Table 2.—Means and Standard Deviations (Between Brackets) per Cement of the Push-out Strength and SEM Evaluation Scores of Irregularities for the 3 Sections (Apical, Medial, and Coronal) for Control (Nonfatigued) and Fatigued Specimens Apical Section
SEM evaluation (Scores 0-12)*
Panavia 21 Rely X-ARC Rely X Panavia 21 Rely X-ARC Rely X
3.5 (0.6) 4.5 (2.4) 6.3 (1.7) 5.5 (2.3) 2.1 (1.2) 3.2 (1.0)
5.5 (2.9) 6.0 (3.7) 9.3 (3.8) 4.9 (0.8) 2.1 (0.5) 3.6 (1.9)
1.8 (1.5) 3.0 (1.6) 6.5 (3.1) 6.1 (0.9) 6.4 (0.9) 4.2 (2.1)
4.5 (2.1) 6.3 (1.0) 9.3 (3.0) 5.5 (1.7) 3.4 (1.5) 4.5 (2.3)
1.5 (0.6) 3.5 (1.9) 6.3 (2.8) 6.4 (2.3) 6.6 (2.6) 2.4 (1.1)
2.5 (1.0) 5.0 (4.1) 8.3 (2.9) 6.3 (2.2) 3.9 (2.5) 2.7 (0.9)
Push-out Strength (MPa)
*If no irregularities were found, an SEM evaluation score of 0 was assigned. A score of 1 was assigned when irregularities occupied 1/12 or less (8.3% or less) of the cement circumference. The highest score level of 12 indicates irregularities occupying 91.7% to 100% of the cement circumference. (Courtesy of Bolhuis HPB, de Gee AJ, Feilzer AJ: The influence of fatigue loading on the quality of the cement layer and retention strength of carbon fiber post–resin composite core restorations. Oper Dent 30:220-227, 2005.)
results improving from the apical to the coronal location. Significant differences were noted between the apical and medial locations and between the apical and coronal locations. On SEM there were significant differences between the coronal and apical locations and between the coronal and medial locations. Discussion.—All specimens revealed that the use of quartz-coated carbon fiber posts of 6 mm and adhesively bonded composite core build-ups had the ability to resist 1 million fatigue load cycles regardless of the adhesive cement chosen. In addition, resin composite cements performed better than resin-modified glass-ionomer cements with respect to cement layer integrity and retention strength.
Clinical Significance.—The choice of cement had little effect on resistance to fatigue load, but the composite cements provided better cement layer integrity and retentive strength compared with a resinmodified glass ionomer cement.
Bolhuis HPB, de Gee AJ, Feilzer AJ: The influence of fatigue loading on the quality of the cement layer and retention strength of carbon fiber post–resin composite core restorations. Oper Dent 30:220-227, 2005 Reprints available from P Bolhuis, Louwesweg 1, 1066 EA Amsterdam, The Netherlands; e-mail: [email protected]
Oral Biology Effects of platelet-rich plasma on cell proliferation and differentiation Background.—Platelet-rich plasma (PRP) contains various growth factors and has proved useful in promoting tissue healing. Specific to dentistry, osseointegration and bone regeneration have been enhanced. However, scientific evidence supporting the validity of use of PRP in dental,
oral, and maxillofacial procedures has been lacking. PRP was specifically evaluated for its effects on the proliferation and differentiation of human osteoblast-like cells. The biological effects of PRP at the molecular level in an in vitro model were documented.
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Methods.—Two human osteosarcoma cell lines (HOS and SaOS-2) were used. The PRP was obtained from freshly drawn human venous blood that contained many platelets. The effects of PRP on osteoblast viability were determined based on the ability of mitochondrial dehydrogenases to oxidize thiazolyl blue to an insoluble blue formazan product (the MTT assay). The growth and differentiation effects were documented with use of alkaline phosphatase activity assessment, and the expression of procollagen type I, osteopontin, and osteoprotegerin mRNA was tested via semiquantitative reverse transcriptase-polymerase chain reaction. Osteoblast differentiation was also measured with use of the critical regulator core binding factor alpha 1 (cbfa1/Runx2/AML3/PebpαA). Results.—The growth rate of HOS cells exposed to PRP showed a dose-related increase. During the cell growth phase, PRP reduced alkaline phosphatase activity by nearly 50%, but when the cells reached confluence, the alkaline phosphatase activity was greatly enhanced. The levels of procollagen type I, osteopontin, osteoprotegerin, and core binding factor alpha 1 mRNA all fell during the cell growth phase and increased with cell confluence. Discussion.—The alkaline phosphatase activity responded differently depending on when during the cell condition the PRP was administered. During cell growth
this activity was suppressed, and after confluence it was greatly increased. Similar effects were noted by means of the semiquantitative reverse transcriptase-polymerase chain reaction assessment to determine PRP’s effects on osteoblast growth and differentiation. PRP exerted a favorable effect on human osteoblast-like cells, enhancing bone regeneration and activating wound healing.
Clinical Significance.—Its use is generally accepted as an adjunct to healing, but documentation of the biologic mechanism of platelet-rich plasma (PRP) has been thin. Presented here are the biological effects of PRP on the proliferation and differentiation of human osteoblasts.
Kanno T, Takahashi T, Tsujisawa T, et al: Platelet-rich plasma enhances human osteoblast-like cell proliferation and differentiation. J Oral Maxillofac Surg 63:362-369, 2005 Reprints available from T Kanno, Second Dept of Oral and Maxillofacial Surgery, Kyushu Dental College, 2-6-1 Manazuru Kokurakita-ku, Kitakyushu, Fukuoka 803-8580, Japan; e-mail: tkanno @kyu-dent.ac.jp
Inflammation with dentin bonding agent used for direct capping Background.—Pulp tissue heals better when there is reorganization of the damaged soft tissue, differentiation of odontoblast-like cells from subodontoblast cells, and repair of exposed dentin tissue with reparative dentin bridge formation. Factors that have adverse effect on healing include leakage of bacteria through the interface between the restoration and the tooth, cytotoxic dental materials, the sensitivity of operative procedures, and the effects of aging. Clinically, teeth without bridge formation and without inflammatory response are not considered unsuccessful. Biologically, the absence of dentin bridges and inflammation indicates a failure of differentiation of competent pulp
304 Dental Abstracts
cells to odontoblast-like cells. Pulp healing in the absence of dentin bridge formation often occurs with Teflon and amalgam materials placed directly on pulp exposures in animals. Dentin bonding agents (DBAs) offer promise as direct capping materials, having superior ability to adhere to demineralized enamel and dentin tissues. Hybrid DBAs formed with demineralized intertubular collagen may be able to seal vital dentin against bacterial leakage and reduce secondary inflammation of the pulp. In vitro studies have found, however, that acid etchants, monomers, and other constituents of DBAs have toxic, cytotoxic, or mutagenic effects on nerves, cultured cell lines, microorganisms, and