Characteristics of noncarious cervical lesions: a clinical investigation

BACKGROUND

The purpose of the authors' in vivo investigation was to analyze the characteristics of noncarious cervical lesions, or NCCLs, in adult patients who had a high incidence of them.

METHODS

The patient pool consisted of a total of 57 patients and 171 teeth (three teeth per patient), with one NCCL per tooth. The characteristics the authors evaluated were shape, dimensions, sensitivity, sclerosis and occlusion.

RESULTS

In terms of lesion characteristics, 91 percent of the lesions had axial depths of 1 to 2 millimeters, 49 percent had occlusogingival widths of 1 to 2 mm, 74 percent had an angular shape of 45 to 135 degrees, 76 percent had mild or moderate sclerosis, and 73 percent had no or mild sensitivity. In terms of occlusion, 75 percent of teeth had an Angle Class I occlusion on the involved side, 60 percent had group function or mixed excursive guidance, 82 percent had wear facets, and 99 percent had Type 0 or I mobility. In terms of tooth location, 70 percent of NCCLs were on posterior teeth, 65 percent were on maxillary teeth, and 46 percent were on premolars.

CONCLUSIONS

The evaluated NCCLs were found mainly to have small dimensions of depth and width (< 2 mm) and to be roughly right-angled in shape, and many had sclerosis and low sensitivity. A majority of the dentitions studied had Class I occlusion, with group function, prevalent wear facets, and little or no mobility. Cervical lesions were more common with posterior maxillary teeth and premolars, especially first premolars, which had the highest prevalence of lesions. Older patients were more likely to exhibit noncarious cervical lesions, but no great difference in incidence was found between men and women. Clinical Implications. A knowledge of the NCCL characteristics and etiologic covariables aids in proper case selection for treatment, aids in selection of appropriate treatment protocols and improves assessment of prognosis.

Preserving the vital pulp in operative dentistry: 3. Thickness of remaining cavity dentine as a key mediator of pulpal injury and repair responses

Confusion surrounds the pivotal role played by the remaining dentine thickness in a cavity in determining pulpal injury and repair response outcomes after restorative treatment. The multifactorial nature of the injury repair response requires that attention is focused on the most important factors, including remaining dentine thickness, to harness the natural regenerative properties of the pulp and to avoid postoperative treatment complications.

Preserving the vital pulp in operative dentistry: 2. Guidelines for successful restoration of unexposed dentinal lesions

The exciting treatment possibilities arising from tissue engineering approaches are still some years away from involvement in dentistry. Meanwhile, it is important to optimize conventional treatments, although precise information on pulp responses to cavity preparation and restoration variables are limited. Odontoblast survival, pulp inflammation, and tertiary dentine area are used as measures of pulp injury and repair.

Expression of amelin and trauma-induced dentin formation

According to recent studies, amelin (ameloblastin, sheathlin) is expressed in young odontoblasts at the initiation of dentin formation during odontogenesis. The purpose of the present investigation was to study whether amelin is also expressed at the onset of trauma-induced reparative dentin formation. The mandibular developing first molars of 5-day-old rats were surgically taken out, and their pulp tissue briefly separated from the inner dentin surface and immediately repositioned. Then the teeth were re-implanted in their alveoli. At 0, 2, 4, 6, 8, 12 or 14 days after surgery, the animals were sacrificed and the experimental teeth evaluated by histology and immunohistochemistry for amelin. At 2, 4, 6 and 8 days after surgery, the detached and traumatized odontoblasts in the experimental teeth exhibited increasing signs of degeneration and loss of intracellular structures. At days 6 and 8 after surgery, immunohistochemistry revealed a strong staining for amelin in the traumatized odontoblastic layer. Twelve and 14 days after replantation, only necrotic cell remnants of the traumatized odontoblasts were discernible. At this stage, no amelin could be detected by immunostaining. A wide zone of an unorganized mineralized tissue surrounded the odontoblastic cell remnants. On the pulpal side of the unorganized tissue, a new, highly organized tubular reparative dentin layer was observed, bordered by columnar odontoblast-like cells abutting on newly formed predentin. The results indicate that the initiation of trauma-induced reparative dentin formation mimics that of primary dentin formation and that amelin seems to be involved in both processes, possibly as a signaling molecule.

Preserving the vital pulp in operative dentistry: I. A biological approach

This is the first in a series of four papers aimed at understanding human pulpal responses to tissue injury, cavity preparation and restorative events. This article provides an insight into the exquisite regenerative potential of the dentine-pulp complex which underpins the success of restorative dentistry.

Cavity remaining dentin thickness and pulpal activity

PURPOSE

To investigate pulpal injury by measuring odontoblast numbers, and pulp dentin repair activity by measuring reactionary dentin area, in relation to the remaining dentin thickness (RDT) of cavity preparations in 217 human teeth.

MATERIALS AND METHODS

Cavities were restored with adhesive bonded composite, resin-modified glass-ionomer cement, zinc oxide-eugenol or calcium hydroxide materials. The teeth were extracted for orthodontic reasons between 20-381 days post-operatively, and odontoblast numbers and reactionary dentin area were analyzed histomorphometrically, and statistically using ANOVA.

RESULTS

Reactionary dentin deposition was observed beneath cavities with a RDT above 0.5 mm as well as beneath cavities with a RDT below 0.25 mm; however maximal reactionary dentin appeared to be beneath cavities with an a RDT between 0.5-0.25 mm (P= 0.0001). The area of reactionary repair was also influenced by the choice of restoration material (P= 0.0385) from greatest to least; calcium hydroxide, composite, resin-modified glass-ionomer cement and zinc oxide-eugenol. Odontoblast numbers were maintained beneath cavities with a RDT above 0.25 mm, cavities placed closer to the pulp appeared to injure underlying odontoblasts, reducing their numbers (P= 0.0001). The choice of cavity restoration material also influenced the survival of underlying odontoblasts (P= 0.0061).

A study in two centres of variations in the time of apical barrier detection and barrier position in nonvital immature permanent incisors

OBJECTIVES

To study barrier formation in nonvital, immature permanent incisors being treated using the apexification technique in two centres, and to establish the effect of the frequency of change of calcium hydroxide (CaOH) on barrier detection times.

DESIGN

A retrospective study of the time of detection and the position of barriers.

RESULTS

There were no significant differences between the two centres in terms of the average frequency of change of each CaOH dressing, the distribution of barrier detection times or the position of barriers (P > 0.05). There was a total of 107 teeth and the time of barrier detection was significantly earlier in more frequently dressed teeth (P = 0.013). Of the teeth with a barrier detection time of less than 9 months, 60.7% were dressed more frequently than every 3 months, as opposed to 39.1% of teeth with longer barrier times (P = 0.027). The mean time of barrier detection for all cases was 43.3 weeks. The majority of barriers were located at or near the apex.

CONCLUSION

The frequency of change of CaOH can increase the speed of barrier detection but does not appear to affect the position.

Pattern of transmission of laser light through carious molar teeth

AIMS

The aims of this study were to investigate the pattern of transmission of laser light through carious human molar teeth, and to examine the effect on light transmission of reactions to caries in the dentine.

METHODOLOGY

Sectioned carious human molars were examined whilst illuminated from their external surfaces by a helium-neon laser probe of 0.5 mm diameter. The pattern of light transmission was observed and selected specimens were photographed. The passage of light through the surrounding dentine toward the pulp space was investigated by confocal microscopy. Further carious and restored teeth were illuminated from three buccal and three lingual sites to establish the probability of light being able to reach the coronal pulp space.

RESULTS

For all 31 teeth examined, it was possible to illuminate the pulp space from a position on the buccal side. The presence of intracoronal restorations did not necessarily prevent light transmission to the pulp. Confocal microscopy demonstrated conduction of light within dystrophic deposits of irregular secondary dentine.

CONCLUSIONS

The presence of carious lesions or restorations in molar teeth does not necessarily interfere with transmission of laser light to the pulp space. Light is conducted within irregular secondary dentine. With appropriate probe placement, assessments of pulp health in diseased posterior teeth may be possible using laser Doppler flowmetry.

Application of bioactive molecules in pulp-capping situations

To evaluate the effects of bioactive molecules in pulpal wound healing, we carried out experiments using the rat upper molars as an in vivo model. Cavities were prepared on the mesial aspect, and pulp perforation was accomplished by the application of pressure with the tip of a steel probe. After the pulp-capping procedure, the cavities were filled with a glass-ionomer cement. Comparison was made between and among: (1) sham-operated controls with dentin and predentin fragments implanted in the pulp during perforation after 8, 14, and 28 days; (2) carrier without bioactive substance; (3) calcium hydroxide; (4) Bone Sialoprotein (BSP); (5) different concentrations of Bone Morphogenetic Protein-7 (BMP-7), also termed Osteogenic Protein-1 (OP-1); and (6) N-Acetyl Cysteine (NAC), an anti-oxidant agent preventing glutathione depletion. Histologic and morphometric comparison, carried out among the first 4 groups on demineralized tissue sections, indicated that, at 28 days after implantation, BSP was the most efficient bioactive molecule, inducing homogeneous and well-mineralized reparative dentin. BMP-7 gave reparative dentin of the osteodentin type in the coronal part of the pulp, and generated the formation of a homogeneous mineralized structure in the root canal. These findings indicate that the crown and radicular parts of the pulp bear their own specificity. Both BSP and BMP-7 were superior to calcium hydroxide in their mineralization-inducing properties, and displayed larger areas of mineralization containing fewer pulp tissue inclusions. The overall mineralization process to these molecules appeared to proceed by mechanisms that involved the recruitment of cells which differentiate into osteoblast-like cells, producing a mineralizing extracellular matrix. We also provide preliminary evidence that NAC induces reparative dentin formation in the rat molar model. Pulp-capping with bioactive molecules provides new prospects for dental therapy.

Enamel matrix derivative promotes reparative processes in the dental pulp

During odontogenesis, amelogenins from the preameloblasts are translocated to differentiating odontoblasts in the dental papilla, suggesting that amelogenins may be associated with odontoblast changes during development. In the present study, we have explored the effects of enamel matrix derivative (EMD) on the healing of a pulpal wound. Coronal pulp tissue of permanent maxillary premolars of miniature swine were exposed through buccal class V cavities. The exposed pulp was capped with EMD. The contralateral teeth served as controls and were capped with a calcium hydroxide paste (Dycal). The cavities were sealed with glass-ionomer cement. After 2 and 4 weeks, the histology of the teeth was analyzed. In the EMD-treated teeth, large amounts of newly formed dentin-like hard tissue with associated formative cells outlined the pulpal wound separating the cavity area from the remaining pulp tissue. Inflammatory cells were present in the wound area but not subjacent to the newly formed hard tissue. Morphometric analysis showed that the amount of hard tissue formed in EMD-treated teeth was more than twice that of the calcium-hydroxide-treated control teeth (p < 0.001), suggesting that EMD is capable of promoting reparative processes in the wounded pulp more strongly than is calcium hydroxide.

Further observations on tertiary dentin in human deciduous teeth

The structure of reparative tertiary dentin in human deciduous teeth has been studied. Reparative dentin is secreted by a new generation of odontoblast-like cells which have been subject to strong stimuli, e.g., trauma or deep active caries lesions with associated pulp inflammation. Ground sections of 25 teeth were prepared, and contact microradiographs were produced. Another 30 teeth were demineralized, embedded in paraffin, sectioned, and stained with hematoxylin and eosin. Some demineralized sections from each tooth were also studied in the scanning electron microscope. Most of the teeth showed some type of tertiary dentin formation. Mineralized tissue with a varied morphology was observed. In teeth which had been subject to trauma, the entire pulp chamber was sometimes obliterated. Mineralization seemed to start in the incisal region, and the central part of the pulp was the last part to be obliterated. Radiolucent voids and canals were seen. The organic matrix was dense and fibrous. In the pulp chamber and especially in the root canals, resorption had often occurred, indicating that signals giving rise to odontoclasts were also present. Resorption was often followed by deposition of various amounts of cementum-like repair tissue. The cells responsible for the formation of reparative dentin are believed to be subodontoblasts or undifferentiated ectomesenchymal cells. The varied morphology of the reparative dentin, observed in the pulp of the teeth examined, indicates that different stimuli lead to induction of hard-tissue-forming cells which produce different types of hard tissue.

Pulp-capping with recombinant human insulin-like growth factor I (rhIGF-I) in rat molars

The aim of this study was to explore pulp healing and reparative dentinogenesis following pulp-capping by using recombinant human insulin-like growth factor I (rhIGF-I). Exposures were made through the mesial pulp horn in first upper molars in two-month-old Wistar rats. The pulp was covered with one dose of sterile 4% methylcellulose gel containing either 400 ng rhIGF-I or saline in contralateral controls. The exposure site was closed with sterile Teflon membrane, and the cavity was filled with IRM cement. Additional molars were capped with Dycal as controls. After 3, 7, or 28 days, animals were anesthetized and fixed by intravascular glutaraldehyde perfusion. Molars were decalcified and processed for histological analysis and cut with membrane and residual methacrylate from IRM in situ. Only specimens with acceptable pulp sealing according to blinded microscopy control were included. On day 3, identical inflammatory responses in the upper pulp were observed in molars with rhIGF-I gel or control gel. On day 7, granulation tissue ingrowth had partly replaced inflammatory infiltration in both groups. After 28 days, complete dentin bridging and tubular dentin formation were observed more frequently and closer to the test substance containing rhIGF-I. The reparative dentin response to capping with rhIGF-I was similar to that after the use of Dycal. In conclusion, microscopic control of membrane sealing in situ gives valid information on the more subtle pulp effects of growth factors. The observations suggest that pulp-capping of rat molars by means of rhIGF-I enhances reparative dentinogenesis in comparison with vehicle controls.

Bonding of a self-etching primer to non-carious cervical sclerotic dentin: interfacial ultrastructure and microtensile bond strength evaluation

PURPOSE

The objectives of this study were 1) to examine the ultrastructural features of the resin-sclerotic dentin interface following the application of Clearfil Liner Bond II sigma to natural cervical wedge-shaped lesions, and 2) to evaluate the regional tensile bond strength of this self-etching primer at different locations on natural and artificially-created cervical lesions.

MATERIALS AND METHODS

Deep cervical natural lesions were bonded using the self-etching primer. Micromorphology of the bonded interface at different locations within the lesions were examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and scanning transmission electron microscopy/energy dispersive x-ray analysis (STEM/EDX). Ultrastructural features were further compared with the use of the same self-etching primer on artificial lesions created in sound cervical dentin. A nontrimming technique was used to evaluate the regional tensile bond strength from the occlusal, gingival, and the deepest central part of both natural and artificial cervical lesions. Beams with a mean area of 0.46 +/- 0.03 mm2 were prepared and were pulled to failure using a Bencor Multi-T testing device attached to an Instron universal tester. Bond strength results were evaluated using a two-way ANOVA design.

RESULTS

A hypermineralized layer devoid of intact, banded collagen was invariably present on the surface of the natural lesions. Depending upon its thickness at different locations of the lesion, the action of a self-etching primer may be limited to this surface layer alone, producing a hybridized hypermineralized surface layer. Penetration of the self-etching primer into the underlying sclerotic dentin produced a hybridized complex containing a hybridized hypermineralized surface layer as well as a subsurface layer of hybridized intertubular dentin. Bacterial colonization of the lesion surface resulted in the formation of an additional zone of hybridized intermicrobial matrix over the surface of the lesions. Dentinal tubules remained blocked with sclerotic casts, and resin tags were rarely observed. Regional tensile bond strength results showed that the overall bond strength to natural sclerotic dentin was about 20% lower than sound cervical dentin, but was independent of the different locations within the lesions from which bond strength was evaluated.

CONCLUSION

There were four factors that may have influenced the overall decrease in bond strength in natural cervical sclerotic lesions: a) the presence of a hybridized intermicrobial matrix together with entrapped bacteria may have weakened the bonds, b) inability of a self-etching primer to etch through a thick, hypermineralized surface layer, c) presence of a layer of possibly remineralized, denatured collagen at the base of the hypermineralized surface layer, and d) retention of acid-resistant sclerotic casts that obliterate the tubular lumina and prevent effective resin tag formation.

Histopathology of the pulp of primary molars with active and arrested dentinal caries

The purpose of this study was to compare the histological appearance of the pulp of human primary molars with active and arrested lesions. The sample consisted of 36 primary molars (18 with active lesions and 18 with arrested lesions) extracted from 35 children between 5 to 9 years of age. The histological diagnosis was classified in normal pulp, transitional stage, partial pulpitis, total pulpitis and total necrosis, and then subdivided in three subgroups: treatable, untreatable and questionable. Results showed that normal pulp or transitional stage (treatable category) was diagnosed in 50% of teeth with arrested lesions, compared to 11.1% of teeth with active lesions. Partial pulpitis (questionable category) was present in 38.8% with arrested lesions compared to 22.2% with active lesions. Total pulpitis and total necrosis (untreatable category) was diagnosed in 11.2% with arrested lesions compared to 66.7% with active lesions. The observed frequencies of histological categories between both groups were statistically significant (P < 0.05). Histologically, pulp reaction under active and arrested lesions in primary molars revealed the formation of a basophilic calcio-traumatic line at the junction of the primary and reparative dentin, formation of reparative dentin and a regular odontoblastic layer in 60% of the cases. Results indicated that the type of lesion (active or arrested) is a good indicator of the histological status of the pulp.

Pulpal evaluation of two adhesive systems in rat teeth

Formocresol is the agent most frequently used with pulpotomies in primary teeth, but its use is currently under discussion in regard to its possible toxic effects. Some current works suggest the use of dentinal adhesives in cavities with minimal dentinal thickness and even in small pulpal exposures. Our objective was to evaluate pulpal response to the application of two dentinal adhesives Syntac and Prime & Bond NT in pulpal exposures in rat teeth. Sprague Dawley rats were used, male, 150 to 200 gm in weight. The maxillary first molar, left and right, was employed in each case, a total of twelve teeth. Duration of the study was 45 days. Sections were evaluated using a light microscope in order to determine pulpal response to the two adhesives. In both groups the persistence of chronic inflammation was associated with the absence of dentinal bridges in the affected specimens. Areas of necrosis and absence of regularity of the odontoblastic layer could also be seen.

Response of human pulps capped with a self-etching adhesive system

OBJECTIVE

The aim of this study was to evaluate the human pulp response following direct pulp capping with a current self-etching bonding agent and calcium hydroxide (CH).

METHODS

Thirty-three sound human premolars had their pulp tissue mechanically exposed. Sterile distilled water was used to control the hemorrhage and exudation from the pulp exposure site. The pulps were capped with Clearfil Liner Bond 2 (CLB-2) or CH and the cavities were filled with a resin composite (Z-100) according to the manufacturer's instructions. After 5, 30 and 120-300 days, the teeth were extracted and processed for microscopic examination.

RESULTS

At short-term, CLB-2 elicited a mild to moderate inflammatory pulp response with dilated and congested blood vessels adjacent to pulp exposure site. With time, macrophages and giant cells engulfing globules and particulates of resinous material displaced into the pulp space were observed. This chronic inflammatory pulp response triggered by fragments of bonding agent displaced into the pulp space did not allow pulp repair interfering with the dentin bridging. On the other hand, pulps capped with CH exhibited an initial organization of elongated pulp cells underneath the coagulation necrosis. Pulp repair and complete dentin bridge formation was observed at long-term evaluation.

SIGNIFICANCE

The present study demonstrated that CH remains the pulp capping agent of choice for mechanically exposed human pulps. CLB-2 did not allow complete connective tissue repair adjacent to the pulp exposure site. Consequently, this bonding agent cannot be recommended for pulp therapy of sound human teeth.

Unusual fracture of a mandibular second premolar: a case report

Root fractures of posterior teeth, which are defined as fractures involving cementum, dentin, and pulp, are relatively uncommon among dental traumas. This study describes an unusual horizontal fracture of a mandibular second premolar. The tooth was asymptomatic and the fracture unnoticed until the crown broke off completely. The patient had no recollection of a causative event nor was there any evidence of previous physical trauma. The tooth was extracted, embedded in resin, sliced, and examined with different light microscopes. It was concluded that the tooth had been damaged previously but not to the extent that the pulp was seriously damaged. Resorption over a period of time eventually caused the final fracture.

Reaction of rat connective tissue to implanted dentin tube filled with mineral trioxide aggregate, Portland cement or calcium hydroxide

The subject of this study was to observe the rat subcutaneous connective tissue reaction to implanted dentin tubes filled with mineral trioxide aggregate, Portland cement or calcium hydroxide. The animals were sacrificed after 7 or 30 days and the undecalcified specimens were prepared for histological analysis with polarized light and Von Kossa technique for mineralized tissues. The results were similar for the studied materials. At the tube openings, there were Von Kossa-positive granules that were birefringent to polarized light. Next to these granulations, there was an irregular tissue like a bridge that was Von Kossa-positive. The dentin walls of the tubes exhibited in the tubules a structure highly birefringent to polarized light, usually like a layer and at different depths. The mechanism of action of the studied materials has some similarity.

The anti-inflammatory effects of human recombinant copper-zinc superoxide dismutase on pulp inflammation

Inflammation in the dental pulp is accompanied by release of a wide variety of highly oxidative molecules known as reactive oxygen species (ROS). ROS concentrations are controlled in vivo by an antioxidant enzyme scavenger system that may be overwhelmed by the increases in ROS production seen during inflammation. Supplementation of the antioxidant defense system, therefore, may limit the severity of the inflammatory response to injury due to this component. To test this hypothesis, this study examined the effects of superoxide radical scavenging on pulpal inflammation induced in rat molars by standardized cavity preparation. The extent of pulp inflammation was compared histomorphometrically between animals treated with exogenous administration of a human recombinant antioxidant enzyme, copper-zinc superoxide dismutase, conjugated to polyethylene glycol (hr-CuZn-SOD), versus saline-vehicle controls. There was a statistically significant reduction in area of inflammation involvement in those animals treated with hrCuZn-SOD, compared with controls. Although hrCuZn-SOD administration did not completely eliminate inflammation in all animals treated, there was a statistically significant lessening of the severity of the inflammatory response, as well as a greater degree of reparative dentin observed in the hrCuZn-SOD-treated animals.

Pulpal response to exposure with Er:YAG laser

OBJECTIVE

The purpose of this study was to evaluate the pulpal response to the Er:YAG laser after accidental exposure of the pulp.

STUDY DESIGN

Cavities were prepared, and pulps were exposed by either Er:YAG laser or mechanically by a slow-speed conventional handpiece (control group) in 76 maxillary first molars of male Wistar rats. Rats were killed immediately, at 3 days, 1 week, and 2 weeks. Histopathologic examinations of the pulp at the exposure site were performed and evaluated with the Mann-Whitney U test (P <.05).

RESULTS

The Er:YAG laser group showed no bleeding and no dentin chips at the exposure site immediately after pulp exposure. However, they displayed an area of blood extravasation near the exposure site. Subsequently, the Er:YAG laser group formed dentin bridges at the exposure site more frequently than the control group. The Er:YAG laser group demonstrated more reparative dentin formation near the exposure site than the control group, especially at 2 weeks, which was highly significant (P <.01).

CONCLUSION

According to the results of this study, Er:YAG laser-exposed pulp tissue demonstrated good healing capacity with the formation of a dentin bridge and reparative dentin. However, further investigations are suggested to study the effect of the blood extravasation, which appeared near the laser exposure sites.

Demineralization of caries-affected transparent dentin by citric acid: an atomic force microscopy study

OBJECTIVES

This study determined recession rates of peritubular dentin and intertubular dentin in citric acid solution (0.018M, pH=2.5) for caries-affected transparent dentin, one of the major components of dentin substrate as altered by caries, with comparisons made with non-carious dentin.

METHODS

Transparent dentin was identified by sagittally sectioning five obviously carious teeth. Sections were then cut through the transparent dentin area perpendicular to the course of the dentinal tubules. Polished dentin samples of the transparent dentin and non-carious dentin were prepared with an internal reference layer and studied at specific intervals for citric acid etching in an atomic force microscope (AFM).

RESULTS

At baseline, transparent dentin was identified by dentinal tubules that were largely occluded with mineral deposits that on etching proved to be acid resistant. Peritubular dentin etched rapidly and linearly over time until it could no longer be measured, yielding etching rates for transparent dentin that could not be distinguished from normal dentin. The normal and transparent intertubular dentin surfaces began etching at nearly the same rate, but then surface recession stabilized after less than 1 microm depth change for both dentin types.

SIGNIFICANCE

Most previous studies have focused on demineralization and bonding to normal dentin, although many bonding procedures involve altered dentin substrates, such as those modified by caries. In this study, peritubular and intertubular dentin from normal and caries-affected dentin exhibited similar behavior. The major difference was the presence of acid resistant mineral in most of tubule lumens in the transparent dentin.

Primary molar pulp therapy--histological evaluation of failure

OBJECTIVES

Qualitative comparison of the clinical, radiographic and histological outcomes in a small sample of cariously exposed primary molars, extracted after unsuccessful pulp treatment by two vital pulpotomy methods.

SUBJECTS AND METHODS

The primary molars were extracted, because of treatment failure, during a longitudinal clinical investigation of the relative efficacy of 20% Buckley's Formocresol versus calcium hydroxide powder as pulp dressings in vital pulp therapy (in press). Fifty-two child patients were sequentially enrolled in the longitudinal clinical investigation, 26 boys and 26 girls. Primary molar teeth requiring vital pulp therapy were randomly allocated to either the formocresol group (F) or the calcium hydroxide group (C). Coronal pulp amputation was prescribed only in teeth with vital, cariously-exposed pulp tissue. All cases were reviewed using predefined clinical and radiological criteria. Seventy-nine cariously-exposed primary molars required vital pulp therapy. Forty-four teeth were included in group F and 35 in group C. Five per cent (n = 2) of teeth in group F and 11 per cent of teeth (n = 4) in group C were terminated from the trial due to clinical and/or radiographic failure. Of the six teeth extracted, five were sufficiently intact to be retained for histological evaluation.

RESULTS

Post-extraction radiographs taken before specimen preparation showed reactionary dentine barrier (bridge) formation in teeth treated with calcium hydroxide. However, the narrowing of root canals, indicative of appositional reactionary dentine deposition, was seen in both groups (F and C). Histological examination confirmed these findings and revealed that pus cells were evident in all specimens examined. There was also histological evidence of resorption of reactionary dentine within the root canal and that forming the calcified barrier (dentine bridge).

CONCLUSION

The clinical and radiographic outcomes for the five teeth correlate well with the reported findings from decalcified histological section. Although numbers are small, the histological findings may indicate possible reasons for treatment failure. There are few reports of this sort in the literature of this under-researched treatment modality.

Immunolocalization of heat shock protein 70 during reparative dentinogenesis

OBJECTIVE

To investigate the immunolocalization of heat shock protein 70 (hsp 70) during reparative formation and to discuss the role of heat shock response in dental pulp injury and repair.

METHODS

A single cavity was prepared in the mesial surface of the first molars of both maxilla and mandible in Wistar rat. The animals were sacrificed at 3, 15, and 30 days post-operation. After the histological process, the paraffin sections were reacted with monoclonal antibodies against rat hsp 70 using the strept-avidin-biotin-peroxidase complex method.

RESULTS

Immunolocalization demonstrated heavy staining for hsp 70 in normal pulp and at different stages of dental pulp repair. In normal pulp, immunoreactivity was visualized in the odontoblasts and the pulp fibroblast. In the group sacrificed at 3 days, heavy staining was located in the odontoblast process and cytoplasm. After 15 days, the newly formed odontoblast-like cells were strongly stained. At 30 days, the same staining intensity was observed in odontoblast-like cells and in pulp cells. No staining was seen in reparative dentin.

CONCLUSION

These results demonstrated that heat shock protein 70 might play an important role as a molecular chaperone during reparative dentin formation.

A quantitative light microscopic study of the odontoblast and subodontoblastic reactions to active and arrested enamel caries without cavitation

This study describes cellular and microradiographic findings in thin undemineralized enamel-dentine sections from 36 enamel caries lesions from freshly extracted third molars. Lesions activity was determined by clinical examination and the estimated age of the lesion at extraction time. The cellular reactions to the enamel/dentine lesion complex were measured using computerized histomorphometry under the following conditions: (a) the cytoplasm:nucleus ratio of the odontoblast cell; (b) the odontoblast cell:dentinal tubule ratio, and (c) the adjacent predentine area (microm2). The first cellular reactions were observed beneath superficial enamel lesions before visible alterations in dentine mineralization. The cytoplasm:nucleus ratio of the odontoblast cells was markedly reduced, and only active lesions showed evidence of cellular proliferation into the cell-free zone. In more advanced active lesions the affected odontoblast cells had a significantly lower cytoplasm:nucleus ratio compared with the controls. Similar changes were not seen in arrested or slow-progressing lesions. Before onset of tertiary dentine formation there was a positive correlation between odontoblast cell size and predentine formation. Primary odontoblast cells were involved in early tertiary or reactionary dentine formation without odontoblast cell replacement. Reactionary dentine was only seen in active lesions, suggesting that reactions in the dentine/pulp complex are closely associated with the external environment.