|Year : 2022 | Volume
| Issue : 1 | Page : 52-59
Comparative evaluation of the efficacy of two medical grade adhesives for the retention of extraoral maxillofacial prosthesis
Ankita Chitnis, Padmapriya Puppala, Gaurang Mistry, Omkar Shetty, Rishabh Shetty
Department of Prosthodontics, DY Patil School of Dentistry, Mumbai, Maharashtra, India
|Date of Submission||01-Jun-2021|
|Date of Decision||14-Aug-2021|
|Date of Acceptance||23-Sep-2021|
|Date of Web Publication||31-Dec-2021|
3/63, Parag, New Mig Colony, Bandra East, Mumbai - 400 051, Maharashtra
Source of Support: None, Conflict of Interest: None
Introduction: The retention of an extraoral maxillofacial prosthesis poses a big challenge to the prosthodontist due to the complex and varied nature of facial defects. Several methods are available to enhance the retention of this prosthesis. This study was conducted to compare the efficacy of polysiloxane adhesives and n-butyl cyanoacrylate adhesives in providing retention for an extra-oral maxillofacial prosthesis. Materials and Methods: The samples were prepared by bonding silicone sheets with pigskin. These samples to be studied were divided into two groups of 20 samples each depending on the adhesive used for bonding the silicone sheets to the pigskin. Ten samples from each group were subjected to 180° and T-peel tests, respectively. Results: The results showed that the mean peel strength (PS) in the T peel test was higher for polysiloxane adhesive as compared to n-butyl cyanoacrylate adhesive, but the difference was not statistically significant. Whereas the mean PS in the 180° peel test was higher for n-butyl cyanoacrylate adhesive as compared to polysiloxane adhesive and the difference was statistically significant. Conclusion: The cyanoacrylate adhesives proved to be better in terms of PS.
Keywords: Adhesive, cyanoacrylate, peel strength, silicone
|How to cite this article:|
Chitnis A, Puppala P, Mistry G, Shetty O, Shetty R. Comparative evaluation of the efficacy of two medical grade adhesives for the retention of extraoral maxillofacial prosthesis. Adv Hum Biol 2022;12:52-9
|How to cite this URL:|
Chitnis A, Puppala P, Mistry G, Shetty O, Shetty R. Comparative evaluation of the efficacy of two medical grade adhesives for the retention of extraoral maxillofacial prosthesis. Adv Hum Biol [serial online] 2022 [cited 2022 Jan 25];12:52-9. Available from: https://www.aihbonline.com/text.asp?2022/12/1/52/334589
| Introduction|| |
Facial defects secondary to the treatment of neoplasms, congenital malformations and trauma result in multiple functional and psychosocial difficulties. Prosthetic rehabilitation attempts to restore these facial disfigurements and may improve the level of function and self-esteem for these patients. The prosthetic rehabilitation is an alternative to surgical treatment in functional aesthetic facial reconstruction when the conventional reconstructive surgery cannot be applied either because of the psychophysical conditions of the patient or because of an excessive substance loss.
Retention of the prosthesis plays a major role in the success of a facial prosthesis. A prosthesis can be retained either by surgical or non-surgical means. Non-surgical means include mechanical means, with the use of available anatomical undercuts, skin adhesives, both undercuts and adhesives or more recently by the extraoral placement of osseointegrated implants.
As the maxillofacial patients undergo the trauma of multiple surgeries for their treatment, repeated surgery is not favoured by the patient. Hence, non-surgical methods such as adhesives have proved beneficial in the medical field. Adhesives, in general, maybe classified by intended purpose, physical properties or chemical structure. The compositions of adhesives are also diverse such as acrylic, latex and silicone.
The acrylic-based adhesives were widely used in the 19th century because of their advantage over other adhesives. However, toxicity was a major drawback. Alongside the acrylates, silicone adhesives such as polysiloxanes were used due to their better biocompatibility. However, the major downside encountered by the patient was reduced bond strength with the substrate.
Several authors in the medical field have conducted studies on the bond strength with polysiloxane adhesive DC 355. DC 355 is one of the best available materials,, at that time fulfilled a lot of properties, but the major disadvantage of this material was that it was found to be unfriendly to the environment and hence was discontinued. Following this, the silicone adhesive which has gained popularity is Telesis 8. These adhesives are characterised by providing good oxygen permeability as well as adhesion.
In the medical field, the use of long-chain cyanoacrylate molecule has been recently reported with improved properties such as clear colour, bonding to moist material (skin), high tensile strength and active temperature range, reduced toxicity and have been successfully used as tissue adhesives., These adhesives are being used in wound closure, bone fixation, cleft lip and palate surgeries, flap surgeries, skin grafting, hair transplant surgeries and other cosmetic procedures., The n-butyl group of cyanoacrylates has shown excellent bonding to the skin when used for these procedures. However, their function as retentive aids for maxillofacial prostheses has not been explored.
Hence, this study was conducted to compare the efficacy of polysiloxane adhesives and n-butyl cyanoacrylate adhesives in providing retention for an extra-oral maxillofacial prosthesis.
| Materials and Methods|| |
The study was divided into the following steps: (a) preparation of the samples and (b) experimental setup [Figure 1].
Preparation of the samples
Modelling wax was used to create a template for silicone sheets which was then flasked, and dewaxing was done [Figure 2]. Silicone elastomer was mixed using the manufacturer's instructions and was packed into the flasks [Figure 3] and [Figure 4].
Forty samples measuring 60 mm × 30 mm × 3 mm in dimensions as per the specifications of the universal spring testing machine were obtained.
Forty samples of porcine skin were obtained, each of them measuring 100 mm × 30 mm × 3 mm in dimensions.
The specimens to be studied were divided according to the type of adhesive used to bond the silicone samples to the porcine skin. Each group consisted of 20 samples. Group A − 20 samples of heat vulcanising silicone sheets bonded with the polysiloxane medical-grade adhesive to the porcine skin sheets [Figure 5]. Group B − 20 samples of heat vulcanising silicone sheets bonded with the n-butyl cyanoacrylate medical-grade adhesive to the porcine skin sheets [Figure 6]. External colour coding was done for easy identification of samples, i.e. Group A − Orange colour and Group B − blue colour.
The samples used for testing were then categorised as follows [Figure 7] and [Figure 8]:
Group A1: [Figure 9] Ten samples were prepared by applying polysiloxane medical-grade adhesive between silicone sheets and porcine skin, which were subjected to a T peel test [Figure 10].
Group A2: Ten samples were prepared by applying polysiloxane medical-grade adhesive between silicone sheets and porcine skin, which were subjected to a 180° peel test.
Group B1: Ten samples were prepared by applying n-butyl cyanoacrylate medical-grade adhesive between sheets of silicone elastomer and porcine skin, which were subjected to a T peel test [Figure 11].
Group B2: Ten samples were prepared by applying n-butyl cyanoacrylate medical-grade adhesive between sheets of silicone elastomer and porcine skin, which were subjected to 180° peel test [Figure 12].
Each sample in each group was further labelled from a to j.
Samples in Group A1 and Group B1 were subjected to a T peel test according to ASTM D1876-08, and samples in Gro up A2 and Group B2 were subjected to a 180° peel test according to ASTM D903-98 using a universal spring testing machine. The amount of tensile force required to rupture the bond will be used to calculate the peel strength (PS). The crosshead speed was adjusted at 20 mm/min. The force required to induce failure was registered. PS (N/mm) was calculated according to equation, (Eq. 1).
Where F indicates the maximum force (N), W is the width of the individual specimen (mm), λ and is the extension ratio (the ratio of stretched to unstretched length) of silicone elastomer. The acquired data were passed through the Shapiro − Wilk test for normality for the determination of the distribution of data, and then, an unpaired t-test was applied to compare the said data.
| Results|| |
The mean PSs for Group A1, B1, A2 and B2 was 0.036, 0.030, 0.021 and 0.102, respectively [Table 1].
A comparison between the mean PS between Group A1 and A2 was found to be higher in Group A1 (mean = 0.0368) when compared to Group A2 (mean = 0.0211). The mean difference was 0.01570 statistically significant (P < 0.05) [Table 2].
|Table 2: Comparison of mean peel strength (N/mm) between Group A1 and A2|
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The comparison of the mean PS was found to be low in Group B1 (mean = 0.03050) than in Group B2 (mean = 0.1021). The mean difference was −0.07160 and was statistically significant (P < 0.05) [Table 3].
|Table 3: Comparison of mean peel strength (N/mm) between Group B1 and B2|
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A comparison of the mean PS was found to be higher in Group A1 (mean = 0.0368) than in Group B1 (mean = 0.0305). The mean difference was 0.0063 and was statistically insignificant (P > 0.05) [Table 4].
|Table 4: Comparison of mean peel strength (N/mm) between Group A1 and B1|
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A comparison between the mean PS of Group A2 and B2 showed that the mean PS was higher in Group B2 (mean = 0.1021) than in Group A2 (mean = 0.0211). The mean difference was –0.08100 and was statistically significant (P < 0.05) [Table 5].
|Table 5: Comparison of mean peel strength (N/mm) between Group A2 and B2|
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[Graph 1] showed the mean comparative value graph for the PS of Group A1 and Group B1. The mean PS was higher for Group A1 when compared to Group B1.
[Graph 2] showed the mean comparative value graph for the PS of Group A2 and Group B2. The mean PS was higher for Group B2 when compared to Group A2.
| Discussion|| |
Cancer surgery, malformation or trauma may cause broad facial defects that cannot be covered by patients because of their exposed site. Such defects lead to functional deficits and enormous psychological strain and require rehabilitation at all ages. The correction of a facial defect is commonly believed to significantly reduce feelings of anxiety, shame, self-consciousness, inferiority and social inadequacy. The basic tenet holds that rendering a patient less conspicuous significantly contributes to social readjustment. Considerable advances have been made in the treatment of patients with maxillofacial defects during the past few decades.
Prosthetic restoration of facial defects is the treatment of choice where surgical reconstruction is not advisable. Because of their training in anatomy, materials, art and tissues, it is the province of the maxillofacial prosthetists to construct facial prostheses to rehabilitate persons with these defects.
Facial prostheses may be retained by mechanical means or by the use of adhesives. A wide variety of adhesives have been developed and studied for use in the retention of the maxillofacial prosthesis. The clinical selection of a facial prosthetic adhesive is made subjectively. Although no standard exists for facial prosthetic adhesives, the ideal characteristics for this group of materials have been stated by several investigators, as have the reasons for selecting an adhesive.
In a study by Dootz et al, Ahmed et al., and Schaaf et al.,, on adhesion to the skin, objective goals were established for the development of skin adhesives through mechanical and chemical analysis of adhesive-substrate behaviour. To illustrate the value of this type of research, one of their findings based on objective results was that adhesives should be engineered to be absorbent to remove surface secretions, thereby allowing good adhesive-substrate bonding. In addition, the adhesive should be porous to allow the passage of secretions. In this way, scientifically established criteria can lead to the development of adhesives designed for a particular purpose.
Liu et al. maintained that adhesives exhibit a viscoelastic form and develop adhesion to the skin and cohesion to resist debonding. They described peel adhesion as a phenomenon that is determined by the ability of adhesives to resist separation from the skin surface after a period of application. It is complex, multifaceted and broadly applicable from cell adhesion to bio-fouling; thus, it is one of the most ubiquitous phenomena in nature and technology. Adhesive use in facial prostheses is easily accepted by patients and families because of its cost-effectiveness as compared to other means of retention such as implants, non-invasiveness and lack of aggressive side effects. Patients should be told to remove the prosthesis once a day to clear the surrounding tissue. It is highly recommended that the prosthesis be removed before resting in order to decrease the risk of skin contact disorders and to allow the tissues to rest.
According to Chen and Flavin, peeling is the most commonly observed mode of adhesive bond failure. The peel force or peel adhesion, which is applied to rupture the adhesive bond, is often used as an index of bond quality and was described by Zhang and Wang This force can be quantified by performing a controlled peel test that is conducted by pulling the adhesive at a constant rate from a known substrate.
In addition to having the appropriate PS, adhesives designed for human skin must also be sticky, comfortable to wear, non-irritant and residue-free. The three most commonly used commercial adhesive materials today are rubbers, acrylics and silicones. Natural rubber adhesives prevailed in the market until the 1960s, but their high cost, the shortage of supply and the advances in polymer chemistry rendered the dominance to synthetic materials.
The silicone adhesives, which possess several potential advantages, would be an ideal solution for prolonged use of the dressing and electronic patch. The silicone adhesives' viscoelastic flow characteristics can create a large intimate contact area on the skin, where the surface topography is extremely uneven. Their tackiness may not decay or increase over time, whereas the strength of adhesion is adequate for skin application. The silicone adhesives are residue-free and relatively inert with minimum risk of skin intolerance.,, They have significantly higher moisture vapour transmission rate and fluid handling capacity than other adhesives, which are crucial factors that govern patients' comfort during long-term applications.
Venkatraman and Gale stated that traditionally, acrylate-based adhesives had been widely used for skin contact applications due to their inherent tack, strong oxidative stability and easy adaptability to a variety of needs. However, nowadays, adhesives for medical applications are called upon to meet a multitude of requirements, including less skin irritation and better reusability.
Amongst these, the cyanoacrylate group of adhesives which were developed in 1949 have been used widely. The first cyanoacrylates were short-chained, poorly manufactured and toxic to animals at pharmacologic doses. Research showed that changing the type of alcohol in the compound to one with a longer molecular chain reduced tissue toxicity. Over time, nontoxic LCCA, such as butyl-cyanoacrylate, were manufactured, leading to their use once again in clinical medicine. Longer-chain derivatives lacking the associated toxicity of the short-chain derivatives and more sophisticated manufacturing techniques have led to the development of pure nontoxic monomers and the acceptance of the adhesives into clinical practice. N-butyl cyanoacrylates have wide use in wound closure, bone fixation, cleft lip and palate surgeries, flap surgeries, skin grafting and other cosmetic procedures.,
The n-butyl group of cyanoacrylate adhesives has been recently reported to be used in hair transplant therapy over the grafted areas to keep the grafts in place during the immediate postoperative period with good results. These cyanoacrylate groups of adhesives share common properties of clear colour, bonding to moist material (skin), high tensile strength and active temperature range and have been successfully used as tissue adhesives., The adhesive almost universally holds the grafts in place so that they heal flat to the skin. It offers the advantages of low viscosity but does not permeate all the way to the capillary level and thereby avoids tissue death. Borie E et al. reviewed that in vivo and clinical studies have demonstrated convincing results regarding the safety, efficacy, ease of application and feasibility of all types of cyanoacrylate adhesives used in intraoral and extraoral procedures. Due to the wide application of this adhesive with satisfactory results, it was chosen as the material of choice for comparison with the popular silicone adhesives.
As maxillofacial adhesives can be tested using peel tests, obtaining peel test data on human skin is highly complex, primarily due to the great variability of skin and its properties as well as the difficulty of executing realistic experimental setups. Considering these difficulties, pigskin has been suggested to be a suitable model to replace human skin during a peel test. The anatomy, topical features such as texture and roughness (Ra values, the arithmetical mean value of the amounts of the ordinate value within an individual measuring distance, for both human and porcine skin are 20 ± 3 μm), and the biochemical property of pigskin is remarkably similar to those of human skin. Therefore, hair-removed pig skins have gained popularity as a substrate material to mimic human skin for topical adhesion studies.,
This in vitro study was conducted to evaluate and compare the efficacy of two medical-grade adhesives for the retention of the extraoral maxillofacial prosthesis. The specimens to be studied were divided according to the type of adhesive used to bond the silicone samples to the porcine skin.
Soft tissue around midfacial defects may undergo movement during smiling and grimacing and may compromise adaptation of prostheses margins. The muscles of facial expression are directly subjacent to the freely movable elastic skin. Martone AL stated Camper's observation that when these muscles contract, the skin folds perpendicularly to the direction of the pull of the muscles since this is not the only direction in which forces of displacement act. The samples were also tested for their resistance to tangential forces. Such forced lead to the curling up of the margins of the prosthesis.
Samples in Group A1 and Group B1 were subjected to a T peel test, whereas the samples in Group A2 and Group B2 were subjected to a 180° peel test. The amount of tensile force required to rupture the bond was used to calculate the PS. PS (N/mm) was calculated according to Eq. 1 as described before.
These data obtained were then subjected to statistical analysis using the Shapiro − Wilk test for normality. It was found that the data were normally distributed and required parametric tests to be done to determine the statistical significance of the data. An independent t-test was used to determine the same.
Samples in Group A1 showed greater mean PS as compared to the samples in Group A2 when subjected to the T peel test and 180° peel test, respectively, and the difference was statistically significant (P < 0.05). Tam et al. in 1992 showed that DC 355 adhesive, a silicone adhesive, was statistically significantly stronger than the other adhesives evaluated by means of tensile and combined tensile-torsional tests. Polyzois et al. showed that silicone adhesives showed higher bond strengths as compared to other groups of adhesives. In this study, the polysiloxane adhesive showed better resistance against perpendicular forces as compared to tangential forces.
The samples in Group B2 showed greater mean PS as compared to the samples in Group B1 when subjected to 180° peel test and T peel test, respectively, and the difference was statistically significant (P < 0.05).
Facial prostheses are known to have thin edges which blend with the surrounding tissue to camouflage the demarcation between the prosthesis and the patient's skin. These thin edges tend to peel off under tangential forces and cause an unsightly appearance. The cyanoacrylate group showed better resistance against these forces.
Samples in Group A1 show greater mean PS as compared to the samples in Group B1 when subjected to the T peel test. However, this difference was not statistically significant (P > 0.05). This indicates that the PS for the silicone adhesives, when subjected to loads that are perpendicular to the direction of removal, was greater than that for the cyanoacrylate adhesives by a small margin.
The samples in Group B2 show greater mean PS as compared to the samples in Group A2 when subjected to 180° peel test, and the difference was statistically significant (P < 0.05). The cyanoacrylate adhesives tested in this study showed significantly higher PS as compared to silicone adhesives when subjected to forces at 180°, thus showing better resistance against the curling of prosthetic margins.
It was observed that even though the strengths of the adhesives were not very high, they were satisfactory enough to withstand forces that were expected to be seen in the facial region. The failure of the bond was cohesive in nature in most samples of the silicone adhesive. However, this was not as widely seen in the samples bonded with cyanoacrylate adhesive suggesting a stronger bond with either of the substrates.
The adhesive thickness has an important effect on the peel adhesion property of adhesives. In this study, it was observed that on the application of a single layer of each adhesive, the silicone adhesive showed a weaker bond as compared to the cyanoacrylate adhesive. Multiple applications of the silicone adhesive were required to achieve a similar PS. However, this leads to an increase in thickness of the adhesive layer, which is not advisable as the junction between the edges of the prosthesis and the skin need to blend as much as possible in order to achieve aesthetic results. The cyanoacrylates required the application of a thin layer and produced a better bond.
| Conclusion|| |
Within the limitations of this study, it was observed that the cyanoacrylate adhesives proved to be better in terms of the PS when forces were applied tangentially, had a better bond with the silicone sample and the pigskin and required a lesser amount of material to obtain satisfactory bond strength. Thus, this material can be used for the retention of the extraoral prosthesis as an adjunct to other modes of retention.
Further in vivo investigations of the above study to evaluate the effect of loads on the polysiloxane and cyanoacrylate adhesives could be conducted to evaluate their efficacy in the retention of the extraoral maxillofacial prosthesis in a dynamic situation, the nature of bond failure interface and the feasibility of their use in day-to-day life. Other factors such as peel rate, contact pressure, property of the substrate, withdrawal speed, temperature and humidity of the environment could be taken into consideration for further studies.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]