#DEN4001
#D4/S1/W9
#ORTHO

Expansion and Airways

• maximum is always at the level of inferior turbinates with a variable degree of expansion superiorly

Boundaries / anatomy of the airways

• hard tissue boundaries
  • upper and lower incisors
  • anteriorly piri form rim
  • superiorly cranial base
  • posteriorly cervical vertebrae
  • inferiorsly hyoid bone
  • laterally: width of palate, middle cranial fossa, distance between ascending rami
• soft tissue
  • pharyngeal muscles
  • tongue
  • soft palate
  • turbinates
  • pharyngeal tonsils
  • adenoids, nares

Hard tissue growth

• anterior cranial base increases in length via growth at sphenoepthmoidal synchondrosis until age of 7
• increases in posterior cranial base relate to growth at sphenooccipital synchondrosis until age 13
• anterior cranial base carries nasomaxillary complex forward, at same time midface bones are displaced anteriorly and inferiorly
• mandible elongates, displaced downward and forward with deposition of bone on posterior and superior borders of the ramus, increasing height of rami and increasing distance between ascending rami
• resorption of anterior border of ramus increases corpus length (oropharyngeal length)

Soft tissue growth

• skeletal boundaries of airway increasing, lymphatic tissues are shrinking
• decrease in tonsils/adenoids result in enormous increase in size of upper airway in adolescence/childhood
• these changes in growth exceed any ortho/orthopaedic effects on airway shape or size

Childhood sleep disordered breathing

• significant problem for proportion of children
• ranges from loud snoring to obstructive sleep apnoea
• childhood OSA often remits without any intervention during growth phases
• certain craniofacial, genetic syndromes and obesity = higher prevalence of OSA /SDB

How is sleep disordered breathing treated

• adenoidectomy
• half had normalised by 7months
• can spontaneously resolve over time
• dentist perform clinical risk assessment for OSA and refer at risk patients to appropriate physician for definitive diagnosis of OSA
• examples
  • snoring
  • sleep related behaviours
  • daytime sleepiness
  • difficulty concentrating
  • formal diagnosis of ADHD
  • mouth breathing during sleep
  • medications
  • developmental delays
  • bed wetting that is not age appropriate
  • hard to wake up in the morning
  • morning headaches
  • difficult breathing during sleep
  • pauses in breathing during sleep
  • fall asleep quickly
  • nasal obstruction

Developing airway

Consequences of OSA / SDB

• 
• true measure is going to be an overnight sleep study
• consequences in children
  • cardiovascular
    • increased BP during sleep
    • ventricular wall thickening
    • increase risk of life long hypertension
  • neurocognitive / behavioural
    • memory impairment
    • attention deficit
    • daytime behavioural difficulties
    • learning and behaviour impairments
      
• msot common cause of childhood OSA is enlargement of the tonsils and adenoids
• allergic rhinitis
• obesity - up to 50% overweight children, compared to 1-5% of normal weight children
• more common in
  • hypotonia
  • micrognathia
  • cleft palate
  • down syndrome
  • achondroplasia

Maxillary expansion and expanders

3 types

• rapid maxillary expansion RME
• slow maxillary expansion SME
• surgically assisted maxillary expansion SAME
  • for adults or fused sutures

Types of expanders

• removeable or fixed
• rate of activation should not exceed one turn a week in 0.25mm / turn screw
• fixed
  • bonded
    • 
    • flat plane occlusal splint wiht haas appliance
    • recomended for AOB, perio compromised, TMD symptoms
    • very hard to clean
  • banded
    • 
    • Haas type with acrylic palatal flanges
    • Hyrax: expansion screw and metal framework without acrylic palatal coverage
    • 
  • other types
    • minne
    • fan shaped
    • quad helix (bottom right)
    • 

Expansion effects on airway

• assessment
  • study casts - not useful
  • ceph studies - PA head films, occlusal radio, lat cephs - hard to determine airway
  • 3d imaging - MRI CT CBCT computational fluid dynamics
• are airway measurements using cbct accurate
  • large amont of inaccuracy in airway measurement from CBCT
  • positioning or patient, swallowing, breathing during scan etc.
  • low inter and intra examiner reliability
• assessment of airway patency
  • rhinoscopy or nasoendoscopy
  • rhinomanometry and acoustic rhinometry have been proven to be useful to provide objective assessment of airflow through nose and to measure nasal cavity measurements
  • AR, CT MRI are good correlation

RME effect on airway

• increase nasal cavity width, volume, and minimal cross sectional area
• palatal disjunction causes separation of inferior turbinates as lateral walls are carried away from each other
• displaces palate downward, result in opening of posterior nasal aperture, allowing easier passage of air
• anterior tongue position has been found in some studies, which could improve airflow
• once RME results in increased nasal airway patency and reduced nasal airway resistance (NAR), airway flow increases, craniocervical angulation consequently reduced
• some studies show mandibular forward repositioning in all patients except CIII
• palatal flattening when present may contribute to lowering of nasal floor and improvement of nasal permeability
• greater impact on anterior region of nasal cavity, perhaps due to greatest site of separation at the incisal level
• nasal resistance after RME significantly lower than prior
• oropharyngeal no changes
• 12yo prospective cohort study for OSA in children RME, hypoxic events lowered, o2 sat up

Quality of life

• ten children SDB longitudinal study for RME,
  • might aid in quality of life for kids with narrow maxilla

Airway patency and breathing mode

• RME may permanently change functional matrix of upper airway since it results in increase in nasal airflow and thoracic capacity
• resistance after RME drops to predominantly nasal breathing subjects values
• breathing mode is unconscious motor function, change from predominantly oral to nasal is difficult to achieve

RME SUMMARY

• not recommended alone if main purpose is to improve nasal breathing
• only for skeletal crossbite

Jaws Dr Sandra Kahn

Harvold et al 1982

• 16 three year old rhesus monkeys
• occluded nostrils of 8 of them
• observed facial growth over 3 years by taking and analysing serial cephalograms
• 
• no data presented within study, magnitude of chance
• statement only explaining significant different between groups
  • steep mandibular plane angle and increased face height can be viewed as a result of induced neuromuscular imbalance between neck and facial muscles in the experimental monkeys
• critique
  • difficult to apply findings to humans
  • definitely wouldn't be accepted on peer review
  • rhesus monkeys are obligate nasal breathers

Linder aronson et al 1986, Woodside et al 1991

• facial growth following adenectomies
• 
• severe nasopharyngeal obstruction
• 48 changed from mouth to nasal breathing
• results 1986
  • girls post op had more horizontal growth (wide CI though)
  • difference not found in boys
  • growth direction more variable for adenectomy group
  • actual difference is 3.1 degree in mandibular plane error (within standard variation)
• results 1991
  • mandibular length 3.8mm and 2.5mm
  • effect size small, large 95% CI, uncertainty in data
• critique
  • only children with severe nasopharyngeal obstruction
  • ceph differences minimal and not clinically significant
  • sample had severe attrition bias
  • genders analysed separately

Conclusion

• minimal evidence mode of breathing influences the craniofacial skeletal and facial growth

Neanderthal

Magdalenian girl

• earliest case of impacted wisdom teeth 13-15k year old skeleton
•