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Purpose: To determine the long-term ultimate tensile strength (UTS) and modulus of elasticity (E) of EDTA-demineralized human dentin after storage in PBS (phosphate buffered saline) for up to 48 months., Materials and Methods: Dentin beams measuring 0.7 x 0.7 x 8.0 mm were prepared from the crowns of extracted human third molars. The ends of the beams were covered with resin composite and demineralized for 6 days in 0.5 mol/L EDTA (pH = 7.0). Demineralized control specimens were subjected to tensile testing at 0.5 mm/min after 24 hours of immersion in PBS solution. Experimental specimens were stored in PBS at room temperature (25 degrees C) and tested after 18 and 48 months. The maximum load at failure and the load/displacement curves were used to calculate the UTS as a function of the cross-sectional area and E, respectively. The results were analyzed by ANOVA and Student Neuman Keuls tests. TEM micrographs were obtained from the control specimens and from those that were stored and tested after 48 months., Results: No significant changes in either UTS or E were observed in the specimens after long-term storage. The 48-month values were not statistically significantly different from the values obtained at 24 hours (p > 0.05). TEM images revealed a normal, intact structure of the collagen fibrils with no signs of degradation or denaturation., Conclusion: Long-term storage of EDTA-demineralized human dentin in PBS solution did not cause any significant reduction of its mechanical properties. The structure of the collagen fibrils as observed by TEM appeared normal and did not seem affected by long-term storage.

This article describes the pulp reactions to caries and operative procedures and emphasizes the importance of a clinical diagnosis to evaluate the most appropriate pulp treatment. Conservative and radical treatments are described, stressing the differences between primary and young permanent dentitions.

Temperature variations are expected to influence measurement error in electrical resistance of teeth. It was the aim of this study to determine the changes in electrical behavior of extracted human teeth due to temperature changes in the range of room temperature to intra-oral temperature. Nine extracted teeth were selected, and the occlusal or an approximal surface was chosen for measurement. Carious involvement of the surfaces ranged from sound to cavitated. Electrical impedance spectroscopy sweeps in a frequency range of about 100 kHz to 10 Hz were completed at selected temperatures between 22 degrees C and 40 degrees C. After fitting the data to equivalent circuits that yielded parameter values for components of the equivalent circuit, we calculated the dc bulk resistance (Rh). The temperature dependence of Rb of the surfaces with different carious involvement was very similar, and the mean drop of Rb from 20 to 35 degrees C was 45% (SD 2%). It was concluded that the electrical resistance of sound and carious tooth surfaces is inversely related to temperature.

Artificial caries lesions were produced in roots of teeth using an acetate buffer system, when the layer of cementum was either normal in thickness, excessively thickened by hypercementosis, or had been removed completely. The rates of lesion progression were measured in each case using polarized light microscopy to measure lesion depth. Analysis of calcium (Ca) and phosphorus (P) loss during the demineralizing process was carried out. The removal of cementum was found to significantly increase the initial rate of penetration of the lesion into the root, although this rate progressively reduced to a level consistent with that found in normal roots after seven days of demineralization. The overall depth remained consistently greater than that observed in normal roots, or when lesions were produced entirely within hyperplastic cementum. Chemical analysis also showed removal of cementum resulted in an initial doubling of the Ca and P lost from the root surface. Prior direct exposure of segments of normal roots to the oral environment was found not to significantly alter the rate of artificial lesion progression, in comparison with that in the originally protected segment of the root surface. It was concluded that an intact cementum layer has the intrinsic ability to protect the underlying dentine of exposed tooth roots against acidic demineralization and that prior exposure to the oral environment does not significantly alter this ability.

Objectives: Ingress of bacteria at sites of marginal leakage has been suggested to cause pulpal inflammation. The purpose of this in vitro study was to evaluate the validity of a new electrical method to detect marginal leakage of restoratives by comparing the results obtained with those of a dye penetration test., Methods: After cavities were prepared on the buccal coronal surfaces and root surfaces of 16 extracted non-carious human molar teeth, eight specimens were treated with a dentin bonding system (bonding group) and the other eight specimens were not treated (non-bonding group). Resin composites were filled in the cavities of all specimens, and physiological saline was applied to the margin of the restorative. Any excess saline was wiped off, leaving only the electrolyte, which had penetrated into the marginal gap. The change in conductance was measured continuously across the margin of each specimen during this process. The marginal leakage of specimens was confirmed using the dye penetration test, and the results were evaluated by the microleakage score., Results: In both coronal and root surface cavities, the changes in conductance in the non-bonding group after filling were significantly larger than those of the bonding group (p<0.05). The change in conductance of each specimen correlated with the microleakage score (p<0.05)., Conclusions: It was concluded that the relative electrical method could detect marginal leakage in both coronal and root surface cavities.

Purpose: To measure, in vitro the strength of intact teeth, fracture-bonded teeth, and fracture-bonded teeth bonded after a preliminary calcium hydroxide lining of the dentin part of the remaining tooth., Materials and Methods: The study used 30 young, similarly aged sheep incisors. Twenty incisors were fractured 2.5 mm from the incisal edge and another 10 incisors remained non-fractured and served as control (Group 1). Group 2 comprised 10 fractured incisors, which after 3 weeks water storage were bonded by use of acid etching and a dentin bonding agent. In Group 3, the root part of 10 fractured incisors were lined with calcium hydroxide and kept in water for 3 weeks. Then the lining was removed with a hand instrument before bonding as above. The strength of the teeth in Groups 1-3 was measured and the mean fracture strengths representing the three groups were compared by Newman-Keuls' multiple range tests at a 5% level of significance., Results: The mean fracture strength of the lined teeth (9.6 MPa) was significantly different from that of intact teeth (17.8 MPa) as well as from that of the bonded but unlined teeth (15.8 MPa). The latter two means were not significantly different. It is concluded that the use of calcium hydroxide on the fracture surfaces of fractured teeth before bonding lowers the fracture strength of the restored teeth.

Pulp tissue may suffer from carious invasion, direct or indirect trauma and last but not least from dental treatment. As the general population grows older and retains longer its dentition, teeth will inevitably experience a complex history of multiple episodes of aggressions. It is therefore not surprising that the dental practitioner is confronted more and more with teeth reacting acutely or chronically (in other words, painfully or not) after proper dental treatment. This paper describes the common pathologic and iatrogenic events that may have an effect on the pulpal health status. Preventive endodontic treatment is to be considered in cases of extensive dental treatment.

The interface between dentin and an acetone-based single-component adhesive system (Prime&Bond 2.1, DeTrey Dentsply, Germany) was morphologically investigated by scanning electron microscopy (SEM). Interaction patterns of human teeth were correlated in vivo and in vitro. The SEM examination proved that the formation of a hybrid and an adhesive layer, the peri- and intratubular adhesive penetration, as well as hiatus and nanoleakage formation were no different on vital and nonvital dentin within the limitation of the experimental arrangement of this study., (Copyright 2000 John Wiley & Sons, Inc.)

Previous in-vitro studies have described the relation between rates of enamel wear and variables such as applied load and lubricant pH. The aim here was to extend understanding of tooth-wear processes by considering the rate of wear in human dentine. Enamel was removed from extracted third molar teeth that had been sectioned mesiodistally. Moisture fluctuation within dentine was minimized by conducting all procedures under copious irrigation or in sealed containers of lubricant at pH 7.0. Specimens were subjected to wear using a purpose-built apparatus at loads of 6.2, 9.95 and 13.2 kg. All experiments were done with a unidirectional wear stroke of 3 mm at a rate of 80 cycles/min for 75 min and repeated for 75 min. Dentine wear was assessed by specimen weight loss. At pH 7.0, wear rates ranged from 0.50 mg/10(3) cycles at a load of 6.2 kg to 0.77 mg/10(3) cycles when a load of 13.2 kg was applied. At higher loads, dentine wear rates were similar to those of enamel. Increasing load is thus associated with a progressive increase in the rate of dentine wear. This relation differs significantly from that for enamel, reflecting fundamental differences in the composition and structure of these tissues.

The dentin-pulp complex is sensitive to infection. Restorative treatment should function as a Band-Aid protecting the dentin-pulp complex from bacteria and their byproducts. This article describes different ways of treating the exposed dentin-pulp complex in such a way that bacterial infection can be avoided.

Statement of Problem: Several studies have investigated the adhesion of glass ionomer-based restorative materials to nonfluorotic teeth, but there appears to be no information on the bond strength of these restorative materials to dentin in fluorotic teeth., Purpose: This study investigated the effect of dental fluorosis on the bond strength of Ketac-fil conventional glass ionomer cement, Vitremer resin-modified glass ionomer cement, and Dyract polyacid modified resin to dentin., Material and Methods: Ninety posterior teeth were classified according to the severity of fluorosis, by using the Thylstrup and Fejerskov index, TFI. The teeth were divided into 3 equal groups (TFI = 0,TFI = 1-3, TFI = 4+) of 30 teeth, which were again divided into 3 equal subgroups for testing each of the3 restorative materials. Occlusal surfaces of mounted teeth were ground flat to expose dentin. Cylindrical specimens (4 mm diameter and 4 mm high) of the restorative materials were bonded to the middle of the cleaned exposed dentin surfaces, according to the manufacturers' instructions. After storing the specimens in 100% humidity at 37 degrees C for 24 hours, shear bond strengths of the restorative materials were measured with an Instron testing machine at crosshead speed of 0.5 mm/min., Results: Two-way analysis of variance and Tukey-B test revealed that Dyract had significantly higher shear bond strength to dentin than Ketac-fil or Vitremer cements, regardless of severity of fluorosis (P <.05). Furthermore, there was an inverse relationship between shear bond strength and the severity of fluorosis for each of the restorative materials. Cohesive mode of failure was most prevalent in nonfluorotic teeth (TFI = 0), especially with Ketac-fil cement, whereas Dyract cement had the greatest propensity for adhesive failure., Conclusion: Fluorosis reduces the shear bond strength of glass ionomer-based restorative materials to dentin.

The present study reveals the inhibitory effect of iron intoxication on the process of dentine mineralization. Wistar rats were injected intraperitoneally with iron dextran at 0.88 g/kg body weight per day for 10 days during the period of odontogenesis. An age-matched group was injected intraperitoneally with bisodium etidronate (EHBP) at 20 mg/kg body weight per day for 10 days. Another age-matched group was treated with similar amounts of saline intraperitoneally and considered as control. At the end of the experimental period the animals intoxicated with iron exhibited non-mineralized dentine and mineralized bone. The animals treated with EHBP showed non-mineralized dentine and bone. These findings would suggest the existence of different mineralization mechanisms for bone and dentine.

Diagnosis of pulpal disease can be difficult due to the lack of diagnostic signs and symptoms available to the practitioner. An understanding of the possible underlying pathological processes, combined with an exact assessment of the pain history, and appropriate clinical tests, should aid the practitioner in determining the nature of pulpal inflammation, and differentiating it from dentine sensitivity and cracked teeth. The responses of the pulp to traumatic injury to the periodontal membrane (PDM) require special consideration, particularly with respect to the assessment of pulp vitality, and the determination of cases requiring pulp extirpation in order to avoid inflammatory root resorption. Although the pulp is relatively isolated from the rest of the dentoalveolar complex by a dentine/cementum barrier, it is important to remember that it can communicate with the PDM through apical and lateral foramina, and areas of damaged cementum. Hence, it is a priority to both preserve the integrity of the cemental layer in cases of traumatic injury and periodontal disease, and to prevent the inflammation and resorption associated with periapical lesions by accurate diagnosis of irreversible pulpitis and pulp necrosis, followed by appropriate endodontic debridement procedures.

Objective: To investigate the distribution of stresses that occur in a maxillary canine tooth during vertical and lateral condensation of gutta-percha in the root canal., Design: An elaborate three-dimensional finite element model of a maxillary canine tooth was developed for the purposes of stress analysis. A sample stress analysis was also performed to demonstrate the variations in stress values that occur between different solutions of the same problem., Methods: A 3D finite element analysis was performed on a maxillary canine tooth model which was created using the dimensions of computer tomographic scans of a cadaveric maxilla as reference., Results: If the manual operations of the endodontist are transcribed to the software by considering the finite size of the plugger or the spreader, then the maximum stresses generated in the dentine are much smaller than the reported tensile strength of this material., Conclusion: The causes of the fractures in the dentine reported by previous investigators must be traced to conditions which were not considered in this study. These include aspects of modelling, which is the most important single parameter on which the final results depend. Stresses calculated by means of the complicated 3D model appear to agree with those recovered from a simpler 2D idealisation.

This study aimed to (1) record the plaque and gingival status on sound and carious approximal surfaces and (2) investigate whether the two parameters could predict approximal lesion progression. For this purpose two samples were selected among 18- to 25-year-old patients at the Dental Faculty in Copenhagen. Sample 1 consisted of 45 patients, each having an approximal posterior surface requiring operative treatment and a contralateral approximal space, where both surfaces were radiographically sound. Sample 2 consisted of 25 patients, each having a posterior approximal tooth surface with an enamel/initial dentinal lesion recorded on a bitewing. Plaque and gingival status were classified using 4-point ranked scales. The recordings were performed once on each participant in sample 1. The recordings in sample 2 were repeated 5 times during a 15-month period. In order to assess lesion progression in sample 2, two serial intraoral examinations were performed, i.e. at the beginning and end of the study. Less than 10% of the sound and carious surfaces were recorded as plaque-free, while about 40% had a thick or heavy plaque accumulation. No significant difference was observed between plaque scores on sound and carious surfaces (p = 0.5), in contrast to findings representing the gingival status (p < 0.001). Tooth surfaces requiring operative treatment were associated with bleeding of the gingiva after probing. In sample 2, 3 of the 25 participants did not finish the study. On the remaining participants caries progression was observed in 9 cases (41%), while no progression was observed in 13 cases. Analyses showed that there were no significant differences between plaque scores in cases with caries progression, as compared with no caries progression (p > 0.05). Similar analyses concerning gingival status showed that bleeding of the gingiva was related to cases with progressing caries. Analyses also disclosed no direct association between plaque and gingival status (Spearman correlation coefficient 0.39). Thus, the occurrence of plaque does not have the same predictive power as bleeding after probing in decision-making as to whether or not a lesion progresses.

The purpose of this study was to perform in vitro measurements of the temperature increase at the enamel-dentine interface during electrothermal removal of ceramic brackets, and to analyse, in vivo, whether signs of pulp damage can be observed 4 weeks after the procedure. In vitro study: a total of 29 caries-free human teeth were cut into buccal and lingual halves. The buccal halves were bonded with ceramic brackets, and miniature thermocouples were placed from the pulpal side into holes drilled to the enamel-dentine interface under the centre of the bracket slot. From the onset of thermodebonding, the temperature increase relative to room temperature was recorded for a period of 43 seconds. The maximum temperature increase at the enamel-dentine interface was 6.9 degrees C. In vivo study: a total of 12 human premolars scheduled for extraction for orthodontic reasons were bonded with ceramic brackets. Electrothermal debonding was performed the following day. After 4 weeks, the teeth were extracted and prepared for histological examination. Following demineralization, sections were prepared for light microscopic examination. No signs of pulpal inflammation were observed.

The effect on healthy dental pulp of thermal increases ranging from 8.9 to 14.7 degrees C was evaluated. These temperature increases correspond approximately to those caused by certain restorative procedures, such as tooth preparation with high-speed instruments and the fabrication of direct provisional crowns. Two criteria of evaluation have been used in conjunction, a clinical (symptomatic) and a histological one, to assert with greater precision potential damage to the pulp. The results suggest a low susceptibility of cells to heat, which does not appear to be a major factor of injury, at least in the short term. The main cause of postoperative inflammation or necrosis of the pulp is probably the injury of the dentine, a tissue in direct functional and physiological connection with the pulp.

Ascorbic acid is essential to the biosynthesis of collagen, the major organic matrix component of dentine. The ODS rat is a mutant strain of Wistar rat characterized by hereditary lack of L-gulono-gamma-lactone oxidase and thus is unable to synthesize ascorbic acid. ODS rats were given an ascorbic acid-free diet to investigate how ascorbic acid deficiency affects dentine formation in vivo. Histomorphometric analysis on their growing molars and incisors showed a significant reduction in both size and mineral apposition rate of dentine, as revealed by contact microradiography and fluorescent time-marking, respectively. A similar reduction in bone formation was simultaneously demonstrated in the mandible, confirming the previously reported osteopathic effects of ascorbic acid deficiency. When pulp inflammation was induced in lower first molars by making unsealed pulp exposures, specimens from control animals showed continuous deposition of an osteodentine-like tissue in the radicular pulp chamber; this type of mineralized tissue formation was greatly reduced in ascorbic acid-deprived animals. These results indicate that ascorbic acid deficiency hampers dentine formation under both physiological and pathological conditions of the dentine/pulp complex. ODS rats could be useful in investigating in vivo effects of ascorbic acid deficiency on the formation of dentine and other dental mineralized tissues.

The purpose of the present study was to histologically assess the effect of enamel matrix derivative on periodontal regeneration in one human experimental defect. Experimental surgery was performed in a healthy male volunteer to create a buccal dehiscence defect in a mandibular incisor. Following bone removal and conditioning of the exposed root surface, enamel matrix derivative was applied onto the root surface. The flaps were then replaced and sutured. Clinical healing was uneventful. After 4 months, the experimental tooth together with the surrounding soft and hard tissues were removed surgically for histological evaluation. The microscopic examination revealed formation of a new acellular extrinsic fibre cementum, which was firmly attached to the underlying dentin. A new periodontal ligament with inserting and functionally-oriented collagen fibres and an associated alveolar bone was also present. The new cementum covered 73% of the original defect. Regain of bone was 65% of the presurgical bone height. It was concluded that adjunctive use of enamel matrix derivative could provide a regenerative technology with a potential for true periodontal regeneration.

Objectives: The aim of this investigation was to determine the influence of a variety of parameters on the effectiveness of hard substance ablation and the thermal side effects when using Er:YAG laser (Key I and II, KaVo) and Nd:YAG laser (SunLase 800, Sunrise Technologies/Orbis)., Methods: For this study, ablation and temperature measurements were carried out on 170 dentin slices and 170 extracted teeth via computer-controlled cavity preparation. The Er:YAG laser settings varied from 250-400 mJ/pulse, 3-15 pps and 20-180 s processing time, and in the case of the Nd:YAG laser from 83-100 mJ/pulse, 10-20 pps, and 20-260 s processing time. The ablation rate was measured volumetrically via a 3D sensor. Temperatures were measured for each setting both on the dentin slice and in the pulp of the extracted teeth. The results were analyzed using a t-test for independent samples and a one-way ANOVA (Bonferroni). Also a liner regression analysis was done using Pearson's coefficient., Results: The results show that with the Er:YAG laser, in combination with water-spray cooling, an effective 3D ablation rate (up to 0.017 mm3/pulse = 50 microns linear) can be achieved without raising the temperature of the surrounding tissue. In the case of the Nd:YAG laser, no measurable ablation rate was evident without conditioning of the dentin surface and, in the case of conditioning with black ink, a low ablation rate (0.00004 mm3/pulse = linear 0.2 micron/pulse) was found., Significance: In contrast to the Er:YAG laser, it is apparent, that with the Nd:YAG laser from a total energy of 80 J onwards, the rise in temperature in the pulp is above 8 degrees C. For that reason, the use of the Nd:YAG laser at higher total energies is not recommended. The temperature rise with the Nd:YAG laser is dependent on the direction of the dentin tubuli. Dentin tubuli running parallel to the surface prevent significant heat penetration, whereas those running in a transverse direction to the surface (= parallel to the laser beam) support the penetration of heat. This finding supports the light-propagating theory for spreading effects of laser beams in dentin.

Objectives: The fracture toughness test was recently introduced as a clinically relevant method for assessing the fracture resistance of the dentine-composite interface. The objective of this study was to evaluate the effect of dentine depth on the interfacial fracture toughness test of several dentine-composite interfaces using some new proprietary dentine bonding agents., Methods: Miniature short rod fracture toughness specimens containing a chevron-shaped dentine-composite-bonded interface were prepared for each group (n = 12). Six different dentine bonding agents and two dentine depths were the variables assessed at the dentine-composite interfaces. After 24 h at 37 degrees C in water, the specimens were tested by loading at 0.5 mm/min in the Instron Universal Testing Machine. The interfacial KIC results were analysed by ANOVA, unpaired Student's t-tests and Fisher's LSD test (P < 0.05)., Results: The interfacial KIC results in MN.m-3/2 (S.D.) on superficial and deep dentine, respectively, were: All-Bond 2, 0.80 (0.21), 0.44 (0.13); Bond-lt, 0.75 (0.20), 0.38 (0.19); Prime and Bond, 0.56 (0.11), 0.28 (0.10); Scotchbond Multi-Purpose, 0.45 (0.23), 0.26 (0.15); One-Step and OptiBond, insufficient results due to premature specimen failures., Conclusions: The results from this study should contribute to the development of the fracture toughness test as a method for assessing the integrity of the dentine-composite interface. The interfacial fracture toughness test determined significant differences among the different dentine bonding agents and between the superficial and deep dentine substrates. The dentine bonding agents showed significantly reduced interfacial fracture toughness results when bonding to deep versus superficial dentine.

The effects of serum phosphate level on the formation of incisor dentine were investigated in hypophosphatemic (Hyp) mice fed a diet high in calcium and phosphorus (high Ca/P diet). Feeding a high Ca/P diet for more than 10 days resulted in an increase in the serum phosphate level in Hyp mice to one similar to that of normal mice. Lower incisors were cut transversely at the centre of the length of the incisor, a point that had taken approximately 40 days to be reached from the start of dentine formation in Hyp mice. Transverse views of the incisors showed a triangle-like outline in Hyp mice fed a control diet, while the outline became rounded in Hyp mice fed the high Ca/P diet for more than 40 days. In Hyp mice fed the high Ca/P diet for 40 days interglobular dentine was still observed and fluorescent lines produced by tetracycline showed a diffuse and wavy pattern in incisor dentine; however, interglobular dentine became indistinct and fluorescent lines showed a relatively smooth pattern in the incisor dentine of Hyp mice fed the diet for more than 60 days.

Diagnosis of occlusal caries is difficult from visual and radiographic examination. The use of electrical resistance measurement has been described previously and reported to be a potentially sensitive alternative technique. This is possibly due to the decreased resistance of carious pits and fissures. The aim of this study was to validate a prototype electrical caries monitor for the diagnosis of caries in pits and fissures in vitro using a microfocal radiographic technique. Thirty discrete sites were investigated in 10 extracted molar teeth. Electrical resistance measurements were recorded at each site and thick sections (approximately 0.65 mm) prepared for microfocal radiography. Microfocal radiography indicated that six sites were sound, 10 had enamel caries and 14 dentine caries. At a resistance value of 2.2 M(OMEGA), below which a site was regarded as carious and above which it was regarded as sound, electrical resistance measurements proved sensitive (92%) and specific (100%). Quantification of mineral content indicated that mineral loss in enamel may influence resistance measurement more than lesion depth.

In this study, intracanal laser-softened gutta-percha, Ultrafil, and intracanal laser-cured composite resin techniques were compared with respect to the temperature elevation induced on the outer root surface. The temperature at the root surface of 50 single-rooted teeth was measured using a thermovision camera. Argon laser produced a rise in temperature of +12.9 degrees C (gutta-percha) and +13.3 degrees C (composite resin), respectively. The CO2 laser produced +10.3 degrees C and Nd:YAG laser produced the highest temperature elevation of +14.4 degrees C. Low-temperature gutta-percha obturation technique did not produce a measurable temperature change on the external root surfaces.

The influence of different obturation techniques (lateral condensation, Obtura, and Thermafil) on root strains was assessed in 27 upper central incisors using strain gauges mounted on the coronal and apical one-thirds of the root surface. The vertical load applied with each obturation technique was also measured. Comparison of the strains was conducted with two-way analysis of covariance (with condensation load as covariate). The technique of obturation significantly influenced the root strains, with the Obtura generating the highest strains. The Thermafil group showed significantly less strain than the Obtura or lateral condensation groups. Thermal expansion of dentin was an unexpected finding. A large proportion of strain in the Obtura and Thermafil groups was found to be thermal strain. The mean load required to cause vertical root fracture was five to six times higher than the load used in obturation.

A case of multiple fractures of the mandible following a car accident in a five-year-old patient is reported. The fracture line passed distal to the first molar tooth bud. The fracture was treated by wire osteosynthesis and skeletal fixation. During the ensuing 18 months, a gradual arrest of the development of the first molar tooth bud was radiologically observed. The eruption process had not been disturbed, and the tooth erupted at the age of 6 1/2 years. Since the distal root had completely failed to develop and the mesial roots showed a diminished size, the tooth was extracted. Histopathological examination revealed disturbed dentin apposition, there was almost complete obliteration of the pulp chamber by globular dentin, and evidence of root resorption.

Electrical conductance measurements are being used experimentally to diagnose caries. Current equipment, e.g. the electronic caries monitor (ECM), uses a probe to scan occlusal fissures. For full-mouth examination this method is rather time-consuming. A method with which only one measurement is needed for an entire (occlusal) surface would be preferable. However, the enlargement of the area being measured will influence the conductance. It was the purpose of this study to investigate the relationship between the electrical conductance of human teeth and the enamel electrode area, and to compare the range of results of surface measurements with those of the scanning method. Twenty-five sound extracted teeth were selected for the study. The reference electrode of the ECM was connected to the roots. The buccal surface was blotted dry, and a coloured dentifrice was syringed in increments onto the surface. After each increment the surface was photographed together with a metric reference, a conductance measurement was performed by holding the ECM probe tip in the dentifrice, and the ECM reading was recorded. For each tooth between 5 and 10 increments were applied and measured. The photographs were digitised and the electrode areas were calculated. A least squares curve fitting procedure yielded a linear relationship between conductance and electrode area (0.88 < or = R2 < or = 1.0, mean R2 = 0.97). For most teeth the threshold for dentinal caries as used for scanning ECM measurements (ECM reading = 6.00) was reached only when the electrode area exceeded 12 mm2. For 6 teeth this conductance was already reached between 5 and 12 mm2.(ABSTRACT TRUNCATED AT 250 WORDS)

Pressure changes in the pulp chamber resulting from crown cementation have not been previously quantified. An experiment was designed to investigate the effect of smear layer removal on the peak pressure transmitted to the pulp chamber with crown cementation. Ten matched pairs of single-rooted premolar teeth were collected from adolescents and prepared for full-coverage crowns. The pulp tissue from each tooth was removed. One tooth from each pair had the smear layer removed with the application of 37% phosphoric acid for 30 s. The null hypothesis states that the removal of the dentinal smear layer will not change pressure in the pulp chamber resulting from the cementation. Before cementation, a hydrostatic head of pressure was used to perfuse the tooth, and the perfusion rate was recorded. Crowns were cemented with zinc phosphate cement with a seating force of 100 N. The mean peak pressures recorded were 85 Pa (SE 12 Pa) with the smear layer intact, and 194 Pa (SE 49 Pa) when the dentin was etched. The difference in the peak pressures transmitted to the pulp chamber with the two groups was significant (p < or = 0.05). A significant negative correlation was found between dentin thickness and the peak pressure transmitted to the pulp chamber (r = -0.5531, p < or = 0.01). We have shown that the pressure transmission to the pulp chamber during crown cementation can be measured. Since smear layer removal significantly influences the peak pressure, it is concluded that the pressure detected is at least partially dependent on the fluid flow through the dentin.

The aim of the present study was to compare periodontal healing after successive removal of periodontal tissue components, from the alveolar bone to the dentin surface. The prevailing tissue reaction when adhering PDM was left on the exposed roots was that most of the bone tissue that had been removed from the buccal surfaces had regenerated and the integrity of the PDM between the new alveolar bone and cementum surface had been reestablished. On exposed etched cementum surfaces, 2 prevailing healing results were recorded. In half the number of the roots, the root surfaces were covered by connective tissue with fibers running parallel to the root surfaces in a capsule-like arrangement. The other prevailing reaction was a thin epithelial cell-lining running parallel to the root surfaces in close contact or partly penetrating the adjacent connective tissue. On exposed denuded dentin surfaces, gingival retraction was a constant finding, associated with an epithelial cell-lining of varying thickness sometimes with rete pegs and cyst-like formations. Gingival retraction was also a constant finding on etched dentin surfaces. This was associated with pathological pockets outlined by epithelial cell-layers of varying thicknesses. The significance of these findings were discussed with special emphasis on dynamics of recurrent periodontitis.

Since acute osteoporosis is known to enhance bone remodeling and osteoid formation, it may also affect dentin apposition. We induced osteoporosis in 15-week-old Wistar rats by ovariectomy and dental caries by Streptococcus sobrinus infection in the presence of either a high sucrose (cariogenic) diet or a non-cariogenic diet. Intact animals with the same diets served as controls. After 99 days of cariogenic challenge the rats were killed, and the success of ovariectomy was confirmed by failure to detect ovarian tissue and observation of marked atrophy of the uterine horns. Areas of dentinal apposition during the experiment and carious lesions were quantified with a tetracycline method. Ovariectomy activated dentin formation significantly in rats fed either a high-sucrose or a non-cariogenic diet, indicating enhanced odontoblast function. The rate of dentinal apposition in adult rats was smaller than reported in young animals. The effect of ovariectomy on caries remained negligible.

This study compared biomechanical properties (punch shear strength, toughness, hardness, and load to fracture) of 23 endodontically treated teeth (mean time since endodontic treatment: 10.1 yr) and their contralateral vital pairs. Analyses using paired t tests revealed no significant differences in punch shear strength, toughness, and load to fracture between the two groups. Vital dentin was 3.5% harder than dentin from contralateral endodontically treated teeth (p = 0.002). The similarity between the biomechanical properties of endodontically treated teeth and their contralateral vital pairs indicates that teeth do not become more brittle following endodontic treatment. Other factors may be more critical to failure of endodontically treated teeth.

The objective of this study was to determine whether significant differences exist between the mechanical properties of human dentin from treated pulpless teeth and dentin from normal vital teeth. Dentin specimens (n = 262) were obtained from 54 freshly extracted normal vital human teeth and 24 treated human pulpless teeth. These specimens were subjected to different experimental conditions (wet, air dried, desiccated, and rehydrated). Compression, indirect tensile, and impact tests were conducted to measure the mechanical properties of those specimens. All data obtained were analyzed with t tests. The results showed that the dehydration of dentin increases the Young's modulus, proportional limit (in compression), and especially the ultimate strength (in both compression and tension). Substantial dehydration changes the fracture characteristics of dentin specimens under static compressive and indirect tensile loadings. The measurements of impact-breaking energies of desiccated dentin were not found to be significantly decreased. The compressive and tensile strengths of dentin from treated pulpless teeth obtained in this study do not appear to be significantly different from those of normal dentin (p > 0.05), while the mean values of Young's modulus and proportional limit in compression tests appear to be lower. Fifty percent of the dentin specimens from treated pulpless teeth exhibit greater plastic deformation than normal dentin in compression. The results of this study do not support the theory that dehydration after endodontic treatment per se weakens dentin structure in terms of compressive and tensile strengths. Other mechanical properties of treated pulpless teeth, however, may not be the same as those of normal vital teeth.

The posterior bitewing radiographs of 50 children from a Duraphat clinical trial were re-examined to compare the information provided on progression of caries of two scoring systems, that of Murray & Majid (1) and that of Pitts (2). Pitts' scoring system (Method 1), by recording the disease process at an earlier stage, and by avoiding the unnecessary loss of data, provided a more complete overall picture of the carious process than the scoring system used by Murray & Majid (Method 2). The progression rates were found to be significantly faster with Method 2 (P less than 0.05). With Method 1, a mean of 60% of enamel lesions per subject had remained confined to enamel 12 months later, the corresponding figure for Method 2 was 37%. Method 2, by excluding outer enamel lesions and overlapped surfaces, introduces biases which favour overestimating the proportion of lesions deemed to have progressed. The diagnostic criteria used by Murray & Majid lead to an overestimation of the rate of progression of caries in primary teeth.

Dentin permeability at the bottom of carious cavities of 124 teeth was studied by electrometry. Dentin permeability was found to be higher in deep caries than in moderate-severe and higher in the teeth that had not been treated before than in those filled. Treatment of the cavities with potassium oxalate before filling helped rapidly and effectively lower the dentin permeability in order to prevent involvement of the pulp.

The mechanisms by which pain develops in carious teeth are poorly understood. The variability of dentin and pulp responses to carious attack is probably the cause for the variations in the pain symptoms presented by patients. This article is a review of the available data regarding the changes that dentin and pulp undergo in carious teeth. Such changes are discussed in relation to their possible influence on intradental sensory nerve excitability. Special emphasis is given to the various bacterial metabolites produced and accumulated in carious dentin and their ability to modulate pain symptoms from carious teeth.

The objective of this study was to compare the performance in occlusal caries diagnosis of various available diagnostic systems when applied to the same teeth. The sample investigated consisted of 13 children for whom 4 premolar and 19 molar teeth were judged to require a sealant. The indication was based on the criteria 'fissure discoloration', 'enamel decalcification' and 'absence of dentinal decay'. For predefined locations within these occlusal fissures a diagnosis was obtained by the following diagnostic systems: clinical examination, examination on fiber-optic transillumination (FOTI), fissure discoloration, electrical resistance measurement, radiographic examination and ratings of fissure morphology. Tooth material was removed until no (more) carious enamel or dentin was left. Two dentists then jointly decided on the status of decay for each of the defined locations within the fissure. These ratings served as the 'gold standard' diagnoses. The electrical resistance measurement with a sensitivity of 0.96 and a specificity of 0.71 was the only diagnostic tool with acceptable performance. Radiographic diagnosis was characterized by a moderate sensitivity and specificity. All other diagnostic systems had either very low sensitivities or very low specificities, or both. The positive predictive value of FOTI examination and the negative predictive value of the electrical resistance measurements were very high, irrespective of the prevalence of occlusal dentinal decay.

The local regulation of odontoblast response to caries is viewed through initiation and elaboration of sclerotic as well as reparative dentin. Dentin tissue represents a multiple source of potent environment factors when teeth are affected by the demineralization phases of carious process. Some of them have already been identified in sound tissue (matrix glycoproteins, proteoglycans, growth factors, Bone Morphogenetic Protein) and may act on the cell through membrane receptors. Thus, the amplification in collagen synthesis and alkaline phosphatase activity previously observed during sclerotic dentin deposition can be related to the interaction between matrix signals and cell receptors such as the 165 kDa protein shown only by odontoblasts under the affected zone. Similarly, under established lesions generating cell death, the specific matrix made of odontoblasts debris and damage tissues, probably rich in active molecules, may trigger pulp cells to elaborate a cartilage-like layer (identified by type II and XI collagen) followed by odontoblast-like cells to give rise to abnormal tubular dentin. Here, odontoblast response is identical to bone-cells response to injury. What remains to be elucidated concern: The nature of signals found in carious dentin (matrix components, growth factors, bacterial products). The nature and regulation of expression of cell membrane receptors during tooth repair. How the odontoblast produces specific responses to each of these signaling molecules will be the focus of important new investigations.

Although a number of reports have been published demonstrating that carious dentin is less permeable than normal dentin, these reports have been qualitative rather than quantitative. The purpose of this in vitro study was to apply a quantitative technique to the study of the permeability of carious human teeth before and after excavation, before and after removal of the smear layer and before and after preparation of a control cavity of similar size and depth in normal dentin subjected to the same measurements, for comparative purposes. Dentin permeability was measured as a hydraulic conductance. The permeability values measured at each step in the protocol were expressed as a percent of the maximum permeability of both cavities, permitting each tooth the serve as its own control. Carious lesions exhibited a slight degree of permeability (2.3 +/- 0.6% of controls) which remained unchanged after excavation of the lesions. Removal of the smear layer in the excavated carious lesions increased the permeability significantly to 6.9 +/- 3.2%. Preparation of a control cavity of the same area and depth increased the permeability slightly. Removal of its smear layer increased the permeability of the dentin 91%. These results confirm previous qualitative studies that carious dentin, even after excavation and removal of the smear layer has a very low permeability.

Rapid maxillary expansion (RME) is a useful orthodontic technique for correction of posterior cross-bite of skeletal origin. The aim of the present study was to compare the frequency and nature of root resorption in premolars subjected to RME by means of either a tissue-borne, fixed split acrylic (Haas) palatal expansion applicance, or an all-wire framework appliance. Another factor examined was the relationship between the pattern of resorption and the duration of the retention period. RME was performed on five patients using the fixed split acrylic appliance and on four patients with the all-wire framework appliance. Following the transverse expansion, two upper and two lower premolars were extracted and processed for histological examination. Root resorption was found mainly on the buccal surfaces of all maxillary premolars. The resorption lacunae covered more of the root surface in premolars treated with an all-wire framework appliance compared to premolars treated with the acrylic expansion plate. The largest resorption areas were found on teeth extracted shortly after the expansion period and the smallest on premolars retained for a relatively longer period. Mandibular premolars showed neither buccal nor lingual resorptions. It was concluded that maximum anchorage of the expansion device, using the tissue-borne acrylic appliance, seems preferable in order to minimize the incidence of buccal surface root resorption. A longer post-treatment observation time is needed in order to draw more specific conclusions regarding the healing process of the damaged root surface.

This study deals with the role of collagen in the remineralization of bovine incisor root lesions. The degradability of the collagenous matrix after in vitro remineralization was also investigated. The root surfaces were exposed to 0.1 M acetic acid, pH 4.0, to produce erosive lesions or to 0.1 M lactic acid, 0.2 mM methane hydroxy diphosphonate, pH 5.0, to produce subsurface lesions. After demineralization, the roots were subjected to remineralization, with or without prior treatment with a bacterial collagenase to remove accessible collagen. Remineralization was carried out in solutions with a Ca/Pi molar ratio of 1.67, and [Ca]. [Pi] concentration products of 0.6, 1.35 or 2.4 mM2, with all solutions having an ionic strength of 0.15 M, and a pH of 7.0. After remineralization, the roots that were not treated with collagenase were incubated with the enzyme. The results indicate that remineralization of erosive lesions is surface-controlled and that of subsurface lesions diffusion-controlled. For both lesion types it was shown that the removal of collagen before remineralization did not affect the rate of mineral deposition in the root lesions. Nevertheless, remineralization in those lesions where accessible collagen had not been removed resulted in a significant reduction in the amount of degradable collagen. The observations of this study suggest that remineralization did not occur by nucleation of mineral on the organic matrix but rather by growth of residual crystals in the partially demineralized root tissue.

The objective of these studies was to follow early healing at the dentin-connective tissue interface. Small dentin blocks were surgically implanted in bone cavities under mucoperiosteal flaps in the edentulous alveolar ridges of five beagle dogs at various times. In two separate experiments, wound maturation on native dentin surfaces and on citric acid or heparin conditioned dentin surfaces was observed. Block specimens including bone, dentin, and surrounding soft tissues were obtained at 10 minutes, 1 and 6 hours, and 1, 3, and 7 days after flap closure and prepared for light and transmission electron microscopic examination of the interface. The very initial attachment to native dentin was mediated by a granular precipitate. At 1 and 6 hours, the intercellular matrix was more organized with fibrin formation around red blood cell aggregates and at the dentin surface. Polymorphonuclear leukocytes were observed throughout the interface. Red blood cells were undergoing degradation at day 1 and polymorphonuclear cells were prevalent at the dentin surface. The 3-day observation interval was characterized by further maturation of the fibrin clot. Macrophages were observed near the dentin surface and fibroblasts could be identified. The 7-day specimens exhibited areas of cell rich connective tissue attachment without inflammatory cells as well as areas showing the fibrin clot in various stages of decomposition. These observations suggest that connective tissue attachment to dentin surfaces is mediated by adsorption of plasma proteins to the surface and subsequent development and maturation of a fibrin clot. The sequence of healing events at dentin surfaces conditioned with citric acid or heparin was largely similar to healing at native dentin surfaces. However, at day 1 and later time points, clot adhesion to heparin-conditioned dentin appeared compromised, whereas the fibrin clot seemed to adhere to citric acid-conditioned dentin at all observation periods. These observations indicate that in the absence of mechanical trauma, epithelial proliferation, and infection, wound maturation at the dentin-connective tissue interface may not necessarily be affected by treatments that either enhance or inhibit clot adhesion to the dentin surface.

Extracted teeth with preexisting carious lesions were incubated in vitro at 37 degrees C in an artificial saliva buffer. Four teeth were exposed to buffer alone, four to buffer containing 5% glucose, and four to buffer containing 5% sucrose. Time-lapse radiographs were made of the carious lesions using an orienting device that fixed the position of the tooth, x-ray film, and x-ray tube collimator. The radiographs were analyzed over a period of 8 weeks using digital subtraction radiography. The subtracted images revealed that three of the four teeth incubated in saliva alone showed an increase in radiodensity (remineralization) at the depths of the lesion; one tooth showed no detectable change. Three of the four teeth incubated in the presence of 5% glucose showed increased radiolucency (demineralization); one showed no detectable change. The four teeth incubated in the presence of 5% sucrose exhibited results similar to those teeth incubated in 5% glucose.

After the periodontium of the rat was wounded, the formation of acellular extrinsic fiber cementum (AEFC) did not appear to be restricted to the hard dental tissues (pre-existing cementum, dentin, and enamel). Layers resembling AEFC were also deposited along the inner wall of the alveolar bone. At the time of observation (six weeks after being wounded), cells other than fibroblast-like cells could not be distinguished close to the newly formed AEFC-like layers. We suggest that the deposition of this material was related to the activity of periodontal ligament fibroblasts.

For well over a century, there has been cognizance that sensitivity is a serious problem, that it arises when the dentin and cementum are exposed, that fluid movement within the dentinal tubules acts as a provocative stimulus, that tubules can be sealed off (apparently in most instances) without damage to the tooth or the dental pulp, and that the problem can also be at least partially resolved by suppressing nerve firing within the pulp. Most of the therapies proposed to date for treatment rely on one of two major suppressive mechanisms, that is, sealing off the dentinal tubules or dampening neural impulses, even though at the time of their development and use they have been mostly empiric in nature. At present, there appear to be a number of effective therapies, although admittedly none meet all of the hypothetic requirements proposed by Grossman over 50 years ago. Included among the agents with reasonable documentation of effectiveness and little in the way of negatives are fluorides, strontium chloride, potassium nitrate, potassium oxalate, sodium citrate, surface sealing agents (varnishes, resins, cyanoacrylate), calcium hydroxide, and others. There are many dedicated workers who are still concerned with achieving better insight into the problem and methods to resolve it.

The anatomical and physiological characteristics of the pulpal and dentinal sensitive system are described. Some different theories about the transmission of the dentinal sensitivity are also explained. Finally, the different desensitizing agents, their main characteristics and mechanisms of action are analyzed.

The development of a caries lesion is a dynamic process that includes frequently alternating periods of de- and remineralization, a process for which no in vitro models currently exists. The aim of this study was to develop a model which could repeatedly generate identical pH versus time curves over extended periods of time. To test the model demineralization studies on cementum/dentin were performed. Cementum/dentin blocks were repeatedly subjected to de- and remineralizing solutions delivered by a computerized pump system connected to a pH-meter and a recorder. pH versus time curves similar to those produced in plaque after carbohydrate intake were generated 18 times during 15 h followed by a remineralizing period of 9 h every day for 16 days. The intra-day and inter-day variation of the pH-cycling model were found to be low. The mineral change of the blocks was followed by 125I absorptiometry and the transmission through the blocks during the experimental period increased in average by 1.4 +/- (SE) 0.18%. Microradiographic analysis of the transversal sections of the blocks confirmed the development of lesions resembling root caries.