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Wear of Primary Teeth Caused by Opposed All-Ceramic or Stainless Steel Crowns
Purpose: This study was conducted to evaluate the effects of full-coverage all-ceramic zirconia, lithium disilicate glass-ceramic, leucite glass-ceramic, or stainless steel crowns on antagonistic primary tooth wear.
Method: There were four study groups: the stainless steel (Steel) group, the leucite glass-ceramic (Leucite) group, the lithium disilicate glass-ceramic (Lithium) group, and the monolithic zirconia (Zirconia) group. Ten flat crown specimens were prepared per group; opposing teeth were prepared using primary canines. A wear test was conducted over 100,000 chewing cycles using a dual-axis chewing simulator and a 50 N masticating force, and wear losses of antagonistic teeth and restorative materials were calculated using a three-dimensional profiling system and an electronic scale, respectively. Statistical significance was determined using One-way ANOVA and Tukey’s test (P<.05).
Results: The Leucite group (2.670±1.471 mm3) showed the greatest amount of antagonist tooth wear, followed by in decreasing order by the Lithium (2.042±0.696 mm3), Zirconia (1.426±0.477 mm3), and Steel groups (0.397±0.192 mm3). Mean volume losses in the Leucite and Lithium groups were significantly greater than in the Steel group (P<.05). No significant difference was observed between mean volume losses in the Zirconia and Steel groups (P>.05).
Conclusion: Leucite glass-ceramic and lithium disilicate glass-ceramic cause more primary tooth wear than stainless steel or zirconia. [J Adv Prosthodont 2016;8:43-52]
Clinical Evaluation and Parental Satisfaction With Pediatric Zirconia Anterior Crowns
Purpose: The purpose of this study was to evaluate the clinical success of and parental satisfaction with anterior pediatric zirconia crowns. Methods: A retrospective analysis of maxillary anterior pediatric zirconia crowns was performed. Crowns were evaluated for retention, gingival health, color match, contour, marginal integrity, and opposing tooth wear. Parental satisfaction regarding the esthetics of the crowns and parental perception of the impact of treatment on the child’s appearance and oral health were evaluated by questionnaire.
Results: Fifty-seven crowns were evaluated in 18 children. Eight teeth were lost to exfoliation, three were extracted due to pathology, and two crowns debonded, leaving 44 available for examination. The average crown age at time of examination was 20.8 months. Sixteen crowns (36 percent) displayed gingival inflammation and color mismatch. No recurrent caries or opposing tooth wear was noted. Parents reported high satisfaction with the color, size, and shape of the crowns. The majority of parents reported that crowns improved the appearance and oral health of their child (78 percent and 83 percent, respectively). Eight-nine percent of parents reported that they would highly recommend these crowns.
Conclusions: Zirconia crowns are clinically acceptable restorations in the primary maxillary anterior dentition. Parental satisfaction with zirconia crowns is high. (Pediatr Dent 2016;38(3):192-7) Received October 9, 2015 | Last Revision March 8, 2016 | Accepted March 9, 2016
Comparison of Amount of Primary Tooth Reduction Required for Anterior and Posterior Zirconia and Stainless Steel Crowns
Purpose: To determine if aggressiveness of primary tooth preparation varied among different brands of zirconia and stainless steel (SSC) crowns.
Method: One hundred primary typodont teeth were divided into five groups (10 posterior and 10 anterior) and assigned to: Cheng Crowns (CC); EZ Pedo (EZP); Kinder Krowns (KKZ); NuSmile (NSZ); and SSC. Teeth were prepared, and assigned crowns were fitted. Teeth were weighed prior to and after preparation. Weight changes served as a surrogate measure of tooth reduction.
Results: Analysis of variance showed a significant difference in tooth reduction among brand/type for both the anterior and posterior. Tukey’s honest significant difference test (HSD), when applied to anterior data, revealed that SSCs required significantly less tooth removal compared to the composite of the four zirconia brands, which showed no significant difference among them. Tukey’s HSD test, applied to posterior data, revealed that CC required significantly greater removal of crown structure, while EZP, KKZ, and NSZ were statistically equivalent, and SSCs required significantly less removal.
Conclusion: Zirconia crowns required more tooth reduction than stainless steel crowns for primary anterior and posterior teeth. Tooth reduction for anterior zirconia crowns was equivalent among brands. For posterior teeth, reduction for three brands (EZ Pedo, Kinder Krowns, NuSmile) did not differ, while Cheng Crowns required more reduction. (Pediatr Dent 2016;38(1):42-6) Received July 14, 2015 | Last Revision September 26, 2015 | Accepted October 3, 2015
Twenty-Nine-Month Follow-Up of a Paediatric Zirconia Dental Crown
Abstract: The aim of this paper is to present the long-term follow-up of one paediatric zirconia crown on a deciduous molar. Preformed crowns are part of the armamentarium in paediatric dentistry. In recent years, aesthetic alternatives to preformed metal crowns have been developed, first preveneered crowns and then zirconia crowns. This paper describes the restoration of a primary molar with a zirconia crown (Sprig formerly EZ-Pedo, Loomis, California, USA) in an 8-year-old boy. In this clinical case, the protocol for the implementation and maintenance of zirconia crowns is detailed. The patient was followed up for 29 months until the natural exfoliation of his primary molar. The adaptation of the zirconia crown, the gingival health and the wear on the opposing tooth were considered. In this case, the paediatric zirconia crown allowed sustainable functional restoration while restoring a natural appearance of the tooth.
In Vitro Fracture Resistance of Three Commercially Available Zirconia Crowns for Primary Molars
Purpose: The purpose of this study was to measure the fracture resistance of primary mandibular first molar zirconia crowns from three different manufacturers—EZ Pedo (EZP), NuSmile (NSZ), and Kinder Krowns (KK)—and compare it with the thickness of the zirconia crowns and the measured fracture resistance of preveneered stainless steel crowns (SSCs).
Method: The thickness of 20 zirconia crowns from three manufacturers were measured. The mean force required to fracture the crowns was determined. Preveneered NuSmile (NSW) SSCs were tested as a control.
Results: EZP crowns were significantly thicker in three of the six measured locations. The force required to fracture the EZP crown was significantly higher than that required for NSZ and KK. There was a positive correlation between fracture resistance and crown thickness in the mesial, distal, mesioocclusal, and distoocclusal dimensions. None of the zirconia crowns proved to be as resistant to fracture as the preveneered SSCs.
Conclusion: Statistically significant differences were found among the forces required to fracture zirconia crowns by three different manufacturers. The increase in force correlated with crown thickness. The forces required to fracture the preveneered stainless steel crowns were greater than the forces required to fracture all manufacturers’ zirconia crowns. (Pediatr Dent 2014;36:E125-E129) Received September 4, 2013 | Last Revision June 9, 2014 | Accepted June 20, 2014
Surface, Microstructural, and Mechanical Characterization of Prefabricated Pediatric Zirconia Crowns
Abstract: The purpose of this study was to characterize the surface roughness, the microstructure, and mechanical properties of four prefabricated zirconia pediatric crowns. Ten prefabricated crowns from four different manufacturers (Cheng Crowns Zirconia), (EZCrowns), (NuSmile ZR), and (Zirconia Pediatric Crowns) were included in this study. The surface roughness parameters (Sa, Sq, Sz, Sc, and Sv) of all samples were studied by optical profilometry and then the microstructure was studied by Raman spectroscopy. Then, all samples were embedded in epoxy resin and after metallographic polishing, the Martens hardness (HM), indentation modulus (EIT), elastic index (ηIT), Vickers hardness (HV), and fracture toughness (KIC) were identified by the Instrumented Indentation Testing (IIT). All data were statistically analyzed by a one-way ANOVA and a Tukey multiple comparison test at α = 0.05. Only the tetragonal phase of zirconia for all materials tested was identified after Raman analysis. However, statistically significant differences were found among the surface roughness parameters, HV and KIC, while no differences were allocated for HM, EIT, and ηIT. Although the materials tested shared a similar microstructure, significant differences in surface roughness parameters HV and KIC were identified and, thus, differences in their clinical performance were anticipated.
Comparison of Retentive Strengths Among Four Different Prefabricated Primary Posterior Zirconia Crowns
Purpose: To assess retentive strengths of four commercially available posterior primary prefabricated zirconia crowns using a novel epoxy-resin block anchorage system.
Method: 60 extracted human teeth were mounted in epoxy resin blocks compatible with the Instron E3000, and prepared with a single standard prep design. Cheng Crowns (N=15), Kinder Krowns (N=15), NuSmile (N=15), and EZ-Pedo (N=15) were cemented using automix glass ionomer cement. Following thermocycling 5000 cycles from 5º to 55º C, crown retentive strengths were determined and statistically analyzed using one-way ANOVA with LSD post hoc test (P <0.05). Cement failure pattern was also recorded.
Results: Mean retentive strengths: Cheng Crowns 397.4±178.7 N, Kinder Krowns 158.2±58.9 N, NuSmile 183.5±55.5 N, and EZ-Pedo 482.5±87.4 N. EZ-Pedo had the most significant retentive strength, followed by Cheng Crowns (P<0.05). NuSmile and Kinder Krowns followed with no statistical significance between the two.
Conclusion: Retentive strengths among the four prefabricated zirconia crowns are significantly different. EZ-Pedo and Cheng Crowns have statistically significantly greater retentive strength than Kinder Krowns and NuSmile. EZ-Pedo and Cheng Crowns show greater adhesive failure to the tooth, whereas Kinder Krowns and NuSmile show greater adhesive failure to the crown.
Retentive Strengths for Prefabricated Primary Molar Zirconia Crowns Using Five Different Cements
Purpose: To assess retentive strengths of 5 commercially available cements with prefabricated primary molar zirconia crowns.
Method: Seventy five prefabricated primary molar zirconia crowns were cemented on extracted human teeth using 5 different cements (Ketac Cem Maxicap, FujiCEM 2, BioCem, RelyX Unicem 2 and RelyX Luting Plus Automix N=15 per group). Following thermocycling, 5000 cycles from 5o to 55o C, crown retentive strengths data were collected and statistically analyzed using one-way ANOVA with LSD post hoc test (P <0.05).
Results: Mean retentive strengths are: Ketac Cem 482.4N±87, FujiCEM 2 354.9N±121, BioCem 462.7N±138, RelyX Unicem 2 409.0N±171 and RelyX Luting 233.5N±170. The retentive strengths were statistically significant (P=0.014) among the 5 groups, but not the cement failure rankings (P=0.47).
Conclusion: There is a significant difference in the retentive strengths for cementing prefabricated primary molar zirconia crowns among the 5 different cements. Ketac Cem has the highest retention force, followed by BioCem, RelyX Unicem, Fuji CEM II, and RelyX Luting. The majority of cement failures occurred between the cement and the tooth.