|Year : 2015 | Volume
| Issue : 4 | Page : 236-240
Comparison of patient sensitivity using dentin bonding agent versus zinc phosphate base beneath the amalgam restorations: An in vivo comparative study
Sarjeev Singh Yadav1, Jagadeeswara Rao Sukhabogi2, Vemala Bharath Kumar3, Muralikrishnam S Raju4, Venkat V Giri3, Gopi Pulivarthi1
1 Department of Conservative Dentistry and Endodontic, Government Dental College and Hospital, Hyderabad, Telangana, India
2 Department of Public Health Dentistry, Government Dental College and Hospital, Hyderabad, Telangana, India
3 Dental Practitioner, Andhra Pradesh, India
4 Department of Conservative Dentistry and Endodontic, GSL Dental College, Rajahmundry, India
|Date of Web Publication||14-Dec-2015|
Sarjeev Singh Yadav
Professor and H.O.D, Department of Conservative Dentistry and Endodontic, Government Dental College & Hospital, Afzalgunj, Hyderabad, Telangana 500012
Source of Support: None, Conflict of Interest: None
Aim: The aim of the present study is to evaluate and compare patient sensitivity following the amalgam restorations using two different materials beneath them - zinc phosphate base and dentin bonding agent.
Materials and Methods: Thirty individuals aged between 20 years and 60 years were selected who presented with two class I carious lesions located in different quadrants. Both the teeth were filled at the same appointment. Following rubber dam isolation, conventional cavities were prepared for the amalgam restorations. One tooth received zinc phosphate base while the other received dentin bonding agent beneath the amalgam restoration. High copper non-γ2 amalgam was triturated using amalgamator by condensing it into the cavity. Questionnaires were given to the patients for recording sensitivity scores to heat, cold, or biting at the end of 1, 3, 7, and 14 days.
Results: Significance was determined based on the P values obtained from the simple curve z-test. On day 1, when groups I and II were compared, no significant difference in number of patients reporting postoperative sensitivity was found. On day 3, more number of patients reported sensitivity with zinc phosphate cement compared to those with dentin bonding agent. On day 7, there was great reduction in sensitivity in both groups compared to day 1 and day 3 but comparatively more in teeth with zinc phosphate base. On day 14, there was no significant sensitivity in both groups, patients showing no sensitivity to both zinc phosphate base and dentin bonding agent.
Conclusion: Postoperative sensitivity was relatively more in teeth restored with zinc phosphate base compared to that restored with dentin bonding agent. Postoperative sensitivity resolved earlier in restorations with dentin bonding agent compared to zinc phosphate base, and sensitivity resolved with time in both the restorations.
Keywords: Amalgam, amalgam restoration, dentine bonding agent, in vivo study zinc phosphate, postoperative sensitivity, zinc phosphate base
|How to cite this article:|
Yadav SS, Sukhabogi JR, Kumar VB, Raju MS, Giri VV, Pulivarthi G. Comparison of patient sensitivity using dentin bonding agent versus zinc phosphate base beneath the amalgam restorations: An in vivo comparative study. J NTR Univ Health Sci 2015;4:236-40
|How to cite this URL:|
Yadav SS, Sukhabogi JR, Kumar VB, Raju MS, Giri VV, Pulivarthi G. Comparison of patient sensitivity using dentin bonding agent versus zinc phosphate base beneath the amalgam restorations: An in vivo comparative study. J NTR Univ Health Sci [serial online] 2015 [cited 2020 Apr 5];4:236-40. Available from: http://www.jdrntruhs.org/text.asp?2015/4/4/236/171731
| Introduction|| |
Amalgam has been used to restore posterior teeth  since 1826 because of its ease of handling, physical properties, biocompatibility, self-sealing of margins, and less cost. In spite of excellent esthetic results with tooth colored restorative materials, amalgam is still the most widely used restorative material in our country. There are certain advantages inherent with amalgam, such as technique insensitive, excellent wear resistant, less time-consuming, less expensive, which are not present in the newer materials. These factors will continue to make amalgam the material of choice for many more years to come. However, amalgam has got certain disadvantages such as inferior esthetics, more invasive procedure, mercury toxicity, and reported high incidence of postoperative sensitivity.
Postoperative sensitivity is one of the most commonly reported problems with the amalgam restorations with a prevalence rate of 8-30% among adult populations commonly aged 20-40 years.  Postrestoration sensitivity can cause discomfort to the patient, though it resolves over time within a few days or weeks. Transmission of heat/cold excites nerve fibers whose threshold is further reduced by inflammation due to trauma/bacterial products of carious dentin. 
Various theories have been proposed explaining postrestoration sensitivity such as the direct nerve stimulation theory, dentinal receptor theory, direct ionic diffusion hypothesis, and hydrodynamic theory. Of these theories, the most accepted one is hydrodynamic in nature. In 1965, Brannstrom proposed the hydrodynamic theory that states that pain/sensitivity to hot/cold is because of fluid shift inside the dentinal tubules that physically distort the nerve fibers close to the odontoblast layer. 
The methods to reduce postrestorative sensitivity beneath the amalgam restorations are as follows: using a base beneath the restorations, which acts as a thermal insulating layer, forms a mechanical barrier for pulp, and acts as a pharmacotherapeutic agent; using dentin bonding agents beneath restorations, which forms hybrid layer,  reduces microleakage,  and also forms a mechanical barrier between the restorative material and pulp.
| Materials and Methods|| |
Thirty healthy individuals (male/female) aged 20-60 years were included in the study. Each subject presented with two class I carious lesions of size 1 and size 2 as per Mount's classification of dental caries located in different quadrants. Only permanent molar teeth were used. Both the teeth were filled at the same appointment. Following rubber dam isolation, conventional cavities were prepared for the amalgam restorations standardized at a depth of 2.5 mm pulpally and Ό intercuspal width with the help of high speed handpiece, water coolant, and periodontal probe. One tooth received zinc phosphate base that was mixed according to the operator's instructions, and the thickness of the mixture was 0.5 mm (Harvard cement). The other tooth received dentin bonding agent (Tetric N-Bond). Etching was done using N-Etch for 15 s - Rinsed, dried followed by bonding agent application, light cured for 15 s. High copper non-γ2 amalgam (DPI Alloy) was triturated using amalgamator (Dentsply), following which it was packed into the prepared cavity. Condensation of the amalgam was done in increments with the help of hand condensers. Care was taken so that there was perfect adaptation of the amalgam to all parts of the prepared cavity and a good bonding between the increment layers. Excess material was removed using Hollenback instrument. Thereafter, burnishing and polishing was done to rebuild the anatomy of the tooth and to reestablish its original form, and finally, to provide a lustrous surface with an acceptable appearance and best corrosion resistance.
The sensitivity scoring criteria followed in this study was given by Johnson et al. in 1988 that is shown in [Table 1].
All the teeth restored in this study can be classified in the following three groups:
GROUP I - Teeth exhibiting sensitivity with zinc phosphate base beneath the amalgam restoration.
GROUP II - Teeth exhibiting sensitivity with dentin bonding agent beneath the amalgam restoration.
GROUP III - Teeth exhibiting no postoperative sensitivity following the amalgam restoration with either zinc phosphate base or dentin bonding agent.
Questionnaires were given to the patients regarding presence/absence of sensitivity at the end of 1, 3, 7, and 14 days. Questionnaire given to patient for recording sensitivity scores contained information regarding patient's name, age, address, sensitivity scores on day 1, day 3, day 7, and day 14. Patients were asked to mark the relevant score regarding postrestoration sensitivity in the questionnaires that were given to them at the beginning of the study and were collected at the end of day 14.
| Results|| |
The present study was done taking into consideration the environmental factors. Operative variations (like the method of condensation, carving, and burnishing) and the final response (postoperative sensitivity) shown were found to be influencing the treatment outcome.
The scores obtained were then statistically analyzed and significance was determined based on the P-values obtained from the simple curve z-test. The present in vivo study was conducted to evaluate the postoperative sensitivity in the patients following the use of zinc phosphate base and dentin bonding agent beneath the amalgam restorations.
[Table 2] indicates the number of teeth exhibiting postrestoration sensitivity on day 1, day 3, day 7, and day 14.
|Table 2: The Number of Teeth Exhibiting Postrestoration Sensitivity on Day 1, Day 3, Day 7, and Day 14|
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On day 1, when group I and group II were compared, no significant difference in number of patients reporting postoperative sensitivity was found that may be due to the pulpal inflammation as a result of trauma of tooth preparation.
On day 3, more number of patients reported sensitivity with zinc phosphate cement (group I). The number of patients in group II showing sensitivity to dentin bonding agent reduced significantly compared to day 1 as sensitivity resolved in restorations with dentin bonding agent.
On day 7, there was a great reduction in sensitivity in both group I and group II compared to day 1 and day 3. Sensitivity was relatively more in teeth restored with zinc phosphate base.
On day 14, there was no significant sensitivity in both group I and group II, patients showed no sensitivity to both zinc phosphate base and dentin bonding agent.
[Table 3] indicates the levels of sensitivity in teeth restored with zinc phosphate base or dentin bonding agent beneath the amalgam restorations.
|Table 3: The Levels of Sensitivity In Teeth Restored With Zinc Phosphate Base or Dentin Bonding Agent Beneath The Amalgam Restorations|
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The graphical representation of stastical analysis done for comparing the patient sensitivity with zinc phosphate and dentin bonding agent is given in [Graph 1].
The graphical representation of sensitivity levels with zinc phosphate base or dentin bonding agent beneath the amalgam is given in the following Graphs 2 and 3.
On day 1, out of 30 teeth that received zinc phosphate base, 80% of restorations exhibited postrestoration sensitivity while no sensitivity was reported in 20% of restorations, whereas out of 30 teeth that received dentin bonding agent, 60% of restorations exhibited postrestoration sensitivity while no sensitivity was reported in 40% of restorations.
On day 3, the number of patients exhibiting sensitivity gradually reduced in both the groups and sensitivity was comparatively less in restorations receiving dentin bonding agent.
On day 7, 30% of the teeth that received zinc phosphate base exhibited sensitivity, whereas only 10% that received dentin bonding agent exhibited sensitivity.
On day 14, there was no sensitivity in teeth receiving dentin bonding agent, whereas 6.66% of the teeth (2 out of 30) receiving zinc phosphate base exhibited sensitivity but it was not statistically significant.
Also, the levels of sensitivity that was initially moderate gradually changed to slight sensitivity and then finally to no sensitivity at the end of 14 days.
| Discussion|| |
Postoperative sensitivity is very commonly reported with the amalgam restorations. Harper et al. (1980)  suggested that thermal sensitivity is the result of thermal shock/thermal changes transferred to the pulp through the restorative material. Hence, prevention of postoperative sensitivity is the most important jurisdiction for placing base beneath the amalgam restorations. Spierings et al. (1984)  suggested that cavity preparation and restoration may result in thermal loading over pulp with subsequent pulpal irritation resulting in hyperemia and pulpitis. Cox (1987)  reported that zinc phosphate cement is very acidic after mixing that along with poor sealing properties and bacterial invasion may be responsible for pulpal inflammation and postrestorative sensitivity.
The initial sensory response is quite rapid in comparison with time it takes for heat/cold to diffuse through the dentinal tissues to the pulpodentinal junction that earlier was thought to be due to direct stimulation of Aδ nerve fibers. But the nerve fibers do not penetrate dentin to an appreciable distance.  According to Brannstrom's hydrodynamic theory, pain or sensitivity to thermal changes is due to fluid shift in dentinal tubules that physically distort Aδ fibers, which lie close to the odontoblast layer. 
Postoperative sensitivity is due to permeability of dentin that increases with exposed dentinal tubules on cavity preparation. More permeable the dentin more is the sensitivity. Hence, effective sealing of dentinal tubules is required to reduce postrestorative sensitivity. Effective sealing of dentinal tubules has been reported with dentin bonding agents due to hybrid layer formation hence reducing microleakage/postrestorative sensitivity. 
Using a zinc phosphate base/dentin bonding agent beneath the amalgam restorations a mechanical barrier against the penetration of microorganisms is formed and by sealing the dentinal tubules permeability of dentin is reduced. Significantly, more number of patients reported postoperative sensitivity with zinc phosphate base beneath the amalgam restorations than dentin bonding agent.
According to Brannstrom, the sensitivity is diminished within a few weeks due to partial occlusion of gap between restoration and cavity wall by corrosion products or accumulation of plasma proteins and cell remnants in dentinal tubules or both. Post operative sensitivity is comparatively less in restorations with dentin bonding agent when compared with zinc phosphate base because of formation of hybrid layer there was complete sealing of dentinal tubules, reduction in fluid movement in dentinal tubules and less micro leakage.  Restorations with zinc phosphate base showed more postoperative sensitivity that may be because of its acidic nature increasing pulpal inflammation or because of lack of adequate marginal seal.
| Conclusion|| |
In restorations with dentin bonding agent beneath amalgam, significantly less number of patients reported postoperative sensitivity. Significantly more number of patients with zinc phosphate base reported postoperative sensitivity. Postoperative sensitivity resolved earlier in restorations with dentin bonding agent compared to zinc phosphate base, and sensitivity resolves with time in both the restorations.
However, further long-term studies are still required to assess the effectiveness of the long-term sequelae of dentin bonding agent beneath the amalgam restorations.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]