Penetration and Marginal Leakage of Embrace WetBond Pit & Fissure Sealant

Summary of studies conducted at the Biomaterials Innovations Research Development Laboratory, Paris, France. Supervision by Professor Michel DEGRANGE. Conducted by Frédéric COURSON, Stéphane LEGOFF and Wladimir ARANDA (2001, 2002)

Aim: Determine penetration depth of Embrace material in vitro in a pit and fissure application. Measure sealing ability or marginal leakage of Embrace, in vitro after thermocycling. Compare these results to other materials and previous studies of this type.

Methodology
Two parameters were used for this evaluation:

1. Penetration depth of the material into the pits and fissures of the permanent teeth. The result was expressed as a percentage of the total depth of the fissure.
2. Microleakage test using the method described by Övrebö and Raadal in 1990. A dye (silver nitrate) was used to test the microleakage. The scoring system used for this evaluation is given below:
   • Score 0 : no penetration of the dye seen in the section
   • Score 1 : penetration into the part around the sealant
   • Score 2 : penetration to the part below the sealant
   • Score 3 : penetration at the base of the fissure
   The materials used were:
   
   • Embrace WetBond viscosity 1 (Pulpdent)
   • Embrace WetBond viscosity 2 (Pulpdent)
   • Delton FS+ (Dentsply)
   Delton FS+ is a traditional, 55% filled, light-cured sealant with fluoride release. Its matrix is composed to TEGDMA (55%) and bis-GMA (45%)/bis-MA(5%)

This evaluation was carried out on specimens consisting of recently-extracted human molar teeth stored in 1% chloramine T at 4ºC. Only unerupted third molars are used for evaluating sealants, since these teeth have not been affected by contaminants from the external environment. Each group consisted of 10 teeth, except for the Delton FS+ group (15 teeth). Each tooth was first cleaned using a brush mounted on a contra-angle handpiece, with pumice. The same operator applied the different materials.

Procedure

1. The tooth was cleaned with pumice by brushing and rinsing with spray and air.
2. Sealant was applied according to the manufacturer’s instructions for each product. All teeth were numbered.
3. Specimens were subjected to thermal cycling for 1800 cycles alternating between 5ºC and 55ºC (10 s immersion in each bath).
4. The apex of each tooth was sealed to prevent penetration of dye (Scotchbond™ Multi-Purpose Plus – Z100, 3M).
5. Two layers of varnish were applied to within 1 millimetre of the sealant margin (interface tooth-material).
6. The teeth were immersed in 50% silver nitrate solution (AgNO3) under inactinic light, and placed on a vibrator for two hours.
7. The teeth were rinsed with distilled water and exposed to visible light for at least 12 hours.
8. Developed (Kodak developer) for two hours.
9. Teeth were rinsed in distilled water and cleaned with acetone and then brushed with pumice to allow better adhesion between the tooth and the embedding resin.
10. Embedded in acrylic resin (Pexil-Escil, France).
11. Each specimen was sectioned (3-5 sections) using a circular saw with diamond disc, under water (Isomet® Buehler).
12. Sections were examined under a binocular microscope (Olympus SZH10) at 10x magnification, and photographed.
13. The penetration depth of the material into the pits and fissures of the different interfaces thus obtained were measured with a curvimeter (expressed in %) and the percolation of the dye at the tooth-material interface evaluated using the method described by Övrebö and Raadal (expressed as scores). In the present study, only the worst section score for each tooth was used for the microleakage.

Statistical analysis: ANOVA analysis of variance (if there was equality of variance and as a function of the results, PLSD-Fisher tests for between-group comparison). Taking into account the quantification of dye penetration as whole numbers, these data on microleakage were treated with a non-parametric chi-square test.

Results
Tables 1-3 show the results of the three products studied. Table 1 indicates the penetration depth, in %, for each material. Table 2 shows the marginal leakage scores for each material. Table 3 is a statistical analysis of the microleakage data.

The test of equality of variance allowed us to use a parametric test (ANOVA) to analyse the penetration depth of the different materials. This test shows a significant difference between the products (p=0.007). The Fisher PLSD test particularly shows a difference in favour of Embrace V2 compared with Delton FS+ (p=0.007). Considering the microleakage, there was also a difference between the products (p=0.012). A two-sided comparison is given in Table 3.

Table 1. Filling of the different materials

Lot	Abbreviation	N	Penetration	Standard	Coefficient
			depth %	deviation %	of variation %
Embrace viscosity 1	EmbV1	10	91.3	6.6	7.2
Embrace viscosity 2	EmbV2	10	97.3	4.5	4.6
Delton FS+	DFS+	10	86.6	7.3	8.4

Table 2. Distribution of scores for the different materials (in %)

Score	EmbV1	EmbV2	DFS+
0	30	60	20
1	20	30	73
2	50	10	7
3	0	0	0

Table 3. Statistical results of the two-sided comparison (Chi²)

	Delton FS+	Embrace V1	Embrace V2
Delton FS+	-	0.44	0.09
Embrace V1		-	0.39
Embrace V2			-

Significance
With respect to the penetration depth of the different materials, Embrace viscosity 2 gave the best results with a particularly high penetration, 97.3%. This value was statistically significantly higher than the other materials. The standard deviation and coefficient of variation were lower for this material, suggesting less technique sensitivity in using Embrace.

Regarding microleakage there was also a significant difference statistically, with Embrace showing the least microleakage. Embrace also had the greatest number of scores showing no leakage – or a score of zero. The fact that this material is tolerant of residual humidity (wet-bonding) partly explains these good results. It certainly confers an advantage on its clinical use in children, where a perfectly dry occlusal surface is sometimes difficult to obtain.

Good isolation during application of the sealant is always necessary – this hydrophilic resin has a clear advantage over traditional sealants, which are mostly hydrophobic. Examination of the tooth / Embrace interface indicates that Embrace shows good resistance to polymerization retraction in an unfavorable geometry (such as pit and fissures) and under simulated adverse hydrothermal conditions.

Conclusion
Embrace WetBond Pit and Fissure Sealant and Small Lesion Restorative material was shown to penetrate into a fissure exceptionally well. An average percent penetration score of 97.3% was measured for Embrace WetBond viscosity 2 (36.6% filled resin). Embrace was shown to protect a tooth from microleakage and penetration of fluids during thermocycling. The combination of excellent penetration and marginal sealing offer significant advantages to Embrace as a pit and fissure sealant material when compared to other products. Embrace™ WetBond is the sealant of choice and is superior to Delton FS in sealing ability, microleakage and fissure penetration.