|Year : 2017 | Volume
| Issue : 4 | Page : 359-366
A comparative evaluation of retention of pit and fissure sealant bonded using sixth-, seventh-, and eighth-generation adhesives: An in vivo study
Mitakshra Nirwan1, Anant Gopal Nigam1, Nikhil Marwah1, Ullal Anand Nayak2, Aayushi Bansal3, Manvendra Singh Gahlot4
1 Department of Pedodontics and Preventive Dentistry, Mahatma Gandhi Dental College and Hospital, Jaipur, Rajasthan, India
2 Department of Pediatric Dentistry, Ibn Sina National College for Medical Studies, Jeddah, Saudi Arabia
3 Department of Pedodontics and Preventive Dentistry, Sir Padampat Mother and Child Hospital (J.K. Lon Hospital), Jaipur, Rajasthan, India
4 Department of Prosthodontics Crown and Bridge, Jaipur Dental College, Jaipur, Rajasthan, India
|Date of Web Publication||15-Sep-2017|
Shalimar Bagh Colony, Jaipur, Rajasthan
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Introduction: Dental caries is one of the most common preventable childhood infections. a number of measures are available to prevent occlusal caries; pit and fissure sealants are one of the various methods currently available to cost effectively reduce dental caries. Aim: To evaluate the retention of pit and fissure sealant bonded using sixth (Adper promt), seventh (Optibond) and eighth (Futurabond Dual Cure) generations of adhesives. Settings and Design: A total of 37 healthy children who fulfilled the inclusion were randomly selected. A total of 148 teeth (4 in each subject) were used as samples for the study. Methods and Material: The teeth to be sealed were then isolated using rubber dam. The placement of adhesives was done using split mouth design. The first permanent molars were randomly divided into four groups on the basis of sealant placed without and with using 6th, 7th and 8th generation bonding agents as follows:
GROUP A (N=37):- Pit and fissure sealant placed without bonding agent.
GROUP B (N=37):- Pit and fissure sealant placed following sixth generation bonding agent (ADPER PROMT).
GROUP C (N=37):- Pit and fissure sealant placed following seventh generation bonding agent. (OPTIBOND).
GROUP D (N=37):- Pit and fissure sealant placed following eighth generation bonding agent. (FUTURA BOND DUAL CURE).
The integrity of the sealant placed was assessed immediately after completion of the procedure, 3 months and 6 months after placement. The post-operative evaluation for retention was done using Simonsen criteria. A score of 0 was given for complete retention, 1 for partial retention and 2 for no retention. Statistical analysis used: The statistical analysis was done using SPSS (Statistical Package for Social Sciences) software version 21. Results: It was found that there was no statistically significant difference between the groups after 3 and 6 months as the value obtained (0.133) was much greater than the p-value (0.05). Conclusions: This study concluded that the use of bonding agent prior to application of pit and fissure sealant does not necessarily aid in retention of sealant as compared to pit and fissure sealant placed without bonding agent, Sealants effectiveness is directly related to its retention and it dependent on application procedures. The failure of retention of pit and fissure sealants can attribute to moisture contamination, improper curing methods, inadequate adhesion, improper application procedure or early age placement.
Keywords: Bonding agents, dental caries, occlusal caries, prevention, sealants
|How to cite this article:|
Nirwan M, Nigam AG, Marwah N, Nayak UA, Bansal A, Gahlot MS. A comparative evaluation of retention of pit and fissure sealant bonded using sixth-, seventh-, and eighth-generation adhesives: An in vivo study. J Indian Soc Pedod Prev Dent 2017;35:359-66
|How to cite this URL:|
Nirwan M, Nigam AG, Marwah N, Nayak UA, Bansal A, Gahlot MS. A comparative evaluation of retention of pit and fissure sealant bonded using sixth-, seventh-, and eighth-generation adhesives: An in vivo study. J Indian Soc Pedod Prev Dent [serial online] 2017 [cited 2019 Sep 21];35:359-66. Available from: http://www.jisppd.com/text.asp?2017/35/4/359/214929
| Introduction|| |
Dental caries can be defined as a bacterial disease of the calcified tissues of the teeth characterized by demineralization of the inorganic and destruction of the organic substance of the tooth. It is one of the most common preventable childhood infections. The history of occlusal caries dates back for more than 100 years when Black  reported that more than 40% of all caries in the permanent teeth occurs in the occlusal pit and fissure surfaces. The high susceptibility of occlusal surface of molars and premolars to dental decay may be attributed to the complex morphology of pits and fissures, which are considered to be an ideal site for retention of bacteria and food remnants. Paynter and Grainger  stated that the presence of pits and fissures that harbor food and microorganisms is the single most important factor in determining whether caries occurs. Nagano (1960) described four principal types of fissures, based on the alphabetical description of shape, i.e., Type V – 34%, Type U – 14%, Type I – 19%, Type IK – 26%, and Type Y and others – 7%.
The term pit and fissure sealant is used to describe a material that is introduced into the occlusal pits and fissures of caries-susceptible teeth, thus forming a micromechanically bonded, protective layer cutting access of caries-producing bacteria from their source of nutrients. Numerous methods were tried to seal the pits and fissures, including radical procedures such as prophylactic odontotomy  and conservative procedures such as placement of silver nitrate  or cellulose nitrate, but these techniques did not arrest carious lesions efficiently.
The introduction of adhesive dentistry dates back to 1955 when Dr. Michael Buonocore postulated that before application of resins, acid could be used as a surface treatment. The first dental pit and fissure sealant was introduced by Nuva-Seal (L. D. Caulk) in February 1971, along with its curing initiator, and ultraviolet light source, the Caulk Nuva Lite. The first plastic materials used as occlusal sealants were polyurethanes and cyanoacrylates. Bowen designed a plastic resin, bisphenol-A-glycidyl dimethacrylate (Bis-GMA), that became the main component of modern sealants.
The use of bonding agent under sealants on etched enamel surface increases bond strength, controls moisture, reduces microleakage, and enhances flow of resins into fissures. Dentin bonding systems have been classified under various generations according to various components used.
Thus, this study aims to evaluate the retention of pit and fissure sealant bonded using sixth-generation (Adper Prompt), seventh-generation (OptiBond), and eighth-generation (Futurabond Dual Cure [DC]) of adhesives.
| Methods|| |
The prospective clinical trial was conducted in the Department of Pedodontics and Preventive Dentistry, Mahatma Gandhi Dental College and Hospital, Jaipur. Ethical approval from the Institutional Ethics Committee, Mahatma Gandhi University of Medical Sciences, was obtained before the commencement of the study.
A total of 37 healthy children who fulfilled the inclusion criteria as mentioned below were randomly selected as subjects for the study. The sound and caries free all permanent first molars were selected among those 37 children. A total of 148 teeth (4 in each subject) were used as samples for the study. Patients between 6 and 11 years of age with a decayed missing filled surfaces score of 1–3 were included in the study. All the four permanent first molars were caries free with sound occlusal surface, deep and narrow pits and fissures. Dentition status allows rubber dam placement. Patients with rampant caries; with well-coalesced, self-cleansing pits and fissures; with no previous caries experience were excluded from the study. Furthermore, patients in whom the isolation of tooth was not possible were excluded from the study.
Sample size was calculated at study power of 80% and error of 0.05, considering complete retention of sealant using Simonsen method as 30%, 50%, 60%, and 70% in control group and in sixth-, seventh-, and eighth-generation, respectively, in accordance with the pilot study conducted on 10 patients (40 teeth). Sample size of 123 teeth was obtained which is further enhanced to 148 teeth assuming 20% drop-out/loss to follow-up. Therefore, final sample size was 148 teeth (37 patients) divided into four equal groups.
Children who fulfilled the inclusion criteria were selected for the study. The subjects were informed about the nature of the study, and a consent form was made to sign by the parents who wanted to participate in the study. All the records including address and contact numbers were obtained from the parents so as to ease in the recall procedure. In the selected subjects, thorough oral prophylaxis was done and all the first molars were subsequently polished with pumice using rubber cup. The teeth to be sealed were then isolated using rubber dam. The placement of adhesives was done using split mouth design. The first permanent molars were randomly divided into four groups on the basis of sealant placed without and with using sixth-, seventh-, and eighth-generation bonding agents as follows:
- Group A (n = 37): Pit and fissure sealant placed without bonding agent
- Group B (n = 37): Pit and fissure sealant placed following sixth-generation bonding agent (Adper Prompt)
- Group C (n = 37): Pit and fissure sealant placed following seventh-generation bonding agent (OptiBond)
- Group D (n = 37): Pit and fissure sealant placed following eighth-generation bonding agent (Futurabond DC).
All groups and teeth were randomized such that all permanent molars received equal distribution of all the bonding agents. All the four molars were sealed with respective sealants on the single visit. Teeth under Group A and Group B were etched using 37% orthophosphoric acid, whereas the teeth under Group C and Group D were etched using self-etch adhesives, i.e., OptiBond and Futurabond DC, respectively. Helioseal-F sealant was then applied to the prepared fissure. Any air bubble or void observed was removed before the curing. Then, the sealant was cured for 20 s as instructed by the manufacturer using light emitting diode curing light (3M ESPE) The sealant was then checked for high points using articulating paper. All the manufacturer's instructions were followed regarding manipulation, placement, and curing for all the materials. The integrity of the sealant placed was assessed immediately after completion of the procedure. After 3 months, the parents were informed 2 days before the recall visit. Recall examination was done with magnifying glass and under ambient light. The sealants were examined for their integrity, and any discrepancy was noted down. A similar procedure was followed for recall after another 3 months. The postoperative evaluation for retention was done using Simonsen's criteria by an independent single, trained, and calibrated examiner. A score of 0 was given for complete retention, 1 for partial retention, and 2 for no retention. The completely retained sealant category did not address sealant wear. If some peripheral fissures were uncovered following sealant wear, but no ledges were present, the sealant was classified as completely retained (ledges indicate bulk loss of some adjacent sealant). Partially retained sealants were those where, following either wear or material loss, part of a previously sealed pit/fissure was exposed. Missing sealants were those where no trace of sealant was detectable. The collected scores were tabulated and were subjected to statistical analysis.
| Results|| |
The observations were done after 3 and 6 months of sealant placement and the data were tabulated. [Table 1] shows the descriptive data which show mean and standard deviation of the age and all the four groups. [Table 2] shows the retention of sealants in all the 37 children at the end of 3 months. [Graph 1],[Graph 2],[Graph 3],[Graph 4] represent retention of sealant in Group A (without any bonding agent), Group B (sixth-generation bonding agent), Group C (seventh-generation bonding agent), and Group D (eighth-generation bonding agent), respectively, after 3 months. It was observed that maximum retention of sealants was found in control group after 3 months. [Table 3] shows Kruskal–Wallis ANOVA test to evaluate retention at 3 months. It was found that there was no statistically significant difference between the groups as the value obtained (0.133) was much P > 0.05. Since there was no statistically significant difference between the groups and within the groups, no post hoc test was performed.
Similarly, [Table 4] shows the retention of sealants in all the 37 children at the end of 6 months. [Graph 5],[Graph 6],[Graph 7],[Graph 8] represent the retention of sealant in Groups A, B, C, and D, respectively, after 6 months recall. [Table 5] shows that Kruskal–Wallis ANOVA test was done to evaluate retention at 6 months. It was found that there was no statistically significant difference between the groups as the value obtained (0.211) was much P > 0.05. Since there was no statistically significant difference between the groups and within the groups, no post hoc test was performed.
The statistical analysis was done using Statistical Package for the Social Sciences software version 21 (SPSS Inc., Chicago, III, USA). Continuous data were summarized as mean and standard deviation while nominal data as percentage. Since the data were nonparametric, Kruskal–Wallis ANOVA test was applied using SPSS software version 21, followed by post hoc test used for continuous data. P < 0.05 was taken as statistically significant. Kruskal–Wallis ANOVA test was applied to evaluate retention at 3 and 6 months, and it was found that there was no statistically significant difference between the groups. Since there was no statistically significant difference between the groups and within the groups, no post hoc test was performed.
| Discussion|| |
The occlusal surface is at high risk for caries. This is especially true for newly erupted molars, where anatomic characteristics cause difficult access for cleaning procedures and incomplete maturation of enamel adds to caries susceptibility. The complex morphology of the occlusal surface also reduces the effectiveness of fluorides in the remineralizing phases. Pit and fissure sealants have been effective in reducing occlusal caries, but their effectiveness may be precluded by technical problems during application, such as salivary contamination. Application under optimal conditions determines the success of pit and fissure sealant. The use of bonding agent under sealants on etched enamel surface increases bond strength, reduces microleakage, and enhances flow of resins into fissures.
Bunocore (1955) initially introduced a technique for adhesive bonding of resin material to enamel. The procedure utilized phosphoric acid conditioning of the enamel, which altered the surface morphology to create microporosity and showed that resin materials were bonded to this surface primarily through micromechanical adhesion. Cueto and Buonocore  first reported sealing of pits and fissures with an adhesive resin and its use in caries prevention. Hitt and Feigal (1992) first reported the benefit of adding a dentin-bonding agent between the etched enamel and sealant as a way of optimizing bond strength in the phase of moisture and salivary contamination. Borem and Feigal  showed that the use of bonding agent under sealants on contaminated enamel increases bond strength, reduces microleakage, and enhances flow of resins into wetting the substrate to form a strong bond.
The sixth-generation bonding agent used in the present study was Adper Prompt which falls under type II self-etch category. It consists of acidic primer and bonding resin separately. This eliminates the requirement for postconditioning rinsing, reducing working time.
Development in bonding agents has moved from multistep bonding process (etching, washing, drying, primer, and adhesive) to simplification, i.e., total-etch and single bottle system. Ideal bonding agent should be biocompatible, should have adequate bond strength, and should bond to enamel and dentin., The seventh-generation bonding agents are total-etch adhesives with combination of etchant, primer, and bonding agent in one (OptiBond all-in-one system, Kerr) component and applied as single step. It is composed of monomers (glycerol phosphate dimethacrylate), co-monomers (including mono- and di-functional methacrylate monomers), solvents (water, acetone, and ethanol), photo-initiator (camphorquinone based), fillers (three nanosized fillers), and fluoride-releasing fillers (sodium hexafluorosilicate and ytterbium fluoride). Ideal features of a seventh-generation bonding agent are high bond strength (20–30 MPa) to dentin, thin film thickness, fluoride-releasing, tolerant to moist and dry environment. They use the smear layer as a bonding substrate. The acidic primer demineralizes the smear layer and the top layer of the underlying dentin surface. The acidic primer also infiltrates the exposed collagen along with the hydrophilic monomers, which then copolymerize. Because the etched surface is not rinsed, the demineralized smear layer is incorporated into the hybrid layer.
Development in nanotechnology dentistry has led to development of nanocomposites and nano-adhesives which contain nanosized fillers. Recently, the manufacturer of nanofilled dentin adhesives (Futurabond DC, Voco, Germany) has claimed it as eighth-generation bonding agent. It is dual-cured and works with all light. The highly functionalized SiO2 nanoparticles (Ø 20 nm) in Futurabond DC facilitate a crosslink of the resin components. On fresh-cut enamel, an infiltration of the bond takes place simultaneously to the etching process. On dentin, it dissolves the smear layer with special hydrophilic and acidic components.
The sealant used in the present study was Helioseal-F, which is a light-cured and release fluoride. It comprises monomer matrix consisting of Bis-GMA, urethane dimethacrylate, and triethylene glycol dimethacrylate (58.6 wt%). The fillers are highly dispersed silicon dioxide and fluorosilicate glass (40.5 wt%). Additional contents are titanium dioxide, stabilizers, and catalysts (<1 wt%).
Baca et al. compared the retention three fissure sealants (Delton, Delton Plus, and Concise) and a filled dentin bonding system (OptiBond Solo ®) and concluded that one bottle dentin bonding system used as a sealant does not improve the retention of conventional fissure sealants and this was in accordance with our findings. Maher et al. also stated that replacing phosphoric acid-etching with self-etching adhesive Adper Prompt L-Pop does not compromise sealant retention.
In contrast to our findings, Sakkas et al. evaluated the sealant retention rate and caries-preventive efficacy of two fissure sealing techniques over a 3-year period using OptiBond FL, OptiBond Solo plus, Prompt-L-Pop, or the conventional acid-etch technique. Sealed teeth were evaluated at baseline and 6-, 12-, 18-, 24-, and 36-month intervals with regard to retention and new caries development. They concluded that the use of adhesive systems OptiBond FL and Optibond Solo plus yielded better fissure sealing performance. Furthermore, Joseph et al. compared the in vitro bonding efficacy of sixth-, seventh-, and eighth-generation bonding agent (Futurabond DC) and concluded that eighth-generation bonding agent appeared to be more advantageous in bonding than sixth and seventh generations.
In our study, the sealants placed without using bonding agent and etching the teeth with phosphoric acid had maximum retention though statistically not significant. This might be due to the fact that etching enamel is efficient in removing the smear layer, demineralizing the inorganic enamel surface, creating microporosities for a patent and mechanical bond as stated by Perdigão (2003) and Erikson (2008). Our study also concluded that retention of sealant was less when using self-etch and total etch as compared to etching with phosphoric acid. This might be attributed to the improper enamel tags formed as conventional etching technique is not used. Further, in our study, we used noninvasive technique for sealant placement, so etching the tooth would have retained the sealant in its place. Self-etching may be better when used with composite restorations as the prepared tooth structure may aid to its retention. However, self-etching adhesives were not satisfactory when used under pit and fissure sealants as stated by Baca et al.
All-in-one self-etch systems are not as acidic as the phosphoric acid used with the etch-and-rinse adhesives. This characteristic has raised concerns about the performance of all-in-one self-etch systems on intact enamel. Several in vitro investigations have reported low resin-enamel bond strength of all-in-one self-etch materials. Grinding the enamel during a bevel or cavity preparation, for instance, makes the substrate more receptive for bonding with all-in-one self-etch systems. As the smear layer might not be totally removed by these systems, the partially demineralized smear layer becomes incorporated into a hybrid layer. Thus, self-etching primer produces a thinner hybrid layer than systems using etchants such as phosphoric acid. Two-step self-etch adhesives may not bond as well to intact enamel.
Despite the increased popularity of self-etch adhesives, etching with phosphoric acid is still considered the golden standard against which new materials are tested.
A 1-year clinical evaluation of the effectiveness of Helioseal-F sealant in comparison to Glass ionomer Fuji VII sealant was carried out by Ninawe et al., and it was found that Helioseal-F was better sealant with respect to retention, anatomic form, and surface texture. The present trend of using self-etching adhesives may be of benefit if applied to pit and fissure sealants. Our study incorporated the use of recently introduced seventh- and eighth-generation bonding agents, which had the unique advantages of etching, disinfecting, desensitizing, priming, and bonding in a single step was not that effective in retention of pit and fissure sealants when compared to the conventional phosphoric acid-etching technique.
The results of our study showed that there was no statistically significant difference in the retention of sealants when used without or with bonding agents and the use of bonding agent does not improve the retention of pit and fissure sealants.
| Conclusion|| |
The placement of sealants and their continued maintenance are scientifically sound and cost-effective techniques for preventing pit and fissure caries in children. Sealants effectiveness is directly related to its retention, and it depends on application procedures. The failure of retention of pit and fissure sealants can attribute to moisture contamination, improper curing methods, inadequate adhesion, improper application procedure, early age placement, varying behavior in children, and visually apparent variations in enamel.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Carvalho JC, Ekstrand KR, Thylstrup A. Dental plaque and caries on occlusal surfaces of first permanent molars in relation to stage of eruption. J Dent Res 1989;68:773-9.
Black GV. A work on operative dentistry. The technical procedures in filling teeth. Chicago Medico-Dental Publishing; 2:1908.p63.
Li SH, Kingman A, Forthofer R, Swango P. Comparison of tooth surface-specific dental caries attack patterns in US schoolchildren from two national surveys. J Dent Res 1993;72:1398-405.
Paynter KJ, Grainger RM. Relationship of morphology and size of teeth to caries. Int Dent J 1962;12:147-60.
Simonsen RJ. Pit and fissure sealant: Review of the literature. Pediatr Dent 2002;24:393-414.
Hyatt TP. Prophylactic odontotomy: The cutting into the tooth for the prevention of disease. Dent Cosm 1923;65:234-41.
Klein H, Knutson JW. Studies on dental caries. (Pt 13). Effect of ammoniacal silver nitrate on caries in the first permanent molar. J Am Dent Assoc 1942;29:1420.
Simonsen RJ. Retention and effectiveness of dental sealant after 15 years. J Am Dent Assoc 1991;122:34-42.
Bowen RL. Properties of a silica-reinforced polymer for dental restorations. J Am Dent Assoc 1963;66:57-64.
Estafan D, Agosta C. Eliminating microleakage from the composite resin system. Gen Dent 2003;51:506-9.
Hebling J, Feigal RJ. Use of one-bottle adhesive as an intermediate bonding layer to reduce sealant microleakage on saliva-contaminated enamel. Am J Dent 2000;13:187-91.
Buonocore MG. A simple method of increasing the adhesion of acrylic filling materials to enamel surfaces. J Dent Res. 1955;34:849-853.
Simonsen RJ. The clinical effectiveness of a colored pit and fissure sealant at 36 months. J Am Dent Assoc 1981;102:323-7.
Dennison JB, Straffon LH, More FG. Evaluating tooth eruption on sealant efficacy. J Am Dent Assoc 1990;121:610-4.
Cueto EL, Buonocore MG. Adhesive sealing of pits and fissures for caries prevention. J Dent Res 1965;44:137.
Hitt JC, Feigal RJ. Use of a bonding agent to reduce sealant sensitivity to moisture contamination: An in vitro
study. Pediatr Dent 1992;14:41-6.
Borem LM, Feigal RJ. Reducing microleakage of sealants under salivary contamination: Digital-image analysis evaluation. Quintessence Int 1994;25:283-9.
Ferrari M, Mannocci F, Vichi A, Davidson CL. Effect of two etching times on the sealing ability of clearfil liner bond 2 in class V restorations. Am J Dent 1997;10:66-70.
Nikhil V, Singh V, Chaudhry S. Comparative evaluation of bond strength of three contemporary self-etch adhesives: An ex vivo
study. Contemp Clin Dent 2011;2:94-7.
] [Full text]
Yaseen SM, Subba Reddy VV. Comparative evaluation of shear bond strength of two self-etching adhesives (sixth and seventh generation) on dentin of primary and permanent teeth: An in vitro
study. J Indian Soc Pedod Prev Dent 2009;27:33-8.
] [Full text]
Gupta N, Kathuria N, Gulati M, Mehta LK. Review article on“Bonding”: Foundation of dentistry. J Innov Dent 2011;1:60-6.
Chandki R, Kala M. Total etch vs. self etch: Still a controversy in the science of bonding. AOSR 2011;1:38-42.
Joseph P, Yada C, Satheesh K, Rahna R. Comparative evaluation of the bonding efficacy of sixth, seventh and eighth generation bonding agents. Int Res J Pharma 2013;4:143-147.
Pashley EL, Agee KA, Pashley DH, Tay FR. Effects of one versus two applications of an unfilled, all-in-one adhesive on dentine bonding. J Dent 2002;30:83-90.
Ninawe N, Ullal NA, Khandelwal V. A 1-year clinical evaluation of fissure sealants on permanent first molars. Contemp Clin Dent 2012;3:54-9.
] [Full text]
Baca P, Bravo M, Baca AP, Jiménez A. Retention of three fissure sealants and a dentin bonding system used as fissure sealant in caries prevention: 12-month follow-up results. Med Oral Patol Oral Cir Bucal 2007;12:E459-63.
Maher MM, Elkashlan HI, El-Housseiny AA. Effectiveness of a self-etching adhesive on sealant retention in primary teeth. Pediatr Dent 2013;35:351-4.
Sakkas C, Khomenko L, Trachuk I. A comparative study of clinical effectiveness of fissure sealing with and without bonding systems: 3-year results. Eur Arch Paediatr Dent 2013;14:73-81.
Erickson RL, De Gee AJ, Feilzer AJ. Effect of pre-etching enamel on fatigue of self-etch adhesive bonds. Dent Mater 2008;24:117-23.
Buch A, Choksi D, Idnani B, Shah I. Current concepts in dental adhesion: A review. J Dent Sci 2012;3:21-5.
Goracci C, Sadek FT, Monticelli F, Cardoso PE, Ferrari M. Microtensile bond strength of self-etching adhesives to enamel and dentin. J Adhes Dent 2004;6:313-8.
Tay FR, Pashley DH, Suh BI, Carvalho RM, Itthagarun A. Single-step adhesives are permeable membranes. J Dent 2002;30:371-82.
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]