Research Spotlight

Khanlar, L. N., A. Salazar Rios, A. Tahmaseb and A. Zandinejad (2021). “Additive Manufacturing of Zirconia Ceramic and Its Application in Clinical Dentistry: A Review.” Dent J (Basel) 9(9).

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Additive manufacturing (AM) has many advantages and became a valid manufacturing technique for polymers and metals in dentistry. However, its application for dental ceramics is still in process. Among dental ceramics, zirconia is becoming popular and widely used in dentistry mainly due to its outstanding properties. Although subtractive technology or milling is the state of art for manufacturing zirconia restorations but still has shortcomings. Utilizing AM in fabricating ceramics restorations is a new topic for many researchers and companies across the globe and a good understanding of AM of zirconia is essential for dental professional. Therefore, the aim of this narrative review is to illustrate different AM technologies available for processing zirconia and discus their advantages and future potential. A comprehensive literature review was completed to summarize different AM technologies that are available to fabricate zirconia and their clinical application is reported. The results show a promising outcome for utilizing AM of zirconia in restorative, implant and regenerative dentistry. However further improvements and validation is necessary to approve its clinical application.

Zandinejad, A., O. Das, A. B. Barmak, M. Kuttolamadom and M. Revilla-León (2021). “The Flexural Strength and Flexural Modulus of Stereolithography Additively Manufactured Zirconia with different Porosities.” J Prosthodont.

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PURPOSE: Additive manufacturing (AM) technologies are capable of fabricating complex geometries with different porosities. However, the effect of such porosities on mechanical properties of stereolithography (SLA) AM zirconia with different porosities is unclear. The purpose of this in vitro study was to investigate the mechanical properties namely flexural strength, and flexural modulus of AM zirconia with different porosities. MATERIALS AND METHODS: A bar (25×4×3 mm) for flexural strength test (ISO standard 6872/2015) was designed by CAD software program and standard tessellation language (STL) file was obtained. STL file was used to fabricate a total of 80 bars in four groups. Three experimental groups each contained 20 samples were manufactured using SLA ceramic printer (CeraMaker 900; 3DCeram Co) and zirconia material (3DMix ZrO2 paste; 3DCeram Co) with different sintering post process to achieve different porosities including 0%-porosity (AMZ0), 20%-porosity (AMZ20), and 40%-porosity (AMZ40). The same STL file was used for subtractive manufacturing or milling of 20 zirconia bars as control group (CNCZ) with the same dimensions using a commercial zirconia. Three-point bending tests were performed for all groups following ISO standard 6872/2015 specification using a universal testing machine. Outcomes measured included load at fracture, mean flexural strength, and flexural modulus were compared across the experimental groups using a 1-way ANOVA. Post-hoc pair wise comparison between each pair of the groups were performed using Tukey test. RESULTS: There was a significant difference between the four groups, in terms of fracture load, flexural strength and flexural modulus using one-way ANOVA. AM zirconia with 0% porosity (AMZ0) showed the highest value for fracture load (1,132.7 ±220.6 N), flexural Strength (755.1 ±147.1 MPa) and flexural modulus (4,1273 ±2193 MPa) and AM zirconia with 40% porosity (AMZ40) showed the lowest fracture load (72.13 ±13.42 N), flexural strength (48.09 ±8.95 MPa) and flexural modulus (7,177 ±506 MPa). Tukey’s pairwise comparisons detected a significant difference between all the possible pairs for all variables except flexural modulus between AMZ0 and CNCZ. The Weibull moduli presented the lowest value for AMZ20 (4.4) followed by AMZ40 (6.1), AMZ0 (6.1) and the highest value was for CNCZ (8.1). CONCLUSION: AM zirconia with 0% porosity shows significantly higher flexural strength and flexural modulus when compared to milled and AM zirconia with 20% and 40% porosities.

Weiss, R. O., 2nd, A. A. Ong, L. V. Reddy, S. Bahmanyar, A. G. Vincent and Y. Ducic (2021). “Orthognathic Surgery-LeFort I Osteotomy.” Facial Plast Surg.

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Orthognathic surgery is a complex type of facial surgery that can have a profound impact on a patient’s occlusal function and facial aesthetics. Close collaboration between the maxillofacial surgeon and an orthodontist is required, and the surgical team must have a strong foundation in facial analysis and firm understanding of the maxillofacial skeleton to achieve surgical success. Herein, we review the maxillary LeFort I osteotomy as it pertains to orthognathic surgery, with particular attention to the indications, contraindications, preoperative assessment, surgical technique, and possible complications encountered.

Warner, B. E., W. F. Goins, P. R. Kramer and P. R. Kinchington (2021). “A Guide to Preclinical Models of Zoster-Associated Pain and Postherpetic Neuralgia.” Curr Top Microbiol Immunol.

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Reactivation of latent varicella-zoster virus (VZV) causes herpes zoster (HZ), which is commonly accompanied by acute pain and pruritus over the time course of a zosteriform rash. Although the rash and associated pain are self-limiting, a considerable fraction of HZ cases will subsequently develop debilitating chronic pain states termed postherpetic neuralgia (PHN). How VZV causes acute pain and the mechanisms underlying the transition to PHN are far from clear. The human-specific nature of VZV has made in vivo modeling of pain following reactivation difficult to study because no single animal can reproduce reactivated VZV disease as observed in the clinic. Investigations of VZV pathogenesis following primary infection have benefited greatly from human tissues harbored in immune-deficient mice, but modeling of acute and chronic pain requires an intact nervous system with the capability of transmitting ascending and descending sensory signals. Several groups have found that subcutaneous VZV inoculation of the rat induces prolonged and measurable changes in nociceptive behavior, indicating sensitivity that partially mimics the development of mechanical allodynia and thermal hyperalgesia seen in HZ and PHN patients. Although it is not a model of reactivation, the rat is beginning to inform how VZV infection can evoke a pain response and induce long-lasting alterations to nociception. In this review, we will summarize the rat pain models from a practical perspective and discuss avenues that have opened for testing of novel treatments for both zoster-associated pain and chronic PHN conditions, which remain in critical need of effective therapies.

Elnagdy, S., M. Raptopoulos, I. Kormas, A. Pedercini and L. F. Wolff (2021). “Local Oral Delivery Agents with Anti-Biofilm Properties for the Treatment of Periodontitis and Peri-Implantitis. A Narrative Review.” Molecules 26(18).

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Despite many discoveries over the past 20 years regarding the etiopathogenesis of periodontal and peri-implant diseases, as well as significant advances in our understanding of microbial biofilms, the incidence of these pathologies continues to rise. For this reason, it was clear that other strategies were needed to eliminate biofilms. In this review, the literature database was searched for studies on locally delivered synthetic agents that exhibit anti-biofilm properties and their potential use in the treatment of two important oral diseases: periodontitis and peri-implantitis.