The regenerative potential of the periodontal ligament

Abstract The aim of the present study was to examine if new cementum and new attachment may form during healing of a wound prepared in such a way that preference is given to periodontal ligament ceils to repopulate the wound area adjacent to a root which has been surgically deprived of its periodontal ligament and cementum layer. The maxillary lateral incisors and mandibular canines in three monkeys were used for experimentation. Following elevation of a mucoperiosteal flap, the buccal and approximal alveolar bone was removed within an area extending from the mid-root level to a level 2 mm apical to the marginal bone crest. Following bone removal, the root surfaces were curetted in order to remove the cementum layer. Notches were prepared in the roots to demarcate the denuded root portion. Prior to repositioning of the tissue flap a millipore filter was placed over the treated area in order to prevent the gingival connective tissue from coming into contact with the root surface during healing. The animals were sacrificed 6 months after surgery. The jaws were removed and histological sections of the experimental teeth and surrounding periodontal tissues were produced. New cementum with inserting collagen fibers was observed on the curetted root surfaces. However, this result of healing did not consistently occur along the entire length of the curetted root portion. In the coronal part of the wound, healing was frequently characterized by connective tissue adhesion to the root surface without signs of cementum formation and fibrous attachment. The results of the experiment suggest that the periodontal ligament cells possess the ability to reestablish connective tissue attachment.     

New attachment formation as the result of controlled tissue regeneration

The present study was designed to examine whether new attachment forms on root surfaces previously exposed to plaque by preventing the oral epithelium and the gingival connective tissue from participating in the process of healing following treatment. 4 roots in each of 3 monkeys were used as test units while the roots of contralateral teeth served as controls. A surgical procedure was first used to expose the coronal half of the buccal root surfaces. Plaque was allowed to accumulate on the exposed surfaces for a period of 6 months. Subsequently, soft tissue flaps were raised and the root surfaces were carefully scaled and planed. The crowns of the test and control teeth were resected and the mucosal flaps were repositioned and sutured in such a way that the roots were properly covered. Immediately prior to suturing, membranes (Millipore filter or Gore-tex membrane) were placed over the denuded root surfaces of the test teeth in order to prevent granulation tissue from the soft tissue flaps from reaching the roots during healing. The monkeys were sacrificed 3 months later. The jaws were removed and histological sections of test and control roots including their periodontal tissues were produced. New cementum with inserting collagen fibers was observed on the previously exposed surfaces of both test and control roots. However, the test surfaces exhibited considerably more new attachment than the control surfaces, indicating that the placement of the membrane favoured repopulation of the wound area adjacent to the roots by cells originating from the periodontal ligament.     

Connective tissue attachment formation following exclusion of gingival connective tissue and epithelium during healing

The present investigation was designed to evaluate the potential for reformation of connective tissue attachment on exposed and planed root surfaces by preventing the dentogingival epithelium and the gingival connective tissue from interfering with healing following periodontal surgery. Following the elevation of soft tissue flaps, the buccal and proximal alveolar bone of 24 teeth (48 roots) was removed to mid-root level in 6 monkeys and the exposed root surfaces were carefully planed in order to remove the root cementum. Before the flaps were repositioned and sutured, a membrane (Millipore® filter) was placed over the denuded part of the root surfaces of 16 teeth (test teeth) in order to prevent the epithelium and the gingival connective tissue from interfering with healing. The membrane was adjusted to cover the tooth surfaces from midcrown level to approximately l mm apical to the bone crest. No membranes were placed around the remaining 8 teeth (control teeth) before flap repositioning. The animals were sacrificed 6 months after surgery. The jaws were removed and histological sections of test and control teeth including their buccal periodontal tissues were produced. Nine of the test teeth had to be excluded from examination due to technical failures in the surgical procedure or tissue preparation. New cementum with inserting collagen fibers was observed on all remaining 14 test roots. The length of this newly formed fibrous attachment corresponded to approximately 50% of the distance from the apical extension of root planing to the cemento-enamel junction. In the majority of the control teeth no new attachment had formed but a “long” junctional epithelium was lining the root surfaces to the apical extension of root planing. In 3 control roots a small amount of new cementum with inserting collagen fibers was found in the most apical area of root planing. The results showed that the reformation of a connective tissue attachment was considerably favored by the placement of membranes which prevented the dentogingival epithelium and the gingival connective tissue from interfering with healing.     

New attachment formation on teeth with a reduced but healthy periodontal ligament

The present investigation was undertaken to examine whether a new connective tissue attachment will form on previously periodontitis-involved roots when reduced but healthy periodontal ligament tissue persists following periodontal treatment and the epithelium is prevented from migrating into the wound. In each of 4 monkeys, periodontal tissue breakdown was induced around one maxillary and one mandibular second premolar or first molar by placing orthodontic elastics around the teeth. The elastics were kept in situ until about 50% of the supporting tissues had been lost. 3 months following removal of the elastics, the crowns of the teeth were resected. The pocket epithelium and subjacent granulation tissue were excised and the cementum of the periodontitis-involved part of the roots was removed using a diamond bur. The roots were covered with a mucosal flap. The animals were sacrificed after 3 months of healing. The jaws were removed and histological sections of the experimental roots including their surrounding periodontal tissues were produced. The microscopic analysis disclosed that in all roots, new cementum with inserting collagen fibers had formed in the apical portion of the previously exposed root surfaces. It was always in continuity with the original cementum layer apical to the instrumental part of the root and was thickest in its apical portion, becoming gradually thinner in the coronal direction. In the roots, which for the entire length of the study remained covered by the oral mucosa, the extension in the coronal direction of this newly formed fibrous attachment amounted to an average of 1.0 mm with a range from 0.1 mm to 2.6 mm. These findings were interpreted to mean that new attachment is formed by coronal migration of cells originating from the periodontal ligament.     

Healing following implantation of periodontitis-affected roots into gingival connective tissue

Abstract The aim of the present investigation was to examine if a new connective tissue attachment can be established on a previously periodontitis involved root surface, located in contact with gingival connective tissue during healing. A total of 28 teeth in one dog (beagle) and two monkeys (Macaca cynomolgus) were subjected to experimental periodontal tissue breakdown by placing cotton floss ligatures or orthodontic elastics around the teeth. The ligatures were left in situ until about 50% of the supporting tissues had been lost. Following resection of the crowns, the teeth were root filled and the exposed parts of the roots thoroughly scaled and planed. Each root was extracted and implanted into grooves prepared in edentulous areas of the jaws in such a way that the root was embedded to half its circumference in bone, leaving the remaining part to be covered by the gingival connective tissue of the repositioned flap of the recipient site. Root implantation and sacrifice of the animals were scheduled to allow for observation periods of 2 and 3 months of healing. An analysis of histologic specimens, obtained from biopsies of the recipient site tissues, disclosed that a new fibrous attachment failed to form on a previously “exposed” root surface located in contact with gingival connective tissue. In areas of the roots where the periodontal ligament tissue was preserved prior to transplantation, a fibrous reattachment occurred between the root and the adjacent gingival tissue. The results indicate that gingival connective tissue does not possess the ability to establish conditions which enable the formation of a new connective tissue attachment.     

Healing after root reimplantation in the monkey

The aim of the present investigation was to evaluate the regenerative potential of the periodontal tissues following tooth reimplantation using a model which excluded the dentogingival epithelium from the process of healing. Maxillary and mandibular incisors, premolars and molars of 5 monkeys were used. Following root filling of all experimental teeth, the teeth were divided into 3 experimental groups. In 1 group, the teeth were extracted following the elevation of full thickness flaps. The crowns were separated from the roots at the level of the buccal cemento-enamel junction and the roots immediately reimplanted into their sockets. The flaps were replaced and sutured to accomplish complete coverage of the roots. In a 2nd group, the teeth were subjected to the same experimental procedure, but in addition, the buccal alveolar bone was removed to about half its original height prior to root reimplantation. The teeth of the 3rd group were subjected to identical experimental procedures as for group II with the addition that the buccal root surfaces were planed to the level of the surgically created bone crest. The animals were sacrificed after 6 months of healing. The jaws were removed and histological specimens prepared for microscopic examination. The results showed that a complete fibrous re-attachment formed onto roots on which the original periodontal ligament tissue was preserved. This occurred irrespective of whether the roots were reimplanted into sockets with normal (group I) or reduced (group II) bone height. When the original periodontal ligament tissue was removed by root planing before reimplantation (group III), healing resulted in a significant amount of new connective tissue attachment. However, coronal to the newly formed fibrous attachment, the root surface frequently showed signs of resorption and particularly so in those roots which remained covered by the soft tissue during the entire course of healing. In the majority of the roots which perforated the covering soft tissue during the early phase of healing, the dentogingival epithelium had migrated apically into contact with the coronally generated fibrous attachment. In these cases, root resorption was never discernible. New bone formation occurred to a variable extent in the roots of groups II-III. No relationship was found, however, between the amount of connective tissue reattachment or new attachment and newly formed alveolar bone, which in turn indicates that bone tissue regrowth and periodontal ligament regeneration are unrelated phenomena.     

The potential coronal migration of periodontal ligament tissue following experimental regeneration

The aim of the present study was to determine if the periodontal ligament cells can migrate onto curretted root surfaces following an experimental regeneration procedure. Buccal mucoperiosteal flaps were elevated in all three premolar regions in 5 mongrel dogs. The buccal bone was reduced to approximately 7 mm from its original level on 30 roots. Before the elevated flaps were replaced and sutured, Gore-Tex filters were adjusted to cover exposed root surfaces. No membranes were placed over 10 root surfaces, which served as controls. After 7 weeks of healing, the animals were sacrificed and all the roots were examined for histological evaluation of contralateral experimental and control teeth. With polychrome staining, the new periodontal ligament fibers of the curetted root surfaces were dyed methyl blue and the adjacent gingival collagen fibers were dyed red. On the experimental surface, coronal migration of periodontal ligament cells and connective tissue attachment were identified over long distances of curetted root surface. Periodontal ligament spaces were more prevalent in experimental sites than in control root surfaces. The results of the experiment suggest that the periodontal ligament cells actually migrated onto the curetted root surfaces when a periodontal space was created by physical barriers.     

Healing following citric acid conditioning of roots implanted into bone and gingival connective tissue

The aim of the present investigation was to examine if a new connective tissue attachment is established following citric acid treatment of previously periodontitis involved roots, transplanted and placed in contact with gingival connective tissue or bone during healing. Periodontal tissue breakdown was produced around the mandibular third and fourth premolars in six beagle dogs by the placement of cotton floss ligatures around the neck of the teeth. When the destruction of the supporting tissues had progressed to the mid-root level, the ligatures were removed. Following resection of the crowns, the teeth were root filled and the exposed parts of the roots thoroughly scaled and planed during a flap procedure. Half the number of the teeth were subsequently treated with citric acid at pH₁ for 3 min while the remaining teeth were treated with sterile saline for the same period of time. Each root was extracted and implanted into grooves prepared in edentulous areas of the jaws in such a way that the root was embedded to half its circumference into bone, leaving the remaining part to be covered by the connective tissue of the repositioned flap of the recipient site.
After a healing period of 2 months, an analysis of histological specimens, obtained from biopsies of the recipient site tissues, disclosed that new connective tissue attachment failed to form on the previously periodontitis involved roots whether or not these roots had been subjected to citric acid conditioning. On the contrary, healing consistently resulted in extensive resorption of the roots. The results indicate that citric acid does not alter the biological ability of bone and gingival connective tissue to induce root resorption.     

Placement of a porous membrane underneath the mucoperiosteal flap and its effect on periodontal wound healing in dogs

This study was designed to investigate the healing of surgically induced, horizontal periodontal defects in dogs following placement of a biocompatible, porous polytetrafluorethylene membrane around the roots of the treated teeth and to compare the healing to that of control teeth without membrane. Mandibular premolar teeth of 5 beagle dogs were used for experimentation. Specimen blocks were removed 3 months postoperatively for histological evaluation of contralateral experimental and control teeth. Mean apical migration of junctional epithelium among the experimental surfaces amounted to 0.1 mm as compared to 1.3 mm for the control surfaces. Accordingly, the amount of connective tissue attachment, defined by the distance from the base of the junctional epithelium to the apical termination of root planing, was greater for experimental than for control surfaces. As this increased amount of connective tissue attachment was associated with more coronal bone apposition, a periodontal ligament space was more prevalent in experimental than in control surfaces. A limited amount of ankylosis was observed for both experimental and control surfaces. Root resorption was more prevalent in control than in experimental surfaces. Conceivable reasons for the differences in healing between experimental and control teeth are discussed.     

Potentials for root resorption during periodontal wound healing

The present study was undertaken to examine whether (1) the process of resorption, which invariably affects periodontitis involved reimplanted roots facing bone or gingival connective tissue during healing, is a transient phenomenon and, (2) root resorption can be prevented by permitting downgrowth of epithelium along the root surface. A total of 24 teeth in 2 monkeys (Macaca cynomolgus) was subjected to experimental periodontal tissue breakdown by the placement of elastic ligatures around the teeth. The ligatures were left in situ until about 50% of the supporting tissues had been lost. Following removal of the ligatures, the teeth were extracted and the denuded portions of the roots were scaled and planed. The crowns of the teeth were resected and the root canals filled with guttapercha. The roots were subsequently implanted into sockets prepared in the jaw bone in such a way that each root was embedded in bone except for a portion which was in contact with gingival connective tissue. 1 month prior to sacrifice of the animals, the cut surface of the coronal part of the roots was exposed by removal of the covering soft tissue. The epithelium was thereby allowed to migrate into the wound. Implantation of the roots was scheduled to provide healing periods of 1, 2, 3, 4, 8, 12, 16, 20 and 24 weeks before exposure of the roots. The histologic examination of the implant specimens disclosed that replacement resorption was a progressive process which eventually resulted in the elimination of the transplanted roots. It was possible to prevent root resorption in this model by permitting apical downgrowth of epithelium along the root surface during the initial phase of healing. The results are discussed in relation to procedures used in periodontal therapy.     

New attachment formation following controlled tissue regeneration using biodegradable membranes

The present study evaluated the potential for reestablishment of connective tissue attachment after exclusion of the gingival connective tissue and epithelium during healing after periodontal surgery in a dog model. Buccal mucoperiosteal flaps were elevated in all four premolar regions in two dogs. The buccal bone was reduced to approximately 25% of its original level on 24 roots. Before the elevated flaps were replaced and sutured, membranes were adjusted to cover the exposed root surfaces. On eight surfaces Millipore filters were used and on eight surfaces biodegradable polylactic acid membranes were used. No membranes were placed over the remaining eight root surfaces which served as controls. After two months of healing, the animals were sacrificed and all the roots were subjected to histological analysis. In all of the roots covered with the polylactic acid membrane, newly formed cementum with inserting collagen fibers was observed and covered on the average 46% of the initial defect. Newly formed bone covered 39% of the initial defect. The roots covered by Millipore filters were characterized by significantly less new attachment and bone. In the control roots only minor new attachment was found in the bottom of the defect in some roots. The results suggest that the establishment of a connective tissue attachment is clearly favored by the placement of a polylactic acid membrane to exclude the epithelium and gingival connective tissue during healing.     

Cell and fiber attachment to demoralized dentin A comparison between normal and periodontitis-affected root surfaces

The purpose of the present study was to compare and contrast cellular, connective tissue, and epithelial responses to dentin specimens derived from the roots of either normal or periodontitis-affected human teeth after surface demineralization. Rectangular dentin specimens, with opposite faces of root and pulpal dentin, were derived from beneath root surfaces covered by periodontal ligament (normal) or calculus-covered areas of periodontitis-affected teeth. In each of the groups, the specimens were treated with citric acid (pH 1 for 3 min), whereupon they were implanted transcutaneously into incisional wounds on the dorsal surface of rats with one end of the implant protruding through the skin. 4 specimens were available in each group at 10 days after implantation. Histologic and histometric analyses of the root surfaces of the implants included counts of adhering cells, evaluation of connective tissue fiber relationships, and assessment of epithelial migration. New connective tissue attachment with inhibition of epithelial migration occurred in both groups. Cementum formation was not present. Comparisons between the groups showed no significant differences regarding length of implant surface adjacent to connective tissue, number of attached cells, or density and diameter of attached fibers. The fiber attachment system which had developed on these demineralized surfaces seemed intrinsic to the connective tissue location, and differed morphologically from corresponding fibers attaching the root surface in a normal periodontium. It was concluded that there were no observable differences between the new connective tissue attachment systems which developed on demineralized dentin from either normal or periodontitis-affected root surfaces.     

A histometric evaluation of the effect of citric acid preparation upon healing of coronally positioned flaps in nonhuman primates

Facial recession defects were created on maxillary canine teeth of six Macaca irus monkeys and left untreated and exposed to oral fluids for 6 to 12 weeks. Notches were placed in the exposed root surfaces at the level of the free gingival margins. Following root planing with the addition of topical citric acid application on experimental surfaces, pedicle flaps were coronally positioned over the previously exposed roots. After euthanasia, block sections representing postsurgical time periods of 0, 3, 7, 14, 21, 28 and 42 days were secured and tissues were processed for histologic evaluation. All citric acid-treated surfaces exhibited new connective tissue attachment of pedicle flaps to previously exposed areas by 14 days with transmission electron micrographs confirming beginning cementum deposition. In contrast, controls demonstrated epithelial migration to, or apical to, reference notches. Although the total number of samples available for statistical comparison was small, a two-tailed t test for correlated samples showed citric acid application did not result in enhanced clinical root coverage, but did result in significantly greater amounts of new connective tissue attachment (P less than 0.05, df = 3). Pedicle flap healing against teeth with devital pulps was identical to that seen in teeth with vital pulps, while citric acid application to root-planed surfaces of vital teeth had no observable effect upon pulpal tissues.     

An experimental study of new attachment procedure in beagle dogs

The present pilot study was designed to examine the healing sequence when cells from the PDL are allowed to migrate coronally and populate the curetted root surface.
Mucoperiosteal flaps were reflected around the premolars and mandibular incisors of two beagle dogs with naturally-occurring periodontal disease. The roots were thoroughly planed, and grooves were marked at the level of the crest of remaining alveolar bone. Millipore filters (pore size 3 microns) were adapted circumferentially to the roots and sealed to the teeth above the CEJ with cyanoacrylate before suturing the flaps. Histologic analysis of the experimental and sham-operated control teeth was done at 5, 7, 8, 10, and 12 weeks after the surgery.
An initial phase of root resorption was followed by new connective tissue attachment coronal to the groove in successful experimental teeth. No new connective tissue attachment could be seen in the controls although the JE appeared to be located slightly coronal to the groove with time.
The findings of the present study suggest that the chances of obtaining a new connective tissue attachment may be enhanced if surgical procedures are designed to allow selective population of curetted root surfaces by cells arising from the PDL.     

Healing following reimplantation of teeth subjected to root planing and citric acid treatment

The aim of the present study was to examine the effect of citric acid treatment on periodontal healing around teeth which were extracted, root planed and then reimplanted. Maxillary incisors and mandibular incisors, premolars and molars of 5 monkeys were used. The teeth were divided into 3 experimental groups. In 1 group, the teeth were extracted and immediately reimplanted into their own sockets. In a 2nd group, the teeth were extracted, root planed to a level corresponding to 50-75% of the root length and then reimplanted. In the 3rd group, periodontal breakdown extending to 50-75% of the root length was first induced by placing orthodontic elastic ligatures around the teeth. They were then extracted and root planed and transplanted into the sockets of the contralateral, periodontally healthy teeth which had just been extracted. Half the number of the teeth of groups 2 and 3 were treated with citric acid before reimplantation or transplantation. The animals were sacrificed after 6 months of healing. The jaws were removed and histological specimens prepared for microscopic examination. With the exception of a limited coronal regrowth of new cementum in the apical part of the planed portion of a few roots, connective tissue attachment failed to reform on most root surfaces deprived of their periodontal ligament tissue. Healing was most frequently characterized by root resorption and ankylosis. These were the most predominant features of healing both on root surfaces which had been deprived of the ligament tissue by mechanical means or during a course of experimentally-induced periodontal disease, and occurred in citric acid as well as non-citric acid treated roots. The findings imply that the result of healing following tooth reimplantation or transplantation is determined by the type of cells that repopulate the wound area adjacent to the denuded root surface.     

Healing following surgical treatment and root demineralization in monkeys with periodontal disease

Abstract The aim of the present investigation was to study the potential for new attachment to root surfaces which 1) had become devoid of attachment either by mechanical removal or in conjunction with experimental periodontal tissue breakdown and 2) subsequently had been conditioned with citric acid. Three adult monkeys (Macaca cynomolgus) were used. Periodontal pockets were produced during a 2–6-month period around the maxillary central incisors and first and second premolars and around the mandibular central incisors by the placement of orthodontic elastics. Surgical treatment of the pockets was carried out with the use of a flap procedure. During surgery, the roots of the premolars on the right side of the jaws were first scaled and planed and subsequently treated with citric acid. Citric acid conditioning was not performed on the premolars of the left side. In the front tooth regions the surgical treatment included citric acid conditioning of the mandibular central incisors in two animals and of the maxillary central incisors in one animal. Surgical procedures were also carried out around the mandibular second premolars and first molars which had not been exposed to periodontal tissue breakdown. Folio wing flap elevation, the buccal bone plate was mechanically removed within an area corresponding to that of bone loss produced by the experimental periodontitis model in the maxillary premolars. The cementum layer of the surgically denuded portion of the roots was removed by root planing. In all treated teeth, a notch was prepared in the buccal root surfaces at the level of the alveolar bone crest. Six months following treatment the animals were sacrificed and histologic sections prepared. Linear measurements were made along the root surface from the apical border of the prepared notch to the apical termination of the junctional epithelium and to the crest of the alveolar bone. The results demonstrated that cementum formation and new connective tissue attachment did not occur on root surfaces previously exposed to periodontal pockets and subsequently subjected to scaling and root planing or on root surfaces surgically deprived of their supporting bone and previously “non-exposed” cementum layer. Cementum formation and new connective tissue attachment also failed to occur following citric acid conditioning of root dentin surfaces. In all sections representing all three treatment groups, the attachment between the gingiva and the root was established by epithelium.     

Guided tissue regeneration following treatment of recession-type defects in the monkey

Recent studies have demonstrated extensive amounts of new attachment formation following reconstructive surgery based on the biological principle of guided tissue regeneration (GTR). The aim of the present investigation was to evaluate the effect of using a polytetrafluorethylene (PTFE) membrane in GTR-treatment of recession-type defects and to examine the interrelationship between the PTFE membrane and surrounding periodontal tissues. Full-thickness flaps were raised around 24 maxillary premolar and molar teeth in 6 monkeys. The buccal alveolar bone was surgically removed to a level corresponding to the apical third of the roots. The exposed root surfaces were scaled and planed. In 12 teeth, PTFE membranes were adjusted to cover the exposed root surfaces from a level 1 to 2 mm apical to the CEJ, to a level 3 to 4 mm apical to the alveolar crest. The coronal border of the membranes was tightly adapted to the root surfaces by sling sutures. Twelve teeth served as control teeth without placement of membranes. The flaps were placed with the margin coronal to the CEJ and sutured. The animals were sacrificed after 3 months of healing and all experimental teeth were subjected to histological analysis. The membranes were found to be incorporated with the surrounding connective tissue, and the apical extension of the junctional epithelium terminated at the coronal border of the membranes. The amount of new attachment formation was on the average 74.3% of the defect height in the test teeth, which corresponded to 100% of the membrane covered root portion. Newly formed connective tissue attachment in the controls amounted to an average of 36.9% of the defect height.(ABSTRACT TRUNCATED AT 250 WORDS)     

New attachment and bone formation in periodontal defects following treatment of submerged roots with guided tissue regeneration

Abstract The purpose of the present study was to examine the effect on periodontal regeneration of preventing bacterial contamination of the membrane material following the guided tissue regeneration procedure (GTR). Periodontal dehiscence defects were surgically produced in 2 monkeys. In each monkey, 8 of these defects were submerged after resection of the crowns of the teeth and a teflon (Gore-Tex Periodontal Material®) or a polyglactin (Vicryl Mesh®) membrane was adjusted to cover the defect and the exposed root surface. 4 defects on non-crown resected teeth were treated with either a teflon or a polyglactin membrane positioned with the coronal border approximately 2 mm below the margin of the covering tissue flap. Following 6 months of healing, the animals were sacrificed. Histological evaluation of the specimens revealed that roots which were kept completely covered during the healing period demonstrated new connective tissue attachment and bone formation corresponding to 67–100% of the length of the initial defect depth, whereas the amount of new connective tissue attachment and bone on non-submerged roots ranged between 30–59% and 11–31%, respectively. It seems reasonable to anticipate that it is bacterial contamination of the membrane material which jeopardizes the formation of new connective tissue attachment but in particular bone formation following the GTR-procedure.     

Effect of root surface alterations on periodontal healing.

Abstract A companion study reported that new connective tissue attachment did not occur to a surgically denuded root surface when transplanted into a normal periodontium. It was the purpose of this study to evaluate periodontal healing adjacent to a citric acid treated denuded root surface. In four squirrel monkeys, 12 teeth were extracted and reimplanted after surgical denudation and citric acid conditioning of the coronal root surface. The study design provided three teeth for histologic analysis at 1, 3, 7 and 21 days after reimplantation. One and 3 days after reimplantation a zone of fibrin containing inflammatory cells and erythrocytes was interposed between the root surface and remaining periodontal fibers. The fibrin network appeared to be attached to the root surface by arcade-like formations. The apical termination of the epithelium was located at the coronal extent of the fibrin zone. Granulation tissue and new fibers were aggregating along and perpendicular to the root surface at 7 days; and new connective tissue attachment had been established at 21 days. Extensive root resorption was present along the intra-alveolar part of the root surface. Epithelium had not migrated apically along the denuded root surfaces. The results indicated that citric acid treatment of denuded root surfaces resulted in new connective tissue attachment, and the response appeared to be dependent upon early establishment of fibrin linkage with the root surface.     

Healing of horizontal circumferential periodontal defects following regenerative surgery in beagle dogs

Regenerative surgery of dog teeth with reduced periodontal support was undertaken to determine: if new connective tissue attachment could be predictably attained back to the level of the cemento-enamel junction; and to what extent the new attachment would be accompanied by bone regeneration, root resorption, and ankylosis. The alveolar bone around mandibular premolars was surgically reduced up to 6 mm from the cementoenamel junction. The denuded root surfaces were exposed to the oral environment during a period of 3 months without plaque control. Regenerative surgery was then carried out employing citric acid root conditioning and coronally positioned flaps. 6 months later, histologic evaluation of the midbuccal and midlingual areas of mesial and distal roots revealed new attachment over extended portions of the root surfaces. In 91 of 120 available surfaces, there was no epithelial downgrowth apical to the cemento-enamel junction. Bone regeneration varied from negligible amounts to complete reformation. However, root resorption and ankylosis were prevalent features. 2 different types of resorptions could be distinguished: those occurring near the cemento-enamel junction (cervical resorption), and those occurring more apically in areas of newly formed bone (ankylosis-associated resorption). Resorption of either or both types was noted for 92 of the 120 surfaces.