Accuracy of 6 Desktop 3D Printers in Dentistry: A Comparative In Vitro Study

PURPOSE

To compare the accuracy of 6 desktop 3D printers in dentistry.

METHODS

A parallelepiped (PP) with known geometry and holes of different diameters was designed and printed with 6 desktop 3D printers (Sheraprint 40®; Solflex 350®; Form 2®; MoonRay D75®; Vida HD®; XFAB 2000®). For each printer, 9 PPs were printed with proprietary materials; these PPs were not cured and underwent dimensional analysis by optical microscopy and precision probing. A file representative of a dentate model (DM) was also printed with the aforementioned printers. For each printer, 3 DMs were printed with the proprietary materials. These DMs were cured and after 1 month, scanned with a desktop scanner and superimposed on the virtual reference model, to investigate trueness.

RESULTS

Dimensional analysis by optical microscopy and precision probing highlighted the reliability of the 3D printed models; errors were compatible with clinical use. However, both linear and diameter measurements revealed statistically significant differences between the machines. The trueness of the DMs 1 month after printing was low, suggesting that they underwent dimensional contraction over time, albeit with differences between the printers.

CONCLUSIONS

The 3D printed models showed acceptable accuracy, although statistically significant differences were found among them.

Primordial odontogenic tumour: A systematic review of the common but also unusual features of this novel entity

BACKGROUND

Primordial odontogenic tumour (POT) is a novel entity that was described in 2014 and that is included in the group of benign mixed epithelial and mesenchymal odontogenic tumours. In recent years, several papers have added new cases with some clinical and histopathological aspects that slightly differ from those described in the original report. The aim of this systematic review is to update all available data on POT published in the literature and to identify those features of the neoplasm that require further investigation.

MATERIALS AND METHODS

A systematic review of literature was conducted using PubMed, Embase, Web of Science and Scopus. Additional sources were also checked. Publications reporting cases with enough clinicopathological information were included, without any time or language restrictions. Histopathological or radiological studies were considered for qualitative analysis.

RESULTS

A total of 30 publications were included. Seventeen papers were used for quantitative analysis while 13 papers were used only for qualitative analysis. A total of 18 cases of POT were identified. Some clinical, radiographic, histopathological and therapeutic features were common in all reported cases, while other aspects of the neoplasm were inconsistent through published cases. This inconsistency was particularly remarkable when dealing with the histopathological features of the neoplasm.

DISCUSSION

Some issues about POT remain unclear and deserve to be clarified by future reports. The description of the odontogenic epithelium covering the ectomesenchyme is often contradictory, while it remains debatable whether peripheral ameloblastic epithelial islands or hard dental tissue deposition can occasionally occur within the tumour.

Clinical, histomorphological and therapeutic features of the Van der Woude Syndrome: literature review and presentation of an unusual case

BACKGROUND

Van der Woude syndrome (VWS), an autosomal dominant condition associated with lower lip pits and/or cleft palate, is caused by mutations in the interferon regulatory factor 6 gene (lRF6 gene). The genetic alterations identified to date that contribute to expression of the syndrome are chiefly mutations located on chromosome 1 (the largest of our chromosomes), mutations at p36 that codifies the gene GRHL (grainy-head transcriptor factor) and mutations involving IRF6 (interferon regulatory factor). With frequency ranging from 1:35,000 to 1:100,000, depending on ethnicity, gender, and socio-economic status, the syndrome accounts for about 2% of orofacial clefts. The clinical and histomorphological aspects of VWS are studied, and a case of heterozygous female twins of whom only one was affected with VWS is reported.

CONCLUSION

This very rare case (no similar case has been reported to date) contributes further evidence on modifying factors in the expression of this condition.

Characterization of human apical papilla-derived stem cells

Dental tissues represent an alternative and promising source of post-natal Mesenchymal stem cells (MSCs) for tissue engineering. Furthermore, dental stem cells from apical papilla (SCAPs) cells can be obtained from the wisdom tooth which is unnecessary for human masticatory function and frequently extracted for orthodontic reasons or dysodontiasis. More precisely, apical papilla is the immature, mostly uncalcified, precursor of the tooth root, therefore is composed of more undifferentiated cells than dental pulp. In addition, tooth extraction, especially by piezosurgery technique, can be considered less invasive in comparison to bone marrow or other tissues biopsy. Our work is aimed to investigate the safety of and predictable procedure on surgical immature third molar extraction and to provide new insight on SCAP research for future biomedical applications. The isolated cells were examined for stem cell properties by analyzing their colony-forming efficiency, differentiation characteristics and the expression of MSC markers.

Platelet rich fibrin in the management of medication-related osteonecrosis of the jaw: a clinical and histopathological evaluation

Bisphosphonates are antiresorptive pharmacological agents used in the treatment of osteoporosis. Recently, osteonecrosis of the jaw has been recognized as a potential side effect in patients on long-term bisphosphonate therapy. This condition, popularly called bisphosphonate-related osteonecrosis of the jaw (BRONJ), has been rechristened as MRONJ (medication-related osteonecrosis of the jaw) to accommodate the increasing number of cases of osteonecrosis of jaws associated with various other antiresorptive and antigiogenic pharmacological therapies. The aim of the present study was to assess the outcome of using platelet-rich fibrin (PRF) for the treatment of MRONJ in a single study group. Twenty-three consecutive patients (15 females and 8 males; aged 52-73 years) with MRONJ were enrolled in this study. These patients presented a history of bisphosphonate medication of varying duration, presence of exposed bone in the maxillofacial region for more than eight weeks, and no history of radiation therapy to the jaws. These patients were managed by surgical curettage and application of platelet rich fibrin (PRF). The outcomes were assessed using clinical and histopathological methods. On the basis of the present findings, we can conclude that PRF can act as an effective barrier membrane between the alveolar bone and the oral cavity and may offer a fast, easy and effective alternative method for the closure of bone exposure in MRONJ patients.

Oral manifestations of selective IgA-deficiency: review and case-report

Immunoglobulin A deficiency is the most common primary immunodeficiency defined as decreased serum level of IgA (less than 7 mg/dl) in the presence of normal levels of other immunoglobulin isotypes. Most individuals with IgA deficiency are asymptomatic and identified coincidentally. However, some patients may present with recurrent infections, allergic disorders and autoimmune manifestations, such as diabetes mellitus, Graves disease and celiac disease. The international literature has not produced any kind of review yet about intra-oral manifestations of selective IgA-deficiency. L.S., a 7-year-old Caucasian girl, was examined at our hospital. After she had undergone a professional dental cleaning, a symmetric, bilateral ulcerative gingivitis developed nearby the upper second primary molars. The gingival ulcers were persistent and did not disappear in the following 3 weeks. In the meantime, the young patient reported the presence of gastrointestinal symptoms. IgA serum level was 4.5 mg/dl, while the other isotypes levels were in the common range. The diagnosis of selective IgA-deficiency was formulated and the girl underwent further examination for the specific IgG autoantibodies in celiac disease, which were not present. Consequently, a full prevention program was planned. This case report emphasizes the role of the paediatric dentist in the early detection of systemic disorder, such as the immunological diseases. The oral cavity often reveals to be the first site of manifestation of important systemic diseases. Immunoglobulin A (IgA) deficiency is the most common primary immunodeficiency and is defined as a decrease in serum IgA levels in the presence of normal levels of other immunoglobulin isotypes (1). Serum IgA deficiency was first described in children with ataxia-telangiectasia (2) and has since been identified in other patients, including normal patients. The prevalence of IgA deficiency ranges from 1:223 to 1:1000 in community studies and from 1:400 to 1:3000 in healthy blood donors (3).

Periodontal microbioma and rheumatoid arthritis: The role of Porhyromonas gingivalis

Rheumatoid Arthritis is a disease, which can be described as an autoimmune response after molecular mimicry caused by infective agents. The current study aims at evaluating the correlation between Rhematoid Arthritis (RA) and Periodontal Disease (PD), with special attention to the microbioma detected in the gums. Thirty-four patients with RD were recruited into the current study. Among rheumatic parameters, Rheumatoid Factor (RF), anti-citrullinated protein antibody (CCP), HLA-BDR1 and DAS28 were collected. A dental clinician evaluated the periodontal screening record (PSR). Afterwards, 1 paper cone was inserted for 30 seconds into the gingival sulcus then sent to the laboratory for evaluation. Quantitative PCR of 16S rRNA genes was performed with the hydrolysis probes method to identify and evaluate the amount Porphyromonas gingivalis, Tannerella forsythensis, Treponema denticola, Fusobacterium nucleatum and Campylobacter rectus. There were no statistical differences in the composition of oral microbioma between PSR groups. There were no statistical significant differences between bacterial loads and serum values. On the contrary, a positive correlation was found between the presence of Porphyromonas gingivalis in periodontal pockets on one side and RF and CCP on the other. Therefore, the presence of Porhyromonas gingivalis in periodontal pockets is associated to RA inflammatory indices.

Space-maintaining management in maxillary sinus lifting: a novel technique using a resorbable polymeric thermo-reversible gel

Several techniques have been proposed to achieve sinus floor elevation and the formation of new bone through the grafting of autologous, heterologous, or alloplastic materials. The grafted materials act as a scaffold for bone formation inside the maxillary sinus. This study investigated a non-graft sinus lifting procedure using a resorbable polymeric thermo-reversible gel. A space-maintaining approach to sinus lifting, using a resorbable polymeric thermo-reversible gel, was applied in 11 patients undergoing implant treatment in the atrophic posterior maxilla. After a healing period of 6 months, a total of 14 implants were placed; biopsies were taken and evaluated histologically and histomorphometrically. The parameters evaluated included the percentages of new bone formation, residual gel, and fibrous tissue. Histological examination showed the formation of new bone with no fibrous tissue or severe inflammatory cellular infiltration. The percentage of newly formed bone was in the range of 54-60%; this consisted of both lamellar and woven bone. No foreign-body reaction was observed. The mean quantities of both residual gel and connective tissue were small. This non-graft sinus lifting procedure using a space-maintaining gel appears to stimulate predictable bone formation; it is thus a useful technique for promoting bone formation in the sinus.

Immediately loaded dental implants bioactivated with platelet-rich plasma (PRP) placed in maxillary and mandibular region

BACKGROUND AND AIM

Dental implants have today deeply changed the dental field. In fact, after almost 50 years, the permanent placement of a titanium screw with an attached tooth have, step by step, changed the society's standard toward a permanently replacement of missed or severely damaged teeth. In fact, the host of benefits born from dental implants have affected both patients and dental professionals. The aim of the present study is to report the outcomes of an implant therapy protocol supporting fixed prostheses implanted soon after extractions and loaded with flapless guided surgery by a 3D software planning.

MATERIALS AND METHODS

37 patients, requiring rehabilitation of booth dental arches with a one-to-one technique, were enrolled in a follow-up study plan which established clinical and radiological examinations on the day after surgery, seven months and one year later. Platelet Rich Plasma (PRP), in combination with autogenous bone, organic bone material and organic bone substitutes, was used before implant-prosthetic rehabilitation with an its prompt loading just before the implant insertion phase.

RESULTS

Definitive restorations were delivered at 6-12 months after surgical procedure. One year after loading there were no dropouts and no failure of the definitive prosthesis. Furthermore, the feedback from patients resulted positive.

CONCLUSIONS

Patients resulted satisfied both aesthetically and functionally regarding these types of prosthetic reconstructions made at the time.

Evaluation of an oral appliance in patients with mild to moderate obstructive sleep apnea syndrome intolerant to continuous positive airway pressure use: Preliminary results

Obstructive sleep apnea syndrome (OSAS) is a phenomenon of repeated, episodic reduction, or cessation of airflow (hypopnea/apnea) as a result of upper airways obstruction. First-line treatment in younger children is adenotonsillectomy, although other available treatment options in middle-aged adults include continuous positive airways pressure (CPAP) and airway adjuncts. Oral appliances (OA) are a viable treatment alternative in patients with OSAS.The objective of this study was to assess, in a 1-year follow-up study, an OA in OSAS patients. The participants were subjected to polysomnographic examination with a validated device (MicroMESAM). Eight participants were fitted with a Thornton Adjustable Positioner (TAP). The participants were asked to wear the test appliance for 7 nights, and in case of compliance, for 6 months. The selected patients record their usage of the appliance and any adverse effects in a treatment journal. The research focused on the following outcomes: sleep apnea (i.e. reduction in the apnea/hypopnea index) and the effect of oral appliances on daytime function.In conclusion, the results suggest that OA have a definite role in the treatment of snoring and sleep apnea.

Use of platelet rich fibrin and Bio-OSS/SINT-Oss for implant-prosthetic rehabilitation in maxillary atrophy with sinus pathology: A 48-month follow-up

The maxillary sinus floor elevation procedure has gained popularity with predictable results, and is a safe, acceptable technique for bone augmentation, providing a base for dental implant treatment. Faint radiopaque lesions at the base of the maxillary sinus are frequent diagnoses on radiographs and must be identified during dental implant planning. The use of autografts, xenografts, allografts, and alloplasts or a combination between them has been demonstrated to be effective for increasing bone height and bone volume in maxillary sinus. The objective of this study was to evaluate the outcome of subjects with considerable sinus membrane pathology (test group) undergoing maxillary sinus floor augmentation using Platelet Rich Fibrin (PRF) as a filling material, in association with the Bio-Oss and Sint-Oss and simultaneous implant placement in a one-stage surgical procedure. All patients reported no pain to percussion, no sign of tissue suffering to the soft peri-implant tissues, the presence of an optimal primary stability of the inserted implants, and the increase in the peri-implant bone density. No complications were encountered during follow-up periods in these patients, including no negative evolution in the sinusitis and all implants are functioning successfully. In conclusion, the use of PRF and Piezosurgery reduced the healing time, favoring optimal bone regeneration and allowing sinus membrane integrity to be maintained during surgical procedures, according to evidence-based dentistry.

Periodontal disease and bone pathogenesis: the crosstalk between cytokines and porphyromonas gingivalis

Periodontal disease is the most frequent cause of tooth loss among adults. It is defined as a plaque-induced inflammation of the periodontal tissues that results in a loss of support of the affected teeth. This process is characterized by destruction of the periodontal attachment apparatus, increased bone resorption with loss of crestal alveolar bone, apical migration of the epithelial attachment, and formation of periodontal pockets. Although the presence of periodontal pathogens such as Porphyromonas gingivalis is a prerequisite, the progression of periodontal disease is dependent on the host response to pathogenic bacteria that colonize the tooth surface. Nowadays, a growing body of literature has accumulated to investigate the association between bone diseases, periodontal pathogens and periodontal diseases. The integration of pathogen-associated molecular patterns from microorganisms with their surface receptors in the immune cells, induces the production of several cytokines and chemokines that present either a pro- and/or anti-inflammatory role and the activation of mechanisms of controlling this and the related disease, such as osteoporosis and rheumatoid arthritis. This review focuses on the evidence and significance of bone host cell invasion by Porphyromonas gingivalis in the pathogenesis of bone disorders, as well as the different lines of evidence supporting the role of cytokines in bone diseases.

MIXED DENTITION SPACE ANALYSIS OF A SOUTHERN ITALIAN POPULATION: NEW REGRESSION EQUATIONS FOR UNERUPTED TEETH

Mixed dentition analysis forms a critical aspect of early orthodontic treatment. In fact an accurate space analysis is one of the important criteria in determining whether the treatment plan may involve serial extraction, guidance of eruption, space maintenance, space regaining or just periodic observation of the patients. The aim of the present study was to calculate linear regression equations in mixed dentition space analysis, measuring 230 dental casts mesiodistal tooth widths, obtained from southern Italian patients (118 females, 112 males, mean age 15±3 years). Student’s t-test or Wilcoxon test for independent and paired samples were used to determine right/left side and male/female differences. On the basis of the sum of the mesiodistal diameters of the 4 mandibular incisors as predictors for the sum of the widths of the canines and premolars in the mandibular mixed dentition, a new linear regression equation was found: y = 0.613x+7.294 (r= 0.701) for both genders in a southern Italian population. To better estimate the size of leeway space, a new regression equation was found to calculate the mesiodistal size of the second premolar using the sum of the four mandibular incisors, canine and first premolar as a predictor. The equation is y = 0.241x+1.224 (r= 0.732). In conclusion, new regression equations were derived for a southern Italian population.

Soft tissue conditions and marginal bone levels of implants with a laser-microtextured collar: a 5-year, retrospective, controlled study

AIM

To compare clinical and radiographic outcomes of implants with a Laser-Lok®-microtextured collar to implants with a resorbable blast textured (RBT) collar after a 5-year follow-up period.

MATERIALS AND METHODS

Thirty-four implants with a Laser-Lok®-microtextured collar (test group [TG]) and 31 implants with an RBT collar (control group [CG]) were placed in 45 non-smoking, periodontally healthy patients. The full-mouth plaque score, full-mouth bleeding score, number of sites with plaque, and the number of sites with bleeding on probing (BOP) were recorded at baseline, and at 1-, 2-, 3-, 4-, and 5-year follow-up. Probing depth (PD) and mucosal recession were assessed at baseline and after the 5-year follow-up period. The radiographic marginal bone loss (MBL) was calculated by subtracting the bone level at the time of crown insertion from the bone level at the 5-year follow-up.

RESULTS

An implant survival rate of 94% and of 90% was reported for the TG and the CG, respectively. No statistical differences were found between the study groups for presence of plaque (10.1% vs. 25%) or for number of sites with BOP (10.3% vs. 23%). The differences between both study groups were statistically significant for mean MBL (0.81 ± 0.24 vs. 2.02 ± 0.32 mm), mean PD (2.32 ± 0.44 vs. 4.25 ± 0.87 mm), and mean mucosal recession (0.16 ± 0.3 vs. 0.22 ± 0.3 mm).

CONCLUSIONS

Within the limitations of this study, results suggest that the laser-microtextured implant collar surface may provide more favorable conditions for the attachment of hard and soft tissues, and reduce the level of MBL.

Custom-made, selective laser sintering (SLS) blade implants as a non-conventional solution for the prosthetic rehabilitation of extremely atrophied posterior mandible

The treatment of severely atrophied posterior mandibles with standard-diameter root-form implants may present a challenge. Bone reconstructive surgery represents the treatment of choice; however, it may not be accepted by some patients for economic reasons or due to higher morbidity. Computer-aided design/computer-aided manufacturing (CAD/CAM) technologies have recently opened new frontiers in biomedical applications. Selective laser sintering (SLS) is a CAD/CAM technique that allows the fabrication of complex three-dimensional (3D) structures created by computer-generated image-based design techniques. The aim of this study is to present a protocol for the manufacture and clinical use of custom-made SLS titanium blade implants as a non-conventional therapeutic treatment for the prosthetic rehabilitation of extremely atrophied posterior mandibles. Computed tomography datasets of five patients were transferred to a specific reconstruction software, where a 3D projection of the atrophied mandible was obtained, and custom-made endosseous blade implants were designed. The custom-made implants were fabricated with SLS technique, placed in the extremely atrophied posterior (<4 mm width) mandible, and immediately restored with fixed partial restorations. After 2 years of loading, all implants were in function, showing a good esthetic integration. Blade implants can be fabricated on an individual basis as a custom-designed device. This non-conventional approach may represent an option for restoring the atrophied posterior mandible of elderly patients.

A new methodological and clinical approach for the treatment of upper lateral incisors agenesis: the posterior space opening

AIM The purpose of this study is to present a new clinical approach for the treatment of upper lateral incisor agenesis.

MATERIALS AND METHODS

A new treatment option was conceived and applied: posterior space opening as a safeguard of occlusal integrity and dental and periodontal aesthetics of the front teeth. This is acheved by means of the anterior space closure, with the mesialisation of the canines and the bicuspids, combined with a posterior space opening to create adequate room for the placement of an implant in the second premolar area. The obtained space should be maintained with a space retainer or a provisional Maryland bridge until the patient is old enough to undergo implant rehabilitation and the canines must be reshaped into a lateral incisor.

CONCLUSION

The results of this treatment are a correct teeth alignment, without diastema, Class I occlusion, and occlusal integrity with all natural teeth in the anterior area. In this way there are many advantages for the patient; so it is an effective approach.

Do malocclusion and Helkimo Index ≥ 5 correlate with body posture?

Whether there are correlations between the stomatognathic system and body posture remains controversial. Here, we have investigated whether malocclusal traits and having a Helkimo Index ≥ 5 show detectable correlations with body-posture alterations in children and young adults. A total of 1178 11- to 19-year-old subjects were divided into four groups: (i) controls; (ii) malocclusion; (iii) Helkimo Index ≥ 5 and (iv) malocclusion + Helkimo Index ≥ 5. Dental occlusion assessment included the following: overbite, overjet, posterior crossbite, scissorbite, mandibular crowding and dental class. Subsequently, body-posture assessments were performed through static analyses of body inclination and trunk asymmetry, and according to the dynamic Fukuda stepping test. Univariate and multivariate statistical analyses were performed. Although at the univariate level both the trunk asymmetry and Fukuda stepping test showed significant differences among the groups, the multivariate level revealed that age and gender were mostly responsible for this. The only significant correlation that was seen was for the malocclusion + Helkimo Index ≥ 5 group: these subjects had a positive (worse) trunk asymmetry and a negative (better) Fukuda stepping test performance. At the further multivariate analyses of each single malocclusal trait ⁄Helkimo Index ≥ 5 (irrespective of the groups), only an increased overbite showed a statistically significant association with a slightly better Fukuda stepping test performance. Given the small number of significant associations seen and their limited entities, this study does not support the existence of clinically relevant correlations for malocclusal traits and Helkimo Index ≥ 5 with body posture in children and young adults.

Juvenile Idiopathic Arthritis with temporomandibular joint involvement: functional treatment

AIM

Juvenile Idiopathic Arthritis is a disease that can involve the temporomandibular joint unilaterally or bilaterally causing specific malocclusions.

CASE REPORT

This paper reports a case of Juvenile Idiopathic Arthritis in an 8-year-old male with unilateral involvement of the temporomandibular joint, with remarkable asymmetry of the left mandible and reduced left facial height. The management of the temporomandibular damage consisted in the treatment with an activator in order to help mandibular ramus growth with a subsequent enhancement in occlusion, masticatory function and profile. This treatment has several advantages and permits to correct the typical malocclusion exhibited by these patients, to improve the clinical signs of the disease and to obtain stability over time.

Change in condylar and mandibular morphology in juvenile idiopathic arthritis: Cone Beam volumetric imaging

The aim of this study was to show the importance of Cone Beam Computerized Tomography (CBCT) to volumetrically quantify temporomandibular joint (TMJ) damage in patients with juvenile idiopathic arthritis (JIA), measuring condylar and mandibular real volumes. Methods. Thirty-four children with temporomandibular involvement by JIA were observed by CBCT. Four were excluded because of several imaging noises. The mandible was isolated from others craniofacial structures; the whole mandibular volume and its components' volumes (condyle, ramus, emibody, emisymphysis on right side and on left side) has been calculated by a 3D volume rendering technique. Results. The results show a highly significant statistical difference between affected side volumetric values versus normal side volumetric values, above all on condyle region (P<0.01), while there was no statistical difference between right versus left side. Conclusion. The CBCT represents a huge improvement in understanding of the condyle and mandibular morphological changes, even in the early stages of the JIA. In children the JIA can lead to TMJ damage with facial development and growth alterations.

Alteration of activity and survival of osteoblasts obtained from human periodontitis patients: role of TRAIL

Periodontal disease (Pd) is characterized by extensive alveolar bone loss, that occurs as a consequence of the impairment of the normal bone remodelling. Bone remodelling is regulated by the correct balance between osteoclast and osteoblast formation and activity. Alveolar bone loss could be due to an increased bone resorption by osteoclasts or a decreased bone formation by osteoblasts (OBs) or both. Although the role played by osteoclasts in increasing bone resorption in Pd is already known, the behaviour of OBs in this disease is poorly understood. In the present study we hypothesized that activity and survival of OBs, locally present in alveolar bone of Pd patients, are altered. Thus, we studied the activity and survival of OBs obtained from alveolar bone fragments of Pd patients. The results, obtained in OBs from the patients were compared with those from OBs obtained from healthy donors. We demonstrated that OBs from Pd patients weakly express OB phenotype in respect to the control cells. In particular, the alkaline phosphatase activity and the collagen type I production, as well as the formation of mineralized nodules, typical markers of differentiated OBs, were significantly lower in Pd patients. Interestingly, we also demonstrated that OBs from the patients were more sensitive to the apoptotic effect induced by TNF-related apoptosis-inducing ligand (TRAIL). TRAIL, a member of the TNF superfamily, induces apoptosis by interacting with its death receptors, (DR4, DR5). However, its activity can be modulated by two decoy receptors, DcR1 and DcR2. Thus, the sensitiveness of TRAIL induced apoptosis is determined by the ratio of death and decoy receptor. We demonstrated that OBs from Pd patients showed an imbalanced ratio between death and decoy TRAIL receptors due to the down-regulation of DcR2 expression. Furthermore, the levels of TRAIL in the serum of the same patients were significantly higher than those detected in the controls. In conclusion, we show for the first time that the alveolar bone loss in Pd patients could be due to the increased TRAIL-mediated apoptosis of OBs.