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PubMed2006

Methods for assessment of dental erosion.

Various assessment techniques have been applied to evaluate the loss of dental hard tissue and the surface-softened zone in enamel induced by erosive challenges. In this chapter, the most frequently adopted techniques for analyzing the erosively altered dental hard tissues are reviewed, such as profilometry, microradiography, scanning electron microscopy, atom force microscopy, nano- and microhardness tests and iodide permeability test. Moreover, methods for chemical analysis of minerals dissolved from dental hard tissue are discussed. It becomes evident that the complex nature of erosive mineral loss and dissolution might not be comprehended by a single technique, but needs application of different approaches for full understanding.

Fluorescence↗
PubMed1998

[The role of cell adhesion molecules in the formation of periapical granulomas].

Cell adhesion molecules (CAMs) are cell surface proteins involved in the binding of cells, usually leukocytes, to each other, to endothelial cells, or to extracellular matrix. Specific signals produced in response to wounding and infection control the expression and activation of certain of these adhesion molecules. The interactions and responses then initiated by binding of these CAMs to their receptors/ligands play important roles in the mediation of the inflammatory and immune reactions that consult one line of the body's defense against these insults. Most of the CAMs characterized so far fall into three general families of proteins: the immunoglobulin (Ig) superfamily, the integrin family, or the selectine family. Recent studies have indicated that selectins (E,L,P) are implicated in cell trafficking, an important aspect of inflammation-related process. Regulation of white blood cell trafficking from the blood vascular compartment to regions of pathogenic exposure is one of the most important functions of the immune system. The distinct phases of leukocyte migration include: rolling, activation, firm adhesion, transendothelial migration and subendothelial migration. The selectins have been implicated in the first step of this cascade. An inflammatory response is first evoked in the pulpal tissue in an attempt to neutralize the injurious agent and to dispose of damaged tissue and cells. The pulpal vessels dilate and blood flow to the tooth increases. At the same time, permeability of the vessels increases allowing leakage of fluid and leukocytes into the tissue.

Cell Adhesion Molecules↗
PubMed1989

Tubular permeability to calcium hydroxide and to bleaching agents.

Recent reports of clinical cases suggest that cervical root resorption may follow bleaching of endodontically treated teeth. Inflammatory root resorption may be arrested by placement of calcium hydroxide into the root canal. The dentinal tubules are assumed to be a possible route of action for both agents. pH Values of the medium surrounding the tooth after placement of bleaching agents and calcium hydroxide within the root canals were determined in this study. Thirty extracted single-rooted human teeth were divided into three equal groups. The pulp cavity of the experimental teeth was filled with either bleaching agents or calcium hydroxide. In the control group it was left empty. Dipping in paraffin sealed the access cavity and the apical foramina and isolated the teeth except at the cervical root surface. The teeth were placed in vials containing distilled water and the pH of the medium was measured after 1 h, 3 days, and 7 days following renewal of the medium. The level of the pH in the first group increased, indicating that the bleaching agents leaked from the root canal to the medium surrounding the teeth. The pH in other two groups did not change noticeably. The results suggest that bleaching agents may leak from the root canal toward the periodontal tissues but calcium hydroxide does not alkalinize the medium surrounding the teeth. Leakage of the bleaching agents through dentin may, therefore, be considered as a possible etiological factor that initiates an inflammatory process around the teeth that may be followed by cervical root resorption.

Calcium Hydroxide↗
PubMed2002

The morphology and stability of resin-modified glass-ionomer adhesive at the dentin/resin-based composite interface.

PURPOSE: To evaluate the interface with tooth structure, mode of failure and stability of Fuji Bond LC (FBLC) resin-modified glass-ionomer bonding system. MATERIALS AND METHODS: The study was in three main parts. The first part with interfacial characteristics of FBLC. The micropermeability of the FBLC/dentin interface of restored cavities in extracted teeth, after fluorescent dye was introduced into the pulp chamber, was assessed by confocal microscopy. In other teeth, confocal microscopy was also used to examine trhe failure of FBLC bonded to flat dentin surfaces, on shear loading. In the second part, cervical cavities restored with FBLC (with and without light-curing) and a resin-based composite were examined for stability of the interface over the first 15 minutes. In the last part of the study, a new fluorescent dye was mixed with FBLC for restoration of cavities and subsequent examination using 2-photon imaging techniques. RESULTS: FBLC adapted well to tooth structure, had an interface with dentin that was permeable to fluid and displayed the absorption layer. Shear loading at the dentin interface resulted in complex failure with areas of cohesive failure where the absorption layer was present. Light-curing of FBLC seemed to produce a stable restorative while "co-curing" resulted in an unstable situation, with the appearance of an emmisable exudate from the FBLC. Advanced fluorescent imaging of the material itself seemed to suggest that there was a movement of aluminum ions in a manner similar to other glass-ionomer cements. The presence of HEMA in the matrix of the cement associated with the absorption layer was also demonstrated.

Absorption↗
PubMed1994

Intracoronal bleaching: concerns and considerations.

The history of intracoronal bleaching and the development of the walking bleach technique are reviewed. External cervical resorption associated with intracoronal bleaching is a serious sequela that has been reported in the literature. One explanation given for this phenomenon is that it results from an inflammatory process initiated by the presence of bleaching agents in the attachment apparatus. The basis for this conclusion is discussed. A review of published case reports on external cervical resorption associated with intracoronal bleaching revealed that: 100 per cent of the affected teeth had no intermediate dental base placed, 84 per cent were treated with a thermocatalytic technique, 80 per cent were bleached after the root canal sealer was fully set and 72 per cent had a history of trauma before bleaching. Based on these observations, it should be possible to safely bleach teeth intracoronally provided specific concerns and considerations are taken into account. These are: 1) the use of heat should be avoided; 2) an intermediate dental base should be placed with due respect to the attachment level; and 3) a base should be selected with due respect to its effectiveness in sealing tooth structure.

Borates↗
PubMed1997

The use of extracted teeth for in vitro bonding studies: a review of infection control considerations.

OBJECTIVE: Infection control concerns regarding the handling of teeth for research purposes have prompted investigators to evaluate the effects of disinfection/sterilization on extracted teeth. The objectives of this literature review were to assess the reported findings of the effect of disinfection or sterilization on teeth used for in vitro bonding studies and make recommendations on their use. METHODS: A search of the literature was performed to obtain background information on infection control guidelines and current findings regarding disinfection or sterilization of extracted teeth. Published articles addressing the effects of different disinfection and sterilizing procedures on the tooth, such as structural changes of dentin and dentin permeability or effect on bond strengths, were examined and compared for agreement or disagreement of findings. The review was organized by the type of disinfection or sterilization method utilized by the investigators. These methods were evaluated in an attempt to address whether disinfection/sterilization of extracted teeth can be recommended or if the procedure simply produces another variable. RESULTS: Formalin, chemical heat sterilization (Chemiclave), autoclave, ethylene oxide and gamma radiation methods of disinfection/sterilization have been investigated for their effects on extracted teeth. When the effect of formalin storage on dentin bond strengths was examined, investigator results were extremely varied. Autoclave and chemical sterilization were found to produce comparable dentin bond results when compared to controls. Gamma radiation did not produce structural changes in the dentin but it currently has not been investigated for its effect on dentin bond strength. And while ethylene oxide produced similar dentin bond strength results when compared to controls, its use as a sterilant was determined to be ineffective. SIGNIFICANCE: Investigators have found formalin storage to be effective for infection control purposes. It cannot, however, be recommended as a storage medium for dentin bonding studies due to the variability in dentin bond strengths resulting from its use. Ethylene oxide is also not recommended due to its inability to effectively sterilize teeth. Chemical heat and autoclave sterilization methods are recommended for preventing cross-contamination during in vitro dentin bonding research. This recommendation is based on current research findings which examined the effect of these sterilization methods on dentin and dentin bond strengths.

Dental Bonding↗
PubMed1992

The role of selected cations in the desensitization of intradental nerves.

Dentinal sensitivity is a common complaint of patients. Removal of cementum or enamel leaves the dentin exposed allowing various stimuli to produce fluid movement through the dentinal tubules. These fluid movements are believed to activate pulpal sensory nerves leading to pain. Various therapeutic approaches have been investigated to treat this problem. Resins, fluoride compounds and oxalate solutions have been used to block the dentinal tubules. KNO3 and SrCl2 are active ingredients in desensitizing tooth pastes but neither compound reduces the permeability of dentine. The ability of various solutions to decrease hypertonic (3M NaCl) evoked nerve activity was tested in the canine teeth of anesthetized cats. Excitatory and desensitizing solutions were placed into a deep dentinal cavity prepared over the incisal pulp horn. An electrode used to record nerve activity was also placed into this deep cavity. KNO3 and other K+ ion containing solutions elicit a biphasic effect on nerve activity. Immediately following application of these solutions into the deep dentinal cavity there is a brief burst of high frequency spike activity. Following this brief period of excitation, the intradental nerves are silent and respond weakly to hypertonic NaCl. CaCl2 and other divalent cation solutions also inhibit hypertonic NaCl induced nerve activity, but have a weaker effect than that exerted by K+. These observations can be explained based on the effects of various ions on nerve excitability. Increasing the K+ ion concentration in the vicinity of the dentinal nerve terminal depolarize and activates the nerve fibers. Following a prolonged period of depolarization the action potential mechanism is inactivated. Divalent cation solutions stabilize the nerve membrane without changing the membrane potential. Desensitizing solutions do not decrease nerve activity by an effect on pulpal blood flow. This experimental model does not entirely explain the clinical action of these desensitizing agents. The role of inflammation in hypersensitivity and dental pain is currently being investigated.

Animals↗
PubMed1989

The penetration of exogenous tracers through the enameloid organ of developing teleost fish teeth.

In order to determine whether exogenous materials permeate to the forming tooth enameloid matrix, teleost species were injected intramuscularly with horseradish peroxidase (HRP) or myoglobin, or; intracardially with lanthanum nitrate or HRP, then killed a predetermined intervals post-injection. Tooth bearing bones were processed for transmission electron microscopy. At the enameloid matrix formation stage, capillaries associated with the enameloid organ were few in number and rarely fenestrated. Both organic tracers reached the matrix at cervical but not coronal, regions of the teeth in all species examined. Lanthanum was rarely observed extravascularly and never extended to the enameloid matrix at the secretion stage. At the enameloid mineralization stage, fenestrated capillaries were closely associated with the outer dental epithelial cells (ODE). All tracers were observed in the plasma membrane invaginations of the ODE. Only intracardially injected HRP compromised the apical intercellular junctions of the inner dental epithelial cells (IDE) to reach the mineralizing enameloid Lanthanum did not extend past the ODE-IDE cell junctions. It is concluded that the close association of mineralization stage fenestrated capillaries with the highly invaginated ODE cells result in increased tracer penetration compared to the secretory stage. The deeper penetration of the organic tracers, compared with lanthanum, between mineralization stage IDE cells may be due to longer in vivo circulation of the former material. The apical junctions of mineralization stage IDE cells, however, remained impermeable to the organic tracers. The absence of mineral in secretory stage enameloid mineral could not be due to specialized cell junctions preventing access of molecules to the matrix. It is suggested that controlling factors other than cellular permeability initiate enameloid mineralization.

Animals↗
PubMed1993

Effect of smear layer removal on the diffusion of calcium hydroxide through radicular dentin.

Forty single-rooted teeth were sectioned transversely through the cementoenamel junction and instrumented to a size #50 K-Flex file at the working length by saline irrigation. Each root was placed in a dilution vial containing 10 ml of normal saline, and the pH and Ca2+ levels were recorded after 24 h. The roots in group 1 then received a final irrigation with 20 ml of normal saline. Group 2 received a final irrigation with 10 ml of 17% ethylenediaminetetraacetic acid followed by 10 ml of 5.25% NaOCl to remove the smear layer. Group 3 was irrigated in the same manner as group 2, but calcium hydroxide (CH) was placed into the root canal. Group 4 was irrigated with 20 ml of NaOCl, and CH was placed into the root canal. The pH and Ca2+ levels were recorded at 1, 3, 5, and 7 days. After 7 days a 3- x 3- x 1-mm external defect was created in the coronal one third of the root surface. The pH and Ca2+ levels were subsequently recorded at 1, 3, and 7 days. Groups 3 and 4 demonstrated significantly higher H+ and Ca2+ levels than did groups 1 and 2 three days after CH placement and at all subsequent intervals. Group 3 demonstrated significantly higher H+ and Ca2+ readings at some but not all intervals. The results demonstrated that CH diffuses from the root canal to the exterior surface of the root and that the removal of the smear layer may facilitate this diffusion.

Analysis of Variance↗
PubMed1989

The use of dentinal etching with endodontic bleaching procedures.

The removal of the smear layer from dentinal surfaces has been shown to increase significantly the permeability of dentin in both vital and endodontically treated teeth by opening the orifices of the dentinal tubules. This knowledge has led to the practice of acid etching the intracoronal dentin of endodontically treated teeth prior to nonvital bleaching procedures in order to increase the speed and effectiveness of the bleach. In this study extracted human teeth, which had been stained in vitro, were used to compare the effects of dentinal etching of the pulp chambers with no acid etching in conjunction with "walking bleach" procedures. In one experimental group, the pulp chambers were acid etched with 50% phosphoric acid for 1 min to remove the smear layer prior to insertion of the 30% hydrogen peroxide/sodium perborate bleaching agents. The second group had the same chamber preparation except the acid etching was deleted. Evaluators were unable to distinguish a significant difference between the effectiveness of the bleaching procedures in the two experimental groups.

Acid Etching, Dental↗
PubMed2004

Use of the Nd:YAG laser in the treatment of Early Childhood Caries.

AIM: This was to demonstrate that traditional therapy of Early Childhood Caries (ECC) can be improved with the use of the Nd:YAG laser. METHODS: This investigation was conducted on three 3 year-old children in which the four maxillary primary incisors were affected by ECC. The teeth were treated with the Nd:YAG laser and one unrestorable tooth for each child was extracted for investigation by scanning electron microscopy. RESULTS: The laser therapy provided several clinical advantages (reduction of dentine permeability and hypersensitivity, sterilization of the lased surface, and fluoride penetration within the tooth). Good patient compliance was also achieved due to the type of appliance and materials used, absence of noise and vibration, a lack of need for local analgesia, and the reduced number of brief appointments. CONCLUSION: This approach to treatment of ECC permits teeth to be retained in the dental arch and delays the use of traditional methods to a later time when the child has reached an age sufficient for cooperation with the practitioner.

Child, Preschool↗
PubMedDate not supplied

Comparison of the in vitro permeability of human dentine according to the dentinal region and the composition of the simulated dentinal fluid.

OBJECTIVE: To compare the permeability of the occlusal and the cervical dentinal regions within the same tooth, which represent the bottom of Class I and V cavities, respectively, with two different compositions of perfusion fluid, in vitro. METHODS: An occlusal and a buccal disc were cut from each extracted third molar at a level close to the pulp chamber. The convective permeability of the discs was measured in a fluid transport model using de-ionised water or 1:3 diluted bovine serum and the hydraulic conductance was determined. RESULTS: The mean hydraulic conductance values of the occlusal and the buccal cervical human dentine to water were 0.069 and 0.047 microl min(-1) cm(-2) cm H(2)O(-1), respectively. When diluted bovine serum was used, the corresponding values were 0.036 and 0.012 microl min(-1) cm(-2) cm H(2)O(-1), respectively. Statistical analysis revealed no significant difference between the permeability of these two regions. The composition of the perfusion fluid significantly influenced the permeability of dentine. CONCLUSIONS: The occlusal and the buccal cervical regions of human dentine have similar permeability characteristics in vitro. There is a strong reverse correlation between the viscosity of the perfusion fluid and the perfusion through the dentine.

Animals↗