Metabolism of TEGDMA and HEMA in human cells.

Previous in vivo studies have shown that the comonomers triethylene glycol dimethacrylate (TEGDMA) and 2-hydroxyethyl methacrylate (HEMA) from dental materials can be metabolised to CO(2) by two postulated pathways: an epoxide and a valine pathway. In the epoxide pathway the formation of pyruvate is postulated and in valine pathway the formation of l-malate. The aim of this investigation was to quantify the formation of the intermediates pyruvate and l-malate to show which pathway may be preferred in A549 cells. Therefore A549 cells were incubated with TEGDMA or HEMA (with a tracer dose 14C-TEGDMA or 14C-HEMA) and afterwards 14C-TEGDMA or 14C-HEMA, 14C-methacrylate, 14C-l-malate and 14C-pyruvate were identified and quantified by thin layer chromatography at different time intervals from the extracellular and intracellular fluid. Our results show that in the metabolism of both comonomers more 14C-pyruvate was formed compared to 14C-l-malate for 14C-HEMA metabolisation during 0.5 up to 6h after 14C-HEMA exposure and for 14C-TEGDMA metabolisation >4h after 14C-TEGDMA exposure. Therefore the epoxide pathway with formation of the epoxy-intermediate 2,3-epoxymethacrylic acid is the main route of metabolisation of HEMA and TEGDMA.

Eluted substances from unpolymerized and polymerized dental restorative materials and their Nernst partition coefficient.

OBJECTIVES: Components released from resin-based dental materials are important factors in the assessment of the biocompatibility of these materials. The study was performed to investigate the elution of substances from unpolymerized and polymerized composites (Tetric=TET; Arabesk=ARA), ormoceres (Admira)=ADM; Definite=DEF) and the compomere (Hytac=HYT). METHODS: Specimens were polymerized and immersed in either water or methanol. Besides the unpolymerized specimens were dissolved in methanol. Eluted substances were detected by gas chromatography/mass spectroscopy. The Nernst partition coefficient (DC) of 64 substances, eluted from various resin-based dental materials was determined. RESULTS: Only in methanolic and aqueous eluates from unpolymerized and polymerized specimens of DEF and ADM, the comonomere 1,2/1,3-glycerol dimethacrylate was measured. Triethylene glycol dimethacrylate was eluted into the aqueous and methanolic phase from polymerized specimens from TET and ARA. 2-Hydroxyethyl methacrylate was eluted into the methanolic phase from polymerized specimen from TET and HYT. Residuals of monomer synthesis like triphenyl stibane were found in unpolymerized specimens of TET and ARA. Camphorquinone was eluted into the methanolic eluate from polymerized and unpolymerized specimens from all tested dental materials. Highest DC of 20.8 was found for 1/2-cyclohexene methacrylate. DC of urethane dimethacrylate and bisphenol-A-glycidyldimethacrylate varies from different manufacturers. SIGNIFICANCE: Impurities from manufacturing process were found in some resin-based materials. Various well-known substances causing allergic reactions were found in aqueous or methanolic elutes. Patients, dental and manufacturing personnel are exposed to these substances.

Autologous bone graft versus demineralized bone matrix in internal fixation of ununited long bones.

BACKGROUND: Non-unions are severe complications in orthopaedic trauma care and occur in 10% of all fractures. The golden standard for the treatment of ununited fractures includes open reduction and internal fixation (ORIF) as well as augmentation with autologous-bone-grafting. However, there is morbidity associated with the bone-graft donor site and some patients offer limited quantity or quality of autologous-bone graft material. Since allogene bone-grafts are introduced on the market, this comparative study aims to evaluate healing characteristics of ununited bones treated with ORIF combined with either iliac-crest-autologous-bone-grafting (ICABG) or demineralized-bone-matrix (DBM). METHODS AND RESULTS: From 2000 to 2006 out of sixty-two consecutive patients with non-unions presenting at our Level I Trauma Center, twenty patients had ununited diaphyseal fractures of long bones and were treated by ORIF combined either by ICABG- (n = 10) or DBM-augmentation (n = 10). At the time of index-operation, patients of the DBM-group had a higher level of comorbidity (ASA-value: p = 0.014). Mean duration of follow-up was 56.6 months (ICABG-group) and 41.2 months (DBM-group). All patients were clinically and radiographically assessed and adverse effects related to bone grafting were documented. The results showed that two non-unions augmented with ICABG failed osseous healing (20%) whereas all non-unions grafted by DBM showed successful consolidation during the first year after the index operation (p = 0.146). No early complications were documented in both groups but two patients of the ICABG-group suffered long-term problems at the donor site (20%) (p = 0.146). Pain intensity were comparable in both groups (p = 0.326). However, patients treated with DBM were more satisfied with the surgical procedure (p = 0.031). CONCLUSION: With the use of DBM, the costs for augmentation of the non-union-site are more expensive compared to ICABG (calculated difference: 160 euro/case). Nevertheless, this study demonstrated that the application of DBM compared to ICABG led to an advanced outcome in the treatment of non-unions and simultaneously to a decreased quantity of adverse effects. Therefore we conclude that DBM should be offered as an alternative to ICABG, in particular to patients with elevated comorbidity and those with limited availability or reduced quality of autologous-bone graft material.

Titanium alloy pins versus stainless steel pins in external fixation at the wrist: a randomized prospective study.

BACKGROUND: Pin-track complications remain the most troublesome disadvantages of external fixation. The purpose of this study was to compare pin-related complications and pain levels after the use of external fixation for the stabilization of distal radial fractures with pins composed of two different materials. METHODS: In a prospective trail 80 patients (320 pins) with unstable distal radial fracture were randomized for standard small AO-external fixator treatment with the use of identical pin geometry either composed of stainless-steel (Ss) (n = 40) or titanium alloy (Ti6Al4V) (n = 40). The patients were followed at biweekly intervals until the external fixators were removed (44 days after surgery). The patients were evaluated with regard to erythema, drainage, cellulitis, occurrence of pain at each pin-site, clinical or radiographic evidence of pin-loosening, the need for antibiotics, and the need for pin removal before fracture-healing due to infection. RESULTS: The complication rate was 21%, and age was found to be significantly associated with an increased risk of pin-loosening (p = 0.003). There were no significant differences among the two groups with regard to the prevalence of pin-site complications. However, the rate of premature removal of fixator because of severe pin-track infection (5% vs. 0%) and the rate of pin-loosening (10% vs. 5%) was higher in the Ss-pin group. Furthermore, pain values were significantly reduced in the Ti6Al4V-pin group. CONCLUSIONS: The use of Ti6Al4V-pin external fixator in distal radial fractures yields a trend of reduced pin-related complications and significantly reduced pain levels than does the Ss-pin fixator.

Imaging in early posttraumatic complex regional pain syndrome: a comparison of diagnostic methods.

OBJECTIVES: The complex regional pain syndrome type I (CRPS I) still is difficult to diagnose in posttraumatic patients. As CRPS I is a clinical diagnosis the characteristic symptoms have to be differentiated from normal posttraumatic states. Several diagnostic procedures are applied to facilitate an early diagnosis, although their value for diagnosing posttraumatic CRPS I is unclear. METHODS: One hundred fifty-eight consecutive patients with distal radial fracture were followed up for 16 weeks after trauma. To assess the diagnostic value of the commonly applied methods a detailed clinical examination was carried out 2, 8, and 16 weeks after trauma in conjunction with bilateral thermography, plain radiographs of the hand skeleton, three phase bone scans (TPBSs), and contrast-enhanced magnetic resonance imaging (MRI). All imaging procedures were assessed blinded. RESULTS: At the end of the observation period 18 patients (11%) were clinically identified as having CRPS I and 13 patients (8%) revealed an incomplete clinical picture which were defined as CRPS borderline cases. The sensitivity of all diagnostic procedures used was poor and decreased between the first and the last examinations (thermography: 45% to 29%; TPBS: 19% to 14%; MRI: 43% to 13%; bilateral radiographs: 36%). In contrast a high specificity was observed in the TPBS and MRI at the eighth and sixteenth-week examinations (TPBS: 96%, 100%; MRI: 78%, 98%) and for bilateral radiographs 8 weeks after trauma (94%). The thermography presented a fair specificity that improved from the second to the sixteenth week (50% to 89%). DISCUSSION: The poor sensitivity of all tested procedures combined with a reasonable specificity produced a low positive predictive value (17% to 60%) and a moderate negative predictive value (79% to 86%). These results suggest, that those procedures cannot be used as screening tests. Imaging methods are not able to reliably differentiate between normal posttraumatic changes and changes due to CRPS I. Clinical findings remain the gold standard for the diagnosis of CRPS I and the procedures described above may serve as additional tools to establish the diagnosis in doubtful cases.

Inflammatory mediators are altered in the acute phase of posttraumatic complex regional pain syndrome.

OBJECTIVES: Complex regional pain syndrome type 1 (CRPS 1) is a disorder that can affect an extremity after minor trauma or surgery. The pathogenesis of this syndrome is unclear. It has clinical signs of severe local inflammation as a result of an exaggerated inflammatory response, but neurogenic dysregulation also may contribute to it. METHODS: For further insights into the pathogenesis of CRPS 1, the authors investigated inflammatory and neurogenic mediators-C-reactive protein (CRP), interleukin-6 (IL-6), interleukin-8 (IL-8), soluble tumor necrosis factor receptor I/II (sTNFR I/II), sE-selectin, sL-selectin, sP-selectin, substance P, neuropeptide Y, and calcitonin gene-related peptide-in venous blood from both the healthy arm and the arm with acute CRPS I from 25 patients and from 30 healthy volunteers. RESULTS: Levels of IL-8 and sTNFR I/II were significantly elevated in patients, whereas all soluble forms of selectins were significantly suppressed. There was no significant difference in white blood cell count (WBC), CRP, and IL-6. Substance P was significantly elevated in patients. The other two neuropeptides were unchanged. None of the parameters studied showed any differences between the CRPS I-affected arm and the normal arm. CONCLUSIONS: Elevated IL-8 and sTNFR I/II levels indicate an association between CRPS I and an inflammatory process. Normal WBC, CRP, and IL-6 give evidence for localized inflammation. The hypothesis of neurogenic-induced inflammation mediated by neuropeptides is supported by elevated substance P levels.