Atmospheric contamination during ultrasonic scaling.

OBJECTIVE: The aim of this study was to determine the microbial atmospheric contamination during initial periodontal treatment using a piezoelectric ultrasonic scaler in combination with either high-volume evacuation (HVE) or conventional dental suction (CDS). METHODS: The study included 17 treatment sessions, consisting of a 40-min episode of continuous plaque and calculus removal using an ultrasonic unit (EMS). The treatment sessions were carried out in six patients with generalized adult periodontitis and ranged from two to four sessions per patient according to their needs. The use of HVE and CDS was randomly assigned over the sessions within each patient. Before each treatment, the operating room was not used for 15 h. To measure baseline microbial air pollution two Petri dishes containing blood agar were exposed for 10 min to the air. At the start of each treatment session, two Petri dishes were exposed for 5 min at a distance of 40 cm from the mouth of the patients. After 20 min, this procedure was repeated. At a distance of 150 cm, two Petri dishes were exposed for 20 min followed by exposure of two new Petri dishes for the rest of the session. The plates were cultured aerobically and anaerobically for 3 and 7 days, respectively. RESULTS: The mean colony forming units (CFU) before treatment never exceeded 0.6 colonies per plate. At 40 cm, the mean CFU, when considering a period of 40 min, was 8.0 for HVE and 17.0 for CDS. The mean CFU at 150 cm during this period was 8.1 with HVE and 10.3 with the CDS. With reference to the Air Microbial Index the operatory atmosphere was considered to be in a good condition during 40 min of continuous use of the ultrasonic scaler in combination with both HVE and CDS. CONCLUSION: Within the restrictions of this study, only limited atmospheric microbial contamination is produced when using a piezoelectric ultrasonic scaler.

Functional heterogeneity of osteoclasts: matrix metalloproteinases participate in osteoclastic resorption of calvarial bone but not in resorption of long bone.

Data in the literature suggest that site-specific differences exist in the skeleton with respect to digestion of bone by osteoclasts. Therefore, we investigated whether bone resorption by calvarial osteoclasts (intramembranous bone) differs from resorption by long bone osteoclasts (endochondral bone). The involvement of two major classes of proteolytic enzymes, the cysteine proteinases (CPs) and matrix metalloproteinases (MMPs), was studied by analyzing the effects of selective low molecular weight inhibitors of these enzymes on bone resorption. Mouse tissue explants (calvariae and long bones) as well as rabbit osteoclasts, which had been isolated from both skeletal sites and subsequently seeded on bone slices, were cultured in the presence of inhibitors and resorption was analyzed. The activity of the CP cathepsins B and K and of MMPs was determined biochemically (CPs and MMPs) and enzyme histochemically (CPs) in explants and isolated osteoclasts. We show that osteoclastic resorption of calvarial bone depends on activity of both CPs and MMPs, whereas long bone resorption depends on CPs, but not on the activity of MMPs. Furthermore, significantly higher levels of cathepsin B and cathepsin K activities were expressed by long bone osteoclasts than by calvarial osteoclasts. Resorption of slices of bovine skull or cortical bone by osteoclasts isolated from long bones was not affected by MMP inhibitors, whereas resorption by calvarial osteoclasts was inhibited. Inhibition of CP activity affected the resorption by the two populations of osteoclasts in a similar way. We conclude that this is the first report to show that significant differences exist between osteoclasts of calvariae and long bones with respect to their bone resorbing activities. Resorption by calvarial osteoclasts depends on the activity of CPs and MMPs, whereas resorption by long bone osteoclasts depends primarily on the activity of CPs. We hypothesize that functionally different subpopulations of osteoclasts, such as those described here, originate from different sets of progenitors.

The inhibitory effect of combining chlorhexidine and hydrogen peroxide on 3-day plaque accumulation.

In a blind, randomised, 4-cell, cross-over study, the effect of rinsing with a perborate solution (1.9 g sodium perborate-monohydrate dissolved in 30 ml water/Bocasan, Oral-B) on the in vivo plaque-inhibiting effect of 0.12% chlorhexidine (Oral-B) was examined. After a thorough professional prophylaxis including interdental cleaning, 12 subjects started to rinse according to 4 different regimens: regimen (C-P-C): chlorhexidine in the morning, perborate at noon and chlorhexidine in the evening; regimen (CP-CP): chlorhexidine immediately followed by perborate in the morning and in the evening; regimen (PC-PC): perborate immediately followed by chlorhexidine in the morning and in the evening; regimen (C-C): chlorhexidine in the morning and in the evening. No further oral hygiene measures were allowed for the next 72 h. After 72 h, the subjects were scored for plaque, and a washout period of 4 days followed; cross-over was randomly assigned according to a Latin square design. Following this procedure, all subjects went through all 4 regimens. The regimens C-P-C and PC-PC resulted in significantly lower plaque-scores, 0.27 and 0.28 respectively, than regimen C-C (0.40). For the regimen CP-CP, the plaque-score was 0.28, which was not significantly different from the C-C regimen. The results suggest a positive interaction between chlorhexidine and hydrogen peroxide. Rinsing with a combination of 0.12% chlorhexidine (Oral-B) and a perborate solution (Bocasan Oral-B) can result in more effective short-term plaque growth inhibition than rinsing with chlorhexidine alone.

Identification of new rat dentin proteoglycans utilizing C18 chromatography.

Although only one small PG has been identified in dentin until now, a preliminary investigation has shown indications of the presence of several new proteoglycans (PGs) in rat incisor dentin. The aim of the present investigation was to isolate and characterize these PGs, which were labeled with 35S to facilitate the analysis. C18 chromatography resolved five dentin PGs. Based on SDS-polyacrylamide gel electrophoresis, their size varied from 100 to 400 kDa. The core proteins of the first four PGs appeared as 25, 40, 70, and 115 kDa bands. They stained turquoise with Stains All but did not stain with Coomassie Brilliant Blue. The core protein of the fifth PG appeared at about 45 kDa. This core protein stained with Coomassie Brilliant Blue but not with Stains All. In all PGs, the glycosaminoglycans consisted mainly of chondroitin 4-sulfate. To investigate their incorporation into predentin (young dentin that is not yet mineralized) and dentin, rat dentin PGs were pulse-labeled by injecting rats with [35S]sulfate at 5, 28, 55, or 177 h before killing the animals. Radiolabeling of predentin PGs was highest after 5 h and decreased rapidly (76%) over the next 50 h. In dentin PGs, a large percentage (34%) of the final quantity of incorporated 35S (at 177 h) was already present at 5 h. C18 chromatography of dentin PGs for each of the four time intervals showed similar 35S distribution patterns representing all five PGs, whereas the predentin appeared to contain mainly the fifth PG. This study demonstrates the existence of several apparently novel PGs in dentin that can be resolved by the use of a new method. These PGs were found in mineralized dentin and are thought to be rapidly transported toward the mineralization front. Part of the predentin PGs, on the other hand, seems to be lost as mineralization proceeds.

Effect of bound phosphoproteins and other organic phosphates on alkaline phosphatase-induced mineralization of collagenous matrices in vitro.

The aim of the present study was to determine to what extent the rate at which collagen mineralizes correlates with the amount and nature of bound phosphate groups. Sheets of collagen prepared from demineralized bovine dentin or cortical bone were complexed with various concentrations of phosphoserine [(P)Ser] or rat dentin phosphoproteins (PP; lowly or highly phosphorylated PP, LPP or HPP). Alternatively, phosphate groups were removed from the collagenous carrier material by treatment with phosphatases. Mineralization was achieved by incubation in culture medium supplemented with 45Ca, alkaline phosphatase and 10 mM beta-glycerophosphate. The sheets were monitored for uptake of 45Ca and lag times calculated and plotted against the amount of bound phosphate. It was observed that dephosphorylation of the carrier causes an increase in lag time and that rat PP decreases lag times in a concentration-dependent way. HPP were more effective than LPP. (P)Ser or other small organic P-containing molecules had hardly any influence on lag time. It is concluded that next to the amount of bound phosphate, the nature of phosphorylated substances has considerable influence on the rate of mineralization of a collagenous carrier.

The distribution of magnesium in developing rat incisor dentin.

Previous studies have shown that rat incisor dentin contains a considerable amount of magnesium that is distributed heterogeneously. The cementum-related dentin, especially its incisal portion, is richest in magnesium. It was the purpose of the present study to investigate the changes that occur in the magnesium content during dentin maturation. Cross-sections were prepared from rat incisors at the apical, middle, and incisal levels. By means of an electron microprobe, tracings were made of the Ca-, Mg-, and P- signal frequencies. Comparison of corresponding dentin layers within and between the cross-sections showed that the Mg/P molar ratio was always higher in the cementum-related dentin (CRD) than in the enamel-related dentin (ERD) and increased from the apex toward the incisal edge. Especially in the incisal cross-section, an increase in Mg/P was found from the older (peripheral) toward the younger (central) dentin layers. As the Mg/P ratio varied from 0.07 to 0.33, the Ca/P ratio was found to fluctuate from 1.48 to 1.15. The two ratios appeared to be highly correlated (r = -0.97; p less than 0.001), suggesting that Mg replaces Ca and is bound to phosphate.

The possible relationship between the mineralization of dentin and the composition of its organic matrix.

Using the rat incisor as a model, evidence is presented that enamel-related (ERD) and cementum-related (CRD) dentins exhibit differences in composition. Whereas the ERD is rich in highly phosphorylated phosphoproteins, the CRD is rich in lowly phosphorylated phosphoproteins. These differences are accompanied by and possibly related to differences in composition and physical properties of the mineral phase.

The inorganic components of cementum- and enamel-related dentin in the rat incisor.

Recently, we have shown that, in rodent incisors, the crown- and root-analogue dentin (enamel- and cementum-related dentin) show differences in mineralization rates (Beertsen and Niehof, 1986) and composition of the organic matrices (Steinfort et al., 1989). It was the aim of the present study to determine whether these differences were accompanied by differences in the inorganic components. Rat incisors were analyzed by means of hardness measurements, microradiography, and the determination of Ca, Mg, and PO4 content. The outer circumpulpal dentin layer of the enamel-related dentin (ERD) was considerably harder and denser than the comparable layer of the cementum-related dentin (CRD). Concomitantly, a higher Ca and PO4 content was found for the ERD than for the CRD, while the reverse occurred with respect to Mg. From the apical end of the incisor toward the incisal edge, the Ca/PO4 ratio tended to decrease for both ERD and CRD, while the Mg/PO4 ratio increased. All differences appeared to be statistically significant. It is concluded that differences in the non-collagenous organic matrix were accompanied by differences in the inorganic components. More specifically, a relatively high content of highly phosphorylated phosphoproteins (ERD) was associated with a higher Ca and a lower Mg content.

Differences between enamel-related and cementum-related dentin in the rat incisor with special emphasis on the phosphoproteins.

In order to determine whether qualitative and quantitative differences exist between the non-collagenous proteins of crown and root dentin, rat incisors were separated into their enamel- and cementum-related dentin portions (ERD and CRD, respectively). Isolation of the mineral-bound proteins was performed under nondegradative conditions. Analytical procedures included DEAE-chromatography on high pressure liquid chromatography, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and determination of phosphate, protein, and hydroxyproline. The results have shown that considerable differences exist among the two dentins with respect to the quantity of the various phosphoproteins. For this group of proteins as a whole, the ERD contains about 2 times the amount of organic phosphate found in the CRD and about 1.4 times the amount of protein. The content of higher phosphorylated phosphoproteins was about 4 times higher in the ERD than in the CRD, whereas the reverse was shown for the lower phosphorylated phosphoproteins. All differences were found to be statistically significant. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that while the ERD contains phosphoproteins with an apparent molecular mass of 98 kDa, the CRD contains two classes of phosphoproteins one of 98 and one of 88 kDa. The relevance of the observed differences in phosphoprotein distribution is discussed in relation to their possible role in mineralization.