Effect of Different Cleaning Regimes on Biofilm Formation of Acrylic Based Removable Orthodontic Appliance

It is double-blind, parallel, randomized clinical trial conducted in the orthodontic clinic after obtaining the ethical approval from the ethics committee of the department. Thirty nine orthodontic patients who meet the eligibility criteria will be included in the study and will be provided by the patient information sheet and consent form that will explain the nature of the study. After initial approval from the patient an alginate impression of the maxillary arch will be taken and a negative replica will be made by type IV stone. The wire framework of the removable appliance will be fabricated according to the design for the case. After applying a separating medium, an acrylic base will be fabricated using the orthodontic acrylic powder and liquid (Orthocryle, Dentaurum, Ispringen, German) with a ratio of (2.5 parts powder to 1 part liquid) according to the manufacturer's instruction with four wells on each side of the fitting surface of the appliance. Acrylic samples i.e. tiles of different surface texture will be made. An acrylic sheet of 1 mm thickness will be made using a mold material. One sheet will be polished using a conventional polishing technique until a glossy surface appears, whereas, the other sheet will be kept without modification. Tiles of 5mm in diameter will be bored using a trephine bur on both sides of the acrylic sheets and each set of tiles i.e. the polished and unpolished samples will be color coated from its seated surface. The acrylic tiles (5mm in diameter and 1mm thickness) will be placed and fixed into the holes created using sticky wax. The acrylic samples will be randomly seated, The appliance will be sterilized using proper sterilization protocol. The removable appliance will be assigned randomly and blindly and fitted into the oral cavity of the patient for one week. Each individual will be given by an independent person a pack containing the cleansing pack and an instruction sheet describing the cleaning regimen for his/ her appliance. The packs are similar in shape and color and will be prepared by a third person who does not know the purpose of the study. The participant will be grouped into three groups:

1. Brushing with denture brush and chlorhexidine (CHX) toothpaste (lacalut Active, Germany) for one minute.
2. Chemical cleaning i.e. Lacalut cleaning tablet (lacalut DENT cleaning tab, Germany), fill the cup to the marked line (150 mL) with tap water, dissolve one cleansing tablet and wait for 20 minutes then wash it with tap water.
3. Combination of brushing with CHX toothpaste and cleaning tablet. At the end of the study period, the acrylic samples will be removed carefully and applied into a petri dish containing PBS via a sterile tweezer. The samples will be then immersed twice in a 25ml sterile tubes containing PBS to remove the planktonic bacteria and inserted into 5ml bijou tube containing 1mm PBS. The sample will be vortex mixed for 1 minute to disseminate the biofilm and create a homogenous solution. Ten-fold serial dilutions will be carried out in PBS before the samples are plated onto blood agar (BA), to give the total anaerobic count, mitis salivarius agar (MS), a selective agar for streptococci spp. and Mannitol salt agar (MA) for Staphylococci spp. BA and MS plates will be incubated anaerobically for 2-4 days at 37ºC using anaerobic cabinet whereas the MA will be incubated for 2 days in aerobic condition. All organisms from both selective and nonselective agars will be distinguished by colony morphology and will be characterized by Gram reaction and other confirmatory tests: 1. Catalase testing 2. Coagulase testing