Cardiovascular and Autonomic Dysfunction in Murine Ligature-Induced Periodontitis

The present study examined the hemodynamics [arterial pressure (AP), AP variability (APV), heart rate (HR), and heart rate variability (HRV)], cardiac function (echocardiographycally), and myocardial inflammation in Balb/c mice submitted to Periodontitis, through the ligation of the left first molar, or Sham surgical procedure. The first protocol indicated that the AP was similar (136 ± 2 vs. 132 ± 3 mmHg in Sham), while the HR was higher in mice with Periodontitis (475 ± 20 vs. 412 ± 18 bpm in Sham), compared to their Sham counterparts. The APV was higher in mice with Periodontitis when evaluated in the time domain (4.5 ± 0.3 vs. 3.4 ± 0.2 mmHg in Sham), frequency domain (power of the LF band of systolic AP), or through symbolic analysis (patterns 0V + 1V), indicating a sympathetic overactivity. The HRV was similar in the mice with Periodontitis, as compared to their Sham counterparts. In the second protocol, the mice with Periodontitis showed decreased cardiac output (10 ± 0.8 vs. 15 ± 1.4 mL/min in Sham) and ejection fraction (37 ± 3 vs. 47 ± 2% in Sham) associated with increased myocardial cytokines (Interleukin-17, Interleukin-6, and Interleukin-4). This study shows that experimental Periodontitis caused cardiac dysfunction, increased heart cytokines, and sympathetic overactivity, in line with epidemiological studies indicating an increased risk of cardiovascular events in clinical Periodontitis.

WNT3A accelerates delayed alveolar bone repair in ovariectomized mice

Our goal was to evaluate alveolar bone healing in OVX mice, and to assess the functional utility of a WNT-based treatment to accelerate healing in mice with an osteoporotic-like bony phenotype.

INTRODUCTION

Is osteoporosis a risk factor for dental procedures? This relatively simple question is exceedingly difficult to answer in a clinical setting, for two reasons. First, as an age-related disease, osteoporosis is frequently accompanied by age-related co-morbidities that can contribute to slower tissue repair. Second, the intervals at which alveolar bone repair are assessed in a clinical study are often measured in months to years. This study aimed to evaluate alveolar bone repair in ovariectomized (OVX) mice and provide preclinical evidence to support a WNT-based treatment to accelerate alveolar bone formation.

METHODS

OVX was performed in young mice to produce an osteoporotic-like bone phenotype. Thereafter, the rate of extraction socket healing and osteotomy repair was assessed. A liposomal WNT3A treatment was tested for its ability to promote alveolar bone formation in this OVX-induced model of bone loss.

RESULTS

Bone loss was observed throughout the murine skeleton, including the maxilla, and mirrored the pattern of bone loss observed in aged mice. Injuries to the alveolar bone, including tooth extraction and osteotomy site preparation, both healed significantly slower than the same injuries produced in young controls. Given sufficient time, however, all injuries eventually healed. In OVX mice, osteotomies healed significantly faster if they were treated with L-WNT3A.

CONCLUSIONS

Alveolar bone injuries heal slower in OVX mice that exhibit an osteoporotic-like phenotype. The rate of alveolar bone repair in OVX mice can be significantly promoted with local delivery of L-WNT3A.

Notch signaling pathway mediates alveolar bone resorption in apical periodontitis

Apical periodontitis represents a chronic inflammatory process within periapical tissues, mostly caused by etiological agents of endodontic origin. Progressive bone resorption in the periapical region represents the hallmark of apical periodontitis and occurs as the consequence of interplay between polymicrobial infections and host response. The Notch signaling pathway is an evolutionary conserved cell-signaling system that plays an important role in a variety of cell functions including proliferation, differentiation and apoptosis. In recent years its involvement in bone homeostasis has attracted a significant consideration. We hypothesized that Notch signaling pathway, which has a complex interplay with proinflammatory cytokines and bone resorption regulators, contributes to alveolar bone resorption via increased Notch receptors on immune cell surface and stimulates Notch receptor intracellular domain (NICD) translocation into the nucleus. The potential benefit of medications aimed to down-regulate these pathways in apical periodontitis treatment remains to be assessed.

Splinted and unsplinted overdenture attachment systems: A systematic review and meta-analysis

Splinted and unsplinted overdenture attachment systems have unique advantages and disadvantages. The aim of the present systematic review was to determine the influence of splinted and unsplinted overdenture attachment systems on the marginal bone loss, prosthetic complications and implant survival rate. PubMed/MEDLINE, Scopus and Cochrane databases were searched for articles published up to October 2017, using the following search terms: "overdenture AND attachment OR overdenture AND bar OR overdenture splinted." The PICO question "Do splinted overdenture attachment systems promote better clinical results in comparison to unsplinted systems?" was evaluated. Eligible studies included randomized controlled clinical trials, prospective studies with at least 10 participants and a minimum follow-up of 6 months, and studies published in English that compared splinted and unsplinted attachment systems within the same study. The 95% confidence interval (CI) was considered for all outcomes analysed. After completion of the different steps in the article selection process, nine articles were included in the qualitative and quantitative analyses. A total of 984 implants were placed in 380 patients (mean age: 62.8 years). The meta-analysis demonstrated no statistically significant differences between splinted and unsplinted attachment systems with regard to marginal bone loss (P = .39; MD: -0.11; 95% CI: -0.37 to 0.14), complications (P = .31; RR: 1.26; CI: 0.80-1.99) and implant survival rate (P = .14; RR: 0.37% CI: 0.10-1.36). In addition, splinted and unsplinted overdenture attachment systems achieved similar results with regard to marginal bone loss, prosthetic complications and implant survival rate.

The Effect of Moderately Controlled Type 2 Diabetes on Dental Implant Survival and Peri-implant Bone Loss: A Long-Term Retrospective Study

PURPOSE

The objective of this study was to assess whether long-term implant survival rates and bone loss in patients with moderately controlled type 2 diabetes is similar to the rates reported in the nondiabetic population.

MATERIALS AND METHODS

This retrospective observational study utilized patient medical records from a general practitioner's dental office. The records of patients who had moderately controlled type 2 diabetes with hemoglobin A1C (HbA1c) up to 8% and glucose level below 150 mg/dL were reviewed, as patients with HbA1c up to 7% are considered to be well-controlled type 2 diabetes. Follow-up data were recorded and analyzed. Inclusion criteria were as follows: partially edentulous patients with missing teeth who were subsequently treated with implant-supported prosthetic restorations; patients were at least 18 years of age and demonstrated the ability to maintain oral hygiene. Exclusion criteria were as follows: patients did not present for annual follow-up visits; patients presented with a neglected periodontal status; patient records had incomplete surgical or restorative data or nondiagnostic radiographs; implants with external hexagonal and machined surfaces. All the restorations were cement-retained. Three different implant insertion/placement methods were used: (1) implants immediately inserted following tooth extraction; (2) implants inserted 6 to 8 weeks after tooth extraction to allow for primary healing; and (3) implants inserted 4 to 6 months after tooth extraction.

RESULTS

After review of more than 3,256 medical records, 169 patients were identified (with 1,112 implants) who met the inclusion criteria. The mean follow-up time was 8.7 years, with a minimum of 4.9 years. Sixty-seven implants failed, yielding a 94% overall implant survival rate. The overall mean bone loss around the implants was 1.98 (± 1.81) mm. Comparable to data published earlier, no statistical significance in survival rate was found between the nondiabetic and diabetic population. The delayed insertion protocol presented the least bone loss, compared with immediate insertion (P = .06), and compared with early insertion (P = .046).

CONCLUSION

The results show that implant survival and bone loss levels were comparable to reported outcomes in the nondiabetic population. The delayed insertion protocol presented less bone loss compared with other insertion methods. Likewise, less bone loss was found in implants placed in the posterior region.

An osteopenic/osteoporotic phenotype delays alveolar bone repair

Aging is associated with a function decline in tissue homeostasis and tissue repair. Aging is also associated with an increased incidence in osteopenia and osteoporosis, but whether these low bone mass diseases are a risk factor for delayed bone healing still remains controversial. Addressing this question is of direct clinical relevance for dental patients, since most implants are performed in older patients who are at risk of developing low bone mass conditions. The objective of this study was to assess how an osteopenic/osteoporotic phenotype affected the rate of new alveolar bone formation. Using an ovariectomized (OVX) rat model, the rates of tooth extraction socket and osteotomy healing were compared with age-matched controls. Imaging, along with molecular, cellular, and histologic analyses, demonstrated that OVX produced an overt osteoporotic phenotype in long bones, but only a subtle phenotype in alveolar bone. Nonetheless, the OVX group demonstrated significantly slower alveolar bone healing in both the extraction socket, and in the osteotomy produced in a healed extraction site. Most notably, osteotomy site preparation created a dramatically wider zone of dying and dead osteocytes in the OVX group, which was coupled with more extensive bone remodeling and a delay in the differentiation of osteoblasts. Collectively, these analyses demonstrate that the emergence of an osteoporotic phenotype delays new alveolar bone formation.

The effects of dentoalveolar distraction extraction on alveolar ridge preservation: Cone-beam computed tomography and X-ray analysis in canine model

OBJECTIVE

This study aims to evaluate the effect of dentoalveolar distraction extraction (DDE) on site preservation, and to evaluate how the technique keeps the height and width of alveolar bones to a greater extent.

METHODS

12 beagle dogs, randomly divided into three groups (DDE group, NH group, BOG group), were used. In the dogs of three groups, the root of the left or right third mandibular premolars were respectively extracted by three methods namely, DDE, traditional extraction with natural healing, and traditional extraction with Bio-Oss bone dust implanted and guided bone regeneration (GBR). Cone-beam computed tomography (CBCT) scans and X-rays were taken immediately and three months after the tooth extraction. The height and width of the alveolar ridges were compared among different groups.

RESULTS

Three months after tooth extraction, at the 1 mm level below the alveolar ridge crest, the amount and degree of buccal alveolar ridge width resorption in DDE group were significantly lower than that of NH and BOG group (P < 0.05). At the 2 mm and 3 mm level below the alveolar ridge crest, the amount and degree of buccal alveolar ridge width resorption in DDE group and BOG had no significant difference, and both were significant lower than that of NH group (P < 0.05). The height resorption of alveolar ridge in DDE group was significantly lower than NH and BOG groups (P < 0.05), while NH and BOG group had no statistically significant.

CONCLUSIONS

To a greater extent, the alveolar ridge preservation through DDE could preserve the height and width of alveolar ridge crest.

Immediate post-extraction implants with or without pure platelet-rich plasma: a 5-year follow-up study

PURPOSE

The purpose of this study was comparison of clinical and radiographic outcomes of immediate post-extraction implants with or without the use of pure platelet-rich plasma (P-PRP) in the short- and medium-term follow-up.

METHODS

A retrospective analysis was performed to assess soft tissue healing, implant and prosthesis survival, marginal bone level changes and biological complications.

RESULTS

A total of 109 partially edentulous patients with 126 implants were included in this analysis. At 4-5 years after loading, cumulative survival rate in test group was 97.4% and in control group was 97.8%, with no significant differences. After 5 years of function, marginal bone loss (MBL) in test group was 0.8 ± 0.35 and 1.02 ± 0.27 mm for immediate and delayed loading, respectively, and in control group was 0.6 ± 0.16 and 0.8 ± 0.89 mm for immediate and delayed loading, respectively. No significant differences in MBL were observed intragroups and intergroups at any time point considered. Soft tissue healing score was significantly higher in test group compared to the control at 3 and 7 days after surgery, with significant differences.

CONCLUSIONS

P-PRP implant group showed a better soft tissue management and wound healing in the first 7 days after surgery compared to non-P-PRP implant group. In the medium-term follow-up, comparable clinical and radiographic outcomes were noticed between two groups.

[Effect of molar ligation and local Porphyromonas gingivalis inoculation on alveolar bone loss in the mouse]

OBJECTIVE

To compare the extent and time course of alveolar bone loss and osteoclast activation in two murine models of periodontal disease: molar ligation and Porphyromonas gingivalis (P. gingivalis) oral inoculation.

METHODS

A split-mouth design was applied to two groups of mice (C57BL6, 6-8 weeks old, n=24 in both groups), resulting in four treatment groups: (1) Control group: unligated upper right 2nd molars receiving CMC only, (2)Ligature group: ligation of a 9-0 suture around the upper left 2nd molar, (3) P. gingivalis group: unligated upper right 2nd molar receiving P. gingivalis challenge only, (4)Ligature+P.gingivalis group: ligation of the upper left 2nd molar in combination with oral inoculation with 109 colony-forming units(CFU) P. gingivalis. Alveolar bone loss was measured as the cementoenamel junction and alveolar bone crest (CEJ-ABC) distance. In the study, 48 C57BL6 mice were designed and treated as described above, and osteoclasts were counted on histological sections following tartrate-resistant acid phosphatase (TRAP) staining and counts were normalized to alveolar bone surface distance. Then 36 C57BL6 mice were investigated, of which 30 were ligated a 9-0 silk ligature around the 2nd molar in the left maxillary quadrant and 6 were not ligated. After ligation for 1 week, the ligatures in 12 mice were taken off for either 1 week or 2 weeks. The CEJ-ABC distance of the 6 mice without ligation was baseline. The CEJ-ABC distances were measured and analyzed. The data were analyzed with one-way ANOVA.

RESULTS

Molar ligation induced marked alveolar bone loss after 3, 6, 9 and 12 weeks [(0.16±0.04) mm, (0.16±0.02) mm, (0.18±0.03) mm, (0.17±0.02) mm], vs. corresponding controls [(0.09±0.03)mm,(0.10±0.01)mm,(0.12±0.04)mm,(0.12±0.01)mm] and P. gingivalis group [(0.09±0.03)mm, (0.12±0.01)mm,(0.12±0.02)mm,(0.10±0.01)mm], P<0.05. Combined treatment with molar ligation and P. gingivalis did not further increase the CEJ-ABC distance. Evidence for osteoclast activation was found one day after molar ligation, and TRAP-positive cell numbers peaked on day 3 (12±4 vs. control 2±2, P<0.01). After taking off ligature following ligation for 2 weeks, it showed significantly regrowth of alveolar bone compared with that before removal of the ligature on day 7 [(0.07±0.02)mm vs. (0.13±0.01)mm, P<0.01].

CONCLUSION

Molar ligation is a rapid and effective way to induce periodontal bone loss in mice. Osteoclast activation occurs within 24 hours of ligature placement, and the extent of bone loss well exceeds that of the P.gingivalis-induced bone loss. Removing ligature after periodontal disease might help bone regeneration by regrowth of the alveolar bone.

[The characteristics of microbiota of periodontal recesses in smoking patients with chronic generalized periodontitis]

The clinical examination of 36 tobacco smokers with chronic generalized periodontitis of light, average and severe degree was carried out. The examination established poor hygienic condition of oral cavity, less expressed inflammatory reaction of tissues of periodont and predominance of occurrences of destruction of alveolar portion of bone as compared with the group of 59 non-smoking patients with chronic generalized periodontitis of light, average and severe degree. The study demonstrated higher rate of detection of T. forsythia in smokers as compared with non-smoking patients at all stages of of development of chronic generalized periodontitis. Under light stage of chronic generalized periodontitis increasing of rate of detection of T. forsythia more than twice was registered. P.gigngivalis and P.intermedia were detected in smoking patients with light stage of chronic generalized periodontitis either in the same values or more rarely as compared with non-smokers. In the group of smokers with average stage of chronic generalized periodontitis increasing of rate of occurrence of association of T. forsythia-P. gigngivalis-P. intermedia occurred more than five times in comparison with non-smokers. The obtained results indicate on relationship between alterations of microbiota and aggressive development of chronic generalized periodontitis in smoking patients and on development in periodontal recesses of smokers of favorable conditions for growth of T. forsythia. The presence of T. forsythia is a significant factor of development of destructive processes in tissues of periodont.

Zanthoxylum piperitum reversed alveolar bone loss of periodontitis via regulation of bone remodeling-related factors

ETHNOPHARMACOLOGICAL RELEVANCE

Zanthoxylum piperitum (ZP) has been used to prevent toothache in East Asia.

AIM OF STUDY

In this study, we investigated the effects of ZP on periodontitis along with alveolar bone loss.

MATERIALS AND METHODS

Twenty-eight male Sprague-Dawley rats were assigned into 4 groups; non-ligated (NOR), ligated and treated vehicle (CTR), ligated and treated 1mg/mL ZP (ZP1), and ligated and treated 100mg/mL ZP (ZP100). Sterilized 3-0 nylon ligature was placed into the subgingival sulcus around the both sides of mandibular first molar. After topical application of 1 and 100mg/mL ZP for 2 weeks, mandibles was removed for histology. In addition, SaOS-2 osteoblast cells were treated 1, 10 and 100μg/mL ZP for 24h to analyze the expressions of alveolar bone-related markers.

RESULTS

Several alveolar bone resorption pits, which indicate cementum demineralization were decreased by ZP treatment. Topical ZP treatment inhibited periodontitis-induced alveolar bone loss. In addition, there were significant reduction of osteoclastic activities following topical ZP treatment in periodontium. The expression of RANKL was decreased in SaOS-2 osteoblast cells by treating ZP, while that of OPG was increased. ZP treatment increased the expressions of Runx2 and Osterix in SaOS-2 cells.

CONCLUSION

In summary, ZP treatment inhibited alveolar bone loss as well as maintained the integrity of periodontal structures via regulation of bone remodeling. ZP may be a therapeutic target for treating periodontitis.

Marginal Bone Level Evaluation after Functional Loading Around Two Different Dental Implant Designs

Purpose. To investigate peri-implant alveolar bone changes using periapical radiographs before and after prosthetic delivery in submerged and nonsubmerged dental implants. Methods. Digital periapical films of 60 ITI Straumann nonsubmerged dental implants and 60 Xive Dentsply submerged dental implants were taken before, immediately after, and 12 and 24 weeks after the prosthetic restoration was delivered. Results. The 60-nonsubmerged dental implant group showed mean marginal bone resorption at baseline of 0.10 ± 0.23 mm and 24 weeks later, marginal bone resorption was 0.16 ± 0.25 mm. The submerged dental implant group showed a significantly higher distal marginal bone resorption over the mesial side. Mean marginal bone resorption at baseline was 0.16 ± 0.32 on the mesial and 0.41 ± 0.56 on the distal side. Twenty-four weeks later, it was 0.69 ± 0.69 mm on the mesial and 0.99 ± 0.90 mm on the distal side. Conclusion. First, it was possible to determine that submerged implants had a higher mean marginal bone resorption and less bone-to-implant contact than nonsubmerged implants. And second, the distal side of submerged dental implants presented higher marginal bone loss than the mesial side.

Inflammation-induced Bone Remodeling in Periodontal Disease and the Influence of Post-menopausal Osteoporosis

During physiological conditions, the skeleton is remodeled in so-called bone multi-cellular units. Such units have been estimated to exist at 1–2 x 106 sites in the adult skeleton. The number and activities of these units are regulated by a variety of hormones and cytokines. In post-menopausal osteoporosis, lack of estrogen leads to increased numbers of bone multi-cellular units and to uncoupling of bone formation and bone resorption, resulting in too little bone laid down by osteoblasts compared with the amount of bone resorbed by osteoclasts. Inflammatory processes in the vicinity of the skeleton, e.g., marginal and apical periodontitis, will affect the remodeling of the nearby bone tissue in such a way that, in most patients, the amount of bone resorbed exceeds that being formed, resulting in net bone loss (inflammation-induced osteolysis). In some patients, however, inflammation-induced bone formation exceeds resorption, and a sclerotic lesion will develop. The cellular and molecular pathogenetic mechanisms in inflammation-induced osteolysis and sclerosis are discussed in the present review. The cytokines believed to be involved in inflammation-induced remodeling are very similar to those suggested to play crucial roles in post-menopausal osteoporosis. In patients with periodontal disease and concomitant post-menopausal osteoporosis, the possibility exists that the lack of estrogen influences the activities of bone cells and immune cells in such a way that the progression of alveolar bone loss will be enhanced. In the present paper, the evidence for and against this hypothesis is presented.

[Influence of the alveolar bone height on stress distribution of post and core restored maxillary premolar]

OBJECTIVE

To investigate the stress distribution of post and core restored maxillary premolar with reduced alveolar bone support.

METHODS

Cone-beam CT based 3D finite element models of post and core restored maxillary premolar were established, with 3 different alveolar bone support. Group I (control) simulated a clinical situation without horizontal bone loss. In group II, a horizontal bone loss of 25% and in group III of 50% were simulated. Both cast-metal post and prefabricated-fiber post were used. The influence of the alveolar bone height was investigated through three-dimensional elastic finite element static analyses by comparison of the resulting stress field, under vertical and oblique load. Local stress measures were introduced to allow for the assessment of tooth fracture.

RESULTS

The von Mises stress value (vertical/oblique) on dentin were measured as follows: group I-gold=22.570/66.354, group I-fiber=16.480/58.103; group II-gold=27.690/95.192, group II-fiber=18.260/68.452; group III-gold=37.363/135.010, group III-fiber=24.291/110.170.

CONCLUSION

For post and core restored teeth with horizontal bone loss, the alveolar bone support may affect the stress distribution under vertical and oblique load. Reduction of the alveolar bone support may lead to severely increased stress concentration in the root dentin.

The use of tapered implants in the maxillae of periodontally susceptible patients: 10-year outcomes

PURPOSE

This study is a retrospective assessment of the long-term efficacy of dental implant therapy in periodontally susceptible patients.

MATERIALS AND METHODS

A private-practice chart review was conducted to identify partially dentate subjects treated with implant-supported restorations that had been monitored annually for at least 9.5 years. Subjects were assigned to either a periodontal group or a control group according to their health histories. Data were entered into spreadsheets on a personal computer and analyzed statistically with dedicated software.

RESULTS

Thirty periodontal subjects were treated with 138 implants and 45 prostheses, and 16 control subjects were treated with 35 implants and 21 prostheses. The mean follow-up was 130 months. One implant failed before loading in the periodontal group. Cumulative 10-year survival rates were 99.3% (n = 137/138) for periodontal implants and 100% (n = 35/35) for control implants. Most surviving implants had no bone loss (n = 109/172, 63.4%). Most of the surviving implants with bone loss (n = 63/172, 36.6%) were concentrated in the periodontal cohort (90%, n = 57/63) and among women (60%, n = 15/25) regardless of cohort. Prosthesis failure was 25.2% (n = 16/66), with 12 porcelain fractures, 2 cement failures, and 2 framework fractures. In all cases, failed prostheses were immediately replaced and patients continued to function.

CONCLUSIONS

Periodontal susceptibility resulted in increased bone loss but did not affect implant survival. The cause of greater bone loss in women could not be determined from the data but may have been related to the postmenopausal status of the subject population (mean age = 54 years).

On osseointegration: the healing adaptation principle in the context of osseosufficiency, osseoseparation, and dental implant failure

The host-implant interface is remarkably enduring given the functional and biologic challenges it faces, and our success in assisting patients to lead better lives because of implant biotechnology is the envy of many other health care practitioners. It is therefore vital that dentists accept that clinically significant marginal bone loss is uncommon and that implant failure is rare. In this paper, important elements regarding why implants experience marginal bone loss, why implants may fail as a result of such bone loss, and how to describe the continuum of bone loss with respect to patient-mediated outcomes are outlined.

Long-term neuromuscular status in overdenture and complete denture patients with severe mandibular atrophy

PURPOSE

The long-term neuromuscular status of edentulous patients with severe mandibular atrophy who wore complete dentures (CDs) or implant-supported overdentures (ISOs) was investigated in the present study.

MATERIALS AND METHODS

Eleven CD patients and 11 patients with ISOs supported by two implants took part in the study. All patients had used their dentures for more than a decade. All patients (average age, 76 years) suffered from severe mandibular atrophy, which was to be quantified using panoramic radiographs and computer software. Kinesiographic parameters such as opening and extension movements as well as opening and closing velocities were recorded by means of a sirognathograph during test food chewing on the left and right sides. Simultaneously, electromyographic recording of masseter and temporalis activities was performed using surface electrodes.

RESULTS

The kinesiographic values obtained from ISO patients were higher than those for CD patients: 12.65 mm for vertical opening (CD, 11.79 mm) and 5.66 mm for horizontal extension (CD, 5.11 mm). Opening velocity values were 100.93 mm/s and 91.74 mm/s, respectively. Closing velocity of 78.16 mm/s in ISO patients was significantly different from that measured in CD patients (58.45 mm/s). With regard to electromyographic activities, the increase was significant for the masseter during chewing on the working side (ISO: 189.79 μV, CD: 78.05 μV) and on the nonworking side (ISO: 130.53 μV, CD: 47.25 μV). For the temporalis, values of 194.11 μV and 119.02 μV in the ISO and CD patients, respectively, were observed for working side chewing. Nonworking side values reached 155.48 μV for ISO subjects and 78.35 μV for CD subjects, which was significantly different. The degree of atrophy in both groups did not differ statistically.

CONCLUSIONS

The use of two interforaminal implants with an overdenture can provide long-term neuromuscular benefits for edentulous patients.

Immediate loading of unsplinted implants in the anterior mandible for overdentures: 3-year results

PURPOSE

This 3-year study evaluated the implant survival rate, peri-implant tissue response, prosthetic maintenance, and prosthetic complications in a series of patients who received two immediately loaded unsplinted threaded implants to retain a mandibular overdenture.

MATERIALS AND METHODS

Eight completely edentulous patients were evaluated clinically and radiographically immediately after implant placement, at 3 months, and at 1, 2, and 3 years after implant placement. Data were analyzed using repeated-measures one-way analysis of variance and the Wilcoxon signed rank test at a significance level of α = .05.

RESULTS

At 3 years, all implants remained osseointegrated (16/16), with an overall mean marginal bone change of -0.58 ± 0.39 mm and a mean Periotest value of -7.19 ± 0.54. The modified Plaque Index scores showed marked improvement in oral hygiene during the first year, but some relapse was observed thereafter. Prosthetic maintenance and complications included replacement of the attachment inserts, abutment loosening, dislodgement of the attachment housing, overdenture reline, denture tooth fracture, and overdenture base fracture.

CONCLUSIONS

This 3-year study suggests that, despite less than ideal oral hygiene and a high incidence of complete/partial fracture of overdentures, favorable implant survival rate and peri-implant tissue responses can be achieved in mandibular overdentures retained with two immediately loaded unsplinted threaded implants.

In-vitro simulation of tooth mobility for static and dynamic load tests: a pilot study

OBJECTIVE

Simulation of tooth mobility in vitro with or without reduced bone support is an aspect of particular interest from the clinical perspective. To elucidate adequate simulation of the periodontal ligament in terms of tooth mobility, three materials were investigated.

METHODS

Human lower sound premolars were selected and randomly assigned to six groups (n = 5) and stored at 37°C in a 0.5%-chloramine solution. For tooth mobility simulation, roots were covered with a thin layer of three types of material: (i) polyurethane elastomeric material, (ii) polyether impression material and (iii) A-polysiloxane soft cushion material. Teeth were embedded in an acrylic resin block simulating no and 50% bone loss, respectively. Specimens were statically subjected up to a maximum load of 30 N perpendicular to tooth axis (crosshead speed = 1 mm/min) in a universal material testing machine. Load-deflexion curves and periotest values were recorded. Statistical analysis was performed using 2-way Anova and post-hoc Bonferroni Test (p = 0.05). The Pearson's correlation coefficient between deflexion and periotest values was calculated.

RESULTS

Median horizontal deflexion values (μm) of specimen crowns with no bone loss were significant higher for polysiloxane (210) compared to polyurethan (24) (p < 0.001). The tooth deflexion, e.g. tooth mobility, increased significantly as the bone level decreased only when specimens were embedded in polysiloxane (iii) (1150) (p = 0.045). All specimens with reduced bone support layered with polyether were dislocated. Deflexion was significantly positive correlated with periotest values (p = 0.01).

CONCLUSION

Using A-polysiloxane soft cushion material combined with autopolymerizing acrylic resin may be suitable to simulate increased tooth mobility in vitro.

Functional tooth regeneration using a bioengineered tooth unit as a mature organ replacement regenerative therapy

Donor organ transplantation is currently an essential therapeutic approach to the replacement of a dysfunctional organ as a result of disease, injury or aging in vivo. Recent progress in the area of regenerative therapy has the potential to lead to bioengineered mature organ replacement in the future. In this proof of concept study, we here report a further development in this regard in which a bioengineered tooth unit comprising mature tooth, periodontal ligament and alveolar bone, was successfully transplanted into a properly-sized bony hole in the alveolar bone through bone integration by recipient bone remodeling in a murine transplantation model system. The bioengineered tooth unit restored enough the alveolar bone in a vertical direction into an extensive bone defect of murine lower jaw. Engrafted bioengineered tooth displayed physiological tooth functions such as mastication, periodontal ligament function for bone remodeling and responsiveness to noxious stimulations. This study thus represents a substantial advance and demonstrates the real potential for bioengineered mature organ replacement as a next generation regenerative therapy.

Serum alkaline phosphatase: a potential marker in the progression of periodontal disease in cirrhosis patients

OBJECTIVE

As a consequence of their liver dysfunction, cirrhotic patients have elevated levels of serum alkaline phosphatase (ALP). Increased ALP activity is seen in periodontal tissues during the progression of periodontitis. The present study was carried out to compare ALP levels in cirrhosis patients with and without periodontitis and to correlate ALP levels with the severity of periodontitis.

METHOD AND MATERIALS

Both the test and control groups consisted of 30 liver cirrhosis patients with or without periodontitis. The parameters recorded were modified OHI-S Index, Gingival Index (GI), and clinical attachment level (CAL). All patients underwent standardized panoramic radiographs to assess alveolar bone height. The total serum ALP was determined with the kinetic method (R.A 50).

RESULTS

Alveolar bone loss (ABL) was 1.62 ± 0.32 mm in the test group and 0.28 ± 0.04 mm in the control group. Mean clinical attachment level (CAL) for the test group was greater than the control group: 2.34 ± 0.67 mm and 0.43 ± 0.14 mm, respectively. The mean serum alkaline phosphatase level in the test group was higher (39.94 ± 3.34) than the control group (29.42 ± 6.11) and the differences was statistically significant (P > .05). When comparison was made between age group (20 to 40 years and 41 to 60 years), the older age group liver cirrhosis patients exhibited significantly higher values for bone loss, clinical attachment level, and serum ALP level.

CONCLUSION

There is strong positive correlation between periodontal breakdown and serum alkaline phosphatase level in liver cirrhosis patients.

Rehabilitation of the edentulous maxilla with the zygoma concept: a 7-year prospective study

PURPOSE

The success of zygomatic implants following the two-stage, as well as the immediate loading, concept has been well documented. This graftless approach for the treatment of the completely edentulous resorbed maxilla allows for rehabilitation with an implant-supported fixed prosthesis. The purpose of this prospective study is to report on the 7-year follow-up of patients treated with zygomatic implants in conjunction with two to four anterior maxillary implants placed into immediate function and restored with a definitive fixed prosthesis.

MATERIALS AND METHODS

This prospective study involved 36 patients treated with 74 zygomatic implants and 98 anterior maxillary implants supporting fixed prostheses between 2003 and 2005.

RESULTS

Two zygomatic implants in two patients were identified as mobile at stage-two surgery; replacement implants resulted in successful osseointegration. All anterior maxillary implants were determined as osseointegrated at stage two. Three patients experienced unilateral maxillary sinus infections that were refractory to oral antibiotics and were treated with functional endoscopic sinus surgery, which resolved the infections. All patients treated with the immediate loading concept were restored with definitive fixed profile prostheses as planned.

CONCLUSION

The high survival rate, reduced morbidity, and high rate of patient acceptance for the zygomatic implant concept allowed the rehabilitation of the resorbed edentulous maxilla with fixed implant-supported prosthesis, rendering this procedure a viable and a predictable treatment option.

Biomechanical behaviour of tooth-supported fixed partial dentures by 3D FEA

This three-dimensional finite element analysis first described stresses distribution in loaded posterior fixed partial dentures, then compared the influences of bone height, abutment roots number and pontic length on their displacements. Twelve mandibular (three to five unit) FDPs integrating periodontal ligaments were designed. Stresses were localized in connectors and cervical areas of abutments near the edentulous span. The main FDPs' displacements consisted of vertical translation increasing with low bone height. FDPs underwent simultaneously an anteroposterior displacement (about ten times smaller) towards the weakest abutment side. Splinted abutments affected this anteroposterior displacement. Span length was associated with small beam deflection.

Biomechanical repercussions of bone resorption related to biologic width: a finite element analysis of three implant-abutment configurations

Most biomechanical studies of implant-supported restorations have not taken into account the biologic changes that occur following exposure of the implants to the oral environment. Therefore, the present finite element analysis study was designed to compare the biomechanical response of three types of implant-abutment configurations both before and after establishment of a new biologic width. The three functional units studied were: a 5-mm implant platform connected with an external hexagon to a 5-mm-diameter abutment (type 1), a 5-mm implant platform connected with an external hexagon to a 4.1-mm-diameter abutment (type 2), and a 4.8-mm implant platform connected with an internal hexagon to a 4.1-mm-diameter abutment (type 3). The type 3 design, which combined platform switching with an internal connection, exhibited the smallest distortions in stress distribution after bone modeling, and the stress was distributed over the entire contact surface most smoothly and uniformly. Bone resorption following creation of the biologic width changes the biomechanical behavior of a restoration. In this study, the two implant-abutment designs featuring a smaller-diameter abutment on a larger-diameter implant platform achieved better results than the implant featuring the same-diameter implant platform and abutment, even though their initial bio?mechanical load potential was lower. (Int J Periodontics Restorative Dent 2009;29:479-487.).

Effect of homologous PRP on proliferation of human periodontally affected osteoblasts. In vitro preliminary study. Report of a case

OBJECTIVE

The purpose of this in vitro study was to evaluate the effect of two concentrations of homologous platelet-rich plasma (PRP) on the proliferative response of osteoblasts derived from a patient with aggressive periodontitis.

METHODS

8.5 ml of venous blood were taken from 1 healthy and non-smoker volunteer. PRP was prepared following the protocol of Curasan. Osteoblasts were derived from alveolar bone chips obtained from a patient with aggressive periodontitis during conventional periodontal surgery and a clinically healthy person during crown lengthening surgical procedure. Cells were grown in 24-well dishes and on day 2 of quiescence were treated with 1% and 5% (v/v) of PRP. The effect on cell proliferation was estimated by measuring [3H] thymidine incorporation. After 48h of incubation, cells were processed to subject to scintillation counting. Counts per minute were determined for each sample.

RESULTS

The addition of 1% and 5% of PRP provoked a statistical significant (p<0.05) increase in cell growth.

CONCLUSIONS

Data revealed significant enhancement of proliferative response of osteoblasts in the presence of PRP, which might serve as a source of growth factors promoting periodontal repair by modulating cell response and activities.

Parametric analysis of the strength in the ''Toronto'' osseous-prosthesis system

AIM

The aim of this work is to analyze how the different distributions of the chewing load could be related to dental prosthesis fractures of the Toronto restoration via the fulfilment of a virtual parametric model. Moreover investigation about implant positions and perspectives in comparison with a virtual medial plane was made to evaluate the incidence of screw and prosthesis breakage.

METHODS

Finite element analysis of the lower jaw was performed to underline parameters and mechanical features of dental implants connected with the fractures of the prosthetic restoration. Jaw virtual model and 3D fixtures (Global Sweden and Martina) were created by Cosmos-Solid Works. Matlab was used to recreate the distribution of an unspecific chewing phase analyzing the overall load on the fixtures of the lower jaw.

RESULTS

Four virtual 3D models were performed with Matchad 14, for data analysis. The study investigated frontal and horizontal planes and vertical direction of the occlusal forces. Data results showed how position and perspective of fixtures strongly influenced the stress distribution upon the bone of the jaw; safeguard of prostheses elements like cantilever, passing screws, and dental implants are strictly related to a correct selection of the dental implant position.

CONCLUSIONS

The 3D geometry of the jaw is an important condition for the choice of position, number, diameter and length of dental implants used for Toronto prostheses. This study would suggest a virtual ''method'' to help the surgeon choosing a correct model for a prosthetic rehabilitation evaluating position, perspective, and stress distribution of the chewing strengths.

The effects of systemic stress on orthodontic tooth movement

OBJECTIVES

To determine if systemic stress affects the biological reactions occurring during orthodontic tooth movement.

METHODS

Four groups of male 10 week-old Wistar rats were used. Group A animals (N=10) were restrained for one hour per day for 40 days; Group B animals (N=10) were restrained for one hour per day for three days; Group C (N=10) and Group D (N=8) animals were unrestrained. The upper left first molars in the rats in Groups A (long-term stress), B (short-term stress) and C (control) were moved mesially during the last 14 days of the experiment. The animals in Group D (N=8) were used for body weight and hormonal dosage comparisons only. They were not subjected to any stress and did not have appliances fitted. All animals were killed at 18 weeks of age and blood collected for measurement of plasma corticosterone. Tooth movement was measured with an electronic caliper. The right and left hemi-maxillae of five rats from each group were removed and the number of tartrate-resistant acid phosphatase (TRAP) positive cells, defined as osteoclasts, adjacent to the mesial roots of the upper first molars counted. The contralateral side in each animal served as the control (split-mouth design).

RESULTS

Corticosterone levels were significantly higher in the stressed groups (Groups A and B) than in the control group (Group C). Tooth movement was significantly greater in Group A (long-term stress) compared with Group B (short-term stress) and Group C (control), which did not differ from each other. There were significantly more osteoclasts in the long-term stress group than in the short-term stress and control groups.

CONCLUSION

Persistent systemic stress increases bone resorption during orthodontic tooth movement. Systemic stress may affect the rate of tooth movement during orthodontic treatment.

Prosthodontic treatment of a patient with Papillon Lefevre syndrome

Papillon Lefevre Syndrome is an autosomal recessive disorder. One of the most destructive forms is a periodontal disease. A 19 year female with the syndrome, came for dental treatment. Most of her natural dentition was missing. The remaining five natural teeth had extensive carious and periodontal lesions. Two poor dentures replaced the missing teeth. Her main oral complaints were poor esthetics, teeth sensitiveness, and dentures instability. All the remaining natural teeth were removed and the dentures repaired and rebased in one session. Following wound healing and the maturation of the residual ridge, a set of complete dentures was made. Two years after the delivery of the full dentures, an additional set of dentures were provided for social and emotional reasons. 9 years after the last extractions, the patient refuses to undergo bone augmentation and osseointegrated implant procedures, for future preventive and oral rehabilitation care. There is a strong possibility of chronic bone tissue resorption conducive to dentures instability, mandibular nerves exposures and or, perforation of the maxillary sinuses.

Factors affecting mandibular residual ridge resorption in edentulous patients: a preliminary report

The aim of the study was to assess the rate of mandibular residual ridge resorption in edentulous patients and to analyse the factors which determine this process. A group of 35 edentulous patients aged between 51 and 89 years, with a mean age of 74 (65-78) years, were included in the study. Individual factors (age, gender and duration of edentulousness), local biochemical parameters (oral hygiene and history of periodontal diseases) and systemic biochemical parameters (calcium and phosphate metabolism, diet, smoking, alcohol intake and systemic diseases), as well as physical factors involved in the process (the use of prosthetic dentures), were analysed. The study was performed on the basis of the results of dental examinations, assessment of panoramic radiograms, research surveys and total calcium and phosphate serum levels, which were determined using a calorimetric method. Bone resorption in the mandible affected all the study patients to varying extents. More than half the edentulous patients showed a high degree of mandibular residual ridge resorption. The duration of mandibular edentulism was found to be closely associated with values of the radiological IC/IM index, which is generally considered to reflect the degree of mandibular resorption. Total calcium serum levels were shown to correlate positively with the value of IC/IM index in these patients.

Gingival blood flow in periodontitis patients before and after periodontal surgery assessed in smokers and non-smokers

BACKGROUND

The aim of this study was to evaluate the gingival blood flow of smokers and non-smokers with periodontal disease before and after surgical periodontal treatment.

METHODS

Nine smokers and six non-smokers with at least two periodontal lesions were included in the study. Laser Doppler flowmetry was used to measure blood flow in two gingival sites and two skin sites. Two intrabony defects were treated surgically at the same time; enamel matrix derivative was applied at random to one of the sites, whereas the other site received a placebo gel. We measured resting gingival blood flow (GBF) and responses to cold pressor test (CPT) and to smoking and made continuous measurements of blood pressure (BP). Resting GBF levels of 26 young healthy subjects were used as a reference value.

RESULTS

Resting GBF was significantly lower for the periodontitis patients compared to the reference subjects, regardless of smoking habits. GBF and gingival vascular conductance (VC) decreased significantly pre- and postoperatively in response to smoking. CPT evoked significant decreases in VC in smokers and non-smokers. Skin blood flow decreased significantly in response to CPT, more so in the non-smokers. BP was significantly higher in the non-smokers.

CONCLUSIONS

Resting GBF of periodontitis patients was not lower in smokers than in non-smokers, but it was significantly lower than in the younger reference subjects. In contrast to our earlier findings in healthy subjects, smoking one cigarette may cause a decrease in GBF and VC in periodontitis patients. These observations suggested the existence of a dysfunction in the gingival vasculature in smokers and non-smokers with periodontitis.

Impact of implant overloading on the peri-implant bone in inflamed and non-inflamed peri-implant mucosa

OBJECTIVE

To assess the impact of overloading on peri-implant bone level and the bone-to-implant contact (BIC) in the presence of healthy or inflamed peri-implant tissues.

MATERIALS AND METHODS

Four screw-shaped machined implants were placed bilaterally in the mandible of four beagle dogs and left submerged for 3 months. Prosthetic abutments were connected either in supra-occlusal contact with the opposite teeth (overloaded) or in infra-occlusal position (unloaded). In each dog, cotton floss ligatures were placed unilaterally around abutments to promote plaque accumulation; the contralateral side was brushed three times a week. There were four experimental sites, two implants in each: loaded uninflamed (LU), loaded inflamed (LI), unloaded uninflamed (UU), and unloaded inflamed (UI). Clinical and radiographic parameters were recorded at baseline and every 3 months throughout the observation period. At 12 months, the dogs were sacrificed and histomorphometric analysis was performed.

RESULTS

Implants with ligature-induced peri-implantitis presented high inflammatory indices throughout the observation period. Clinical parameters did not change from baseline for both LU and UU. Loading significantly increased the percentage of BIC (BIC%) (P<0.05) and slightly increased crestal bone resorption, but not apical to the implant neck. Both LI and UI groups showed significant peri-implant bone loss (P<0.01), mostly horizontal on the buccal aspect and angular on the lingual aspect, which exposed implant threads. Loading significantly (P<0.05) increased implant thread exposure due to buccal and lingual vertical bone resorption.

CONCLUSIONS

In the presence of uninflamed peri-implant mucosa, overloading of implants in the dog model increased BIC% and slightly reduced marginal bone level. However, resorption did not progress beyond the implant neck. Overloading aggravated the plaque-induced bone resorption when peri-implant inflammation was present.

Mechanical stress induces osteopontin expression in human periodontal ligament cells through rho kinase

BACKGROUND

Mechanical stress such as orthodontic forces can produce mechanical damage and inflammatory reaction in the periodontium. Osteopontin (OPN) is a multifunctional cytokine that has been correlated with periodontal disease progression. Because the periodontal ligament (PDL) can be affected by stress and PDL cells are involved in periodontal destruction and remodeling, we aimed to study the influence of mechanical stress on the expression and regulation of OPN in human PDL (HPDL) cells.

METHODS

The mechanical stress was generated by continuous compressive force, and the expression of OPN was examined by reverse transcription-polymerase chain reaction and Western analysis. The application of inhibitors was used to examine the mechanism involved.

RESULTS

Both mRNA and protein expression of OPN significantly increased in a force-dependent manner. Increase of receptor activator of nuclear factor-kappa B ligand (RANKL) was also observed. Interestingly, application of indomethacin could abolish the induction of RANKL but not that of OPN, suggesting the cyclooxygenase-independent mechanism for stress-induced OPN expression. In addition, the upregulation of OPN was diminished by Rho kinase inhibitor but not by cytochalasin B.

CONCLUSIONS

Mechanical stress affects OPN expression in HPDL cells through the Rho kinase pathway. Because OPN participates in bone resorption and remodeling induced by mechanical and biologic signals, these results suggest the significance of stress-induced OPN in HPDL cells in alveolar bone resorption and remodeling.

A study to assess the relative influence of age and edentulousness upon mandibular bone mineral density in female subjects

OBJECTIVE

The aim of this study was to assess the relative influence of age and edentulousness upon mandibular bone mineral density (BMD) in a sample of dentate and edentulous female subjects.

STUDY DESIGN

Seventy-two patients (43-79 years of age; mean age, 62.5 years), of whom 49 were edentulous and 23 dentate, underwent dual x-ray energy absorptiometry (DXA) to determine the BMD of the body of mandible. Mandibular BMD was measured using DXA. The investigators independently determined rectangular regions of interest (ROIs) on the mandibular images, and the computer calculated the BMD of these specified regions. For the dentate patients, the ROIs were placed to exclude the roots of teeth.

RESULTS

A linear multiple regression model was fitted to the dependent variable, mandibular body BMD, with age and whether the patient was edentulous or dentate being explanatory factors in the statistical model. The variable describing the dentate/edentulous state was not significant in the statistical model (P = .91). The model showed that age was significantly related negatively to the BMD of the mandibular body (P = .01).

CONCLUSION

Age was a predictor of mandibular BMD but edentulousness was not.

Spontaneous progression of ligature induced peri-implantitis at implants with different surface roughness: an experimental study in dogs

BACKGROUND

Peri-implantitis is associated with the presence of submarginal plaque, soft-tissue inflammation and advanced breakdown of the supporting bone. The progression of peri-implantitis following varying periods of continuing plaque accumulation has been studied in animal models.

OBJECTIVE

The aim of the current experiment was to study the progression of peri-implantitis around implants with different surface roughness.

MATERIAL AND METHODS

In five beagle dogs, three implants with either a sandblasted acid-etched surface (SLA) or a polished surface (P) were installed bilaterally in the edentulous premolar regions. After 3 months on a plaque control regimen, experimental peri-implantitis was induced by ligature placement and plaque accumulation was allowed to progress until about 40% of the height of the supporting bone had been lost. After this 4-month period, ligatures were removed and plaque accumulation was continued for an additional 5 months. Radiographs of all implant sites were obtained before and after 'active' experimental peri-implantitis as well as at the end of the experiment. Biopsies were harvested and the tissue samples were prepared for light microscopy. The sections were used for histometric and morphometric examinations.

RESULTS

The radiographic examinations indicated that similar amounts of bone loss occurred at SLA and P sites during the active breakdown period, while the progression of bone loss was larger at SLA than at polished sites following ligature removal. The histological examination revealed that both bone loss and the size of the inflammatory lesion in the connective tissue were larger in SLA than in polished implant sites. The area of plaque was also larger at implants with an SLA surface than at implants with a polished surface.

CONCLUSION

It is suggested that the progression of peri-implantitis, if left untreated, is more pronounced at implants with a moderately rough surface than at implants with a polished surface.

Periodontal healing following orthodontic movement of rat molars with intact versus damaged periodontia towards a bony defect

The aim of this research was to determine whether orthodontic tooth movement influences periodontal healing. In 16 male Wistar rats, 12 week of age, a bony defect was created mesial to both maxillary first molars, not including the attachment apparatus (group 1), and in 15 animals, the defect included the periodontal ligament (group 2). In both groups, the right first molar was moved mesially (orthodontic side) for 2 weeks followed by a 1-week retention period; the contralateral molar was not moved (control side). Histomorphometric analysis was performed. The results within and between the different treatment groups and sides were statistically compared by t-test and analysis of variance with repeated measures on logarithmic transformation. Junctional epithelium was significantly larger at the control than at the orthodontic side of both groups (P = 0.024), and significantly larger in group 2 than in group 1 (P < 0.001). A significantly (P = 0.034) larger pocket depth was found at the control side in group 1. Supracrestal connective tissue was larger at the control than at the orthodontic side for both groups and significantly larger in group 2 than in group 1 (P = 0.004). Root resorption was found infrequently only at the orthodontic side in both groups (five out of 31 cases). The principal findings suggest favourable effects of orthodontic tooth movement on restraining epithelial apical down-growth and decreasing pocket depth. Orthodontic treatment could not completely avoid formation of a long epithelial attachment. Therefore, periodontal regenerative surgery might be indicated prior to orthodontic tooth movement. Orthodontic movement, shortly after periodontal surgery, had no detrimental effect on periodontal soft tissue healing or on diminished but non-inflamed periodontal tissues.

Comparison of naturally occurring and ligature-induced peri-implantitis bone defects in humans and dogs

OBJECTIVES

The aim of the present study was to evaluate and compare naturally occuring and ligature-induced peri-implantitis bone defects in humans and dogs.

MATERIAL AND METHODS

Twenty-four partially and fully edentulous patients undergoing peri-implant bone augmentation procedures due to advanced peri-implant infections were included in this study (n=40 implants). Furthermore, peri-implantitis was induced by ligature placement and plaque accumulation in five beagle dogs for three months following implant insertion (n=15 implants). The ligatures were removed when about 30% of the initial bone was lost. During open flap surgery, configuration and defect characteristics of the peri-implant bone loss were recorded in both humans and dogs.

RESULTS

Open flap surgery generally revealed two different classes of peri-implant bone defects. While Class I defects featured well-defined intrabony components, Class II defects were characterized by consistent horizontal bone loss. The allocation of intrabony components of Class I defects regarding the implant body allowed a subdivision of five different configurations (Classes Ia-e). In particular, human defects were most frequently Class Ie (55.3%), followed by Ib (15.8%), Ic (13.3%), Id (10.2%), and Ia (5.4%). Similarly, bone defects in dogs were also most frequently Class Ie (86.6%), while merely two out of 15 defects were Classes Ia and Ic (6.7%, respectively).

CONCLUSIONS

Within the limits of the present study, it might be concluded that configurations and sizes of ligature-induced peri-implantitis bone defects in dogs seemed to resemble naturally occurring lesions in humans.

Effects of lactation on alveolar bone loss in experimental periodontitis

BACKGROUND

The development and progression of periodontitis are accelerated by various systemic conditions. The present study was designed to determine whether lactation affects alveolar bone loss in rat models of experimental periodontitis.

METHODS

Sixty-two female Wistar rats were bred with male rats and divided into three groups that were fed diets containing 0.9%, 0.3%, and 0.02% calcium. They were divided further into two subgroups of lactating and non-lactating animals. An elastic ring was placed around the neck of the right mandibular first molar to induce periodontitis (experimental side) on day 32 after mating. The left first molar was not fitted with an elastic ring (control side). After the lactation period, bone mineral density (BMD) was determined, and a histologic examination of the interdental alveolar bone was performed.

RESULTS

On the experimental and control sides, BMD decreased significantly according to the amount of calcium in the diet; however, the magnitude of this decrease was much greater in the lactating group. Histologic examination revealed that in lactating and non-lactating rats, the decrease in BMD was accompanied by a decrease in alveolar bone height on the experimental side, whereas similar results were not seen on the control side.

CONCLUSIONS

Lactation could be a risk factor for alveolar bone loss, especially under conditions of calcium insufficiency. Increased systemic demand for calcium and an insufficient supply of calcium might enhance the development of alveolar bone loss in periodontitis.

Analysis of stress and strain around orthodontically loaded implants: an animal study

PURPOSE

The aim of this study was to describe the stress and strain fields around orthodontically loaded dental implants using the finite element method and to evaluate the relationship between the generated strain and the biologic reaction expressed through histomorphometric parameters. Finally, this study aimed to evaluate the interaction between the orthodontic loading and the deformation generated by normal occlusal function.

MATERIALS AND METHODS

Sixteen titanium dental implants were inserted in extraction sockets after the removal of the second premolars and first molars of 4 adult Macaca fascicularis monkeys. After 17 weeks of healing, the implants were loaded by a pair of Sentalloy springs (50 cN) for 16 weeks. After sacrifice, tissue blocks including the implants and surrounding bone were excised. Five tissue blocks were scanned with a synchrotron radiation-based microtomography (microCT) scanner and sample-specific finite element models were generated. Subsequently all samples were prepared for histomorphometric analysis.

RESULTS

All implants were osseointegrated, although the surrounding alveolar bone differed from sample to sample. As a consequence the finite element analyses showed that the stresses and strains in the peri-implant alveolar bone greatly varied among the samples. A high level of remodeling activity was found close to the implants.

DISCUSSION

Individual differences between the receptors (in this case, the monkeys) have a large effect on both the biologic and morphologic parameters. These variations were indeed found to have a substantial impact on the (re)modeling dynamics and the load transfer mechanisms around the implants.

CONCLUSIONS

By integrating different analysis techniques to evaluate bone (re)modeling around orthodontically loaded implants, this study has demonstrated the complexity and case-specific character of alveolar adaptation to orthodontic loading. Furthermore, stresses generated by combined functional and orthodontic forces should not be neglected.

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.

Influence of alveolar support on stress in periodontal structures

The influence of alveolar bone support on the functional capability of a tooth remains unclear. It was hypothesized that a reduction in alveolar support causes an increase of maximum stress in the periodontal structures. Mathematical models of the maxillary incisor to simulate in vivo tooth movement were constructed with periodontium of normal or reduced bone height, and normal or widened periodontal ligament (PDL) space. Under simulated bite force, the maximum tensile stress at the lingual cervical region in the PDL increased with bone height reduction, but decreased with PDL widening. The compressive stress at the cervical region in the cortical bone was no more than 22% of the yield strength of bone, and did not increase by the height reduction with widened PDL. The result suggests that the height reduction potentially causes mechanical damage to the PDL, but, of itself, is not likely to have a negative effect on the bone.

Bone regeneration in dehiscence-type defects at chemically modified (SLActive�) and conventional SLA titanium implants: a pilot study in dogs

OBJECTIVES

The aim of the present study was to evaluate bone regeneration in dehiscence-type defects at titanium implants with chemically modified (mod) and conventional sand-blasted/acid-etched (SLA) surfaces.

MATERIAL AND METHODS

Standardized buccal dehiscence defects (height: 3 mm, width: 3 mm) were surgically created following implant site preparation in both the upper and lower jaws of four beagle dogs. modSLA and SLA implants were inserted bilaterally according to a split-mouth design. The animals were sacrificed after 2 and 12 weeks (n=2 animals each). Dissected blocks were processed for histomorphometrical analysis: defect length, new bone height (NBH), percent linear fill (PLF), percent of bone-to-implant contact (BIC-D) and area of new bone fill (BF).

RESULTS

Wound healing at SLA implants was predominantly characterized by the formation of a dense connective tissue at 2 and 12 weeks, without significant increases in mean NBH, PLF, BIC-D or BF values. In contrast, modSLA implants exhibited a complete defect fill at 12 weeks following implant placement. In particular, histomorphometrical analysis revealed the following mean values at 12 weeks: NBH (3.2+/-0.3 mm), PLF (98%), BIC-D (82%) and BF (2.3+/-0.4 mm(2)).

CONCLUSION

Within the limits of the present study, it was concluded that modSLA titanium surfaces may promote bone regeneration in acute-type buccal dehiscence defects at submerged implants.

Influence of the Period After Ovariectomy on Femoral and Mandibular Bone Density and on Induced Periodontal Disease

BACKGROUND

This study investigated the influence of the period after ovariectomy on femoral and mandibular bone mineral density (BMD) and on induced periodontal disease.

METHODS

One hundred and twenty-six female Holtzman rats were divided into nine groups: control, sham surgery (SHAM) with and without induction of periodontal disease for 51 and 150 days, and ovariectomy (OVX) with and without induction of periodontal disease for 51 and 150 days. Periodontal disease was induced by placing ligatures on the first lower molars during the last 30 days of each period. BMD was measured by dual-energy x-ray absorptiometry. Vertical bone loss was determined by measuring the distance from the alveolar bone crest to the cemento-enamel junction on the mesial side of the first lower molar.

RESULTS

Statistical analyses (Kruskal-Wallis test) revealed a significant difference between the OVX and SHAM groups' global and femoral proximal epiphysis BMD (P <0.001) for 150 days and in the global evaluation for 51 days. For mandibular BMD, no difference was found between the groups of each period. Influence of the period on femoral BMD was found only for the SHAM groups, with lower BMD for the 51-day period compared to the 150-day period (P <0.05). In the global evaluation of the mandible, a lower BMD was found after 51 days. The period was a contributing factor for the vertical bone loss, and it resulted in higher values for the 51-day period (P <0.05).

CONCLUSION

The period influenced the femoral BMD and the vertical bone loss in induced periodontal disease.

IFN-gamma stimulates osteoclast formation and bone loss in vivo via antigen-driven T cell activation

T cell-produced cytokines play a pivotal role in the bone loss caused by inflammation, infection, and estrogen deficiency. IFN-gamma is a major product of activated T helper cells that can function as a pro- or antiresorptive cytokine, but the reason why IFN-gamma has variable effects in bone is unknown. Here we show that IFN-gamma blunts osteoclast formation through direct targeting of osteoclast precursors but indirectly stimulates osteoclast formation and promotes bone resorption by stimulating antigen-dependent T cell activation and T cell secretion of the osteoclastogenic factors RANKL and TNF-alpha. Analysis of the in vivo effects of IFN-gamma in 3 mouse models of bone loss - ovariectomy, LPS injection, and inflammation via silencing of TGF-beta signaling in T cells - reveals that the net effect of IFN-gamma in these conditions is that of stimulating bone resorption and bone loss. In summary, IFN-gamma has both direct anti-osteoclastogenic and indirect pro-osteoclastogenic properties in vivo. Under conditions of estrogen deficiency, infection, and inflammation, the net balance of these 2 opposing forces is biased toward bone resorption. Inhibition of IFN-gamma signaling may thus represent a novel strategy to simultaneously reduce inflammation and bone loss in common forms of osteoporosis.

Threaded versus porous-surfaced implants as anchorage units for orthodontic treatment: three-dimensional finite element analysis of peri-implant bone tissue stresses

PURPOSE

A 3-dimensional finite element model was developed to investigate the cause of different crestal bone loss patterns observed around sintered porous-surfaced and machined (turned) threaded dental implants used for orthodontic anchorage in a previously reported animal study.

MATERIALS AND METHODS

Twenty-noded structural solid elements with parabolic interpolation between nodes were used for modeling the bone-implant interface zone. A 3-N traction force acting between either 2 porous-surfaced or 2 machined threaded implants placed in canine premolar mandibular sites and bone profiles observed at initiation and 22 weeks of orthodontic loading were modeled.

RESULTS

Higher maximum stresses in peri-implant bone next to the coronal region of the implants were predicted with the machined threaded implants at both the initial and final time points, with the values 20% greater than those predicted after the 22-week loading period. These values were approximately 200% greater than those predicted for the porous-surfaced implants, for which a more uniform stress distribution was predicted.

DISCUSSION

The finite element model results indicated that the observed greater retention of crestal bone next to the porous-surfaced implants was attributable to lower peak stresses developing in crestal peri-implant bone with this design, which decreased the probability of bone loss related to local overstressing and bone microfracture.

CONCLUSION

The predicted lower stresses were a result of the more uniform transfer of force from implant to bone with the porous-surfaced implants, which was a consequence of the interlocking of bone and implant possible with this design.

Impaired Masticatory Behavior in Subjects With Reduced Periodontal Tissue Support

BACKGROUND

Mechanoreceptors situated in the periodontal ligament provide detailed information about intensive and spatial aspects of tooth loads, which support the neural control of masticatory forces. We asked whether a reduced periodontal ligament due to periodontitis, and, thus, an altered mechanoreceptive innervation of the teeth, would affect masticatory behavior when subjects used incisors to hold and split food.

METHODS

We tested 11 subjects with reduced periodontal tissue support that rendered 30% to 70% alveolar bone loss for at least one pair of opposing anterior incisors. Forces were recorded when subjects used their affected incisors to hold half of a peanut for approximately 4 seconds and then split it. Age- and gender-matched healthy subjects served as the control group. None of the participants showed acute oral symptoms or massive periodontal inflammation.

RESULTS

The test group used greater force when holding food between the teeth (1.1+/-0.4 N [ mean+/-1 SD]) compared to the control group (0.4+/-0.2 N). Hold forces used by subjects in the test group were also more variable, both within and between trials. The increase in bite force applied to split the peanut was slower and more hesitant for subjects in the test group compared to the control group.

CONCLUSIONS

Reduced periodontal tissue support accompanies impaired regulation of masticatory forces. Faulty mechanoreceptive innervation of the periodontal ligament explains the elevated hold force, whereas a change in biting strategy due to the weakened support of the teeth may account for the more defensive food-splitting behavior.