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Molecular evolutionary rate variation is a key aspect of the evolution of many organisms that can be modeled using molecular clock models. For example, fixed local clocks revealed the role of episodic evolution in the emergence of SARS-CoV-2 variants of concern. Like all statistical models, however, the reliability of such inferences is contingent on an assessment of statistical evidence. We present a novel Bayesian phylogenetic approach for detecting episodic evolution. It consists of computing Bayes factors, as the ratio of posterior and prior odds of evolutionary rate increases, effectively quantifying support for the effect size. We conducted an extensive simulation study to illustrate the power of this method and benchmarked it to formal model comparison of a range of molecular clock models using (log) marginal likelihood estimation, and to inference under a random local clock model. Quantifying support for the effect size has higher sensitivity than formal model testing and is straight-forward to compute, because it only needs samples from the posterior and prior distribution. However, formal model testing has the advantage of accommodating a wide range molecular clock models. We also assessed the ability of an automated approach, known as the random local clock, where branches under episodic evolution may be detected without their a priori definition. In an empirical analysis of a data set of SARS-CoV-2 genomes, we find "very strong" evidence for episodic evolution. Our results provide guidelines and practical methods for Bayesian detection of episodic evolution, as well as avenues for further research into this phenomenon.
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The ongoing SARS-CoV-2 pandemic has seen an unprecedented amount of rapidly generated genome data. These data have revealed the emergence of lineages with mutations associated to transmissibility and antigenicity, known as variants of concern (VOCs). A striking aspect of VOCs is that many of them involve an unusually large number of defining mutations. Current phylogenetic estimates of the substitution rate of SARS-CoV-2 suggest that its genome accrues around two mutations per month. However, VOCs can have 15 or more defining mutations and it is hypothesized that they emerged over the course of a few months, implying that they must have evolved faster for a period of time. We analyzed genome sequence data from the GISAID database to assess whether the emergence of VOCs can be attributed to changes in the substitution rate of the virus and whether this pattern can be detected at a phylogenetic level using genome data. We fit a range of molecular clock models and assessed their statistical performance. Our analyses indicate that the emergence of VOCs is driven by an episodic increase in the substitution rate of around 4-fold the background phylogenetic rate estimate that may have lasted several weeks or months. These results underscore the importance of monitoring the molecular evolution of the virus as a means of understanding the circumstances under which VOCs may emerge.
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COVID-19 , SARS-CoV-2 , Aceleración , Humanos , Mutación , Filogenia , Glicoproteína de la Espiga del Coronavirus/genéticaRESUMEN
Systemic antibiotics are an effective adjunct in the treatment of periodontitis, but their judicious use is necessary as antimicrobial resistance is a growing global concern. This review aims to explore the current understanding and insight related to antibiotic resistance in the subgingival microbiota of periodontitis patients. A search of MEDLINE (PubMed) was carried out from 1 January 2012 to 25 November 2021 for studies related to antibiotic resistance in periodontitis patients. Of the 90 articles identified, 12 studies were selected for inclusion. A significant incidence of antibiotic resistant isolates was reported for Porphyromonas gingivalis, Prevotella intermedia, Prevotella denticola, Prevotella melaninogenica, Fusobacterium nucleatum, Tanerella forsythia, Aggretibacter actinomycetemcomitans, Streptococcus constellatus, Streptococcus intermedius, and Parvimonas micra, but resistance to specific antibiotics did not reach above 10% of isolates in most studies except for amoxicillin resistance in Aggretibacter actinomycetemcomitans. The highest frequency of resistance across all bacterial species was for amoxicillin, clindamycin, and metronidazole. However, resistance patterns were widely variable across geographical locations, and the high heterogeneity between antibiotic-resistant isolates across studies precludes any clinical recommendations from this study. Although antibiotic resistance has yet to reach critical levels in periodontitis patients, an emphasis on antibiotic stewardship interventions such as point-of-care diagnostics and education for key stakeholders is needed to curb a growing problem.
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Although the efficacy of ridge preservation is well documented, there is a lack of robust evidence regarding the influence of different surgical techniques. Flapless approaches are thought to be better at preserving soft tissue architecture and have been suggested for mild to moderate defects. This review investigates the efficacy of different flapless techniques for ridge preservation in mild to moderate defects with <50% buccal bone loss. PubMed, EMBASE, and Cochrane Library databases were searched to obtain relevant articles published in English from 1974 to December 2019. The primary outcome was horizontal and vertical hard tissue dimensional changes. Soft tissue changes were evaluated as a secondary outcome. The Bio-Col technique, subperiosteal tunnel technique, and hard tissue with autogenous soft tissue graft/collagen matrix technique were identified. Eight studies were included, and quantitative analyses were performed for 4 studies for the primary outcome variables. The meta-analysis revealed significant reductions for horizontal changes (weighted mean difference [WMD] = 2.56 mm, 95% CI [2.18, 2.95]), vertical mid-buccal (WMD = 1.47 mm, 95% CI [1.04, 1.90]), and vertical mid-lingual (WMD = 1.28 mm, 95% CI [0.68, 1.87]) in favor of flapless ridge preservation techniques. Subgroup analysis based on technique suggests minimal hard tissue differences. The efficacy of flapless ridge preservation techniques on soft tissue changes was inconclusive. In conclusion, flapless ridge preservation techniques are effective for mild to moderate defects. The technique or material used to close the extraction socket does not seem to significantly affect hard tissue changes, while the effect on soft tissue changes warrants further investigation.
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Pérdida de Hueso Alveolar , Aumento de la Cresta Alveolar , Humanos , Alveolo Dental/cirugía , Extracción Dental/métodos , Aumento de la Cresta Alveolar/métodos , Proceso Alveolar/cirugía , Colágeno/uso terapéutico , Pérdida de Hueso Alveolar/prevención & control , Pérdida de Hueso Alveolar/cirugíaRESUMEN
OBJECTIVES: To evaluate the efficacy of probiotics in reducing halitosis of dental origin. METHODS: MEDLINE, EMBASE, and CENTRAL were searched up to and including June 2020. Randomised placebo-controlled, double-blinded clinical trials in systemically healthy adult patients who were given any form of probiotics to manage halitosis of dental origin were included. Primary outcome measures were organoleptic scores and volatile sulphur concentration levels. Secondary outcome measures were microbiologic parameters and quality of life (QOL). RESULTS: Of the 301 potentially relevant articles, eight articles were selected for the review. The risk of bias assessment showed that two studies were of low risk of bias, four studies had some concerns, and two studies had a high risk of bias. The beneficial effect of probiotics could neither be confirmed in periodontally treated patients administered with up to 8 weeks of probiotics, nor in periodontitis patients who received both non-surgical periodontal therapy and adjunctive probiotics up to 90 days. Microbiological findings 1 month after probiotics administration and QOL measures showed no significant differences compared to control. Considerable heterogeneity was observed among probiotic administration protocols. CONCLUSIONS: The available evidence suggests no convincing benefit for the use of probiotics in the management of halitosis. Standardised protocols on recruitment of halitosis subjects and organoleptic measurements are required for future studies on probiotics as an intervention. CLINICAL RELEVANCE: The lack of well-conducted studies with a low risk of bias precludes any clinical recommendation. Further research is needed to verify the efficacy of probiotics in the management of intra-oral halitosis.
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Halitosis , Probióticos , Adulto , Halitosis/terapia , Humanos , Probióticos/uso terapéutico , Calidad de Vida , SensaciónRESUMEN
OBJECTIVE: To comprehensively investigate the efficacy of adjunctive probiotics compared to placebo, using conventional and novel treatment outcomes. MATERIALS AND METHODS: Three databases (MEDLINE, EMBASE, and CENTRAL) were searched. Outcomes included percent change in the total number of deep sites before and after therapy, change in mean probing pocket depth (mm), percentage patients requiring additional therapy, risk for disease progression, and microbiological and immunological results. Meta-analysis was conducted to evaluate treatment effects wherever appropriate. RESULTS: Ten studies were selected from 818 records. Meta-analysis showed that adjunctive probiotics had no additional benefit for percentage change of the total number of deeper sites (≥5 mm, ≥6 mm, ≥7 mm) before and after therapy. No significant difference was observed for mean probing pocket depth reduction at 3 and 6 months. Statistically significant beneficial odds ratios for need for additional therapy (OR = 0.19, 95% CI [0.07-0.56]) and risk of disease progression (OR = 0.32, 95% CI [0.14-0.73]) were observed with probiotic administration. Immunological rather than microbiological outcomes correlated more consistently with clinical findings. No adverse events were reported. CONCLUSIONS: Adjunctive probiotics are safe in systemically healthy individuals and could offer additional patient-level benefits compared to placebo, hence its use can sometimes be justified.
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Desbridamiento Periodontal , Probióticos , Atención Odontológica , Raspado Dental , Humanos , Probióticos/efectos adversosRESUMEN
"Open-ended" molecular techniques such as 16S rRNA sequencing have revealed that the oral bacteriome of subgingival plaque is more diverse than originally thought. 16S rRNA analysis has demonstrated that constituents of the overall bacterial community are qualitatively similar in health and disease, differing mainly in their relative proportions with respect to each other. Species in low abundance can also act as critical species, leading to the concept of global community dysbiosis which relates to shifts in community structure, rather than shifts in membership. Correlation analysis suggests that coordinated interactions in the community are essential for incipient dysbiosis and disease pathogenesis. The subgingival bacteriome also provides biomarkers that are useful for disease detection and management. Combined with clinical and biological parameters, these may assist clinicians in developing and implementing effective treatment strategies to restore microbial homeostasis and monitor disease. Identification of higher risk groups or poor responders to treatment using unique subgingival bacteriome signatures may also lead to early intervention.
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Placa Dental , Microbiota , Periodontitis , Disbiosis , Humanos , Microbiota/genética , Periodontitis/genética , Periodontitis/terapia , ARN Ribosómico 16S/genéticaRESUMEN
AIM: To evaluate the types and quality of reporting of economic evaluations carried out in the clinical management of periodontal disease over 32 years from 1987 to 2019. MATERIAL AND METHODS: A systematic search of articles from 1987 to 2019 was conducted using PubMed, Web of Science, The Cochrane Central Register of Controlled Trials, Health Technology Assessment Database and Embase. The quality of the economic evaluations was assessed based on the Consolidated Health Economic Evaluation Reporting Standard checklist. Due to considerable between-study heterogeneity, a meta-analysis was not performed. RESULTS: Twenty one publications were included. 11 studies used cost-effectiveness analysis, five used cost-minimization analysis, four used cost-utility analysis and two used cost-benefit analysis. Comparators, choice of health outcomes, estimating resources and costs were fully reported in all studies. Many studies had inadequate reporting in terms of estimating resources and costs, choice of health outcomes, characterizing heterogeneity and study perspective. CONCLUSIONS: There has been an increase in health economics studies in the field of clinical periodontology over the past decade. Several studies did not report study perspective, and the health outcomes chosen were not relevant for some studies. Future studies should follow an economic evaluation checklist for high-quality reporting and consistency.
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Enfermedades Periodontales , Análisis Costo-Beneficio , Humanos , Enfermedades Periodontales/terapiaRESUMEN
One of the main environmental threats in the tropics is selective logging, which has degraded large areas of forest. In southeast Asia, enrichment planting with seedlings of the dominant group of dipterocarp tree species aims to accelerate restoration of forest structure and functioning. The role of tree diversity in forest restoration is still unclear, but the 'insurance hypothesis' predicts that in temporally and spatially varying environments planting mixtures may stabilize functioning owing to differences in species traits and ecologies. To test for potential insurance effects, we analyse the patterns of seedling mortality and growth in monoculture and mixture plots over the first decade of the Sabah biodiversity experiment. Our results reveal the species differences required for potential insurance effects including a trade-off in which species with denser wood have lower growth rates but higher survival. This trade-off was consistent over time during the first decade, but growth and mortality varied spatially across our 500 ha experiment with species responding to changing conditions in different ways. Overall, average survival rates were extreme in monocultures than mixtures consistent with a potential insurance effect in which monocultures of poorly surviving species risk recruitment failure, whereas monocultures of species with high survival have rates of self-thinning that are potentially wasteful when seedling stocks are limited. Longer-term monitoring as species interactions strengthen will be needed to more comprehensively test to what degree mixtures of species spread risk and use limited seedling stocks more efficiently to increase diversity and restore ecosystem structure and functioning.
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Biodiversidad , Bosques , Árboles/crecimiento & desarrollo , Clima Tropical , Malasia , Plantones/crecimiento & desarrolloRESUMEN
Drought regimes can be characterized by the variability in the quantity of rainfall and the duration of rainless periods. However, most research on plant response to drought has ignored the impacts of rainfall variation, especially with regard to the influence of nonstructural carbohydrates (NSCs) in promoting drought resistance. To test the hypothesis that these components of drought differentially affect NSC dynamics and seedling resistance, we tracked NSC in plant tissues of tropical tree seedlings in response to manipulations of the volume and frequency of water applied. NSC concentrations decreased in woody tissues under infrequent-high watering but increased under no watering. A faster decline of growth relative to stomatal conductance in the no watering treatment was consistent with NSC accumulation as a result of an uncoupling of growth and photosynthesis, while usage of stored NSCs in woody tissues to maintain function may account for the NSC decline under infrequent-high watering. NSCs, and specifically stem NSCs, contributed to drought resistance under severe water deficits, while NSCs had a less clear role in drought resistance to variability in water availability. The contrasting response of NSCs to water variability and deficit indicates that unique processes support seedling resistance to these components of drought.
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Adaptación Fisiológica , Metabolismo de los Hidratos de Carbono , Sequías , Tallos de la Planta/metabolismo , Estrés Fisiológico , Árboles/metabolismo , Agua , Fotosíntesis , Estomas de Plantas/fisiología , Transpiración de Plantas , Lluvia , Plantones/metabolismo , Árboles/crecimiento & desarrollo , MaderaRESUMEN
Teeth with attachment loss involving the root apex are severely compromised and have a poor periodontal prognosis. In cases where periodontal regeneration is possible, current guidelines suggest that endodontic treatment is performed first. However, root canal treatment increases the overall treatment time and costs, has risks of endodontic complications, and could predispose teeth to mechanical failure. In this case report, two patients diagnosed with periodontitis stage III/IV grade C, no history of smoking or diabetes, and attachment loss involving the root apex of a tooth, were treated with guided tissue regeneration. These two cases are unique because successful periodontal regeneration was carried out without endodontic treatment, and the vitality of these teeth was maintained longitudinally. This report presents the management that led to this clinical outcome, and important guidelines for case selection are identified. Within the limitations of this study, vital teeth with radiographic bone loss involving the apex may be treated successfully with periodontal regeneration and remain vital at least in the short- to medium-term.
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This mapping review highlights the need for a new paradigm in the understanding of peri-implantitis pathogenesis. The biofilm-mediated inflammation and bone dysregulation (BIND) hypothesis is proposed, focusing on the relationship between biofilm, inflammation, and bone biology. The close interactions between immune and bone cells are discussed, with multiple stable states likely existing between clinically observable definitions of peri-implant health and peri-implantitis. The framework presented aims to explain the transition from health to disease as a staged and incremental process, where multiple factors contribute to distinct steps towards a tipping point where disease is manifested clinically. These steps might be reached in different ways in different patients and may constitute highly individualised paths. Notably, factors affecting the underlying biology are identified in the pathogenesis of peri-implantitis, highlighting that disruptions to the host-microbe homeostasis at the implant-mucosa interface may not be the sole factor. An improved understanding of disease pathogenesis will allow for intervention on multiple levels and a personalised treatment approach. Further research areas are identified, such as the use of novel biomarkers to detect changes in macrophage polarisation and activation status, and bone turnover.
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Periimplantitis , Humanos , Inflamación , Biopelículas , Membrana Mucosa , OseointegraciónRESUMEN
Background: There have been no reports of sepsis-induced agranulocytosis causing gingival necrosis in otherwise medically healthy patients to the authors' best knowledge. Even though there are several case reports of gingival necrosis secondary to medication-induced agranulocytosis, they have not systematically described the natural progression of agranulocytosis-related gingival necrosis. Methods: This paper presents a case report of a 29-year-old female Indian patient with generalised gingival necrosis and constitutive signs of intermittent fever, nausea, and vomiting. She also complained of abdominal pains. Blood counts showed agranulocytosis, and the patient was admitted for a workup of the underlying cause. Parenteral broad-spectrum antibiotics were administered, which brought about clinical resolution. Results: Her gingival necrosis was attributed to sepsis-induced agranulocytosis triggered by Pseudomonas aeruginosa bacteraemia, and upon clinical recovery, spontaneous exfoliation left behind exposed bone. Secondary healing over the exposed alveolar bone was noted after a year-long follow-up, albeit with some residual gingival recession. Conclusions: Oral manifestations of gingival necrosis, when present with concomitant constitutive symptoms, could indicate a serious underlying systemic condition that could be potentially life-threatening if left untreated. Dentists should be cognizant of this possibility so that timely intervention is not delayed.
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OBJECTIVES: Artificial intelligence (AI) has the potential to aid in constant, non-invasive monitoring of daily oral hygiene practices, potentially on behalf of a dentist or healthcare provider. This review summarises the evidence around the use of AI in the context of oral hygiene education. DATA & SOURCES: This scoping review was developed according to the Joanna Briggs Institute scoping review protocol guidelines and the PRISMA-ScR guidelines. Publications that involved the use of AI for oral hygiene education in any population and setting were included. A systematic electronic database search (MEDLINE via PubMed, EMBASE, Web of Science, Scopus, Cochrane Library, and IEEE Xplore, arXiv, Proquest, Google Scholar, ClinicalTrials.gov, and PROSPERO) up to, and including 4 February 2023 was carried out. Citation searching from the full-text of included publications was also performed. RESULTS: Of the 3215 publications screened, 20 were selected for qualitative synthesis. These were broadly divided into two categories of AI-assisted feedback: (1) synchronous and (2) asynchronous monitoring. There is a lack of high-quality studies, scarce reflection on possible ethical concerns on AI, and of studies comparing qualitative feedback to quantitative clinical outcomes with a control. Barriers to adoption of AI technologies, patient privacy, and specific areas for improvement were identified. CONCLUSION: Within the limitations of this study, the use of AI to modify oral hygiene behaviour is promising. Further work is required in generating higher quality intra-oral images for dental biofilm detection, and in developing more personalised feedback for users. CLINICAL SIGNIFICANCE: This is the first review to map out the available literature on AI in providing oral hygiene education. It may be useful to dental researchers in appraising AI-assisted technologies in the context of oral health.
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Inteligencia Artificial , Higiene Bucal , Humanos , Salud Bucal , Atención OdontológicaRESUMEN
PURPOSE: Guided bone regeneration (GBR) utilizes a barrier membrane to allow osteogenic cells to populate a space by excluding epithelial and connective tissue cells. The purpose of this systematic review was to investigate the ratio of means (RoM) of vertical bone gained (Outcome) in vertical GBR procedures with healing complications (Intervention) and in vertical GBR procedures without healing complications (Comparison) in patients with vertically resorbed edentulous ridges that require dental implant placement (Population). A further aim was to investigate the incidence of complications after vertical GBR, and the influence of the timing of implant placement and regenerative devices on complications. MATERIALS AND METHODS: MEDLINE (through PubMed), EMBASE, and Cochrane Central Register of Controlled Trials (CENTRAL) were searched in duplicate up to, and including, November 2020 for randomized and controlled clinical trials and prospective and retrospective case series. Outcomes included patient-level and site-level RoM of vertical bone gain between healing complications and uneventful healing, and incidences of complications that occurred after vertical GBR. Random-effects and fixed-effects meta-analyses were performed where appropriate. This study was registered on PROSPERO (CRD42021226432). RESULTS: A total of 31 publications were selected for the qualitative and quantitative analyses. The RoM of vertical bone gained was 0.65 [95% CI = 0.47, 0.91] and 0.62 [95% CI = 0.45, 0.85] when membrane exposure without suppuration and abscess formation without membrane exposure occurred respectively, in comparison to uneventful healing. The overall incidence proportion of healing complications occurring at the augmented site at a site- and patient-level was 11.0% [95% CI = 7.0, 15.6] and 10.8% [95% CI = 6.6, 15.7]. At a patient-level, there were no significant differences between a simultaneous or staged approach, or with the regenerative device used. The site-level incidence proportion of membrane exposure without suppuration, membrane exposure with suppuration, and with abscess formation without membrane exposure was 8.7% [95% CI = 4.2, 14.2], 0.7% [95% CI = 0.0, 2.9], and 0.5% [95% CI = 0.0, 1.7], respectively. The site-level weighted mean incidence proportion of neurologic complications occurring at the donor site was 0.8% [95% CI = 0.0, 5.3]. CONCLUSIONS: There is a significant reduction in bone gain when healing complications occur. However, healing complications are relatively uncommon surgical complications after vertical GBR.
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Aumento de la Cresta Alveolar , Implantes Dentales , Aumento de la Cresta Alveolar/métodos , Regeneración Ósea , Implantación Dental Endoósea/efectos adversos , Implantes Dentales/efectos adversos , Regeneración Tisular Guiada Periodontal/métodos , Humanos , Estudios Prospectivos , Estudios RetrospectivosRESUMEN
Severe periodontitis is a highly prevalent dental disease. With the advent of implant dentistry, teeth are often extracted and replaced. Periodontal surgery, where indicated, could also result in increased trauma to the patient. This literature review discusses different treatment modalities for periodontitis and proposes a treatment approach emphasizing maximum preservation of teeth while minimizing morbidity to the patient. Scientific articles were retrieved from the MEDLINE/PubMed database up to January 2021 to identify appropriate articles that addressed the objectives of this review. This was supplemented with hand searching using reference lists from relevant articles. As tooth prognostication does not have a high predictive value, a more conservative approach in extracting teeth should be abided by. This may involve repeated rounds of nonsurgical periodontal therapy, and adjuncts such as locally delivered statin gels and subantimicrobial-dose doxycycline appear to be effective. Periodontal surgery should not be carried out at an early phase in therapy as improvements in nonsurgical therapy may be observed up to 12 months from initial treatment. Periodontal surgery, where indicated, should also be minimally invasive, with periodontal regeneration being shown to be effective over 20 years of follow-up. Biomarkers provide an opportunity for early detection of disease activity and personalised treatment. Quality of life is proposed as an alternative end point to the traditional biomedical paradigm focused on the disease state and clinical outcomes. In summary, minimally invasive therapy aims to preserve health and function of the natural dentition, thus improving the quality of life for patients with periodontitis.
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It is not uncommon to encounter post-surgical complications after horizontal guided bone regeneration (GBR). The primary aim of this review was to evaluate the incidence and types of complications that occur after horizontal GBR and propose management strategies to deal with these clinical situations. A secondary aim was to conduct a histomorphometric review of the wound healing process at sites that experienced post-surgical complications after GBR. A keyword search of MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials for studies published in English from January 2015 to January 2020 was conducted for the primary aim and 23 studies were selected. A second search addressing the secondary aim was conducted, and five studies were included. Site-level analysis showed that the weighted mean incidence proportion of minor wound dehiscence and minor infections occurring at the augmented site was 9.9% [95% CI 6.4, 13.9, P < 0.01] and 1.5% [95% CI 0.4, 3.1, P = 0.21) respectively. Patient-level analysis showed minor and major complications occurring at a weighted mean incidence proportion of 16.1% [95% CI 11.9, 20.8, P = 0.01] and 1.6% [95% CI 0.0, 4.7, P < 0.01] respectively, while neurosensory alterations at the donor site was 7.0% [95% CI 1.3, 15.5, P < 0.01]. Subgroup analysis also revealed that the use of block grafts increased the incidence proportion of minor post-surgical complications, whereas a staged GBR procedure increased the incidence proportion of both minor and major post-surgical complications. Although exposure of the barrier membrane is often associated with less bone regeneration and graft resorption, the type of membrane used (resorbable or non-resorbable) had no statistically significant influence on any post-surgical complication. Histologically, a layer of fibrous connective tissue instead of bone is commonly observed at the interface between the native bone at the recipient site and the regenerated bone in cases with membrane exposure after GBR procedure. Minor wound dehiscence was the highest incidence proportion of post-surgical complications. Methods ranging from daily application of antiseptics, use of systemic antimicrobials, regular reviews, and total removal of the non-integrated biomaterials are commonly prescribed to manage these post-surgical complications in attempt to minimise the loss of tissue at the surgical site.
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The emergence of a highly infectious coronavirus strain, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has led to a major global public health emergency. The increasing number of infected cases and fatalities worldwide forced several countries into lockdown in a bid to control virus transmission. The practice of dentistry is considered high-risk due to the generation of aerosols associated with most dental procedures, and healthcare professionals must take appropriate precautions whilst working in this challenging environment. This review aims to provide an overview on transmission routes and shares a risk-based approach to coronavirus disease 2019 (COVID-19) in a specialty tertiary center. Risk assessment and mitigation focussed on staff and patient safety, adopting a wide safety margin, and responding dynamically to the level of risk at the workplace. As the severity of the pandemic depends on many still-unknown factors and shows little sign of abating, the routine practice of dentistry will continue to be disrupted in the near future. We describe a color-coded framework to maximize safety and to minimize disease spread. Areas covered include healthcare team management, personal protective equipment, clinical work, and dental education. Guidelines in each category change with the corresponding severity of the situation, and we believe it will be useful for the safer practice of dentistry in this current climate and can be modified for future similar disease outbreaks.
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Climate change induced alterations to rainfall patterns have the potential to affect the regeneration dynamics of plant species, especially in historically everwet tropical rainforest. Differential species response to infrequent rainfall may influence seed germination and seedling establishment in turn affecting species distributions. We tested the role of watering frequency intervals (from daily to six-day watering) on the germination and the early growth of Dipterocarpaceae seedlings in Borneo. We used seeds that ranged in size from 500 to 20,000 mg in order to test the role of seed mass in mediating the effects of infrequent watering. With frequent rainfall, germination and seedling development traits bore no relationship to seed mass, but all metrics of seedling growth increased with increasing seed mass. Cumulative germination declined by 39.4% on average for all species when plants were watered at six-day intervals, and days to germination increased by 76.5% on average for all species from daily to six-day intervals. Final height and biomass declined on average in the six-day interval by 16% and 30%, respectively, but the percentage decrease in final size was greater for large-seeded species. Rooting depth per leaf area also significantly declined with seed mass indicating large-seeded species allocate relatively more biomass for leaf production. This difference in allocation provided an establishment advantage to large-seeded species when water was non-limiting but inhibited their growth under infrequent rainfall. The observed reduction in the growth of large-seeded species under infrequent rainfall would likely restrict their establishment in drier microsites associated with coarse sandy soils and ridge tops. In total, these species differences in germination and initial seedling growth indicates a possible niche axis that may help explain both current species distributions and future responses to climate change.