Original research

 

Curing depth of pit and fissure sealants with use of light emitting diode (LED) at different distances

 

Azucena Villarreal Rojas,^* Jorge Guerrero Ibarra,^§ Adolfo Yamamoto Nagano,^II Federico Humberto Barceló Santana^§

 

* Graduate at Pedodontics Specialty.

^§ Dental Material Laboratory.

^II Pedodontics Specialty Coordinator.

Graduate and Research School, National School of Dentistry, National Autonomous University of Mexico (UNAM).

Correspondence

 

ABSTRACT

In the process of caries prevention, placement of pit and fissure sealants is a low-priced, effective and safe procedure. Presently, clinical operators prefer LED lamps. In pediatric dentistry, certain complications might arise such as lack of patient cooperation and small oral opening. This could result in increase of distance between light source and sealant. Objective: The purpose of the present study was to determine whether increase of distance between light source and pit and fissure sealant affected curing depth. Material and methods: 90 samples of pit and fissure sealant Helioseal F^® were light-cured for 20 seconds with a Bluephase C5 LED lamp (Ivoclar Vivadent^®), 30 seconds with the light source at a distance of 0 mm, 30 seconds at 5 mm and 30 seconds at 10 mm. Non-polymerized material was removed with a spatula for resin (Suter Dental^®). The sample was measured in mm with an electronic Vernier caliper; obtained value was divided into two (ADA's Norm 27). Results were assessed with ANOVA and Tukey tests. Results: The group treated at 0 mm exhibited curing depth of 2.01 mm (SD 0.11). The group treated at 10 mm, with 1.62 mm (SD 0.08) showed the least amount of curing depth. Statistically significant differences were found in average values when comparing the three groups (p < 0.05). Conclusion: Distancing light source from sealants affects their curing depth.

Key words: Curing depth, pits and fissure sealants, LED.

 

INTRODUCTION

Food remnants and caries-causing bacteria tend to accumulate on molars and premolars due to their morphology as well as deficient cleansing habits. For that reason, different techniques have been implemented with the aim of achieving less plaque retention in pits and fissures.¹

Dr. Buonocore, in 1955 developed the first pit and fissure sealant.² Presently, after the incorporation of acidetch techniques, pits and fissure sealants are almost routinely used in young patients.¹

Efficiency of sealants in caries prevention varies from 83% after one year, to 53% after 15 years.³

Sealant retention and longevity depend on three factors:

1) Ease of penetration of etching acid into the enamel.

2) Marginal sealing.

3) Resistance to abrasion.

This latter aspect is the most affected by decreases in the polymerization of the material.⁴

Presently, pits and fissure sealants are resin-based compounds, which include photo-initiators in their composition. Among these, we can count camphoroquinone, which is sensitive to wave lengths from 450 to 490 mm, and a strength of around 300 mW/mm².^5,6 This wave length and strength are achieved by several light sources such as halogen light lamps, plasma arch lamps, argon laser lamps and light emitting diode lamps (LED). Presently there is a tendency to use LED lamps.

Taking into account the fact that sealants are resin-based composites, their polymerization is affected by the intensity of the light impacting upon them. When only partial polymerization is achieved, their physical and mechanical properties will be affected.

It is important to undertake the material's light curing with suitable distance between sealer surface and light source so as to allow for total polymerization of the material.

Halogen light lamps have the disadvantage of functioning through the heating of a tungsten fiber, which brings about heat generation, their designs are relatively large. Fiber optic lamps are very fragile and therefore susceptible to breakage.

LED lamps have certain advantages over halogen light lamps: they do not generate heat and their designs are light and ergonomic.^6-8 A published study informed that the degree of conversion reached by diode-based curing units (LED) is only 5-10% lesser than the degree of conversion achieved by halogen cured units.⁷ Consequenceof the aforementioned reasons is the current tendency to use LED lamps.

Presently, certain questions on LED lamp polymerization effectiveness still persist. This subject has been approached in different studies.^9-11 Some of these studies consider the technique used during polymerization^12-15 while others have compared LED lamps with halogen lamps.^13,15-20

Partial polymerization can increase water absorption and unreacted monomer solubility; this impacts on the restoration's longevity and esthetics.⁵

In pediatric dentistry, frequently one encounters the disadvantage of not having ideal circumstances for placement of pits and fissure sealants. One of these disadvantages could be the consideration that pediatric patient's mouth opening is much smaller than that of adolescent or adult patients. This in turn could result in the need to increase distance between light source and sealer, which would probably decrease polymerization depth, thus negatively impacting on mechanical and physical properties.

The aim of the present article was to determine whether distance between the light source (LED) and sealant affected curing depth of pits and fissure sealants.

 

MATERIAL AND METHODS

A Bluephase C5 LED lamp (Ivoclar Vivadent) was used for the present study. Sealant employed was Helioseal F (Ivoclar Vivadent).

Specification number 27 of the American Dental Association (ADA) was followed: a 20 mm x 20 mm, 2 mm thick glass was used. On it, a sample-making mold was placed (with it, 4 mm diameter and 6 mm long samples were obtained). In order to preserve distance between pits and fissure sealant surface and light source, a 5 mm long and 6 mm diameter glass tube was used. The tube was of 10 mm length and 6 mm diameter (Figure 1). Polymerization depth was measured in 90 pits and fissures specimens.

Specimens were assembled into three groups (30 specimens per group). One group was light-cured by placing the lamp directly upon the sealant's surface; another group was light-cured at a controlled 5 mm distance, by placing the lamp on the 5 mm long glass tube, and the last group was light-cured at a 10 mm controlled distance by placing the lamp on the 10 mm long glass tube. All specimens were light-cured for 20 seconds, following manufacturer's instructions.

Once the light-curing process was completed, specimens were removed from the sample-maker and non-polymerized material was removed with a spatula for resin (Suter Dental^®) (Figures 2 to 7)(3, 4, 5, 6).

The height of the cured material was measured in mm with a digital Vernier caliper (Maxcal, USA) and the obtained figure was divided into two (specification number 27 of the ADA). Obtained values were considered as curing depth.

Results were included in an Excel calculus sheet and processed for analysis in a Sigma Stat 2.0 statistical package. A one way ANOVA test was used as well as a Tukey group comparison test.

 

RESULTS

The group light-cured at 0 mm recorded a 2.014 mm curing depth average (SD0.113) (Table I), whereas the 10 mm group with 1.623 mm (SD 0.0847) presented the least curing depth (Figure 8). Statistically significant differences were found in average values when comparing the three groups to a p < 0.05 (Tukey) test (Table II).

 

DISCUSSION

It has been proven that resin-based compounds' polymerization with a LED lamp is 6% higher than that achieved with a halogen lamp.⁸ Therefore, current trend favors use of LED lamps.

Drs Soh et al, found that curing depth of composite resins depended on lighting unit (lamp used) as well as on the exposition method.¹⁰

Drs Santos et al reported that composite resins' curing depth drastically decreased between 4 and 5 mm when using a halogen lamp, and it decreased by 2-3 mm when using a LED lamp, by placing the light source directly on the resin.²¹ These results concurred with ours, since we found significant differences in curing depth when the light source was placed directly upon the pit and fissure sealant (2.014 mm) at a 5 mm distance (1.843 mm) and 10 mm distance (1.623 mm).

Many studies have been conducted with the aim of determining the efficiency of pits and fissure sealants when considering their viscosity,^17,22,23 their filling material,^2,22 comparing sealants with and without pigments,^2,17 comparing self-curing and light-curing sealants, comparing different light sources for photo-curing,^2,6,17,24 comparing photo-curing time^6,17,25-27 as well as comparing different preparation techniques for enamel surface (acid etch, abrasive air with acid etch, enameloplasty with acid etch).^2,22,23 Nevertheless, studies conducted in order to determine LED lamps efficiency have not taken into consideration the distance between light source and material to be light-cured. Therefore, the present study offers a new research line.

Our results revealed that distance between light source and material to be light-cured considerably affected the light-curing quality of resin-based materials.

Depth of pits and fissures varies from 1 to 3 mm, cusps height can reach 3 mm, therefore, pits and fissure sealants will not be able to be light-cured at a distance lesser than 3 mm.

For these aforementioned reasons, we recommend that during pits and fissures' light-curing processes, the tip of the lamp should be placed directly upon the occlusal surface of molar or premolar, so as to optimize results.

Future studies are recommended, in order to determine the conversion degree of pits and fissure sealants using LED and halogen lamps at different distances, and thus determine which of the two types of lamps is more affected by the increase in distance.

 

CONCLUSIONS

In the present study and following the aforementioned methodology, it was proven that curing depth of pits and fissure sealants decreases when the distance between the light source and the sealant surface increases.

We therefore can state that inadvertently distancing the sealants from the light source negatively affects their curing process, decreasing thus the quality and permanence of the material in the mouth.

 

REFERENCES

1. Pinkham J. Odontología pediátrica. 2a edición. México, D.F.: Ed. McGraw-Hill Interamericana; 1998: pp. 529-537.         [ Links ]

2. Simoensen R. Pit and fissure sealant: review of the literature. Pediatr Dent. 2002; 24: 393-414.         [ Links ]

3. Irinoda Y, Matsumura Y, Kito H, Nakano T, Toyama T, Nakagaki H et al. Effect of sealant viscosity on the penetration of resin into etched human enamel. Oper Dent. 2000; 25: 274-282.         [ Links ]

4. Barberia E. Odontopediatría. 2a edición. Barcelona, España: Ed. Masson; 2001: pp. 190-191.         [ Links ]

5. Deb S, Mallet R, Millar B. The effect of curing with plasma light on the shrinkage of dental restorative materials. J Oral Rehabil. 2003; 30: 723-728.         [ Links ]

6. Gigo D, De Oliveira G, Carneiro C, Pereira J, De Lima M. Microhardness of resin-based materials polymerized with LED and halogen curing units. Braz Dent J. 2005; 16 (2): 98-102.         [ Links ]

7. Knezevic A, Tarle Z, Meniga A, Sutalo J, Pichler G. Influence of light intensity from different curing units upon composite temperature rise. J Oral Rehabil. 2005; 32: 362-367.         [ Links ]

8. Halvorson R, Erickson R, Davidson C. Polymerization efficiency of curing lamps: a universal energy conversion relationship predictive of conversion of resin-based composite. Oper Dent. 2004; 29 (1): 105-111.         [ Links ]

9. Yap A, Saw T, Cao T. Composite cure and pulp-cell cytotoxicity associated with LED curing lights. Oper Dent. 2004; 29 (1): 92-99.         [ Links ]

10. Soh M, Yap A, Siow K. Comparative depths of cure among various curing light types and methods. Oper Dent. 2004; 29 (1): 9-15.         [ Links ]

11. Yap A, Soh M. Curing efficacy of a new generation high-power LED lamp. Oper Dent. 2005; 30 (6): 758-763.         [ Links ]

12. Coelho M, Santos G, Nagem H, Mondelli R, El-Mowafy O. Effect of light curing method on volumetric polymerization shrinkage of resin composites. Oper Dent. 2004; 29 (2): 157-161.         [ Links ]

13. Yap A, Soh M, Han V, Siow K. Influence of curing lights and modes on cross-link density of dental composites. Oper Dent. 2004; 29 (4): 410-415.         [ Links ]

14. Neo B, Soh M, Teo J, Yap A. Effectiveness of composite cure associated with different light-curing regimes. Oper Dent. 2005; 30 (6): 671-675.         [ Links ]

15. Tarle Z, Knezevic A, Demoli N, Meniga A, Unterbrink G, Ristic M et al. Comparison of composite curing parameters: effects of light source and curing mode on conversion, temperature rise and polymerization shrinkage. Oper Dent. 2006; 31 (2): 219-226.         [ Links ]

16. Vandewalle K, Roberts H, Tiba A, Charlton D. Thermal emission and curing efficiency of LED and halogen curing lights. Oper Dent. 2005; 30 (2): 257-264.         [ Links ]

17. Mavropoulos A, Staudt C, Kiliaridis S, Krejci I. Light curing time reduction: in vitro evaluation of new intensive light-emitting diode curing units. Eur J Orthod. 2005; 27: 408-412.         [ Links ]

18. Nomoto R, McCabe J, Hirano S. Comparison of halogen, plasma and LED curing units. Oper Dent. 2004; 29 (3): 287-294.         [ Links ]

19. Soh M, Yap A, Yu T, Shen Z. Analysis of the degree of conversion of LED and halogen lights using micro-raman spectroscopy. Oper Dent. 2004; 29 (5): 571-577.         [ Links ]

20. Bala O, Üctasli M, Tüz M. Barcoll hardness of different resin-based composites cured by halogen of light emitting diode (LED). Oper Dent. 2005; 30 (1): 69-74.         [ Links ]

21. Santos G, Medeiros I, Fellows C, Muench A, Braga R. Composite depth of cure obtained with QTH and LED units assessed by microhardness and micro-raman spectroscopy. Oper Dent. 2007; 31 (1): 79-83.         [ Links ]

22. Barnes D, Kihn P, Fraunhofer J, Elsabach A. Flow characteristics and sealing ability of fissure sealants. Oper Dent. 2000; 25: 306-310.         [ Links ]

23. Hatibovik S, Braverman I. Microleakage of sealants after conventional, bur, and air-abrasion preparation of pits and fissures. Pediatr Dent. 1998; 20 (3): 173-176.         [ Links ]

24. Millar B, Nicholson J. Effect of curing with anplasma light on the properties of polymerizable dental restorative materials. J Oral Rehabil. 2001; 28: 549-552.         [ Links ]

25. Shortall A.Howlightsourceand product shade influence cure depth for a contemporary composite. J Oral Rehabil. 2005; 32: 906-911.         [ Links ]

26. Silta T, Dunn W, Peters C. Effect of shorter polymerization times when using the latest generation of light-emitting diodes. Am J Orthod Dentofacial Orthop. 2005; 128: 744-748.         [ Links ]

27. Staudt C, Marvopoulos A, Boullaguet S, Kiliaridis S, Krejci I. Light-curing time reduction with a new high-power halogen lamp. Am J Orthod Dentofacial Orthop. 2005; 128: 749-754.         [ Links ]

Mailing address:
Azucena Villarreal Rojas
E-mail: azucenavr@yahoo.com.mx

 

Note

This article can be read in its full version in the following page: http://www.medigraphic.com/facultadodontologiaunam