The porphyromonas gingivalis prtP/kgp homologue exists as two open reading frames in strain 381

P- gingivalis is considered to be a major pathogen of adult periodontitis. Among its cadre of putative virulence factors are hemagglutinins (adhesins) and proteases. We here report the cloning, sequencing and characterization of two genes, designated kgp(381) and hagD. Kgp(381), an open reading frame (ORF) of 1095 bp encoding a 40.1 kda protein, has high homology to the proteolytic domain of cysteine protease/hemagglutinin genes. HagD, an ORF of 4077 bp encoding a 147.1 kda protein, contains one HArep sequence which establishes it as an additional member of the HArep multigene family. Although similar in sequence to kgp and prtP which were identified from strains HG66 and W12, respectively, the kgp(381)-hagD genes have several characteristics which distinguish them from kgp and prtP. Foremost among these is a single base difference which produces a termination codon and an immediate frame shift resulting in two ORFs in strain 381 as compared to one ORF in strains HG66 and W12. In addition, a 172 amino acid sequence near the C-terminal end of hagD has very low identity (20.5–27.8%) to the corresponding region of kgp and prtP. These demonstrate that the homologue of kgp and prtP in strain 381 occurs as two separate genes which may genetically separate the adhesive and enzymatic domains of Kgp and PrtP proteins. Reverse polymerase chain reaction (PCR) analysis indicates that hagD expression is regulated by hemin concentration.     

Comparison of Radiovisiography with radiographic film in root length determination

Radiovisiography is a digital intraoral radiographic imaging system requiring a substantial reduction of radiation dosage to the patient over film. For Radiovisiography to replace film, it must be shown to be as efficacious. In this study, a technique of obtaining Radiovisiography and D-speed film images from the same X- ray beam was developed with the use of rare-earth filters. The quality of the resultant radiovisiographic images was verified in vitro with pure radiovisiographic images of teeth in a dried mandible with soft tissue simulation. Two examiners compared Radiovisiography with D-speed film for 20 root length estimations using the same in-vitro model. A clinical study was then carried out on mandibular molars of patients undergoing endodontic treatment, where 35 root lengths were obtained. The results of both in vitro and clinical studies showed no statistical differences in the estimated root lengths using the two imaging systems. The measuring grid available in the Radiovisiography unit produced similarly accurate results. Furthermore, the clinical study demonstrated the effective use of Radiovisiography during root canal treatment, with instant images.     

Site-specific subgingival colonization by Actinobacillus actinomycetemcomitans in orthodontic patients.

A high prevalence of Actinobacillus actinomycetemcomitans (Aa) in subgingival plaque in patients for orthodontia already has been observed. The present study had the following aims: 1) to ascertain a direct relationship between the orthodontic appliance placement and the subgingival colonization by Aa, and 2) to determine whether the Aa growth specifically occurred on teeth with braces attached or whether the presence of orthodontic appliances could also cause the isolation of Aa in teeth free from therapeutic appliances. Twenty-four young systemically and periodontally healthy subjects with malaligned and crowded teeth in the anterior sextants of both dental arches participated in this study. After 1 session of ultrasonic scaling with oral hygiene instructions during the first experimental session, the mesiobuccal sites of the first molars and the distobuccal sites of the lateral incisors in both dental arches in each participant were subjected to clinical and microbiologic examination for the recovery of Aa. Clinical examination consisted of recording the presence of plaque and the examination of gingival bleeding on probing and probing depth. Microbiologic sampling was obtained with the insertion of 3 sterile paper points at the deepest part of each gingival sulcus. Altogether, 192 periodontal sites were examined. After the examinations, the patients received fixed orthodontic appliances in only 1 dental arch (test sites) and the other one was left free from appliances (control sites). Clinical examination and microbiologic sampling were repeated in the same experimental test and control sites after 4, 8, and 12 weeks. At the 12-week session, the orthodontic appliance was removed from the test arch, and, 4 weeks later, a further clinical and microbiologic examination was performed. The results showed that, during the period with orthodontic appliances, the presence of plaque scores and the gingival bleeding on probing scores were increased significantly and that Aa, initially absent from all but 1 subject, was isolated in 19 and 20 subjects after 4 and 8 weeks, respectively. Furthermore, no gingival sites from the control teeth (free from Aa colonization at baseline) showed positive results for the sought-after bacterium throughout the entire length of the study. It was concluded that the placement of orthodontic appliances promotes the subgingival growth of Aa; this specific microbial change is specifically restricted to subgingival plaque from orthodontic appliance-bearing teeth. The presence of orthodontic bands and brackets therefore cannot affect the microbiologic condition of the whole mouth.     

In vivo evaluation of the biocompatibility of implanted biomaterials: morphology of the implant-tissue interactions

Electron microscopic observations were made from tissues apposing titanium and ceramic root form and blade implants. The tissue was serially sectioned from the most coronal epithelium, through the gingival connective tissue, to the osseous support tissues, and directly to the most apical tissue support. Of the thousands of sections analyzed for each implant, 500 micrographs were routinely viewed for each of the implants analyzed by this study. Of the 120 total implants placed in 30 adult dogs, 60 were used for electron microscopy. Osseointegrated implants were often apposed by a mineralized matrix of collagenous fibers. The dense mineralized collagen matrix was often separated from the implant by only a ruthenium positive electron dense deposit 20 to 50 nanometers thick. Areas of the same implant were also apposed by an unmineralized collagen fiber stroma, which ranged in thickness, that contained osteoblasts. Interaction of the osteoblasts and the unmineralized collagen fibers resulted in the mineralization events of osteogenesis. Also apposing other areas of the same integrated implants were lacunar areas containing osteoclasts and vessels. These zones were similar to Howship's Lacunae. These results demonstrated that a normal homeostasis of catabolic osteoclastic activity and metabolic osteoblastic activity resulted in a dynamic implant-tissue interface. This biocompatible and dynamic support complex provides a construct for the long-term clinical serviceability of osseointegrated implants.     

Attachment loss with postmenopausal age and smoking

To determine whether postmenopausal bone loss and factors associated with osteoporosis affect tooth retention, we examined vertebral and proximal femoral (postcranial) bone mineral density in relation to tooth loss and attachment loss in a cross-sectional study of 135 postmenopausal women (age range 41–70 yr). Women had at least 10 teeth and no evidence of moderate or severe periodontal disease. Full-mouth attachment loss measurements were made using a pressure-sensitive probe, and bone density was determined by dual-energy X-ray absorptiometry. Attachment loss was correlated with tooth loss (number of remaining teeth, radiologically determined), but not with vertebral or proximal femur bone density. Multivariate analysis showed current smoking (p = 0.01), years since menopause (p = 0.02) and the interaction of age and current smoking (p < 0.01), to be statistically significant predictors of attachment loss in our study population.     

Comparison of the pattern of agenesis in the primary and permanent dentitions in a population characterized by agenesis in the primary dentition

The first aim of this study was to collect a large sample of radiographs from children with congenitally missing teeth (CMT) in the primary dentition and to analyse the local relationship between agenesis of a primary tooth and the presence/absence of its permanent successor. The second aim was to compare, in the same sample, the pattern of agenesis in the primary dentition with the developmental pattern seen in the permanent dentition. 124 dentists from 72 municipalities contributed to the investigation of a total of 213 children. The dentists were asked to lend existing radiographic material from patients with agenesis in the primary dentition. The analysis of the local occurrence of agenesis showed that agenesis of a primary incisor was often but not always followed by agenesis of the succedaneous tooth. In the molar region, agenesis of a primary tooth was in all cases but one followed by agenesis of the succedaneous tooth. Comparison of the pattern of CMT in the primary dentition with the pattern of tooth presence/absence in the permanent dentition in a group of 33 patients, for whom complete radiographic material was available showed that agenesis always occurred in the permanent dentition and that the pattern of agenesis in the permanent dentition differed from that in the primary dentition. Incisors were most frequently missing in the primary dentition and premolars in the permanent dentition. The number of congenitally missing teeth was substantially larger in the permanent dentition than in the primary dentition. Also, permanent teeth that are very rarely congenitally missing were missing in this sample, characterized by the occurrence of agenesis in the primary dentition.     

Molecular signaling mechanisms of the periopathogen, Treponema denticola

In the healthy subgingiva, oral treponemes account for a small percentage of the total bacteria. However, in diseased periodontal pockets, treponemes thrive and become a dominant component of the bacterial population. Oral treponemes are uniquely adept at capitalizing on the environmental conditions that develop with periodontal disease. The molecular basis of adaptive responses of oral treponemes is just beginning to be investigated and defined. The completion of several treponeme genome sequences and the characterization of global regulatory systems provide an important starting point in the analysis of signaling and adaptive responses. In this review, we discuss existing literature focused on the genetic regulatory mechanisms of Treponema denticola and present an overview of the possible roles of regulatory proteins identified through genome analyses. This information provides insight into the possible molecular mechanisms utilized by oral spirochetes to survive in the periodontal pocket and transition from a minor to a dominant organism.     

Effect of titanium tetrafluoride and sodium fluoride on erosion progression in enamel and dentine in vitro

Our aim was to investigate the effect of TiF4 solutions on mineral loss on enamel and dentine in vitro. Samples were fluoridated 1 x 5 min per day with 1.64% w/v TiF4 or 2.2% w/v NaF solutions, each with a pH of 1.2, and then subjected to a cyclic de- and remineralization procedure for 5 days. Demineralization was performed for 6 x 10 min per day with citric acid (pH 2.3). In controls no fluoridation was performed. Mineral content was determined by longitudinal microradiography. Enamel mineral loss was markedly reduced by both fluoride solutions, but TiF4 was significantly more effective than NaF: cumulative mineral loss on day 3 was 61.7 +/- 15.0 microm in the NaF and 34.2 +/- 13.1 microm in the TiF4 group (p < or = 0.001) compared with 121.0 +/- 27.0 microm in the control group. Dentine mineral loss ceased after both TiF4 and NaF applications (cumulative mineral loss on day 5 in controls: 61.0 +/- 17.0 microm, in the TiF4 group: 15.4 +/- 13.4 microm and in the NaF group: 21.8 +/- 11.8 microm). Both TiF4 and NaF application reduced mineral loss both on enamel and dentine, which could open new possibilities for a symptomatic therapy of erosions.     

Effect of loading mode on bond strength of orthodontic brackets bonded with 2 systems.

INTRODUCTION: A new orthodontic bracket bonding method or material invariably spawns bond strength studies examining the efficacy of the innovation. The primary purpose of this project was to ascertain whether the mode of in-vitro bracket debonding used in a study affects the measured bond strength. The secondary aim was to compare the bond strengths of 2 different bonding systems. METHODS: Flattened stainless steel orthodontic brackets were bonded to flattened bovine enamel with a resin composite bonding agent (Transbond XT, 3M Unitek, Monrovia, Calif). The enamel was prepared with traditional acid etching and priming (37% phosphoric acid gel and Transbond XT Primer, 3M Unitek) or a single-step method (Transbond Plus, 3M Unitek) that combined etching and priming. Cement thickness was kept constant, and bonding was done under controlled temperature and humidity. Brackets were debonded in shear-peel, tension, or torsion. RESULTS: When tested in shear-peel mode, traditional etching and priming produced a stronger bond than the single-step self-etch system. When tested in tension, the traditional bond was weaker than the single-step bond, and when tested in torsion, the bond strengths were similar. CONCLUSIONS: Bond strength can vary depending on the method of testing. Claims of clinical efficacy might not be valid.