Histometric study of root resorption on human premolars following experimental replantation

Abstract – A histometric method was applied for evaluation of root resorption in 57 experimentally replanted teeth and 22 controls. Representative axiobuccolingual sections were selected for measurement of resorptions at a magnification of × 40. The frequency of root resorption in the control teeth was low. In replanted teeth marked resorptive activity elicited by the trauma appeared after 2 wk. The extent of active resorptions increased until the third postoperative week. On an average 14% of the root periphery was affected at this stage. After the sixth postoperative week progressive cement deposition took place in the resorption lacunae. Incidental ankylosis of the periodontal membrane also occurred from this observation time but there was no increase among the long-term groups.     

Some microbiological, histopathological and immunohistochemical characteristics of progressive periodontal disease

Abstract The aim of the present investigation was to study the local nature of human periodontal disease by assessing the microbiota and the composition of the tissue lesions at sites with progressive attachment loss in periodontitis susceptible subjects. 300 subjects with periodontal disease were monitored for 2 years without treatment. 8 subjects lost >2 mm of attachment at 3 sites during both the first and the second 12 month interval. These 8 subjects (progressive disease group; PD)were recalled for a microbiological and histopathological examination. A group of age- and sex-matched subjects were identified who during the 2 years of monitoring exhibited gingivitis and deep pockets, but no further attachment loss. This group of 11 subjects (non-progressive disease group; NPD) served as controls. From the 8 active disease subjects, 1 interproximal site which had displayed disease activity (progressive disease active; PDA) and 1 contralateral site without disease progression (progressive disease inactive; PDI) were sampled. From the 11 control subjects, 1 site/subject was sampled (NPD). The total number of viable micro-organisms (TVC) in the subgingival microbiota was estimated and a series of bacterial species were identified and enumerated. The gingival tissue of the sampling site was excised and the soft tissue prepared for morphometrical and immunohistochemical analyses. No differences were observed in the subgingival microbiota of the sample sites in the subjects who exhibited disease progression (PD) when compared with the subjects with periodontally diseased but stable conditions (NPD). Furthermore, no marked difference could be noted between progressive (PDA) and non-progressive (PDI) sites in the PD group of subjects. The results from the morphometric determinations revealed that the lesions from the PD and NPD subjects on the average were of similar size, but the PD lesions were comprised of a larger relative volume of plasma cells, a higher % number of plasma cells and monocytes/macrophages and a lower numerical density of lymphocytes than the corresponding sites in the NPD group. Both T cell markers (CDS and CD4) and B cell markers (CD22) examined were significantly elevated in the PDA compared to the PDI lesions. The CD4/CD8 ratios calculated from assessments made in the PD and NPD tissue samples were 2.4 and 2, while the corresponding ratios for PDA and PDI lesions were 3 and 2.1 (p<0.05) respectively. The present data indicate that differences exist between disease active and inactive subjects and sites and it is suggested that the human model described may be used to study disease progression using shorter time intervals between examinations and additional parameters.     

Porous hydroxyapatite as a bone graft substitute in alveolar ridge augmentation: A histometric study

Following bilateral alveolectomy, the ridge form was restored in 10 dogs with blocks of porous HA matrix and bicortical iliac autografts. The specimens were retrieved after 11 to 17 months and undecalcified sections were prepared for microscopy and histometry. Within the HA implants, bone ingrowth extended throughout the pores. This bone appeared mature and well vascularized. The autografts united to the mandible. However bone ingrowth into the cancellous spaces of the grafts was minimal or absent. Measurement of implant and graft cross-sectional areas showed the maintenance of alveolar ridge form to be equally permanent for the 2 materials over the 1.5 year duration of the study. The implant specimens were composed of 43.1% HA matrix, 45.2% bone and 11.7% soft tissue. The HA matrix had a surface area averaging 9.3 mm2/mm3 that was 91.1% covered with bone ingrowth. Although this study supported the thesis that a porous HA matrix can function as a bone graft substitute, it is noted that the unyielding nature of the implant blocks, compared to granules, requires a solution to the challenge of long-term denture support without ulceration before it can be used with clinical confidence.     

Radiographical and histological characteristics of ssubmerged and nonsubmerged titanium implants. An experimental study in the Labrador dog.

Using 5 Labrador dogs, certain characteristics of the peri-implant tissues were analyzed after using a 1-step surgical procedure for installation of Brånemark® implants. Six titanium implants, 3 in each mandibular quadrant, were installed in the regions of the right and left first molars and the fourth and third premolars. In the right mandibular quadrant, a traditional 2-step procedure was employed, whilst in the left quadrant, a 1-step procedure was carried out. The animals were monitored during a 6-month period. Biopsies of the healed peri-implant mucosa showed signs of superficial inflammation. The histological analysis revealed that i) the connective tissue lateral to the junctional epithelium showed limited accumulations of inflammatory cells (PICT), and ii) that at implant sites that had been exposed to the oral cavity for 6 months (1-step implants), an inflammatory cell infiltrate (abutment ICT) consistently was present in the tissues facing the abutment-fixture junction (AFJ). This infiltrate was separated from the bone crest by a 0.8mm-wide zone of normal connective tissue. Irrespective of the surgical procedure applied, the radiographic and histometric measurements disclosed that i) the crestal bone loss was about 2.4mm, ii) the height of the peri-implant mucosa varied from 3.5mm to 3.9mm, iii) the bone crest was located 1.1–1.5 mm apical of AFJ as well as of the apical termination of the junctional epithelium (aJE), and iv) a junctional epithelium of 2.1–2.4mm faced the implant surface. In conclusion, this study demonstrates that, using a dog model, titanium dental implants ad modum Branemark installed according to a 1-step or to a 2-step surgical procedure will obtain similar soft tissue adaptation and proper bone anchorage (osseointegration). Further studies are, however, required to ascertain the long-term clinical feasibility of the 1-step approach.     

Effects of cyclosporine A on plasma cells in experimental gingivitis in dogs

Abstract The aim of the present investigation was to evaluate the effect of Cyclosporine A (CsA) on the inflammatory lesion formed in the gingival tissues during de novo plaque formation. 5 beagle dogs were used. On day 0, all teeth of the 5 dogs were scaled and polished. A 6-week period of plaque control including daily tooth cleaning with toothbrush and dentifrice was initiated. A clinical examination regarding plaque and gingivitis was performed, and the plaque control measures were abandoned on the right side of mandible. 3 weeks later, the clinical examination was repeated, samples of subgingival plaque harvested and biopsies obtained from the 3rd and 4th right mandibular premolar regions. The tooth cleaning measures on the left side of the mandible were terminated at this interval. During the following 3 weeks, the animals formed plaque in the lower left premolar regions, and received, 1 × daily, a subcutaneous injection of CsA. At the end of this 2nd plaque formation period (test), the clinical examination was repeated, subgingival plaque was sampled and biopsies from the 3rd and 4th left mandibular premolar regions harvested. The biopsies were prepared for histometric and morphometric analyses. The clinical and histological examinations demonstrated that plaque formation resulted in a gingival lesion (ICT) which, in the 2 periods, had similar size and apical extension. The ICT formed during the CsA administration period, however, harbored an increased number of plasma cells and a reduced macrophage density than the control lesion. It is suggested that CsA administration may result in a Th-2 (T-helper 2-cell) dependent activation of B-lymphocytes.     

Influence of various implant platform configurations on peri-implant tissue dimensions: an experimental study in dog

Aim: To evaluate the influence (i) of various implant platform configurations and (ii) of implant surface characteristics on peri‐implant tissue dimensions in a dog model. Material and methods: Mandibular premolars and first molars were extracted bilaterally in six Labrador dogs. After 3 months of healing, two implants, one with a turned and a second with a moderately rough surface, were installed on each side of the mandible in the premolar region. On the right side of the mandible, implants with a tapered and enlarged platform were used, while standard cylindrical implants were installed in the left side of the mandible. Abutments with the diameter of the cylindrical implants were used resulting in a mismatch of 0.25 mm at the tapered implant sites. The flaps were sutured to allow a non‐submerged healing. After 4 months, the animals were sacrificed and ground sections were obtained for histometric assessment. Results: All implants were completely osseointegrated. A minimal buccal bone resorption was observed for both implant configurations and surface topographies. Considering the animals as the statistical unit, no significant differences were found at the buccal aspect in relation to bone levels and soft tissue dimensions. The surface topographies did not influence the outcomes either. Conclusions: The present study failed to show differences in peri‐implant tissue dimensions when a mismatch of 0.25 mm from a tapered platform to an abutment was applied. The surface topographies influence a neither marginal bone resorption or peri‐implant soft tissue dimension. To cite this article:
Baffone GM, Botticelli D, Pantani F, Cardoso LC, Schweikert MT, Lang NP. Influence of various implant platform configurations on peri‐implant tissue dimensions: an experimental study in dog.
Clin. Oral Impl. Res. 22 , 2011; 438–444.     

Modeling of the buccal and lingual bone walls of fresh extraction sites following implant installation

OBJECTIVE: To determine whether the reduction of the alveolar ridge that occurs following tooth extraction and implant placement is influenced by the size of the hard tissue walls of the socket. MATERIAL AND METHODS: Six beagle dogs were used. The third premolar and first molar in both quadrants of the mandible were used. Mucoperiostal flaps were elevated and the distal roots were removed. Implants were installed in the fresh extraction socket in one side of the mandible. The flaps were replaced to allow a semi-submerged healing. The procedure was repeated in the contra later side of the mandible after 2 months. The animals were sacrificed 1 month after the final implant installation. The mandibles were dissected, and each implant site was removed and processed for ground sectioning. RESULTS: Marked hard tissue alterations occurred during healing following tooth extraction and implant installation in the socket. The marginal gap that was present between the implant and the walls of the socket at implantation disappeared as a result of bone fill and resorption of the bone crest. The modeling in the marginal defect region was accompanied by marked attenuation of the dimensions of both the delicate buccal and the wider lingual bone wall. Bone loss at molar sites was more pronounced than at the premolar locations. CONCLUSION: Implant placement failed to preserve the hard tissue dimension of the ridge following tooth extraction. The buccal as well as the lingual bone walls were resorbed. At the buccal aspect, this resulted in some marginal loss of osseointegration.