Soft Tissue Morphology PDF

# Soft Tissue Morphology ## Lecture Outline: 1. Facial index and vertical proportions of the face 2. Lips morphology and behavior 3. Tongue morphology and behavior 4. Swallowing ## Facial Index and Vertical Proportions of the Face - The orthodontist should know the ideal facial proportions and b...

# Soft Tissue Morphology ## Lecture Outline: 1. Facial index and vertical proportions of the face 2. Lips morphology and behavior 3. Tongue morphology and behavior 4. Swallowing ## Facial Index and Vertical Proportions of the Face - The orthodontist should know the ideal facial proportions and balance in order to make proper diagnosis and treatment planning. - The orthodontist is concerned with three things: *dental*, *skeletal*, and *soft tissues*. - **Facial Index** is the proportional relationship of facial height to width. - FI = (Facial height x 100)/(bizygomatic width) = 84 to 88 (average) - **Mesoprosopic:** having a face of average width with a facial index of 84.0 to 87.9. - **Facial Height** is the height between *glabella* and *menton*. - Vertically, the face is divided into 3 thirds: - **Upper 1/3rd:** forehead from hairline to glabella. - **Middle 1/3rd:** extends from the supraorbital ridge to the base of the nose (subnasal). - **Lower 1/3rd:** extends from the base of the nose to *menton*. The upper lip occupies one third and the lower lip and chin occupy two thirds. - **Note:** - *Glabella:* between two eyebrows. - *Menton:* most inferior point on the chin. - *Base of nose:* subnasal point. - There is no complete symmetry between two halves of the face (never 100% symmetrical). - We try to reach *divine proportion*, not complete symmetry. - Divine proportion = golden ratio = 1.618. ## Lips Morphology and Behavior - The lips form the *anterior seal* of the oral cavity, whereas the soft palate and the dorsum of the tongue form the *posterior seal*. ### Competent Lips - Lips are normally in contact when the mandible is at the rest position without any active contraction of the *orofacial muscles*. ### Incompetent Lips - Lips fail to meet in this position. This can be *primary* or *secondary*. - **Primary:** Upper lip is anatomically short. - **Secondary: ** the lips are held apart at rest due to *skeletal or dental causes*. - Causes: 1. Increased length of the lower third of the face 2. Upper anterior proclined teeth with the lower lip falling between the upper and lower anterior teeth (may be associated with lower lip biting) - *Class II Div. I* 3. Skeletal anteroposterior disproportion between the maxilla and mandible (on severe cases of Class II or Class III). - A severely prognathic maxilla may lead to lip incompetence. - **Hypertonicity** of the *mentalis* and *obicularis oris* muscle, crowding and retroclination of the anterior teeth may happen (potentially bad habit). - **Habitual lip posture:** the upper incisors are labially tipped and their incisal margins interpose between the lips, preventing the normal lip seal. - **Habitual lip sucking and biting or thumb sucking** can lead to retroclination of lower incisors, then crowding and proclination of upper incisors, leading to an increase in overjet. ## Tongue Morphology and Behavior - **Tongue** is important in determining the shape of the dental arches by: 1. Size 2. Rest position 3. Activity of the tongue. ### Tongue Posture - **Neonate:** The tongue is positioned more forward and it touches the lips while the gum pads (separate gum pads or anterior open bite gum pads). - **Adults:** By the eruption of the incisors, the tongue posture changes to the mature position and it is *restrained* with the oral cavity proper. ### Tongue Size - A large tongue or one positioned forward (thrusting) can cause increased bimaxillary labial proclination of the incisor teeth. - The reverse may occur with a small backwardly placed tongue: crowding and retroclination of the incisors. ### Tongue Activity - Described in the swallowing behavior. - **Tongue Thrust**: protruded tongue through anteriors during swallowing and speech. - In adults, the tongue thrust may be caused by *proclination* of upper and lower anterior teeth, due to a bad habit. - Relapse may occur after orthodontic treatment, as we treat symptoms and not the *actual cause*. ## Deglutition or Swallowing - Defined as the semiautomatic motor action of the muscles of the respiratory and gastrointestinal tracts to propel food from the oral cavity to the stomach. - Two different swallowing mechanisms due to the difference in the nature of food consumed by an infant and adult. - **Infantile Type of Swallowing:** - Most children gradually achieve most features of mature swallowing at 12 to 15 months of age, coinciding with the eruption of primary molars and the gradual shift to solid food. - **Mature Swallowing:** 1. Teeth are together (in contact) for swallowing a food bolus. 2. The mandible is *stabilized* by contraction of the muscles enervated by the fifth cranial nerve, which supply muscles of mastication. 3. The tongue is held against the palate above and behind the incisors. 4. Lips are minimally contracted during swallowing. **Note:** This swallow can be called: *Mature, Adult, Normal, or Teeth Together*. ## Infantile Type of Swallowing - Also called **Immature, Infantile, Abnormal, or A-typical** if in adult, **Teeth Apart, Tongue Thrust Swallow**. - Associated with *suckling*: the nipple is enveloped by the upper lip, upper gum pad, and palate above, and the tongue below. The tongue will lie over the lower gum pad and protrudes to touch the lower lip. - The muscles of the tongue provide a *continuous peristaltic action* which compresses the nipple in a wavelike fashion and allows the infant to express liquid. - The entire tongue, mandible, and the lower lip are moved forward and backward. - At birth, the infant's anatomic structure dictates that the tongue moves in an *extension-retraction pattern* because of the limited room within the oral cavity. This initial *in-and-out pattern* is called *suckling*. ## Sucking vs. Suckling ### Suckling Reflex - Involves a front to back "in and out" movement of the tongue. - The tongue is deeply cupped and this allows the infant to extract liquid from a breast or bottle. - For the first 3 months. ### Sucking Action - "True suck" - Involves more of an *up and down movement*. - Sucking involves more active use of the lips (close more tightly) and elevation of the tongue than suckling (more negative pressure than that of suckling). - A variation of this basic, reflexive *suckle pattern* is recognized as *true suck*. In the true suck, the body or dorsum of the tongue moves up and down in conjunction with the mandible. The lips close more tightly around the nipple, and more negative pressure is created in the oral cavity to extract fluid. - Most infants utilize a mixture of *suck* and *suckle* until 6 months of age. - By 6 months, the *true suck* predominates, as it is generally more efficient and negative pressure is stronger. - The main difference is that *suckling is primitive* and *sucking is a more mature pattern*. - In the true suck, the body or dorsum of the tongue moves up & down in conjunction with the mandible. ## Transition From Infantile to Adult Swallowing - This transition occurs where: 1. Teeth are not placed into occlusion during swallowing ("teeth are apart"). 2. The tongue is brought between the separated teeth until it touches the cheek and lips. 3. *Active contraction* of the cheeks and lips to provide a firm box for the tongue action, and the *mentalis muscle* shows active contraction too. ## Phases of Adult Swallowing - For descriptive purposes, the adult swallowing is divided into four phases: 1. Preparatory Phase 2. Oral Phase 3. Pharyngeal Phase 4. Oesophageal Phase ### Mature Swallowing - Teeth are together. - The tongue is above and forward. - Lip seal with minimal lip activity. - Can be called: *Matured, Adult, Normal, or Teeth Together*. ### Atypical or Infantile Swallowing - **Infant:** Upper and lower gum pads are separated. - **Adult:** Teeth are separated (dis-occluded). - The tongue is below and forward. - *Active contraction* of cheeks and lips. - Can be called: *Immature, Infantile, Atypical, Abnormal (if found in adults), Teeth Apart, or Tongue Thrust*.