Evaluating the effectiveness of color changing adhesives versus ultraviolet absorbent dye additive adhesives in the removal of adhesive remnants after orthodontic debonding

Introduction

The fixed orthodontic treatment initiates with the bonding of brackets and attachments for orthodontic tooth movement and it terminates with the removal of those brackets and attachments from the surface of the teeth. Bonding of brackets must ensure a good shear bond strength and low bond failure to the orthodontic forces that are applied during orthodontic tooth movement and the forces of mastication on the teeth surface.1, 2 Therefore, this bond strength should cause no or minimal enamel damage while removal of the brackets from the enamel surface after treatment completion.

Various methods of debonding techniques are practiced and the common method of debonding is done with pliers which apply a shear or tensile force to the bonded surface without any potential damage to enamel. Unfortunately there is no standard protocol for the debonding procedure.3, 4 While debonding there is minimal enamel damage which is inescapable because of the micro-mechanical bond between the etched enamel and adhesive utilized for orthodontic bonding. While removing the brackets from the teeth structure there is a bond failure occurring between adhesive-enamel or adhesive-bracket interface (adhesive failure) or within the adhesive (cohesive failure). Usually, the combination of adhesive-enamel failure occurs leaving a considerable amount of adhesive remnants on the enamel surface.5 Metallic orthodontic brackets are widely used for fixed orthodontic treatment and the cris-cross wire mesh fused to the base of the metal brackets provide for mechanical interlocking of metal brackets to the composite resin and hence constituting to a clinically efficient adhesion between bracket base-adhesive-enamel.6

Artun and Bergland used Adhesive Remnant Index (ARI) system to measure the amount of adhesive left on the enamel surface after debonding. The differences in ARI scores reflect a difference in bond strength between the enamel and the adhesive. The complete removal of adhesive remnants is an important procedure because it results in excessive plaque accumulation, periodontitis, white spot lesions and enamel discoloration. For achieving a complete removal of adhesive remnants from the tooth surface with negligible damage to the enamel surface, the Orthodontists must take adequate care to remove the adhesive remnants from the enamel surface. This procedure involves a high challenge due to the shade similarities between enamel surface and adhesives as noted by various studies in Orthodontics and Restorative dentistry forums.7, 8, 9

The fluorescent material used in the study emits more visible light than it receives and thus they are utilized for distinguishing the enamel surface and the adhesives for identifying and removal of the adhesive remnants.[9] Various authors and studies have evaluated UV light source as an aid for detecting the composite restoration in Dentistry journals and forensic investigations.3, 10, 11 The objective of this study was to compare the effectiveness of color changing bonding adhesives versus UV absorbent dye additive adhesives in the removal of adhesive remnants after orthodontic debonding.

Materials and Methods

This in-vitro study was conducted in the Department of Orthodontics and Dentofacial Orthopedics, in tertiary dental college and Department of Manufacturing Engineering and Centralized Instrumentation and Service Laboratory (CISL) in a government affiliated laboratory. Prior to the start of the study the approval was obtained from the Institutional Ethics Committee (IGIDSIEC2020NRP25PGUDODO)]. Based on the findings from Connie Lai and associates sample size was calculated using the formula - n = (Zσ/E)² (α = 0.05 , Z = 1.96 , σ= 0.08 , E = 0.05), power of 95% to detect a difference greater than 0.5 mm², and a standard deviation of 0.4 mm². A sample size of 10 premolar teeth was found to be adequate for each group. Therefore, 40 extracted premolar teeth from patients undergoing therapeutic extractions during Orthodontic treatment were collected. Only teeth with normal tooth morphology, intact buccal enamel, devoid of caries, plaque and calculus were included and teeth treated with chemical agents and visible cracks were excluded. Conventional metal brackets with MBT prescription 0.022” slot were bonded by a single trained investigator with different orthodontic bonding adhesives to the buccal surface of the premolars which were divided randomly into four different groups as mentioned in (Table 1). Teeth from each group were cleaned with water to remove blood stains and tissue remnants which were then polished with ICPA Smile and Shine Polishing kit. Each tooth was mounted on an acrylic block (15×10cm), such that the facial surface of the premolar teeth is perpendicular to the base of the acrylic block.

The enamel surface of each sample was conditioned with 37% Phosphoric acid (EZ Etch) for 30 seconds as instructed by the manufacturer and rinsed with water for 10 seconds. Following the brackets were bonded in each group with respective adhesives (Figure 1, Figure 2), (Table 1). All the samples were placed in a closed container under distilled water for 24 hours before debonding procedure was carried out.

The samples were fixed in the lower jaw of INSTRON (Universal Testing Machine) (Figure 3) and debonded by a sharp pointed device loaded on the upper jaw which moved at a crosshead speed of 1.0 mm/min for debonding of the brackets to standardize the debonding force (1.0 k N) employed during debonding procedure. The tooth surface after debonding procedure were subjected to stereomicroscope and microphotographs were obtained to measure the adhesive remnant index (ARI) score according to Artun J, Bergland (score 0 – no adhesive left on tooth, score 1 - <50% of adhesive on tooth, score 2 - > 50% adhesive left on tooth, score 3 – all adhesive left on tooth), (Figure 4).

The enamel surface with adhesive remnants were removed thoroughly with Tungsten Carbide (12-bladed, SYNDENT) bur in a low speed hand-piece by utilizing the light sources for the specific groups and the time taken for the removal was noted by the same investigator with an assistant to hold the UV flashlight from the point of applying the bur to the end of removal of adhesives. (Table 1), (Figure 5, Figure 6).

The tooth surface after adhesive removal were subjected to stereomicroscope for assessing the adhesive remnant index score for each specimen and photographs were obtained and the images were scaled for the surface area of adhesive remnants which was again traced and calculated using Image J software (National Institutes of Health, Rockville) precisely marked with the end points of the adhesive remnants and joined them to obtain the surface area of the adhesive remnants with respect to length and breadth (Figure 7). All measurements were made twice, 1 week apart by the same trained operator. The repeated measurements were used for assessing intra-rater reliability, and the average was used in the statistical analysis. For assessment under Scanning Electron Microscope (JSM-IT200, In Touch Scope ^TM). The enamel damage score in all the samples were evaluated according to Howell and Weekes (grade 0 – smooth surface, no scratches, grade 1 - acceptable surface, fine scratches, grade 2 – rough surface, coarse scratches, grade 3 – very rough surface, deep scratches visible in naked eye), (Figure 8).

Statistical analysis

All statistical analyses were performed using the SPSS software. One way ANOVA and Post – Hoc tukey test were used to assess the difference in continuous variables between different groups. Chi square test was used to assess the difference in categorical variables in different groups. p -value of <0.05 was accepted as statistically significant.

Figure 1

Group1 (Enlight + Ortho Solo)

Figure 2

Group2 (Grengloo + Ortho Solo)

Figure 3

Group3 (Brace Paste + Ortho Solo)

Figure 4

Group4 (Enlight + Ortho Solo + UV dye)

Figure 5

Deboning– Universal testing machine

Figure 6

a: Group 1 – Enlight b: Group 2 – Grengloo c: Group 3 – Brace Paste under UV illumination d: Group 4 – Enlight + UV dye e: Group 4 – Enlight + UV dye + UV flashlight illumination

Figure 7

UVdye lipstick and UV flash light

Figure 8

Adhesiveremnant removal

Figure 9

Tungsten carbide bur

Figure 10

Adhesive remnant measurement in Image J software

Figure 11

Scanningelectron microscope

Figure 12

Scanningelectron microscope evaluation

Table 1

Experimental groups

Groups	Bonding adhesives	Evaluating light source
Group 1	Enlight (ormco)	Conventional yellow light
Group 2	Grengloo (ormco)	Conventional yellow light
Group 3	Brace paste (american orthodontics)	Ultra violet light – 395 nm
Group 4	Enlight (ormco) with uv dye additive (uv lipstick - moon glow) incorporated with primer	Ultra violet light – 395 nm

Table 2

ARIindex

Score 0	No adhesive left on the tooth,
Score 1	Less than half of the adhesive left on the tooth
Score 2	More than half of the adhesive left on the tooth
Score 3	All adhesive left on the tooth with distinct impression of the bracket mesh

Table 3

EDIindex

GRADE 0	Perfect and smooth surface. No scratches, distinct intact perikymata;
GRADE 1	Satisfactory surface. Fine scratches, some perikymata;
GRADE 2	Acceptable surface. Several marked and some deeper scratches, no perikymata;
GRADE 3	Imperfect surface. Several distinct deep and coarse scratches, no perikymata;

Table 4

The mean shear bond strength and standard deviation of orthodontic adhesives

		Mean (MPa)	Std. Deviation	F - value	p - value
Group – 1	10	14.0090	1.02569	100.685	<0.001
Group – 2	10	22.0820	1.60458
Group – 3	10	17.4550	1.12369

[i] *(Group 1 -Enlight, Group 2 – Grengloo, Group 3 – Brace paste)

Table 5

Post hoc test

(I) Group	(J) Group	Mean Difference (I-J)	Sig.
Group - 1	Group – 2	-8.07300	<0.001
	Group – 3	-3.44600	<0.001
Group - 2	Group – 3	4.62700	<0.001

[i] *(Group 1 -Enlight, Group 2 – Grengloo, Group 3 – Brace paste)

Table 6

The mean time taken for adhesive removal, Standard deviation and Standard error values of time taken for removal of adhesive remnants after debonding.

		Mean (seconds)	Std. Deviation	p - value
Group 1	10	10.1410	1.02024	0.033
Group 2	10	9.6210	1.50655
Group 3	10	8.5450	1.50945
Group 4	10	8.8160	1.02140

[i] *(Group1 - Enlight, Group 2 – Grengloo, Group 3 – Brace paste, Group 4 – Enlight withUV additive)

Table 7

: Post– Hoc tests

(I) Group	(J) Group	Mean Difference (I-J)	Std. Error	Sig.	95% Confidence Interval
					Lower Bound	Upper Bound
Group 1	Group 2	.52000	.57586	.845	-1.1686	2.2086
	Group 3	1.59600	.57586	.043	-.0926	3.2846
	Group 4	1.32500	.57586	.171	-.3636	3.0136
Group 2	Group 3	1.07600	.57586	.337	-.6126	2.7646
	Group 4	.80500	.57586	.587	-.8836	2.4936
Group 3	Group 4	-.27100*	.57586	.974	-1.9596	1.4176

[i] *(Group1 - Enlight, Group 2 – Grengloo, Group 3 – Brace paste, Group 4 – Enlight withUV additive)

Table 8

ARI score distribution and Chi – square test

				Ari Score				Total	Chi-square value	p-value
				0	1	2	3
GROUP	1		Count %	1	5	3	1	10
				10.0%	50.0%	30.0%	10.0%	100.0%
	2		Count %	2	5	3	0	10	2.882	0.969
				20.0%	50.0%	30.0%	.0%	100.0%
	3		Count %	2	4	4	0	10
				20.0%	40.0%	40.0%	.0%	100.0%
	4		Count %	2	4	3	1	10
				20.0%	40.0%	30.0%	10.0%	100.0%
Total			Count %	7	18	13	2	40
				17.5%	45.0%	32.5%	5.0%	100.0%

[i] *(Group1 - Enlight, Group 2 – Grengloo, Group 3 – Brace paste, Group 4 – Enlight withUV additive)

Table 9

The mean area and standard deviation values ofsurface area of adhesive remnants present on the tooth surface after debonding.

		Mean	Std. Deviation	p - value
Group 1	10	3.5700	1.54146	0.878
Group 2	10	3.0330	1.63750
Group 3	10	3.4270	1.79859
Group 4	10	3.5650	1.75063

[i] *(Group1 - Enlight, Group 2 – Grengloo, Group 3 – Brace paste, Group 4 – Enlight withUV additive)

Table 9 denotes the mean, standard deviation of the surface area of adhesive remnants present on the tooth surface after debonding of the attachments. Group 1exhibits the highest mean surface area when compared with the other groups. The surface area of adhesive remnants present over the tooth surface between the groups reveals no statistically significant difference. (p>0.05).

Table 10

EDI score distribution and Chi – square test

				EDI Score						Total		Chi – square test	p - value
				0	1	2			3
Group	1	Count		3	5	2			0	10		2.242	.896
		%		30.0%	50.0%	20.0%			0.0%	100.0%
	2	Count		4	4	2			0	10
		%		40.0%	40.0%	20.0%			0.0%	100.0%
	3	Count		3	6	1			0	10
		%		30.0%	60.0%	10.0%			0.0%	100.0%
	4	Count		2	7	1			0	10
		%		20.0%	70.0%	10.0%			0.0%	100.0%
Total		Count %	12		22		6	0			40
			30.0%		55.0%		15.0%	0.0%			100.0%

[i] (Group 1 - Enlight, Group 2 –Grengloo, Group 3 – Brace paste, Group 4 – Enlight with UV additive)

Results

Table 1 shows descriptive statistics of mean and standard deviation of shear bond strength between groups. Inferential statistics using post hoc tukey test showed the shear bond strength between the three groups were statistically significant (p<0.05). Group 2 showed highest shear bond strength between the groups. (Table 2)

Table 3 shows time taken parameter for the removal of adhesive remnants between the groups and indicates a statistically significant difference (p<0.05). Group 3 showed the least time taken for the removal of adhesive remnants between the groups. (Table 4 ) Frequency distribution of adhesive remnant index score, enamel damage index scores and descriptive analysis of surface area evaluation revealed a statistically insignificant difference between the experimental groups. (Table 5, Table 6, Table 7)

Discussion

The fixed orthodontic treatment initiates with bonding of brackets for orthodontic tooth movement and the treatment terminates with the debonding of the bonded brackets from the enamel surface. The adhesive remnants present over the enamel surface after the debonding procedure lead to the accumulation of plaque and calculus, esthetically compromised appearance, white spot lesions etc. Therefore the knowledge on adhesive remnant removal after debonding procedure in fixed orthodontic treatment has not been clear till now and there is no standard protocol to remove the remnants completely from the enamel surface. Thus the current study was designed to compare and evaluate the effectiveness between the color changing orthodontic bonding adhesives and the UV dye additive orthodontic bonding adhesives in the removal of adhesive remnants (AR) after debonding.

Conclusion

The current study concluded with the introduction of a new auxiliary and a bio - compatible additive (UV dye additive) for the removal of adhesive remnants from the enamel surface with clear visual distinction between the enamel surface and the adhesive and the color changing bonding adhesives included in the study has their own unique property of color change and fluorescence which has been incorporated in the material which resulted in reduction in time taken for the removal of the adhesive remnants without any potential enamel damage respectively. Future research with the available resources would benefit the Orthodontists and the patients as well for betterment in treatment outcome.

Source of Funding

None.

Conflict of Interest

None.