In Vitro Evaluation of marginal adaptation of polyether ether ketone and zirconia copings

Background

Polyether ether ketone (PEEK) has emerged as a new thermoplastic material with potential applications as a restorative material. Aim: This study aimed to evaluate the marginal adaptation of PEEK copings compared to zirconia copings using field emission scanning electron microscopy.

Materials and Methods

A freshly extracted maxillary central incisor was prepared for a full-coverage restoration following standard principles of tooth preparation. The tooth was sent to a laboratory for fabrication of samples using computer-aided design and manufacturing (CAD/CAM). Twenty samples of polyether ether ketone (PEEK) copings (group A) and 20 of zirconia copings were fabricated (group B). The copings were scanned under a field emission scanning electron microscope and measurements were taken at four distinct points. The marginal adaptation over the buccal, lingual, mesial, and distal margins for both groups was evaluated. One-way analysis of variance (ANOVA) and independent t test were applied.

Results

Our findings indicate that PEEK showed better marginal adaptation than zirconia at all measurement points. The mean marginal gap value of the PEEK group was 33.99 ± 8.81 μm and of the zirconia group was 56.21 ± 15.07 μm. On comparing marginal adaptation among the mesial, distal, buccal, and lingual aspects, PEEK showed better adaptation on all four margins, with the best adaptation on the buccal margin that had the lowest mean gap value of 29.27 ± 6.07 μm. The zirconia group adapted best at the distal margin, with a lowest mean gap value of 53.58 ± 15.25 μm (P ≤ 0.05).

Conclusion

PEEK copings had better marginal adaptation and fit compared to zirconia copings. It may have applications as a restorative material in fixed prostheses.

Effect of ten different biomarkers in the gingival crevicular fluid of obese and non-obese undergoing fixed orthodontic treatment

OBJECTIVE

The aim of this study is to evaluate the effect of ten proinflammatory cytokines in GCF of participants with raised body mass index (BMI) compared to non-obese subjects undergoing fixed orthodontic treatment.

PATIENTS AND METHODS

In the cross-sectional cohort, subjects were shortlisted through the purposive sampling method with the same age and gender and similar characteristics (cohort). For inclusion and exclusion, predefined criteria were followed. In all included participants obese and non-obese collection of GCF was made from mandibular canine to canine. Identification of inflammatory mediators (MPO and CRP) leptin, adiponectin, and resistin (pg/mL). Bone remodeling biomarkers RANKL (pg/mL) and tissue remodeling biomarkers MMP8, MMP9, TIMP1, and MMP8/TIMP1, MMP9/TIMP1 ratio were collected and blinded by the investigator. Normal distribution of data i.e., age, BMI, the flow rate of GCF, indices plaque and gingival, and uWMS were compared using a t-test. Non-normality biomarker data were evaluated using Mann-Whitney U-test. To assess the relationship between the concentration of GCF biomarkers and plaque and gingival indices Pearson and Spearman correlation coefficients were used.

RESULTS

The total number of participants included was 44. In the obese and non-obese groups, the male/female ratio was the same i.e., (n=11 each). The mean age of participants in the obese group was (25.7±1.55 years), whereas the non-obese group was (26.1±1.29 years). In obese the mean BMI was (33.6±2.1 kg/m2) whereas in non-obese (22.9±1.9 kg/m2) (p<0.02). Among the levels of biomarkers adiponectin (p<0.006) and leptin (p<0.028) demonstrated a significant difference between obese and non-obese participants. Also, a significant difference was noted between obese and non-obese in tissue remodeling biomarker MMP9 (p<0.03).

CONCLUSIONS

A surge in the level of the biomarkers, i.e., MMP9, leptin, and adiponectin in the gingival crevicular fluid is found in obese undergoing fixed orthodontic treatment.

Labial alveolar bone thickness and its correlation with buccolingual maxillary incisors angulation: a CBCT based study

OBJECTIVE

Understanding the labial alveolar bone thickness (ABT) and buccolingual teeth angulation may reduce the complication that might arise during or post-operative treatment. The operator could determine the precise method to ensure long-term treatment success. This study aimed to evaluate the ABT with buccolingual upper incisor teeth angulation based on the maxillary plane by using the cone-beam computed tomography (CBCT).

MATERIALS AND METHODS

A total of 371 CBCT radiographs were initially assessed and 100 CBCT radiographs were included. On the maxillary incisors, the labial alveolar bone thickness is evaluated at three points (Point A: Four mm below from CEJ, Point B: Midpoint from the labial alveolar-palatal alveolar crest plane and root apex. Point C: Root Apex of the tooth). The distance from these points to labial alveolar bone was measured for the ABT. Moreover, buccolingual angulation of the tooth was measured by the angle formed by the maxillary plane and the long axis of the tooth.

RESULTS

There is no significant difference observed between genders in the labial alveolar bone thickness. The labial alveolar bone thickness grew gradually from the cementoenamel junction (CEJ) level to the apical level. Moreover, there was a statistically significant positive correlation observed between labial alveolar bone thickness at the apical level (Point C) and angulation (p<0.05).

CONCLUSIONS

The labial bone thickness was less than 2 mm in the majority of cases at the three points among maxillary incisors. In addition, there is a correlation between buccolingual angulation of the maxillary incisors and labial alveolar bone thickness.

Evaluation of the marginal microleakage of CAD-CAM compared with conventional interim crowns luted with different types of cement: An in-vitro study

Background

Temporary stage in crowns and bridgework plays an important role in the success and failure of the final restorations. Lack of marginal seal of the temporary restorations can lead to further complications. Recently, digital dentistry has been improved in terms of marginal integrity.

Aims

The aim of this study was to evaluate and compare the marginal leakage between CAD/CAM and conventionally made Polymethyl methacrylate (PMMA) interim crowns cemented with different temporary luting cements.

Materials and Methods

Sixty resin dies of a maxillary right first premolar were prepared according to the protocol of the tooth preparation for all-ceramic crown. Interim crowns were then fabricated and assigned to two main groups according to the fabrication technique (CAD/CAM technique and conventional technique). Furthermore, the samples were sub-grouped (n = 10) according to the type of the luting cements: Zinc oxide eugenol (RelyX temp E), Zinc oxide non-eugenol (RelyX temp NE), and Zinc polycarboxylate cement (pentron). The specimens were then subjected to thermocycling at 5°C and 55°CC for 30 sec and transfer time of 15 seconds for 1500 cycles. After that, the specimens were immersed in a 2% methylene blue solution for 24 hours. The cemented specimens were sectioned buccolingually and the amount of marginal leakage was evaluated under digital microscope at magnification 50x. The scores of dye penetration were recorded and analyzed using one-way ANOVA at P < 0.05 for all tests.

Results

For the fabrication technique, CAD/CAM-made interim crowns had significantly better performance in terms of lower microleakage in comparison to conventionally built interim crowns (P < 0.001). Overall, Zinc Oxide non-eugenol also showed significantly least microleakage as a luting cement then Zinc Oxide Eugenol and the most microleakage was found with Zinc Polycarboxylate regardless of the fabrication method.

Conclusion

Interim crowns fabricated by CAD-CAM system are better suited for temporization. Zinc-oxide non-eugenol cements showed the least amount of microleakage in both types of crown.