in results in minimum adhesive left on tooth surface. Flash free brackets showed less ARI as shown in (Table/Fig 8). Distribution is shown in (Table/Fig 9).
This study explored the differences between two different systems in SBS, BT and ARI. This is the first study evaluating all three parameters in two systems especially metal brackets.
Difference in SBS found in the present study was non significant between CAS (10.35±3.55 MPa) and FFAS (11.23±3.82 MPa). Furthermore, Akl R et al., and Guzman UA et al., reported no statistically significant differences between CAS and FFAS after 824 hours postbonding (p-value=0.574 and p=0.574, respectively) (16),(17). The difference between FFAS (10.97 MPa) and CAS (8.23 MPa) was statistically significant, as reported by Szuhanek C et al., (18). Both methods had comparable binding strength according to Grünheid T and Larson BE (19). According to Lee M and Kanavakis G, the SBS of the FFAS was 13.7MPa, whereas that of the CAS was only 10.8 2.0 MPa (20). Reynolds IR suggests that the SBS values obtained in the current investigation are sufficient however this is not the case (21). The FFAS contains a uniform layer of adhesive on non woven matrix on base of the bracket base eliminating the time to put adhesive on the base of bracket and remove excess flash after the bracket positioning. In our study, BT found was significantly different in the CAS (140.85±16.62 seconds) and FFAS (95.54±8.72 seconds). The average BT required for FFAS (19.5 seconds each tooth) was much lower than that for CAS (33.8 seconds per tooth) (22), as reported by Foersch M et al., Bonding took much less time (30.7 3.3 seconds) in the FFAS (P. 001) compared to the CAS (41.8 4.0 seconds) (20); this difference was statistically significant. In their study, Tumoglu M and Akkurt A found that BT administered via FFAS was over 4.22 minutes shorter per patient (23). The bonding period in the investigation was more extensive than that in the aforementioned studies. The same operator, with just two years of clinical experience, bonded all of the patients’ brackets, although a more skilled dentist could have been able to do so in less time. Usage of FFAS prevents excess adhesive to flow out of expected area of base of bracket compared to CAS resulting in lesser adhesive left on tooth surface. Results of present study indicate that the FFAS (1.23±0.74) exhibited significantly less mean ARI compared with CAS (1.79±0.80). ARI evaluation according to Artun J and Bergland S criteria explored a higher number of Score-2 in CAS (48.7%) and Score-1 in FFAS (56.4%) (9). This indicates that the tested samples in FFAS showed a greater number of bond failures occurring at the enamel to adhesive interface than CAS, which is consonant with reports by Henkin FS et al., and Lin CL et al., (24),(25). Vig P et al., suggested that bond failure at enamel to adhesive interface is favourable as clean up procedure required after debonding will be less, preventing loss of enamel surface making it less susceptible to plaque accumulation and sensitivity on exposure of the prism endings (26). Maxfield BJ et al., explains plaque accumulation leads to demineralisation and white spot lesions (27). Even the appearance may be unesthetic and unsatisfying. Studies by Hosein I et al., Ireland AJ et al., and Day CJ et al., suggest that production of airborne particles and inhalation of aerosols was result of more residual adhesive (28),(29),(30). A recent study by Brown JS et al., has explored the overestimation of concentration of particulates by sampling studies that will reach the lower respiratory tract (31). Penetration is affected by respiratory functions, e.g., nose versus mouth breathing and breathing patterns. This explores a fact that lesser the adhesive remnants better the cleanup and lesser amount of enamel loss and airborne particles. Previous comparative studies and results of present study are summarised in (Table/Fig 10) (16),(17),(20),(32),(33),(34),(35).
Limitation(s)
Present in-vitro study was done on human premolars. Thus, generalisation of results in clinical procedures should be done with caution. As the both adhesive systems belong to same manufacturer variability is limited. Thermocycling was not considered that could help in betterment of simulation in clinical process. High cost of FFAS should be considered. Future studies are required to evaluate relation between factors affecting SBS, BT and ARI in adhesives by different manufacturers and coloured adhesive system using metal brackets.
While bonding metal brackets, no significant variation in SBS was discovered between the two adhesives. The chances of bracket failure are lesser in APC™ FFAS according to absolute numbers. FFAS reduced time consumed by picking and holding bracket for application of adhesive, as well as the more important removal of flash which in conventional system increases the chair side time. This led to less BT in FFAS. FFAS resulted in less ARI compared to conventional system. This prevents enamel loss and smoother surface post debonding. APC™ FFAS performs well on base of all three parameters compared to CAS.
DOI: 10.7860/JCDR/2023/62414.17875
Date of Submission: Dec 21, 2022
Date of Peer Review: Feb 02, 2023
Date of Acceptance: Apr 07, 2023
Date of Publishing: May 01, 2023
AUTHOR DECLARATION:
• Financial or Other Competing Interests: None
• Was Ethics Committee Approval obtained for this study? Yes
• Was informed consent obtained from the subjects involved in the study? No
• For any images presented appropriate consent has been obtained from the subjects. NA
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