Investigation of a maxillary nerve block technique in guinea pigs (Cavia porcellus): A cadaveric study comparing two injectate volumes.

OBJECTIVE: To investigate and describe an extraoral approach to perform a maxillary nerve block in guinea pigs. STUDY DESIGN: Prospective, randomized, blinded, descriptive, cadaveric study. ANIMALS: A total of 14 adult guinea pig cadavers. METHODS: Two cadavers were used for anatomic dissection and determination of maxillary nerve block approach. A maxillary nerve block via infraorbital approach was then performed in 12 cadavers. A low volume (0.1 mL) or high volume (0.2 mL) of diluted methylene blue injectate was randomly assigned to the right or left side, with the other volume used for the contralateral side. The maxillary nerve was dissected after each injection by an investigator blinded to injectate volume. The region of dye distribution was identified, and the degree of staining assigned an accuracy score (0-2). Nerve coverage was considered adequate if ≥6 mm of circumferential staining was present. RESULTS: Accuracy evaluation indicated successful dye deposition in 10/12 [2 (0-2), median (range)] injections in the low volume group and 8/12 [2 (1-2)] injections in the high volume group. The majority (79.2%) of injections resulted in adequate nerve staining. There were no statistically significant differences between injectate volumes for accuracy (p = 0.64) or adequacy (p > 0.99) of staining. CONCLUSIONS: The infraorbital approach is a simple and practical method for maxillary nerve blockade in guinea pigs. An injectate volume of 0.1 mL results in adequate maxillary nerve coverage; however, additional studies are needed to assess the efficacy in clinical use.

Temporomandibular Joint Gape Angles in Normal and Painful Domestic Felines.

The purpose of this study was to determine and compare the gape angles (temporomandibular joint range of motion with mouth opening) of conscious and anesthetized domestic felines and to compare gape angles with and without evidence of oral pain. This prospective study evaluated the gape angle of 58 domestic felines. The cats were grouped into painful (n = 33) and nonpainful cohorts (n = 25) and gape angles were compared during conscious and anesthetized conditions. Gape angles were determined based on measurements of the maximal interincisal distance and lengths of the mandible and maxilla followed by calculation of the law of cosines. The mean feline gape angle (standard deviation) was determined to be 45.3° (8.6°) and 50.8° (6.2°) for conscious and anesthetized felines respectively. There was no significant difference between painful and non-painful feline gape angles during conscious (P = .613) or anesthetized (P = .605) evaluations. There was a significant difference between anesthetized and conscious gape angles (P < .001) for both painful and non-painful cohorts. This study determined the standardized, normal feline temporomandibular joint (TMJ) gape angle in both conscious and anesthetized states. This study suggests that the feline gape angle is not a useful indicator of oral pain. By determining the feline gape angle, which was previously unknown, further evaluation of its utility as a non-invasive clinical parameter for evaluation of restrictive TMJ motions as well as its use for serial evaluations may be pursued.

Synthesis, Characterization, and Energetic Properties of Nitrate Ester Acrylate Polymer.

An energetic nitrate ester acrylate monomer (4) was synthesized in a total yield of 68% and polymerized to form the energetic nitrate ester acrylate polymer (NEAP). Compound 4 is a liquid at room temperature with a melting point of -8.6 °C and NEAP is a solid with a glass-transition temperature of -8.8 °C. Intermediates leading to 4 and NEAP were characterized by high-resolution mass spectrometry, elemental analysis, Fourier transform infrared spectroscopy, and proton and carbon nuclear magnetic resonance spectroscopies (1H and 13C{1H} NMR). Both 4 and NEAP have electrostatic discharge, friction, and impact sensitivities comparable to those of trinitrotoluene, making NEAP a potential candidate for advanced energetic formulations.

Investigation into a Conformationally Locked (Z)-Azidoxime.

High nitrogen compounds find wide use in the development of new propellants and explosives as well as pharmaceutical chemistry as bioisosteres, bacterial stains, and antifungal agents. A class of underexplored high-nitrogen materials includes azidoximes and their 1-hydroxytetrazole isomers. Azidoximes possess an energetic azide group and are quite sensitive to impact, spark, and friction. Therefore, these materials are generated in situ and cyclized under mild acidic conditions to their 1-hydroxytetrazole isomers. Recently, we synthesized a novel 1,2,4-triazine-derived azidoxime; however, upon subjecting this material to established cyclization conditions, no reaction was observed, even after prolonged reaction times with heating. Additional 1,2,4-triazine-derived azidoximes also displayed a similar lack of reactivities. This observation led us to probe the reactivity of these materials with both a DFT investigation and crystallographically based electrostatic potential mapping. In all, the lack of reactivity toward cyclization was found to be due to an inability of 1,2,4-triazine-based azidoximes to isomerize into the reactive (E)-conformation, requiring an activation energy of 26.4 kcal mol-1.

Synthesis and Energetic Properties of N-Substituted 3,4- and 3,5-Dinitropyrazoles.

3,4- and 3,5-Dinitropyrazoles (DNPs) were substituted with acryl and allyl groups on the N1 nitrogen atom, resulting in three novel energetic materials. These compounds are all liquids at room temperature with melting points ranging from -60.2 to -38.6 °C and were fully characterized by high-resolution mass spectrometry, elemental analysis, proton and carbon nuclear magnetic resonance spectroscopy, and Fourier transform infrared spectroscopy. These materials were also tested for electrostatic discharge, friction, and impact sensitivities and then compared to DNP starting materials and to the explosive nitroglycerin (NG). These results indicate that the synthesized compounds are less sensitive to impact compared to NG and have higher thermal stabilities to decomposition.

Radiolytic degradation of dodecane substituted with common energetic functional groups.

Explosives exist in and are expected to withstand a variety of harsh environments up to and including ionizing radiation, though little is known about the chemical consequences of exposing explosives to an ionizing radiation field. This study focused on the radiation-induced chemical changes to a variety of common energetic functional groups by utilizing a consistent molecular backbone. Dodecane was substituted with azide, nitro, nitrate ester, and nitramine functional groups and γ-irradiated with 60Co in order to study how the functional group degraded along with what the relative stability to ionizing radiation was. Chemical changes were assessed using a combination of analysis techniques including: nuclear magnetic resonance (NMR) spectroscopy, gas chromatography of both the condensed and gas phases, Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. Results revealed that much of the damage to the molecules was on the energetic functional group and often concentrated on the trigger linkage, also known as the weakest bond in the molecule. The general trend from most to least susceptible to radiolytic damage was found to be D-ONO2 → D-N3 → D-NHNO2 → D-NO2. These results also appear to be in line with the relative stability of these functional groups to things such as photolysis, thermolysis, and explosive insults.

Investigation into the Decomposition Pathways of an Acetal-Based Plasticizer.

Until now, it has been assumed that the primary decomposition pathway for the liquid plasticizer bis(2,2-dinitropropyl)acetal and bis(2,2-dinitropropyl)formal (BDNPA/F) was nitrous acid elimination (NAE). An ultrahigh-performance liquid chromatography (UHPLC) coupled to quadrupole time-of-flight mass spectrometry (QTOF) methodology was developed to discover and identify the degradation products of BDNPA/F. No evidence of NAE was found. However, two other degradation pathways were found: (1) hydrolysis of the acetal/formal functional group and (2) radical-based homolysis of the C-N bond, followed by hydrogen atom abstraction. Hydrolysis of BDNPA/F proceeds by the formation of 2,2-dinitropropanol (DNPOH) and 2,2-dinitropropyl hemiacetal/hemiformal, which further decompose into DNPOH and ethanal/methanal, respectively. Hydrolysis is the dominant decomposition pathway in all samples; however, at higher temperatures, C-N homolysis becomes more significant. Also, the solid PBX 9501 has different ratios of decomposition products than the liquid BDNPA/F due to the slower rate of diffusion through solids than liquids.

Patient Triage, First Aid Care, and Management of Oral and Maxillofacial Trauma.

Maxillofacial trauma is a common presentation in veterinary medical practice. Accurate assessment, diagnostics, pain management, and finally repair are tenants to treatment. In addition to typical tenants for fracture repair, the restoration of occlusion and return to function (eating, drinking, grooming) are unique to trauma management in these patients. Options for repair include conservative management (tape muzzles), noninvasive repair techniques (interdental wiring and composite splinting), and invasive repair techniques (interfragmentary wiring and plate and screw fixation).

Gape Angle in Asymptomatic Dogs with Normal Occlusion.

This study reports the gape angle (vertical temporomandibular joint range of motion for mouth opening) in conscious and anesthetized dogs. Mouth opening was reported as an angle in this study. Additionally, conscious and anesthetized measurements were compared to see if the state of anesthesia affected this measurement in asymptomatic patients. This prospective study evaluated 165 anesthetized dogs. Patients were placed in 1 of 2 groups: dental patients or non-dental patients. Only patients who were reported by owners to be asymptomatic for oral pain were included in the study. All dogs that met inclusion criteria had the maxillary length and interincisal distance measured. There was no difference (p = 0.590) between the mean (+/-SD) gape angle of conscious 44.0o (+/- 4.1+o) and anesthetized patients 43.9o (+/- 3.9o). No difference was seen in the gape angle between dental (44.2o) and non-dental patients (43.2o) (p = 0.183), or between conscious (43.8o) and anesthetized patients (43.7o) (p = 0.610). This study suggests that a consistent gape angle of 44o exists in dogs not exhibiting overt signs of oral pain and the gape angle is easy to measure in conscious patients and may be a useful tool during routine physical examination to identify patients with restricted range of motion. Immediate clinical application of this information can be used to monitor progress of treated patients affected by disorders that cause a decreased gape angle.

Management of Severe Periodontal Disease and Gingival Enlargement in a Dwarf Mongoose (Helogale parvula).

Development of gingival enlargement and periodontitis is described in a young dwarf mongoose. Repeated treatments resulted in gingival resection and histologic evaluation however gingival enlargement was ultimately responsive to extraction of associated teeth. In cases such as these, surgical extraction of teeth associated with severe recurrent gingival enlargement should be considered to avoid the stress and risk of repeated immobilizations.

Biomechanical Testing of a Calcium Phosphate-Phosphoserine-Based Mineral-Organic Adhesive for Non-invasive Fracture Repair of Mandibular Fractures in Dogs.

Mandibular fracture repair is complicated by limited availability of bone as well as the presence of the neurovascular bundle and an abundance of tooth roots. Fractures at the location of the mandibular first molar teeth are common and it can be particularly challenging to apply stable fixation. Non-invasive fracture repair techniques utilize intraoral placement of fixation devices typically involving polymerized composites and/or interdental wiring. A novel calcium phosphate-phosphoserine-based mineral-organic adhesive was tested ex vivo to determine its effects on augmenting strength of different non-invasive fracture fixation techniques. This study both tested the use of mineral-organic adhesive for the purpose of stabilizing currently used non-invasive fracture repair constructs (intraoral composite splinting ± interdental wiring) and evaluated adhesive alone or with subperiosteally placed plates on buccal cortical bone surface. Aside from controls, not receiving an osteotomy along the mesial root of the mandibular first molar tooth, six treatment groups were tested to evaluate ultimate strength, stiffness, angular displacement, bending moment, and application time. All forms of fixation were found to be significantly weaker than control (p < 0.001). Only the control (p < 0.001) and mineral-organic adhesive and composite (P = 0.002) groups were found to be significantly stronger than wire and composite. No difference was noted in stiffness between any groups with control or wire and composite. Application times varied from the mineral-organic adhesive group (mean = 206 s) to mineral-organic adhesive and composite (mean = 1,281 s). Twenty-three fixation devices exhibited adhesive failure, 20 demonstrated cohesive failure, and 5 failed by cohesive and adhesive failure. When evaluating the ultimate strength of the fixation device groups, mineral-organic adhesive, and composite was shown to be the strongest construct. The use of resorbable bone adhesive and composite may provide a stronger fixation construct over interdental wire and composite for mandibular fracture repair in dogs.

Evaluation of Perceived Technical Skill Development by Students During Instruction in Dental Extractions in Different Laboratory Settings-A Pilot Study.

In veterinary general practice, dental extractions are common procedures that require a specific set of surgical skills. Veterinary medical educators are tasked with preparing students for general practice, equipping them with medical knowledge and surgical skills. Results of this pilot study demonstrate students' preference for circle-based laboratory setup, a perceived high value of immediate feedback when performing laboratory exercises, and a lack of preference for timing of the laboratory relative to the relevant material provided in lecture. The impact of lecture, supplemental information, and laboratory setup on development of these surgical skills are explored.

Assessment of the Role of the Mandibular First Molar Tooth in Mandibular Fracture Patterns of 29 Dogs.

Mandibular fractures at the level of the first molar tooth (M1) were assessed in 29 dogs. Patients included in this study demonstrated fractures involving the M1 tooth, tooth bud, or alveolus (if tooth was absent). Diagnostic imaging evaluation included intraoral dental radiography and/or computed tomography (CT) with 3D reconstruction. The distal root was involved in 55.2% of cases, mesial root involvement in 34.5% of cases, and the tooth was absent in 10.3% of cases. Fractures were described in the rostral-to-caudal direction. Fractures tended to occur in the caudoventral direction ( P = .057). Cases with CT imaging were also evaluated in the buccolingual direction. Fractures were found to occur significantly more frequently in the caudolingual direction ( P = .022). When classifying fracture patterns along M1 according to a previously published fracture classification system, it was noted that fractures occurred significantly more frequently in either the mesial ( P < .001) or distal ( P < .001) roots by coursing along the periodontal ligament space and communicating with the periapical region. Active or nonworsening periodontitis was described as radiographic or tomographic evidence of (>25%) bone loss in the vertical or horizontal direction. Periodontitis was associated with 7 (24.1%) cases. These results help frame the challenges associated with fracture repair at the M1 location. Treatment planning considerations should include limited structural support caudal to fractures involving the distal root, more frequent involvement of the distal root over the mesial root, risk for poor endodontic prognosis, and the predilection for unfavorable fracture patterns to occur.

N-Acetylcysteine (NAC) for the Prevention of Liver Failure in Heat Injury-Mediated Ischemic Hepatitis.

Exertional Heat Illness with associated ischemic hepatitis (IH) is a common occurrence among military trainees; however, few specific therapies exist if unresponsive to appropriate supportive measures. A 27-year-old basic combat trainee presented with altered mental status, renal insufficiency, rhabdomyolysis, and a core temp of 107.9 °F after collapsing during a run, leading to the diagnosis of heat stroke. While the patient's azotemia and creatinine kinase levels rapidly improved with aggressive intravenous hydration, transaminases continued to increase to nearly 155 times the upper limit of normal. Further laboratory evaluation revealed coagulopathy and thrombocytopenia suggestive of acute liver failure (ALF). On hospital day three, the patient was started on N-acetylcysteine (NAC). Evaluation for infectious and autoimmune etiologies of ALF was unremarkable; thus, the patient's symptomatology was attributed to IH resulting from heat stroke. Liver function normalized on NAC. Heat Injury is common among US Army recruits and results in thousands of hospitalizations in recent years. IH is characterized by diffuse hepatocyte necrosis following an episode of hemodynamic instability, and is an established sequela of Heat Injury. The mortality of IH among critically ill patients has been estimated to be as high as 60%, with those demonstrating coagulopathy especially at risk. NAC is shown to improve the transplant-free survival rate in non-acetaminophen related ALF, consistent with its proposed mechanisms of improving hepatic blood flow and conjugating toxic metabolites. NAC therapy should be considered early in the course of heat injury-mediated IH to reduce reperfusion injury, improving transplant free outcomes.

Polycyclic N-oxides: high performing, low sensitivity energetic materials.

Polycyclic N-oxides were developed based on the heterocycles 1,2,4,5-tetrazine and 4H,8H-difurazano[3,4-b:3',4'-e]pyrazine. The new compounds are energetic and have excellent explosive properties, while maintaining low mechanical sensitivities. Most notably, compound 7 is thermally stable, insensitive, and has superior detonation properties to the state-of-the-art insensitive high explosive, 1,3,5-triamino-2,4,6-trinitrobenzene.

2019 AAHA Dental Care Guidelines for Dogs and Cats.

The 2019 AAHA Dental Care Guidelines for Dogs and Cats outline a comprehensive approach to support companion animal practices in improving the oral health and often, the quality of life of their canine and feline patients. The guidelines are an update of the 2013 AAHA Dental Care Guidelines for Dogs and Cats. A photographically illustrated, 12-step protocol describes the essential steps in an oral health assessment, dental cleaning, and periodontal therapy. Recommendations are given for general anesthesia, pain management, facilities, and equipment necessary for safe and effective delivery of care. To promote the wellbeing of dogs and cats through decreasing the adverse effects and pain of periodontal disease, these guidelines emphasize the critical role of client education and effective, preventive oral healthcare.

Analysis of the Anatomic Relationship Between the Mandibular First Molar Roots and Mandibular Canal Using Cone-Beam Computed-Tomography in 101 Dogs.

The mandibular first molar (M1) tooth of the dog is commonly involved in dental procedures. Tooth roots and the mandibular canal can vary in location, which has not been described on a large scale. The objective of this study was to describe the three-dimensional anatomic relationship of the mandibular M1 tooth roots and the mandibular canal in dogs. Cone-beam computed tomography (CBCT) was used to evaluate the anatomic relationship between the M1 tooth roots and the mandibular canal. CBCT images were collected from 101 canine cadaver heads from a variety of unknown breeds. All skulls used in this study were mesaticephalic, confirmed by facial index calculations. The position of the apex in relation to the mandibular canal and in relation to the buccal and lingual cortices was recorded and analyzed in relation to mandibular bone height: root length ratio. When evaluating the apex in a buccal-lingual relationship, the tooth roots were found to be located closer to the lingual cortex in 73.3% of M1 roots. Tooth root apical positions were found to be symmetric between the right and left side of the mouth in 93% of mesial roots and 95% of distal roots. Apical positions relative to the mandibular canal within the same tooth were found to be consistent in 52% of teeth. Teeth with roots dorsal to the mandibular canal were associated with the largest mandibular bone height: root length ratio. CBCT provides a more precise overview than dental radiographs of three-dimensional anatomy. The tooth root position can be estimated in a clinical setting based on the ratio of mandibular bone height to tooth root length obtained from intraoral radiographs. Understanding the relative location of important anatomic structures is key to avoiding complications associated with various dental procedures. This study has documented that assessing anatomic structures with 2D imaging alone is flawed, and the large majority of dogs have M1 roots closer to the lingual aspect than the buccal aspect of the mandible.

A Volumetric Assessment Using Computed Tomography of Canine and First Molar Roots in Dogs of Varying Weight.

Mandibular volume and tooth root volumes were shown to increase at different rates at locations containing the roots of the canine (C) and mesial and distal roots of the first molar (M1). Thirty-six dogs were included in this study. Data were generated using computed tomography at locations of the mandible involving the roots of the C and M1 teeth. Software was used to trace the external surface of the mandible, calculating the volume of the mandible at each location. Similar techniques were used to trace and calculate the volume of the C and M1 roots. Mandible volume, tooth root volume, and root percentage of mandible volume were analyzed and compared using the slopes of the best fit line. At the M1 mesial and distal roots, mandible volume ( P < .001) and root volume ( P < .001) were both noted to increase, with increasing weight at different rates. The rate of change in the root percentage by weight of M1 roots was not different ( P = .214). Each location demonstrated a different increasing rate of change for mandibular volume and increasing root volume. Results show that as patient's weight increases, the mandible and root volumes increase at different rates. Root percentage by volume at all three locations was noted to decrease by the same rate. Canine and M1 roots are proportionally larger than the supporting mandibular bone in smaller patients. Care should be taken to recommend periodontal disease prevention for owners of small dogs and consideration made when performing extractions or other surgery that may destabilize the mandible.

Examining the chemical and structural properties that influence the sensitivity of energetic nitrate esters.

The sensitivity of explosives is controlled by factors that span from intrinsic chemical reactivity and chemical intramolecular effects to mesoscale structure and defects, and has been a topic of extensive study for over 50 years. Due to these complex competing chemical and physical elements, a unifying relationship between molecular framework, crystal structure, and sensitivity has yet to be developed. In order to move towards this goal, ideally experimental studies should be performed on systems with small, systematic structural modifications, with modeling utilized to interpret experimental results. Pentaerythritol tetranitrate (PETN) is a common nitrate ester explosive that has been widely studied due to its use in military and commercial explosives. We have synthesized PETN derivatives with modified sensitivity characteristics by substituting one -CCH2ONO2 moiety with other substituents, including -CH, -CNH2, -CNH3X, -CCH3, and -PO. We relate the handling sensitivity properties of each PETN derivative to its structural properties, and discuss the potential roles of thermodynamic properties such as heat capacity and heat of formation, thermal stability, crystal structure, compressibility, and inter- and intramolecular hydrogen bonding on impact sensitivity. Reactive molecular dynamics (MD) simulations of the C/H/N/O-based PETN-derivatives have been performed under cook-off conditions that mimic those accessed in impact tests. These simulations infer how changes in chemistry affect the subsequent decomposition pathways.

Simple and Efficient Synthesis of Explosive Cocrystals containing 3,5-Dimethylpyrazol-1-yl-substituted-1,2,4,5-tetrazines.

The reaction of 3,4-dinitropyrazole, 5-nitrotetrazole, or 4-nitro-1,2,3-triazole with 1,2,4,5-tetrazines substituted with 3,5-dimethylpyrazolyl (dmp) groups results in energetic cocrystals after 1 minute of reflux and cooling to room temperature in yields of 89-92 %. Hydrogen-bonding between the dmp group to the N-H of the energetic heterocycles are the predominant interaction that stabilizes the new cocrystals. Each cocrystal packs in a different lattice structure and the cocrystals with sheet-like and herring-bone crystal packing orientations are less sensitive than the cocrystal with the interlocked structure. Electrostatic potential mapping helps rationalize why dmp-substituted tetrazines readily form cocrystals, whereas more electron-deficient pyrazolyl tetrazines do not. The calculated energetic performance of the new cocrystals approaches that of 2,4,6-trinitrotoluene (TNT) and importantly, these materials will aid in the rational design of new cocrystalline energetic materials.