Modeling Progressive Damage Accumulation in Bone Remodeling Explains the Thermodynamic Basis of Bone Resorption by Overloading.

Computational modeling of skeletal tissue seeks to predict the structural adaptation of bone in response to mechanical loading. The theory of continuum damage-repair, a mathematical description of structural adaptation based on principles of damage mechanics, continues to be developed and utilized for the prediction of long-term peri-implant outcomes. Despite its technical soundness, CDR does not account for the accumulation of mechanical damage and irreversible deformation. In this work, a nonlinear mathematical model of independent damage accumulation and plastic deformation is developed in terms of the CDR formulation. The proposed model incorporates empirical correlations from uniaxial experiments. Supporting elements of the model are derived, including damage and yielding criteria, corresponding consistency conditions, and the basic, necessary forms for integration during loading. Positivity of mechanical dissipation due to damage is proved, while strain-based, associative plastic flow and linear hardening describe post-yield behavior. Calibration of model parameters to the empirical correlations from which the model was derived is then accomplished. Results of numerical experiments on a point-wise specimen show that damage and plasticity inhibit bone formation by dissipation of energy available to biological processes, leading to material failure that would otherwise be predicted to experience a net gain of bone.

Impact of diabetes on clinical periodontal outcomes following non-surgical periodontal therapy.

AIM: This systematic review aimed to evaluate the impact of diabetes mellitus on clinical outcomes of non-surgical periodontal therapy. MATERIALS AND METHODS: Searches were conducted in electronic databases to screen studies published from January 1960 to August 2018. The included studies had at least two groups of patients: chronic periodontitis only (P) or both diabetes and chronic periodontitis (DMP). Outcomes of interest included the difference between the two groups in probing depth (PD) reduction and clinical attachment level (CAL) gain following non-surgical periodontal therapy. Meta-regression was conducted to evaluate the correlation between the outcomes of interest and contributing factors. RESULTS: A total of 12 studies with a follow-up period up to 6 months were included. There was no significant difference in PD reduction (p = 0.55) or CAL gain (p = 0.65) between the two groups. A positive association between PD reduction and baseline PD difference (p = 0.03), and a negative association between PD reduction and age (p = 0.04) were found. The level of HbA1c at baseline did not significantly affect the difference in PD reduction (p = 0.39) or CAL gain (p = 0.44) between two groups. CONCLUSIONS: Recognizing the study's limitations, we conclude that diabetes mellitus (HbA1c ≤ 8.5%) does not appear to significantly affect short-term clinical periodontal outcomes of non-surgical periodontal treatment.

Biological implant complications and their management.

BACKGROUND: Background: With the increasing popularity of dental implants the presence of implant complications is rising, and the question of how to best manage these complications still lingers in most clinicians' minds. This paper aims to provide clinicians with an overview of the most commonly encountered biologic implant complications as well as to provide guidelines as to how to treat them. METHODS: Available English literature was reviewed, including peer-reviewed journal publications and online resources. Several treatment modalities have been proposed to manage these complications, including non-surgical mechanical debridement, antiseptics, local and/or systemic antibiotics, lasers, resection with or without implantoplasty and regenerative approaches. RESULTS: In this guideline, it is suggested that the treatment modalities should be chosen based on the severity of peri-implant diseases, amount of bone loss and the morphology of peri-implant bony defects. For peri-implant mucositis or peri-implant defects with less than 2 mm destruction, non-surgical treatments are recommended. For peri-implant defects with more than 2 mm destruction, surgical treatments (e.g., resection with or without implantoplasty, guided bone regeneration) are suggested that include removal of the implant if the bone loss is beyond repair. CONCLUSION: The prevention of biological implant complications relies on careful planning, a thorough examination to assess etiological factors and a regular maintenance recall schedule. With early diagnosis, biological implant complications should be managed based on the severity of peri-implant disease, the amount of bone loss and the morphology of the peri-implant bony defects.

Inflammation and tissue remodeling mediator expression during gingivitis: A comparison between experimental, naturally occurring gingivitis, and periodontal health.

BACKGROUND: The aim of this study is to evaluate the immune regulation and tissue remodeling responses during experimental gingivitis (EG) and naturally occurring gingivitis (NG) to provide a comprehensive analysis of host responses. Gingival crevicular fluid (GCF) was obtained from 2 human studies conducted in university settings. METHODS: The EG study enrolling 26 volunteers provided controls for the baseline (Day 0) from healthy disease-free participants, while Day 21 (the end of EG induction of the same group) was used to represent EG. Twenty-six NG participants age-matched with those of the EG group were recruited. GCF samples were analyzed for 39 mediators of inflammatory/immune responses and tissue remodeling using commercially available bead-based multiplex immunoassays. The differences in GI and mediator expression among groups were determined at a 95% confidence level (p ≤ 0.05) by a 2-way analysis of variance (ANOVA) with a post-hoc Tukey's test. RESULTS: Our findings showed that EG had a greater gingival index than NG and was healthy (p < 0.01 of all comparisons). Furthermore, EG showed significantly higher levels of MPO (p < 0.001), CCL3 (p < 0.05), and IL-1B (p < 0.001) than NG. In contrast, NG had increased levels of MIF (p < 0.05), Fractalkine (p < 0.001), angiogenin (p < 0.05), C3a (p < 0.001), BMP-2 (p < 0.001), OPN (p < 0.05), RANKL (p < 0.001), and MMP-13 (p < 0.001) than EG. CONCLUSIONS: Consistent with the findings from chronic (NG) versus acute (EG) inflammatory lesions, these data reveal that NG displays greater immune regulation, angiogenesis, and bone remodeling compared to EG.

Inducing cyclooxygenase-2 expression, prostaglandin E2 and prostaglandin F2α production of human dental pulp cells by activation of toll-like receptor-3, mitogen-activated protein kinase kinase/extracellular signal-regulated kinase and p38 signaling.

Background/purpose: Bacterial infection was the major etiology for pulpal/root canal infection. This study aimed to investigate the activation of toll-like receptor-3 (TLR) on cyclooxygenase-2 (COX-2) expression and prostaglandin E2 (PGE2) and PGF2α production of human dental pulp cells (HDPCs) and associated signaling. Materials and methods: HDPCs were exposed to different concentrations of Poly (I:C) (a TLR3 activator). Cell viability was determined by 3- (4,5-Dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay and alkaline phosphatase (ALP) activity was evaluated by ALP staining. Activation of extracellular signal-regulated kinase (ERK) and p38 by Poly (I:C) was determined by immunofluorescent staining. The COX-2 protein expression was analyzed by Western blot. PGE2 and PGF2α production was measured by enzyme-linked immunosorbent assay. The mRNA expression was studied by real-time polymerase-chain reaction. Moreover, HDPCs were exposed to Poly(I:C) with/without U0126 or SB203580 treatment and analysis of COX-2 expression and prostanoid production were conducted. Results: Poly (I:C) showed little effect on ALP activity, but decreased viability of HDPCs. It stimulated COX-2 mRNA and protein expression. Poly (I:C) induced PGE2 and PGF2α production of HDPCs. Poly (I:C) activated p-ERK, and p-p38 protein expression. Treatment by U0126 (a mitogen-activated protein kinase kinase (MEK)/ERK inhibitor) and SB203580 (a p38 inhibitor) attenuated Poly (I:C)-induced COX-2 mRNA and protein expression as well as PGE2 and PGF2α production. Conclusion: TLR3 activation is involved in the infection and inflammatory responses of pulp tissues, via MEK/ERK, and p38 signaling to mediate COX-2 expression as well as PGE2 and PGF2α production, contributing to the pathogenesis and progression of pulpal/periapical diseases.

Role of Keratinized Tissue on the Management of Peri-implantitis: A Case Report.

Peri-implantitis is an inflammatory condition that involves the loss of attachment and support around dental implants. In this case report, a middle-aged woman presented with two implants in the mandibular right quadrant that were diagnosed with peri-implantitis. The patient also had tenderness around the implants and reported sensitivity when performing oral hygiene procedures. Surgical treatment comprised a free gingival graft to augment the keratinized tissue width around the implants, followed by a second procedure of implantoplasty and surface decontamination. The outcome showed radiographic resolution of the peri-implant defect around the premolar implant with a marked increase of keratinized tissue (> 4 mm) around both implants after 1 year of follow up. On a patient level, significantly reduced sensitivity around the implants and better home care were reported. This case report showed that the increase of keratinized tissue may benefit the clinical and patient outcomes of peri-implantitis treatment in terms of decreased probing depths, absence of inflammation, and improved radiographic crestal stability. The combined correction of both hard and soft tissue defects around peri-implantitis lesions may facilitate treatment success and help maintain peri-implant stability.

Risk factors and longitudinal regenerative outcomes of sinus membrane perforation during lateral window sinus floor elevation: A retrospective analysis up to 9 years.

BACKGROUND: Lateral-window sinus floor elevation (LSFE) is a reliable procedure to reconstruct the posterior maxilla for implant therapy. This retrospective study aimed to investigate risk factors associated with Schneiderian membrane perforation (SMP) occurrence during LSFE and longitudinal regenerative outcomes following LSFE up to 9 years. METHODS: Patients who had LSFE between 2010 and 2019 were included. All demographic and surgical-related data were retrieved from existing electronic health records. Radiographs were used to evaluate the vertical dimensional changes of ridge and graft materials and the potential anatomic factors of SMP. RESULTS: A total of 122 LSFE procedures in 99 patients were included in the study. Mean ridge height gain and graft shrinkages were 9.5 ± 3.47 and 1.57 ± 2.85 mm. The influence of the healing period on graft shrinkage showed a positive trend; the longer the healing period, the greater the graft shrinkage (p = 0.09). The pathology in the sinus showed a positive correlation with SMP (p = 0.07). However, other anatomical factors did not negatively impact SMP and subsequent ridge height gain (p > 0.05). CONCLUSIONS: With inherent limitation, the findings with up to 9 years of follow-up indicate a consistent ridge remodeling lasting for about 3 years after LSFE procedures. SMP or membrane thickening may not significantly affect the ridge gain following LSFE. The healing period had the most significant influence on graft shrinkage, showing that the longer the healing time between LSFE and implant placement, the greater the graft shrinkage.

The Impact of Sinus Floor Elevation Techniques on Sinus Membrane Perforation: A Systematic Review and Network Meta-analysis.

Purpose: To compare the risk of sinus membrane perforation (SMP) among lateral window sinus floor elevation (LSFE) and transcrestal sinus floor elevation (TSFE) techniques in prospective and retrospective studies for patients who underwent sinus augmentation for dental implant placement. Materials and Methods: A database search was conducted to screen the literature published from January 1960 to August 2021. The associations between SMP and surgical techniques as well as other clinical factors were evaluated via network meta-analysis. The impact of SMP on vertical ridge gain and implant survival was also evaluated. Results: Eighty-five studies with 5,551 SFE procedures were included. In LSFE techniques, using rotary burs showed the highest risk of SMP (surface under the cumulative ranking area [SUCRA] = 0.0745). In TSFE techniques, using reamers had the lowest risk of SMP (SUCRA = 0.9444). Increased SMP prevalence was significantly associated with reduced implant survival rate (odds ratio [OR] = 0.45 per 10% increase of SMP rate [95% credible interval (CreI): 0.21, 0.71], P < .001). Conclusions: With the inherent limitations, this network meta-analysis suggested that some techniques within either the LSFE or TSFE group may reduce SMP risk. Additional randomized controlled trials and better assessment of SMP are required to directly compare the risk of SMP between LSFE and TSFE.

Using soft tissue graft to prevent mid-facial mucosal recession following immediate implant placement.

BACKGROUND: With advances in dental technology, the placement of immediate implants has progressively gained popularity. However, a common complication that surfaced was mid-facial mucosal recession, which impaired esthetic outcomes. The use of soft tissue grafts has thus been introduced to manage and prevent this undesirable result. To date, no guidelines have been put forward for clinicians to identify the indications for a soft tissue graft during immediate implant placement. Therefore, this manuscript aimed to propose a decision-making model to prevent mid-facial mucosal recession following immediate implant placement. METHOD: An electronic search of the PubMed database for literature published in English on the occurrence and management of soft tissue alterations following immediate implant placement was performed. RESULTS: Several factors, including implant position, buccal plate thickness, tissue thickness and width of keratinized mucosa, were found to influence the need for soft tissue grafting during immediate implant placement. For sockets with at least 2 mm of buccal plate thickness, a soft tissue graft was recommended for immediate implants placed at the incisal position. For sockets with less than 2 mm of buccal plate thickness, immediate implant placement in combination with bone or soft tissue augmentation was necessary. This was especially critical in scenarios with thin tissue biotypes or inadequate width of keratinized mucosa. CONCLUSION: Soft tissue grafts can maintain soft tissue stability following immediate implant placement.

Complications of sinus floor elevation procedure and management strategies: A systematic review.

AIM: This systematic review aimed to investigates the types and incidences of complications following sinus floor elevations (SFE) along with their prevention and management strategies. MATERIALS AND METHODS: Electronic database and hand search were conducted to screen the literature published from January 1960 to June 2021. The selected studies had to report well-described SFE techniques, complications during, and post-SFE. Data extraction included types of SFE techniques, complications, and their treatment strategies. RESULTS: A total of 74 studies with 4411 SFE procedures met the inclusion criteria. Different SFE techniques demonstrated varying patterns for both complications and complication rates. Postoperative pain, swelling, and edema were widely reported. The most common complications that required intervention following Lateral SFE (LSFE) were sinus membrane perforation (SMP), wound dehiscence, graft exposure and failure, and sinusitis. LSFE had more SMPs and sinusitis cases compared with a transcrestal SFE (TSFE). The presence of benign paroxysmal positional vertigo following TSFE was significant in certain selected studies. CONCLUSION: Given the inherent limitations, this systematic review showed distinct features of complications in SFE using varying techniques. Treatment planning for these procedures should incorporate strategies to avoid complication occurrence.

Periodontal Risk Assessment Based on Dental and Gingival Morphology: A Comparative Analysis of African Versus Asian American Cohorts.

FOCUSED CLINICAL QUESTION: With the 2018 AAP/EFP disease classification with the staging and grading systems, does risk assessment for different ethnic group result in a different focus for clinical needs? This comparative analysis aimed to assess two previously reported cohort studies in African-American (Af-A) and Asian-American (As-A) as to the risk for these two populations for clinical attachment loss (CAL) and gingival phenotype. SUMMARY: In comparison of As-A and Af-A cohorts, As-A had higher frequency of thin tissue phenotype, less width of keratinized gingiva (KGW), and more gingival recession (GR). On other hands, Af-A showed higher prevalence of thick phenotype, longer total tooth length and root length (RL). These gingival and dental anatomical patterns suggest there are differential risk for GR, patterns for CAL, and periodontal prognosis between two cohorts. CONCLUSION(S): Because of nature of dental and gingival anatomy between these two cohorts, As-A are more susceptible in GR and the short RL affords this population less ability to withstand the clinical presentation of periodontal disease. From a therapeutic perspective, clinicians should evaluate patients with different risk assessment based on their dental and gingival characterization. Af-A may have clinical characteristics that makes this population less at risk for mucogingival defects. Conversely, phenotype modification therapy should be considered when treating As-A because of the high prevalence of thin tissue phenotype, inadequate KGW, and GR. Clinicians should also diligently monitor periodontal CAL around the teeth with shorter RL in periodontal or orthodontic therapy for better teeth prognosis.

Partly Deepithelialized Free Gingival Graft for Treatment of Lingual Recession.

INTRODUCTION: Gingival recession (GR) is an unhealthy root exposure that could result in sensitivity, abrasion, root caries and higher chance of plaque collection. The prevalence of GR is higher on the facial surfaces but could also affect the lingual tooth surfaces. Despite the etiology and location of GR, treatment is warranted to improve the long-term periodontal stability around the affected teeth. This case report describes the use of partly deepithelialized free gingival graft (PE-FGG) to augment lingual GR post orthodontic treatment. CASE PRESENTATION: The current report evaluates the results of PG-FGG to correct lingual recession in a 21-year-old female. The patient presented with 5 mm lingual recession on a previously orthodontically rotated tooth (#21). The recession was treated using a PE-FGG to increase keratinized gingiva (KG) and reduce root exposure. Follow-up at 24 months showed adequate root coverage and KG. CONCLUSION: The use of PE-FGG can be used to enhance KG for lingual recession with adequate root coverage.

Effects of Platform-Switching on Peri-implant Soft and Hard Tissue Outcomes: A Systematic Review and Meta-analysis.

PURPOSE: This systematic review and meta-analysis was aimed at evaluating the longitudinal effect of platform switching on implant survival rates as well as on soft and hard tissue outcomes. MATERIALS AND METHODS: An electronic search of the databases of the National Center for Biotechnology Information, PubMed, Ovid (MEDLINE), EMBASE, Web of Science, and Cochrane Collaboration Library was conducted in February 2015. Studies published in English with at least 10 human participants and a 12-month post-loading follow-up were included. Random effects meta-analyses of selected studies were applied to compare the primary and secondary outcomes of platform-switched (PS) and regular-platform (RP) implants, as well as the experimental designs and clinical outcomes. RESULTS: A total of 26 studies involving 1,511 PS implants and 1,123 RP implants were evaluated. Compared to RP implants, PS implants showed a slight increase in vertical marginal bone loss (VMBL) and pocket depth reduction (weighted mean differences were -0.23 mm and -0.20 mm, respectively). The PS implants had a mean VMBL of 0.36 ± 0.15 mm within the first year of service. The meta-regression suggested a trend of decreased bone resorption at sites with thick soft tissues at baseline. CONCLUSION: This study suggested that platform switching may have an indirect protective effect on implant hard tissue outcomes.

Effects of Recombinant Human Bone Morphogenetic Protein-2 on Vertical Bone Augmentation in a Canine Model.

BACKGROUND: Vertical bone augmentation (VBA) remains unpredictable and challenging for most clinicians. This study aims to compare hard tissue outcomes of VBA, with and without recombinant human bone morphogenetic protein (rhBMP)-2, under space-making titanium mesh in a canine model. METHODS: Eleven male beagle dogs were used in the study. Experimental ridge defects were created to form atrophic ridges. VBA was performed via guided bone regeneration using titanium mesh and allografts. In experimental hemimandibles, rhBMP-2/absorbable collagen sponge was well mixed with allografts prior to procedures, whereas a control buffer was applied within controls. Dogs were euthanized after a 4-month healing period. Clinical and radiographic examinations were performed to assess ridge dimensional changes. In addition, specimens were used for microcomputed tomography (micro-CT) assessment and histologic analysis. RESULTS: Membrane exposure was found on five of 11 (45.5%) rhBMP-2-treated sites, whereas it was found on nine of 11 (81.8%) non-rhBMP-2-treated sites. Within 4 months of healing, rhBMP-2-treated sites showed better radiographic bone density, greater defect fill, and significantly more bone gain in ridge height (P <0.05) than controls. Experimental hemimandibles exhibited lower rates of membrane exposure and a noteworthy, ectopic bone formation above the mesh in 72% of sites. Results from micro-CT also suggested a trend of less vertical bone gain and bone mineral density in controls (P >0.05). Under light microscope, predominant lamellar patterns were found in the specimen obtained from rhBMP-2 sites. CONCLUSION: With inherent limitations of the canine model and the concern of such a demanding surgical technique, current findings suggest that the presence of rhBMP-2 in a composite graft allows an increase of vertical gain, with formation of ectopic bone over the titanium mesh in comparison with non-rhBMP-2 sites.

The Effect of Inital-Phase Bone Remodeling on Implant Wound Healing.

This case series aimed to investigate the initial-phase bone remodeling during implant wound healing and to discuss the possible contributing factors. A total of 11 implants with polished collars were placed in premaxillary regions via flapless approach with the aid of computer technology. After 15 months of follow-up, the results suggested that the presence of polished collars triggered bone resorption via a bone remodeling mechanism. The overall vertical crestal resorption was 0.78 ± 0.46 mm on average. This initial-phase bone remodeling primarily occurred within the first 3 months postoperatively. The slightly exposed polished collar may not worsen crestal bone level.

Comparison of Clinical and Radiographic Outcomes of Platform-Switched Implants with a Rough Collar and Platform-Matched Implants with a Smooth Collar: A 1-Year Randomized Clinical Trial.

PURPOSE: The aim of this study was to evaluate and compare the clinical and radiographic outcomes of single implants with a platform-switched rough collar (PSRC) and a platform-matched smooth collar (PMSC). MATERIALS AND METHODS: Twenty-six patients missing a tooth in the anterior maxilla (through the premolars) were randomly assigned to the PSRC or the PMSC group. All implants were placed in a flapless approach and restored with an early loading protocol. Clinical measurements were performed at surgery, loading, and at 3, 6, and 12 months after loading. In addition, radiographic evaluations were carried out using standardized periapical radiographs and cone beam computed tomography. Patient satisfaction surveys were completed, and microbial analysis with DNA probes was performed. RESULTS: The implant survival rate was 100% for both groups. The mean marginal bone level (MBL) was significantly higher in the PSRC group compared to the PMSC group at all time points. From the 2-week postoperative visit to 1 year postloading, the mean MBL change in the PSRC group was 0.21 ± 0.56 mm and in the PMSC group it was 0.74 ± 0.47 mm. Soft tissue profiles were stable over time, with no significant differences between groups. There were no significant differences between groups in the number of microbial species seen. Patients in both groups were highly satisfied with postoperative and postprosthetic experiences. CONCLUSION: In this study, the PSRC method preserved marginal bone by a mean of 0.53 mm more than the standard PMSC protocol. Within the limitations of the present study, it can be concluded that the PSRC protocol may be beneficial in marginal bone preservation. Longitudinal studies are needed to verify the long-term effects of this approach.

Identifying occlusal overload and how to deal with it to avoid marginal bone loss around implants.

BACKGROUND: Occlusal overloading is the primary cause of biomechanical implant complications, which include fracture and/or loosening of the implant fixture and/or prosthetic components. It may also disrupt the intricate bond between the implant surface and bone, leading to peri-implant bone loss and eventual implant failure. PURPOSE: This paper was aimed at identifying and evaluating clinical and radiographic parameters relevant for diagnosing occlusal overloading of oral implants. It also discusses its management in order to prevent peri-implant marginal bone loss. MATERIALS AND METHODS: An electronic literature search for relevant studies, examining the relationship between occlusal overloading and peri-implant bone loss, was conducted in the PubMed database. Clinical human studies published in English with a minimum of 10 implants were included. RESULTS: Seven articles were identified. Occlusal overloading was found to be positively associated with peri-implant marginal bone loss. CONCLUSION: Preventing occlusal overloading involves conducting comprehensive examinations, treatment planning, precise surgical and prosthetic treatment executions, and regular maintenance. If occlusal overloading occurs, management of biomechanical implant complications and preventing/treating peri-implant bone loss involves surgical and prosthetic treatment modalities. They include occlusal treatment, repair and replacement of defective prosthetic components, and surgical treatment of the bony craters.

Biomechanical implant treatment complications: a systematic review of clinical studies of implants with at least 1 year of functional loading.

PURPOSE: The aim of this article is to discuss the current literature available on the etiology and management of biomechanical complications of dental implant treatment. MATERIALS AND METHODS: An electronic search of the PubMed database for English-language articles published before May 31, 2011, was performed based on a focus question: "How can biomechanical implant treatment complications be managed and identified?" The key words used were "dental implant," "etiology," "management," "excessive occlusal forces," "occlusal forces," "occlusion," "parafunctional habits," "biomechanical failure," "biomechanical complications," and "occlusal overloading." Clinical trials with a minimum of 10 implants followed for at least 1 year after functional loading were included. RESULTS: The initial electronic search identified 2,087 publications, most of which were eliminated, as they were animal studies, finite element analyses, bench-top studies, case reports, and literature reviews. After the titles, abstracts, and full text of 39 potentially eligible publications were reviewed, 15 studies were found to fulfill the inclusion criteria. CONCLUSION: Occlusal overloading was thought to be the primary etiologic factor in biomechanical implant treatment complications, which commonly included marginal bone loss, fracture of resin/ceramic veneers and porcelain, retention device or denture base fracture of implant-supported overdentures, loosening or fracture of abutment screws, and even implant failure. Occlusal overloading was positively associated with parafunctional habits such as bruxism. An appreciation of the intricacy of implant occlusion would allow clinicians to take a more preventive approach when performing implant treatment planning, as avoidance of implant overloading helps to ensure the long-term stability of implant-supported prostheses.