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NORDIN-Dossiers Scientifiques LINING MATERIAL WITH SPECIAL REFERENCE TO DROPSIN A comparative study by C.G. Plant, B.D.S, F.D.S and M. J. Tyas, B.D.S The pH of Dropsin and three other cavity lining materials was measured. The histological effects on the pulp of Dropsin and two of these materials is described and compared. There was no direct correlation between the pH of the materials during setting and the changes they caused in the pulp. Water absorption by a setting lining material as a possible cause of pulpal damage. A survey was undertaken of 1,000 den- Dynacap (Pye) pH meter was the instru- Results tal practitioners throughout the United ment used in these measurements, with Figure 1 shows the pH during setting Kingdom. This showed that Dropsin both electrodes and material enclosed of the four materials tested in 87 % was widely used, being the fifth most in a humidity oven at 37°C. relative humidity at 37°C. The first pH popular lining material. 16.3 % of 686 Moisture or fluid from two sources may measurement for each material was dentists, who replied to the survey, sta- affect a lining material whilst it is in the made at the first full minute after ted that they used Dropsin as a cavity mouth. The first is the moisture in the air mixing. Because the mixing time for liner. Despite this wide use there are no in the oral cavity and this can be simu- each material was different this made reports in the literature about the mate- lated in vitro by using a humidity oven. the time from the start of the mix to the rial or its effect on the dental pulp. The second source of moisture, that first pH measurement vary according Dropsin cavity lining material is marke- from vital dentine, cannot be simulated to the material used. ted by Harald Nordin SA in vitro. Neither was it possible, with the (Chailly/Switzerland). The manufacturer equipment available, to measure the pH Fig. 1. Variation of pH with time for state that the material has a neutral pH of lining material in vivo on vital dentine. lining materials. 1_ minutes after mixing and is, there- As the passage of fluid from non-vital fore, harmless to the dental tissues. dentine to lining material is artificial, it Dropsin: at 1 minute after the start of The purpose of this work was twofold: was decided to provide the maximum mixing, the pH of Dropsin was 2.2. A first, to investigate the pH of Dropsin amount of moisture by surrounding the pH of 4 was reached after 9 minutes whilst it was setting; secondly, to setting material with air with as high a and after 24 hours the pH was 6.8. observe any effects it might have on the relative humidity as possible. SS White cavity lining: 2 minutes after pulp and to investigate any correlation This was achieved by placing the set- the start of mixing the pH was 4.5. it of these effects with the pH. ting material in a humidity oven at 37+- then rose sharply to pH 6.4 at 5 minu- Composition 1°C with distilled water thus providing a tes then fell to the region of pH 5. At 30 The manufacturer would not divulge the relative humidity of 87+-5 %. The pH minutes the pH began to rise and rea- exact composition of Dropsin but they was measured over a period of 24 ched pH 6.8 at 24 hours. indicated that the constituents were: hours, each material being tested three Zinc phosphate cement: a pH of 1.7 Liquid Phosphoric acid-25 % times. Before each test the electrodes was recorded at 2 minutes. The pH Aluminium hxdroxide-8% were cleaned, washed and buffered rose gradually but did not reach pH4 Distilled water-67% using standard buffer solutions; at the for 1 hour. Thereafter the pH rose stea- end of each test the validity of the pH dily to rach 6.4 at 24 hours. Powder Zinc oxide measurements were checked with a Zinc oxide/eugenol: the pH fell from Calcium hydroxide standard buffer solution. 5.8 at 5 minutes to 5.1 at 7 minutes Magnesium oxide A standardized powder/liquid ratio and and maintained this level until 1 hour. Aluminium hydroxide mixing time was used for each material From this time the pH rose gradually to to determine the standard reach 6.6 at 24 hours. (I)pH of Dropsin during Setting powder/liquid ratio and mixing time These results apply to one batch of The object of the first part of this work several trial mixes were made. Due material in each case; different bat- was to establish the pH of Dropsin attention was paid to the manufacturers ches were not evaluated. immediately after mixing and to record general instructions regarding the Discussion the changes in the pH during the consistency of each material. The pow- The pH values of the four materials ensuing 24 hours. For purposes of der/liquid ratio of the mix giving the were very similar after 24 hours, and comparison the pH changes of three consistency most suitable for the stan- were in the range of 6 to 7. in the first other lining materials were also recor- dard. These ratios and mixing times, as 10 minutes, however, two distinct pairs ded over the same period of time. The given below were used throughout all of material were seen. other lining materials used were S.S. the investigation. White cavity lining, S.S. whit zinc phos- phate cement and zinc oxide/eugenol Powder/Liquid Ratio and Mixing time for materials used (B.P.) Materials and Method Material Manufacturer P/L ratio Mixing time The pH of Dropsin and the three mate- Dropsin Nordin SA, Switzerland 2/1 0.5 rials listed above were measured by S.S. White cavity lining SS White (GB) 3/1 1.5 using a glass electrode with a calomel Zinc phosphate cement " 1.5/1 1.5 reference electrode inserted into the Zinc oxide/eugenol " 5/1 4 setting material on a glass stab. A (1)SS White cavity lining and zinc methods shown below. After was suffered by the pulp with any oxide/eugenol, having almost iden- extraction the apical third of the of the material used in this survey. tical pH in the 5 and 6 region.. root was removed by means of a Only one tooth showed evidence of (2)Dropsin and zinc phosphate hand saw and the tooth placed into inflammation-this being with the which have a much more acid reac- 10 % neutral buffered formalin. control material SS White cavity tion of between pH 1.6 and 4.4. The teeth were decalcified and lining, where a mild degree of If the hydrogen ion concentration is serial sections prepared through inflammation of the odontoblast a major factor in causing pulpal the cavity site where the minimum layer was seen. damage it would be reasonable to thickness of dentine between cavity Very small isolated areas of inflam- assume from the above results that: floor and pulp remained. Sections matory cells were seen in the body (1)SS White cavity lining and zinc were stained with haematoxylin and of the pulp in three sections. These oxide/eugenol would cause similar eosin. were well away from the zone of charges in the pulp and that these The sections were examined for the tubules cut during cavity prepara- would be relatively mild. features listed in the tables; reduc- tion and their presence is thought (2)Dropsin and zinc phosphate, tion in odontoblasts, vacuolisation to be unrelated to this procedure. because of their early acidity, would in the odontoblast layer, aspiration Similar focal collections of inflam- cause more severe changes. The of odontoblasts, hyperaemia, matory cells have been reported by changes due to Dropsin, however, vacuoles I the pulp and inflamma- Shovelton and Marsland(1960) should be less severe, particularly if tory cells in the odontoblast layer. beneath cavities prepared with an the pulp only undergoes marked An arbitrary scale for degrees of air turbine handpiece. change when the hydrogen ion change was used, 0=no change, concentration remains high for 1=mild, 2=moderate, 3=severe. All Table II shows that Dropsin caused more than a few minutes. slides carried one number only, so a small degree of change in the that there was no indication of the pulp, mainly in the form of a mild (II) Effect of Dropsin in the Pulp material used in the cavity. The reduction I odontoblasts. The The main aim of this section was to examinations were carried out by control materials, SS White cavity establish the histological response one person so that the arbitrary lining and zinc oxide/eugenol if of the pulp to Dropsin when this scale of change was applied considered as a single group (Table material is used as a cavity lining. A consistently. III), caused a more marked change further aim was to attempt to corre- than Dropsin. In 7 of the 18 teeth a late this histological response with Grouping of Teeth moderate or severe reduction in the pH of Dropsin. (1) Dropsin lining-29 teeth. odontoblasts took place whereas For purposes of comparison and to A creamy mix of Dropsin was used with Dropsin only 4 out of 29 teeth act as controls, SS White cavity to build up a lining of normal thick- suffered similar effects. lining and zinc oxide/eugenol were ness. Care was taken to cover all also used to obtain a histological exposed dentine on the cavity floor.
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