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Periodontal repair in dogs
Uif M. E. Wikesjd and Rolf Nilveus School of Dentistry, Loma Linda University, Loma Linda, CA, USA
Healing patterns in large circumferential periodontal defects Wikesjd UME and Nilveus R: Periodontal repair in dogs: Healing patterns in large circumferential periodontal defects. J Clin Periodontol; 1991; 18: 49-59.
Abstract. This report describes the healing patterns of large circumferential periodontal defects in the beagle dog. Approximately 5 mm large periodontal defects were created around the mandibular premolars (P2, P3 and P4) in 13 animals. The root surfaces were then instrumented to remove all cementum and the wounds immediately closed by replacing and suturing the flaps just coronal to the cemento-enamel junction. Block biopsies were harvested after 4 weeks. Most of the surgically denuded root surface healed with connective tissue repair. Cementum formation and regeneration of alveolar bone was limited and averaged approximately 30% and 20%, respectively, of the defect height. Almost all teeth exhibited root resorption. Ankylosis was observed in 14 of the teeth. There was no difference in the healing response between the 3 premolars or their buccal and lingual surfaces. The range of healing responses indicates that a biological potential exists which makes this model useful for testing the effect of various root and wound conditioners in (1) enhancing cementum formation on the root surface, (2) increasing regeneration of alveolar bone and (3) preventing aberrant healing events such as root resorption and ankylosis. Conversely, whether such agents may compromise wound healing and result in reduced connective tissue repair may concomitantly be tested.
Recent studies concerning reconstructive periodontal therapy in man have used somewhat different biological rationales for their surgical approaches. In spite of disparate rationales there seem to be several reconstructive techniques that have merit and can result in a meaningful gain of clinical attachment, regeneration of alveolar bone and histological new attachment. Thus, root surface and wound-conditioning (Caffesse et al. 1988, Gantes et al. 1988, Garrett et al. 1988, Pini-Prato et al. 1988, Schallhorn & McClain 1988), bone and ceramic grafts (Bowers et al. 1985, Gantes et al. 1988, Garrett et al. 1988, Kenney et al. 1988, Schallhorn & McClain 1988) and barrier membranes (Gottlow et al. 1986, Becker et al. 1987, Pontoriero et al. 1988, Garrett et al. 1988, Pini-Prato et al. 1988, Schallhorn & McClain 1988) have been used to promote repair or regeneration of tooth supporting structures. It is not clear, however, which factors are essential to the outcome of the different regenerative procedures. The favorable healing results may be dependent on factors unique to each therapeutic mode or may be dependent on
biologic factors which are operative regardless of surgical approach. One such common factor may be the stability of a fibrin clot linking the root surface and the internal aspect of the flap. Estabhshment of a fibrin linkage may be critical in order to negate epithelialization and allow for a connective tissue repair to the root surface (Poison & Proye 1983). In previous experimental studies in animal models, we have focused on aspects of wound manipulation that may affect clot stability and ultimately periodontal repair. We have used large chronic circumferential or natural periodontal defects around the mandibular premolars in the dog to study the impact of various flap manipulations and root surface treatments as well as the effect of implant materials. Periodontal repair in these reports has included, to varying degrees, epithelial proliferation and new attachment/reattachment with new cementum and bone regeneration as well as root resorption and ankylosis (for review, see Egelberg (1987)). We have, more recently, furthered our observations of the healing dentin-connective tissue interface to include the influence of various
Key words: ankylosis; new attachment; periodontal regeneration; root resorption. Accepted for publication 10 January 1990
other root surface treatments (Wikesjo et al. 1990, 1991, Wikesjo & Nilveus 1990) and implant materials (Claffey et al. 1989a, Wikesjo & Nilveus 1990) using an acute surgical wound model. The aim of this report is to present the morphometric basis needed to make this model useful in evaluating the effect of various modifiers on periodontal healing. Material and Methods Animals
13 male beagle dogs, 18-24 months old, were used. Periodontal defects were surgically created in the mandibular right and left jaw quadrants and was followed by immediate wound closure attampting to reconstruct lost connective tissue support. 1 jaw quadrant in each dog received additional experimental treatment. The results of that experimentation are reported elsewhere (Wikesjo et al. 1990,1991). The material for this report consisted of a total of 38 teeth from the 13 dogs. All surgical procedures were performed under intravenous sodium pentobarbital anesthesia (Nembutal®
50
Wikesjo & Nilveus
Sodium Solution, Abbott Laboratories, North Chicago, IL; 20 mg/kg). During surgery, the dogs received lactated Ringer's solution intravenously (Lactated Ringer's Inj., USP, Abbott Laboratories, North Chicago, IL). The animals were fed a standard laboratory diet of soft consistency throughout the experimental period. induction of defects
Horizontal circumferential periodontal defects were surgically created around the 2nd, 3rd and 4th mandibular premolars (P2, P3 and P4; Fig. 1). Following sulcular incisions and elevation of buccal and lingual mucoperiosteal flaps alveolar bone was removed around the full circumference of the teeth including the interproximal and the furcation areas with chisels and water cooled rotating burs. The created defect height, measured from the cemento-enamel junction to the bone margin, approximated 4.5, 5.5 and 6 mm for P2, P3 and P4, respectively. The 1st mandibular premolar was extracted and the crown of the 1st molar amputated at the level of the surgically reduced alveolar bone crest. In 1 dog, the 3rd premolar was also removed due to severe crowding of the teeth. Wound management
Immediately following bone reduction, the root surfaces were planed with curettes and chisels and the furcation fornices instrumented with a flame shaped, water cooled rotating diamond to remove the cementum. The teeth were then isolated with rubber dam, irrigated with saline and the root surfaces allowed to dry for 2 min assisted by a gentle stream of air. Following removal of the rubber dam, the periosteum was fenestrated at the base of the buccal and lingual flaps, and the flaps were replaced to a position' 1-2 mm coronal to the cemento-enamel junction. Interdentally, single interrupted sutures were used, whereas the mesial and distal extensions of the wound were closed with vertical mattress sutures. Care was taken to proximate the connective tissue surfaces of the buccal and lingual flap margins at wound closure. Sutures were removed ater 1 week. A broad spectrum antibiotic (Combiotic®, Pfizer Inc., New York, NY) was administered intramuscularly daily during the first 2 weeks following surgery. For the remaining 2
Fig. 1. The mandibular premolar teeth (P2, P3 and P4) (A), after surgical reduction of the bone and root preparation (B), following wound closure and suturing (C) and following 4 weeks of wound healing (D).
weeks of healing, daily plaque control was maintained by gently wiping the teeth with gauze soaked in a 2% chlorhexidine solution (Hibitane®, ICI Ltd, Macclesfield, Great Britain).
Histoiogicai procedures
The dogs were sacrificed 4 weeks after surgery by intravenous injection of concentrated sodium pentobarbital. Tissue
Periodontal repair in dogs blocks including teeth, bone, and soft tissues were removed. The blocks were fixed in 10% buffered formalin, decalcified in 10% formic acid, trimmed, dehydrated and embedded in paraffin. Serial sections, 7 /mi thick, were cut in a bucco-lingual direction throughout the entire mesio-distal extension of the teeth. Every 14th section was stained with Masson's trichrome and the adjacent section with hematoxylin and eosin allowing for observations at an interval of approximately 100 //m. The most centrally located stained section of the mesial and the distal root of each tooth was identified by the size of the pulp chamber and the root canal. This section and the 2 step serial sections on either side stained with Masson's trichrome were subjected to histometric analysis. Extent of new cementum formation was additionally confirmed in adjacent hematoxylin and eosin stained sections. Consequently, 5 subsequent step serial sections, representing approximately 0.4 mm of the mid-portion from both the mesial and distal roots of each tooth, were used for analysis. Measurements were performed using a microscope connected to a measuring system for computer aided manual data collection of geometrical
structures (Videoplan, Carl Zeiss Inc., Kontron, Eching bei Miinchen, West Germany). The quahty of the histotechnical preparation did not allow meaningful data collection from 4 tooth surfaces in 2 teeth, each from a separate dog. The following measurements were taken for the buccal and lingual surfaces of each root (Fig. 2). ^ • Defect height: the distance between the apical extension of the root planing and the cemento-enamel junction. Junctional epithelium: the distance from the apical to the coronal extension of the junctional epithelium along the root surface. Connective tissue repair: the distance between the apical extension of the root planing and the apical termination of the junctional epithelium. Cementum formation: the distance between the apical extension of the root planing and the coronal extension of a continuous layer of cementum or a cementum-like deposit on the root surface. Bone formation: the distance between the apical extension of the root planing and the coronal extension of newly formed alveolar bone along the root surface. Root resorption: the combined linear heights of distinct resorption lacunae along the root surface. Ankylosis: the combined linear heights of an ankylotic union of newly formed alveolar bone and the root surface. Data analysis
Fig. 2. Histometric parameters and landmarks in bucco-lingual sections. (CEJ) cemento-enamel junction, (JE) junctional epithelium, (RR) root resorption, (NAB) new alveolar bone, (NC) new cementum/cementum-like deposit, (ARP) apical extension of root planing.
Means and ranges for each of the measured parameters were calculated per surface, tooth and dog. In addition, root resorption and ankylosis were dichotomously scored and recorded as present if observed in 1 or more of the 5 sections for each root surface. ANOVA (SPSS-X, SPSS Inc., Chicago, IL) was used to analyze homogeneity of the healing dentin-connective tissue interface (connective tissue repair, cementum and bone formation and root resorption) between dogs, tooth types and tooth surfaces using defect height as a covariate. Results Clinical and histological observations
During the 1-month postoperative interval, a slight recession of the gingival
51
margin from its position at wound closure was generally observed. At sacrifice, the gingival margin was usually located approximately at the cementoenamel junction (Fig. 1). The light microscopic observations revealed that most of the surgically denuded root surface healed with connective tissue interfacing the dentin (Fig. A thin layer of a cementum-like deposit was observed extending coronally from the old cementum at the base of the wound in most specimens (Figs. 3, 4). However, the extent of this cementum varied and it could not be detected in some root surfaces, while in others the deposit covered a major part of the root surface. New cementum was mostly found on root surfaces unaffected by resorption, but on occasion this could also be seen lining lacunar bays indicative of prior resorptive activity (Figs. 5, 6). In some cases, isolated islands of cementum-like tissue were observed in the coronal aspect of the root without any apparent continuity with more apical deposits, or without continuity with the old cementum at the base of the wound. In particular, such isolated cementum was observed lining root resorption bays immediately apical to the junctional epithelium (Fig. 6). In areas void of cementum, a connective tissue of variable cell density interfaced directly with the root surface (Figs. 3, 5, 6). Regeneration of alveolar bone from the base of the wound was limited (Fig. 3). With few exceptions, the new bone formation along the root surface did not extend more coronally than the cementum formation. Almost all teeth exhibited root resorption (Figs. 3-6). Resorption lacunae of various dimensions could be observed throughout the dentin-connective tissue interface (Fig. 5). More prominent resorption bays were frequently observed immediately apical to the junctional epithelium (Figs. 3, 4, 6). Multinucleated cells were infrequent occupants of the resorption areas (Figs. 4, 5). Ankylosis was observed in approximately !^ of the teeth (Figs. 4,5). An ankylotic union between the root surface and newly formed alveolar bone was often associated with areas of root resorption and/or a cementum-like deposit (Figs. 4,5). In the latter case, the alveolar bone fused with the new cementum into one entity having similar structural and staining characteristics (Fig. 4).
52
Wikesjo & Nilveus Histometric observations
Mean connective tissue repair of the periodontal defects amounted to 4.6 mm, or 90% of the total defect height (Table 1, Fig. 7). The residual part of the involved root surface interfaced a junctional epithelium (8%) or was exposed to the oral cavity (2%). Although the connective tissue repair ranged from 100% to 2 1 % of the defect height, approximately 90% of the examined root surfaces presented with connective tissue repair amounting to 70% or more. ; There were no differences in relative amount of connective tissue repair between the 3 teeth (P2, P3 and P4) or between their buccal and lingual aspects (Table 2). Similarly, initial defect height did not influence the relative amount of connective tissue repair (Table 3). New cementum in continuity with root cementum at the base of the wound extended to 30% of the defect height (Table 1, Fig. 7). The extent of cementum formation did not appear to correlate with the total amount of connective tissue repair obtained (Table 4). Mean regeneration of alveolar bone amounted to 19% of the defect height (Table 1, Fig. 7). Similar to cementum formation, the extent of bone regeneration was limited and independent of the total amount of connective tissue repair obtained (Table 4). 93% of the tooth surfaces exhibited signs of past or present root resorption (Table 5). The incidence of root resorption was 70% in the coronal % and 56% in each of the mid and apical % of the defect. Mean linear root resorption amountd to 20% of the total defectheight with a mean distribution of 10, 5 and 5% of the defect height for the coronal, mid and apical % of the surgically denuded root surface. An ankylotic union between root dentin and newly formed alveolar bone Table 1. Periodontal repair of circumferential horizontal periodontal defects following replacement of mucoperiosteal flaps to slightly above the cemento-enamel junction; means ±s.d. (mm), A''=13 dogs . 3. Bucco-lingual section with complete connective tissue repair to the root surface. The defect height approximates 5 mm from the cemento-enamel junction to the apical extension of the root planing. (1) commonly found root resorption at the cemento-enamel junction, (2) connective tissue repair without new cementum formation on the root surface and (3) frequently observed limited formation of new cementum and new alveolar bone at the apical extension of the periodontal wound.
defect height junctional epithelium connective tissue repair cementum formation bone formation root resorption ankylosis
5.1+0.5 0.4 + 0.4 4.6 + 0.5 1.4+1.3 0.9 + 0.6 1.1+0.6 0.1+0.2
Periodontal repair in dogs
Fig. 4. Bucco-lingual section with complete connective tissue repair to the root surface. Total defect height was approximately 5 mm: (1) root resorption apical to the cemento-enamel junction with rarely encountered multinucleated giant cells (arrow heads); (2) area of connective tissue repair with a cementum-like deposit on the root surface; (3) the cemen- I tum deposit merges with the alveolar ^ bone into an ankylotic union (ANK), artifactual separation (AS); (4) more apical aspect with a thin layer of new cementum: (5) healing at the apical extension of the defect: note how the new cementum/cementum-like deposit merges with the old cementum.
ARP
53
54
Wikesjo & Nilveus
was observed in 11 % of the root surfaces and occurred primarly in the mid % of the defect (Table 5). Analysis of variance disclosed significant variability between dogs for connective tissue repair, cementum and bone formation and root resorption
(/7< 0.001). Additionally, bone formation exhibited significant tooth (p
Periodontal repair in dogs
Uif M. E. Wikesjd and Rolf Nilveus School of Dentistry, Loma Linda University, Loma Linda, CA, USA
Healing patterns in large circumferential periodontal defects Wikesjd UME and Nilveus R: Periodontal repair in dogs: Healing patterns in large circumferential periodontal defects. J Clin Periodontol; 1991; 18: 49-59.
Abstract. This report describes the healing patterns of large circumferential periodontal defects in the beagle dog. Approximately 5 mm large periodontal defects were created around the mandibular premolars (P2, P3 and P4) in 13 animals. The root surfaces were then instrumented to remove all cementum and the wounds immediately closed by replacing and suturing the flaps just coronal to the cemento-enamel junction. Block biopsies were harvested after 4 weeks. Most of the surgically denuded root surface healed with connective tissue repair. Cementum formation and regeneration of alveolar bone was limited and averaged approximately 30% and 20%, respectively, of the defect height. Almost all teeth exhibited root resorption. Ankylosis was observed in 14 of the teeth. There was no difference in the healing response between the 3 premolars or their buccal and lingual surfaces. The range of healing responses indicates that a biological potential exists which makes this model useful for testing the effect of various root and wound conditioners in (1) enhancing cementum formation on the root surface, (2) increasing regeneration of alveolar bone and (3) preventing aberrant healing events such as root resorption and ankylosis. Conversely, whether such agents may compromise wound healing and result in reduced connective tissue repair may concomitantly be tested.
Recent studies concerning reconstructive periodontal therapy in man have used somewhat different biological rationales for their surgical approaches. In spite of disparate rationales there seem to be several reconstructive techniques that have merit and can result in a meaningful gain of clinical attachment, regeneration of alveolar bone and histological new attachment. Thus, root surface and wound-conditioning (Caffesse et al. 1988, Gantes et al. 1988, Garrett et al. 1988, Pini-Prato et al. 1988, Schallhorn & McClain 1988), bone and ceramic grafts (Bowers et al. 1985, Gantes et al. 1988, Garrett et al. 1988, Kenney et al. 1988, Schallhorn & McClain 1988) and barrier membranes (Gottlow et al. 1986, Becker et al. 1987, Pontoriero et al. 1988, Garrett et al. 1988, Pini-Prato et al. 1988, Schallhorn & McClain 1988) have been used to promote repair or regeneration of tooth supporting structures. It is not clear, however, which factors are essential to the outcome of the different regenerative procedures. The favorable healing results may be dependent on factors unique to each therapeutic mode or may be dependent on
biologic factors which are operative regardless of surgical approach. One such common factor may be the stability of a fibrin clot linking the root surface and the internal aspect of the flap. Estabhshment of a fibrin linkage may be critical in order to negate epithelialization and allow for a connective tissue repair to the root surface (Poison & Proye 1983). In previous experimental studies in animal models, we have focused on aspects of wound manipulation that may affect clot stability and ultimately periodontal repair. We have used large chronic circumferential or natural periodontal defects around the mandibular premolars in the dog to study the impact of various flap manipulations and root surface treatments as well as the effect of implant materials. Periodontal repair in these reports has included, to varying degrees, epithelial proliferation and new attachment/reattachment with new cementum and bone regeneration as well as root resorption and ankylosis (for review, see Egelberg (1987)). We have, more recently, furthered our observations of the healing dentin-connective tissue interface to include the influence of various
Key words: ankylosis; new attachment; periodontal regeneration; root resorption. Accepted for publication 10 January 1990
other root surface treatments (Wikesjo et al. 1990, 1991, Wikesjo & Nilveus 1990) and implant materials (Claffey et al. 1989a, Wikesjo & Nilveus 1990) using an acute surgical wound model. The aim of this report is to present the morphometric basis needed to make this model useful in evaluating the effect of various modifiers on periodontal healing. Material and Methods Animals
13 male beagle dogs, 18-24 months old, were used. Periodontal defects were surgically created in the mandibular right and left jaw quadrants and was followed by immediate wound closure attampting to reconstruct lost connective tissue support. 1 jaw quadrant in each dog received additional experimental treatment. The results of that experimentation are reported elsewhere (Wikesjo et al. 1990,1991). The material for this report consisted of a total of 38 teeth from the 13 dogs. All surgical procedures were performed under intravenous sodium pentobarbital anesthesia (Nembutal®
50
Wikesjo & Nilveus
Sodium Solution, Abbott Laboratories, North Chicago, IL; 20 mg/kg). During surgery, the dogs received lactated Ringer's solution intravenously (Lactated Ringer's Inj., USP, Abbott Laboratories, North Chicago, IL). The animals were fed a standard laboratory diet of soft consistency throughout the experimental period. induction of defects
Horizontal circumferential periodontal defects were surgically created around the 2nd, 3rd and 4th mandibular premolars (P2, P3 and P4; Fig. 1). Following sulcular incisions and elevation of buccal and lingual mucoperiosteal flaps alveolar bone was removed around the full circumference of the teeth including the interproximal and the furcation areas with chisels and water cooled rotating burs. The created defect height, measured from the cemento-enamel junction to the bone margin, approximated 4.5, 5.5 and 6 mm for P2, P3 and P4, respectively. The 1st mandibular premolar was extracted and the crown of the 1st molar amputated at the level of the surgically reduced alveolar bone crest. In 1 dog, the 3rd premolar was also removed due to severe crowding of the teeth. Wound management
Immediately following bone reduction, the root surfaces were planed with curettes and chisels and the furcation fornices instrumented with a flame shaped, water cooled rotating diamond to remove the cementum. The teeth were then isolated with rubber dam, irrigated with saline and the root surfaces allowed to dry for 2 min assisted by a gentle stream of air. Following removal of the rubber dam, the periosteum was fenestrated at the base of the buccal and lingual flaps, and the flaps were replaced to a position' 1-2 mm coronal to the cemento-enamel junction. Interdentally, single interrupted sutures were used, whereas the mesial and distal extensions of the wound were closed with vertical mattress sutures. Care was taken to proximate the connective tissue surfaces of the buccal and lingual flap margins at wound closure. Sutures were removed ater 1 week. A broad spectrum antibiotic (Combiotic®, Pfizer Inc., New York, NY) was administered intramuscularly daily during the first 2 weeks following surgery. For the remaining 2
Fig. 1. The mandibular premolar teeth (P2, P3 and P4) (A), after surgical reduction of the bone and root preparation (B), following wound closure and suturing (C) and following 4 weeks of wound healing (D).
weeks of healing, daily plaque control was maintained by gently wiping the teeth with gauze soaked in a 2% chlorhexidine solution (Hibitane®, ICI Ltd, Macclesfield, Great Britain).
Histoiogicai procedures
The dogs were sacrificed 4 weeks after surgery by intravenous injection of concentrated sodium pentobarbital. Tissue
Periodontal repair in dogs blocks including teeth, bone, and soft tissues were removed. The blocks were fixed in 10% buffered formalin, decalcified in 10% formic acid, trimmed, dehydrated and embedded in paraffin. Serial sections, 7 /mi thick, were cut in a bucco-lingual direction throughout the entire mesio-distal extension of the teeth. Every 14th section was stained with Masson's trichrome and the adjacent section with hematoxylin and eosin allowing for observations at an interval of approximately 100 //m. The most centrally located stained section of the mesial and the distal root of each tooth was identified by the size of the pulp chamber and the root canal. This section and the 2 step serial sections on either side stained with Masson's trichrome were subjected to histometric analysis. Extent of new cementum formation was additionally confirmed in adjacent hematoxylin and eosin stained sections. Consequently, 5 subsequent step serial sections, representing approximately 0.4 mm of the mid-portion from both the mesial and distal roots of each tooth, were used for analysis. Measurements were performed using a microscope connected to a measuring system for computer aided manual data collection of geometrical
structures (Videoplan, Carl Zeiss Inc., Kontron, Eching bei Miinchen, West Germany). The quahty of the histotechnical preparation did not allow meaningful data collection from 4 tooth surfaces in 2 teeth, each from a separate dog. The following measurements were taken for the buccal and lingual surfaces of each root (Fig. 2). ^ • Defect height: the distance between the apical extension of the root planing and the cemento-enamel junction. Junctional epithelium: the distance from the apical to the coronal extension of the junctional epithelium along the root surface. Connective tissue repair: the distance between the apical extension of the root planing and the apical termination of the junctional epithelium. Cementum formation: the distance between the apical extension of the root planing and the coronal extension of a continuous layer of cementum or a cementum-like deposit on the root surface. Bone formation: the distance between the apical extension of the root planing and the coronal extension of newly formed alveolar bone along the root surface. Root resorption: the combined linear heights of distinct resorption lacunae along the root surface. Ankylosis: the combined linear heights of an ankylotic union of newly formed alveolar bone and the root surface. Data analysis
Fig. 2. Histometric parameters and landmarks in bucco-lingual sections. (CEJ) cemento-enamel junction, (JE) junctional epithelium, (RR) root resorption, (NAB) new alveolar bone, (NC) new cementum/cementum-like deposit, (ARP) apical extension of root planing.
Means and ranges for each of the measured parameters were calculated per surface, tooth and dog. In addition, root resorption and ankylosis were dichotomously scored and recorded as present if observed in 1 or more of the 5 sections for each root surface. ANOVA (SPSS-X, SPSS Inc., Chicago, IL) was used to analyze homogeneity of the healing dentin-connective tissue interface (connective tissue repair, cementum and bone formation and root resorption) between dogs, tooth types and tooth surfaces using defect height as a covariate. Results Clinical and histological observations
During the 1-month postoperative interval, a slight recession of the gingival
51
margin from its position at wound closure was generally observed. At sacrifice, the gingival margin was usually located approximately at the cementoenamel junction (Fig. 1). The light microscopic observations revealed that most of the surgically denuded root surface healed with connective tissue interfacing the dentin (Fig. A thin layer of a cementum-like deposit was observed extending coronally from the old cementum at the base of the wound in most specimens (Figs. 3, 4). However, the extent of this cementum varied and it could not be detected in some root surfaces, while in others the deposit covered a major part of the root surface. New cementum was mostly found on root surfaces unaffected by resorption, but on occasion this could also be seen lining lacunar bays indicative of prior resorptive activity (Figs. 5, 6). In some cases, isolated islands of cementum-like tissue were observed in the coronal aspect of the root without any apparent continuity with more apical deposits, or without continuity with the old cementum at the base of the wound. In particular, such isolated cementum was observed lining root resorption bays immediately apical to the junctional epithelium (Fig. 6). In areas void of cementum, a connective tissue of variable cell density interfaced directly with the root surface (Figs. 3, 5, 6). Regeneration of alveolar bone from the base of the wound was limited (Fig. 3). With few exceptions, the new bone formation along the root surface did not extend more coronally than the cementum formation. Almost all teeth exhibited root resorption (Figs. 3-6). Resorption lacunae of various dimensions could be observed throughout the dentin-connective tissue interface (Fig. 5). More prominent resorption bays were frequently observed immediately apical to the junctional epithelium (Figs. 3, 4, 6). Multinucleated cells were infrequent occupants of the resorption areas (Figs. 4, 5). Ankylosis was observed in approximately !^ of the teeth (Figs. 4,5). An ankylotic union between the root surface and newly formed alveolar bone was often associated with areas of root resorption and/or a cementum-like deposit (Figs. 4,5). In the latter case, the alveolar bone fused with the new cementum into one entity having similar structural and staining characteristics (Fig. 4).
52
Wikesjo & Nilveus Histometric observations
Mean connective tissue repair of the periodontal defects amounted to 4.6 mm, or 90% of the total defect height (Table 1, Fig. 7). The residual part of the involved root surface interfaced a junctional epithelium (8%) or was exposed to the oral cavity (2%). Although the connective tissue repair ranged from 100% to 2 1 % of the defect height, approximately 90% of the examined root surfaces presented with connective tissue repair amounting to 70% or more. ; There were no differences in relative amount of connective tissue repair between the 3 teeth (P2, P3 and P4) or between their buccal and lingual aspects (Table 2). Similarly, initial defect height did not influence the relative amount of connective tissue repair (Table 3). New cementum in continuity with root cementum at the base of the wound extended to 30% of the defect height (Table 1, Fig. 7). The extent of cementum formation did not appear to correlate with the total amount of connective tissue repair obtained (Table 4). Mean regeneration of alveolar bone amounted to 19% of the defect height (Table 1, Fig. 7). Similar to cementum formation, the extent of bone regeneration was limited and independent of the total amount of connective tissue repair obtained (Table 4). 93% of the tooth surfaces exhibited signs of past or present root resorption (Table 5). The incidence of root resorption was 70% in the coronal % and 56% in each of the mid and apical % of the defect. Mean linear root resorption amountd to 20% of the total defectheight with a mean distribution of 10, 5 and 5% of the defect height for the coronal, mid and apical % of the surgically denuded root surface. An ankylotic union between root dentin and newly formed alveolar bone Table 1. Periodontal repair of circumferential horizontal periodontal defects following replacement of mucoperiosteal flaps to slightly above the cemento-enamel junction; means ±s.d. (mm), A''=13 dogs . 3. Bucco-lingual section with complete connective tissue repair to the root surface. The defect height approximates 5 mm from the cemento-enamel junction to the apical extension of the root planing. (1) commonly found root resorption at the cemento-enamel junction, (2) connective tissue repair without new cementum formation on the root surface and (3) frequently observed limited formation of new cementum and new alveolar bone at the apical extension of the periodontal wound.
defect height junctional epithelium connective tissue repair cementum formation bone formation root resorption ankylosis
5.1+0.5 0.4 + 0.4 4.6 + 0.5 1.4+1.3 0.9 + 0.6 1.1+0.6 0.1+0.2
Periodontal repair in dogs
Fig. 4. Bucco-lingual section with complete connective tissue repair to the root surface. Total defect height was approximately 5 mm: (1) root resorption apical to the cemento-enamel junction with rarely encountered multinucleated giant cells (arrow heads); (2) area of connective tissue repair with a cementum-like deposit on the root surface; (3) the cemen- I tum deposit merges with the alveolar ^ bone into an ankylotic union (ANK), artifactual separation (AS); (4) more apical aspect with a thin layer of new cementum: (5) healing at the apical extension of the defect: note how the new cementum/cementum-like deposit merges with the old cementum.
ARP
53
54
Wikesjo & Nilveus
was observed in 11 % of the root surfaces and occurred primarly in the mid % of the defect (Table 5). Analysis of variance disclosed significant variability between dogs for connective tissue repair, cementum and bone formation and root resorption
(/7< 0.001). Additionally, bone formation exhibited significant tooth (p
