Histological findings in soft tissues around temporomandibular joint prostheses after up to eight years of function.

Early temporomandibular joint (TMJ) prostheses articulated on material with poor wear resistance. Wear debris was deposited in the surrounding tissues, causing severe foreign body cell reactions. Recent TMJ prostheses use modern orthopaedic materials, such as ultra high molecular weight polyethylene (UHMWPE) for the fossa component, and cobalt-chromium, or cobalt-chromium-molybdenum for the condylar head. These designs are reliable in long-term follow-up studies. The authors report histological findings in soft tissue samples obtained from around two types of TMJ prostheses after up to 8 years of function. The devices were four Biomet (Biomet Microfixation, Jacksonville, FL, USA), and two TMJ Concepts (TMJ Concepts, Ventura, CA, USA). All joint capsule samples demonstrated dense, fibrous connective tissue with no inflammatory cells or foreign body reactions. The joint disc tissues showed even denser fibrous connective tissue, free from inflammatory reactions. Some samples from the junction between capsule and disk demonstrated synovial-like tissue. The observations reported in this paper indicate that modern TMJ prostheses with Cr-Co-Mb or Cr-Co articular condyles articulating on UHMWPE fossa components appear to function without foreign body reactions in he surrounding tissues.

Phenotypic expression of a family with multiple endocrine neoplasia type 2A due to a RET mutation at codon 618.

BACKGROUND: Multiple endocrine neoplasia type 2A (MEN2A) is caused by missense mutations in the RET proto-oncogene on chromosome 10. This paper reports the phenotypic expression of a family with MEN2A, in which serine substitutes for cysteine at codon 618 in exon 10 of the RET gene. It was first claimed that medullary thyroid cancer (MTC) with this rare mutation led to mild disease; this has recently been updated to intermediate-high risk, based on stratified genetic information. METHODS: The family was mapped over six generations. In 1971 family members were invited to join a screening programme. Genetic testing was started in 1994. RESULTS: Twenty-two individuals with MTC were identified, 16 by the screening programme. One screened patient had a phaeochromocytoma and four had hyperparathyroidism. At surgery for MTC 12 patients had local tumour metastases and two young patients also had liver metastases. No screened patient died from MTC during a mean observation time of 19 years. Six other family members were diagnosed with MTC by signs and symptoms, five of whom died from MTC. CONCLUSION: Because of the great interindividual differences in tumour aggressiveness within the family it is impossible to predict whether an individual gene carrier will have an aggressive MTC or not. This unpredictability is an additional argument, besides those obtained in stratified genetic studies, for operating on gene carriers at young age.

Clinical, histopathologic, and genetic investigation in two large families with dentinogenesis imperfecta type II.

Dentinogenesis imperfecta (DI) type II, an inherited disorder affecting dentin, has been linked to mutations in the dentin sialophosphoprotein ( DSPP) gene on chromosome 4q21. The gene product is cleaved into two dentin-specific matrix proteins, dentin sialoprotein (DSP) and dentin phosphoprotein. The aim of this investigation was to study genotypes and phenotypes in two affected families with special reference to clinical, radiographic, and histopathologic manifestations. Seven affected members of Family A and five of Family B were documented clinically and radiographically; 14 and 10 teeth, respectively, were available for histopathologic investigation and prepared for ground sections, which were assessed semiquantitatively for dysplastic manifestations in the dentin according to the scoring system, dysplastic dentin score (DDS). Venous blood samples were collected from six affected and ten unaffected members of Family A, and from eight affected and six unaffected members of Family B. Genomic DNA was extracted and used for sequence analyses. The two families presented with different missense mutations. An Arg68Trp missense mutation in the DSP part of the gene was revealed in all six analyzed affected individuals in Family A. This mutation was not present in any of the ten healthy members. In Family B, an Ala15Val missense mutation involving the last residue of the signal peptide was found in all eight affected but in none of the six healthy members. The clinical and radiographic disturbances and DDS were more severe in Family B. The data indicate the presence of a genotype-phenotype correlation in DI type II.

[Phenotypic expression of a mutation in MEN 2A documented in a family in the western part of Sweden]. / Fenotypiskt uttryck av mutation vid MEN 2A kartlagd i västsvensk familj.

A missense mutation at codon 618 of the RET proto-oncogene is a rather unusual cause of multiple endocrine neoplasia 2A. We report the phenotypic expression of this specific RET mutation in a large Swedish family. The family was mapped back to the 18th century. Since 1971 the family has been included in a biochemical screening program, and since 1994 has undergone genetic screening. Twenty-seven individuals were found to have medullary thyroid carcinoma (MTC). Eighteen were detected by screening. The incidence of pheochromocytoma (4%) and hyperparathyroidism (7%) was low. Five individuals died of MTC, but of these none had been included in the screening program. One patient underwent prophylactic thyroidectomy after positive genetic screening. MTC tumor aggressivity differed markedly between gene carriers. The screening program shows that the clinical aggressivity of MTC can be mitigated by early and adequate surgical intervention.

Cloning, expression and some properties of alpha-carbonic anhydrase from Helicobacter pylori.

The alpha-carbonic anhydrase gene from Helicobacter pylori strain 26695 has been cloned and sequenced. The full-length protein appears to be toxic to Escherichia coli, so we prepared a modified form of the gene lacking a part that presumably encodes a cleavable signal peptide. This truncated gene could be expressed in E. coli yielding an active enzyme comprising 229 amino acid residues. The amino acid sequence shows 36% identity with that of the enzyme from Neisseria gonorrhoeae and 28% with that of human carbonic anhydrase II. The H. pylori enzyme was purified by sulfonamide affinity chromatography and its circular dichroism spectrum and denaturation profile in guanidine hydrochloride have been measured. Kinetic parameters for CO2 hydration catalyzed by the H. pylori enzyme at pH 8.9 and 25 degrees C are kcat=2.4x10(5) s(-1), KM=17 mM and kcat/KM=1.4x10(7) M(-1) x s(-1). The pH dependence of kcat/KM fits with a simple titration curve with pK(a)=7.5. Thiocyanate yields an uncompetitive inhibition pattern at pH 9 indicating that the maximal rate of CO2 hydration is limited by proton transfer between a zinc-bound water molecule and the reaction medium in analogy to other forms of the enzyme. The 4-nitrophenyl acetate hydrolase activity of the H. pylori enzyme is quite low with an apparent catalytic second-order rate constant, k(enz), of 24 M(-1) x s(-1) at pH 8.8 and 25 degrees C. However, with 2-nitrophenyl acetate as substrate a k(enz) value of 665 M(-1) x s(-1) was obtained under similar conditions.

Characterization of carbonic anhydrase from Neisseria gonorrhoeae.

We have investigated the steady state and equilibrium kinetic properties of carbonic anhydrase from Neisseria gonorrhoeae (NGCA). Qualitatively, the enzyme shows the same kinetic behaviour as the well studied human carbonic anhydrase II (HCA II). This is reflected in the similar pH dependencies of the kinetic parameters for CO(2) hydration and the similar behaviour of the kinetics of (18)O exchange between CO(2) and water at chemical equilibrium. The pH profile of the turnover number, k(cat), can be described as a titration curve with an exceptionally high maximal value of 1.7 x 10(6) s(-1) at alkaline pH and a pK(a) of 7.2. At pH 9, k(cat) is buffer dependent in a saturable manner, suggesting a ping-pong mechanism with buffer as the second substrate. The ratio k(cat)/K(m) is dependent on two ionizations with pK(a) values of 6.4 and 8.2. However, an (18)O-exchange assay identified only one ionizable group in the pH profile of k(cat)/K(m) with an apparent pK(a) of 6.5. The results of a kinetic analysis of a His66-->Ala variant of the bacterial enzyme suggest that His66 in NGCA has the same function as a proton shuttle as His64 in HCA II. The kinetic defect in the mutant can partially be overcome by certain buffers, such as imidazole and 1,2-dimethylimidazole. The bacterial enzyme shows similar K(i) values for the inhibitors NCO(-), SCN(-) and N(3)(-) as HCA II, while CN(-) and the sulfonamide ethoxzolamide are considerably weaker inhibitors of the bacterial enzyme than of HCA II. The absorption spectra of the adducts of Co(II)-substituted NGCA with acetazolamide, NCO(-), SCN(-), CN(-) and N(3)(-) resemble the corresponding spectra obtained with human Co(II)-isozymes I and II. Measurements of guanidine hydrochloride (GdnHCl)-induced denaturation reveal a sensitivity of the CO(2) hydration activity to the reducing agent tris(2-carboxyethyl)phosphine (TCEP). However, the A(292)/A(260) ratio was not affected by the presence of TCEP, and a structural transition at 2.8--2.9 M GdnHCl was observed.

A clinical histologic study of bovine hydroxyapatite in combination with autogenous bone and fibrin glue for maxillary sinus floor augmentation. Results after 6 to 8 months of healing.

Biopsies were taken from 16 out of 20 consecutive referral patients 6 to 8 months after maxillary sinus floor augmentation with a mixture of bovine hydroxyapatite (BH), autogenous bone particles and fibrin glue. Four days prior to biopsy retrieval the patients were given a single dose of tetracycline to label bone forming sites. Fluorescence microscopy of 100 microm thick sections revealed active bone formation in conjunction with the BH particles in 14 of 15 specimens analysed. Light microscopy and morphometry of ground sections from 16 patients showed various amounts of mineralised bone tissue in all except one specimen. In the latter case, the BH particles were encapsulated by a dense fibrous connective tissue. Sections from the augmented areas were occupied by non-mineralized tissue (54.1+12.6%), lamellar bone (21.2+24.5%), BH particles (14.5+10.3%) and woven bone (10.2+13.4%). The non-mineralized tissue seen in bone forming areas consisted of a loose connective tissue, rich of vessels and cells, and in the periphery of a more dense fibrous connective tissue. Woven bone with large and scattered osteocyte lacunae was bridging between the BH particles and the lamellar trabecular bone. There were no signs of resorption of the BH particles. The lamellar bone appeared to have originated from the recipient site and was seldom in contact with the BH particles. It is concluded that the tested implant material has bone conducting properties. The bone associated with the BH particles after 6 to 8 months of healing was mainly woven.

Enhancement of catalytic efficiency by the combination of site-specific mutations in a carbonic anhydrase-related protein.

A single mutation, involving the replacement of an arginine residue with histidine to reconstruct a zinc-binding site, suffices to change a catalytically inactive murine carbonic anhydrase-related protein (CARP) to an active carbonic anhydrase with a CO2-hydration turnover number of 1.2 x 104 s-1. Further mutations, leading to a more 'carbonic anhydrase-like' active-site cavity, results in increased activity. A quintuple mutant having His94, Gln92, Val121, Val143, and Thr200 (human carbonic anhydrase I numbering system) shows kcat = 4 x 104 s-1 and kcat/Km = 2 x 107 M-1.s-1, greatly exceeding the corresponding values for carbonic anhydrase isozyme III and approaching those characterizing carbonic anhydrase I. In addition, a buffer change from 50 mM Taps/NaOH to 50 mM 1, 2-dimethylimidazole/H2SO4 at pH 9 results in a 14-fold increase in kcat for this quintuple mutant. The CO2-hydrating activity of a double mutant with His94 and Gln92 shows complex pH-dependence, but the other mutants investigated behave as if the activity (kcat/Km) is controlled by the basic form of a single group with pKa near 7.7. In a similar way to human carbonic anhydrase II, the buffer behaves formally as a second substrate in a ping-pong pattern, suggesting that proton transfer between a zinc-bound water molecule and buffer limits the maximal rate of catalysis in both systems at low buffer concentrations. However, the results of isotope-exchange kinetic studies suggest that proton shuttling via His64 is insignificant in the CARP mutant in contrast with carbonic anhydrase II. The replacement of Ile residues with Val in positions 121 or 143 results in measurable 4-nitrophenyl acetate hydrolase activity. The pH-rate profile for this activity has a similar shape to those of carbonic anhydrase I and II. CD spectra of the double mutant with His94 and Gln92 are variable, indicating an equilibrium between a compact form of the protein and a 'molten globule'-like form. The introduction of Thr200 seems to stabilize the protein.

Lingual BDNF and NT-3 mRNA expression patterns and their relation to innervation in the human tongue: similarities and differences compared with rodents.

Brain-derived neurotrophic factor (BDNF) and neurotrophin 3 (NT-3) mRNAs are expressed in developing and adult rodent tongue and are important for the proper development of lingual gustatory and somatosensory innervation in rodents. Here, we wished to determine whether the findings in rodents apply to humans. By using in situ hybridization histochemistry, distinct, specific, and in some instances overlapping patterns of BDNF and NT-3 mRNA expression were found in the developing and adult human tongue, gustatory papillae, and taste buds. BDNF mRNA was expressed in the superior surface epithelium of the developing fungiform papillae (i.e., developing taste buds), in the epithelium covering the circumvallate papillae, and in the subepithelial mesenchyme. Interestingly, BDNF mRNA was expressed in the lingual epithelium before nerve fibers reached the epithelium, indicating a prespecialization of the gustatory epithelium before the arrival of nerves. In the adult fungiform papillae, BDNF mRNA labeling was found in taste buds and in restricted areas in the non-gustatory lingual epithelium. NT-3 mRNA was found in the developing lingual epithelium and gustatory papillae. NT-3 mRNA labeling was observed in the adult fungiform taste buds, overlapping with BDNF mRNA labeling, in contrast to what was seen in rodents. NT-3 mRNA was additionally found in restricted areas in filiform papillae. Protein gene product 9.5 (PGP) antibodies were used to investigate a possible correlation between lingual innervation and sites of neurotrophin gene activity. Adult human tongue innervation differed from that of rodents, possibly in part due to a different neurotrophin expression pattern in the human tongue. Based on these findings, we suggest that BDNF and NT-3 are important for the initiation and maintenance of the gustatory and somatosensory innervation also in humans. The broader and somewhat overlapping expression patterns of BDNF and NT-3 mRNAs, compared with rodents, suggest additional and possibly somewhat overlapping roles for BDNF and NT-3 in the human tongue and also indicate differences between species. It is important that interspecies differences be taken into consideration.

Palatal growth and chemotherapy: effects of cyclophosphamide on bone formation in the intermaxillary suture in growing rats.

OBJECTIVE: To study the effect of cyclophosphamide (Cy) on bone formation in the maxillary median suture of young rats. STUDY DESIGN: Doses of 30 mg/kg body weight of Cy were administered to 12 experimental rats at 10 and 13 days of age. A corresponding amount of 0.9% sodium chloride was given to 6 control rats at the same ages. At 31 days, the median maxillary suture was studied histologically in the experimental and control rats. RESULTS: Structural changes of the osteogenic layers and cartilage components of the suture could be seen in the experimental rats. The thickness of the palatal bone was only 66% of that of the control rats, and the experimental rats also exhibited significantly reduced width of the suture. CONCLUSION: This study shows that Cy by itself can cause disturbances in bone formation in rats.

Hypothermic insult to the periodontium: a model for the study of aseptic tooth resorption.

The aim of the current investigation was to define an animal model for the study of hard tissue resorption by examining the responses of the periodontal ligament (PDL) to both single and multiple episodes of hypothermic injury to the crowns of rat teeth. A group of 12 male rats weighing 200-250 g were anesthetized, and pellets of dry ice (CO2) were applied once to the crowns of the right first maxillary molars for continuous periods of 10 or 20 min. Animals were sacrificed at 2, 7, 14 and 28 days and tissues were processed for routine histological examination. A second group of eight animals and a third group of 12 animals were subjected to three applications of dry ice over a period of 1 week and sacrificed at 2 and 14 days respectively after the final application. In addition to thermal insult, the periodontium of teeth from a fourth group of six rats was subjected to mechanical trauma. Examination of the sections from the group undergoing a single freezing episode revealed that, by 1 week, shallow resorption lacunae had appeared on the root surface. These became more extensive after 14 days. At the same time hyaline degeneration was evident in the PDL. Within this group, teeth subjected to the longer 20-min application times generally showed more extensive injuries. By 28 days, evidence of repair was observed with reparative cementum beginning to line the resorption lacunae in the root dentin. Sections from animals subjected to multiple episodes of thermal trauma and those subjected to additional mechanical insult showed more extensive external root resorption than those from single-injury animals. It was concluded that low temperature stimuli applied to the crowns of rat molars were capable of eliciting a sterile degenerative response in the PDL which, in turn, resulted in external root resorption. Furthermore, the degree of this tissue injury was commensurate with the duration and number of exposures to the trauma. The results also indicated that progression of the resorptive process required periodic exposure to the injury, in the absence of which repair to the damaged root occurred.

A clinical study of root surface conditioning with an EDTA gel. I. Nonsurgical periodontal treatment.

The present study was undertaken to investigate if subgingival administration of an EDTA gel has any adjunctive effect to subgingival and supragingival root debridement. The investigation was performed in one study center involving 6 clinical investigators and 91 patients. The patients were selected from 2 patient populations: 41 were included from a consecutive referral material on a voluntary basis, and 50 were included from a maintenance care material at the clinic. No significant differences were found between the EDTA-treated and control groups with respect to clinical attachment gain or probing pocket depth reduction. The referral patients showed a significant improvement of pocket depth and attachment gain compared to maintenance care patients at the clinic. In multiple regression analyses, it was found that patients with small attachment losses at baseline responded better to treatment than patients with severe periodontitis. Also, in multivariate analyses, referral patients responded better than maintenance patients when controlling for other predictors.

A clinical study of root surface conditioning with an EDTA gel. II. Surgical periodontal treatment.

The objective of the present trial was to assess the effect of an EDTA gel applied during surgical periodontal therapy on probing depth reduction and periodontal attachment gain, allowing for the influence on healing of smoking as well as postsurgical oral hygiene. For comparison, citric acid treatment and control surgery only were included. The investigation was performed in one study center involving one clinical investigator and 68 patients. The patients were selected from a consecutive referral material on a voluntary basis. No statistically significant differences between treatment groups concerning attachment gain or pocket depth reduction could be seen after 3 and 6 months. A subgroup of the sample--21 patients who scored zero on the bleeding index at 3 and 6 months postsurgery and did not smoke--had a borderline significantly higher attachment gain in response to experimental treatment as well as a significant pocket depth reduction 6 months postsurgery when controlling for age, gender, Plaque Index at baseline, and treatment in multiple regression analyses. However, this was true not only for EDTA treatment but for citric acid and control treatment as well.

Effect of a chemo-mechanical caries removal system (Carisolv) on dentin topography of non-carious dentin.

The purpose of the present study was to examine the morphology of healthy dentin surfaces after treatment with Carisolv followed by conditioning with phosphoric acid and EDTA, since surface morphology may be of interest for dentin bonding. Another purpose was to evaluate the effect of treatment with Carisolv on healthy non-carious dentin surfaces with exposed collagen fibers. Scanning electron microscopy was utilized to carry out a detailed morphological examination of the dentin surfaces with regard to presence or absence of both smear layer and collagen fibers. Twelve premolars extracted for orthodontic reasons from young adults were used. The two etchants appeared to have produced two distinctly different surfaces. Etching with phosphoric acid following Carisolv treatment resulted in a porous dentin surface, while EDTA etching without prior Carisolv treatment appeared to have uncovered an intact collagen network. In contrast, the surfaces treated with Carisolv prior to EDTA etching displayed smooth intertubular surfaces with only occasional fibers. Apparently, the ability of EDTA to expose collagen in the dentin surface is counteracted or inhibited by the Carisolv treatment. Furthermore, it cannot be excluded that the Carisolv treatment in itself may have dissolved collagen fibers. Since most bonding systems claim bonding to the collagenous component of dentin, the question arises which of the etched surfaces is preferable and to what degree the collagenous component contributes to bonding strength. Further studies are thus needed to evaluate the micromechanical retention of a restoration to the different surfaces described in the present study.

A new concept for etching in restorative dentistry?

The purpose of the present study was to investigate the scanning electron microscopic texture of enamel and dentin cavity surfaces in extracted human teeth following different etching modalities, specifically combinations of etchants adapted to the tissue composition of the cavity walls. It was concluded that an etching technique that combined the action of 2 different etchants--ethylenediaminetetraacetic acid (EDTA) on dentin and phosphoric acid on enamel--optimized retention structures on each tissue surface of a dental cavity better than either 1 of the 2 etchants that were applied to both types of tissue in the cavity walls.

Changing the efficiency and specificity of the esterase activity of human carbonic anhydrase II by site-specific mutagenesis.

Rates of hydrolysis of 4-, 3-, and 2-nitrophenyl acetate and 4-nitrophenyl propionate catalyzed by wild-type and mutant forms of human carbonic anhydrase II have been measured. The results show that the mutations Tyr7-->Phe and Ala65-->Leu lead to activity enhancements with all the investigated substrates, but there is no significant effect on the specificity. In contrast, some mutations at sequence position 200 have large effects on specificity. For example, while the mutation Thr200-->Gly results in a threefold increase of the rate of hydrolysis of 4-nitrophenyl acetate, the activity is enhanced 10 times with the meta-substituted substrate and 380 times with the ortho-substituted substrate. These results are interpreted in terms of the removal in the mutant of a steric interference between the 2-NO2 group, in particular, and the side chain of Thr200. Mutants involving residues lining a hydrophobic pocket near the catalytically essential zinc ion have also been investigated. The most pronounced effect on specificity was found for the Val143-->Gly mutant. This mutation leads to a sixfold decrease of the rate of hydrolysis of 4-nitrophenyl acetate but a 20-fold increase of the activity with the propionyl ester as substrate. These results suggest that the side chain of Val143 interferes sterically with the acyl moiety of 4-nitrophenyl propionate. Based on these results, we have constructed a hypothetical model of the location of these ester substrates in the enzymic active site.

Skin-prick test for severe marginal periodontitis.

The present study tested the hypothesis that treatment-resistant periodontitis patients present with a more intense inflammatory response to marginal bacterial plaque as a sign of an inflammatory overreaction. Patients with severe marginal periodontitis (Gingival Index > 20%) who had not responded to treatment showed almost no positive response to lipid A in a skin-prick test, which was significantly different from the results from patients with severe marginal periodontitis who had responded to treatment and from healthy control individuals without marginal periodontitis. This finding can be interpreted as an impaired inflammatory reactivity to periodontitis pathogens in treatment-resistant patients, rejecting the hypothesis.

Efficacy of Carisolv-assisted caries excavation.

As a possible alternative to conventional techniques for excavating caries chemomechanical methods have been developed. Caridex has so far been the dominating product. However, a new system, Carisolv, was recently introduced. The purpose of the present study was to evaluate the caries-dissolving efficacy of Carisolv in vitro. After excavation with Carisolv all dentin surfaces were caries free. However, 6 of the 10 cavities showed residual caries in the dentinoenamel junction. The dentin and enamel surfaces were covered by smear and debris. Since there may be a risk of leaving caries in the dentinoenamel junction proper case selection appears to be of importance to ensure a successful result.