3D printing of ultra-thin veneers made of lithium disilicate using the LCM method in a digital workflow: A feasibility study

OBJECTIVE

This article highlights the feasibility of the additive fabrication of ultra-thin veneers made of lithium disilicate using the lithography-based ceramic manufacturing (LCM) method.

CLINICAL CONSIDERATIONS

An esthetical appealing restoration of anterior teeth with thin ceramic veneers is considered one of the ultimate challenges in restorative dental prosthetics. These sophisticated restorations can be fabricated in different ways. Both analog and digital subtractive manufacturing processes have been used to date. Either of the methods is highly demanding for the dental technician and dental engineering due to the required low ceramic layer thickness.

CONCLUSION

Modern additive manufacturing methods, for example LCM technology, enable the production of ultra-thin lithium disilicate veneers with layer thicknesses of down to 0.2 mm and could therefore represent a viable alternative for this indication in the future.

CLINICAL SIGNIFICANCE

Digital technologies can help streamline workflows, make the outcome more predictable and reproducible, and even further optimize therapeutic restorative options such as highly esthetic veneers for anterior teeth. The reduced material thickness allows for a true non-prep solution or minimally invasive preparation.

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.

Total Rehabilitation Using Adhesive Dental Restorations in Patients with Severe Tooth Wear: A 5-Year Retrospective Case Series Study

INTRODUCTION

Currently, there is little clinical evidence to support the medium- and long-term survival and clinical performance of ultraconservative approaches using adhesive restorations in full-mouth restorations. The aim of this case series study was to evaluate the medium-term clinical performance of anterior and posterior adhesive restorations applied with direct and indirect techniques using resin composites and glass-ceramic-based materials.

MATERIALS AND METHODS

The inclusion criteria were an esthetic problem as the main reason for consultation and severe generalized wear of grade 2 to 4 according to the Tooth Wear Evaluation System (TWES 2.0). In addition, at each follow-up appointment, patients were required to submit a clinical-parameter-monitoring record according to the modified United States Public Health Service (USPHS) criteria.

RESULTS

Eight patients with severe tooth wear were treated through full rehabilitation in a private dental clinic in Spain by a single operator (AFC). A total of 212 restorations were performed, which were distributed as follows: 66 occlusal veneers, 26 palatal veneers and 120 vestibular veneers. No signs of marginal microleakage or postoperative sensitivity were observed in any occlusal, vestibular and/or palatal restoration after the follow-up period. The estimated survival rate of the 212 restorations was 90.1% over 60 months of observation, with a survival time of 57.6 months. Only 21 restorations had complications, which were mostly resolved with a direct composite resin. The dichotomous variables of the restoration type (posterior veneer, anterior veneer) and the type of restored tooth (anterior, posterior) were the risk predictors with statistically significant influences (p < 0.005) on the survival of the restorations.

CONCLUSION

According to the results of this study, there is a significantly higher risk of restorative complications in posterior teeth compared to anterior teeth. Also, it can be concluded that the indication of adhesive anterior and posterior restorations is justified in the total oral rehabilitation of patients with severe multifactorial tooth wear, as they are associated with a low risk of failure.

Effect of thickness and CAD-CAM material on fatigue resistance of endodontically treated molars restored with occlusal veneers

PURPOSE

To evaluate the influence of the thickness and type of computer-aided design and computer-aided manufacturing (CAD-CAM) material on the fatigue resistance and failure mode of endodontically treated teeth (ETT) restored with occlusal veneers (OV).

MATERIALS AND METHODS

Seventy-five (N = 75) ETT were restored with Herculite XRV in the endodontic access. Five experimental groups (n = 15) were tested. Four groups had two different thicknesses (0.6-0.7 mm or 1.4-1.6 mm) and two different CAD-CAM materials: zirconia-reinforced lithium-silicate (LS/Celtra Duo) and composite resin (RC/Cerasmart). The fifth group (control) did not have occlusal veneers. All the specimens were subjected to accelerated fatigue (5 Hz frequency) with an occlusal load increasing up to 1800 N and 131,000 cycles. The number of cycles was recorded when the machine stopped or at the completion of the test. Fatigue resistance was analyzed using the Kaplan-Meier survival test (95% significance level, log-rank post hoc pairwise comparisons). The samples were categorized according to failure mode. The CAD-CAM materials were examined through scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS).

RESULTS

No differences were found between the thicknesses, regardless of the type of the CAD-CAM material. The thick LS OV outperformed the RC and control groups. The thin RC OV and control groups showed a higher percentage of repairable and possibly repairable failures than the other groups. LS was more homogeneous under SEM, and the EDS analysis detected Si and Zr, but not Li.

CONCLUSIONS

A larger thickness did not improve the resistance of the CAD-CAM materials. Thick LS showed a higher cumulative survival rate to fatigue than the RC and control groups. The direct composite alone (control) survived similarly to the experimental groups, except for the thick LS.

Clinical outcomes and influence of material parameters on the behavior and survival rate of thin and ultrathin occlusal veneers: A systematic review

PURPOSE

Various oral rehabilitation approaches are available for severely worn dentition. However, evidence-based guidelines for permanent treatment are limited. This review aims to investigate clinical observational findings and compare in-vitro outcomes of thin and ultrathin occlusal veneers using different materials and approaches.

METHODS

An electronic search of online databases, such as PubMed (MEDLINE), BioMed Central (BMC), Cochrane, and Scopus, was performed for the 2009 - Jun 2021 period, following the PRISMA 2020 criteria. The reports sought for retrieval were all the articles evaluating the clinical outcomes of permanent full-mouth rehabilitation, and all in-vitro records that investigated and compared fracture strength, survival rate, and modes of failure of ultrathin (0.3 - 0.6 mm), thin (0.5 - 0.8 mm), and thick (0.8-1.5 mm) occlusal veneer restorations, with regard to the available indirect restorative materials. The Newcastle Ottawa risk of bias criteria was used to judge the clinical studies and a modified consort statement was used for the evaluation of in-vitro studies. The data of the included studies were extracted and grouped based on the similarity of the outcomes and study protocols. Data heterogeneity determined the qualitative and quantitative grouping of the results.

RESULTS

Two clinical and 17 in-vitro studies were included. Data exhibited heterogeneity within the materials, variables, testing protocols and observation periods. Therefore, only qualitative synthesis of the results was feasible. Clinically used 1 mm lithium disilicate overlays and ultrathin one-step no-prep polymer infiltrated ceramic network (PICN) occlusal veneers exhibited very high success and survival rates. The analysis of in-vitro studies exhibited variable survival rates and fracture load values, based on materials, thickness, and restorative approaches used.

CONCLUSIONS

Within the limitations of this systematic review, it can be concluded that the clinical outcomes of thin and ultrathin occlusal veneers/overlays are auspicious. In-vitro experimental results support the usage of the thin and ultrathin occlusal veneers.

Ultrathin CAD-CAM glass ceramic and composite resin occlusal veneers for the treatment of severe dental erosion: An up to 3-year randomized clinical trial

STATEMENT OF PROBLEM

Ultrathin bonded posterior occlusal veneers represent a conservative alternative to traditional onlays and complete coverage crowns for the treatment of erosive dental wear. Data regarding the clinical performance of ceramic and composite resin ultrathin occlusal veneers are lacking.

PURPOSE

The purpose of this prospective randomized clinical trial was to evaluate the influence of computer-aided design and computer-aided manufacturing (CAD-CAM) restorative material (ceramic versus composite resin) on the clinical performance of ultrathin occlusal veneers bonded to worn posterior teeth.

MATERIAL AND METHODS

Eleven participants (mean age, 30.4 years) had their posterior teeth restored with 24 ceramic (e.max CAD) and 36 composite resin (Lava Ultimate) ultrathin occlusal veneers. The material type was assigned randomly. The tooth preparations were trial restoration driven and included immediate dentin sealing (OptiBond FL). The intaglio surfaces of the ceramic restorations were etched with hydrofluoric acid and silanated, and the composite resins were airborne-particle abraded and silanated. The tooth preparations were airborne-particle abraded and etched with phosphoric acid before restoration insertion. All restorations were adhesively luted with preheated composite resin (Filtek Z100). The participants were evaluated according to the modified United States Public Health Service (USPHS) criteria at baseline and then each year for up to 3 years. Survival rates were estimated with time to failure (primary outcome of interest) as the endpoint (scores 4 or 5).

RESULTS

No restorations were lost. Five partial failures, in the form of chipping (all scored 4), were observed in the composite resin group (Lava Ultimate). The Kaplan-Meier survival rates were 100% for ceramic and 84.7% (SE 0.065%) for composite resin. Differences between the 2 groups were not statistically significant (P=.124). In the surviving restorations, significant difference (P=.003) was found for surface roughness as restorations in the composite resin group experienced some surface degradation.

CONCLUSIONS

The findings of this medium-term clinical trial suggest that ceramic (e.max CAD) and composite resin (Lava Ultimate) CAD-CAM ultrathin occlusal veneers presented statistically comparable performance regardless of the minor partial failures (restorable chipping) observed in the composite resin group. Higher surface degradation was observed in the composite resin group.

Clinical and Biomechanical Performance of Occlusal Veneers: A Scoping Review

AIM

This manuscript aims to evaluate, through a scoping review, current knowledge of the biomechanical behavior, materials, preparations, and limitations of occlusal veneers.

BACKGROUND

Occlusal veneers are a minimally invasive alternative for the additive restoration of posterior teeth with significant loss of the occlusal structure. This type of restoration has been emerged in recent years as an alternative to invasive treatment, which in the same way seeks to restore the structure of the posterior teeth. All this is because in recent years restorative dentistry has focused a large part of its objectives on conservative therapies.

REVIEW RESULTS

Five electronic databases-PubMed, Cochrane, LILACS, EMBASE, and Google Scholar-were searched. Title and abstracts were independently screened by three reviewers, followed by a full-text review. A total of 42 articles met our inclusion criteria; most of these studies were in vitro (n = 35) and other studies were clinical studies (n = 7). These in vitro studies included 21 studies that analyzed the type of preparation and 6 studies that evaluated the limitations of occlusal veneers.

CONCLUSION

Thicknesses between 0.7 and 1.0 mm are recommended for ceramic materials; in addition, thicknesses less than 0.7 mm are recommended to use polymeric materials. The materials used for this type of restoration are plastic- and ceramic-based materials, whose load resistance values were found to exceed 2000 N in most studies. It is recommended to carry out a minimally invasive preparation or not to carry out a dental preparation, as long as there is a peripheral enamel to make an external bevel that redirects the eccentric forces to the axis of the tooth.

CLINICAL SIGNIFICANCE

Restorative dentistry has moved toward conservative treatments with the least amount of dental tissue being removed. Occlusal veneers appear to be a conservative option in the reconstruction of tooth tissues lost due to tooth wear and in cases where it is necessary to restore or increase the vertical dimension.

Fracture Resistance and Failure Mode of Mandibular Molar Restored by Occlusal Veneer: Effect of Material Type and Dental Bonding Surface

This study assesses the effect of the material type (lithium disilicate, zirconia, and polymer-infiltrated ceramic) and dental bonding substrates (dentin, dentin with intra-coronal cavity, and dentin with composite filling) on the fracture resistance and failure mode of molars restored by occlusal veneers. Methods: Ninety occlusal veneers, fabricated from either lithium disilicate, zirconia, or polymer-infiltrated ceramic, were adhesively bonded to teeth prepared with either dentin, dentin with intra-coronal cavity, or dentin with composite filling. All specimens were thermally aged (5000 cycles), then load cycled (120,000 cycles). Each specimen was subjected to a compressive load through fracture, then was examined (×20) to identify the fracture type. Data were statistically analyzed. Results: Material type and dental substrate had no significant effect on the fracture resistance of adhesively retained occlusal veneer restorations. For each material, no significant differences were found between veneers bonded to dentin, dentin with intra-coronal cavity, and dentin with composite filling. Additionally, within each bonding substrate, there were no significant differences between lithium disilicate, zirconia, and polymer-infiltrated ceramic veneers. The adhesive failure was recorded mainly with zirconia occlusal veneer restorations. Conclusions: Considering the fracture results, lithium disilicate, zirconia, and polymer-infiltrated ceramic occlusal veneers perform well whatever the type of dental bonding surface. When the dental bonding surface varies, different occlusal veneer materials should be considered. Occlusal veneers bonded to dentin, dentin with composite filling, or dentin with an intra-coronal cavity exhibited a fracture resistance exceeding the average human masticatory forces in the molar area.

Comparison of Fracture Resistance for Chairside CAD/CAM Lithium Disilicate Crowns and Overlays with Different Designs

PURPOSE

To determine the fracture resistance of chairside computer-aided design and computer-assisted manufacturing (CAD/CAM) lithium disilicate full coverage crowns and two different designs of overlay restorations for premolars.

MATERIALS AND METHODS

CAD/CAM lithium disilicate (IPS e.max CAD for CEREC/HT A1 C14, Ivoclar Vivadent) restorations (15 specimens/group) with 1.5 mm occlusal thickness and 1.0 mm chamfer were designed and fabricated with a chairside CAD/CAM system (CEREC, Dentsply Sirona). The restorations were prepared in three different designs: (1) full coverage crowns, (2) overlays with the margin located 2 mm above the gingiva, and (3) overlays with the margin located 4 mm above the gingiva. Restorations were cemented using conventional resin luting cement (Multilink, Ivoclar Vivadent) with primer system (Monobond Plus, Ivoclar Vivadent) to resin printed dies, load cycled (2,000,000 load cycles at 1 Hz with 275 N force), and then finally loaded with a steel indenter until failure. Scanning electron microscopy observations of fractured surfaces were also conducted. Group results were analyzed with one-way analysis of variance, and the medians were evaluated independently with Kruskal-Wallis.

RESULTS

The fracture force of CAD/CAM lithium disilicate restorations was significantly different (p < 0.001) depending on the design of the restoration. Full coverage crowns showed significantly higher force to fracture (1018.8 N) than both types of overlays (p = 0.002 for overlay 2.0 mm and p < 0.001 for overlay 4.0 mm above gingiva). Among the two overlays, the restoration with the margin located 2 mm above the gingiva showed significantly higher fracture force (813.8 N) than the overlay with margin at 4 mm above the gingiva (436.1 N; p < 0.001). The fracture appearance of the crowns was much more complex than that of the overlay restorations.

CONCLUSIONS

Full coverage chairside CAD/CAM lithium disilicate premolar crown showed higher fracture resistance than overlay restorations. Overlays with the margin located 2 mm above the margin demonstrated higher resistance than those with the margin located 4 mm above the gingiva.

Fracture load of CAD/CAM ultrathin occlusal veneers luted to enamel or dentin

OBJECTIVES

To evaluate, in vitro, the fracture load of IPS e.max CAD occlusal veneers at thicknesses of either 0.3 or 0.6 mm luted to enamel or dentin.

MATERIALS AND METHODS

Fifty human molars were randomly distributed into five groups (n = 10): G1 - healthy teeth (control); G2-0.3-mm-thick veneers luted to enamel; G3-0.6-mm-thick veneers luted to enamel; G4-0.3-mm-thick veneers luted to dentin; and G5-0.6-mm-thick veneers luted to dentin. After the luting procedures, the specimens were immersed in distilled water at 37°C for 24 hours and then subjected to mechanical loading (10⁶  cycles at 200 N load). The specimens were subjected to a fracture load test in a universal testing machine. Two-way ANOVA and Tukey's test (α = 0.05) were used to analyze data.

RESULTS

Only the thickness factor was significant (P = .002). Values of fracture load followed by distinct letters represent significant differences (P < .05): G1 (3204 N ± 730)^ab ; G2 (3144 N ± 729)^ab ; G3 (2489 N ± 606)^b ; G4 (3591 N ± 776)^a ; and G5 (2770 N ± 598)^ab .

CONCLUSION

IPS e.max ultrathin occlusal veneers luted to enamel or dentin obtained fracture load comparable to that of the healthy tooth.

CLINICAL SIGNIFICANCE

IPS e.max CAD ultrathin occlusal veneers at 0.3 or 0.6-mm-thick seem to provide good perspectives in relation to the clinical use.

Adapted Three-step Restorative Technique: Recovering Dental Substrate Compromised by Complex Erosive Wear in a Young Patient

Clinical Relevance

This article presents the dental restoration of a young female patient complaining of erosive dental wear using a three-step restorative technique, an alternative approach with some novel adjustments.

SUMMARY

For successful tooth wear treatment, determining the etiological systemic and local factors is the main priority before deciding on effective and long-term preventive and/or therapeutic restorative approaches. In addition to professional intervention, achieving optimal outcomes requires patients to control their diet and/or gastric issues, thus minimizing the wear process. However, continuous wear constitutes the most challenging scenario, mainly when it affects young patients’ dentitions. This article describes the dental restoration of posterior teeth with reestablishment of occlusal vertical dimension before treating the anterior teeth, while educating the patient and providing medical monitoring. The three-step restorative technique seems to be properly applicable in cases of significant dental compromise due mainly to erosive wear and is based on direct procedures, which can assure a reliable and feasible approach.