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Ecosystem, which consists of the physical environment and all the living organisms, on which we all depend, is declining rapidly because of its destruction caused by humans. It’s a two-way relationship between the humans and mother nature. If we destroy the natural environment around us, human life will be seriously affected, and the life of next generation will be endangered unless serious steps are taken. One such effect of human overexploitations has come in the form of coronavirus outbreak. Coronavirus, a contagious disease of 2019 known as Covid-19, is the latest swiftly spreading global infection. The aetiology of Covid-19 is different from SARS-CoV which has the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), but it has the same host receptor, human angiotensin converting enzyme 2 (ACE2). The novel coronavirus which is zoonotic (spreading from an animal to a human) and mainly found in the bats and pangolins is a single stranded ribonucleic acid virus of Coronaviridae family. 1 The typical structure of 2019-nCoV possessed ‘spike protein’ in the membrane envelope, also expressed various polyproteins, nucleoproteins and membrane protein. The S protein binds to the receptor cell of host to facilitate the entry of virus in the host. Currently four genera for coronavirus are found α-CoV, ßCoV, γ-CoV, δ-CoV. SARS-CoV first originated in Wuhan, China and has spread across the globe. World Health Organization (WHO) and public health emergency of international concern declared it as 2019 - 2020 pandemic disease.2 According to WHO report, (7th April 2020) update on this pandemic coronavirus disease, there have been more than 13,65,004 confirmed cases and 76,507 deaths across the world and these figures are rapidly increasing. Therefore, actions for proper recognition, management and its prevention must be prompted for relevant alleviation of its outspread.3 Health care professionals are mainly indulged in the national crises and are working diligently around-the-clock, small ratio of the health care workers have become affected and few died tragically. Dentists are most often the first ones to be affected because they work with patients in close proximity. On 15th March 2020, the New York Times published an article titled “The workers who face the greatest Coronavirus risk” described the dentists are highly exposed, than the paramedical staffs and general physicians, to the risk of novel coronavirus disease 19.4

All efforts to save the natural teeth should be made during restoration to achieve optimum functionality and aesthetics. Tooth loss is associated with appetite loss and loss of nutritional values. Thus, rehabilitating complete or partial edentulous conditions contributes to improvement in the functioning of the masticatory system. In the latter case of partially dentate condition, the natural teeth present preserve the residual ridges. Extraction of teeth causes alveolar ridge resorption. Poor foundation or ridge form donot provide support for the denture bases which is the factor of utmost consideration for stabilisation of the denture bases. In these instances, use of the telescopic dentures may be indicated. A telescopic denture retains and preserves the natural teeth beneath it. Every dentist aims at preserving the natural and restoring the lost. Preservation of the remaining teeth in turn preserves the natural proprioception mechanism, was thus followed and applied in this case report in which a 25-year-old female patient with diabetic history and on medication since past four years, presented with multiple missing teeth in December 2019. After thorough evaluation, the patient was treated by Marburg double crown system or synonymously termed as telescopic denture opposing the tooth supported overdenture. Follow-up and recall schedule was then explained and operator noted a satisfactory response from the patient. Consecutive follow-ups were maintained.

BACKGROUND The restoration of endodontically treated teeth is a challenge as these teeth loose significant part of the tooth structure due to caries, previous restorative procedures, endodontic access cavity preparation or due to loss of moisture supplied by dentin, which makes them weak. The restoration of such teeth is accomplished by using post and core, to prevent further destruction and to provide retention for the core, before a crown or a fixed partial denture can be placed. Post-retained crowns are indicated for endodontically treated teeth (ETT) with severely damaged coronal tissue. There are still controversies for the most suitable choice of restorative material and the placement method that will result in the highest success rate. This clinical study compares the para post, fiber post and ceramic post in the restoration of the endodontically treated teeth. We wanted to evaluate and compare the retentive properties of three different post systems used for endodontically treated teeth for providing restoration. METHODS Sixty extracted human, single rooted, caries free, non-fractured tooth were selected and disinfected using 2% chlorhexidine solution and subsequently stored in distilled water. Each group consists of 20 samples. The crown structures of teeth were separated from root at cemento-enamel junction. Canal was obturated with gutta-percha and endodontic sealer. The posts were coated with Selfcem and also the resin cement was transported into the canal by the lentulospiral. A custom made two-piece stainless-steel mould was used for fabrication of standard size resin blocks in which teeth specimens were mounted. After the complete curing of autopolymerising acrylic resin, after 30-45 minutes, the block was retrieved from the mould. The specimen with acrylic block was mounted on lower jaw of universal testing machine. The retentive strength was calculated as maximum tensile load that a sample can withstand post dislodgement. RESULTS Descriptive statistical analysis, one-way ANOVA, multiple comparison Tukey test were used. SPSS Ver. 16.0 was used for statistical analysis. Statistical analysis showed significant difference between the retentive strengths of all the three post systems (p<0.05). Group I: 259.17±27.37, Group II: 153.83±29.16, and group III: 118.40 ± 12.95. Paraposts showed highest retention followed by Fiberposts and then followed by Ceramic posts. CONCLUSIONS Prefabricated metal posts have the highest retention when compared with the other two post systems.