Ans is B

Ans is C

Weakest link of any cast restoration is the tooth- cement-restoration interface. So special attention should be given to the given to design the margins of the preparation. The peripheral marginal anatomy of the preparation is called Circumferential tie. For the occlusal and gingival walls in Circumferential inlay preparations, the tooth circumferential tie is in the form of bevels. Bevels as part of circumferential tie are one of the major retention forms for a cast restoration as it increases possibility of a direct retentive frictional component between the casting and the tooth. 

Functions of Occlusal bevel in cast restorations:

Bevels create obtuse-angled140°-150° marginal tooth structures, which are the bulkiest and the strongest configuration of marginal tooth anatomy.

They also produce an acute-angled 30°-40°  marginal metal wall, which can be easily burnished and adapted. The marginal gold alloy will be too thin and weak if the angle of the gold bevel is less than30°.If greater than 40°, this metal would be too thick to burnish satisfactorily. 

They make it possible to decrease the 'cement line by bringing the cast alloy closer to the tooth structure. The error factor (space between cast restoration and tooth) is reduced three fold or more, as compared with external dimensions, depending on the bevel's angulation.

Bevels, being part of the circumferential tie, are one of the major retentive features for a cast restoration.

They are flexible extensions' of a cavity preparation, allowing the inclusion of surface defects or supplementary grooves

Ans is B

Maxillary sinus is a four-sided pyramid and opens into the middle meatus of nose through ostium. It is closer to the roots of maxillary first molar, followed by second premolar and second molar in decreasing order of frequency

Ans is B

Demineralized bone matrix (DBM) is often applied in orthopedics, periodontics, oral and maxillofacial surgery because of its inherent osteoconductive and osteoinductive properties. The process of bone demineralization is normally carried out by immersing the sample in a variety of strong and/or weak acids. When demineralization is done using HCl, it was recognized 1C that the process of demineralization exposes proteins, growth factors [specifically the bone morphogenetic proteins (BMPs)] and other bioactive molecules. Because of this, demineralized bone matrix (DBM) not only provides a scaffold for bone formation -meaning it is osteoconductive -but it also promotes differentiation 11 of precursor cells into viable bone-forming cells, a process termed as osteoinductivity.

Ans is C