Gary D. Hack

Anatomic Relation between the Rectus Capitis Posterior Minor Muscle and the Dura Mater

Study Design Anatomic study of the suboccipital region, specifically the deep muscles of the suboccipital triangle, was performed in cadaveric specimens. Objective To observe and describe the relationship between the deep subocipitel musculature and the spinal dura. Summary of Background Data A review of the literature revealed no reports describing a physical connection between suboccipital musculature and the spinal dura. Methods Dissections of the suboccipital region were performed in 10 embalmed and one fresh sagittally hemisected head and neck specimens. Results Aconnective tissue bridge between the rectuss capitis posterior minor muscle and the dorsal spinal sura at the atlanto-occipital junction was observed in every specimen. the fibers of the connective tissue bridge were oriented primarily parpondicular to the dura. This arrangement of fibers appears to resist movement of the dura toward the spinal cord. Conclusions Awareness of the physical relation between the rectus capitis posterior minor muscle and spinal dura via this connective tissue bridge should lesson the potential risk of durel damage during surgery. This connective tissue bridge may help resist dural infolding during head and meck extension.

Chronic Headache Relief After Section of Suboccipital Muscle Dural Connections: A Case Report

The presence of a connective tissue bridge, attaching suboccipital muscles to the dura mater, is now recognized as a feature of normal human anatomy. The role that this myodural bridge may play in headache production is uncertain; however, a new conceptual model is emerging. Postsurgical myodural adhesions have been reported as a complication resulting from excision of acoustic tumors. Extensive research now exists implicating these myodural adhesions as a possible source of postoperative headache. Integrating these 2 types of myodural unions (anatomic and pathologic) into a unified theory of headache production, we report a single patient who experienced relief from chronic headache after surgical separation of the myodural bridge from the suboccipital musculature.

Rechargeable dental adhesive with calcium phosphate nanoparticles for long-term ion release

OBJECTIVES The tooth-resin bond is the weak link of restoration, with secondary caries as a main reason for failure. Calcium phosphate-containing resins are promising for remineralization; however, calcium (Ca) and phosphate (P) ion releases last only a couple of months. The objectives of this study were to develop the first rechargeable CaP bonding agent and investigate the key factors that determine CaP ion recharge and re-release. METHODS Nanoparticles of amorphous calcium phosphate (NACP) were synthesized. Pyromellitic glycerol dimethacrylate (PMGDM), ethoxylated bisphenol-A dimethacrylate (EBPADMA), 2-hydroxyethyl methacrylate (HEMA), and bisphenol-A glycidyl dimethacrylate (BisGMA) were used to synthesize three adhesives (denoted PE, PEH and PEHB). NACP were mixed into adhesive at 0-30% by mass. Dentin shear bond strengths were measured. Adhesive specimens were tested for Ca and P initial ion release. Then the ion-exhausted specimens were immersed in Ca and P solution to recharge the specimens, and the recharged specimens were then used to measure ion re-release for 7 days as one cycle. Then these specimens were again recharged and the re-release was measured for 7 days as the second cycle. Three recharge/re-release cycles were tested. RESULTS PEHB had the highest dentin bond strength (p<0.05). Increasing NACP content from 0 to 30% did not affect dentin bond strength (p>0.1), but increased CaP release and re-release (p<0.05). PEHB-NACP had the greatest recharge/re-release, and PE-NACP had the least (p<0.05). Ion release remained high and did not decrease with increasing the number of recharge/re-release cycles (p>0.1). After the third cycle, specimens without further recharge had continuous CaP ion release for 2-3 weeks. SIGNIFICANCE Rechargeable CaP bonding agents were developed for the first time to provide long-term Ca and P ions to promote remineralization and reduce caries. Incorporation of NACP into adhesive had no negative effect on dentin bond strength. Increasing NACP filler level increased the ion recharge and re-release capability. The new CaP recharge method and PMGDM-EBPADMA-NACP composition may have wide application in adhesives, composites and cements, to combat caries and remineralize lesions.

Tetracalcium phosphate composite containing quaternary ammonium dimethacrylate with antibacterial properties

Tooth caries is a carbohydrate-modified bacterial infectious disease, and recurrent caries is a frequent reason for restoration failure. The objective of this study was to develop a novel antibacterial composite using tetracalcium phosphate (TTCP) fillers and bis(2-methacryloyloxy-ethyl) dimethyl-ammonium bromide, which is a quaternary ammonium dimethacrylate (QADM). QADM was synthesized using 2-(N,N-dimethylamino)ethyl methacrylate and 2-bromoethyl methacrylate and incorporated into a resin. The resin was filled with 40% TTCP and 30% glass particles. The following QADM mass fractions in the composite were tested: 0%, 6%, 12%, and 18%. Streptococcus mutans biofilms were formed on the composites and the colony-forming units (CFUs), metabolic activity, and lactic acid production were measured. The TTCP-QADM composite had flexural strength and elastic modulus similar to those of two commercial composites (p > 0.1). Increasing the QADM content in TTCP composite greatly decreased the bacteria growth and biofilm matrix production. There were significantly more dead bacteria with increasing QADM content. TTCP composite containing 18% QADM had biofilm CFU, metabolic activity, and acid production about half of those without QADM. Inversely linear relationships were established between QADM mass fraction and S. mutans biofilm CFU, metabolic activity, and acid production, with correlation coefficients R(2) ≥ 0.98. In conclusion, TTCP-QADM composites were developed and the effect of QADM mass fraction on the antibacterial properties of the composite was determined for the first time. The novel TTCP-QADM composites possessing a strong antibacterial capability, together with calcium phosphate ion release and good mechanical properties, are promising for dental restorations to reduce biofilm growth and recurrent caries.

Human paranasal sinuses and selective brain cooling: A ventilation system activated by yawning?

The function of the paranasal sinuses has been a controversial subject since the time of Galen, with many different theories advanced about their biological significance. For one, the paranasal sinuses have been regarded as warmers of respiratory air, when in actuality these structures appear to function in cooling the blood. In fact, human paranasal sinuses have been shown to have higher volumes in individuals living in warmer climates, and thus may be considered radiators of the brain. The literature suggests that the transfer of cool venous blood from the paranasal sinuses to the dura mater may provide a mechanism for the convection process of cooling produced by the evaporation of mucus within human sinuses. In turn, the dura mater may transmit these temperature changes, initiated by the cool venous blood from the heat-dissipating surfaces of the sinuses, to the cerebrospinal fluid compartments. Furthermore, it has recently been demonstrated in cadaveric dissections that the thin bony posterior wall of the maxillary sinus serves as an origin for both medial and lateral pterygoid muscle segments, an anatomic finding that had been previously underappreciated in the literature. The present authors hypothesize that the thin posterior wall of the maxillary sinus may flex during yawning, operating like a bellows pump, actively ventilating the sinus system, and thus facilitating brain cooling. Such a powered ventilation system has not previously been described in humans, although an analogous system has been reported in birds.

Palate and dentition in schizophrenia

OBJECTIVE Although psychotic symptoms are central to the diagnostic criteria for schizophrenia, other neuropsychiatric syndromes as well as widespread anatomical and physiological abnormalities in the periphery are also common in the disorder. We decided to test the hypothesis that developmental abnormalities are present throughout the body by examining the oral cavity and in particular the teeth and dimensions of the palate of patients with schizophrenia. METHOD Dental stone models (casts) were made from impressions of the teeth and palate in schizophrenia (N=28) and control (N=25) subjects. Blind to group membership, the palate height, palate width, and other features of each subjects cast were assessed by a dentist. RESULTS Patients with schizophrenia had significantly wider palates than control subjects; the palatal height did not differ between the two groups. The patients also had a high prevalence of several other anatomical abnormalities, few of which were present in the control subjects. CONCLUSIONS This first blind, quantitative assessment of the palate and teeth of patients with schizophrenia revealed a wide palate and an increased prevalence of developmental abnormalities in the teeth. These findings are consistent with the emerging concept that schizophrenia is not so much a psychotic disorder as a developmental disorder in which psychosis is present, and in which there are a number of other abnormalities in the brain and the periphery.