Alveolar bone resorption following coronal versus apical approach in a mucoperiosteal flap surgery procedure in the rat mandible

Learn, unlearn, and relearn post-extraction alveolar socket healing: Evolving knowledge and practices

OBJECTIVE

This review was to offer a comprehensive analysis of currently available evidence on post-extraction alveolar socket healing, including i) the histological and molecular events during alveolar socket healing, ii) the dimensional ridge alterations after socket healing and controversies relating to sinus pneumatisation, iii) the patient-specific factors, procedural elements, and site-related variables influencing socket healing, iv) techniques and effectiveness of alveolar ridge preservation (ARP) procedure, and v) the philosophies and cost-effectiveness of ARP in clinical practice.

SOURCES AND STUDY SELECTION

To investigate the dimensional profiles of the alveolar ridge following unassisted healing, an overview of systematic reviews was conducted in February 2024 by two independent reviewers. Four electronic databases were searched in Pubmed, Embase, Web of science and Cochrane Library between 2004 and 2024 to identify all relevant systematic reviews on post-extraction healing. A further manual search of reviews was also conducted. The articles were further reviewed in full text for relevance. The AMSTAR-2 appraisal tool was adopted to assess methodological quality. Current research pertaining to other listed objectives was objectively analysed in narration.

DATA

11 out of 459 retrieved studies were selected and ultimately covered in this review on the dimensional changes of alveolar ridge following natural healing: Seven systematic reviews and four systematic reviews with meta-analyses. The methodological quality of all included reviews was critically low.

CONCLUSION

This review thoroughly examines the healing profiles of post-extraction alveolar sockets and highlights the dynamic process with overlapping phases and the inter-individual variability in outcomes. ARP procedure is a potential strategy for facilitating prosthetic site development, while the current evidence is limited. Herein, an individualised and prosthetically driven approach is crucial. Further well sized and designed trials with novel biomaterials need to be undertaken, and the role of artificial intelligence in predicting healing and assisting clinical decision-making could be explored.

CLINICAL SIGNIFICANCE

By advancing our understanding of alveolar socket healing and its management strategies, clinicians can make more informed decisions regarding patient and site level assessment and selection, surgical techniques, and biomaterial choices, ultimately contributing to the enhanced healing process with reduced complications and improved quality of life for patients undergoing tooth extraction and dental implant treatments.

Effects of socket-shield therapy on inter-implant papilla preservation between upper central and lateral incisors: A case series with 3-5 year follow-up

OBJECTIVE

Despite significant progress within implant prosthetic therapy, preserving the papilla between two adjacent implants in the esthetic zone, particularly between central and lateral incisors, remains challenging. This case series aims to report a papilla preservation approach between adjacent upper central-lateral incisor implants using the socket-shield technique.

CLINICAL CONSIDERATIONS

Six patients with natural dentition received unilateral adjacent central-lateral incisor implants with different socket shield configurations. The esthetic outcomes were clinically assessed after 3-5 years of follow-up. Post-operative papilla fill was evaluated on intraoral images compared to baseline characteristics and the contralateral papilla. Papilla height was preserved in all cases, with minimal alterations observed.

CONCLUSIONS

Within the limitations of the present case series, the socket-shield technique demonstrated favorable outcomes in preserving the papilla between adjacent upper central-lateral incisor implants in the midterm follow-up. Clinical studies are warranted to validate these results.

CLINICAL SIGNIFICANCE

The socket-shield technique seems promising in preserving the inter-implant papilla between adjacent central-lateral incisor implants.

Avoiding errors and complications related to immediate implant placement in the esthetic area with a mucogingival approach

Immediate implant placement is considered the treatment of choice for single tooth replacement in the esthetic area. However, this treatment is associated with several critical drawbacks related to the inadequate assessment/management of the soft and hard peri-implant tissues and their subsequent remodeling, resulting in peri-implant soft-tissue defects that can lead to impaired esthetic outcomes in time. We describe in detail how the mucogingival approach to immediate implant placement ensures a standard result regardless of the baseline soft-hard tissue situation. Fully guided implant placement guarantees an adequate three-dimensional implant placement, the flap design makes it possible to perform bone augmentation with complete visibility of the area being treated, allows soft tissue augmentation with proper fixation of the connective tissue graft, and the placement of an immediate provisional ensures stabilization of the peri-implant tissues throughout the healing period.

Flapless Er,Cr:YSGG laser versus traditional flap in crown lengthening procedure

Background/purpose

Laser technology and minimally invasive therapy has gained attention in many dentistry fields. Er,Cr:YSGG laser is the latest laser type that can be applied on both soft tissue and hard tissue. This study presents periodontal outcome of Er,Cr:YSGG laser flapless crown lengthening procedure compared with traditional technique.

Materials and methods

Twenty-five participants were divided into two groups: 13 patients were treated with the traditional method of crown lengthening and 12 patients were treated using a flapless Er,Cr:YSGG laser. Their periodontal status were measured and compared at baseline, immediately, one month, and three months after surgery.

Results

The results showed a significant increase in clinical crown length immediately after surgery in both groups. After a three-month follow-up, the gingival margin of the laser group remained at stable height with 0.17 ± 0.31 mm increase after surgery, while the gingival margin of traditional group showed both recession and rebounding by -0.13 ± 0.63 mm (p > 0.05) average.

Conclusion

The flapless Er,Cr:YSGG laser crown lengthening with its minimally invasive approach without flap reflection may be an alternative treatment for providing an adequate height of tooth for restoration.

Long-Term Assessment of Periodontal Tissues after Corticotomy-Assisted Orthodontic Arch Expansion

OBJECTIVES

The aim of the study was the long-term assessment of the condition of periodontal tissues after corticotomy-assisted orthodontic expansion in patients with transverse maxillary deficiency.

MATERIALS AND METHODS

The study included a group of 18 adults (9 women, 9 men) aged between 24 and 40 years who were at least 5 years post treatment. The following parameters were assessed: the full mouth plaque index (FMPI), full mouth bleeding on probing (FMBOP), probing depth (PD), clinical attachment level (CAL), gingival recession height (GR), recession width (RW), papilla height (PH), papilla width (PW), bone sounding (BS), phenotype, and KT.

RESULTS

During examination performed at least 5 years after the completion of orthodontic treatment, the values of PD and CAL were found to be considerably decreased compared to the examination one year post treatment (PD: -0.23; 95% Cl: -0.29, -0.16) (CAL: -0.04; 95% Cl: -0.17, 0.10). The other parameters-FMPI, FMBOP, GR, RW, PH, PW, BS, phenotype, and KT-did not change significantly.

CONCLUSIONS

Corticotomy-assisted orthodontic arch expansion does not have a negative effect on the periodontium in long-term observations.

CLINICAL RELEVANCE

Orthodontic arch expansion can lead to bone dehiscence and gingival recession. Long-term observations revealed that corticotomy-assisted orthodontic expansion of the upper arch is not followed by negative changes in periodontal status.

Effect of Using a Plastic Stent with Apically Repositioned Flap in Peri-Implant Soft Tissue Augmentation: A Randomized Controlled Clinical Trial

Objectives

This study aimed to clinically assess and compare the width of peri-implant keratinized mucosa following the use of a readymade plastic stent with apically repositioned flap versus conventional apically repositioned flap with papillary sparing incisions during single-stage implant placement protocol.

Materials and Methods

A total of 20 patients were enrolled in this study. In the test group, a prefabricated implant-retained stent was clipped on the healing abutment after implant surgery to reposition the keratinized tissue buccoapically. In the control group, simple interrupted sutures were applied instead of using a stent. After the surgical procedure, the width of the buccal keratinized mucosa was measured at the mesial, middle, and distal aspects of the healing abutment. The change in the width of the buccal keratinized mucosa was assessed at 3 months and 6 months.

Results

No statistically significant difference was found between the stent group and control group in 6 months' interval where p=0.840, where both groups showed the same mean value of 4.70 ± 0.35 and 4.70 ± 0.63, respectively. The percent of change in the width of KM was found to be higher in the stent group than in the control group with no statistical significance.

Conclusion

The use of a readymade plastic stent in combined full/partial-thickness apically repositioned flap shows to be effective in increasing the width of KM compared to the conventional technique. This trial is registered with NCT03754894.

Role of UDP-Sugar Receptor P2Y14 in Murine Osteoblasts

The purinergic (P2) receptor P2Y₁₄ is the only P2 receptor that is stimulated by uridine diphosphate (UDP)-sugars and its role in bone formation is unknown. We confirmed P2Y₁₄ expression in primary murine osteoblasts (CB-Ob) and the C2C12-BMP2 osteoblastic cell line (C2-Ob). UDP-glucose (UDPG) had undiscernible effects on cAMP levels, however, induced dose-dependent elevations in the cytosolic free calcium concentration ([Ca²⁺]_i) in CB-Ob, but not C2-Ob cells. To antagonize the P2Y₁₄ function, we used the P2Y₁₄ inhibitor PPTN or generated CRISPR-Cas9-mediated P2Y₁₄ knockout C2-Ob clones (Y14_KO). P2Y₁₄ inhibition facilitated calcium signalling and altered basal cAMP levels in both models of osteoblasts. Importantly, P2Y₁₄ inhibition augmented Ca²⁺ signalling in response to ATP, ADP and mechanical stimulation. P2Y₁₄ knockout or inhibition reduced osteoblast proliferation and decreased ERK1/2 phosphorylation and increased AMPKα phosphorylation. During in vitro osteogenic differentiation, P2Y₁₄ inhibition modulated the timing of osteogenic gene expression, collagen deposition, and mineralization, but did not significantly affect differentiation status by day 28. Of interest, while P2ry14^-/- mice from the International Mouse Phenotyping Consortium were similar to wild-type controls in bone mineral density, their tibia length was significantly increased. We conclude that P2Y₁₄ in osteoblasts reduces cell responsiveness to mechanical stimulation and mechanotransductive signalling and modulates osteoblast differentiation.

Injectable Alginate-Peptide Composite Hydrogel as a Scaffold for Bone Tissue Regeneration

The high demand for tissue engineering scaffolds capable of inducing bone regeneration using minimally invasive techniques prompts the need for the development of new biomaterials. Herein, we investigate the ability of Alginate incorporated with the fluorenylmethoxycarbonyl-diphenylalanine (FmocFF) peptide composite hydrogel to serve as a potential biomaterial for bone regeneration. We demonstrate that the incorporation of the self-assembling peptide, FmocFF, in sodium alginate leads to the production of a rigid, yet injectable, hydrogel without the addition of cross-linking agents. Scanning electron microscopy reveals a nanofibrous structure which mimics the natural bone extracellular matrix. The formed composite hydrogel exhibits thixotropic behavior and a high storage modulus of approximately 10 kPA, as observed in rheological measurements. The in vitro biocompatibility tests carried out with MC3T3-E1 preosteoblast cells demonstrate good cell viability and adhesion to the hydrogel fibers. This composite scaffold can induce osteogenic differentiation and facilitate calcium mineralization, as shown by Alizarin red staining, alkaline phosphatase activity and RT-PCR analysis. The high biocompatibility, excellent mechanical properties and similarity to the native extracellular matrix suggest the utilization of this hydrogel as a temporary three-dimensional cellular microenvironment promoting bone regeneration.

Periodontal cell mechanotransduction

The periodontium is a structurally and functionally complex tissue that facilitates the anchorage of teeth in jaws. The periodontium consists of various cell types including stem cells, fibroblasts and epithelial cells. Cells of the periodontium are constantly exposed to mechanical stresses generated by biological processes such as the chewing motions of teeth, by flows generated by tongue motions and by forces generated by implants. Mechanical stresses modulate the function of cells in the periodontium, and may play a significant role in the development of periodontal disease. Here, we review the literature on the effect of mechanical forces on periodontal cells in health and disease with an emphasis on molecular and cellular mechanisms.

Effect of incision design on interproximal bone loss of teeth adjacent to single implants. A randomized controlled clinical trial comparing intrasulcular vs paramarginal incision

PURPOSE

To evaluate the effect of incision design in implant surgery on interproximal bone loss of posterior teeth adjacent to interdental single implants, comparing intrasulcular and paramarginal incision. A further aim was to assess the influence of the incision technique on peri-implant bone remodeling.

MATERIALS AND METHODS

A controlled randomized clinical trial was carried out in a University Clinic. All the patients received an interdental posterior single implant. The incision type was randomly divided into two groups: (a) intrasulcular or (b) paramarginal. Standardized periapical digital radiographs were made with the parallel technique and a silicone index individualized in each patient. Radiographs were made immediately after implant placement, at abutment connection, 6 and 12 months post-loading. Two radiographic reference points were detected at the interproximal aspect of the adjacent teeth: (A) the cementoenamel junction and (B) the most coronal aspect of the bone crest. The interproximal bone loss of the adjacent teeth was calculated as the difference from A to B between the different follow-up periods and baseline. Two different examiners evaluated the radiographic measurements twice.

RESULTS

Sixty patients, each with one implant, were included, 30 in each group. A mean interproximal bone loss in teeth of 0.09 mm in the intrasulcular and 0.10 mm in the paramarginal group was found at 12 months post-loading. Mean peri-implant bone remodeling was 0.17 mm in the intrasulcular group and 0.15 mm in the paramarginal group. Differences between incision types were not statistically significant (p > .05).

CONCLUSIONS

Both incision designs used to place interdental single implants resulted in minimum bone loss at the interproximal aspect of adjacent teeth. The incision design did not significantly influence the radiographically assessed interproximal bone loss nor peri-implant bone remodeling.

Extracellular ATP is a key modulator of alveolar bone loss in periodontitis

Periodontal diseases are initiated by pathogenic bacterial biofilm activity that induces a host inflammatory cells immune response, degradation of dento gingival fibrous tissue and its detachment from root cementum. It is well accepted, that osteoclastic alveolar bone loss is governed exclusively through secretion of proinflammatory cytokines. Nevertheless, our findings suggest that once degradation of collagen fibers by MMPs occurs, a drop of cellular strains cause immediate release of ATP from marginal gingival fibroblasts, cell deformation and influx of Ca+2. Increased extracellular ATP (eATP) by interacting with P2×7 purinoreceptors, present on fibroblasts and osteoblasts, induces generation of receptor activator of nuclear factor kB ligand (RANKL) that further activates osteoclastic alveolar bone resorption and bone loss. In addition, increased eATP levels may amplify inflammation by promoting leukocyte recruitment and NALP3-inflammasome activation via P2×7. Then, the inflammatory cells secrete cytokines, interleukin IL-1, TNF and RANKL that further trigger alveolar bone resorption. Moreover, eATP can be secreted from periodontal bacteria that may further contribute to inflammation and bone loss in periodontitis. It seems therefore, that eATP is a key modulator that initiates the pathway of alveolar bone resorption and bone loss in patients with periodontal disease. In conclusion, we propose that strain release in gingival fibroblasts aligned on collagen fibers, due to activity of MMP, activates release of ATP that triggers the pathway of alveolar bone resorption in periodontitis. We predict that by controlling the eATP interaction with its cellular purinoreceptors will reduce significantly bone loss in periodontitis.

Impact of Second Stage Surgery on Bone Remodeling Around New Hybrid Titanium Implants: A Prospective Clinical Study in Humans

OBJECTIVE

The present prospective study aimed to more precisely identify the time points of bone changes around hybrid titanium implants up to 30 months of follow-up.

MATERIALS AND METHODS

Twelve hybrid T3 implants (Biomet 3i) were placed in 9 healthy patients with the 2-stage surgical approach. Standardized digital Rx were taken at implant insertion (T0); healing-abutment connection after 3.1 ± 0.2 weeks (TX); loading stage after 7.5 ± 0.6 weeks (T1); after 12 months (T2); and after 30 months (T3) of functional loading. The marginal bone loss was digitally measured.

RESULTS

The mean marginal bone loss was 0.76 ± 0.37 mm after 30 months. More than 60% (0.42 ± 0.29 mm) of the bone loss took place at healing-abutment connection (TX-T1). No statistically significant bone loss was found between T1-T2 and T2-T3, after 12 and 30 months, respectively. Approximately 40% of bone loss (0.34 mm) was noted between T1 and T3 (P < 0.05), which corresponds to the loading period.

CONCLUSIONS

The implant-oral environment connection represents a critical step point in crestal bone loss. The amount of marginal bone loss, measured after 30 months of loading (T1-T3), was much less than that reported in the literature, showing that correct loading has a minor impact on the periimplant bone remodeling as compared to surgical implant reopening.

Influence of local administration of pamidronate on extraction socket healing--a histomorphometric proof-of-principle pre-clinical in vivo evaluation

OBJECTIVES

To evaluate the influence of local administration of pamidronate histomorphometrically, adsorbed on a collagenated porcine bone substitute, on extraction socket healing.

MATERIAL AND METHODS

Two American Fox-hound dogs were used within this proof-of-principle study. Following endodontic treatment of the distal root of the three lower premolars, the teeth were hemisected, and the mesial roots were extracted flapless. The sockets were then loosely filled, in a split-mouth fashion, with a collagenated porcine bone substitute (Osteobiol Gen-Os; CPB), rehydrated either with 90 mg/ml pamidronate (Aredia(®) ; test) or with sterile saline (control). Extraction sockets were sealed with connective tissue punches obtained from the palate and secured with sutures. After 4 months of healing, specimens containing the socket sites and remaining roots were retrieved and histomorphometrically examined.

RESULTS

Histological evaluation of the sections revealed substantial differences in healing patterns. Control sites presented with various amounts of newly formed bone and no evidence of CPB inside the socket; in contrast, limited amounts of bone were observed at test sites, which were filled with CPB mainly embedded in connective tissue. Only minor differences were observed between test and control sites regarding vertical bone loss (buccal bone: -1.01 mm vs. -1.15 mm; lingual bone: -0.92 mm vs. -1.15 mm). Horizontal bone loss was nearly three times higher in control sites comparing to sites treated with pamidronate (-2.19 ± 1.81 mm vs. -0.80 ± 0.91 mm) at a level corresponding to 3 mm below the cemento-enamel junction (CEJ).

CONCLUSION

Local administration of pamidronate adsorbed on a collagenated porcine bone substitute in particulate form appeared to delay extraction socket healing, but may also reduce post-extraction dimensional changes in terms of horizontal bone width. Additionally, pamidronate appears to obstruct resorption of the porcine bone substitute.

Periodontal disease and high doses of inhaled corticosteroids alter NTPDase activity in the blood serum of rats

BACKGROUND

Certain drugs such as glucocorticoids may interfere with the modulation of periodontal disease. In contrast, corticosteroid treatment has been associated with a protective effect with regard to periodontal breakdown, depending on the dose, pathway, and exposure time. Considering the potential relevance of nucleotidases in coordinating the cardiovascular system and inflammation processes, the aim of this study was to investigate the nucleotidase activities in the blood serum of rats with periodontal disease exposed chronically to inhaled corticosteroids.

METHODS

Adult male Wistar rats (n=26) were randomly assigned to one of the following four study groups: a control group that received no intervention; a periodontal disease group that received saline solution; a 'low dose' group that received 30 μg of budesonide daily; and a corresponding 'high dose' group that received 100 μg daily over a 15-day time course. The hydrolysis of ATP, ADP, and AMP were analysed in blood serum.

RESULTS

Periodontal disease diminished the hydrolysis of ATP and enhanced the hydrolysis of ADP. Repeated administration of either a low or high dose in the periodontal disease model of inhaled corticosteroids reversed the observed increase in ADP hydrolysis, and only the repeated administration of low doses of inhaled corticosteroids was able to reverse the decrease in the hydrolysis of ATP induced by periodontal disease.

CONCLUSION

The variables investigated in this study may be involved in the pathophysiology of periodontal disease and may participate in the mechanisms that mediate the development of some of the side effects of inhaled corticosteroids.

Tissue response following papilla-sparing and sulcular incisions in oral surgery--an experimental study

OBJECTIVES

The objective of this study is to compare tissue reduction following papilla-sparing and sulcular incisions in oral surgical indications.

MATERIAL AND METHODS

Five beagle dogs were used. Three months after tooth extraction of P2-M1, notches were prepared at the height of the interproximal gingiva into M2 and P1. Papilla-sparing and sulcular incisions were randomly performed, full-thickness flaps elevated and flaps repositioned. Three months postoperatively, tissue reduction was assessed using a digital calliper, mean values were calculated per group and analysed using a Wilcoxon matched-pair rank test.

RESULTS

Papilla-sparing incisions revealed significantly less (p < 0.05) tissue reduction than sulcular incision techniques.

CONCLUSION

Papilla-sparing incisions seem to induce less tissue response following flap surgery compared to sulcular incisions in oral surgical indications. Nevertheless, tissue reduction was seen in both groups.

CLINICAL RELEVANCE

For surgical approaches without the necessity of direct access to the root surface (i.e., implantology, oral surgery), papilla-sparing incisions may be superior compared to sulcular incisions.

Fiberotomy enhances orthodontic tooth movement and diminishes relapse in a rat model

OBJECTIVES

Accelerated orthodontic tooth movement is triggered by procedures that include mucoperiosteum flap surgery and surgical scarring of cortical bone. Our aim was to test whether fiberotomy by itself will accelerate orthodontic tooth movement and diminish relapse.

MATERIALS AND METHODS

In 34 Wistar rats, alveolar bone resorption and molar tooth movement were measured after fiberotomy, apical full-thickness flap without detachment of gingiva from the roots, or no surgery. Orthodontic appliance was installed at time of surgery and activated for 14 days, generating movement of the first maxillary molar buccal and then removed.

RESULTS

Percent of sections in which alveolar bone resorption was detected was significantly higher (p < 0.05) after fiberotomy (27%) in comparison with apical flap surgery (12%) or no surgery (6%), after 30 days. Also, at the end of active phase, the molar moved significantly faster (p < 0.01) and twice the distance after fiberotomy (0.54 ± 0.33) in comparison with apical surgery (0.26 ± 0.12) or no surgery (0.3 ± 0.09). Sixteen days after the appliance was removed, only 12% relapse was recorded in the fiberotomy group, while almost total relapse in other two groups.

CONCLUSION

We conclude that fiberotomy solely accelerated orthodontic tooth movement and diminished relapse.

Bone loss after full-thickness and partial-thickness flap elevation

OBJECTIVES

the aim of this study was to histologically assess whether elevation of partial-thickness flaps results in reduced bone alterations, as compared with full-thickness flap preparations.

MATERIAL AND METHODS

in five beagle dogs, both mandibular second premolars (split-mouth design) were subjected to one of the following treatments: Tx1: elevation of a partial-thickness flap over the mesial root of P(2) and performing a notch at the height of the bone. Tx2: elevation of a full-thickness flap over the mesial root of P(2) and performing a notch at the height of the bone. After 4 months, sections were evaluated for: (i) vertical bone loss and (ii) osteoclastic activity using histometry.

RESULTS

elevation of both full- and partial-thickness flaps results in bone loss and elevated osteoclastic activity. Partial-thickness flaps can result in less bone loss than full-thickness flaps, but are subject to some variability.

CONCLUSION

use of partial-thickness flaps does not prevent from all bone loss. The procedure may result most of the times in less bone loss than the elevation of full-thickness flaps. Further research has to evaluate the determinants of effective outcomes of partial-thickness flap procedures.

Reproducibility of a hemi mandible positioning device and a method for measuring alveolar bone loss area in mice

The objective of this study was to determine the reproducibility of a positioning device and a method for measuring the area of alveolar bone loss (ABL) in hemi mandibles of mice. Mucoperiosteal flaps were raised in CF1 Mus domesticus mice (n = 10) on the buccal aspects of the left side of the mandibles. Twenty-one days after surgery, the animals were sacrificed, and the mandibles were resected and stained with 1% toluidine blue. Two positioning devices, one for the buccal and the other for lingual aspect, were fabricated to keep the hemi mandibles in a standard position. The reliabilities of the positioning device and the method for measuring ABL area were analyzed using two series of pictures. The photographs were digitized and ABL measured as the exposed root area. Measurements were performed by two blinded examiners using image analysis software. Intra- and inter-examiner reproducibility of the positioning method ranged from -1.5 to +1.33 mm, while intra- and inter-examiner reproducibility of the measurement technique ranged from -3.37 to 14.70. Our results indicate that, due to the small variation observed in ABL area assessment, the positioning device and method for measuring ABL area represent useful techniques for evaluating ABL in mice.

P2X4 is up-regulated in gingival fibroblasts after periodontal surgery

Several studies have shown that surgical detachment of marginal gingiva close to the cervical cementum of molar teeth in a rat mandible is a distinct stimulus for alveolar bone resorption. Recently, we found that P2X4, an ATP-receptor, is significantly up-regulated in marginal gingival cells soon after surgery. We hypothesized that local release of ATP signaling through P2X4 elicits activation of osteoclasts on the alveolar bone surface. In this study, we identified intense immunoreactivity of gingival fibroblasts to P2X4-specific antibodies and a 6.4-fold increase in expression by real-time RT-PCR. Moreover, a single local application, at the time of surgery, of Apyrase (which degrades ATP) or Coomassie Brilliant Blue (an antagonist of purinoreceptors) significantly reduced alveolar bone loss. We propose that ATP flowing from cells after surgery can directly activate P2X4 receptors in the sensor cells of marginal gingiva through Ca(2+) signaling, or by direct activation of osteoclasts on the bone surface.

Topical Application of Drugs Influencing Cytoskeleton and Cell Contractility Affects Alveolar Bone Loss in Rats

BACKGROUND

Several studies have shown that sectioning bundles of collagen fibers in the marginal gingiva during surgical procedures in animals is a distinct stimulus for alveolar bone resorption. Normally, gingival and periodontal fibroblasts, which reside on these collagen fibers, create physiological traction forces generated by the cytoskeleton. By splitting the fibers, traction forces are released, inducing changes in the cytoskeleton and cell shape. In this study, four drugs were selected, including cytochalasin D, EDTA, sodium orthovanadate, and H-7, all influencing the cytoskeleton-integrin-extracellular matrix (ECM) pathway, for their ability to reduce alveolar bone loss by local application.

METHODS

The drugs were applied locally only once at the site of mucoperiosteal flap surgery in a rat model. Cytochalasin D (1 microl/microl), EDTA (0.24 mg/microl), sodium orthovanadate (0.02 mg/microl), and H-7 (0.10 microl/microl), each separately, were carried by a protective paste and placed immediately after elevating the flap. The analysis of alveolar bone loss was performed 3 weeks after surgery by scanning the microradiographic films of the mandible cross-sections. The percentages of cross sections with no, moderate, or severe bone loss in treated in comparison to non-treated rats are presented.

RESULTS

EDTA, sodium orthovanadate, and H-7 were significantly effective in reducing alveolar bone loss. They were effective in reducing the amount of severe bone loss by 53%, 20%, and 58% while increasing the number of sections with no bone loss by 25%, 23%, and 35%, respectively. Cytochalasin D reduced alveolar bone loss insignificantly.

CONCLUSION

EDTA, sodium orthovanadate, and H-7 are effective in reducing alveolar bone loss in rats following mucoperiosteum surgery.

Alveolar bone loss and aging: a model for the study in mice

BACKGROUND

Several animal studies have shown a positive correlation between aging and alveolar bone loss (ABL). The purpose of this study was to develop a model for the study of ABL in mice and aging.

METHODS

Mucoperiosteal flap surgery (MFS) was performed on the buccal aspect of the left side of the mandible (BL) in 72 CF(1) Mus domesticus mice and divided into three groups as follows: males, breeding (non-virgin) females, and virgin females. The MFS was performed in 3-, 6-, 9-, and 12-month-old animals under anesthesia. The buccal aspects of right hemimandibles were used as controls (BR). Animals were sacrificed under anesthesia 21 days after surgery. Mandibles were removed, defleshed, stained with toluidine blue, and photographed in a microscope. The photographs were digitized, and ABL was measured as the exposed root surface area (mm(2)). Blinded measurements were performed using a computer-assisted image analysis system.

RESULTS

In terms of alveolar bone loss, the BL (operated) area showed a significant difference (paired Student t test; P <0.001) when compared to the BR area in all three groups. Sex and breeding differences were not observed in this experiment. ABL in the left hemimandibles was significantly larger in 3- (mean: 0.70; 95% confidence interval [CI]: 0.59 to 0.80) and 12-month-old animals (mean: 0.58; 95% CI: 0.46 to 0.71) than in 6- (mean: 0.39; 95% CI: 0.33 to 0.46) and 9-month-old animals (mean: 0.42; 95% CI: 0.35 to 0.48); P <0.001.

CONCLUSION

The results suggest that 3-month-old CF(1) mice, in a sex and breeding independent process, could be a useful model for provoked alveolar bone loss studies in aging.

Microvascular response in the periodontal ligament following mucoperiosteal flap surgery

BACKGROUND

When the mucoperiosteal flap is elevated, the gingivo-periosteal vascular plexus and periodontal ligament (PDL) vascular plexus sever their connection with the circulatory tracts that pass through alveolar bone. We studied the effect exerted on the PDL vascular plexus during restoration of the circulatory tract.

METHODS

We performed experimental mucoperiosteal flap surgery in adult beagle dogs. Histological specimens, prepared after injecting India ink into the blood vessels on postoperative days 5, 7, 14, 21, 28, and 42, were examined under a light microscope. In addition, vascular corrosion cast specimens of the PDL, into which acrylic resin was injected, were observed using a scanning electron microscope.

RESULTS

On postoperative day 5, the PDL vascular plexus had formed new blood vessels toward the bone side and root side, and bone resorption of the alveolar bone proper had initiated primarily around the opening of the Volkmann's canal. From postoperative day 7 to 14, the PDL vascular plexus formed new vessels on the bone side and root side accompanied by bone resorption of the alveolus, and demonstrated a complicated vascular architecture, which gradually organized and transformed into a mesh structure from postoperative day 21. Osteogenesis was initiated and encircled the newly formed vessels, and the alveolar bone proper recovered to a flat morphology. Judging from the quantity of new vessels and bone resorption, the width of the PDL space seemed to be the greatest on postoperative day 14.

CONCLUSIONS

When the mucoperiosteal flap was elevated, active wound healing was activated because of angiogenesis from the PDL, which possesses a microcirculatory system. Moreover, it was suggested that angiogenesis of the PDL vascular plexus and subsequent bone resorption of alveolar bone might temporarily reduce the tooth-supporting function and cause postoperative mobility.

Strain relaxation of fibroblasts in the marginal periodontium is the common trigger for alveolar bone resorption: a novel hypothesis

In summary, the present commentary proposes a hypothesis that alveolar bone remodeling and bone loss in periodontitis, periodontal surgery, and in orthodontic tooth movement is triggered by a common "strain relaxation" signaling pathway of gingival and periodontal fibroblasts. The abrupt splitting, degradation, or relaxation of collagen fibers in the marginal periodontium produces a "strain relaxation" signal in the local fibroblasts which reside on these fibers, activating an ECM-integrin-cytoskeleton pathway. A cascade of cellular reactions which lead to osteoclastic bone resorption starting on the inner aspect (periodontal) of the alveolar bone then persists. A novel therapeutic approach is suggested here by using locally delivered drugs intervening in the cell contractile apparatus.