Zvi Metzger

• DMD
• Chair at Tel Aviv University

Simple Summary The complete instrumentation of oval root canals remains practically unattainable. The majority of studies show that shaping oval, flat, and irregularly shaped canals is challenging, with more than half of the root canal area remaining unaltered. Furthermore, both rotary and reciprocating files compact hard tissue debris into the ist...

Aim To investigate macrophage function in the presence of sustained infection with Enterococcus faecalis, a prevalent root canal resident in asymptomatic apical periodontitis. Methodology The human monocyte cell line (THP1) was differentiated into macrophages by exposure to phorbol myristate acetate (PMA) and the cultures were inoculated with E. f...

Objectives To compare the cleanliness and erosion of root canal walls after the use of a new HEDP (1-hydroxyethane-1,1-diphosphonic acid) -based irrigant with that achieved by irrigation with sodium hypochlorite followed by EDTA.Materials and methodsForty recently extracted single-rooted teeth were prepared with ProTaper Next files to size X3, usin...

Objectives: The aim of this study was to carry out a morphometric analysis of small oval root canals filled with GuttaFlow 2 sealer (Coltène/Whaledent) using different methods of sealer placement and different root canal filling techniques. Method and materials: Eighty extracted mandibular incisors with small oval root canals were instrumented w...

Anatomical features of first maxillary premolars may greatly affect endodontic and following restorative treatments. The aim of this study was to evaluate root canal configuration and root wall thickness of first maxillary premolars using a preexisting CBCT database. A CBCT database of 400 first maxillary premolar was used to study canal configurat...

The circumferential strains created in the radicular dentin by nickel‐titanium (NiTi) and stainless steel (SS) finger spreaders (FSs) during a simulated clinical procedure of lateral compaction were compared after minimal (size 50) and extensive (size 100) canal preparations. Nineteen maxillary central incisors underwent minimal preparation, while...

Vertical root fracture (VRF) of endodontically treated teeth is relatively common, and the involved teeth have a poor prognosis. Previous destructive methodologies applied force to the root in an uneven manner; thus, the associated experiments could not truly assess the mechanical behavior of VRF. This problem was resolved in the current study via...

Aim To precisely quantify the circumferential strains created along the radicular dentin of maxillary incisors during a simulated clinical procedure of lateral compaction. Methods Six miniature strain gauges were bonded on the roots of fourteen recently extracted maxillary central incisors that were subjected to root canal instrumentation. The str...

Aim: To examine whether local anaesthesia is required for treating teeth with necrotic pulps (TNP) and retreatment cases (RCs) associated with periapical lesions. Methodology: Root canal treatment was performed in TNP and RCs without the administration of local anaesthesia. Patients were assured that if they experienced pain, local anaesthesia w...

Aim: This study evaluated whether using supplementary files for removing root canal filling residues after ProTaper Universal Retreatment files (RFs) increased the debris extrusion apically. Materials and methods: Eighty mandibular premolars with single root and canal were instrumented with ProTaper Universal rotary system (SX-F3) and obturated....

Aim: Current ex vivo study compared fracture resistance of teeth instrumented using 5 endodontic files, filled with Gutta-percha and AH Plus. Materials and methods: Sixty freshly extracted, single-rooted mandibular premolars were acquired and decoronated to obtain 15 mm segments. These samples were randomly divided into six groups (n = 10). Grou...

Aim: The current ex vivo study compared the efficacy of removing root fillings using ProTaper retreatment files followed by either WaveOne reciprocating file or the Self-Adjusting File (SAF). Materials and methods: Forty maxillary canines with single oval root canal were selected and sectioned to obtain 18-mm root segments. The root canals were...

Aim: The current study aimed to compare, bond strength exhibited by root fillings made with gutta-percha/AH Plus after instrumenting oval root canals with different file systems. Material and Methods: 60 recently extracted mandibular premolars exhibiting oval canals were selected for the study. These samples were randomly divided into 3 groups (n=2...

Familiarity with the shape of the root canal system is essential for the quality of endodontic treatment. C-shaped canals are anatomic variations most often encountered in mandibular second molars, and they pose an operational challenge to the clinician. The incidence of C-shaped canals varies widely in different populations. The aim of this study...

The present ex vivo study aimed to evaluate the debris extrusion after instrumenting the root canals by three different files systems. Sixty extracted human mandibular premolars with single canals were selected and randomly divided into three groups (n = 20) for instrumentation with three different files. Group 1: WaveOne (primary) single reciproca...

The recently introduced self-adjusting file (SAF) system is the first of its kind, performing continuous and simultaneous instrumentation and irrigation. As an instrumentation device it adapts itself to the shape of the canal, including its cross section, as opposed to most rotary file systems that machine the canal to the shape of the file. The SA...

Apical lesions are radiolucent lesions that appear in the bone surrounding portals of exit from infected root canal systems. Many but not all apical lesions will heal in response to adequate debridement, disinfection, and obturation of the root canal. Such healing may be a prolonged process, and some lesions will fail to heal. To understand why the...

Current rotary file systems are effective tools. Nevertheless, they have two main shortcomings: They are unable to effectively clean and shape oval canals and depend too much on the irrigant to do the cleaning, which is an unrealistic illusionThey may jeopardize the long-term survival of the tooth via unnecessary, excessive removal of sound dentin...

The cleaning and shaping of the root canal is a key procedure in root canal treatment. The aim of cleaning is the removal of tissue remnants and bacterial biofilms in order to allow close adaptation of the root filling to the canal walls. In simple straight canals with a round cross-section, this aim is easily attained by mechanical instrumentation...

Great progress has been made over the years in the technology of rotary nickel-titanium file systems. Nevertheless, both the oldest and the newest systems all use the same principle of a rotating blade with flutes, designed to carry off or contain the cut material and/or debris. While this concept may provide adequate results in narrow, straight ca...

To investigate the use of 3D plastic models, printed from cone beam computed tomography (CBCT) data, for accurate diagnosis and conservative treatment of a complex case of dens invaginatus. A chronic apical abscess with a draining sinus tract was diagnosed during the treatment planning stage of orthodontic therapy. Radiographic examination revealed...

Objectives: To evaluate the antibacterial activity and Diametral Tensile Strength of three provisional aged-cements mixed with Duraphat- varnish (Colgate-Germany). Methods: The tested cements were: TempBond NE, (TBNE, Kerr-US), Freegenol (FG, GC-Japan) and Rely-X (RX, 3M-ESPE) with and without the addition of Duraphat. 12 disks-specimens (6 mm in d...

3D cleaning, shaping and obturation of root canals has always been the desired goal of endodontic treatment which in many cases is difficult to attain. The introduction of NiTi rotary files made a major change in endodontic practice, making treatment easier, safer and faster. Nevertheless, after 16 years of intensive development, most of these inst...

The study was designed to quantitatively evaluate the quality of root canal preparation and root canal obturation in canals treated with either rotary or self adjusting files, using three-dimensional micro-computed tomographic (CT) analysis. Pair-matched root canals were instrumented with either rotary nickel-titanium files or self-adjusting files...

Aim: To introduce a new concept, the self-adjusting file (SAF), and discuss its unique features compared with current rotary nickel-titanium file systems. The new concept: The SAF file is hollow and designed as a thin cylindrical nickel-titanium lattice that adapts to the cross-section of the root canal. A single file is used throughout the proc...

The study was designed to explore the mechanical properties of the self-adjusting file (SAF) and its application in the root canal using continuous irrigation. The compressibility of the SAF file and the resulting peripheral force were measured using specially designed systems. The abrasivity of the file was tested on dentin blocks representing a f...

The aim of this study was to evaluate the cleaning ability of the Self-Adjusting File (SAF) system in terms of removal of debris and smear layer. Root canal preparations were performed in 20 root canals using an SAF operated with a continuous irrigation device. The glide path was initially established using a size 20 K-file followed by the SAF file...

Coaggregation is a key mechanism in biofilm formation. The aim of this study was to characterize the coaggregation of Fusobacterium nucleatum PK1594 with six Porphyromonas gingivalis strains in terms of kinetics and sugars inhibition. This coaggregation was quantitatively characterized by using a kinetic coaggregation assay. Sugar inhibition profil...

The new Apexum procedure (Apexum Ltd, Or-Yehuda, Israel) is based on a minimally invasive removal of periapical chronically inflamed tissues through a root canal access. Its goal is to enhance healing kinetics of periapical lesions. This clinical study was conducted to explore the safety and efficacy of this procedure. The Apexum procedure was appl...

In nonsurgical endodontic procedures, the healing of apical periodontitis is achieved by treatment provided within the root canal system. The new Apexum procedure is based on advancing the debridement one step further by minimally invasive removal of the inflamed periapical tissues through root canal access, thereby enhancing the healing kinetics o...

Fusobacterium nucleatum and Porphyromonas gingivalis are often co-isolated from endodontic infection sites. The present study tested the hypothesis that adhesin-mediated reactions might contribute to this phenomenon. F. nucleaum PK1594 and P. gingivalis PK1924 were selectively labeled with fluorochromes and allowed to adhere to human fibroblasts, e...

Porphyromonas gingivalis and Fusobacterium nucleatum are often coisolated from sites of infection, such as suppurative apical periodontitis. The synergistic pathogenicity of mixed infection of P. gingivalis HG 405 with F. nucleatum PK 1594 was studied in the mouse subcutaneous chamber model in groups of seven animals. The minimal dose for P. gingiv...

Successful periodontal healing and pulpal revascularization after trauma may be age-related. After dental trauma, age-related impaired angiogenesis may play a role in the revascularization rate during the healing process. The aim of the present preliminary in vivo study was to detect the presence of vascular endothelial growth factor (VEGF) in veno...

To assess bacteria in the apical portion of the root end after 45 degrees root-end resection in teeth with persistent periapical lesions. The study included 27 apical root segments from patients with persistent periapical lesions. Histological sections of the coronal part of the amputated root segment were stained with Brown and Brenn to detect the...

To test the effect of low-dose doxycycline on bone resorption associated with apical periodontitis. Apical periodontitis was induced by occlusal pulp exposure in the mandibular first molars of 36 rats. Animals were divided into three groups of 12: group A received doxycycline in drinking water at a dose of 5.85 mg day(-1); group B received a dose o...

The study was designed to test application of ultraviolet light to root canal walls, as a mean of complementary immediate disinfection after the use of sodium hypochlorite. Root canals were infected ex vivo with Enterococcus faecalis for 48 hours. Non-attached bacteria were washed away, and the remaining attached bacteria were subjected to disinfec...

"Flare-ups" during or following endodontic treatment are not uncommon. A "Flare-up" refers to post-operative pain and/or swelling resulting from bacterial, mechanical or chemical irritation. Prompt diagnosis and treatment are essential for reducing patients' pain and discomfort. Prevention of bacterial, chemical or mechanical invasion to the periap...

To explore the sensitivity of bacteria commonly found in root canals to 254 nm ultraviolet (UV) light, either as individual cells or as participants of a bacterial multilayer. The sensitivity of oral bacteria, as individual cells, to UV light was tested by subjecting plates streaked with bacteria to 254 nm UV, at a fluence of 1-20 mJ cm(-2). An exp...

This study was designed to test the ability of a virtual reality dental simulator to predict the performance of students in a traditional operative dentistry manikin course. Twenty-six dental students were pre-tested on the simulator, prior to the course. They were briefly instructed and asked to prepare 12 class I cavities which were automatically...

We sought to evaluate the incidence and clinical outcome of an accidental finding of actinomycotic colonies in periapical lesions submitted for histologic examination. The study included all periapical biopsy specimens submitted for histologic examination between 1997 and 2000. Sections of paraffin-embedded tissues, 5 microm, were cut and stained b...

Bone resorption is one of the hallmarks of inflammatory periapical lesions and is mediated by cytokines. Recent insights into the immunobiology of these lesions indicate that pharmacological modulation of their bone resorbing activity may be possible. Periapical lesions were induced in rats by occlusal exposure of the pulps of their lower first mol...

Endodontic failures associated with poor quality of endodontics respond favorably to retreatment. Nevertheless, under certain clinical conditions, apicoectomy should be the preferred procedure. A retrospective survey of 200 roots that were referred for apical surgery revealed that 83% of the roots were inadequately obturated, including 8.5% with no...

Wound healing in the oral cavity occurs in a bacteria-rich environment, which may affect its outcome. Furthermore, it takes place where forces are frequently applied to the healing tissue. The effect of bacterial endotoxin on the development of tensile strength in healing wounds was studied using surgical skin wounds in rats as a model. Collagen me...

Temporary fillings are commonly used to seal endodontic access cavities between visits. IRM and Cavidentin were selected to represent two widely used groups of temporary filling materials. The first is a reinforced zinc oxide-eugenol preparation that is mixed at chairside, whereas the second is a ready-to-use calcium sulfate-based material that gai...

Coaggregation between Porphyromonas gingivalis and Fusobacterium nucleatum strains was previously studied using either a semi-quantitative macroscopic assay or radioactive tracer assays. A new automated microtiter plate assay is introduced, in which the plate reader (Vmax) was adapted to allow quantitative evaluation of the kinetics of coaggregatio...

Amalgam cores with cemented dowels are commonly used to restore endodontically treated teeth. These restorations were widely studied for their mechanical properties; however, less is known about their sealing ability. The effect of the cement type used for the dowel and that of a bonding agent application were studied in a radioactive tracer corona...

A root canal filling remaining after post space preparation is commonly expected to provide adequate seal. Coronal leakage of 30 endodontically treated teeth was measured before post space preparation using a fluid transport assay. In 10 of these teeth post space was prepared, using a two-step procedure, first to a remaining filling of 6 mm and the...

Calcium hydroxide (CH) is used to induce apexification in immature, pulpless teeth with wide root canals and flaring apices. Three placement methods of CH were compared in vitro, for their ability to enhance CH retention in the canal. Barium sulfate (BS), added as radiopacifier, was studied for its effects on the radiographic follow up of CH retent...

The seal provided by root canal fillings after post space preparation was studied using a pressure-driven radioactive tracer assay. The coronal part of root canal fillings was immediately removed, using a hot plugger, to a remaining length of either 3, 5, 7, or 9 mm. Intact root canal fillings of 14 mm served as control. Application of air pressure...

It has been shown that Fusobacterium nucleatum PK1594 coaggregates with Prophyromonas gingivalis PK1924 through a galactose-binding adhesin. In the present study, attachment of F. nucleatum PK1594 to a variety of mammalian cells was characterized. F. nucleatum PK1594 attached to all eukaryotic cells tested, including human buccal epithelial cells,...

A 5 mm remaining length of root canal filling, after post space preparation, is commonly assumed to maintain sealing ability similar to that of the intact filling. Post spaces were prepared either immediately using hot pluggers, or later, using drills. The sealing ability of the fillings, 5 mm remaining length, were compared with each other and wit...

Furcation perforations sealed with silver glass ionomer cement (Chelon Silver) were evaluated in vitro compared with amalgam. Access cavities were prepared in 25 extracted human molar teeth. The coronal orifices of the root canals were sealed with amalgam and varnish. Naturally occurring coronal leakage through the intact pulp chamber floor was det...

The putative hazardous nature of chloroform and xylene implies that safer substitutes should be considered. Standard cylindrical gutta-percha samples were immersed in Hemo-De, a xylene substitute, for 60 s at 37 degrees C. Weight loss of a sample, after drying, was used as a measure of its solubility. Master and accessory cone gutta-percha of three...

Macrophages are major constituents of periapical granulomas. They have a central protective role in both innate immunity and adoptive, antigen-specific immune response. Macrophage activation may occur in periapical granulomas by cytokines produced by antigen-activated T-lymphocytes; by bacterial endotoxin, as part of the innate immunity; or by both...

Straightening of curved canals is one of the most common procedural errors in endodontic instrumentation. This problem is commonly encountered when dental students perform molar endodontics. The purpose of this study was to compare the effect of the type of instrument used by these students on the extent of straightening and on the incidence of oth...

The purpose of the present investigation was to evaluate histologically the effect of dexamethasone on root resorption in stored and replanted dogs' teeth. Twenty-nine roots from three beagle dogs were endodontically treated to prevent subsequent inflammatory root resorption of pulpal origin. The teeth were extracted and randomly assigned to three...

Selective re-population of the root surface by periodontal ligament cells is considered a key factor in periodontal regeneration. A recently isolated cementum attachment protein (CAP) has been shown to enhance fibroblast attachment. In the present study the potential of CAP to selectively attract periodontal ligament cells (PLC) was studied in vitr...

Activated macrophages are among the major constituents of the periapical granuloma. Their state of activation may persist for long periods after the local irritant is removed and may delay resolution and repair of the lesion. The effect of activated macrophages on fibroblast growth was studied in vitro. Circular fibroblast colonies were formed usin...

A specific cementum attachment protein (CAP) was identified in human cementum and found to bind with high affinity to non-demineralized root surfaces, hydroxyapatite and fibronectin. Attempting to elucidate the biological function of this protein and its possible role in cementogenesis the capacity of CAP to promote selective cell migration towards...

A procedure is proposed for the complete removal of an overextended root canal filling when associated with a root canal treatment failure. First, the gutta-percha is softened with xylene and removed to a distance of 2 to 3 mm short of the apex. Second, the remaining gutta-percha, which is preserved as solid as possible, is removed by a Hedstrom fi...

In the present study, and in vitro system was developed and designed to examine the interaction between gingival fibroblasts (GF) and epithelial cells (EC) on the tooth surface. Porcine roots were cut transversely into 300 microns-thick root slices (RS). Gingival explants were placed on the upper RS surface and cultured in a defined medium permissi...

Bacterial endotoxin inhibits the attachment of human gingival fibroblasts to collagen. The present study attempted to elucidate the possible mechanism of this inhibition. Two mechanisms were considered: direct toxicity to the cells and steric interference. Collagen substrates were prepared by rat type I collagen being air-dried in the wells of 24 m...

Drying before use has been recommended for customizedmaster cones prepared with the chloroform dip technique. This was suggested to minimize future shrinkage of the cone. The effect of drying time on residual chloroform in customized gutta-percha master cones and on their plasticity was studied by gravimetric and indirect plasticity assays. Gutta-p...

Master cone adaptation is a crucial step of root canal obturation with the lateral condensation technique. In regular canals such adaptation is facilitated by the use of standardized instruments and master cones, using a “tug-back” sensation as a guide. Standardized master cones are not easily adapted to flat canals and preparation of customized ma...

In this laboratory study, the effect of retention grooves in the proximal portion of class II cavities on the marginal microleakage using light-cured composite resin was examined. The retention grooves were placed at the axio-facial and axio-lingual line angles and in the gingival floor of the cavities. The teeth were restored with Herculite compos...

In the present study, we examined the potential roles of cell surface hydrophobicity and mannose-sensitive (MS) interactions in blood clearance of Serratia marcescens in mice. Hydrophobic strain RZ, partially hydrophobic mutant 3162, and nonhydrophobic mutant 3164 were coinoculated into BALB/c male mice, and blood samples were plated out at differe...

A device for subgingival margin preparation is presented. The gingival guard consists of a clamp attached to the high-speed handpiece supporting a stainless steel shank terminating in a sphere. The guard permits nontraumatic subgingival margin preparation.

Actinomyces viscosus, a normal inhabitant of the oral cavity, has previously been shown to evoke immune responses in the host. Macrophage activation by this microorganism was studied in a murine system. Peritoneal macrophages, activated in vivo by A. viscosus had a suppressive effect on lymphocyte proliferation in vitro; total suppression occurred...

The purpose of this study was to assess the effect of endotoxin adsorbed to dental surfaces and to collagen type I on the migration, attachment, and orientation of human gingival fibroblasts (HGF). Transversely cut porcine tooth root slices (RS), 200 μm thick, were prepared. Half of the RS obtained were partially demineralized in EDTA. Half of the...

Oral bacteria colonize the dento-gingival tissues in a selective manner. Hydrophobic reactions have been suggested as one of the major mechanisms of adhesion. Hydrophobicity of Actinobacillus actinomycetemcomitans Y4 (Aa) cells was studied in vitro using adherence to the liquid hydrocarbon, octane. Adherence of Aa cells to octane varied from 60-90%...

Preparation design for posterior composite restorations should differ from that for amalgam restorations in the following manner. • 1. Occlusal form should be narrower and the depth shallower. • 2. The proximal extensions (facial and lingual) should be placed in areas that can be seen, probed, and polished. • 3. Internal line angles should be ro...

Four designs of amalgam-core anchorage were compared in a laboratory study for the inability to withstand the horizontal component of occlusal force. Amalgam cores were constructed for extracted teeth with either composite resin-cemented Dentatus dowels, or with Para-post or Flexi-post dowels cemented with phosphate cement. All the posts were of co...

Gutta-percha solvents are used for both root canal filling and removal of root canal filling materials. A method is presented in which four gutta-percha solvents (chloroform, xylene, Endosolv-E, and orange terpenes) were compared for their effect on three brands of gutta-percha. Chloroform was the most effective solvent for all gutta-percha brands...

Macrophages are considered promoters of fibroblast proliferation; however, suppression by activated macrophages may outweigh this effect. Activated murine peritoneal macrophages obtained by in vivo exposure to C. parvum or by in vitro LPS-activation of thioglycollate-induced macrophages, were tested for their effect on normal syngeneic dermal fibro...

A procedure is described for the construction of composite resin veneers for large amalgam restorations. The resulting restoration combines the physical qualities of amalgam with the esthetic benefits of composite resins. Among the 14 restorations that have been studied for 2 years, none failed mechanically and minor surface discolorations have bee...

Neutrophils (PMN) are considered to be key components in the protection of the periodontium against pathogenic bacteria. We therefore compared five of the major characteristics of peripheral blood PMN (PB-PMN) (adherence, chemotaxis, phagocytosis, oxidaiive metabolism, and lysosomal granules) to those of normal crevicular neutrophils (CR-PMN) isola...

This study was performed to see if adherent cell-derived toxic oxygen metabolites contribute to the suppression of mononuclear cell blastogenic responses in Hodgkin's disease. Peripheral blood mononuclear cells from 10 patients with Hodgkin's disease were stimulated in culture with the mitogen PHA in the presence of the prostaglandin inhibitor indo...

The regulation by prostaglandin E2 (PGE2) of production of oxygen radicals by bacterial lipopolysaccharide-(LPS) activated macrophages was studied in vitro. A 48-hr incubation of murine thioglycollate-elicited macrophages with LPS (0.1 micrograms/ml) resulted in an enhanced ability of these cells to produce oxygen radicals when challenged with phor...

A case of iatrogenic perforations of the roots of two maxillary central incisors, which demonstrates the importance of examining the alveolar process before endodontic treatment, was presented.

Bacterial cells and their products are among the most potent inducers of macrophage activation (2). In turn, activated macrophages can be both stimulators and suppressors of lymphocyte functions. Dr. Oppenheim has already detailed what we believe to be the stimulatory macrophage mechanisms (22). The suppression of lymphocyte function in vitro and/o...

Gustafson's method for age determination from teeth is based on the evaluation of ground sections of teeth. Six age-associated parameters are evaluated in the ground section and are compared to a regression curve of age versus the age-associated changes. Two of these changes, transparency of radicular dentin and secondary dentin, have the highest c...

Therapeutic administration of tetracyclines, widely used antibiotic drugs, permanently labels layers of dentin that are calcifying at the same time. A method is described for detecting and photographing these stained layers of dentin. The presence of tetracycline-labeled dentin layers in the teeth of subjects of a forensic science investigation can...

Macrophage-mediated suppression of Con A induced proliferation of murine splenic lymphocytes was studied in vitro. Either Corynebacterium parvrum-induced peritoneal exudate cells (PEC) or thioglycollate-induced PEC could totally suppress lymphocyte proliferation at a PEC:lymphocyte ratio of 2:10, whereas a ratio of 1 to 1.5: 10 caused a partial (60...