Streptococcus mutans adherence to conventional and self-ligating brackets: an in vitro study

Abstract

Introduction: Although self-ligating brackets presumably provide better hygiene conditions, no consensus has been reached so far. Objective: Therefore, the objective of this study was to evaluate, in an in vitro experimental design, the adherence of Streptococcus mutans (SM) in self-ligating and conventional brackets of different manufacturers and ligature types. Methods: Four commercial brands of maxillary premolar metal brackets were tested (Abzil®; Morelli®; 3M Unitek®; and GAC®). Each one was subdivided into three groups, which varied according to the type of ligature and bracket model (metallic, elastic, and self-ligating), totalizing twelve groups, composed of six brackets each. Previously sterilized brackets were initially immersed in saliva for one hour, and subsequently washed and added in a bacterial suspension, maintained in aerobiosis for 72 hours. The adhered bacteria were then separated and quantified by colony forming units (CFU/mL) counting after 48 hours of growth. The groups were compared by Kruskal-Wallis and Dunn post-hoc tests (p< 0.05). Results: Regardless of the commercial brand, self-ligating brackets had significantly less CFU/mL. However, according to comparisons performed within each commercial brand, only Abzil® self-ligating brackets had significantly lower biofilm adhesion. Among all of the self-ligating models, GAC® brackets presented the highest bacterial adhesion rate. Conclusions: Self-ligating brackets are likely to present lower rates of biofilm adhesion. Particularly, Abzil® and GAC® self-ligating brackets are less likely to accumulate biofilm. Although such results are derived from an in vitro study, practitioners might acknowledge findings concerning bacterial adhesion as one of the relevant features to be considered during bracket selection.

Bacterial biofilm accumulation on self-ligating vs. elastomeric metal brackets: A review study

“…Plaque biofilm-forming bacteria are sensitive to a variety of stimuli, including signals from feeding and cellular recognition of particular or non-specific attachment sites on a surface. The development and growth of oral biofilm were categorized into five stages by Marsh and Martin (Figure 1) [9,11,18]. Each of the five developmental stages is depicted in the bottom panels (a-e) by a photomicrograph of P. aeruginosa grown on a glass substrate in continuous flow [19].…”

“…S. salivarius types increased by 1.8 x 10 10 and S. mitis by 1.5 x 10 14 , accounting for the two different halves of the streptococci rise. The statistical comparison and analysis of these observations was done to determine the consequences for dental health [1,9,11,29].…”

“…Comparing metallic ligatures with traditional brackets, the elastomer's deterioration may facilitate the growth of biofilm [9]. In order to address this issue, innovative techniques and materials were used to create orthodontic appliances, such as self-ligating brackets, which hold the orthodontic wire in place without the need for metallic or elastic ligatures [10].…”

“…It's been demonstrated that having brackets and ligatures increases the risk of tooth surface decalcification, which eventually leads to the development of caries and white spots on teeth. It also increases gingival irritation [9,10,39].…”

“…One such example is the self-ligating bracket, which eliminates the need for metallic or elastic ligatures to hold the orthodontic wire in place [8]. Because of their design and lack of metal and elastomeric ligatures, self-ligating brackets, according to the producers, are less prone to bacterial colonization [8,9]. However, it is controversial if using self-ligating systems' opening and closing mechanisms and removing the ligatures from conventional brackets can lessen the adherence of microbes and the formation of biofilm.…”