Evaluation of Surface Roughness and Microbial Adhesion of Primary Esthetic Crowns: An In Vitro Study

ABSTRACT

Background

Surface roughness plays a crucial role in microbial adhesion and retention on dental crowns, contributing to secondary infections and the development of periodontal diseases through bacterial plaque accumulation. In treating pulpitis of primary teeth via pulpectomy, dental crowns are often used as full-coverage restorative solutions. Among the most widely utilized crowns are stainless steel and zirconia crowns. However, zirconia crowns present drawbacks, such as excessive tooth reduction and increased wear on opposing teeth, while stainless steel crowns (SSCs) pose esthetic limitations. A new alternative, Edelweiss crowns, made from laser-sintered barium and vitrified composite, is gaining attention. These crowns offer esthetic appeal, biocompatibility, reduced tooth reduction, high flexural strength, and minimal abrasivity against opposing natural teeth.

Aim

This study aimed to assess the microbial adherence and surface roughness of primary esthetic crown (Edelweiss crowns) following simulated toothbrushing.

Materials and methods

About 10 pediatric posterior Edelweiss crowns were subjected to surface roughness analysis using a stylus profilometer. The crowns underwent 10,000 brushing cycles in a toothbrush simulator (ZM3.8 SD-Mechatronik). Surface roughness measurements were recorded before and after brushing. To evaluate microbial adhesion, the crowns were incubated with Streptococcus mutans suspension, and colony-forming units (CFUs) were quantified pre- and postbrushing simulation. The data were analyzed statistically using Statistical Package for the Social Sciences (SPSS) software (version 29).

Results

The average surface roughness (Ra) values pre- and postbrushing were 10.517 and 7.541 µm, respectively. The average CFU of S. mutans on the crowns decreased from 1 × 10⁸ CFU/mL prebrushing to 3 × 10⁷ CFU/mL postbrushing.

Conclusion

Edelweiss crowns demonstrated a reduction in both surface roughness and microbial adhesion after simulated brushing, suggesting that they may help reduce the risk of gingival infections in pediatric patients while providing durable full coronal restorative outcomes.

Clinical significance

Edelweiss crowns represent a valuable alternative to traditional crowns in pediatric dentistry in terms of surface roughness and microbial adhesion.

How to cite this article

Shabnam TI, Pooja VR. Evaluation of Surface Roughness and Microbial Adhesion of Primary Esthetic Crowns: An In Vitro Study. Int J Clin Pediatr Dent 2025;18(6):683–687.

INTRODUCTION

Tooth decay in children can lead to irreversible pulpitis or periapical inflammation, affecting the dental pulp and resulting in functional impairments. The prevalence of dental caries varies on the basis of socioeconomic factors¹ and parental awareness, directly influencing the need for timely restorative care.^2,3 In pediatric dentistry, the primary objectives are to preserve tooth structure, minimize damage from caries, and maintain pulp vitality.⁴ When treating pulpitis in primary teeth through pulpectomy, full-coverage dental crowns are commonly used to protect and restore the tooth.

Stainless steel crowns (SSCs) have been the standard in pediatric restorative care due to their clinical effectiveness,⁵ but they lack esthetic appeal.⁶ In response to this, prefabricated SSCs and nano-zirconia-coated crowns have gained popularity for their excellent abrasion resistance.⁷ However, the increasing demand for more esthetic restorations has led to a rise in the use of prefabricated zirconia crowns. Despite their esthetic benefits, zirconia crowns come with significant drawbacks. The large pulp chambers and prominent pulpal horns of deciduous teeth require more aggressive tooth reduction for zirconia crown placement, which increases the risk of pulpal exposure. Additionally, zirconia crowns cannot be crimped, necessitating longer preparation and fitting times, while subgingival preparation margins often cause gingival hemorrhage, potentially jeopardizing crown retention.⁸

To address these challenges, Edelweiss crowns, made from laser-sintered barium and vitrified composite, offer an innovative solution. These crowns combine esthetic appeal with functional advantages, requiring less invasive tooth preparation compared to zirconia crowns. Furthermore, they are biocompatible, nonabrasive to opposing teeth, and possess antibacterial and plaque-resistant properties, making them ideal for both immediate and long-term restorative use in pediatric patients.⁹

An ideal crown for pediatric use should not only provide mechanical strength and durability but also be esthetically pleasing and biocompatible. The longevity and performance of these crowns, along with the preservation of pulpal health, are influenced by the extent of bacterial adherence to the crown surface. The presence of bacterial plaque due to the colonization of Streptococcus mutans, is a key factor in the development of dental caries and periodontal diseases.^10,11 Surface roughness directly impacts microbial adhesion; rougher surfaces promote greater bacterial retention. The roughness of dental materials is typically quantified using the Ra (average roughness) value, with smoother surfaces generally leading to reduced microbial colonization.¹² Therefore, selecting crown materials that minimize surface roughness and microbial adhesion is critical in preventing secondary infections.

Hence, the aim of this study was to assess the microbial adherence and surface roughness of primary esthetic crowns (Edelweiss crowns) after artificial brushing simulation.

MATERIALS AND METHODS

Study Setting

The current in vitro study was done in Saveetha Dental College after approval from the Institutional Review Board.

Specimen Preparation

Utilizing the G*Power software, the sample size was determined to perform independent t-tests on one group. The results showed that n = 8 was the minimum sample size needed to obtain a power of 0.90 with an α error of 0.05. To mitigate sampling mistakes, additional samples were included leading to n = 10 sample size. Edelweiss crowns (n = 10) made of laser-sintered barium and vitrified composite were used for this study. The crowns were inserted with putty for stability.

Surface Roughness

The surface roughness on the buccal surface of the crowns was measured using a stylus profilometer (Mitutoyo SJ-310 stylus profilometer)¹³ containing a tip that is 2 μ and 60° angulated (Fig. 1). Then, the buccal surface of the Edelweiss crown samples was set up on die stone for better retention, while brushing in a simulator with a toothbrush (ZM3.8 SD Mechatronik) with a minimum pressure of 3 N. A total of 10,000 cycles of brushing at the speed of 30 mm/s and distance of 8 mm was done, depicting 1 year of brushing (Fig. 2).¹⁴ Following the brushing simulation, the surface roughness was assessed once again, and the results were compared. Surface roughness is measured on the basis of three parameters: (1) Ra, (2) Rq, and (3) Rz which provides the surface data as two dimensional, three dimensional, and peaks and valleys, respectively.

Fig. 1:

Crown sample subjected to surface roughness evaluation using stylus profilometer

Fig. 2:

Crown sample subjected to brushing simulation

Microbial Adhesion

Prior to assessing S. mutans adhesion, the crowns were chemically sterilized using 70% ethanol for 20 minutes. In a beaker, artificial saliva was prepared, and the specimens were placed in it.¹⁵ The current study employed clinical samples of S. mutans that were collected from Saveetha Dental College in Tamil Nadu, India. In bovine serum albumin (BSA) broth culture, bacteria were routinely cultivated at 37°C in a shaking incubator (100 rpm) for 48 hours. The bacterial suspension was then added to the beaker containing artificial saliva and was incubated at room temperature for 5 hours. The specimens were then flushed with saline and isolated in different containers with 5 mL of saline. A total of 50 μL from each container was taken and streaked onto petri dishes containing Mutans-Sanguis Agar and allowed to incubate for 24 hours (Fig. 3). This procedure was done pre- and postbrushing, and colony-forming units (CFUs) were calculated both the times using the following formula:

Fig. 3:

S. mutans colonies formed on Edelweiss crowns after incubation for 24 hours

$$CFU/mL=\frac{\mathit{\text{No. of colonies}}\times \mathit{\text{dilution factor}}}{\mathit{\text{Volume of culture plates}}}$$

Statistical Analysis

A software application [IBM Statistical Package for the Social Sciences (SPSS) Statistics 29] was used to statistically evaluate the data. Data were presented as mean, standard deviation (SD), and independent t-test was done for surface roughness and bacterial adhesion. Pearson correlation was then done to assess the relation between surface roughness and bacterial adhesion postbrushing. A p-value of 0.05 or less was regarded as statistically significant.

RESULTS

Surface Roughness Evaluation

The mean surface roughness (Ra) before brushing was 1.93830 μm, while the postbrushing value decreased to 1.10690 μm, with a SD of 0.8 and 0.82, respectively. The Rq values were found to be 2.65370 and 1.63070 μm with a SD of 0.97 and 0.99 pre- and postbrushing, respectively. The Rz values were noted as 9.4450 and 5.54490 μm with SD of 4.5 and 3.2 pre- and postbrushing, respectively. According to the independent t-test, the reduction in surface roughness was statistically significant (Table 1). This indicates a marked reduction in surface roughness following brushing over 1 year, with brushing occurring twice daily. Figure 4 illustrates the surface roughness of Edelweiss crowns, as measured by a profilometer before and after simulated toothbrushing.

Table 1:

Surface roughness of crowns pre- and postbrushing simulation

Samples	Pre (μm)	Post (μm)	*p-value
Ra ± SD	1.93830 ± 0.8	1.10690 ± 0.82	0.03
Rq ± SD	2.65370 ± 0.97	1.63070 ± 0.99	0.03
Rz ± SD	9.4450 ± 4.5	5.54490 ± 3.2	0.04

Ra, average roughness; Rq, root mean square roughness; Rz, peak and depth average roughness; SD, standard deviation; *p-value < 0.05

Fig. 4:

Depicting the surface roughness of crowns pre- and postbrushing simulation

Microbial Adhesion Assessment

The CFU/mL of S. mutans were assessed before and after brushing, as shown in Table 2. The results reveal a significant decrease in microbial adhesion postbrushing, with a p-value of 0.0002. The mean microbial adhesion before brushing was 1 × 10⁸ CFU/mL, while the postbrushing value dropped to 3 × 10⁷ CFU/mL, reflecting a substantial reduction.

Table 2:

Mean CFU pre- and postbrushing simulation

Samples	Pre (CFU/mL)	Post (CFU/mL)	*p-value
Mean	1 × 108	3 × 107	0.0002
SD	0	48304096.38	0.0002

*p-value < 0.05

Correlation between Surface Roughness and Microbial Adhesion

The Pearson correlation analysis revealed a positive correlation between postbrushing surface roughness and microbial adhesion, with an r² value of 0.003. This indicates that as surface roughness decreases postbrushing, microbial adhesion is also reduced, reinforcing the efficacy of Edelweiss crowns in minimizing bacterial accumulation.

DISCUSSION

Surface roughness of dental crowns can cause surface deformations, plaque buildup, food accumulation, stains, and oral microbial adherence by increasing the surface area of the crown, which can further lead to tooth decay and periodontal diseases.¹⁶ Among oral pathogens, S. mutans is the most predominant in causing caries and further failure of restorations. Therefore, a perfect crown should have less surface roughness and microbial adhesion. This study assessed these vital characteristics of newly popularized Edelweiss crowns.

Brushing is known to produce surface texture variations depending upon the technique, frequency, force, and types of bristles of the brush used in the process. On the tooth surface, brushing tends to create minor abrasions. In this study, there was a significant decrease in the surface roughness of Edelweiss crowns postbrushing. Since the simulated toothbrushing abrasion is a significant in vitro abrasion component and may mimic a clinical situation, it is regarded as an established model in the literature. It has been stated that an individual completes around 15 cycles of brushing per session. Consequently, by practicing dental hygiene that involves brushing twice a day for a year, 10,000 cycles are completed.¹⁷ The current study was done as per the same guidelines, and the results obtained were correlated with brushing twice for 1 year. A study conducted by Monteiro ad Spohr in 2015 has shown that higher the cycles of brushing, higher is the variation in surface roughness.¹⁸ Studies conducted previously that compared various brands of pediatric crowns¹⁹ have not described the effect of brushing on the surface roughness and associated microbial adhesion on the crown structures, which is the main highlight of the current study.

Mean Ra pre- and postbrushing as recorded by the surface profilometer was found to be 1.94 and 1.11, respectively. The laser sintering of barium glass to create Edelweiss crowns can confer abrasion resistance of the crowns to brushing. Sintering increases the density of the crown, making it less prone to surface roughness.²⁰ Previous study by Yuan et al. that assessed the surface roughness of zirconia and other ceramic crowns [lithium disilicate computer-aided design (CAD)] showed that there was significant increase in surface roughness postbrushing.²¹ Limited literature is available for comparison of the surface roughness of pediatric esthetic crowns pre- and postbrushing. A study by Walia et al. showed that the surface roughness seemed to be lesser in polished prefabricated pediatric zirconia crowns in comparison with polished-glazed primary crowns.²² In comparison with composite-based restorative crowns, ceramics seemed to have a lesser increase in surface roughness postbrushing.²³

It has been found that S. mutans is the most prevalent bacteria in dental plaque.²⁴ It exhibits great adherence to all oral surfaces and is pathogenic due to its acidogenic and aciduric features.²² Although in vitro research has demonstrated that it does not replicate every characteristic of natural saliva, in order to standardize, artificial saliva is used.²⁵ The current study demonstrated the positive correlation between surface roughness and microbial adhesion. Higher surface roughness values indicate higher amounts of microbial (S. mutans) colonies formed. The bacterial adhesion prior to brushing was found to be 1 × 10⁸ CFU/mL which dropped to a mean of 3 × 10 CFU/mL. Previous studies have provided results that substantiate the results of the present study. One study reported by Aykent et al. in 2010 observed a positive link between the surface roughness and bacterial adherence of restorative materials polished using various processes showed similar results.²⁶ The current study showed that microbial adhesion (CFU/mL) decreased postbrushing as the surface roughness had also decreased. Go et al. assessed the surface roughness and microbial adhesion of pediatric crowns after polishing, and the results showed that reduced surface roughness had less microbial adhesion.²⁷

Study Highlights

To our knowledge, this is the first study to examine the surface properties of pediatric Edelweiss crowns. The simulated brushing environment effectively reproduced oral abrasive factors, resulting in a significant reduction in surface roughness and microbial adhesion.

Study Limitations

The study's in vitro design did not consider real-life factors, such as saliva composition, dietary influences, and varied oral hygiene practices. The sample size was limited, which may affect the generalizability of the results.

CONCLUSION

Edelweiss pediatric prefabricated crowns offer an innovative solution for restoring carious deciduous teeth, combining esthetics, minimal invasiveness, and long-lasting durability. This study demonstrated that the surface roughness of Edelweiss crowns significantly decreases after exposure to simulated abrasive forces, such as brushing, which correlates with reduced microbial adhesion. These findings suggest that Edelweiss crowns are not only effective in preserving tooth structure but also in minimizing the risk of secondary infections due to reduced plaque retention.

Clinical Significance

Edelweiss crowns represent a valuable alternative to traditional ceramic and composite restorative materials in pediatric dentistry. Their reduced surface roughness postbrushing helps limit bacterial colonization, particularly of S. mutans, which plays a key role in caries development. These crowns can be considered long-lasting, biocompatible, and tooth-preserving, making them an excellent option for full-coverage restorations in primary teeth. Future clinical studies could further validate these findings by evaluating additional surface properties, such as color stability and hardness, enhancing their application in daily pediatric practice.

ORCID

Shabnam TI https://orcid.org/0009-0006-3575-4197

Pooja VR https://orcid.org/0000-0003-4576-3071