|Year : 2018 | Volume
| Issue : 4 | Page : 64-68
Effect of two desensitizing agents on crown retention using zinc phosphate cement
Mohammed A Mapkar1, Amit Jagtap2, Syed Ruby Syed Asadullah3
1 Department of Prosthodontics, Government Dental College and Hospital, Aurangabad, India
2 Department of Prosthodontics, Dr. D. Y. Patil Dental College and Hospital, Pimpri, India
3 Dental Surgeon, Dental Department, Civil Hospital, Selu, Parbhani, Maharashtra, India
|Date of Web Publication||14-May-2019|
Dr. Mohammed A Mapkar
Department of Prosthodontics, Government Dental College and Hospital, Aurangabad, Maharashtra.
Source of Support: None, Conflict of Interest: None
Introduction: Preparation of vital teeth involves removal of sound tooth structure, which causes opening of dentinal tubules, thereby causing displacement of the dentinal tubular fluid, leading to dentinal hypersensitivity. After cementation of crowns in such teeth, incidence of pain and hypersensitivity has been reported. An extensive use of desensitizing agents has been observed over the past few decades because of the introduction of newer agents and the increased incidence of post-cementation sensitivity. Dentin desensitizing agents are commonly used in dental practice. But their effects on crown retention have been anecdotal. Materials and Methods: Thirty-three extracted human maxillary first premolar teeth were selected for the study, which were prepared using a special assembly and divided into three groups (i.e., ZP + U, ZP + G, and ZP) to compare the effect of Gluma (Heraeus-Kulzer, Germany) and Ultraseal (Ultradent, USA) on crown retention using zinc phosphate cement. Results: It was seen that the group ZP + G was statistically significant with groups ZP and ZP + U. However, no such difference was observed between ZP and ZP + U. Conclusion: Both the agents can be used and prove effective when used with zinc phosphate cement. However, the major mode of failure was adhesive in nature with the cement being retained on both the crown and the tooth structure.
Keywords: Crown retention, desensitizing agent, Gluma, Ultraseal, zinc phosphate cement
|How to cite this article:|
Mapkar MA, Jagtap A, Asadullah SR. Effect of two desensitizing agents on crown retention using zinc phosphate cement. Int J Oral Care Res 2018;6:64-8
|How to cite this URL:|
Mapkar MA, Jagtap A, Asadullah SR. Effect of two desensitizing agents on crown retention using zinc phosphate cement. Int J Oral Care Res [serial online] 2018 [cited 2019 Jul 16];6:64-8. Available from: http://www.ijocr.org/text.asp?2018/6/4/64/253708
| Introduction|| |
Fixed partial denture is relatively more common among the masses who can afford them because of it feeling “natural or fixed.” It is, however, an invasive therapy, which leads to sensitivity in vital teeth. Depending on the amount of tooth structure modified, it may result in a reversible pulpitis or irreversible pulpitis. Preparation of vital teeth involves removal of sound tooth structure. This exposes a large number of traumatized dentinal tubules to the oral cavity. Up to a million or more dentinal tubules may be exposed during tooth preparation for a posterior crown. Fluctuations in temperature and osmotic pressure bring about the displacement of the dentinal tubular fluid in the odontoblastic processes of the pulp. This fluid movement causes stimulation of the nerve fibers in the pulp manifesting as pain. This is the Brannstromm’s hydrodynamic theory., Desiccation and frictional heat generated during the course of preparation only accentuate the problem and increase the likelihood of hypersensitivity.
The “temporization” procedure, performed after the crown preparation, acts as physical barrier providing insulation to the pulp besides maintaining space. However, most temporary crowns display substantial amount of microleakage. The pH of luting agents such as zinc phosphate cement and glass ionomer cement is acidic. Studies have shown that the cement is forced into the tubules many a times causing irritation and pain to the patient. These factors compound the problem leading to irreversible pulpitis, which necessitates a root canal therapy. To address the dilemma of tooth sensitivity, dentists increasingly use bonding systems to seal dentine after crown preparation. This is often done without the proper technical know-how. Two methods commonly used to reduce tooth sensitivity after crown preparation are as follows:
- Application of calcium hydroxide suspension
- Application of various sealing systems
The sealing systems are further subclassified into non-resin, low-filled resin, and highly filled resin sealers.
Adhesives such as One-Step, (Germany) mechanically occlude open tubules with resin, thus sealing them from the oral environment. Primers, such as Gluma (Heraeus-Kulzer, Germany), reduce hypersensitivity by the precipitation of plasma proteins in the dentinal fluid.,,
Studies carried out in the past using Gluma revealed no effect on the shear bond strength of the cement to the dentin or on the retention of crowns luted with resin cement., However, crown retention was reduced when zinc phosphate cement was used. Another study showed a 42% decrease in the retention of castings cemented with zinc phosphate., By contrast, however, a study that used both Gluma and resin systems did not reveal any significant effect with zinc phosphate, glass ionomer, Resinomer (Conway avenue, st. Paul, USA) or cement. An in vivo study was also conducted using calcium hydroxide suspension with glass ionomer and zinc phosphate cement–luting agents. No decementation of crowns was observed for 17 months. Other studies also did not reveal a negative effect on retention.,
The aim of this study was to evaluate and compare the effect of two dentin desensitizing agents applied to the prepared dentin on crown retention using zinc phosphate cement.
| Materials and Methods|| |
Thirty-three extracted human maxillary first premolar teeth were selected for the study. Only non-carious, non-restored teeth were chosen. Teeth were cleaned using a scaler and then disinfected with 0.5% sodium hypochlorite and stored in distilled water. Roots were roughened and the teeth were mounted in a special circular jig fabricated for the purpose, with cold cure acrylic resin. The teeth were mounted with the Cemento-enamel Junction (CEJ) 1mm above the cold cure resin. The entire procedure was carried out on a special assembly fabricated for the purpose and mounted on a surveyor [Figure 1]. The flat end tapering bur was used for the axial preparation and ensured a uniform convergence angle of 20degrees. A shoulder finish margin was given. The depth of the axial preparation was kept equal to the diameter of the tapering bur. The length of the preparation was 4mm above the CEJ. A new diamond point and finishing point was used for each sample for the purpose of standardization. An elastomeric impression of each prepared sample was made and dies were poured and labeled. The axial surface area of each sample was calculated by an electronic scanner. The same procedure was repeated for all the samples. All of the above was carried out by the same individual. The samples were then redistributed such that the total mean surface area of all the groups was the same. Die hardener was applied to each die followed by a single layer of die spacer. This was followed by the application of die lubricator. Wax patterns were then fabricated by dipping the master die in a wax bath. Two coatings were applied, allowing previous layer to set. Prefabricated wax loops were then attached to the wax patterns to facilitate the testing on a universal testing machine. The completed pattern with the loop was then invested and cast using base metal alloy to obtain individual coping [Figure 2].,
Two dentin sealers (Ultraseal [Ultradent, USA] and Gluma) were used to seal the dentin. Crowns in the control group were cemented without any dentin sealer. The dentin was etched for 15s in 32% phosphoric acid and then washed for 20s. Moisture was removed and two coats of sealer were applied allowing the previous layer to dry. The application of desensitizers was carried out just before cementation.
An electronic microbalance was used to ensure equal amounts of powder and liquid. The castings were then lined with cement and seated using a loading machine, 20kg for 10min. The excess cement was removed before the final setting of the cement (10min). The specimens were then stored in water for 24h. To simulate stress, the crowns were thermocycled from 5°C to 55°C for 2500 cycles using a dwell time of 30s. A universal testing machine was used to dislodge the crowns [Figure 3]. Axial dislodgement forces were then applied until failure at a crosshead speed of 0.5mm/min via a universal testing machine. Both the dislodged crowns and the teeth samples were examined for the type of failure under an optical microscope.
The mean values and standard deviations of each treatment group were determined. The data were analyzed using one-way analysis of variance (ANOVA). Tukey’s honestly significant difference test was used to determine the significance of differences between the mean values.
| Results|| |
The type of cementing agent used in the study will, henceforth, be referred to as Type ZP for ease in comparison.
Type ZP: control specimens luted with zinc phosphate cement MEDIcept (Middlesex, UK).
Type ZP + U: specimens treated with Ultraseal dentin sealant and luted with zinc phosphate cement.
Type ZP + G: specimens treated with Gluma and luted with zinc phosphate cement.
The specimens were hence divided into three groups, each comprising 11 specimens. Statistical analysis was carried out by one-way ANOVA initially to analyze the effect of the two desensitizing agents compared vis-a-vis the control group.
It was observed that the group ZP + G was statistically significant with ZP and ZP + U. However, no such difference was observed between ZP and ZP + U. Hence, the statistical significance correlated with the clinical significance [Table 1].
| Discussion|| |
Vital tooth preparation elicits pain and sensitivity, as does any procedure that injures any tissue of the human body. Yet, this is an essential requirement to restore the function and prevent further deterioration of health. Depending on the extent of preparation, the pain may be mild, which is addressed by analgesics, to severe pain, which warrants intentional root canal. To deal with this agonizing issue, dentinal desensitizers were introduced. These range from lasers to a wide range of sealing systems and calcium hydroxide, oxalates, and potassium nitrate. Desensitizing agents may reduce tooth sensitivity by forming a thin barrier that protects the tooth structure from external insults but then deprives the cement of micromechanical retention on the tooth structure., However, the surface roughness of the crown is yet available and the cements may interlock in them [Figure 4].
|Figure 4: Bar diagram showing comparison of the dislodgement forces of the three groups|
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Earlier studies were carried out on All-Bond, One-Step, and Gluma., For this study, a resin primer “Gluma” from Heraeus-Kulzer and “Ultraseal” from Ultradent was selected as desensitizing agents. Gluma is composed of glutaraldehyde (5%) and 2-hydroxyethyl methacrylate (35%). Ultraseal is a resin sealant from Ultradent. It is composed of non-polymerizable, high-molecular-weight resin in a volatile organic solvent. It forms a virtually impenetrable barrier against acids, cements, and restoratives.
Zinc phosphate attains its retentive qualities by finding irregularities in the prepared dentin and the internal surface of the casting. Over the past 20 years, numerous studies have been carried out to assess the effect of dentinal sealants on crown retention. Johnson et al. showed a 42% decrease in the retention of castings cemented with zinc phosphate. By contrast, however, another study that used both Gluma and zinc phosphate cement did not reveal a significant effect. 
Results in this have been summarized as follows:
- ♫The greatest values of dislodgement forces were recorded for group ZP + G. This value was greater than group ZP and group ZP + U. The difference in each case being statistically significant.
- ♫The second greatest values were shown by group ZP as control without any desensitizer. This value was greater than that of group ZP+U; however, this difference was not statistically significant.
- ♫Group ZP + U showed mean values lower than that by group ZP + G and group ZP, but these values were not statistically significant.
Majority of the decementation tests resulted in an adhesive type of failure for all groups, ranging from mixed type to complete stripping of the cement from the tooth structure.
Crown retention values for Gluma combined with zinc phosphate are increased in this study; this is in accordance with the results obtained in a previous study carried out by Johnson et al. 1998. Studies with similar results were also obtained by Reinhardt et al. Crown retention values for Ultraseal and zinc phosphate cement decreased in this study, this was also in accordance with past results obtained by Mausner et al.
| Conclusion|| |
Dentinal sensitivity either delayed or immediate is often reported by patients with vital teeth undergoing tooth modification procedures. Some practitioners even prefer to carry out an intentional root canal therapy as they consider it to be the inevitable. Desensitizing agents not only provide relief against postoperative pain but also form a thin protective barrier that protects the vitality of the pulp. Use of desensitizing agents provides a logical and economical answer to address this problem.
In vitro test is the most common method used to test the crown retention. These tests are used as they are faster, less expensive, and less controversial, offering more experimental control than animal or human tests. An in vitro test has hence been used in this study. However, an important factor that limits the relevance of in vitro tests is the absence of saliva and the occlusal masticatory forces.
Within the limitations of the study, the following conclusions can be drawn:
- Application of Gluma desensitizing agent resulted in an increase in retention that was statistically significant and should be advocated.
- Application of Ultraseal desensitizing agent resulted in a decrease in crown retention. However, no statistical significance was observed. Hence, such a combination may be safely used.
- The major mode of failure was adhesive in nature with the cement being retained on both the crown and the tooth structure.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]