| Abstract|| |
Objective: Guedes-Pinto paste (GPP) is an iodoform paste used in most dental schools in Brazil. The paste is a composite of medicines (Rifocort® , camphorated paramonochlorophenol [PMCC], and iodoform) used for endodontic treatment of primary teeth. The aim of this study was to evaluate the proportion variability of GPP components when mixed by undergraduate dentistry students and pediatric dentists.
Materials and Methods: The study was divided into 4 groups: G1 (15 undergraduate students), G2 (15 specialists in Pediatric Dentistry), G3 (15 professors with clinical activity), and G4 (7 professors-researchers). All volunteers prepared GPP according to the original specifications: the same visual proportion for each component. The components were weighed using an analytical balance and the percentage was calculated.
Result: After normality (Kolmogorov-Smirnov) and homogeneity tests (Levene test), the data were submitted to analysis of variance and intraclass correlation coefficient tests (P<0.05). The percentage means of each respective group were as follows: Rifocort® 20.2%, 20.8%, 26.7%, 27.3%; camphorated PMCC 9.2%, 8.1%, 6.7%, 5.1%; and the iodoform 70.6%, 71.1%, 64.7%, 67.6%. There were no significant differences between groups for the component percentages. There was a high intraclass correlation coefficient (G1 0.945; G2 0.951; G3 0.921; and G4 0.870).
Conclusion: The proportion of GPP was similar in all the groups, allowing us to conclude that ideal GPP proportion, based on the entire group mean, was 23.8% of Rifocort® ; 7.0% of camphorated PMCC; and 69.2% of iodoform.
Keywords: Endodontics, endodontic medication, primary teeth
|How to cite this article:|
Mello-Moura AV, Fanaro J, Nicoletti MA, Mendes FM, Wanderley MT, Guedes-Pinto AC. Variability in the proportion of components of iodoform-based Guedes-Pinto paste mixed by dental students and pediatric dentists. Indian J Dent Res 2011;22:781-5
Some materials have been proposed for endodontic filling of primary teeth. In contrast to materials used in permanent teeth, these materials should present specific properties due to the anatomical characteristics inherent in the primary teeth and the physiologic root resorption process. Among these properties, the material should be able to be reabsorbed, have potent antibacterial properties, and should not provoke undesirable effect in both periapical tissues and permanent successors. In addition, it should be radiopaque, and easily deposited and removed from the canal, as well as not change the color of the teeth. ,,,,, The antimicrobial property is critical for treatment success since endodontic preparation and disinfection of the primary teeth are difficult to achieve. Because of these requirements, endodontic filling material is crucial in increasing the probability of success in endodontic therapy of primary teeth. 
|How to cite this URL:|
Mello-Moura AV, Fanaro J, Nicoletti MA, Mendes FM, Wanderley MT, Guedes-Pinto AC. Variability in the proportion of components of iodoform-based Guedes-Pinto paste mixed by dental students and pediatric dentists. Indian J Dent Res [serial online] 2011 [cited 2015 Mar 6];22:781-5. Available from: http://www.ijdr.in/text.asp?2011/22/6/781/94668
Several clinical guides on pulp therapy of primary teeth have recommended different materials suitable for endodontic filling, such as zinc oxide-eugenol, calcium hydroxide, and iodoform paste. Iodoform paste, however, has been the preferred material for endodontic treatment since it has most of the required characteristics. ,,,,
In Brazil, an iodoform paste, named Guedes-Pinto paste (GPP), has become the material of choice for endodontic therapy of primary teeth in most dental schools. , GPP is a composite of 3 medications: Rifocort® (dermatologic ointment), camphorated paramonochlorophenol (PMCC) and iodoform.  It may be prepared at the moment of use with the same proportion in volume of 3 visually identical parts, one for each of its components [Table 1]. 
GPP, Guedes-Pinto paste; PMCC, paramonochlorophenol.
A problem with regard to GPP is the manipulation of the paste, because different clinicians could alter the concentration of each part, especially because of the different physical aspects of each component (liquid, powder, and ointment). This fact could change the biological properties of the paste, and may affect the clinical performance or increase the toxicity. Consequently, since the role of each drug in the GPP is associated with a specific concentration, the proportion of the components of the paste should be standardized during preparation. Furthermore, the preference for the consistency of GPP (fluid or paste) is determined by the clinical experience and the preference of each clinical practitioner. Although some studies about GPP have been previously published, ,,,,,,,,, there is no research about the variation in quantifying GPP components when mixed by clinicians with different experience.
Therefore, the aim of this study was to evaluate the proportion variability of GPP components when mixed by undergraduate students and pediatric dentists. Furthermore, we intend to standardize the most common concentration of each component and to find a simple way of supplying the paste in clinical setting.
| Materials and Methods|| |
This study was conducted after approval of the Ethical Committee of the School of Dentistry of the University of São Paulo (Process: 16/07). Fifty-two volunteers with clinical experience in pediatric dentistry participated in this study. They were divided into 4 groups [Table 2].
The subjects in each group mixed the GPP as proposed by Guedes-Pinto et al. (1981):  : 3 parts visually similar to each other in volume. Thus, the Rifocort® (Medley, Campinas, SP, Brazil), PMCC (Inodon, Porto Alegre, RS, Brazil), and the iodoform (Quimidrol, Joinville, SC, Brazil) were visually proportional to each other [Figure 1]. After the operator had disposed the materials, they were weighed on an analytical scale (Voyager Pro, Toledo do Brasil, São Bernardo do Campo, Brazil) If the subject was not pleased with the paste consistency, more medicine could be added in grams to the initial value of the component. Then, the final proportion of each medicine for each operator was recorded.
The data regarding the concentration of the medicines provided by the subjects were submitted to statistical analysis using SPSS software (Statistical Package for Social Sciences, version 13.0, SPSS Inc., Chicago, IL, USA). The normal distribution was verified by the Kolmogorov-Smirnov test and the homogeneity by Levene test. The data were submitted to analysis of variance test to compare the concentration of each component between the groups. Additionally, the variability within each group of subjects was evaluated through intraclass correlation coefficient analysis. A P value <0.05 was considered as significant for all the tests.
| Results|| |
To determine the mean concentration of each GPP component for all the groups, Box plot [Graph 1], [Graph 2] and [Graph 3] were made and the outliers were excluded.
After excluding the outliers, the mean of each GPP component per group was defined, as shown in [Table 3]. The means of each drug were not significantly different from the percentages of the drugs among groups (P>0.05). Consequently, the proportion of each GPP component based on the mean of each component for all the groups can be defined according to the following values: 23.8% of Rifocort® , 7.0% of PMCC, and 69.2% of iodoform.
|Table 3: Mean (M) and standard deviation (SD) of the proportion (%) of the GPP components in each group*|
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The intraclass correlation coefficients were near the maximum value (1) in all the groups. The coefficients of groups G1, G2, G3, and G4 were of 0.945, 0.951, 0.921, and 0.870, respectively.
| Discussion|| |
GPP is the most used material for endodontic treatment in primary teeth in Brazilian dental schools , because of its efficacy previously demonstrated by various laboratory and clinical studies, ,,,,,, including antimicrobial ability, ,, antiinflammatory ability, and high tolerance in periapical tissue. ,
Since the role of each drug present in the GPP is associated with a specific concentration, the proportion of the components of the paste should be standardized during preparation. Nevertheless, maintaining the same concentration of each GPP component may be difficult due to the different physical properties of each component (powder, liquid, and ointment), and because of the variability concerning the consistency desired by the clinician.
The cytotoxicity of each GPP component was previously studied, and PMCC was found to be the most cytotoxic compared with the other components. In fact, PMCC has shown the greatest overall cell death.  Using the same method the cytotoxicity of GPP was evaluated in different storage periods (1, 2, and 3 months) under refrigeration and environment temperature. Cytotoxicity increased significantly under a storage period with both storage conditions; however, refrigeration gave more stability to the paste. 
Because of these facts, it is important to emphasize the importance of standardization of the concentration of each GPP component since any change to the amount of the components might change the biological effects of the material. For instance, addition of PMCC can increase the toxicity of the paste. For these reasons, the importance in standardizing the proportion of the components of the paste is essential.
According to the GPP's inventors,  the proportion of the components should be visibly equivalent in volume. However, reaching such accurate proportions is usually difficult, as previously mentioned. In addition, the practitioners preferred manipulating a slightly more consistent paste with less PMCC. This can be seen in the different final proportions obtained throughout the components, even though the practitioners were advised to follow the orientations provided by the authors.  The low variability throughout the subjects in each group and the absence of differences among groups (after the exclusion of the outliers) corroborates this preference, independent of the experience of the practitioner.
Two outliers were found in the sample, probably because each practitioner attributes different consistencies to the paste based on his/her clinical experience. Consequently, they were not included in the sample and a mean concentration was determined for each component after removal of these outliers. The results on the variance for each group were not statistically significant, and there was a high interclass correlation coefficient. Thus, with the means of each component obtained in all the samples without the outliers, we calculated an ideal proportion for each component in order to standardize the manipulation of GPP and to supply a simple method of standardization of the material in the clinical practice.
Therefore, the proportion of each GPP component can be defined considering the mean of each component for all the groups. Hence, the proportion of the GPP components obtained in the present study is 23.8% Rifocort® , 7.0% PMCC, and 69.2% iodoform. This proportion follows the recommendations of the original article,  taking into account the preference of several professionals with different experience using the medicine in daily clinical practice. Another advantage of this proportion is the reduction of the amount of PMCC, which is the most toxic GPP component.  The possibility of substituting other drugs for PMCC should be further evaluated.
Therefore, the proportions obtained in this study can be considered a good standard for current clinical practices. To standardize this proportion in dental offices and clinics, the following guidelines should be followed while manipulating 1 g of GPP: 1 cm of Rifocort® , 2 drops of PMCC (using a bottle dropper), and 1 cm length of a tube of anesthetic filled with iodoform. This syringe must be completely empty, and the plunger must be set 1 cm from the end of the barrel, which determines the part that must be filled with iodoform [Figure 2].
Further studies to evaluate the biocompatibility and clinical efficacy of this proportion should be conducted. In addition, further studies are needed to develop excipients for long-term stabilization of the formulation, allowing for the commercial production of the GPP.
| Conclusion|| |
The proportion of GPP was similar in all the groups, allowing us to conclude that ideal GPP proportion, based on the entire group mean, was 23.8% of Rifocort® ; 7.0% of camphorated PMCC, and 69.2% of iodoform. Little variation exists in the manipulation of the GPP by undergraduate students and pediatric dentists. Thus, adequate concentration of components for use in daily clinical practice should be defined, measured, and manipulated in the moment of the use.
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Anna Carolina Volpi Mello-Moura
Department of Orthodontics and Pediatric Dentistry, Dental School, University of Sao Paulo, Sao Paulo
[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]