1. MANDIBULA Lower jaw

2. Anatomy (repetition)
Widespread description and clinical notes
Dentoalveolar topography: transverse asymmetry of alveolus rate of spongy and compact bone the relationship of root to neighouring structures
Nerve and blood supply (repetition)

3. A single facial bone that is the only freely movable
part of the skull
During the development the mandible originates
from two bones which unite together and form the
lower jaw

4. Newborn mandibular corpus is low
Foramen mentale is running backward and sideways upwards - it has practical significance for local anaesthesia. When performing local anaesthesia, the puncture with needle is necessary to be directed from cranial and dorsal direction into anterior, caudal and medial direction.
The lower margin of corpus mandibulae is reinforced (basis mandibulae), the reinforcement passes also onto ramus mandibulae. It is conditioned by internal modification of the bone (basal arch ), and represents a significant biomechanical factor.
Below trigonum retromolare there is a very porous bone - this can be an advantage during extraction of the last molar.
Increased lingula mandibulae can represent a significant obstacle, during local anaesthesia of n. alveolaris inferior.
Mandibular shape changes in the course of life. In newborns, corpus mandibulae is low, foramen mentale lies on the lower edge of corpus mandibulae. Corpus mandibulae is still paired, both mandibular bases are meeting into so-called symphysis menti. Symphysis ossifies in first year of life, from the top downwards. Angulus mandibulae is obtuse – 150 to 170O (widely opened) in newborns, processus coronoideus is longer than processus condylaris. Only with development and eruption of teeth, processus alveolaris appears ; foramen mentale is projecting into the middle height of corpus mandibulae, most often below the second premolar. Angulus mandibulae is much sharper (125O), processus condylaris is elongated, and reaches the level of processus coronoideus. After loss of teeth, the corpus of mandibulae is lowered (atrophy of processus alveolaris), foramen mentale is opening at the upper margin of corpus mandibulae. The mandibular angle is increased, and its value is about 140O.
From traumatological point of view, the surface position of mandible is disadvantageous. Fractures can often affect corpus mandibulae in the area of foramen mentale, mandibular angle and processus condylaris of collum mandibulae.
Mandibula can also crack open during harsh teeth extraction (not only interalveolar septa) and also during surgical teeth extraction using raspatorium.
mandibular corpus is low
the body contains the sockets of deciduous teeth
the angle between corpus and ramus is 150°
mental foramen lies on the lower edge of corpus

5. Adulthood the angle is much sharper – about 120°
Růst
Růst dolní čelisti primárně vychází z kloubní chrupavky (až do dospělosti) a z chrupavky symphysis menti (do 1. roku života), modeluje se však v podstatě periostálním růstem (udržuje se až do vysokého věku) vlivem funkčního zatížení (také dýchání, mimika, řeč, nervové a cévní zásobení, které působí stimulačně na růst). Předpokladem formativních procesů kostí je rovnováha mezi apozicí a resorpcí.
DČ roste intenzivně do délky kondylárním růstem v chrupavce (dopředu a dolů). Růst doprovází na přední straně apozice, na zadní resorpce kosti.. Tato přestavba je zodpovědná za zmenšování čelistního úhlu. Růstem kloubní chrupavky se prodlužuje ramus mandibulae dozadu a nahoru a jeho úhel se zmenšuje na 120 st. Tento proces podporuje současná apozice kosti na úhlu čelisti. Apozicí kosti na zadním okraji ramena, současnou resorpcí na jeho přední hraně a vytvořením brady se čelist posouvá dopředu. Růstem těla dozadu se vytváří prostor pro stálé zuby.Na ventrálním okraji těla dolní čelisti se ukládá kost a současně vzniká alveolární část, přičemž oba procesy posouvají corpus mandibulae dolů, co se projevuje i na změně směru foramen mentale, ze kterého vystupuje cévně-nervový svazek původně svisle, ale později uhýbá dozadu a nahoru.
Směr růstu dopředu a dolů se částečně kompenzuje dorzálním posunem base lebky a kloubních jamek.
Brada
se formuje apozicí kosti. V alveolární oblasti nad bradou se kost rezorbuje, čímž vzniká supramentální konkavita (bod supramentale v antropologii a čelistní ortopedii jako bod B). S růstemd bradového výběžku v prvních 2 letech se mění směr for. mentale: ze směru dopředu postupně nahoru a dozadu, jak je tomu u dospělého.
Během remodelace čelisti dochází k resorpci vytvořené kosti (na přední ploše r. mandiublae v proc. condylaris) a současně k apozici (zadní hrany r. mandibulae). Tělo mandibuly se tak prodlužuje směrem vzad a r. mandib. se zvětšuje vertikálně a dozadu.. Čelistní aparát i proporce obličejové části lebky jsou významným způsobem ovlivněny rozvojem pr. alveolaris av souvislosti s prořezáváním doč. a st. zubů.
Konec předchozího slidu:
Dolní čelist je možné rozdělit na funkční jednotky, ze kterých každá má vlastní růstovou charakteristiku.
1. alveolární část, která se vytváří vlivem zubů
2. proc. coronoideus, který se formuje působením tahu m. temporalis.
3. úhel čelisti vystupuje silnější tahem masetero-pterygoidní smyčku a pr. condylaris se rozvíjí dále vlivem funkce ATM.
Růst čelisti dále stimuluje jazyk, svaly spodiny ústní a hltanu a také mimické svaly.
the angle is much sharper – about 120°
condylar process is higher than the coronoid process and the sigmoid notch becomes deeper

6. Old age
Ve stáří
Tělo bezzubé stařecké mandibuly se pomalu redukuje na podkovovitě zahnutý kostěný trámec. S atrofií alv. části se mandibulární kanál posouvá směrem nahoru. V extrémních případech může být redukována i kompaktní vrstva, která kanál ohraničuje a mandibulární kanál pak může být proti d. ústní překryt jen sliznicí. Podobně otevřený může být v oblasti řezáků canalis incisivus. To bývá příčinou bolestí vznikajících např. tlakem protézy.
Linea mylohyoidea vystupuje jako ostrá hrany dovnitř a spina mentalis bývá často prodloužená. Tyto změny jsou následkem činnosti m. mylohyoideus a m. genioglossus, které tlačí jazyk proti patru při rozmělňování potravy.
Oblast kostí, ke kterým jsou připojeny svaly se až do vysokého stáří nemění.
Páč:
po ztrátě zubů alv. i bazální část postupně atrofuje. Na straně orální se projeví involuce výrazněji než na straně vestibulární.
Změna úhlu ovlivní významně tvar retromolárního trigona. Tato oblast podléhá postupně depresi kosti, kompaktní ploténka klesá do hloubky a povrch trigona se výrazně přiblíží k zakřivenému úseku canalis mandibulae. Proto není trigonum retromolare stařeckých bezzubých čelistí vhodným místem pro zavádění dentálních implantátů.
Po ztrátě zubů dochází na ramus mandib. k resorpci kosti až do úrovně svalových úponů, tedy např. až ke crista mylohyoidea. Spina mentalis přitom zbytňuje. Resorpce kosti jde tedy hlouběji, než je dolní apikální baze, takže se na horní ploše těla mandibuly může objevit v určitém rozsahu canalis mandibulae i foramen mentale. To je komplikace při výrobě a nošení úplných zubních náhrad.
after the loss of teeth, the body is reduced in volume (atrophy of the alveolar process) → mandibular foramen is closer to the alveolar border
enlargement of the angle to 160°
deepen pterygoid fovea → neck is tapered

7. Alveolar process
The portion of the jawbone that contains the teeth and the alveoli in which they are suspended
The development is dependent on tooth eruption and its maintenance on tooth retention
Is composed of compact bone ( mm) that enclose the spongiosa

8. Alveolus
Compact bone (labial cortical plate)
Compact bone (lingual cortical plate)
Spongy bone

9. Alveolus
Is composed of a thin plate of cortical bone with numerous perforations (or cribriform plate) that allow the passage of blood vessels between the bone marrow spaces and the periodontal ligament
The coronal rim of the alveolar bone forms the alveolar crest, which generally parallels the cemento-enamel junction at a distance of 1-2 mm apical to it

10. Bundle bone
= the inner portion of the bone of the alveolus that surrounds teeth and into which the collagen fibers of the periodontal ligament are embedded
Radiographically, the bundle bone is the lamina dura

11. Septum interalveolare (spongy bone)mm
Alveolus (compact bone)

12. Resorption of alveolar bone
Decreased bone (osteopenia) of alveolar process is noted when there is inactivity of tooth that does not have an antagonist

13. Reconstruction of alveolar bone
The whole life the bone keep the potential to reconstruction
Bone is resorbed on the side of pressure and opposed on the site of tension is regenerated
Movement of a tooth by extrusion involves applying traction forces in all regions of the periodontal ligament to stimulate marginal apposition of crestal bone

14. Lingual foramen (canal)
The contents of the foramen (foramina) were found to be an artery
Median

15. Lateral (orifices accessories)
Inner area of mentum
sup. and inf. retromental for.
Unilateral, bilateral or mutliple
In neighbourhood of mylohyoid line CT
CAVE! Bleeding (implant placement)

16. Mandibular foramen Beginning of canalis mandibulae
Inner surface of ramus mandibulae
middleline between anterior and posterior edge of ramus
1 cm above M3
2 cm behind M3
CAVE! Local anesthesy

17. Mandibular canal
Is placed under the alveoli and communicates with them by small openings
Contains the inferior alveolar nerve, artery, vein

18. Demarcate of the compact bone (noticeable to x-ray)
On arriving at the incisor teeth, it turns back to communicate with the mental foramen, giving off a small canal known as the mandibular incisive canal

19. Canalis mandib. bifidus
Summary 0.9%

20. Mental foramen
The position of this foramen is most frequently near the apex of the mandibular second premolar and rested between the premolars
The foramen open upward and slightly posteriorly in adults
The foramen open straight upward in newborns

21. CAVE ! Local anesthesy

22. Incisive canal Summary 96%
Demarcate of the compact bone (noticeable to x-ray)

23. Dentoalveolar topography
Important for anesthesia, extraction, injury, implantology, endodontic treatment ...
The transverse asymmetry of alveolus
The rate of the spongy and the compact bone
The relationship the roots the lower jaw to neighbouring structures

24. 1. The transverse asymmetry of alveolus
The dental and skeletal arch are asymmetric !

25. 2. The rate of the spongy and the compact bone
The layer of compact bone is thicker than in the upper jaw
Roots of the incisivi and canini teeth are surrounded by the compact bone
Roots of the premolars and molars are surrounded by the pre- and retroalveolar spongy bone that is thin, fragible

26. Fractures by extraction !
Incisivi, Canini
Compact bone only
CAVE!
Fractures by extraction !
Root of the 3nd tooth – fracture of mandible !

27. Premolars
Molars
Compact bone and variable thickness of spongy bone bucally and lingually (linea mylohyoidea)

28. Spongy bone is distally to 8

29. 3. The relationship the roots the lower jaw to neighbouring structures
Canalis mandibulae
(incisivus, mentalis)

30. Variable layer of spongy bone between canals and teeth´s roots
CAVE!
Dehiscence the canal and the alveolus
Implants

31. CAVE! The endodontic treatment

32. Nerve and blood supply

33. Trigeminal nerve Alveolar inferior nerve mental nerve incisive nerves
Mylohyoid nerve
Buccal nerve
Lingual nerve

35. Variation Important for anesthesy !1.
Mylohyoid nerve
Can conveys impulses from the incisive, canine and premolar teeth and gingiva !
Dissection of the mandibular nerve in a cadaver of southern Chinese origin showed the mylohyoid nerve arising from the lingual nerve and the buccal nerve arising from the inferior alveolar nerve within the mandibular ramus. It is estimated that this variation in the origin of the buccal nerve occurs in 6.1% of the southern Chinese population.
Indian J Dent Res Jan-Mar;21(1):141-2.
An unusual communication between the mylohyoid and lingual nerves in man: its significance in lingual nerve injury.
Potu BK, D'Silva SS, Thejodhar P, Jattanna NC.
Department of Anatomy, Kasturba Medical College, Manipal University, Karnataka , India.
Abstract
The mylohyoid nerve is the branch of the inferior alveolar nerve (IAN) which arises above the mandibular foramen. An abnormal communication between the mylohyoid nerve and lingual nerve (LN) was noted during the routine dissection of a male cadaver. Communicating branches between IAN and LN have been identified as a possible explanation for the inefficiency of mandibular anesthesia. The communication between mylohyoid and lingual nerve was found in this case after the LN passes in close relation to third molar tooth, which makes it more susceptible to injury during third molar extractions.
Rom J Morphol Embryol. 2009;50(1):145-6.
Unusual communication between the lingual nerve and mylohyoid nerves in a South Indian male cadaver: its clinical significance.
Potu BK, Pulakunta T, Ray B, Rao MS, Bhat KM, D'Silva SS, Nayak SR.
Department of Anatomy, Centre for Basic Sciences, Kasturba Medical College, Manipal University, Manipal, Karnataka, India.
It is well known that variations in the branching pattern of the mandibular nerve frequently account for the failure to obtain adequate local anesthesia in routine oral and dental procedures, and also for the unexpected injury to branches of the nerves during surgery. During our routine dissection, we found the presence of a communicating branch between the mylohyoid and lingual nerves in a middle aged male cadaver. We also discussed its clinical and surgical implications in this report

36. After branching from the inferior alveolar nerve, the nerve to the mylohyoid courses anteriorly along the lingual surface of the mandible in the mylohyoid groove. This groove runs parallel to the mandibular canal, traveling medial to it for 20 mm prior to terminating inferior to the posterior edge of the mylohyoid line. After exiting the mylohyoid groove or canal, motor fibers from the nerve to the mylohyoid travel between the mylohyoid muscle and the anterior belly of digastric muscle. The nerve to the mylohyoid innervates the mylohyoid muscle on its infero-lateral superficial surface, whereas it supplies the anterior belly of digastric on its supero-medial deep surface. Often a branch from the nerve to the mylohyoid pierces the mylohyoid muscle and joins the lingual nerve.
Although the nerve to the mylohyoid has traditionally been considered a motor nerve, it has been suggested that sensory fibers carried by the nerve supply the skin over the chin and mandibular teeth as well as medial portions of the submandibular triangle.
However, the nerve to the mylohyoid may escape anesthesia AIN because it may arise at some distance higher than the mandibular foramen. The point from which the nerve to the mylohyoid arises from the inferior alveolar nerve demonstrates significant variability.

37. 2.
Sometimes the branches entering separated bony channels laterocranial of mandible foramen and M3, M2
The nerves entering the mandible at the retromolar fossa

38. Maxillary artery Inferior alveolar artery mylohyoid a.
dent. et interalveolar a.
mental a.
incisive a.
Facial artery
submental a.
Lingual artery
sublingual a.