Dental Asia May/Jun 2020

T raditional techniques correcting ove r b i t e f ea tu res i n a l l malocclusions have been known to be quite complicated, and challenging to orthodontists. Strong mechanical background, sophisticated appliance designs, diligent patient’s cooperation and multiple adjustment visits over a long treatment time are crucial elements for successful treatment prognosis of this dento-alveolar deformity. Despite the overwhelming advances that already modernised many orthodontic concepts, techniques, and practice, nonetheless modalities correcting overbites did not witness significant advances. To date super elastic wires have only been principally used in their straight prefabricated form for the sole purpose of initial teeth levelling, until the Bendistal Pliers demonstrated their unique ability to cinch- back and bend NiTi wires, for the first time 1 . The possibility of placing permanent V-bends on super elastic archwires intraorally armed orthodontists with full control of super elastic wires and resurrected their advanced mechanical properties that were overlooked after performing initial teeth alignment. By providing light and consistent force, these bends could effectively move groups of teeth in both transverse and vertical planes of space. Clinical application of this concept has resulted in evolution of new techniques that showed efficiency in correcting amultitude of major orthodontic dentoalveolar deformities with unprecedented simplicity, convenience and time savings 2 . This article elaborates on one new technique that corrects dental and skeletal deep overbite mostly featured in Class I and Class II malocclusions using simple routine wire adjustments during patient’s regular visits. Literature review Orthodontic literature had described myriad approaches for overbite correction. Some approaches used fabricated loops, helices and springs made of stainless- steel wires to create the bite-opening force system 3,10-14 . Others used functional appliances with and without headgears 4,5 ; while severe skeletal cases were managed with surgical approaches 6-9 . Ever since the inception of their use in orthodontic practice, the impossibility of bending super elastic archwires has restricted orthodontists to use them only in their prefabricated straight arch forms in initial teeth levelling. Subsequently they couldn’t use the superior elasticity of those wires in other orthodontic tooth moments. They could not even bend distal ends of such wires without annealing that ruins the entire wire’s resiliency and defeats the only purpose of their use. Many researchers demonstrated the validity of using intrusion appliances, helices and springs made of super elastic wires in their prefabricated forms 15-17 . Despite this success, however, the inability to bend these wires made it impossible to customise the costly intrusion appliances, and resulted in the limited use of prefabricated elastic appliances and even wires. Bending titanium wires without annealing or breakage requires specially designed pliers. Khouri developed one such set of pliers – Bendistal Pliers – and subsequently showed how clinicians could use them for many intraoral sundry super elastic wire activations that moved segments of teeth and corrected overbites, crossbites, expanded and constricted dental arches, tip backs and rotate molars 2 . The mechanical principles underlying bite-opening techniques have been we l l e s t ab l i shed and appreciated in literature 3, 16, 19, 20 . Dake and Sinclair 13 reported that intrusions and extrusions achieved by both Ricketts and modified Tweed techniques remained stable. Hans et al 18 compared the efficiency of the headgear and bionator with fixed appliances in bite opening and found that both approaches produced incisor intrusion combined with skeletal mandibular changes that contributed to the correction of deep overbites. Burstone 3 has advocated that not all patients with overbites require incisor intrusion exclusively; rather, some require posterior teeth extrusion to open their bite. He presented upright intrusion springs that intrude anterior teeth with minimal effect on posterior teeth. He recommended spring appliances with low load deflection rates to produce the optimal intrusive forces. Sander et al 16 described intrusion mechanics completed with NiTi uprighting springs with low load deflection rates that could intrude incisors a magnitude of 7mm. Shroff et al 11 found it difficult to correct deep overbites when accompanied with flared incisors by conventional orthodontic therapies. They subsequently recommended the Burstone segmented arch approach for achieving precise vertical and horizontal simultaneous moments of teeth. Davidovitch and Rebella 12 described an intrusion archwire that uses only tip back bends close to molars, to achieve bite opening. Nanda has also described appliance systems and biomechanical techniques for incisor Part I: Correcting Excessive Overbites with V-Bend Activations of Super Elastic Wires By Dr. Suhail Khouri and Dr. Derek Mahony This two-part article describes a simple, effective and clinically applicable alternative bite-opening technique using V-bends on super elastic wires that are created by new orthodontic pliers. Clinical Feature DENTAL ASIA MAY / JUNE 2020 32