Cristina Allievi

Soft tissues around long-term platform switching implant restorations: a histological human evaluation. Preliminary results.

BACKGROUND Switching platform restorations seems to reduce the peri-implant bone resorption and to preserve the peri-implant soft tissues. AIM The aim of the present human study was to compare histologically the peri-implant soft tissue in switching and traditional platform implants 4 years after restoration. MATERIALS AND METHODS Forty-eight months after implant restoration, 37 peri-implant soft tissue samples from 14 patients were harvested from traditionally restored implants (control group) and from three different platforms mismatching 0.25-0.85 mm (test groups). At the harvesting time, all sites were clinically healthy. Samples were processed to evaluate the inflammatory infiltrate area [inflamed connective tissue (ICT)], the microvascular density (MVD) and the collagen content (AA%). RESULTS At the analyses, no significant differences were found between groups in terms of ICT, MVD and AA% (p>0.05). In all groups, most samples with a well-preserved junctional epithelium showed a small and localized inflammatory infiltrated associated with not-well-oriented collagen fibres and an increased MVD. CONCLUSIONS Forty-eight months after restoration, switching and traditional platform implants had similar histological peri-implant soft tissue features, despite different bone level changes detected radiographically and published in a previous parent study. The present study seems to confirm platform switching as a safe prosthetic concept leading to better maintenance of peri-implant bone levels. However, further histological studies are required to longitudinally confirm the present data.

A Photographic System for the Three-Dimensional Study of Facial Morphology

OBJECTIVES To test whether digital photographs supported by three-dimensional (3D) software are suitable for measuring the facial soft tissues of healthy subjects as compared with data obtained by a certified 3D computerized electromagnetic digitizer. MATERIALS AND METHODS Three-dimensional soft tissue facial landmarks were obtained from the faces of 15 healthy young adults, using a 3D computerized electromagnetic digitizer and a new low-cost photogrammetry system. Twelve linear and 18 angular measurements were computed. Errors between methods and repeatability of the new method were calculated. RESULTS Systematic errors between methods were found for only two distances and three angles (paired t-test, P < .05). The mean absolute differences between methods were always lower than 3 mm and 3 degrees. Repeated digitization of photographs showed that the method was repeatable (no systematic differences; random errors lower than 1.6 mm and 3 degrees). Repeated sets of photographs showed random errors of up to 5.3 mm and 5.6 degrees, without systematic biases. CONCLUSION The 3D photogrammetry system can provide reliable facial measurements. The method is relatively fast and requires only inexpensive equipment. It is simple to use for private practice, research, or other practice.

Oral health conditions in Italian Special Olympics athletes.

During three Italian Special Olympics National Games, 365 athletes were screened. Dental and medical conditions and demographic data were recorded. The athletes were divided into two groups: those with Down syndrome (DS) and those without DS but who had intellectual disabilities (non-DS). Most of the subjects were in good systemic health. Total DMFt was 10.3 (SD 5.8; D=1.3; M=6.1; F=2.8). Decayed and filled teeth were significantly more frequent in athletes who did not have DS compared to those with DS. No significant differences were found between the two groups in the number of subjects with filled, sealed, or traumatized teeth. Athletes with DS and without DS who participated in the Italian Special Olympics had a similar oral status, which was better than Italian persons who were institutionalized and who had an intellectual disability.

Human palatal and tuberosity mucosa as donor sites for ridge augmentation

Since different clinical outcomes of periodontal bilaminar surgeries using the palate or the maxillary tuberosity as connective tissue (CT) donor sites have been observed, tissues grafted with CT from the palate or the tuberosity 1 year after surgical procedures for ridge augmentation were compared with nongrafted tissues by using morphologic and molecular methods. Collagen content and matrix metalloproteinases 1 and 2 expression were similar in tissues and cultured fibroblasts from the palate and tuberosity, although with interindividual differences. In contrast, differences in collagen cross-linking and maturation in the tuberosity fibroblasts were observed, suggesting a possible role in determining hyperplastic responses in some patients.

Soft tissue surrounding switched platform implants: an immunohistochemical evaluation.

OBJECTIVES This clinical and immunohistochemical study was designed to characterize the cellular and molecular patterns for bone loss of soft tissues surrounding implants restored with different implant platform configurations. MATERIAL AND METHODS A total of 32 implants were restored using abutments with the following mismatches: 0 mm (control group), 0.25 mm (test group(1)), 0.5 mm (test group(2)) and 0.85 mm (test group(3)). Four years after, loading all sites were clinically healthy, and soft tissue samples were harvested and processed for immunohistochemical analysis. Amounts of lymphocytes T (LyT) -B (LyB), IL-17 and RANKL were assessed. RESULTS No significant difference was found between groups (P > 0.05) in terms of infiltrated T and B cell counts, IL-17 and RANKL expressions. When pooled data were analysed, lymphocytes T counts and IL-17 were higher than lymphocytes B counts and RANKL. LyT and LyB counts were highly negatively correlated (Pearsons r > 0.7) and IL-17 was correlated (Pearsons r > 0.4, <0.7) to LyT and LyB. CONCLUSIONS After prolonged exposure of abutments in the oral cavity, the configuration of the implant abutment interface does not seem to affect the inflammatory cellular and molecular pattern responsible for bone loss.

Anthropometric Indices of Facial Features in Down’s Syndrome Subjects

Down’s Syndrome (DS) is the most frequent live-born autosomal aneuploidy in humans, and it is characterized by a distinctive craniofacial phenotype. Qualitative reports and quantitative investigations comparing subjects with DS to normal subjects found modifications in head size (overall reduction) and shape (brachycephaly with a flattened occipital bone). The faces of subjects with DS are narrower, less deep, and shorter than normal faces, with a global anomalous relationship between individual measurements. In the upper part of the face, the interorbital width is decreased, the palpebral fissures are reduced with slanted eyelids, and the forehead is prominent with a depressed nasal bridge. The middle part of the face (maxillary region) is hypoplasic, with reduced vertical, lateral, and anteroposterior dimensions. Overall, the nose is significantly smaller; its vertical and anteroposterior dimensions are reduced, but its horizontal dimensions are increased. In DS subjects the nose is shorter and less protruding, but with larger nostrils, a flatter angle of alar slope, and a more acute nasal tip angle. The mandible is small, with more acute gonial angles, and a more prominent position. Overall, there is a tendency toward a skeletal Class III pattern; the prominent forehead and mandible, associated with midfacial hypoplasia, may result in a concave sagittal plane facial profile. In the horizontal plane, the face is less prominent. Mouth width is reduced, with a smaller lower lip and a larger upper lip, with increased vermilion area and height. The lips are prominent, with reduced nasolabial, interlabial (soft tissues), and interincisal (teeth) angles. There are alterations in ear dimensions (global reduction), position and shape, with a significant larger asymmetry than in normal subjects. The ears are usually more prominent from head surface in DS subjects than in normal subjects. Persons with DS also possess several alterations in the hard- and soft-tissue structures of the oral cavity (teeth and dental arches, palate, tongue, oral mucosa), with reduced hard tissue palatal dimensions. In conclusion, the facial soft-tissue of subjects with Down’ syndrome can be successfully measured and monitored with noninvasive computerized anthropometry. A global, three-dimensional, quantitative assessment of the craniofacial characteristics may help in clinical diagnosis.

Analysis of tissue structure and remodeling ion alveolar ridges augmented with human palate or tuberosity mucosa

Previous clinical reports found different clinical outcomes of localized alveolar ridge augmentation with soft tissue harvested either from the palate or from the tuberosity over time, showing that the palatal grafts had a better tissue stability than those from the tuberosity, which tended to a hyperplastic reaction. The mechanisms responsible for a different maturation of the grafted tissue using the two donor sites are still unclear, very likely depending on differences of the structure and extracellular matrix of connective tissue (CT). The current study aimed at comparing the morphology and collagen turnover-related molecular pathways of sites grafted with CT from either the palate (group A = 7 patients) or the tuberosity (group B = 7 patients) one year after surgical procedures for ridge augmentation. Cultured fibroblasts were obtained to analyze by real-time PCR the mRNA levels for collagen type I and III (COL-I, COL-III), matrix metalloproteinases (MMP-1 and 2), long lysyl hydroxylase 2b (LH2b). Collagen protein levels were assessed by slot blot, collagen degradation by SDS-zymography. No significant differences in collagen content were found. COLI and III, MMP-1 and 2 expression was similar in cell culture supernatants from palate and tuberosity fibroblasts, although COL-I and COL-III protein levels resulted up-regulated, respectively, in 57% and 66% of the samples. LH2b/COL-I mRNA ratio 69% was higher in the tuberosity fibroblasts, suggesting that the tuberosity collagen could be cross-linked at a higher extent, and therefore less susceptible to degradation by MMPs, leading to its excessive accumulation. Our data show that in group B the higher LH2b/COL-I mRNA ratio may be responsible for differences in collagen maturation as the major determinants in the hyperplastic response, and that grafting using the maxillary tuberosity could avoid unwanted tissue contraction over time.

Histological and immunohistochemical analysis of the bone-implant interface during early phases of osseointegration in different bone defects

The present study aimed to evaluate the histological features of bone healing around dental implants placed in bone defects of different sizes [1]. In the mandible of 12 Labrador dogs the premolar and molar teeth were extracted bilaterally. After 6 months of healing six implants were placed in two conventional sites, in two sites with a marginal gap of 0.5 mm (small defects) and in two sites with a marginal gap of 1.25 mm (large defects). Bone biopsies harvesting was scheduled in order to obtain healing times of 5, 10, 20 and 30 days. Before decalcification with EDTA was completed, mesial and distal cuts parallel to the long axis of the implant were made through the tissues and a buccal and lingual portion of the tissue block were separated from the implant. The soft tissue portions were dehydrated in ethanol, embedded in paraffin and sectioned with the microtome set at 7 μm. Mayer-Haematoxylin/Eosin was used to show the presence of the inflammatory infiltrate and to evaluate the percentage of newly formed microvessels at the different time points around the implants. Picrosirius Red was used to evaluate the collagen content while polarized light was used to enhance the birefringency of the staining and show collagen bundles distribution [2]. Immunohistochemistry with osteopontin (OPN) was performed to evaluate its distribution. In all groups, angiogenesis increased from 5 to 20 days and then decreased slightly. The collagen distribution had a similar behavior. In all defects, OPN expression increased until the 10th day, decreased at 20 days and then stabilized. Control sites showed a lower percentage of OPN compared to the sites with marginal gaps. The small defects showed the highest OPN concentration and the largest value of collagen content. Apparently a small marginal gap around the dental implant during the early phases of healing may accelerate bone regeneration.

Histologic evaluation of bone tissue affected by bisphosphonates related osteonecrosis of the jaws

Introduction. Bisphosphonates are medications widely used in the management of osteoporosis, Paget’s disease and cancer affecting the bone. They are taken up in the skeleton at sites with increased bone remodeling. Bisphosphonates treatment rapidly decreases bone resorption and progressively decreases bone formation by inhibiting osteoclastic activity in the first place and consequently affecting osteoclastic induced osteoblastic activity. Bone turnover is therefore suppressed. Angiogenesis is reduced and keratinocytes are inhibited. A complication observed following treatment with bisphosphonates is osteonecrosis of the jaws. The aim of this study was to characterize the histological features of bone tissue obtained by patients affected by bisphosphonates related osteonecrosis of the jaws. Material and methods. Ten bone tissue samples were obtained from 8 oncologic patients and 2 patients with osteoporosis. After surgical procedure the samples were immediately placed in formalin and processed for ground sections according to Donath and Breuner1. Briefly, the specimens were dehydrated by increasing ethanol concentrations and embedded in Kulzer Technovit 7200 VLC® resin. The cores were cut longitudinally in two mid-sections. All slices were subsequently reduced by microgrinding and polishing to an even thickness of 80 µm. The sections were stained with Toluidine blue/Pyronine G, observed using a light microscope and photographed. On the pictures at the total magnification of 100x, the perimeter of mineralized tissue presenting resorption lacunae was measured using a dedicated software, and expressed as a percentage of the total bone tissue perimeter (RP%). Mean and standard deviation of RP% were computed from 20 histologic sections. Results. Different histomorphological features were detected between samples, but no apparent differences were found between osteoporotic and oncologic specimens. Some areas were rich in lacunae filled with viable cells, while other areas presented empty osteocytic lacunae; some spots showed hypercellularity. In all specimens the mineralized tissue border appeared very irregular and was characterized by frequent resorption lacunae (RP: mean 92.5%±2.1). Also, bacteria and infiltrated inflammatory cells with chronic appearance were observed in all samples. The connective matrix seemed to have lost its physiologic structure. Conclusion. it seems that osteonecrotic lesions had typical features such as bone resorption lacunae, bacteria and inflammatory cell infiltrated. 1. Donath, K., Breuner, G. 1982. J. Oral Pathol. 11: 318-326.

Histomorphometric analysis of intraoral bone grafts harvested by different methods

Autogenous bone is considered the “gold standard” among graft materials for alveolar ridge augmentation, because of its osteogenic, osteconductive and osteoinductive features. In clinical practice, autogenous bone chips can be obtained by using different methods, and several studies demonstrated the influence of devices used for tissue harvesting on bone chip morphology and vitality. Aim of the present study was to compare histologically and histomophometrically the morphological features and the vitality of bone chips harvested intraorally with five different methods. Material and Methods Five young adult men were recruited for this study. Five bone samples were harvested from the alveolar process of each patient by means of different methods: 1) bone scraper, 2) stainless steel round bur, 3) stainless steel implant spiral bur, 4) piezoelectric device, 5) trephine bur+manual mill. Samples were processed for undecalcified histology and stained with toluidine blue/ pyronine G (Sigma-Aldrich, St Louis, MO). The sections were photographed in a Nikon light microscope (Eclipse E600) equipped with a calibrated digital camera (DXM1200, Nikon, Tokyo, Japan). Histomorphometric analyses were performed to evaluate bone fragment dimensions: fragments with dimensions comprised between 100μm and 1000μm (medium size fragments = MF), fragments smaller than 100μm (small size fragments = SF) and those greater than 1000μm (large size fragments = LF) were differentiated. Total area and percentage area were also evaluated. A stereologic method was used to calculate the percentage of vital bone. Results Five samples for each harvesting procedure were analyzed. Bone fragments harvested using Trephine bur mostly resulted vital and of large dimensions. Spiral and implant bur produced only small and medium fragments but the percentage of nonvital bone was higher than in the other groups. Bone scraper and piezoelectric device produced vital bone fragments with medium-large dimensions. Conclusions Within the limited number of samples evaluated, results of the present study claim that bone scraper and piezoelectric device are the most efficacious procedure on harvesting vital bone fragments.