|Year : 2012 | Volume
| Issue : 3 | Page : 206-211
Comparative study on the microbial adhesion to preveneered and stainless steel crowns
Waleed M Bin AlShaibah, Fatma A El-Shehaby, Norhan A El-Dokky, Ala'a R Reda
Department of Pediatric Dentistry, BDs, Cairo University, Cairo, Egypt
|Date of Web Publication||21-Dec-2012|
Waleed M Bin AlShaibah
24903 Jeddah 21456, Kingdom of Saudi Arabia
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Context: The extensive plaque formation on dental restorations may contribute to secondary caries or periodontal inflammation. Therefore, it is important to know how different types of dental restorations may prevent or promote the accumulation of microorganisms. Aims: The aim of this in vivo study was to evaluate the adhesion of Streptococcus mutans to preveneered and stainless steel crowns (SSCs) and to evaluate the effects of these restorations on the gingival health and oral hygiene. Materials and Methods: Twenty patients (age 3-5 years) were selected from the outpatient clinic of the pedodontics department, Faculty of Oral and Dental Medicine, Cairo University. The selected patients had (dmf) index for primary dentition ≤4, including lower right and left first primary molars. Each tooth was pulpotomy-treated and restored with either type of crowns (split-mouth technique). Then, ten swabs from the buccal mucosa, preveneered crown, and SSC surfaces were taken from each patient. Also, the gingival index (GI) and oral hygiene index (OHI-S) were measured at different times during the study. Mitis Salivarius Bacitracin agar (MSBA) was used as a selective medium for S. mutans growth. MSBA plates were taken in candle jar and incubated aerobically in 37°C for 48 h. Finally, bacteria were counted and expressed in colony forming unit (CFU). Results: After 1, 2, and 4 weeks, mucosa and crown swabs of preveneered crown showed statistically significant higher mean CFU counts than SSC. Through the whole study period, the two restorations revealed a statistically significant decrease in mean CFU counts. Also, there was a statistically significant positive (direct) correlation between OHI-S, GI, and S. mutans counts on both restorations. Conclusions: The adhesion of S. mutans to preveneered crowns was higher than to SSC. Full mouth rehabilitation led to significant decrease in S. mutans count in the short term. An increase in S. mutans counts is associated with an increase in OHI-S and GI.
Keywords: Preveneered crown, primary teeth, stainless steel crown, Streptococcus mutans
|How to cite this article:|
Bin AlShaibah WM, El-Shehaby FA, El-Dokky NA, Reda AR. Comparative study on the microbial adhesion to preveneered and stainless steel crowns. J Indian Soc Pedod Prev Dent 2012;30:206-11
|How to cite this URL:|
Bin AlShaibah WM, El-Shehaby FA, El-Dokky NA, Reda AR. Comparative study on the microbial adhesion to preveneered and stainless steel crowns. J Indian Soc Pedod Prev Dent [serial online] 2012 [cited 2020 Feb 27];30:206-11. Available from: http://www.jisppd.com/text.asp?2012/30/3/206/105012
| Introduction|| |
Stainless steel crowns (SSCs) were introduced to pediatric dentistry by Humphrey in 1950.  Since that time, SSCs have become an invaluable restorative technique for the treatment of badly broken down primary teeth. The superiority and durability of SSCs over multi-surface amalgam and other restorations in the primary dentition has been documented in the literature.  Unfortunately, SSCs offer poor esthetics and some parents reported that they would rather have incisors extracted if SSCs are the only restorative option.  Because crowns play a crucial role in restoring a child's carious anterior teeth, esthetic alternatives to SSCs have been developed.  Preveneered crowns resolve some problems associated with SSCs, open-faced crowns, and composite strip crowns, and serve as a solution to restore severely carious primary incisors. Preveneered crowns were introduced to dentistry in the early 1990s. Preveneered crown is a traditional SSC with mechanically or chemically bonded esthetic material covering one or more surfaces of the crown. Preveneered crowns were initially developed for primary anterior teeth; later, preveneered crowns for primary molars became available. The objective of developing preveneered crown was to provide a convenient, durable, and esthetic solution to restore severely carious primary teeth.  Adhesion and colonization of oral microbes on tooth surfaces and restoratives is considered crucial in the development of secondary caries and periodontal disease.  In vivo and in vitro studies have shown that Streptococcus mutans is one of the bacteria isolated in plaque samples from natural and artificial surfaces during early stages of caries development. However, it is well known that the first stage of colonization by an organism involves adherence of the organism to a host surface. From this viewpoint, evaluation of S. mutans adhesion to tooth surfaces and restorative materials is of most importance for their success.  Among the properties required of materials used in dental restoration are those related to the surface, for example, roughness, free surface energy, surface tension, wettability, hydrophobicity, hydrophilicity, electrostatic interactions, and microhardness are of clinical importance since they may affect plaque accumulation and staining. The higher the surface free energy, the higher will be the adhesion of microorganisms, and alternatively, the more hydrophobic the surface, the less microorganism adherence is expected.  The presence of saliva is known to change this scenario. The nature of the substratum may influence the formation and composition of the salivary pellicle, which later may then become more relevant than the surface properties of the dental material itself.  Inflammation of the surrounding gingival tissue is a problem frequently associated with SSC. The incidence of gingivitis has been reported to be higher around poorly fitting crowns than around the crowns considered to be well adapted.  Gingivitis adjacent to restorative materials is likely to be the result of bacterial plaque rather than direct mechanical irritation from the material. 
| Materials and Methods|| |
The tested materials used in this study were SSC (3M ESPE, Minnesota, USA, St. Paul) and preveneered crown (Kinder Krowns, Mayclin Dental Studio, Inc., Minnesota, USA, St. Paul). Twenty patients were selected from the outpatient clinic of the pedodontics department, Faculty of Oral and Dental Medicine, Cairo University. They fulfilled the following criteria: Free of systemic diseases, age between 3 and 5 years, the selected patient had (dmf) index for primary dentition (WHO 1987 criteria) ≤4, including lower right and left first primary molars, the tooth indicated for crown restoration, no history of antibiotic intake for the past 2 weeks, no history of fluoride treatment for the past 2 weeks, and signed informed consent form given by parents or guardian. Each tooth was pulpotomy-treated according to the guidelines of American Academy of Pediatric Dentistry  and restored with either type of crowns (split-mouth technique) [Figure 1]. Then, ten swabs from buccal mucosa facing the crowns (at the beginning and end of study) and from crowns surfaces (at the end of 1 st , 2 nd , and 4 th weeks) were taken from each patient. Also, the gingival index (GI) and oral hygiene index (OHI-S) were measured (four times and two times, respectively). Mitis Salivarius Bacitracin agar (MSBA) was used as a selective medium for S. mutans growth. MSBA plates were taken in candle jar and incubated aerobically in 37°C for 48 h. Finally, S. mutans were counted and expressed in colony forming unit (CFU). Data were presented as mean and standard deviation (SD) values. A logarithmic transformation (log 10 transformation) of each CFU count was performed to normalize the data before statistical evaluation because of the high range of S. mutans counts. Paired t-test was used to compare between the two types of crowns. Repeated-measures analysis of variance (ANOVA) was used for studying the changes by time within each group. Tukey's post-hoc test was used for pair-wise comparison between the means when ANOVA test was significant. Wilcoxon signed-rank test was used to study the changes by time in OHI-S due to the non-parametric distribution of OHI-S data. This test is the non-parametric alternative to paired t-test. Pearson's correlation coefficient was used to determine significant correlations between bacterial counts, OHI-S, and GI. The significance level was set at P ≤ 0.05. Statistical analysis was performed with SPSS 16.0® (Statistical Package for Scientific Studies; SPSS, Inc., Chicago, IL, USA) for Windows.
| Results|| |
S. mutans counts: Comparison between the two crowns
Before cementation, there was no statistically significant difference between mean CFU in the two groups. After 4 weeks, mucosal swab of preveneered crown showed statistically significant higher mean CFU counts than SSC [Table 1].
|Table 1: The means and standard deviation values of S. mutans count (log10 values of CFU) from mucosal and crown swabs before and after crown application|
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After 1, 2, and 4 weeks, crown swab of preveneered crown showed statistically significant higher mean CFU counts than SSC [Table 1].
Changes by time with each crown (mucosal swab)
There was a statistically significant decrease in mean CFU counts after 4 weeks for both SSC and preveneered crown. There was a statistically significant decrease in mean CFU counts after 4 weeks for both SSC and preveneered crown [Figure 2].
|Figure 2: Line chart showing changes after 4 weeks in mean log10 values of CFU of S. mutans count|
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Changes by time with each crown (crown swab)
Stainless steel crown
There was a statistically significant decrease in mean CFU counts after 2 weeks. From 2 to 4 weeks, there was non-statistically significant decrease in mean CFU counts. Through the whole study period (from 1 to 4 weeks), there was a statistically significant decrease in mean CFU counts.
There was a statistically significant decrease in mean CFU counts after 2 weeks. From 2 to 4 weeks, there was non-statistically significant decrease in mean CFU counts. Through the whole study period (from 1 to 4 weeks), there was a statistically significant decrease in mean CFU counts [Figure 3].
|Figure 3: Line chart showing changes by time in mean log10 values of CFU of S. mutans count|
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Oral hygiene index-S
There was no statistically significant change in mean OHI-S after 4 weeks.
Comparison between the two crowns
At the first visit, there was no statistically significant difference between mean GI with the two crowns.
After 1, 2, and 4 weeks, preveneered crown showed statistically significant higher mean GI than SSC [Table 2].
|Table 2: The means and standard deviation values for the comparison between GI with the two types of crowns|
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Correlation between OHI-S and bacterial counts
There was a statistically significant positive (direct) correlation between OHI-S and bacterial counts. An increase in bacterial counts was associated with an increase in OHI-S.
There was a statistically significant positive (direct) correlation between OHI-S and bacterial counts. An increase in bacterial counts was associated with an increase in OHI-S.
Correlation between GI and bacterial counts
There was no statistically significant correlation between GI and bacterial counts at the first visit (before cementation). There was a statistically significant positive (direct) correlation between GI and bacterial counts after 1, 2, and 4 weeks. An increase in bacterial counts was associated with an increase in GI.
There was a statistically significant positive (direct) correlation between GI and bacterial counts through all periods. An increase in bacterial counts was associated with an increase in GI.
| Discussion|| |
The ideal restorative technique should assure strength, durability, esthetics, and efficiency in placement.  Many of the currently available restorative regimens fail to fulfill one or more of the goals mentioned above. Most efforts have been directed to improve esthetics for primary anterior teeth. Restorative techniques currently in use to treat these teeth include composite strip crowns, polycarbonate crowns, open faced stainless steel crowns, and commercially veneered SSCs. Each of these techniques presents technical, functional, or esthetic compromises that complicate their efficient and effective use.  Less effort has been taken in finding an esthetic solution for primary posterior teeth, probably based on these difficulties.  In the last decade, esthetic crowns for primary molars appeared on the market, definitely an asset if they could keep the advantages of the conventional SSC. In this study, Kinder Krowns (KK) was selected for testing due to the growing interest in esthetic restorations. , SSCs have been the easiest placed and most durable restoration for severely decayed primary teeth, outperforming amalgam and composite.  Patients were carefully selected according to the inclusion criteria, in order to standardize the clinical situation. Patients were free of systemic diseases which may lead to increase the microbial adhesion and have an effect over the gingival health. ,, Patients had no history of antibiotic intake for the past 2 weeks, which was recommended by Fukuda et al, Crown et al ,, who found that the composition of normal commercial bacteria of oropharynx and nose (viridans streptococci) may be disrupted by the frequent use of broad-spectrum antibiotics. Patients had no history of fluoride treatment for the past 2 weeks as Killian et al , reported that fluoride does not significantly influence the bacterial composition of plaque, but higher levels of fluoride could eliminate susceptible microorganisms and modify the plaque ecosystem. A split-mouth study design was used, as both preveneered and SSCs would be subjected to a similar oral environment and comparable hygiene habits.  The study was limited to mandibular primary first molars for financial reasons, as it would become too expensive to purchase starter kits for first and second primary molars of both arches. In this study, teeth preparation was done using the conventional technique,  except for the occlusal surface reduction, which was more extensive for the preveneered crowns than for the SSC (1.5 mm approximately), to allow for proper occlusion, as the esthetic crowns are thicker.  Regarding crown cementation, there is some evidence suggesting that the specific choice of cement does not significantly affect retention, the most important retentive components being derived from correct contouring and crimping of the crown.  So, glass ionomer cement was used as recommended by the manufacturer. The analysis of newly developed dental materials with regard to the accumulation of dental plaque is commonly used in dental material science. ,, S. mutans has been chosen as a representative oral bacterium as it is considered as one of the most abundant microorganisms in the oral cavity.  Moreover, S. mutans has been discovered in early dental plaque, and is regarded as one of the major causative agents for dental caries.  Also, adhesion of S. mutans to dental restorative materials is an important component in the etiology of secondary caries formation.  The isolation of S. mutans in this study was done with a sterile cotton swab in accordance with the report of Motisuki et al.  Who found that there was no difference between swab samples and pooled plaque because the non significance between both techniques in the detection of the bacteria in oral cavity. While taking the cotton swab samples, we wiped areas of the mouth including the surfaces of teeth, and it is likely that in addition to saliva, S. mutans from plaque were also collected in this sample. This may be the reason for the comparability between swab samples and plaque samples in detecting the first appearance of S. mutans in the mouth. Thus, one could argue that swabbing is the preferred method for detecting S. mutans because it combines both plaque and saliva samples and makes single plating possible. , In the present study, MSBA was used to detect and quantify S. mutans in the swab samples collected from the patients. ,,, MSBA is a selective medium for S. mutans because of the presence of sucrose and bacitracin at critical concentrations which are tolerated by S. mutans but not by other oral viridans streptococci.  In this study, the mucosal and crown swabs of preveneered crown showed statistically significant higher mean CFU counts than SSC, which agreed with the results of Padbury et al., who stated that the greater the amount of facial and occlusal bulge of an artificial crown, the more the plaque retained at the surface.  Also, these results are in accordance with those of Willershausen et al. who found a potential positive inhibitory effect of SSC restorations as compared to composite fillings with respect to the oral bacterial colonization. The role of surface properties such as chemical composition, surface free energy, and surface roughness may influence the adhesion of S. mutans, and this may explain the difference in the count of S. mutans on preveneered crowns and SSC.  Scheuerman et al. stated that the irregularities of polymeric surfaces promote bacterial adhesion and biofilm deposition, whereas the ultra-smooth surface does not favor bacterial adhesion and biofilm deposition. Also, if we take into account the point that SSC is highly polished and lustrous, it will give us better understanding of these results.  As regards to both restorations used in our study, there was a statistically significant decrease in mean CFU counts through the whole study period (from 1 st to 4 th week). This may be explained by the fact that all patients in our study sample had received full mouth rehabilitation under local anesthesia. These findings are in agreement with those of Litsas  who found that full mouth rehabilitation under general anesthesia produces a statistically significant decrease in S. mutans levels for at least 3 months.  The results of this study showed that there was a statistically significant positive (direct) correlation between OHI-S, GI, and S. mutans counts for both restorations. An increase in S. mutans counts is associated with an increase in OHI-S and GI. These results are in agreement with those of Sharaf and Farsi  who found that oral hygiene factor affected the gingival health. Children with poor oral hygiene showed higher incidence of gingivitis, while children with good oral hygiene maintained healthy gingivae around SSCs. Also, these findings are in agreement with those of Checchio et al. who concluded that individuals with poor oral hygiene showed pronounced tissue degeneration despite the quality of the SSC and that improperly contoured restorations predispose the gingivae to more severe inflammation. Again, Myers et al. reported that plaque will readily form on the surface of SSC regardless of the polishing procedures; therefore, oral hygiene procedures should be emphasized to minimize accumulation of plaque. Our results agree with those of Webber  who stated that preformed SSC can be used successfully to restore primary molars without adversely affecting the health of the gingival, provided that good status of the patient's oral hygiene is maintained. In this study, after 1, 2, and 4 weeks, preveneered crown showed a statistically significant higher mean GI than SSC. This result is in accordance with that of Fuks et al. who stated that GI was definitely superior in the conventional crowns. This was probably due to the bulk of the veneer on the esthetic crown, resulting in a thicker margin. The thickness of the preveneered crown walls was measured with a caliper and varied from 0.7 to 1.7 mm depending on the part of the surface checked, and it was much thicker than the SSC (about 0.2 mm). This difference could lead to plaque accumulation, as it seems to be more difficult to brush and keep the gingival margin area clean. 
| Conclusions|| |
Under the limitations of this investigation, the following conclusions could be drawn:
- S. mutans adhesion to preveneered crowns was significantly higher than to SSC.
- Full mouth rehabilitation led to significant decrease in S. mutans count.
- An increase in S. mutans counts is associated with an increase in OHIS.
- An increase in S. mutans counts is associated with an increase in GI.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2]