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Biomedical subjects

C F Cox

Publications and source records attributed to C F Cox.

At least 55 records · Page 3Linked to original sources
PubMed1994

Pulpal response after complete crown preparation, dentinal sealing, and provisional restoration.

This study evaluated the acute pulpal healing response following preparation, etching, and sealing of the prepared vital dentin with a 4-methacryloxyethyl trimellitate anhydride (4-META) bonding system. Adult monkey teeth received crown preparations with chamfer margins, prepared with a diamond used at ultra high speed with water cooling. Vital dentin was etched with 10% citric acid-3% ferric chloride, rinsed, and sealed with 4-META system. A provisional crown was formed with a low-viscosity light-curing adhesive resin. Teeth were fixed and evaluated histopathologically. Pulpal responses at 3 days showed only minimal disruption of the odontoblastic zone. At 7 days, the pulps presented reorganizing odontoblastoid cells, and, at 10 days, the pulps showed new odontoblastoid cells with a thin rim of reparative dentin. Pulps of crown preparations that were etched and then sealed with the 4-META system presented healing patterns similar to those of pulps associated with Class V preparations lined with calcium hydroxide, observed in (previous) similar studies.

Acid Etching, Dental↗
PubMed1994

Pulpal response to adhesive resin systems applied to acid-etched vital dentin: damp versus dry primer application.

A number of studies have reported that acid etching of dentin is toxic to the cells of the odontoblastic layer and dental pulp. Other studies report that pulpal inflammation is a consequence of bacterial microleakage. The purpose of this study was to observe the degree of pulpal healing after pretreatment of vital dentin prior to placement of All-Bond and Scotch-bond 2 composite resin adhesives. Zinc oxide-eugenol cement and an acidic cement were employed as controls. One hundred twelve Class V nonexposed cavity preparations were placed throughout the dentitions of five healthy adult rhesus monkeys and observed at 3, 25, and 80 days. Various dentinal pretreatment procedures were employed. The All-Bond Universal primer system was placed on air-dried vital dentin in 23 cavities and on damp vital dentin in 27 cavities. Scotchbond 2 was placed as per manufacturer's instructions. All treatment procedures, materials, and times were represented in all animals. Placement of silicate cement resulted in the most severe pulpal responses at all time periods. Stained bacterial profiles in the remaining dentin on the axial walls of inflamed control pulps were associated with severe pulpal inflammation. These results indicate that acid etching of vital dentin does not impair pulpal healing in deep Class V cavities.

Acid Etching, Dental↗
PubMed1994

Biologic and clinical evaluation of Syntac and Variolink systems for cohesive pretreatment of hypersensitivity and definitive cementation.

Adhesive resin systems have become increasingly popular as they have been demonstrated to infiltrate conditioned vital dentin to cohesively hybridize the biologically altered substrates for adhesive bonding. This paper is a review of the biologic and clinical use of Syntac (Ivoclar Vivadent) and Variolink (Ivoclar Vivadent) adhesive systems for cohesive hybridization of vital dentin to prevent patient postoperative hypersensitivity and bacterial microleakage following clinical preparation.

Cementation↗
PubMed1993

A test for teratological effects of power frequency magnetic fields on chick embryos.

An analysis of 13 studies of the teratological effects of pulsed magnetic fields on chick embryos from ten independent laboratories permits no clear conclusions. Comparatively little has been done to follow up on the reports by Juutilainen and coworkers on the effects of extremely low-frequency, sinusoidal magnetic fields on the malformation rate in chick embryos. Our attempt to follow up on their results using similar but not identical exposures of 10 microT, 50 Hz magnetic fields produced negative results.

Animals↗
PubMed1993

Pulpal healing and dentinal bridge formation in an acidic environment.

This study was designed to observe the healing and bridging capacity of mechanically exposed pulps that were capped with silicate or zinc phosphate cements and biologically sealed with zinc oxide-eugenol cement to exclude bacteria. In six monkeys, Class V facial cavities with pulpal exposures were randomly distributed throughout 105 teeth, of which 80 were directly capped, 40 with silicate cement and 40 with zinc phosphate cement. Twenty of each group were filled to the cavosurface margin with the respective cement and 20 were surface sealed to the cavosurface margin with zinc oxide-eugenol cement. The remaining 25 exposures were capped with calcium hydroxide and amalgam as controls. Tissues were obtained by perfusion fixation after intervals of 21, 14, 10, 5 and 3 days. The 25 pulps capped with calcium hydroxide showed cell migration and organization at 5 days and dentinal matrix deposition at 10 days. At 3 and 5 days, all exposures in the experimental groups showed clot resolution. At 10 days, fibroblasts had stratified against the cement interface. At 14 days, pulps in both experimental groups showed new dentinal bridge formation directly adjacent to the acidic cements. The 21-day experimentally capped and sealed pulps presented healing similar to the controls. This study indicates that acidic components of silicate and Zinc phosphate cements are not directly responsible for pulpal inflammation or necrosis. The exposed dental pulp possesses an inherent healing capacity for cell reorganization and dentinal bridge formation when a bacterial seal is provided.

Animals↗
PubMed1993

The effect of citric acid application on periodontally involved root surfaces. II. An in vitro scanning electron microscopic study.

The in vitro effect of citric acid application on periodontally involved root surfaces was investigated using scanning electron microscopy. Teeth were selected following specific criteria. The specimens were prepared for observation, and the features of the root surface were studied. The results demonstrated that a 3-minute application of citric acid (pH = 1.0) to the root surface after scaling and root planing demineralized the outer root surface, opened the dentinal tubules, and exposed collagen fibers. Scaling and root planing alone left the surface with a smear layer, scattered islands of cementum, and no collagen fibers or exposed dentinal tubules.

Citrates↗
PubMed1993

Patterns of nerve regeneration in dental pulps of monkeys following surgical transection at 1 year.

Previous studies have reported revascularization and reorganization of dental pulp chambers with periodontal tissues of monkeys following complete surgical transection through a portion of the apical roots. This study observed 128 teeth in four adult monkeys. Following surgical transection, the tissues were acquired by perfusion fixation, serially sectioned, and stained for cellular detail with hematoxylin and eosin. Collagen tissues were stained with Preece's trichrome and neural tissues with Rowles' silver cyanate for controlled impregnation. At 1 and 2 weeks the coronal tissues showed tissue disruption, necrosis, and degenerating nerves. The 3- and 4-week tissues that had been completely transected showed replacement healing of the pulp tissue with periodontal ligament connective tissue, but no nerves were present. At 6 weeks, no nerves were present in the coronal chambers of those teeth with complete vital transection. The 24-, 36-, and 52-week pulp chambers with complete transection failed to show nerve fibers in their reorganized connective tissues.

Animals↗
PubMed1992

Reparative dentin: factors affecting its deposition.

Results of this study showed no correlation between the thickness or amount of reparative dentin deposited and the type of dental restorative material placed at either 5 or 8 weeks in controlled Class V cavity preparations in monkey teeth. Factors such as preparation trauma from the bur, operator hand instrumentation, and microleakage of bacterial toxins played a greater role in the stimulation of reparative dentin than did material irritation or toxicity. Some differences in the thickness of the reparative dentin deposited were noted when teeth were grouped according to the amount of remaining dentin.

Analysis of Variance↗
PubMed1992

Microleakage related to restorative procedures.

A current Med-line search from 1966 to present cited over 344 juried publications employing the term microleakage. Dentistry recognizes microleakage as a multifaceted biological phenomenon. Brännström et al. (1967), Trowbridge (1982), Närhi (1983), and others have reported the sensory component of microleakage as a consequence of hydrodynamic fluid movement within the dentinal tubule complex. This movement of dentinal fluid has been demonstrated to displace nociceptive receptors which stimulate the nerves of the Group A fibers which run and terminate within the odontoblastic layer (see Matthews 1992). Penetration of oral fluids, bacteria and their toxic products within the preparation-material interface following material insertion accounts for the pathological component of microleakage (Browne and Tobias 1986). Continued microleakage of bacterial infiltrates eventually present as an inflammatory process which may initially signal the dentin complex to respond by deposition of a hypermineralized or sclerotic dentin. The pulp-dentin interface will repair with a specialized zone of reparative dentin. An overwhelming carious lesion often results in pulp infection and eventual necrosis. Vital dentin is an extension of the pulp, presenting the first line of defense to the consequences of microleakage. Recent publications have demonstrated that microleakage of dental materials in non-exposed and exposed pulps is a function of controlling bacterial infection. In an exposed mature dental pulp, the mesenchymal tissue permits the reorganization of pulp tissue and regeneration of a new dentin bridge in the presence of a biological seal. New odontoblastoid cells appear to regenerate from deeper pulpoblasts in the presence of various dental materials, apparently without an epithelial stimulating factor (Yamamura 1985). This inherent healing of the dental pulp and regeneration of a new dentin bridge is expressed in the presence of various dental materials, but only in the absence of bacterial infection. Data which evaluates the biological deposition of reparative and dentin bridges as either repair or regeneration are presented as a basis for considering the clinical selections of dental materials. Recent data demonstrate that dentin and pulp healing are ensured when a proper biological seal is provided to control and prevent microleakage.

Animals↗
PubMed1991

Pulpal response to chemically cured and experimental light-cured glass ionomer cavity liners.

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 microns, 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.

Acid Etching, Dental↗
PubMed1991

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.

Animals↗
PubMed1991

Healing of pulp exposures: an ultrastructural study.

The fine structure of tissue changes during the first 14 days following pulp exposure and capping with a hard setting Ca(OH)2 cement has been studied. The early changes included hemorrhage and moderate inflammation which were largely resolved during the first week. During the second week differentiation of cells occurred at the wound surface. These cells had the characteristic features of odontoblasts and formed a predentin-like collagen matrix. The capping material was closely adapted to cellular structures at the wound surface or to the predentin-like matrix at all observation periods. Dentin fragments displaced into the pulp tissue during cavity preparation, acted as sites for pulp stone formation.

Animals↗
PubMed1990

Effects of lithotripter fields on development of chick embryos.

Chick embryos at 72 h incubation were subjected to three double shock waves from a Wolf Model 2137.50 Electrohydraulic Lithotripter. The pressure amplitude at the embryo was adjusted by variation of the distance from the source to the embryo. After a total of 120 h of incubation, they were assessed for developmental abnormalities. Early deaths, delayed deaths and malformations were all significantly increased at pressures of 10 MPa with suggestions of possible effects at lower pressure levels.

Animals↗
PubMed1990

[Characterizing the smear layer].

The smear layer was first described as a debris layer which is left on all cavity walls following tooth preparation. It is composed of an outer contiguous layer of amorphous instrumentation matrix which covers all cavity walls, and a deeper zone of matrix plugs which obturate the cut tubules. Recent scanning electron microscopic (SEM) studies have characterized the smear layer as mineralized collagen fibers appearing as globules dispersed within an amorphous cutting matrix. Removal of smear plugs increases the outward hydraulic conductance (Lp) of dentinal fluid flow which may lead to dentinal hyperalgesia, bacterial infection and pulp pathosis if left untreated.

Collagen↗
PubMed1990

[Microleakage: evaluation and treatment].

Microleakage is a biological phenomenon with several implications. The affective component patient hyperalgesia (pain/hypersensitivity) of dentin which is a function of episodic hydrodynan (fluid) movement. The effective component is the disease process which signals the dentin-pulp complex to respond by disposition of sclerotic and/or reparative dentin. Vital dentin is an extension the pulp, presenting the first line of response to the consequences of microleakage. Recent data has demonstrated a correlation between pulp response and material biocompatibility when microleakage is prevented. Dentin-pulp healing is ensured when a proper hermetic seal is provided to control prevent microleakage. A critical evaluation of various clinical procedures is discussed.

Dental Leakage↗
PubMed1989

Inhibition of bacterial growth under composite restorations following GLUMA pretreatment.

The purpose of this investigation was to test in five adult monkeys the effects of a glutaraldehyde-containing dentin bonding agent, GLUMA, on bacterial colonization in Class V cavities restored with composite resin. Experimental groups consisted of immediate placement of GLUMA and composite resin as well as placement of GLUMA or Scotchbond (control) in acid-etched cavities that had been left open to the oral environment for 48 hours. Various procedures for pretreatment of the cavities were included. Tissue specimens were prepared for light microscopy for observation of bacterial presence and pulp tissue reactions after eight days and 90 days. Bacteria were not detected in any of the 54 cavities treated with GLUMA regardless of observation period or use of enamel-etching procedure prior to placement of composite resin. When cavities were restored with composite resin without prior GLUMA pretreatment or with Scotchbond, bacteria were present under the majority of restorations at both time intervals. Pulpal inflammation of varying extent and character was seen after eight days in teeth that had been previously infected. At 90 days, pulps showed repair and healing regardless of treatment protocol. Data indicate that GLUMA has a distinct in vivo antibacterial effect that seems to prevent bacterial growth in tooth/restoration interfaces.

Aldehydes↗