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At least 451 records · Page 25Linked to original sources

PubMed2000

Dental optical coherence tomography: a comparison of two in vitro systems.

OBJECTIVE: To compare the imaging results obtained with two different in vitro prototype dental optical coherence tomography (OCT) systems. METHODS: Two prototypes were evaluated: an 850 nm wavelength, 700 microW OCT system with a relatively low numerical aperture (0.03) and a 1310 nm wavelength, 140 microW system with a higher numerical aperture (0.20). RESULTS: Using the 850 nm system a characteristic scattering signal was observed that correlated with the depth of a periodontal probe. There was, however, insufficient light penetration to create images with adequate resolution. Improved image quality was achieved with the 1310 nm OCT system; these images had sufficient resolution to allow identification of anatomical structures important for the diagnostic assessment of oral structures. CONCLUSIONS: These results illustrate the improvement in imaging dental structures that can be obtained with a prototype 1310 nm OCT system. The feasibility of OCT as a dental imaging technique is verified.

Amplifiers, Electronic↗

PubMed2004

The accuracy of the cementoenamel junction identification on periapical films.

In the study of orthodontically induced inflammatory root resorption, many researchers use the cementoenamel junction (CEJ) as a bisecting reference point to measure the amount of root shortening. The accuracy of the identification of the CEJ point might affect the conclusions of those studies. This study aims to find the effects of angular changes between the tooth and the film on the validity and reproducibility of identifying three different CEJ points, ie, the most apical CEJ point between the crown and the root, the most mesial CEJ point, and the most distal CEJ point. An extracted maxillary central incisor was placed in a special jig and radiographed at four different tooth to film angulations. Eight examiners were asked to identify the buccal and palatal CEJ, whereas six examiners were asked to identify the mesial and distal CEJ points, all on a computer monitor. The distances between the identified points and the apex were computed and compared with the actual ones. The angular changes between the tooth and the film did have a statistically significant effect on the identification of some of these CEJ points. The difference was significant on the identification of the buccal and palatal points but not on the mesial and the distal ones.

Analysis of Variance↗

PubMed2003

Signs of carotid calcification from dental panoramic radiographs are in agreement with Doppler sonography results.

BACKGROUND: Duplex ultrasonography (DS) is a frequently used noninvasive method for assessing carotid artery stenosis. The level of agreement between panoramic radiographs (PMX) findings of radiopacities in the area of C3-C4 and DS results has not been established. AIMS: (1) to examine the level of agreement between DS results and PMX signs of carotid calcification and (2) to evaluate the association between periodontitis and DS results. MATERIAL AND METHODS: Eighty-three subjects who had received a DS assessment at the University of Washington Medical Center within 36 months volunteered for a periodontal examination, including assessments of probing pocket depth (PPD), attachment level (PAL), evidence of bleeding on probing and bone loss from PMX. Two examiners independently analyzed the radiographs for evidence of carotid calcifications. The distance between the cemento-enamel junction (CEJ) to bone level (BL) CEJ-BL was used to assess alveolar bone loss as a criteria for periodontitis. RESULTS: Twenty-nine subjects (34.9%) presented with positive DS readings. The Mantel-Haentszel common odds ratio estimate for a positive DS score and periodontitis (> 30% of teeth with distance CEJ-BL > or = 4.0 mm) was 38.4 (95% CI: 10.6-138.7, p < 0.0001). For nonsmokers only (n = 72) the odds ratio was 43.0 (95% CI: 16.7-1178.0, p < 0.0001). Evidence of bleeding on probing was 16% of sites both in the DS-positive and -negative subjects. Subjects with a positive DS result had significantly more teeth with clinical evidence of attachment loss > or = 5.0 mm (p < 0.001). The odds ratio of having periodontitis (CEJ-BL > or = 4.0 mm at > or = 30% of the teeth) and medical records confirmed diagnosis of either a stroke or an infarct or both was 7.8 (95% CI: 2.6-23.8, p < 0.001). CONCLUSIONS: Subjects with positive DS readings of the carotid arteries due to calcified arterial plaque are accurately detected by means of conventional PMX. The likelihood of being DS positive and having radiographic evidence of periodontitis is high. A dose-response relationship between the extent of carotid calcification and severity of periodontitis was demonstrated, supporting the hypothesis of an association between periodontitis and cardiovascular diseases.

Aged↗

PubMed2004

Effects of occlusal load on cervical lesions.

Toothbrush abrasion has been considered to cause cervical lesions. However, some investigators have proposed that occlusal loading factors direct tensile stresses at the cervical area, resulting in wedge-shaped abfraction defects. The purpose of this study is to investigate the role of axial and non-axial load on the development of cervical lesions. Matched paired premolars, extracted for orthodontic purposes, were used in a custom-fabricated toothbrushing apparatus. A periodontal sulcus width of 0b1 mm with 1 mm gingival recession was simulated with denture base resin. In phase 1, eight matched premolar pairs were subjected to 80 h (1b4 million strokes) of brushing and 300 g of toothbrush force. Toothpaste slurry was applied continuously through the toothbrush. One specimen in each pair was subjected to 250 h and 45 kg of continuous axial load, while the other unloaded tooth served as a negative control. In phase 2, 10 matched premolar pairs were subjected to the same conditions; however, the experimental teeth were subjected to 250 h and 45 kg of intermittent non-axial load, directed at a 45 degrees angle to the buccal cusp. Rubber impressions were made of the cervical lesions, then trimmed, weighed, and compared to determine the amount of tooth material lost. When teeth were loaded axially, there was significantly less tooth material loss (P < 0b02); however, when teeth were loaded non-axially, there was no significant difference (P =0b80) when compared with controls. Optical and scanning electron microscopy did not reveal any significant differences in the morphology between pairs. Our data suggest that the application of occlusal load may not necessarily play a significant role in the progression of cervical tooth wear commonly referred to as abfraction.

Bicuspid↗

PubMed1999

In vitro dentin pretreatment: surface roughness and adhesive shear bond strength.

The aim was to define the morphology and roughness of dentin from different tooth areas after various pretreatments to identify the effect of hybrid layer, resin tags, and mineralised dentin surface on shear bond strength. Thirty-eight extracted molars were used, each providing two sections of cervical (c) and lateral (l) dentin. Five pretreatments were performed: A) 0.2% EDTA; B) abrasion with Al2O3 particles, 0.2% EDTA; C) 10% H3PO4; D) 10% H3PO4 and immersion in a collagenase solution; E) control: no treatment. Z100 composite resin cylinders were bonded to the specimens with All Bond 2 bonding resin and tested for shear bond strength. Twelve other specimens from each group were analysed with an optical profilometer and an atomic force microscope, and four were further examined by scanning electron microscopy (SEM). Mean shear strength values in MPa were: Ac: 8.36 +/- 4.23; Al: 8.77 +/- 3.68; Bc: 6.05 +/- 3.62; Bl: 8.39 +/- 4.60; Cc: 6.87 +/- 3.45; Cl: 9.00 +/- 5.62; Dc: 13.30 +/- 5.45; Dl: 8.44 +/- 4.47; Ec: 4.10 +/- 1.54; El: 6.09 +/- 4.34. No statistically significant difference for cervical versus lateral dentin was found within treatments except for group D. Treatments performed on lateral dentin did not differ significantly. In cervical dentin, A differed from E; C from E; and D from A, B, C and E. An increased surface roughness was found in group D. Shear bond strength to dentin did not seem to depend on a hybrid layer formation, but on the direct contact of the adhesive with the mineralised dentinal surface and partly on the orientation of the dentinal tubules.

Acid Etching, Dental↗

PubMed2000

A comparison of the relative efficacies of four hand and rotary instrumentation techniques during endodontic retreatment.

AIM: The purpose of this study was to quantify the amount of remaining gutta-percha/scaler on the walls of root canals when two engine-driven instruments (Quantec and ProFile) and two hand instruments (K-file and Hedström file) were used to remove these materials. The amount of apically extruded debris and the time required for treatment were also recorded. METHODOLOGY: One hundred extracted mandibular premolars were prepared using a modified step-back, flare technique and obturated with the lateral condensation technique. After repreparation with the test instruments, the specimens were cut transversally at the cervical, middle and apical thirds with steel discs and the three sections were split longitudinally. The amount of residual debris on the canal walls in each section was examined using a stereomicroscope. RESULTS: In all groups the cervical and middle thirds showed no debris. In the apical third, obturating material was observed in some specimens. No statistically significant difference was found between the two groups for incidence of debris, although the Hedström group showed a greater number of samples with remaining gutta-percha/sealer. When analysing dirty specimens only, there was a statistically significant difference between the four groups (P < 0.01) with the Hedström group having significantly less length of canal wall with remaining obturation material than the Quantec group. There was no significant difference amongst the groups for weight of extruded debris. However, there was a significant difference amongst the groups for mean treatment time with the Hedström file group requiring significantly less time than the Quantec group (P < 0.001); no significant differences were found between the other groups. Six instruments fractured in the Quantec group, four in the ProFile group, two in the Hedström group and two in the K-type group. CONCLUSIONS: The results showed that overall, all instruments may leave filling material inside the root canal. During retreatment there is a risk of instrument breakage, especially rotary instruments.

Analysis of Variance↗

PubMed2001

Three phosphor plate systems and film compared for imaging root canals.

AIM: The aim of this study was to compare three phosphor plate intraoral imaging systems (Digora (DA), Digident (DT), Denoptix (DX)) and E-speed conventional film (CF) for the imaging of root canals. METHODOLOGY: Sixty extracted permanent teeth were exposed using CF, DA, DT and DX. The length of root canal visible from its most apical extent to a line drawn at the level of the cementoenamel junction was measured and this was expressed as a percentage of the distance between the radiographic apex and the cementoenamel line. All images were examined concurrently by two examiners. Films were viewed under standardized conditions and DA, DT and DX images were viewed directly from the monitor screen. The images on the monitor were enhanced to give the subjectively clearest image. RESULTS: The mean percentage of canal visible on CF was 90%, DA 78%, DT 81% and DX 83%. The difference was significant for CF-DA (P < 0.001) and CF-DT (P = 0.001). There was no statistically significant difference for CF-DX or between any of the three phosphor plate imaging systems. CONCLUSIONS: It is concluded that a greater length of root canal was visible on conventional film than on three phosphor plate imaging systems and that this may be of clinical significance.

Analysis of Variance↗

PubMed2002

The effect of instrument type and preflaring on apical file size determination.

AIM: The aim of this study was to investigate the effect of instrument type (K-files and Lightspeed (LS) instruments) and the impact of preflaring on the first file size that binds at working length (WL) in a range of canal types of varying sizes and curvatures. METHODOLOGY: One hundred and twenty-one canals from 60 extracted intact human maxillary and mandibular premolars and molars were utilized. After standard access cavities, a size 6 K-file was inserted into each canal until the tip of the file was visible outside the apical foramen. WL were set 0.5 mm short of these measurements. Each canal was sized using consecutively larger K-files and hand-held LS instruments until one bound at WL. The file sizes were recorded. The same procedures were repeated after coronal and middle third flaring using Profile rotary instruments. RESULTS: Statistical analysis (univariate analysis of variance: ANOVA) showed that overall, the estimate of mean apical diameter with the LS instrument was larger than with the K-file by 9.4 x 10(-2) mm (P < 0.001; 95% confidence interval: 8.7 x 10(-2), 10.2 x 10(-2)), i.e. almost 2 ISO file sizes larger. Flaring of the cervical and middle thirds of the canal had an impact on apical sizing by both types of instruments, with an average increase of 5.3 x 10(-2) mm (P < 0.001; 95% confidence interval: 4.5 x 10(-2), 6.0 x 10(-2)), i.e. approximately 1 ISO file size larger. CONCLUSIONS: Preflaring and use of hand-held LS instruments resulted in an increase in the instrument size that bound at WL. If an operator wishes to determine an accurate master apical file size, canal orifice enlargement should be performed first before the placement of the assessment file.

Analysis of Variance↗

PubMed1997

Aetiology, prevalence and clinical features of cervical dentine sensitivity.

Cervical dentine sensitivity (CDS) is a painful response to thermal, physical or chemical stimulation of the cervical area of the tooth. The reported prevalence of this clinical condition ranges from 8 to 35% depending on the population studied and methodology used to evaluate CDS. Detailed epidemiology is lacking with regard to possible causal factors. Well conducted studies in larger populations using accepted standardized methodology for both questionnaire and clinical examination are essential if these factors are to be identified and the condition successfully prevented and treated. This paper reviews current literature on the prevalence, aetiology and oral distribution of this troublesome condition.

Dentin Sensitivity↗

PubMed1997

The effect of dentine thickness on diffusion of resin monomers in vitro.

Forty extracted human third molar teeth were divided into four groups, each of 10 teeth, to test the hypothesis that dentine thickness variation influences diffusion of the monomers 2-hydroxyethylmethacrylate (HEMA) and triethylene glycol dimethacrylate (TEGDMA) from light-cured bonding resin-composite resin restorations to the pulp space. An occlusal cavity 6 mm in diameter was prepared in each tooth of four groups with remaining dentine thickness of 3.4-3.6, 2.4-2.6, 1.4-1.6 and 0.4-0.6 mm, respectively. A polypropylene chamber was attached to the cemento-enamel junction of each tooth to contain 1 mL of distilled water. Each cavity was treated with Scotchbond Multipurpose (3 M, U.S.A.) then restored with Z100 (3 M) and light activated for 30 s. Water samples were retrieved over a time course up to 30 days and analysed by high performance liquid chromatography. Both HEMA and TEGDMA were detected in the pulp samples for all teeth. Decreasing dentine thickness substantially increased pulpward diffusion rate of both HEMA and TEGDMA during the first day after placement, as well as the total release of both components from a bonding resin-composite combination in vitro.

Chromatography, High Pressure Liquid↗

PubMed1997

Clinical evaluation of cervical dentine sensitivity in a population of patients referred to a specialist periodontology department: a pilot study.

The prevalence of tooth sensitivity [Cervical Dentine Sensitivity (CDS)] in adult populations indicates that 8-35% of subjects reported CDS depending on the population studied and the methodology used. Few studies, however, have reported on the prevalence of CDS in periodontal patients. The aim of the study was to determine the prevalence, severity and distribution of CDS in patients referred for specialist periodontal diagnosis. Fifty-one patients [27 male, 24 female; mean age 48.5 years (standard deviation 11.63)] who gave their informed written consent were clinically evaluated for CDS using recognized methods of assessment, namely Yeaple probe, cold air blast and subjective evaluation. Other clinical variables (e.g. plaque and recession scores) were also recorded at this visit. Regression analysis and correlation coefficients were used to determine the relationship between the clinical variables. The results demonstrated a prevalence of CDS ranging between 72.5 and 98% of patients, with no significant gender difference. Results for the distribution of tooth types showed that molar teeth were mainly affected, followed by left canines and premolars. No correlation was noted between plaque, recession, response to tactile or thermal stimulation. Pain response from tactile and thermal stimulation showed no significant difference between tooth surfaces. Cold stimulation was perceived to be the dominant pain-producing stimulus as had been previously reported. The results of this investigation support those from another study, which found the prevalence of CDS to be higher in periodontal patients than has been reported elsewhere. This finding would suggest that previous periodontal treatment and/or periodontal disease may play a role in the aetiology of CDS.

Adolescent↗

PubMed1997

Proximo-cervical adaptation of Class II-composite restorations after thermocycling: a quantitative and qualitative study.

Sixty caries-free extracted human molars were used to determine the proximo-cervical adaptation and sealing of Class II-composite restorations related to the location of the cavity margins: 1.0 mm or 0.5 mm coronal to the cementum-enamel-junction (CEJ), at the CEJ, and 0.5 mm apical to the CEJ. All cavities were filled with a hybride type composite resin, which was combined at the CEJ and apical to the CEJ with a dentine adhesive in half of the specimens. The proximo-cervical adaptation and sealing was determined before and after thermocycling (TC, 2000 cycles, 5-55 degrees C) by SEM and dye penetration tests. Furthermore, an analysis of the interfaces between the enamel or dentine and the filling material was performed to determine whether or not there is a significant correlation between micromorphological factors of the dental hard tissues (enamel acid etch pattern, dentine resin tag pattern) and the marginal adaptation of the composite restorations. The data were statistically evaluated by means of H-tests (Kruskall-Wallis), U-tests (Mann-Whitney), and Chi2-tests (P < 0.05). It was found that the proximo-cervical adaptation is statistically significant dependent on the position of the margin. 1.0 mm coronal to the CEJ an excellent marginal sealing was found before and after TC, whereas all other groups revealed a significant deterioration of the marginal integrity after TC. Using a dentine adhesive significantly improved the marginal sealing in cavities at the CEJ before and after TC, however the marginal quality was not achieved as in the case of the normally structured enamel 1.0 mm coronal to the CEJ following acid etching. In defects 0.5 mm apical to the CEJ the dentine adhesive only improved the cervical adaptation before TC. The evaluation of the tooth/filling interfaces revealed that there is no statistically significant correlation between the enamel acid etch pattern resp. dentine resin tag pattern and the marginal sealing.

Acid Etching, Dental↗

PubMed1998

Component release from light-activated glass ionomer and compomer cements.

The purpose of this study was to identify and quantify any component released from seven commercially available light-cured or resin-modified glass ionomer and compomer cements. Twenty-one separate cylindrical stainless steel moulds 6 mm in diameter and 1.0 mm deep were filled with one of seven glass ionomer or compomer cements, light activated and then immediately immersed in separate containers of distilled water. Water samples were retrieved over a time period of up to 30 days and retained for analysis. An occlusal cavity 6 mm in diameter was prepared in extracted human third molar teeth with a remaining dentin thickness of 1.6-2.0 mm. A polypropylene chamber was attached to the cemento-enamel junction of each tooth to contain 1 mL of distilled water. Ten teeth were each filled with one of three cements and light activated. Water samples (eluates) were retrieved over a period of time. All samples were analysed by high performance liquid chromatography. Only one component, hydroxyethyl methacrylate (HEMA), was detected in the eluates from both tooth and mould samples. Analysis of diffusion of the HEMA through dentin showed a relatively sustained movement into the pulp space during the first day, with exponential decline thereafter. Our data show that HEMA was released from all of the light activated glass ionomer cements studied and from the compomer, both directly into water and through dentin. This release may be relevant both to the risk of adverse pulpal responses in patients and to the risk of allergy in patients and dental personnel.

Chromatography, High Pressure Liquid↗

PubMed1999

The influence of finishing time on the marginal seal of a resin-modified glass-ionomer and polyacid-modified resin composite.

The aim of this study was to compare the effect of immediate and delayed finishing on the microleakage of encapsulated resin-modified glass-ionomer, Fuji II LC and a polyacid-modified resin composite, Dyract compomer at both the enamel and dentine margins. Standardized Class V cavities were prepared along the cemento-enamel junction on buccal and palatal surfaces of 24 freshly extracted non-carious premolars. Equal numbers of buccal and palatal cavities in each group were restored with Fuji II LC and Dyract compomer following the manufacturer's instructions. The groups with delayed finishing were restored 1 week earlier, stored in saline at 37 degrees C and finished on the same day as the groups with immediate finishing. The specimens were then thermocycled 500 times and subjected to dye penetration testing. The results showed that both materials leaked more at the dentine than enamel margins for both regimes of finishing methods. There was no statistical difference in the microleakage of Dyract finished immediately or later at enamel and dentine margins and Fuji II LC finished immediately or later in dentine. However, a statistical difference existed between the microleakage in Fuji II LC finished immediately and later in enamel.

Bicuspid↗

PubMed2000

The effect of polishing systems on microleakage of tooth coloured restoratives: Part 1. Conventional and resin-modified glass-ionomer cements.

The purpose of this in vitro study was to investigate the effect of polishing systems on the microleakage of conventional and resin-modified glass-ionomer cements. Class V cavities were prepared at the cemento-enamel junction of 80 freshly extracted posterior teeth. The prepared teeth were randomly divided into two groups and restored with conventional or resin-modified glass-ionomer cements. The restored teeth were stored in distilled water at 37 degrees C for 1 week after removal of excess restorative with diamond finishing burs. The restored teeth were then divided into four groups of 10 and finished and polished using the following systems: Two Striper MFS; Sof-Lex XT; Enhance Composite Finishing and Polishing System; Shofu Composite Finishing Kit. The finished restorations were subjected to dye penetration testing. Results showed that the microleakage at dentin margins of conventional glass-ionomer cements and enamel margins of resin-modified glass-ionomer cements are significantly affected by the different polishing systems.

Analysis of Variance↗

PubMed2000

The effect of polishing systems on microleakage of tooth-coloured restoratives. Part 2: composite and polyacid-modified composite resins.

The purpose of this in vitro study was to investigate the effect of polishing systems on the microleakage of composite and polyacid-modified composite resins. Class V cavities were prepared at the cemento-enamel junction of 80 freshly extracted posterior teeth. The prepared teeth were randomly divided into two groups and restored with conventional or polyacid-modified composite resins. The restored teeth were stored in distilled water at 37 degrees C for 1 week after removal of excess restorative with diamond finishing burs. The restored teeth were then divided into four groups of ten and finished/polished using the following systems: Two Striper micron finishing system (MFS), Sof-Lex XT (Sof-Lex), Enhance composite finishing and polishing system (Enhance), and Shofu composite finishing kit (Shofu). The finished restorations were subjected to dye penetration testing. Results showed that the microleakage resistance at both enamel and dentin margins of composite and polyacid-modified composite resins are not significantly affected by the different polishing systems.

Adhesives↗

PubMed2000

A natural tooth's stress distribution in occlusion with a dental implant.

The loss of one or more teeth is normally treated with conventional fixed or removable partial dentures or with implant supported fixed or removable dentures. This study investigated stresses formed around the implant and the antagonist natural tooth under occlusal force in the substitution of a missing lower first molar with a rigid or resilient IMZ (Intra Mobil Zylinder) implant, using the finite element stress analysis method. The results indicate that a bite force of 143 N resulted in high compressive stresses around the roots of a natural tooth opposing a restoration supported by an IMZ implant with rigid type abutment. It is speculated that these high compressive stresses may contribute to intrusion of the tooth.

Bite Force↗

PubMed2001

The efficiency of dentine adhesives in treating non-caries cervical lesions.

The aim of this study was to prove the hypothesis that dentine adhesives can be used as therapeutic material in treating dentine hypersensitivity, regardless of aetiology. The research was conducted on 492 students of Zagreb University School of Dental Medicine (154 male, 338 female), 20-25-years-old. The defects of the tooth neck were found in 38 patients, on 133 teeth (38 of male patients, 95 of female) and dentine hypersensitivity was recorded according to the subjective sensations of patients. Therapeutic characteristics of three adhesive materials were examined simultaneously: All Bond 2, fourth generation adhesive, Syntac Single Component and One Step, fifth generation adhesives. Teeth treated with dentine lacquer Cervitec were used as a control group. Tooth necks were treated with selected materials according to instructions of a manufacturer. A completed statistical survey of the results has clearly shown that dentine adhesives can be used in symptomatic therapy of dentine hypersensitivity of the non-caries cervical lesions (NCCL). The survey has also shown that dentine adhesives of the fifth generation (Syntac Single Component and One Step) have much higher efficiency rate than dentine adhesives of the fourth generation (All Bond 2) and dentine lacquer (Cervitec). According to data complied through this study the conclusion can be brought forward that dentine adhesives are not a final solution to the problem of dentine hypersensitivity, because their efficiency decreases with time.

Adult↗