Areas for use of PEEK material in dentistry

Polyetheretherketone (PEEK) material is a polycyclic, aromatic, thermoplastic polymer that is semi-crystalline and has a linear structure. PEEK has good mechanical and electrical properties such as resistance to high temperature and resistance to hydrolysis. In addition, because of the property of high biocompatibility, use of PEEK has increased in orthopaedic and trauma cases. The most characteristic property of PEEK material is that it has a low elasticity modulus, close to that of bone. It has been suggested that stress-based problems could be reduced with this material due to the low elasticity modulus. In the light of this information, PEEK material could be considered as an alternative to conventional materials in the field of dentistry.

Evaluation of Temperature and Stress Distribution on 2 Different Post Systems Using 3-Dimensional Finite Element Analysis

BACKGROUND The mouth is exposed to thermal irritation from hot and cold food and drinks. Thermal changes in the oral cavity produce expansions and contractions in tooth structures and restorative materials. The aim of this study was to investigate the effect of temperature and stress distribution on 2 different post systems using the 3-dimensional (3D) finite element method. MATERIAL AND METHODS The 3D finite element model shows a labio-lingual cross-sectional view of the endodontically treated upper right central incisor and supporting periodontal ligament with bone structures. Stainless steel and glass fiber post systems with different physical and thermal properties were modelled in the tooth restored with composite core and ceramic crown. We placed 100 N static vertical occlusal loading onto the center of the incisal surface of the tooth. Thermal loads of 0°C and 65°C were applied on the model for 5 s. Temperature and thermal stresses were determined on the labio-lingual section of the model at 6 different points. RESULTS The distribution of stress, including thermal stress values, was calculated using 3D finite element analysis. The stainless steel post system produced more temperature and thermal stresses on the restorative materials, tooth structures, and posts than did the glass fiber reinforced composite posts. CONCLUSIONS Thermal changes generated stresses in the restorative materials, tooth, and supporting structures.

Microtensile bond strength of root canal dentin treated with adhesive and fiber-reinforced post systems

Nowadays, demand for esthetic restorations has risen considerably; thus, nonmetal esthetic posts made of either high-strength ceramics or reinforced resins, such as fiber-reinforced resin posts, have become more and more popular. Important characteristics of fiber-reinforced posts involve a modulus of elasticity similar to dentin and their ability to be cemented by an adhesive technique. A total of 36 maxillary incisors were divided into four groups. In this study, four adhesively luted fiber-reinforced (glass fiber, quartz glass fiber, zirconia glass fiber and woven polyethylene fiber ribbon) post systems were used. Post spaces were prepared by employing drills according to the protocol established for each group, and each post was adhesively luted with one of three adhesive systems. Three segments per root apical to the cementoenamel junction (CEJ) were obtained by sectioning the root under distilled water with a carbon spare saw. The samples (total of 108 sections) were 2.0±0.1 mm in thickness and they were stored individually in black film canisters with sterile distilled water. In order to determine the bond strength, the bonding area of each specimen was measured, and specimens were attached to a device to test microtensile strength at a speed of 1 mm/min. The analyses revealed no statistically significant differences between the adhesive systems and fiber-reinforced posts. (P> 0.05). However, the coronal portion of the root dentin had the highest bond strength. Adhesive systems used along with fiber-reinforced resin posts demonstrated reliable bonding.

Comparison of apical microleakage of dual-curing resin cements with fluid-filtration and dye extraction techniques

BACKGROUND

Endodontically treated teeth with excessive loss of tooth structure are frequently restored using fiber posts. In this in vitro study, the apical leakage of self- and dual-activated curing modes for dual-curing resins cementing a translucent fiber post was evaluated using computerized fluid filtration meter and dye extraction method.

MATERIAL AND METHODS

One hundred and four extracted human maxillary incisors with single root and canal were used. Experimental samples embedded in a closed system were divided into 4 groups (n=20) according to 2 dual-curing luting systems, with 2 different curing modes (either with self- or light-activation): (1) Panavia F 2.0 with self-cure, (2) Panavia F 2.0 with light-activation, (3) Clearfill SA with self-cure, and (4) Clearfill SA with light activation. Twenty-four teeth served as negative and positive controls. Translucent fiber posts were luted in the roots except in the control groups.

RESULTS

Statistical analysis indicated no significant difference in leakage among groups (p>0.05) with 4.12 × 10(-4) (Panavia self-cure), 4.55 × 10(-4) (Clearfill SA self-cure), 5.17 × 10(-4) (Panavia dual-cure), and 5.59 × 10(-4) (Clearfill SA dual-cure) in fluid-filtration method. Absorbance values for dye-extraction method were 266 nanometer (nm) (Panavia self-cure), 268 nm (Clearfill SA self-cure), 270 nm (Panavia dual-cure), and 271 nm (Clearfill SA dual-cure), in which difference among the groups were not statistically significant (p>0.05). When comparing the leakage, assessment methods results showed no statistically significant difference between the tested evaluation techniques (p>0.05).

CONCLUSIONS

Light- and self-activation curing modes of Panavia F 2.0 and Clearfill SA perform similar to each other in a closed system.

Directly fabricated inlay-retained glass- and polyethylene fiber-reinforced composite fixed dental prostheses in posterior single missing teeth: a short-term clinical observation

PURPOSE

To evaluate the clinical usefulness of directly fabricated glass and polyethylene resin-bonded fiberreinforced composite (FRC) inlay-retained fixed dental prostheses (FDPs) in posterior single missing teeth over a short period of time.

MATERIALS AND METHODS

Fourteen inlay-retained FRC FDPs with tub-shaped or box-shaped retainers were directly constructed in patients of both genders. A baseline examination was performed and the patients were examined regularly at 6-month intervals. The sulcus bleeding index, Silness-Löe plaque index, and probing depths of the abutments were checked regularly. Modified US Public Health Service (USPHS) parameters were used to compare the restorations at baseline and final examination. The Kaplan-Meier survival estimation method was performed to detect the overall survival rates and mean survival times of the restorations at the end of the follow-up.

RESULTS

The length of the clinical observation was between 16 and 40 months for the FDPs still functioning after the end of the follow-up. No partial or total debonding of the prostheses or fracture of the frameworks was detected. Four veneering composite fractures at the veneer layer/fiber framework interface occurred in the pontic elements of 2 glass FRC FDPs and 2 polyethylene FRC FDPs after 6 and 10 months, and 20 and 22 months, respectively. Periodontal evaluation revealed clinically acceptable results, as did the USPHS evaluation. The overall survival curves of Kaplan-Meier at the end of the follow-up illustrated a 71% survival rate for the both glass and polyethylene FRC FDPs with mean survival times of 27 and 35 months, respectively.

CONCLUSION

This study reported a mean period of service of 19 and 31 months for directly fabricated inlayretained glass and polyethylene FRC FDPs, respectively, with a 71% survival rate for the two framework constructions. Within the limitations of the study, these results can only be considered as preliminary. However, because of the lack of clinical data available for directly fabricated inlay-retained FRC FDPs, the results of this clinical observation may contribute to the still-evolving clinical knowledge of the FRC restorations.

The Impact of Chitosan on Oxidative Stress in Liver of Rats Loaded With Lead Acetate

This study was conducted to determine the impact of chitosan on lead (Pb)-induced hepatotoxicity. Thus, lead acetate was administered intraperitoneally (50 mg/kg for 5 days) and chitosan was given as 200 mg/kg via oral gavage for 28 days. When the trial was terminated, it was determined that aspartate aminotransferase (AST), alanine aminotransferase  (ALT) and alkaline phosphatase (ALP) activities in serum as well as Pb, 8-hydroxy-deoxyguanosine (8-OHdG) and malondialdehyde (MDA) levels and catalase (CAT) activity in liver tissue significantly increased, however reduced glutathione (GSH) and ceruloplasmin (Cp) levels in liver and high density lipoproteins (HDL) in serum had a significant decrease in the Pb group when compared to the control group. The administration of chitosan significantly prevented Pb-induced changes in serum liver enzyme activities, 8-OHdG and MDA levels. In addition, chitosan showed a statistically insignificant effect on reduced GSH, Cp, HDL levels and CAT activity. Accordingly, administration of chitosan can strengthen the antioxidant defence system of liver tissue and may decrease oxidative stress.