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.

A study of routine exposure of recurrent laryngeal nerve during thyroid surgery.

One of the main complications of thyroid surgery is injury to recurrent laryngeal nerve (RLN), which causes severe morbidity to the patient in postoperative period. To find out the incidence of RLN injury and its consequences, a prospective study was done in a group of 142 cases during the years 1999-2000. Different types of thyroidectomies for various diseases lbw of the thyroid gland, wherein a routine identification and exposure of the P-R was done through out its full course till its entry into the larynx at cricothyroid membrane. Three cases of temporary RLN injury were found and not a single case of permanent nerve injury was seen during our study. Three cases of nonre current LN were found on the right side of the gland. The temporary injury of the nerve completely recovered during 2-5 months of follow-up. We present some reviews of the literature to provide various authors, views and experiences regarding injury of RLN associated with thyroid urgery.