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Int Chin J Dent 2007; 7: 69-74.

In vitro pulp chamber temperature rise during fabrication ofprovisional restorations on different types of teeth
Chao Xie, DDS, PhD, Zhong-yi Wang, DDS, PhD, Hui-ming He, DDS, PhD, and Ying
Han, MS
Department of Prosthodontics, College of Stomatology, The Fourth Military Medical University, Xi’an,
P. R. China
Purpose: This in vitro study compared the temperature rise in the pulp chamber during fabrication ofprovisional resinous restorations on three types of teeth by a direct method.
Materials and Methods: The tip of a thermocouple was positioned into the pulp chamber of thirty intact
extracted human teeth. Then the teeth were divided into three different tooth groups (incisor, premolar, molar)
and prepared for a complete crown. One poly(methyl methacrylate) (Quick Resin) and two composites (Protemp
3 Garant and Luxatemp) were measured and mixed according to manufacturer's instructions. The resin mixture
was placed into a poly(vinyl siloxane) impression and was then positioned on the prepared teeth. Temperaturechange in the pulp chamber during polymerization of the resin mixture was recorded. The results were analyzed
with a two-way ANOVA and the LSD test (α=0.05).
Results: Two-way ANOVA revealed that intrapulpal temperature changes were significantly influenced by toothtypes (p<0.01) and provisional resinous materials tested (p<0.01), but no significant interaction between thetooth types and the tested materials (p=0.575) was observed. LSD test revealed that the intrapulpal temperaturerise was higher when provisional resinous materials were fabricated on incisors than on premolars (p<0.01) or on
molars (p<0.01).
Conclusion: Within the limitations of this in vitro study, the results indicate that the poly(methyl methacrylate)
produced the higher exothermic reaction than the composite resins. Fabrication of provisional restorations
directly on incisors could induce higher temperature rise than on premolars or on molars.
(Int Chin J Dent 2007; 7: 69-74.)
Key Words: intrapulpal temperature rise, provisional restoration, thermocouple.

Introduction
Provisional restorations are an essential part of fixed prosthodontic treatment. Their purposes are to provide
stabilization of occlusion, protection of the teeth and the periodontal tissues, function, esthetic enhancement, andprovision of diagnostic information.1-2 Patients must be provided with a provisional restoration from initial toothpreparation until the definitive prosthesis is placed. When fabricating provisional resinous restorations using a
direct method, clinicians have to face two major problems. The first problem results from the presence of
uncured free monomer, which can be harmful to the pulp, especially when placed in direct contact with newly
cut dentinal tubules.3 Secondly, most of provisional resinous materials generate exothermic polymerization
reaction, which can cause a temperature rise in the pulp chamber. This temperature rise may injure the dental
pulp.4-7 In general, temperature increases more than 5.5˚C in the pulp lead to considerable damage, resulting in
15% of the pulps tested to lose vitality, according to Zach and Cohen.8
Previous in vitro studies have compared intrapulpal temperature rise during fabrication of provisional resinous
restorations.4,7,9 These results suggested the possibility of thermal damage to dental pulp and odontoblasts
during the setting of provisional resins. Moulding and Teplitsky10 suggested that intrapulpal temperature riseduring polymerization of provisional resinous materials were dependent on the type of provisional resin, and thetype of matrix used to retain the material on the tooth during polymerization. The poly(methyl methacrylate)(PMMA) resin produced significantly higher temperature rise than did for poly(vinylethyl methacrylate)(PVEMA), visible-light-polymerizing urethane dimethacrylate (UDMA) composite, and bis-GMA composite,with the UDMA exhibiting significantly less polymerization temperature rise than the other resins.6,11 When69

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Int Chin J Dent 2007; 7: 69-74.

provisional resins were used in combination with matrix made from siloxane and irreversible hydrocolloid
materials, the intrapulpal temperature rise could be reduced.7,10,11 The aim of this in vitro study was to compare
the temperature changes in the pulpal chamber during fabrication of provisional resinous crowns on different
types of teeth using a direct method.

Materials and Methods
A PMMA resin (Quick Resin) and two bis-GMA composites (Protemp 3 Garant and Luxatemp) were
evaluated in this study (Table 1).
Table 1.

Provisional resinous materials.

Trade name

Material type

Manufacturer

Lot number

Quick Resin

MMA-PMMA

Shofu Inc., Kyoto, Japan

Power, 060409; Liquid, 060517

Luxatemp

Bis-GMA composite

DMG, Hamburg, Germany

Base, 534515; Catalyst, 560401

Protemp 3 Garant

Bis-GMA composite

3M ESPE, Seefeld, Germany

Base, 227117; Catalyst, 223201

The methodology applied in this study was authorized by the Ethics Committee of the Fourth Military
Medical University. Thirty intact, freshly extracted human teeth were used in this study. The teeth wereseparated into three groups of 10 teeth each. To evaluate temperature changes in teeth with different dentin
thickness and different tooth structure, three different types of human teeth were selected (10 teeth of each type,i.e., maxillary incisors, maxillary premolars, and mandibular molars). In each group, teeth of homogeneous sizeand shape were selected to provide similar hard tissue structure and ensure equal distances from the pulp to thesurface of the tooth.
All the thirty teeth were sectioned with a cutting disk approximately 2 mm below the cementoenamel junction
perpendicular to the long axis of the teeth. The opening into the pulpal chamber from the radicular portions of
the teeth was enlarged as needed to insert the thermocouple wire. The pulpal chambers were cleaned of remnant
pulp tissues with a spoon excavator and sodium hypochlorite application for 1 minute. The pulp chambers of theteeth were rinsed with distilled water and air-dried. A J-type thermocouple wire (Omega Engineering Inc.,
Stamford, CT, USA) was insert into the pulpal chamber, touching the roof of the chamber. Silicone transfer
compound (Philips ECG Inc., Waltham, MA, USA) was then injected into the pulp chamber, surrounding andstabilizing the thermocouple in position. This compound facilitated the transfer of heat from the walls of thepulp chamber to the thermocouple. Before temperature measurements were made, radiographs were made of theteeth to ensure that tips of the thermocouples were in contact with the roofs of the chambers. After that, root
stubs of the teeth were secured to acrylic resin bases with an auto-polymerizing resin (Unifast LC; GC America,
Alsip, IL, USA). After complete polymerization of the acrylic resin, a polyether impression material (Impregum,
3M ESPE, Seefeld, Germany) of the tooth/resin base assembly was made using a custom tray. All the teeth werethen prepared for a metal-ceramic complete crown with a 1.5 mm shoulder, and the occlusal reduction was 2.0
mm. The acrylic resin base/prepared tooth/engaged thermocouple assembly was then submerged in a water bath
(Water Bath; Whip Mix Corp., Louisville, KY, USA) containing distilled water at a temperature of 37˚C. The
tooth was preheated and allowed to thermally equilibrate. The water bath was used to simulate intraoral
conditions.

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The provisional resinous materials tested were measured and mixed according to the manufacturer’s
instructions. For Quick Resin material, the ratio of the powder-liquid was standardized on a precision scale: 1 gof powder and 0.5 g of liquid were mixed in a disposable cup with a clean plastic spatula for 15 s. For Protemp
3 Garant and Luxatemp, the paste-to-paste ratios were mixed automatically proportioned with a special auto-mix
gun applicator provided by their manufacturers. The poly(vinyl siloxane) impression matrix was full-filled withthe mixed resinous materials and then positioned on the prepared tooth preparation.

All excess resinous

materials were removed from the margins of the tooth by the use of an explorer. The J-type thermocouple wire
was connected to a digital precision thermometer (XSTC, Beijing Kunlun Tianchen Instrument Technology Co.,
Beijing, P. R. China). The temperature rise in the pulpal chamber was recorded every 2 s over a 10-minuteperiod using the digital thermometer which read in 0.1˚C increments. Calibration of the thermometer was not
required. Specification accuracy was maintained without user adjustment. The collected data were monitored inreal time and stored in its memory before the data were transferred to the computer.

After complete

polymerization of the resinous material, the matrix was removed from the tooth, and the provisional crown was
retrieved. Each material was tested 10 times.
For each group, the temperature variation (∆T) was determined as the increase from baseline temperature to
the highest temperature recorded during the polymerization of resinous materials. Ten calculated temperaturechanges were averaged to determine the mean values in temperature rise. A temperature increase of less than
5.5˚C was considered favorable and set as the baseline according to Zach and Cohen.8 The values of each groupwere compared by two-way analysis of variance (ANOVA). The two factors analyzed were provisional resinous
material and tooth type. After the two-way ANOVA, the least significant difference tests (LSD test) were
performed for comparisons among groups at the 0.05 level of significance.

Results
Table 2 presents the descriptive statistics results, including the mean, standard deviation, minimum andmaximum values, and comparisons for tooth types and different provisional materials.
Table 2.

The descriptive statistic values of intrapulpal temperature changes during polymerization ofaprovisional materials on different types of teeth

Group

Tooth
type

Provisonal materials

Sample
size

ΔT

SD

Temperature
Minimum

Maximum

1

IncisorLuxatemp

10

4.27

0.25

3.9

4.6

A

2

IncisorProtemp 3 Garant

10

4.33

0.41

3.6

4.8

A

3

IncisorQuick Resin

10

10.84

0.87

9.8

12.1

C

4

Premolar

Luxatemp

10

3.90

0.35

3.2

4.4

A

5

PremolarProtemp 3 Garant

10

3.87

0.39

3.1

4.5

A

6

Premolar

Quick Resin

10

9.95

0.82

8.7

11.4

B

7

Molar

Luxatemp

10

3.90

0.19

3.6

4.2

A

8

Molar

Protemp 3 Garant

10

4.01

0.26

3.6

4.4

A

9

Molar

Quick Resin

10

10.09

0.91

8.9

11.5

B

Testb

a, ΔT indicates mean difference between maximum and minimum temperature values; SD, standard deviation;b, Group with different letters are significantly different from each other.

71

P-value

P<0.05

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Int Chin J Dent 2007; 7: 69-74.

For incisors, the average temperature rise in the pulp chamber ranged from 4.27˚C (Luxatemp, Group 1) to
10.84˚C (Quick Resin, Group 3). For premolars, temperature rise ranged from 3.87˚C (Protemp 3 Garant, Group5) to 9.95˚C (Quick Resin, Group 6). For molars, temperature increases ranged from 3.90˚C (Luxatemp, Group7) to 10.09˚C (QuickResin, Group 9).
According to two-way ANOVA, temperature rise in the pulp chamber varied significantly depending on the
different tooth types (p<0.01) and different provisional materials (p<0.01). ANOVA revealed no significant
differences for combination of tooth types and provisional materials (p=0.575). LSD test revealed statisticallysignificant differences among the groups (p<0.05). Quick Resin induced much higher intrapulpal temperaturerise than Protemp 3 Garant and Luxatemp did. However, there were no statistically significant differences
between Protemp 3 Garant and Luxatemp (Table 2).
When Quick Resin was used on maxillary incisors (Group 3), the temperature rise in the pulp chamber was
statistically significantly higher than it used on maxillary premolars (Group 6) and mandibular molars (Group 9).
This phenomenon did not happened to Protemp 3 Garant and Luxatemp. Although the temperature rise of thetwo bis-GMA composites used on maxillary premolars was higher than they used on maxillary premolars andmandibular molars, the differences were not statistically significant. The temperature rise plotted against time isdepicted in Fig. 1 for each material tested. A sudden decrease in temperature was measured when the preheated
tooth came in contact with the cold, freshly mixed resin within the poly(vinyl siloxane) matrix.

Fig. 1.

abcTemperature rise versus time of three provisional materials tested. Note initial decrease in temperaturecaused by contact with cold mixed resin. a, Luxatemp; b, Protemp 3 Garant; and c, Quick Resin.

Discussion
The thermal effect during the polymerization of provisional resinous materials is well known. A few ofstudies revealed temperature changes in pulpal chamber were affected by several factors including material
types6,11 and matrix types.7,10,11 In this in vitro study the heat generated during the fabrication of provisional
resinous crowns on different tooth types using a direct method were measured. Under the conditions of thepresent study, the PMMA resin produced much more intrapulpal temperature rise than the other two bis-GMA
composite resins on all the three types of teeth. Also, the temperature rise in pulpal chamber differed among thethree types of teeth. When provisional materials were used on maxillary incisors, the temperature rise in thepulp chamber was higher than those used on maxillary premolars and mandibular molars.

However, thedifferences were statistically significant only with Quick Resin (p<0.05). As far as Luxatemp and Protemp 3
Garant were concerned, the differences were not statistically significant (p>0.05) (Table 2). These findings werein accordance with the previous results.12,13
For the present comparative study, extracted adult incisors, premolars, and molars were selected to assess the72

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Int Chin J Dent 2007; 7: 69-74.

thermal changes in different tooth groups with different dentin thickness and dentin structure.14 Teeth withabnormally large or small pulp chambers were excluded from the study. This procedure was followed byelimination of any possible structural variables of teeth that may manifest as differences in the thermal
conductivity and specific heat. However, even after stringent selection, teeth exhibited some differences in toothmorphology, dentin structure and thickness. This may explain the temperature differences between the teeth
tested in the same group.15,16 On the other hand, the teeth used in this study were collected from an adult sample,
so the thermal conduction to the pulp chamber during polymerization procedures might have been limited
compared with the clinic situation. Therefore, one would expect to record higher temperature increases when
younger teeth are used for a similar study.
The remaining dentin thickness and its poor thermal conductivity was the critical factors in reducing theintrapulpal temperature rise for the present study.16 The thermal effect on the pulp tissue depends on thevariations in the dentin thickness of the pulp chamber.17 The incisors exhibit a higher risk of thermal damage
because of thinner dentin thickness on the labial side.12 Uzel et al.18 investigate the temperature changes in thepulp chamber during bracket bonding using different light sources. They found that all light sources produced
higher intrapulpal temperature rise in the incisor than in the premolar. Other researchers also considered thecomparison of tooth types.12,13 Unfortunately, to the best of our knowledge, there is no paper in the open
literature dealing with the effect of tooth types on the temperature changes in the pulp chamber during thepolymerization of provisional resinous materials.
Thus, 30 teeth selected stringently were divided into three tooth types of 10 teeth each in the present study.
Though the teeth in the same group exhibited some differences in remaining dentin thickness, the standard
deviation for temperature rise in same tooth type group was small compared to the mean value. This is probably
due to the fact that the dentin thickness was positive correlation with tooth size.19 After all the teeth wereprepared to gain a same size shoulder with 1.5mm thickness, the remaining dentin thickness of relatively bigger
tooth was larger than that of relatively smaller tooth. Simultaneously, the quantity of the provisional resinous
material used in relatively bigger tooth was also larger than that used in relatively smaller tooth. Tjan et al.9
indicated that the flow of heat through the dentin was inversely proportional to the remaining dentin thickness
and directly proportional to the amount of material used. Thus the quantity of heat flowing through the dentin
barrier to the pulp chamber of the same group tended to be equal during the setting of the same material.
Zach and Cohen8 demonstrated that a 5.5˚C intrapulpal temperature rise led to necrosis of the pulp in 15% ofteeth, an 11.1˚C rise resulted in necrosis of the pulp in 60% of teeth, and a 16.6˚C rise led to necrosis of the pulp
in 100% of teeth. These results as well as the findings of Pohto and Scheinin20 indicate that the criticaltemperature for irreversible damage to the pulp begins at 42-42.58˚C. The temperature rise resulting from thepolymerization process of the Quick Resin material ranged between 8.7˚C and 12.1˚C. Considering these crucial
values, the intrapulpal temperature rise detected in Quick Resin groups must be viewed as dangerous. Carefulmanagement should be required when using PMMA resin like Quick Resin for fabrication of provisional
restoration by the direct method.
It should be noted that this is an in vitro study and, like other in vitro studies, has some limitations. The
experimental design of the present study did not consider the effect of blood circulation in the pulp chamber andfluid motion in the dentinal tubules and surrounding periodontal tissues on promoting heat conduction in vivo,
limiting intrapulpal temperature rise. Further in vivo animal studies are necessary to verify the results of the73Xie et al.

Int Chin J Dent 2007; 7: 69-74.

present study.

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Correspondence to:Dr. Hui-ming He
Department of Prosthodontics, College of Stomatology, The Fourth Military Medical University
145 Changle Xi Road, Xi’an, 710032, P. R. China
Fax: +86-29-84776469 E-mail: xchy2006@fmmu.edu.cn
Received September 25, 2007. Accepted November 4, 2007.
Copyright ©2007 by the International Chinese Journal of Dentistry.

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