|Year : 2017 | Volume
| Issue : 2 | Page : 106-111
Clinical outcome and parental satisfaction of maxillary anterior teeth treated with NuSmile preveneered crowns and Kinder Krowns
Priya Subramaniam1, KL Girish Babu2, Harsha Gona1
1 Department of Pedodontics and Preventive Dentistry, The Oxford Dental College and Hospital, Bengaluru, Karnataka, India
2 Department of Dentistry, Hassan Institute of Medical Sciences, Hassan, Karnataka, India
|Date of Web Publication||25-Jul-2017|
Department of Pedodontics and Preventive Dentistry, The Oxford Dental College and Hospital, Bommanahalli, Hosur Road, Bengaluru - 560 068, Karnataka
Source of Support: None, Conflict of Interest: None
Background: Treatment of primary maxillary incisors in early childhood caries is problematic because the teeth are small and a restoration should be retentive and esthetic.
Aim: The aim of this study was to evaluate the esthetics and durability of two types of preveneered stainless steel crowns by assessing their parental acceptance and clinical outcome over a period of 24 months.
Materials and Methods: Forty maxillary primary incisors which had undergone pulpectomy procedure were randomly divided into two groups of twenty teeth each. A split-mouth design was followed wherein every child received at least one each of the two commercially available preveneered stainless steel crowns, namely, NuSmile crowns and Kinder Krowns. Patients were recalled after 6, 9, 12, and 24 months and the crowns were evaluated for clinical outcome and parental satisfaction. Data obtained were collected and subjected to statistical analysis using Chi-square/Fisher's exact test.
Results: Overall clinical outcome did not show a significant difference between the two types of crowns. Parental satisfaction for NuSmile crowns and Kinder Krowns was similar.
Conclusions: (1) NuSmile and Kinder Krowns performed well over a period of 24 months. (2) Parental satisfaction for both types of preveneered crowns was very high.
Keywords: Kinder Krowns, NuSmile crowns, preveneered crowns
|How to cite this article:|
Subramaniam P, Girish Babu K L, Gona H. Clinical outcome and parental satisfaction of maxillary anterior teeth treated with NuSmile preveneered crowns and Kinder Krowns. Saudi J Oral Sci 2017;4:106-11
|How to cite this URL:|
Subramaniam P, Girish Babu K L, Gona H. Clinical outcome and parental satisfaction of maxillary anterior teeth treated with NuSmile preveneered crowns and Kinder Krowns. Saudi J Oral Sci [serial online] 2017 [cited 2023 Jan 27];4:106-11. Available from: https://www.saudijos.org/text.asp?2017/4/2/106/211569
| Introduction|| |
The ideal full coronal restoration for a primary incisor should be tooth colored and imperceptible, durable enough to last in the mouth, with no additional treatment, until normal exfoliation time of the tooth. This means that the crown should neither fracture nor detach from the prepared tooth once cemented into place. It should be adhesively attached to the prepared tooth with cement that will be biocompatible with pulp tissue. The crown must be easily and rapidly placed by a dentist during one treatment visit without the need for laboratory fabrication of the crown.
Preveneered crowns are traditional stainless steel crowns with mechanically or chemically bonded esthetic material covering one or more surfaces of the crown. They are esthetic and can be placed in a single appointment. Their cementation is not significantly affected by hemorrhage and saliva.
Today, there are a number of preveneered stainless steel crowns available in the dental market. Many claims are made by each manufacturer regarding the esthetics and durability of their individual crown products. The two popularly used preveneered crowns for primary anterior teeth are NuSmile and Kinder Krowns. Earlier studies have compared these crowns individually with that of other anterior restorations such as pedo strip crowns, glass ionomer restorations, and composite restorations.,, However, clinical studies directly comparing the acceptability and durability of two types of preveneered stainless steel crowns are very few. In developing countries, wide use of preveenerd crowns is still not prevalent due to the high costs and limited availability. Indian studies on preveneered stainless steel crowns are lacking. Hence, this study was undertaken to evaluate the esthetics and durability of two types of preveneered stainless steel crowns by assessing their parental acceptance and clinical outcome over a period of 24 months.
| Materials and Methods|| |
Healthy, cooperative children for the study were selected from the patients attending the Department of Pedodontics and Preventive Dentistry. Criteria for selection of children were as follows:,,, Inclusion criteria included (1) children with no history of systemic illness, (2) carious primary maxillary incisors with extensive caries on one surface or moderate carious lesions on two or more surfaces, (3) endodontically treated primary maxillary incisors obturated with zinc oxide eugenol cement, (4) radiographically at least two-third of root to be present, (5) sufficient overjet of 2 mm between primary upper and lower incisors, and (6) no aberrant oral habits. Exclusion criteria  included (1) children who require dental treatment under sedation and/or general anesthesia, (2) teeth nearing normal exfoliation, (3) children with bruxism and excessive deep bite, (4) children with special health care needs, (5) traumatized teeth, and (6) teeth with no coronal structure or coronal restoration requiring intracanal posts.
A total of forty primary maxillary incisors requiring full coronal restoration were selected from children aged 3 to 4 years. The parents and/or guardians were informed about the condition of the child's dentition and the treatment indicated for these teeth. The nature of the study was briefly explained. Participation in the study was voluntary, and prior written consent was obtained from the parents or guardians. Ethical clearance to conduct the study was obtained from the Institutional Review Board.
Forty maxillary primary incisors which had undergone pulpectomy procedure were randomly divided into two groups of twenty teeth each. A split-mouth design was followed wherein every child received at least one each of the two commercially available preveneered stainless steel crowns, namely NuSmile crowns (Orthodontic Technologies, Houston) and Kinder Krowns (Mayclin Laboratory, Minneapolis). Parents were blinded regarding the type of preveneered crown cemented on the primary teeth.
Following administration of local anesthesia, the teeth were prepared under high-speed suction being used throughout the procedure. Cotton gauze shield 4 × 4 was used to protect the oropharynx. Tooth preparation involved debridement of carious substance and reduction of tooth structure in all dimensions with the help of water-cooled, high-speed, 169 L fine-tapered diamond bur. About 1.5 mm of tooth structure was removed from the axial surfaces. Axial reduction paralleled the long axis of the tooth, but with slight convergence toward the incisal aspect. The incisal edge was also reduced by about 1.5 mm. The cervical enamel bulge was reduced minimally.
The crown forms were positioned simultaneously to evaluate spatial relationships and respective crown form orientation. Palatal margins of the crowns were crimped, and the labial margins were spared. Margins were then finished and polished with rotary stones and rubber wheels. The occlusion was evaluated before the cementation of the crowns. Using a resin-modified glass ionomer luting cement (Vitremer Luting Cement 3M ESPE, USA), the crowns were cemented one by one, using finger pressure and without the use of hand instruments.
Once hardened, the excess cement was removed with a hand scaler taking care not to damage the resin facing. After completion of treatment, the child and parents were instructed on the importance of oral hygiene and diet to maintain the restored primary teeth.
Patients were recalled after 6, 9, 12, and 24 months, and the crowns were evaluated using criteria given by Roberts et al. Parental satisfaction was evaluated using a 5-point Likert-type scale.
Data obtained were collected and subjected to statistical analysis using Chi-square/Fisher's exact test to find the significance of study parameters on categorical scale between two or more groups. SPSS software 19.0 (IBM Corp. Released 2010. IBM SPSS Statistics for Windows, Version 19.0. Armonk, NY: IBM Corp.) were used for the analysis of the data.
| Results|| |
At 24 months, three teeth restored with NuSmile crowns had exfoliated and four of the crowns (20%) had minor color deviation of the facing from the original. With Kinder Krowns, there was exfoliation of one tooth and minor color deviation of the crown facing was observed in five teeth (25%) [Table 1]. Overall clinical outcome did not show significant difference between the two types of crowns [Table 2]. Parental satisfaction for NuSmile crowns and Kinder Krowns was similar with no significant difference between both types of crowns [Table 3].
|Table 1: Clinical outcome of Preveneered NuSmile and Kinder Krowns at 24 months (n=20)|
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|Table 2: Comparison of clinical outcome of NuSmile crowns and Kinder Krowns at 24 months (n=20)|
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|Table 3: Comparison of parental satisfaction for NuSmile crowns and Kinder Krowns|
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| Discussion|| |
There is a lack of supporting clinical data with regard to the restoration of primary incisors. According to Waggoner, there are several difficulties in designing clinical studies to evaluate restorative options of primary incisors. First, children with dental caries in their primary incisors are generally very young and due to their lack of cognitive ability are usually very uncooperative for dental treatment. Parental attitude, cost of treatment, reluctance on the part of the clinician, and differences in caries risk may be obstacles in obtaining well-controlled, prospective clinical data on restorative options for primary incisors.
Most of the clinical studies on preveneered stainless steel crowns have been carried out on children treated under conscious sedation or general anesthesia.,, However, clinical studies on direct comparison of two types of anterior preveneered stainless steel crowns are lacking. Perhaps, this is the first study to evaluate and compare the clinical outcome and parental satisfaction of two anterior preveneered stainless steel crowns in a split-mouth design. Moreover, the crowns were placed on primary maxillary incisors in young children treated on the dental chair, without any form of sedation or general anesthesia. To standardize the study protocol, children presenting with similar behavior during the restorative procedures were selected.
The preveneered primary stainless steel crowns offer many advantages over other esthetic alternatives. Chairside time is shorter and their esthetic quality is not affected by saliva and blood. However, one of the major concerns regarding the preveneered stainless steel crowns is retention of the esthetic facing. When the facing fractures, dislodges, deforms, or falls off, it leaves the metallic crown on the tooth and could present an esthetic problem to the child. The shearing forces necessary to dislodge or deform the esthetic veneer facings of NuSmile and Kinder Krowns in vitro was found to be essentially the same. A study determined that the veneer facings of these crowns have a fracture resistance greater than the average bite force of a 5–10-year-old child (375 N). Hence, in this study, clinical evaluation of the preveneered stainless steel crowns was mainly in regard to their crown facing. The main variable between manufacturers of these crowns is not the crown material, but the veneer component itself. Retention of facing could be attributed to the attachment of the veneer to the stainless steel crowns. Unlike other preveneered crowns, these crowns have no metal meshwork to retain the facing. The veneered facings are composite resins and are bonded to the stainless steel crowns by processes that the manufacturers generally do not reveal.
With Kinder Krowns, a small portion of the metal in the mesial/incisal and distal/incisal of the crown is removed, leaving two small holes. The composite material is placed in these holes during the veneer and bonding process. This is done to strengthen the bond of the resin material to the metal crown. Previous clinical studies showed stainless steel crowns to be highly retentive for both anterior and posterior primary teeth., In our study, both NuSmile crowns and Kinder Krowns did not show any fracture, wear or loss of the facing. One of the probable reasons could be that crimping was not carried out for both types of crowns. Crimping and contouring of preveneered crowns may cause the veneers to fracture. Crimping is limited essentially to the lingual surface due to the facial veneer. Crimping of the metal portion can weaken the aesthetic facing and may lead to premature failure. Crimped preveneered crowns have been associated with greater veneer surface area loss.
The results of this study are in contrast to a retrospective cross-sectional study that reported of resin fracture resulting in partial or total facing loss in 24% of Kinder Krowns placed on 46 anterior primary teeth in 12 children. This difference could be due to the longer age of the crown (17.5 months) at the time of examination.
In the present study, two children reported with exfoliation of three primary incisors. The parent of one of these children returned the crowns that remained intact on the exfoliated teeth. The crowns did not show any facing loss, fracture, and roughness. Surface texture of both the crowns was assessed using only visual and tactile methods. An explorer was passed over the crown surface to check for any roughness and irregularities. Therefore, any microscopic discrepancies could have been overlooked.
Another concern with preveneered stainless steel crowns is the color stability of the veneered facing. Wickersham et al. showed that all commercially available veneered facings are capable of staining and undergoing color changes. In our study, at the 18th month of placement, there was only a minor deviation in facing color of four Kinder Krowns in comparison to only one seen with NuSmile crown. This finding was similar to a retrospective study on clinical outcome of 226 anterior preveneered NuSmile stainless steel crowns, with a mean postplacement time of 12.9 months.
Parents tend to remember the pretreatment condition of their child's teeth and the possible loss of these anterior teeth at an early age. Often, general practitioners and clinicians are reluctant to treat these young children and extraction of the primary incisors may have been the only treatment option. The pretreatment condition of the child's carious and frequently discolored teeth is compared to their esthetic transformation following treatment.
In addition, what is important to the clinician may not necessarily be of importance to the parent. To the dentist, ease of clinical procedure and biological response may be of paramount importance. While to the parent, esthetics, durability, and cost of treatment may be of concern. Therefore, even if the crowns are not esthetically pleasing to the discerning eye of the clinician, parents may express high satisfaction because of restoration of the grossly broken down carious teeth to their near natural resemblance. The fact that the decayed primary teeth have been salvaged and continue to be retained has a positive effect on both parent and child. An earlier study reported of high parental satisfaction with Kinder Krowns, in spite of 39% of the crowns presenting with some loss of the esthetic facing either from fracture or wear. In the present study, parental acceptance for both preveneered stainless steel crowns was found to be more than satisfactory, with the satisfaction for appearance being the lowest.
When parents state their overall satisfaction, they often include many dimensions of treatment that the clinical evaluation may not include. Parents may cognitively construct their experience with the child's treatment by evaluating three distinct areas: (1) psychosocial outcomes, (2) clinical outcomes, and (3) the treatment process. The durability and psychosocial benefits of treatment can outweigh the visible clinical outcome. Furthermore, children with primary anterior teeth restored with preveneered stainless steel crowns will always look better than they did before the treatment. In such circumstances, it may be very difficult, if not impossible, for many parents to give a negative response. To begin with, parents could have been given a choice of treatment options that ranged from anesthetic restorations of questionable durability to extraction of the affected tooth itself. Strong psychological forces mitigate against negative evaluation of a decision made by free choice.
From the observations of this study, NuSmile crowns and Kinder Krowns were clinically successful as determined by retention of the crowns and absence of fracture or distortion of the preveneered facing. Further clinical evaluation and comparison of these preveneered stainless steel crowns over longer periods are necessary.
| Conclusions|| |
- NuSmile and Kinder Krowns performed well over a period of 24 months, with 100% of the crowns being retained
- Parental satisfaction with the appearance, color, shape, size, and durability of both types of preveneered crowns was very high.
Preveneered stainless steel crowns should be considered as a highly retentive and protective restorative option for grossly carious anterior primary teeth. Their near-natural appearance and level of durability make these crowns a desirable option for treating very young children.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]