Types and Forces of Elastics
- Elastics are used to correct malocclusions in orthodontic treatment.
- They can be worn for varying durations, from two weeks to several months.
- The recommended wear time is 12 to 23 hours per day.
- Different types of elastics produce different forces on teeth.
- Specific forces are critical for achieving a good orthodontic occlusion.
- Elastics are available in different forces, depending on the manufacturer.
- Intermaxillary elastics have force ratings ranging from light to extra heavy.
- Light force: 2 oz. (56.7 g)
- Medium-light force: 3 1/2 oz. (99.2 g)
- Medium force: 4 oz. (113.4 g)
- Medium-heavy force: 5 1/2 oz. (155.9 g)
- Heavy force: 6 oz. (170.1 g)
- Extra heavy force: 8 oz. (226.8 g)

History of Elastics
- Natural rubber was the first known elastomer used by ancient cultures.
- Charles Goodyear developed the vulcanization process, increasing the use of natural rubber.
- Henry Albert Baker was the first to use elastics for teeth correction.
- Calvin Case may have been the first to use intermaxillary elastics.
- Latex elastics became prominent in the early 1900s, replacing natural rubber.

Class II Elastics
- Used from the lower first molar to the upper canine tooth.
- Used for Class II malocclusions, anchorage reinforcement, and other purposes.
- Different elastic forces are used based on extraction or non-extraction cases.
- Side effects include extrusion of upper incisors and lower first molars, flaring of lower incisors, and more.
- Orthodontists generally use 12-16 oz elastics or 2x 6 oz elastics on either side of the mouth.

Class III Elastics
- Used when the molar relationship is close to Class I malocclusion.
- Cannot correct Class III malocclusions due to skeletal discrepancy.
- Soft and hard tissue esthetics should be evaluated before using Class III elastics.
- Side effects include distal movement of lower teeth, mesial movement of upper teeth, flaring of upper incisors, and more.
- Elastic wear only produces changes in dentition, not soft and hard tissue.

Pioneers, Notable Orthodontists, Contributions, and Innovations in Orthodontics
- Earl W. Renfroe, Robert M. Ricketts, Alfred Paul Rogers, Ronald Roth, and Everett Shapiro are pioneers in orthodontics.
- L. F. Andrews, Frederick Lester Stanton, Earl Emanuel Shepard, Cecil C. Steiner, and David L. Turpin are notable orthodontists.
- Earl W. Renfroe's advancements in wire technology, Robert M. Ricketts' development of the Bioprogressive Technique, Alfred Paul Rogers' research on facial growth and development, Ronald Roth's introduction of the Roth Prescription, and Everett Shapiro's work on the Straight-Wire Appliance System are contributions to orthodontics.
- L. F. Andrews' invention of the Andrews Straight-Wire Appliance, Frederick Lester Stanton's development of the Edgewise Appliance, Earl Emanuel Shepard's contributions to the expansion arch technique, Cecil C. Steiner's advancements in cephalometric analysis, and David L. Turpin's research on craniofacial growth and development are innovations in orthodontics.
- Charles H. Tweed's establishment of the Tweed Study Course, Earl W. Renfroe's influence on the use of elastics in orthodontics, Robert M. Ricketts' emphasis on the importance of functional occlusion, Alfred Paul Rogers' contributions to orthodontic education, and Ronald Roth's impact on the field through his publications and teachings are the impact on orthodontic practice.