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palate The bone and soft tissue closing the space encompassed by the upper alveolar arch, with a posterior extension to the pharynx. Forms the roof of the mouth and is connected to the nasal septum and floor of the nose in the midline.

hard palate The anterior part of the palate that is supported by and includes the palatal extensions of the maxillary and palatine bones.

soft palate The part of the palate lying posterior to the hard palate, composed only of soft tissues without underlying bony support.

velum Posterior appendicular portion of soft palate.

palatal bar Maxillary lingual appliance, usually transpalatal, connected to the first molars and used to maintain width and increase anchorage.

palpation Digital manipulation and assessment of tissue in physical diagnosis.

panoramic radiograph A radiographic tomograph of the jaws, taken with a specialized machine designed to present a panoramic view of the full circumferential length of the jaws on a single film. Also know by several proprietary brand names of machines, most of which include 'pan' as a part of the name. (Also termed panoral or panorex.)

papilla (interdental) The gingival structures occupying the space between adjoining teeth.

periapical Pertaining to the area and tissues around the apex (tip) of the root of a tooth.

periodontal ligament The periodontal membrane, which serves a ligamentous function in tooth attachment.

periodontal membrane (or ligament) The fibrous tissue that occupies the space between tooth root and alveolar bone, providing a ligamentous physical attachment of the tooth to the bone and nourishment to the cementum surface of the root and the cells that permit tooth movement.

periodontal pocket A periodontal disease condition characterized by an abnormally enlarged space between tooth and alveolar bone with destruction of the attaching periodontal membrane and invasion by oral epithelium. Often progressive, resulting in bone and tooth loss if not arrested by treatment.

periodontics That dental specially concerned with the maintenance of the health and integrity of the periodontal tissues that support the teeth.

periodontium The investing and supporting tissues of the teeth; the periodontal membrane and alveolar process.

permanent dentition Those teeth that succeed the primary teeth and the additional permanent molars.

pharynx That part of the respiratory tract extending from the larynx to the nasal cavity; the throat is a part of the pharynx. 

pogonion The most anterior point on the chin. A cephalometric landmark in the lateral view.

point A The deepest point in the bony concavity in the midline below the anterior nasal spine, in the region of the incisor roots. Often called maxillary apical base. This is a landmark on the lateral cephalometric radiograph.

point B The deepest point in the profile curvature of the mandible, from pogonion on the chin to infradentale (junction of alveolar bone and the lower incisors). Also mandibular apical base. A landmark on the lateral cephalometric film.

porion The superior surface of the external auditory meatus. In craniometry it is identified as the margin of the bony canal on the skull. In cephalometrics it may be identified from the earpost of the cephalostat (machine porion) or from bony landmarks on the film (anatomical porion).

positioner (tooth positioner) A removable elastic orthodontic appliance molded to fit the teeth on a 'setup' made by repositioning the teeth from a plaster cast. The material may be rubber or elastomeric plastic. It is typically used to achieve fine adjustments and retain corrected positions during the finishing stages of treatment.

posterior nasal spine The radiographic image on the lateral cephalogram that denotes the posterior terminus of the palatal plane.

postural rest position The resting position of the mandible in normal posture. See freeway space, rest position.

preangulated bracket An orthodontic bracket having its slot inclined to the ordinary mesiodistal direction, permitting the generation of second-order action from a passive straight wire.  See straight-wire.

PPO (Preferred Provider Organization) A formal agreement between a purchaser of a dental benefits program and a defined group of dentists for the delivery of dental services to a specific patient population, as an adjunct to a traditional plan.

preventive orthodontic treatment Dental services intended to prevent the development of a malocclusion by maintaining the integrity of an otherwise normally developing dentition. Typical services include dental restorations, temporary prostheses (space maintainers) to replace prematurely lost primary teeth and removal of primary teeth that fail to shed normally when this will allow the permanent successors to erupt satisfactorily.

primary dentition See dentition.

proclination Anterior coronal tipping of anterior teeth, as opposed to bodily protrusion, which indicates positional variation.

prognathic A forward relationship of the mandible or maxilla, relative to the craniofacial skeleton.

prognathism See prognathic.

pronasale Most forward point of the tip of the nose.

prosthion The lowest and most forward point of the alveolar process between the maxillary central incisors.

protraction Anterior displacement of the teeth and/or bones of the face.

protrusion The state of being anteriorly positioned.

proximal segment In surgery that portion of a sectioned mandible containing the articulating portion.

pulp (dental) The soft tissue occupying the inner (pulp) chamber of a tooth. Consists of specialized loose connective tissue, blood vessels and nerves.