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AIM: To assess the location, arrangement and possible function of interodontoblastic collagen fibres in association with calcium hydroxide-induced hard tissue bridges by using light and transmission electron microscopy techniques and immunohistochemical staining localization. METHODOLOGY: Prior to the study, an animal use protocol form was reviewed and approved by the Screening Committee for Animal Research of the Tokyo Medical and Dental University. Exposed monkey pulps were capped with a hard-set calcium hydroxide and histopathologically evaluated at 3, 14, 21, 30 and 90 days, using light microscopy with silver staining and transmission electron microscopy to differentiate structural features of interodontoblastic collagen fibres. In addition, an attempt was made to identify and to differentiate between several types of collagen and fibronectin using immunohistochemical localization techniques. RESULTS: At 14 days, interodontoblastic collagen fibres were observed extending from the original dentine, passing through the odontoblasts, and consisted of two portions: a thick fibril and a thin fibril. At 21 days, interodontoblastic collagen fibres were seen penetrating into the predentine and becoming incorporated into the mineralized dentine. At 30 days, interodontoblastic collagen fibres reached the cell process. Although interodontoblastic collagen fibres were no longer observed near the odontoblastoid cells at the area of the newly formed tubular dentine, interodontoblastic collagen fibres were observed embedded within the primary formed dentine bridge. Immunohistochemical staining demonstrated type I collagen and fibronectin within the interodontoblastic collagen fibres. CONCLUSIONS: Interodontoblastic collagen fibres were routinely detected throughout early dentine bridges. Interodontoblastic collagen fibres are thought to be important for initial dentine bridging to induce and support a dentinogenesis framework.

The sequence of factors that mediate pulp inflammation and necrosis are unclear, and controversy surrounds the effects of different pulp capping materials on exposed pulps. Clinicians have few quantitative studies that rank the in vivo pulp capping effects of commonly used restorative materials.

Alternatives to calcium hydroxide liners in reducing sensitivity after amalgam placement are considered. Certain clinical and biological studies have reported that prepared dentin and the underlying pulp must be protected with a calcium hydroxide base and liners that supposedly impart biological and structural integrity to tissues. Since the mid-1950s, dentists have relied on a number of calcium hydroxide medicaments for this goal. But recent studies imply that clinicians need to re-evaluate the generous use of certain calcium hydroxide medicaments under restorations.

This investigation evaluated the effects of an experimental light-cured glass ionomer (LCGI) cavity liner and chemically cured Ketac-Bond glass ionomer restorative material on the pulpal tissues of monkeys. Class V cavities were prepared in 71 teeth of three adult Macaca mulatta monkeys at 7- and 35-day intervals. Ketac-Bond or LCGI cavity liners were placed in cavities with the smear layer intact (groups I and II) or with the smear layer removed (groups III and IV) and were restored with composite resin. Tissues were acquired, sectioned at 7 μm, stained for microscopic evaluation, or prepared for SEM evaluation. No statistically significant differences between materials existed at either time interval, regardless of smear layer presence. Histopathologic results demonstrated minimal pulpal reactions for groups I through IV. SEM analysis showed tenacious bonding of the LCGI material to prepared cavity walls, with absence of contraction gap formation. The results indicated excellent pulpal responses to both materials.

The purpose of this study was to collect quantitative information about the numbers and dentine bridge secretory activity of odontoblast-like cells following dental pulp exposure.The numbers and secretory activity of odontoblast-like cells were measured histomorphometrically between 7 days and 2 years in 161 pulp-exposed nonhuman primate teeth. The area of dentine bridges and the dimensions of cavity preparations were measured. The density of odontoblast-like cells and subjacent reorganizing tissue cells were measured beneath dentine bridge formation. The presence of operative dentine debris and tunnel defects in bridges was noted. Pulp inflammation was categorized according to ISO standards. Bacteria were detected using McKay's stain.The area of dentine bridges was mediated by the density and secretory activity of odontoblast-like cells over time. The cell density of subjacent reorganizing tissue was found to be strongly associated with that of odontoblast-like cells. Bacterial microleakage was found to impede dentine bridge secretion by odontoblast-like cells.Pulp reparative activity occurs naturally beneath capping materials in the absence of bacterial microleakage. The outcome of pulp-capping treatments could be beneficially influenced by concentrating attention on limiting the width of pulp exposure, minimizing pulp injury by limiting the creation of operative debris and placing materials which prevent bacterial microleakage.

This article provides biological and technological information that strengthens clinicians' understanding of cohesive hybridization and pulp therapy in order to support their routine use of bonding and resin systems. Utilizing cohesive systems, clinicians should experience several advantages over traditional water-soluble base and liner systems. When properly applied, cohesive hybridization of vital dentin prevents immediate postoperative hypersensitivity under all restorations and completely seals the entire tooth-restoration interface, which provides a reduction in recurrent caries.

Objective: The aim of this study was to investigate the human pulp response to Scotchbond Multi Purpose Plus (SMPP) bonding agent in non-exposed Class V cavities. Methods : SMPP was placed in 24 of 40 cavites according to manufacturer's instructions and the cavities were restored with amalgam. The remaining 16 cavities were capped with a calcium hydroxide formulation (Dycal) sealed with zinc-oxide eugenol, and restored with the amalgam. After extraction at 10 and 35 days, the teeth were fixed, sectioned and stained for light microscopy. Results : All Dycal-capped teeth, at both 10 and 35 days, exhibited no pulp inflammation and no demonstrable bacteria. Six cases sealed with SMPP at 10 days showed no pulp inflammation or stained bacterial profiles. The remaining six teeth demonstrated mild to moderate inflammatory pulpal responses and five out of these six cases exhibited stained bacterial profiles. Nine out of 12 teeth showed no inflammatory pulp responses at 35 days, the remaining three cases exhibited mild to moderate pulp inflammation without stained bacteria. Conclusions : None of the teeth sealed with SMPP presented severe inflammatory pulpal reactions histologically. SMPP did not exhibit significant deleterious effects on the human pulp tissue during the test periods.

The aim of this investigation was to assess the role of the von Korff-like fibers (VKF) during the process of dentin bridging.The monkey pulps, exposed to a hard-set calcium hydroxide, were evaluated at 3, 7, 14, 21, 30, 90, and 180 days.At 21 days, longitudinal and transverse collagen fibrils were organized as lamellar structures in close proximity to and subjacent to the newly formed predentin. VKF bundles were present between newly formed odontoblastoid cells. The VKF were bundles of thin collagen fibrils inserted into the predentin, which consisted of thick collagen fibrils. At 30 days, the exposure site was completely occluded with a new predentin matrix; lamellar structures and VKF were no longer present.The VKF may play a role in the connective tissue attachment to the dentin bridge, early in its formation.

This study evaluated the biocompatibility of a resin-modified glass-ionomer material on monkey pulps.Standardized Class V cavities were prepared in 112 teeth distributed in six healthy adult monkeys. The resin-modified glass-ionomer cement was placed in 24 nonexposed and 36 exposed pulps according to manufacturer's instructions. ZOE was used as a control in nonexposed pulps, while calcium hydroxide was used as a control for exposed pulps. Tissues were collected at 6 to 7, 21 to 27, and 90 to 97 days. After demineralization, the teeth were serially sectioned, stained, and observed by light microscopy.Except for one resin-modified glass-ionomer pulp at 6 days, there were no differences between the responses of nonexposed pulps to resin-modified glass-ionomer specimens and ZOE controls. In exposed pulps, eight of 36 resin-modified glass-ionomer pulps showed various grades of inflammatory response, all associated with stained bacteria. Pulpal healing was similar in both resin-modified glass-ionomer and calcium hydroxide direct-capped exposures. Twenty-two of 26 exposed pulps restored with the resin-modified glass-ionomer cement showed dentin bridge formation at 21 and 97 days.The resin-modified glass-ionomer material exhibited acceptable biologic compatibility in exposed and nonexposed cavities.

To evaluate the histologic response of 332 non-exposed and 127 exposed monkey pulps applying nine adhesive systems.Class V and Class I cavities were used in non-exposed and exposed monkey pulps at the three ISO usage time intervals.There were no histologic differences in pulp responses among the nine adhesive systems used in either Class V and/or Class I cavities when compared to pulp responses of Ca(OH)2 controls at the ISO time intervals. The nine adhesive systems and resin composites are non-toxic to either non-exposed or exposed pulps, being biologically compatible to pulp tissues when placed on mechanical pulp exposures following hemorrhage control with a 2.5% NaOCl and per manufacturers' directions. It is imperative that clinicians understand the biological importance of hemorrhage control as well as the technique sensitivity of hydrophilic primers in order to optimize the efficacy of adhesives for clinical success against microleakage of bacterial factors.

Recent studies have demonstrated that acid etching of vital dentin and pulpal tissue does not retard pulpal healing, odontoblastoid cell differentiation, or dentinal bridge formation when the pulp is capped with adhesive resins. The purpose of this study was to evaluate the pulpal response in nonexposed and exposed monkey pulps to treatment with the Clearfil Liner Bond 2 and Clearfil AP-X system.Class V and Class I cavities in nonexposed and exposed pulps were observed at 7 or 8, 27, and 97 days.There were no differences in pulpal inflammation between the Clearfil Liner Bond 2/Clearfil AP-X specimens and calcium hydroxide controls in either Class V or Class I cavities at the various time periods.Clearfil Liner Bond 2 and Clearfil AP-X system is not toxic to either nonexposed or exposed pulpal tissues when placed according to manufacturer's directions.

This study evaluated the histologic responses of two different adhesive systems on the teeth of seven healthy adult monkeys. Class V cavities in 128 teeth were observed at 7,21 to 27, and 90 to 97 days. Statistical data showed no significant differences in pulp inflammation between the Optibond (Kerr), XR-Bond (Kerr), and IRM (Caulk) groups in pulps at the three time intervals. Some odontoblastic disruption and inflammation was seen in pulps restored with XR-Primer at the three time intervals. Pulp healing was similar in teeth treated with both direct-capped Optibond and calcium hydroxide, and there was no significant increase in pulpal inflammation with time. No abscesses or necrotic pulps were seen in any teeth. Optibond and XR-Bond adhesive systems are biologically acceptable in nonhuman primate pulp tissues.

Class V cavities with mechanical exposures were prepared in 178 teeth of seven monkeys to observe the temporal healing of exposed pulps in direct contact with various dental materials, with or without a biologic seal of zinc-oxide eugenol cement against microleakage. Thirty pulps were direct capped as calcium hydroxide controls. The remaining 148 exposures were direct capped, 41 with silicate, 39 with zinc phosphate, 33 with amalgam, and 35 with an auto-cured composite. Sixty-four were restored to their cavosurface margin with their respective material and 84 were sealed to the covosurface margin with zinc-oxide eugenol cement. Tissues were obtained by perfusion fixation at intervals of 35, 21, 14, 10, 5, and 3 days, and then processed and evaluated. The results of this study demonstrated that exposed dental pulps possess an inherent healing capacity, allowing cell reorganization and dentin bridge formation when adequately sealed with zinc-oxide eugenol cement to prevent bacterial microleakage.

Twenty human permanent teeth were used to study the pulpal response of two calcium hydroxide products, Dycal and Pulpdent Multi-Cal, after partial pulpotomy. Teeth were extracted at 4 months, fixed, and prepared for histologic examination. All 10 teeth treated with Dycal showed complete soft tissue healing and bridge formation. No stained bacteria were seen throughout the serial sections. One tooth treated with Dycal showed acceptable histologic results, dentin deposition in the root canal. Six cases dressed with Pulpdent Multi-Cal showed acceptable histologic results, whereas four teeth showed severe inflammation or necrosis associated with bacterial penetration into the pulp tissue. Clinically, one tooth treated with Pulpdent Multi-Cal showed pulpal pain and was extracted at 90 days. Our data support the thesis that human permanent pulps will promote tissue healing and dentin bridge formation as long as bacterial microleakage is excluded.

Summary. Buccal class V cavities were prepared in 35 teeth of five adult Rhesus monkeys. Pulpal exposures were left open to the oral microflora for 24 hours. Twenty-eight teeth were pulp-capped with a hard setting Ca(OH)2 medicament and restored with amalgam. Pulpal responses were observed after 24 hours (non-restored), 3, 5, 10 and 14 days. The pulps of teeth capped 3 days previously were dominated by polymorphonuclear leucocytes at the exposure site. Five-day pulp-capped teeth showed clot resolution, areas of necrosis and disintegrating polymorphonuclear leucocytes. Some pulps showed reorganization and stratification of fibroblasts adjacent to the medicament interface. Ten-day pulp-capped teeth showed dentine matrix mineralization directly adjacent to some portion of the medicament interface. Fourteen-day pulp-capped teeth showed complete soft-tissue reorganization and new hardtissue formation. This study demonstrates that complete pulp healing and new hard-tissue deposition will occur within 14 days, following an acute inflammatory lesion in monkeys.