Jacques Holz

Dentinal Fluid Dynamics in Human Teeth, In Vivo

Cavities were prepared in human premolars scheduled for extraction for orthodontic reasons. The smear layer was removed from the dentin surface by acid etching, and the cavity was sealed using a hollow chamber. The chamber was filled with sterile saline solution and connected via tubing to a hydraulic circuit featuring an adjustable pressure reservoir and a device that measures fluid movement across dentin. In the absence of any exogenous pressure, all cavities exhibited an outward fluid flow rate of 0.36 microliters min-1 cm-2. As exogenous pressure was applied to the cavity, the outward flow slowed. The exogenous pressure that stopped outward fluid flow was taken to be equal to normal pulpal tissue pressure. The mean value was 14.1 cm H2O in five teeth. This simple method permits measurement of dentinal fluid flux, the hydraulic conductance of dentin, and estimates pulpal tissue pressure.

In vitro cytotoxicity and dentin permeability of HEMA

An in vitro diffusion chamber was used to measure the diffusion of 2-hydroxyethyl methacrylate (HEMA) through etched human dentin disks. Concentrations of HEMA, which diffused through dentin, were measured by ultraviolet spectroscopy, and the effect of initial HEMA concentration, dentin thickness, and back pressure on diffusion were assessed. The cytotoxicity of HEMA was determined using BALB/c 3T3 mouse fibroblasts in direct contact with HEMA for 12 or 24 h. HEMA diffused rapidly through dentin under all conditions, but increased thickness, back pressure, or decreased initial concentration all reduced diffusion. The permeability coefficient of HEMA was approximately 0.0003 cm/min, and diffusion through 0.5 mm of dentin reduced the HEMA concentration by a factor of approximately 6,000 (with 10 cm of H2O back pressure). It was concluded that the risk of acute cytotoxicity to HEMA through dentin was probably low, but that decreased dentin thickness, lack of polymerization, or extended exposure times might increase the risk significantly.

Volume of the internal gap formed under composite restorations in vitro

OBJECTIVES The gap that develops at the interface of dentin composite restoration during the polymerization of the resin can be subsequently filled by fluid filtrating from the pulp via the dentinal tubules. This in vitro study was designed to determine the volume of such a gap, at the occlusal floor of class I restoration and as a result of different dentin treatments and restoration procedures. METHODS Fifty-six human third molars had their pulp chambers first sealed and connected to a hydraulic apparatus permitting microlitre fluid shift recordings. The teeth then received class I cavities of uniform dimensions and were sampled into nine groups for three dentin treatments (bonding with a dentin bonding agent, lining with a resin modified light-cured glass ionomer, lining with a zinc phosphate cement) and three restoration procedures (Bulk placement of the composite material, Multilayer, Indirect inlay). Fluid displacements were recorded during the filling procedures and stopped 30 min after the completion of the restorations. RESULTS Dentin bonding agent treated cavities consistently presented the smallest gap volumes, followed by the GI and the ZnPO4 lined specimen. Multilayer and Indirect restoration techniques reduced the formation of gaps. CONCLUSIONS None of the materials or techniques tested assured a gap-free interface and more effort should be directed at increasing the adhesive and sealing properties of restorative materials to be placed on the dentin.

Ontogenesis of the Human Temporomandibular Joint: 2. Development of the Temporal Components

The embryologically unique origin of the temporomandibular joint from two separately (in time and space) developing blastemas was further studied in relation to temporal structures. Both coronal and sagittal sections of 11 human fetuses from the 24 mm to 72 mm crown-rump (C-R) stage showed that the glenoid blastema developed in close relationship with the primordial quadrate-meckelian joint to form the bony temporal joint components, including the capsular elements of the upper joint story. The disk developed independently of the tendon of the external pterygoid muscle as a derivative of both the condylar and the glenoid blastemas.

Dark-field Observation of the Bacterial Distribution in Root Canals Following Pulp Necrosis

The purpose of this investigation was to study, by dark-field microscopy, the distribution of five types of bacteria in the coronal and apical thirds of root canals of teeth that had undergone pulpal necrosis. Twenty single-rooted teeth from 19 patients were sectioned after extraction into three equally long parts. Bacterial samples were taken from the apical and coronal thirds of the root canals and observed under a dark-field microscope. Data of bacterial counts were computerized and subjected to statistical correlation analysis. The results showed a significantly greater percentage of coccoids and rods in the coronal part than in the apical part. The percentage of motile rods did not differ in the coronal and the apical thirds. On the other hand, the percentage of filaments and spirochetes was slightly higher in the apical than in the coronal third, but showed no significant difference. A significant positive correlation was observed between the percentage of spirochetes in the apical third and the size of the radiographically visible lesion. The significance of these findings are discussed.

Clinical evaluation of four amalgam alloys: A five-year report

In this study 96 teeth of 12 patients were restored with either the conventional alloy Premix, the blended non-gamma 2 amalgam Dispersalloy, or one of the spherical alloys Sybraloy and Tytin. To ascertain an objective comparison of the clinical performance of these alloys, two different alloys were used in each of at least two dental arch quadrants in the same patient and consequently were placed in the same oral environment. Clinical performance of the restorations was evaluated by macrophotography and scanning electron microphotography of replicas made after placement and 2, 3, and 5 years thereafter. Standard criteria were used for the evaluation of anatomic form, surface condition, and marginal adaptation of the fillings. In addition, the filling-enamel interface was assessed from the microphotographs. The three high-copper alloys performed better clinically than the conventional alloy, and the spherical alloys had the best qualifications. In addition to visual examination and photographic evaluation of restorations, the micrometric assessment of replica photographs from the scanning electron microscope may render clinical trials of amalgam alloys measurable and less subjective.

Radicular pulpotomy of category III pulps. Part III. Histologic evaluation

Abstract Twenty-two sound or symptom-free restored teeth (indicated for extraction) of patients 18 to 60 years of age were subjected to radicular pulpotomy and immediate root canal filling. 2 Eight contralateral teeth served as untreated controls. The histologic evaluation led to these results. The untreated control teeth showed regressive changes in the apical third of the radicular pulps consisting of the disappearance of the odontoblasts, von Korff fibers, and the subodontoblastic vascular network starting at the apex and gradually ascending. The regression increased with age. All the treated teeth showed a vital remaining pulp free of inflammation and necrosis. One month postoperatively capping was effected by dentinal chips encapsulated by a fibrotic tissue. Osteodentin matrix formation had begun around advanced dentin chips and at discrete sites of the dentinal walls, while at other areas modeling resorption took place. The frequency and extent of dentinoclasia seemed to depend on the height of the pulpotomy, but they never constituted a clinical problem since dentinoclasia would repair with osteodentin. The remaining tissue had the characteristics of loose connective tissue. Three months postoperatively, the remaining pulp size had been reduced by osteodentin deposition along the dentinal walls and around the dentinal chips thus forming a more or less complete seal. Calcific obliteration depended on the presence of a dentinal plug and its proximity (3 to 5 mm.) to the apex. This was associated with a progressive fibrosis of the remaining pulp tissue in the absence of inflammatory changes. In the light of the favorable biologic results obtained, it may be justified to introduce radicular pulpotomy into daily practice under the conditions that its specific indications for category III pulps are respected and its exacting techniques applied.

Microradiographic assessment of neodentinal bridging following direct pulp capping in human teeth

Neodentinal bridges formed in 14 human premolars following direct pulp capping with a calcium hydroxide paste (Pulpdent) were microradiographically assessed. Densitometric measurements were made in the longitudinal sections of the bridges, revealing an increase in the mean mineral content per volume after progressively longer postoperative periods ranging from 2 to 15 wk. Transverse measurements made through each of two 15-wk bridges confirmed the presence of three layers: the superior amorphous layer yielded the lowest mineral content of 32.3 and 34.8% by volume; the medial (atubular) fibrodentine layer exhibited the highest scores of 48.1 and 50.1%, greater than those of the lateral dentine walls (43 to 48%); and the inferior juxtapulpal layer of tubular orthodentine contained 41.0 and 42.2% mineral per volume. With the new photoelectronic ASBA equipment the presence of centers of high mineral density within the medial fibrodentinal layer was confirmed.

Radicular pulpotomy for category III pulps. Part I. Biologic and diagnostic aspects

Abstract 1. Data gained from a comprehensive review of the literature (Table I) and from our histopathologic studies offer biologic support for a one-visit method of pulp therapy. 2. Diagnosis of the pulpal state has been hampered by a lack of correlation between clinical signs and pulpal pathosis. 3. A new histopathologic classification of pulpitis (Table II) has been developed exclusively for differential diagnosis at the histologic level. It offers distinct diagnostic criteria. 4. A relationship between the depth of the carious lesion and the severity of pulpal pathosis was found (Table III). 5. A new clinical classification has been introduced for use in everyday practice (Table IV). This classification is based upon four major types of endodontic treatment now employed. 6. Category III classification includes those vital pulps which, for pathologic, prosthetic, iatrogenic, or prognostic reasons, are amenable to radicular pulpotomy and immediate root canal filling. The presence of vital noninfected pulp tissue in the apical third and the use of a root canal filling material well tolerated by the remaining vital pulp were shown to be the basic prerequisites for category III pulp treatment. 7. Correct application of the principles described and the use of an adequate technique should result in considerable work simplification and a greater success rate in endodontics.