Trueness of vat-photopolymerization printing technology of interim fixed partial denture with different building orientation: A Microcomputed tomography study

Background

The aim was to assess the consequence of different printing orientation on the marginal misfit and internal gap of 3-unit interim fixed partial denture manufactured by two different additive manufacturing technologies compared to milling technique.

Material and Methods

Three-unit interim fixed partial denture (FPD) was designed by using exocad software (Dental CAD 3.0 Galway) in the format of standard tessellation language (STL) , which was transferred to a nesting software (PreForm) and printed by A Next Dent C&B resin liquid (NextDent; Soesterberg, Neitherland) by using two printing technologies; stereolithography (SLA, n=30) and digital light processing (DLP, n=30) with 3 different orientations (occlusal direction [0°] ,buccal direction [90°] & lingual direction [270°]) for each technology (n=10). Additionally, a control group was milled (CAD/Milling, n=10) from DC PMMA A1 Disc (White peaks dental solutions; Gmbh& co., Germany). A Microcomputed tomography was used to measure the marginal misfit and internal gap for each specimen in 12 different points. The average value of the marginal and internal gaps measurements was calculated, and one-way ANOVA was used for the comparison between groups.

Results

SLA printing technology showed a similar result to CAD/Milling with all different printing orientations tested. DLP printing technology showed the highest gap values within all the printing orientations with significant difference (p< 0.001) with the CAD/Milling and SLA.

Conclusions

Regarding the trueness of the interim FPDs, SLA was a promising technology for its superior adaptation. Marginal misfit and Internal gap for DLP printing technology limiting the use of that technology as it exceeded the acceptable clinical range. Key words:3D Printing, Microcomputed topography, Marginal Gap, Internal Misfit.

Marginal adaptation and fracture resistance of virgilite-based occlusal veneers with varying thickness

STATEMENT OF PROBLEM

CAD/CAM occlusal veneers have been developed for minimally invasive prosthetic restoration of eroded teeth. Marginal adaptation and fracture resistance are crucial for the long-term survivability and clinical success of such restorations. Virgilite-based lithium disilicate glass-ceramic is a newly introduced material with claims of high strength. However, constructing occlusal veneers from this material of varying thickness has not been investigated.

PURPOSE

The current study aimed to assess the impact of CAD/CAM occlusal veneer thickness and materials on marginal adaptation and fracture resistance.

MATERIALS AND METHODS

Thirty-two occlusal veneers were constructed and divided into two groups (n = 16) based on the CAD/CAM material into Brilliant Crios and CEREC Tessera. Each group was further subdivided into two subgroups (n = 8) according to the thickness: 0.6 and 0.9 mm. Occlusal veneers were bonded to epoxy resin dies. The marginal gap was evaluated before and after thermodynamic aging. Fracture resistance and failure mode were evaluated for the same samples after aging. Marginal adaptation was analyzed using the Mann-Whitney U test. Fracture resistance was analyzed using Weibull analysis (α = 0.05).

RESULTS

The marginal gap was significantly increased following thermodynamic aging for tested groups (P < 0.001). CEREC Tessera showed a significantly higher marginal gap than Brilliant Crios before and after aging for both thicknesses (P < 0.05). CEREC Tessera recorded lower significant fracture load values compared to Brilliant Crios (P < 0.05).

CONCLUSIONS

Both CEREC Tessera and Brilliant Crios demonstrated clinically accepted marginal gap values. All groups showed fracture resistance values higher than the average masticatory forces in the premolar region except for 0.6 mm CEREC Tessera.

CLINICAL IMPLICATIONS

Reinforced composite occlusal veneers demonstrated more favorable outcomes in terms of marginal gap and fracture resistance at both tested thicknesses compared to virgilite-based lithium disilicate glass-ceramic. Additionally, caution should be exercised during the construction of occlusal veneers from virgilite-based lithium disilicate glass-ceramic with reduced thickness.

MDP-salts as an adhesion promoter with MDP-primers and self-adhesive resin cement for zirconia cementation

PURPOSE

To evaluate the effect of zirconia priming with MDP-Salt before MDP containing primers and self-adhesive cement on the shear bond strength.

MATERIALS AND METHODS

Fully sintered high translucent zirconia specimens (n = 120) were assigned into 2 groups (n = 60 each): Control (No Pretreatment) and Methacryloyloxydecyl dihydrogen phosphate salt (MDP-Salt) pretreated. Each group was divided into 3 subgroups (n = 20) according to cementation protocol: 1) MDP + Silane primer and conventional resin cement, 2) MDP+ Bisphenyl dimethacrylate (BPDM) primer and conventional resin cement, and 3) MDP containing self-adhesive resin cement. Shear bond strength (SBS) was measured after 10,000 thermocycling. Contact angle was measured for tested groups. Surface topography was assessed using a 3D confocal laser scanning microscope (CLSM). Weibull analysis was performed for SBS and one-way ANOVA for contact angle and surface topography measurements (α = 0.05).

RESULTS

The use of MDP-Salt significantly improved the SBS (p < .05) for all tested subgroups. Self-adhesive cement showed an insignificant difference with MDP + Silane group for both groups (p > .05). MDP + BPDM showed a significantly lower characteristic strength compared to self-adhesive resin cement when both were pretreated with MDP-Salt. No difference between all tested groups in the surface topographic measurements while MDP-Salt showed the highest contact angle.

CONCLUSION

MDP-Salt pretreatment can improve bonding performance between zirconia and MDP containing products.

Alumina and glass-bead blasting effect on bond strength of zirconia using 10-methacryloyloxydecyl dihydrogen phosphate (MDP) containing self-adhesive resin cement and primers

In fact, bonding of zirconia restorations is still a big challenge in clinical situations and many bonding protocols discussed in literature might be still controversial. The aim of this was to study assess the bond strength of zirconia after alumina and glass-bead pre-treatments with two different primers in combination with conventional resin cement and 10-methacryloyloxydecyl dihydrogen phosphate (MDP) containing self-adhesive resin cement without priming. Fully sintered high translucent zirconia samples (n = 160) were assigned into 2 groups of pre-treatments (n  = 80): Alumina-sandblasting (AB) and Glass-bead (GB). Then, each group was divided into 4 sub-groups according to priming and cement used (n  = 20 each): conventional self-adhesive resin cement, MDP-silane Primer, MDP primer both with conventional self-adhesive resin cement, and MDP contained cement. Shear bond strength (SBS) was measured after thermocycling. Failure mode was analyzed using stereomicroscope. Contact angle and surface topography were investigated using other fully sintered samples (n  = 30) constructed for that sole purpose, divided into control (no pre-treatment [unmodified], alumina-, and glass-bead sandblasted groups). Two-way ANOVA was performed for SBS and failure mode was analyzed. The use of Alumina-sandblasting showed higher SBS compared to Glass-bead pre-treatment for MDP-silane primer (p = 0.034) and MDP primer (p < 0.001). While MDP contained cement showed higher but insignificant SBS when pre-treated with glass-beads. Alumina-sandblasting and glass-bead pre-treatments improve bond strength of zirconia combined using primers before cementation with conventional resin cement. Also, self-adhesive MDP contained cement along with surface pre-treatment showed the highest achievable bond strength. It was concluded that both alumina-sandblasting and glass-bead blasting improved SBS combined with MDP containing self-adhesive resin cement reducing the required clinical steps during cementation of zirconia restorations.

Effect of silver diamine fluoride activation on bond strength to root dentin

BACKGROUND

To investigate the effect of silver diamine fluoride (SDF) application and activation on the bond strength of gutta-percha to dentin and resin bonded post to dentin.

METHODS

Thirty-six human premolar teeth were used. The coronal part tooth was removed, and endodontic mechanical preparation was performed for all the teeth. The teeth were divided according to final rinse protocol (n = 9) as follows: Control group; no SDF application, SDF/NA; 38% SDF as a final rinse with no activation, SDF/MDA; 38% SDF as a final rinse with manual dynamic activation and SDF/US; 38% SDF as a final rinse with ultrasonic activation. Root canal obturation using lateral condensation technique followed by fiber post insertion after 48 h in the root canal after corresponding preparations. The roots were cut with a low-speed precision saw creating 2 mm thickness sections. A total of 4 sections were obtained from each tooth, 2 coronal specimens (with post) and 2 apical specimens (with Gutta percha). Each specimen was subjected to push-out bond strength test with a universal testing machine. Data were analyzed using two-way ANOVA.

RESULTS

The Push-out bond strength at the apical root section was significantly higher in SDF/MDA and SDF/US groups compared to control group. While for the coronal part, all SDF treated specimen showed reduced Push-out bond strength.

CONCLUSION

SDF application as final rinse may reduce the bonding performance between fiber post and dentine. Activation with manual and ultrasonic methods improved the bond strength at the apical root section.

Effect of etch-and-rinse and self-etch modes in universal adhesives on push-out bond strength of fiber post

Background

Nowadays, the universal adhesive become more popular among clinicians due to its simple procedure. The application of universal adhesive on root canal dentin prior the self-adhesive resin cement may increase bond-strength between fiber post and dentin. The objective of this study was to evaluate the effect of different etching modes (etch-and-rinse and self-etch) to universal adhesives on push-out bond strength of fiber post.

Material and Methods

Thirty extracted sound human lower premolars were randomly divided into three groups based on adhesives systems prior to fiber post cementation; two-step etch-and-rinse (group A, Adper Scotchbond), etch-and-rinse universal (group B, Prime & Bond Universal), and self-etch universal (group C, Prime & Bond Universal). After adhesive application, self-adhesive resin cement was filled to the prepared root canal (Smart CEM2, Dentsply) for fiber post cementation. The adhesion between the fiber post and root canal walls was investigated using push-out test after 24 h water storage at 37◦C and the modes of failure were determined under SEM. Data were analyzed using two-way ANOVA test and the Bonferroni test was used to compare values among the three adhesives groups, followed by Tukey HSD for multiple comparisons. Furthermore, Weibull parameters were calculated for tested groups.

Results

Universal adhesive with self-etch mode significantly improved bond-strength compared to the two-step etch-and-rinse group (p<0.05). The coronal part has higher bond strength than the apical section (p<0.05). However, the bond-strength in two-step etch-and-rinse and etch-and-rinse universal was not significantly different. Self-etch mode showed higher bond strength compared to etch-and-rinse universal adhesive in the apical root section (p<0.05). SEM revealed that all tested groups predominantly had an adhesive failure (p>0.05).

Conclusions

Self-etch mode in universal adhesive system were effectively improved the push-out bond strength of fiber post to root canal dentin, especially in apical root section.

Key words:Push-out bond-strength, self-adhesive resin cement, self-etch adhesive, total-etch.

Replacement of Two Failed Indirect Restorations with Direct Bonded Restorations Using Minimally Invasive Strategy

Deciding on what treatment (repair or replacement) to provide for a failed indirect restoration can be challenging. Notably, the strength of the residual tooth structure could be improved after replacing the failed indirect restoration using a minimally invasive strategy. Objective: To describe the use of a minimally invasive strategy for the successful clinical replacement of two failed indirect metal restorations with direct composite restorations and the attainment of bonded restoration. Case Report: Case 1. A 52-year-old male patient came to the dental hospital complaining of discomfort when drinking cold beverages and food impaction on the proximal area of the upper left first molar. Case 2. A 45-year-old female patient complained about her debonded metal onlay and secondary caries in the upper right second molar. Both of these indirect restoration failures were treated with direct resin composite restoration. Both patients were highly satisfied with the results. Conclusion: This report presents the benefits of adopting a minimally invasive strategy approach for replacing failed indirect restorations (inlays and onlays) with direct-bonded composite restorations. Minimally invasive direct restorations are designed to maximize the preservation of tooth structure, thereby ensuring a long-term bonded restoration and leaving future options open when a failure occurs.

Deproteinization of caries-affected dentin with chemo-mechanical caries removal agents and its effect on dentin bonding with self-etch adhesives

OBJECTIVES

To evaluate the micro-tensile bond strength (μTBS) of self-etch adhesives (SEA) to normal and caries-affected dentin after smear layer deproteinization with papain enzyme-based and NaOCl-based chemo-mechanical caries removal agents (CRAs) and to compare their efficacy to a 6 % NaOCl solution.

METHODS

Forty extracted human molars with occlusal carious lesions were randomly divided into four pretreatment groups: no treatment (control), Papacarie for 60 s, Carisolv for 60 s, and 6 % NaOCl for 15 s. After pretreatment, Universal Bond Quick ER (UBQ, one-step, 1-SEA) or Clearfil SE Bond 2 (CSE, two-step, 2-SEA) was applied to the pre-treated surface, and built-up with resin composite (Clearfil AP-X). The μTBS test was performed after 24 h water storage of the specimens at 37 °C, and the modes of failure were determined under SEM. Deproteinizing effects of the tested agents on smear layer-covered dentin was quantified by changes in the amide:phosphate ratio using attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) analysis.

RESULTS

On caries-affected dentin the μTBS improved significantly after pretreatment with Papacarie, Carisolv, and 6 % NaOCl with both SEAs (p < 0.05). Papacarie pretreatment significantly improved the μTBS of UBQ on normal dentin compared to NaOCl pretreatment (p < 0.05). ATR-FTIR revealed that all agents significantly decreased the amide:phosphate ratio on the smear layer-covered normal and caries-affected dentin (p < 0.05).

CONCLUSIONS

Smear layer deproteinizing with papain enzyme-based and NaOCl-based gel CRAs was effective in improving the micro-tensile bond strength of self-etch adhesives to caries-affected dentin.

CLINICAL SIGNIFICANCE

Smear layer deproteinization with Papacarie (a papain enzyme-based gel) or Carisolv (a NaOCl-based gel) can improve the μTBS to normal and caries-affected dentin bonded with 2-step self-etch adhesives.