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Biomedical subjects

M Quirynen

Publications and source records attributed to M Quirynen.

At least 19 recordsLinked to original sources
PubMed2006

Bactericidal effect of Nd:YAG laser irradiation on some endodontic pathogens ex vivo.

AIM: To define the role of neodymium:yttrium-aluminum-garnet (Nd:YAG) lasers in root canal disinfection along with a minimally invasive treatment concept. METHODOLOGY: The hypothesis was tested ex vivo that Nd:YAG laser irradiation has a bactericidal effect on endodontic pathogens inoculated in root canals. Resultant colony-forming unit counts were associated with observations of bacterial cell structural changes using conventional scanning electron microscopy (CSEM) and environmental scanning electron microscopy (ESEM) on inoculated dentine surfaces, following indirect and direct Nd:YAG laser irradiation, respectively. RESULTS: The Nd:YAG laser irradiation (1.5 W, 15 Hz, four times for 5 s) of Enterococcus faecalis inoculated canals resulted in a significant reduction (P < 0.05, Wilcoxon signed rank test) of the bacterial load, meaning a 99.7% kill, but no sterilization. The CSEM procedure verified that the extent of radiation damage was in line with the total amount of laser energy applied. After 2 h of incubation and three cycles of indirect laser treatment (i.e. through a 1-mm-thick dentine disc), no morphologically intact bacteria of Actinomyces naeslundii or Streptococcus anginosus were discernible. However, when micro-colonies of S. anginosus and specially biofilms of E. faecalis were present after 2 days, the in situ experiment using ESEM and direct laser treatment showed that bacterial eradication was reduced in deep layers. CONCLUSIONS: The Nd:YAG laser irradiation is not an alternative but a possible supplement to existing protocols for canal disinfection as the properties of laser light may allow a bactericidal effect beyond 1 mm of dentine. Endodontic pathogens that grow as biofilms, however, are difficult to eradicate even upon direct laser exposure.

Actinomyces↗
PubMed2005

Microscopic observation of bacteria: review highlighting the use of environmental SEM.

Throughout the years, various methods have been adopted to investigate bacteria involved in root canal infection and apical periodontitis. This paper reviews the most commonly used microscopic techniques and discusses their possibilities, limitations and sample preparation. In particular, a recently developed variant of scanning electron microscope (SEM), referred to as environmental SEM (ESEM), is highlighted due to its potential impact across the diverse field of biomaterials research. The performance of this ESEM technique for bacterial observation of endodontic pathogens was illustrated by a practical approach. The paper concludes with a discussion on the possible use of ESEM for testing endodontic treatment modalities under environmental conditions in situ.

Bacteria↗
PubMed2005

Influence of genetic background on transformation and expression of Green Fluorescent Protein in Actinobacillus actinomycetemcomitans.

BACKGROUND/AIMS: The development of an electro-transformation system and the construction of shuttle plasmids for Actinobacillus actinomycetemcomitans have enhanced the molecular analysis of virulence factors. However, inefficient transformation is frequently encountered. This study investigated the efficiency of electro-transformation and expression of Green Fluorescent Protein (GFP) in 12 different A. actinomycetemcomitans strains. The influence of the plasmid vector, serotype, and phenotype were the major factors taken into consideration. MATERIAL AND METHODS: Twelve serotyped A. actinomycetemcomitans strains were independently electro-transformed with two different Escherichia coli-A. actinomycetemcomitans shuttle plasmids (pVT1303 and pVT1304), both containing an identical ltx-GFPmut2 gene construct but a different backbone (pDMG4 and pPK1, respectively). The transformation efficiency, transformation frequency, and electro-transformation survival rate were determined by culture techniques. GFP expression was observed at the colony level by fluorescence microscopy. RESULTS: All strains could be transformed with both plasmids. However, major differences were observed for the transformation efficiency, transformation frequency, and electro-transformation survival rate between strains. The data demonstrated that plasmid vector, serotype, and phenotype are key players for obtaining a successful transformation. An inverted relationship between the electro-transformation survival rate and tranformation frequency was also observed. GFP expression was also influenced by phenotype, serotype and plasmid vector. CONCLUSIONS: The serotype of A. actinomycetemcomitans has an important influence on its survival after electro-transformation and on transformation frequency. The expression of GFP is strain and plasmid vector dependent.

Aggregatibacter actinomycetemcomitans↗
PubMed2005

Increase in cariogenic bacteria after initial periodontal therapy.

This study examined the hypothesis of an intra-oral shift, during initial periodontal therapy, from a periopathogenic to a cariogenic flora. Seventy-one patients with periodontitis were randomly allocated to one of the following treatment strategies: (1) scaling and root planing, quadrant by quadrant, at two-week intervals (NC); (2) full-mouth scaling and root planing within 24 hrs (FRP); or (3) full-mouth disinfection within 24 hrs, including antiseptics [chlorhexidine (CHX) or amine fluoride/stannous fluoride (F) for 2 mos, or CHX for 2 mos followed by F for 6 mos (CHX+F)]. At baseline and after 2, 4, and 8 mos, bacterial samples were taken from supra- and subgingival plaque, saliva, and tongue. The detection frequencies and relative proportions of Streptococcus mutans increased in the NC and FRP groups, but decreased in the F group. In the CHX group, these species disappeared temporarily, but they disappeared for the entire 8 mos in the CHX+F group. These observations were similar for all sample locations. The periopathogens decreased in all groups. This finding confirms the abovementioned hypothesis and indicates a need for caries prophylactic regimens.

Adult↗
PubMed2005

Initial subgingival colonization of 'pristine' pockets.

The treatment of periodontitis/peri-implantitis involves the reduction/eradication of periopathogens. After therapy, beneficial and pathogenic species recolonize the subgingival area. The dynamics of recolonization and especially the role of the supragingival environment in this process are still not well-understood. This prospective, split-mouth study followed the early colonization of 'pristine' pockets created during implant surgery (16 partially edentulous patients), to record the time needed before a complex subgingival flora could be established with the supragingival area as the single source. Four subgingival plaque samples were taken from shallow and medium pockets around implants (test), and neighboring teeth (undisturbed microbiota as reference) 1, 2, and 4 wks after abutment connection. Checkerboard DNA-DNA hybridization and culture data revealed a complex microbiota (including several pathogenic species) in the pristine pockets within a wk, with a minimal increase in counts up to 4 wks. Analysis of these data demonstrated that, even with the supragingival environment as the single source for colonizing bacteria, a complex subgingival microbiota can develop within 1 wk.

Adult↗
PubMed2004

The safety and efficacy of a powered toothbrush on soft tissues in patients with implant-supported fixed prostheses.

The safety, efficacy and acceptability of an oscillating/rotating powered toothbrush was assessed in patients rehabilitated with fixed prostheses on implants. One hundred consecutive patients (aged 18-80; mean 56.3; 51 females), who met the inclusion/exclusion criteria and who participated in a regular annual recall scheme, were enrolled. They were instructed on how to use the powered toothbrush, as well as on classical interdental plaque control. The electric toothbrush had to be used twice daily for 2 min. The following periodontal parameters were measured at baseline and at 3 months, 6 months and 12 months: presence/absence of gingival and/or mucosal ulceration/desquamation; sulcus bleeding index; probing pocket depth; periodontal pocket-bleeding index and gingival recession. At 3 months and at the end of the study, patients completed a questionnaire concerning the overall acceptability and convenience of the powered toothbrush, as compared with their habitual manual toothbrush. A total of 80 patients completed the study. No dropouts were related to the use of the powered toothbrush. All parameters improved over the course of the study. The mean overall pocket depth decreased from 3.3 mm at baseline to 3.0 mm at 12 months, while the mean decrease in recession was 0.1 mm at 12 months. During the 1-year observation, there was a slight gain in periodontal attachment level. Gingival ulcerations were not observed at any point in the study. High scores for convenience and comfort of the powered toothbrush were reported, and the majority (95%) said that they would continue to use it for habitual oral hygiene. It is concluded that the powered toothbrush investigated is effective, safe and comfortable for patients rehabilitated by means of oral implant-supported prostheses.

Adolescent↗
PubMed2004

Appearance of the mandibular incisive canal on panoramic radiographs.

Panoramic radiographs are routinely used in the dental office for various diagnostic purposes. This study aimed to evaluate the visibility of neurovascular structures in the mandibular interforaminal region on such radiographs. Panoramic radiographs were obtained with a Cranex Tome (Soredex) from 545 consecutive patients using a standard exposure and positioning protocol. For visibility scoring of neurovascular structures, a four-point rating scale was used. The mandibular canal and the mental foramen could be observed in the majority of the cases with good visibility. The lingual foramen was visualized in 71% of the cases, with good visibility in 12%. An incisive canal was identified in 15% of the images, with good visibility in only 1%. An anatomical variation to be considered is the anterior looping of the mental nerve (in 11% of images). Panoramic radiographs can be used for visualization of the mental foramen and a potential anterior looping but not for locating the mandibular incisive canal. To verify its existence for preoperative planning purposes, cross-sectional imaging modalities (HR-CT or spiral tomography) should be preferred.

Adult↗
PubMed2004

Impact of tongue cleansers on microbial load and taste.

OBJECTIVES: Tongue cleaning has been advocated to improve oral malodor and to reduce reinfection of periodontal niches by eliminating tongue coating and/or reducing putrefaction by bacteria. MATERIAL AND METHODS: This cross-over, single-blind study on periodontitis-free, non-smoking, subjects with habitual oral hygiene (n=16), evaluated the effect of tongue cleaning (with either plastic scraper or nylon multi-tufted toothbrush), on the microbial load of the tongue dorsum (anterior and posterior of the sulcus terminalis), the extent of tongue coating, and taste sensation for bitter, sweet, salt, and sour. Both devices had been used twice daily for 2 weeks (toothbrush three forward-backward movements along the linea mediana and for each longitudinal third of the tongue; two strokes with the scraper along the linea mediana and along the borders of the tongue). RESULTS: Two weeks of tongue brushing or scraping resulted in only negligible reductions in aerobic and anaerobic bacteria on the tongue (reductions <0.5 log). The amount of tongue coating, however, decreased significantly (p<0.05), with both devices. The taste sensation improved after 2 weeks of tongue cleaning, especially with the scraper (significant improvements for quinine and sodium chloride). CONCLUSION: Tongue cleaning improves taste sensation and seems to reduce the substrata for putrefaction, rather than the bacterial load.

Adult↗
PubMed2004

The immediate rehabilitation by means of a ready-made final fixed prosthesis in the edentulous mandible: a 1-year follow-up study on 50 consecutive patients.

Although a two-stage procedure with symphyseal oral implants can lead to a long-term (15 years) 99% cumulative survival rate, a one-stage approach with immediate loading via prefabricated elements seems to offer a short-term acceptable outcome with significantly lower costs. A series of 50 consecutive patients, not eliminated for any systemic or smoking condition, received at the department of periodontology three implants in the symphyseal area, connected by a very rigid horse shoe-shaped titanium bar. A final screw retained prosthetic framework was placed on top of it at the department of prosthetic dentistry within 2 days after surgery (44) or after a delay, due to purely external factors, of up to 10 days (6). Forty-five patients were followed for 1 year. In one patient, all three implants failed and another four patients were lost to follow-up. The cumulative failure rates for implants and prostheses at 1 year were, respectively, 7.3% and 5%. The mean marginal bone loss at 1 year was 1.08 mm (SD: 1.62; range -5.68 to +2.55). This study shows that stable marginal bone levels can be maintained around immediately loaded implants in the lower jaw in an average patient population for at least 1 year. The survival rate is, however, lower than for a staged approach.

Aged↗
PubMed2004

The nasopalatine canal revisited using 2D and 3D CT imaging.

OBJECTIVES: To assess the location, morphology and dimensions of the nasopalatine canal on two-dimensional and three-dimensional (2D and 3D) CT images. METHODS: Material included 34 spiral CT scans for pre-operative planning of implant placement in the maxilla. Scanning was performed using a standard exposure and patient positioning protocol. 2D and 3D spiral CT images were carefully examined for the location, morphology and dimensions of the nasopalatine canal by two independent observers. A comparison was made between 2D observations and a 2D/3D combined observation strategy (paired t-tests). RESULTS: The nasopalatine canal typically appeared as a canal with a mean (standard deviation (SD)) length of 8.1 (3.4) mm. Its palatal opening is the incisive foramen with a mean (SD) inner Ø of 4.6 (1.8) mm. At the level of the nasal floor often 2 (Y-canal morphology), but sometimes 3 or 4 openings could be observed. In particular cases, the canal showed up as a cylinder with only one nasal opening. The average (SD) maximum width of the nasopalatine canal structure at the level of the nasal floor was 4.9 (1.2) mm. The buccopalatal width of the jaw, anterior to the canal was 7.4 (2.6) mm. Interpretation of canal morphology was significantly different when comparing 2D image observation with a 2D/3D combined observation strategy. However, dimensional measurements of the canal were not significantly different for a 2D and a combined 2D/3D approach. CONCLUSIONS: The nasopalatine canal may show important anatomical variations, both with regard to morphology and dimensions. To avoid any potential complications during surgical procedures such as implant placement, a careful pre-operative observation is required. Cross-sectional imaging may be advocated to determine canal morphology and dimensions and to assess anterior bone width for potential implant placement buccally to the canal.

Adult↗
PubMed2003

Presence and course of the incisive canal in the human mandibular interforaminal region: two-dimensional imaging versus anatomical observations.

The objective of the present study was to evaluate the presence and course of the incisive canal in the mental interforaminal region of the human mandible and to describe the occurrence of anatomical variations. Mandibles of 50 adult human cadavers were retrieved from the Department of Anatomy of the Faculty of Medicine, Katholieke Universiteit Leuven (Leuven, Belgium). Forty mandibles were edentulous, while 10 mandibles were partially dentate. Intra-oral, panoramic and tomographic imaging of the interforaminal region of the human mandible were performed. Afterwards, mandibles were sawn into vertical sections according to the respective tomographic cross-sections. The latter allowed exploration for the presence and course of an anterior prolongation of the mandibular canal. Measurements of the location of the incisive canal towards the base of the mandible were made using a digital-sliding caliper. Results indicated a well-defined incisive canal [mean (SD) inner diameter 1.8 (0.5 mm)], macroscopically observed in 96% of mandibles. The incisive canal was located on average 9.7 mm (SD 1.8 mm) from the lower cortical border and continued towards the incisor region in a slightly downward direction, with a mean (SD) distance to the lower cortical border of 7.2 (2.1) mm. It was concluded that there is an anterior intraosseous extension of the mandibular canal, denoted as the incisive canal. The latter might be considered as a true anterior extension of the neurovascular bundle. Histological and neurophysiological studies are needed to verify this hypothesis and evaluate its potential clinical implications.

Adult↗
PubMed2003

Adhesion of Porphyromonas gingivalis to cultured pocket epithelium: mono- and multi-layered.

Adhesion of bacteria to epithelial cells might be influenced by the degree of cell differentiation, as observed in the multi-layering process of epithelial cells. In the present study, the adhesion of a large group of clinical Porphyromonas gingivalis strains (n=11) to in vitro cultured mono- and multi-layers of epithelial cells was examined and compared. The tissue samples originated from 6 patients with chronic adult periodontitis. Porphyromonas gingivalis bacteria adhered more to mono-layers as opposed to the more differentiated multi-layers. Differences between the clinical P. gingivalis strains, however, became obvious only on multi-layers. These partially differentiated cells may also better represent the individual subject variations. Mono-layer cultures, which are simpler to obtain, seem to be less precise. The importance of cell differentiation on bacterial adhesion needs more attention.

Adult↗
PubMed2003

A split-mouth study on periodontal and microbial parameters in children with complete unilateral cleft lip and palate.

BACKGROUND: Complete unilateral cleft lip and palate (UCLP) is a hereditary or multifactorial malformation that can be corrected successfully with a combined orthodontic, surgical and restorative treatment. Such multidisciplinary treatment takes many years and demands a lot of attention to both patients' teeth and periodontium. OBJECTIVES: This split-mouth study aimed to compare the periodontal health as well as the microbial parameters between cleft and non-cleft region. MATERIAL AND METHODS: 75 patients (52 males, 23 females) between 8 and 20 years with a complete unilateral cleft lip and palate (before (n = 30), during (n = 34) and after (n = 11) the active orthodontic treatment) volunteered for this study. Four regions were defined for the split-mouth comparison: teeth neighbouring cleft (site 1), tooth in cleft (site 2), and the corresponding contra-lateral teeth, respectively, in the unaffected quadrants (sites 3 and 4). At all sites the following periodontal parameters were recorded: plaque and gingivitis indices, pocket depth, attachment loss, bleeding on probing, tooth mobility (visual and Periotest), radiographic bone loss and gingival width. In addition, three pooled subgingival plaque samples were taken (around tooth in cleft, teeth facing the cleft, and contra-lateral teeth of the latter). RESULTS: The differences between the teeth neighbouring the cleft and the corresponding contra-lateral opponents were of borderline significance (P <or= 0.05) for the plaque index, the approximal probing depths and the attachment loss (teeth facing the cleft always had slightly higher parameters). When the tooth in the cleft was compared to the contra-lateral tooth, differences were only found for both the approximal probing depths, attachment loss and bone loss, which were significantly higher for the tooth in the cleft. The microbial analysis did not reveal differences between the different sites, neither in the proportion of aerobic and anaerobic bacteria (differences < 0.5 log), nor in the detection frequency of periopathogens. CONCLUSIONS: These data indicate that the periodontium in UCLP patients can cope well with a long-term orthodontic treatment, even in unfavourable conditions (like absence of attached gingiva and poor oral hygiene).

Adolescent↗
PubMed2003

Management of oral malodour.

Halitosis is a common problem. Its aetiology is multifactorial, but oral malodour is usually caused by microbial metabolism from the tongue, saliva or dental plaque. Mouthwashes are only effective against halitosis caused by intraoral factors. The principal causative agents of oral malodour are volatile sulphide compounds (VSCs), including hydrogen sulphide, methyl mercaptan and dimethyl sulphide. Data suggest that oral VSC levels correlate with the depth of periodontal pockets. Trials have shown that both mechanical oral care and mouthwash use can reduce halitosis levels. The majority of studies involving mouthwashes have investigated chlorhexidine and essential oil mouthwashes, although comparative studies are sparse.

Anti-Infective Agents, Local↗
PubMed2003

Microbial shifts after subgingival debridement and formation of bacterial resistance when combined with local or systemic antimicrobials.

Antibiotics have played a major role in the improvement of life expectancy in the last 50 years and have led many to believe that bacterial infections were about to vanish as a disease entity of any importance. Emerging problems resulting from a widespread use of antibiotics have modified the general perception of the capabilities of antimicrobial agents. Over the years, bacteria have become increasingly resistant to formerly potent antimicrobial agents, including some antiseptics. The use of antimicrobials may also disturb the delicate ecological equilibrium of the body, allowing the proliferation of resistant bacteria or non-bacterial micro-organisms. This shift may initiate new infections that are worse than the ones originally treated. No antimicrobial drug is absolutely non-toxic and the use of an agent carries accompanying risks. This paper discusses the development and occurrence of antimicrobial resistance in the subgingival flora towards antiseptics and local or systemic antibiotics and is focussed on the question: how can the outcome of periodontal therapy with/without antimicrobials be improved?

Administration, Topical↗
PubMed2003

Dental abnormalities, bone graft quality, and periodontal conditions in patients with unilateral cleft lip and palate at different phases of orthodontic treatment.

OBJECTIVES: To evaluate the dental and periodontal condition of patients with unilateral cleft lip and palate (UCLP) before orthodontic treatment and evaluate whether the dental and periodontal condition of these patients during and after orthodontic treatment was jeopardized by the duration of the orthodontic and surgical treatment. DESIGN: Seventy-five individuals with UCLP (52 males, 23 females), between ages 8 and 20 years, participated in a retrospective study during their final follow-up visit with regard to dental abnormalities, such as hypodontia, external root resorption, crown and root malformation, and supernumerary teeth. Alveolar bone height and periodontal attachment loss on the cleft side were also screened before or after bone grafting and at different stages of orthodontic treatment. RESULTS: Hypodontia of the lateral incisor was found in more than 50% of the patients on the cleft side. Second premolars and/or lateral incisors outside the cleft area were missing in 27.2% of the patients. In 32%, malformations of the teeth near the cleft were noticed. In general, the teeth around and in the cleft of the patients showed normal septal bone heights and a healthy periodontium. Sixty of the 75 patients received a bone graft to restore the interrupted alveolar process. In 93.3% of these patients, the cleft was grafted before the eruption of the canine. CONCLUSION: The periodontium of the teeth in and around the cleft in patients with UCLP observed during and after orthodontic treatment can cope relatively well with the long orthodontic treatment and combined surgical interventions. The children, who had not yet started treatment, also showed enough bone support and no periodontal problems of the teeth besides the cleft. Early secondary bone grafting seems to give optimal periodontal results.

Adolescent↗
PubMed2002

Viability of cultured periodontal pocket epithelium cells and Porphyromonas gingivalis association.

OBJECTIVES: Porphyromonas gingivalis, one of the key pathogens in the development of periodontitis, produces a number of virulence factors that might explain its pathogenicity. One of them is the ability to adhere and invade pocket epithelium. The aim of this study was to follow, over time, the association of P. gingivalis and consequent morphological changes of the pocket epithelium cells. MATERIAL AND METHODS: The association capacity of four P. gingivalis serotypes [K1, K2, K4, K- (nonencapsulated)] with in vitro cultured mono-layers from periodontal pocket epithelial cells of patients with periodontitis, was followed by fluorescence microscopy and bacterial culture. The contact time between bacteria and epithelium cells ranged from 45 min to 8 h. The microscopic evaluation allowed differentiation between dead and living cells (bacteria as well as epithelium) and description of the morphological changes after association. RESULTS: A highly significant difference in the number of associating bacteria was found between dead and living epithelium cells, and between non-capsulated and capsulated strains. A significant increase in the proportion of dead pocket epithelium cells was found with prolonged association time. The morphological changes (rounding of the epithelial cell, detachment from the glass cover-slip and loss of intercellular contact) occurred faster for mono-layers inoculated with the non-encapsulated P. gingivalis strain. CONCLUSIONS: This study indicates that dead pocket epithelium cells harbor more P. gingivalis cells, and that a positive correlation exists between contact time and cell death. For the P. ginigvalis species, non-encapsulated strains associate in higher number. As a result, the damage they cause to the host cell seems to occur faster than occurs in encapsulated strains. As such, cell death can be seen as the end-result of bacterial association.

Bacterial Adhesion↗