Roots Of Human Teeth Research Articles

In vitro bactericidal activity of recombinant human β-defensin-3 against pathogenic bacterial strains in human tooth root canal

Human β-defensin-3 (HBD3), an endogenous antimicrobial peptide, has strong broad-spectrum antimicrobial activity. This study aimed to obtain recombinant HBD3 (rHBD3) and to test the hypothesis that the antimicrobial characteristics of HBD3 may offer an advantage over conventional medicine in reducing intracanal bacteria. Genetic engineering was used to obtain active rHBD3 and analysis revealed that it exhibited a broad spectrum of antibacterial activity at low micromolar concentrations against not only Staphylococcus aureus and Escherichia coli but also against some critical pathogenic microbes in infected root canals, including Fusobacterium nucleatum, Prevotella melaninogenica, Peptostreptococcus anaerobius, Streptococcus mutans, Actinomyces naeslundii, Enterococcus faecalis and Candida albicans. In an in vitro antibacterial experiment, rHBD3 significantly eliminated pathogenic bacteria in root canals. The ratio of bacterial death was up to 98%. We conclude that HBD3 has the potential to eliminate bacteria effectively and rapidly in the local microenvironment of the root canal system and that it may contribute to successful endodontic treatment.

Biofilm on the apical region of roots in primary teeth with vital and necrotic pulps with or without radiographically evident apical pathosis

To evaluate, by scanning electron microscopy (SEM), the presence of biofilms on the external surfaces of the apical third of roots of human primary teeth with vital or necrotic pulps with and without radiographically evident periradicular pathosis. Eighteen teeth were selected: group I - normal pulp (n = 5), group II - pulp necrosis without radiographic evidence of periapical pathosis (n = 7) and group III - pulp necrosis with well-defined radiographic periapical pathosis (n = 6). After extraction, the teeth were washed with saline and immersed in 0.03 g mL(-1) trypsin solution for 20 min. The teeth were then washed in sodium cacodilate buffer and stored in receptacles containing modified Karnovsky solution. The teeth were sectioned, dehydrated in an ethanol series, critical-point dried with CO(2), sputter coated with gold and the external root surface in the apical third examined by SEM. In the teeth of groups I and II, the apical root surfaces were covered by collagen fibres, with no evidence of bacteria (100%). In the teeth of group III, the root apices had no collagen fibres but revealed resorptive areas containing microorganisms (cocci, bacilli, filaments and spirochetes) in all cases (100%). Microorganisms organized as biofilms on the external root surface (extraradicular infection) were detected in primary teeth with pulp necrosis and radiographically visible periapical pathosis.

Impedance Characteristics of Mimic Human Tooth Root Canal and Its Equivalent Circuit Model

This investigation examined the complicated impedance characteristics of the human tooth root canal using a mimic system that comprised a cylindrical tubule and 5% agar-gel. The in vitro impedance measurements of root canals were made using a frequency response analyzer and a tubule filled with distilled water or normal saline. An equivalent circuit model of this bioelectric system was proposed; it closely corresponds to the experimental results. On the basis of the proposed equivalent circuit model, the experimental results can be explained reasonably and the effect of the filling of the canal with the electrolytes can be clearly understood. The modified impedance quotient and the variation ratio of the impedance quotient are taken as the useful indices of the apex. Different impedance behaviors have been identified from values in under-apex and over-apex regions, respectively. The was at the apex location as well as in the overapex region for all electrolytes and could be used to eliminate the effect of the electrolytic conductivity. This study elucidates the complicated electric mechanisms of electrolytic systems and improves clinical applications in the endodontic treatment.

Preliminary observations on increasing root length during the eruptive phase of tooth development in modern humans and great apes

Ground sections of incisors, canines, and molars were selected that showed clear incremental markings in root dentine. The sample comprised 98 Homo sapiens, 53 Pan troglodytes, and a more limited combined sample of 51 Gorilla and Pongo sections. Daily rates of root dentine formation, together with the orientation of incremental markings in roots close to the cement-dentine junction (CDJ), were used to calculate root extension rates for the first 10 mm of root formed beyond the buccal enamel cervix. Modern human anterior tooth roots showed a more regular pattern of increase in root length than those in great apes. In Pan, root growth rose quickly to higher rates but then flattened off. The fastest extension rates in modern humans were in incisor roots (10–12 μm per day), followed by canines (8–9 μm per day). Extension rates in Pan rose to slightly greater values in canines (∼12–14 μm per day) than in incisors (∼10–11 μm per day). Molar tooth roots in both modern humans and great apes grew in a nonlinear manner. Peak rates in molars reduced from M1 to M3 (8, 7, and 6 μm per day, respectively). Like humans, root growth in Pan peaked earlier in M1s at rates of between 8 and 9 μm per day, and later in M3s at rates of 7 to 8 μm per day. The more limited data set for Gorilla and Pongo molars suggests that extension rates were generally higher than in Pan by approximately 1.0–1.5 μm per day. There were greater differences in peak extension rates, with Gorilla and Pongo extension rates being between 2.5 and 4.5 μm per day higher than those in Pan. These findings highlight for the first time that root growth rates differ between tooth types in both pattern and rate and between taxa. They provide the basis with which to explore further the potential comparative relationships between root growth, jaw growth, and the eruption process.

Alternative Adhesive Strategies to Optimize Bonding to Radicular Dentin

This study tested the hypothesis that bond strengths of filling materials to radicular dentin might be optimized by using an indirect dentin bonding procedure with an acrylic core material. Roots of human teeth were endodontically prepared and obturated with EndoREZ, Epiphany, or the bonding of an acrylic point with SE Bond by using a direct or an indirect bonding technique. Bond strengths of endodontic sealers to radicular dentin were measured with a thin slice push-out test. Push-out strengths of EndoREZ and Epiphany to radicular dentin were less than 5 megapascals (MPa). The direct bonding technique with acrylic points and the self-etching adhesive had push-out strengths of 10 MPa, increasing to 18 MPa with the indirect technique. The use of the indirect bonding protocol with an acrylic point to compensate for polymerization stresses appears to be a viable means for optimizing bond strengths of endodontic filling materials to radicular dentin.

The antimicrobial efficacy of the erbium, chromium:yttrium-scandium-gallium-garnet laser with radial emitting tips on root canal dentin walls infected with Enterococcus faecalis

The authors used an in vitro model to investigate the ability of an erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser with radial emitting tips to disinfect Enterococcus faecalis-infected dentin. The in vitro infected-dentin model system consisted of a dentin cylinder, prepared from a human anterior tooth root, cemented into a sealable two-chamber device fabricated from a syringe needle cap. The model's lower chamber contained a buffer solution, and the dentin cylinder was placed between the upper and lower chambers. After sterilization, the authors inoculated the root canal of each dentin cylinder with E. faecalis. They used an Er,Cr:YSGG laser with radial emitting tips to irradiate the root canal of each infected dentin cylinder (varying laser power and exposure time). After laser treatment, the authors machined the root canal dentin walls and collected the resulting dentin fillings in the buffer-reservoir. They quantified the E. faecalis titer of each buffer-reservoir by using selective agar plates. The authors found that bacterial recovery decreased when laser irradiation duration or power increased. A greater degree of disinfection was achieved with a 120-second application of laser than with sodium hypochlorite treatment. Finally, they found that a 99.7 percent reduction in bacterial counts could be obtained using the laser. The results of this study suggest that the Er,Cr:YSGG laser with a radial emitting tip has a significant antimicrobial effect on dentinal tubules infected with E. faecalis. Er,Cr:YSGG laser treatment could be a valuable tool for root canal disinfection during endodontic treatment.

Antibacterial effect of root canal preparation and calcium hydroxide paste (Calen) intracanal dressing in primary teeth with apical periodontitis

The aim of this study was to evaluate the antibacterial action of root canal mechanical preparation using 2.5% sodium hypochlorite as the irrigating solution and a calcium hydroxide paste as the antibacterial intracanal dressing in human primary teeth root canals with pulp necrosis and apical periodontitis by means of microbial culture. A total of 26 root canals of human primary teeth with pulp necrosis and apical periodontitis were used. Samples were collected before, 72h after biomechanical treatment and 72h after removal of the intracanal dressing. Comparison by Wilcoxon test showed that root canal mechanical preparation effectively eliminated all microorganisms in 20% of the root canals, and the intracanal dressing in 62.5%; however, the cumulative action of biomechanical treatment and intracanal dressing eliminated the microorganisms of 70% of the root canals (p<0.001). Isolated root canal mechanical preparation presented poorer microbiological results that those obtained with root canal mechanical preparation and the use of an intracanal dressing indicating the necessity of topical application of an intracanal medication between sessions in primary teeth with pulp necrosis and apical periodontitis.

The potential for dental plaque to protect against erosion using an in vivo‐in vitro model — A pilot study

Tooth erosion is a problem for professional wine tasters (exogenous erosion from frequent exposure to wine acids) and for people with gastro oesophageal reflux disease (GORD) and bulimia who experience frequent reflux of gastric contents into the mouth (endogenous erosion from mainly HCl). The objective in this study was to determine whether plaque/pellicle could provide teeth with any protection from two common erosive acids, using an in vivo-in vitro technique. Tiles of human tooth enamel and root surfaces were prepared from six extracted, unerupted third molar teeth and sterilized. Mandibular stents were prepared for six volunteer subjects and the tiles bonded to the buccal flanges of these stents. They were worn initially for three days to permit a layer of pellicle and plaque to form over the tile surfaces, and for a further 10 days of experimentation. Following cleaning of the plaque/ pellicle layer from the tiles on the right side flange, all the tiles were submerged in either 0.06M HCl or white wine for an accumulated time of 600 and 1500 minutes, respectively. Depths of erosion were determined using light microscopy of sections of the enamel and root tiles. SEM of the lesion surfaces was carried out to investigate the nature of erosive damage and of plaque/pellicle remnants. Retained plaque was found to significantly inhibit dental erosion on enamel, from contact with both HCl and wine, compared with that resulting following its removal. However, it was found to provide no significant protection on root surfaces. SEM analysis of the tile surfaces revealed marked etching of enamel on the cleaned surfaces, and considerable alteration to the appearance of remaining plaque and pellicle on most surfaces. Within the limitations of numbers of specimens, dental plaque/pellicle provided a significant level of protection to tooth enamel against dental erosion from simulated gastric acids and from white wine, using an in vivo-in vitro model. It was unable to provide any significant protection to root surfaces from these erosive agents. Possible reasons for this difference are explored.

Temperature evolution on human teeth root surface after diode laser assisted endodontic treatment

The thermal rise threshold of an 810-nm semi-conductor diode laser on the root surface when used in root canals in vitro for laser assisted root canal treatment is investigated in this study. A total of 50 human single-rooted extracted teeth were included. For this study, the canals were enlarged up to an apical size of ISO#50 file. Laser irradiation was performed with six different settings. Specimens were irradiated at 0.6-1 W output power at the distal end of the fiber and about 1-1.5 W output power in the continuous mode (CW) as two groups. In the third group, 0.6-1 W output power, 10 ms pulse length (PL) and 10 ms interval duration (ID) were selected. In three other groups 1-1.5 W output power were used with different PL and ID as following: PL 10 and ID 10 ms, PL 10 and ID 20 ms and PL 20 and ID 20 ms. The total irradiation time was from 5 to 20 s per canal with a 200 mum in diameter and 25 mm long tip. After laser treatment, the temperature changes at the outer root surface were registered by means of NiCr-Ni measuring sensors and a T 202 thermometer. The safe temperature threshold for applying this diode laser in root canal is considered as 7 degrees C increase. To avoid increasing the temperature changes at the outer root surface related to this threshold, following total irradiation times were found: 0.6-1 W output power (10 ms PL/10 ms ID): 20 s (s), 1-1.5 W output power (10 ms/10 ms and 20 ms/20 ms): 15 s, 0.6-1 W output power CW and 1-1.5 W output power (20 ms PL/10 ms ID): 10 s and 1-1.5 W output power CW: 5 s. In the first three groups, 5 s irradiation and 5 s rest period avoided a temperature increase above the threshold of 7 degrees C).

Effects of enamel matrix proteins on tissue formation along the roots of human teeth

Enamel matrix-derived proteins (EMD) are thought to trigger the formation of acellular extrinsic fibre cementum (AEFC), while other reports indicate that EMD may have osteogenic potential. The aim of the present study was to characterize the tissues developing on the root surface following application of EMD. Twelve human periodontitis-affected teeth, scheduled for extraction, were treated with EMD. Two to 6 weeks later, the teeth were extracted, demineralized and processed for embedding in acrylic and epoxy resins. New tissue formation was analysed by light and transmission electron microscopy. New tissue formation on the root was observed in the notch and on both scaled and unscaled root surfaces distant of the notch area in six defects. The newly formed tissues on the root were thick, collagenous, devoid of extrinsic fibres, and had an irregular surface contour. The presence of electron-dense, organic material in the collagenous matrix indicated at least partial mineralization. Embedded cells were numerous and the cells on the matrix surface were very large in size. Abundant rough endoplasmic reticulum and a prominent Golgi complex were evident. The presence of a split between the treated root surfaces and the newly formed tissue was a common observation, as was the presence of bacteria and host cells in the interfacial gap. Following treatment with EMD, a bone-like tissue resembling cellular intrinsic fibre cementum may develop on the root surfaces, instead of AEFC. Furthermore, EMD may both induce de novo formation of a mineralized connective tissue on scaled root surfaces and stimulate matrix deposition on old native cementum. Interfacial bonding appeared to be weak after 6 weeks of healing.

Spatial distribution of lead in the roots of human primary teeth

Lead remains one of the most hazardous metals in our environment. The concentrations of lead in coronal dentine and enamel have previously been reported but limited information is available regarding lead levels in radicular dentine and cementum. This study reports the distribution of lead in 26 roots of 16 human maxillary primary teeth from seven individuals. In addition, calcium and phosphorous concentrations were also measured to detect any variations in the degree of mineralization in different regions of the roots. The mean lead concentration in these roots was 1.67±1.43 μg/g, which is comparable to other studies. In all cases there were higher lead concentrations in the apices of non-resorbed roots of primary maxillary teeth relative to middle and cervical regions. The findings reported here are of potential significance during the process of physiological root resorption whence periapical tissue may be exposed to higher levels of lead.

Root resorption of human deciduous teeth with apical periodontitis by cultured osteoclasts

Roots of human deciduous teeth with apical periodontitis frequently show abnormal resorption as well as cementum deposition, and features that are different from those of physiological root resorption. The aim of this study was to determine the relationship between the appearance of cultured osteoclasts and the condition of dentin slices of human deciduous teeth. Bone marrow obtained from femora of 3- and 4-week-old male C57BL/6 mice was used for cell culture. The cells used in this study were osteoclasts, bone cells and bone marrow cells. Root dentin slices were prepared from human deciduous teeth with apical periodontitis (group and from sound deciduous teeth (group 2, control group). The dentin surfaces were polished with grindstones. Cell suspension in α-MEM supplemented with 10% fetal bovine serum was seeded on the dentin slices and incubated for 96 hours at 37°C under 5% CO 2 in air. After incubation, specimens were removed and fixed with glutaraldehyde and paraformaldehyde, and then tartrate-resistant acid phosphatase (TRAP) activity, which is considered to be specific to osteoclasts and odontoclasts, was detected. The number of TRAP-positive cells on the dentin were calculated by light microscopic observation. Specimens were then prepared and observed under a scanning electron microscope (SEM). TRAP-positive cells, visible as small red dots, were observed on dentin slices of both groups (n=50: each group). The densities of TRAP-positive cells in group 1 and group 2 were 2.98 ± 2.57 cells/mm 2 and 2.90 ± 2.22 cells/mm 2 , respectively. The difference between densities of TRAP-positive cells in group 1 and group 2 was not significant by the Mann-Whitney U-test ( P > 0.05). Shallow resorbed lacunae were observed on the specimens by scanning electron microscopy. It was shown that root dentin with apical periodontitis was resorbed by clastic cells such as cultured osteoclasts, suggesting that cell growth on dentin is not affected by apical periodontitis.

Prevalence of microorganisms in root canals of human deciduous teeth with necrotic pulp and chronic periapical lesions.

The objective of this study was to evaluate bacterial prevalence in 31 root canals of human deciduous teeth with necrotic pulp and periapical lesions using bacterial culture. After crown access, the material was collected using absorbent paper points for microbiological evaluation and determination of colony forming units (CFU). Anaerobic microorganisms were found in 96.7% of the samples, black-pigmented bacilli in 35.5%, aerobic microorganisms in 93.5%, streptococci in 96.7%, and S. mutans in 48.4%. We concluded that in human deciduous teeth root canals with necrotic pulp and periapical lesions the infection is polymicrobial, with a large number of microorganisms and a predominance of streptococci and anaerobic microorganisms.

Patterns of Vertical Root Fracture: Factors Affecting Stress Distribution in the Root Canal

Previous studies have indicated that vertical root fracture tends to occur in a buccolingual direction, where dentin thickness is greatest. Factors potentially influencing the location and direction of root fracture include root canal shape, external root morphology, and dentin thickness. In this finite-element study, simulated root sections were varied systematically with respect to canal size and shape, external root morphology, and dentin thickness to determine their relative contribution to vertical root fracture. Similar models were constructed based on cross-sections of human tooth roots that had been fractured clinically or experimentally. Finite-element models demonstrated that canal curvature seems more important than external root morphology, in terms of stress concentration, and that reduced dentin thickness increases the magnitude but not the direction of maximum tensile stress. Models based on actual root fractures showed a strong similarity between tensile-stress distribution and fracture patterns.

Effect of a high power diode laser irradiation in root canals contaminated with Enterococcus faecalis. “In vitro” study

The purpose of this study was to evaluate the effectiveness of a high power diode laser irradiation to reduce bacteria in contaminated canals, and to analyze the effect of irradiation associated with paste of calcium hydroxide plus paramonochlorophenol camphorated. Eighty-two human teeth root canals, infected with Enterococcus faecalis suspension (1×10 8 CFU/ml), were irradiated with a high power diode laser (830 nm), using 2.5W and 3W (CW), 360 μm fiber. Temperature was monitored at apex with a K-pipe thermocouple. Maximum Δ T was 7.45 °C. Aliquots were plated and CFU of all groups was counted. The results showed a significant reduction of bacteria on all groups after laser irradiation. The structural and morphological changes of root canal walls dentin produced by the diode laser irradiation were evaluated under a scanning electron microscope (SEM).

Correlation between clinical success and apical dye penetration.

This study was undertaken to examine whether a correlation exists between apical dye penetration and the clinical performance of root fillings. Apical dye penetration into 116 roots of human teeth that had been root-filled at least 6 months prior to extraction was tested in vitro using a vacuum technique and by measuring the length of dye penetration. Endodontic treatment was classified as clinically successful or unsuccessful and results for these groups were compared using analysis of variance and the Student's t-test. Positive and negative controls were used to test the experimental system. All controls performed as expected. Dye penetrated significantly further in unsuccessful cases although the raw data suggested little difference. Overall, dye penetrated 99.5% of the specimens, indicating that the presence of dye in the canal is a poor indicator of whether the technique or material will succeed. However, the extent of dye penetration may be related to the clinical outcome. Clinically placed root canal fillings do not provide an apical seal that prevents fluid penetration. The outcome of treatment cannot be predicted from the results of apical dye leakage studies.

Physical properties of root cementum: Part I. A new method for 3-dimensional evaluation.

Cementum is a nonuniform connective tissue that covers the roots of human teeth. Investigation of the physical properties of cementum may help in understanding or evaluating any possible connection to root resorption. A variety of engineering tests are available to investigate these properties. However, the thickness of the cementum layer varies, and this limits the applicability of these techniques in determining the physical properties of cementum. Hardness testing with Knoop and Vickers indentations overcame some of these limitations, but they prohibited the retrieval and retesting of the sample and therefore the testing was restricted to one area or section of the tooth. Another limiting factor with the existing techniques was the risk of artifacts related to the embedding material such as acrylic. A new method to investigate the physical properties of human premolar cementum was developed to obtain a 3-dimensional map of these properties with the Ultra Micro Indentation System (UMIS-2000; Commonwealth Scientific and Industrial Research Organization, Campbell, Australia). UMIS-2000 is a nano-indentation instrument for investigation of the properties of the near-surface region of materials. Premolars were harvested from orthodontic patients requiring extractions and then mounted on a newly designed surveyor that allowed sample retrieval and 3-dimensional rotation. This novel method enabled the quantitative testing of root surface cementum, on all 4 root surfaces, extending from the apex to the cementoenamel junction at 60 different sites.

A novel in vitro model system to grow films of oral bacteria for the study of human tooth root surface caries.

To develop a simple and flexible novel in vitro model system to grow films of oral bacteria that could be used to study aspects of dental caries. Standardized suspensions of bacteria were inoculated into Ultrafree-CL (Millipore) ultrafiltration units at various densities. These were incubated for varying time intervals with a range of carbon sources. The bacterial films reproducibly achieved between 107 and 108 cfu cm-2, irrespective of the number inoculated and with no significant changes for 14 d. However, Streptococcus mutans grew through membranes with pores of diameter greater than 0.1 microm after 6 d. Culture of films in sucrose or water for 6 d led to a decreased number of colony-forming units, but returning them to broth reversed this. Reproducible films of oral bacteria can be cultured in Ultrafree-CL units. This study has shown that Ultrafree-CL units can be used as a simple model system to grow biofilms that could be used for dental caries research.

Prevalence and extent of long oval canals in the apical third

The aim of this study was to investigate the canal diameters in the apical roots of human teeth to determine prevalence and extent of long oval canals. This investigation was carried out on 180 extracted human teeth, 20 for each tooth group. Each root was horizontally sectioned at 1, 2, 3, 4, and 5 mm from the apex. Canal diameters were measured with a measuring microscope. In 293 (25%) of the 1181 cross sections investigated, a long oval canal (the long canal diameter was at least 2 times the short canal diameter) was identified. In some tooth groups, the percentage of long oval canals exceeded 50%. In most cases, the long diameter decreased apically; that is, the canal tended toward a rounder cross section. A wide range of diameters existed in all canals. Long oval canal is common in the apical 5 mm in human teeth. Many long and narrow oval canals would be impossible to instrument completely without perforating or significantly weakening the roots. Care should be taken in cleaning, shaping, and obturating these oval canals.

Distribution of Interglobular Dentine in Human Tooth Roots

The present study was designed to examine the distribution of interglobular dentine in human tooth roots. The material comprised 17 teeth, of which 3 were premolars extracted for orthodontic reasons from children 10–12 years of age and the other teeth (4 incisors, 3 canines and 7 molars) were extracted for periodontitis from individuals aged 32–63 years. All teeth were free of caries and cervical dentine defects. Ground sections of the teeth cut longitudinally were stained with basic fuchsin and observed by fluorescence and confocal microscopy as well as transmitted light microscopy. Basic fuchsin stained the dentinal tubules, interglobular dentine and the granular layer of Tomes. These structures appeared intense blue to faint violet with transmitted light microscopy, whereas their staining displayed intense fluorescence with fluorescence microscopy. Therefore, the interglobular dentine could be detected more sensitively with fluorescence and confocal microscopy than with transmitted light microscopy. Typical interglobular dentine was present in coronal dentine in most of the teeth. In the radicular dentin, position and size of the interglobular dentine was different among the teeth examined. Most of the teeth had the interglobular dentine in the cervical part of the roots (type A). Two premolars displayed the interglobular dentine in the coronal half of the root (type B). The types A and B contained large interglobular areas. A small amount of interglobular dentine was restricted to the apical half of the roots of two canines and one molar (type C). In contrast to types A and B which were seen at both labial or buccal and lingual sides of roots, the interglobular dentine of type C was seen only at one side, labial or lingual. Some of the tooth roots did not show any interglobular dentine (type D). Most of the incisors, canines and premolar were types A, B, and C, respectively, and the molars were mixed types A, C, and D. These results suggest that the factors affecting dentinogenesis during root formation are unique for each tooth.