3D printing pens are often used to make beautiful and fun artwork, as well as for educational purposes, but have also proven useful for medical applications. A trio of researchers from KM Shah Dental College and Hospital published a paper, “3D Printing Pen: A Novel Add-on for Indirect Bonding,” about their work using a 3D printing pen to create partial and full transfer trays for bonding. indirect orthodontic brackets. which takes much less time in the office than direct bonding.
“The main drawback of indirect bonding is incomplete penetration of curing light through the transfer trays, leading to bracket bond failure,” the researchers explained. “The main goal in a clinical setting is to minimize chair time. This indirect bonding technique reduces chair time, is inexpensive, uses minimal hardware, and provides adequate light penetration and precision.”
Indirect orthodontic bonding first came about in the 1970s and interestingly, caramel candy, which is water soluble, was used as an adhesive for braces back then. We have obviously come a long way, moving on to thermally cured compounds, sticky wax and dissolvable wallpaper paste, until the tray transfer system was developed in the 1990s.
“Read and O’Brien (15) and Read and Pearson (16) suggested the use of a transparent thermoplastic tray transfer sheet to make the indirect bonding technique compatible with the light-cured composite,” the researchers wrote.
While faster for the patient and more accurate, indirect bonding has its own problems, including increased lab time, the need for an additional set of impressions, and weaker bracket bonding due to incomplete curing of the composite due to partial penetration of light. That’s why the researchers wanted to see if they could use a 3D printing pen to improve the process, along with the popular biodegradable polymer PLA, which is good for making the transfer tray due to its transparency and rigidity.
The team selected five consenting orthodontic patients and made alginate impressions of their upper and lower arches and poured models of them, which were then marked for the ideal bracket position as per MBT’s prescription before applying a layer. of bonding agent and photopolymerize. The brackets were added and light-cured again, then another layer of bonding agent was added for added stability. A 3Doodler PRO, set to 210°C and max flow, was used to help make the transfer trays out of MatterHackers PRO PLA.
“The tip of the 3D printing pen was kept close to the supports; molten PLA was blasted such that three bracket margins, ie mesial, distal and gingival, remained free of PLA; however, it did fit into the bracket slot and spread over the occlusal and palatal surfaces of the tooth. Once the transfer tray was fabricated, the supports were removed from the study model with the help of boning pliers, keeping the PLA tray intact,” the team explained.
The researchers then transferred the 3D-printed tray, with the brackets inside, into the mouth and light-cured it after determining a good fit. A straight probe was used to remove the tray from the brackets, any PLA that broke in the bracket slot was removed with a heated probe and a tungsten carbide bur completed the process, which was used to remove any resin residue on the brackets. “the incisal margin of the bracket.” Of the five study participants, only three total bracket failures were observed.
The team did not find any other studies in which supports were attached to study models using a bonding agent as an adhesive. It is a highly biocompatible material and was also unaffected by the heat of the molten PLA.
“We used a bonding agent as an adhesive to bond the brackets to the study casts in this case because it can be applied over the bracket base and layered over the cast effortlessly. It also forms a very thin interface between the base of the bracket and the study model, thus increasing the precision in the expression of the bracket prescription”, they explained.
While the 3D-printed PLA tray took longer to make than a vacuum-formed thermoplastic, it had a better fit and stiffness, as well as being easier to make and handle, easier for the doctor to use, and resulted in less in-office corrections, was easier to remove from the mouth, and offered three surfaces for curing and “optimal bond strength.” Additionally, when the researchers compared their 3D-printed tray to other indirect bonding methods, they found that theirs enabled the removal of burrs, a major element of plaque buildup, from bracket bases.
A previous study found that the average time required for both laboratory and clinical steps for indirect bracket placement was almost 39 minutes, while it took just under 30 minutes for direct bracket placement. In this study, it took 18.44 minutes for the lab procedures with the bonding agent and 3D printing pen, and 11.86 minutes for the clinical procedures, for a total of 30.3 minutes, right in between the average times for the direct and indirect bonding of brackets with conventional methods.
Researchers evaluated five patients for bracket failure every four weeks for a year and concluded that using a 3D printing pen, PLA, and a bonding agent to fabricate full or partial indirect bonding trays is “an accurate and easy way to use”. , economical and reliable method that reduces the time in the office”.
“A 3D printing pen and PLA were used to fabricate transfer trays for indirect bonding, which gave us advantages such as ease of handling, great control over material flow, and the parts of the bracket and cast to be covered. with PLA, profitability and transparency. This method does not require any expensive equipment and the materials used are easy to transport,” the team concluded.
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