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Dental Tribune Middle East & Africa Edition

15Dental Tribune Middle East & Africa Edition | January - February 2014 oral health Following a sucrose rinse the plaque pH is reduced from ap- proximately 6.7 to less than 5.0 within a few minutes. Demin- eralisation of the enamel takes place below the critical pH of about 5.5. Plaque pH stays be- low the critical pH for approxi- mately 15-20 minutes and does not return to normal un- til about 40 minutes after the ingestion of the sucrose rinse. Once plaque pH recovers to a level above the critical pH, the enamel may be remineralised in the presence of saliva and oral fluids which are super- saturated with respect to hy- droxyapatite and fluorapatite. Anatomy and histology The type of salivary secretion varies according to gland. Se- cretions from the parotid gland are watery in consistency, those from the submandibu- lar and sublingual glands, and particularly the minor mucous glands, are much more vis- cous, due to their glycoprotein content. The histology of the gland therefore varies accord- ing to gland type. All of the salivary glands de- velop in a similar way. An in- growth of epithelium from the stomatodeum extends deeply into the ectomesenchyme and branches profusely to form all the working parts of the gland. The surrounding ectomes- enchyme then differentiates to form the connective tissue component of the gland i.e. the capsule and fibrous septa that divide the major glands into lobes. These developments take place between 4 and 12 weeks of embryonic life, the parotids being the first and the sublingual and the minor salivary glands being the last to develop. The minor salivary glands are not surrounded by a capsule but are embedded within the connective tissue. Formation of saliva The fluid formation in salivary glands occurs in the end piec- es (acini) where serous cells produce a watery seromucous secretion and mucous cells produce a viscous mucin-rich secretion. These secretions arise by the formation of inter- stitial fluid from blood in capil- laries, which is then modified by the end piece cells. This modified interstitial fluid is secreted into the lumen. From the lumen it passes through the ductal system where it is further modified. Most of the modification occurs in the stri- ated ducts where ion exchange takes place and the secretion is changed from an isotonic solu- tion to a hypotonic one. The composition of saliva is further modified in the excretory ducts before it is finally secreted into the mouth. Physiology of saliva forma- tion Composition and flow rate The composition of saliva var- ies according to many factors including the gland type from which it is secreted. Salivary flow rate exhibits circadian variation and peaks in the late afternoon. Normal salivary flow rates are in the region of 0.3-0.4 ml/min when unstimu- lated and 1.5-2.0 ml/min when stimulated. Approximately 0.5 – 0.6 litres of saliva is secreted per day. Many drugs used for the treatment of common con- ditions such as hypertension, depression and allergies (to mention but a few), also in- fluence salivary flow rate and composition. Saliva as a diagnostic fluid Caries risk assessment A number of caries risk as- sessment tests based on meas- urements in saliva have been developed, for example tests which measure salivary mu- tans streptococci and lacto- bacilli and salivary buffering capacity. High levels of mutans strep- tococci, i.e. >105 colony form- ing units (CFUs) per ml of saliva, are associated with an increased risk of developing caries. High levels of Lactoba- cilli (>105 CFUs per ml saliva) are found amongst individuals with frequent carbohydrate consumption and are also as- sociated with an increased risk of caries. Buffering capacity is a meas- ure of the host’s ability to neu- tralise the reduction in plaque pH produced by acidogenic organisms. Salivary tests are useful indicators of caries sus- ceptibility at the individual lev- el where they can be used for prospective monitoring of car- ies preventive interventions and for profiling of patient dis- ease susceptibility. Although many efforts have been made to identify a test or combina- tion of tests to predict caries development, no one test has been found to predict this mul- tifactorial disease accurately. Salivary variables measured for caries risk assessment in dentistry include: Flow rate – At extremes of flow, flow rate is related to caries ac- tivity. Low flow rate is associ- ated with increased caries and high flow rate is related to re- duced caries risk. Buffering capacity – Higher buffering capacity indicates better ability to neutralise acid and therefore more resistance to demineralisation. In addition to showing promise for the prediction of periodon- tal disease progression and caries levels, analysis of saliva has been employed in phar- macogenomics, as well as the evaluation and assessment of endocrine studies. Saliva not only plays a pivotal role in the maintenance of a healthy homeostatic condition in the oral cavity, but contrib- utes to one’s overall health and wellbeing. Components from saliva interact in differ- ent ways with the dentition to protect the teeth. Patients who lack sufficient saliva suf- fer from many oral diseases, of which caries is only one. To al- leviate discomfort they are ad- vised to use saliva stimulants and substitutes which have the function of lubricating the oral surfaces. Chewing gum is increasingly being viewed as a delivery system for active agents that could potentially provide direct oral care ben- efits, as it promotes a strong flow of stimulated saliva. The fourth edition of Saliva and Oral Health is available in hard copy or e-book format at www.shancocksltd.com. A full list of references is included in the book. *Underwriting costs for this Saliva and Oral Health edition were provided by Dr. Michael Dodds and The Wrigley Com- pany. “Pediatric dental community has evolved” By Dental Tribune Middle East D UBAI, UAE: Recently the Emirates Pediatric Dental Club was formed spearheaded by elected Presi- dent (with the support of Crest & Oral-B) Dr. Dina Debaybo – Assistant Clinical Professor of > Page 16 > Page 14 Dr. Dina Debaybo

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