Influence of Cyclic Loading on Load to Failure of Different Ceramic CAD/CAM Implant-Supported Single Crowns

PURPOSE: To compare the load to failure values of different ceramic CAD/CAM implant crown materials with drilled screw access holes with and without cyclic loading applied. MATERIALS AND METHODS: Forty zirconia abutments with a titanium base were pre-loaded onto implants to support maxillary right first premolar crowns that were milled from four different CAD/CAM ceramic materials (zirconia reinforced lithium silicate, hybrid ceramic, lithium disilicate, and zirconia; n = 10 each). After cementing the crowns, screw access channels were prepared by drilling through occlusal surfaces. Half of the specimens were subjected to cyclic loading for 5 million cycles at 2 Hz (n = 5/material). After cyclic loading, vertical loads were applied to failure, and the load to failure values of all crowns were recorded and statistically analyzed. Two-way analysis of variance was used with restricted maximum likelihood estimation and Tukey-Kramer adjustments (α = .05). RESULTS: During cyclic loading, the zirconia abutment in one lithium disilicate specimen cracked at 2 million cycles, as well as a zirconia-reinforced lithium silicate crown. Results for the load to failure test series showed statistical differences between the materials. Zirconia resulted in significantly higher failure loads when compared to the other materials (P < .001). Cyclic loading did not significantly affect the load to failure values. CONCLUSION: Cyclic loading did not significantly influence the load to failure of any of the materials tested. Zirconia crowns with drilled screw access channels cemented on zirconia abutments with a titanium base had higher load to failure values compared to the other ceramic crown materials.

The effect of leading edge porosity on airfoil turbulence interaction noise.

Airfoil turbulence interaction noise and the flow field up to and over the porous leading edge is experimentally studied. The porous leading edges were of the same base triply periodic minimal surface structure with varying porosity to enable us to understand how the porosity, permeability, and pore size affect the generated turbulence interaction noise. The turbulent flow was generated by means of a passive turbulence grid that does not affect the normal background noise of the wind tunnel. Far-field noise results were obtained from a polar microphone array to assess the directivity of the sound as well as the narrowband frequency contributions. Far-field noise results demonstrate that increasing porosity reduces the turbulence interaction noise over low-to-mid frequencies, with a penalty of a high frequency noise increase. Flow measurement results indicate hydrodynamic penetration of the flow into the porous structure at the leading edge. Furthermore, the two-point correlation analysis of the velocity fluctuations approaching the leading edge shows that the turbulent structures approaching the solid leading edge appear to deform into more two-dimensional structures, whereas in the case of the porous leading edge, the turbulent structures appear to retain a strong spanwise coherence up to the point of hydrodynamic penetration.

Sublingual Gland and Mylohyoid Muscle Advancement: A Novel Combined Local Soft Tissue Reconstruction.

ABSTRACT: Here the authors present the surgical management of a 78-year-old female with a superficial squamous cell carcinoma of the mucosa overlying her edentulous mandibular alveolus with no evidence of bony invasion.Combining the superficial nature of the lesion, patient age and substantial medical comorbidities, a limited intra-oral resection was planned, to avoid the need for free flap reconstruction. The operation required a wide local excision with clear clinical margins and a mandibular rim resection.All of the currently available reconstructions would result in prolonged surgical time, donor site morbidity, and possible secondary procedures. To overcome these pitfalls, a sublingual gland and mylohyoid muscle advancement flap was designed and executed. By combining the mylohyoid muscle and sublingual gland tissue as an advancement flap in a tension-free manner, secured to the remaining circumferential mucosa, a watertight closure was achieved.After an uneventful recovery without complication the patient was discharged the following day. Complete epithelialization was observed on day 25. Adjuvant radiotherapy was offered to reduce the risk of recurrence and progression. To date, no bony exposure and no pathological fractures have occurred.In conclusion, the entire procedure is simple and innovative. There is minimal donor site morbidity, with an immediate return to oral diet and tolerable surgical risks. It requires a small amount of surgical time compared to other reconstructive options and an overall reduced inpatient stay.

Custom-Made Three-Dimensional Models for Craniosynostosis.

The use of computer-aided design and computer-aided manufacturing in oral and maxillofacial surgery is an ever-growing field.The availability of 3D models, cutting guides, and customised surgical instruments gives surgeons the opportunity to modify and improve their surgical procedures.Here, we discuss the use of computer-aided design-computer-aided manufacturing to improve the management of a case of nonsyndromic metopic synostosis through the construction of: A cutting guide for the cranium, custom-made orbital protectors, a 3D model of the predicted postoperative meninges to allow off the table bone recontouring, and a template frontal bar to allow more specific recontouring of the frontal bar.