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Year : 2006  |  Volume : 9  |  Issue : 3  |  Page : 110-112
Effect of pulpal temperature changes on finishing and polishing of composites- An in-vitro study


Department of Conservative Dentistry and Endodontics, College of Dental Sciences, Davangere-577004, Karnataka, India

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   Abstract 

The aim of the study was to find the pulpal temperature changes during finishing of composite restorative material. 180 teeth were taken and divided into 3 groups with 60 teeth in each group. The 3 groups were again divided into six sub groups with ten teeth in each group. Class v cavities were made in all the teeth and a base of glass ionomer cement was given, and it was then restored with z250 composite. Apical 5 mm of all the teeth were cut and a thermocouple probe was then inserted into the canal till it reached the roof of the pulp chamber. Apical orifice was closed with silicone impression material. The teeth were immersed in a water bath to maintain a steady temperature of 36 C. Finishing was done in all the 3 groups with coarse, medium and fine grit discs respectively with Shofu super snap. In 6 subgroups, 4 were finished with continuous pressure and no water coolant at 4000 rpm, 6000 rpm, 8000 rpm and 10000 rpm. The other two subgroups were finished with intermittent pressure and no water coolant at 10,000 rpm while the other was finished with 10000 rpm in continuous pressure and water coolant. Results showed a lesser rise in temperature with the use of lower speeds, water coolant and intermittent pressure. Coarse discs produced more temperature rise when compared to medium and fine grit discs. The study concluded that finishing should he in lower speeds, with intermittent pressure and with the use of water coolants to reduce the rise in intra pulpal temperature.

How to cite this article:
Daniel JP, Shivanna V. Effect of pulpal temperature changes on finishing and polishing of composites- An in-vitro study. J Conserv Dent 2006;9:110-2

How to cite this URL:
Daniel JP, Shivanna V. Effect of pulpal temperature changes on finishing and polishing of composites- An in-vitro study. J Conserv Dent [serial online] 2006 [cited 2020 Aug 5];9:110-2. Available from: http://www.jcd.org.in/text.asp?2006/9/3/110/42383

   Introduction Top


Polishing of restorations without taking precautions for dissipating heat is dangerous to the pulp (Alpine et.al 1967) [1] . A significant elevation in temperature occurs as a result of friction. Sand paper discs or rubber cups run dry at high speeds can generate sufficient heat to damage the pulp. The generated heat can also cause enamel to fracture (Brown et.al 1978 ) [2] . Therefore polishing instruments are to be used intermittently at low speeds or in conjunction with coolants in order to reduce heat generation (Christensen and Dilts, 1968) [3] .

There is a less likely hood of pulpal damage when water is used as the coolant (Zach and Cohen 1962. 1965) [4],[5] . Marsland and Shovelton (1970) stated that immediate damage to the pulp was greater when air cooled than in water cooled teeth. Furthermore, with water cooled teeth, the removal of debris is improved (Lloyd et al 1978).

To ignore the cooling of the teeth while operating at higher speeds is an invitation to disaster. As Bodecker (1939) pointed out graphically, it is comparable with '`cooking the pulp in its own juice


   Methodology Top


The 180 teeth were randomly divided into 3 groups (coarse,medium and fine grit finishing discs of Shofu super snap), with 60 teeth in each group. All the three main groups were again divided into six subgroups with ten teeth in each group and were finished with Shofu super snap finishing discs, in the following manner.

Subgroup I: Ten teeth were finished without water coolant at 4000 rpm continuously for two minutes.

Subgroup II: Ten teeth were finished without water coolant at 6000 rpm continuously for two minutes.

Subgroup III: Ten teeth were finished without water coolant at 8000 rpm continuously for two minutes.

Subgroup IV: Ten teeth were finished without water coolant at 10,000 rpm, continuously for two minutes.

Subgroup V: Ten teeth were finished without water coolant at 10,000 rpm intermittently for two minutes.

Subgroup VI: Ten teeth were finished with water coolant at 10,000 rpm continuously for two minutes.

Class V cavities were made in all the teeth and a base of glass ionomer cement was given, and it was then restored with z 250 composite. Apical 5 mm of all the teeth were cut and a thermocouple probe was then inserted into the canal till it reached the roof of the pulp chamber. Apical orifice was closed with silicone impression material. The tooth was immersed in a water bath to maintain a steady temperature of 36C. Finishing was done in all the 3 groups with coarse, medium and fine grit discs respectively with Shofu super snap. In 6 subgroups, 4 were finished with continuous pressure and no water coolant at 4000 rpm, 6000 rpm, 8000 rpm and 10000 rpm. The other two subgroups were finished with intermittent pressure and no water coolant at 10,000 rpm while the other was finished with 10000 rpm in continuous pressure and water coolant.


   Results Top


Using water coolant at 10,000 rpm gave the lowest rise in temperature in all the three groups on finishing (p < .001). Increasing the speed of rotation from 4000 rpm to 10000 rpm gave a significant rise in temperature (p< .001). Intermittent pressure produced lesser rise in temperature when compared to continuous pressure application( p<.001).When using coarse flexible discs, there was a significant rise in temperature when compared to medium grit and fine grit finishing discs (p< .001).Results showed that 4000 rpm was the safest working speed for finishing composites without water coolant, as any speed of 6000 rpm or above can cause a temperature range above 41.6 0c, endangering pulp.


   Discussion Top


Thermogenesis is directly propotional to an increase in speed of a hand piece , the pressure applied , the area of instrument contact and the cutting time. A reduction of any of these factors or the adequate use of a coolant will reduce the heat production.

Water coolant if used in the point of contact between the disc and the restoration will cause a reduction in the pulpal temperature. The temperature of the water coolant used should not be above 35C. If the temperature of the coolant is more than 35 C, it can cause a rise in intra pulpal temperature, since the temperature of the water coolant is more than the temperature of the pulp. Water coolants, when used effectively at the point of contact between the disc and the tooth, can dissipate the frictional heat produced during the finishing procedure and thereby can reduce the inflammatory reaction of the pulp. Water has high heat capacity. Also the temperature of the water spray is cooler than the temperature of the pulp allowing a decrease in pulpal temperature. Intermittent pressure application reduces the time of contact the finishing disc comes in direct contact with the restoration. This in turn, reduces the rise in intra pulpal temperature As the speed of rotation increases, the frictional heat produced on the restorative surface increases giving a rise in intra pulpal temperature and causing inflammatory reactions in the pulp.

The limitation of this study was that it was done in vitro and so the blood circulation of pulp was not taken into consideration. If the study was in vivo, the blood circulation of the pulp could have to a limit, reduced the rise in pulpal temperature produced during the finishing of composite restorations.


   Conclusion Top


All the various factors like speed of rotation, the amount of pressure applied, use of water coolants, the grit of the finishing discs used , are all directly related to the rise in intra pulpal temperature during finishing of composite restorations.

 
   References Top

1.Alpin AW, Sorenson FW, Cantwell KR: Temperature Change In Dental Polishing: J Dent Res 1967; 46: 325.  Back to cited text no. 1    
2.Brown WS, Christenson DO, Lloyd BA: Numerical And Experimental Evaluation of Energy Inputs, Temperature Gradients and Thermal Stresses During Restorative Procedures JADA 1978; 96; 45 1.  Back to cited text no. 2    
3.Christensen G, Dilts WE: Thermal Change During Dental Polishing: J. Dent. Res 1968; 47: 690.  Back to cited text no. 3    
4.Zach L , Cohen G : Thermogenesis in Operative Dentistry : Comparison of Four Methods : J Prosthet Dent 1962; 12: 977 984.  Back to cited text no. 4    
5.Zach L, Cohen G: Pulp Response to Externally Applied Heat: Oral Surg 1965; 19: 515 530.  Back to cited text no. 5    

Top
Correspondence Address:
Jaya P Daniel
Department of Conservative Dentistry and Endodontics, College of Dental Sciences, Davangere-577004, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-0707.42383

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    Abstract
    Introduction
    Methodology
    Results
    Discussion
    Conclusion
    References

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