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ORIGINAL ARTICLE
Year : 2017  |  Volume : 5  |  Issue : 1  |  Page : 21-27

Clinical evaluation between zirconia crowns and stainless steel crowns in primary molars teeth


Department of Pediatric Dentistry, Faculty of Dentistry, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia

Date of Web Publication5-Oct-2017

Correspondence Address:
Bashaer S Abdulhadi
Faculty of Dentistry, King Abdulaziz University, Jeddah
Kingdom of Saudi Arabia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jpd.jpd_21_17

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  Abstract 

This randomized clinical trial compared the clinical outcomes of two full-coronal restorations (stainless steel crowns [SSCs] and zirconia crowns Nu/ZR) in carious primary molars teeth. Children attending the King Abdulaziz University, Faculty of Dentistry clinics who need restorations will be screened for inclusion criteria till 120 teeth are recruited (60 teeth for SSC restorations and 60 for Nu/ZR restorations). Split mouth technique will be used to ensure equalizing variables for both groups. Randomization will be done using SPSS software version 20.0 (Armonk, NY; IBM Corp., USA). A simple descriptive statistic will be used for analysis using Wilcoxon Signed-Rank test. The level of significance will be set at (α = 0.05) and level of confidence at (95%). While looking at the improvements in gingival health relative to interventions, both Zirconia and SSC have significant changes through all time points. However, Zirconia performed better at the 3rd month with 80% compared to SSC with only 13.3% improvement with P < 0.001 and 0.005, respectively. At 6th month, all samples under group zirconia already improved whereas only 73.3% from SSC show improvement. The remaining samples happened to have positive changes at the 12th month. Regarding the plaque retention also the Zirconia Crowns shows improve performance than SSC. As both SSC and Zirconia crowns presented to be an excellent choice for posterior teeth restorations, however, we can conclude that Zirconia crowns performed better regarding gingival response to the material of restoration and plaque retention despite its high cost.

Keywords: Primary posterior teeth, stainless steel crown, zirconia crown


How to cite this article:
Abdulhadi BS, Abdullah MM, Alaki SM, Alamoudi NM, Attar MH. Clinical evaluation between zirconia crowns and stainless steel crowns in primary molars teeth. J Pediatr Dent 2017;5:21-7

How to cite this URL:
Abdulhadi BS, Abdullah MM, Alaki SM, Alamoudi NM, Attar MH. Clinical evaluation between zirconia crowns and stainless steel crowns in primary molars teeth. J Pediatr Dent [serial online] 2017 [cited 2017 Dec 13];5:21-7. Available from: http://www.jpediatrdent.org/text.asp?2017/5/1/21/215982


  Introduction Top


Early childhood caries (ECC) is a protracted multifactorial disorder which continues to be dominant in children, especially in the families with low socioeconomic class.[1],[2],[3],[4],[5],[6] ECC is construed as “the existence of one or more tooth decays (noncavitated or cavitated lesions), removed (due to caries), or filled tooth surfaces in any primary dentition of children under the age of 6 years.”[7] ECC remains to be a global health problem, involving the foremost carious lesion of the primary maxillary incisors, then the mandibular, maxillary first primary molars and mandibular cuspids.[8] Stainless steel crowns (SSCs) has been utilized for the restoration of primary dentition affected by caries, decalcification in the neck of the tooth, and developmental defects (e.g., hypoplasia, hypo calcification).[9] It is also used when the downfall of further accessible restorative supplies is more probable (e.g., interproximal caries ranging farther than line angles, children with bruxism).[9] Moreover, next to pulpotomy or pulpectomy, SSC is used in the restoration of a primary tooth which will be exploited as an abutment to maintain space or to be used as interposed rehabilitation of severed teeth.[9]

In children with high-caries-risk, absolute management of primary dentition with SSCs is indicated over time compared to multi-surface intra-coronal restorations. After scrutinizing of available literature concerning the comparison of SSCs and Class II amalgams the conclusion is that, for multi-surface restorations in primary teeth, SSCs are superior to amalgams.[10] SSCs have a success rate greater than that of amalgams in children under the age of 4 years. Over the years, numerous clinical studies including the longitudinal studies by Messer and Levering, 1988[11] and Einwag and Dünninger 1996[12] have demonstrated the superiority of SSCs in restoring primary molars with multi-surface involvement.[10],[11],[12],[13],[14]

Usage of SSCs should also be accounted in patients with heightened risk of caries whose participation is distressed by age, behavior, or medical history. Most often, these patients obtain treatment under sedatives or general anesthetics. SSCs tends to last long in patients with developmental or medical conditions that do not improve as they age thus reducing the possible usage of sedatives and general anesthetics considering that it is costly and its inherent perils. However then again, severely damaged primary dentitions among pediatric patients is deemed to be one with immense difficulties, to treat esthetically. During the past 50 years, the prominence on taking care of mostly degenerating primary dentition changed from removal to rehabilitation. Early recovery includes employment of stainless steel binding or crowns on critically damaged dentition. While working, they were unesthetic, and its usage is confined to posterior dentures. The mesial buccal area of the first primary molars and second maxillary primary molars may be seen when the child smiles.

During the past 20 years, there was an increased demand by adults in the esthetic restoration of their jeopardized dentures. Equivalently, a higher esthetic standard is expected by parents for the recovery of their children's carious teeth. More recently, zirconia esthetic crowns appeared on the market. Zirconia is a crystalline dioxide of zirconium that has mechanical properties similar to those of metals, and its color is similar to that of teeth. Ready-made first zirconia crowns are now available for both, primary incisors and molars.

The aim of this clinical research is to evaluate and compare two full coronal restorations on primary posterior molars over 3, 6, and 12 months regarding recovery failure, marginal integrity, proximal contact, secondary caries, occlusion, and gingival response. The restorations type included are prefabricated SSCs and prefabricated primary zirconia crowns.


  Materials and Methods Top


Study design

The study is a randomized regulated clinical trial that followed the standards published by Consolidated Standards of Reporting Trials.[15]

The study is authorized by the Research Ethics Committee of King Abdulaziz University Faculty of Dentistry with reference no. 076-16 before enrolment, a consent form were distributed to the children's parents or guardians. This study is also registered at ClinicalTrials.gov under registration number NCT03067337.

Sample size

Using G*Power 3.1.9.2 software (Franz Faul, Universität Kiel, Germany, 2014)[16] for power analysis, it was indicated that we need a total of 120 teeth (corresponding to around 60 children to achieve 80% power with 95% confidence) assuming medium effect size in the mean change in gingival health 6 months after crown application between Zirconia and SSC group with the assumption of nonnormal distribution. The number of crowns in each arm will be 60.

Sample selection

A sample of 120 contralateral primary molars in 26 patients were treated in the Pediatric Dental Clinics, King Abdulaziz University, Faculty of Dentistry, Jeddah. All patient who presented from August 1, 2015, until September 30, 2015, and met specific inclusion criteria were included in the study [Figure 1].
Figure 1: A consort diagram showing the flow of patients

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Inclusion criteria

  • Patient within the age group of four to 8 years
  • Patient with at least two matched bilateral carious primary molars indicated for full coverage
  • Healthy children free of any systemic disease or any developmental disturbances of the teeth and jaws that would have affected dietary patterns, caries, susceptibility or the selection of restorative materials to the best of the current knowledge
  • Minimal of two surfaces of caries in the targeted tooth
  • Patient with ECC as defined by the American Academy for Pediatric Dentistry
  • Cooperative patient who had the behavioral rating “no undercuts or ledges are remaining” or “definitely positive” according to the Frankl behavior classification scale[17]
  • Penned authorization was obtained from the parent/guardian after explaining the full details of the treatment procedure and its possible outcomes, discomfort, risks, and benefits
  • No patient was excluded by gender, race, social, or economic background [Figure 1].


Clinical procedure

One operator completed all teeth preparations and restorations procedures. Local anesthesia was achieved using lidocaine hydrochloride 2% with epinephrine 1:100,000. The teeth were isolated using a rubber dam. After caries, excavation tooth was prepared according to manufactural instructions.

Teeth restored were assigned to a certain group according to the type of crown applied to each tooth. Sixty teeth were assigned to Group A and restored with SSCs, another sixty teeth were assigned to Group B which restored with zirconia crowns.

Group A (stainless steel crown)

Reduction of the occlusal surface by about 1.5 mm using a flame shape or tapered diamond bur to produce uniform occlusal reduction. Employing gilt-edged, long, and tapered diamond bur, adhered marginally convergent to the remote access of the denture and cut interproximal slices mesially and distally. The reduction should allow the probe to pass through the contact area.

An appropriate size was chosen according to mesiodistal width of the prepared tooth and trail fit carried out before cementation. The crown should remain no more than 1 mm subgingivally if there is an excessive shrinking of the gingival tissues the segment of the crown should be decreased.

The margins should be smoothed after reduction with white stone.

Group B (zirconia crowns)

After anesthesia execution and rubber dam placement next was the crown size selection. Suitable crown size can be identified using NuSmile (Houston, TX, USA) Try-In Crowns and should always be selected on the start of tooth reduction.

Occlusal, proximal, and supragingival reduction

Decrease the occlusal surface next to the natural occlusal profile by roughly 1—1.5 mm. Unfasten the interproximal contacts. The proximal abatement should be enough to permit the chosen crown to fit passively. The tooth should be trimmed down circumferentially by around 20%—30%, or 0.5—1.25 mm as needed.

Such procedures can be administered with the use, of course, tapered diamond or carbide burs; a coarse football diamond bur can be utilized to decrease the occlusal area of hindmost dentition.

Subgingival reduction

The anticipated edge should be anxiously stretched out and polished to a feather-edge so that no undercuts or subgingival ridges stay roughly 1—2 mm subgingivally on every area. A slim, narrowed diamond bur should be utilized to prevent the breaking up of tissue during the execution of such subgingival tooth modifications.

Completion of the preparation

Eliminate line and point angles to allow all areas of the prepared denture to be marginally rounded. Now analyze once more for adequate occlusal allowance with the divergent teeth as well as to ensure the lack of undercuts or ledges subgingivally.

Crowns seating

Prepared teeth should be free from any blood or residues, saliva, and gingival blood. Compression or hemostatic tools can be utilized for such intent as needed. NuSmile BioCem® Universal BioActive cement, resin cement, or resin-modified glass ionomer can be employed to sit NuSmile ZR Crowns. If pulpal therapy was enforced using a eugenol based substance in the pulp compartment, conceal the eugenol substance using glass ionomer before cementation.

Evaluation criteria

The evaluation of each crown restoration was assessed at the baseline which is the same day of the procedure, 3, 6, and 12 months. Clinical failure parameters were evaluated with visual assessment of the restoration, according to the United States Public Health Service (USPHS), alpha criteria rating system.[18] As if the crown appears normal, no cracks, chips, or fracture, or small but noticeable area of loss of material, or large loss of crown material and finally if there was a complete loss of crown.

The performance of the two restorations was evaluated using the modified USPHS criteria, in terms of marginal integrity, gingival health, secondary caries, proximal contact, and occlusion.

The gingival health and plaque index were assessed using a blunt periodontal probe (Double ended probe Williams 1-2-3-5-7-8-9-10 Goldman Fox Flat) according to the Löe.[19]

Statistical analysis

This study will be analyzed using IBM SPSS version 23 (Armonk, NY, USA). Simple descriptive statistics will be applied to characterize the variables of the study through tally and percentages for the definitive and nominal variables, whereas mean and standard deviations will represent the constant variable. In comparing the distributions of two variables, two-related-samples tests with Wilcoxon signed-rank will be used. These tests are assumed to be observing normal distribution. In rejecting the null hypothesis, the standard P < 0.05 will be applied.


  Results Top


Application of full coronal restorations was done on maxillary and mandibular first and second primary molars summing to 120 molar teeth (60 males and 60 females). The average age at the baseline was 5.57 with no drop out happened until the 12 months follow up [Table 1].
Table 1: Demographics

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Regarding the gingival health, all teeth were examined at the baseline, 3, 6, and 12 months and scored according to the gingival health status. All molar teeth included in the study showed no gingival bleeding with a probe at the baseline examination. On the other hand, during the 3 months follow-up, 80% of the teeth restored with zirconia showed no gingival bleeding compared to the 13% no bleeding in the group of teeth restored by SSC. During the 6 months follow-up, the percentage of the teeth covered by zirconia crowns reach 100% healed gingivae with all teeth shows no gingival bleeding upon probing. However, the SSC group still had 26.7% bleeding with probing on the 6 months' follow-up. Finally, all teeth gingival health on both groups were no signs of gingival inflammation when they reach the 12 months follow-up [Table 2].
Table 2: Gingival health

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Both groups were checked regarding the plaque index and scored according to Silness, and Loe criteria at the baseline all showed 100% no plaque as the treatment started after prophylaxis was done to all teeth and also dental health-care instructions to the patients and their parents. Although oral hygiene training has been done for all the patients under their parents' supervision, 73.3% of teeth covered by zirconia crowns showed a plaque film sticking to the free gingival margin which can only be observed with the use of the probe in the three months' follow-up. Contralaterally, the teeth covered with SSCs presented at the same follow-up period with 53% having moderate deposit accumulations within the gingival compartment, on gingival border and neighboring tooth façade, visible to the eye. After three more months of the 6 months follow-up, the majority of the zirconia covered teeth improved reaching 83.3% without plaque accumulation on crowns surfaces. On the other hand, 66.7% of the teeth covered with SSCs still presented a plaque film sticking to free gingival margin that cannot be seen with the naked eye at the 6 months follow-up. Finally, at the 12 months follow-up of the zirconia group all teeth scored zero with 100% no plaque accumulations, whereas in the SSC group, 75% of the teeth have no plaque accumulations [Table 3].
Table 3: Plaque index

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All teeth on both groups were presented at the 12 months follow-up without caries and showed normal occlusion and with normal appearance; no crack, chips, or fractures in the crowns [Table 4].
Table 4: Restoration failure

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The proximal contact of all teeth was restored after crowns placement to the same situation before restoration. All the criteria of resistance were met when passing floss except two teeth that were spaced before doing the restoration as they showed floss passage without resistance but contact is present.

Moreover, all teeth included in the study showed no recurrent caries after the whole 12 months follow-up period. This is also explained by the success of all restoration over the 12 months as the teeth under full coverage crowns.


  Discussion Top


After the 12 months follow-up, the success rate of both crowns tested in this study (Zirconia and SSC for posterior teeth) showed 100% success with all crowns appear healthy with no chips, cracks, or fractures. Regarding the SSCs our result comes along with many studies tested the SSCs and compared it with many different restorative materials. In 2008, Atieh[20] did a randomized control trial for 2 years concerning the restoration of primary teeth from a pulpotomy procedure with a survival rate for restored teeth having performed metal crowns to be 95%. On the other hand, no published data yet available about zirconia crowns restorations success for next primary molar teeth except for the studies done by the product company (Nusmile, Houston, TX, USA).

Results showed that gingival health was better in teeth restored with Zirconia crowns than those which treated with SSCs during 3 and 6 months follow-up, but later 12 months follow-up revealed both groups presented with healthy gingiva. These results could be explained as Zirconia used for tooth component exhibits remarkable biocompatibility as well as shows smooth plus polished exterior which lead to the lower tendency of plaque build-up and thus lower chance of gingival irritation. Earlier publications on fixed partial dentures using zirconia structure on fixed dentition observed similar outcomes: decreased plaque build-up.[21],[22] While another study done by Walia, et al., in 2014[23] examined Zirconia teeth on primary anterior teeth shows favorable gingival health toward those crowns.

Regarding gum condition with preformed SSC, a year-long arbitrarily regulated test revealed a lack of disparity in gum inflammation comparing preformed metal crowns plus composite restorations on pulpotomy.[24] An arbitrary clinical research with a duration of 2 years revealed an increased gum bleeding on preformed metal crowns compared to composite/glass ionomer reinstallations. Insufficiently shaped crown as well as set cement debris staying associated with gum sulcus result to gingivitis linked to preformed metal crowns, hence precautionary routine which includes oral hygiene teaching is suggested to be added to the treatment plan.[10]

This may justify the improvement of the gingival health adjacent to SSCs with time as the remnant cement materials washed away and degraded with time and oral fluids.

Regardless, the oral hygiene instructions have been given to the patients and their parents. However, they still keep coming with plaque accumulations in each follow-up but with different percentages between the two tested groups. As mentioned earlier in the results, the Zirconia crowns group presented fewer plaque accumulations during the follow-up periods and also improved with time. On the other hand, SSCs showed more plaque accumulations, and statistically significant difference between the two groups regarding the plaque index toward the zirconia group (P < 0.001) was observed. Some researches have been conducted regarding the gingival health of primary teeth restored with SSCs. Goto, et al., in 1970[25] recorded that the frequency of gingivitis in primary dentition replaced with nickel-chromium crowns. It was disclosed that the rate of gingivitis identified including a crown above the posterior portion of the mouth rather than the anterior is greatly correlated with badly fitted crowns. The occurrence of gingivitis in controlled teeth was not disclosed.

In 1973,[26] Henderson stated that the plaque index for SSC teeth is relatively lower than that in the whole oral cavity. Degrees of marginal gingivitis neighboring the crowns measured for the fixture as “good” or “fair” were found to be the same statistically, showing a greater level of gingivitis linked to the crowns with a “poor” fit. On the other hand, information regarding control teeth was not stated.

Moreover, shaping of metal borders improperly as well as adhesive residues in the sulcus in a case of SSCs causes irritation in the gingiva as well, resulting to plaque accumulations and gingival inflammation as stated by Maclean et al., 2007.[27] While Sailer, et al., in 2007[21] reported that the polished and smooth surface of zirconia crowns lead to less plaque accumulation.

NuSmile Zirconia crowns have improved marginal adoption to the tooth and are meager at the cervical crevice than the other brands. This results in lower likability of cement washout, reducing the possibility of cementation failure or subsequent decay.


  Conclusion Top


Both stainless steel and zirconia crowns presented to be an excellent choice for posterior teeth full coverage restorations. However, zirconia crowns performed better in the aspect of aesthetic, gingival response and plaque retention despite its high cost.

Recommendations

  • Using SSC's and Zirconia crowns for posterior teeth due to satisfactory gingival response, less plaque accumulation, low restoration failure, although the Zirconia crowns presented with excellent esthetical appearance.
  • It is recommended to continue the study for a longer follow-up period.


Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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    Tables

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