fillings or missing teeth. Toothpaste was often not available, and toothbrushes did not conform to standards of modern dentistry. Language Under Lenin, the government gave small language groups their own writing systems. The development of these writing systems was highly successful, even though some flaws were detected. During the later days of the USSR, countries with the same multilingual situation implemented similar policies. A serious problem when creating these writing systems was that the languages differed dialectally greatly from each other. When a language had been given a writing system and appeared in a notable publication, it would attain ‘official language’ status. There were many minority languages which never received their own writing system; therefore, their speakers were forced to have a second language. There are examples where the government retreated from this policy, most notably under Stalin where education was discontinued in languages that were not widespread. These languages were then assimilated into another language, mostly Russian. During World War II, some minority languages were banned, and their speakers accused of collaborating with the enemy. As the most widely spoken of the Soviet Union's many languages, Russian de facto functioned as an official language, as the ‘language of interethnic communication’ (), but only assumed the de jure status as the official national language in 1990. Religion Christianity and Islam had the highest number of adherents among the religious citizens. Eastern Christianity predominated among Christians, with Russia's traditional Russian Orthodox Church being the largest Christian denomination. About 90% of the Soviet Union's Muslims were Sunnis, with Shias being concentrated in the Azerbaijan SSR. Smaller groups included Roman Catholics, Jews, Buddhists, and a variety of Protestant denominations (especially Baptists and Lutherans). Religious influence had been strong in the Russian Empire. The Russian Orthodox Church enjoyed a privileged status as the church of the monarchy and took part in carrying out official state functions. The immediate period following the establishment of the Soviet state included a struggle against the Orthodox Church, which the revolutionaries considered an ally of the former ruling classes. In Soviet law, the ‘freedom to hold religious services’ was constitutionally guaranteed, although the ruling Communist Party regarded religion as incompatible with the Marxist spirit of scientific materialism. In practice, the Soviet system subscribed to a narrow interpretation of this right, and in fact used a range of official measures to discourage religion and curb the activities of religious groups.