Evaluation of different sterilization and disinfection ...

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(NuSmile Primary Anterior Crown (NSC), Kinder Krowns (KK), Pedo Pearls (PP) and polycarbonate crowns (PC)) .... Mayclin Dental Studio, 2629 Louisiana Ave.
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ISSN 0970 - 4388

Evaluation of different sterilization and disinfection methods on commercially made preformed crowns YILMAZ Y.1, GULER C.2

Abstract The aim of this study was to evaluate the changes caused by different sterilization or disinfection methods on the vestibular surface of four commercially made preformed crowns using stereomicroscopy and scanning electron microscopy (SEM). Preformed crowns (NuSmile Primary Anterior Crown (NSC), Kinder Krowns (KK), Pedo Pearls (PP) and polycarbonate crowns (PC)) were sterilized and/or disinfected by one of the following techniques: no sterilization or disinfection (G1 control group); steam autoclaving at 134 °C (30 psi) for 4 min (G2); steam autoclaving at 134 °C (30 psi) for 12 min (G3); steam autoclaving at 121 °C (15 psi) for 30 min (G4); and ultrasonication in a bath containing 4% Lysetol® AF for 5 min at room temperature (chemical disinfection) (G5). Scanning electron micrographs of the crowns were taken before and after their sterilization or disinfection. The changes on the vestibular surface were then scored for the presence or absence of crazing, contour alteration, fracturing, and vestibular surface changes. The data were analyzed statistically using the chi-square test. No changes were observed before and after sterilization or disinfection in the stereomicroscopic evaluation of the vestibular surface of the crowns. However, all methods in which steam autoclaving was used to sterilize the crowns caused significant (P < 0.05) crazing and contour alterations of the vestibular surface of the crowns when they were examined by SEM. Chemical disinfection using an aldehyde-free disinfectant is the preferred method of disinfection for crowns that have been used previously in other dental patients. Keywords: Disinfection, preformed crowns, sterilization

(chemiclave sterilization) using formaldehyde vapor and a 2% gluteraldehyde solution. They reported that there were no changes on the vestibular surfaces of the crowns following these sterilization and disinfection methods.

Introduction Preformed crowns are still commonly used for complete coronal coverage in the treatment of severely carious, malformed or fractured primary anterior teeth. Before fitting the crown, the tooth is prepared by reducing its occlusal, aproximal and peripheral surfaces. During the fitting of these preformed crowns to the reduced tooth, the selected preformed crown might not always fit the prepared tooth properly, and the dentist will need to try differently sized crowns in order to gain the desired fit. During test fitting, unwanted crowns become contaminated with blood and saliva and also may carry many microorganisms such as human immunodeficiency virus or hepatitis B virus, which can cause infection if the crown is used in another patient.[1] Therefore, the direct and indirect contact surfaces of such crowns need to be sterilized and/or disinfected before their re-use in another patient.[2] Although there is much information about the sterilization and/or disinfected of dental prostheses,[3-9] there are only a few studies on the effect of the sterilization and/or disinfection on preformed crowns. Wickersham et al, [10] subjected commercially available preveneered stainless steel crowns (SSCs) to various sterilization and disinfection methods, such as steam autoclaving at various high temperatures and pressures and chemical sterilization

To date, there is no study which has reported changes in the surface texture of the veneer of the preformed crowns after sterilization or application of a disinfectant. Therefore, the objective of the present study was to evaluate the changes caused by sterilization or disinfection methods on the vestibular surface of four commercially-made preformed crowns using stereomicroscopy and scanning electron microscopy (SEM).

Materials and Methods For this study, 80 crowns were obtained from four different manufacturers [Table 1]. The study included one control group (G1) and the four experimental groups (G2 to G5) [Table 2]. The control group consisted of five crowns randomly chosen from each crown type. First, the selected crowns were examined under a stereomicroscope at x60 magnification. Second, the selected crowns were then sputter-coated with carbon using an ion coater (SEM Coating Unit E 500, POLARON Equipment Limited, Barcelona, Spain) before undergoing SEM. The vestibular surface of each crown was then examined and photographed from the incisal edge to the gingival edge (2 mm in width) using a scanning electron microscope (JSM-6400, JEOL, Tokyo, Japan). These micrographs were used as the reference data

1

Associate Professor, 2Research Assistant, Department of Pedodontics, Ataturk University, Faculty of Dentistry, ErzurumTurkey

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Pedodontic crown sterilization

Figure 1: (a) Control group for PC crowns; (b) Control group for NSC crowns; (c) Control group for KK crowns; (d) Control group for PP crowns

Figure 2: (a) Crazing in PC crowns after steam autoclaving at 134 oC at 30 psi for 12 min (G3); (b) Crazing in KK crowns after steam autoclaving at 134 oC at 15 psi for 30 min (G4)

Experimental Procedures and Assessment Details of the different sterilization or disinfection methods that were used in this investigation are summarized in Table 2.

to disclose the presence of changes on the vestibular surface after sterilization or disinfection. The crowns were cleaned by removing the carbon coating using a rotating brush without prophylaxis paste. Each crown in the control group was then returned to its original group of crown type. The four experimental groups consisted of five crowns randomly chosen from the four crown types.

All crowns in the four experimental groups were examined under a stereomicroscope at x60 magnification before and after a particular sterilization or disinfection method. 163

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Pedodontic crown sterilization

Figure 3: (a) Contour alteration in PC crowns after steam autoclaving at 134 oC at 30 psi for 4 min (G2); (b) Contour alteration in NSC crowns after steam autoclaving at 134 oC at 15 psi for 30 min (G4); (c) Contour alteration in PP crowns after steam autoclaving at 134 oC at 30 psi for 4 min (G2)

Scanning electron micrographs were taken of all crowns in the four experimental groups before and after a particular sterilization or disinfection method as described for the control group. The vestibular surfaces were then scored for the presence or absence of a change using the criteria of Wickersham et al,[10] with modifications. These criteria were crazing (internal cracks of vestibular surface), contour alteration (changes in vestibular surface contour such as melting, flow or flattening), fracturing (chipping) and vestibular surface changes (crazing + contour alterations). The scoring for each crown was performed under the stereomicroscope while a dental explorer was moved gently over the vestibular surface, and from scanning electron micrographs of the vestibular surface of each crown.

statistically significant differences between the effects of the sterilization or disinfection methods with respect to crazing, contour alterations, fracturing, and vestibular surface changes of the crowns. In addition, this statistical test was used to identify which type(s) of crown and/or treatment(s) was responsible for any observed differences. The critical value for statistical significance was set at P=0.05.

Results The strength of the agreement between the two assessments for each criterion was almost perfect (Kappa value = 0.9). No changes were observed after sterilization or disinfection in the stereomicroscopic evaluation of the vestibular surfaces of the crowns.

Data analysis To validate examiner reproducibility for assessing each criterion, all micrographs were re-evaluated after one week by the same examiner. Kappa statistics were used to measure the extent of agreement between the repeated measurements performed by the same examiner. The Chi-square test was used in order to determine whether there were any J Indian Soc Pedod Prevent Dent - December 2008

Micrographs of the vestibular surfaces of the crowns in the control and experimental groups are displayed in Figures 1-3 and the results of the evaluation of scanning electron micrographs of the vestibular surface changes of the crowns following sterilization or disinfection are summarized in 164

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Pedodontic crown sterilization Table 1: Crowns used for the study Product Name Polycarbonate crowns (PC) NuSmile crowns (NSC) Kinder krowns (KK) Pedo pearls crowns (PP)

Manufacturer 3M Dental Products St. Paul, MN 55144-1000,USA NuSmile Primary Crowns. 5524 Cornish, Houston, Texas 77007-4304,USA Mayclin Dental Studio, 2629 Louisiana Ave. S. St. Louis Park, MN. 55426,USA Pedo Pearls, 6111 FM 1960 West Suite 215 Houston, TX 77069,USA

Table 2: Sterilization and disinfection techniques Groups G1 G2 G3 G4 G5

Sterilization and disinfection techniques No sterilization or disinfection application, control group Steam autoclaving, 134 °C, 30 psi, 4 min, fast sterilization Steam autoclaving, 134 °C, 30 psi, 12 min, sterilization Steam autoclaving, 121 °C, 15 psi, 30 min, sterilization Chemical disinfection at room temperature for 5 min using ultrasonication in a bath containing 4% Lysetol® AF

Table 3: Distribution of the scores of the various criteria to assess changes in the vestibular surface of SSC when they were examined by SEM Criterion

Crowns

Crazing

PC NSC KK PP Total PC NSC KK PP Total PC NSC KK PP Total PC NSC KK PP Total

Contour alterations

Fracturing

Vestibular surface changes

Groups G1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

G2 4 3 4 2 13 5 1 0 4 10 0 0 0 0 0 5 3 4 3 15

G3 5 4 4 1 14 4 0 4 5 13 0 0 0 0 0 5 4 4 5 18

G4 4 2 4 3 13 5 0 4 3 12 0 0 0 0 0 5 2 4 3 14

G5 3 1 2 0 6 4 0 0 3 7 0 0 0 0 0 4 1 2 3 10

Total 16 10 14 6 46 18 1 8 15 42 0 0 0 0 0 19 10 14 14 57

Table 4: Results of Chi-square test Criterion Crazing Contour alteration Vestibular surface changes

PCa PCa PCa

Crowns NSCab KKa NSCb KKc NSCb KKb

PPb PPa PPb

G1a G1a G1a

G2b G2b G2b

Groups G3b G3b G3b

G4b G4b G4b

G5c G5b G5c

a,b,c

The differences between the crowns and groups marked by the same letter or letters are not statistically significant (P > 0.05)

Table 3. All the methods in which steam autoclaving was used to sterilize the crowns caused surface changes when the crowns were examined by SEM. Furthermore, combined ultrasonication and chemical disinfection was the method of sterilization and disinfection that caused the smallest number of changes to the vestibular surfaces of preformed crowns.

the sources of these significant differences the sample was divided into subgroups for chi-square analyses whose results are presented in Table 4. There were statistically significant differences (P