Zirconia crowns for children: A systematic review

Investigating the impact of surface treatments on tensile bond strength between pediatric prefabricated zirconia crowns and primary maxillary incisors with various types of luting cement: an in vitro study

PURPOSE

This study aimed to evaluate the effects of two surface treatments on the tensile bond strength of prefabricated zirconia crowns (PZCs) using bioactive and resin cements.

METHODS

Forty extracted human primary maxillary incisors were prepared and divided into four groups based on surface treatment and cement type: (1) sandblast with bioactive cement, (2) sandblast with resin cement, (3) 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) with bioactive cement, and (4) 10-MDP with resin cement. After 24 h of cementation, specimens underwent 5000 thermocycling cycles between 5 °C and 55 °C. Tensile bond strengths were measured using a universal testing machine. The data were analyzed using two-way ANOVA and Tukey's post hoc test, with significance set at p < 0.05.

RESULTS

The mean tensile bond strengths observed were 2.25 ± 1.27 MPa for sandblast with bioactive cement, 1.39 ± 0.95 MPa for sandblast with resin cement, 2.45 ± 1.15 MPa for 10-MDP with bioactive cement, and 1.68 ± 1.03 MPa for 10-MDP with resin cement. Significant improvements in bond strength were observed in the bioactive cement group treated with 10-MDP compared to those treated with sandblasting (p < 0.05). The 10-MDP treatment did not enhance bond strength for the resin cement compared to sandblasting.

CONCLUSIONS

Bioactive cement generally provides a higher tensile bond strength than resin cement. While 10-MDP treatment enhances bond strength when used with bioactive cement, it does not show a similar enhancement when used with resin cement compared to sandblasting, indicating its effectiveness is selective based on the type of cement used.

Stress Distribution of Pediatric Zirconia and Stainless Steel Crowns after Pulpotomy Procedure under Vertical Loading: A Patient-Specific Finite Element Analysis

Aim: With modern dentistry advancements, children and parents have significantly raised aesthetic expectations in pediatric dentistry. Pediatric zirconia crowns (PZCs) provide a superior aesthetic appearance compared with stainless steel crowns (SSCs), making them a popular treatment option. However, a comparison of the compressive stresses caused by these crowns on the roots of primary teeth and alveolar bones has not been conducted. Materials and Methods: Cone beam computed tomography (CBCT) images of an eight-year-old female patient who experienced premature loss of a primary mandibular left second molar were obtained from a dental hospital database. Rhinoceros 4.0 software was used to process and simulate images. Under simulated chewing forces, stress on the PZC, SSC, and intact primary first molars as control groups, as well as their roots and alveolar bone structures, was assessed with finite element analysis. Statistical Analyses: Depending on whether the descriptive data were normally distributed, the Student t-test and Mann-Whitney U test were used. Quantitative variables differ between the two categories of qualitative variables. One-way ANOVA and Kruskal-Wallis H tests were used depending on standard distribution assumptions. p < 0.05 indicates statistical significance differences. Results: PZCs, SSCs, and cement layers were stressed according to von Mises values, while roots and alveolar bones were stressed according to maximum and minimum stress values. When assessing crowns, SSCs exhibited the highest von Mises stress values, followed by PZCs and control groups (p < 0.001). In the cement layer, SSCs obtained significantly higher values (p = 0.003). In the root area, minimum principal stress values are more critical. The highest values were obtained from the intact tooth, PZC, and SSC, respectively (p < 0.001). Alveolar bones did not differ significantly in minimum principal stress (p = 0.950). Conclusions: Restorative full-coverage crowns exhibited higher von Mises values than intact teeth, as per current research findings. The von Mises values were highest in SSC, while lowest in PZC. As a result of this condition, the cement layer and root areas had higher von Mises stress and compressive stress. Alveolar bones were not affected regardless of restoration type. PZC transmits higher stress due to its properties.

Clinical Outcome of Prefabricated Zirconia Crowns Cemented with Self-Adhesive Resin and Pure Glass Ionomer on Primary Teeth: A Retrospective Cohort Study

Retentive strength data are critical to predicting the long-term clinical performance of zirconia crowns for primary teeth. Objectives: This research assessed the clinical outcome of prefabricated zirconia crowns (PZCs) cemented with either self-adhesive resin cement or pure glass ionomer cement in the primary teeth of children. Method: In the present research, a sample of 162 prefabricated zirconia crowns were collected through convenience sampling. A follow-up examination was conducted at 12 and 24 months to assess the clinical outcomes of PZCs post cementation. Results: Zirconia crowns cemented with self-adhesive resin showed high clinical outcomes at both 12 and 24 months, with 95.1% of crowns retained. In contrast, crowns cemented with glass ionomer cement had slightly lower clinical outcomes, with 91.4% retained at 12 months and 84.0% retained at 24 months, indicating a significant difference (p-value). Long-term follow-up is crucial for the optimal maintenance of crown stability. Conclusions: Self-adhesive resin cement is a viable option for cementing PZCs in pediatric dentistry, demonstrating satisfactory clinical performance over both 12 and 24 months. Future studies comparing different types of cement are recommended for further validation of these results.

Qualitative surface roughness of lithium disilicate endo-crown for pulpotomized primary molars

Rehabilitation of pulpotomized primary molars with an appropriate restoration is essential for recovering function and safeguarding the durability of the treatment. This study aimed to assess and compare the surface roughness of stainless steel (ST) crowns, zirconia (ZR) crowns, fiberglass (FG) crowns, and lithium disilicate (LD) endo-crowns as a restoration for pulpotomized primary molars also, evaluating the surface roughness of their antagonists. Sixty pulpotomized primary mandibular first molars were used for qualitative surface roughness evaluation and divided into four groups (n = 15/group) according to the crown type (group-ST, group-ZR, group-FG, group-LD). While the other sixty sound, unprepared primary maxillary first molars were used for evaluation of their surface roughness against the tested crowns. Specimens' preparation and cementation were carried out according to each crown type and manufacturer's instructions. The surface roughness was done using a two-body wear test. The data were statistically analyzed. All tested crowns showed an increased change in surface roughness, except group-ZR, which had the least change in surface roughness after mechanical wear with no statistically significant difference(P = 0.681). All crown types significantly increased the surface roughness of their antagonists after mechanical wear, except group-ST which showed insignificant affection (p ≥ 0.05). Zirconia crowns and lithium disilicate endo-crowns had the least change in surface roughness compared to other groups while SSCs showed the least tooth loss in the antagonist enamel.

Tensile bond strength between paediatric prefabricated zirconia crowns and primary maxillary incisors when using various types of luting cements: an in vitro study

PURPOSE

There is limited evidence regarding the most appropriate type of luting cement for paediatric prefabricated zirconia crowns (PZCs) in primary maxillary incisors. The retention of PZCs is dependent on the bond strength of luting cement between PZCs and primary maxillary incisors. The aim of this study was to evaluate the tensile bond strengths between PZCs and primary maxillary incisors with different types of luting cements.

METHODS

Thirty freshly extracted human primary maxillary incisors were prepared and randomly divided into three groups corresponding to three luting cements: bioactive cement, resin cement, and resin-modified glass ionomer cement (RMGIC), and then restored with PZCs. Tensile bond strengths were evaluated by a universal testing machine. The results were analysed using one-way ANOVA with Tukey's post-hoc test (p < 0.05).

RESULTS

The means of the tensile bond strengths were 1.43 ± 0.85 MPa, 0.91 ± 0.63 MPa, and 0.56 ± 0.39 MPa for the bioactive cement, resin cement, and RMGIC groups, respectively. A significant difference in tensile bond strength was observed between the bioactive cement and the RMGIC group (p < 0.05) but there was no significant difference in tensile bond strength between the resin cement group and the others.

CONCLUSION

Types of luting cement influenced the tensile bond strength between PZCs and primary maxillary incisors. The bioactive cement showed higher tensile bond strength than the resin cement and RMGIC.

Bacterial Adhesion in Pediatric Crowns: A Systematic and Meta-Analytical Review

Stainless steel crowns (SSC) have long been the standard choice due to their durability, ease of use, and cost-effectiveness. Other esthetic crowns, known for their superior esthetic properties and biocompatibility, have emerged as a popular option in recent years. A comprehensive literature search was conducted across multiple databases, including PubMed, Scopus, and Cochrane Library, up to June 2024. The population under study was primary teeth, with the intervention being the application of aesthetic crowns. These were compared against SSC, with the primary outcome being the level of microbial adhesion on the crowns in primary teeth. Data extraction and quality assessment were performed independently by two reviewers. Meta-analyses were conducted using random-effects models to estimate pooled differences in microbial adhesion levels. A total of five studies were included in the review. The meta-analysis revealed a statistically significant difference in microbial adhesion between esthetic and SSC, with esthetic crowns showing lower levels of bacterial colonization. Specifically, the mean difference in colony-forming units (CFU). Esthetic crowns exhibit significantly lower microbial adhesion compared to SSC in pediatric patients, suggesting a potential advantage in reducing the risk of secondary caries and other microbial-related complications. However, further long-term clinical studies are warranted to confirm these results and assess their clinical implications.

Survival of pre-formed zirconia crowns in primary teeth: a prospective practice-based cohort study

BACKGROUND

This study aimed to investigate the (1) survival probabilities of prefabricated zirconia crowns (PZCs) placed on primary teeth and (2) identify demographic and tooth-related factors that might affect survival probability.

METHODS

This study prospectively followed children treated under general anaesthesia by a single practitioner between 2012 and 2020. Demographic variables including the age at treatment, gender and tooth-related variables including FDI tooth number, crown size used and any procedural complications at postoperative reviews were collected.

RESULTS

A total of 155 children involving 319 teeth with PZCs were followed up between 12 and 78 months postoperatively with a mean of 38 months. Of the 319 crowns followed, five failures were observed in three patients requiring extraction. Other procedural complications noted included fracture (n = 3), overhangs (n = 3), internal resorption (n = 5) and 24% of crowns showed signs of radiographic changes on postoperative radiographs when these were taken. Age at treatment, tooth type and need for pulp therapy were not statistically associated with clinical success (P > 0.1).

CONCLUSIONS

PZCs provide an aesthetic and durable solution in the management of children with early childhood caries. This study shows very good clinical success and survival extending up to 78 months for PZCs placed on primary teeth under general anaesthesia.

Biocompatibility and acid resistance of preformed crowns in children: an in vitro study

PURPOSE

To investigate the in vitro biocompatibility of human gingival fibroblasts with preformed paediatric crowns and resistance to acid exposure at levels that simulate the oral environment.

METHODS

This laboratory study investigated primary HGFs viability, metabolic activity, cytotoxicity, and apoptotic events on preformed metal crown discs, composite resin-coated wells, and monolithic zirconia fragments at 24, 48, and 72 h using the ApoTox-Glo Triplex assay. The PPCs were also immersed in 0.1% lactic acid, 0.2% phosphoric acid, or 10% citric acid for 7 days at 37 °C to reproduce conditions associated with dietary intake or gastric reflux. Samples were then subject to inductively coupled plasma optical emission spectrometry to quantitate the release of ions.

RESULTS

The viability of HGFs on stainless steel and CR significantly declined at 48 and 72 h, representing potential cytotoxicity (p < 0.05). Cytotoxicity of HGFs was also higher for stainless steel and ZR compared to control (p < 0.05). PMCs and ZR crowns gave minimal ion release. Meanwhile, significant quantities of metallic ions, including copper (Cu), iron (Fe), nickel (Ni), and zinc (Zn), were present in eluates from veneered-preformed metal crowns.

CONCLUSION

As PPCs can be exposed to highly acidic environments for many years, thus the release of metallic ions from V-PMCs should form the further investigation in future studies.

Custom-made versus prefabricated zirconia crowns for primary molars: A 12-month follow-up

BACKGROUND

Many practitioners have questioned whether the construction method of pediatric zirconia crowns impacts the periodontal health and clinical performance of severely decayed primary molars. The objective of this study was to compare the periodontal health and clinical performance of primary molars restored with custom-made zirconia crowns (CZCs) and prefabricated zirconia crowns.

METHODS

Twenty primary molars indicated for crown restorations were selected from ten patients (5-9 years old) randomly. Each patient received two pediatric zirconia crowns constructed by two different methods: one custom-made and one prefabricated. The primary molars were divided into two groups: Group 1: primary molars received CZCs and Group 2: primary molars received prefabricated zirconia crowns (PZCs).

RESULTS

After a 12-month follow-up, there was no statistically significant difference between the periodontal health of primary molars restored with custom-made and prefabricated zirconia crowns. The clinical performance of primary molars restored with CZCs was statistically significantly higher than those restored with PZCs in terms of retention and fracture resistance (P ≤ 0.05).

CONCLUSIONS

The construction method of pediatric zirconia crowns does not significantly affect the periodontal health of primary molars; however, clinical performance is significantly affected in terms of retention and fracture resistance.

CLINICAL SIGNIFICANCE

A CZC is an excellent alternative option, especially for primary molars whose permanent successors still have a long time to erupt. The PZC is a quick and easy restoration, but the technique is sensitive.

Effects of design software program and manufacturing method on the marginal and internal adaptation of esthetic crowns for primary teeth: A microcomputed tomography evaluation

STATEMENT OF PROBLEM

The adaptation of digitally produced crowns is affected by the design software program and manufacturing method. The effect of artificial intelligence (AI) software program design on the adaptation of the crowns is unclear and comparative evaluations should be documented.

PURPOSE

The purpose of this study was to assess the marginal and internal gaps, the absolute marginal discrepancies, and the 3-dimensional (3D) discrepancy volumes of the resin-based milled and 3D printed crowns for primary teeth designed with computer-aided design (CAD) and AI software programs by using microcomputed tomography (µCT).

MATERIAL AND METHODS

A total of 40 resin-based esthetic crowns were produced for a prepared typodont tooth (right mandibular primary second molar) according to the design software program (CAD and AI) and manufacturing method (milling and 3D printing) (n=10). Four experimental groups were generated as CAD-milled, CAD-3D printed, AI-milled, and AI-3D printed. The marginal, axial, and occlusal gap values, the absolute marginal discrepancies, and the 3D discrepancy volumes of the specimens were measured by using µCT. The data were analyzed by using 2-way ANOVA and the Tukey HSD tests (α=.05).

RESULTS

The lowest value for the marginal gap (54 ±43 µm) was observed in the CAD-milled group and the marginal gap value of the AI-3D printed group was significantly lower than the AI-milled group (P<.05). The lowest value for the axial gap (63 ±7 µm) was observed in the AI-3D printed group, and the highest value (145 ±58 µm) was observed in the CAD-milled group; the result for the occlusal gap value was opposite. The highest absolute marginal discrepancy value was observed in the CAD-milled group. The 3D discrepancy volumes increased in the order of the CAD-3D printed, AI-milled, CAD-milled, and AI-3D printed groups.

CONCLUSIONS

The marginal and internal gap values of the resin-based crowns were affected by the design software program and manufacturing method; however, tested groups showed clinically acceptable gap values.

Prefabricated Zirconia Crowns and Preformed Metal Crowns in the Treatment of Severely Childhood Caries and Anterior Crossbite in a Child with Autistic Spectrum Disorder

Crowns have been recommended to treat decayed teeth and rebuild teeth function. The dental management of children with autism is a tremendous challenge for pediatric dentists due to the impaired behaviors and communication disorders. In this context, a 5-year-old boy with autism was treated to solve carious lesions under the assistance of general anesthesia. The posterior occlusal function was restored, and the crossbite existing in the primary anterior teeth was approached merely by NuSmile® zirconia crowns (ZCs) rather than orthodontic intervention. We conducted an 18-month period. Throughout the long-term follow-up, the boy's masticatory efficiency was remarkably improved and the anterior teeth had transferred into the correct position with adequate overbite to maintain the new relationship, thus ameliorating the appearance of tissue on the labial surface and enhancing his quality of life and oral health.

Fracture resistance evaluation of CAD/CAM zirconia and composite primary molar crowns with different occlusal thicknesses

OBJECTIVE

To evaluate the effect of different CAD/CAM materials and occlusal thicknesses on the fracture resistance of primary molar crowns.

METHODS

Sixty extracted primary molar teeth were prepared and randomly divided into six experimental groups according to the material and thickness. Primary molar crowns with a central groove thickness of 0.3 and 0.5 mm were fabricated from CAD/CAM zirconia (group Z), zirconia-reinforced lithium silicate (group ZLS), and pre-polymerized composite resin blocks (group C). Each crown was cemented with self-adhesive resin cement on the prepared tooth. All specimens were subjected to fracture tests until fracture. Fracture load values were recorded in Newtons (N). Data were statistically analyzed using a two-way analysis of variance (ANOVA) followed by Tukey multiple comparison test.

RESULTS

The highest fracture load values were obtained in group Z at 0.5 mm occlusal thickness and were significantly higher compared with the other experimental groups (p < 0.05). Although the lowest fracture load values were obtained in group ZLS at 0.3 mm occlusal thickness, all the tested CAD/CAM primary molar crowns at both thicknesses demonstrated fracture load values exceeding reported chewing force in pediatric patients.

CONCLUSION

CAD/CAM primary molar crowns with reduced occlusal thickness may be used for the full-coverage restoration of primary molar teeth.

Clinical and radiographic performance of preformed zirconia crowns and stainless-steel crowns in permanent first molars: 18-month results of a prospective, randomized trial

BACKGROUND

The treatment of young permanent first molars with extensive carious tissue loss may often require restoration with preformed crowns. This study compared the clinical and radiographic performance of stainless-steel crowns (SSCs) and preformed zirconia crowns (ZCs).

METHODS

Forty-eight molar incisor hypomineralisation (MIH)- or caries-affected permanent molars in 20 healthy patients between 6-13-year-old were randomly divided into ZC and SSC groups (n = 24 teeth/group) in a split-mouth design. The oral hygiene levels of patients were assessed using Greene and Vermillion simplified oral hygiene index (OHI-S). Plaque accumulation and gingival health were evaluated using the Silness&Löe plaque index (PI) and Löe&Silness gingival index (GI), respectively. Clinical retention, marginal extension level, marginal adaptation of crowns and wear of the antagonist teeth were assessed at baseline, 1, 6, 12 and 18 months. The radiological assessments for evaluating the marginal adaptation of crowns and periapical pathology of crowned teeth were performed at 6 and 12 months. The data were analyzed using Kaplan-Meier analysis, Mann-Whitney U test, and two-way ANOVA.

RESULTS

A total of forty teeth in 17 children were evaluated for 18 months. ZCs had significantly lower gingival and plaque index values than teeth restored with SSCs during all evaluation periods (p < 0.05). Neither crown type resulted in clinically-detectable wear on opposing dentition or periapical pathology. One ZC was lost at 13 months, while all SSCs survived in function clinically. The cumulative survival rates of ZCs and SSCs were 95.2% and 100% respectively.

CONCLUSIONS

Both ZCs and SSCs showed high clinical retention rates in young permanent molars. ZCs had lower plaque accumulation and better gingival health than SSCs, which were consistently associated with mild gingival inflammation.

CLINICAL TRIAL REGISTRATION NUMBER

NCT05049694.

Annual review of selected scientific literature: A report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

The Scientific Investigation Committee of the American Academy of Restorative Dentistry offers this review of the 2022 dental literature to briefly touch on several topics of interest to modern restorative dentistry. Each committee member brings discipline-specific expertise in their subject areas that include (in order of the appearance in this report): prosthodontics; periodontics, alveolar bone, and peri-implant tissues; dental materials and therapeutics; occlusion and temporomandibular disorders; sleep-related breathing disorders; oral medicine and oral and maxillofacial surgery; and dental caries and cariology. The authors focused their efforts on reporting information likely to influence the daily dental treatment decisions of the reader with an emphasis on innovations, new materials and processes, and future trends in dentistry. With the tremendous volume of literature published daily in dentistry and related disciplines, this review cannot be comprehensive. Instead, its purpose is to update interested readers and provide valuable resource material for those willing to subsequently pursue greater detail on their own. Our intent remains to assist colleagues in navigating the tremendous volume of newly minted information produced annually. Finally, we hope that readers find this work helpful in managing patients.

Assessment of the reliability of YouTube™ videos about zirconia crowns in pediatric dentistry

PURPOSE

To evaluate the reliability of YouTube™ videos on zirconia crowns in pediatric dentistry.

METHODS

On January 4, 2022, a search was performed using the term "pediatric zirconia crown". The first 100 videos on the subject were included. Non-English videos, duplicates, and off-topic videos were excluded. For each video, an examiner recorded the number of views, likes, comments, channel followers, upload date, duration, and category rating. Two examiners assessed the reliability of the information presented in the videos using DISCERN, a brief questionnaire and scale score used to assess in a valid and reliable way the quality of information on treatment choices for health problems. Descriptive and inferential analyses were performed (p < 0.05).

RESULTS

Of the initial 100 videos, 72 were excluded because of language, duplication, and subject matter. The 28 remaining videos had an average of 3.5 comments, 8,896.18 channel followers, 5,614.00 views, 19.14 likes, and a duration of 840.32 s. The average view rate was 7.54 per day ± 10,206.81. There was a statistically significant difference between the number of views and comments (p < 0.001), likes and comments (p < 0.001), and likes and views (p = 0.006). According to the DISCERN, none of the videos received the maximum grade to be considered very good. Two were considered good, nine fair, fourteen poor, and three very poor.

CONCLUSION

Given that the majority of YouTube™ videos currently available on zirconia crowns in pediatric dentistry were deemed unreliable according to the DISCERN questionnaire, caution should be exercised when using the information presented.

The Clinical Potential of 3D-Printed Crowns Reinforced with Zirconia and Glass Silica Microfillers

The development of 3D-printed crown resin materials with improved mechanical and physical properties is an area of growing interest in dentistry. This study aimed to develop a 3D-printed crown resin material modified with zirconia glass (ZG) and glass silica (GS) microfillers to enhance overall mechanical and physical properties. A total of 125 specimens were created and divided into five groups: control unmodified resin, 5% either ZG or GS reinforced 3D-printed resin, and 10% either ZG or GS reinforced 3D-printed resin. The fracture resistance, surface roughness, and translucency parameter were measured, and fractured crowns were studied under a scanning electron microscope. The results showed that 3D-printed parts that were strengthened with ZG and GS microfillers demonstrated comparable mechanical performance to unmodified crown resin but resulted in greater surface roughness, and only the group that contained 5% ZG showed an increase in translucency. However, it should be noted that increased surface roughness may impact the aesthetics of the crowns, and further optimisation of microfillers concentrations may be necessary. These findings suggest that the newly developed dental-based resins that incorporate microfillers could be suitable for clinical applications, but further studies are necessary to optimise the nanoparticle concentrations and investigate their long-term clinical outcomes.

Full Mouth Treatment of Early Childhood Caries with Zirconia Dental Crowns: A Case Report

Pediatric dentists should always strive for cosmetic and functional rehabilitation when treating decaying or injured primary teeth. The most popular restoration technique for such teeth is "strip crowns" made of composite materials, but more recently, zirconia and preveneered stainless steel crowns have gained popularity. Moreover, zirconia crowns are usually preferred over stainless steel crowns for aesthetic reasons. The aim of this case report is to present a 4-year-old patient with a high caries risk who underwent a full-mouth pediatric zirconia crown treatment. The operation was performed under general anesthesia. This article describes the restoration of all primary teeth and the follow-up 6 months after the parents' request to improve the aesthetics. The gingival health and the adaptation of the zirconia crown were evaluated both clinically and radiologically. In this case, the preformed pediatric zirconia crowns provided functional and durable restoration while restoring the natural appearance of the teeth. However, primary dental prevention, including education on oral hygiene and dietary habits, remains the cornerstone in preventing early childhood caries and promoting oral health in pediatric patients. It is important to note that dental intervention under general anesthesia should only be considered as a last resort after all other options have been exhausted, due to the potential risks associated with the use of general anesthesia.

Case Series on Personalized Pediatric Posterior Zirconia Crowns

Pediatric dentists must comprehend children's aesthetic perception because kids are increasingly aware of their own and other children's appearance. Many aesthetic restorations are available on the market, including open-faced stainless-steel crowns, pre-veneered stainless-steel crowns, strip crowns, and polycarbonate crowns, but each has its own drawbacks. Prefabricated zirconia crowns are a new trend among pediatric dentists for restoring carious, damaged, and malformed primary molars and anteriors. Customized zirconia crowns, on the other hand, may be able to overcome the limitations of prefabricated crowns in certain situations, particularly molars, resulting in excellent aesthetics and longevity. Our case series illustrates the use and performance of personalized zirconia crowns in a variety of challenging clinical circumstances.

Fracture resistance of prefabricated versus custom-made zirconia crowns after thermo-mechanical aging: an in-vitro study

BACKGROUND

Prefabricated zirconia crowns for a young permanent molar is a child-friendly solution for restoring a permanent molar at a young age. This in-vitro study aimed to compare the fracture resistance of prefabricated versus custom-made permanent molar crowns.

METHODS

16 identical resin dies were fabricated to receive permanent molar zirconia crowns, dies were divided into 2 groups, 1) received perfricated crowns, 2) custom-made crowns. Thermo-dynamic cycling was performed to simulate 6 months in the oral cavity, Fracture resistance of each group was assessed by applying increasing load till fracture. Data were tested for normality using Shapiro-Wilk and Levene's tests. Data were analyzed using independent t test.

RESULTS

No statistically significant difference was found between fracture resistance of prefabricated and custom-made crowns (1793.54 ± 423.82) and (1987.38 ± 414.88) respectively. 3 crowns of the custom-made group fractured with the underlying die, versus zero dies fractured in the prefabricated group.

CONCLUSIONS

Prefabricated permanent molars zirconia crowns can perform as well as custom-made crowns for an adult in terms of fracture resistance, it is suitable for children and can withstand the occlusal forces of an adult.

Stress distribution in pediatric zirconia crowns depending on different tooth preparation and cement type: a finite element analysis

BACKGROUND

In clinical settings, tooth preparation for prefabricated zirconia crowns (PZCs) in the primary dentition varies widely. However, knowledge about the biomechanical behavior of PZCs in various clinical settings is limited. This study was conducted to evaluate the biomechanical behavior of PZCs in different clinical settings using 3-dimensional finite element analysis.

METHODS

3-dimensional models of the PZC, cement, and tooth with six different conditions were simulated in primary molar teeth, incorporating cement thickness (100, 500, and 1000 μm) and cement type (resin-modified glass ionomer cement and resin cement). A total of 200 N of occlusal force was applied to the models, both vertically and obliquely as representative cases. A general linear model univariate analysis with partial eta-squared (ηp²) was performed to evaluate the relative effects of the variables.

RESULTS

The overall stress of tooth was increased as the cement space increases under oblique loading. The von Mises stress values of the resin cements were significantly higher than those of the resin-modified glass ionomer cements for all cement thicknesses (p < .05). The effect size of the cement type (η_p² = .519) was more dominant than the cement thickness (η_p² = .132) in the cement layer.

CONCLUSIONS

Within the limits of this study, cement type has a greater influence on the biomechanical behavior of PZCs than cement thickness.

Novel 3D Printed Resin Crowns for Primary Molars: In Vitro Study of Fracture Resistance, Biaxial Flexural Strength, and Dynamic Mechanical Analysis

This study evaluated the fracture resistance, biaxial flexural strength (BFS), and dynamic mechanical analysis (DMA) of three-dimensional (3D) printing resins for the esthetic restoration of primary molars. Two 3D printing resins, Graphy (GP) and NextDent (NXT), and a prefabricated zirconia crown, NuSmile (NS), were tested. GP and NXT samples were 3D printed using the workflow recommended by each manufacturer. Data were collected and statistically analyzed. As a result of the fracture resistance test of 0.7-mm-thick 3D printed resin crowns with a thickness similar to that of the NS crown, there was no statistically significant difference among GP (1491.6 ± 394.6 N), NXT (1634.4 ± 289.3 N), and NS (1622.8 ± 323.9 N). The BFS of GP was higher for all thicknesses than that of NXT. Both resins showed high survival probabilities (more than 90%) when subjected to 50 and 150 MPa. Through DMA, the glass transition temperatures of GP and NXT were above 120 °C and the rheological behavior of GP and NXT according to temperature and frequency were analyzed. In conclusion, GP and NXT showed optimum strength to withstand bite forces in children, and 3D printed resin crowns could be an acceptable option for fixed prostheses of primary teeth.

Clinical effectiveness of restorative materials for the restoration of carious lesions in pulp treated primary teeth: a systematic review

Purpose

To systematically review the clinical performance of restorative materials after pulp therapy of carious primary teeth. It is part 2 of a systematic review on the clinical effectiveness of restorative materials for the management of carious primary teeth supporting the European Academy of Paediatric Dentistry (EAPD) guideline development.

Methods

Four electronic databases were systematically searched up to December 28th, 2020. Randomised controlled clinical trials (RCTs) on restorative materials for the restoration of carious primary teeth after pulp therapy were included. Failure rate, annual failure rate (AFR) and reasons for failure were recorded. Studies were sorted by restorative materials. The Cochrane Risk of bias tool for randomised trials (RoB 2.0) was used for quality assessment.

Results

After identification of 1685 articles and screening of 41 papers from EAPD review group 1, 5 RCTs were included. Restored primary molars with pulpotomy presented the following AFRs: composite resin (CR) 0%, preformed metal crowns (PMCs) 2.4–2.5%, resin-modified glass-ionomer cement combined with CR 3.8%, compomer 8.9%, and amalgam 14.3%. Maxillary primary incisors receiving pulpectomy exhibited AFRs of 0–2.3% for composite strip crowns (CSCs) depending on the post chosen. Reasons for failure were secondary caries, poor marginal adaptation, loss of retention and fracture of restoration. All studies were classified as high risk of bias. Meta-analyses were not feasible given the clinical/methodological heterogeneity amongst studies.

Conclusion

Considering any limitations of this review, CR and PMCs can be recommended for primary molars after pulpotomy, and CSCs for primary incisors receiving pulpectomy. However, a need for further well-designed RCTs was observed.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40368-022-00744-4.

Clinical effectiveness of restorative materials for the restoration of carious primary teeth without pulp therapy: a systematic review

Purpose

To systematically search the available evidence and evaluate the clinical effectiveness of restorative materials for restoration of carious primary teeth. The findings aimed to support the European Academy of Paediatric Dentistry (EAPD) guidelines development.

Methods

Literature search was performed by searching 4 electronic databases for eligible randomised controlled clinical trials (RCTs) comparing restorative materials for the restoration of carious primary teeth up to December 28th, 2020. Quality assessment was performed with the revised Cochrane risk-of-bias tool for randomized trials (RoB 2).

Results

Of 1685 identified articles 29 RCTs were finally deemed as eligible for inclusion. Annual failure rates were: Amalgam 1–28%; atraumatic restorative treatment 1.2–37.1%; glass-ionomer cement (GIC) 7.6–16.6%, metal-reinforced GIC 29.9%, resin-modified GIC 1.9–16.9%, high-viscosity GIC 2.9–25.6%; glass carbomer ≤ 46.2%; compomer 0–14.7%; composite resin (CR) 0–19.5%, bulk-fill CR 0–16.9%; zirconia crowns 3.3%, composite strip crowns 15%, and preformed metal crowns (Hall-Technique) 3.1%. Secondary caries, poor marginal adaptation, loss of retention, and fracture of restoration were reported as reasons for failure. Four studies were evaluated at unclear and 25 at high risk of bias. Clinical and methodological heterogeneity, and the diversity of tested materials across included studies did not allow for meta-analyses.

Conclusions

Within the limitations of this systematic review, namely, the heterogeneity and the overall high risk of bias among included studies, clear recommendations based on solid evidence for the best restorative approach in primary teeth cannot be drawn. There is a need for future thoroughly implemented RCTs evaluating restorations in primary teeth to close this knowledge gap.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40368-022-00725-7.

Caries Experience and Increment in Children Attending Kindergartens with an Early Childhood Caries Preventive Program Compared to Basic Prophylaxis Measures-A Retrospective Cohort Study

Dental caries constitutes a public health challenge. As preventive strategies are desirable, this retrospective cohort study aimed to assess the caries experience and increment in children attending kindergartens with an early childhood caries (ECC) preventive program (intervention group, IG) compared to basic prophylaxis measures (control group, CG) located in areas of different socioeconomic status (SES) within Marburg (Germany). The long-term caries experience (2009−2019) of these 3−5-year-old kindergarten children was evaluated. For the caries increment, dental records of 2019 were screened for the availability of a minimum of two dental examinations at least 8 months apart. Caries was scored according to the WHO criteria (dmf−t). The data were split by observation period (300−550 and >550 days). Overall, 135 children (Ø 3.7 years) attended IG, and 132 children (Ø 3.6 years) attended CG. After 300−550 days, no significant differences were found between both groups regarding mean caries increment and experience (p > 0.05). After >550 days, IG with low SES exhibited a high caries experience. Fluoride varnish applications could not reduce the caries increment compared to CG in the short-term but slightly decreased the long-term caries experience. Comprehensive ECC prevention measures actively involving parents are needed to overcome the caries burden.

Effects of decontamination protocols on the aesthetic, morphological, and material composition of preformed paediatric crowns

BACKGROUND

Preformed crowns (PCs) are exposed to potentially infectious bodily fluids during the trial fit; however, whether they can be safely re-used remains uncertain. This study determined the effects of decontamination methods on various PCs. The key criteria examined were aesthetic, morphological, and elemental characteristics.

DESIGN

This is a laboratory-based experimental study. Stainless steel, pre-veneered stainless steel, and zirconia PCs underwent either: (a) ultrasonic cleaning with EmPower^® followed by steam sterilisation, (b) thermal disinfection in an instrument washer with Asepti^® Neutraliser/Asepti^® followed by steam sterilisation, or (c) immersion in an ortho-phthalaldehyde (OPA) instrument-level disinfectant. The methods were performed for 1, 5, or 10 cycles, and scanning electron microscopy (SEM); red, green, and blue (RGB) value; and luminosity value were tracked (using a histogram of individual colour reference chips in Adobe Photoshop^® ) to assess colour changes, and energy-dispersive X-ray (EDX) spectroscopy to characterise the material composition.

RESULTS

Pre-veneered stainless steel crowns showed isolated zones of darkening with loss of luminosity and variations in green and blue values after ultrasonic or thermal washer disinfection combined with steam autoclaving at 5 and 10 cycles. No changes occurred with OPA. Both SEM imaging and EDX analysis identified no changes to crown materials from any of the three reprocessing methods.

CONCLUSIONS

Reprocessing protocols need to reflect the differing responses of various types of PCs. Repeated steam sterilisation causes slight aesthetic alterations by way of colour instability and loss of luminosity to pre-veneered stainless steel crowns, but no issues with stainless steel or zirconia PCs.

Wear and marginal quality of aesthetic crowns for primary molars

BACKGROUND

Due to limited aesthetics of stainless-steel crowns, the demand for tooth-coloured crowns has recently risen. Few studies have investigated the marginal integrity and wear behaviour of tooth-coloured primary molar crowns under subcritical load in vitro.

AIM

This in vitro study evaluated the marginal quality and wear of newly introduced resin composite and hybrid ceramic crowns compared with metal and zirconia crowns.

DESIGN

Metal, resin composite, hybrid ceramic (CAD/CAM), and various zirconia crowns were investigated. After thermomechanical loading (2,500 thermocycles/100,000 × 50N), marginal quality of luting gaps and wear of crowns/antagonists were evaluated using replicas under a light or 3D laser scanning microscope. Results were analysed with the Mann-Whitney U test or one-way ANOVA (p < .05).

RESULTS

Marginal quality of the new resin composite and hybrid ceramic crowns performed well in comparison with SSC and zirconia crowns. Adhesive bonding of crowns resulted in superior marginal seal compared with conventional GIC (Mann-Whitney U test, p < .05). Regarding wear, zirconia crowns exhibited significantly worse results than resin composite or hybrid ceramic crowns and SSCs (ANOVA, p < 0.05).

CONCLUSION

The new resin composite and hybrid ceramic crown exhibited good performance in comparison with SSCs and zirconia crowns considering both wear and marginal quality after subcritical loading.

Zirconia Crowns for Primary Teeth: A Systematic Review and Meta-Analyses

Objective: The aim of this systematic review was to summarize the literature regarding the clinical performance of zirconia crowns for primary teeth. Materials and Methods: Four electronic databases, Ovid, PubMed, Scopus, and Web of Science were searched. Clinical, observational, and laboratory studies were included. Studies that assessed the performance of zirconia crowns for primary teeth using outcomes such as gingival and periodontal health, parental satisfaction, color stability, crown retention, contour, fracture resistance, marginal integrity, surface roughness, and recurrent caries were included. Risk of bias was assessed using different assessment tools depending on the type of the assessed study. Results: Out of the 2400 retrieved records, 73 full-text records were assessed for eligibility. Thirty-six studies were included for qualitative analysis. The included studies reported that zirconia crowns for primary teeth were associated with better gingival and periodontal health, good retention, high fracture resistance, color stability, high parental acceptance, good marginal adaptation, smooth cosmetic surface, and no recurrent caries. Conclusion: Zirconia crowns are promising alternative to other restorative materials and crowns in the field of pediatric dentistry. They showed higher properties and performance in different clinical aspects and great parental satisfaction.