Introduction

Pulpotomy is the most widely accepted clinical procedure for treating primary teeth with inflammation of the coronal pulp caused by caries with no involvement of the radicular pulp.1,2,3,4,5,6,7 Basically, this technique consists of removing the coronal pulp and maintaining the vitality of the radicular pulp. The purpose is to remove the bacterial infection leaving the treated tooth asymptomatic until its exfoliation.3,4,5,6,7

Medicaments applied to radicular pulp tissue after pulpotomy have included formocresol,1,3,4 ferric sulphate,3,4 calcium hydroxide4 and mineral trioxide aggregate (MTA).1,8,9,10,11,12,13,14

With the development of materials which are not only biocompatible but also bio-inductive, the emphasis has shifted from mere preservation to regeneration of the remaining pulp tissue. One such material which has shown immense potential for regeneration is MTA.15 MTA was developed with the purpose of serving as a root end filling material, but it has also proven to be successful in vital pulp therapy procedures both in animals16,17 and humans.2,8,11,12,18 MTA is a biocompatible material and its sealing ability is better than that of amalgam or zinc oxide-eugenol.2,14,15 Furthermore, its ability to stimulate cytokine release from bone cells has been demonstrated, indicating that it actively promotes hard tissue formation.2

Recently, great interest has been focused on the evolution of Portland cement (PC) as an alternative to MTA, and several experimental studies have compared both materials.16,19,20,21,22,23,24 PC differs from MTA by the absence of bismuth ions14,22,23,25,26 and presence of potassium ions.26 Both materials have comparable antibacterial activity22 and almost identical properties macroscopically, microscopically and by X-ray diffraction analysis.23,24,26 It has also been shown that PC and MTA have similar effects on pulp cells when used for direct pulp-capping in rat teeth.24 Holland et al.16 studied the rat subcutaneous connective tissue response to implanted dentin tubes filled with MTA, PC and calcium hydroxide and found very similar histological results. In addition, both MTA and PC allowed for dentin bridge formation after pulpotomy performed on dogs.16 Min et al.27 observed that PC allowed the expression of mRNAs of a dentin-specific protein and a noncollagenous protein involved in mineralisation in cultured human pulp cells. De-Deus et al.28 presented a case in which substantial periapical healing occurred with the use of PC to create an apical plug in the root of an immature tooth in human. Finally, Conti et al.29 have recently documented the clinical success of two cases in which PC was applied as a medicament after pulpotomy of mandibular primary molars in children.

Taking into account the low cost and apparently similar properties of PC in comparison with MTA, it is reasonable to consider PC as a possible substitute for MTA in endodontic applications.17,21,24,27,30,31 Therefore, the purpose of this study was to compare the clinical and radiographic effectiveness of MTA and PC as pulp dressing agents in human carious primary teeth.

Material and methods

Participants

The Brazilian Health Ministry and the Ethics Committee of the Bauru School of Dentistry, University of São Paulo approved the protocol of this study (#34/2005 and #134/2004, respectively). During the pretreatment screening period, the parents or guardians of the children received detailed information concerning the nature and the procedures involved in the study and signed informed consent forms.

The criteria for selection of the teeth to be included in the study were: children between the ages of 5 and 9 years old, with one carious mandibular primary molar tooth with vital pulp and absence of history of pain, thus requiring a pulpotomy therapy; no clinical or radiographic evidence of pulp degeneration, such as excessive bleeding from the root canal, internal root resorption and furcal bone destruction; no physiological root resorption of more than one-third, as observed in periapical radiographs; and the possibility of proper restoration of the teeth. Exclusion criteria included the presence of systemic pathology and any history of allergic reaction to latex, local anesthetics or to the constituents of the tested pulp dressing agents.

Technique

The suitability of the teeth for pulpotomy was assessed by two of the authors, who also performed the procedures. The authors were previously involved in several pulpotomy studies and used a standardised technique.

The primary mandibular molars were randomly assigned to MTA or PC groups by the toss of a coin. In both groups, after local anaesthesia with 2% mepivacaine with 1:100,000 adrenaline and rubber dam isolation, caries removal was accomplished using a handpiece with a round bur. The opening of the pulp chambers was conducted with round carbide bur. Full coronal pulp tissues were removed manually with an excavator, followed by irrigation with saline solution in order to clear the debris. The wound surface was continuously irrigated with saline solution until bleeding ceased.

In the MTA group, a paste was obtained by mixing 0.16 g grey MTA powder (Ângelus, Londrina, PR, Brazil) with sterile saline to produce a homogeneous paste. The paste was placed in the pulp chamber. In the other group, 0.16 g of PC (Votorantim-Cimentos, São Paulo, SP, Brazil) was previously sterilised with ethylene oxide and then mixed with sterile water. PC was mixed to a consistency similar to that of MTA, and applied into the pulp chambers with a spatula. In both groups, a layer of reinforced zinc oxide-eugenol (IRM®, Dentsply, Petrópolis, PR, Brazil) was placed before restoration with resin modified glass ionomer cement (Vitremer®, 3M ESPE, São Paulo, SP, Brazil). Immediate postoperative periapical radiographs were taken.

Follow-up

At follow-up appointments, clinical success was confirmed in teeth presenting with no spontaneous pain, mobility, swelling, fistula, or smell. Radiographic success was considered if internal root resorption and furcation radiolucency were absent. Dentine bridge formation was also considered a radiographic success, and intra-canal calcifications were not considered as failures.

Periodic follow-up examinations were carried out 6, 12, 18 and 24 months after the end of the treatment. Each check-up involved a clinical and periapical radiographic examination of the pulpotomised teeth, which was performed by two blinded and previously calibrated investigators (kappa values of 0.83 and 0.96 for inter- and intra-examiner reproducibility, respectively). When disagreement arose, a consensus approach was adopted.

Data were submitted to statistical analysis using the Chi-square test followed by Fisher's exact test. Statistical significance was established at 5%.

Results

Thirty primary molars in 30 children (11 girls and 19 boys, with mean age of 6 years and 9 months) were randomly allocated to the PC (15 teeth) or MTA (15 teeth) groups. One tooth in the MTA group was lost to follow-up.

In both groups, 100% of the available teeth were clinically and radiographically successful during all the follow-up appointments. No teeth showed signs of mobility, sinus tract, swelling, or inflammation of the surrounding gingival tissue, and none showed radiographs suggestive of internal root resorption and furcation radiolucency. Six out of 15 teeth in the PC group and five out of 14 teeth in the MTA group exfoliated throughout the follow-up period (Fig. 1).

Figure 1
figure 1

Flow of patients and pulpotomised teeth up to 24 months

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The formation of dentine bridges could be radiographically observed in two teeth treated with PC during all the follow-up appointments. In the MTA group, a dentine bridge was detected in one tooth during the 6-month follow-up and in four teeth in the subsequent follow-up appointments. However, no statistically significant difference regarding this parameter was found between both groups throughout the follow-up period.

Regarding pulp canal obliteration, a statistically significant difference was found between both groups at 6-month follow-up (p <0.05). In the PC group, the beginning of mineralised material deposition could be radiographically detected in all of the available teeth 6 months after the placement of the dressing agent over the remaining pulp tissue. In the MTA group, eight teeth (57.14%) presented mineralized material deposition obliterating the root canal at 6-month follow-up and 11 teeth (78.6%) at 12-month follow-up.

Additionally, a greyish colour change of the crowns was observed in all pulpotomised teeth in both groups, although this feature was slighter in the PC group. Radiographs of clinical cases in which MTA and PC were used as pulp capping agents are shown in Figures 2 and 3, respectively.

Figure 2: Pulpotomy treatment performed in a mandibular left primary second molar with the use of MTA in a 9-year-old male patient.
figure 2

(A) Preoperative periapical radiograph of the tooth showing an extensive caries lesion, more than two thirds of root length, and no signs of periapical lesion. (B) Immediate postoperative periapical radiograph of the pulpotomised tooth with MTA. (C) 12-month follow-up periapical radiograph suggesting the initial obliteration of the roots and absence of periapical lesion in the pulpotomised molar. (D) 24-month follow-up periapical radiograph suggesting the obliteration of the roots and their progressive resorption caused by the eruption of the permanent successor

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Figure 3: Pulpotomy treatment performed in a mandibular left primary second molar with the use of PC in an 8-year-old female patient.
figure 3

(A) Preoperative periapical radiograph of the tooth showing an extensive caries lesion, more than two thirds of root length, and no signs of periapical lesion. (B) Immediate postoperative periapical radiograph of the pulpotomised tooth with PC. (C) 12-month follow-up periapical radiograph suggesting the absence of periapical lesion in the pulpotomised molar and the progressive resorption of the roots, mainly the distal one, due to the eruption of the permanent successor. (D) 24-month follow-up periapical radiograph showing the complete resorption of the roots of the pulpotomised tooth caused by eruption of the permanent successor

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Discussion

Several studies have reported excellent results when using MTA over pulp.1,6,8,10,11,12,17 The factor responsible for the beneficial effects in MTA is also found in PC,31 although it is important to emphasize that they are not identical materials.13 This has resulted in a significant body of research showing that PC appears to be a useful substitute for MTA.17,21,24,27,31,32 However, only four studies reported the use of PC in conservative pulp therapy with considerable success in rats24 and dogs.16,17,23 To the best of our knowledge, this is the first randomised controlled clinical trial assessing the effectiveness of PC in human primary teeth and comparing this regenerative dressing agent with MTA.

Danesh et al.20 showed that MTA displayed superior material properties to PC, which was significantly more soluble, reached lower microhardness values and was less radiopaque. The lack of radiopacity in pure PC is due to the absence of bismuth, a chemically inert radiopacifier, in its composition.25 However, this feature compromises neither the execution of pulpotomy procedures with PC nor their follow-up assessments, which is not the case when this material is used for root-end fillings. In these situations, a radiopacifier is necessary to enable the peri- and postoperative assessment of the cement placement reaching the root apex.

A major concern regarding the use of water-based cements is the amount of leachable arsenic present in the material, which arises from impurities in the limestone used in the manufacture of PC.23 Duarte et al.30 showed that the concentration of arsenic is low in PC and closely similar to that present in MTA, demonstrating no contraindication due to arsenic for the use of PC in clinical practice. Although one could consider the use of PC in humans a risk, it is noteworthy that its use was assessed by the Brazilian Health Ministry and further approved by the Ethics Committee of the Bauru School of Dentistry, University of São Paulo, thus validating the execution of the present clinical study in human primary teeth.

The concept of dentine bridging is controversial because the presence of a bridge can be viewed as either a healing response or a pulp reaction to irritation.15,33 Waterhouse et al.34 suggested that reactionary dentine formation is a sign or consequence of attempted repair processes within the pulp tissue. Nevertheless, after an initial attempt by the pulp tissue to 'wall-off' the insult, the protective or reactive process may fail, leading to clinical failure. In the present study, none of the teeth with dentine bridges had other concomitant radiographic or clinical signs of failure, and therefore the presence of dentine bridges was categorised as a radiographic success.

Another radiographic finding in both groups that was not regarded as failure was pulp canal obliteration. The active deposition of tertiary reparative dentine and consequently the narrowing of the canals is the result of extensive activity of odontoblast-like cells, thus indicating the presence of pulp vitality.6,35 However, it is worth mentioning that histological analysis would be an important approach to assess pulp tissue condition of all pulpotomised teeth as well as to determine the nature and quality of the dentine bridges and the calcified tissues that obliterated the pulp canals. Thus, the histological failure and success rates could also be determined.

Healing of the dental pulp is not exclusively dependent on the supposed stimulatory effect of a particular type of medicament, but is directly related to the capacity of both the dressing and definitive restorative material to provide a biological seal against immediate and long-term microleakage along the entire restoration interface.5,15 One such material that provides optimal coronal seal is a stainless steel crown.1,2,5,10,11,12 However, in this study, all pulpotomised teeth were restored with resin modified glass ionomer cement (RMGIC), which has good sealing properties, is easy to handle36 and has adhesion properties that impart adequate retention even if mechanical undercuts are absent. Coverage of exposed dentine and sharp margins with RMGIC to provide patient comfort is possible with minimal chair time.12,36 Therefore, the impaction of the restorative material was not a discriminating factor between the two groups. Additionally, it is important that the absence of evidence for RMGIC should not be misinterpreted as evidence for its lack of efficacy.

Taken together, the present data support the suggestion that PC may serve as an effective and less expensive MTA substitute in primary molar pulpotomies. Although our results are very encouraging, further studies with a larger number of samples and longer follow-up assessments are needed in order to determine the suitability of PC before unlimited clinical use can be recommended.