title: An in vitro comparison of two orthodontic band cements
Creators: name: Gillgrass, Toby Jonathan
Publisher: name: University of Glasgow
Year: 1998

description: AIMS: 
The aims of this in vitro study were to compare the fluoride release and antimicrobial properties of a light-cured hybrid glass-ionomer cement (Ultra Band-Lok, Reliance Orthodontics, Itasca, Ill., USA) with a conventional glass-ionomer cement (Ketac-Cem, Espe Oberbay, Gmbh). The pattern of microleakage when the two cements were used to cement orthodontic bands was assessed also.

MATERIALS AND METHODS:
Five discs (3.0mm diameter and 1.5mm thick) were prepared of each material. The discs were immersed in 2ml of deionised water which was changed daily. Measurements of fluoride concentration from the water were taken at regular intervals over a 40 day period using an Orion fluoride ion-selective electrode. Antimicrobial properties were determined using an agar diffusion test. Unset cement was placed into 5mm wells in freshly prepared tryptic soy agar plates, two wells for each material per plate. The plates were inoculated with one of four different strains of Streptococcus mutans (NCTC 10499; Glasgow Dental Hospital strains (GDH) 96/1743; 96/1821; 96/1143). Six wells of each cement were tested for each bacterium. The plates were then incubated for 24 hours at 37 °C in a microaerophilic atmosphere. The zone of inhibition associated with each test cement well was taken as a measure of its antimicrobial activity against each Streptococcus mutans. To assess microleakage, 15 bands were cemented with each material to intact caries-free third molar teeth. After storage in deionised water at 37°C for l month, specimens underwent thennocycling (850 cycles at 5, 37 and 50°C with a dwell time of IO seconds). followed by immersion for 12 hours in 2% methylene blue dye buffered to pH 7. Microleakage was assessed by two examiners independently using a photographic record of an occluso-cervical section through the mesiobuccal groove of each tooth and a microleakage index. A random sample of 12 photographs were re-examined two weeks after the initial assessment to give an indication of inter- and intra-examiner reliability.

RESULTS:
The cumulative and daily fluoride release for days 5, 15 and 40 was significantly greater for Ketac -Cem than Ultra Band-Lok (Mann Whitney U test, p &lt;0.05).The antimicrobial activity of Ketac-Cem was significantly greater for Ketac-Cem than Ultra Band-Lok over a 24 hour period for all four strains of Streptococcus mutans (Mann Whitney U test p &lt;0.05). Intra-examiner (Kappa = 0 . 84 and 0.92) and inter-examiner (Kappa = 0.71) reliability were substantial when assessing microleakage. There was no significant difference (Mann-Whitney U test, p &gt; 0.05) between the two cement groups for the enamel/cement interface (p=0.657) but a borderline significance was detected for the band/cement interface (p=0.051).

CONCLUSIONS:
The cumulative and daily fluoride release from Ketac-Cem was greater than for Ultra Band-Lok at days 5, 15 and 40. The antimicrobial activity, over the first 24 hours, for Ketac-Cem was greater than for Ultra Band-Lok against the four types of Streptococcus mutans tested.
There was no significant difference in microleakage between Ketac-Cem and Ultra Band­ Lok at the cement/enamel interface but there was a suggestion that there may re more microleakage with Ketac-Cem at the cement/band interface than with Ultra Band-Lok.