Foundation knowledge
DENT 5315 Oral Histology Dr. Koutlas’ salivary gland lectures
Ten Cate’s Oral Histology Chapter on Salivary Glands
General attributes of saliva
Clear fluid Slightly alkaline pH (from the glands) Viscous Multiple contributions from:
Major (parotid, SM/SL) and minor glands Extraneous contributors
Gingival crevicular fluid• Serum proteins, WBC and their products
Oral epithelial cells and their proteinsOral bacteria and their proteinsFood debris and dissolved food components
General composition Saliva is hypotonic - 99.5% water Remaining 0.5%
IonsK+, Na+, Ca2+, Mg2+, H+
Cl-, HCO3-, I-, F-, HPO4
2-
Small organic moleculesUrea, hormones, lipids, DNA, RNA
An extremely complex “proteome”106 D glycoproteins to 1000 D peptidespI range from 11.5 - 3.0Secretory products of salivary gland cellsProducts of B cells, PMNs, epithelial cells, bacteria
Protective functions of saliva Deduced from our knowledge of saliva components Mechanical cleansing (water/flow) Lubrication of tissues and teeth (secreted proteins) Buffering of acids (HCO3
-, HPO42-, peptides)
Maintaining tooth integrity Post-eruptive maturation (Ca2+, F-, HPO4
2-)
Mineralization equilibrium (Ca2+, F-, HPO42-)
Pellicle (proteome components) Maintaining tissue integrity (proteome components) Regulation of the oral flora (proteome components)
Saliva and oral functions
Food processing (water) Taste solute Bolus formation and swallowing (secreted proteins) Digestion (secreted proteins)
Speech (water, secreted proteins) Lubrication and rehydration
Excretion (the long way around) Small molecules (nitrate, thiocyanate. etc.) May interact with salivary proteins, oral bacteria
Complications
Saliva from different glands differs in composition Parotid - dominated by serous secretory cells SM/SL minor - mixed serous or mostly mucous Qualitative and quantitative differences in output
Composition is affected by level of gland activity Spontaneous (baseline) activity (during sleep) Unstimulated/”resting” (awake, but mouth at rest) Stimulated (eating or talking) Qualitative and quantitative differences in output
Stimulation and flow rate
Cumulative daily flow rates for whole saliva Spontaneous (asleep): 8 hr at 0.05/ml/min = 25 ml Unstimulated (awake): 12 hr at 0.7/ml/min = 504 ml Stimulated (eating,talking) 4 hr at 2.0ml/min = 480 ml 24 hour total = 1009 ml
These are average values Individual flow rates vary widely in healthy persons Variation at each level of stimulation At each level of stimulation
Variation in flow rate affects saliva compositionThere is circadian variation during the day
Changes with stimulation
P, K, duct cell proteins, immunoglobulins decrease
Ca, Na, Cl, Bicarbonate, secretory cell proteins increase
Stimulation and gland output
Level of stimulation
Low Moderate High
Parotid 25% 35% 44%
Submandibular 62% 53% 44%
Sublingual 5% 4% 4%
Minor 8% 8% 8%
Whole (mixed) saliva The actual fluid present in the mouth
Mixture from all the glandsPlus GCF, cells, bacteria, debris
The mixture is uneven at different oral sites Varies according to duct locations
Lecomte and Dawes, J. Dent. Res. 66:1614
Research design issues Collect glandular or whole saliva?
Glandular - harder to get, “purer”?, which gland(s)? Whole - easy to get, messier, more representative?
Stimulated or resting? Stimulated - faster - what level of stimulation? Resting - slower - more representative?
What time of day? - standardization needed How to control for variation in flow rate?
Xerostomia - dry mouth Range of dryness
Profound - saliva flow absent or greatly reduced The subjective perception of dry mouth Difficult to define normal flow rate
Normal for one person may be too low for another Causes of profound xerostomia
Head and neck radiotherapy for cancer Absence or surgical removal of salivary glands Inflammatory disease of salivary glands
Sjogren's syndromeOther autoimmune diseasesParotitis
Medication and xerostomia 1800 drugs in 80 drug classes report this as a side effect
www.drymouth.info Great variation in frequency and severity
Opiates, anti-cholinergics, anti-depressives, anti-hypertensives, anti-histamines, bronchodilators
• Variation within drug classes Multiple medications increase risk
No direct correlation with aging In unmedicated healthy adults
Parotid flow does not decrease with ageSM/SL, minor glands may decrease with age
Very difficult to disentangle effects of aging and meds