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

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.

Flexural strength, flexural modulus and microhardness of milled vs. fused deposition modeling printed Zirconia; effect of conventional vs. speed sintering

BACKGROUND

Various methods can be used for creating zirconia dental restorations, including 3-dimensional (3D) printing and computer-aided design/ computer-aided manufacturing (CAD/CAM) milling. The fused deposition modeling (FDM) printing method for zirconia presents numerous advantages, albeit research on the mechanical properties of these materials and resultant restorations remains scarce. Such developments are undeniably intriguing and warrant further investigation. The objective of the present study was to evaluate the impact of the sintering firing cycle (Conventional vs. Speed sintering) on the flexural strength, flexural modulus, and Vickers Microhardness of milled vs. FDM printed zirconia.

METHODS

A total of 60 bars (2 × 5 × 27 mm) were fabricated for flexural strength testing, along with 40 discs (12 × 1.5 mm) for Vickers microhardness testing. Half of the specimens underwent conventional sintering, while the other half underwent a speed sintering cycle. The flexural strength and modulus were determined by a three-point bending test in a universal testing machine. The microhardness of the specimens was evaluated using a Vickers microhardness tester. Statistical analysis was performed using a two-way ANOVA test with a post-hoc Tukey test (p < 0.05).

RESULTS

CAD/CAM milled zirconia had significantly higher flexural strength and modulus than FDM-printed zirconia. The sintering process did not significantly affect the flexural strength or modulus of milled or FDM-printed zirconia. The milled speed sintering group had significantly higher values in the Vickers microhardness test compared to the other groups.

CONCLUSIONS

The mechanical properties of FDM-printed zirconia specimens were not found to be comparable to those of milled zirconia. Speed sintering cycle may produce milled zirconia restorations with similar flexural strength and modulus to conventional sintering, and even higher Vickers Microhardness values.

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.

Fracture resistance of monolithic translucent zirconia crown bonded with different self-adhesive resin cement: influence of MDP-containing zirconia primer after aging

OBJECTIVES

Successful ceramic restorations depend on the strong bonding with resin cement and even stress distribution. The aim of this study was to evaluate the impact of adding MDP-containing zirconia primer before self-adhesive resin cements with different functional acidic monomers on fracture resistance of monolithic zirconia crown.

MATERIALS AND METHODS

Eighty defect-free human maxillary premolars were divided according to the cement type and application of MDP-containing zirconia primer into eight groups (n = 10): Calibra Universal (C), Calibra Universal combined with zirconia primer (CZ), RelyX U200 (R), RelyXU200 combined with zirconia primer (RZ), Panavia SA Cement Plus (P), Panavia SA Cement Plus combined with zirconia primer (PZ), Multilink Speed (M), and Multilink Speed combined with zirconia primer (MZ). After teeth preparation and fabrication of zirconia crowns, each crown was bonded to its corresponding tooth. All specimens were subjected to 10,000 thermocycles between 5 and 55°C, followed by cyclic load (50 N) for 240,000 cycles. Each specimen was subjected to a static axial load until fracture using universal testing machine and the fracture load was recorded. The fracture mode studied and recorded. The fracture load results were analyzed using two-way ANOVA test (α = 0.05).

RESULTS

A significant interaction (P = 0.038) of combining MDP-containing zirconia primer and cement type on fracture resistance of monolithic zirconia crown was detected. The mean fracture load values of zirconia crown were significantly influenced by the combined application of the MDP-containing zirconia primer with Calibra Universal (P = 0.01), RelyX U200 (P < 0.001), and Multilink Speed (P = 0.038), while there was no significant difference with Panavia SA Cement Plus (P = 0.660). There was significant difference (F = 20.69, P < 0.001) between the mean fracture loads of groups with self-adhesive cements (C, R, P, and M groups). The highest fracture load was recorded with RZ group (2446.90 ± 126.72 N) while the lowest fracture load was recorded with C group (1623.18 ± 149.86 N).

CONCLUSIONS

The self-adhesive resin cement with different acidic functional monomer affects the fracture resistance of monolithic zirconia crown. Application of MDP-containing primer could improve the fracture resistance of monolithic zirconia crown with most self-adhesive cements. The application of an MDP-containing primer had no impact on the fracture resistance of monolithic translucent zirconia crown bonded by MDP-containing self-adhesive resin cement.