Clinical and Radiographic Assessments of Potassium Nitrate in Polycarboxylate Versus Mineral Trioxide Aggregate as Pulpotomy Biomaterials in Immature Mandibular First Permanent Molars

introduction: Vital pulp therapy (VPT) is defined as a treatment which aims to preserve and maintain pulp tissue that has been compromised but not destroyed by caries, trauma, or restorative procedures in a healthy state. Pulpotomy is one of the techniques of VPT where unhealthy pulp in pulp chamber is amputated leaving the healthy one in radicular part in root canal. This is particularly important in the young adult tooth with incomplete apical root development.

An important benefit for preservation of vital pulp is the protective resistance to mastication forces compared with a root-canal-filled tooth. It is reported that the survival rate of endodontically treated teeth is not as good as vital teeth especially in molars.

VPT is primarily recommended to be performed in young patients because of the high healing capacity of pulp tissue compared to older patients. The presence of an adequate blood supply is required for the maintenance of the pulp vitality. In addition, the presence of a healthy periodontium is necessary for success of VPT, where teeth with moderate to severe periodontal disease are not suitable candidates for the treatment.The prognosis of VPT is significantly reduced in cases with inadequate coronal seal and subsequent bacterial microleakage.

One of the most important issues in VPT is the status of the pulp tissue. The traditional school of thought is that VPT should only be carried out in teeth with signs and symptoms of reversible pulpitis.

After amputation of coronal pulp tissues Control of hemorrhage is also necessary for the success of VPT. Various options are available for the achievement of pulp hemostasis such as mechanical pressure using a sterile cotton pellet which may be soaked in sterile water, sodium hypochlorite and saline. Cases with signs of prolonged bleeding for more than 5 minutes are not candidates for pulpotomy.

Ferric sulfate (Fe2 [SO4]3) solution, 15.5%, is used commonly as a hemostatic retraction agent for crown and bridge impressions. Ferric sulfate is proposed as a pulpotomy agent on the theory that its mechanism of controlling hemorrhage might minimize the chances for inflammation and internal resorption believed by some investigators (Schroeder). The mechanism of action of ferric sulfate is probably by agglutination of ferric ion proteins complex results from the reaction of blood with both the ferric and sulfate ions that occlude the capillary orifices.

An appropriate pulp-capping agent establishes a biologically acceptable environment for the pulp tissue and prevents future bacterial contamination. The material should be biocompatible, bactericidal, provide a biologic seal, and induce hard tissue formation.

For many decades, calcium hydroxide has been the material of choice amongst the various pulp capping materials that are available. Clinical studies have reported a high rate of favorable outcomes of partial pulpotomies carried out with calcium hydroxide in cariously exposed young permanent molars. Despite its common use, it has several disadvantages including the presence of tunnel defects in induced dentinal bridges, obliteration of root canals making future endodontic treatment difficult, poor adherence to dentine, soluble, degrades with time and lack of long-term seal.

Currently, mineral trioxide aggregates (MTA) is accepted as an optimum material for use in vital pulp therapy of permanent teeth. MTA successful clinical outcome is reported to be due mainly to its long-term sealing ability and the stimulation of a high quality and a great amount of reparative dentin. In human clinical trials carried out on cariously exposed permanent teeth, the success rate of vital pulp therapy using MTA was considered to be high and ranged from 93 to 100%.

Despite its many advantages, MTA has some drawbacks that include the presence of toxic elements in the material composition, difficult handling characteristics, long setting time , tooth discoloration , and high cost, thus is an alternative material to MTA as a pulpotomy agent would be highly recommended.

Potassium nitrate (KNO3) is a superior desensitizer for hypersensitive teeth. Used with polycarboxylate cement, it serves as an effective liner for deep carious lesions. Also when placed under deep restorations with less than 1 mm of protective dentin remaining, it was effective in preserving pulpal vitality and it diminished the incidence and severity of post-restoration pain (27). As temporary cement (Kno3/zinc oxide eugenol [ZOE]) It reduced pain following full crown preparation.

Interestingly, using Potassium Nitrate with Dimethyl Isosorbide and Polycarboxylate Cement proved to be an effective direct capping agent for carious exposed vital pulps.

Polycarboxylate cement has very thin film thickness and bonds firmly to the tooth structure, is capable of withstanding the overlying pressure during restoration procedures. The good adhesive properties of polycarboxylate cement containing 5% KNO3 guaranteed the closure of cavity, good and lasting protection of traumatically exposed dental pulp and the formation of alkaline environment possessing a strong antiacidic, anti-inflammatory and antibacterial effect of this pulp capping material, creating optimal conditions for expression of its natural reparative potential. The increased release of potassium nitrate from polycarboxylate cement by time, might be the cause of decreasing the inflammatory intensity due to its antimicrobial action.

The application of polycarboxylate cement containing 5% KNO3 for direct capping of traumatically exposed pulp in animal models did not result in any degenerative changes in dental pulp. In fact, polycarboxylate cement containing 5% KNO3 was recommended as a basis for clinical investigations as a direct capping material.

So the present study seeks to investigate the clinical usefulness of applying polycarboxylate cement containing 5% KNO3 as a pulpotomy agent material of exposed immature permanent molars, thought creating optimal conditions for preservation of pulp vitality and root completion.

Up to the author knowledge, no previous randomized clinical trials (RCT) have evaluated the use of polycarboxylate containing KNO3 as a pulpotomy material, presenting a knowledge gap regarding this point.

Methods:

Source of patients: Out patients of the clinic of pedodontic at the faculty of oral and dental medicine, Cairo University.

Medical and dental history, will be obtained from all patients participating in this research followed by a thorough clinical and radiographic examination of deep carious mandibular first molar with no signs of irrivirsable pulpitis.

Preoperative radiographs will be acquired by using the standardized paralleling technique with the Rinn XCP alignment system (Rinn Corporation, Elgin, IL). Periapical radiographs will digitized and measurement done via Image J software (ImageJ v1.44; National Institutes of Health, Bethesda, MD).

Grouping of participants

According to sample size calculation, figure 2, fifty patients will be equally divided according to randomization table in to two groups:

• Experimental group: patient will be treated with 5% potassium nitrate and carboxylate cement pulpotomy.
• Control group: patient will be treated with MTA pulpotomy. Procedure steps

1. Anesthesia Patient will be anesthetized by using nerve block local anesthesia (Carpule Mepecaine-L, Alexandria Company for Pharmaceuticals and Chemical Industries, Egypt).
2. Access cavity All caries will be removed and the pulp chamber will be accessed with sterile high speed carbide round bur and endo-z bur bur to reflect the internal anatomy of the pulp chamber, and to remove its roof, taking the exposure as a starting point. The teeth were isolated with a rubber dam. The pulps will be amputated with a sterile # 5 round bur or a sharp spoon excavator, producing minimal trauma. Bleeding will controlled by placing a sterile cotton pellet on the amputated pulp soaked in saline to achieve a complete hemostasis at this stage for success of pulpotomy agent.
3. Control of bleeding Ferric sulfate 15.5% solution in a plastic syringe and a cotton-tipped needle (viscostat, ultradent products Inc, Salt Lake City, USA) as a hemostatic and preservative agent. A small amount of ferric sulfate will be applied by gently wiping the cotton tip of the needle against the amputated pulp for 15 sec., flushed from the pulp chamber with a saline in order to remove any pieces of blood clot formation, dried with sterile cotton pellet and the access cavity will be dressed with pulpotomy agent; either mineral trioxide aggregate (white MTA Angelus,londrina,pr,brazil) or 5% potassium nitrate in polycarboxylate cement.(potassiun nitrate (KNO3),Merck,Darmstadt,Germany) according to randomization.

In the control group (MTA), the cavity will be covered with white MTA. One gram of cement powder will be mixed with a premeasured unit dose of 0.3 mL distilled water to achieve a powder/liquid ratio of 3:1 as per manufacturer's instructions. After 30 seconds of mixing, a putty consistency was obtained with a working time of about 5 minutes. The mix will delivered to the pulp stumps with the help of an MTA applicator (Angelus, Londrina, Brazil) and condensed lightly with a moistened sterile cotton pellet to ensure a 3- to 4-mm thickness. Because the setting time of MTA is about 4 hours, the MTA mixture will covered with a moistened cotton pellet, and the cavity will temporized with Cavit (ESPE, Seefeld, Germany), radiographic image will be taken to assure the level of the material in canal orifices. The following day the patient will be recalled, the cotton pellet will be removed, and the coronal pulp chamber will be sealed with resin modified glass ionomer (prime dent, Chicago, USA). The cavity will be filled with composite as a permanent restoration.

In the intervention group (potassium nitrate in polycrboxylate) the cavity will covered with 5% potassium nitrate (powder) (potassiun nitrate (KNO3),Merck,darmstadt,germany) which will mixed with the polyacrylic acid (liquid) (SIMENT P,Deepak product, inc, florida, USA) in 1:1 P/L ratio according to manufacturer directions. The mixed material will placed in the access cavity and light pressure will applied with a wet cotton pellet to contact the material with the pulp tissue. And the cavity will temporized with Cavit (ESPE, Seefeld, Germany), radiographic image will be taken to assure the level of the material in canal orifices. The following day the patient will be recalled, the temporary filling will removed, and the coronal pulp chamber will sealed with resien modified glass ionomer(prime dent, chicago,usa) the cavity will sealed with resien modified glass ionomer(prime dent, chicago,usa). The cavity will then filled with composit as a permanent restoration.

The patient will recalled for clinical evaluations at five follow up periods, and radiographic evaluations four follow up periods.

In case of post operative emergency (pain and/or swelling) an emergency appointment will be scheduled and shift of treatment to total pulpectomy and total root canal treatment will be done.

• Outcome If the tooth will functional without signs ⁄symptoms of pulp and periradicular inflammation⁄ infection (including spontaneous pain, sensitivity to percussion ⁄ palpation, soft tissue swelling or sinus tract and excessive mobility) in each follow-up time (24hr post operative,1 week, 3 month, 6 and 12 months after treatment), the treatment will clinically considered a success.

If root maturegenesis is evident radiographically without signs of failure (including formation of periradicular ⁄ interradicular lesion, internal ⁄ external root resorption) in each follow- up time (3 month, 6 and 12 months after treatment), the treatment will radiographically considered a success.

Radiometric analysis will be done via measurements throw image J software to evaluate the change in root length, dentin thickness and apical diameter measurement via ImageJ software (ImageJ v1.44; National Institutes of Health, Bethesda, MD).