The nanostructure of murine alveolar bone and its changes due to type 2 diabetes.

Alveolar bone - the bony ridge containing the tooth sockets - stands out by its remodeling activity where bone is being formed and resorbed at a much higher rate than in any other bony tissue. Teeth that are anchored in the jaw through the periodontal ligament exert very large localized loads during mastication that could lead to a unique adaptation of the collagen/mineral structure in the bone. Our aim was to characterize the nanostructure of alveolar bone and to determine the influence of diabetes on structural characteristics of the mineralized matrix. Using small- and wide-angle X-ray scattering (SAXS/WAXS), we studied a spontaneous diabetic mouse model (KK+) and its corresponding healthy controls (KK-) (n=6) to determine the size and mutual alignment of the mineral nanoparticles embedded in the collagen matrix. On cross-sections (buccal-lingual) of the first molar multiple line scans with a spatial resolution of 30µm were performed on each sample, from the lingual to the buccal side of the mandible. Mineral particle thickness and length are decreasing towards the tooth in both buccal and lingual sides of alveolar bone. While mineral particles are well aligned with the long axis of the tooth on the buccal side, they are in a quarter of the measurements oriented along two preferred directions on the lingual side. These nanostructural differences can be interpreted as the result of an asymmetric loading during mastication, leading to a tilting of the tooth in its socket. In diabetic mice particle thicknesses are smaller compared to control animals.

Comparison of Gene Expression in Peri-implant Soft Tissue and Oral Mucosal Tissue by Microarray Analysis.

PURPOSE: Implant placement entails disruption of the epithelial continuity, which can lead to various complications. Therefore, the area of mucosal penetration is of particular interest clinically. The goal of the present study was to compare gene expression in peri-implant soft tissue (PIST) with that in oral mucosal tissue (OMT) using microarray analysis, and to investigate which genes were specifically expressed in PIST. MATERIALS AND METHODS: The bilateral upper first molars were extracted from 4-week-old rats and titanium alloy implants placed only in the left-side extraction sockets. Four weeks after surgery, samples were harvested from the left-side PIST and right-side OMT and total RNA samples isolated. Microarray analysis was used to compare gene expression in PIST and OMT, which was then confirmed using quantitative real-time polymerase chain reaction. Immunohistochemical staining was also performed to confirm protein level expression. RESULTS: The number of genes expressed with more than a twofold change in PIST compared with OMT was 1,102, of which 750 genes were upregulated and 352 genes were downregulated. The messenger RNA (mRNA) expression of three selected genes-Ceacam1, Ifitm1, and MUC4-were more significantly expressed in PIST than in OMT(P < .01). Immunohistochemical localization of CEACAM1, IFITM1, and MUC4 was observed in PIST, but no immunoreaction was recognized in OMT. CONCLUSION: The result of microarray analysis showed that, because of implant placement, 750 genes were upregulated in PIST compared with OMT. CEACAM1, IFITM1, and MUC4 were specifically upregulated in PIST.

Molecular events on tooth socket healing in diabetic rabbits.

Healing of extraction sockets involves complex cellular events such as repair and regeneration of tissue. These events are precisely controlled and regulated by specific signalling molecules such as transforming growth factor beta (TGF-ß), vascular endothelial growth factor (VEGF), bone morphogenetic protein (BMP), and insulin-like growth factor (IGF), which are well-conserved proteins involved in the initial response to injury and repair in soft and hard tissues. We studied 48 rabbits, which were divided into 3 groups of 16 each: the control group, the untreated diabetic group, and the insulin-treated diabetic group. The lower incisor of each rabbit was extracted and, after 2, 10, 20, and 30 days of healing, the expression of TGFß-3, VEGF, IGF-1R, and BMP-4 in the sockets was measured immunohistochemically. Rabbits with untreated diabetes expressed less TGFß-3 than the other groups throughout the healing periods, whereas IGF-1R expression was higher than that in the other groups. This increase in IGF-1R expression was responsible for increasing the healing time in rabbits in the untreated group. The healing of bone in diabetic rabbits that were not treated with insulin was prolonged because of a delay in the onset of cell proliferation and osteoblast differentiation, and the insulin treatment had a direct effect on the expression of TGFß-3 and IGF-1R, which accelerated healing of the socket.

Temporal localization of osteocalcin protein during healing of tooth extraction sockets in rats.

AIM: The aim of this study was to evaluate the expression of osteocalcin protein during the alveolar bone healing process in rats. METHODS: Twenty four rats were used in this study and, after anesthetic induction, they had their right upper incisors extracted. At 7, 14, 21 and 28 days after the tooth extraction, the animals were injected 4% formaldehyde. The histological tissue pieces were colored in hematoxilin and eosin and the immunohistochemistry reaction for osteocalcin was performed. RESULTS: At seven days lesser neoformed trabeculae bone and a small quantity of osteocalcin labeling were observed. At 14 and 21 days a larger quantity of neoformed trabeculae bone and higher osteocalcin values were detected. At 28 days the largest quantity of neoformed trabeculae bone and a decrease on the amount of osteocalcin immunolabelling were noticed. CONCLUSION: According to our results and considering the limits of the present study it is possible to conclude that a greater osteocalcin expression is observed at 14 and 21 days postoperatively, characterizing the periods when intense mineralization of the bone tissue occurs during the alveolar bone healing process.

Evaluation of bone height and bone density after tooth extraction: an experimental study in minipigs.

OBJECTIVE: The objective of this study was to radiographically quantify bone density and bone height preservation in tooth extraction alveolus filled with xenograft. STUDY DESIGN: The maxillary and mandibular fourth deciduous molars and fourth premolars of 6 minipigs were removed. Randomly, in 3 animals the right side was used as the test side and in the other 3 animals the left side was the test side. Intraoral radiographs were performed to compare the condition at the initial time and 3 months later. Measurements of bone height and bone density were performed using KS300 (Zeiss) software. RESULTS: After 3 months, there was a statistically significant smaller bone height loss for the test group. The test group presented a statistically greater bone density immediately after tooth extraction. However, after 3 months there was no statistically significant difference between the groups. CONCLUSIONS: The results suggest that treatment of postextraction alveolus with xenograft can preserve bone height initially but differences in bone density compared to when no xenograft is used are not sustained.

Immediate loaded dental implants: comparison between fixtures inserted in postextractive and healed bone sites.

In the last two decades, several investigators have reported immediate placement of dental implants into extraction sockets achieving excellent results with a two-stage surgical procedure. Recently, immediate loading (IL) has become an emerging technique because it has been documented to be a successful and time-saving procedure. Regarding the possibility of immediate/early loading of implants placed in fresh extraction sockets, few reports are available. In addition, they are based on limited series with short follow up. Thus, we decided to perform a retrospective study on a large series of postextractive IL implants. From January 1995 to October 2004, 416 IL fixtures were placed immediately after extraction and 658 IL fixtures in healed sites. The mean follow up is 3 years. Multiple implant systems were used. Because only eight of 1,074 implants were lost (i.e., survival rate, 99.3%) and no statistical differences were detected among the studied variables, no or reduced marginal bone loss was considered as an indicator of success rate to evaluate the effect of several host-, surgery-, and implant-related factors. A general linear model was then performed to detect those variables statistically associated with marginal bone loss. Only eight of 1,074 implants were lost (i.e., survival rate, 99.3%) and no differences were detected among the studied variables. On the contrary, the general linear model showed that younger age (cutoff, 55 years) and harder bone are related to a lower delta insertion abutment junction (or marginal bone loss) and thus a better outcome. We demonstrated that postextractive IL implants have a high survival rate and success rate that are similar to those reported in previous studies of two-stage procedures or in IL implants inserted in healed bone. Poor bone quality and older age correlate with a slight higher bone resorption.

Comparative evaluation of the peri-implant bone tissue mineral density around unloaded titanium dental implants.

OBJECTIVE: The mechanical properties of bone are greatly influenced by the percentages of organic and mineral constituents. Nevertheless, the information about the mineral content on a microscopic scale in peri-implant bone is scarce. The aim of this work was to analyze the bone mineral density of peri-implant bone under different techniques. DESIGN: Five unloaded titanium dental implants with a micro-structured surface (three XiVE plus and two Frialit 2, DENTSPLY-Friadent, Mannheim, Germany) were retrieved from the mandible of five patients after a 6-month period. scanning electron microscopy with backscattered electron signal (BSE), light microscopy (LM) with a double staining technique, fluorescence microscopy and confocal laser microscopy were used for measuring microscopic mineral content variations in peri-implant bone. Histomorphometry and image intensity (grey level) were evaluated using a software package for image analysis. RESULTS: The low mineral density index (LMDI) for LM was of 29.2+/-3.1 (mean+/-S.D.), while the high mineral density index (HMDI) was of 88.2+/-3.6 (mean+/-S.D.). The one-way ANOVA analysis showed a significant difference (P<0.001) among the groups. The pairwise Holm-Sidak test identified the differences among HMDI indexes for both LM and SEM values and also for cross-evaluation of the LMDI and HMDI values. The comparison between LMDI indexes for both SEM and LM did not show any significance. The fluorescence microscopy analysis showed clearly the difference between old (high mineralized) and new (low mineralized) bone tissue near the implant surface. Under confocal laser microscopy the same sections showed the area of bone modelling closest to implant surface. CONCLUSION: In this study it was found that bone around unloaded implants showed a low mineral density index under all the investigation methods used. It was also found that the conventional LM technique with the double staining method was able to intensely stain the bone area with a low mineral content.

Spatial and temporal localization of FGF-2 and VEGF in healing tooth extraction sockets in a rabbit model.

PURPOSE: The purpose of this study was to test the hypothesis that spatial and temporal localization of growth factors FGF-2 and VEGF in a rabbit tooth extraction socket model correlate with the histologic events of healing. MATERIALS AND METHODS: Twenty-four male New Zealand white rabbits divided into 8 groups of 3 were used in the study. Incisor teeth were extracted from both jaws and the healing extraction socket with surrounding jaw bone was harvested at 48 hours, 4 days, 1, 2, 4, 8, 12, and 16 weeks. Tissues were fixed, decalcified, and processed for hematoxylin-eosin and immunohistochemical staining. The sections were stained to detect FGF-2 and VEGF. The stained sections were then imaged and an automated computer program was used to detect the brown diaminobenzidine stain that represented the growth factors of interest. Data was obtained in the form of percentage area and intensity of stain and analyzed using the analysis of variance (ANOVA - Tukey Kramer and Scheffe's post-test). RESULTS: Spatial and temporal differences in localization of FGF-2 and VEGF were observed across all time frames in both jaws. Statistically significant differences in percentage area and intensity of brown diaminobenzidine stain were seen temporally between FGF-2 and VEGF (P < .05). CONCLUSION: The results of this study showed positive correlation of histologic events to spatial and temporal localization of FGF-2 and VEGF in a rabbit tooth extraction model.

A role for TNF in bone resorption of deciduous molars in human beings.

In this study, tumor necrosis-alpha was sampled from the gingival crevice of human deciduous molars; this was compared with values measured from the crevice of those deciduous molars missing a permanent successor, and from the crevice of deciduous ankylosed molars. Tumor necrosis-alpha was harvested from the gingival crevice with magnetic microspheres coated with tumor necrosis-alpha antibodies. The amount of bead-bound tumor necrosis-alpha was quantified with the use of an enzyme-linked immunosorbent assay. One hundred seven sites (from 41 patients) were sampled; for each patient, the normal value was compared with either the molars missing a permanent successor or ankylosed value. The tumor necrosis-alpha levels were 1.6 times higher from the crevice of ankylosed deciduous molars when compared with normal deciduous molars and 2.6 times higher from the crevice of sites with a molar missing a permanent successor. The mean and standard error mean distribution of tumor necrosis-alpha expressed as picograms was: normal molars 91 pg (standard error mean +/- 20), ankylosed molars 150 pg (standard error mean +/- 31), and missing permanent successor 236 pg (standard error mean +/- 67). Analysis of variance showed the difference among the 3 means was close to attaining significant difference (F [2.104] = 2.7905, P =.066). Multiple comparison procedures indicated that the mean for molars missing a permanent successor and the normal groups were significantly different, P =.05. The results of this study suggest tumor necrosis-alpha values are elevated in the gingival crevice of deciduous molars with ankylosis and where the permanent tooth bud is congenitally missing.