全英文复习题 中山大学 口腔医学.doc

Single choice questions:n What is considered to be the primary cause of dental caries? (B) A. sugar B. plaque C. saliva D. materia alban The first step in the formation of dental plaque is (A) A. acquired pellicle B. materia alba C. food debrisD. bacterial colonizationn Which of the following nutrient has been found to be an overwhelming cause of the development of plaque and dental caries? (B) A. proteins B. carbohydrates C. minerals D. vitaminsn Which of the following microorganisms has been implicated in the dental caries process? (C) A. Streptococcus salivarius B. Streptococcus mitis C. Streptococcus mutansD. Veillonella sp.n The MOST cariogenic carbohydrate is (A) A. sucrose B. fructose C. glucose D. maltosen The state of teeth joined together only by cementum is diagnosed as (B) A. fusion B. concrescence C. budding D. geminationn The process of demineralization will occur with (A) A. caries B. calculus C. green stain D. yellow stainn Dental handpieces must be sterilized (B) A. once a day B. after each patient C. lubricated once a day D. after working on a patient with a known communicable diseasen The most frequently isolated microorganism on root surface caries is (C) A. Lactobacillus B. Streptococcus mutans C. Actinomyces D. Streptococcus mitisn The ancient book recorded a silver amalgam paste for dental fillings over 14 centuries ago was written by (D) A. Egyptians B. Greeks C. Romans D. ChineseShort note questions:1. DMF index：An index for managing statistically the number of decayed, missing, or filled teeth in the oral cavity. 2. Trends of dental caries in epidemiology The prevalence rate has decreased in developed countries, and this decline is usually attributed to increasingly better oral hygiene practices and preventive measures such as fluoride treatment. In China and other developing countries, the prevalence rate of dental caries has increased due to the rising sugar consumption and imperfection in oral hygiene prophylaxis.3. Dental plaque: Dental plaque is unmineralized bacterial deposite that builds up on the teeth. It consists of adhesive matrix and bacteria. If not removed, it can lead to dental caries or periodontal diseases.4. Purposes of dental caries restoration : To restore the integrity of the tooth surface. To restore the function of the tooth. To restore the appearance of the tooth. To remove the diseased tissue from the tooth.Essay questions:1. Hypothesis about the etiology of dental Caries: Four-factor theoryThere are four main factors required for caries formation: a tooth surface (enamel or dentin); caries-causing bacteria; fermentable carbohydrates (such as sucrose) and time.TeethThere are certain diseases affecting teeth which may leave an individual at a greater risk for caries. Dentin and cementum are more susceptible to caries than enamel because they have lower mineral content. Thus, when root surfaces of teeth are exposed from gingival recession or periodontal disease, caries can develop more readily.The anatomy of teeth may affect the likelihood of caries formation. Pit and fissure are more likely to develop dental caries.BacteriaThe mouth contains a wide variety of oral bacteria, but only a few specific species of bacteria are believed to cause dental caries. Among them, Lactobacillus, Actinomyces and especially Streptococcus mutans are most closely associated with caries. Bacteria collect around the teeth and gums in a sticky mass called plaque, which serves as a biofilm in cariogenecity process.Fermentable carbohydratesBacteria convert carbohydrates into acids such as lactic acid through fermentation process. If left in contact with the tooth, these acids may cause demineralization. If demineralization continues over time, enough mineral content may be lost so that the soft organic material left behind disintegrates, forming a cavity or hole. Sucrose is more cariogenic than other carbohydrates. TimeEvery stage in the carious process needs time. Dental caries is usually a chronic disease with a long process. For example, proximal caries take an average of four years to pass through enamel in permanent teeth. So only with the existence of time factor could the other three factors play their roles in cariogenecity.2. The relationships of Streptococcus mutans, Lactobacillus and Actinomyces with dental caries. Streptococcus mutans is the leading cause of dental caries and is considered to be the most cariogenic of all of the oral streptococci. Streptococcus mutans sticks to the surface of teeth. While metabolising sugar and other energy sources, the microbe produces acid that causes cavities in teeth. Lactobacillus bacteria are more involved in dentinal caries, and play a role in carious process rather than in the initial stage of dental caries. So the increase of Lactobacillus in denta