Mark S. Wolff

Oral mucosal wetness in hypo- and normosalivators

After a person swallows, a film of residual saliva covers the oral hard- and soft-tissue surfaces. Here, the thickness of this film was measured at 11 selected mucosal surfaces on each side of the mouth (22 sites total) in two groups of dry-mouth and one group of normal individuals. Each group contained 25 individuals; one of the dry-mouth groups had resting flow rates < or = 0.1 ml/min while the other and the normal had flow rates above that. Residual saliva thickness was determined by placing frying-pan-shaped filter-paper strips (Sialopaper) against the mucosa at each site for 5 s and measuring the saliva volume collected with a modified Periotron 6000 micro-moisture meter; the thickness was then calculated by dividing the collected saliva volume by the strip area. The two groups with dry-mouth symptoms had mean resting (unstimulated) saliva flow rates of 0.04 and 0.19 ml/min and mean mucosal saliva thicknesses of 22.4 and 27.8 microns, respectively. The control group had a higher mean saliva flow rate of 0.39 ml/min and mucosal saliva thickness of 41.8 microns. As was observed in a previous study on normosalivators, the various sites had a characteristic pattern of wetness, with the hard palate and lips the least moist regions. In this study, these observations, were also true in the two dry-mouth groups. Lower resting saliva flow rates were associated with lower mucosal thickness of saliva and with dryness symptoms becoming evident when hyposalivation was below about 0.1-0.2 ml/min. The characteristic pattern of mucosal wetness was not affected by saliva flow rate. As saliva readily collects in the floor of the mouth and is then spread over other mucosal surfaces upon swallowing, it was suggested that hyposalivation could also lead to the dryness symptoms because there was not enough saliva to cover the various oral surfaces, especially the palate and the lips. In this regard, a critical level of moisture was proposed as necessary to protect vulnerable mucosal surfaces from becoming dry. Lower resting saliva flow rates and correspondingly lower mucosal wetness were also associated with a more acidic salivary pH, which was shown earlier to be associated with lower dental plaque pH.

Residual stresses in porcelain-veneered zirconia prostheses.

OBJECTIVES Compressive stress has been intentionally introduced into the overlay porcelain of zirconia-ceramic prostheses to prevent veneer fracture. However, recent theoretical analysis has predicted that the residual stresses in the porcelain may be also tensile in nature. This study aims to determine the type and magnitude of the residual stresses in the porcelain veneers of full-contour fixed-dental prostheses (FDPs) with an anatomic zirconia coping design and in control porcelain with the zirconia removed using a well-established Vickers indentation method. METHODS Six 3-unit zirconia FDPs were manufactured (NobelBiocare, Gothenburg, Sweden). Porcelain was hand-veneered using a slow cooling rate. Each FDP was sectioned parallel to the occlusal plane for Vickers indentations (n = 143; load = 9.8 N; dwell time = 5s). Tests were performed in the veneer of porcelain-zirconia specimens (bilayers, n=4) and porcelain specimens without zirconia cores (monolayers, n = 2). RESULTS The average crack lengths and standard deviation, in the transverse and radial directions (i.e. parallel and perpendicular to the veneer/core interface, respectively), were 67 ± 12 μm and 52 ± 8 μm for the bilayers and 64 ± 8 μm and 64 ± 7 μm for the monolayers. These results indicated a major hoop compressive stress (~40-50 MPa) and a moderate radial tensile stress (~10 MPa) in the bulk of the porcelain veneer. SIGNIFICANCE Vickers indentation is a powerful method to determine the residual stresses in veneered zirconia systems. Our findings revealed the presence of a radial tensile stress in the overlay porcelain, which may contribute to the large clinical chip fractures observed in these prostheses.

Defining Dental Caries for 2010 and Beyond

This introductory article provides an overview of the caries disease process that will help guide readers into the world of evidence-based caries management in the beginning of the twenty-first century and help them understand the ongoing need to update in this field. This issue of Dental Clinics of North America provides clinically relevant reviews, full of chair-side recommendations based on best available evidence, on epidemiology, nomenclature, disease process, and management. A glossary of common terms in cariology is included.

Characteristics of collagenase-2 from gingival crevicular fluid and peri-implant sulcular fluid in periodontitis and peri-implantitis patients: pilot study

Objective. To compare collagenase activity and collagenolytic matrix metalloproteinase (MMP) levels in gingival crevicular fluid (GCF) and in peri-implant sulcular fluid (PISF) in gingivitis (G), chronic periodontitis (CP), and peri-implantitis (PI) human subjects. Material and Methods. GCF and PISF were collected on filter paper strips, volume was determined, and samples were extracted in buffer containing general proteinase but not MMP inhibitors. Collagenase activity was measured using a DNP-synthetic octapeptide, and molecular and activation forms of collagenase-2 by Western immunoblotting. Results. GCF from CP and G sites exhibited elevated collagenase activity and flow, but collagenase concentrations expressed per µl were not significantly different between the healthy and G sites. Minimal fluid was obtained from healthy PISF, and collagenase concentration was the same or lower than in healthy GCF. Although PISF flow was 34% lower than GCF flow in CP subjects, collagenase concentration in CP and in PI sites was 78% and 971% greater, respectively, than in the appropriate healthy sites. Western immunoblot revealed MMP-8 in both PISF and GCF; fibroblast-type MMP-8 was not detected in healthy GCF and PISF. Immunoreactivity level and inactive and activated forms of PMN-type MMP-8 in GCF and PISF increased with the severity of periodontitis and peri-implantitis. Enhanced levels of fibroblast-type MMP-8 in active form were detected only in severe CP GCF and PI PISF. Conclusions. Peri-implantitis PISF contained higher collagenase-2 levels and activity than GCF from similar deep CP sites. GCF and PISF from severe CP and PI exhibited the highest activation of MMP-8 isoenzymes species (PMN and fibroblast-type).

Measurement of tooth hypersensitivity and oral factors involved in its development

The various methods of measurement of dentinal hypersensitivity are based upon the types of stimuli used to elicit a pain response in teeth, which include thermal, tactile, evaporative, electrical and osmotic. Pulpal inflammation in its early stages reduce the threshold of pain response to these stimuli but electrical stimulation may make it possible to assess the possible contribution of such inflammation to sensitivity determinations. Although the magnitude of each stimulus is quantifiable, patient response is subjective, which necessarily makes measurements of dentinal sensitivity semisubjective. Various methods of testing dentinal sensitivity are discussed, along with their advantages and disadvantages. The teeth most suited for measurement in clinical studies are the canines and premolars. This is because approx. 80% of the sensitivity lesions are associated with these teeth, which have similar thicknesses of root dentine. Data from several studies involving the same subjects indicate that individual measurements readily return to baseline and that the commonly seen placebo effect is probably due to some as yet unidentified factor in desensitizing formulations. Possible roles of salivary and plaque environmental factors in the development of dentinal sensitivity are discussed, as well as methods for their measurement.

The effect of ammonium glycopyrrolate (Robinul®)-induced xerostomia on oral mucosal wetness and flow of gingival crevicular fluid in humans

The antisialogogue, ammonium glycopyrrolate (Robinul), was used to reduce the salivary flow rate in healthy individuals with normal salivary function to determine whether the dry-mouth symptoms and reduced amounts and patterns of oral mucosal wetness found previously in hyposalivators could be induced by this means. After baseline measurements, the drug was given to 10 healthy volunteers and their resting whole-saliva flow rate was measured at 0, 15, 60, 105 and 150 min thereafter. At the same times, the thickness of the layer of residual mucosal saliva (a measure of residual mucosal wetness) at each of 22 intraoral sites was also determined. The saliva flow rate fell from a mean of 0.45 +/- 0.07 ml/min to a mean of 0.05 +/- 0.02 ml/mm by 1 h and slowly thereafter to a mean of 0.02 +/- 0.01 to 0.03 +/- 0.01 ml/min for the remainder of the experiment. Onset of dryness symptoms was observed approx. 30 min after giving the drug. Simultaneously, the residual saliva at each of the 22 sites teted decreased to a thickness level previously found in patients with hyposalivation and who exhibited an intense feeling of dry mouth. Despite these decreases in thickness, the pattern of residual mucosal wetness throughout the mouth remained more or less unchanged. As in earlier studies, wetness was least on the hard palate and highest on the posterior dorsum of the tongue. An altered taste of the residual saliva in the mouth and an increased feeling of roughness as the tongue was passed over labial and buccal mucosal surfaces were noted. The amount of gingival crevicular fluid (GCF) in 12 gingival sites in each of the participants was also measured. Unlike the reduction in salivary flow, changes in GCF over the 150 min of the study were negligible. From this it was concluded that GCF could contribute much more to the oral fluids in dry-mouth than in normal individuals, especially when there is greater gingival inflammation.

The cariogenic dental biofilm: good, bad or just something to control?

This paper discusses the role of dental biofilm and adjunctive therapies in the management of dental caries. Dental biofilm is a site of bacterial proliferation and growth, in addition to being a location of acid production. It also serves as a reservoir for calcium exchange between the tooth and saliva. The salivary pellicle, a protein-rich biofilm layer, regulates the reaction between tooth surface, saliva and erosive acids. The protective effects of this pellicle on enamel are well established. However, understanding the effects of the pellicle/biofilm interaction in protecting dentin from erosive conditions requires further research. Saliva interacts with the biofilm, and is important in reducing the cariogenic effects of dental plaque as acidogenic bacteria consume fermentable carbohydrates producing acids that may result in tooth demineralization. Adequate supplies of healthy saliva can provide ingredients for successful remineralization. Strategies for managing the cariogenic biofilm are discussed with emphasis on the effectiveness of over-the-counter (OTC) products. However, since many toothpaste components have been altered recently, new clinical trials may be required for true validation of product effectiveness. A new generation of calcium-based remineralizing technologies may offer the ability to reverse the effects of demineralization. Nevertheless, remineralization is a microscopic subsurface phenomenon, and it will not macroscopically replace tooth structure lost in a cavitated lesion. Optimal management of cavitations requires early detection. This, coupled with advances in adhesive restorative materials and microsurgical technique, will allow the tooth to be restored with minimal destruction to nearby healthy tissue.

Development of the rat sublingual gland: a light and electron microscopic immunocytochemical study.

Cell differentiation in the rat sublingual gland occurs rapidly and is largely complete by birth. To study differentiation of the serous and mucous cells of the sublingual gland, we used antibodies to the secretory proteins CSP‐1, SMGB, PSP, and SMGD, and sublingual mucin as specific cell markers. Glands from rats at ages 18, 19, and 20 days in utero, and postnatal days 0, 1, 5, 9, 14, 18, 25, 40, and 60 were fixed and prepared for morphological analysis and immunocytochemical labeling. At age 18 days in utero, a few cells in the developing terminal bulbs contained mucous‐like apical granules that labeled with anti‐mucin. Other cells had mixed granules with a peripheral lucent region and a dense core of variable size that occasionally labeled with anti‐SMGD. Additionally, presumptive serous cells with small dense granules that contained CSP‐1 and SMGB were present. At age 19 days in utero, the dense granules of these cells also labeled with anti‐SMGD. By age 20 days in utero, mucous cells were filled with large, pale granules that labeled with anti‐mucin, and serous cells had numerous dense granules containing CSP‐1, SMGB, PSP, and SMGD. Fewer cells with mixed granules were seen, but dense regions present in some mucous granules (MGs) labeled with anti‐SMGD. After birth, fewer MGs had dense regions, and serous cells were organized into well‐formed demilunes. Except for PSP, which was undetectable after the fifth postnatal day, the pattern of immunoreactivity observed in glands of neonatal and adult animals was similar to that seen by age 20 days in utero. These results suggest that mucous and serous cells have separate developmental origins, mucous cells differentiate earlier than serous cells, and cells with mixed granules may become mucous cells. Anat Rec 266:30–42, 2002.

Chewing variation in lepidosaurs and primates.

SUMMARY Mammals chew more rhythmically than lepidosaurs. The research presented here evaluated possible reasons for this difference in relation to differences between lepidosaurs and mammals in sensorimotor systems. Variance in the absolute and relative durations of the phases of the gape cycle was calculated from kinematic data from four species of primates and eight species of lepidosaurs. The primates exhibit less variance in the duration of the gape cycle than in the durations of the four phases making up the gape cycle. This suggests that increases in the durations of some gape cycle phases are accompanied by decreases in others. Similar effects are much less pronounced in the lepidosaurs. In addition, the primates show isometric changes in gape cycle phase durations, i.e. the relative durations of the phases of the gape cycle change little with increasing cycle time. In contrast, in the lepidosaurs variance in total gape cycle duration is associated with increases in the proportion of the cycle made up by the slow open phase. We hypothesize that in mammals the central nervous system includes a representation of the optimal chew cycle duration maintained using afferent feedback about the ongoing state of the chew cycle. The differences between lepidosaurs and primates do not lie in the nature of the sensory information collected and its feedback to the feeding system, but rather the processing of that information by the CNS and its use feed-forward for modulating jaw movements and gape cycle phase durations during chewing.

The Seattle Care Pathway for securing oral health in older patients

There is a need for a structured, evidence based approach to care for older dental patients. The following article describes the development of the Seattle Care Pathway based upon a workshop held in 2013. An overview is provided on the key issues of older persons dental care including the demography shift, the concept of frailty, the need for effective prevention and treatment to be linked to levels of dependency and the need for a varied and well educated work force. The pathway is presented in tabular form and further illustrated by the examples in the form of clinical scenarios. The pathway is an evidence based, pragmatic approach to care designed to be globally applicable but flexible enough to be adapted for local needs and circumstances. Research will be required to evaluate the pathways application to this important group of patients.