PubMed Health⌕ Search

Biomedical subjects

Peter E Murray

Publications and source records attributed to Peter E Murray.

At least 19 recordsLinked to original sources
PubMed2007

Comparison of the clinical and preclinical biocompatibility testing of dental materials: are the ISO usage tests meaningful?

International Organization for Standardization (ISO 10993 and 7405) guidelines recommends the preclinical screening of dental materials using non-human primates. The literature contains no comparisons of responses to dental materials. To test the accuracy of preclinical screening tests for predicting human clinical responses, 106 class V pulp exposed cavities were prepared in human and non-human primate teeth. Teeth were restored with calcium hydroxide and amalgam, zinc oxide eugenol or resin-modified glass ionomer. Teeth were extracted after 10-163 days and prepared for histological analysis. Pulp cell numbers were compared and their reactionary dentin activity measured in response to cavity preparation. Pulp inflammatory activity was categorized according to ISO standards. There were no statistically significant differences between human and non-human primate teeth in terms of pulp reactions to dental materials. The use of non-human primates for preclinical biocompatibility investigation provided an accurate method of evaluating clinical responses to dental materials.

Adolescent↗
PubMed2007

The effect of calcium hydroxide root filling on dentin fracture strength.

This in vitro study measured the effect of calcium hydroxide root filling on the microtensile fracture strength (MTFS) of teeth. A total of 40 extracted human disease-free permanent maxillary incisors were hand and rotary instrumented and vertically compacted with United States Pharmacopeia (USP) calcium hydroxide. The teeth were stored in a moist environment for 7, 28, and 84 days. As a control group, 10 teeth were vertically compacted with gutta percha and sealer. The MTFS of the teeth was measured (Mpa) using an Instron machine. Data were assessed statistically using an unpaired t-test (P value). The intracanal placement of calcium hydroxide weakened the MTFS of teeth by 13.9 Mpa per 77 days: an average of 0.157 MPa day-1. Between 7 and 84 days, the MTFS of the dentin was reduced by 43.9%. This difference was statistically significant (P < 0.05). A statistical difference (P < 0.05) was observed between the mean MTFS of the calcium hydroxide-filled dentin between 7 days (45.7 MPa) and 28 days (35.6 MPa) and also between 7 and 84 days (31.8 MPa). There was also a significant difference (P < 0.05) between the MTFS of the calcium hydroxide-filled dentin after 84 days (31.8 MPa) and the gutta percha-filled dentin (41.3 MPa) when used as a control root filling material. The weakening of the dentin by 23-43.9% following root canal filling with calcium hydroxide provides compelling evidence to re-evaluate the daily usage of this material in endodontic therapy.

Calcium Hydroxide↗
PubMed2006

The outlook for implants and endodontics: a review of the tissue engineering strategies to create replacement teeth for patients.

Ideally, root canal therapy involves the removal of diseased pulp tissues and permanent replacement with healthy pulp to revitalize teeth. Rather than placing implants, the ideal solution is to grow new replacement teeth. Success rates of implants and endodontic treatments can exceed 90%, which presents a formidable challenge to tissue engineering researchers to ensure that future dental treatments are even more successful. The purpose of this article is to explain how tissue engineering can be used to create replacement teeth. The science of tissue engineering has evolved from growing simple tissues in cell culture incubators to a multistep process. Although the problems of introducing tissue engineering therapies as part of routine dental treatments are substantial, the potential benefits are equally ground breaking.

Biomimetic Materials↗
PubMed2006

Interleukin-1 alpha alters the expression of matrix metalloproteinases and collagen degradation by pulp fibroblasts.

Matrix metalloproteinases (MMPs) and the tissue inhibitors of MMPs (TIMPs) have been suggested to play a role in dental pulp destruction. This study examined the effects of interleukin (IL)-1 alpha on pulp fibroblasts. The ability of these cells to degrade collagen was determined with or without IL-1 alpha utilizing a cell-mediated collagen degradation assay. Reverse transcriptase-polymerase chain reaction was utilized to examine the mRNA expression of multiple MMPs and TIMPs with and without IL-1 alpha, while Western blot analyses and zymography were utilized to examine their protein expression. The collagen degradation mediated by these cells was stimulated by IL-1 alpha and inhibited by MMP inhibitors. IL-1 alpha increased the mRNA expression of MMP-1 and MMP-3, as well as induced MMP-7. Western blot analyses confirmed these results. IL-1 alpha increased the secreted protein level of TIMP-1, while only slightly affected the level of TIMP-2. These results suggest that IL-1 alpha can induce pulp destruction by differentially regulating MMPs and TIMPs.

Adult↗
PubMed2006

The incidence of pulp healing defects with direct capping materials.

PURPOSE: To (1) study the injury and healing activity of the pulp tissue to calcium hydroxide [Ca(OH)2], resin composite (RC) and resin-modified glass-ionomer (RMGI) materials when used as direct pulp capping agents, and (2) compare the incidence of healing defects between these materials. METHODS: 135 Class V pulp exposed cavities were prepared in non-human primate teeth. Direct pulp capping was conducted over 6 to 730 days with hard set Ca(OH)2, RMGI and CR materials. Healing defects recorded were: (1) bacterial leakage with McKays stain; (2) operative debris including dentin fragments and particles of capping material; (3) pulpal inflammatory activity according to FDI standards; (4) area and absence of dentin bridge formation; and (5) presence of tunnel defects in bridge. Statistical analysis was evaluated using ANOVA. RESULTS: The capping materials were associated with varying levels of pulp healing defects, including tunnel defects (P= 0.0001); operative debris (P= 0.0001); pulpal inflammatory cell activity (P= 0.0073) and bacterial leakage (P= 0.0260). Other healing defects, and the area of dentin bridge were not influenced by capping materials (P> 0.05).

Analysis of Variance↗
PubMed2005

Application of biologically-oriented dentin bonding principles to the use of endodontic irrigants.

PURPOSE: To compare the removal of smear layer and the structure of the hybrid layer formed after the use of EDTA or MTAD solutions when used as a final flush. METHODS: Single-rooted extracted premolars (n=18) were collected and treated for root canal therapy using NaOCl irrigation followed by a final rinse of 17% EDTA, Biopure MTAD, or saline (negative control). The roots were obturated with gutta-percha and a hydrophilic HEMA-containing root canal sealer. The TEM specimens were impregnated with 50% silver nitrate to visualize sealing imperfections and nanoleakage. The structure of the coronal, middle and apical parts of root canal walls was examined using transmission electron microscopy. RESULTS: After NaOCl irrigation, a final rinse with BioPure MTAD or 17% EDTA completely removed the 2 microm-thick smear layer on mechanically instrumented root canal walls. The BioPure MTAD hybrid layer was thicker than the 17% EDTA hybrid layer. Both the BioPure MTAD and EDTA caused a collapse of the dentin matrix structure which impeded sealer infiltration and the formation of high quality hybrid layer bonding. The hybrid layers created in smear layer-covered dentin exhibited less potential for nanoleakage than the MTAD or EDTA hybrid layers.

Bicuspid↗
PubMed2004

Stem cell responses in tooth regeneration.

Scientific advances in the creation of restorative biomaterials, in vitro cell culture technology, tissue grafting, tissue engineering, molecular biology, and the human genome project provide the basis for the introduction of new technologies into dentistry. This review is intended to facilitate the development of stem cell therapy for use with established therapeutic modalities to restore and regenerate oral tissues. Teeth have been shown to mineralize in response to injury for many decades, but only in recent years has the position of the stem cells been localized around blood vessels. The cells have been identified as myofibroblastoid pericytes. The ability to control the differentiation and proliferation of these cells is being examined to create stem cell therapies that can solve dental problems more effectively than current treatment regimes. Although the problems of introducing these technologies are substantial, the potential benefits to patients and the profession are equally promising - a cure for caries and diseases, a cure for oral cancer, correction of congenital defects, and the regeneration of teeth and tissues to restore oral functions. The purpose of this review is to describe how these new technologies can most usefully be employed in dentistry to enable clinicians to satisfy patient demand for a nondefective dentition.

Animals↗
PubMed2003

Identification of hierarchical factors to guide clinical decision making for successful long-term pulp capping.

OBJECTIVE: Clinicians have few quantitative studies that rank the in vivo pulp capping effects of commonly used restorative materials. These factors were investigated to provide guidance to clinicians. METHOD AND MATERIALS: One hundred sixty-one standardized pulp-exposed cavities were prepared in nonhuman primate teeth. Exposed pulps were capped with calcium hydroxide, resin-modified glass-ionomer cements, and resin composites. Teeth were collected from 7 to 720 days to observe a full range of responses. Pulpal reactions were categorized according to the standards set by the International Standards Organization. Bacteria were detected with McKay's stain. RESULTS: The incidence of bacterial microleakage was 19.7% with resin composite, 21.1% with resin-modified glass-ionomer cement, and 47.0% with calcium hydroxide. The severity of pulpal inflammation increased with the presence of bacteria or tunnel defects. The severity of pulpal inflammation prevented dentinal bridge formation at varying levels: slight for resin composite and resin-modified glass-ionomer cement, and severe with calcium hydroxide. The incidence of severe inflammation or pulpal necrosis was 7.9% with resin composite, 10.6% with calcium hydroxide, and 10.5% with resin-modified glass-ionomer cement. Other variables, such as pulpal exposure width and tertiary dentin formation, were not highly correlated to pulpal inflammation. CONCLUSION: Pulp capping with resin composite provided the lowest incidence of bacterial microleakage, the lowest levels of pulpal inflammation, and the lowest incidence of necrosis.

Analysis of Variance↗
PubMed2002

Bacterial microleakage and pulp inflammation associated with various restorative materials.

OBJECTIVES: Many restorative materials are claimed to be successful in preventing bacterial microleakage and minimizing pulp inflammation. However, information regarding the in vivo performance of materials in comparison with each other is limited. The aim of this study was to evaluate and compare the pulp response of nine restorative materials when placed in non-exposed monkey cavities. METHODS: 279 standardized non-exposed Class V cavities, were prepared into buccal dentin. Cavities were restored with a number of materials in the following categories: Zinc oxide eugenol (ZnOE), Calcium hydroxide [Ca(OH)(2)], zinc phosphate (ZP), Resin-modified glass ionomer (RMGI), Composite resin (CR), Bonded amalgam (BA), Gutta-percha (GP), Compomer and Silicate. Pulp tissues were collected and evaluated at short, intermediate and long-term intervals according to ISO guidelines; employing histomorphometric analysis, Spearman's rho and ANOVA statistics. Pulp responses were categorized according to FDI, ISO and ADA standards. Bacteria were detected using McKay stains. RESULTS: Pulp inflammation was found to be correlated to bacterial microleakage around the restoration (p < or =0.0001). The frequency of bacterial microleakage was found to vary between restorative materials (p < or =0.0001). In rank order of preventing bacterial microleakage from best to the worst; RMGI (100%), BA (88%), ZnOE (86%), CR (80%), GP (64%), Ca(OH)(2) (58%), compomer (42%), silicate (36%) and ZP (0%). SIGNIFICANCE: The most effective restorative materials to prevent bacterial microleakage and pulp injury from inflammatory activity were RMGI, BA, ZnOE and CR restorations.

Analysis of Variance↗
PubMed2002

The effect of etching on bacterial microleakage of an adhesive composite restoration.

OBJECTIVES: The incidence of bacterial microleakage, pulp inflammation and necrosis associated with dentine etching treatments prior to restoration are not known. Consequently, to resolve some of the controversy surrounding the effects and importance of vital dentine etching, the authors investigated these factors. METHODS: 110 standardised class V cavities were cut into buccal dentine, without exposing the pulp of teeth scheduled for extraction for orthodontic reasons. Cavities were either left unetched, or etched with the non-equivalent treatments of phosphoric acid gel for 60s or Ethylenediaminetetraacetic acid (EDTA) for 30s, prior to placement of composite resin. Teeth were collected and pulp responses were evaluated according to ISO guidelines, using pathohistomorphometric analysis and ANOVA statistics. RESULTS: Etching was found to be correlated to bacterial microleakage (p=0.0001) and tertiary dentine formation (p=0.0023). Bacterial microleakage was correlated to inflammatory activity (p=0.0001). The frequency of bacterial microleakage was: no etching (65%), EDTA (51%) and phosphoric acid (PA) (20%). SIGNIFICANCE: Vital dentine etching treatment is of extreme importance for the placement of RC to minimise bacterial microleakage. PA etching proved to be more effective at preventing bacterial microleakage than non-etching, and etching with EDTA.

Acid Etching, Dental↗
PubMed2002

Age-related odontometric changes of human teeth.

OBJECTIVE: The number of older patients requiring restorative treatment are likely to increase due to improvements in oral health and increased longevity. However, aging odontometric data are lacking. The aim of this study was to determine possible changes in pulp cell density, pulp area, and dentinal thickness with age. STUDY DESIGN: Incisors (50), canines (39), premolars (51), and molars (7) extracted from 60 patients aged between 10 and 59 years, were analyzed histomorphometrically for cell density (odontoblasts, subodontoblasts, and pulp core fibroblasts) and dentinal thickness. RESULTS: With increasing patient age, in both crown and root aspects of teeth, dentinal thickness increased (P <.001), while the density of odontoblasts (P <.001), subodontoblasts (P = 0.001), and pulp fibroblasts (crown, P <.011; root, P =.0015) decreased. The degree of age-related changes in teeth appeared to be asymmetrical, with decreases in the root being greater than in the crown. At all ages pulp cell densities, including odontoblasts, within the crown were greater than in the root (P <.001), even though the calculated rate of dentinal deposition was greatest in the root. CONCLUSION: Decreases in pulp cell density may reduce pulp repair activity after restorative treatments, although increases in dentinal thickness may aid pulp protection. An understanding of these age-related changes will influence the provision of restorative and endodontic care and benefit older patients.

Adolescent↗
PubMed2002

Analysis of pulpal reactions to restorative procedures, materials, pulp capping, and future therapies.

Every year, despite the effectiveness of preventive dentistry and dental health care, 290 million fillings are placed each year in the United States; two-thirds of these involve the replacement of failed restorations. Improvements in the success of restorative treatments may be possible if caries management strategies, selection of restorative materials, and their proper use to avoid post-operative complications were investigated from a biological perspective. Consequently, this review will examine pulp injury and healing reactions to different restorative variables. The application of tissue engineering approaches to restorative dentistry will require the transplantation, replacement, or regeneration of cells, and/or stimulation of mineralized tissue formation. This might solve major dental problems, by remineralizing caries lesions, vaccinating against caries and oral diseases, and restoring injured or replacing lost teeth. However, until these therapies can be introduced clinically, the avoidance of post-operative complications with conventional therapies requires attention to numerous aspects of treatment highlighted in this review.

Bacterial Vaccines↗
PubMed2002

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.

Acid Etching, Dental↗
PubMed2002

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.

Analysis of Variance↗
PubMed2002

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.

Cell Count↗
PubMed2002

Saving pulps--a biological basis. An overview.

AIM: Cavity preparation and restoration variables have an uncertain relationship to pulp injury and repair responses. The purpose of this paper is to determine the importance of cavity preparation and restoration variables, by ranking them according to their effect on pulp injury (odontoblast survival) and pulp repair (reactionary dentine secretion). METHOD: The seven studies reviewed are all based on the protocols described by Murray, Smith and colleagues in 2000 and 2001. RESULTS: The studies reviewed provide new perspectives on the importance of cavity preparation and restoration variables in mediating pulp activity. CONCLUSIONS: The onset of post-operative complications may be most productively minimised by focusing practitioner attention to aspects of treatment highlighted in this review.

Adolescent↗