Clinical findings and history of bone loss at implant sites

Prediabetes and poorly controlled type-2 diabetes as risk indicators for peri-implant diseases:A systematic review and meta-analysis

OBJECTIVE

The study answers the PECO question: "In adults with dental implants (P), do subjects suffering from type-2 diabetes or prediabetes (E) have worse peri-implant conditions (O) than subjects without type-2 diabetes and prediabetes (C)?". Prediabetes (5.7-6.4 % HbA1c), and the different qualities of glycemic control in type-2 diabetes; well-controlled (>8 % HbA1c), and poorly controlled (>8 % HbA1c) individuals; were classified according to the recommendations of the American Diabetes Association.

DATA

Predefined search keys were used with search terms including: Dental implant, diabetes mellitus, glycemic control and HbA1c.

SOURCES

An electronic search in the MEDLINE, Embase, and Cochrane libraries were conducted without any filters or language restrictions. Additionally, manual search of the reference lists were carried out to identify all relevant articles.

STUDY SELECTION

Eligibility criteria were cohort, case-control and cross-sectional studies that answerd our PECO question with at least 1 year of follow-up. From a total of 2660 records, 35 articles (1761 individuals) were included in the analysis. Meta-analytic difference in means for crestal bone loss was 1.2 mm [95 % CI=0.4; 2.1] in patients with prediabetes, 1.8 mm [CI=1.0; 2.7] in poorly controlled patients, whereas 0.4 mm [CI=-0.3; 1.1] in well-controlled individuals. Meta-regression showed that 1 % increase in HbA1c increased crestal bone loss by 0.24 mm.

CONCLUSIONS

Within the limitations of the study, patients with poorly controlled type-2 diabetes or prediabetes may have worse peri-implant conditions compared to patients without diabetes and well-controlled type-2 diabetes. Well-controlled type-2 diabetes is not a risk indicator for peri-implant diseases.

CLINICAL SIGNIFICANCE

Clinicians should measure blood HbA1c levels when planning implant-supported restorations, thus patients with undiagnosed or poorly controlled type-2 diabetes can be identified, that allows for glycemic level adjustment prior to dental implant surgery, ensuring peri-implant health. PROTOCOL REGISTRATION NUMBER: (CRD42022375263).

Radiographic evaluation of marginal bone levels around implants supporting splinted fixed bridges: A retrospective study on 412 implants

OBJECTIVES

The effect of the implant position within the prosthesis on bone remodeling is scarcely documented so far. Thus, the aim of the present study was to investigate whether central implants may suffer higher peri-implant marginal bone levels (MBL) compared to laterals in case of fixed splinted bridges supported by ≥ three implants.

MATERIALS AND METHODS

Partially edentulous subjects rehabilitated with at least one fixed bridge supported by ≥ three dental implants were enrolled. MBL was assessed radiographically by means of intraoral radiographs acquired with phosphor plates and imported in a dedicated software. MBL was calculated as the distance between the implant platform level and the most coronal visible bone-to-implant contact. A three-level linear mixed effects model was used for investigating the fixed effect of patient-, prosthesis-, and implant-level variables on the MBL.

RESULTS

Overall, 90 patients rehabilitated with 130 splinted fixed bridges supported by 412 implants were included. The median follow-up was 136 months. The mean peri-implant MBL resulted statistically significantly higher at central implants if compared to lateral implants (p < .01). The estimated MBL averages for central and external implants were 1.68 and 1.18 mm, respectively. The prosthesis-level variables suggested that a cement-retained bridge was prone to a significant 0.82 mm higher MBL than a screw-retained one. Implant surface showed an association with MBL changes, although less pronounced than implant retention.

CONCLUSIONS

In case of ≥3 adjacent implants supporting splinted bridges, central implants were more predisposed to MBL compared to laterals. At the prosthesis level, implants supporting cement-retained bridges were statistically more susceptible to MBL compared to screw-retained ones. Surface characteristics can also influence MBL stability at the implant level.

Long-term outcomes and prognostic factors of surgical treatment of peri-implantitis - A retrospective study

AIM

To evaluate long-term outcomes and prognostic factors of non-reconstructive surgical treatment of peri-implantitis.

MATERIALS AND METHODS

One hundred forty-nine patients (267 implants) were surgically treated for peri-implantitis and followed for an average of 7.0 (SD: 3.6) years. The primary outcome was implant loss. Additional bone loss and surgical retreatment were secondary outcomes. Patient/implant characteristics, as well as clinical and radiographic parameters collected prior to initial surgery, were evaluated as potential predictors of implant loss. Flexible parametric survival models using restricted cubic spline functions were used; 5- and 10-year predicted rates of implant loss were calculated according to different scenarios.

RESULTS

Fifty-three implants (19.9%) in 35 patients (23.5%) were lost during the observation period. Implant loss occurred after a mean period of 4.4 (SD: 3.0) years and was predicted by implant surface characteristics (modified surface; HR 4.5), implant length (HR 0.8 by mm), suppuration at baseline (HR 2.7) and disease severity (baseline bone loss: HR 1.2 by mm). Estimates of 5- and 10-year implant loss ranged from 1% (best prognostic scenario; initial bone loss <40% of implant length, turned implant surface and absence of suppuration on probing (SoP)) to 63% (worst prognostic scenario; initial bone loss ≥60% of implant length, modified implant surface and SoP) and from 3% to 89%, respectively. Surgical retreatment was performed at 65 implants (24.3%) in 36 patients (24.2%) after a mean time period of 4.5 (3.1) years. In all, 59.5% of implants showed additional bone loss, were surgically retreated or lost.

CONCLUSIONS

Recurrence of disease is common following surgical treatment of peri-implantitis. The strongest predictor for implant loss was implant surface characteristics. Implant length as well as suppuration and disease severity at baseline were also relevant factors.

Efficacy of a Solution Containing 33% Trichloroacetic Acid and Hydrogen Peroxide in Decontaminating Machined vs. Sand-Blasted Acid-Etched Titanium Surfaces

This in vitro study assessed the efficacy of a solution containing 33% trichloroacetic acid (CCl3COOH; TCA) and hydrogen peroxide (H2O2) in decontaminating machined (MAC) and sand-blasted acid-etched (SBAE) titanium surfaces. A total of 80 titanium disks were prepared (40 MAC and 40 SBAE). Streptococcus sanguinis and Enterococcus faecalis strains were incubated on 36 samples, while the remaining 44 were kept as controls. Roughness analysis and scanning electron microscopy were used to evaluate the surface features before and after TCAH2O2 treatment. The viability of human adipose-derived mesenchymal stem cells (ASCs) after TCAH2O2 decontamination was assessed with a chemiluminescent assay along with cell morphology through fluorescent staining. TCAH2O2 preserved the surface topography of MAC and SBAE specimens. It also effectively eradicated bacteria on both types of specimens without altering the surface roughness (p > 0.05). Also, no significant differences in protein adsorption between the pristine and TCAH2O2-treated surfaces were found (p = 0.71 and p = 0.94). While ASC proliferation remained unchanged on MAC surfaces, a decrease was observed on the decontaminated SBAE specimens at 24 and 48 h (p < 0.05), with no difference at 72 h (p > 0.05). Cell morphology showed no significant changes after 72 h on both surface types even after decontamination. This study suggests TCAH2O2 as a promising decontamination agent for titanium surfaces, with potential implications for peri-implant health and treatment outcomes.

Diagnosis and Treatment of Periimplant Mucositis and Periimplantitis: An Overview and Related Controversial Issues

Periimplant mucositis and periimplantitis are common complications of dental implant. This article provides a comprehensive overview of the 2017 World Workshop's new definition, clinical and radiographic presentation, pathogenesis, risk factors, and classification of periimplant diseases. Also, the authors discuss various types of instruments, materials, and techniques commonly used for treatment of nonsurgical and surgical periimplantitis. Lastly, the authors include some controversial topics surrounding this subject.

Microbiota associated with peri-implantitis-A systematic review with meta-analyses

AIM

To answer the following PECO question: "In systemically healthy human subjects (P), which are the differences between peri-implantitis (E) and peri-implant health/mucositis (C) in terms of bacterial presence/count (O)?"

MATERIALS AND METHODS

Cross-sectional studies fulfilling specific inclusion criteria established to answer the PECO question were included. Two review authors independently searched for studies, screened the titles and abstracts, did full-text analysis, extracted the data from the included reports, and performed the risk of bias assessment through an adaptation of the Newcastle/Ottawa tool for cross-sectional studies and of the JBI critical appraisal checklist. In case of disagreement, a third reviewer author took the final decision. Study results were summarized using random effects meta-analyses.

RESULTS

A total of 12 studies were included, involving 1233 participants and 1513 implants. Peri-implantitis was associated with the presence of S. epidermidis (Odds ratio, OR = 10.28 [95% Confidence interval, CI: 1.26-83.98]), F. nucleatum (OR = 7.83 [95% CI: 2.24-27.36]), T. denticola (OR = 6.11 [95% CI: 2.72-13.76]), T. forsythia (OR = 4.25 [95% CI: 1.71-10.57]), P. intermedia (OR = 3.79 [95% CI: 1.07-13.35]), and P. gingivalis (OR = 2.46 [95% CI: 1.21-5.00]). Conversely, the presence of A. actinomycetemcomitans (OR = 3.82 [95% CI: 0.59-24.68]), S. aureus (OR = 1.05 [95% CI: 0.06-17.08]), and C. rectus (OR = 1.48 [95% CI: 0.69-3.17]) was not associated with peri-implantitis.

CONCLUSIONS

Peri-implantitis is associated with the presence of S. epidermidis and specific periodontopathogens (P. gingivalis, T. forsythia, T. denticola, F. nucleatum, and P. intermedia). (CRD42021254589).

Evaluation of the adjunctive use of Er:YAG laser or erythritol powder air-polishing in the treatment of peri-implant mucositis: A randomized clinical trial

AIM

To assess the efficacy of Er:YAG laser (ERL) and erythritol powder air-polishing (AP) in addition to the submarginal instrumentation in the non-surgical treatment of peri-implant mucositis (PM).

MATERIALS AND METHODS

Patients with at least one implant diagnosed with PM were included in the present 6-month randomized clinical trial (RCT). Implants were randomly assigned to one of the three treatment groups after submarginal instrumentation: AP (test 1 group), ERL (test 2 group) or no adjunctive methods (control group). The primary and secondary outcomes were, respectively, bleeding on probing (BoP) reduction and, complete disease resolution (total absence of BoP) and probing pocket depth (PPD) changes. The patient and the implant were considered the statistical unit. A multivariate logistic regression analysis was performed.

RESULTS

A total of 75 patients were enrolled in the study. At each time point, significant BoP and PPD reductions were observed within each group. Intergroup analysis did not show statistically significant differences. Complete disease resolution ranged between 29% and 31%. The logistic regression showed that supramucosal restoration margin, PPD < 4 mm and vestibular keratinized mucosa (KM) significantly influenced the probability to obtain treatment success.

CONCLUSION

The adjunctive use of AP and ERL in PM non-surgical therapy does not seem to provide any significant or clinically relevant benefit in terms of BoP and PPD reductions and complete disease resolution, over the use of submarginal instrumentation alone. Baseline PPD < 4 mm, presence of buccal KM and supramucosal restoration margin may play a role in the complete resolution of PM.

The efficacy of different implant surface decontamination methods using spectrophotometric analysis: an in vitro study

PURPOSE

Various methods have been proposed to achieve the nearly complete decontamination of the surface of implants affected by peri-implantitis. We investigated the in vitro debridement efficiency of multiple decontamination methods (Gracey curettes [GC], glycine air-polishing [G-Air], erythritol air-polishing [E-Air] and titanium brushes [TiB]) using a novel spectrophotometric ink-model in 3 different bone defect settings (30°, 60°, and 90°).

METHODS

Forty-five dental implants were stained with indelible ink and mounted in resin models, which simulated standardised peri-implantitis defects with different bone defect angulations (30°, 60°, and 90°). After each run of instrumentation, the implants were removed from the resin model, and the ink was dissolved in ethanol (97%). A spectrophotometric analysis was performed to detect colour remnants in order to measure the cumulative uncleaned surface area of the implants. Scanning electron microscopy images were taken to assess micromorphological surface changes.

RESULTS

Generally, the 60° bone defects were the easiest to debride, and the 30° defects were the most difficult (ink absorption peak: 0.26±0.04 for 60° defects; 0.32±0.06 for 30° defects; 0.27±0.04 for 90° defects). The most effective debridement method was TiB, independently of the bone defect type (TiB vs. GC: P<0.0001; TiB vs. G-Air: P=0.0017; TiB vs. GE-Air: P=0.0007). GE-Air appeared to be the least efficient method for biofilm debridement.

CONCLUSIONS

T-brushes seem to be a promising decontamination method compared to the other techniques, whereas G-Air was less aggressive on the implant surface. The use of a spectrophotometric model was shown to be a novel but promising assessment method for in vitro ink studies.

Efficacy of mechanical/physical approaches for implant surface decontamination in non-surgical submarginal instrumentation of peri-implantitis. A systematic review

AIM

To evaluate the efficacy of non-surgical submarginal peri-implant instrumentation with mechanical/physical decontamination compared to non-surgical submarginal instrumentation alone or with placebo decontamination in patients with peri-implantitis.

MATERIALS AND METHODS

Three focused questions were addressed, and a systematic search for randomized controlled clinical trials (RCTs), controlled clinical trials, and prospective cohort studies with definitions of peri-implantitis and a minimal follow-up of 6 months was conducted. The main outcome variables were reduction in pocket probing depth (PD) and bleeding on probing (BOP). Suppuration on probing, marginal peri-implant bone level changes, patient-related outcomes and adverse events, implant survival, treatment success, and disease resolution were assessed as secondary outcomes.

RESULTS

Out of 239 findings, full-text articles were assessed for eligibility, and 9 (n = 9 RCTs) were included in the present review. Five studies evaluated the effects of various laser types, and in four studies efficacy of air-abrasive mechanisms and of a novel ultrasonic device was determined. At 6 months, PD reductions were observed in nine studies but only Er, Cr:YSGG laser-treated group showed statistically significant higher reductions compared to the control group. BOP was statistically significantly reduced at 6 months in two studies following the application of Er:YAG laser compared to controls. One study reported statistically significant reduction in BOP following application of air-polishing device compared to control treatment. No statistically significant differences between treatment groups were reported for the secondary outcome variables. Owing to the large heterogeneity of study designs, no meta-analysis was performed.

CONCLUSIONS

Available evidence on the efficacy of non-surgical submarginal peri-implant instrumentation with mechanical/physical decontamination is limited by the small number of controlled studies and the high heterogeneity of study protocols. Clinical and patient-reported benefits remain to be demonstrated.

The adjunctive effect of a resorbable membrane to a xenogeneic bone replacement graft in the reconstructive surgical therapy of peri-implantitis: A randomized clinical trial

AIM

To evaluate the potential adjunctive effect of a resorbable collagen membrane covering a xenogeneic bone replacement graft in the reconstructive surgical therapy of peri-implantitis.

MATERIALS AND METHODS

Forty-three patients (43 implants) diagnosed with peri-implantitis associated with intra-bony defects were treated with a surgical reconstructive approach that included a xenogeneic bone substitute material. Additionally, resorbable collagen membranes were placed over the grafting material at sites randomly allocated to the test group; conversely, no membranes were placed in the control group. Clinical outcomes, namely probing pocket depth (PPD), bleeding and suppuration on probing (BoP and SoP), marginal mucosal level (REC) and keratinized mucosa width (KMW), were recorded at baseline and 6 and 12 months after surgery. Radiographic marginal bone levels (MBLs) and patient-reported outcomes (PROs) were assessed at baseline and 12 months. A composite outcome (success) was evaluated at 12 months, which included the absence of BoP/SoP, PPD ≤5 mm and reduction of buccal marginal mucosal level (buccal REC) of ≤1 mm.

RESULTS

At 12 months, no implants were lost and treatment success was observed at 36.8% and 45.0% of implants in the test and control groups, respectively (p = .61). Similarly, there were no significant differences between groups in terms of changes of PPD, BoP/SoP, KMW, MBL or buccal REC. Post-surgical complications were observed in the test group only (e.g., soft tissue dehiscence, exposure of particulate bone graft and/or resorbable membrane). Longer surgical times (~10 min; p < .05) and higher levels of self-reported pain at 2 weeks (p < .01) were observed in the test group.

CONCLUSIONS

This study failed to demonstrate the presence of added clinical or radiographic benefits of the use of a resorbable membrane to cover a bone substitute material within the reconstructive surgical therapy of peri-implantitis associated with intra-bony defects.

Two-piece zirconia implants in the posterior mandible and maxilla: A cohort study with a follow-up period of 9 years

OBJECTIVES

Long-term follow-up observations of zirconia implants are rare. This study aimed at evaluating the clinical performance of two-piece zirconia implants in the posterior jaws over 9 years.

MATERIALS AND METHODS

Sixty partially edentulous patients were treated with two-piece zirconia implants. In eight no primary stability could be achieved. Fifty-two patients received the final restoration (i.e., cemented fibreglass abutments and all-ceramic crowns). After 2 years, 2 implants failed and 4 dropouts were recorded. The remaining 46 patients with one target implant each were recalled at 9 years. Besides implant survival, clinical parameters at the implant level (plaque index-PI, bleeding on probing-BOP, probing depth-PD, mucosal recession-MR) were recorded and compared with previously collected data. Mechanical and technical complications were assessed.

RESULTS

Thirty patients responded. The mean observation period was of 111.1 ± 2.2 months. One implant was lost. Data recorded from the remaining 29 implants were analysed. PI values increased overtime. Mean BOP and PD remained unchanged during follow-up. No additional cases of peri-implantitis were recorded over the 10 diagnosed during the first 2 years of follow-up. No significant changes in mean MR values were detected over time, with 65% of the all included implants exhibiting no recession at 9 years and all the others, but one, a maximum MR of 1 mm. Three technical and 6 mechanical complications occurred in 7 patients between 2- and 9-years (6.9% and 20.7%, respectively, at patient level).

CONCLUSION

Within the limitations of the present study, a high survival rate was registered. Albeit frequent mechanical and technical complications, two-piece zirconia implants could represent a valid solution for the replacement of single teeth in the posterior jaws.

Effect of sub-marginal instrumentation before surgical treatment of peri-implantitis: A multi-centre randomized clinical trial

AIM

The present multi-centre randomized clinical trial with 12 months of follow-up aimed at studying the added effect of sub-marginal instrumentation before surgical treatment of peri-implantitis.

MATERIALS AND METHODS

Forty-two patients diagnosed with peri-implantitis were recruited. After a behavioural intervention phase including oral hygiene instructions, patients were randomized to either receiving supra- and sub-marginal instrumentation on their affected implants (control group: 21 patients and 29 implants) or only supra-marginal instrumentation (test group: 21 patients and 24 implants), before undergoing surgery. Changes in the deepest probing pocket depth (PPD) with respect to baseline and a composite outcome of treatment success (no implant loss, no bone loss &gt; 0.5 mm, no bleeding or suppuration on probing [BoP/SoP], and PPD ≤ 5 mm) at the 12-month examination were regarded as the primary outcomes of the trial.

RESULTS

At the 12-month examination, changes in the deepest PPD with respect to baseline amounted to -2.96 mm in the control group and to -3.11 mm in the test one (MD = -0.16; SE = 0.56; p = .769), while 21.4% of the implants in the control group and 33.3% in the test group presented treatment success (OR = 1.83; SE = 1.15; p = .338). With the exception of a longer non-surgical treatment duration in the control group (differences in  = -14.29 min; SE = 2.91; p &lt; .001), no other secondary (e.g., soft-tissue recession, keratinized mucosa height, and bone level changes, as well as BoP, SoP, profuse bleeding and implant loss rates) or exploratory (i.e., early wound healing, aesthetics, surgical and total treatment duration, surgery difficulty, intra-operative bleeding, and adverse events) outcome demonstrated statistically significant differences between groups.

CONCLUSIONS

The present multi-centre randomized clinical trial did not demonstrate an added effect of performing sub-marginal instrumentation 6 weeks before the surgical treatment of peri-implantitis. Larger clinical trials are however needed to confirm the present findings (Clinicaltrials.gov: NCT03620331).

Early marginal bone loss around dental implants to define success in implant dentistry: A retrospective study

PURPOSE

The aim of this study was to establish an objective criterion in terms of marginal bone level (MBL) to know the prognosis of an implant.

MATERIALS AND METHODS

A group of 176 patients in whom 590 implants were placed were included in this retrospective study. Patients older than 18 years, presenting either Kennedy class I or II edentulous section, or totally edentulous at least in one of the dental arches were included in this study. Those with any type of disturbance able to alter bone metabolism or with nontreated periodontal disease were excluded. Data on radiographic MBL at loading, 6 and 18 months later, age, gender, smoking habits, history of periodontitis, bone substratum, implant, and prosthetic features were recorded. Nonparametric receiver operating curves (ROC) were constructed for the MBL at 18 months in order to establish a distinction among high bone loser (HBL) and low bone loser (LBL) implants. Differences as a function of main variables were also determined, particularly abutment height and periodontal disease.

RESULTS

HBL implants lost at least 0.48 mm of MBL 6 months after loading; they reached at least 2 mm of MBL 18 months after loading. MBL rate followed a nonlinear trend, except in implants restored over long prosthetic abutments and in patients with history of severe periodontitis; in whom the rate of MBL over the time was nearly zero.

CONCLUSION

Implants that lose more than 0.5 mm of marginal bone 6 months after loading are at great risk of not being radiographically successful anymore. Therefore, 0.5 mm of MBL is proposed as a distinctive and objective criterion of success in Implant Dentistry within a 6-month follow-up period. A prosthetic abutment height ≥2 mm resulted the most protective factor in the peri-implant bone maintenance.

Prevention and management of peri-implant mucositis and peri-implantitis: a systematic review of outcome measures used in clinical studies in the last 10 years

OBJECTIVES

To evaluate outcome measures, methods of assessment and analysis in clinical studies on the prevention and management of peri-implant mucositis and peri-implantitis.

METHODS

Systematic electronic searches (CENTRAL/MEDLINE/SCOPUS) up to April 2021 were conducted to identify longitudinal clinical studies with ≥10 patients on either the prevention or management of peri-implant diseases. Outcome measures of this analysis were the choice of outcome measures, methods of assessment and analytical methods. Risk of Bias was evaluated according to study design. Data were extracted into evidence tables and outcomes were analyzed in a descriptive manner.

RESULTS

The analysis of the 159 selected studies revealed that probing pocket depth (PPD) and bleeding/suppuration on probing (BOP) were reported in 89% and 87% of all studies, respectively. Additional outcome measures included plaque scores (reported in 64% of studies), radiographic outcomes (49%), soft tissue dimensions (34%) and composite outcomes (26%). Adverse events (8%) and patient-reported outcomes (6%) were only rarely mentioned. A total of 36% of studies clearly defined a primary outcome measure. Data on PPD, radiographic outcomes and soft tissue dimensions were primarily reported as mean values and rarely as frequency distributions. For radiographic outcomes and soft tissue dimensions, it was frequently unclear how clustered data were handled.

CONCLUSIONS

PPD and BOP were routinely reported in studies on prevention and management of peri-implant mucositis and peri-implantitis, while composite outcomes, adverse events and patient-reported outcomes were infrequently described.

Prevention and management of peri-implant mucositis and peri-implantitis: a systematic review of outcome measures used in clinical studies in the last 10 years

OBJECTIVES

To evaluate outcome measures, methods of assessment and analysis in clinical studies on the prevention and management of peri-implant mucositis and peri-implantitis.

METHODS

Systematic electronic searches (CENTRAL/MEDLINE/SCOPUS) up to April 2021 were conducted to identify longitudinal clinical studies with ≥10 patients on either the prevention or management of peri-implant diseases. Outcome measures of this analysis were the choice of outcome measures, methods of assessment and analytical methods. Risk of Bias was evaluated according to study design. Data were extracted into evidence tables and outcomes were analyzed in a descriptive manner.

RESULTS

The analysis of the 159 selected studies revealed that probing pocket depth (PPD) and bleeding/suppuration on probing (BOP) were reported in 89% and 87% of all studies, respectively. Additional outcome measures included plaque scores (reported in 64% of studies), radiographic outcomes (49%), soft tissue dimensions (34%) and composite outcomes (26%). Adverse events (8%) and patient-reported outcomes (6%) were only rarely mentioned. A total of 36% of studies clearly defined a primary outcome measure. Data on PPD, radiographic outcomes and soft tissue dimensions were primarily reported as mean values and rarely as frequency distributions. For radiographic outcomes and soft tissue dimensions, it was frequently unclear how clustered data were handled.

CONCLUSIONS

PPD and BOP were routinely reported in studies on prevention and management of peri-implant mucositis and peri-implantitis, while composite outcomes, adverse events and patient-reported outcomes were infrequently described. This article is protected by copyright. All rights reserved.