Interfacial fracture toughness of different surface treatments on zirconia-reinforced lithium silicate glass-ceramics

This study investigated the influence of different surface treatments on unfiring or firing zirconia-reinforced lithium silicate (ZLS) glass-ceramics. Celtra Duo and IPS e.max CAD blocks were cut and process following manufacturer protocols. The specimen surface was treated with seven different protocols. Two ceramic blocks with the same surface treatment were bonded with luting agent and prepared for mini-interfacial fracture toughness tests (mini-iFT). The specimens were tested after 1-week storage. The data was statistically analyzed using two-way ANOVA and Dunnett's T3 comparison (α=0.05). The highest mini-iFT of both Celtra Duo unfired and fired was shown in the HF+S group, which was not significantly different from HF+S+UA. For IPS e.max CAD, the mini-iFT was higher in the groups treated with hydrofluoric acid. Additional adhesive after silane application did not significantly improve bonding effectiveness. Therefore, surface treatment with hydrofluoric acid and silane is recommended for both unfiring and firing ZLS glass ceramics.

Fracture resistance of CAD/CAM blocks cemented on dentin using different cementation strategies

PURPOSE

To determine whether the fracture resistance of computer-aided design/computer-aided manufacturing (CAD/CAM) resin-based composites and polymer-infiltrated ceramic network materials cemented on dentin is influenced by the restoration thickness and composite cement application strategy.

METHODS

Disc-shaped specimens (Ø = 7 mm) of 0.8 mm and 1.5 mm thicknesses were milled from two CAD/CAM materials: resin-based composite (RBC, Cerasmart 270) and polymer-infiltrated ceramic network (PICN, Vita Enamic). The discs (n = 8 per group) were cemented on flattened dentin using three different cementation strategies: 1) self-adhesive composite cement (RelyX U200) in light-curing mode (LC-SAC), 2) universal adhesive (Single Bond Universal) with composite cement (RelyX Ultimate) in auto-curing mode (AC cement), and 3) adhesive and composite cement as in 2) but in light-curing mode (LC cement). The restorative surface was indented perpendicularly with a compressive load using a universal testing machine until fracture. The fracture resistance (N) of RBC and PICN was separately analyzed using two-way ANOVA and Tukey's post-hoc test (α = 0.05).

RESULTS

The fracture resistance of each material was significantly influenced by the material thickness and cementation strategy (P < 0.05). Irrespective of the material type and cementation strategy, thicker materials exhibit higher fracture resistance. For RBC, the fracture resistance of the LC cement group was significantly higher than that of AC cement only at 0.8 mm thickness. For PICN, the LC-cement cementation strategy produced superior fracture resistance, regardless of the restoration thickness.

CONCLUSIONS

The fracture resistance of Cerasmart 270 was higher for the thicker material; the fracture resistance of LC cement was higher than that of AC cement at 0.8 mm thickness cemented to dentin. In comparison, LC cement showed the highest fracture resistance for Vita Enamic for both material thicknesses.

The accuracy of virtual setup in simulating treatment outcomes in orthodontic practice: a systematic review

OBJECTIVES

To evaluate the accuracy of virtual orthodontic setup in simulating treatment outcomes and to determine whether virtual setup should be used in orthodontic practice and education.

MATERIALS AND METHODS

A systematic search was performed in five electronic databases: PubMed, Scopus, Embase, ProQuest Dissertations & Theses Global, and Google Scholar from January 2000 to November 2022 to identify all potentially relevant evidence. The reference lists of identified articles were also screened for relevant literature. The last search was conducted on 30 November 2022.

RESULTS

This systematic review included twenty-one articles, where all of them were assessed as moderate risk of bias. The extracted data were categorized into three groups, which were: (1) Virtual setup and manual setup; (2) Virtual setup and actual outcomes in clear aligner treatment; (3) Virtual setup and actual outcomes in fixed appliance treatment. There appeared to be statistically significant differences between virtual setups and actual treatment outcomes, however the discrepancies were clinically acceptable.

CONCLUSION

This systematic review supports the use of orthodontic virtual setups, and therefore they should be implemented in orthodontic practice and education with clinically acceptable accuracy. However, high-quality research should be required to confirm the accuracy of virtual setups in simulating treatment outcomes.

Accuracy of the Intraoral Scanner for Detection of Tooth Wear

OBJECTIVE

The aim of this work was to study the accuracy of the intraoral scanner for detection of tooth wear in natural teeth by using micro-computed tomography (micro-CT) as a gold standard.

MATERIALS AND METHODS

Twenty premolars were prepared, fixed in acrylic blocks, and scanned with an intraoral scanner (iTero Element® 2) and micro-CT for baseline reference images before artificial tooth wear induction. The samples were then scrubbed with abrasive sandpaper 20 times and scanned with the intraoral scanner. They were then superimposed with the reference images utilising the "TimeLapse" feature of the scanner until the abraded area appeared yellow, indicating tooth surface loss in the 50-200 μm range. The same samples were then rescanned by micro-CT to measure the actual tooth surface loss. This procedure was repeated for the subsequent experimental tooth surface loss of 200-400 μm range (orange areas) and 400-750 μm range (red areas). The collected data were analysed for sensitivity, positive predictive value (PPV), and accuracy. Level of statistical significance was set at .05.

RESULTS

In the detection of experimental tooth surface loss, the specificity, PPV, and accuracy of the intraoral scanner were 98%, 98%, and 97%, respectively.

CONCLUSIONS

The iTero® intraoral scanner can be recommended to be a suitable screening tool for tooth wear in routine dental practice.

Treatment outcome differences between pass and fail scores and correlation between cephalometric changes and cast-radiograph evaluation of the American Board of Orthodontics

OBJECTIVE:

Using the cast-radiograph evaluation (CRE) score of the American Board of Orthodontics (ABO), the purpose of this study was 1) to find the post-treatment discrepancies that contributed to low-quality outcomes and 2) to identify if there might be any correlation between cephalometric changes and post-treatment discrepancies.

MATERIALS AND METHODS:

About 200 records submitted for the Thai Board of Orthodontics examination were analyzed. Overall, 23 parameters of the CRE scores and 12 cephalometric changes were collected. Based on the total CRE score, the cases were classified into three categories: pass (score <20), undetermined (score 20–30), and fail (score >30). Kruskall–Wallis was used to analyze the differences of mean CRE scores among these three categories. In addition, the cases were further classified into fixed appliance, two-phase and orthognathic surgery groups. Correlation tests were carried out to determine if there might be any association between cephalometric changes and CRE parameters.

RESULTS:

Significant differences of mean CRE scores were found for all CRE components except interproximal contacts. Significant correlation coefficients with the total CRE scores were found for all parameters except interproximal contacts. Significant moderate association was found between lower incisor changes and CRE scores in the two-phase and orthognathic surgery group.

CONCLUSIONS:

In order to improve treatment outcome quality, the top four parameters that orthodontists should pay attention to are occlusal contacts, occlusal relationship, marginal ridges, and alignment and rotations. Cephalometric changes were not suitable as weighting factors for total CRE scores.