Effect of dental chair light on metal bracket bond failure rate in orthodontic patients using light cure based adhesive system: A randomized controlled trial.

Title - Effect of dental chair light on metal bracket bond failure rate in orthodontic patients using light cure based adhesive system: A randomized controlled trial.

Introduction-

development of firm attachment of bracket to the teeth is one

of the prominent milestones in the orthodontic field as it enables efficient movement of the teeth. Firm attachment was initially achieved by cementing bands on all the teeth1.

Since the introduction of light cure system in the 1970s, they have become an important part of modern adhesive dentistry. They are used to cure resin-based composite restorative materials, resin -modified glass ionomer cement, preventive pit and fissure sealants, etc., and most important to the orthodontist, to bond orthodontic bracket to the teeth1.

The inefficient bracket bonding can increase the chances of appliance breakage, which results in prolonged treatment duration, increased chair side time and the greater inconvenience to the orthodontist and the patient2.

Light polymerization, or light curing, is needed in order to physically adhere the bracket to the enamel surface by initiation of a chemical reaction in which the adhesive is changed from a paste to a hardened resin. The polymerization is initiated through the use of visible light in the blue range of the electromagnetic spectrum to excite the outermost layer of the camphoroquinone that possesses an absorption spectrum between 400 and 500 nm, being most efficient in the 468 to 470 nm range3.

While using light cured composite adhesive system, a streamlined bonding process is an important consideration, and the choice of

light source is critical. Light curing sources include halogen, plasma arc, argon laser, and light-emitting diode unit2.

During the light cure bonding procedure in dental office, it is as usual routine for orthodontist to switch off the dental chair light. This is done in anticipation that the light of the dental chair may interfere with blue light of the light curing source, this can further influence the bond strength2. Dental chair light is an important source of visibility to place the orthodontic bracket at an accurate position on the tooth.

Newer models of overhead dental chair lights with LED have setting that use the yellow spectrum of light instead of blue during the curing process. This is an important factor to prevent premature curing of the dental composite3.

Bond failure hinders the efficiency of fixed orthodontic appliance therapy. Thus, a bond failure rate as low as possible is fundamental4.

Rationale of the study:

In vitro study has been conducted to evaluate the influence of the dental chair light on the bond strength of light cured composite resin and concluded that the LED light curing with dental chair light on produced higher shear bond strength than the light curing without dental chair light2.

Further, in vitro study has been conducted to determine if the duration of exposure to the halogen overhead dental chair light has an effect on shear bond strength of metal orthodontic brackets and concluded that dental chair light exposure in the 5-minute, 10 minute and 15-minute groups produced higher shear bond strength than those of the control, 1 minute and 2.5-minute groups3.

Both studies were an in vitro study, the result of study can be more authentic if the same investigation is repeated in an in vivo set up2.

Therefore, this study will be conducted in vivo to check the effect of dental chair light on bracket bond failure rate using light cure based adhesive system.

Primary Objectives: -

1. To evaluate the metal bracket bond failure rate in orthodontic patients bonded with light cure based adhesive system while keeping dental chair light on.

2. To evaluate the metal bracket bond failure rate in orthodontic patients bonded with light cure based adhesive system while keeping dental chair light off.

3. To compare the metal bracket bond failure rate in orthodontic patients between metal bracket bonded with light cure based adhesive system while keeping dental chair light on and dental chair light off.

Methodology :-

I) Study design: Split mouth randomized controlled trial.

II)Study setting: Department of Orthodontics and Dentofacial Orthopaedics of our institute.

III)Study population: Patients indicated for orthodontic treatment with bilaterally symmetrical arches.

IV) Sample size: 30

SAMPLE SIZE DERIVATION

Type of test = t-test

Analysis: A priori: Compute required sample size

Input: Effect size d = 0.95

α err prob = 0.05

Power (1-β err prob) =0.8

Output: Noncentrally parameter δ = 2.60

Critical t =1.7011

Number of groups = 2

Sample size group 1 = 15

Sample size group 2 = 15

Total sample size = 30

V) Sampling Technique: A simple random sampling technique. The oral cavity of the patient will be divided into four quadrants. Each quadrant should consist central incisor, lateral incisor, canine, first premolar, second premolars. Each quadrant will represent one site. A pair of quadrants will be used for study design. Split mouth study design will be followed. Coin toss method will be performed to randomly select the dental chair light on or off use in a specific pair of sites namely,

1)Upper Right and Lower left.

2. Upper Left and Lower Right.

VI) Method of selection of study subjects:

Inclusion criteria

1. Patient indicated for orthodontic treatment with bilaterally symmetrical arches.

2)Completely erupted permanent dentition.

Exclusion criteria

1. Patient teeth with any visible or detectable buccal caries.

2. Patient teeth with any white spot lesion.

3. Patient teeth with microcracks.

4. Patient teeth with abrasion, erosion or abfraction.

5. Patient with moderate to severe skeletal discrepancy and craniofacial anomalies.

6. Mentally challenged patient.

7. Enamel with the buccal enamel defect, restoration, veneer or

crown.

Subject Withdrawal criteria;

1. Patient do not wish to continue orthodontic treatment.

VII) Operational definition:

Bond failure rate – It is a total number of brackets debonded. The rate of bond failure is a recognized approach to evaluate the performance of brackets4.

VIII) Method of measurement:

The oral cavity of the patient will be divided into four quadrants. Each quadrant will represent one site. A pair of quadrants will be use for the selected study design. Split mouth design will be followed. Thirty patients will be selected for the study meeting the inclusion criteria. Coin toss method will be performed to randomly select the option of keeping dental chair light on or off while curing in a specific pair of sites. Heads will be allocated in group A and tails will be allocated in group B. Patient will be assess every month for six months duration after bonding to check the adherence of the metal bracket to the tooth.

Pair of sites according to quadrants used will be:

Group - A

1)Upper Right (Dental chair light on), Upper Left (Dental chair light off) and Lower Right (Dental chair light off), Lower Left (Dental chair light on).

Group - B

2)Upper Right (Dental chair light off), Upper Left (Dental chair light on) and Lower Right (Dental chair light on), Lower left (Dental chair light off).

For curing with Dental chair light off:

1. Tooth surface will be cleaned with pumice slurry for 5 seconds.

2. Etching with 37% phosphoric acid will be done for thirty seconds.

3. The teeth will be then rinsed and air dried until a frosted enamel appears.

4. The etched surface will be primed and cure with the help of curing light keeping dental chair light off.

5. The stainless-steel bracket will be gripped with the help of reverse action tweezer and a thin layer of adhesive will be applied to the bracket base.

6. The adhesive will be uniformly distributed over the meshed surface of the bracket taking care not to leave any gaps between the adhesive and bracket base.

7. The bracket will be placed at a desire place and will be cure with curing light by keeping dental chair light off.

For curing with dental chair light on:

1. Tooth surface will be cleaned with pumice slurry for 5 seconds.

2. Etching with 37% phosphoric acid will be done for thirty seconds.

3. The teeth will be then rinsed and air dried until a frosted enamel appears.

4. The etched surface will be primed and cure with the help of curing light keeping dental chair light On.

5. The stainless-steel bracket will be gripped with the help of reverse action tweezer and a thin layer of adhesive will be applied to the bracket base.

6. The adhesive will be uniformly distributed over the meshed surface of the bracket taking care not to leave any gaps between the adhesive and bracket base.

7. The bracket will be placed at a desire place and will be cure with curing light by keeping dental chair light on at 50-centimeter distance above the subject.

IX) Data collection tool:

1.Metal brackets

2.Bracket holding pliers

3.Acid etchant, bonding agent, applicators

4.Light cure composite resin

5.LED light Cure unit

6.Explorer

7.Mouth mirror

8.Gloves

X) Methods of Data Collection: -

Follow up visit no:

Maxillary Arch

Left

Right

TOOTH NO.

BRACKET STATUS

TOOTH NO.

BRACKET STATUS

1Intact/ Detached

1Intact/ Detached

2Intact/ Detached

2Intact/ Detached

3Intact/ Detached

3Intact/ Detached

4Intact/ Detached

4Intact/ Detached

5Intact/ Detached

5Intact/ Detached

Mandibular Arch

Left

Right

TOOTH NO.

BRACKET STATUS

TOOTH NO.

BRACKET STATUS

1Intact/ Detached

1Intact/ Detached

2Intact/ Detached

2Intact/ Detached

3Intact/ Detached

3Intact/ Detached

4Intact/ Detached

4Intact/ Detached

5Intact/ Detached

5Intact/ Detached

XI) Data Management and analysis procedure: -

Statistical analysis will be performed using Statistical Package for Social science (SPSS) version 21 for Windows (SPSSInc Chicago, IL).

Binary qualitative data will be expressed in mean and standard deviation respectively.

Data normality will be checked by using Shapiro – Wilk test.

Confidence interval is set at 95% and probability of alpha error (level of significance) set at 5%.

Power of the study set at 80%.

Actual power =

A power analysis was established by G*Power version 3.0.1 (Franz Faul universitat, Kiel, Germany). Total minimum calculated sample size of 30 samples (total 2 groups) would yield 95% power to detect significant differences with effect size of 1.0 and significance level of 0.05.

XII) Data analysis plan and method: -

The comparison between the two groups will be done using independent t- test.

XIII) Aditional points for research in AYUSH

Not applicable.

XIV) Additional Points for RCT: -

I.

Randomization Proposed: Simple random sampling technique by using coin toss method to randomly select the option of keeping dental chair light on or off while curing in a specific pair of sites.

II.

Allocation concealment proposed: It will be done by SNOSE technique. Sequentially numbered opaque sealed envelopes (SNOSE) will be prepared for each sample. Group allocation number will be mentioned in each envelope. Envelopes will be prepared by a person who is not aware of the study and after random allocation, these envelopes will be opened by operator just before intervention.

III.

Blinding proposed: Single blinding (Patient will be blind)

XV) Method Of Intervention: -

Dental Chair light effect on metal bracket bond failure rate.