Is orthodontia and dental work much more expensive in california than other states?

Expensive everywhere. Great quality orthodontic and dental treatment takes time, great materials and great doctors. That i'd costly everywhere. You get what you pay for in all aspects of life.
Yes. Orthodontic treatment tends to be higher on both coasts, similar to cost of living. Similar houses in boston and malibu will be more expensive than in biloxi or cheyenne. The same is true for orthodontic care. See an orthodontic specialist for a cost estimate in your area.
Orthodontia. Traditionally yes. The overall cost of living in ca is higher than other places. Other expensive areas are ny and hi.
Yes. Braces cost more than the national average if done in california. Overhead costs (employees must live in an expensive region) make the fees a bit higher. The southeast United States may have the highest. A recent journal article in jco broke down the stats.
Not always. I can argue that in the los angeles area, outside of some distict areas (beverly hills, newport beach, pasadena, etc) dentistry is the most competitive in the nation and fees reflect that. Insurance contracted fees are probably the lowest in the la area when compared to other states. If anything we probably have the highest spread of differing fees.
No. There are regional differences in dental fees. I am sure there are dentists in orange county or beverly hills that charge a lot higher than the average, but they are offset by other dentists in rural area that charge less than the average. I can assure you that dental work in the state of california is not much more expensive than other states, and i don't even work there!
Probably not. Costs for dental care can very dramatically- usually reflecting the costs of operating the business in that particular area. Most dental practitioners in any particular area have similar fees that have been determined to be " usual, customary, and reasonable" for that area.