Healing following simulated fiber retention procedures in rats

The histopathological comparison on the destruction of the periodontal tissue between normal junctional epithelium and long junctional epithelium

BACKGROUND AND OBJECTIVE

The barrier function of long junctional epithelium is thought to be important after periodontal initial therapy and periodontal surgery. Although the difference between long junctional epithelium and normal junctional epithelium regarding their resistance to destruction of periodontal tissue has been investigated, the mechanism still remains unclear. Using our rat experimental periodontitis model in which loss of attachment and resorption of alveolar bone is induced by the formation of immune complexes, we investigated the resistance of periodontal tissue containing long junctional epithelium and normal junctional epithelium to destruction.

MATERIAL AND METHODS

Rats were divided into four groups. In the immunized long junctional epithelium (I-LJE) group, rats were immunized with lipopolysaccharide (LPS), and curettage and root planing procedures were performed on the palatal gingiva of the maxillary first molars to obtain reattachment by long junctional epithelium. In the immunized normal junctional epithelium (I-JE) group, rats were immunized without curettage and root planing procedures. In the nonimmunized long junctional epithelium (nI-LJE) group, rats were not immunized but curettage and root-planing procedures were performed. In the control group, neither immunization nor curettage and root-planing was performed. In all rats, periodontal inflammation was induced by topical application of LPS into the palatal gingival sulcus of maxillary first molars. The rats were killed at baseline and after the third and fifth applications of LPS. Attachment loss and the number of inflammatory cells and osteoclasts in the four groups were compared histopathologically and histometrically.

RESULTS

After the third application of LPS in the I-LJE group, attachment loss showed a greater increase than in control and nI-LJE groups, and inflammatory cell infiltration and osteoclasts were increased more than in the other groups. After the fifth application of LPS, attachment loss was greater and there was a higher degree of inflammatory cell infiltration in nI-LJE and I-LJE groups than in control and I-JE groups.

CONCLUSION

Our findings suggest that the destruction of periodontal tissue is increased in tissue containing long junctional epithelium compared with normal junctional epithelium and that the immunized condition accelerates the destruction by forming immune complexes.

Evaluation of gingival fiber retention technique on the treatment of patients with chronic periodontitis: A comparative study

The destructive action of the chronic periodontitis on the periodontal tissues has provided a continuous challenge to the dental profession to develop better methods to achieve repair of the recession regions and even regeneration of post periodontal tissues.

AIMS

To assess the effect of periodontal muco-periostal flap surgery with gingival fiber retention technique on minimizing the post surgical recession.

MATERIALS AND METHODS

The sample for the study comprised of 20 patients. The criteria for selection included patients with moderate periodontitis, with minimum recession in the anterior teeth, with adequate width of the attached gingiva, and with no traumatic occlusion. Periodontal muco-periosteal flap surgery with gingival fiber retention technique was done in the experimental site with internal bevel incision, and in control site, muco periosteal flap surgery with crevicular incision was done. Thereafter, observation period was of one week, four weeks, and eight weeks were done for both the sites.

STATISTICAL ANALYSIS USED

The results were subjected to statistical analysis using student's t'-test.

RESULTS

The result of this study suggests that the periodontal flap surgery with gingival fiber retention technique has a beneficial effect on the anterior teeth, as it maintains the esthetics, recontours the gingiva with minimal recession. The area of recession was more on the control site as compared to experimental site at 4 weeks, 8 weeks and 12 weeks.

CONCLUSIONS

Gingival fiber retention technique showed less post-surgical recession and also there was fall in values of plaque index, gingival index, and periodontal index scores, throughout the study.

Mandibular second molar periodontal status after third molar extraction

BACKGROUND

Extraction and treatment of third molars have been cited as causing periodontal problems. To evaluate the long-term effects of third molar extraction on the periodontal health of the mandibular second molar, a comparison of the periodontal status was performed around 2 groups of mandibular second molars, with and without third molar extraction.

METHODS

A total of 312 sites in 57 adult periodontitis patients were examined and the buccal and lingual locations of the mesial and distal root surfaces around the second molars were recorded. Two-hundred and thirty-two sites were experimental teeth; i.e., third molars had been surgically removed more than 5 years ago, 80 sites served as control molars; i.e., congenitally missing third molars. Clinical periodontal parameters including probing depth, attachment loss, and gingival recession and radiographic intrabony level were measured. The effects of the surgery and the examination (buccal or lingual) locations on the measurements were statistically analyzed.

RESULTS

Neither extraction history nor examination location affected the probing depth on mesial surfaces. However, significant effects of the surgical history on the probing depth were observed on the distal surfaces. Similar results of greater attachment loss and radiographic alveolar bone loss were observed only at the distal sites of the experimental group. In addition, the increased radiographic bone loss was only found at the distal sites (adjacent to the surgical location) and not at the mesial sites (distant from the surgical location) on the experimental group.

CONCLUSIONS

In this study, greater periodontal breakdown, including probing depth, attachment loss, and radiographic alveolar bone loss, was found at the distal sites, but not at the mesial sites, of the experimental molars where the third molar was surgically extracted compared with the control teeth (no surgery). In the experimental molars, more radiographic bone loss was found at the sites adjacent to the surgical location than at the sites distant to the surgical location. Therefore, we suggest that the surgical removal of the mandibular third molar may lead to a periodontal breakdown on the distal surface of the second molar. Periodontal re-evaluation after the initial healing of third molar extraction is indicated.

Wound healing after mucoperiosteal surgery in the cat

The purpose of this study was to examine possible tissue-dependent differences in rate of healing after mucogingival flap surgery. After intrasulcular incision and a vertical-releasing incision distal to the maxillary and mandibular cuspids, buccal, full-thickness mucogingival flaps were raised in four quadrants of 10 adult cats. The triangular flaps were left open for 30 min and then repositioned and sutured. Tissue reactions were studied histologically after 1, 3, 7, 14, and 28 days of healing. Although new collagen occasionally was observed in the wound space in the free gingiva at 3 days, collagenous union between the cut dentogingival fibers and the flap seemed well established at 7 days. Flap reattachment to the denuded cortical bone was seen at 14 days in the region of the attached gingiva. In the region of the alveolar mucosa, however, residual coagulum and inflammatory reaction was present as late as at 28 days in several specimens. These observations indicate a marked difference in rate of healing among the different interfaces involved. These variations seem to be related to variations in size of the resulting wound space when a full-thickness mucoperiosteal flap is readapted over cervical root surfaces, alveolar bone crest, and denuded cortical bone, respectively.

Regeneration of junctional epithelium and its innervation in adult rats: a study using immunocytochemistry for p75 nerve growth factor receptor and calcitonin gene-related peptide

Junctional epithelium (JE) is a rapidly proliferating tissue that connects the gum to the tooth, that provides a free surface for bidirectional movement of substances between the body and the oral cavity, and that participates in defense against bacterial infection. It is innervated by numerous sensory nerve fibers that are immunoreactive (IR) for neuropeptides such as calcitonin gene-related peptide (CGRP), and for low affinity nerve growth factor receptor (p75-NGFR). Basal epithelial cells of the JE and of adjacent sulcular epithelium also have intense p75-NGFR-IR. In the present study we removed a wedge of the free gingiva and JE from the anterior side of the maxillary first molar of adult rats, and then studied the return of nerve fibers during tissue regeneration from 1-63 days after gingivectomy. The nerve fibers entered the adjacent healing sulcular epithelium before innervating the new JE, in both cases prior to return of epithelial cell p75-NGFR-IR. The regenerating nerve fibers completely bypassed the zone of epithelial down-growth (long junctional epithelium, LJE) that was briefly present along the tooth from 1-3 weeks after injury. The LJE did not have p75-NGFR-IR and was gradually replaced by a modified thicker regenerated junctional epithelium (RJE). The RJE was attached along the injured root surface, had numerous nerves in basal layers, and it had begun to regain p75-NGFR-IR staining of basal epithelial cells by 22 d. Regenerating nerve fibers at 6-10 d had unusually weak CGRP-IR and greatly increased p75-NGFR-IR. Both nerve stains had returned to normal by 3-6 weeks. The intense p75-NGFR-IR of regenerating nerves was found on both axonal and Schwann cell membranes using electron microscopic immunocytochemistry. In both the normal and regenerating JE, nerve fibers were rare in the attachment layers next to the anterior side of the maxillary first molar, compared to well-innervated basal layers. The complete avoidance of LJE by regenerating nerve fibers and its lack of p75-NGFR-IR suggest that its functions do not require innervation and that it does not make neurotrophic growth factors.

Changes in amount of gingival crevicular fluid after a single episode of periodontal treatment

A total of 51 periodontal sites from 6 adults with no systemic diseases or medication were selected for the study. All sites showed radiologic bone loss and pockets of 4 mm or more. Crevicular fluid (CF) was collected by inserting filter paper strips into periodontal pockets for 5 s and was measured by Periotron. Samples were collected before and 2, 5, 10, 20, and 40 days after a single episode of periodontal treatment (scaling, root planing and curettage). Plaque Index (P1I), Papilla Bleeding Index (PBI) and pocket depth (PD) were measured before and 40 days after treatment. The amount of bone loss was estimated from orthopantomograms taken immediately before the trial. Two days after treatment an increase in the amount of CF was seen. After this the amount of CF decreased, reaching the pretreatment level on day 5 after treatment and a level clearly below pretreatment level on day 10 after treatment. Forty days after treatment a slight increase in the amount of CF was seen. The difference between pretreatment values and values at days 2, 10, 20, and 40 was highly significant. In pretreatment samples, positive correlations were found between the amount of CF and PD, PBI and bone loss and, in samples collected 40 days after treatment between CF and PD. CF measurements made before treatment were of no value in predicting the changes in clinical parameters after treatment.

The role of connective tissue in inhibiting epithelial downgrowth on titanium-coated percutaneous implants

Ideally, the surface of epithelium-penetrating implants should impede apical epithelial migration. Previous studies have shown that micromachined grooved surfaces can produce connective-tissue ingrowth, which inhibits epithelial downgrowth on percutaneous implants [Chehroudi et al., J. Biomed. Mater. Res., 24, 9, (1990)]. However, in those studies, connective tissue and epithelium interacted with the same surface so that the effects of the surfaces on each population could not be determined separately. The objectives of this study were (a) to examine cell behavior on implants in which connective tissue contacted surfaces of various topographies and epithelium encountered only a smooth surface, and (b) to compare one-stage and two-stage surgical techniques. Implants had a base component (BC) which was either smooth or had a surface with 19-micron- or 30-micron-deep grooves or 120-micron-deep tapered pits, and a skin-penetrating component (SPC) which was smooth. In the two-stage technique, the BC was implanted subcutaneously for 8 weeks, which permitted the healing of the peri-implant connective tissue. In the second stage the SPC was connected to the BC. For one-stage implants, BC & SPC were connected and implanted percutaneously. Implants (BC & SPC) were removed 1, 2, or 3 weeks after percutaneous implantation and histological sections were measured for recession, connective tissue and epithelial attachment as well as capsule thickness. Light microscopy indicated that both grooved and tapered pitted surfaces encouraged connective tissue ingrowth. On the grooved surfaces, the orientation of fibroblasts changed from an oblique to a more complex pattern which included cells having round nuclei within the grooves, as well as cells oriented oblique or perpendicular to the grooves. In the tapered pits a hammock-like arrangement of fibroblasts was observed. In some cases, foci of mineralization and formation of bonelike tissue were found on the grooved and pitted surfaces. The apical migration of the epithelium was significantly (p less than 0.05) inhibited by those micromachined surfaces which produced connective tissue ingrowth to the BC. This study found that placing the implants in two stages improved the performance of percutaneous devices, and that a further improvement was achieved if the implant had a surface promoting connective tissue ingrowth.

A light and electron microscopic study of the effects of surface topography on the behavior of cells attached to titanium-coated percutaneous implants

Previous studies using light microscopy have demonstrated that micromachined grooved surfaces inhibit epithelial (E) downgrowth and affect cell orientation at the tissue/implant interface. This study investigates the ultrastructure of the epithelial and connective-tissue attachment to titanium-coated micromachined grooved, as well as smooth control, implant surfaces. V-shaped grooves, 3, 10, or 22 microns deep, were produced in silicon wafers by micromachining, replicated in epoxy resin, and coated with 50-nm titanium. These grooved, as well as smooth, titanium-coated surfaces were implanted percutaneously in the parietal area of rats and after 7 days processed for electron microscopy. The tissue preparation technique used in this study enabled us to obtain ultrathin sections with few artifacts from the area of epithelial and connective-tissue attachment. The histological observations demonstrated that E cells closely attached to, and interdigitated with, the 3-microns and 10-microns grooves. In contrast, E cells were not found inside the 22-microns-deep grooves and made contact only with the flat ridges between the grooves. As a general rule, fibroblasts (F) were oriented parallel to the long axis of the implants and produced a connective tissue capsule with 3-microns and 10-microns-deep grooved surfaces as well as smooth surfaces. On the 22-microns-deep grooved surfaces, however, F inserted obliquely into the implant. The attachment of F to the titanium surface was mediated by two zones; a thin (approximately 20 nm), amorphous, electron dense zone immediately contacting the titanium surface, and a fine fibrillar zone extending from the amorphous zone to the cell membrane. As oblique orientation of F has been associated with the inhibition of epithelial downgrowth, micromachined grooved surfaces of appropriate dimensions have the potential to improve the performance of percutaneous devices.

Collagen fiber reunion in wound repair: transmission electron microscopic study of rat gingiva

The purpose of this study was to characterize connective tissue at the site of reunion following surgical injury of the transseptal fiber system in rat molars. Eight conventional albino rats aged 50 days were incised interdentally and the lesions allowed to heal for 14 days followed by specimen preparation for transmission electron microscopy. Four specimens with identifiable areas of fiber attachment at the light microscopic level of magnification were selected for a detailed ultrastructural examination. Transitional connective tissue consisted of thin (250-375 A) and thick (greater than or equal to 450 A) collagen fibrils at a ratio of 41/59 mainly arranged as aggregates of uniformly sized fibrils. Fibril thickness in the vicinity of fibroblasts (n = 40) varied at a ratio of 65 (thin)/35 (thick). Distribution and spatial arrangement of fibrillar components indicate that the site of reunion is characterized by separate aggregates of fibrils rather than alignment of individual collagen fibrils of varying thickness suggestive of covalent linkage.

Identification of connective tissue components in healing rat gingiva

The aim of the study was to examine connective tissue fiber organization during healing of an incisional wound in rat molar gingiva. Forty rats 50 days old were divided into 10 experimental groups each comprising four animals. Following interdental incisions, healing periods of 11-20 days, and then 3H-proline injection, the animals were sacrificed and specimens prepared for light microscopy, autoradiography, and transmission electron microscopy. Isotope labeling with 3H-proline occurred over newly formed collagen in the path of incision, while preexisting tissue was unlabeled. Ultrastructurally, preexisting and new tissue were identified by measurement of collagen fibril thickness. The spatial relationship between new and remaining fibrous tissue in the transitional zone suggests that reunion is established by side-by-side alignment of new and severed fibrils.

Effects of atelocollagen on the wound healing reaction following palatal gingivectomy in rats

Collagen membrane preparations have been manufactured with the aim of enhancing wound healing following periodontal surgery. After cross-linking by various processing methods (with ultraviolet radiation or hexamethylenediisocyanate) and to various extents, atelocollagen membranes were applied into dissection sites within palatal gingival tissue. Applied atelocollagen was histopathologically compared with applied lyophilized porcine dermis (LPD) and controls in rats, with regard to the time course of healing. The atelocollagen-applied group showed more satisfactory regeneration of the epithelium and connective tissue in an artificially created gingival defect than did the control group or the LPD-applied group. Epithelial downgrowth along the root surface was significantly suppressed by the use of atelocollagen. In addition, the post-operative inflammatory reaction and foreign body giant cell reaction subsided rapidly after surgery in the atelocollgen-applied group. Our results show that the use of atelocollagen membrane in periodontal wounds should be the method of choice.

Different cross-linked types of collagen implanted in rat palatal gingiva

Collagen membrane preparations were manufactured with the aim of enhancing wound healing following periodontal surgery. After crosslinking by various processing methods (with ultraviolet and hexamethylenediisocyanate) and to various extents, two types of collagen (atelocollagen and tendon collagen) were implanted into a dissection site within palatal gingival tissue. The time course of healing responses was investigated histologically. Collagen implantation was found to accelerate fibrous connective tissue attachment to the root surface and inhibit apical migration of the junctional epithelium. Cross-linked atelocollagen was superior in biocompatibility to the other collagen membranes studied.

Collagen deposition during wound repair in rat gingiva

The aim of this study was to examine day-by-day changes at incisional wound edge in rat molar interdental tissue with special reference to early interactions of new and pre-existing collagen fibrils. Twenty rats aged 50 days were divided into experimental groups each comprising two animals. Following incision and post-injury observation periods of 1-10 days, the rats were given an overdose of sodium pentothal and specimens prepared for light and electron microscopy. In 1-3-day post-injury specimens fibrin was replaced by inflammatory cells. Fibroblasts were found along the cut edge in 4-day post-injury specimens. Fibrillogenesis had started at 5 days post-injury. During the period of 5-10 days post-injury increasing amounts of new collagen fibrils were laid down at the wound edge. No granular material was identified at the interface of new and preexisting collagen. In standardized mesiodistal sections, bundles of newly formed fibrils regularly appeared cross-cut in relation to the tangentially cut transseptal fiber system, suggestive of a buccolingual fibril orientation at the wound edge. The ultrastructural observations indicate that during early stages of wound repair, connective tissue continuity is generally established without direct splicing of severed fibers.

Human gingival attachment responses to subgingival crown placement. Marginal remodelling

13 teeth in block were extracted from 2 patients. Their facial periodontal condition was essentially within normal clinical limits. Temporary crowns covering the bevel were placed below the base of the crevice 1 to 8 weeks prior to extraction. At time of extraction, all blocks were decalcified, the temporary crown dissolved, and the blocks prepared for histologic examinations using buccolingual cut, step serial sections. Histologic data revealed reformation of a new supracrestal attachment unit within 1 week following crown placement. The reformation of the gingival unit consisted of marginal recession with apical and lateral migration of the junctional epithelium to the level of remaining cementum inserted fibers. With gingival recession and migration of junctional epithelium, resorption of crestal portions of the facial plate occurred. However, periodontal fibers anchored into cementum opposite the resorbed bone were not lysed. Rather, the attached fibrillar ends appeared to interdigitate with fibers from the corium of the facial gingiva at this site, thereby forming a more apically located crestal attachment. This response may be one mechanism of reformation of the gingival attachment unit taking place following mechanical and/or surgical injury to this site and is completed often, within 2 weeks after injury.

Speculations on periodontal attachment loss

A hypothesis is presented depicting patterns of human periodontal attachment loss. The patterns described occur rapidly, are site-specific and take place in response to virulence and duration of local irritants. They appear to mirror current clinical observations regarding the nature and progress of site-specific periodontal lesions.

Surgical removal of the fully impacted mandibular third molar. The influence of flap design and alveolar bone height on the periodontal status of the second molar

This study was carried out because a great deal of uncertainty exists as to he effect of the surgical removal of the fully impacted third molar on the periodontal status of the second molar. The objectives were to determine the effect of surgical removal of the third molar on the periodontal status of the second molar; the influence of flap design on these results; the influence of the initial height of the alveolar bone on the distal of the second molar on subsequent changes in attachment level. The study included 30 patients with bilateral mandibular impactions. A split-mouth experimental design was used, with one side of the mandible being randomly allocated to one of two flap design groups. Plaque level, gingival inflammation, probing depth and attachment level measurements around the second molar were taken at baseline and then at monthly intervals for a period of 6 months. Alveolar bone height was measured from panoramic radiographs. Six months postsurgically, both flap design groups exhibited a statistically significant loss of attachment level on the distal surface of the second molar with no difference between the two flap groups. The initial height of the alveolar bone on the distal of the second molar had no influence on the loss of attachment. It was concluded that the surgical removal of the fully impacted mandibular third molar led to the loss of attachment on the distal of the second molar; flap design had no influence on the degree of attachment loss; the initial height of the alveolar bone on the distal of the second molar had no influence on the loss of attachment.

Epithelial reattachment after gingivectomy in the rat

It is known that an epithelial reattachment occurs a few days after gingivectomy. Depending upon the surgical procedure and the animal species used, different times have been proposed to obtain a complete reattachment. Nevertheless, it is not known whether there is a correlation between the time required and the sequence of morphologic events involved in this process. To investigate this matter, gingivectomies were performed in the maxillary molars of rats. Specimens were taken 1 to 14 days after the operation and processed for light and electron microscopy. The new junctional epithelium appeared at the 5th day, but the earliest signs of reattachment complex formation were evident at the 8th day. Rudimentary hemidesmosomes and lamina lucida appeared in epithelial cells bordering remnants of fibrin. Anchoring filaments that formed between the earliest hemidesmosomes and the subjacent fibrin crossed the lamina lucida. Simultaneously, segments of lamina densa appeared. At the 11th day insertion of tonofilaments into the attachment plaques and insertion of anchoring filaments in the lamina densa were observed. At the 14th day, full development of the reattachment complex was evident.

A scanning electron microscope study of the effects of various agents on instrumented periodontally involved root surfaces

This study evaluated the effects of chemical and biologic agents on periodontally diseased root surfaces which had been scaled or root planed. The proximal surfaces of 25 teeth were scaled to remove all visible calculus, and the proximal surfaces of another 25 teeth were vigorously root planed to remove all cementum and to achieve a hard, smooth, glass-like surface. Five scaled and five root planed specimens were randomly selected for light microscopic examination to determine the amount of cementum removed. Cementum remained on all scaled surfaces but root planing had removed most of the more coronal cementum. Each of the 40 remaining teeth (20 scaled and 20 root planed) was longitudinally sectioned to obtain an experimental and control specimen. Four scaled and four root planed sections were randomly selected as experimental specimens for a test of each of the following five agents: (1) saturated citric acid for three minutes; (2) 15% EDTA for 5 minutes; (3) sodium hypochlorite for 5 minutes, followed by a 30-second application of 5% citric acid; (4) sodium hypochlorite alone for 5 minutes; and (5) 2% sodium deoxycholate (NAD) for 1 minute, followed by a 1-minute rinse in distilled water, and then a 1-minute application of 5% Cohn's fraction IV1. The control for each experimental specimen was treated with saline. All samples were prepared for SEM and examined at 3,000 X. Areas of particular interest were also examined at 12,000 X. The chemical treatments exposed only individual collagen fibers or irregular fiber bundles on the scaled surfaces. Saturated citric acid, EDTA, and sodium hypochlorite with citric acid neutralization removed debris and exposed openings in the root surfaces. Sodium hypochlorite alone and NaD/Cohn's fraction IV1 were less effective in removing surface debris and had an effect similar to that seen in the saline controls. Application to root planed specimens of saturated citric acid, EDTA, and sodium hypochlorite followed by 30 seconds of citric acid neutralization resulted in surfaces virtually free of debris and with numerous collagen fibers exposed on the surface. EDTA appeared to cause a morphologic change in the collagen fibers. Sodium hypochlorite alone, sodium deoxycholate followed by Cohn's fraction IV1, and physiologic saline were relatively ineffective in surface debridement.

Progressive replacement of epithelial attachment by a connective tissue junction after experimental periodontal surgery in rats

The purpose of this study was to test the hypothesis that the long junctional epithelium formed during the early stages of periodontal wound healing can become replaced, at least in part, by a connective tissue attachment. A surgical wound was created on the mesial surface of the left maxillary first molar of 4-month-old rats and the mesial root surface curetted free of soft tissue and cementum. The contralateral molar served as an unoperated control. Groups of five to eight animals were killed at intervals of 10 days, 3 and 6 weeks, and 3, 6 and 12 months after surgery. The histometric data demonstrated a progressive apical recession of the entire gingival unit on the unoperated control side during the experimental period. On the operated side, the junctional epithelium became reestablished by migration of epithelium from the wound edge along the cut gingival surface facing the tooth, until contact was established near the apical border of the instrumented root surface. Coronal migration of the epithelium from that level accounted for most of the lengthening of the junctional epithelium observed in 3 weeks. During the balance of the experimental period the junctional epithelium did not change in length significantly. However, the entire epithelial attachment was displaced coronally, primarily at the expense of sulcus depth which decreased with time, and by replacement of the apical portion of the junctional epithelium by a connective tissue junction of increasing dimension. These findings challenge the widely held belief that, once established, the dentoepithelial junction cannot be replaced by a connective tissue attachment.

Effect of root surface alterations on periodontal healing. I. Surgical denudation

The present study was undertaken to evaluate the effect of root surface denudation on periodontal healing. Twelve teeth, distributed in four squirrel monkeys, were extracted and reimplanted after surgically denuding the coronal root surface of connective tissue fibers and cementum by root planing. The reimplantation schedule provided three teeth for histologic analysis at 1, 3, 7 and 21 days after reimplantation. One day after reimplantation a zone of fibrin enmeshing erythrocytes and inflammatory cells was interposed between th root surface and the remaining periodontal fibers attached to the alveolar bone. Epithelium migrated rapidly along the denuded root, had reached the alveolar crest at 3 days, and was within the ligament space at 7 days. At 21 days, the epithelium was at the apical limit of root instrumentation, which corresponded to the level of attached connective tissue fibers on the root surface. No evidence of new connective tissue attachment was observed on the denuded root surface. It was concluded that the absence of fibers on the root surface resulted in apical migration of the epithelium, and precluded formation of new connective tissue attachment.

Topography of root surfaces treated in vitro with citric acid, elastase and hyaluronidase. A scanning electron microscopy study. Part II

Sixteen extracted human teeth were separated into two groups, root planed, and treated with either elastase or hyaluronidase following acid demineralization. The duration of enzyme application varied from 5 to 20 minutes. From scanning electron micrographs the following was concluded: (1) The cemental collagen network is composed of previously described extrinsic and intrinsic fiber systems. (2) Root planing, using tactile sense as the final criteria, does not always result in complete elimination of contaminants. (3) Citric acid (pH = 1), applied for 3 to 4 minutes, is an effective means of exposing cemental collagen. (4) Qualitatively, the enzyme treatment subsequent to acid demineralization seemed to result in more effective exposure of the collagen mantle of cementum. (5) Further definitive research must be done to determine, both the usefulness of enzymatic treatment in vitro and in vivo and the optimum enzyme concentrations and duration of application.

Use of the fiber retention procedure in treating the maxillary anterior region

THE MAXILLARY anterior region presents a difficult and unique therapeutic challenge to both the periodontist and restorative dentist. Although access for surgical and prosthetic procedures is certainly easiest in this part of the mouth, the problem of esthetics, in terms of increased tooth length and loss of interdental papillae, creates an environment in which the clinician's therapeutic choices may either be severely limited or the result compromised. The two cases presented show how this area can be successfully treated using fiber retention procedures to eliminate pathologic periodontal pockets effectively while minimizing root exposure, loss of interdental papillae and root sensitivity. This type of procedure enables the clinician to provide the patient with an acceptable biologic, functional and esthetic result.