Biomedical subjects

Peter J Bush

Publications and source records attributed to Peter J Bush.

9 recordsLinked to original sources

PubMed2007

Identification through X-ray fluorescence analysis of dental restorative resin materials: a comprehensive study of noncremated, cremated, and processed-cremated individuals.

Tooth-colored restorative materials are increasingly being placed in the practice of modern dentistry, replacing traditional materials such as amalgam. Many restorative resins have distinct elemental compositions that allow identification of brand. Not only are resins classifiable by elemental content, but they also survive extreme conditions such as cremation. This is of significance to the forensic odontologist because resin uniqueness adds another level of certainty in victim identification, especially when traditional means are exhausted. In this three-part study, unique combinations of resins were placed in six human cadavers (total 70 restorations). Simulated ante-mortem dental records were created. In a blind experiment, a portable X-ray fluorescence (XRF) unit was used to locate and identify the resin brands placed in the dentition. The technique was successful in location and brand identification of 53 of the restorations, which was sufficient to enable positive victim identification among the study group. This part of the experiment demonstrated the utility of portable XRF in detection and analysis of restorative materials for victim identification in field or morgue settings. Identification of individuals after cremation is a more difficult task, as the dentition is altered by shrinkage and fragmentation, and may not be comparable with a dental chart. Identification of processed cremains is a much greater challenge, as comminution obliterates all structural relationships. Under both circumstances, it is the nonbiological artifacts that aid in identification. Restorative resin fillings can survive these conditions, and can still be named by brand utilizing elemental analysis. In a continuation of the study, the cadavers were cremated in a cremation retort under standard mortuary conditions. XRF was again used to analyze retrieved resins and to identify the individuals based on restorative materials known to exist from dental records. The cremains were then processed and the analysis was repeated to determine whether restorative resins could be found under this extreme condition. Under both circumstances, sufficient surviving resin material was found to distinguish positively each individual in the study group. This study showed the utility of XRF as an analytical tool for forensic odontology and also the significance of the role of restorative resins in victim identification, even after cremation.

Bone and Bones↗

PubMed2006

Detection and classification of composite resins in incinerated teeth for forensic purposes.

The great demand for esthetic restorations has resulted in placement of large numbers of composite resin fillings. The popularity of these materials is reflected in the quantity and variety of resin brands currently on the market. The ability to distinguish resin brands can aid in positive identification of burn victims, assuming that appropriate dental records exist. Scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) was used to characterize the structure and composition of 10 modern resins. The structure of each resin was unique to manufacturer, and elemental analysis allowed separation into distinct groups. These 10 resins were also placed in extracted teeth and incinerated at 900 degrees C for 30 min, simulating near cremation conditions. The resins were identifiable by SEM/EDS after incineration, and the elemental composition remained almost unchanged. The data produced are immediately useful for resin identification in forensics, and comparative analysis can be readily performed using standard equipment. This work represents the initial stage of database generation.

Acrylic Resins↗

PubMed2005

A new model for nanoscale enamel dissolution.

The dissolution kinetics of human tooth enamel surfaces was investigated using nanomolar-sensitive constant composition (CC) and in situ atomic force microscopy (AFM) under simulated caries formation conditions (relative undersaturation with respect to hydroxyapatite = 0.902, pH = 4.5). Scanning electron microscopic (SEM) examination of the resulting etched enamel surfaces showed that deminerzalization, initiated at core/wall interfaces of rods, developed anisotropically along the c-axes. After an initial rapid removal of surface polishing artifacts, the dissolution rate decreased as the reaction proceeded in accordance with our recently proposed crystal dissolution model, resulting in hollow enamel cores and nanosized remaining crystallites, resistant to further dissolution. Generally, dissolution of minerals is regarded as a spontaneous reaction in which all the solid phase can be dissolved in undersaturated solutions. However, the dissolution of some biominerals may be suppressed when the crystallites approach nanometer size. This study shows that CC demineralization of enamel in acidic medium follows this new model that can be used to mimic carious lesion formation. In dissolution studies, nanosized enamel crystallites exhibit a remarkable degree of self-preservation in the fluctuating physiological milieu.

Dental Caries↗

PubMed2005

Evaluation of varied repair protocols applied to aged composite resin.

PURPOSE: This paper aims to examine varied surface treatments combined with adhesive bonding to ascertain the highest bond strength of the composite resin repair. MATERIALS AND METHODS: A total of 100 specimens was made using an increment technique. The prepared specimens were aged for 20 days in 37 degrees +/- 20 degrees C water and then kept for 24 h at room temperature. The samples were separated into 5 groups of 20, and each group then received a different surface treatment (control group, phosphoric acid, diamond bur, air abrasion, silane primer combined with a diamond bur treatment). The effect of each surface treatment on the bond strength was determined by a shear bond test. RESULTS: Specimens that received surface treatment with a diamond bur exhibited higher shear bond strengths than any of the other repaired groups (p < 0.05). Those treated with air abrasion had the second highest shear bond strengths, but without a statistically significant difference when compared to the control group (p > 0.05). Specimens treated with phosphoric acid showed virtually no difference compared to the specimens of the control group (p > 0.05). CONCLUSION: Statistical analysis revealed that surface treatment with a diamond bur results in higher shear bond strength than other tested methods.

Air Abrasion, Dental↗

PubMed2004

Wedged cervical lesions produced by toothbrushing.

PURPOSE: To compare the morphology of experimentally induced cervical toothbrush abrasion lesions to teeth demonstrating non-carious cervical lesions in vivo. METHODS: Eighteen premolars extracted for orthodontic reasons were each subjected to 80 hours (1.4 million strokes) of horizontal brushing in a custom fabricated toothbrushing machine. Toothpaste slurry was applied continuously and specimens were subjected to 300 gms of toothbrushing force. Denture base resin was used to simulate gingival recession of 1 mm and a sulcus width of 0.1 mm. Cervical abrasions were analyzed by optical and scanning electron microscopy and classified as either V-shape/wedged vs. U-shape/rounded lesions. When lesions exhibited both shapes, they were classified as mixed. Shapes of experimentally induced lesions then were compared to naturally occurring ones found on extracted premolars. RESULTSts: Experimentally induced toothbrush abrasion duplicated the classical clinical shapes. Half (9/18) of the experimentally induced toothbrush abrasions exhibited wedged lesions, 28% (5/18) showed a mixed wedged/rounded lesion, and 22% (4/18) showed rounded lesions. Serial photography showed progression of the morphology of the lesions. Toothbrush abrasion apparently begins apical to the cemento-enamel junction, progresses to dentin, and then undermines enamel with loss of the original cemento-enamel junction. Wedged lesions may appear with the apex oriented coronal or apical, or may be symmetrical.

Bicuspid↗

PubMed2003

Toothbrushing and gingival recession.

AIM: To review the hypothesis that toothbrushing leads to gingival recession. Gingival recession develops due to anatomical and pathological factors. The prevalence of recession is dependent on the age and characteristic of the population because it usually presents in individuals with periodontal disease or those who practise zealous or improper oral hygiene methods. Gingival trauma and gingival abrasion from toothbrushing is thought to progress directly to gingival recession. Case studies documenting recession from toothbrush trauma are speculative. Short-term studies suggest that gingival trauma and gingival abrasion may result from toothbrushing, but the direct relationship between traumatic home care and gingival recession is inconclusive. Long-term studies remain elusive or do not support the development of recession following toothbrushing. Nevertheless, tooth abrasion may be an integral part in the aetiology of recession. Toothbrush abrasion also may cause wear at the cemento-enamel junction resulting in the destruction of the supporting periodontium leading to recession.

Gingival Recession↗

PubMed2003

Noncarious cervical lesions and abfractions: a re-evaluation.

BACKGROUND: The concept of abfraction is controversial. The authors present the fundamental basis of abfraction and review studies that describe the condition. TYPES OF STUDIES REVIEWED: The authors used data on masticatory forces, enamel and dentin properties, as well as stress studies related to abfraction, for background information. They also analyzed the genesis of the abfraction theory, experimental evidence, case presentations, clinical investigations and restorative studies. RESULTS: The theory of abfraction is based primarily on engineering analyses that demonstrate theoretical stress concentration at the cervical areas of teeth. While some recent stress studies support earlier findings, others have provided significant deviating information. Few controlled studies exist that demonstrate the relationship between occlusal loading and abfraction lesions. The role of occlusal loading in noncarious cervical lesions (as shown by clinical data) appears to be part of a multifactorial event that may not necessarily follow the proposed classic abfraction mechanism, and other mechanisms or factors may explain cervical restoration failure just as well. CLINICAL IMPLICATIONS: There is little direct evidence supporting the theory of abfraction as the primary factor in the formation of noncarious cervical lesions. Controlled clinical trials are necessary to elucidate more fully the etiology of those lesions.

Bite Force↗

PubMed2003

Tooth wear: attrition, erosion, and abrasion.

Attrition, erosion, and abrasion result in alterations to the tooth and manifest as tooth wear. Each classification acts through a distinct process that is associated with unique clinical characteristics. Accurate prevalence data for each classification are not available since indices do not necessarily measure one specific etiology, or the study populations may be too diverse in age and characteristics. The treatment of teeth in each classification will depend on identifying the factors associated with each etiology. Some cases may require specific restorative procedures, while others will not require treatment. A review of the literature points to the interaction of the three entities in the initiation and progression of lesions that may act synchronously or sequentially, synergistically or additively, or in conjunction with other entities to mask the true nature of tooth wear, which appears to be multifactorial.

Acids↗

PubMed2002

Engineering a bioactive matrix by modifications of calcium sulfate.

The goal of this study was to define the conditions for the fabrication of a bioactive matrix that induces and supports cell proliferation and tissue regeneration. The proposed hypothesis was that a composite graft could be engineered by the absorption of platelet-rich plasma (PRP) onto calcium sulfate (CS). Evaluation of the biological activity of the engineered grafts was based on osteoblast proliferation studies and scanning electron microscopy (SEM) analyses. Graft samples were created in a standard size and shape so that the surface available for attachment and cell proliferation was always identical. Proliferation data were expressed as counts per minute per group and differences among groups were statistically analyzed by analysis of variance followed by the Scheffé test (alpha = 0.1). SEM analysis showed that the combination of CS and PRP presents a preserved crystalline structure well integrated by organic matrix. This combination showed the highest cell proliferation levels (p < 0.001). Further evaluations demonstrated that PRP is activated when combined with CS. When tested as a possible carrier for biologically active molecules such as platelet-derived growth factor (PDGF), CS showed increased cell proliferation (p < 0.001). SEM revealed adherent osteoblasts with broad flattened edges on CS-PRP. This study proposes CS as an efficient carrier for PRP or PDGF and supports the use of these combinations as bioactive matrices in clinical or laboratory applications.

Calcium Sulfate↗