Attenuation of radiation‐ and chemoradiation‐induced mucositis using gamma‐d‐glutamyl‐l‐tryptophan (SCV‐07)

Oral Diseases (2010) 16 , 655–660 Objective: To evaluate the efficacy of a novel immunomodulating peptide (SCV‐07) in attenuating the course of radiation‐induced mucositis in an established animal model of oral mucositis (OM). Material and Methods: In three separate experiments, golden Syrian hamsters received either an acute radiation challenge to the buccal mucosa of eight fractionated doses of 7.5 Gy of radiation over a 2‐week‐period, or a combination of acute radiation and cisplatin. In each experiment, animals were treated with varying doses or schedules of SCV‐07 or placebo. OM was scored in a blinded fashion using digital images obtained during the experimental period. Results: We found that SCV‐07 reduced the severity and duration of both acute and fractionated radiation‐induced OM. Similarly, when radiation and chemotherapy were used to induce OM, treatment with SCV‐07 significantly reduced the duration of ulcerative OM. The therapeutic benefit was dependent on both dose and schedule of administration. Conclusion: Taken together, we found SCV‐07 was able to modify the duration and severity of oral mucositis and was dependent on schedule and dose.     

Cell‐to‐cell interactions

The narrow anatomic periodontal space between the root surface and the alveolar bone is relatively poor in cells. However, a broad range of noxious stimuli, most frequently root canal infection, will result in the accumulation of a large number of inflammatory cells in the periapical region of the affected tooth/root. The encounter between invading microorganisms and host cells as well as the interactions of resident and immigrating cells will determine the course of the inflammatory events that may take place. This review attempts to summarize current knowledge on how cellular interactions may contribute to dynamic equilibrium between protective, self‐maintaining, propagating, destructive and downregulating events in apical periodontitis.     

Interleukin‐1 and interleukin‐8 in nicotine‐ and lipopolysaccharide‐exposed gingival keratinocyte cultures

Johnson GK, Guthmiller JM, Joly S, Organ CC, Dawson DV. Interleukin‐1 and interleukin‐8 in nicotine‐ and lipopolysaccharide‐exposed gingival keratinocyte cultures. J Periodont Res 2010; 45: 583–588. © 2010 John Wiley & Sons A/S Background and Objective: Tobacco use is associated with increased periodontal destruction in both cigarette smokers and smokeless tobacco users. Gingival keratinocytes are the first cells in contact with microbial and tobacco components and play a key role in the innate immune response to these agents. The objective of this study was to evaluate the effect of nicotine and bacterial lipopolysaccharide (LPS) alone and in combination on gingival keratinocyte production of interleukin‐1α (IL‐1α) and interleukin‐8 (IL‐8). Material and Methods: Gingival keratinocyte cultures were established from 10 healthy, non‐tobacco‐using subjects. The cells were stimulated for 24 h with 1 μm or 1 mm nicotine and/or 10 μg/mL Escherichia coli or Porphyromonas gingivalis LPS. Interleukin‐1α and IL‐8 proteins were quantified using ELISAs. Results: Compared with untreated cultures, 1 mm nicotine stimulated production of IL‐1α (p < 0.001); E. coli and P. gingivalis LPS increased IL‐8 production (p = 0.0014 and p = 0.0232, respectively). A combination of nicotine and LPS produced the highest cytokine quantities. Amounts of IL‐1α and IL‐8 following 1 mm nicotine and LPS exposure were significantly greater than in untreated cultures (p < 0.001). Interleukin‐8 was also responsive to 0.1 μm nicotine combined with E. coli or P. gingivalis LPS compared with control cultures (p < 0.0001 and p = 0.0029, respectively). Both cytokines tended to be elevated following the combined treatment relative to nicotine or LPS treatment alone. Conclusion: These results demonstrate that nicotine and LPS differentially regulate IL‐1 and IL‐8 production by gingival keratinocytes. Combined treatment tended to elevate cytokine production further, which may have implications for the progression of periodontitis in tobacco users.     

Porcelain Fracture Resistance of Screw‐Retained,Cement‐Retained,and Screw‐Cement‐Retained Implant‐Supported Metal Ceramic Posterior Crowns

Purpose: The purpose of this in vitro study was to compare the porcelain fracture resistance between screw‐retained, cement‐retained, and combined screw‐ and cement‐retained metal–ceramic (MC) implant‐supported posterior single crowns; and to investigate the effect of offsetting the occlusal screw‐access opening on porcelain fracture resistance of screw‐retained and cement‐retained MC implant‐supported posterior single crowns. Materials and Methods: Forty standardized MC molar‐shaped restorations were fabricated. The 40 restorations were divided into four groups (SRC, SRO, CRP, and CSC) of 10 specimens each. Group SRC: screw‐retained, screw‐access hole placed in the center of the occlusal surface; Group SRO: screw‐retained, screw access hole placed 1 mm offset from the center of the occlusal surface toward the buccal cusp; Group CRP: cement‐retained, zinc phosphate cement was used; Group CSC: cement‐retained with a screw‐access hole in the center of the occlusal surface. The screw‐retained restorations and abutments were directly attached to 3i implant fixtures embedded in acrylic resin blocks. Subsequently, all test specimens were thermocycled and vertically loaded in a universal testing machine at a crosshead speed of 2 mm/min until fracture. Mean values of load at fracture (in N) were calculated in each group and compared with a one‐way ANOVA and Tukey's Studentized test (α= 0.05). Results: Mean values of loads required to fracture the restorations were as follows (N): Group SRC: 1721 ± 593; Group SRO: 1885 ± 491; Group CRP: 3707 ± 1086; Group CSC: 1700 ± 526. Groups SRC, SRO, and CSC required a significantly lower force to fracture the porcelain than did the CRP group (p < 0.05). Conclusion: The cement‐retained restorations showed significantly higher mean fracture loads than the restorations having screw‐access openings in their occlusal surface. The position of the screw‐access hole within the occlusal surface did not significantly affect the porcelain fracture resistance.