Retention of maxillary complete denture bases achieved through posterior palatal seal registrations with conventional and functional swallow methods using two different border moulding materials - An In-vivo study

The commonly used treatment modality to rehabilitate the completely edentulous patient is tissue supported complete denture. The complete denture success depends on the retention, as it is one of the important objectives. The retention is influenced by various anatomical, physiological, physical, mechanical, and muscular factors. Retention of maxillary denture depends on incorporation of posterior palatal seal. Posterior palatal seal area is the soft tissue area between the movable and non-movable tissues of the soft palate and anteriorly by the junction of the hard and soft palates on which pressure within physiologic limits can be placed to aid in the retention. The additional rationale behind recording posterior palatal seal are to prevent entrapment of food underneath denture, to compensates for the polymerization shrinkage and to reduce gagging. Border moulding is shaping of impression material by functional or manual manipulation of the soft tissue along the border areas of an impression tray to record the contour and size of the vestibule. There are three approaches in recording posterior palatal seal, which includes Functional, Semi functional and Empirical technique. The functional method includes Fluid wax technique. In semi functional, low fusing impression compound is used for border moulding. The empirical techniques includes conventional (Winkler), Boucher’s, Bernard Levin’s, Swenson’s, Pound’s, Silverman’s, Hardy and Kapur method. In conventional method described by Winkler, a T burnisher is used to locate the hamular notch, followed by identifying anterior and posterior vibrating line and marked using indelible pencil. Anterior vibrating line is identified by performing Valsalva maneuver or by saying “ah” with short vigorous bursts. Posterior vibrating line is identified by saying “ah” in short but normal, unexaggerated fashion. Resin denture base is placed in the mouth to transfer all the marking into the master cast. Scraping of the master cast is done using a Kingsley scraper. Median palatine raphae region is scraped to a depth of 0.5-1 mm and area between middle to hamular notch in its deepest point which is one third distance anterior to posterior vibrating line is scraped 1-1.5 mm depth which should merges with the palatal tissues in all direction. The non-scraping Functional swallow method is used wherein inherent swallowing force of the tongue is used to place the soft palate in passive position (ie) downward and forward when head is flexed forward. The dorsum of the tongue will have intimate contact with tray carrying impression material when the patient swallows. Patient is trained to flex the head forward such that the chin is close to or nearly touching the chest and instructed to position the tongue against the palate during swallowing. When the head is bent forward there is 45° angle created between Frankfort plane and horizontal plane. Low fusing impression compound is commonly used material for sectional border moulding. Heavy bodied polyvinyl siloxane impression material with single step technique is used with advantage of excellent manipulative consistency, adequate flow, dimensional stability and adequate working time. Conventionally, functional border moulding is done followed by scraping of the master cast. Despite having good retention, this has disadvantage of over compression of posterior palatal seal tissues. To overcome this disadvantage, functional swallow method is used were patient’s inherent swallowing force is used to displace the soft palate functionally when the head is flexed forwardand scraping of the master cast is avoided. In this study, border mouldings will be done with conventional scraping and functional swallow method using low fusing impression compound and heavy bodied polyvinyl siloxane elastomeric material. zinc oxide eugenol and light body polyvinyl siloxane will be used as final impression materials. Hence, this study is done to compare the maxillary denture bases retention fabricated with posterior palatal seal registrations with different border moulding methods and using two different materials.