line of occlusion and connected so that the mesiobuccal cusp of the upper molar occluded in the buccal groove of the lower molar, then normal occlusion would result. Concurrently, this comprehensive system provided clarity and simplicity to defining healthy dentition alignment with its categorization of major types of malocclusion. Angle delineated three distinct forms of malocclusion, as determined by the occlusal relationship of the first molars: Class I: An incorrect line of occlusion due to misaligned teeth, rotations or other issues Class II: A distal positioning of the lower molar against its upper equivalent, with no reference to line of occlusion given Class III: The lower molar being mesial to its counterpart, again without a noted line of occlusion. The Angle classification divides occlusion and malocclusion into four distinct classes: normal occlusion, Class I, II, and III. Although both normal occlusion and Class I have the same molar alignment relationship, there is a distinction in how their teeth are organized in relation to the line of occlusion. As for Classes II and III malocclusion, it depends whether or not the line of occlusion is accurate. Once a molar position is determined, a line of occlusion forms along its central fossa that smoothly meanders across both upper and lower teeth. This line follows through on all canine and incisor cingulums as well as down along buccal cusps and incisal edges of lower teeth. All this establishes both interarch and occlusal relationships. Appliances E (expansion) Arch Appliance (1907) - There were two types: Basic & Ribbed. This applianced only allowed tipping movement and provided poor control of individual tooth position. Pin & Tube Appliance (1910) - Consisted of Gold and Platinum bands and had attachment to all the teeth. These bands had vertical tubes that were soldered to them and a Pin was passed through it to achieve tooth movement. Root parallelism and rotation was difficult to achieve with this appliance. In addition, the pins had to be repositioned every appointment through the process of re-soldering. Ribbon Arch Appliance (1915) - This appliance was created after the Pin and Tube appliance. This device consisted of a Vertical bracket soldered to a band. It allowed rotation to be possible. Dr. Raymond Begg eventually used this appliance to create his light wire technique. Edgewise Appliance (1925) - These were identical brackets for all teeth and it allowed tooth movement in all 3 planes of