Fracture resistance and failure mode of endodontically treated premolars reconstructed by different preparation approaches: Cervical margin relocation and crown lengthening with complete and partial ferrule with three different post and core systems

PURPOSE

To assess the fracture resistance and failure mode of endodontically treated premolars reconstructed by different preparation approaches: cervical margin relocation (CMR) and crown lengthening (CL) with complete ferrule (CLF) and partial ferrule (CLPF) with three different post and core systems.

MATERIALS AND METHODS

In this in vitro study, 100 maxillary premolars were assigned to the following 10 groups according to their preparation approach and type of post and core system (n = 10): (I) control (intact teeth), (II) prefabricated fiber post (PFP) and composite core with CMR (PFP-CMR), (III) polyethylene fiber-reinforced composite (PEFRC) with CMR (PEFRC-CMR), (IV) casting post (CP) and core with CMR (CP-CMR), (V) PFP-CLPF, (VI) PEFRC-CLPF, (VII) CP-CLPF, (VIII) PFP-CLF, (IX) PEFRC-CLF, and (X) CP-CLF. After thermomechanical loading, the fracture resistance and failure mode were assessed. Data were analyzed statistically (α = 0.05).

RESULTS

In all post and core systems, the CLPF approach had lower fracture resistance than CMR (p < 0.05); CLF showed higher fracture resistance than CLPF only in the PFP system (p = 0.038). In PEFRC and CP systems, the difference between CLF and CLPF was not significant (p > 0.05). No significant difference was found in fracture resistance of different post and core systems with the same preparation approach (p > 0.05). CLPF showed the highest frequency of favorable, and CLF showed the highest frequency of unfavorable fractures.

CONCLUSION

CLPF yielded lower fracture resistance than CMR. The difference in fracture resistance was not significant between CLF and CMR but the frequency of unfavorable fractures was higher in CLF than in other groups.

Effect of orthodontic bonding with different surface treatments on color stability and translucency of full cubic stabilized zirconia after coffee thermocycling

Objective

To assess the color stability and translucency of full cubic stabilized zirconia (FSZ) following orthodontic bonding with different surface treatments and coffee thermocycling (CTC).

Methods

This in vitro study was conducted on 120 disc-shaped specimens of FSZ. Thirty specimens were selected as the control group and remained intact. The remaining specimens were randomly divided into three groups based on the type of surface treatment (n = 30): airborne particle abrasion (APA), silica-coating (CoJet), and carbon dioxide (CO₂) laser. After metal bracket bonding in the test groups, debonding and polishing were performed. Subsequently, all specimens underwent CTC (10,000 cycles). Color parameters, color difference (ΔE₀₀), and translucency parameter (TP) were measured three times at baseline (t0), after debonding and polishing (t1), and after CTC (t2). Data were statistically analyzed (α = 0.05).

Results

Significant difference existed among the groups regarding ΔE₀₀t0t2 (p < 0.001). The APA group showed minimum (ΔE₀₀ = 1.15 ± 0.53) and the control group showed maximum (ΔE₀₀ = 0.19 ± 0.02) color stability, with no significant difference between the laser and CoJet groups (p = 0.511). The four groups were significantly different regarding ∆TPt0t2 (p < 0.001). Maximal increases in TP were noted in the CoJet (1.00 ± 0.18) and APA (1.04 ± 0.38) groups while minimal increase was recorded in the control group (0.1 ± 0.02).

Conclusions

Orthodontic treatment makes zirconia restorations susceptible to discoloration and increased translucency. Nonetheless, the recorded ΔE₀₀ and ∆TP did not exceed the acceptability threshold.

Marginal and internal fit and fracture resistance of three-unit provisional restorations fabricated by additive, subtractive, and conventional methods

OBJECTIVES

To compare the marginal and internal fit and fracture resistance of three-unit provisional fixed dental prostheses (FDPs) fabricated by additive, subtractive, and conventional methods.

MATERIAL AND METHODS

Eighty 3-unit FDPs were fabricated on metal dies of the maxillary right second premolar and second molar by four different techniques (n = 20): The direct method by using autopolymerizing polymethyl methacrylate (PMMA), indirect method by the compression molding technique, subtractive manufacturing by using PMMA blocks, and additive manufacturing by using digital light processing technology. The adaptation of restorations at the marginal, axial, cuspal, and fossa areas was assessed by using the silicone replica technique. After thermocycling and cyclic loading, the fracture resistance was measured by a universal testing machine. Data were analyzed by a two-way analysis of variance (ANOVA), ANOVA, and Tukey test (α = .05).

RESULTS

The mean gap measured in the additive group was lower than that in all other groups at all points (p < .05); however, the difference in the marginal gap with the subtractive group was not significant (p = .995). The mean marginal and axial gaps in the subtractive group were significantly lower than the corresponding values in both conventional groups (p < .05). A significant difference existed between all groups regarding the mean cuspal and fossa gaps (p < .05). The mean fracture resistance of the additive group was significantly higher than that of indirect (p = .018) and direct (p < .001) groups, and the fracture resistance of the subtractive group was significantly higher than that of the direct group (p = .020).

CONCLUSION

The digitally fabricated provisional FDPs showed superior marginal and internal fit and higher fracture resistance than the conventionally fabricated FDPs. Between the digital methods, the additive technique yielded superior internal fit.

Eating‐ and oral health‐related quality of life in patients under fixed orthodontic treatment

Objective

The eating problems and changes in the diet and dietary intake of patients under orthodontic treatment are of great importance, and the available studies on this topic are mostly qualitative. Thus, this study aimed to assess the oral health‐related quality of life (OHRQoL) and the eating‐related quality of life (ERQoL) of patients under fixed orthodontic treatment.

Materials and Methods

This prospective study evaluated 105 patients (65 males, 40 females) with a mean age of 26 ± 1.1 years, who required fixed orthodontic treatment. All participants filled out the Oral Health Impact Profile‐14 (OHIP‐14) questionnaire before treatment (T0), and at 1 (T1), 3 (T2), and 6 (T3) months after treatment, and the ERQoL questionnaire at 1 (T1), 3 (T2), and 6 (T3) months after treatment. Data were analyzed using repeated measures analysis of variance with Greenhouse–Geisser and Huynh‐Feldt corrections and Bonferroni test for pairwise comparisons (α = .05).

Results

The OHIP‐14 total score increased at T1 and decreased at T2 and T3, with significant differences between all four time points (p < .001). The ERQoL total score decreased over time, and significant differences were noted between all three time points (p < .001). No significant difference existed in OHRQoL or ERQoL with regard to gender at any time point (p > .05).

Conclusion

The reduction in OHRQoL due to fixed orthodontic treatment was temporary and improved over time. The eating problems also decreased with time.

Three-dimensional accuracy of innovative implant-level impression techniques with plastic snap-on impression copings

BACKGROUND

Several studies have assessed the accuracy of the indirect snap-on impression technique. However, some impression techniques that utilize plastic snap-on impression copings have not yet been investigated.

OBJECTIVES

This study aimed to assess the three-dimensional (3D) accuracy of innovative implant-level impression techniques with plastic impression copings and the splinted open-tray technique with metal impression copings.

MATERIAL AND METHODS

This in vitro study used a reference model of the mandible with 4 parallel dental implants. Forty impressions were made with polyether impression material, using the splinted opentray technique with metal impression copings (SOM group), the non-splinted closed-tray technique with snap-on impression copings (NCS group), the non-splinted open-tray technique with snap-on impression copings (NOS group), or the splinted open-tray technique with snap-on impression copings (SOS group); n = 10 per group. Linear discrepancies in the inter-implant distances on the obtained casts were determined in the X, Y and Z axes with the use of a coordinate measuring machine. Subsequently, the 3D accuracy of each impression technique was calculated. Data was analyzed by means of the one-way analysis of variance (ANOVA) followed by Tukey's post-hoc tests.

RESULTS

Among different impression techniques, the amount of linear discrepancy was significant only for the Z axis. The SOM, NOS and SOS groups showed less discrepancy in this axis as compared to the NCS group (p < 0.001). A significant difference was also noted in 3D discrepancy (p = 0.022), with the SOM group showing a significantly higher discrepancy as compared to the SOS group (p = 0.016).

CONCLUSIONS

The 3D accuracy of the implant-level splinted open-tray impression technique with plastic snap-on impression copings was significantly higher than that of the splinted open-tray technique with metal impression copings.

Effect of different surface treatments on surface roughness and flexural strength of repaired 3D-printed denture base: An in vitro study

STATEMENT OF PROBLEM

Information regarding three-dimensional-printed (3D-printed) dentures, especially when using the additive manufacturing technique, and the repair strength of this type of denture is sparse.

PURPOSE

The purpose of this in vitro study was to assess the effect of different surface treatments on the surface roughness and flexural strength of repaired 3D-printed denture base.

MATERIAL AND METHODS

One hundred and twenty 3D-printed bar-shaped specimens were fabricated from acrylic resin and divided into 6 groups (n=20). The positive control group consisted of intact specimens. The other specimens were sectioned in half with a 1-mm gap. Except for the specimens in the negative control group, the remaining specimens were treated with erbium: yttrium-aluminum-garnet (Er:YAG) laser, airborne-particle abrasion, a combination of laser and airborne-particle abrasion, and bur grinding. All sectioned specimens were repaired by autopolymerizing acrylic resin and thermocycled after measuring their surface roughness with a profilometer. The flexural strength test was performed with a universal testing machine. One specimen of each group was inspected under a scanning electron microscope. The data were analyzed with ANOVA, followed by the Games-Howell post hoc test or the Kruskal-Wallis test followed by the Mann-Whitney test with Bonferroni adjustment.

RESULTS

The mean flexural strength of the PC group was significantly higher than that of all repaired groups (P<.001). All surface-treated groups showed significantly higher flexural strength (P<.05) and surface roughness (P<.004) than the negative control group. Bur grinding provided significantly higher flexural strength than other surface treatments (P<.001) and higher surface roughness than laser and airborne-particle abrasion plus laser (P<.001).

CONCLUSIONS

All surface treatments significantly increased the surface roughness and flexural strength, but none of them yielded a strength comparable with that of the intact group. Bur grinding provided the highest flexural strength.

Analyzing the relationship between learning styles (Kolb and VARK) and creativity with the academic achievement of dental students

BACKGROUND

One of the influential factors in students' learning is their learning styles which have the capacity to change. Furthermore, creativity is considered one of the essential cognitive features of humans. Thus, this study aimed to analyze the relationship between learning styles (Kolb and VARK) and emotional creativity with the academic achievement of dental students.

MATERIALS AND METHODS

In this descriptive-analytical study, the statistical population included dental students of the third semester and above (250 persons). The data collection tools included Kolb and VARK learning style questionnaires, Averill emotional creativity questionnaire, the total Grade Point Average (GPA), and the GPA over the past two semesters of students to measure academic achievement. The data were analyzed using the measures of the descriptive (mean and standard deviation) and the inferential statistics tests including one-sample t-test, independent t-test, correlation coefficients of Pearson, and Eta squared.

RESULTS

Based on Kolb and VARK learning styles, the majority of the students had accommodating learning style (64%) and read-write style (31.6%) and also were single-styled (80.4%). No significant relationship was found between the learning styles (Kolb and VARK) and creativity with academic achievement. The students scored higher than average in emotional creativity and all of its three elements. Moreover, there was a significant relationship between emotional creativity and the gender of the students (P = 0.01). Female students showed higher emotional creativity (97.26 ± 10.34) compared to the male students (94.24 ± 8.96).

CONCLUSION

There was no significant relationship between learning styles and emotional creativity of the students with their academic achievement. The accommodating and read-write learning styles were more prevalent among students and they showed high emotional creativity.

Marginal gap of monolithic zirconia endocrowns fabricated by using digital scanning and conventional impressions

STATEMENT OF PROBLEM

The digital scanning technique has been introduced as an alternative to the conventional impression technique for the fabrication of fixed restorations. However, adequate information is not available on the efficacy of digital scanning for the fabrication of endocrowns regarding their marginal accuracy.

PURPOSE

The purpose of this in vitro study was to compare the marginal gap of endocrowns fabricated by computer-aided design and computer-aided manufacturing (CAD-CAM) technology and digital scanning and conventional impression techniques.

MATERIAL AND METHODS

An endodontically treated mandibular molar tooth was prepared to receive an endocrown. The impressions were made by using the conventional impression technique with polyvinyl siloxane material (n=11) and digital scanning by using an intraoral scanner (n=11). Endocrowns were fabricated from monolithic zirconia blocks by using a milling machine. Each restoration was seated on the prepared tooth, and the marginal gap was measured by using a video measuring machine at 8 points under magnification. The mean marginal gap for each restoration and the overall mean marginal gap for each group were calculated. Data were analyzed by using a statistical software program. Marginal gaps were compared with the Mann-Whitney U test (α=.05).

RESULTS

The mean marginal gap was 74 μm for the conventional impression group. A similar mean marginal gap (70 μm) was found for the digital scanning group. No statistically significant difference was found between the groups (P=.375).

CONCLUSIONS

The digital scanning technique and the conventional impression technique yielded crowns with comparable marginal adaptation.

Dental care management during the COVID-19 outbreak

Aim

The level of preparedness of the healthcare system plays an important role in management of coronavirus disease 2019 (COVID‐19). This study attempted to devise a comprehensive protocol regarding dental care during the COVID‐19 outbreak.

Methods and result

Embase, PubMed, and Google Scholar were searched until March 2020 for relevant papers. Sixteen English papers were enrolled to answer questions about procedures that are allowed to perform during the COVID‐19 outbreak, patients who are in priority to receive dental care services, the conditions and necessities for patient admission, waiting room and operatory room, and personal protective equipment (PPE) that is necessary for dental clinicians and the office staff.

Conclusion

Dental treatment should be limited to patients with urgent or emergency situation. By screening questionnaires for COVID‐19, patients are divided into three groups of (a) apparently healthy, (b) suspected for COVID‐19, and (c) confirmed for COVID‐19. Separate waiting and operating rooms should be assigned to each group of patients to minimize the risk of disease transmission. All groups should be treated with the same protective measures with regard to PPE for the dental clinicians and staff.

The effect of naproxen patches on relieving orthodontic pain by evaluation of VAS and IL-1β inflammatory factor: a split-mouth study

Introduction:

Pain related to orthodontic tooth movement is common and cause dissatisfaction and discomfort. Objective: The present study aimed to compare the efficacy of naproxen patches in pain control during orthodontic tooth separation, by means of visual analogue scale (VAS) and interleukin 1β (IL-1β) levels in gingival crevicular fluid (GCF).

Methods:

In this split-mouth triple-blind clinical trial, with 40 patients following separation, 5% naproxen or placebo patches were randomly placed on the upper right or left first molars every 8 hours. Pain intensity scores were determined after 2 and 6 hours, sleep time, 24 hours, days 2, 3 and 7 by the patients using a 100-mm VAS ruler. IL-1β levels in GCF were evaluated by ELISA at baseline, 1 and 24 hours and 7 days. Paired samples t-tests and two-way repeated measures ANOVA analysis of variance with a significance level of 0.05 were applied.

Results:

A total number of 30 patients (13 males and 17 females) finished the trial. Significant differences were found in pain scores (p< 0.0001) and IL-1β levels (p= 0.047) between naproxen and placebo groups. Lower pain scores were reported for the patients using naproxen patches at all time points, except 1 hour after separation. IL-1β levels were lower for the patients using naproxen patches only 1 hour after separation (p= 0.047). The peak of pain scores and IL-1β levels were calculated at 24 hours.

Conclusion:

In the light of VAS scores and IL-1β levels, naproxen patches reduced the pain caused by separator placement.