Fracture Load of an Orthodontic Appliance for Robin Sequence Treatment in a Digital Workflow

Abstract

CAD/CAM technologies and materials have the potential to improve the treatment of Robin Sequence with orthodontic appliances (Tübingen palatal plate, TPP). However, studies on the provided suitability and safety are lacking. The present study evaluates CAD/CAM technologies and materials for implementation into the workflow for producing these orthodontic appliances (TPPs), manufactured by different techniques and materials: additive manufacturing (AM) and subtractive manufacturing (SM) technologies vs. conventional manufacturing. The fracture load was obtained in a universal testing machine, and the breaking behavior of each bunch, as well as the necessity of adding a safety wire, was evaluated. The minimum fracture load was used to calculate the safety factor (SF) provided by each material. Secondary factors included manufacturing time, material cost and reproducibility. Dental LT clear showed the highest fracture load and best breaking behavior among AM materials. The highest fracture load and safety factor were obtained with Smile polyether ether ketone (PEEK). For the prototyping stage, the use of a Freeprint tray (SF = 114.145) is recommended. For final manufacturing, either the cost-effective approach, Dental LT clear (SF = 232.13%), or the safest but most expensive approach, Smile PEEK (SF = 491.48%), can be recommended.

Accuracy Evaluation of Additively and Subtractively Fabricated Palatal Plate Orthodontic Appliances for Newborns and Infants – An In-vitro Study

“…The effect of the build angle was not evaluated in this study. This is known to influence not only the accuracy but also the manufacturing time of vat polymerization techniques [2,3,11,32]. Vertical positioning, leads to an increase of layers, and thus, the sum of repeated errors or inaccuracies grows [2].…”

“…SM and SLA should be employed for applications were a greater surface finishing and higher mechanical properties are necessary. The TPP for example, requires a high flexural strength [11,21]. From the other side, DLP should be prioritized in cases where a faster manufacturing time and higher trueness and precision are necessary, for example prototyping of the TPP and manufacturing of cleft palatal plates.…”

“…The TPP aids in relieving the upper airway obstruction present in RS patients, by pushing the base of the tongue forward. When RS is accompanied by a cleft palate, the TPP is also responsible of covering the cleft area [11]. Orthodontic treatment of these patients starts with an impression of the upper jaw, as soon as possible after birth.…”

“…A digital workflow for direct appliance manufacturing has already been established for each palatal plate case [7,12]. Besides making a physical model obsolete, it decreases hands-on time [11,14] and enables digital archiving [3,16].…”

“…With regards to AM technologies, stereolithography (SLA) and direct light processing (DLP) have been widely applied in the dental field and bear potential for palatal plate fabrication. DLP is particularly advantageous for simultaneous fabrication of multiple appliances [11]. Meanwhile, milled blanks are preferred in dentistry as they are less prone to suffer from shrinkage and deformation [17][18][19][20], as well as providing superior mechanical properties [21].…”