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.     

Experimental periodontal breakdown in the dog

abstract – This paper describes a method for inducing rapidly progressing and reproducible periodontal lesions around selected teeth in dogs. The experiments were performed on 10 beagles which were fed a diet favoring gross formation of plaque. Approximately 1 mm of the marginal alveolar bone around ₄P and P₄ was removed and a notch prepared in the root. A ligature of cotton floss was placed around ₄P and P₄ at the cemento-enamel junction. Radiographs and sections prepared 230 d later revealed that a progressive breakdown of the periodontal tissues had occurred. The average bone loss was 2.4 mm and the distance between the apical cells of the pocket epithelium and the notch was 854μm.     

Clinical and histological findings in ligature-induced experimental periodontitis in dogs A pilot study

Prior to experimental periodontal regenerative procedures in animals, the process of destruction due to periodontitis is often simulated by placing ligatures around the necks of teeth. 2 models, one using cotton floss ligatures and the other elastic rubber ligatures, have been widely used. The aim of this study was to compare these 2 methods using clinical and histometric criteria. Premolars on both sides of the mandibular jaw were used in 2 beagle dogs. Periodontal tissue breakdown was induced during a 48-day period using cotton floss ligatures on one side of the mandible and contra-laterally by elastic rubber ligatures. At weekly intervals, the ligatures were changed and pocket depth and loss of probing attachment were recorded. All the ligatures were removed after 7 weeks. The animals were fed a soft, plaque-promoting diet during the experimental period. 20 days after ligature removal, the teeth were hemisected and the 2 roots extracted. From each tooth, 1 root was prepared for scanning electron microscopy and one for light microscopy. At the time of extraction, no differences regarding pocket depth or probing attachment level were found between the 2 groups. Root resorption was observed in all elastic ligature teeth, whereas only minor alterations at the root surface were observed on cotton ligature teeth. This finding may be of particular interest to investigators designing studies evaluating the healing sequalae of regenerative surgery in animals. As was observed in this study, root resorption can already be present in the pre-experimental phase of periodontal tissue breakdown, particularly if elastic ligatures are used.     

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.     

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.     

Lack of significance of increased tooth mobility in experimental periodontitis

This experiment was carried out in order to study the rate of progression of experimentally produced periodontal tissue breakdown in teeth which prior to the placement of cotton floss ligatures either had a normal or a permanently increased tooth mobility. Six beagle dogs were used. Trauma from occlusion of the jiggling type was produced on test teeth using a model previously described. Four months later experimental periodontal tissue breakdown was induced around both control and test teeth by placing cotton floss ligatures around the necks of the teeth. The ligatures which were exchanged once every 4 weeks during a 4-month period were replaced at the level of the gingival margin. Tooth mobility measurements and radiographic examinations were performed on Days 0, 30, 60, 90, 120, 160, 240 and 300. One dog was killed on Day 120 and the remaining 5 dogs on Day 300. Biopsies of the test and control teeth were fixed in formalin, decalcified, embedded in paraffin and mesiodistal sections cut with the microtome set at 4 micron. The results demonstrated that the degree of periodontal breakdown, initiated and maintained by ligature placement and plaque accumulation, was similar around teeth with a wide periodontal ligament space and in teeth with a normal width of the periodontium. In other words, progression of the plaque-associated lesions appeared to be unrelated to the width of the periodontal ligament space, i.e., to the degree of horizontal tooth mobility.     

Suppression of inflammation and bone resorption by indomethacin during experimental periodontitis in dogs.

1. The placement of cotton floss ligatures in a position apical to the gingival margin of premolars and molars in young dogs induced an acute inflammatory reaction in the periodontal tissues resulting in loss of connective tissue attachment and alveolar bone. 2. Bone resorption could be observed histologically within 7 days, and radiographically within 2 to 3 weeks after ligature placement. 3. Daily administration of indomethacin interfered with the periodontal tissue response to ligature placement. Indomethacin was shown to (i) delay the onset and to suppress the magnitude of the acute inflammatory reaction, and (ii) decrease the degree of alveolar bone resorption.     

Predictability of probing depths in ligature-induced periodontal defects in beagle dogs

The aim of the present study was to evaluate the predictability of a method of creating periodontal defects in dogs. The dentogingival fibres around the lower premolars of 12 beagle dogs were cut to the level of the alveolar bone and closely adapted copper bands were cemented to the teeth. After 3 weeks the copper bands were replaced by cotton ligatures which were left in place for 11 weeks. After this active phase the ligatures were removed, and the defects were allowed to heal for varying periods up to 30 weeks. Probing depths were recorded at different stages of the experiment. Indications for predictability were: 1° the magnitude of the standard deviations of the mean probing depths and 2° the differences between results from contralateral areas. Relatively deep defects were obtained immediately after creation, but the magnitude of the standard deviation of the mean indicated wide variations in probing depths. Following ligature removal probing depths decreased but were of a more uniform depth. These results indicate that variation of probing depths in artificial periodontal defects is rather high immediately after creation but decreases drastically during the healing phase. It was concluded that in young adult beagle dogs predictable periodontal defects, 3.0–3.5 millimeters in depth, can be produced artificially provided that the initial deeper artificially created defects are allowed to heal for at least 3 months.     

A long junctional epithelium - A locus minoris resistentiae in plaque infection?

Abstract The present experiment was undertaken to examine whether a gingival unit with a long junctional epithelium provides a. less efficient seal against plaque infection than a unit with a junctional epithelium of normal length. Periodontal tissue breakdown was produced around 8 teeth (test teeth) in each of 4 monkeys by placing elastic ligatures around the neck of the teeth. When the periodontal pockets at the approximal tooth surfaces were 4–5 mm deep and angular bony defects had been produced, the ligatures were removed. The periodontal tissues of the test teeth were subjected to flap surgery. The exposed root surfaces were scaled and planed but no osseous surgery was carried out. Following surgery, plaque control comprising all teeth of the dentition was instituted and maintained for 4 months. Healing following this type of surgical treatment involved the establishment of a long junctional epithelium. During the final 6 months of experimentation, oral hygiene measures were abandoned and plaque was allowed to accumulate. In each animal, 4 test teeth and 3 normal control teeth were selected to study gingival inflammation resulting from undisturbed plaque accumulation. In order to enhance subgingival plaque formation, in each animal cotton floss ligatures were placed in the entrance of the gingival sulci of the remaining 4 test teeth and in 3 controls. The animals were sacrificed 10 months after surgery. The jaws were removed and histological sections of the teeth including surrounding periodontal tissues were produced. The histological analysis revealed that the inflammatory lesion in the gingival connective tissue (the ICT area) resulting from plaque infection did not extend deeper into the periodontal tissues in sites with a long junctional epithelium than in gingival units of normal height. The results were interpreted to indicate that the barrier function of a long junctional epithelium against plaque infection is not inferior to that provided by a dentogingival epithelium of normal length.     

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.     

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.     

Resolution of ligature-induced peri-implantitis lesions in the dog

Abstract The present experiment in the Labrador dog was performed to study tissue alterations that occurred in a peri-implantitis lesion following ligature removal. The study was carried out in 5, 1-year old Labrador dogs. The mandibular right and left 1st molars and 4th and 3rd premolars were extracted to establish recipient sites for implants. After 3 months of healing, 4 titanium fixtures, 2 in each jaw quadrant, were installed and abutment connection carried out in a 2nd stage procedure after another 3 months. After a 6-month period of healing, cotton floss ligatures were placed in a submarginal position around the neck of the fixture abutments. The ligatures were forced into a position “apical” of the margin of the peri-implant mucosa and secured. When the tissue destruction after 4–6 weeks was found to amount to about 25% of the original bone height at each individual implant, the ligatures were removed. 2 dogs were sacrified 1 month and 3 dogs 3 months after ligature removal. The animals were perfused with a fixative and block biopsies were obtained from the implant sites. The biopsies were prepared for histometric and morphometric analyses. The results from the clinical examinations and the microscopic analyses of the peri-implant tissues revealed that: (i) 1 month after ligature removal, an active, destructive inflammatory lesion was present in the soft and mineralized tissues adjacent the implants; while (ii) 2 months later, this lesion at most implant sites had become resting and encapsulated, was confined to the connective tissue adjacent to a pocket epithelium, and was separated from the bone surface by a dense collar of fibrous connective tissue. In 1 of the 3 dogs that were monitored for 3 months, however, 3 out of the 4 implants installed exhibited continued loss of bone, became unstable and were lost between the 10- and 12-week examination interval. The remaining peri-implant tissue at the 4th and remaining implant in this animal was found to harbor an active lesion that involved osteoclastic activity on the surface of the bone crest.     

Experimental breakdown of peri‐implant and periodontal tissues. A study in the beagle dog

The objective of the present experiment was to study lesions in the peri-implant and periodontal tissues resulting from ligature placement and subgingival plaque formation. The experiment was performed in 5 beagle dogs which at the start of the study were about 15 months old. They were given a diet which allowed gross plaque formation. The mandibular right premolars were extracted, 3 fixtures (a.m. Brånemark) installed and abutment connection performed. Towards the end of a 6-month plaque control period, a clinical and radiographic examination was performed. Ligatures were placed in a subgingival position at 2 of the implants and the contralateral premolars. Plaque was allowed to accumulate. After 6 weeks, the ligatures were removed. 1 month later, the clinical and radiographical examination was repeated and samples from the subgingival microbiota obtained. Biopsies from the teeth and implant sites were harvested and processed for histometric and morphometric analyses. The results from the clinical and histological examinations revealed that:(i) clinical and radiographic signs of tissue destruction were more pronounced at implants than at teeth;(ii) the size of the soft tissue lesion was larger at implants than at teeth;(iii) the lesion at implants but 1 not at teeth extended into the bone marrow.     

The significance of alveolar bone in periodontal disease

The present experiment was designed to study if a gingival unit with a long supraalveolar connective tissue attachment provides less resistance against progression of periodontal disease than a unit with a supraalveolar connective tissue attachment of normal length. A long supraalveolar connective tissue attachment was established at the buccal aspect of mandibular premolars and molars in dogs by surgical removal of the marginal portion of the buccal alveolar bone after elevation of a muco-periosteal flap. Attempts were made to minimize mechanical injury to the root cementum and the supraalveolar fibrous attachment during the surgical procedure. Contralateral, non-operated teeth with a supraalveolar connective tissue attachment of normal length were used as controls. Following surgery, plaque control was initiated and maintained for 3 months by topical application of 0.2% chlorhexidine digluconate solution twice daily. During the following 6 months, the oral hygiene measures were abandoned and plaque was allowed to accumulate on both groups of teeth. In order to enhance plaque formation and to promote the development of subgingival plaque, cotton floss ligatures were placed at the entrance of the gingival sulci. The dogs were sacrificed 6 months after the initiation of the plaque accumulation period. The jaws were removed and histological sections prepared of test and control teeth including their surrounding periodontal tissues. The histological analysis revealed that the plaque induced inflammatory lesion in the gingival connective tissue did not extend more apically in sites with a long supraalveolar connective tissue attachment than in sites with a supraalveolar fibrous attachment of normal length. A small but statistically significant loss of connective tissue attachment had occurred in both groups of teeth. This attachment loss, however, was similar in sites with a long supraalveolar connective tissue attachment and in sites with a supraalveolar fibrous attachment of normal length. These findings suggest that the loss of attachment in periodontal disease is unrelated to the presence or absence of the bony component of the periodontium.     

Partial pulpotomy on caries-free teeth using enamel matrix derivative or calcium hydroxide: a randomized controlled trial

Aim  To compare the effect of enamel matrix derivative (EMD) and calcium hydroxide [Ca(OH)₂] on exposed human pulp.
Methodology  Fifteen pairs of human contralateral premolars were intentionally and partially pulpotomized. The exposed pulps were randomly capped with either EMDgel (Emdogain^®) or a mix of Ca(OH)₂ and sterile water. The subjects recorded pain or discomfort during the first 10 days and were also interviewed and examined by a blinded examiner at 1 day, 2 weeks, 3 and 6 months post-operation. Periapical radiographs were taken prior to the operation, and 3 and 6 months post-operation. After 6 months, the teeth were extracted and processed for histological evaluation. The data were described and analysed using McNemar test and Kaplan–Meier survival analysis.
Results  The EMDgel-treated teeth had significantly less tooth hypersensitivity than the Ca(OH)₂-treated teeth during the first 2 weeks ( P  =   0.031) but were not significantly different after 2 weeks ( P  =   0.125). No detectable periapical radiographic changes were observed in any teeth and radiographic evidence of dentine bridge formation from both groups were not significantly different during the follow-up periods ( P  >   0.05). Histological evaluation demonstrated that the Ca(OH)₂-treated teeth had less inflammation and more dentine bridge formation than those in the EMDgel-treated teeth.
Conclusions  After 6 months, healthy pulps capped with Ca(OH)₂ had more favourable results than counterparts capped with EMDgel. However, similar clinical and radiographic results were seen in both groups.     

Lack of bacterial invasion in experimental periodontitis

The present study in the beagle dog was performed to analyze whether micro-organisms from a subgingival microbiota could be translocated into or had the potential to invade the pocket epithelium and the gingival connective tissue during a phase of rapid breakdown of the attachment apparatus. An attempt was also made to assess whether tetracycline therapy suppressed the subgingival microbiota and changed the size and quality of the lesions in the gingival tissue. 5 inbred beagle dogs were used. Throughout the period of experimentation, the animals were fed a soft diet permitting gross accumulation of plaque and calculus. No mechanical plaque control measures were performed during the course of the study. On day 0, a 120-day period of periodontal tissue breakdown was initiated at the right mandibular 3rd and 4th premolars by tying cotton floss ligatures around the neck of these teeth. The process of tissue breakdown at the mandibular left 3rd and 4th premolars was started 30 days later. The ligatures were replaced once every 2 weeks during the subsequent 4-month period. On experimental day 120, the first biopsy was performed and gingival tissue sections prepared for light and electron microscopic assessment of a series of histometric characteristics. On day 120, a 30-day period of tetracycline (per os) administration was initiated. Each dog was given a dose of 500 mg tetracycline twice daily. On day 150, the biopsy procedure was repeated in the mandibular left premolar regions.(ABSTRACT TRUNCATED AT 250 WORDS)     

The appearance of bone resorbing activity in ligature induced gingivitis in dogs

The in vitro bone resorbing activity of extracts from healthy and inflamed dog gingiva were compared and the appearance of the resorbing factor between 1 and 6 weeks of gingivitis was measured. Seven adult dogs were used. The gingiva were initially rendered healthy by scaling and polishing. Plaque retentive ligatures were placed around the necks of teeth so that at the end of the experiment samples of healthy gingiva and gingiva with 1 and 6 week old ligature induced gingivitis could be harvested from each dog. The bone resorbing activity of extracts from these gingival samples was studied by measuring the release of ⁴⁵Ca from prelabeled fetal rat long bones in organ culture. Six out of 7 extracts from healthy quadrants had no bone resorbing potential whereas 13 out of 14 extracts from ligatured quadrants stimulated significant amounts of bone resorption. The resorbing activity appeared during the first week after ligature placement and no significant increase in resorbing potential was noted between extracts obtained 1 and 6 weeks after ligature placement. It was concluded that the appearance of the bone resorbing factor(s) is related to the accumulation of plaque and/or the resultant inflammation and that it may be responsible for the alveolar bone loss seen in ligature induced periodontal disease in dogs.     

New attachment – reattachment following reconstructive periodontal surgery

The present study was designed to evaluate if the conditions for reformation of a connective tissue attachment are less favorable on root surfaces which have lost their fibrous attachment because of periodontal disease than on root surfaces surgically deprived of their attachment apparatus. In each of 4 Green monkeys, 2 maxillary and 2 mandibular teeth were selected for experimentation. Periodontal breakdown was produced and allowed to progress to the mid-root level around one of the experimental teeth in both the maxilla and mandible by placing elastic ligatures around the neck of these teeth. 3 months after removal of the ligatures, the crown of the teeth was resected and the epithelium and the subjacent granulation tissue were removed. Using a diamond bur, circumferential defects similar to those obtained by the ligature induced destruction were then produced around the remaining 2 experimental teeth following resection of the crown. The root cementum on both groups of teeth was removed to the level of the reduced bone height. Finally, all roots were submerged to complete coverage by a mucosal flap. After 3 months of healing, the animals were sacrificed and the jaws removed and placed in fixative. After decalcification, histological sections of the experimental roots and their surrounding periodontal tissues were produced. No histological differences in the result of healing were discernible between the specimens of previously periodontitis-affected roots and roots with surgically created defects. New cementum with inserting collagen fibers had formed in the apical part of the instrumented surface in both groups of teeth.(ABSTRACT TRUNCATED AT 250 WORDS)     

Susceptibility of GTR-regenerated periodontal attachment to ligature-induced periodontitis

AIM: This study aimed to compare the susceptibility of guided tissue regeneration (GTR)-regenerated periodontal attachment to ligature-induced periodontitis with that of the pristine periodontium. METHODS: Periodontal breakdown was produced in four monkeys by the placement of orthodontic elastics around experimental teeth (test teeth). During a flap operation, the root surfaces were scaled and planed, and a notch indicating the apical termination of scaling and root planing was made in the root surface. Following resection of the crowns and endodontic treatment, an e-PTFE membrane was adapted over the roots. Subsequently, the flaps were sutured to complete closure of the wound (submerged). At membrane removal after 5 weeks, the crowns of the contralateral teeth serving as controls were resected, and the roots treated endodontically during a flap operation. Artificial composite crowns were then placed on both test and control roots. After 3 months of tooth cleaning, cotton floss ligatures were placed passively around both test and control teeth for a period of 6 months. Two weeks later the animals were sacrificed. RESULTS: Histological analysis demonstrated that the instrumented root surfaces of the test teeth were covered by newly formed cementum of the reparative, cellular, extrinsic and intrinsic fiber type, while the cementum on the controls was mainly acellular extrinsic fiber cementum. Histometric assessments demonstrated that similar attachment loss had occurred on test (1.0+/-0.5 mm) and control roots (1.0+/-0.4 mm) during the 6 months of ligature-induced plaque accumulation. CONCLUSION: The results indicate that teeth with a periodontal attachment apparatus formed by GTR is not more susceptible to periodontitis than those with a pristine periodontium.     

Healing following implantation of periodontitis affected roots into bone tissue

The aim of the present experiment was to study whether new connective tissue attachment can occur to root surfaces which have been exposed to the oral environment and subsequently implanted into bone tissue. Twelve teeth in three beagle dogs were subjected to progressive periodontal breakdown to half the root length by placing cotton floss ligatures around the neck of the teeth. Following crown resection and root hemisection, the teeth were root filled and the roots thoroughly scaled and planed. Each root was extracted and implanted into bone cavities prepared in edentolous areas of the jaws in such a way that epithelial migration into the wound and bacterial infection were prevented during healing. Root implantation and sacrifice of the animals were scheduled to allow for observation periods of 1, 2 and 3 months. The results demonstrated that new connective tissue attachment did not occur to root surfaces which had been exposed to the oral environment, but healing was characterized by repair phenomena, i.e. mainly root resorption and ankylosis. In those areas of the roots where periodontal ligament tissue was preserved following tooth extraction, a functionally oriented attachment apparatus was reformed. The results indicate that in addition to apical migration of junctional epithelium and regrowth of subgingival plaque, the type of cells which repopulate the wound area may jeopardize new connective tissue attachment.