Biomedical subjects

S Lindskog

Publications and source records attributed to S Lindskog.

At least 55 records · Page 3Linked to original sources

PubMed1996

Root surface etching at neutral pH promotes periodontal healing.

The purpose of the present investigation was to examine whether an etching agent operating at neutral pH (EDTA) can enhance healing compared to a low pH etching agent (citric acid) in an animal model. Maxillary molars and premolars, in total 32 teeth, in 4 monkeys were divided between test (EDTA or citric acid treatment) and matched control groups. Periodontal surgery on both palatal and buccal roots using the dehiscence model was performed with or without root surface etching. Healing results were evaluated histomorphometrically after 8 weeks. The statistically significant differences between EDTA treated surfaces (n=15) and control surfaces (n=11) were approximately 10% less failure (gingival recession and periodontal pocket), 10 to 15% more total histological attachment (long epithelial junction, connective tissue and reparative cementum), approximately 20% less long epithelial junction and approximately 20% more connective tissue in roots etched with EDTA. The statistically significant differences between citric-acid-treated surfaces (n=14) and control surfaces (n=11) were approximately 10% more connective tissue and 15% less long epithelial junction in the citric acid etched roots. Thus, etching with EDTA appeared to improve healing, avoiding the superficial necrotizing effect on exposed periodontal tissues by citric acid documented in previous studies. Although etching at present is not routinely applied in conventional periodontal therapy, future potential applications of etching at neutral pH may include exposure of the collagenous matrix of dentin for retention of biologically active substances, such as growth factors. Such treatment may be argued to produce a biocompatible surface more conducive to periodontal membrane cell colonization after removal of root-surface- associated smear without compromising the vitality of the surrounding periodontium.

Acid Etching, Dental↗

PubMed1996

Effects of glucagon-like peptide-I on glucose turnover in rats.

The influences of glucagon-like peptide-I-(7-36) amide (GLP-I; 15 mumol. kg-1.min-1) on glucose turnover were studied in freely moving Wistar rats. In fed rats, GLP-1 reduced plasma glucose (from 7.3 +/- 0.2 to 5.6 +/- 0.3 mmol/l; P = 0.017), increased plasma insulin (from 20 +/- 3 to 89 +/- 11 mU/l; P = 0.002), and reduced plasma glucagon (from 44 +/- 1 to 35 +/- 2 pg/ml; P = 0.009) and glucose appearance rate (Ra; from 3.9 +/- 0.2 to 1.7 +/- 0.7 micromol.min-1. 100 g-1 after 30 min; P = 0.049) without affecting glucose disappearance rate (Rd). The glucose clearance rate (MCR) was increased (P = 0.048). In 48-h-fasted rats, GLP-I reduced plasma glucose (from 5.0 +/- 0.2 to 4.4 +/- 0.3 mmol/l; P = 0.035) and increased plasma insulin (from 4 +/- 1 to 25 +/- 10 mU/l; P = 0.042) and plasma glucagon (from 43 +/- 3 to 61 +/- 7 pg/ml; P = 0.046). Ra and Rd were not significantly affected, although Ra was lower than Rd after 15-30 min (P = 0.005) and MCR was increased (P = 0.049). Thus GLP-I reduces Ra in fed rats and increases MCR in fed and fasted rats. The reduced Ra seems mediated by an increased insulin-to-glucagon ratio; the increased glucose clearance seems dependent on insulin and a peripheral effect of GLP-I.

Animals↗

PubMed1995

Effects of galanin on proinsulin mRNA and insulin biosynthesis in normal islets.

Whether the potent insulinostatic neuropeptide galanin also inhibits insulin production in normal islets is not known. Therefore, isolated mouse islets were incubated for 90 min in 2.8 or 16.7 mmol/l glucose and 3H-labelled leucine with addition of mouse galanin at 1, 10 or 100 nmol/l. Galanin potently inhibited glucose-stimulated insulin secretion at both 10 and 100 nmol/l (P < 0.05), and proinsulin biosynthesis was slightly inhibited at 100 nmol/l (P < 0.05). Also, mouse islets were incubated for 48 h at 5 or 16.7 mmol/l glucose with galanin at 1, 10 or 100 nmol/l and proinsulin mRNA was determined by hybridisation of extracted RNA with digoxigenin-labelled oligonucleotide insulin probe. Proinsulin mRNA levels were approximately doubled by glucose at 16.7 mmol/l compared at 5 mmol/l (P < 0.05). Galanin did not affect islet proinsulin mRNA levels. Therefore, galanin seems to mainly regulate insulin secretion without any important role in the regulation of insulin availability in normal islets.

Animals↗

PubMed1995

Catalytic and inhibitor-binding properties of some active-site mutants of human carbonic anhydrase I.

Three isozyme-specific residues in the active site of human carbonic anhydrase I, Val62, His67, and His200, have been changed by site-directed mutagenesis to their counterparts in human carbonic anhydrase II, Asn62, Asn67, and Thr200. A double mutant, containing Asn62 and Asn67, and a triple mutant, containing all three alterations, were also produced. The rates of CO2 hydration and ester hydrolysis catalyzed by these mutants, the inhibition of these enzymes by the anions, SCN-, and I-, and the binding of the sulfonamide inhibitors, dansylamide and MK-417 (a thienothiopyran-2-sulfonamide) have been measured. The results suggest that the effect of His200 in isozyme I is to prolong the lifetime of the enzyme-bicarbonate complex and to increase the pKa of the catalytic group, a zinc-coordinated water molecule. For isozyme I, Val62 and His67 might interfere with the function of a proton 'shuttle' group in the active site, thus maintaining the buffer specificity of a compulsory proton-transfer step. The single mutations have small effects on anion binding. Only the triple mutant has anion-binding properties resembling those of isozyme II. All mutants show altered sulfonamide-binding properties. In particular, the binding specificity is affected. While wild-type isozyme I binds dansylamide 50 times more strongly than MK-417, the triple mutant shows a reversed selectivity and binds MK-417 nearly 50 times more strongly than dansylamide.

Amino Acids↗

PubMed1995

Effects of GLP-1 and 2,5-anhydro-D-mannitol on insulin secretion and plasma glucose in mice.

The truncated glucagon-like peptide-1 (GLP-1(7-36)amide or GLP-1) stimulates insulin secretion, enhances glucose elimination and is of potential interest in diabetes treatment. We studied the hypoglycemic action of GLP-1 in normal mice when given alone or together with the fructose analogue, 2,5-anhydro-D-mannitol (2,5-AM), which inhibits glycogenolysis and gluconeogenesis. GLP-1 (32 nmol/kg iv) lowered plasma glucose levels after 25 min to 4.6 +/- 0.2 mmol/l compared with 7.3 +/- 0.4 mmol/l in controls (P < 0.001). Also 2,5-AM (0.5 mumol/kg iv) reduced plasma glucose levels, to 5.6 +/- 0.3 mmol/l (P < 0.01). When given together, the glucose lowering action of GLP-1 and 2,5-AM was additive, since the 25 min glucose level was 2.8 +/- 0.2 mmol/l. At 5 min after injection, GLP-1 had increased plasma insulin levels to 693 +/- 68 pmol/l compared with 342 +/- 42 pmol/l in controls (P < 0.01). 2,5-AM abolished this increase. Furthermore, GLP-1 (32 nmol/kg) did not affect the glycogen content, neither in the liver nor in the gastrocnemic muscle in samples taken at 30 min after injection. Moreover, in isolated islets incubated at 3.3 and 8.3 mmol/l glucose, 2,5-AM at 75 mmol/l inhibited glucose-stimulated insulin secretion (P < 0.05) showing that 2,5-AM inhibits insulin secretion both in vivo and in vitro. We conclude that GLP-1 may reduce plasma glucose levels also to levels below the basal levels under normal conditions, and that an insulin- and liver-independent action of the peptide contributes to its hypoglycemic action in normal animals.

Animals↗

PubMed1995

Long-time etching at low pH jeopardizes periodontal healing.

The purpose of the present investigation was to examine whether the immediate necrotizing effects of low pH etching agents also impair periodontal healing in the long-term perspective. It was concluded that long-time etching (3 min) at low pH of root surfaces surrounded by vital periodontal issues resulted in impaired periodontal healing. In contrast, short-time etching appeared to promote connective tissue formation by preventing epithelialization of the periodontal wound despite its low pH. However, clinical inferences should be drawn with caution from the present results, since healing results recorded at 8 weeks may not prove to be stable, especially for those cases sensitive to the immediate influence of marginal infection such as connective tissue attachments and epithelial junctions, unless optimal oral hygiene is maintained. Furthermore, the choice of acid may be of importance.

Acid Etching, Dental↗

PubMed1995

The influence of endodontic infection on progression of marginal bone loss in periodontitis.

The purpose of the present investigation was to determine magnitude and rate of proximal radiographic attachment loss in relation to endodontic infection in periodontally involved teeth. The investigation was conducted as a retrospective longitudinal study on a periodontitis-prone randomly selected referral population, including 175 single-rooted, root-filled teeth in 133 patients. An observation period of at least 3 years was required. Periapical conditions of the selected sample at baseline and re-examination were evaluated on radiographs, independently by 3 investigators. Each single-rooted, root-filled tooth of the sample was given a score according to the combined registrations. Radiographic attachment level was measured as the distance between the most coronal point of the alveolar bone and the apex at the mesial and distal sides of the tooth, and expressed as relative radiographic attachment level (RRAL) (radiographic attachment level at baseline/root length) at proximal sites for every tooth. Multiple regression analysis was used to study change in RRAL over time. Teeth in periodontitis-prone patients with progressing periapical pathology indicating a continuous root canal infection were found to lose comparatively more radiographic attachment than teeth with no signs of periapical pathology or teeth with an established periapical destruction which subsided during the observation period. An approximate 3-fold amplification of the rate of marginal proximal radiographic bone loss by endodontic infection in periodontitis-prone patients was found with an average 0.19 mm/year, while 0.06 mm/year was lost for teeth without endodontic infection or subsiding endodontic involvement.

Adult↗

PubMed1995

Endodontic pathogens in periodontal disease augmentation.

Periapical pathology indicating endodontic infection, when present in periodontitis-affected teeth, has recently been shown to be correlated to marginal periodontal breakdown. This has been associated with patency of dentinal tubules in the tooth cervix, an area normally devoid of cementum following periodontal therapy. These studies are, however hampered by that only circumstantial evidence such as presence of periapical destruction have been applied as criteria of endodontic infection. The aim of the present investigation was to assess the effects of endodontic pathogens on marginal periodontal wound healing on root surfaces devoid of cementum but surrounded by healthy periodontal membrane. Significant differences between infected and non-infected teeth were found with respect to pathological pocket and connective tissue: The experimental defects were covered by approximately 20% more pocket epithelium in infected teeth while defects in non-infected teeth showed approximately 10% more connective tissue coverage. It was concluded, that an intra-canal infection of endodontic pathogens stimulates epithelial downgrowth along denuded dentin surfaces with marginal communication. Extrapolated to the clinical situation, endodontic infections in periodontitis-prone patients may augment periodontitis propagation.

Animals↗

PubMed1995

Root surface texture and early cell and tissue colonization after different etching modalities.

The purpose of the present study was to compare the texture of dentin surfaces after etching with citric and phosphoric acids as well as EDTA with respect to mode of application and exposure time, and to assess possible effects on early cell and tissue colonization. It was concluded that EDTA operating at neutral pH was able to selectively remove mineral from a dentin surface, exposing a collagenous matrix. This was in contrast to etching with citric and phosphoric acids, both of which operate at a low pH. They both appeared to remove not only the mineral component but also the collagenous matrix. EDTA-treated dentin surfaces, compared to surfaces etched at low pH, appeared to be more inviting for cellular colonization and subsequent connective tissue formation. The reason for this may have been twofold: Dentin surfaces etched with an etching agent operating at neutral pH, as indicated above, retain more exposed collagen fibers than dentin surfaces etched at low pH. Furthermore, it can not be excluded that a low pH etching agent necrotized an area of the periodontal ligament in the immediate vicinity of the denuded dentin surfaces.

Acid Etching, Dental↗

PubMed1995

Enhanced formation of secondary dentin in the absence of nerve supply to feline teeth.

This investigation was designed to study the formation of secondary dentin in permanent teeth of young cats after denervation. In eight animals, cervical dentin was exposed bilaterally in the mandibular canines, 7-10 d after unilateral resection of the inferior alveolar nerve. The observation intervals were 30 d, 90 d and 180 d, after which histological examination of dentin was performed. In order to verify the loss and regeneration of pulpal innervation and an intact blood supply, blood flow responses to electrical stimulation of the tooth and to i.v. injections of substance P (SP) were recorded by laser Doppler flowmetry before and at 7-10 d after denervation, at the end of the experiments, and at predetermined intermediate intervals. SP-induced vasodilation was significantly enhanced at 1 wk and 30 d postoperatively and was normalized to control values at 90 and 180 d. Vasodilation in response to electrical tooth stimulation, which was absent after denervation, reappeared after 90 d in two of four cats. There was no irregular dentin formation under the exposed dentin at any time in denervated or control teeth. Formation of regular secondary dentin appeared to be enhanced on the denervated side at 30 d and 90 d postoperatively, whereas at 180 d there was no difference between sides. The results indicate that intradental nerves influence secondary dentin formation in feline permanent teeth.

Animals↗

PubMed1995

Spatial and temporal repair patterns of orthodontically induced surface resorption patches.

Root resorption appears to be an inevitable sequel to orthodontic tooth movement, occurring either apically or along surfaces in and around the pressure zones. However, there is uncertainty as to the location of initial cementum repair in resorbed areas as well as the time of onset of repair. The aim of the present study was to map the spatial and temporal patterns of cementum repair in orthodontically induced areas of surface resorption following maxillary expansion. Two spatial patterns of repair of orthodontic surface resorption patches were observed with cementum deposition proceeding either from the periphery or starting somewhere in the center of the resorbing areas, although the deposition starting centrally was argued to be artifactual. Furthermore, onset of reparative cementum mineralization appeared to follow within 2 wk after release of the force, involving initially only acellular cementum formation. However, the pattern of formation changed gradually, favouring a slow deposition of cellular cementum at more advanced stages of healing.

Bicuspid↗

PubMed1995

Endodontic pathogens: propagation of infection through patent dentinal tubules in traumatized monkey teeth.

Periapical pathology indicating endodontic infection, when present in marginal periodontitis-affected teeth, has recently been shown to be an aggravating factor in progression of marginal destruction. This has been associated with patency of dentinal tubules in the tooth cervix, an area normally devoid of cementum following periodontal therapy. These studies are, however hampered by that only circumstantial evidence such as presence of periapical destruction have been applied as criteria of endodontic infection. The purpose of the present investigation was to study to what extent a predefined selection of endodontic pathogens inoculated in the root canal can influence periodontal pathology and healing in areas of the root covered by or devoid of cementum, using root resorption as a histomorphometric marker. Exposed dentine surfaces, in the present study showed significantly larger areas of resorption in infected roots compared to non-infected roots, while cementum surfaces showed an almost identical distribution of tissue reactions regardless of root canal infection or not. It was concluded that endodontic pathogens or their products were not able to penetrate the cementum barrier. The significantly larger areas of resorption on exposed dentine surfaces in infected roots compared to non-infected roots indicated that endodontic pathogens or their products could spread through dentinal tubules to a root surface void of cementum. Extrapolated to the marginal situation this indicated that endodontic pathogens in the root canal might be able to aggravate marginal infection in areas of root devoid of cementum.

Animals↗

PubMed1995

Effects of orthodontic magnets on cutaneous epithelial thickness and tibial bone growth in rats.

The use of permanent magnets in orthodontic treatment has increased significantly over the past years, triggered by the introduction of rare earth magnetic alloys. Concerns about possible side effects have been expressed relating to their use in orthodontic treatment. In previous experimental studies evidence of a reduction in bone formation and epithelial turnover close to rare earth magnets has been presented. The aim of the present study was twofold: to confirm earlier results and to study whether the observed changes are reversible. One hind leg in each of 45 rats was fitted with aluminum rings with Co5Sm magnets, whereas the other hind leg was fitted with sham rings. After 8 weeks 25 rats were killed, and the rings in the remaining rats were removed. The latter group was killed after another 11 weeks. The epithelial and bone reactions were evaluated histomorphometrically. Previous results showing thinner epithelium and retarded rate of bone formation close to Co5Sm magnets were confirmed. These effects were also shown to be largely reversible. It was concluded on the basis of this and the magnitude of the effects that any local side effects from orthodontic rare earth magnets appear negligible when extrapolated to the clinical situation.

Animals↗

PubMed1995

Periodontal tissue-vitality after different etching modalities.

The purpose of the present study was to investigate possible immediate necrotizing effects on periodontal tissues of etching agents operating either at low or neutral pH. Phosphoric and citric acids, both of which operate at low pH, exerted immediate (within 20 s) necrotizing effects on both mucosal flaps and periodontal tissues. The penetration depth increased with time up to 1/4 of the circumference of the root after 3 min. This was in sharp contrast to EDTA which operates at neutral pH. EDTA failed to induce any detectable necrosis during the experimental periods. Whether or not the immediate necrotizing effects of low pH etching agents also impair periodontal healing in the long-term perspective, needs to be evaluated with controlled experimental studies in vivo as well as clinically in order to determine whether etching at neutral pH is preferable.

Acid Etching, Dental↗

PubMed1995

Effects of static magnetic fields on human periodontal fibroblasts in vitro.

In orthodontic treatment, the use of mechanical forces generated by magnetic fields have increased significantly over the past years, triggered by the introduction of rare earth permanent magnetic alloys. Rare earth magnets, initially made from cobalt-samarium alloy and later from neodymium-iron-boron alloy generate high mechanical forces in relation to their small size. Relating to their use in orthodontic treatment, queries about possible side effects have been expressed. This study was undertaken in order to determine if cell growth and attachment in vitro is affected over time in a static magnetic field of a magnitude comparable to that used clinically. Significantly and progressively impaired attachment and growth over a 5 week period was observed when human periodontal fibroblasts were cultured in a static magnetic field. These results indicate that a static magnetic field itself is capable of influencing vital cell functions, although they do not exclude the possibility of corrosion products from the magnets contributing to previously observed cytotoxic in vitro and biological in vivo effects.

Alloys↗

PubMed1994

Modification of a metal ligand in carbonic anhydrase: crystal structure of His94-->Glu human isozyme II.

One of the zinc ligands in human carbonic anhydrase II, His94, has been replaced with glutamic acid by site-directed mutagenesis. The mutation leads to a less stable zinc binding site and to significant non-local perturbations of the protein structure. The crystals are composed of a mixture of holo- and apoenzyme, and the side chain of Glu94 has two conformations. In the holoenzyme, Glu94 coordinates to the metal ion and is hydrogen bonded to Gln92. In the apo form, Glu94 is hydrogen bonded to Asn67. The mutation has resulted in a 500-fold decrease of the catalyzed rate of CO2 hydration (kcat/Km).

Apoenzymes↗

PubMed1994

Extraoral root lengthening with titanium screws.

The aim of the present study was to experimentally evaluate marginal and periapical healing in extracted and subsequently replanted teeth following extraoral cementing of apically exposed titanium root screws in the root canal. In 5 out of 6 replanted teeth, the periodontal tissues had healed with a normal periodontal membrane or healed surface resorptions indicating that only minor trauma had been inflicted during the extraoral procedure. In 3 out of 6 teeth, total or partial osseointegration of the titanium screws was seen, while a connective tissue capsule had formed around the remaining 3 screws. It was concluded that both of the healing results described in the present study, osseointegration and connective capsule formation, may be regarded as acceptable as long as inflammation is prevented, although it remains to be shown which one represents the end-point.

Alveolar Process↗

PubMed1994

Proximal restorations and periodontal status.

The purpose of the present investigation was to evaluate the influence of overhanging marginal restorations on periodontal status and whether any such influence is modified by the patient's oral hygiene level and degree of radiographic attachment loss. The investigation was conducted as a retrospective study on a consecutive referral population. Periodontal pockets at proximal sites with marginal overhangs were significantly deeper (0.42 mm) compared to sites with metal restorations without overhangs. This difference was larger (0.62 mm) for sites with radiographic attachment loss < or = 6 mm, while no significant difference was found for sites with radiographic attachment loss > 6 mm. In patients with a mean radiographic attachment loss < or = 5 mm, an overhanging restoration margin was associated with a significantly increased loss of radiographic attachment (0.66 mm). It was concluded that the influence of a marginal overhang on pocket depth and radiographic attachment decreases with increasing loss of periodontal attachment in periodontitis-prone patients. The effect on pocket depth of a marginal overhang may act synergistically, potentiating the effect of poor oral hygiene.

Adult↗