Recolonization of mutans streptococci after application of chlorhexidine gel

Streptococcus mutans is specifically suppressed by intensive treatment with chlorhexidine gel, but the time for recolonization and the effect on other oral bacteria are not totally clear. In this study, recolonization of mutans streptococci was evaluated in nine healthy adult volunteers, who were highly colonized with this microorganism. Stimulated saliva was collected before (baseline) and at 1, 7, 14, 21 and 28 days after application of 1% chlorhexidine gel on volunteers’ teeth for two consecutive days. On each day, the gel was applied using disposable trays for 3 x 5 min with intervals of 5 min between each application. Saliva was plated on blood agar to determine total microorganisms (TM); on mitis salivarius agar to determine total streptococci (TS) and on mitis salivarius agar plus bacitracin to determine mutans streptococci (MS). Chlorhexidine was capable of reducing the counts of MS and the proportion of MS with regard to total microorganisms (%MS/ TM) (p0.05) after 14 days for MS and 21 days for %MS/TM. The counts of TM and TS and the proportion of MS to total streptococci did not differ statistically from baseline (p>0.05) after chlorhexidine treatment. The results suggest that the effect of chlorhexidine gel treatment on suppression of mutans streptococci is limited to less than a month in highly colonized individuals.Streptococcus mutans é especificamente suprimido pelo tratamento intensivo com clorexidina em gel, mas o tempo de recolonização e o efeito em outras bactérias orais não está totalmente claro. Nesse estudo, a recolonização de estreptococos do grupo mutans foi avaliado em nove voluntários adultos saudáveis, os quais eram altamente colonizados por esse microrganismo. Saliva estimulada foi coletada antes (baseline) e 1, 7, 14, 21 e 28 dias após a aplicação de clorexidina em gel a 1% nos dentes dos voluntários por dois dias consecutivos. Em cada dia, o gel foi aplicado utilizando moldeiras descartáveis por 3 x 5 min com intervalos de 5 min entre cada aplicação. A saliva foi inoculada em ágar sangue para determinação dos microrganismos totais (MT); em mitis salivarius ágar para determinação dos estreptococos totais (ET) e em meio mitis salivarius com bacitracina para determinar a contagem de estreptococos do grupo mutans (EGM). O tratamento com clorexidina foi capaz de reduzir as contagens de EGM e a proporção de EGM em relação aos microrganismos totais (%EGM/MT) (p0,05) após 14 dias para EGM e 21 dias para %EGM/MT. As contagens de MT e ET e a proporção de EGM em relação a estreptococos totais não difereriram estatisticamente do baseline (p>0,05) após o tratamento com clorexidina. Os resultados sugerem que o efeito do tratamento com clorexidina em gel na supressão de estreptococos do grupo mutans é limitado a menos de um mês em indivíduos altamente colonizados

Comparison of the effects of lactated Ringer solution with and without hydroxyethyl starch fluid resuscitation on gut edema during severe splanchnic ischemia

The type of fluid used during resuscitation may have an important impact on tissue edema. We evaluated the impact of two different regimens of fluid resuscitation on hemodynamics and on lung and intestinal edema during splanchnic hypoperfusion in rabbits. The study included 16 female New Zealand rabbits (2.9 to 3.3 kg body weight, aged 8 to 12 months) with splanchnic ischemia induced by ligation of the superior mesenteric artery. The animals were randomized into two experimental groups: group I (N = 9) received 12 mL·kg-1·h-1 lactated Ringer solution and 20 mL/kg 6% hydroxyethyl starch solution; group II (N = 7) received 36 mL·kg-1·h-1 lactated Ringer solution and 20 mL/kg 0.9% saline. A segment from the ileum was isolated to be perfused. A tonometric catheter was placed in a second gut segment. Superior mesenteric artery (Q SMA) and aortic (Qaorta) flows were measured using ultrasonic flow probes. After 4 h of fluid resuscitation, tissue specimens were immediately removed for estimations of gut and lung edema. There were no differences in global and regional perfusion variables, lung wet-to-dry weight ratios and oxygenation indices between groups. Gut wet-to-dry weight ratio was significantly lower in the crystalloid/colloid-treated group (4.9 ± 1.5) than in the crystalloid-treated group (7.3 ± 2.4) (P < 0.05). In this model of intestinal ischemia, fluid resuscitation with crystalloids caused more gut edema than a combination of crystalloids and colloids

Hoja de predicción: Número 143 - 2006 Julio 28

Streptococcus mutans is specifically suppressed by intensive treatment with chlorhexidine gel, but the time for recolonization and the effect on other oral bacteria are not totally clear. In this study, recolonization of mutans streptococci was evaluated in nine healthy adult volunteers, who were highly colonized with this microorganism. Stimulated saliva was collected before (baseline) and at 1, 7, 14, 21 and 28 days after application of 1% chlorhexidine gel on volunteers’ teeth for two consecutive days. On each day, the gel was applied using disposable trays for 3 x 5 min with intervals of 5 min between each application. Saliva was plated on blood agar to determine total microorganisms (TM); on mitis salivarius agar to determine total streptococci (TS) and on mitis salivarius agar plus bacitracin to determine mutans streptococci (MS). Chlorhexidine was capable of reducing the counts of MS and the proportion of MS with regard to total microorganisms (%MS/ TM) (p<0.05), but these values did not differ statistically from baseline (p>0.05) after 14 days for MS and 21 days for %MS/TM. The counts of TM and TS and the proportion of MS to total streptococci did not differ statistically from baseline (p>0.05) after chlorhexidine treatment. The results suggest that the effect of chlorhexidine gel treatment on suppression of mutans streptococci is limited to less than a month in highly colonized individuals.Streptococcus mutans é especificamente suprimido pelo tratamento intensivo com clorexidina em gel, mas o tempo de recolonização e o efeito em outras bactérias orais não está totalmente claro. Nesse estudo, a recolonização de estreptococos do grupo mutans foi avaliado em nove voluntários adultos saudáveis, os quais eram altamente colonizados por esse microrganismo. Saliva estimulada foi coletada antes (baseline) e 1, 7, 14, 21 e 28 dias após a aplicação de clorexidina em gel a 1% nos dentes dos voluntários por dois dias consecutivos. Em cada dia, o gel foi aplicado utilizando moldeiras descartáveis por 3 x 5 min com intervalos de 5 min entre cada aplicação. A saliva foi inoculada em ágar sangue para determinação dos microrganismos totais (MT); em mitis salivarius ágar para determinação dos estreptococos totais (ET) e em meio mitis salivarius com bacitracina para determinar a contagem de estreptococos do grupo mutans (EGM). O tratamento com clorexidina foi capaz de reduzir as contagens de EGM e a proporção de EGM em relação aos microrganismos totais (%EGM/MT) (p<0,05), mas esses valores não diferiram estatisticamente do baseline (p>0,05) após 14 dias para EGM e 21 dias para %EGM/MT. As contagens de MT e ET e a proporção de EGM em relação a estreptococos totais não difereriram estatisticamente do baseline (p>0,05) após o tratamento com clorexidina. Os resultados sugerem que o efeito do tratamento com clorexidina em gel na supressão de estreptococos do grupo mutans é limitado a menos de um mês em indivíduos altamente colonizados

Low-fluoride toothpaste and deciduous enamel demineralization under biofilm accumulation and sucrose exposure

FAPESP – FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOBecause low-fluoride toothpaste (500 p.p.m. F) has not clearly been shown to be effective for controlling caries in caries-active children, this experimental in situ study was conducted to evaluate whether its effect, when compared with a conventional toothpaste (1,000-1,500 p.p.m. F), would depend on the cariogenic challenge. During four phases of 14 d each, 14 volunteers used 500 or 1,100 p.p.m. F toothpaste and wore palatal appliances containing deciduous enamel slabs, on which biofilm was accumulated and exposed to 20% sucrose solution at frequencies increasing from two to eight times per day. The F concentration was determined in the biofilm formed, and enamel demineralization was assessed by surface hardness loss (% SHL) and integrated area of hardness x lesion depth (DeltaS). The F uptake by enamel was also determined. Fluoride in biofilm fluid and solids was statistically higher when conventional F toothpaste was used. The toothpastes did not differ statistically in terms of % SHL, DeltaS, and F in enamel, but only the conventional F toothpaste significantly reduced caries-lesion progression according to the frequency of sucrose exposure. The findings suggest that the high-F availability in biofilm, resulting from the use of conventional toothpaste compared with low-F toothpaste, may be important for reducing caries-lesion progression in conjunction with a high frequency of sucrose exposure.Because low-fluoride toothpaste (500 p.p.m. F) has not clearly been shown to be effective for controlling caries in caries-active children, this experimental in situ study was conducted to evaluate whether its effect, when compared with a conventional toothpaste (1,000-1,500 p.p.m. F), would depend on the cariogenic challenge. During four phases of 14 d each, 14 volunteers used 500 or 1,100 p.p.m. F toothpaste and wore palatal appliances containing deciduous enamel slabs, on which biofilm was accumulated and exposed to 20% sucrose solution at frequencies increasing from two to eight times per day. The F concentration was determined in the biofilm formed, and enamel demineralization was assessed by surface hardness loss (% SHL) and integrated area of hardness x lesion depth (DeltaS). The F uptake by enamel was also determined. Fluoride in biofilm fluid and solids was statistically higher when conventional F toothpaste was used. The toothpastes did not differ statistically in terms of % SHL, DeltaS, and F in enamel, but only the conventional F toothpaste significantly reduced caries-lesion progression according to the frequency of sucrose exposure. The findings suggest that the high-F availability in biofilm, resulting from the use of conventional toothpaste compared with low-F toothpaste, may be important for reducing caries-lesion progression in conjunction with a high frequency of sucrose exposure1184370375FAPESP – FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP – FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO2007/05994-

Biomechanical Evaluation Of Subcrestal Dental Implants With Different Bone Anchorages

This study evaluated the biomechanical influence of apical bone anchorage on a single subcrestal dental implant using three-dimensional finite element analysis (FEA). Four different bone anchorage designs were simulated on a posterior maxillary segment using one implant with platform switching and internal Morse taper connection as follows: 2 mm subcrestal placement with (SW) or without (SO) the implant apex engaged into the cortical bone or position at bone level with anchorage only in the crestal cortical (BO) bone or with bicortical fixation (BW). Each implant received a premolar crown, and all models were loaded with 200 N to simulate centric and eccentric occlusion. The peak tensile and compressive stress and strain were calculated at the crestal cortical, trabecular, and apical cortical bone. The vertical and horizontal implant displacements were measured at the platform level. FEA indicated that subcrestal placement (SW and SO) created lower stress and strain in the crestal cortical bone compared with crestal placement (BO and BW models). The SW model exhibited lesser vertical and horizontal implant micromovement compared with the SO and BO models under eccentric loading; however, stress and strain were higher in the apical cortical bone. The BW model exhibited the lowest implant displacement. These results indicate that subcrestal placement decreases the stress in the crestal cortical bone of dental implants, regardless of apical anchorage however, apical cortical anchorage can be effective in limiting implant displacement. Further studies are required to evaluate the effects of possible remodeling around the apex on the success of subcrestal implants.28117Javed, F., Romanos, G.E., The role of primary stability for successful immediate loading of dental implants (2010) A literature review. J Dent., 38 (8), pp. 612-620Szmukler-Moncler, S., Salama, H., Reingewirtz, Y., Dubruille, J.H., Timing of loading and effect of micromotion on bone-dental implant interface: review of experimental literature (1998) J Biomed Mater Res., 43 (2), pp. 192-203. , SummerDevlin, H., Horner, K., Ledgerton, D., A comparison of maxillary and mandibular bone mineral densities (1998) J Prosthet Dent., 79 (3), pp. 323-327. , MarTran, B.L., Chen, S.T., Caiafa, A., Davies, H.M., Darby, I.B., Transmucosal healing around peri-implant defects: crestal and subcrestal implant placement in dogs (2010) Clin Oral Implants Res, 21 (8), pp. 794-803Hammerle, C.H., Bragger, U., Burgin, W., Lang, N.P., The effect of subcrestal placement of the polished surface of ITI implants on marginal soft and hard tissues (1996) Clin Oral Implants Res., 7 (2), pp. 111-119. , JunDonovan, R., Fetner, A., Koutouzis, T., Lundgren, T., Crestal bone changes around implants with reduced abutment diameter placed non-submerged and at subcrestal positions: a 1-year radiographic evaluation (2010) J Periodontol, 81 (3), pp. 428-434Barros, R.R., Novaes Jr, A.B., Muglia, V.A., Lezzi, G., Piattelli, A., Influence of interimplant distances and placement depth on peri-implant bone remodeling of adjacent and immediately loaded morse cone connection implants: a histomorphometric study in dogs (2010) Clin Oral Implants Res., 21 (4), pp. 371-378. , Apr 1Huang, B., Meng, H., Piao, M., Xu, L., Zhang, L., Zhu, W., Influence of placement depth on bone remodeling around tapered internal connection implant: a clinical and radiographic study in dogs (2012) J Periodontol, 83 (9), pp. 1164-1171Canullo, L., Pace, F., Coelho, P., Sciubba, E., Vozza, I., The influence of platform switching on the biomechanical aspects of the implant-abutment system.A three dimensional finite element study. (2011) Med Oral Patol Oral Cir Bucal., 16 (6), pp. e852-e856Huang, C.C., Lan, T.H., Lee, H.E., Wang, C.H., The biomechanical analysis of relative position between implant and alveolar bone: finite element method (2011) J Periodontol, 82 (3), pp. 489-496Chou, H.Y., Muftu, S., Bozkaya, D., Combined effects of implant insertion depth and alveolar bone quality on periimplant bone strain induced by a wide-diameter, short implant and a narrowdiameter, long implant (2010) J Prosthet Dent, 104 (5), pp. 293-300Baggi, L., Cappelloni, I., Di Girolamo, M., Maceri, F., Vairo, G., The influence of implant diameter and length on stress distribution of osseointegrated implants related to crestal bone geometry: a three-dimensional finite element analysis. (2008) J Prosthet Dent., 100 (6), pp. 422-431Ahn, S.J., Leesungbok, R., Lee, S.W., Heo, Y.K., Kang, K.L., Differences in implant stability associated with various methods of preparation of the implant bed: an in vitro study (2012) J Prosthet Dent, 107 (6), pp. 366-372Katranji, A., Misch, K., Wang, H.L., Cortical bone thickness in dentate and edentulous human cadavers (2007) J Periodontol, 78 (5), pp. 874-878Ausiello, P., Apicella, A., Davidson, C.L., Effect of adhesive layer properties on stress distribution in composite restorations--a [3D] finite element analysis (2002) Dent Mater, 18 (4), pp. 295-303Sevimay, M., Turhan, F., Kilicarslan, M.A., Eskitascioglu, G., Three-dimensional finite element analysis of the effect of different bone quality on stress distribution in an implantsupported crown (2005) J Prosthet Dent, 93 (3), pp. 227-234Huang, H.L., Hsu, J.T., Fuh, L.J., Lin, D.J., Chen, M.Y., Biomechanical simulation of various surface roughnesses and geometric designs on an immediately loaded dental implant (2010) Comput Biol Med, 40 (5), pp. 525-532Hattori, Y., Satoh, C., Kunieda, T., Endoh, R., Hisamatsu, H., Watanabe, M., Bite forces and their resultants during forceful intercuspal clenching in humans (2009) J Biomech, 42 (10), pp. 1533-1538Clelland, N.L., Lee, J.K., Bimbenet, O.C., Gilat, A., Use of an axisymmetric finite element method to compare maxillary bone variables for a loaded implant (1993) J Prosthodont, 2 (3), pp. 183-189Frost, H.M., A 2003 update of bone physiology and Wolff's law for clinicians (2004) Angle Orthod, 74 (1), pp. 3-15Natali, A.N., Hart, R.T., Pavan, P.G., Knets, I., Mechanics of bone tissue (2003), pp. 1-19. , Natali AN, editor. Dental biomechanics. London: Taylor & Francis;Lee, E.H., Ryu, S.M., Kim, J.Y., Cho, B.O., Lee, Y.C., Park, Y.J., Effects of installation depth on survival of an hydroxyapatite-coated bicon implant for single-tooth restoration (2010) J Oral Maxillofac Surg, 68 (6), pp. 1345-1352Weinberg, L.A., Reduction of implant loading using a modified centric occlusal anatomy (1998) Int J Prosthodont, 11 (1), pp. 55-69. , Jan-FebCarter, D.R., Caler, W.E., Spengler, D.M., Frankel, V.H., Fatigue behavior of adult cortical bone: the influence of mean strain and strain range (1981) Acta Orthop Scand, 52 (5), pp. 481-490Sato, M., Ochi, T., Nakase, T., Hirota, S., Kitamura, Y., Nomura, S., Mechanical tension-stress induces expression of bone morphogenetic protein (BMP)-2 and BMP-4, but not BMP-6, BMP-7, and GDF-5 mRNA, during distraction osteogenesis (1999) J Bone Miner Res, 14 (7), pp. 1084-1095Carter, D.R., Mechanical loading histories and cortical bone remodeling (1984) Calcif Tissue Int, 36, pp. S19-24Frost, H.M., The role of changes in mechanical usage set points in the pathogenesis of osteoporosis (1992) J Bone Miner Res, 7 (3), pp. 253-261. , MarMorris, H.F., Ochi, S., Crum, P., Orenstein, I.H., Winkler, S., AICRG, Part I: a 6-year multicentered, multidisciplinary clinical study of a new and innovative implant design (2004) J Oral Implantol, 30 (3), pp. 125-133. , JunChang, P.K., Chen, Y.C., Huang, C.C., Lu, W.H., Chen, Y.C., Tsai, H.H., Distribution of micromotion in implants and alveolar bone with different thread profiles in immediate loading: a finite element study (2012) Int J Oral Maxillofac Implants, 27 (6), pp. e96-101. , Nov-DecEngelke, W., Decco, O.A., Rau, M.J., Massoni, M.C., Schwarzwaller, W., In vitro evaluation of horizontal implant micromovement in bone specimen with contact endoscopy (2004) Implant Dent, 13 (1), pp. 88-94. , Ma