Development of soft palate
Triangular area of hard palate anterior to incisive foramen Forms during 4th to 7th week of Gestation Two maxillary swellings merge and two medial nasal swelling fuse Formed by the fusion of medial nasal processes Secondary Palate- Remaining hard palate and all of soft palate Forms in 6th to 9th weeks of gestation Palatal shelves change from vertical to horizontal position and fuse Formed by fusion of maxillary process- Soft palate Is musculo-membranous curtain that separates the oropharynx from the oral space and the nasopharynx from the nasal space.
It functions as flap valve closes off nasopharynx during swallowing. Its anterior margin is attached to the posterior border of hard palate by fibrous tissue known as palatal aponeurosis i. e. It is a collection of muscles with central aponeurosis. It Is continuous with the floor of the nasal cavity and covered with pseudo-stratlfled columnar ciliated epithelium and oral surface is covered by stratified squamous epithelium. Anatomic factors- The anatomy of the soft palate reveals a symmetrical and a radial distribution of the muscles and their fibers.
The soft palate is part of a dual valve system which eparates the oropharynx from the oral space and the nasopharynx from the nasal space. The function of the soft palate in these dual valving actions requires freedom of movement in three dimensions or planes of space, i. e. , superoinferiorly, medlolaterally, and anteroposterlorly. A denture which contacts the soft palate then must conform to the requirements for freedom of movement of the palate. Therefore, an impression should be made when the soft palate is placed at a desired denture border position.
This functional position of the soft palate may be achieved when the atient, seated in the upright position, flexes his head 30 degrees forward and places his tongue under tension against either the handle of the impression tray or the dentist’s finger which is held in the region of the upper maxillary incisors. The tongue should be retained in a state of tension within the arch form, and should not protrude beyond the lips. Neuropnyslologlc Tactors – The soft palate as a component of an oropharyngeal valve may be considered as the analogue of the upper lip and the distal part of the dorsum of the tongue as the analogue of the lower lip.
The soft palate and tongue thus contact and separate as hey protrude backward and forward to selectively permit food and air to pass the fauces for swallowing, speech, and respiration. The neurologic control for the valving action is mediated by the ninth and tenth cranial nerves for the palate and tongue (these nerves have both high somatic conscious and visceral automatic components) and by the twelfth cranial nerve which is dominated by the somatic conscious motor component.
It is this latter phenomenon, wherein the rich conscious nerve control of the tongue muscles prevails, that makes it possible for the patient to respond to erbal and tactile stimuli to alter the position of the contiguous muscles of the soft palate. Even though there is a large proportion of visceral components in the ninth and tenth cranial nerves, it does not imply that the soft palate cannot be conditioned to respond appropriately to the denture which encroaches upon its environment. It merely suggests that more time may be required to condition the soft palate tissue to adapt to the presence of the denture which initiates a gag reflex.
The physical stimuli of the denture base must be inhibited or suppressed so that the posterior border an become an extension of the patient’s biologic self in the same manner as the other borders. To facilitate the patient’s adjustment to the denture touching the soft palate, the border should be convex in contour on both the tongue and soft-palate sides. This recommendation is supported by Litvak, Silverman, and Garfinkels in a recent study wherein patients identified objects with many line angles in the mouth more readily than those with few line angles.