|Year : 2022 | Volume
| Issue : 1 | Page : 34-42
A clinical and radiographic comparative evaluation of custom-made zirconia crowns using CAD-CAM and stainless steel crowns in primary molars
Deepika Prabhu, A Anantharaj, P Praveen, S Prathibha Rani, R Sudhir
Department of Pediatric and Preventive Dentistry, D.A.P.M.R.V. Dental College, Bengaluru, Karnataka, India
|Date of Submission||26-Jul-2021|
|Date of Decision||01-Mar-2022|
|Date of Acceptance||13-Mar-2022|
|Date of Web Publication||13-Apr-2022|
Dr. Deepika Prabhu
D.A.P.M.R.V. Dental College, Bengaluru, Karnataka
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background and Aim of Study: Early childhood caries is a multifactorial disease process affecting children below 71 months of age and continues to be a global health problem. Stainless steel crowns (SSCs) are widely used and are very popular in pediatric dentistry due to its superiority and durability when compared with multisurface amalgam restorations. However, one of the major disadvantages with these crowns is the poor esthetics. Parents often request for a more esthetic alternative to the SSC. Zirconia crowns are one of the tooth-colored full crown restorations currently available for use in primary teeth. These are available as both preformed and custom-made crowns and show excellent esthetics. However, these require extensive tooth preparation with a subgingival finish lines, which would cause gingival trauma and bleeding during the preparation. The present study uses intraoral scanners for making the custom-made zirconia crowns, which will avoid the conventional impressions. Currently, there are no studies available in pediatric dentistry regarding CAD-CAM crowns. Hence, there is a need for the study. Aim: The aim of this study is to clinically evaluate the performance of preformed SSCs and custom-made zirconia crowns in primary molars. To elicit parental and patient satisfaction with respect to preformed SSCs and custom made zirconia crowns and to radiographically compare the interproximal bone height for 1 year. Methods: The patients were selected with purposive sampling. The tooth of interest was prepared according to the crown it would receive. The upper and the lower arch of the tooth receiving custom-made zirconia crown was scanned using an intraoral scanner. The crowns were cemented using Type 1 glass ionomer cement (GIC) (SSC) and resin modified GIC (custom-made zirconia crown). After the crown placement, the patient and the parent's satisfaction was scaled regarding the time taken, comfort, cost of crown, appearance of crown, etc., using a 5-point Likert scale. A baseline radiograph was taken after crown placement. The patient was recalled every 3 months till 1 year for evaluation (loss of retention, loss of proximal contact, gingival inflammation, opposing tooth wear, and marginal integrity). At the end of 1 year, radiographs were taken to check the interproximal bone. Results: After 1 year evaluation of custom-made zirconia crowns and preformed SSCs in primary molars, it was shown that both SSC and zirconia crowns showed good gingival scores but zirconia crown was better than SSC in improving the gingival health. SSCs showed better results with respect to the opposing tooth wear and marginal adaptability. Parents as well as patients preferred a tooth-colored crown as a treatment option. Conclusion: Custom-made zirconia crowns are comparable to the preformed SSCs and they show better gingival scores and excellent color match.
Keywords: Computer-aided-design-computer-aided-manufacturing zirconia crowns, clinical evaluation, parental satisfaction, preformed stainless steel crowns, radiographic evaluation
|How to cite this article:|
Prabhu D, Anantharaj A, Praveen P, Rani S P, Sudhir R. A clinical and radiographic comparative evaluation of custom-made zirconia crowns using CAD-CAM and stainless steel crowns in primary molars. J Indian Soc Pedod Prev Dent 2022;40:34-42
|How to cite this URL:|
Prabhu D, Anantharaj A, Praveen P, Rani S P, Sudhir R. A clinical and radiographic comparative evaluation of custom-made zirconia crowns using CAD-CAM and stainless steel crowns in primary molars. J Indian Soc Pedod Prev Dent [serial online] 2022 [cited 2022 Aug 12];40:34-42. Available from: http://www.jisppd.com/text.asp?2022/40/1/34/343012
| Introduction|| |
Dental decay in children's teeth is a significant public health concern, as it affects a large number of preschool children. Early restoration of cavitated primary molars is essential as it affects normal mastication and function and also affects the child's behavior and self-esteem. This also leads to the development of oral habits. The treatment of severely decayed teeth poses a challenge to the pediatric dentist as three important considerations have to be kept in mind, patient's behavior management, preservation of tooth structure and parental satisfaction. These severely decayed teeth with multi-surface caries, etc., need to be restored with full coverage restorations or crowns to preserve the same till the permanent teeth erupt.
For full crown restoration of primary molars, stainless steel crowns (SSCs) and its modifications and zirconia crowns are used. (Both preformed and custom made crowns).
SSCs were introduced into pediatric dentistry by Rocky Mountain Company in 1947, first described by Engel and then popularized by Humphrey in 1950. They were further modified and used for molars with multisurface carious lesions, postendodontic therapy, for abutment teeth of space maintainers and for hypoplastic teeth. Many studies have concluded that SSCs are effective when compared to conventional glass ionomer cement (GIC) restorations. Despite the clinical success of SSCs, one major disadvantage is the esthetics.
According to various studies such as one conducted by Sharath Chandra Pani, both parents and children preferred esthetic crowns when compared to preformed SSCs in both anterior and posterior teeth.
Recent psychology studies have shown that children become self-aware of their appearance and esthetic needs at the age of 3–5 years.
According to a study conducted by Holsinger et al., parents are demanding more esthetic restorations in the child's tooth.
In order to meet the esthetics, SSCs were modified as open faced crowns, pre veneered crowns. These crowns showed low success rate.
Due to the various disadvantages of the various esthetic crowns used in primary molars, zirconia crowns were introduced in pediatric dentistry.
Prefabricated zirconia crowns for primary teeth were introduced in 2010. They come in various shades and sizes along with a manufacture's instruction on tooth preparation. However, the crowns are bulky which result in extensive tooth preparation when compared to SSCs.
These crowns cannot be modified as SSCs and may fracture during trial or crown cementation.
Various brands manufacture preformed zirconia crown such as nu-smile, 3M, etc.
Disadvantages of preformed zirconia crowns:
- Limited shades are available
- Extensive tooth preparation
- They have a subgingival finish line
- They cannot be modified in any way like in the case of SSCs, as they have low flexural strength.
In order to overcome these disadvantages, custom-made zirconia crowns are an option now. The conventional impressions that are taken can be time-consuming and also uncomfortable. Digital impressions have improved and developed over the past few years. Digital impressions show advantages that include improved patient compliance, decreased time, ease of communication with the lab, and less storage space.
Crowns produced using monolithic blocks show superior mechanical properties.
Most of the studies on preformed zirconia crowns have been done on primary anterior teeth and long-term studies on preformed zirconia crowns in primary molars have not been done.
The present study seeks to evaluate the clinical and radiographic efficacy of preformed SSCs with custom-made zirconia crowns in primary molars.
| Methods|| |
Ethical clearance was obtained from the Institutional Review Board of D. A. P. M. R. V. Dental College, Bangalore, India. (303/VOL-2/2018).
Study design: Comparative, in vivo
This study was conducted in the Department of Pediatric and Preventive Dentistry at DA Pandu Memorial R. V. Dental College, Bangalore, on the OPD patients visiting the Department.
Patients within the age group of 6–10 years and healthy children free of any systemic disease or any developmental disturbances of the teeth that would affect the selection of restorative materials were selected.
Asymptomatic primary molars following pulp therapy indicated for full-coverage restoration. Patients with good oral hygiene. Children with signed consent form after being informed about the various benefits, risks, and treatment outcomes.
Teeth exhibiting preshedding mobility and children with parafunctional habits were excluded from the study.
Based on the inclusion criteria, teeth were selected using purposive sampling and grouped into two groups:
- Group 1–30 zirconia crowns
- Group 2–30 SSCs
Upper and lower primary molars in children aged 6–10 years were selected for the study.
Tooth preparation for stainless steel crown
The tooth preparation for SSC was done by reducing the occlusal surface uniformly by 1–1.5 mm using a No. 330 bur. The interproximal reduction of the mesial and distal surfaces was done using the no 169 L bur. (short tapered diamond bur). Once done, a probe was made to pass through the contact area. Furthermore, while preparing the proximal surface, care was taken to not form any ledges. The line angles were rounded off. The buccal and lingual surfaces were not reduced as they served as a retentive feature. A feather edge finish line was given subgingivally. The SSC was selected according to the mesio-distal width of the tooth. The crown was selected such that it would seat passively with a 2–3 mm. The crown was trimmed accordingly using a green stone bur and the occlusion was checked once the crown was seated. The crown was adapted by contouring and crimping with the use of pliers. Once the crown is seated, the crown is cemented using Type I GIC. Consistent finger pressure was placed while waiting for the cement to set. The excess cement was removed, and the occlusion was once again checked.
Crown preparation for zirconia crowns
The occlusal reduction was done by 1.5–2 mm. The proximal contacts were broken and the entire clinical crown structure was reduced by 0.5–1.75 mm. The resulting preparation was slightly converging occlusally. A subgingival finish line was given with a shoulder finish. The preparation was extended subgingivally by 2 mm. The tooth was checked for any ledges or undercuts and all the line angles were rounded off. A digital impression was taken after the tooth was prepared and sent to the lab. Once the crown was ready, the fit of the crown was noted. The fit of the crown was passive. The occlusion was checked thoroughly and the crown was cemented using resin modified GIC. The excess cement was removed and the occlusion was checked once again.
| Results|| |
The results of the clinical study are given in [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6] and [Graph 1], [Graph 2].
|Table 1: Comparison of Gingival Index Scores Different Time Intervals in each study group using Friedman's Test|
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|Table 2: Comparison of crown adaptability between different time intervals in each study crown group using Friedman's test|
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|Table 3: Comparison of color match of crown between different time intervals in each study group using Friedman's test|
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|Table 4: Comparison of surface roughness of crown between different time intervals in each crown group using Friedman's test|
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|Table 5: Comparison of opposing tooth wear Index scores by Knight and Smith b/w different time intervals in each study group using Friedman's test.|
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|Table 6: Comparison of crown intactness b/w different time intervals in each study group using Friedmen's test|
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As shown in [Table 1], mean gingival index in zirconia crowns showed that 56.3% of crowns showed mild gingivitis at baseline while this value drastically improved as 90.9% of teeth showed no gingivitis.
Mean gingival index in SSCs showed that 71.4% of teeth showed mild gingivitis at baseline while this value drastically improved as 88.5% of teeth showed no gingivitis.
As shown in [Table 2], at baseline, 75% of the crowns showed closed margins and good adaptation while at 9 months, one crown dislodged.
Marginal integrity and crown adaptability for SSCs showed that all 28 of the crowns showed closed margins and good crown adaptability at baseline and after 1 year.
Intergroup comparison showed that SSC has better marginal integrity when compared to zirconia crowns.
As shown in [Table 3], zirconia crowns showed excellent color match while compared to SSCs which was not esthetic.
As shown in [Table 4], from baseline to the 1-year follow-up, the surface roughness with respect to the zirconia crowns as well as the SSC remained alpha.
Opposing tooth wear by knight and smith
As shown in [Table 5], at baseline, there was no opposing tooth loss seen with respect to both SSC as well as zirconia crowns.
At 3-month follow-up, three teeth opposing to zirconia crowns showed score 1 tooth wear, where enamel was worn out.
At 9 months, the same 3 teeth showed a tooth wear of score 1 while none of the teeth opposing SSCs showed tooth wear.
At 1-year follow-up, there was not any change in the number of teeth showing tooth wear.
All teeth opposing SSCs showed no tooth wear.
As shown in [Graph 1] and [Graph 2]
With respect to zirconia crowns, when comparing the mean bone height for mesial bone from baseline to 1 year, the bone height at baseline was 0.95 mm and at 1 year, it was 0.91 mm.
The distal crestal bone height at baseline to 1 year was 0.82–1.0 mm.
With respect to the SSCs, when comparing the mean mesial crestal bone height at baseline and after 1 year, the bone height was 0.35 mm and 0.52 mm.
When comparing the mean distal crestal bone height at baseline and 1 year, the bone height was 0.35 mm and 0.73 mm.
There was a slight decrease in the bone height in the mesial crestal bone with respect to the zirconia crowns.
Type of crown used and tooth number selected
[Table 7] depicts the type of crown used and also the tooth number selected.
|Table 7: Comparison of distribution of study crowns based in the tooth involved using Chi Square Test|
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| Discussion|| |
Unrestored primary teeth pose a major issue with respect to mastication, esthetics, and space management. There are various materials which are used to restore the carious lesions in primary molars. Crowns are used in primary molars when a full coverage restoration in required.
This present study aims to:
- Clinically evaluate the performance of preformed SSCs and custom-made zirconia crowns in primary molars
- To elicit parental and patient satisfaction with respect to preformed SSCs and custom-made zirconia crowns
- To radiographically compare the interproximal bone height for 1 year.
The gingival index scores for zirconia crowns showed a statistical significant difference from baseline to 3 months with P value at 0.01. There was a significant difference in the gingival index scores from 3 months to 9 months. From 9 months to 1 year, the gingival index scores improved with P value at 0.01.
Similarly, the gingival index scores for SSC from baseline to 3 months showed a statistically significant value of 0.02. There was a significant difference in the gingival index score from 3 months to 9 months. From 9 months to 1 year, the gingival index score showed a significant value of <0.01.
When the two Groups were compared, there was no statistical significant difference as the values were comparable to each other.
According to a randomized control trial which compared the clinical outcomes of SSCs and zirconia crowns in carious primary molars teeth. While looking at the improvements in gingival health relative to interventions, both zirconia and SSC have significant changes through all time points. Regarding the plaque retention, the zirconia crowns showed improved performance than SSCs. As both SS and zirconia crowns presented to be excellent choices for posterior teeth restorations, it was concluded that zirconia crowns performed better regarding gingival response and less plaque retention despite its high cost.
Alternatively, according to a study which aimed to clinically and radiographically evaluate the success of SSCs versus zirconia crowns. SSCs showed statistically higher gingival index scores than zirconia crowns at 9 months and 12 months.
While comparing the crown adaptability, 75% of zirconia crowns had good marginal integrity and crown adaptability at baseline while 25% of the crowns had a bravo score for crown adaptibility and marginal integrity. This was attributed to the delay in crown cementation and laboratory errors.
There was a drop out of 1 patient at 3 months, and the percentage of crowns showing alpha score for crown adaptability was 66.7%. 33.3% of the crowns showed bravo scoring at 3 months. At 9 months, 1 crown decemented. The alpha score at 6 months and 9 months was 63.6% and crowns which had a scoring of bravo was 36.4%.
According to an in vitro study conducted which aimed to compare the marginal and internal fit of preformed SSCs in primary molars using different luting cements, they concluded that zirconia crowns cemented with resin cement were the most accurately fitted internally, while marginally, they were not significantly different from the rest of crownluting cement combinations tested.
When comparing opposing tooth loss with crowns restored with preformed SSCs and custom-made zirconia crowns, in SSC group, all crown showed a significant 100% score 0 representing with no wearing of the opposite tooth as compared to 25% of the zirconia crown group showing a score of 1 illustrating that there was minimal wearing of the opposing tooth. This difference in terms of the opposing tooth wear index between 2 Groups at 3 months' period was statistically significant at P = 0.006. At 9 months as well as at 12 months, SSCs showed a significant 100% score 0 representing with no wearing of the opposite tooth as compared to 25% of the zirconia crown group showing a score of 1 illustrating that there was minimal wearing of the opposing tooth. According to a study conducted which compared and assessed the wear of primary teeth against three types of crown coverage, both quantitatively and qualitatively. It was concluded that zirconia crowns induced the most severe wear in primary molars, followed by SSCs, and the least wear was induced by preveneered SSCs.
A study was conducted to compare and evaluate enamel wear caused by monolithic zirconia crowns and to compare this with enamel wear caused by contralateral natural antagonists. It was concluded that under clinical conditions monolithic zirconia crowns seem to be associated with more wear of opposed enamel than are natural teeth.
When comparing the bone loss for alveolar crestal bone height for both SSCs and zirconia crowns after 1 year, there was a slight reduction in mean bone height of the mesial bone height with respect to zirconia crown group. There was an increase in the mean bone height of the distal bone after a year with respect to zirconia crown from 0.82 to 1 mm.
In SSCs, the mean bone height with respect to the mesial bone after a year changed from 0.35 to 0.54 mm. The mean bone height of distal bone increased from 0.35 mm to 0.75 mm. This was not a statistically significant value.
There was no statistical significant difference in bone height after 1 year of crown placement. There is no literature review explaining the proximal bone loss in teeth restored with crowns in primary molars.
According to a study which aimed to compare clinically and radiographically, the success of SSCs, they concluded that there was no significant bone loss in teeth restored with SSCs and they were still a valuable treatment option.
Questionnaires were given to the parents and patients at the time of crown cementation.
56.6% of the parents were satisfied with the color and appearance of the crown, 31.3% of the parents were very satisfied with the color of the crown. 87.5% of the parents were satisfied with the time taken and the number of visits taken for the crown cementation while 12.5% of the cases were not satisfied with the number of visits taken for the crown cementation. 62.5% of the parents were satisfied with the cost of the crown while 25% of the parents were very satisfied with cost of the crown.
53.8% of the patients were satisfied with the color and appearance of the crown, whereas 7.7% of the patients were dissatisfied with the color of the crown.
46.2% of the patients were very satisfied with the procedure of crown preparation and crown cementation while 6.3% of the patients were dissatisfied with the procedure.
At the first follow up after 3 months, 35.7% and 50% of the parents were very satisfied and satisfied with the durability of the crown. 7.1% of parents were dissatisfied with the durability of the crown. 28.6% and 57.1% of the parents were very satisfied and satisfied with the impact of the crown with the oral health of the child while 7.1% of the parents were dissatisfied with the impact of the crown with the oral health of the child. 64.3% of the parents would prefer a tooth colored crown for future treatment options and 35.7% of the parents preferred a SSC.
According to a retrospective study conducted to evaluate the parental satisfaction regarding the esthetics and the impact of treatment on overall health concluded that the parents reported high level of satisfaction with the color, size, and the appearance of the crowns. The majority of parents reported that crowns improved the appearance and oral health of their child (78% and 83%, respectively). Eight-nine percent of parents reported that they would highly recommend these crowns.
[Figure 1] depicts the armamentarium used during the course of study.
[Figure 2] shows the intraoral digital scanner used and [Figure 5] shows the intraoral digital scan post tooth preparation.
[Figure 3], [Figure 4], [Figure 6] and [Figure 7] show preoperative photographs and follow up photographs till 1 year with respect to zirconia crowns.
|Figure 5: Computer-aided-design computer-aided-manufacturing image of tooth prepartation with respect to 75|
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[Figure 8], [Figure 9], [Figure 10] show the preoperative photographs with follow up till 1 year with respect to stainless steel crowns.
| Conclusion|| |
With all the limitations of the study, custom-made zirconia crowns show comparable clinical performance to preformed SSCs while it shows excellent color match although the cost of the crown was high. The gingival health was good with both the crowns.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]