Beware of "black swans" and "perfect storms:" the principle of plenitude and office-based anesthesia.

A paradigm shift in the training, practice, and study of office-based anesthesia is necessary for our specialty. Practice improvement plans are required to prevent low-probability-high-consequence anesthesia mishaps in our offices. A scarcity of statistical data exists regarding the true risk of office-based anesthesia in oral and maxillofacial surgery. Effective proactive risk management mandates accurate data to correctly outline the problem before solutions can be implemented. Only by learning from our mistakes, will we be able to reduce errors and improve patient safety: "The only real mistake is the one from which we learn nothing"--John Powell.

Effect of lignin chemistry on the enzymatic hydrolysis of woody biomass.

The impact of lignin-derived inhibition on enzymatic hydrolysis is investigated by using lignins isolated from untreated woods and pretreated wood pulps. A new method, biomass reconstruction, for which isolated lignins are precipitated onto bleached pulps to mimic lignocellulosic biomass, is introduced, for the first time, to decouple the lignin distribution issue from lignin chemistry. Isolated lignins are physically mixed and reconstructed with bleached pulps. Lignins obtained from pretreated woods adsorb two to six times more cellulase than lignins obtained from untreated woods. The higher adsorption of enzymes on lignin correlates with decreased carbohydrate conversion in enzymatic hydrolysis. In addition, the reconstructed softwood substrate has a lower carbohydrate conversion than the reconstructed hardwood substrate. The degree of condensation of lignin increases significantly after pretreatment, especially with softwood lignins. In this study, the degree of condensation of lignin (0.02 to 0.64) and total OH groups in lignin (1.7 to 1.1) have a critical impact on cellulase adsorption (9 to 70%) and enzymatic hydrolysis (83.2 to 58.2%); this may provide insights into the more recalcitrant nature of softwood substrates.

Craniofacial approaches and reconstruction in skull base surgery: techniques for the oral and maxillofacial surgeon.

Skull base surgery (SBS) is considered the standard of care in treating benign and malignant lesions of the cranial base. SBS is a multidisciplinary team approach used to treat these complex lesions that may have intracranial extension. SBS can be broken down into 3 steps. Transfacial access is performed, followed by resection with sound oncologic principles, and then reconstruction of the cranial base and facial structures. Functional and esthetic concerns must be addressed by the surgeons. Oral and maxillofacial surgeons frequently perform elective facial osteotomies and treat victims of cranial base trauma. These same principles can be applied to SBS as a part of the skull base team.

Impact of hardwood species on production cost of second generation ethanol.

The present work targeted the understanding of the influence of nine different hardwood species as feedstock on ethanol production yield and costs. It was found that the minimum ethanol revenue (MER) ($ per gallon to the producer) to achieve a 12% internal rate of return (IRR) on invested capital was smaller for low lignin content samples and the influence of species characteristics remained restricted to high residual lignin content. We show that if the pretreatment being applied to the feedstock targets or is limited to low lignin removal, one can expect the species to have a significant impact on overall economics, playing important role to project success. This study also showed a variation of up to 40% in relative MER among hardwood species, where maple, globulus and sweet gum varied the least. Sensitivity analysis showed ethanol yield per ton of feedstock had the largest influence in MER, followed by CAPEX.

Poly(propylene fumarate) reinforced dicalcium phosphate dihydrate cement composites for bone tissue engineering.

Calcium phosphate cements have many desirable properties for bone tissue engineering, including osteoconductivity, resorbability, and amenability to rapid prototyping-based methods for scaffold fabrication. In this study, we show that dicalcium phosphate dihydrate (DCPD) cements, which are highly resorbable but also inherently weak and brittle, can be reinforced with poly(propylene fumarate) (PPF) to produce strong composites with mechanical properties suitable for bone tissue engineering. Characterization of DCPD-PPF composites revealed significant improvements in mechanical properties for cements with a 1.0 powder to liquid ratio. Compared with nonreinforced controls, flexural strength improved from 1.80 ± 0.19 MPa to 16.14 ± 1.70 MPa, flexural modulus increased from 1073.01 ± 158.40 MPa to 1303.91 ± 110.41 MPa, maximum displacement during testing increased from 0.11 ± 0.04 mm to 0.51 ± 0.09 mm, and work of fracture improved from 2.74 ± 0.78 J/m(2) to 249.21 ± 81.64 J/m(2) . To demonstrate the utility of our approach for scaffold fabrication, 3D macroporous scaffolds were prepared with rapid prototyping technology. Compressive testing revealed that PPF reinforcement increased scaffold strength from 0.31 ± 0.06 MPa to 7.48 ± 0.77 MPa. Finally, 3D PPF-DCPD scaffolds were implanted into calvarial defects in rabbits for 6 weeks. Although the addition of mesenchymal stem cells to the scaffolds did not significantly improve the extent of regeneration, numerous bone nodules with active osteoblasts were observed within the scaffold pores, especially in the peripheral regions. Overall, the results of this study suggest that PPF-DCPD composites may be promising scaffold materials for bone tissue engineering.

Reduction of enzyme dosage by oxygen delignification and mechanical refining for enzymatic hydrolysis of green liquor-pretreated hardwood.

In this study, a strategy to reduce enzyme dosage is evaluated by applying two post-treatments, oxygen delignification and mechanical refining. The sugar conversion for GL12 substrates was increased from 51.5% to 77.9% with post-treatments at the enzyme dosage of 10 FPU. When the amount of enzyme was reduced to 5 FPU with post-treatments, the conversion of 71.8% was obtained, which was significant higher than the conversion without any post-treatment using 10 FPU (51.5%). This clearly demonstrates the benefit of post-treatments that allows more than 50% of enzyme reduction at the same level of enzymatic conversion. Enzyme-accessible surface area and pore volume were evaluated by Simons' staining and DSC thermoporometry methods, and strong correlations were found with the sugar conversion.

The "bone-less" bone graft: The use of bone morphogenic protein-2 in jaw reconstruction.

A growth factor known as Bone Morphogenic Protein has through recombinant technology been made available to dentists as a "bone-less" bone graft. This recombinant human bone morphogenic protein-2 is placed on an absorbable collagen sponge carrier and delivered to a site of bone deficiency. This material will induce new osteoblasts to form from mesenchymal stem cells in the surrounding recipient site. This eliminates the need for an autogenous bone graft and its inherent surgical morbidity. The new bone formed is of the same quality and quantity as that produced by autogenous grafting. Dentists should be familiar with alternative techniques of bone grafting in contemporary practice.

Cervical necrotizing fasciitis originating with a periapical infection.

BACKGROUND: Necrotizing fasciitis is a rapidly spreading, soft-tissue infection involving the subcutaneous tissues. Necrotizing fasciitis originating from a dental-related source is rare. Practitioners should be aware that this infection could occur in patients who are immunocompromised and in patients who are healthy. Practitioners must treat this disease aggressively with surgical debridement and intensive medical support. CASE DESCRIPTION: The authors present a case report of a man with poorly controlled diabetes mellitus in whom a periapical infection progressed into a maxillofacial space abscess and finally cervical necrotizing fasciitis (CNF). A delay in his initial visit to a dentist was evident. The authors observed a successful outcome in the patient after he underwent several wide surgical debridement procedures, hyperbaric oxygen therapy and a protracted, intensive hospital stay lasting 34 days. CONCLUSIONS: Dentists should suspect that a patient has CNF when maxillofacial cellulitis or an abscess does not respond to conventional therapy. Findings of spreading skin erythema, induration, purple discoloration and anesthesia suggest necrotizing fasciitis. Early computed tomography scans may reveal gas within the deep tissues of the neck, fascial plane involvement or both. CLINICAL IMPLICATIONS: CNF has high morbidity and mortality rates if rapid aggressive therapy is not pursued. Spread of this polymicrobial infection can lead to mediastinitis or cranial base involvement. Mortality is directly proportional to the time to intervention.

Office-based anesthesia.

The practice of office-based oral and maxillofacial surgery is continuously expanding and involves the management of a diverse population in regards to the surgical procedures performed within the office and the age and medical health of the patients treated within the office. Comfort, cooperation, and hemodynamic stability are critical to satisfactorily accomplishing the surgical procedure. Various anesthetic techniques are used, including local anesthesia, anxiolysis, analgesia and sedation, and general anesthesia. The topic is vast and too extensive to be fully discussed in this article. The intent of this article is to provide a discussion of some fundamental concepts that can optimize anesthetic safety and care.