Autogenous dentin graft versus alloplastic graft combined with socket shield for pre-implant socket preservation: a split-mouth randomized clinical trial

After tooth extraction, alveolar bone resorption and labial bone plate thinning occur due to the lack of periodontal ligaments. The socket shield method was developed to preserve the alveolar ridge. A split-mouth study was performed in which eight patients were treated using alloplast with socket shield on one side (alloplast group, control) and autogenous dentin graft with socket shield on the contralateral side (dentin group, test). After 3 months, a trephine bone core was collected from all sites and evaluated by histological, histomorphometric, and radiographic analysis. Thin bony trabeculae were formed surrounding the residual alloplast, while thicker trabeculae of bone formed and fused to the autogenous dentin. The percentage of newly formed bone was significantly higher in the dentin group when compared to the alloplast group (P = 0.020). Radiographically, there was no significant difference in the mean percentage increase in bone density from preoperative to post-grafting between the two groups. Moreover, when comparing the change in labial bone level from preoperative to 3 months post-grafting between the two groups, there was no significant difference. The autogenous dentin graft combined with socket shield could be a promising technique for socket preservation.

Extracellular Matrix Induces Periodontal Ligament Reconstruction In Vivo

One of the problems in dental implant treatment is the lack of periodontal ligament (PDL), which supports teeth, prevents infection, and transduces sensations such as chewiness. The objective of the present study was to develop a decellularized PDL for supporting an artificial tooth. To this end, we prepared mouse decellularized mandible bone with a PDL matrix by high hydrostatic pressure and DNase and detergent treatments and evaluated its reconstruction in vivo. After tooth extraction, the decellularized mandible bone with PDL matrix was implanted under the subrenal capsule in rat and observed that host cells migrated into the matrix and oriented along the PDL collagen fibers. The extracted decellularized tooth and de- and re-calcified teeth, which was used as an artificial tooth model, were re-inserted into the decellularized mandible bone and implanted under the subrenal capsule in rat. The reconstructed PDL matrix for the extracted decellularized tooth resembled the decellularized mandible bone without tooth extraction. This demonstrates that decellularized PDL matrix can reconstruct PDL tissue by controlling host cell migration, which could serve as a novel periodontal treatment approach.

Histological evaluation of periodontal ligament in human after orthodontic treatment with piezosurgery and monolateral tooth dislocation and ligament distraction technique: a first morphologic and histologic evaluation

Traditional orthodontic tooth movement is based on the concept that application of a protracted force causes alveolar bone remodelling and adaptive changes in periodontal and dental tissues. Thus, if orthodontic tooth movement is described as a biological bone reaction to orthodontic forces mediated by the periodontal ligament (PDL), this event involves a series of sophisticated signal transduction processes that allows the PDL compression with specific histologic and biomolecular modifications. However, the preservation of the integrity of the PDL is generally difficult to achieve when it is associated with a long duration of orthodontic treatment. A total of 20 Caucasian patients with different dental-skeletal were treated using the Monocortical Tooth Dislocation and Ligament Distraction (MTDLD) technique with Piezosurgery associated with morphologic and histological evaluation of the PDL. The histological results obtained, confirm a good clinical outcome with an improvement of the speed on orthodontic treatment without any signs of tissue injury of PDL fiber without areas of hyalinization. The data suggests that MTDLD with Piezosurgery seems to be a valid alternative to the traditional orthodontic movement in adult patients preserving the anatomy and the integrity of PDL.

[Different ways to remove necrotic periodontal ligament on delayed tooth replantation: scanning electron microscopy and histomorphometric analysis]

PURPOSE

To seek the most effective technique for removal of root-adhered periodontal ligament.

METHODS

Thirty-five roots of healthy right mandibular first premolars extracted for orthodontic purposes were selected. After extraction, the teeth were kept dry at room temperature for at least 1 h, and then divided into five groups as follows: Group 1(control)-the root-adhered periodontal ligament was preserved; Group 2 (mechanical removal)-periodontal ligament remnants were removed by scraping root surface with a scalpel blade; Group 3 (chemical removal 1)-removal of the periodontal ligament by immersing the root in 1% sodium hypochlorite solution for 5 minutes; Group 4 (chemical removal 2)-removal of the periodontal ligament by immersing the root in 2% sodium hypochlorite solution for 5 minutes; Group 5 (chemical removal 3)-removal of the periodontal ligament by immersing the root in 1% sodium hypochlorite solution for 10 minutes. The specimens were analyzed histomorphometrically and examined under scanning electron microscopy. Both periodontal ligament remnants and preservation or removal of the cementum layer concomitantly with these procedures were assessed. The data were analyzed using one-way ANOVA and Tukey's test with SAS 8.02 software package.

RESULTS

In regard to periodontal ligament remnants, group 1 presented the largest areas(P<0.05), group 2 showed smaller area than group 1 (P<0.05), but much larger than group 3-5 (P<0.05); The three chemical removal groups had no significant difference. As for preserved cementum layer, group 2 lost most areas, which showed the worst result(P<0.05). The other 4 groups had no significant difference.

CONCLUSIONS

Scraping root surface with a scalpel blade could not wipe off the root-adhered periodontal ligament, and might damage the cementum layer. Sodium hypochlorite solution could clean up the periodontal ligament remnants and preserve cementum layer, which might be an ideal choice.

A Biofilm Pocket Model to Evaluate Different Non-Surgical Periodontal Treatment Modalities in Terms of Biofilm Removal and Reformation, Surface Alterations and Attachment of Periodontal Ligament Fibroblasts

BACKGROUND AND AIM

There is a lack of suitable in vitro models to evaluate various treatment modalities intending to remove subgingival bacterial biofilm. Consequently, the aims of this in vitro-study were: a) to establish a pocket model enabling mechanical removal of biofilm and b) to evaluate repeated non-surgical periodontal treatment with respect to biofilm removal and reformation, surface alterations, tooth hard-substance-loss, and attachment of periodontal ligament (PDL) fibroblasts.

MATERIAL AND METHODS

Standardized human dentin specimens were colonized by multi-species biofilms for 3.5 days and subsequently placed into artificially created pockets. Non-surgical periodontal treatment was performed as follows: a) hand-instrumentation with curettes (CUR), b) ultrasonication (US), c) subgingival air-polishing using erythritol (EAP) and d) subgingival air-polishing using erythritol combined with chlorhexidine digluconate (EAP-CHX). The reduction and recolonization of bacterial counts, surface roughness (Ra and Rz), the caused tooth substance-loss (thickness) as well as the attachment of PDL fibroblasts were evaluated and statistically analyzed by means of ANOVA with Post-Hoc LSD.

RESULTS

After 5 treatments, bacterial reduction in biofilms was highest when applying EAP-CHX (4 log10). The lowest reduction was found after CUR (2 log10). Additionally, substance-loss was the highest when using CUR (128±40 µm) in comparison with US (14±12 µm), EAP (6±7 µm) and EAP-CHX (11±10) µm). Surface was roughened when using CUR and US. Surfaces exposed to US and to EAP attracted the highest numbers of PDL fibroblasts.

CONCLUSION

The established biofilm model simulating a periodontal pocket combined with interchangeable placements of test specimens with multi-species biofilms enables the evaluation of different non-surgical treatment modalities on biofilm removal and surface alterations. Compared to hand instrumentation the application of ultrasonication and of air-polishing with erythritol prevents from substance-loss and results in a smooth surface with nearly no residual biofilm that promotes the reattachment of PDL fibroblasts.

Effects of Activin A on the phenotypic properties of human periodontal ligament cells

Periodontal ligament (PDL) tissue plays an important role in tooth preservation by structurally maintaining the connection between the tooth root and the bone. The mechanisms involved in the healing and regeneration of damaged PDL tissue, caused by bacterial infection, caries and trauma, have been explored. Accumulating evidence suggests that Activin A, a member of the transforming growth factor-β (TGF-β) superfamily and a dimer of inhibinβa, contributes to tissue healing through cell proliferation, migration, and differentiation of various target cells. In bone, Activin A has been shown to exert an inhibitory effect on osteoblast maturation and mineralization. However, there have been no reports examining the expression and function of Activin A in human PDL cells (HPDLCs). Thus, we aimed to investigate the biological effects of Activin A on HPDLCs. Activin A was observed to be localized in HPDLCs and rat PDL tissue. When PDL tissue was surgically damaged, Activin A and IL-1β expression increased and the two proteins were shown to be co-localized around the lesion. HPDLCs treated with IL-1β or TNF-α also up-regulated the expression of the gene encoding inhibinβa. Activin A promoted chemotaxis, migration and proliferation of HPDLCs, and caused an increase in fibroblastic differentiation of these cells while down-regulating their osteoblastic differentiation. These osteoblastic inhibitory effects of Activin A, however, were only noted during the early phase of HPDLC osteoblastic differentiation, with later exposures having no effect on differentiation. Collectively, our results suggest that Activin A could be used as a therapeutic agent for healing and regenerating PDL tissue in response to disease, trauma or surgical reconstruction.

A novel porcine acellular dermal matrix scaffold used in periodontal regeneration

Regeneration of periodontal tissue is the most promising method for restoring periodontal structures. To find a suitable bioactive three-dimensional scaffold promoting cell proliferation and differentiation is critical in periodontal tissue engineering. The objective of this study was to evaluate the biocompatibility of a novel porcine acellular dermal matrix as periodontal tissue scaffolds both in vitro and in vivo. The scaffolds in this study were purified porcine acellular dermal matrix (PADM) and hydroxyapatite-treated PADM (HA-PADM). The biodegradation patterns of the scaffolds were evaluated in vitro. The biocompatibility of the scaffolds in vivo was assessed by implanting them into the sacrospinal muscle of 20 New Zealand white rabbits. The hPDL cells were cultured with PADM or HA-PADM scaffolds for 3, 7, 14, 21 and 28 days. Cell viability assay, scanning electron microscopy (SEM), hematoxylin and eosin (H&E) staining, immunohistochemistry and confocal microscopy were used to evaluate the biocompatibility of the scaffolds. In vitro, both PADM and HA-PADM scaffolds displayed appropriate biodegradation pattern, and also, demonstrated favorable tissue compatibility without tissue necrosis, fibrosis and other abnormal response. The absorbance readings of the WST-1 assay were increased with the time course, suggesting the cell proliferation in the scaffolds. The hPDL cells attaching, spreading and morphology on the surface of the scaffold were visualized by SEM, H&E staining, immnuohistochemistry and confocal microscopy, demonstrated that hPDL cells were able to grow into the HA-PADM scaffolds and the amount of cells were growing up in the course of time. This study proved that HA-PADM scaffold had good biocompatibility in animals in vivo and appropriate biodegrading characteristics in vitro. The hPDL cells were able to proliferate and migrate into the scaffold. These observations may suggest that HA-PADM scaffold is a potential cell carrier for periodontal tissue regeneration.

Implementation and validation of an extraction course using mannequin models for undergraduate dental students

OBJECTIVE

There is a gap in the education of dental undergraduate students between theoretical knowledge and the practical procedure of tooth extraction. It was the aim of this study to implement and validate an undergraduate course for oral extraction using mannequin models, in order to enhance practical competence in this field of dentistry.

MATERIAL AND METHODS

A one-term oral extraction course was implemented as part of the oral surgery curriculum for undergraduate dental students, including 4 h of theoretical education, followed by 4 h of practical training in tooth extraction on mannequin models, with the students divided into small groups. Forty-nine students attending this extraction course were asked to validate their training in dental extraction using a questionnaire (TRIL-mod; University of Trier, Trier, Germany). The students' practical competence in oral extraction was assessed by a senior supervisor at the end of the course, using a standardized checklist.

RESULTS

All questionnaires were returned. Overall, the course was rated with an average score of 4.7 (rating range: 1-6; 1 = worst/6 = best). The assessment of practical skills yielded a successful and complete performance of tooth extraction by 94% of the students.

CONCLUSIONS

A tooth extraction course using a mannequin model is appreciated by dental students and can achieve a sufficient level of competence in tooth extraction with reasonable educational efforts.

Atraumatic tooth extraction and immediate implant placement with Piezosurgery: evaluation of 40 sites after at least 1 year of loading

This paper presents ultrasonic surgery (ie, Piezosurgery) as a new, relevant, and predictable method for performing atraumatic tooth extraction and subsequent implant site preparation. Forty noninfected teeth or roots were extracted in 23 patients and replaced immediately with implants. Extraction consisted of cutting the fibers of the periodontal ligament with vibrating tips of up to 10 mm in depth; the teeth or roots were mobilized afterward with an elevator. All teeth/roots were removed without fracture. Implant osteotomies were performed using conical tips of increasing diameters. During implant placement, notching of the apical third of the palatal wall or the interradicular bridge was performed without complication due to uncontrolled movements of the instrument. After a mean healing period of 2.4 months, all implants were osseointegrated and have been successfully loaded for at least 12 months. By implementing Piezosurgery, extraction can be atraumatic and implant placement can be predictable and undemanding compared to the use of burs, which can lead to instruments slipping during the procedure.

Clinical investigation of periodontal ligament distraction osteogenesis for rapid orthodontic canine retraction

AIMS

To investigate rapid canine distalisation by periodontal ligament distraction and to determine the effects of periodontal ligament distraction on the canine root and pulpal vitality.

METHODS

The sample consisted of 16 upper canines in eight patients who required first premolar extractions. The upper first premolars were extracted and the interseptal bone distal to each canine was thinned and undermined surgically. Custom-built distractors were placed and activated immediately to distract the canines into the extraction spaces. Radiographs were taken before canine distraction and at regular intervals thereafter. The upper canine pulps were tested with an electronic pulp tester before and after the distraction and the canines were examined on the post-distraction radiographs for evidence of apical and lateral root resorption.

RESULTS

The canines were retracted to proximal contact with the second premolars in 20.33 +/- 1.87 days. The average amount of retraction was 5.25 mm and the canines tipped distally 15.33 degrees. Although the upper molars did not move mesially, they extruded almost 1 mm. Root resorption was minimal and there was no deterioration in pulp vitality.

CONCLUSION

Canines can be rapidly retracted by periodontal ligament distraction without complications. However, the efficacy of the method depends upon the surgical procedure, which is technique sensitive. Resistance offered by the interseptal bone distal to the apex of the canine was thought to be the reason for the canine tipping during distraction.

Cementogenesis examined from the viewpoint of microcirculation

The purpose of this study was to perform a three-dimensional observation, via microvascular corrosion casts, of the microcirculation system during deposition of cementum after flap surgery and to investigate the permeable structure of the vascular endothelium. Two stages of wound healing after flap surgery were confirmed based on successive vascular changes. The transition between these stages occurred 3 weeks after surgery, at which time new blood vessels disappeared and an early stage of accumulation of new cementum was apparent. Hence, fibrous repair occurred during the first stage, and repair of hard tissue (ie, formation of cementum) occurred during the second stage. These findings suggest that metabolic activity in cementogenesis is low, based on the condition of the blood vessels, and therefore new cementum is not easily formed.

Vertical periodontal ligament distraction--a new method for aligning ankylosed and displaced canines

OBJECTIVE

In the course of a clinical pilot study we tested the vertical periodontal ligament (V-PDL) distraction as a means of aligning ankylosed upper canines. The objective of this study was to analyze the appropriateness und effectiveness of this method.

METHOD AND MATERIALS

The ankylosed upper canines of five female patients aged between 16 und 19 years were surgically exposed, luxated, and after a latency period of 5 to 7 days, distracted at a rate of 0.5 mm per day. The installed distractors were borne by the periodontal-mucosa, the periodontal-mucosa and the bone, or by the bone exclusively. We evaluated the distraction distance and time and degree of hard and soft tissue generation present in the region surrounding the distracted teeth.

RESULTS

All canines were aligned after a mean distraction period of 43.2 days (+/- 3.6 days). The mean distraction distance was 10.8 mm. Three canines had defects at the cemento-enamel junction, and one canine had to be extracted due to a large defect at the root.

CONCLUSIONS

Vertical PDL distraction is a minimally-invasive therapy to align ankylosed impacted canines. Even if the long-term prognosis of distracted canines with defects is uncertain, the patient benefits from the vertical PDL distraction because both hard and soft tissues are generated in the vicinity of the distracted canine.

[Rapid canine distalization through distraction of the periodontal ligament after reducing interseptal bone resistance]

OBJECTIVE

To investigate the effect of rapid canine distalization through distraction of the periodontal ligament after reducing interseptal bone resistance.

METHODS

Twenty canines in 11 patients who needed first premolar extractions were involved. A tooth-borne, custom-made distractor was bonded right after the first premolar extraction and the interseptal bone resistance reduction. Three days post-operatively, the distractor was activated 0.1 mm three times a day. Orthodontic models, panoramic radiographs, periapical radiographs, electrical vitality test were assessed pre- and post distraction procedure and 3 months after the completion of the procedure.

RESULTS

The distraction procedure was completed in 18 to 35 days [mean (25.6 +/- 4.7) days], with the distal displacement of the canines ranging from 3.53 to 8.29 mm [mean (5.56 +/- 1.32) mm]. The canines showed a mean of 12.20 degrees distal tipping and 18.53 degrees rotation. The anchorage teeth showed an average of (0.76 +/- 0.75) mm mesial movement. The mesial contact point of incisors showed a mean of (0.67 +/- 0.55) mm lingual movement. There was no significant root resorption or long-time change on pulp vitality after distraction.

CONCLUSIONS

The canine distalization through distraction of the periodontal ligament after reducing interseptal bone resistance was an effective approach to move canines rapidly.

Rapid tooth movement through distraction osteogenesis of the periodontal ligament in dogs

BACKGROUND

Animal models are needed for the study of rapid tooth movement into the extraction socket through distraction osteogenesis of the periodontal ligament.

METHODS

Modified distraction devices were placed on eight dogs between the first and third mandibular premolars on the left sides; similar placement of traditional straight wise appliances on the right sides served as the control. The experimental distractors were activated (0.25 mm/d) twice a day and the control devices were activated (100 g) for two weeks with consolidation periods at weeks two, three, six, and ten. Two dogs were sacrificed at each consolidation time point; rates and patterns of tooth movement, loss of anchorage, and periapical films were evaluated, and the affected premolars and surrounding periodontal tissues were decalcified and examined histologically. General observations, X-ray periapical filming and histology examination were performed.

RESULTS

Distal movement ((3.66+/-0.14) mm) measured two weeks after modified distraction exceeded that achieved using the traditional device ((1.15+/-0.21) mm; P<0.05). Loss of anchorage was minimally averaged (0.34+/-0.06) mm and (0.32+/-0.07) mm in the experimental and control sides, respectively. By radiography, apical and lateral surface root resorptions on both sides were minimal. Alveolar bone lesions were never evident. Fibroblasts were enriched in periodontal ligaments and bone spicules formed actively along directions of distraction.

CONCLUSIONS

The canine model is suitable for the study of rapid tooth movement through distraction osteogenesis of the periodontal ligament. The technique accelerates tooth movement, periodontal remodeling, alveolar bone absorption, and may induce fibroblast formation, as compared to the traditional orthodontic method, without adversely affecting root absorption, bone loss, tooth mobility and anchorage loss.

Florid cemento-osseous dysplasia: a report of three cases

Florid cemento-osseous dysplasia (FCOD) is a non-neoplastic condition of the jaws that is not associated with inflammation of the pulp or periodontal tissue. This article reports on three cases that were diagnosed as FCOD, demonstrating the importance of both clinical and radiographic diagnosis and the clinical management of these lesions.

Remodeling of alveolar bone crest after molar intrusion with skeletal anchorage system in dogs

INTRODUCTION

The aim of this study was to clarify the influence of supra-alveolar fibers on alveolar bone crest remodeling when several teeth are intruded simultaneously.

METHODS

The skeletal anchorage system was used to bilaterally intrude the second and third premolars of 10 beagles; supracrestal fiberotomies were performed on 1 side only.

RESULTS

The amount of intrusion was greater and the amount of alveolar bone resorption was smaller in the fiberotomy group compared with the nonfiberotomy group. The health status (pocket depth <3 mm) of the dentogingival unit was maintained in the nonfiberotomy group during the experimental period. In the fiberotomy group, the number of osteoclasts on the marginal alveolar crest was less than in the nonfiberotomy group. The dense fiber bundles connecting the second and third premolars and the gingival attachments were maintained in the nonfiberotomy group.

CONCLUSIONS

Pressure from the supra-alveolar fibers generated by segmental molar intrusion with the skeletal anchorage system induced alveolar bone crest resorption and remodeling, and, as a result, it prevented deepening of the gingival pocket. Periodontal status was good during tooth intrusion.

Transplantation of mesenchymal stem cells is an optimal approach for plastic surgery

Mesenchymal stem cells (MSCs) are able to differentiate into a variety of cell types, offering promising approaches for stem cell-mediated tissue regeneration. Here, we explored the potential of utilizing MSCs to reconstruct orofacial tissue, thereby altering the orofacial appearance. We demonstrated that bone marrow MSCs were capable of generating bone structures and bone-associated marrow elements on the surfaces of the orofacial bone. This resulted in significant recontouring of the facial appearance in mouse and swine. Notably, the newly formed bone and associated marrow tissues integrated with the surfaces of the recipient bones and re-established a functional bone marrow organ-like system. These data suggested that MSC-mediated tissue regeneration led to a body structure extension, with the re-establishment of all functional components necessary for maintaining the bone and associated marrow organ. In addition, we found that the subcutaneous transplantation of another population of MSCs, the human periodontal ligament stem cells (PDLSCs), could form substantial amounts of collagen fibers and improve facial wrinkles in mouse. By contrast, bone marrow MSCs failed to survive at 8 weeks post-transplantation under the conditions used for the PDLSC transplantation. This study suggested that the mutual interactions between donor MSCs and recipient microenvironment determine long-term outcome of the functional tissue regeneration. Disclosure of potential conflicts of interest is found at the end of this article.

Nonsurgical treatment with rapid mandibular canine retraction via periodontal ligament distraction in an adult with a Class III malocclusion

A woman with a Class III malocclusion was a poor candidate for orthognathic surgery. An orthodontic treatment plan was developed that incorporated a relatively new and rapid process of canine distraction. The mandibular first premolars were extracted, correcting the anterior crossbite, the Class III canine relationship, and the Class III facial appearance. The canines were distracted, through the periodontal ligament, into the extraction sites. Dental distraction is a breakthrough for orthodontics, especially for adults with critical anchorage requirements.

Surgical extrusion technique for clinical crown lengthening: report of three cases

Although a number of techniques have been proposed for clinical crown lengthening procedures, all have some limitation in terms of function and esthetics. This report presents the clinical and radiographic results of a surgical extrusion technique for clinical crown lengthening. Atraumatic surgical extrusion using a specially designed instrument (Periotome) was performed in three cases in which it was expected that extensive resective osseous surgery would have to be used for crown lengthening. Full-thickness mucoperiosteal flaps were raised both labially and palatally. The tooth was carefully luxated and extruded to the desired position without damaging the marginal bone area or root apex. No rigid splint was applied. Clinical examinations performed for more than 1 year after surgery revealed probing depths < or = 3 mm around the teeth at all sites, without bleeding on probing. The teeth functioned normally, with near-normal mobility. Radiographs showed normal periodontal contour consistent with new bone formation in the periapical area. Radiographic analysis did not show any evidence of root or crestal bone resorption or endodontic problems. The technique presented could constitute an alternative surgical approach to performing crown lengthening; it does not induce functional or esthetic deformities, especially in the anterior region.

Prognostic factors for alveolar regeneration: osteogenic potential of resident bone

OBJECTIVES

There is a limited understanding of the role of resident bone in periodontal regeneration. The objective of this study was to evaluate the influence of the resident alveolar bone on bone regeneration in conjunction with guided tissue regeneration (GTR) in the presence or the absence of cell occlusivity.

METHODS

Critical-size, 6-mm, supra-alveolar periodontal defects were created in six young adult Beagle dogs. Space-providing, occlusive or porous expanded polytetrafluaroethylene devices were implanted to provide for GTR. Treatments were alternated between left and right jaw quadrants in subsequent animals. The gingival flaps were advanced for primary intention healing. The animals were euthanized at week 8 postsurgery. The histometric analysis assessed regeneration of alveolar bone relative to space-provision by the GTR device and width of the alveolar crest at the base of the defect.

RESULTS

There were no significant differences in mean alveolar regeneration between sites receiving the porous GTR device with a narrow versus a wide alveolar ridge after adjusting for wound area (2.22 versus 2.50 mm, respectively; p=0.36). In contrast, analysis using sites receiving the occlusive GTR device revealed significantly greater bone regeneration at sites with a wide compared with a narrow alveolar ridge (3.34 versus 2.53 mm, respectively; p=0.02). Regression analysis showed a significant relationship (p< or =0.05) between space-provision and bone regeneration for all groups except for sites with a wide alveolar ridge receiving the occlusive GTR device (p=0.5).

CONCLUSIONS

The resident alveolar bone may significantly influence the magnitude of alveolar bone regeneration. The relative presence of cells from the gingival connective tissue may attenuate this effect.

Susceptibility of GTR-regenerated periodontal attachment to ligature-induced periodontitis. An experiment in the monkey

AIM

This study aimed to compare the susceptibility of guided tissue regeneration (GTR)-regenerated periodontal attachment to ligature-induced periodontitis with that of the pristine periodontium.

METHODS

Periodontal breakdown was produced in four monkeys by the placement of orthodontic elastics around experimental teeth (test teeth). During a flap operation, the root surfaces were scaled and planed, and a notch indicating the apical termination of scaling and root planing was made in the root surface. Following resection of the crowns and endodontic treatment, an e-PTFE membrane was adapted over the roots. Subsequently, the flaps were sutured to complete closure of the wound (submerged). At membrane removal after 5 weeks, the crowns of the contralateral teeth serving as controls were resected, and the roots treated endodontically during a flap operation. Artificial composite crowns were then placed on both test and control roots. After 3 months of tooth cleaning, cotton floss ligatures were placed passively around both test and control teeth for a period of 6 months. Two weeks later the animals were sacrificed.

RESULTS

Histological analysis demonstrated that the instrumented root surfaces of the test teeth were covered by newly formed cementum of the reparative, cellular, extrinsic and intrinsic fiber type, while the cementum on the controls was mainly acellular extrinsic fiber cementum. Histometric assessments demonstrated that similar attachment loss had occurred on test (1.0+/-0.5 mm) and control roots (1.0+/-0.4 mm) during the 6 months of ligature-induced plaque accumulation.

CONCLUSION

The results indicate that teeth with a periodontal attachment apparatus formed by GTR is not more susceptible to periodontitis than those with a pristine periodontium.

Clinical evaluation of the Er:YAG laser in combination with an enamel matrix protein derivative for the treatment of intrabony periodontal defects: a pilot study

OBJECTIVES

The aim of the present study was to compare the combination therapy of deep intrabony periodontal defects using an Er:YAG laser (ERL) and enamel matrix protein derivative (EMD) to scaling and root planing+ ethylenediaminetetraacetic acid (EDTA)+EMD.

MATERIAL AND METHODS

Twenty-two patients with chronic periodontitis, each of whom displayed 1 intrabony defect, were randomly treated with access flap surgery and defect debridement with an Er:YAG (160 mJ/pulse, 10 Hz) plus EMD (test) or with access flap surgery followed by scaling and root planing (SRP) with hand instruments plus EDTA and EMD (control). The following clinical parameters were recorded at baseline and at 6 months: plaque index, gingival index, bleeding on probing (BOP), probing depth (PD), gingival recession, and clinical attachment level (CAL). No differences in any of the investigated parameters were observed at baseline between the two groups.

RESULTS

Healing was uneventful in all patients. At 6 months after therapy, the sites treated with ERL and EMD showed a reduction in mean PD from 8.6 +/- 1.2 mm to 4.6 +/- 0.8 mm and a change in mean CAL from 10.7 +/- 1.3 mm to 7.5 +/- 1.4 mm (p < 0.001). In the group treated with SRP+EDTA+EMD, the mean PD was reduced from 8.1 +/- 0.8 mm to 4.0 +/- 0.5 mm and the mean CAL changed from 10.4 +/- 1.1 mm to 7.1 +/- 1.2 mm (p < 0.001). No statistically significant differences in any of the investigated parameters were observed between the test and control group.

CONCLUSION

Within the limits of the present study, it may be concluded that both therapies led to short-term improvements of the investigated clinical parameters, and the combination of ERL and EMD does not seem to improve the clinical outcome of the therapy additionally compared to SRP+EDTA+EMD.

Healing of root resorption: a case report

External resorption is sequelae of necrotic periodontal membrane over a large area of root following an injury to the tooth. This usually occurs after severe dental injuries such as intrusion, severe luxations or exarticulation injuries complicated by a prolonged extra oral period. This case report presents a clinical and radiographic follow up (13 months) of treatment of inflammatory external root resorption on maxillary central incisor using Vitapex. Gradual healing of resorption was observed radiographically with no tenderness or pathological mobility.

Autogenous free tooth transplantation with a two-stage operation technique

If tooth transplantation is to succeed, it is crucial to preserve the vitality of the cells on the root surface of the tooth transplant. Insufficient postoperative nutrition to the cells on the root surface of the tooth transplant was thought to contribute to their devitalization of these cells. Impaired nutrition may be a result of poor contact between the recipient bed and the root surface of the transplanted tooth, and development of an interposed blood clot. To improve postoperative nutrition to the root surface cells, teeth were transplanted to the recipient beds in which the tissues were regenerated during a 14 day period, i.e., using the two-stage transplantation technique. In a clinical study of this technique, a total of 95 autogenous teeth with fully developed roots were transplanted in 84 patients, and examined both clinically and radiographically for up to 13 years after the transplantation. In a dog model, a comparative experimental study was made between teeth transplanted to beds left to heal for 5 days and teeth transplanted to beds prepared immediately before the transplantation. The clinical study showed a low prevalence of tooth graft loss and root resorption even when infection of the root canal occurred. Periodontal attachment loss of less than 3 mm was found in 97% of 6 defined surfaces around the transplanted teeth. Transplanted teeth which were later extracted were often hypermobile, and signalled pain when provoked with heavy loading. Excessive extraction trauma, fixation failure, and excessive plaque accumulation after transplantation were all shown to be detrimental to tooth transplant. Transplanted teeth were used as abutments for fixed partial dentures and provided the necessary dental support for crowns and bridges even in patients with atrophic alveolar bone. The experimental histological study showed no differences between test and control teeth in terms of the prevalence of root resorption, which was suspected to be caused by traumatic injuries to the roots during extraction and non-rigid fixation of the transplanted teeth.

Tensile strength, histological and immunohistochemical observations of periodontal wound healing in the dog

This study was designed to study wound strength at the dentine/connective tissue interface and at the bone/connective tissue interface following full thickness flap surgery. Flaps of uniform dimension were outlined in four young adult beagle dogs using a standardised double bladed knife and vertical incisions 10 mm apart, which extended 8 mm apical to the gingival margin. Bone was removed from half the sites (eight sites in each dog), giving 32 flaps replaced on dentine and 32 sites on bone. A tensile force was applied using a microprocessor force gauge at 1, 2, 3, 7, 10, 14, 21, and 28 days. Mean tensile strengths were markedly weaker for the dentine/flap interface. At 7 days the value for flaps to dentine was 1.82 N, in contrast to 5.08 N for flaps replaced on bone. Inflammatory cell counts tended to fall markedly at 3 days for both modalities, but were higher for the dentine/flap modality at all time points. Fibroblast density peaked at 7-14 days but did not vary with type of flap over the time points studied. The amounts of fibrin were greater for the dentine/flap interface at all time points but decreased for both flap types as time progressed. Collagen type V was localised to the basement membrane and blood vessels and tended to show more foci for flaps replaced on dentine. Procollagen levels showed little change over the healing interval for both flap/bone and flap/dentine interfaces. Type III collagen synthesis was at peak levels during the first week. These findings would support efforts to stabilise periodontal flaps at early time points, especially those on dentine.

Tooth auto-transplantation with double periodontal ligament stimulation to replace periodontally compromised teeth

BACKGROUND

The healing process of autotransplantation puts 2 different tissues in competition: the ligament on the root surface and the bone tissue of the alveolus. This study shows the effects of a protocol with 2 surgical stages, which promote ligament repair, inhibit adhesion between bone and dental root, and reduce the occurrence of the ankylosis-root resorption phenomenon.

METHODS

Forty-three patients, 33 to 73 years old, received 47 transplantations of mature teeth (including retained teeth) during a 5-year period. During the first surgical step, the transplanted tooth is extracted, measured, immediately replaced in its origin site, and maintained with an original suture technique. The alveolus to which the tooth will be transplanted is adapted after extraction of the periodontally compromised tooth. The second surgery occurs at day 14, when regeneration of periodontal ligament (PDL) is at a maximum (first stimulation). The tooth is transplanted in its new alveolus and retained using the same suture technique to avoid a rigid splint and to create mechanical stimulation of the PDL (second stimulation).

RESULTS

The results were 95.75% positive with normal PDL, with a 4.25% failure rate (transplant loss) and no ankylosis. Mean probing reduction was 8.37 +/- 3.0 mm. Mean radiographic bone gain was 7.73 +/- 4.32 mm.

CONCLUSIONS

This study suggests that auto-transplantation with double PDL stimulation can be a viable treatment in clinical practice, especially to replace teeth with large periodontal lesions, deep furcation defects, and/or root fractures. This study shows the high potential of stimulated PDL to regenerate alveolar bone and periodontal structures in severe destruction sites.

Surgical crown lengthening: a 12-month clinical wound healing study

BACKGROUND

Surgical crown lengthening has been proposed as a means of facilitating restorative procedures and preventing periodontal injuries in teeth with structurally inadequate clinical crowns or exposing tooth structure in the presence of deep, subgingival pathologies which may hamper the access for proper restorative measures. The few clinical studies in the current literature on postsurgical soft tissue modifications after crown lengthening procedures report conflicting results. The present study was designed to assess the alterations of the marginal periodontal tissues as an immediate outcome of surgical crown lengthening and over a 12-month healing period.

METHODS

The patient sample included 30 patients (84 teeth) who presented with various conditions hampering proper restorative measures in one or more teeth and, therefore, requiring surgical exposure of tooth substance. After initial supportive therapy, the patients were recalled for a baseline examination, and the following parameters were evaluated at interproximal and buccal/lingual sites of each experimental tooth: plaque index, gingival index, position of the gingival margin, probing depth, and attachment level. After baseline examination, the patients underwent apically positioned flap surgery with osseous and connective tissue attachment resection. During surgery, the amount of resection and the achieved lengthening of the clinical crown were evaluated. The patients were enrolled in a maintenance program including professional tooth cleaning every 2 to 4 weeks. The patients were reexamined 1, 3, 6, 9, and 12 months postoperatively.

RESULTS

1) Immediately after surgery, a significantly (P < 0.001) increased clinical crown length of 3.7 +/- 0.8 mm (mean) at interproximal and 4.1 +/- 0.9 mm (mean) at buccal/lingual sites was achieved; 2) healing resulted in a statistically significant coronal displacement of the gingival margin of 3.2 +/- 0.8 mm at interproximal (P < 0.001) and 2.9 +/- 0.6 mm at buccal/lingual (P < 0.002) sites; and 3) as a consequence of this postsurgical soft tissue regrowth, the amount of the available tooth structure immediately after surgery decreased to 0.5 +/- 0.6 mm at interproximal sites (P < 0.0015) and to 1.2 +/- 0.7 mm at buccal/lingual sites (P < 0.001) at the 12-month examination.

CONCLUSIONS

The results of the present clinical investigation demonstrated that during a 1-year period of healing following surgical crown lengthening, the marginal periodontal tissue showed a tendency to grow in a coronal direction from the level defined at surgery. This pattern of coronal displacement of the gingival margin was more pronounced (P < 0.001) in patients with "thick" tissue biotype and also appeared to be influenced by individual variations in the healing response (P < 0.001) not related to age or gender.

Gingivoperiosteoplasty in 3-to-5-year-old patients with cleft lip and palate: a preliminary communication

Closure of the alveolar cleft and the oronasal fistulas was achieved by gingivoperiosteoplasty in 26 patients with unilateral or bilateral cleft of the lip and palate. They were divided in two groups according to whether or not functional cheiloplasty was previously performed (group I comprised 12 patients, group II--14 patients). No systemic pre- or post-surgical orthodontic treatment was administered in both groups. The malocclusions before and after gingivoperiosteoplasty, the postoperative fistulas and the speech were evaluated. Prior to gingivoperiosteoplasty malocclusions were found in 16 children (4 in group I and 12 in group II). After gingivoperiosteoplasty better occlusion was achieved in 6 patients of group II and in 3 of group I. Malocclusions remained in 6 children of group II and in one of group I. Fistulas persisted in 3 children (group II--2, group 1--1). Rhinolalia was found in 7 children of group II and in none of group I. In conclusion, we think that gingivoperiosteoplasty can be performed successfully after eruption of the deciduous teeth, that is between 3 and 5 years of age. The quality of the cheiloplasty and palatoplasty performed prior to it is of great significance. Gingivoperiosteoplasty should be included as a separate surgical stage in the management of total cleft lip and palate.

[A comparative evaluation of the efficacy of the excisional new attachment procedure (ENAP) relative to root planing in the etiological phase of periodontal therapy]

BACKGROUND

In the present study, the effectiveness of root planing has been compared to the excisional new attachment procedure (ENAP) during the etiological phase of periodontal therapy, after the supragingival scaling, in order to establish if a technique offering an easy access to the subgingival areas could reduce the need for a surgical phase in the periodontal treatment.

METHODS

Twenty-seven patients, affected by moderate periodontitis, participated in this study; in each of them root planing was performed in a half of the oral cavity (control site) and the ENAP in the other half (test site). The main clinical parameters of periodontal health (probing depth--PD-, attachment loss--AL-, plaque index--PlI- and gingival index--GI-) were evaluated before and 1, 2 and 6 months after the periodontal treatment.

RESULTS

The results of the study showed that the parameters related with the amount of plaque and with the conditions of the marginal gingival tissue were not influenced by the different treatments used. Better improvements were found in PD and AL values in teeth treated by ENAP compared to those treated by root planing; this result is explained by a better access to the roots offered by the ENAP.

CONCLUSIONS

We can conclude that, within the limits of the present study, the ENAP can reduce the need for a further surgical treatment of the periodontal patient.

Treatment of Class II furcation lesions using an autogenous periosteal barrier

Over the last two decades, guided tissue regeneration has achieved significant advances in periodontal healing that confirm the efficacy of periodontal regeneration. Several types of barriers have been utilized to apply this principle to periodontal wound healing. The objective of this article is to review the literature and principles of guided periodontal tissue regeneration (GPTR) in the treatment of Class II furcation defects and to describe a surgical technique that utilizes the neighboring periosteum of the furcation lesion as a barrier for the clinical application of GPTR.

Rapid canine retraction through distraction of the periodontal ligament

The process of osteogenesis in the periodontal ligament during orthodontic tooth movement is similar to the osteogenesis in the midpalatal suture during rapid palatal expansion. A new concept of "distracting the periodontal ligament" is proposed to elicit rapid canine retraction in 3 weeks. It is called dental distraction. Fifteen orthodontic patients (26 canines, including 15 uppers and 11 lowers) who needed canine retraction and first premolar extraction were included. At the time of first premolar extraction, the interseptal bone distal to the canine was undermined with a bone bur, grooving vertically inside the extraction socket along the buccal and lingual sides and extending obliquely toward the socket base. Then, a tooth-borne, custom-made, intraoral distraction device was placed to distract the canine distally into the extraction space. It was activated 0.5 to 1.0 mm/day immediately after the extraction. The anchor units were the second premolar and first molar. Cephalometric and periapical x-rays were taken before and after the canine retraction. Both the upper and lower canines were distracted bodily 6.5 mm into the extraction space within 3 weeks. New alveolar bone was generated and remodeled rapidly in the mesial periodontal ligament of the canine during and after the distraction. It became mature and indistinguishable from the native alveolar bone 3 months after distraction. During the distraction, 73% of the first molars did not move mesially and 27% of them moved less than 0.5 mm mesially within 3 weeks. The radiographic examination revealed that apical or lateral surface root resorption of the canine was minimal. No periodontal defect or endodontic lesion was observed throughout and after distraction. We concluded that the periodontal ligament could be rapidly distracted without complications. The rapid orthodontic tooth movement through distracting the periodontal ligament cannot be emulated by current conventional orthodontic concepts and methods.

A protocol for maintaining or increasing the width of masticatory mucosa around submerged implants: a 1-year prospective study on 53 patients

Masticatory mucosa around implants may be useful to enhance esthetics and/or plaque control. This study proposes simplified guidelines for maintaining or obtaining a minimal amount of masticatory mucosa around submerged implants in cases of partial edentulism, and for keeping the need for additional surgery to a minimum. Free gingival grafts were used in the mandibular arch when the width of buccal masticatory mucosa was less than 2 mm. The width of masticatory mucosa expected to be available for attachment to the bone surface buccal to implants was estimated by measuring the distance between the emergence of the implant from bone and the mucogingival junction. When this distance was 3 mm or less, the use of an apically positioned flap for implant exposure was preferred over gingivectomy. The amount of masticatory mucosa buccal to implants was measured 2 weeks, 6 months, and 12 months after implant exposure. In no case was the width of masticatory mucosa less than 2 mm at 1 year. Therefore, this protocol is recommended for the treatment of cases where the presence of an adequate amount of masticatory mucosa is necessary to ensure a satisfying appearance or is useful for facilitating oral hygiene.

The circumferential supracrestal fiberotomy

This article addresses the advantages and shortcomings of circumferential supracrestal fiberotomy procedures from the pragmatic perspective of practicing clinicians. The first part of this article reviews the anatomy, surgical techniques, and timing of the procedure. The significance of individual techniques and studies are discussed.

Histologic evaluation of soft tissue attachment to CO2 laser-treated root surfaces: an in vivo study

There is little support in the dental literature to justify the use of lasers for periodontal root therapy. To the contrary, there are several in vitro studies suggesting potentially adverse effects when lasers are applied to root surfaces. The purpose of this study was to evaluate, in vivo, soft tissue attachment to root surfaces following CO2 laser irradiation. Using a four-quadrant design with one quadrant serving as an untreated control, the remaining quadrants in each of two dogs were treated by (1) scaling and root planing, (2) laser only, and (3) laser followed by scaling and root planing. Prior to the assigned treatments, the roots of three teeth in each quadrant (including the control) were exposed by flap reflection and ostectomy. After root therapy the flaps were repositioned and allowed to heal for 28 days. Clinical attachment levels were determined prior to surgery, at 28 days, and by histologic measurement. Results indicate that specimens treated with laser only lost attachment compared to controls and other treatment groups. Furthermore, there was no histologic evidence of soft tissue attachment to a laser-treated surface that featured a residual char layer.

Distraction osteogenesis to widen the mandible

The purpose of this investigation was to elucidate the biology of distraction osteogenesis during mandibular widening. Midsymphyseal vertical interdental osteotomies were performed in nine Macaca mulatta monkeys. After a latency period a tooth-borne appliance was activated at a rate of 0.5 mm twice a day for 7-10 days. The appliance was then stabilized for a period of 4 or 8 weeks. The distraction gap at the inferior portion of the symphysis was bridged completely by new bony trabeculae. Bone formation in the interdental area was apparently related to the surgical technique. Newly formed bony trabeculae were oriented parallel to the direction of distraction. The location of the osteotomy site with an adequate margin of alveolar bone contiguous with the adjacent teeth was necessary for the induction of the distraction osteogenesis. Disproportional movement between superior and inferior portions of the distracted segments was noted.

Cerebral abscess complicating dental treatment. Case report and review of the literature

A case history and brief literature review of cerebral abscess related to dental therapy is presented. The 19-year-old male patient presented with a cerebral abscess caused by Actinobacillus actinomycetamcomitans. He was otherwise healthy, and had a recent history of periodontal surgery prior to the onset of symptoms. The patient was treated successfully with stereotactic aspiration and antibiotics.

Collagen gel and membrane in guided tissue regeneration in periodontal fenestration defects in dogs

The effect of a collagen gel matrix as a submembranous space-maintaining material was evaluated in guided tissue regeneration procedures. In 4 dogs, contralateral surgical circular fenestration defects, 5 mm in diameter, were produced at the midbuccal aspect of the alveolar bone in 8 maxillary canines. Removal of bone, PDL and cementum was complete. Experimental sites were filled with collagen gel and covered with collagen membranes; control sites were covered with collagen membranes and the underlying space was spontaneously filled with blood. Mucogingival flaps were repositioned. Histological and histomorphometric observations, 6 weeks post-surgery, indicated that defects covered by collagen membranes presented the most impressive regeneration with almost complete coverage of the denuded root by new cementum (98.4%) and new bone (63.2%). In the experimental defects, 83.5% coverage of new cementum with only 21.9% new bone regeneration was observed. These results suggest that collagen gel, interfered with healing by PDL and bone-derived cells in the submembranous space.

The effect of post-surgical flap placement on probing depth and attachment level: a 2-year longitudinal study

Postsurgical flap placement might affect the outcome of the operative procedure. Modified Widman flap surgery with primary closure and flap approximation (usually away from the bone crest) and apically positioned flap surgery with near crestal bone positioning are both widely used in surgical periodontal treatment. Several comparative investigations have studied these modalities, however, none have been able to show conclusively that either is superior to the other. The purpose of this longitudinal study was to explore the optimal postsurgical flap placement in respect to final probing depth and changes in clinical attachment level. Following routine hygienic phase of treatment, 12 subjects (186 teeth) with adult periodontitis received surgical periodontal treatment. Prior to the flap surgery, probing depth and clinical attachment level were recorded. Sounding depth measurements were taken to record postoperative flap placement. Patients were placed on a 3-month maintenance program. Probing depth and clinical attachment level were again measured at 2 years postoperatively and compared to baseline measurements. An overall positive correlation (R = 0.43; P = 0.0248) was found between immediate postoperative sounding measurements and probing depth after 2 years. Conversely, attachment level changes over the 2-year period showed only weak inverse correlation (R = 0.27; P = 0.0121) with sounding depth measurement immediately postsurgically. Sites where postoperative sounding depth were < or = 3 mm had a mean probing depth (2.52 mm) which was significantly (P < 0.001) smaller compared to sites with sound depth > or = 4 mm (3.58 mm). Changes in clinical attachment level varied between sites and sounding depth groups; however, none of these differences were statistically significant. Based on our findings it is suggested that following periodontal flap surgery, in those cases where minimal probing depth is desired, the flap be secured to the underlying structures at or slightly coronally to the bone crest (< or = 3 mm).(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment of the palato-gingival groove with guided tissue regeneration. Report of 10 cases

The purpose of this study is to demonstrate the potential of using a barrier in the treatment of palato-gingival groove defects. The study group consisted of 10 patients. Prior to treatment, the palato-gingival groove on maxillary lateral incisors was measured with calibrated periodontal probe from the cemento-enamel junction (CEJ) to the free gingival margin (FGM) and from the FGM to the base of the pocket (BP). Probing depth (PD) was calculated and bleeding on probing indicated. Surgical procedures consisted of flap reflection, removal of granulation tissue, and scaling and root planning of the groove. An expanded polytetrafluoroethylene membrane was sutured over the palato-gingival groove. Six months postsurgery, all measurements were repeated. Statistical analysis compared results using means, standard deviations, and paired t tests. Results showed an improvement in clinical attachment gain, probing depth reduction, and decreased bleeding on probing. This study demonstrates the potential of guided tissue regeneration in the treatment of palato-gingival groove defects. A random blinded clinical trial is necessary, however, to fully assess the potential of this procedure in treatment of palato-gingival groove defects.

Histological evaluation of the effect of transseptal fibre resection on the rate of physiological migration of rat molar teeth

Twenty-seven female Sprague-Dawley rats were given lead acetate as a vital stain, and rates of alveolar bone formation, representative of drift, were measured histologically. Teeth around which the transseptal fibre system had been destroyed drifted less quickly on both functioning (p less than 0.01) and non-functioning (p less than 0.001) sides than those with intact transseptal fibres. Both horizontal and vertical components of physiological drift were equally affected by destruction of the transseptal fibre system. It was felt that the transseptal fibres probably exerted their primary effect on the tooth, with bone remodelling around the drifting tooth being affected secondarily.

Healing of sites within the dog periodontal ligament after application of cold to the periodontal attachment apparatus

The potential of periodontal ligament-derived tissues to regenerate periodontal attachment after cryosurgical trauma to the PDL in dogs was evaluated. The buccal alveolar plate of each canine tooth was exposed by a semi-lunar excision. A 3 mm thick cryoprobe, cooled to -81 degrees C, was placed on the bone 5 mm apical to the crest for 10 s. This induced cellular devitalization in the bone directly in contact with the probe and the PDL under it. The freezing-thawing cycle was repeated 3 times. Control sites were sham-operated at room temperature. Histologic sections from the center of the lesions were obtained from 1 h, 48 h and 30 d specimens. 1-h control and experimental histologic sections were similar. At 48 h post-surgery, the cellular component of the frozen PDL could not be identified and inflammatory response was minimal. The collagenous framework, however, appeared to form a continuum between the alveolar bone and cementum. Lacunae in the bone at the frozen segment were empty. The injured PDL was surrounded by normal PDL. Control specimens appeared normal. At 30 d, the PDL space in the frozen segments was populated by PDL-like tissue which did not differ significantly from the PDL coronal or apical to it. Collagen fibers appeared to be attached to the cementum on one side and to the alveolar bone on the other. Bone resorption or ankylosis was not observed in the experimental sites. It is suggested that the extracellular matrix in the devitalized area was preserved, supporting regeneration of the cryolesion.

Histometric study of the effect of occlusal alteration on periodontal tissue healing after surgical injury

The effect of occlusal alteration upon healing of the periodontium after surgical injury was studied in 62 male Wistar rats, nine weeks of age. An osteotomy was made with a bur through the vestibular bone plate, the periodontal ligaments and into the superficial part of the root surface of the first mandibular molar. In the same session, the occlusion of the antagonistic tooth was altered in the experimental groups by either placing a high amalgam restoration, grinding, or extraction. The occlusion in the control group was unaltered. The rats were killed 70 days after surgery, and examined histologically. A histometric registration of the periodontal repair revealed a significant narrowing of the periodontal ligament width in the non-occluding teeth, as well as significant thickening of cementum at and above the surgical cavity site. The hypo- and hyper-occluding teeth did not show significant changes as compared to the controls.

A modified technique for obliteration of large bony defects after cystectomy

Thirteen cysts treated by enucleation followed by collapsing an osteoperiosteal flap to eliminate dead space are presented. Four of the cysts were dentigerous and nine were radicular. The bony defects ranged in size from 3 to 7 cm in greatest dimension. Healing by primary intention occurred in all cases. This method has been found to be successful in the obliteration of large bony defects after cystectomy.