ORIGINAL RESEARCH |
https://doi.org/10.5005/jp-journals-10005-2608 |
Comparative Evaluation of Preformed Stainless Steel Crown’s Crazing at Different Autoclave Cycles
1-6Department of Pedodontics and Preventive Dentistry, Vivekanandha Dental College for Women, Namakkal, Tamil Nadu, India
Corresponding Author: Palanisamy Sowkarthicaa, Department of Pedodontics and Preventive Dentistry, Vivekanandha Dental College for Women, Namakkal, Tamil Nadu, India, Phone: +91 8675957507, e-mail: sowkarthicaap@gmail.com
ABSTRACT
Aim: The study aimed to assess and compare the crazing of preformed stainless steel (SS) crowns at various autoclave cycles.
Materials and methods: Around 15 SS crowns were subjected to zero (unsterilized), one, three, five, and seven autoclave cycles at 121°C, 15 psi for 20 minutes. After each autoclave cycle, the mesial surface of each crown from occlusal to cervical portions was examined under a 40× stereomicroscope. Crazing was evaluated using Wickersham’s criteria.
Results: One autoclave cycle does not produce any cracks, whereas the higher the number of autoclave cycles, the higher the cracks, which affects the prognosis of the SS crown treatment.
Conclusion: Surface alterations of SS crowns after different autoclave cycles were significant. So, preformed SS crowns should be discarded after sterilizing once or twice during clinical practice.
How to cite this article: Sowkarthicaa P, Mathian VM, Gawthaman M, et al. Comparative Evaluation of Preformed Stainless Steel Crown’s Crazing at Different Autoclave Cycles. Int J Clin Pediatr Dent 2023;16(S-1):S77–S80.
Source of support: Nil
Conflict of interest: None
Keywords: Autoclave, Infection control, Stainless steel crown
INTRODUCTION
Stainless steel (SS) crowns for deciduous molar teeth were introduced by Engel and popularized by Humphrey in 1950.1 These crowns are commonly used for complete coronal coverage in the management of multi-surface carious tooth and postendodontic restoration in pediatric and preventive dentistry.2
Preformed SS crowns are available in different sizes with preformed anatomy of primary molar teeth, which requires trimming, contouring, and crimping before final fitting into individual teeth.
During the process of fitting these preformed SS crowns to the prepared tooth, the selected crowns might not always fit perfectly. Despite this, multiple crowns are tried-in to obtain the accurate fit.3 During this trial procedure, crowns get contaminated with oral fluids that may possibly result in cross-infection.4 To overcome this, the tried-in crowns need to be sterilized/decontaminated before reusing in subsequent patients.5
The most common and widely accepted method of sterilization by dental practitioners is steam under pressure/autoclave, which might affect the surface of crowns.2
Till date, there are no studies that reported the influence of different sterilization cycles by autoclave on the surfaces of SS crown. The present study aimed to assess and compare the crazing of preformed SS crowns at different autoclave cycles.
MATERIALS AND METHODS
A total of 15 SS crowns were taken and subjected to five different groups:
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Group I: Zero autoclave cycle.
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Group II: One autoclave cycle.
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Group III: Three autoclave cycle.
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Group IV: Five autoclave cycle.
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Group V: Seven autoclave cycle.
The sterilizers used were steam autoclave at 121°C, 15 psi for 20 minutes. Surface alterations of SS crowns were assessed using a stereomicroscope at 40× magnification.
Selected 15 crowns were subjected to 40× stereomicroscope evaluation, that is, they were not sterilized (group I), then the same 15 crowns were sterilized under steam autoclave, that is, one autoclave cycle (group II) and examined under 40× stereomicroscope, followed by subjecting the same 15 SS crowns to three autoclave cycle (group III), five autoclave cycle (group IV), seven autoclave cycle (group V) and examined under 40× stereomicroscope after each cycle. For microscopic examination, the mesial surface of each crown from occlusal to cervical portion was examined in all 15 SS crowns as per groups. The crazing of SS crowns was assigned according to the area of the surface involved as per Wickersham’s criteria.
RESULTS
Table 1 and Table 2 show the descriptive statistics of the research data obtained after the conclusion of the study. As observed, zero autoclave cycles had no cracks (100%) after the autoclave cycle. One autoclave cycle had 86.7% no cracks and 13.3% of cracks in less than one-third of the surface, whereas three autoclave cycles had only 20% no cracks and 80% of cracks in less than one-third of the surface. A higher percentage of 93.3% of cracks in less than one-third of the surface was observed in five autoclave cycles. Seven autoclave cycles had a higher percentage (94.7%) of cracks up to one-half of the surface.
| Score | Criteria |
|---|---|
| 1 | A few isolated cracks involving less than one-third of the surface |
| 2 | Cracks involving one-third to one-half of the surface |
| 3 | Cracks involving greater than one-half of the surface |
| Frequency | Percentage | ||
|---|---|---|---|
| Zero autoclave cycle | No cracks | 15 | 100.0 |
| One autoclave cycle | No cracks | 13 | 86.7 |
| A few isolated cracks involving less than one-third of the surface | 13.3 | ||
| Three autoclave cycle | No cracks | 3 | 20.0 |
| A few isolated cracks involving less than one-third of the surface | 12 | 80.0 | |
| Five autoclave cycle | No cracks | 1 | 6.7 |
| A few isolated cracks involving less than one-third of the surface | 14 | 93.3 | |
| Seven autoclave cycle | A few isolated cracks involving less than one-third of the surface | 4 | 5.3 |
| Cracks involving one-third to one-half of the surface | 11 | 94.7 | |
After conducting a normality test using the Shapiro–Wilk test of the obtained data, nonparametric tests, Kruskal–Wallis test, was decided to use for overall group comparison and Mann–Whitney test for individual intergroup comparison as the data obtained was not normally distributed (heterogeneous distribution).
Table 3 shows the overall group comparisons, in which the highest mean rank value is for seven autoclave cycles (64.27) and the least for zero autoclave cycles (16.50).
| Ν | Mean rank | p-value | |
|---|---|---|---|
| Zero autoclave cycle | 15 | 16.50 | <0.001* |
| One autoclave cycle | 15 | 20.77 | |
| Three autoclave cycle | 15 | 42.10 | |
| Five autoclave cycle | 15 | 46.37 | |
| Seven autoclave cycle | 15 | 64.27 |
p-value based on Kruskal–Wallis test* = statistically significant (p < 0.05)
As depicted in Table 4, the individual intergroup comparison showed no statistically significant difference between zero autoclave cycle and one autoclave cycle (p = 0.539) statistically. A similar statistically insignificant difference is observed between three autoclave cycles and five autoclave cycles (p = 0.539). The rest of the autoclave cycles showed statistically significant differences among them.
| p-value | ||
|---|---|---|
| Zero autoclave cycle | One autoclave cycle | 0.539 |
| Three autoclave cycle | <0.001* | |
| Five autoclave cycle | <0.001* | |
| Seven autoclave cycle | <0.001* | |
| One autoclave cycle | Three autoclave cycle | 0.001* |
| Five autoclave cycle | <0.001* | |
| Seven autoclave cycle | <0.001* | |
| Three autoclave cycle | Five autoclave cycle | 0.539 |
| Seven autoclave cycle | <0.001* | |
| Five autoclave cycle | Seven autoclave cycle | <0.001* |
p-value based on Mann–Whitney test* = statistically significant (p < 0.05)
Figure 1 is the bar diagram depicting the overall data representation of the different autoclave cycles. Figure 2 is the graphical trend analysis of the different autoclave cycles preformed in the study.
Fig. 1: Bar graphical representation of the autoclave cycle
Fig. 2: Graphical trend analysis
The clinical significance or the clinical relevance of the study can be drawn based on Table 3 and Figure 2. Both the statistical test and graphical trend analysis show that a zero autoclave cycle does not produce any cracks, whereas a higher number of autoclave cycles produces much more cracks. This can affect the prognosis of treatment using an SS crown on a long-term basis.
DISCUSSION
Dental caries is the most prevalent disease affecting not only deciduous dentition but also permanent dentition.6 Though several efforts have been taken for its total eradication, it is still prevalent.7 These crowns are routinely used in endodontically treated deciduous teeth and young permanent teeth. The other indications for these crowns are managing multi-surface caries, fractured teeth, an abutment for space maintainers, teeth with developmental disturbances of enamel, and dentine.8
As dentists are exposed to numerous types of microorganisms which results in infectious diseases, whereas effective infection control procedures will avoid cross-contamination.
As the main objective of infection control is to protect the dental team and patients from infections (like human immunodeficiency virus, hepatitis B virus, syphilis, and influenza) during dental treatment and to provide a high standard of cross-infection control to prevent the transmission of infection.9
Engel and Humphrey described the SS crowns for deciduous molar teeth, which are preformed crowns that are adapted and cemented with a luting agent and these crowns are durable, less technique sensitive, and economical to patients.10 These SS crowns are reused in day-to-day practice in spite of the “conformité européenne” mark. Hence these crowns are expensive; it is not financially possible to consider them as a single use and discarded after trying-in in the patient’s mouth because of improper size/ill-fitting crown.1
Stainless steel (SS) crowns are selected after tooth preparation by the trial method. These tried-in crowns should be sterilized/disinfected before being placed into the box. During this trial procedure, tried-in crowns get contaminated with oral fluids, which causes cross-infection. Hence these crowns need to be decontaminated before using it in another patient.11
The decontamination process involves three phases, which include cleaning, sterilization/disinfection, and back to storage.12
Even though with the availability of many disinfection methods like sodium hypochlorite, glutaraldehyde, glass bead sterilizer, isopropyl alcohol, ultraviolet chamber, and quaternary ammonium compounds, the most commonly and widely accepted method of sterilization by pediatric dentists is an autoclave. Front loading autoclave with digital display was highly preferred due to the ease of use.3 But there is no data in the literature that how many autoclave cycles can be done for a single SS crown without any surface changes. However, it is mandatory to examine the surface alteration of SS crowns after sterilization in an autoclave and correlated with the multiple autoclave cycles.
Stainless steel (SS) crowns after one, three, five, and seven autoclave cycles were taken for evaluation because consecutive autoclave cycles would have given either similar or very minimal surface changes.
Wickersham et al. studied the fracture resistance and color change of two commonly available preveneered SS crowns (Nusmile and Kinder Krowns on four different sterilization techniques (two steam techniques, chemiclave, and glutaraldehyde solution) and the difference between the results of four sterilization method states that the two steam technique did not produce any changes in color and fracture resistance but chemiclave caused the significant color change and 2% glutaraldehyde reduced fracture resistance. Unlike their study, a constant temperature and time were used in this study on different cycles of autoclave to examine the surface changes on preformed SS crowns based on criteria are given by Wickersham et al. in 1998.13
Razavian et al. evaluated the preformed SS crowns’ crazing by different sterilization techniques of autoclave and concluded that the steam autoclaving had an undesirable effect on the SS crown surface due to the rise in temperature and pressure. Similar surface changes were found in this study on repeated autoclave cycles but with constant temperature and time.14
Padmanabh and Patel evaluated the physical-mechanical properties like color change, crazing, dimensional stability, and fracturing of preformed crowns (zirconia crowns, SS crowns, and preveneered SS crowns) on different sterilization and disinfection methods, which include slow sterilization, fast sterilization, chemical disinfectant and stated that no color change and fracture were found in crowns tested. Preveneered SS crowns were found to be most dimensionally stable than zirconia and SS crowns. But constant temperature and time are used to evaluate the surface changes of preformed crowns in this study.15
CONCLUSION
Preformed SS crowns supplied by the manufacturer do not exhibit any surface changes, whereas sterilization of preformed SS crowns at three autoclave cycles showed a significant increase in crazings. The results obtained in the present study state that preformed SS crowns should be discarded after sterilizing once or twice during clinical practice.
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