The effect of progressive tooth mobility on destructive periodontitis in the dog

Abstract. The aim of the present study was to assess the influence of traumatic forces causing a gradually increasing tooth mobility on an ongoing destructive periodontitis.
The experiments were performed in five dogs fed a diet which permitted dental plaque accumulation. Periodontal breakdown was induced around the mandibular third and fourth premolars (₄P, ₃P and P₃, P₄) by the placement of plaque retention ligatures around the neck of the teeth. After 330 days, when approximally 50 % of the supporting tissues had been lost, mucoperiosteal flaps were raised around the four premolars and notches prepared in the buccal root surfaces at the marginal termination of the alveolar bone. The notches served as landmarks for measurements to be made in histological sections. The flaps were resutured and new plaque retention ligatures placed around the roots of all four teeth.
One week later (Day 0), P₃ and P₄ (test teeth) were subjected to jiggling forces in a bucco-lingual direction with the use of an elevator. The jiggling procedure which had a duration of 30 seconds, was repeated on Days 4, 8, 12 and 16, and was guided in such a way that the tooth mobility gradually increased during the experimental period. The animals were sacrificed on Day 26, and sections of ₄P,₃P and P₃, P₄ were prepared for light microscopic examination.
The results of the study demonstrated that jiggling forces, resulting in a progressive increase of tooth mobility, mediated an enhanced rate of destruction of the supporting apparatus in dogs with an ongoing process of periodontal tissue breakdown.     

Epithelial remnants in the crestal periodontium of the deciduous and permanent dentition of beagle dogs

Abstract. The purpose of this study was to document and characterize epithelial remnants (EPRs) of the crestal periodontium of the deciduous dentition of a diphyodont and compare them with EPR units found in the corresponding area of the permanent dentition. 7 beagle dogs were used. At the age of 10 weeks (deciduous dentition) and 15 months (permanent dentition), respectively, a 6-week plaque control period was initiated. At the end of each plaque control period, biopsies were obtained from the mandibular ₀₂P, ₀₃P (deciduous dentition) and P₃, P₄ (permanent dentition) premolar regions and prepared for histologic analysis. 2 regions, (1) the supracrestal region and (2) the periodontal ligament region, were identified. The supracrestal region was divided into 4 compartments of equal height. The histologic parameters studied included the (i) EPR frequency: number of EPRs/mm of root length, (ii) EPR size, (iii) EPR-root distance, (iv) EPR-bone distance and (v) cell area. No differences were observed between the 2 dentitions with respect to the number, size and relative location of EPR units in the supracrestal regions or the periodontal ligament regions. Epithelial remnants of the supracrestal region in both dentitions tended to be more frequent, larger and positioned further from the root surface than the EPRs of the periodontal ligament region. EPR units of the periodontal ligament region were located significantly further from the bone in the deciduous dentition than in the permanent dentition. The cell area of EPRs did not differ between the 2 dentitions. It was concluded that EPRs are a normal component of the crestal periodontal tissues of the deciduous dentitions of the diphyodont beagle dog and they appear to be similar to those found in the permanent dentition of young dogs.     

Histopathology of artificial periodontal defects in beagle dogs before and after ligature removal

The aim of the resent study was to investigate the histopathological characteristics of artificial periodontal defects before and after removal of ligatures. The defects were created in 12 young adult beagle dogs using cotton floss ligatures. The supracrestal dentogingival fibres were dissected around 6 lower premolars (₂P₂, ₃P₃, and ₄P₄) after which closely adapted copper bands were cemented to the teeth. After 3 weeks these copper bands were replaced by subgingival cotton floss ligatures which were left in place for a further 11 weeks. The placement of ligatures around the different teeth and their removal prior to sacrifice was scheduled to provide histological observations of the periodontal defects both with ligatures in situ, and 1 day and 1, 3, 7, 15, or 31 weeks after their removal.
Defects with ligatures in situ showed histopathological characteristics of advanced chronic periodontitis. Removal of the ligatures and the subsequent production of a notch (to mark the bottom of the pocket) resulted initially in an exacerbation of the inflammatory process but 3 weeks after ligature removal, a distinct decrease in size of the infiltrated connective tissue (I. C. T.) could be observed especially in the deeper part of the lesion. The tissues of the periodontium showed signs of repair whack became more pronounced with time. There was no indication that the lesion had become progressive in the remaining period of 7–31 weeks after ligature removal.
It is concluded that the maintenance of the established lesion is dependent on the persistence of subgingival plaque containing ligatures.     

Histometric analysis of ligature-induced periodontal defects in beagle dogs- evaluation following ligature removalLongitudinal

The aim of the present study was to investigate the sequence of events that takes place in ligature-induced periodontal defects following removal of the ligature.
In eight beagle dogs the dentogingival fibres around six lower premolars (₂P₂, ₃P₃, ₄P₄) were cut to the level of the alveolar bone. Closely adapted copper bands were then cemented around the teeth. After 3 weeks the copper bands were replaced by cotton floss ligatures which were left in place for 11 weeks.
The dogs were sacrificed on different dates so that it was possible to analyse defects 3, 7, 15, or 31 weeks after ligature removal. Contralateral defects one week after ligature removal served as controls. Micrographic color slides of the histological sections were analyzed using a Ferranti-Cetec digitizer.
Mean values for loss of attachment in the 15 and 31 weeks specimens were greater than in the control defects, suggesting that apical positioning of the junctional epithelium was irreversible. However, alveolar bone height tended to increase with experimental time, indicating bone repair. In the 15 and 31 weeks specimens junctional epithelium was occasionally found between the root surface and the alveolar bone
It was concluded that the model does not show all the histological characteristics of naturally occurring periodontitis even in those dogs examined 31 weeks after removal of ligatures.     

Periodontal repair in dogs: effect of recombinant human transfornning growth factor-β1 on guided tissue regeneration

Abstract. This study evaluated alveolar bone and cementum regeneration following surgical implantation of recombinant human transforming growth factor- β₁ (rhTGF-β₁) in conjunction with guided tissue regeneration (GTR). Supraalvcolar, critical size, periodontal defects were surgically created around the 3rd and 4th mandibular premolar teeth in right and left jaw quadrants in 5 beagle dogs. Alternate jaw quadrants in consecutive animals received rhTGF-β₁ in a CaCO₃/ hydroxyethyl starch carrier with GTR, or carrier with GTR alone (control), 20μg of rhTGF-/A in buffer solution was incorporated into approximately 0.8 ml of carrier for each defect scheduled to receive rhTGF-β₁. Animals were sacrificed at week 4 postsurgery and tissue blocks were harvested and processed for histo-metric analysis. Clinical healing was generally uneventful. Minor membrane exposures were observed. Defects with membrane exposure displayed an inflammatory infiltrate underneath the membrane. Bone regeneration of trabecular nature, apparent in all animals, was generally limited to the very apical aspect of the defects. Cementum regeneration was limited without obvious differences between experimental conditions. Comparing rhTGF-β to control defects, statistically significant differences were found for area (1.8±0.4 and 1.3±0.6 mm², respectively: p<0.05) and density (0.3±0.1 and 0.2±0.03. respectively: p<0.05) of alveolar bone regeneration. Observed differences are small and represent a clinically insignificant potential for enhanced regeneration in this preclinieal model. Within the limitations of study, it may be concluded that rhTGF-β₁ has a restricted potential to enhance alveolar bone regeneration in conjunction with GTR.     

Root resorption potentials of granulation tissue from bone and flap connective tissue

The present study was designed to examine the early phases of healing following root implantation in an attempt to compare the potentials of granulation tissue from bone and flap connective tissues to induce root resorption. Three adult beagle dogs with advanced periodontal disease were used and teeth ₁P₁, ₂P₂, ₄P₄, ₁M₁, and ³I³ were extracted to provide implantation sites. Eight weeks later, the root canals of the remaining premolars were filled with guttapercha. Using a flap procedure, the exposed root surfaces were thoroughly planed and the crowns were resected. The roots were then extracted and implanted in grooves prepared in edentulous areas with half the circumference of the root lying in the osseous groove and the other half of the root lying in contact with connective tissue of the mucoperiosteal flap. On one side of the mouth, the planed root surfaces were conditioned with citric acid for 3 minutes before implantation. Histologic sections cut in the transverse axis of the roots were evaluated at 2 wk (non-acid treated) and 3 wk (acid-treated) after implantation. Extensive root resorption and ankylosis were seen on the bone side of the acid-treated (3 wk) and non-acid treated (2 wk) roots. On the flap connective tissue side, connective tissue fibers were seen lying parallel to the root surface and resorption, when present, was minimal and usually confined to that part of the root close to the margins of the groove in bone. The results suggest that root resorption primarily originates from granulation tissue derived from bone. The potential of the flap connective tissue to induce root resorption is either less or delayed compared to the connective tissue derived from bone.     

Periodontal ligament stresses in the initiation of occlusal traumatism

Mechanical stresses in the periodontal ligament which help initiate the lesion of occlusal trauma have been difficult to evaluate. The purpose of this study was to use a mathematical system (finite element analysis) to calculate principal periodontal ligament stresses in primary and secondary occlusal trauma. Maxillary central incisors were modeled in periodontal tissues representing four levels of bone support. Models were partitioned and subjected to three simulated functional loads. Stresses were calculated at multiple nodes in the periodontal ligament adjacent to root and bone. Results showed areas of greatest compressive stress near the alveolar crest and in the apical one-half of the root for all loads at all bone levels. Stress curves correlated well with the histologic lesion of occlusal trauma. Centric contact loads (P₃) consistently produced less ligament stress than protrusive contact (P₁). Reduction of alveolar bone height had little effect on the degree of periodontal ligament stress until six millimeters (60%) of bone support had been lost. Finite element analysis provides a convenient model for the study of the mechanical component of occlusal traumatism.     

Orthodontic anchorage capacity of short titanium screw implants in the maxilla. An experimental study in the dog.

The aim of this study was to investigate experimentally the effect of long term orthodontic loading on the stability as well as on the peri‐implant bone findings of short titanium screw implants (Bonefit®, submersion depth 6 mm, Ø 4 mm) inserted in regions with reduced vertical bone height. For this purpose, 6 maxillary premolars (₁P₁, ₂P₂, ₃P₃) were extracted from each of 2 foxhounds and reduction of alveolar bone height was performed by osteotomy. After a l6‐week healing period, 8 implants (4 per dog) were inserted in the edentulous areas. Simultaneously, 2 implants (1 per dog) were positioned in the palatal suture (one‐stage surgery). After an 5‐week implant healing period, the fixtures in the Pl/P2 areas ( n = 4) and the palate ( n = 2rpar; were loaded (test implants) by means of transpalatal bars running anteriorly, fixed on the implants in the Pl/P2 areas, and Sentalloy traction springs (‐2 N continuous force) inserted midsagittally between palatal implants and bars (force application period: 26 weeks). The fixtures in the P2/P3 areas served as controls ( n = 4). Clinical measurements and histological evaluation revealed no implant dislocation of the loaded fixtures. These results suggest that short titanium screw implants inserted in the alveolar bone and palatal suture region retain their stability during long‐term orthodontic loading, even following a relatively short unloaded implant healing period. Furthermore, it seems that long‐term orthodontic loading may induce marginal bone apposition adjacent to the implants.     

Changes in TGF-β1 levels in gingiva, crevicular fluid and serum associated with periodontal inflammation in humans and dogs

Transforming growth factor-beta (TGF-β) represents a family of polypeptide growth factors, involved in embryogenesis, inflammation, regulation of immune responses and wound healing. To determine whether TGF-β contributes to the evolution of periodontal disease, we assayed TGF-β levels in gingiva and crevicular fluid of patients with gingivitis and periodontitis. In parallel, TGF-β was quantified m gingival fluid and serum of beagles with experimentally-induced periodontitis. Disease was monitored by several clinical parameters including Plaque Index, Gingival Index, probing depth, and epithelial attachment loss. Gingival tissues were obtained from 9 patients at the time of periodontal surgery, and gingival fluid samples were collected from an additional population of 10 periodontal patients. In 14 beagles, experimental periodontitis was induced and gingival fluids collected 6 months later. Fluid was collected by paper strips and volume measured by Periotron. Additionally, sera was collected before and 9 months after the ligature-induced periodontitis in 7 beagles. The levels of TGF-β₁ were measured by ELISA. In the patients, a significantly higher concentration of TGF-β₁ was observed both in the gingival tissues and fluid samples obtained from the sites with deeper periodontal pockets than in the less involved sites. In beagles, TGF-β₁ levels measured in gingival fluid were elevated in moderate disease, declining in fluid samples obtained from the pockets during more advanced experimental periodontitis. Furthermore, with the progression of experimental periodontitis, a decrease in TGF-β₁ occurred in the sera of the beagle dogs. These data suggest that TGF-β₁ may play a řle in the pathogenesis and diagnosis of periodontal disease, and that its actions can be further explored in an animal model.     

Periodontal pocketing in HIV-associated periodontitis

Gingival and periodontal involvement has been described in individuals with Human Immunodeficiency Virus (HIV) infection. The manifestations often include erythematous gingivitis, necrotizing gingivitis, and periodontal involvement characterized by rampant loss of bone and soft tissue, resulting in recession without the formation of periodontal pockets. We present cases of HIV-associated periodontitis (HIV-P) in which advanced periodontal pocket formation was present. Periodontal disease may show a broad range of severity in patients with various T,₄ helper cell counts.     

Cementogenesis and the induction of periodontal tissue regeneration by the osteogenic proteins of the transforming growth factor-beta superfamily

Theantiquity and severity of periodontal diseases are demonstrated by the hard evidence of alveolar bone loss in gnathic remains of the Pliocene/Pleistocene deposits of the Bloubank Valley at Sterkfontein, Swartkrans and Kromdrai in South Africa. Extant Homo has characterized and cloned a superfamily of proteins which include the bone morphogenetic proteins that regulate tooth morphogenesis at different stages of development as temporally and spatially connected events. The induction of cementogenesis, periodontal ligament and alveolar bone regeneration are regulated by the co-ordinated expression of bone morphogenetic proteins. Naturally derived and recombinant human bone morphogenetic proteins induce periodontal tissue regeneration in mammals. Morphological analyses on undecalcified sections cut at 3–6 μm on a series of mandibular molar Class II and III furcation defects induced in the non-human primate Papio ursinus show the induction of cementogenesis. Sharpey's fibers nucleate as a series of composite collagen bundles within the cementoid matrix in close relation to embedded cementocytes. Osteogenic protein-1 and bone morphogenetic protein-2 possess a structure–activity profile, as shown by the morphology of tissue regeneration, preferentially cementogenic and osteogenic, respectively. In Papio ursinus , transforming growth factor-β₃ also induces cementogenesis, with Sharpey's fibers inserting into newly formed alveolar bone. Capillary sprouting and invasion determine the sequential insertion and alignment of individual collagenic bundles. The addition of responding stem cells prepared by finely mincing fragments of autogenous rectus abdominis muscle significantly enhances the induction of periodontal tissue regeneration when combined with transforming growth factor-β₃ implanted in Class II and III furcation defects of Papio ursinus .     

H3-proline study of aging periodontal ligament matrix formation:

Recent publications suggested the presence of a tooth related and alveolar bone related system within the periodontal ligament. To further test this hypothesis, we attempted to histologically and autoradiographically follow matrix formation in mouse PDL at different sites and different ages. Twenty-eight BNL Swiss albino mice 5, 26, 52, and 104 weeks of age were maintained on a standard pellet diet and water ad libitum. Each animal received 4 subcutaneous injections of 2 μCi/gm body weight of H³-proline per dose (Spec. Act. 1·5 Ci/mM) on days t₀, t₄, t₈, and t₁₂. On day t₁₃ animals were sacrificed, the maxillae removed and prepared for histologic and autoradiographic analysis. Grain counts were performed from the midline of the PDL to (a) the bony surface and (b) the cemental surface at 4 specific sites around the mesial root of the first maxillary molar. Differences in results were analyzed statistically and significance was based on Student's t-test and a confidence level of 0·001. From our data, it appeared that under normal functional demands, the rates of matrix formation in the mouse PDL appeared to be similar between alveolar bone surface related and cemental surface related tissues at all sites tested. With advancing age, an overall reduction in PDL matrix formation was also noted.     

Accelerated corrosion analysis of dental amalgams

Abstract – The corrosion of powdered conventional and high Cu dental amalgam was studied in vitro under fixed conditions (100% oxygen, pH 4, and constant weak mechanical action). Results were retrieved from X-ray diffraction of samples of amalgam and solid corrosion products Formed, in combination with recording of the HC1 consumed to maintain the fixed pH. In the conventional amalgam no corrosion of γ₁ occurred until all γ₂ had corroded, whereas in the high Cu amalgam corrosion of γ₁ occurred from the beginning, concurrent with corrosion of ε and ń. Corrosion products found were AgCl, Hg₂Cl₂, CuCl₂-3Cu(OH)₂, and SnO₂. The results may be interpreted as follows: in the conventional amalgam the matrix phase γ₁ is anodically protected against corrosion as long as any γ₂ remians; in the high Gu amalgam the least noble phases ε and ń do not protect γ₁ in a similar way.     

Demineralization of human enamel

abstract — The aim of the present paper is to demonstrate that enamel can be dissolved in two, chemically distinct ways. Each of six premolars were exposed to 8 ml of a pH 5.0 buffer. The ionic activity products for Ca₅(PO₄)₃OH, Ca₅(PO₄)₃F, CaHPO₄, CaF₂andCa₄H(PO₄)₃ were determined. It was found that the liquid phase initially was unsaturated with respect to all solid phases and that hydroxyapatite and fluorapatite were dissolving coincidently. Four hours after initiation of the experiments the liquid phase was supersaturated with respect to fluorapatite while still unsaturated with respect to hydroxyapatite, which resulted in a formation of fluorapatite in the enamel and a dissolution of hydroxyapatite from the enamel, the net result being a loss of mineral.     

The progress of the periodontal syndrome in the rice rat

The effects of a diphosphonate, dichloromethylene diphosphonate (C1₂MDP) were studied using the rice rat as a model of periodontal bone loss. C1₂MDP was given in daily subcutaneous injections at dosages of 0 (control), 0.1, 1.0, or 10.0 mg/kg/day; these treatments were continued for periods of 6, 12, or 18 weeks. The amount of alveolar bone was increased over age matched controls at the 1.0 and 10.0 mg/kg/day doses at 6 weeks; at 12 and 18 weeks, all doses including 0.1 mg/kg/day showed increases in bone over controls. Due to increased connective tissue fibrosis, the CI₂MDP treated animals had fewer vascular spaces. Also, the amount of destroyed tissue in the interdental test site was increased in animals given 10.0 mg/kg/day of C1₂MDP. The number of fibroblasts per mm of bone surface decreased slightly at 6 weeks, but was otherwise not different from controls in treated animals at 12 and 18 weeks. Numbers of osteoblasts decreased greatly at all doses at both 12 and 18 weeks time. There were no significant differences between treated and control animals in the number of osteoclast nuclei per mm bone surface. Also, the numbers of inflammatory cells residing at the bone surface increased at all time periods in the 10.0 mg/kg/day dose group. Finally, the proliferative activity of PDL fibroblasts decreased dramatically at all time periods in the 10.0 mg/kg/day dose group. The response of the proximal tibia to C1₂MDP was compared to the alveolar bone response in these animals by measuring amounts of bone in respective areas. While the dose response curves are similar, the tibiae showed greater increases in bone mass.     

Integrin receptors and their relationship to cellular proliferation and differentiation of oral squamous cell carcinoma. A quantitative immunohistochemical study

The expression of extracellular matrix (ECM) proteins (fibronectin, laminin, collagen IV) and ECM receptors of integrin type (α₂β₁, collagen receptor; α₆ chain of the fibronectin receptor; α₆ chain of the laminin receptor) were examined in normal oral squamous epithelium and in invasive areas of oral squamous cell carcinomas with various differentiation and proliferation activities (Ki-67 antigen labelling), evaluating the presence, quantity (using an image analysis system) and distribution of the integrin subunits. In the mucosa, there was uniform immunostaining for α₂β₁ and α₆ concentrated at the cell membrane in the basal/supra basal cell zone, whereas, α₅ showed a discontinuous staining of the basal cell-basement membrane interface. α₂ and α₆ could be visualized in all carcinomas α₅ showed low expression preferentally in less differentiated carcinomas. In contrast to normal mucosa, there was an increase in α₆ staining in well-differentiated carcinomas. Dedifferentiation of oral carcinomas was accompanied by an increase in cellular proliferation and with a decrease in α₂β₁ and α₆ staining. This reduction of α₆ staining was shown to be statistically significant, suggesting that this integrin may be a valuable grading parameter for oral squamous cell carcinoma.     

Correlations between Color Differences Based on Three Color-Difference Formulas Using Dental Shade Guide Tabs

Purpose: The purpose of this study was to determine the correlation among color-difference values based on three formulas between shade tab pairs from two shade guides [Vita Lumin (VITA) and Chromascop (CHRO)].
Materials and Methods: The color of shade tabs was measured relative to the standard illuminant D₆₅ under the 8° standard observer function, and distributions for CIE L *, a *, and b * values were compared. One hundred and twenty shade pairs from VITA and 190 shade pairs from CHRO were used to calculate color differences using CIELAB, DIN99, and CIEDE2000 formulas (Δ E*_ab , Δ E ₉₉, and Δ E ₀₀, respectively). A paired t- test was used to determine the difference between each pair of the three color-difference values (α= 0.01). Regression analysis was used to determine the correlations between the color differences (α= 0.01).
Results: For both shade guides, there were significant differences between Δ E*_ab and Δ E ₀₀, Δ E*_ab and Δ E ₉₉, and Δ E ₉₉ and Δ E ₀₀ ( p < 0.01). Δ E*_ab and Δ E ₀₀, and Δ E*_ab and Δ E ₉₉ were strongly correlated (r²= 0.90 to 0.94, p < 0.05). Although a simplified a * rescaling function of the CIE a * axis has been added in the CIEDE2000 formula, the influence of the opposite signs in the a * value were found to be irrelevant to the Δ E ₀₀ value.
Conclusion: Δ E*_ab, Δ E ₉₉, and Δ E ₀₀ can be used interchangeably for the evaluation of color difference of shade tabs.     

Immunolocalization of α2, α5, and α6 integrin subunits in salivary tissue and adenomas of the parotid gland

The localization of the integrin subunits α₂, α₅, α₆ was studied immunohistochemically in samples of normal salivary gland and in a series of 8 pleomorphic adenomas, 5 Warthin's tumors, and 2 basal cell adenomas. In normal salivary tissue, acinar and ductal cells expressed α₂ and α₆ chains at the basal cell pole facing the basement membrane. α₂ also localized at sites of cell-cell contact. No staining of the epithelial component was seen with α₅. The polarized expression of α₂ and α₆, subunits was retained in salivary adenomas. These subunits were present at the basal cell pole of solid nests, tubules and ducts of pleomorphic adenomas, as well as of the basal layer of the epithelium of Warthin's tumor, and of the trabecular structures of basal cell adenomas. The α₅ subunit was consistently expressed only by cells embedded in the myxoid or chondroid matrix of pleomorphic adenomas. We conclude that the pattern of a integrin subunit expression in salivary adenomas may be related to the "epithelial" or "mesenchymal" phenotype of the neoplastic cells.     

Stoichiometric and X-ray diffraction analysis on the γ2→η' transformation in a dispresant phase silver amalgam

Abstract— Phase composition of an amalgam prepared from a two-particle alloy was determined over a 2-year period by X-ray diffraction. The γ₂content decreased from 3.6% to 0.3%, and η' increased from 3.9% to 10/0%. These alterations in ph content agreed with stoichiometric calculations performed on the basis of the solid state reaction: γ₂+Ag/Cu→η'+γ₁     

Electron microprobe analysis of the γ2 phase in dental amalgam

A bstract — The microstructure and composition of the γ₂ phase in four conventional lathe-cut or spherical amalgams were investigated using an electron microprobe.
In addition to its presence in the matrix, γ₂ phase was found, in lathe-cut amalgams, in contact with ε (Cu₃Sn) phase, separated from γ (Ag-Sn) phase by a thin band of γ₁ phase and, rarely, in direct contact with γ phase, and, in spherical amalgams, within the relict of partly reacted spherical particles. Inclusions of γ, γ ₁ and Cu-Sn phase were occasionally identified within regions of γ₂ phase. The major element composition of the γ₂ phase was similar in all amalgams (83.0 to 83.2 per cent Sn, 17.0 to 16.8 per cent Hg).