Bacterial profile and bone healing in rats receiving cancer therapeutic doses of bisphosphonates and corticosteroids: a pilot study.

The microbial aetiology of bisphosphonate-related osteonecrosis of the jaw (BRONJ) remains undefined. This study investigated the oral microbiota and socket healing after zoledronic acid (ZA) and dexamethasone (DX) administration. Fourteen rats assigned randomly to experimental (n=8) and control (n=6) groups were injected with ZA+DX or saline, respectively, for 3 weeks prior to and 9 weeks after the extraction of left first upper and lower molars. Whole genomic DNA probes of 38 bacterial species and five Candida species were hybridized to DNA extracted from biofilm samples on exposed bone and adjacent teeth. Only experimental rats exhibited exposed bone at euthanasia. All BRONJ-like lesions were colonized by Staphylococcus pasteuri, Streptococcus parasanguinis, and Streptococcus mitis. A significant correlation was observed between the mean proportions of species colonizing BRONJ-like lesions and the teeth of experimental rats (r=0.818, P<0.001). Significant differences were seen in several species colonizing the teeth of control rats compared to experimental rats (P<0.05). Micro-computed tomography analyses revealed higher residual bone in mandibular (P=0.001) and maxillary (P=0.108) tooth sockets of experimental rats. BRONJ-like lesions were colonized mainly by non-pathogenic bacteria. ZA+DX administered to rats at doses equivalent to those given to cancer patients resulted in changes to the oral biofilm and impaired bone healing following tooth extraction.

Bacterial diversity of periodontal and implant-related sites detected by the DNA Checkerboard method.

The aim of this study was to compare the microbial composition of the subgingival biofilm from teeth and implant sulci in relation to contents originating from internal parts of the implant, abutment and implant prosthesis. Twenty subgingival biofilm samples from the mesial and distal aspects of each tooth/implant and 29 samples from the internal parts of titanium implants, abutments and implant prostheses were evaluated for the presence of 18 bacterial species using DNA Checkerboard and the differences between samples from teeth and implants were assessed with Pearson's correlation analysis. The periodontal and peri-implantar sulci presented significantly higher bacterial counts than the implant-related sites (p < 0.05 and p < 0.01, respectively). The highest counts were observed for Capnocytophaga gingivalis, Prevotella intermedia, P. nigrescens and P. micra. The correlation between the counts in the periodontal and peri-implantar sulci was r = 0.66 (p < 0.001). Weaker correlations between samples from the internal parts of the implants and periodontal sulcus (r = 0.49; p < 0.001) or peri-implant sulcus (r = 0.42; p < 0.001) were found. All 18 bacterial species were detected to be colonising the subgingival sulcus of teeth and implants, and implant components in the evaluated patients. Significant correlations between the microbiota were found, the strongest being between the periodontal and peri-implantar sulci.

Effect of simulated masticatory loading on the retention of stud attachments for implant overdentures.

This study assessed the effect of simulated mastication on the retention of two stud attachment systems for 2-implants overdentures. Sixteen specimens, each simulating an edentulous ridge with implants and an overdenture were divided into two groups, according to the attachment system: Group I (Nobel Biocare ball-socket attachments) and Group II (Locator attachments). Retention forces were measured before and after 400,000 simulated masticatory loads in a customised device. Data were compared by two-way anova followed by Bonferroni test (α = 0·05). Group I presented significantly lower retention forces (Newtons) than Group II at baseline (10·6 ± 3·6 and 66·4 ± 16·0, respectively). However, differences were not significant after 400,000 loads (7·9 ± 4·3 and 21·6 ± 17·0). The number of cycles did not influence the measurements in Group I, whereas a non-linear descending curve was found for Group II. It was concluded that simulated mastication resulted in minor changes for the ball attachment tested. Nevertheless, it reduced the retention of Locator attachments to 40% of the baseline values, what suggests that mastication is a major factor associated with maintenance needs for this system.

Testing the retention of attachments for implant overdentures - validation of an original force measurement system.

The aim of this study was to validate an original portable device to measure attachment retention of implant overdentures both in the lab and in clinical settings. The device was built with a digital force measurement gauge (Imada) secured to a vertical wheel stand associated with a customized support to hold and position the denture in adjustable angulations. Sixteen matrix and patrix cylindrical stud attachments (Locator) were randomly assigned as in vitro test specimens. Attachment abutments were secured in an implant analogue hung to the digital force gauge or to the load cell of a traction machine used as the gold standard (Instron Universal Testing Machine). Matrices were secured in a denture duplicate attached to the customized support, permitting reproducibility of their position on both pulling devices. Attachment retention in the axial direction was evaluated by measuring maximum dislodging force or peak load during five consecutive linear dislodgments of each attachment on both devices. After a wear simulation, retention was measured again at several time periods. The peak load measurements with the customized Imada device were similar to those obtained with the gold standard Instron machine. These findings suggest that the proposed portable device can provide accurate information on the retentive properties of attachment systems for removable dental prostheses.

Within-subject comparison of maxillary long-bar implant-retained prostheses with and without palatal coverage: patient-based outcomes.

Although maxillary implant overdentures are used in oral rehabilitation, different designs have not been compared previously in clinical trials. This crossover trial was designed to measure differences in patient satisfaction with maxillary long-bar implant overdentures with and without palatal coverage opposed by a fixed mandibular implant-supported prosthesis. Data were also gathered on new conventional dentures and on maxillary conventional dentures opposed by mandibular fixed prostheses. Sixteen participants were selected from a population wearing conventional dentures. Fifteen received new upper and lower dentures (1 drop-out). Four implants were placed in the maxilla and mandible (2 drop-outs). A mandibular fixed prosthesis was inserted in 13 participants, who were then divided into 2 groups. One group (n = 7) received long-bar overdentures with palate, then long-bar overdentures without palate. The other group (n = 6) received the same treatments in the reverse order. Mastication tests and psychometric evaluations using Visual Analog Scales and Categorical Scales were performed throughout the study. General satisfaction was very high with both maxillary implant-supported prostheses, as were ratings of almost all psychosocial and functional variables. There were no significant differences between treatments, suggesting that patients are equally satisfied with long-bar overdentures with and without palate when these are opposed by mandibular fixed prostheses. However, the ratings given to the maxillary implant prostheses were not significantly higher than for new conventional maxillary prostheses. This suggests that maxillary implant prostheses should not be considered as a general treatment of choice in patients with good bony support for maxillary conventional prostheses.