Revista de Odontologia da Universidade Cidade de São Paulo
2007 maio-ago; 19(2):160-4
TEMPERATURE EVALUATION DURING THE CAST POST REMOVAL WITH ULTRASONIC VIBRATION
AVALIAÇÃO DA TEMPERATURA DURANTE A REMOÇÃO DE PINOS FUNDIDOS POR VIBRAÇÃO ULTRA-SÔNICA
Elcio Yamamoto *
Angela Toshie Araki ***
Cássia Utiyama Takahashi *
Jose Antonio Lupi da Veiga **
Ivo Contin **
Tomie Nakakuki de Campos ****
ABSTRACT
Introduction: The damaging effects of the heat distribution to periodontal tissues concern every dentist.
The aim of this study is to evaluate the temperature generated during post removal with ultrasonic scaler.
Methods: A total of 20 extracted single root teeth were used and divided into 2 groups; GI(n=10), posts
cast in Cu-Al-Zn alloy (Goldent), and GII(n=10), posts cast in Pd-Ag alloy (Pors-On4). Thermocouples
were fixed around the medium and apical regions of the roots to obtain the temperature records during
the ultrasonic application and they were connected to a digital thermometer. Results: The ANOVA method
demonstrated no statistically significant difference, at level of 5%, between the regions, and between the
alloys used. In the medium region, the mean of temperature increase was 10.15 ± 1.82 °C, and in the
apical region was 9.04 ± 3.16oC. The PdAg alloy reached the highest amplitude of temperature elevation
(10.32 ± 2.41oC), while the CuAlZn alloy has reached a mean of temperature elevation of 8.87 ± 2.67oC.
Conclusions: It can be concluded that the removal of posts using the ultrasonic scaler produces significant
temperature variation no matter neither the employed alloy nor the researched region.
DESCRIPTORS: Dental pins – Post and core technique – Ultrasonics - Heat
RESUMO
Introdução: Os efeitos danosos da transmissão de calor para os tecidos periodontais são motivo de preocupação aos profissionais cirurgiões-dentistas. O objetivo deste estudo é avaliar a temperatura gerada
durante a remoção de pinos intra-radiculares com instrumentos ultra-sônicos. Métodos: Foram utilizados
20 dentes unirradiculares extraídos, divididos em 2 grupos: GI (n=10), pinos fundidos em liga de Cu-AlZn (Goldent), e GII(n=10), pinos fundidos em liga de Pd-Ag (Pors-On4). Termopares, conectados a um
termômetro digital, foram fixados ao redor dos terços médios e apicais das raízes, a fim de registrar a temperatura durante a aplicação do ultra-som. Resultados: Através do método de ANOVA não foi observada
diferença estatisticamente significante, a 5% de confiança, entre as regiões e entre as ligas utilizadas. No
terço médio, o aumento médio de temperatura foi de 10,15 ± 1,82 °C, e na região apical foi 9,04 ± 3,16
o
C. A liga de PdAg atingiu a maior amplitude de elevação de temperatura (10,32 ± 2,41 oC), enquanto que
a liga de CuAlZn alcançou média de elevação de temperatura de 8,87 ± 2,67oC. Conclusões: Concluiu-se
que a remoção de pinos com instrumentos ultra-sônicos produziu variação de temperatura significante,
independente das ligas metálicas utilizadas ou das regiões radiculares pesquisadas.
DESCRITORES: Pinos dentários – Ligas dentárias – Técnicas para retentor intra-radicular – Ultra-som –
Calor.
**** Master in Dental Prosthesis, School of Dentistry, University of São Paulo.
**** PhD, Professors, Department of Prosthodontics, School of Dentistry, University of São Paulo.
**** Phd’s Degree Student of Endodontics, School of Dentistry, University of São Paulo
**** PhD, Associate Professor, Department of Prosthodontics, School of Dentistry, University of São Paulo
160
Yamamoto E, Araki AT, Takahashi CU, Veiga JAL, Contin I, Campos TN. Temperature evaluation during the cast post removal with ultrasonic vibration. Revista de Odontologia da Universidade Cidade de São Paulo 2007 maio-ago; 19(2):160-4
INTRODUCTION
The main functions of cast post and core systems are
to provide additional retention and enable the reconstruction of the coronary portion of hardly damaged endodontically treated teeth, in order to make possible the
morphological and functional rehabilitation. However,
the removal of the posts and cores is necessary in some
clinical situations, for many reasons such as unsatisfactory extension or retention of the post, reduced diameter of canal prepare, when compared with its radicular
volume, insufficient sealing of root canal, associated or
not with periapical diseases (Hulsmann10, 1993). The
removal of cast posts and cores has to be very careful,
since any negligence can generate problems such as root
fracture or canal perforation.
Recent studies have described and analyzed the removal of cast posts using ultrasonic instrumentation
(Altshul et al.1, 1997; Buoncristiani et al.3, 1994; Hauman et al.9, 2003; Silva et al.17, 2004) and those techniques have been considered efficient and conservative to
the remaining tooth structures, and they have decreased
the risk the root wall perforation. The removal occurs
since the ultrasonic energy is transmitted to the metal
pin, generating a vibration that provides the fracture of
the cement (Buoncristiani et al.3, 1994).
However, this technique also presents inherent risks
and one of them is the increased temperatures transmitted to the surrounding periodontium and alveolar
bone.
Moorer and Wesselink12 (1982) have verified that the
temperature increased to 70oC, during the use of ultrasonic scalers in high potency, with irrigation inside the
canal. Cameron4 (1988) verified, during the use of ultrasonic units in endodontic procedures, that the temperature of the external walls of the root reached a highest
value of 40oC.
Saunders 16 (1990) in an in vivo study, has demonstrated that the heat generation at the root surface caused
a superficial resorption of the cement in 27.7% of the
cases, with evidences of ankylosis in 22.2% of them, after a period of 40 days. Further studies have also shown
the propensity of bone ankylosis after thermal injuries.
Campos et al.5 (1998) have studied the temperature generated during the removal of cast posts and cores
using high-speed burs and observed that the average of
temperature raise overtook the critical temperature for
bone tissue.
The purpose of this study was to evaluate the temperature generated at root surface during the removal
of posts and cores cast in Cu-Al-Zn alloy (Goldent LA.,
AJE, São Paulo, Brazil) and Pd-Al alloy (Pors-On4- Degussa, Germany), cemented with zinc phosphate cement,
in extracted teeth, using an ultrasonic unit.
MATERIAL AND METHODS
Twenty extracted human maxillary central incisors,
obtained at the Department of Oral Surgery of the Dentistry School of University of São Paulo, with similar forms and dimensions, were selected for this experiment. In
order to prevent the dehydration of the teeth, they were
stored in humid environment during the whole experiment. The roots were sectioned perpendicularly to their
axis, remaining 14mm from their apex.
The canal contents of each tooth were removed by
file instrumentation and had the apical portion enlarged
until a K type size 45 file (Dentisply Maillefer, Ballaigues, Switzerland), until 1mm from the anatomic apex,
using a 1% hypoclorite solution associated with EndoPTC* (Oficinallis, São Paulo, Brazil) during the whole
chemical-surgical preparation. Then, they were finally
irrigated according to Paiva and Antoniazzi13 (1993).
Initially, the root canals were enlarged with sizes 3
and 4 Peeso-Largo burs and it1 was made a standard
preparation with a tapered bur (302 Edenta, AG Dental, Rodukte, Switzerland) until the depth of 10 mm.
Patterns constructed in chemically achieved resin were
obtained by the direct technique from the prepared root
conducts. These patterns were invested and divided into
two groups: 10 posts were cast in Cu-Al-Zn alloy (Goldent LA.,AJE, São Paulo, Brazil) and 10 posts were cast
in Pd-Ag alloy (Pors-On4, Degussa, Hanau, Germany).
The canals were cleaned with a 1% sodium hypochlorite solution and dried with paper points. The posts
and cores were finished, adapted, received a treatment
of aluminum oxide, 125 µm, and finally cemented with
zinc phosphate cement (S.S.White, Rio de Janeiro, RJ,
Brazil), using a lentulo filler (Dentisply Maillefer, Ballaigues, Switzerland), in order to avoid air inclusion.
The specimens were kept in a 100% moist environment and all the experimental tests were done 48 hours
after the cementation.
In order to avoid the direct touch of the ultrasonic
equipment refrigeration to the root surface that could
1* Endo PTC composition: peroxide of urea (10% ), Tween 80
(15%) , Carbowax (75%)
161
Yamamoto E, Araki AT, Takahashi CU, Veiga JAL, Contin I, Campos TN. Temperature evaluation during the cast post removal with ultrasonic vibration. Revista de Odontologia da Universidade Cidade de São Paulo 2007 maio-ago; 19(2):160-4
Medium
third
Apical
third
Fig.1 Design of the acrylic box containing the specimen and the fixation of two thermocouples around the root
analysis of variance (alloy x region of the root), and the
comparisons between the mean factors were made using
the Student’s t- test. A p< 0.05 factor was accepted as
statistically significant.
modify the temperature register, the specimens were fixed in an acrylic box, and just the cervical portion of the
root was kept out, allowing the access of the ultrasonic
instrument over the cast pin.
The temperature was registered in two regions:
medium and apical thirds, with Cromel-Alumel thermocouples, fixed around the root with cyanoacrylate
adhesive (Fig.1) and connected to a digital thermometer
(Salvterm 1200K. Salcas, São Paulo, Brazil). This method was used by Campos et al 5 (1998).
The specimens were subjected to ultrasonic vibration
with an ENAC ultrasonic unit (OSADA ELETRIC Co,
Tokyo, Japan), based on a piezoelectric system, kept in
maximum power (about 30 KHz). It was registered just
the higher temperature reached in each minute during
the removal procedure.
The results were subjected to ANOVA statistical
RESULTS
Through the descriptive analysis of the data, it can be
observed that the group of pins cast in Pd-Ag (PORSON4) has presented mean of temperature elevation during their removal slightly superior than the group of pins
cast in Cu-Al-Zn (Goldent) (10.32 ± 2.41 °C and 8.87
± 2.67 °C, respectively. Table1). When it was compared
just the region of the root instead of the alloy, it could
observe that the medium third has shown the greatest
mean of temperature increase (10.15 ± 1.82 °C), while
the mean of temperature increase at the apical third was
9.04 ± 3.16 °C (Table 2).
Table 1 - Descriptive statistics of the values obtained from the temperature increase values (oC) during the removal of cast posts and cores with
ultrasonic instrument, comparing the employed alloys.
Alloy
Mean
St. Dev
Median
Minimum
Maximum
Q1
Q3
Pors-on 4 (Pd-Ag)
8.87
2.67
8.90
4.30
14.10
7.05
10.85
Goldent (Cu-Al-Zn)
10.32
2.41
11.05
5.20
15.00
8.20
11.95
Table 2 - Descriptive statistics of the values obtained from the temperature increase values (oC) during the removal of cast pins and cores with ultrasonic instrument, comparing the region the teeth where the measurement was realized.
Location
Mean
St. Dev
Median
Minimum
Maximum
Q1
Q3
Medium
Apical
10.15
9.04
1.83
3.16
10.60
8.65
6.50
4.30
12.80
15.00
8.92
7.05
11.30
11.76
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Yamamoto E, Araki AT, Takahashi CU, Veiga JAL, Contin I, Campos TN. Temperature evaluation during the cast post removal with ultrasonic vibration. Revista de Odontologia da Universidade Cidade de São Paulo 2007 maio-ago; 19(2):160-4
The analysis of variance of ANOVA has shown that
the interaction of the factors (alloy X region of the teeth) was not statistically significant (p=0.378). Through
the Student’s t-test with a significance of 5%, it was also
observed that there is no difference between the mean
values of temperature increase related to the alloy that
was employed (p=0.079) nor between the region of the
teeth (p=0.185).
DISCUSSION
Many authors have studied the changes occurred at
the tissues induced by the temperature elevation. Matthews and Hirsch 11 (1972) observed that at a temperature level around 56°C occurred the denaturation of alkaline phosphatase. Eriksson et al.6 (1982) have observed
that at 53°C, it has occurred irreversible bone injury, after which healing occurred from the surrounding tissues.
In another study, Eriksson and Albrektsson7 (1983) have
affirmed that a temperature of 47°C during 5 minutes
has been the critical temperature level that was capable
to cause injuries for the bone tissue. Many other experiments have shown that the heat production inside the
canal can be transmitted to the external surface of the
root, and it is a considerable risk of damage to dentine,
periodontal membrane and alveolar surrounding bone
(Atrizadeh et al.2, 1971; Campos et al.5,1998; Saunders
and Saunders14, 1989; Saunders15, 1990; Saunders16,
1990).
The heat conduction in temperature range observed
in the present study is entirely a linear process (Fors et
al.8, 1985; Saunders16, 1990). Therefore, the influence of
the difference between the starting temperature and the
actual body temperature can be neglected, and the temperature rise observed in the experiment should be the
same as if the starting temperature had been 37°C. In
order to facilitate the extrapolation to conditions in vivo,
the results have been given as temperature elevations and
not as peak of temperature.
Through the obtained results, it was possible to
observe that all the experimental groups, no matter the
employed alloy nor the region of the teeth has reached
levels of temperature elevation that in an in vivo situation could reach values over 47°C, during the clinical
procedure of removal of pins and cores with ultrasound
instruments.
Although in an in vivo condition, the heat could be
rapidly dissipated by the micro vessels, bloodstream and
poor thermal conductivity of the periodontal membrane
and alveolar bone (Fors et al.8, 1985), and further clinical
implications are still not elucidated, it is presumed that
the heat generation during the removal of pins with ultrasound scalers can result in critical temperatures to the
dental and periondontal tissues.
CONCLUSIONS
Based on the used methodology, this study can conclude that the ultrasonic removal of cast posts and cores
produces a significant temperature variation to the bone
tissue, whatever the employed alloy or the researched region. However, its clinical implication requires further
investigations.
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Yamamoto E, Araki AT, Takahashi CU, Veiga JAL, Contin I, Campos TN. Temperature evaluation during the cast post removal with ultrasonic vibration. Revista de Odontologia da Universidade Cidade de São Paulo 2007 maio-ago; 19(2):160-4
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Recebido em: 07/04/2006
Aceito em: 28/02/2007