Influence of initial implant mobility on the integration of titanium implants. An experimental study in rabbits.

In the present study, the influence of initial instability on the healing of titanium implants was studied in 9 lop‐eared rabbits. Titanium implants (Brånemark System®) were inserted in the tibiae, a location with cortical bone only, in such a way that they were either stable (control), rotation‐mobile, or totally mobile. Implants were also inserted in the distal femoral condyles, representing an implantation bed with mainly cancellous bone, so they either showed no initial mobility (control) or were rotation‐mobile. After 12 weeks of healing, the implants were retrieved, together with surrounding bone, fixed, dehydrated, and embedded in plastic resin. About 10 μm thick ground sections were prepared for light microscopic morphometry. The mineralized bone to titanium contact, and the amount of bone occupying the threads, were calculated, whereafter the outcome of the different locations were compared. All retrieved implants were clinically stable at the end of the experiment. For the tibia sites, a statistically significant less bone to titanium contact, and a less amount of bone in the threads, were found for the totally mobile implants, as compared to the corresponding initially stable controls. Moreover, a statistically significant higher amount of bone was found in the threads of the rotation‐mobile implants inserted in the femoral condyle as compared to their initially stable controls. The study indicated that initial rotation‐mobility. independent if it occurs in cortical or trabecular bone, does not necessarily lead to an inferior integration of unloaded implants. However, initial total implant mobility within the cortical layer results in a statistically significant less amount of lb one around the implants, as compared to stable controls.     

Histopathologic features of the initial and early stages of experimental gingivitis in man

The pathologic alterations occurring in the gingival tissues of humans immediately following the beginning of plaque accumulation have not heen elucidated previously. Seven males, 22--31 years of age, free of clinical manifestations of dental and periodontal disease, and exhibiting a Plaque Index score of zero for the previous 28 days served as subjects. Plaque control measures were discontinued for 8 days and biopsies were taken from the buccal marginal gingiva of the first premolars on days 0, 2, 4, and 8. Paraffin- and Epon-embedded section, treated with a variety of histochemical stains were analyzed microscopically and cell counts were done on 1-micron Epon section. At 2 and 4 days following the beginning of plaque accumulation, the vessels subjacent to the juctional epithelium exhibited vasculitis and alterations in the perivascular collagen. There was a statistically significant increase in the number of neutrophils residing in the junctional epithelium. By the end of the 8-day period, the number of small mononuclear cells, mostly lymphocytes, in the connective tissues had increased by 3-fold and the area of collagen fiber alteration by 4-fold. In addition, the number of fibroblasts per unit area of connective tissue decreased significantly. Thus, within the period of 8 days following the beginning of plaque accumulation, an early lesion exhibiting many features characteristic of delayed hypersensitivity develops.     

Microbial vitality of supragingival dental plaque during initial stages of experimental gingivitis in humans

Although vital plaque micro-organisms are part of the natural ecosystem in the oral cavity they are also the key factor in the development of diseases induced by the human dental plaque. In a previous study (9) the portion of vital bacteria related to the total number of plaque micro-organisms (i.e. the microbial vitality) appeared low in small plaque samples. The objective of this investigation was to determine the exact relationship of microbial vitality and age of supragingival plaque during the early phases of human dental plaque formation. Between intervals of optimal oral hygiene, thirteen participants refrained from all oral hygiene measures for periods of 1, 2, 4, 8, 24 and 72 h. Plaque was completely sampled from a defined area situated on the vestibular surface of the teeth 13, 14, 15, 23, 24 and 25. The pooled plaque from these areas was immediately processed. Total bacterial counts (BC) as enumerated by darkfield microscopy, and colony-forming units (CFU) were recorded. The microbial vitality was calculated indirectly as plating efficiency (PE=CFU per BC) and directly assessed using a vital fluorescence (VF) technique. In the 1 h old plaque samples the median values of PE and VF were 29% and 18%, respectively. Thereafter, the microbial vitality increased significantly with plaque age. The 24 h old plaque samples yielded values of 77% (PE) and 62% (VF). It was concluded that the microbial vitality of the early dental plaque investigated was considerably lower compared to that of a more mature plaque.     

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.     

Development of experimental gingivitis in the juvenile and adult beagle dog

Abstract. In a previous paper a lower tendency to develop gingivitis was reported among preschool children compared to adults. The aim of the present study was to clarify if the same age-dependent difference exists in dogs.
Six beagle dogs from the same litter were used. two periods of discontinued oral hygiene were studied, one period when the dogs were 3 months old and the other at 12 months. Prior to and between the experimental periods the animals were subjected to meticulous toothcleaning. During the experimental periods the Gingival and Plaque Index scores as well as the amounts of gingival exudate and crevicular leukocytes were determined on days 0, 4, 7, 14, 21 and 28.
During the juvenile period the development of dental plaque was lower compared with the adult period. The frequency of gingival units with high Gingival Index scores was lower at every registration interval during the juvenile period. The amounts of gingival exudate and crevicular leukocytes increased to high values during the adult stage but only small increments were found in the juvenile stage. An intraindividual comparison of the increase in the amount of gingival exudate from day 0 to day 28 in areas with the same amount of dental plaque accumulation showed a lower increase in gingival exudate during the juvenile stage in all dogs.     

Comparative study of the osseous healing process following three different techniques of bone augmentation in the mandible: an experimental study

The aim of this study was to evaluate the osseointegration of three different bone grafting techniques. Forty-eight mature New Zealand rabbits were divided randomly into three groups of 16 each. Horizontal augmentation was performed on the corpus of the mandible using three different techniques: free bone graft (FBG), free periosteal bone graft (PBG), pedicled bone flap (BF). The animals were sacrificed at postoperative weeks 1, 3, or 8. Specimens were decalcified for histological examination, and histomorphometric measurements were performed. The histological evaluation demonstrated bony fusion between the grafts and the augmented mandibular bone after 8 weeks in all groups. At week 8, the bone volume was significantly greater in the BF group than in the FBG (P < 0.001) and PBG (P = 0.001) groups, and also the trabecular thickness was significantly greater than in the FBG (P = 0.015) and PBG (P = 0.015) groups. Trabecular separation was significantly lower in the BF group than in the FBG group at week 8 (P = 0.015). BF demonstrated greater osseous healing capacity compared to FBG and PBG. The preserved vascularization in BF improves the bone quality in mandibular bone augmentations.     

Effects of folate mouthwash on experimental gingivitis in man

Although the experimental gingivitis model has been used extensively since 1965, some doubts exist concerning the nature of the tissue response in this model. Accordingly, the present study was designed to determine whether or not experimental gingivitis responded to 0.1% folate mouthwash (MW) in a similar manner to that already reported for established gingivitis. 20 male dental students took part in a double blind cross-over study which involved two 3-week experimental periods with random allocation to folate or placebo MW. The experimental site was the lower anterior area and 24 points of gingival examination were made at baseline and weeks 1, 2 and 3. Inflammation was assessed by presence or absence of colour change, and bleeding being slight, profuse or absent when gingivae were stroked with a blunt probe. A plaque sample was evaluated using dark field microscopy, and dry weight of accumulated plaque was measured at the end of each experimental period. Folate MW did not appear to have any statistically significant effects on accumulated plaque, or clinical signs of experimental gingivitis in this study. The different response of experimental gingivitis to folate MW, compared with the response of established gingivitis already reported, further suggests that experimental gingivitis may not represent an authentic replica of the cellular and immunological responses occurring in established gingivitis.     

PH effects on experimental wound healing of human fibroblasts in vitro

The aim of the present study was to examine to what extent pH affects human fibroblast repopulation of an experimental wound in vitro laying special emphasis on cell migration, DNA synthesis, and alterations in cell morphology. Wounds were simulated in vitro by partially scraping off monolayers of human embryonic diploid lung fibroblast and human periodontal ligament fibroblast-like cells respectively. The wounded monolayers were cultured at pHs ranging from 7.2 to 8.4. The experiments were evaluated by autoradiography as well as light and scanning electron microscopic techniques. A significant, approximately linear, decrease was noted both in cell migration into and DNA synthesis in the experimental wounds as a result of pH increase. The surviving cells in the wounds showed cytoplasmatic vacuoles and blebbing at pH levels above 7.8. Clinical implications of these results for endodontic calcium hydroxide treatment are that hydroxyl ions, diffusing through root dentin, may interfere with vital cell functions necessary for healing on the root surface.     

Effect of experimental neutropenia on initial gingivitis in dogs

Abstract – The role of neutrophilic granulocytes in the loss of gingival collagen has been studied by inducing experimental neutropenia during initial gingivitis in beagle dogs. Neutropenia was induced for 4 d in three animals with normal gingiva by repeated injections of rabbit anti-neutrophil serum. During neutropenia microbial plaque was allowed to form on the teeth. Samples of junctional (crevicular) leukocytes and gingival fluid were taken on days 0 and 4. Block biopsies of buccal gingiva were obtained on day 4. Stained semi- and ultrathin sections were used for histometric and serologic tissue analysis. Gingival fluid flow increased from day 0 to day 4 in all dogs while junctional leukocytes increased in one dog only. Subgingival plaque had formed in most biopsies, and in the junctional epithelium very few neutrophilic granulocytes were present. In the coronal connective tissue subjacent to the junctional epithelium lymphoid cells, structurally abnormal neutrophilic granulocytes and monocytes/macrophages were diffusely scattered. The gingival collagen appeared mainly displaced by the inflammatory cells rather than dissolved. The data suggest that neutrophilic granulocytes may contribute to the loss of gingival collagen during initial gingivitis in dogs. The neutrophils also seem to be of importance for the limitation of subgingival plaque growth along the tooth surface.     

Histologic characteristics of experimental gingivitis in the juvenile and adult beagle dog

Abstract An earlier study (Matsson & Attström 1979) revealed an unexplained difference between juvenile and adult dogs in the propensity to develop clinical signs of gingivitis. The aims of the present investigation were to depict the structural composition of clinically normal gingiva and to analyze the histologic changes in the gingiva during plaque development in juvenile and adult dogs. Six beagle dogs were used. Two periods of discontinued oral hygiene were studied, the first at 3 and the second at 12 months of age. Biopsies were sampled on days 0, 4, 7, 14, 21 and 28 of each period. Sections from the biopsies were analyzed at two levels of magnification. Compared to adult dog gingiva, juvenile gingiva seemed to display: 1) a thicker keratinized layer of the oral epithelium, 2) a junctional epithelium that structurally resembles the oral epithelium, 3) a cuticular structure at the surface of the junctional epithelium, 4) a limited mononuclear inflammatory cell response during experimental gingivitis, and 5) a delayed establishment of an infiltrated connective tissue portion during experimental gingivitis. In addition, during experimental gingivitis, subgingival plaque formed along the tooth surfaces to a lesser extent in the juvenile stage compared to adult dogs.     

A clinical and histometric study of gingivitis associated with the human deciduous dentition

This study examined the relationship between clinical indices and the histologic parameters associated with the gingiva of the human deciduous dentition. The plaque index, gingival swelling and color, probing depth, bleeding on probing, contact with adjacent teeth and the degree of root resorption of 58 deciduous teeth were recorded. The teeth were extracted with their surrounding gingiva and prepared for histologic examination. The area of epithelium and connective tissue with and without inflammatory cells was measured as well as the epithelial length from the gingival margin including the junctional epithelium. When these measurements were grouped according to the values of the clinical indices, nonmobile teeth were found to have less epithelium than those with mobility and gingiva with a healthy color had a significantly smaller inflammatory cell infiltrate than red gingiva. Bleeding and increased probing depth were not associated with the other clinical signs of inflammation. The amount of plaque did not correlate with the measures of clinical inflammation. The inflammatory cell infiltrate was present irrespective of whether the gingiva was clinically normal or not and the inflammation did not correlate with the amount of plaque.     

Mini-implant stability at the initial healing period: A clinical pilot study

Objective:To evaluate the changes of mini-implant stability over the initial healing period in humans.Material and Methods:A sample of 19 consecutively treated patients (mean age 15.5 ± 7.3 years) was examined. In each patient, a mini-implant of a size of 2 × 9 mm was inserted into the anterior palate. Implant stability was assessed using resonance frequency analysis (RFA) immediately after insertion (T0), 2 weeks later (T1), 4 weeks later (T2), and 6 weeks later (T3). Insertion depth (ID) and the maximum insertion torque (IT) were measured. Data were tested for correlations between RFA, ID, and IT. All RFA values were tested for statistically significant differences between the different times.Results:The mean ID was 7.5 ± 0.6 mm, and the mean IT was 16.8 ± 0.6 Ncm. A correlation was found between RFA and ID (r  =  .726, P < .0001), whereas no correlations between RFA and IT or between IT and ID were observed. From T0 to T1, the stability (36.1 ± 6.1 implant stability quotient [ISQ]) decreased nonsignificantly by 4.9 ± 6.1 ISQ values (P > .05). Between T1 and T2, the stability decreased highly significantly (P < .001) by 7.9 ± 5.9 ISQ values. From T2 on, RFA remained nearly unchanged (−1.7 ± 3.5 ISQ; P > .05).Conclusions:Mini-implant stability is subject to changes during the healing process. During weeks 3 and 4, a significant decrease of the stability was observed. After 4 weeks, the stability did not change significantly.     

Evaluation of the healing response following placement of Coe-pak and an experimental pack after periodontal flap surgery

Abstract 2 periodontal dressings. Coe-pak* and RD8 (a product under development). were assessed following periodontal surgery, using a double-blind study of randomised split-mouth design, with each patient acting as their own control. Matched sites were selected for periodontal flap surgery under local analgesia. Sites were randomly allocated to each group. The dressings were applied by a single operator and both patients and clinical assessors were blind as to the dressing employed. The dressings were assessed as to their handling properties, m addition to a 7-day post-operative assessment of the surgical sites and a subjective patient report. Maximum pain levels were relatively low (4 in a scale 0–10); subjects reported more pain and analgesics required with RD8 than with Coe-pak, This was reflected in the results of the patient assessment which indicated that 5O% preferred Coe-pak, compared to 25%. who preferred the RD8 dressing. The results showed RD8 to be an acceptable periodontal dressing when compared to Coe-pak, There were no statistically significant differences between treated sites in both groups with regard to post-operative plaque scores, bleeding scores or tissue healing.     

The impact of nicotine on bone healing and osseointegration

OBJECTIVES: To examine the short-term effect of nicotine on bone healing and osseointegration. MATERIAL AND METHODS: Sixteen female rabbits were divided into two groups. The test group was exposed to nicotine tartrate for 8 weeks and the control group was exposed to placebo. Nicotine or placebo was administered via a miniosmotic pump and plasma cotinine levels were measured weekly. The pump delivered 15 mg of nicotine/day for the animals in the test group. All rabbits had three tibial bone preparations. In the proximal and distal bone bed, implants were placed after 4 weeks (right tibia) and after 6 weeks (left tibia). Thus, 2- and 4-week healing groups were created. Removal torque test (RMT) was performed at the distal implants. Ground sections were made from the proximal and the central bone beds. The fraction of mineralized bone in contact to the implant (BIC) and the bone density within the implant threads (BD-i) were determined for the bone-implant specimens. For the central bone beds without implants the bone density (BD-c) in the bone defects was determined. RESULTS: No significant difference in RMT values was found between the test and the control group. Histomorphometric measurements of the BIC and the peri-implant BD-i showed no significant differences between the test and the control group after 2 or 4 weeks. Significant differences were, however, found between the 2- and 4-week samples. In the central bone beds, there was no significant difference in BD-c between the test and the control group. CONCLUSION: Nicotine exposure in a short period of time did not have a significant impact on bone healing or implant osseointegration in rabbits.