Comparative Study of Amorphous Calcium Phosphate-containing Orthodontic Composite and Conventional Orthodontic Adhesive on Enamel Demineralization around Orthodontic Brackets – An in vivo Study

Introduction: One of the most difficult problems in orthodontic treatment with fixed appliances is enamel demineralization around the brackets. This iatrogenically caused white spot lesions leads to poor esthetics; and in severe cases it may need restorative treatment. objective: To evaluate in vivo effect of Amorphous Calcium Phosphate (ACP)-containing orthodontic composite on enamel demineralization around orthodontic brackets, and to compare it with the conventional resin based orthodontic composite. Materials & Method: 20 orthodontic patients planned for four first premolars extraction were selected for the study. All first premolars were bonded with Aegis Ortho, an ACP-containing orthodontic composite (experimental group), and Transbond XT, a resin-based orthodontic composite (control group). After 45 days teeth were extracted, sectioned for the microhardness group and evaluated by superficial-microhardness analysis and stereomicroscopic study. Unpaired t-test and analysis of variance (ANOVA) test was performed. result: The ANOVA showed statistically significant differences for position, material, depth, and their interactions (p <0.001). The multiple comparison test showed that the ACP-containing orthodontic composite was significantly more efficient than the conventional composite, reducing enamel demineralization in almost all evaluations (p <0.001). The stereomicroscopic examinations showed a lesser extent of demineralization around orthodontic brackets for the ACP-containing orthodontic composite group. conclusion: ACP-containing orthodontic composite for bonding orthodontic brackets successfully inhibited demineralization, which was localized to the area around the brackets.


IntroductIon
Introduction of simplified bonding procedures has improved the efficiency of clinical practice in orthodontics.However, one of the most difficult problems in orthodontic treatment with fixed appliances is enamel demineralization and formation of white spot lesions around the brackets.The bands, brackets and other various orthodontic appliances make patient's dental hygiene more difficult and accumulation of plaque easier.In orthodontically treated cases this iatrogenically caused white spot lesions lead to poor esthetics and in severe cases it may need restorative treatment.
Study by Bloom et al 1 documented significant increase in oral bacteria during orthodontic treatment.The rate of demineralization in orthodontic patients was higher than those without orthodontic treatment. 2The prevalence of demineralization in orthodontic patients has been reported between 2% to 97% by Mizrahi 2 and Gorelick et al. 3 Zachrisson and Zachrisson 4 stated that, although bonding offers better access for cleaning than banding, it does not necessarily guarantee better oral hygiene and improved gingival condition, especially if excess adhesive extends beyond the bracket base.Also, the protection against interproximal caries provided by well-countoured cemented bands is absent.
Schumacher et al 5      The statistically significance level was set at p <0.05 level.

reSult
Cross-sectional microhardness test was conducted for the selected samples, as a strong co-relation existed between microhardness score and mineral loss from the enamel.
Stereomicroscope study was done to evaluate the extent of surface area of demineralization of enamel.

Microhardness Analysis result
The interaction between depth and material on enamel It was observed that the microhardness value of ACPcontaining composite was significantly higher than microhardness of Transbond XT composite (Table 1).

laboratory Procedures & Analyses
Preparation of Group I samples for microharhness analysis: The teeth crowns were hemi-sectioned vertically into mesial and distal halves, leaving a crown and root in each half.
From each half, the roots were removed 2 mm apical to the CEJ, crown portion was preserved and embedded in self-curing acrylic leaving the cut face exposed.Lapping/ final polishing was done on the lapping cloth with alumina powder in suspension and thus the 40 specimens were ready for microhardness analysis (Figure 3).Microhardness value of ACP-containing composite was significantly higher than Transbond XT composite (Table 2).
Greater mineral loss was observed at the cervical region as compared to the occlusal region at 20µm depth, as seen in Graph   A study using visual examination of pictures before and after orthodontic treatment reported demineralization of maxillary anterior teeth to be 77%. 7In another study by Boersma et al; 8 the prevalence of WSL in orthodontic patients at debonding was reported as high as 97%.Therefore, it is important for clinicians to develop preventive measures as soon as appliances are placed.
ACP-filled composite resins and orthodontic adhesives developed by Schumacher et al 5 have shown to recover 71% of the lost mineral content of decalcified teeth. 9According to Skrtic et al; 10 calcium and phosphate ions released from ACP-containing composites, especially in response to the change in oral environment caused by bacterial plaque or acidic foods can be deposited into the tooth structures as an apatite mineral, which is similar to the hydroxyapatite found naturally in teeth.
In the present study, the mean microhardness was tested between the depth and materials for the enamel around orthodontic brackets, at 10µm and 20µm depth from the enamel surface (Table 1).Significant differences were found between the two tested composites at a depth of 10 and 20µm from the enamel surface.
The depth of the lesions (10 and 20µm) was similar to the results seen in previous the studies conducted by O'Reilly et al 11 and Pascotto et al. 12 However, the depth of lesions was not in accordance with the reports of Moura et al, 13 which showed lesion depth up to 70µm from the enamel surface.
This could be attributed to the experimental model used which allowed more plaque accumulation and impaired its removal by tooth brushing.
Mean microhardness comparison between the two materials showed that there was significant difference in enamel loss

Surface demineralization result -Stereomicroscopic Study
Smaller area of demineralization was seen in samples where ACP-containing composite was used as compared to Transbond XT composite.where the mean microhardness of enamel was greater for those teeth where brackets had been bonded using the ACP-containing composite in comparison to conventional resin-based orthodontic composite.
Amasyali et al 17   OJN developed biologically active restorative materials that would stimulate the repair of tooth structure through the release of cavity-fighting components including calcium and phosphate.This material contains amorphous calcium phosphate (ACP) as bioactive filler encapsulated in a polymer binder, which has both preventive and restorative properties that justify its use in dental cements, sealants, composites and, more recently orthodontic bracket adhesives.The present study attempts to evaluate and compare the efficiency of ACP releasing bonding agent (Aegis Ortho) on microhardness and surface demineralization of enamel adjacent to orthodontic brackets with conventional bonding agent (Transbond XT).Thus the aim of this study was to evaluate in vivo effect of ACP-containing orthodontic composite on enamel demineralization around orthodontic brackets, and to compare it with conventional resin based orthodontic composite.The objective of the study were to evaluate and compare the microhardness of enamel around orthodontic brackets using ACP-containing orthodontic composite and Transbond XT composite at 0 µm, 100 µm and 200 µm distance from the brackets, both occlusally and cervically at 10 µm and 20 µm depth.And, to assess and compare the extent of surface enamel demineralization around the orthodontic brackets, with ACP-containing orthodontic composite and Transbond XT composite using stereomicroscope.

A
total of twenty orthodontic patients from Department of Orthodontics, Bharati Vidyapeeth Dental College & Hospital, Pune, who were planned to have four first premolars extractions for orthodontic purpose, were selected for the study.Nature of the study was explained and their written consent were obtained.Eighty first premolar teeth were used for the study.Inclusion criteria were: 1) maxillary and mandibular first premolars to be extracted as a part of treatment protocol, 2) subjects in the permanent dentition stage with all first premolars erupted completely, and 3) absence of any white spot lesions, caries, fluorosis, fracture, restoration, stain or morphological and developmental defect in upper and lower premolars.Materials used in the study were: ACP-containing light cure orthodontic composite (Aegis Ortho -Bosworth Co. Illinois), Transbond XT composite, Etchant (37% Phosphoric acid), Liquid primer, Microhardness tester (Reichert Austria, Sr. No. 363798) (Figure 1), and Stereomicroscope with Image Analysis System (Figure 2).

Microhardness Analysis:Graph 1 :
Twelve indentations were made in each half crown: A) 0µm (edge of the bracket), 100 µm and 200 µm away from the bracket both occlusally and cervically.B) Depth of 10µm and 20 µm each from the external surface of the enamel at the 6 positions (Figure 4).The samples were subjected to a load of 0.1Kg (1 Newton) for 60 seconds and the values of microhardness numbers at these positions and depths were recorded (Vicker's Hardness -HV).Preparation of Group II samples for stereomicroscopic examination:The teeth were mounted on acrylic block with their buccal surfaces exposed, and observed under stereomicroscope with maximum illumination at 10X magnification.The distance between edge of the adhesive on the enamel surface and the border of demineralization zone was viewed on the computer screen; which were measured in micrometers.comparison of microhardness of AcP-containing composite (e) and transbond Xt composite (c) at 10µm.
was observed at the cervical region as compared to the occlusal region at 10µm depth, as seen in Graph 2(a) and 2(b).

3
(a) and 3(b).Agarwal A, Swami V, Sable RB : Comparative Study of ACP-containing Orthodontic Composite and Conventional Orthodontic Adhesive on Enamel Demineralization around Orthodontic Brackets -An in vivo Study Graph 2(a): Mean values and comparison of microhardness for materials at different positions, occlusal (o) and cervical (c) to the brackets on labial surface at 10µm depth for AcP-containing composite.Graph 2(b): Mean values and comparison of microhardness for materials at different positions, occlusal (o) and cervical (c) to the brackets on labial surface at 10µm depth for trandbond Xt composite.

Graph 3 (
a): Mean values and comparison of microhardness for materials at different positions, occlusal (o) and cervical (c) to the brackets on labial surface at 20 µm depth for AcP-containing composite.Graph 3(b): Mean values and comparison of microhardness for materials at different positions, occlusal (o) and cervical (c) to the brackets on labial surface at 20 µm depth for trandbond Xt composite.Swami V, Sable RB : Comparative Study of ACP-containing Orthodontic Composite and Conventional Orthodontic Adhesive on Enamel Demineralization around Orthodontic Brackets -An in vivo Study dIScuSSIon According to Ogaard, 6 demineralization of enamel surrounding the orthodontic brackets is a common complication and a clinical problem during and after orthodontic treatment.It is a major element of risk to patients when considering the riskbenefit balance of orthodontic treatment.
compared the efficacy of ACP-containing orthodontic composite, resin-modified GIC and resin based orthodontic composite on enamel demineralization adjacent to orthodontic brackets and evaluated it by a new laser fluorescence device.The ACP-containing orthodontic composite provided the highest reductions in enamel demineralization when compared to the control.An in vitro and in vivo study conducted by Koyuturk et al 18 also showed significant reduction in enamel mineral loss and white spot formation with the use of a CPP-ACP as a topical coating around orthodontic brackets.On comparison of mean microhardness values for the two composites, occlusal and cervical to the base of the bracket; it was observed that the extent of demineralization was greater (lower microhardness value) in the cervical region, at both depths as seen in Table 2. Comparison of the mean microhardness values by ANOVA test for ACP-containing composite and Transbond XT composite at all 3 positions (0, 100 and 200µm) at the occlusal region of the bracket at both depths showed that there was no significant difference.However, ANOVA comparison at the cervical region of the Orthodontic Journal of Nepal, Vol. 3, No. 2, December 2013 Agarwal A, Swami V, Sable RB : Comparative Study of ACP-containing Orthodontic Composite and Conventional Orthodontic Adhesive on Enamel Demineralization around Orthodontic Brackets -An in vivo Study bracket showed significant difference for various positions at 10µm depth (p-value 0.006) and 20µm depth (p-value 0.027).This difference in the mean microhardness was due to greater dental plaque accumulation and the patient's difficulty in cleaning the cervical area.Similar to the CPP-ACP containing materials, the effect of ACP-containing orthodontic composite occurs on the tooth surface where the patient has difficulty in cleaning dental plaque by brushing.This effect can be attributed to the calcium and phosphate-releasing ability of this orthodontic composite when submitted to cariogenic challenges.5A study by Pascotto et al12 showed similar results of reduced enamel hardness around the composite resin in the cervical region of the bracket compared to that in the occlusal area.In the present study, a significant difference in demineralization inhibition was observed between ACP-containing composite and Transbond XT composite when the samples were observed under stereomicroscope.Transbond XT composite had a greater amount of mean demineralization zone (133.98µm) in comparison to ACP-containing composite (88.12µm).Mean difference was found to be significant.The distance between the edge of adhesive on the enamel surface and border of the demineralised zone was longer for the control group, suggestive of greater area/distance of demineralization.Similar effects of ACP-containing composite was seen on enamel demineralization in a study conducted by Uysal et al.17

concluSIon
Teeth bonded with ACP-containing material are significantly more resistant to demineralization than those bonded with the regular Transbond XT composite even in patients known for high caries risk.ACP-containing orthodontic composite significantly reduces enamel mineral loss around orthodontic brackets in patients' mouth as compared to Transbond XT composites over an experimental period of 45 days.Thus ACP-containing composite is a recent advancement in orthodontics which can be used in routine clinical practice thereby helping the clinicians in reducing demineralization around the orthodontic brackets; improving the overall quality and end results of orthodontic treatment.

table 1 : Mean microhardness comparison (AnoVA) between AcP-containing composite and transbond Xt composite at different positions, occlusal and cervical to the brackets at 10µm depth.
Agarwal A, Swami V, Sable RB : Comparative Study of ACP-containing Orthodontic Composite and Conventional Orthodontic Adhesive on Enamel Demineralization around Orthodontic Brackets -An in vivo Study