In Japan, dentists' salary used to be comparable to that of physicians. But in the last 3 decades, dentists' salary decreased dramatically. After 6 years of dental school, dental associates in Japan are now payed dismal $30,000 a year (please remember that Japan is world's second largest economic power). Medical doctors in Japan easily make over $300,000, whereas dentists who can do orthodontics and maxillofacial surgery make $65,000 on average (the numbers are take-home pay).
In 1970's, dental caries was a big problem in Japan. At that time, numerous profit-run dental schools were established. The main reason behind it was that nation-run dental schools were very difficult to get in, so dentists who wanted their children to become dentists needed such private schools that can allow back-door entry.
30 years later, excess supply of dentists is now becoming a serious social problem in Japan (reference: 歯科医師過剰問題 in Wikipedia). Decreased caries (DMFT in Japan is high compared to other countries, but still it deacreased significantly over the last 30 years) and oversupply of dentists resulted in dramatic decline in dentists' salary.
As a result, the difficulty of the entry into medical school sky-rocketted. Now, top dental schools in Japan are easier to get in than lowest-tier medical schools, and even than almost all pharmacy schools. The table at the bottom (medicine, pharmacy, dentistry from left to right) basically says that in order to get into any nation-run medical school, you need to score at least 84.5 percentile in the nation-wide entrance exam, but all nation-run dental schools accept students who score below 83.5 percentile (nation-run means that you only need to pay $25,000 to become a dentist). Although not shown in the table, most private dental schools accept students below 50 percentile. To translate this concept into North American terms, students who want to go to nation-run medical school need to have have at least 3.9 GPA (maybe 3.7 for private schools), while students with 1.7-2.0 GPA can easily be accepted to dental school if they are willing to pay $600,000 tuition.
Last year, some Carribean, Polish, and Hungarian med schools started a program that cater for Japanese students. There are too many students who want to go to med school so badly in Japan. Dentistry is not considered as a good alternative any more. People would rather choose to study English and go through all the hardships to obtain an M.D. in a foreign country than going into a profession of bleak prospect. Nowadays, it is not uncommon for Japanese dental students to quit dental school, or even after they graduate from dental school, to re-apply to medical schools.
Of course, Americans value beautiful teeth much more than Japanese people do, and Japan has totally different insurance system than North America, so it would be mistaken to simply say that the dental profession in the U.S. will have the same destiny as that of Japan. However, unless dental schools decrease the number of graduating dentists according to the decrease in DMFT, it is not improbable that dentistry in other countries would also experience a similar situation to that of Japan. Japanese National Health Insurance System is like one huge HMO run by the nation, so all the Japanese citizens, including low income social strata, can receive very cheap dental care (wealthy people go to expensive dental offices that do not accept any insurance). But when even low income strata begin to have less and less cavities to begin with, dentists can never make tons of money even with HMOs because there are simply not enough patients. As a result, more and more dentists are filing bankruptcy in Japan.
Dentistry used to be an extremely lucrative profession in Japan, much like that of the U.S. today. The situation changed 180 degrees within a matter of 30 years. A similar situation may or may not happen in the U.S. in your lifetime. So the bottom line is that if you do not have any other reason you want to do dentistry than money, you may regret not choosing medicine just as most Japanese dentists do now.
(P.S. Some dentists in Japan do make a lot of money but they are exceptions. In any profession, top 5% people make tons of money, you know.)
2005センター試験　国公立（前期）　代ゼミボーダーランキング
　　　 【医学科】　　　　　　　　　　　　　　　　　　　　　　 【薬学科】　　　【歯学科】　　　　　
93.5% 東大
93.0%
92.5%
92.0% 京大
91.5% 阪大
91.0%
90.5% 阪市 九大
90.0% 医歯 名大
89.5% 北大 東北 千葉 山梨 神戸
89.0% 筑波 横市 京府 岡山　　　　　　　　　　　　　　 　京大
88.5% 新潟 広島
88.0% 群馬 信州 浜松 三重 滋医 奈医 鳥取 徳島　　阪大
87.5% 山形 金沢 熊本
87.0% 名市 山口 香川 長崎 鹿児.　 　 　 　 　　　　　　九大 　 　 　 　 　 　 　 　　　　　　　
86.5% 福井 岐阜 高知 琉球　　　　　　　　　　　　　　 　千葉
86.0% 旭医 札医 弘前 福島 富山 和歌 愛媛
85.5% 秋田 島根　　　　　　　 　　 　　　 　　　 　　 　　　 　　　　　　　　　　　　　　　　　　　　
85.0% 産業 大分 　 　 　 　 　 　 　　　　　　　　　　　　　東北 岡山　 　 　 　 　 　　　　　　　
84.5% 佐賀 宮崎 　 　 　 　 　 　 　　　　　　　　　　　　　北大
84.0%　　　　 　　　　　　　　　　 　　　　　　　　　　　　　　金沢
83.5%　　　　 　　　　　　　　　　 　　　　　　　　　　　　　　広島 熊本　　阪大
83.0%　　　　 　　　　　　　　　　 　　　　　　　　　　　　　　富山 　 　 　 　 　 　 　 　　　　　　
82.5%　　　　 　　　　　　　　　　 　　　　　　　　　　　　　　徳島 　 　 　　医歯 九大　　　　　　
82.0%　　　　 　　　　　　　　　　 　　　　　　　　　　　　　　長崎 　 　 　　新潟 広島 徳島
81.5%　　　 　　 　　　 　　　 　　　 　　　 　　　 　　　　　　　　　　　　　　東北　 　　 　　　 　　
81.0%　　　 　　 　　　 　　　 　　　 　　　 　　　 　　　　　　　　　　　　　　北大 九歯　　　　　　
80.5%　　　 　　 　　　 　　　 　　　 　　　 　　　 　　　　　　　　　　　　　　岡山
80.0%　　　 　　 　　　 　　　 　　　 　　　 　　　 　　　　　　　　　　　　　　長崎 鹿児　　　　
