# Bacterial Biofilm Growth on Various Dental Stabilization Systems for Avulsed and Luxated Teeth
## 4 Discussion  
Bacterial biofilm is not a static community as it is a continuously growing and striving biosystem [31, 32]. Biofilm composition and virulence level increase with age and the overall growth of the biofilm [33, 34]. As the biofilm matures and bacterial load increases, there is a higher chance for bacteria to expand into the lateral canals and dental tubules, and bacteria found at these sites are reported to become more resistant to antibiotics [35, 36]. Thus, it is critical to select a splint material that allows the least amount of biofilm growth in addition to the physiological stabilization ability. Furthermore, traumatic injuries are commonly associated with soft tissue injuries and lacerations, which are prone to bacterial contamination. Thus, the presence of bacterial biofilm on the splint system and the surrounding teeth exacerbates the inflammation of the surrounding tissues and contributes to delayed healing.  
In addition, bacterial root resorption is the main complication causing the majority of failures detected following trauma [29, 37]. Currently, according to the International Dental Traumatology guidelines for Traumatic Injuries, with the exception of alveolar fractures, the splint should be physiologic (non-rigid) for the duration of two weeks for avulsion and luxation injuries, and 6 to 8 weeks for mid-root horizontal root fractures [4, 38].  
One of the materials we tested is the monofilament nylon line, \"fishing line\". It was introduced in 1982, and has been used with success by some practitioners [39]. Additionally, nylon monofilament has been used as a suture material in several types of surgeries. It has been shown to allow for some but limited biofilm growth compared to other suture materials, especially multifilament ones [40]. Currently, new splint systems have been introduced into the market such as Rebbond [41, 42], OW [43], and TTS [7, 8], and while practitioners differ in their choice, the common agreement is that they should be easy to apply and remove, be esthetic, and facilitate hygiene. However, bacterial growth on these newer systems has not been properly evaluated before.  
Since the presence of bacteria is so detrimental for the healing of post-traumatic injuries, this study focused on determining which type of splint system would favor the least amount of biofilm growth. When splints were bonded with the same amount of composite to the labial surfaces of three maxillary teeth, they all allowed bacterial growth. However, we observed significantly less bacterial growth in TTS when compared to the other three materials, MFL, Ribbond, and OW, which showed comparable bacterial growth to one another. Multiple factors may play a role in the level of bacterial adherence and growth, such as surface roughness, surface area, and splint design. Surface roughness is a critical factor for biofilm adherence to the splint surface [44] or surface treatment that may facilitate bacterial adherence [45, 46]. In addition, the architectural design of the splint system may also play a role in allowing for biofilm detachment. We have shown for the first time that the new TTS system allows for the least amount of biofilm retention in vitro. Our study was limited to the quantification of the bacterial growth on each splint. Further investigation into the types of bacteria collected would provide us with a better understanding if the splint material can select for certain bacterial types. In addition, future clinical studies measuring biofilm adherence and growth in the oral cavity and cleanability by patients would also be desirable.