LOW TEMPERATURE THERMOPLASTICS (LTT) The Invention of… The story of Lester Larson and Dorothy Kester

Most Common Uses… Splints - removable, comfortable casts for almost any part of the body Foot Orthotics – custom- made shoe inserts to relieve back and knee pain

HISTORY 3000 BC - bark and palm ribs held together with egg whites or clay 860 AD - predecessor to plaster: lime/egg white mixture Early 19 th century - leather and straw treated with wine, acetate, spirits and egg whites - hardened quickly, but cast was very heavy lighter-weight, removable bandage made of cardboard and starch - took several days to harden

Plaster of Paris - natural plaster deposits found near Paris, France - plaster powder rubbed into cotton, soaked in water and applied - cast had to be kept dry - very cumbersome HISTORY Cont… 1970’s – fiberglass: light, durable and waterproof, still used today

Casts are not suitable for all injuries—such as tendon damage, soft tissue tears or post healing protection LUCITE – High-temperature thermoplastic Rigid and clear Could not be molded directly on skin Time-consuming process involving a negative cast and a positive mold HISTORY Cont…

The Golf Ball Connection

Lester Larson DuPont Chemist Broken wrist Lucite Splint from Dorothy Kester Occupational Therapist Invented Low Temperature Thermoplastics (LTT) THE INVENTORS:

Eureka!! The Metaphor

Plastic Must meet three conditions: 1.Main ingredient must be a polymer 2.It must be fluid at some point of processing 3.It must be “solid” in its final form The Science of Thermoplastics Polymers Transpolyisoprene

Long Search/Little Apparent Progress: Short process. Aware there was a problem, but no documentation of if there was other experimentation or ideas. Precipitating Event: Visit with OT and receives uncomfortable Lucite splint Eureka! Seeing the warm, moldable golf ball covers – that could be a splint Transformation: Acceptance by the OT community Supplying the product to Orthopedic Shoe Company in NY Lester Larson & Perkins' Model

Swan Neck Deformity - caused by finger injury or rheumatoid arthritis HOW LTT IS USED: Non-extending fingers – caused by injury or arthritis Re-attached fingers – comfortable support and protection Also used in radiation and burn treatment One 18” x 24” sheet of LTT sells for ~$60.00

Question 2: True plastic must meet three conditions. What are they? Question 1: What was the metaphor used by Lester Larson? QUESTIONS