Comparative Assessment of Force Decay of the Elastomeric Chain With the Use of Various Mouth Rinses in Simulated Oral Environment: An In Vitro Study.

AIM: This study is aimed to assess the effect of different mouth rinses and its active components on the force decay of elastomeric chains. Listerine, Colgate Phos-Flur, Clohex Plus mouth rinses, 26.9% alcohol, 0.04% sodium fluoride (NaF), and 0.2% chlorhexidine were used for this study to determine its effects on force decay of elastomeric chains.
MATERIALS AND METHODS: Seven custom-made jigs were constructed on which 120 short module elastomeric chains were stretched to predetermined lengths between the pins. Using calibrated digital force tester, measurements of force exerted by the elastomeric chains while stretched on the framework were recorded at the time of attachment to the frame and after 24 hours, 7 days, 14 days, 21 days, and 28 days. The custom-made jigs and the elastomeric chains were allowed for complete submersion in artificial saliva throughout the test period, as well as in respective control solution and mouth rinses for 60 seconds, twice daily.
RESULTS: All test groups showed significantly more force decay than the control group. Statistically significant differences were observed when comparing force decay among the test groups except between a few. INTERPRETATION AND
CONCLUSION: Mouth rinses cause an increase in force decay of elastomeric chain over the time. Listerine and 26.9% alcohol solution caused maximum force decay by the end of 28 days. Least force degradation of elastomeric chain was seen with the use of 0.2% chlorhexidine.

INTRODUCTION

Synthetic elastomeric chains have been used by orthodontists since 1960s. These polyurethane materials have largely replaced latex elastics for intra-arch tooth movement and to consolidate spaces.[1] Placement and removal of chain elastics require little chair time for the clinician and minimal patient cooperation during application. The synthetic elastomeric materials have also been found to be relatively compatible with the mucosa.[2]

Orthodontic accessories such as elastomeric chains, elastics adhered to the tooth surfaces make it difficult to perform oral hygiene and act as additional bacterial plaque retainers, leading to demineralization of enamel, causing white lesions, dental caries, and gingivitis. Demineralization is more commonly seen on the buccal surfaces of orthodontically treated teeth.

Mouth rinses should be used during the orthodontic mechanotherapy for antimicrobial activity, to decrease the plaque accumulation, and thereby preventing demineralization. Chlorhexidine acts in a preventive manner in the reduction of bacterial plaque in patients undergoing orthodontic treatment. It is a synthetic antimicrobial agent that presents a high level of activity, however, having secondary effects such as staining, ulceration of mucosa. Hence, other mouth rinses such as Listerine and Colgate Phos-Flur are recommended during orthodontic treatment.

The alcohol content of the mouth rinses has shown to cause structural and molecular modification, which results in the decay of elastomeric chain.[3] The recent addition of new mouth rinses without alcohol content and presence of other active ingredients may also have an effect on the elastomeric chains. Hence, the purpose of this study was to assess the effect of different mouth rinses and its active ingredients on the force decay of elastomeric chains.

MATERIALS AND METHODS

The study was performed in the Department of Orthodontics and Dentofacial Orthopaedics, Sree Anjaneya Institute of Dental Sciences, Calicut, Kerala, India. Seven specimen groups were tested with a total sample size of 840 specimens. A specimen is described as a three-link, short module, clear elastomeric chain (Clear Chain Elastic Short; Ortho Organizers®, Carlsbad, California). Specimens were mounted on custom-made test jigs. Seven custom-made jigs, each with a series of pins set 23.5 mm apart, were used to hold stretched elastomeric chains at a constant length [Figure 1]. The control and test groups were independently submerged in separate, 37°C artificial saliva in order to simulate the oral conditions. The formulation of the saliva solution was made by Avinash Chemicals (Bengaluru, India). It was housed in an incubator and maintained at room temperature using thermostat. Control and test groups were each exposed to the respective solutions for 60 seconds twice daily, and force measurements were recorded at six time points during the experiment.

Figure 1

Custom-made jigs with pins

After being submerged in the respective solutions, specimens were dipped in separate, distilled water baths to simulate rinsing of the mouth rinses from the oral cavity. These specimens were then placed back into artificial saliva at 37°C. Six test measurements of the remaining force were made at the following time intervals: initial (0), 1, 7, 14, 21, and 28 days. Force measurements were obtained with a digital force tester [Figure 2] (Lutron FG-5000; Lutron Electronic Enterprise Co Ltd, Taipei, Taiwan). After each measurement, the force tester was reset to a zero reading before taking the next measurement. Measurements were made by leaving one end of the elastomeric chain secured on the pin and fixing the other to the force tester, allowing for the measurement of the tensile force. Measurement readings were taken with the elastomeric chain stretched to the same 23.5-mm length that the jig pins had previously maintained them.

Figure 2

Lutron Force Tester FG-5000A

Statistical analysis: Means, standard deviations, and percentages were determined. The effects of solution on force decay were tested by the analysis of variance repeated measurement analysis. Follow-up Bonferroni simultaneous t tests were used to assess differences among the sets of means with statistical significance set at a family-wise P < 0.05.

Statistical software: Analysis of the data was performed using statistical softwares SAS 9.2, SPSS 15.0, Stata 10.1, MedCalc 9.0.1, Systat 12.0, and R Environment ver. 2.11.1. Graphs and tables were generated using Microsoft Office Word and Excel.

RESULTS

In this experiment, factors influencing force decay of elastomeric chains, that is, exposure to different test solutions, were observed and recorded [Table 1].

Table 1

Mean force decay (cN) recorded during different time durations and in different test solutions

Duration	Solution	Mean	Standard deviation	Standard error of the mean	Median	Min	Max
Initial	Artificial saliva	549.95	11.90	2.66	550.15	532.50	575.65
	26.9% Alcohol	549.76	13.59	3.04	549.17	530.53	571.72
	Listerine	551.13	11.95	2.67	552.60	523.67	568.78
	0.04% NaF	556.28	9.24	2.07	557.99	539.36	571.72
	Phos-Flur	551.52	12.76	2.85	554.07	531.52	570.74
	0.2% Chlorhexidine	556.28	10.18	2.28	556.03	539.36	572.70
	Clohex plus	550.98	11.90	2.66	551.61	523.67	568.78
24 hours	Artificial saliva	285.86	23.90	5.34	280.96	261.83	382.45
	26.9% Alcohol	278.01	10.71	2.39	279.49	259.87	294.19
	Listerine	283.80	7.65	1.71	285.37	267.72	294.19
	0.04% NaF	282.72	9.24	2.07	283.41	261.83	298.12
	Phos-Flur	278.21	16.60	3.71	279.49	221.63	302.04
	0.2% Chlorhexidine	296.50	33.11	7.40	283.41	258.89	365.78
	Clohex plus	283.65	19.28	4.31	278.99	261.83	352.05
7 days	Artificial saliva	277.08	8.71	1.95	277.52	261.83	296.16
	26.9% Alcohol	233.88	8.35	1.87	237.32	215.74	248.10
	Listerine	238.64	9.83	2.20	239.77	209.86	252.03
	0.04% NaF	277.38	40.82	9.13	276.05	228.49	355.98
	Phos-Flur	281.25	26.44	5.91	276.54	245.16	349.11
	0.2% Chlorhexidine	308.25	37.32	8.34	293.70	258.89	384.42
	Clohex plus	302.38	37.05	8.29	311.36	242.22	356.96
14 days	Artificial saliva	277.08	8.71	1.95	277.52	261.83	296.16
	26.9% Alcohol	222.70	12.31	2.75	223.10	200.05	244.18
	Listerine	226.41	8.86	1.98	227.02	209.86	242.22
	0.04% NaF	250.80	35.31	7.90	239.77	196.13	339.31
	Phos-Flur	260.02	24.76	5.54	267.72	215.74	301.06
	0.2% Chlorhexidine	293.26	25.01	5.59	288.80	256.93	337.34
	Clohex plus	300.67	30.23	6.76	293.21	261.83	351.07
21 days	Artificial saliva	263.35	10.86	2.43	261.83	248.10	296.16
	26.9% Alcohol	179.96	26.50	5.93	187.30	136.31	220.64
	Listerine	161.52	21.34	4.77	162.79	126.50	206.92
	0.04% NaF	200.29	34.22	7.65	183.38	156.90	262.81
	Phos-Flur	215.50	35.41	7.92	229.47	141.21	250.06
	0.2% Chlorhexidine	238.25	31.47	7.04	230.45	196.13	284.39
	Clohex plus	256.14	27.78	6.21	263.80	196.13	293.21
28 days	Artificial Saliva	256.88	12.20	2.73	256.93	240.26	296.16
	26.9% Alcohol	189.80	25.92	5.79	187.30	155.92	246.14
	Listerine	173.52	27.25	6.09	174.55	121.60	247.12
	0.04% NaF	197.50	28.02	6.26	187.79	149.06	259.87
	Phos-Flur	191.86	40.64	9.09	173.08	142.19	270.63
	0.2% Chlorhexidine	200.03	27.00	6.04	193.52	161.80	246.14
	Clohex plus	187.84	23.20	5.19	183.38	151.02	235.35

Among the different solutions, higher mean force was recorded in artificial saliva > 0.2% chlorhexidine > Clohex Plus > Colgate Phos-Flur > 0.04% NaF > 26.9% alcohol, and Listerine, respectively [Table 2]. The difference in mean force decay among the different solutions was found to be statistically significant (P < 0.001). The interaction (joint effect) of duration and solution on mean force decay was found to be statistically significant (P < 0.001) [Graph 1].

Table 2

Results of the analysis of variance of elastomeric chain force decay for duration, solution, and the interaction between variables

Source of variation	df	Sum of squares (SS)	Mean SS	F	P value
Solution	6	255,318	42,553	76.56	<0.001*
Duration × Solution	30	223,688	7,456	13.41	<0.001*
Error	798	443,550	556	—	—
Total	839	12,552,891	—	—	—

*denotes significant factor

Graph 1

Interaction effects plot shows the mean force decay recorded in different levels of a factor against different levels of other factor

DISCUSSION

Elastics made from natural rubber continue to be in common use in orthodontics, mainly because of their favorable characteristics of high flexibility and low cost. Elastomeric chains are used as the retractive force to move teeth into extraction sites, closing diastemas, generalized space closure, and correction of rotated teeth. When exposed to an oral environment, they absorb water and saliva, permanently stain, and suffer breakdown of internal bonds leading to permanent deformation.[4] They also experience rapid loss of force due to stress relaxation, resulting in a gradual loss of effectiveness.[5]

The oral hygiene problems have not been completely eliminated because there is greater bulk of material around the bracket when compared with the wire ligature. Considering that deficient oral hygiene generally causes difficulty to achieve successful orthodontic treatment, it is necessary to implement an individualized model of preventive education for each patient. In individuals who cannot or are unable to perform good oral hygiene in addition to mechanical control, it is important to implement chemical plaque control also.

According to Table 1, the mean percentage of force loss after 24 hours was 46%–49% for the tested groups, which is comparable to that reported in the published studies for elastomeric chains.[12567891011] The highest percentage of force decay ie: 49.48% for short module after 24 hours was seen in 26.9% alcohol group, due to hydrolysis caused by alcohol. The lowest percentage of force decay of 46.7% in 0.2% chlorhexidine group.

There is sudden decline of force in the first 24 hours. Subsequent amount of force decay occurred till 21 days and then a plateau was reached. These results support previous studies, that the greatest loss of force in elastomeric chains occurs in the first hour but disagree in the magnitude of the loss.[1213] The discrepancy in the magnitude of force loss of elastomeric chains can be attributed to methodological differences such as, brands of elastomeric chain. Highest mean residual force was recorded in artificial saliva followed by 0.2% chlorhexidine, Clohex Plus, Colgate Phos-Flur, 0.04% sodium flouride (NaF), 26.9% alcohol, and Listerine, respectively. The difference in mean force decay among the different solutions was found to be statistically significant (P < 0.001).

Force decay was highest in Listerine and 26.9% alcohol, which might be caused by the hydrolysis action of alcohol content on elastomeric chain. NaF (0.04%) and Colgate Phos-Flur showed force decay within the range, but it does not have antimicrobial property. Fluoride prevents white spot lesions or demineralization that occurs during orthodontic therapy. Chlorhexidine 0.2% and Clohex Plus showed least force decay of elastomeric chain. Hence, chlorhexidine can be used as a chemical plaque control during orthodontic treatment. As it has a side effect of staining teeth, the patient should be instructed about its usage and made aware of its side effects

The elastomeric chains tested in this study appear to significantly increase force decay with mouth rinses in a simulated oral environment. This study indicates that all the elastomeric chains tested had a residual force after 28 days, which is necessary for canine retraction and space closures.

As this study was conducted under static conditions and in vitro, it was performed short of an exact picture of the degradation in vivo. This would allow us for a better understanding of the physical properties of elastic materials under clinical conditions.

CONCLUSION

On the basis of the analysis of the results obtained and the limitations of the study, the following conclusions were drawn:

Listerine mouthwash (alcohol based) causes maximum force decay (71.61%) of elastomeric chains in 28 days. Clohex Plus mouth rinse (chlorhexidine based) causes least force decay (64.91%) of elastomeric chains. Colgate Phos-Flur (fluoride based) causes force decay of 65.22% on elastomeric chains.

Alcohol (26.9%), which is the component of Listerine, caused 69.26% of force decay by end of 28 days. NaF (0.04%), which is the component of Colgate Phos-Flur, caused 64.2% of force decay. Chlorhexidine (0.2%), the component of Clohex Plus mouth rinse, caused 64% of force decay.

Force decay is more when mouth rinse as a whole is used, in comparison with action of its major components on elastomeric chains at the end of 28 days.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.