X-ray microfocus computer tomography for non-destructive evaluation of the shaping ability of nickel-titanium rotary instruments and subsequent obturation".

De klinische aanpak van een niet-chirurgische endobehandeling bestaat uit het zorgvuldig instrumente ren ( shaping ) van de wortelkanalen met vijlen, het gebruik van antimicrobi ële agentia, en het aanbrengen van een wortelkanaalvulling ( obturation ). H et uiteindelijke biologische doel van deze behandeling is het voorkomen of genezen van parodontitis apicalis, een specifieke aandoening veroorzaakt door ba cteriën in het wortelkanaalstelsel. Het instrumenteren gebeurt traditioneel met handvijlen uit roestvrij staal. Het is een moeilijke en tijdrovende bezigheid die vaak leidt tot iatrogene schade met negatieve weerslag op desinfectie en obturatie. Als oplossing voor dit feit werden nikkel titaan (NiTi) roterende vijlen ontwikkeld. De superelasticiteit van deze legering laat andere ontwerpen toe, terwijl door de invoering van mechan ische rotatie enkele klassieke moeilijkheden worden opgeheven. Een eerste doelstelling van deze thesis was de introductie en optimalisatie van een nieuwe, objectieve me thode voor het in vitro kwantitatief onderzoek van wortelkanaalvormgeving door middel van X-stralen microfocus computer tomografie (micro-CT), beeldregistrati e en eigen software. Met deze techniek werden nadien een aantal NiTi roterend e vijlsystemen op niet-destructieve wijze onderzocht. Het geheel werd afge rond met een validatie. We toetsten de hypothese dat micro-CT dwarsdoorsneden verschaft met betrouwbare en nauwkeurige morfologische informatie over d e uitkomst van vormgeving en obturatie. Micro-CT werd vergeleken met optis che microscopie door middel van eigen software voor kwantitatieve validatie op basis van beeldregistratie. Onze resultaten waren een bevestiging dat micro-CT kan worden gebruikt voor de kwantitatieve bepaling van verwijderd worteldentine. Het verloop van een procedure voor vormgeving kan zo op niet-destructieve wijze, in drie dimensies (3D), en met een ruimtelijke resolutie van mins tens 30 µm worden bepaald. We genereren eerst een nauwkeurige, gedetaill eerde 3D weergave die een visuele beoordeling van de algemene en locale kanaalanatomie voor en na instrumentatie uit alle richtingen mogelijk ma akt. Vervolgens krijgen we waarden voor volume(verandering) en transportatie, terwijl de centrering wordt gezien als centrering verhouding en centrumverplaatsing . De vergelijking van een glad flexibel schacht ontwerp (Lightspeed) met een actief toelopend ( getaper d ) schacht ontwerp (GT Rotary) toont aan dat deze laatste beduidend meer de ntine verwijdert in het midden en apicale deel van het wortelkanaal (een toege nomen deep shape ). Beide groepen tonen vergelijkbare resultaten voor het rechttrekken ( straightening ) terwijl de mate van centrering zeer goe d is. Geen duidelijke fouten worden gevonden. De vergelijking van een toenemend taps schachtontwerp (ProTaper) met een constant taps schachtontwerp (K3) toon t aan dat de hoeveelheid verwijderd dentine per horizontale regio vergelijkbaa r is voor beide systemen. Het globale centrumbehoud is uitstekend en niet bed uidend verschillend. ProTaper toont coronaal een centrumverplaatsing in de rich ting van de furcatie. Voor K3 wordt een verplaatsing naar buiten vastgesteld voor het midden en apicale deel. Ook hier worden er geen duidelijke fouten ge maakt. Uit de validatie besluiten we dat micro-CT dwarsdoorsneden verschaft met betrouwbare en nauwkeurige morfol ogische informatie over de uitkomst van vormgeving als men de juiste instellinge n en software gebruikt. De analyse van gevulde kanalen moet met reserve gebeu ren omdat de aanwezige vulmaterialen en de beperkte resolutie de weergave en analyse bemoeilijken. Het gebruik van geavanceerde technologie wordt aan geraden en besproken.status: publishe

Evaluation of a preparation depth controlling device: a pilot study

OBJECTIVE: To define the reproducibility and accuracy of the Prepometer device (Hager & Werken) and to correlate the measured electrical resistance with the remaining dentin thickness. METHOD AND MATERIALS: In vivo standardized cavities were made on the buccal side in the cervical region of 12 intact teeth. Measurements with the Prepometer were completed before tooth extraction. After extraction, in vitro measurements of the remaining dentin thickness were performed using a microfocus-computerized tomography scanner. These in vitro scan data were compared with the in vivo measurements, and correlation coefficients calculated. The intra- and interinvestigator variability were defined, using a paired 2-tailed Student t test. The level of significance was set at 5%. RESULTS: Although both the intra- and interinvestigator variability scored well, there was no clear correlation between the Prepometer measurements and the remaining dentin thickness. Because the device determines the electrical resistance of the dentin, which is related to dentin permeability, real remaining dentin thickness cannot be measured. A reasonable safety zone (3 of 12 teeth scored false negative and 1 of 12 teeth scored false positive) in terms of remaining dentin thickness was observed. CONCLUSIONS: The Prepometer, a device developed to screen dentin-surface permeability by measuring its electrical resistance, was shown to be reproducible in its use. However, electrical resistance was shown not to correlate with dentin thickness. Although the Prepometer might help to estimate the risk of pulp injury after tooth preparation, its effectiveness still remains to be proven in a randomized clinical trial.status: publishe

A methodology for quantitative evaluation of root canal instrumentation using microcomputed tomography

AIM: The aim of this paper was to present an objective methodology for quantitative evaluation of root canal instrumentation using microcomputer tomography, together with developed software based on a constructed mathematical model. METHODOLOGY: A desktop X-ray micro-CT scanner (SkyScan 1072) was used to provide data sets of an extracted mandibular molar before and after instrumentation (ProFile 0.04 Taper instruments, Dentsply Maillefer, Ballaigues, Switzerland) that were stored for later use by software. A volume visualization package (T3D) was applied to obtain 3D renderings of the molar to illustrate the qualitative visualization capacity. Next, medical image volume fusion software was used to allow alignment of pre and post image volumes. Finally, software was developed to make quantitative measurements and to provide additional qualitative information on the registered image volumes. This procedure implemented a true 3D mathematical model for quantification of instrumentation effects. Using a local co-ordinate frame, perpendicular reslices were made at five different levels within the mesio-buccal canal to evaluate transportation and centring ability. RESULTS: At first accurate and detailed 3D renderings were obtained. The general and local canal shape before and after preparation could visually be examined in 360 degrees rotation. Numerical values were obtained for volume, volume changes and transportation. Centring ability was calculated by centring ratio and centre movement. CONCLUSIONS: This methodology is a new and objective way for quantitative evaluation of root canal instrumentation using microcomputer tomography and dedicated software.Bergmans L., Van Cleynenbreugel J., Wevers M., Lambrechts P., ''A methodology for quantitative evaluation of root canal instrumentation using microcomputed tomography'', International endodontic journal, vol. 34, pp. 390-398, 2001, Blackwell Science Ltd.status: publishe

Void detection in root fillings using intraoral analogue, intraoral digital and cone beam CT images

AIM: To compare void detection in root fillings using different radiographic imaging techniques: intraoral analogue, intraoral digital and cone beam CT (CBCT) images and to assess factors influencing small void detection. METHODOLOGY: Two straight root canals in canine teeth were prepared. Calibrated steel wires of five different diameters (200, 300, 350, 500, 800 microm) were inserted respectively in the canal after the injection of a sealer. To simulate filling voids of known dimensions, the wires were removed after the sealer had set. Each sample was imaged, using a Minray X-ray tube (Soredex, Helsinki, Finland) at optimal clinical settings combined with Vistascan PSP (Dürr Dental, Bietigheim-Bissingen, Germany), Digora Optime PSP (Soredex), Sigma CCD (Instrumentarium, Tuusula, Finland) and E-speed films (Agfa-Gevaert, Mortsel, Belgium). The teeth were also imaged using CBCT (3D Accuitomo, Morita, Japan). A generalized mixed model and ANOVA analysis were used on the acquired data (Tukey-Kramer correction). RESULTS: There was no evidence that the factor 'root level' affected void detection in root fillings. 'Void size' was a main determining factor as all voids larger than 300 microm were determined with all techniques. For the smaller voids, there were significant differences between the 5 imaging techniques at different void sizes and different root levels. CONCLUSIONS: Void size and imaging technique were main determining factors. Voids larger than 300 mum were determined with all imaging techniques. For small void detection, all digital intraoral techniques performed better than intraoral analogue and CBCT images.status: publishe

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.status: publishe

Hierarchical probabilistic framework for fetal R-peak detection, using ECG waveform and heart rate information

The abdominal fetal electrocardiogram (fECG) can provide valuable information about fetal well-being. However, fetal R-peak detection in abdominal fECG recordings is challenging due to the low signal-to-noise ratio (SNR) and the nonstationary nature of the fECG waveform in the abdominal recordings. In this paper, we propose a multichannel hierarchical probabilistic framework for fetal R-peak detection that combines predictive models of the ECG waveform and the heart rate. The performance of our method was evaluated on set-A of the 2013 Physionet/Computing in Cardiology Challenge and compared to the performance of several methods that have been proposed in the literature. The hierarchical probabilistic framework presented in this study outperforms other methods for fetal R-peak detection with a mean overall detection accuracy for set-A of 99.6%. Even for recordings with low SNR our method enables reliable fetal R-peak detection (Ac 99.4%)

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.status: publishe

Effect of photo-activated disinfection on endodontic pathogens ex vivo

AIM: To test the hypothesis that photo-activated disinfection (PAD) has a bactericidal effect on pathogens inoculated in root canals, with emphasis on biofilm formation/destruction. METHODOLOGY: Root canals of extracted teeth (n = 38) were prepared (size 30, 0.10 taper), autoclaved, divided into three groups and two negative controls inoculated (Streptococcus anginosus, Enterococcus faecalis or Fusobacterium nucleatum) and treated (PAD, laser, dye or positive control) according to a cross-sectional design. Resultant colony-forming unit counts were associated with observations of cell structural changes using environmental scanning electron microscopy (ESEM) on inoculated dentinal surfaces (n = 22, two controls) before (1, 2 and 6 days of incubation) and after treatment with PAD. RESULTS: Treatment of root canals with PAD (15 J) caused a significant reduction of the bacterial load, resulting in a 93.8% kill of S. anginosus (P < 0.0001), a 88.4% kill of E. faecalis (P < 0.05) and a 98.5% kill of F. nucleatum (P < 0.0001), but no sterilization. Laser alone had no significant effect on the load nor did the dye without laser. The ESEM experiment showed that individual cells or monolayers were easily eliminated with PAD. But when biofilms were present (2 and 6 days for E. faecalis, 6 days for S. anginosus), bacterial eradication was substantially reduced in deep layers. CONCLUSIONS: Photo-activated disinfection is not an alternative but a possible supplement to the existing protocols for root canal disinfection as the interaction between light (diode laser) and associated dye (TBO) provides a broad-spectrum effect. Some endodontic pathogens that grow as single-species biofilms, however, are difficult to eradicate.status: publishe

External cervical resorption: an analysis using cone beam and microfocus computed tomography and scanning electron microscopy

AIM: To provide a three-dimensional representation of external cervical resorption (ECR) with microscopy, stereo microscopy, cone beam computed tomography (CT), microfocus CT and scanning electron microscopy (SEM). SUMMARY: External cervical resorption is an aggressive form of root resorption, leading to a loss of dental hard tissues. This is due to clastic action, activated by a damage of the covering cementum and stimulated probably by infection. Clinically, it is a challenging situation as it is characterized by a late symptomatology. This is due to the pericanalar protection from a resorption-resistant sheet, composed of pre-dentine and surrounding dentine. The clastic activity is often associated with an attempt to repair, seen by the formation of osteoid tissue. KEY LEARNING POINTS: Cone beam CT is extremely useful in the diagnoses and treatment planning of ECR. SEM analyses provide a better insight into the activity of osteoclasts. The root canal is surrounded by a layer of dentine that is resistant to resorption.status: publishe