Dense innervation of human radicular dental pulp as revealed by immunocytochemistry for protein gene-product 9.5

Protein gene-product 9.5 (PGP 9.5) is a novel neurone-specific protein. At light- and electron-microscopic levels, human radicular dental pulp was heavily innervated by PGP 9.5 nerve fibres. Thick nerve bundles showing intense PGP 9.5 immunoreactivity ascended in the centre of the pulp, with some nerve fibres extending from the trunk towards the peripheral pulp at regular intervals. However, the fibres did not form a plexus (of Raschkow) beneath the odontoblast cell layer. The PGP 9.5-positive nerve fibres penetrated into the predentine and dentine beyond the odontoblast cell layer where some nerves terminated. In the predentine, PGP 9.5-positive nerve fibres were densely distributed. In tangential sections along the pulpodentinal border, the nerve fibres ran in contact with odontoblast processes. Immunoelectron microscopy revealed that all nerve fibres were immunoreactive for PGP 9.5 in the radicular predentine and dentine, and terminated in contact with the odontoblast cell processes. The distribution pattern and terminal formation of predentinal and dentinal nerves were identical to those of coronal pulp, as reported previously. The dense innervation in radicular dental pulp, overlooked in previous reports, might be responsible for dentine hypersensitivity.

Localization of NADPH-diaphorase activity in the dental pulp, periodontium and alveolar bone of the rat

In this study we examined the presence and localization of nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) activity in the dental pulp, periodontal tissues and alveolar bone of the rat. The presence of NADPH-d activity was also examined in cat pulp. The rat histochemical analysis revealed the presence of prominent NADPH-d activity both in cells of the sub-odontoblastic cell layer and in the odontoblasts, in the root as well as in the coronal pulp regions. In the pulpal horns, odontoblasts often had long processes with a high level of labelling indicating NADPH-d activity extending through the predentin and dentin. Moreover, endothelial cells of pulpal blood vessels were positive for NADPH-d in both species. However, no clearcut examples were found of pulpal nerve fibres positive for NADPH-d in the rat or cat and denervation performed in rats did not alter the enzyme staining patterns. In the periodontal tissue, NADPH-d activity was localized to cells on the alveolar bone surface of the periodontal ligament and, in addition, alveolar bone marrow crypts were filled with intensely labelled cells. In the gingival papillae, NADPH-d activity was observed in the basal cell layer of the epithelium. Endothelial cells of periodontal and gingival blood vessels showing positive staining for NADPH-d were occasionally noted.

Induction of reparative dentine formation in monkeys by recombinant human osteogenic protein-1

Osteogenic protein-1 (OP-1, BMP-7), a member of the transforming growth factor-beta supergene family, induces cartilage and bone formation when implanted in intra- and extraskeletal sites in vivo. The human OP-1 gene has been cloned and biologically active recombinant OP-1 homodimers (hOP-1) produced. The amount of bone induced by hOP-1 in vivo is related to the amount of protein implanted. Dentine possesses bone morphogenetic protein (BMP) activity. Impure material from allogenic bone with BMP activity induced reparative dentine formation in dogs. The objective of this study was to determine if the amount of reparative dentine stimulated by hOP-1 is related to the amount of protein utilized in direct pulp-capping experiments. Freshly exposed molar and premolar pulps were treated with varying amounts of a complex comprising hOP-1 and a carrier matrix of purified bovine type-1 collagen powder (CM) moistened with sterile saline. Reparative dentine was present in all hOP-1/CM treated teeth (12 of 15) that remained sealed for the 6 weeks' healing. Substantially more new dentine was present in teeth treated with hOP-1/CM than in those treated with Ca(OH)2 paste and the amount of reparative dentine formed was proportional to the amount of hOP-1/CM (P < 0.05). No reparative dentine formed in collagen carrier or untreated teeth. The appearances of the new tissue suggested that much of the mass of the hOP-1/CM was replaced first by a pulp-like connective tissue, which mineralized to form reparative dentine.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental anatomy portrayed with microscopic volume investigations

The clinical treatment of the root canal of teeth--called endodontics--assumes a precise idea of the spatial arrangement of the anatomy of teeth and their inner structure. By using computer-assisted data acquisition from filmed sequences of histologic serial sections and a special kind of magnetic resonance microscope--the Stray Field Imaging (STRAFI)--volume investigations were carried out using special functions of a newly developed 3D software. Possible applications and future perspectives are discussed.

Lymphatic vessels of the human dental pulp in different conditions

The characteristics of the lymphatic vessel endothelial wall have been investigated in human normal and inflamed dental pulps. In normal pulps the endothelial wall is characterized by the presence of micropinocytotic vesicles and intraparietal channels. In the inflamed pulpal tissue, where an increase in interstitial fluid pressure occurs, the distended endothelial wall presents open junctions between endothelial cells and the openings of the intraparietal channels. Moreover the micropinocytotic vesicles disappear. The cytoplasm of the endothelial cells is characterized by the presence of numerous Weibel-Palade bodies, which increase in number in the dilated vessels. In the fibrillar apparatus surrounding the lymphatic vessel wall collagen fibrils are the prevalent component, while elastic fibers are not present. The different morphological properties of the lymphatic vessels are compared and discussed with regard to the variation of the functional conditions of the tissue.

Amount of secondary dentin as an indicator of age

The amount of secondary dentin in a tooth has been used as one of several parameters in methods for age estimation. Dentin deposition has been measured according to various scoring systems, and the Pearson correlation coefficient with age has been found to be approximately 0.6. In the present study of 1000 teeth, molars excluded, secondary dentin was estimated according to three scoring systems. The teeth were prepared according to the half tooth technique. In addition, the area of the coronal pulp and the widths of the root and pulp chamber were measured in a stereomicroscope at the cemento-enamel junction and at three other defined points along the root. The Pearson correlation coefficient between age and secondary dentin varied in different types of teeth. Of the scoring systems, scores according to Johanson were most strongly correlated with age (r = 0.59 to 0.74). Correlation between age and the coronal pulp area varied from -0.47 to -0.72, and the range between age and ratio between pulp- and tooth width at the cemento-enamel junction was from -0.46 to -0.77. Correlations between age and ratio between sum of pulp widths and the sum of tooth widths for all four such measurements ranged from -0.58 to -0.81. Multiple regression analyses showed that by combining several types of measurements, the correlation with age was increased. A tendency was also observed towards reduced speed of secondary dentin formation in the elderly and in women.

[The nerve fiber projection of trigeminal ganglion cell to dental pulp, dentine and periodontal membrane in the rat]

The nerve fiber projection of the trigeminal ganglion cell to dental pulp, dentine and periodontal membrane was investigated with the technique of anterograde radioautographic neuroanatomical tracing (ARNT) in the rat. Results showed that the innervation in dentine and pulp was not uniform. The nerve endings were most numerous in the pulp horn, and in the tubular dentine of the cusp and cervical regions. In the periodontal membrane, both large- and small-diameter nerve fibers were found. And at least part of the innervation in the periodontal membrane was of trigeminal ganglion origin.

Thermal response to multiple use of a twist drill

The objective of the present investigation was to determine whether injurious thermal changes occur in the pulp chamber if a twist drill is used 10 times, and to find whether there is a correlation between temperature rise and distance between a drilled channel and the pulp chamber. Twenty caries-free, human, premolar teeth were randomly distributed to two dentists. With a new 2 mm twist drill, each dentist prepared 10 pinholes (one hole per tooth). Intrapulpal temperature change during the drilling procedure was recorded. The data were statistically analyzed by the Spearman rank order correlation coefficient. The results showed that twist drills should not be used for more than five pinholes (p less than 0.001). The distance between the pin channel and the pulp chamber does not influence heat generation in the pulp chamber.

Effect of cavity depth on stresses in a restored tooth

Restorative procedures commonly replace lost tooth structure, but redistribution of functional stresses after treatment is not fully understood. Many restorative methods are dictated by the integrity of the remaining tooth structure, because sparse tooth structure can lead to fracture. It is essential to prevent fractures by having a clear concept of the designs for cavity preparations, and to anticipate the stresses of mastication on the remaining tooth structure. Knowledge of various internal parameters of cavity designs would facilitate selection of the appropriate cavity preparation for a specific clinical situation. Three cavity designs and restorations were examined in this study for stresses using the finite element technique. After placement of restorative materials, the dentin experienced a dramatic change in stress gradient immediately below the pulpal wall, and this response was magnified in deeper cavity preparations. Enamel also exhibited major alterations in the stress gradient in all three designs of cavity preparations. The combination of the changes can cause cracks in the remaining tooth structure, leading to cusp fracture immediately adjacent to the deepest portion of the cavity.

Age-related changes of the dental pulp complex and their relationship to systemic aging

The dental pulp and its associated structures, the dentin and the cementum, are discussed. Because many of the age-related pulpal changes have components considered in several of the current theories of aging, these theories are briefly reviewed. Part 2 describes the age-related changes of the dental pulp, the dentin, and the cementum (the dental pulp complex). An attempt is made to differentiate inherent aging changes from physiologic defensive changes and pathologic irritant-induced changes. Part 3 describes the relationship of age-induced changes in the dental pulp complex to components of the current aging theories together with a unified concept of the dental pulp complex aging. Part 4 considers whether dental pulp complex aging can be used as a biomarker for generalized aging. Whether age-related changes of the dental pulp complex can be altered by interventions is discussed.

[Non-invasive method of measuring dentin resistance to the limit of the preparation depth]

Electrical resistance measurements may be used to determine the situation of the pulp horn tips of teeth prepared for crown restorations. The resistance value recorded for these sites of minimum dentin thickness depends on the thickness of the dentin layer and the degree of tooth development. A resistance value of 25 k omega revealed dentin thickness of 0.7-1.45 mm. The teeth of younger patients had thicker dentin layers than those of older patients.

Pulpal response to threaded pin and retentive slot techniques: a pilot investigation

This investigation compared pulpal response to threaded pin techniques with response to retentive slot techniques. The teeth were restored with composite resin. Twenty-four teeth were assigned to three treatment groups in one Macaca mulatta monkey. Ten teeth (group 1) received 32 TMS 0.021-inch self-threading pins. Ten teeth (group II) received circumferential slot retention 1 mm deep, 0.5 mm inside the dentinoenamel junction. Four teeth (group III) served as controls. Groups I and II were restored with composite resin. Fourteen days later, the teeth were removed, demineralized, serially sectioned, and stained with hematoxylin and eosin. Chi-square analysis indicated more pulp inflammation when self-threading pins were used (p less than 0.5). Pins placed within 0.5 mm of the pulp elicited severe inflammatory responses, and those placed further than 1 mm had minimal effect. Little correlation existed between remaining dentin thickness and adverse pulp response when slot retention was used.

[A histological study of hard dental tissues in nondecalcified sections using the cutting-grinding technic]

With the cutting-grinding technique (Exakt System) it is possible to obtain sections with a width of less than 10 microns of specimens such as teeth, crowns, bridges, implants, mineralized structures, which cannot be cut with routine histological techniques. In the present paper the authors study the efficacy of this technique in hard dental tissues.

Histologic evaluation of the pulpal response to temperature probe placement in the Macaca fascicularis monkey

A method to measure intrapulpal temperatures during cavity preparation and restorative procedures has been developed. It involves placement of temperature probes to the dentinoenamel and dentinopulpal junctions. After placement of the probes, the pulps of the test teeth were examined histologically to determine whether their placement caused a pulpal response. The test teeth displayed no adverse response in the areas of the pulp opposite or adjacent to the position of the probes. Therefore the developed method of temperature probe placement to measure intrapulpal temperatures does not interfere with those measurements by adversely affecting the pulp tissues.

[Physiology of autotransplants in the human species. Histological analysis of transplanted upper canine pulps]

10 canine pulps were examined after transplantation. The time of transplant life was not the same in all cases, so it was possible to record all the evolutive patterns during 2 months. Correlating our observations with literature and statistics, it was possible to draw the main aspects of transplant pulp physiology.

In situ testing of CO2 laser on dental pulp function: effects on microcirculation

The effect of CO2 laser irradiation on pulpal microcirculation was studied in cat canines. The enamel surfaces of 4 teeth were exposed with energy densities of 304-1440J/cm2, using either a handpiece or a microslad, with a focal spot of 0.21mm and 0.33mm respectively. Pulpal blood flow (PBF) before and following lasing was recorded through the intact tooth surface by a laser Doppler flowmeter. CO2 laser irradiation caused an increase in PBF, which was immediate and transient. The PBF increase was higher in a large pulp than in a small pulp, and it was inversely related to the focal spot size. These findings confirm that the dental pulp is thermally affected by CO2 lasing of the tooth surface, however, without extensive pulp coagulation. It is concluded that the effects of laser irradiation on the pulpal microcirculation may be studied in situ by means of the presented methodology.

Clinical applicability of the radiographic method for determining the thickness of calcified crown tissues

A previously developed radiologic method for determining the thickness of the mineralized crown tissues was applied clinically to 10 teeth diagnosed for extraction. The thickness of the mineralized crown tissues as measured radiographically was compared with that measured directly on the extracted tooth. A statistical analysis indicated accuracy of 4.46%, equivalent to an error of 0.12 mm.

Peptidergic nerves in human dental pulp. An immunocytochemical study

The peptidergic innervation of human dental pulp was studied with indirect immunofluorescence and immunoperoxidase techniques. Pulpal nerve fibres displaying immunoreactivity for cholecystokinin, calcitonin gene-related peptide, C-terminal flanking peptide of neuropeptide tyrosine, leucine-enkephalin, methionine-enkephalin, neuropeptide K, neuropeptide tyrosine, peptide with N-terminal histidine and C-terminal isoleucine, somatostatin-28, substance P and vasoactive intestinal polypeptide were observed. Immunoreactive axon varicosities were detectable within radicular and coronal nerve trunks and within the nerve plexus of Raschkow in the para-odontoblastic region. Many peptidergic nerve fibres were observed in association with blood vessels of various sizes. Substance P- and calcitonin-gene-related peptide-immunoreactive axons were visible in the odontoblastic layer. The occurrence of VIP- and PHI-immunoreactive fibres lends support to the hypothesis that human tooth may be supplied by parasympathetic nerves. The immunocytochemical results here shown provide a morphological basis to previous experimental studies concerning the possible roles of neuropeptides in nociception mechanisms, control of the blood flow and modulation of the inflammatory response in dental tissues.

Age-progressive changes in pulp widths and root lengths during adulthood: a study of American blacks and whites

The intertwined effects of normal aging processes and time-progressive diseases produce systematic changes in many oral and dental tissues. This cross-sectional study of pulp dimensions and root lengths in sound teeth tested for changes with age in adulthood while controlling for differences in gender and race (black, white). Age was the paramount determinant of pulp size which decreases via the accumulation of secondary dentin. In some instances the rate of change increases in older adults with an inflection point at 35-40 years of age. In contrast, root lengths are statistically independent of age once gender (male greater than female) and race (black greater than white) are controlled. Causes of the lack of association with age are discussed.

An investigation of lymphatic vessels in the feline dental pulp

The existence of lymphatic vessels in the dental pulp has been a matter of continuing controversy. We have now used light microscopy to examine semithin transverse sections of perfusion-fixed incisors and canines in cats. Lymphatics were found in all the teeth studied. In most teeth they were present in the coronal, middle, and apical regions of the pulp; but in a few they were lacking coronally and in the middle. Within individual teeth, lymphatics were found in the subodontoblastic zone or more centrally in the pulp; but none were found in the odontoblast layer or in the pulp horns. Vessels located by light microscopy were subsequently examined by transmission electron microscopy. Their ultrastructural features were typical of lymphatics and included irregular, attenuated endothelium with adjacent cells joined in different ways. Occasional gaps connected the extracellular spaces with their lumens, and abluminal endothelial projections appeared to form open end bulbs. There was very little basement membrane, but anchoring filaments were found near the abluminal surface of the endothelium and near collagen fibrils. The total cross-sectional area of lymphatic vessels was measured in semithin sections and, with pulp area, increased from the coronal region to the middle. However, both areas decreased from the middle to the apical region suggesting either that lymph flows faster as it reaches the foramens of the apical delta or that some vessels leave the tooth through lateral root canals. Using the methods of light and transmission electron microscopy, therefore, we have shown that pulp lymphatic vessels exist. Questions remain, however, about their distribution within teeth, variations between teeth, and routes of exit from teeth.

[The structure and ultrastructure of the pulp in Vipera aspis (Viperidae)]

The present paper using classical and transmission electron microscopy brings the first data on the pulp of the fangs of Viperidae (poisonous serpents with terrestrial or semi-aquatic habits). The pulp of the fangs of Viperidae shows a poor collagen and fibroblast content and a high developed vascular system. The odontoblasts are polarized, with a high organelle content. The interconnections are constituted of lateral "gap junction" systems. At a late secretion stage, the odontoblastic processes show a poor cytoplasm, mainly constituted of microfilaments.

A three-dimensional evaluation of the effects of functional occlusal forces on the morphology of dental and periodontal tissues of the rat incisor

We examined the effect of function on tooth and periodontal ligament (PDL) morphology in 40 lower incisors of adult female rats. Ten teeth were exposed to occlusal hyperfunction for three months, ten to hypofunction for three weeks, ten to hypofunction for three months, while ten teeth in normal occlusion served as control. Transverse ground sections were cut at various levels perpendicular to the tooth long axis, and their distances from the apex were calculated. The outlines of the tissues were traced and fed into a computer. We plotted the measurements according to their location and fitted them by second-order polynomials. We calculated tissue volume for the proximal 18 mm of bone-embedded tooth. Hyperfunction affected tooth shape, in that it became more rounded. The volumes of the dental tissues remained unchanged, while width and volume of the cementum-bordering PDL increased. Hypofunction did not alter tooth shape, but influenced its size: After three weeks, tooth circumference decreased, and after three months, it expanded. Dentin width was reduced, with concomitant increase of pulp size. The amount of enamel diminished initially, but after three months returned to normal values. The PDL bordering enamel expanded proportionally to the duration of hypofunction. The changes in socket size reflected the total dimensional variations in the tooth and its PDL. The results demonstrate that the shape and size of growing teeth and their periodontium are influenced by functional occlusal forces.

Microwave irradiation as a form of fixation for dental pulp

This study investigated developments in microwave energy fixation and the general applicability of microwave fixation to studies of dental pulp. Rat mandibles with incisors were dissected out and immersed in various solutions before and after exposure to microwave energy. Histological examination showed no combination with microwave fixation to be equal in quality to control tissues fixed in formalin. Inferior but satisfactory results could be achieved by immersion of tissues in formalin after microwave irradiation, a step thought to protect the microwave fixed tissue from subsequent damage caused by decalcification. Good fixation of tissues outside the pulp was achieved using microwave energy. Further investigation is required to perfect microwave fixation of pulpal tissue.