Comparision of Biomechanical Effects of Infrazygomatic Crest Bone Screws and Modified C-Palatal Plate Appliance for Total Maxillary Arch Distalization in Treatment of Class II Malocclusion: A Finite Element Study

Author(s): Farath Naseem Romana, Shaik Mobeen, Sara Soja George, Shibu MP, Sravanthi Jagati, Juveria Fathima, Aiysha Nudrath, Mohammad Noorez Nasir

Class II malocclusions may be corrected by combinations of restriction or redirection of maxillary growth, distal movement of maxillary dentition, Experimental studies have shown that forces for Class II correction produced by extraoral traction and intermaxillary elastics cause posterior repositioning of the maxillary dental complex, as well as of the maxilla itself [1]. Besides exploiting the periodontal anchorage potential (teeth), additional anchorage aids are often needed to achieve maximal anchorage. The aids conventionally used for intraoral anchorage to enhance periodontal anchorage quality are trans palatal and lingual bars, Nance holding arch and intermaxillary elastics [2]. The anchorage in edgewise treatment is the most important factor that affects the treatment plan and result. Until now, various techniques to reinforce anchorage have been devised and used in orthodontic practice. Recently, several kinds of implant anchors providing absolute anchorage have attracted the attention of orthodontists. Among them, titanium screws, which were originally used for intermaxillary or bone ?xation, have the following advantages: minimal anatomic limitation for placement, lower medical cost, simpler placement surgery, and less discomfort after implantation when compared with dental implants for abutment. Therefore, titanium screws of various sizes have gradually come to be used for orthodontic absolute anchorage. However, there have been few human studies in which the success rates for various kinds of implant anchors were examined [3]. Anchorage is a critical component of en-masse retraction. Clinicians pay considerable attention to Newton’s third law- the law of action and reaction. They know that every action they take will have an equal and opposite reaction. Many approaches to treatment mechanics have been developed to ef?ciently retract anterior teeth [4]. In tooth-borne anchorage cases, complicated mechanics or supplementary appliances are needed to control anchorage. Extraoral appliances can provide stable anchorage but depend totally on patient cooperation. Lack of cooperation can result in anchorage loss and unsatisfactory treatment results; these have led to greater use of intraosseous anchorage [5]. It has become more practical to use implants for anchorage in orthodontic patients, Orthodontic screws expand the horizons of orthodontic treatment because they allow treatment to proceed successfully with virtually no anchorage loss and minimal patient cooperation. However, they are typically used as auxiliaries to the posterior anchor teeth during en-masse retraction with sliding mechanics. The mechanics of force application can be simple or complicated, according to the anchorage control. For anterior retraction, if the mini-implants are designed to accommodate arch wires, the number of teeth requiring bands or brackets can be reduced, moderating the risk of damage to the periodontium or enamel surfaces. Distalization of the maxillary dentition has been recognized as an important treatment approach for the correction of Class II malocclusions and it has been traditionally performed using headgear. However, known disadvantages of headgear appliances include poor aesthetics and dependence on patient compliance. In an attempt to overcome the limitations of headgear, several noncompliance devices such as distal jet and pendulum appliances were introduced. However, they often resulted in undesirable side effects such as extrusion and protrusion of the maxillary anterior teeth and extrusion, distal tipping, and distal rotation of the maxillary first molars [6].
The advent of temporary anchorage devices (TADs) has allowed better control over unwanted reciprocal movement of the anchor units, although miniscrew insertion in the interradicular region is associated with serious limitations, including a short range of action, coupled with the risk of root injury. Miniplates have been advocated as an alternative to avoid contact with adjacent roots in the area of insertion; however, their placement and removal require more invasive surgical procedures.6Orthodontics in its century of existence have had a lot of landmarks in its evolution, but very few can match the clinical impact made by micro-implants and the recently introduced infra-zygomatic crest (IZC) and buccal shelf (BS) orthodontic bone screws. Orthodontics in its century of existence have had a lot of landmarks in its evolution, but very few can match the clinical impact made by micro-implants and the recently introduced infra-zygomatic crest (IZC) and buccal shelf (BS) orthodontic bone screws. Many studies have been reported on the application and clinical ef?ciency of total arch distalization mechanics; however, studies about biomechanical effects such as stress and displacements on the teeth and the surrounding tissues are limited. finite element analysis (FEA), a common method in engineering, became a valuable option for evaluation of biomechanical factors in orthodontics [7,8].
The purpose of this study was to (1) Evaluate three-dimensional stress distribution and initial displacement of maxillary dentition under total arch distalization mechanics for correction of Angle’s Class II malocclusion using IZC bone screws and C-Palatal plate appliance in Pre-adjusted Edgewise Appliance (PEA) setup and finite element models and to (2) To compare biomechanical effects of the IZC bone screws and MCPP for total maxillary arch distalization.