{'fraction_non_alphanumeric': 0.008849557522123894, 'fraction_numerical': 0.0, 'mean_word_length': 5.65546218487395, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Effect of secular decline in caries on the evaluation of preventive dentistry demonstrations.

Studies of dental preventive interventions often do not incorporate a concurrent, longitudinal control group in their study design. The existence of a secular decline in dental caries during the conduct of these studies may result in an overstatement of the effectiveness of the preventive intervention. Results of a recent large caries preventive study are analyzed using both a concurrent, longitudinal control group and an historical comparison group to demonstrate this effect. Differences in effectiveness of preventive procedures determined using the two types of control groups are sufficient to suggest a probable misinterpretation of results of studies using only historical comparisons.