Third Molars 1 Flashcards
3rd molars extracted where
referred to speciliast/hospital
rare to extract in practice
third molar surgery one of the most common surgerys performed by NHS
true or false?
true
eruption period for third molars
18-24y
crown calcification of third molars
begins 7-10y and completed by 18y
7-9 for upper
8-10 for lower
root calcification for third molars
18-25y
how many adults have at least one third molar missing?
1 in 4 adults
agenesis
failure of an organ to development
e.g. third molar
common site for missing third molar development
maxilla
more in females
what age can be presumed if third molars are missing on radiograph that they will never develop
14
but can erupt at any age (sometimes get 50+ coming in due to denture rocking or pain and 3rd molar is erupting)
impacted means
tooth eruption is blocked
descriptive term
not indicative of surgery
most common reason why third molars fail to erupt
impacted
what can mandibular third molars be impacted against
adjacent tooth
alveolar bone
surrounding mucosal soft tissue
or combination of these factors
options for eruption for impacted M3Ms
unerupted
partially erupted
fully erupted
partially erupted
when some of the tooth has erupted into the oral cavity
unerupted
when the tooth is completely buried (in bone and soft tissue)
can still sometimes have a communication beetween bacteria and oral cavity and tooth
* caries evident on radiograph, despite not being able to see it clincally
incidence of impacted lower third molars
36-59%
consequences of impacted lower third molars
3
caries
pericoronitis
cyst formation
cyst formation from lower third molars
due to failure of the follicle around the crown of tooth not separating
nerves at risk during M3M surgery
4
**inferior alveolar nerve
lingual nerve **
nerve to mylohyoid
long buccal nerve
inferior alveolar nerve
what is it
peripheral sensory nerve from mandibular branch of trigeminal nerve
inferior alveolar nerve
supplies
all mandibular teeth on that side and mucosa, skin of lower lip and chin on that side
inferior alveolar nerve
position
varies greatly from person to person
in a bony cavity
OPT best to see (may need CBCT)
lingual nerve
branch of
mandibular division of trigeminal nerve
lingual nerve
supplies
anteiror 2/3 of dorsal and ventral mucosa of tongue
has branch which supplies lingual gingivae and FOM
lingual nerve
position
- Close relationship to lingual plate in mandibular and retromolar area
- At or above level of lingual plate in 15% - 18% of cases
- Between 0 – 3.5mm medial to the mandible
Guidelines role
help make clinical decisions based on evidence
old Guidelines for third molar surgery
NICE- Guidance on Extraction of Wisdom Teeth, 2000
* National institute for health and care excellence
* Discourage removal unless pathology in them
SIGN Publication Number 43 – Management of Unerupted and Impacted Third Molar Teeth, 2000
* Scottish intercollegiate guidance network
* Due to risks, need to be able to justify removal (caries, infection, perio, cysts)
current used guideline for third molar surgery
FDS, RCS 2020 - Parameters of Care for patients undergoing mandibular third molar surgery
Most up to date
* Consensus document (not systematic review), based on evidence and multidisciplinary review, taking into account views from all disciplines and range of best practice from healthcare providers
* Mixed range of interventions based on more holistic, need agreed by pt
* If leave – cause disease, hard to remove when decay, pt older = more complications
indications for extractions of third molars
8
- therpeutic indications
- surgical indications* i.e. within surgical field (orthognathic, fractured mandible, in resection of diseased tissue)*
- high risk of disease -mesial angular or horizontal impaction meaning limited access for OH
- medical indications e.g. awaiting cardiac surgery, immunosuppressed or to prevent osteonecrosis
- accesibility - limited access to dentist (work abroad, oil rigs etc)
- pt age -* complications and recovery time inc with age *
- autotransplantation (rare, to first molar)
- general anaesthetic -* remove opposing or contralateral at same time, to reduce further GA*
therapeutic indications for extractions of third molars
4
Infection
* most common = caries, pericoronitis, periodontal disease or local bone infection
* periodontal – mesial angular impaction prone to bone loss distal to lower 7, later removal – inc perio damage
Cysts
* Most common is dentinogenous cyst (reduced enamel epithelium separation from crown), more mandible than maxilla (10x)
Tumours
* Prevent ORN, part of resection
External resorption of 7 or 8
* Destruction of tissue, cause unclear, progressive, 21-30y
pericoronitis
inflamation around the crown of partially erupted tooth
tooth is normally partially erupted and visible – but occasionally there may be very little evidence of the communication and careful probing distal to the second molar is required to show that there is a small communication
Food & debris gets trapped under the operculum resulting in inflammation or infection
pericoronitis
features
Usually transient and self-limiting
Usually occurs 20-40 years
General health not related to incidence of pericoronitis, except upper respiratory tract infection (start as URTI then develop pericoronitis)
Second most common indication for M3M extraction
Anaerobic microbes
* Streptococci , Actinomyces, Propionibacterium, a beta-lactamase producing Prevotella, Bacteroides, Fusobacterium, Capnocytophaga and Staphylococci most common
signs and symptoms of periocoronitis
13
Pain – developing, throbbing
Swelling – Intra or extraoral
* Angle of mandible, submandibular, lateral to buccal space, or under tongue to submasseteric space (unable to open mouth/trismus), sublingual, parapharyngeal space (dysphagia (unable to swallow)
Bad taste
Pus discharge
Occlusal trauma to operculum
Ulceration of operculum
Evidence of cheek biting
Foetor oris
Limited mouth opening/ trismus
Dysphagia
Pyrexia
Malaise
Regional lymphadenopathy
tx options for pericoronitis
4
Incision of localised pericoronal abscess if required
+/- local anaesthetic (IDB) – depends on pain/patient
Irrigation with warm saline or chlorhexidine mouthwash (10-20ml syringe with blunt needle – under the operculum).
* Please note some health authorities may recommend that you do not use chlorhexidine due to cases of anaphylaxis. Follow your health authority and local guidelines
Extraction of upper third molar if traumatising the operculum
pt instructions for pericoronitis care
Patient instructed on frequent warm saline or chlorhexidine mouthwashes – reduce chance of pericoronitis returning
Advice regarding analgesia (follow pack)
Instruct patient to keep fluid levels up and keep eating (soft/liquid diet if necessary)
antibiotics for pericoronitis?
Generally do not prescribe antibiotics unless more severe pericoronitis, systemically unwell, extra-oral swelling, immunocompromised e.g. diabetic
If large extra-oral swelling, systemically unwell, trismus, dysphagia – refer to maxillofacial unit or A&E (dysphagia, breathing difficulty or significant trismus)
predisposing factors for pericoronitis
7
Partial eruption and vertical or distoangular impaction
Opposing maxillary M3M or M2M causing mechanical trauma contributing to recurrent infection
Upper respiratory tract infections as well as stress and fatigue pericoronitis
Poor oral hygiene
Insufficient space between the ascending ramus of the lower jaw and the distal aspect of the M2M
White race
A full dentition
