Diet as a Nutrient Source
Three factors influence the effectiveness of the diet as a microbial nutrient source. These are the chemical composition of the diet, the physical consistency of its components and the frequency of its presentation. The macromolecular nutrients, such as starches, proteins and lipids, are normally not available to the oral flora, as their transit time through the oral cavity is too short for them to be degraded to usable nutrients. However, if the physical consistency of the foods which contain them permits retention, such as fibrous foods between the teeth, or sticky foods in fissures, pits and contact points, then some utilization of the starches and proteins could occur. Low molecular weight, soluble carbohydrates, such as sucrose (sugar) and lactose (milk sugar) are readily metabolized by the oral flora.
飲食作為一種營養的來源
有三個因素會影響到飲食作為一種微生物的營養源之效能。 它們是化學成分、組成物的物理性質與其出現的頻率。巨大分子的養份如澱粉、蛋白質及脂質，因為在口腔中通過的時間太短暫，來不及被分解成可利用的養份，所以通常無法被口腔菌群來利用。然而當含有這些成分的食物之物理性質，可使之留置在口腔中，如卡在齒間的纖維食物、或在牙齒凹隙及鄰接點的黏稠食物，則一些澱粉蛋及白質的利用就可以發生。至於小分子量可溶性的碳水化合物，如蔗醣(糖)、乳醣(牛奶糖)，這是可直接被口腔菌群代謝運用的。
All of the information related to diet and the oral flora is usually addressed as the relationship between diet and dental decay. This relationship is discussed in detail in Chapters 10, 11, 16 and 17 and will be only briefly summarized here. Note that this information applies to the plaque flora, which is not synonymous with the oral flora.
所有關於飲食與口腔菌群的資料常被視為飲食與蛀牙之間的關係。這種關係會再在第10,11,16,17章詳細討論，此處只是簡短摘要一下。要注意這些資料是適用於牙菌斑菌群(plaque flora)的，而其並不等同於口腔菌群(oral flora)。
In dental decay the consistency of the diet and the frequency of ingestion may be more important than diet composition. Both consistency and frequency influence the length of time that food remains in contact with plaque and thus is available for bacterial use. The longer bacteria have food available, the more they can grow, the more acid they will produce, and the greater the plaque mass that will accumulate. This is illustrated schematically in Figure 5-3, which shows the increase of plaque mass at each food intake. When snacks are interspersed between meals, they augment the time of nutrient availability, allowing further growth of the plaque organisms. If the plaque is only partially debrided by toothbrushing prior to retiring, the plaque mass remaining on the teeth of the snackers may metabolize stored polysaccharides and produce an appreciable pH drop on the tooth surfaces during sleep. In experimental animals and in clinical studies, frequent eating of a high sucrose diet is associated with high caries activity.
就對蛀牙的影響而言，食物的黏稠度及食入的頻率可能比食物的成分重要。 因為兩者會影響食物與牙菌斑的接觸時間長度，因此可被細菌來利用。 細菌佔有食物的時間愈長、就愈能生長、產愈多的酸，及累積越多的牙菌斑塊。如圖5-3所示， 可見到隨者每次食物攝入，牙菌班的量一直增加。 若兩餐之間還提供點心，這會增加養份存在的時間，使得牙菌斑更進一步滋生。若睡前刷牙沒刷乾淨，那麼有吃點心的人其殘留在牙齒上的的牙菌班仍可代謝已儲存的的多醣體，造成睡眠期間牙齒表面的pH值相當程度的下滑。在實驗動物或是臨床研究中，頻繁食用高蔗糖飲食與高蛀牙率是很有關係的。
The consistency of food also influences the plaque flora. Liquid foods, such as fruit juices and tonics, are usually swallowed quickly, and are therefore, not readily available to the oral flora. Sticky and fibrous foods, however, are retained in those areas which trap food, e.g., fissures, missing contacts, pockets and cavities and can be used by the flora in these areas for extended periods of time. It is no mere coincidence that these sites usually are associated with dental pathology. Hard candy in this context, would be an exceptionally cariogenic foodstuff. The sucrose that is slowly released would bathe the supragingival plaque and lead to the selection of organisms, such as S. mutans, which can efficiently utilize sucrose.
食物的稠度也能影響到菌斑菌群。像液體食物，如果汁、蘇打水往往很快就吞下，因而無法被細菌利用。如果是黏稠的或是多纖維的食物，它可卡在如牙凹隙、牙縫、牙周囊袋和窩洞之中，細菌就有較長時間可利用它們。所以這些地方易蛀牙決非偶然。在這樣的思考背景下，硬糖果是個特別會致齲的食物。因為慢慢釋出的蔗糖會浸潤牙齦上菌斑 (supragingival plaque)，導致某些細菌會勝出， 比方S. mutans，因為它能有效地運用蔗糖。
The importance of between-meal eating of sucrose and the consistency of sucrose-containing foods in dental disease was unequivocally demonstrated by a clinical study conducted in adult residents of a mental hospital in Vipeholm, Sweden (See "Vipeholm" in Chap. 11). The five-year caries attack rate in these subjects on the institutionalized diet, i.e., control group, was about 0.2 DMF teeth per year. The addition of about a half pound of sucrose per day in the form of toffees, caramels, chocolates or in bread at meal times, caused only a slight increase in DMF teeth. However, the ingestion of the same forms of sucrose between meals led to an explosive increase in DMF teeth (See Fig. 11-6). The frequent ingestion of sucrose was shown to cause an elevation in the levels of salivary sugars (Table 11-11), which meant that these sugars would be available for microbial fermentation for long periods during the day.
餐間攝食蔗糖與含糖食物的黏稠性，這兩者對於牙齒疾病的重要性已由瑞典的一個臨床實驗明白地顯現出來，這實驗是以Vipeholm 精神病院的成年住院者為對象所作的。(見11章的 Vipeholm研究) 。在對照組，食用院方飲食下五年的蛀牙率大約是每年會增加0.2顆DMFT的蛀牙。 如果只在用餐時刻每天增加食用0.5磅的蔗糖，如作成太妃糖、焦糖、巧克力或加在麵包中等，僅導致DMFT 稍微上昇。然而，如果將同樣形式的蔗糖改在兩餐之間食用，則會導致DMFT出現爆炸性的增加(見fig.11-6)。頻繁食入蔗糖已被證明會提高唾液中的蔗糖水平，這表示細菌在一整天當中，有更長的時間得以利用蔗糖來進行發酵。
Diet is the single most important nutrient source for the plaque found on the coronal surfaces of teeth. Dietary restriction of carbohydrates, especially sucrose, should profoundly influence the composition of the supragingival microbial flora. Detailed bacteriological studies on individuals maintaining such a restricted diet have yet to be performed. The salivary lactobacilli levels and the plaque levels of intracellular polysaccharide-forming bacteria decrease appreciably on low-carbohydrate diets (See "Therapeutic Diets" in Chap. 16). These low-carbohydrate diets are difficult for patients to maintain and are therefore, essentially impractical for caries control. However, dietary reduction of caries by replacement of sucrose with non-cariogenic sugar substitutes, such as xylitol, mannitol or sorbitol, may be possible. Xylitol, in particular, has been shown in human studies to reduce caries either when a total substitution with sucrose was made or when chewing gum sweetened with xylitol was taken between meals (See "Xylitol" in Chap. 17).
對於在牙冠表面的菌斑來說，飲食是單一最重要的養份來源。如果限制飲食中的碳水化合物，尤其是蔗糖，將會明顯影響到齒齦上菌群的組成。針對食用限糖飲食的人們，目前尚無詳盡的細菌學研究。在低碳水化合物飲食下，唾液中的lactobacilli 以及菌斑中製造細胞內多醣體的細菌都會大大減少(見第16章中的"治療性飲食")。這些低碳水化合物的飲食，對人們而言 不太能持久。所以用之來作齲齒控制的手段並不實際。然而以非致齲性的代糖(non-cariogenic sugar substitutes)來取代蔗糖的飲食齲齒減少法，如使用xylitol[木糖醇]，manitol[甘露醇]， sorbitol[山梨醇]，則可能是可行的。尤其是木糖醇，在人體研究中發現，不論是以完全取代蔗糖的方式或是在兩餐之間嚼木糖醇口香糖，它均可降低蛀牙的發生 。
Saliva
Saliva is quite properly considered a homeostatic fluid, which buffers the plaque. However, saliva can provide nutrients to the flora which resides on the surfaces it bathes. Saliva contains about one percent solids, which include glycoproteins, inorganic salts and most importantly for the plaque flora, mg amounts of amino acids and glucose, and mg amounts of certain vitamins. These quantities are sufficient to sustain some bacterial growth during periods when a person does not eat, e.g., between meals and overnight during sleep. Some investigators suggest that the glycoproteins present in saliva could also serve as nutrient sources, if they are trapped in plaque. Some plaque bacteria possess neuraminidases which break down the terminal sugar residues on certain glycoproteins, but no evidence exists which shows that the neuraminic acid (sialic acid), which is released, can be used by the plaque flora. Those bacteria that can utilize and have access to the salivary nutrients, always have a good source available. This advantage is meaningless, however, for those bacteria which do not grow on surfaces exposed to saliva. The bacteria which reside in the gingival crevices and periodontal pockets have limited access to salivary nutrients and do not appear to be influenced by them.
Saliva[唾液]
唾液可視為穩定的液體 可以緩衝菌斑且唾液可浸潤牙齒使 居住牙齒表面的細菌獲得養分
唾液中有1%是為固體如glycoprotein[糖蛋白], 無機鹽.對菌斑菌群最重要的是氨基酸葡萄糖及某些維他命C 即使在睡眠中或是兩餐之間 人們不進食 這些營養仍足夠維持細菌的生長
有些學者提出 認為唾液中的糖蛋白只要可以留滯在牙菌斑上的話也可成為細菌的養分
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菌斑菌群有些具有”neuraminidase” 它可以切掉糖蛋白末端的糖 但尚無證據顯示切開所生成的neuraminic acid可以因而釋出並被細菌所利用
只要能利用唾液中的養分 細菌都能有充足的食物來源
不過對於那些不適合生存活在有唾液浸潤處的細菌來講 它們就無法取得利用唾液中的營養 比方存活在牙齦溝或是牙周囊袋的菌種 就不受到唾液的影響
Gingival CrevicularFluid
The gingival crevice is bathed by ml amounts of a serum transudate which contains tissue and serum proteins, as well as free amino acids, vitamins, glucose, etc. Under healthy gingival conditions, this gingival crevice fluid is protective, flushing out nonadherent plaque from the sulcus and bringing phagocytic cells and antibodies into the area. The presence of certain serum components may act as a strong selection factor for some of the gingival crevice microbes, such as the spirochetes and black-pigmented bacteroides (See "Nutrient Needs" in this chapter).
Gingival crevice fluid [牙齦縫隙液]
牙齦溝裡有著微量的血清滲出液 內含有組織還有血清蛋白 氨基酸維他命葡萄糖等 在健康的牙齦 這些滲出液具有保護作用 可沖洗掉牙菌斑 並帶來吞噬細胞還有抗體
血清中的某些成分可以強力的選擇牙齦溝的菌種 比方螺旋體，黑色素類桿菌(見本章nutrient needs)
Shed Cells
The epithelial surfaces of the oral cavity undergo a turnover, shedding their surface cells. Also, phagocytic cells enter the oral cavity from the gingival crevice area. These mammalian cells can be lysed by the hypotonicity of saliva and their contents are then available for microbial nutrition. The magnitude of this food source for microbial metabolism is not known.
Shed cells [大棚細胞]
口腔表皮經過週期會脫落 而吞噬細胞也會自牙齦溝跑出來 這些細胞會被唾液這種低張溶液所分解 分解後的物質可供給細菌作養分 但這樣所佔的比重多寡仍不清楚
Bacteria
The bacteria themselves can provide nutrients for each other. In a dense microbial population, such as plaque, one would expect considerable microbial interactions. One well-documented interaction is the relationship between lactic-acid-producing bacteria, such as the streptococci and a lactate-utilizing species, such as Veillonella alkalescens. V. alkalescens has lost the enzyme, hexose kinase, which means that it cannot phosphorylate glucose. Under most conditions this would have been a lethal mutation and the mutant never observed. However, if this mutation occurred in nature in the presence of lactic acid, the mutant could survive because this acid is absorbed by V. alkalescens and fermented so as to yield ATP.
Bacteria [細菌]
細菌們可以互相供應養分 尤其在像菌斑這樣密集的族群裡 想必有許多細菌間的互動
最為人熟知的是 能產乳酸的菌(如streptococcus)與能利用乳酸的菌(Veillonella alkalescens)之間的關係。V. alkalescens 這菌，它不具hexose kinase 這種酵素。這表示它無法幫葡萄糖加上燐氧基。這樣的突變一般來說是致命的而且沒見到有突變物
萬一這種突變在有乳酸的環境下發生了 這突變物是可存活的 因為乳酸會被V. alkalescens所發酵並轉化成ATP.
Many organisms in plaque, including the streptococci, form lactic acid. This would suggest that the Veillonella parasitize the lactate producers. However, the relationship between the Veillonella and organisms such as streptococci may be symbiotic, as the lactic acid is converted to propionate, acetate, and carbon dioxide, with a resultant elevation in pH. This shift away from low pHs would be beneficial for those acid-sensitive streptococci, such as S. sangius. Other examples of plaque-microbial interactions exist. Treponema denticola is dependent upon cohabitant plaque species for isobutyrate and spermine. B. melaninogenicus' requirement for vitamin K can be provided by a variety of other oral bacteria, such as C. sputorum and Bacteroides oralis.
These microbial interactions indicate that some of the oral flora are microbe dependent, i.e., they will not grow in the absence of the provident microbes. This is indeed the case, as none of the cited organisms will establish in pure cultures in germfree animals. The Veillonella can be grown in germfree animals after prior establishment of a Streptococcus. No one has yet established the spirochetal species or B. melaninogenicus in gnotobiotic animals under any circumstances, indicating that parameters other than nutrient availability, such as Eh, may be preventing colonization.
菌斑中有很多細菌會產生乳酸顯然Veillonella是寄生於這類產乳酸者之中
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然而這兩者的關係是為共生，因為乳酸會轉化成propionate,acetate, 及二氧化碳，於是提高pH。這樣一來對於acid-sensitive Streptococci而言是有好處的(比方S. sangius)
另一個互動的例子是Treponema denticola,它依賴同居的菌種而取得isobutyrate[異丁酸], spemin。
還有像B.melaninogenicus 它需要維生素K，可由其他的菌種協助而得到。
由細菌間的互動顯示出有些菌種是 微生物依賴型，即若少了對方就活不下去。
確實，在無菌的動物身上，上述的微生物是無法達成純培養。
像Veillonella必須等到strepotococcus 在無菌動物上生長好了，它才會隨後生存。
尚沒有人能在gnotobiotic anima[悉生動物]l上培養出spirochetal species[螺旋體物種]或是B. melaninogenicus。這顯示出除了養分供應之外，應該還有其他因素會阻止殖民。
ECOLOGICAL NICHES
Thus far we have discussed the oral flora as if it were a single entity. Now it is known that microorganisms which live on the tongue are not necessarily the same organisms which are found in the plaque. Also organisms, like the spirochetes and Gram-negative anaerobic rods, inhabit the subgingival plaque and are rarely found in supragingival plaque, or in high numbers in the saliva. Clearly, there is some heterogeneity within the "oral" flora.
ECOLOGICAL NICHE [生態位]
雖然目前討論口腔菌群我們將它是為單一個體 事實上並非如此 居住在舌頭的菌不見得與牙菌斑當中相同 又好比居住於齒齦下菌斑的菌(如…)就很難得在supra-中見到 也不會大量出現在唾液中 顯然所謂的口腔菌群是存有異質性的
Prior to l963 most bacteriologists had considered the "oral" flora to be uniformly distributed throughout the mouth and concentrated their efforts on the culturing of saliva on the assumption that the saliva reliably reflected the "oral" flora. This approach ignored the unique contributions to the saliva of the bacteria shed from the different anatomical sites within the mouth and accordingly, delayed the understanding of the role of specific microbes in both dental caries and in periodontal disease. For example, if an organism such as S. mutans comprised less than one percent of the salivary flora, it is difficult to conceive how it could be a cariogenic organism. However, if S. mutans comprised 25 percent of the flora in an occlusal fissure, then its role as a cariogenic organism is plausible.
早在1963 大部分細菌學家認為 口腔菌群是均質分布口腔中的 因而致力研究唾液 認為當中的菌種就足以反應口腔菌群 這樣的想法忽略掉了細菌會由口腔中的任何部位脫屑至唾液中 因而延誤了對於蛀牙及牙周疾病的探究
舉例來說S.M.佔saliva flora[唾液菌群]不到1%很難令人聯想到它就是致齲微生物 事實上它佔咬合面牙裂中菌種的25% 如此說來它的齲齒性角色就挺合理的
Plaque
In the late l950s and early l960s quantitative culturing procedures were introduced in which plaques and saliva were dispersed, serially diluted and cultured under an anaerobic atmosphere. We discussed in Chapter Two that these procedures demonstrated the microbial density of the plaque and saliva to be very high, and that the predominant flora was capable of anaerobic growth. These studies also demonstrated that plaque differed from saliva.
Plaque[菌群]
1950~1960 出現了quantitative culture[定量文化] 其中 做法 將菌斑 與唾液散布在燕養的狀態下依序稀釋培養這在第2章探討過這些研究告訴我們菌斑 不同於唾液
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Gibbons, Socransky and their colleagues collected plaque from either the coronal or subgingival surfaces of all the teeth in a mouth and pooled them so as to give a single sample for each subject. The pooled plaques from the coronal surfaces contained mainly Gram-positive saccharolytic organisms (carbohydrate fermenters), whereas the pooled plaques from the subgingival surfaces contained in addition, Gram-negative saccharolytic and asaccharolytic (proteolytic) organisms. Neither plaque contained S. salivarius, although this organism had until this time been considered to be the numerically dominant streptococcus in the oral cavity because of its prominence in the saliva.
Gibbons, Socransky同僚等人收集整個牙齒上的菌斑然後匯集一起
Coronal 的菌包含Gram positive saccharolytic organism[carbohydrate fermenters].
Subgingival 則包含Gram negative saccharolytic 和asaccharolytic[proteolytic] organism.
當中就是沒有S. salivarius 它是口中為數相當多的菌尤其在唾液中很多
When Krasse, in the early 1950s, reported that S. salivarius was not present in the plaque, he said that a discrepancy must exist between salivary sampling techniques and the technique of sampling material from the tooth surface. This discrepancy is now known to be the incorrect assumption that plaque and saliva are bacteriologically identical. The washoff of bacteria from all the surfaces in the oral cavity are found in the saliva. Since the tongue and the cheeks constitute most of the mouth's surface areas, the flora shed from their surfaces are highly prominent in the salivary flora. As S. salivarius is the predominant streptococcus on these surfaces, it becomes also the predominant streptococcus in the saliva.
Krasse 1950發表S. salivarius 不存在於牙菌斑中 他認為應該是在取樣牙齒及唾液技巧上有差異 現今知道這差異原來是因為過去誤以為菌群與saliva中的菌是相同的
因為整口腔表面的菌都會掉落到唾液中 而舌頰面積遠大於牙齒 因此來自他們的菌種會佔了大多數所以說S. salivarius 在舌頰處數量很多自然也成為唾液中的大宗
由表5-2可見到分布
These quantitative culturing studies were extended to look at other sites in the mouth and to look for specific bacterial types, so that eventually the geographic localization of many oral species was determined (Table 5-2). The flora on the tongue, buccal mucosa and in the saliva are similar, whereas the plaque flora differs by having almost undetectab1e levels of S. salivarius and appreciable levels of Actinomyces and Gram-negative species. The Gram-negative species are mainly confined to the subgingival plaque so that it is not even valid to think of plaque as a homogeneous entity.
舌頰唾液三者的菌種類似菌群中幾乎看不到S. salivarius 反而有大量的Actinomyces 還有G(-)(主要在subgingival)可見就連菌群也不是均質的
Not only do microbial populations differ from location to location in the mouth, but the plaque flora in the same location may show definitive changes over time. For example, following cleaning of the teeth, the plaque which initially forms at the dento-gingival margin after one day is made up of primarily cocci. If the plaque remains undisturbed for a few weeks, some Gram-negative, motile species are observed (See Plaque Formation in Chap. 6).
不但如此 同一地區的菌群也將隨時間而有所變化
例如牙齒刷乾淨之後最初在dento-gingival margin 是以cocci為主 假使數週都不被干擾的話慢慢會有G(-) motile 出現(見ch 6)
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These studies with pooled plaques demonstrated the differences in flora between the subgingival and supragingival sites and their respective differences with the salivary flora. However, they did not demonstrate appreciable differences between patients with and without dental diseases. This is because the pooled plaques contained mostly plaque from nondiseased sites, which would dilute out the plaque obtained from single sites that were diseased. It is only in the last few years that plaques from single diseased pockets or single carious fissures have been cultured and compared with plaques from nondiseased sulci or fissures. The differences found are the basis for the specific plaque hypothesis and will be discussed in detail in Chapter 12.
以上的研究都是以匯集菌群 雖顯示出菌群的差異 但沒能顯示出有或沒有牙齒疾病時plaque差異 因為大部分的菌群都是取自非病區 所以病區 的菌將被稀釋 近幾年才有針對患病的袋區或是齲齒裂來做研究(見ch.12)
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Ecological Determinants
What phenomena can explain the microbial diversity that exists in different anatomical sites in the mouth? What ecological differences exist between the teeth and the soft tissue that result in the establishment of distinct flora in these sites? And why does plaque in the supragingival area contain fewer Gram-negative species than does the subgingival plaque? Bacteria establish in sites where they can fulfill their nutrient requirements and do not encounter inhibitory or adverse conditions for their growth. Could these factors be the determinants responsible for the different microbial ecosystems?
Ecological determinants [生態決定因素]
究竟哪些因素造成這麼多部位的細菌如此不同?是什麼因素決定生態系統?
Nutrient Needs. The nutrient sources in the mouth are diverse and should provide a wide variety of organic compounds capable of supporting the growth of the most fastidious organisms. Yet, it is possible that some unique growth factor needed by S. salivarius, for instance, is not present in the plaque microenvironment. Carlsson explored this possibility by developing chemically-defined media for S. salivarius, S. sangius and S. mutans. The three species had similar nutrient requirements except for differences in single amino acids. Thus, nutrient needs could not account for the absence of S. salivarius in the plaque.
Nutrition needs [營養需要]
口中營養是多元化就連最挑剔的微生物也能生存 但是像S. salivarius所獨有的生長因子就可能不存在於菌斑中
Carlsson 利用化學定義的媒體來研究三種菌(S. salivarius, S.mutans, S. sangius)這三種的營養需求類似只差一種氨基酸 所以很難就營養需要來說明為何菌斑中獨缺S. salivarius
Nutrient availability, however, could explain the localization of certain Gram-negative species to the subgingival plaque. B. melaninogenicus, P. gingivalis, and Capnocytophaga either have a requirement for hemin or were stimulated by hemin. Many isolates of the black-pigmented bacteroides were also stimulated by vitamin K, estradiol and progesterone. Treponema denticola has a requirement for spermine.
營養物的可利用性可以解釋為何某些G(-)喜住在齒齦下菌斑像B.melaninogenicus , P.gingivalis ,C apnocytophaga,它們都特別需要hemin ， 有很多黑色素類桿菌需維生素 K, 雌二醇，孕酮。而Treponema denticola 需要spermine。
All of these compounds would be present in serum but not in saliva, foods or shed cells. The only site in the mouth where microbes would have access to these nutrients would be in the flow bed of the gingival crevicular fluid. Thus, the above species could thrive only in the subgingival plaque. If gingival pathology occurs, and the transudate increases in volume, a proliferation of these organisms might occur. In fact, when gingivitis has progressed to the point where bleeding occurs, these organisms can be found among the indigenous flora of the site. This can be documented in pregnancy gingivitis, where a specific increase in B. melaninogenicus ssp. intermedius was found after bleeding occurred. The specificity of this increase could be correlated with the ability of this organism to utilize estradiol and progesterone, both of which would increase in the gingival crevice fluid during pregnancy. Thus, in the case of the spirochetes and B. melaninogenicus nutrient supply appears to be of paramount importance in their localization and actual levels in the plaque.
以上提到的諸多養分都會出現在血清之中 但唾液食物棚細胞中則無 口中只有齦溝液 中才有 所以以上的菌都生存在那。若牙齦疾病變糟 則滲出液的量更多 這些菌還會大量滋生 尤其出現牙齦出血時更明顯
比方妊娠期齦炎 一但出現流血 將可發現到B. melaninogenicus特別增加 這顯然和這菌可以利用estradiol及progesteron 有關(懷孕期間這兩物質在牙齦液中也會增加)
所以對spurochetes 與B. melaninogenicus而言營養供給很重要
p.77
Inhibitory Factors. A variety of inhibitory factors of either host or microbial origin could be responsible for the distinct ecosystems observed in the plaque and soft tissues. The host factors would include specific antibodies, lysozymes, lactoperoxidase, lactoferrin and high molecular weight adhesins, all of which are present in the saliva. These host antibacterial mechanisms are described in detail in Chapter 20 and will not be discussed here, other than to note that they do not appear to be responsible for the establishment or maintenance of the various oral ecosystems.
Inhibitory factors[抑制因子]
這類因子很多
主機因素：特異性抗體，溶菌酶，乳過氧化物，乳鐵蛋白和高分子量粘附素以上在唾液中可見(ch.20)
細菌產生的因素：有機酸(可降低pH) 一些反應的終產物可降低Eh, hydrogen peroxide 強化某些酵素及membrane, fatty acid, bacteriocin(可阻止其他菌的滋生) 以上在in vivo尚未完全了解
a) acidic pHs: Members of the oral flora grow best in vitro at about pH 7.0. This is the level found in saliva and which is maintained by the carbonate buffer in the saliva. However, the plaque pH can drop to below 5.0 during eating (See Fig. l0-3). This low pH could select for aciduric organisms, and this could account for the absence of species such as S. salivarius in the plaque. This possibility was investigated by observing the relative abilities of several oral species, including S. salivarius, to initiate growth in media with acid pHs.
a) acidic pH: 口腔菌群在酸鹼度7長得最好 這也正是唾液經緩衝由之後的數值 進食時pH能下降到5 這正好選擇出耐酸的菌(恰好說plaque中沒有S. salivarius)見表5-3
All tested species grew luxuriantly when the initial pH was 7.0, but exhibited diminished growth when the initial pH was 5.5 (Table 5-3). When the pH was dropped to 5.0 only S. mutans and L. casei were capable of growth. There was no difference in acid tolerance between S. salivarius and such prominent plaque organisms as S. sangius, S. mitis and A. viscosus. Thus, the absence of S. salivarius from the plaque could not be related to it being more sensitive to low pH than S. sangius or S. mitis. Tolerance of low pH may explain the selection of S. mutans and L. casei in the cariogenic plaques and lesions.
b) reduced products and pO2: Bacterial metabolism results in the formation of reduced end-products which lower the Eh. In the dentogingival area and in the pockets, the Eh may be as low as -100 mv and the oxygen tension as low as one percent. (See Fig. 5-1.) Only anaerobes and certain facultative organisms could survive in this environment. The oxygen tension over the dorsum of the tongue and perhaps on certain coronal tooth surfaces would be considerably higher and supportive of more oxygen tolerant organisms, such as the streptococcal species. Organisms, such as the spirochetes, P. melaninogenicus, P. intermedia and F. nucleatum, cannot survive in well-aerated areas such as the tongue and many supragingival sites, but are well adapted to the anaerobic crevicular environment. All streptococcal species tested could grow in air. Thus, oxygen sensitivity cannot explain the absence of S. salivarius from the dental plaque.
b) reduced products and pO2: 細菌代謝的終產物會降低Eh 在dentogingival area , pocket Eh=-100, 而O2 tension只低到1%(fig 5-1) 此環境只有厭氧及某些兼性微生物可長。若在舌背 , 齒冠表面則O2 tension 較高 適合耐氧的菌種如streptococcal species 。
但像spirochetes, P.melaninogenicus , P.intermedia, F.nucleatum它們不宜在充沛氧氣的區域，適合在厭氧的溝區。所以O2-sensitivity也不能解釋菌斑中找不到S. salivarius。
SUMMARY
Nutritional and inhibitory factors, to the extent that they could be identified, can explain the localization of anaerobic and certain fastidious organisms to the subgingival plaque. They explain why saccharolytic-microaerophilic organisms dominate in the supragingival and soft-tissue sites. They do not explain why certain organisms, such as S. salivarius, dominate in the soft tissue but are absent from the plaque. Clearly, other ecological determinants are operative. One of these, the ability of an organism to adhere to a surface, will be described in the next chapter.
SUMMARY [概要]
除了營養及環境抑制因素顯然還有其他因素下一章再研究 ,
因為沒有解釋為什麼某些生物，如S. salivarius，出現於軟組織，而非菌斑。
