Mastication And Deglutition

Mastication And Deglutition

1. PRESENTED BY- DR. AISHWARYA ARYA DR. ENU KAMBOJ DR. KRITTIKA KUHAR FIRST YEAR MDS MASTICATION AND DEGLUTITION

2. CONTENTS INTRODUCTION FACTS ABOUT MASTICATION TYPES OF MUSCLES IMPORTANCE OF MUSCLES OF MASTICATION CHEWING RELEX CLASSIFICATION MASTICATORY MUSCLE DISORDERS DEGLUTITION APPLIED ASPECTS

3. MASTICATION GPT 8- MASTICATION Is defined as a process of chewing food in preparation for swallowing and digestion. The teeth are admirably designed for chewing, the anterior teeth (incisors and canines) providing a strong cutting action and the posterior teeth ( pre molars and molars), providing a grinding action during mastication. The biting stresses that are exerted during mastication is difficult to analyse because of the dynamic nature of different tooth structures Highest biting force- 4337 N Maximum bite force ranges from 400 to 890 N for molars 222-445 N for premolars 133-334 N for canines 89- 111N for incisors Phillip’s Science Of Dental Materials- Anusavice Shen Rawls- 12 th Edition

4. FACTS ABOUT MASTICATION The effects of muscle thickness on bone morphology can be explained by Wolff’s law- states that the internal structure and the shape of the bone are closely related to the bone’s function. Individuals with skeletal class I jaw relationship had thicker muscles of mastication when compared to the skeletal class II subjects . Dental arches are the somatic sites where excessive psychoemotional tension can be diffused and reduced. This is manifested by clenching or grinding the teeth bruxism . Reference -Masseter muscle thickness in different skeletal morphology: An ultrasonographic study Sushma Rani, MS Ravi- ABShetty College of Dental Sciences

5. Mastication or chewing is the first mechanical process to which food is subjected. This process helps in Breakdown of food stuff into smaller particles Mixing of saliva with food substances thoroughly Lubrication and moistening of dry food by saliva so that the bolus formed can be easily swallowed Appreciation of taste of the food by the presence of taste buds on tongue. SIGNIFICANCE OF MASTICATION

6. PHYSIOLOGY The first movement in the digestive tract ( oral cavity) which by nature is voluntary as well as an act of learned reflex . Large pieces of food are broken apart and surface area increased for the efficient action of digestive enzymes and reduced for swallowing. ROLE OF TONGUE : It plays essential role in controlling the movement of food and forming the bolus.

7. MASTICATORY SEQUENCE It consists of a number of masticatory cycles and extends from INGESTION to SWALLOWING . It is divided into 3 consecutive cycles- A- PREPARATORY PERIOD -this is the initial period in which food is transported back to posterior teeth. B- REDUCTION PERIOD – In this period , food is grounded to pieces. C – PRE SWALLOWING – This is the final period in which bolus is formed.

8. Presence of a bolus of food in the mouth at first initiates reflex inhibition of the muscles of mastication, which allows the lower jaw to drop. The drop in turn initiates a stretch reflex of the jaw muscles that leads to rebound contraction . CHEWING REFLEX This automatically raises the jaw to cause closure of the teeth, but it also compress the bolus against the linings of the mouth, which inhibits the jaw muscles once again, allowing the jaw to drop and rebound another time; this is repeated again and again.

9. Depression of jaw Elevation of jaw Protraction of jaw Retraction of jaw MOVEMENTS OF JAW

10. PRIMARY MUSCLES OF MASTICATION

11. It is one of the most important muscle of mastication. It is the superficial, quadrilateral muscle covering the lateral surface of ramus of mandible A- Superficial part B– Middle part C- Deep part MASSETER MUSCLE NERVE SUPPLY – Massetric nerve ,branch of anterior division of mandibular nerve BLOOD SUPPLY- Massetric artery , branch of maxillary artery.

12. TEMPORALIS MUSCLE Fan shaped muscle covering the region of temporal fossa. It is broad , present on each side of head – superior to zygomatic arch. BLOOD SUPPLY- It is supplied by superficial and deep temporal artery and a network of deep plexus of veins NERVE SUPPLY- Two deep temporal branch from the anterior division of mandibular nerve

13. LATERAL PTERYGOID MUSCLE Consists of short conical muscle , fan-shaped muscle located in the infratemporal fossa of the skull. Made up of two heads- A- Upper head B- Lower head NERVE SUPPLY BLOOD SUPPLY A branch of anterior division of mandibular nerve Pterygoid artery , branch of second part of maxillary artery

14. MEDIAL PTERYGOID MUSCLE Also called as the internal pterygoid muscle It is almost mirror image like masseter muscle Rhomboidal in shape and in same direction on the inner surface of mandible SUPERFICIAL HEAD DEEEP HEAD ORIGIN From the tuberosity of maxilla and adjoining bone Medial surface of lateral pterygoid plate and adjoining process of palantine bone INSERTION - superficial and deep insert into the roughened area of medial surface of angle and adjoining ramus of mandible , below and behind the mandibular foramen and mylohyoid groove

15. DEGLUTITION Deglutition or swallowing is the process by which food is passed from mouth into stomach. Stages of Deglutition:- Oral stage when food enters pharynx from mouth. Pharyngeal stage when food enters esophagus from pharynx. Esophageal stage when food enters stomach from esophagus .

16. Oral Stage Or First Stage In this stage the bolus passes through the oral cavity into the pharynx by means of series of actions such as: The bolus is placed over posterodorsal surface of the tongue. It is called the preparatory position . The anterior part of the tongue is retracted and depressed. The posterior part of the tongue is elevated and retracted against the hard palate . This pushes the bolus backwards into the pharynx . The forceful contraction of tongue against the hard palate produces a positive pressure in the posterior part of the oral cavity. This pressure also pushes the food into the pharynx.

17. Pharyngeal Stage Or Second Stage This stage shows involuntary , complex, closely coordinated movements in the pharynx the pushes the bolus into the esophagus . It lasts for 1-2 seconds Features Soft palate is elevated and thrown against posterior pharyngeal wall to close off the nasal cavity . This prevents the food from entering the nasal cavity. Larynx rises with elevation of hyoid bone , vocal cords are approximated and breathing is momentarily inhibited (deglutition apnoea ). Epiglottis guards the laryngeal opening until bolus reaches the esophagus .

18. Posterior pillars of fauces i.e. palatopharyngeal folds approximate to shut off the mouth cavity. Cricopharyngeous muscle briefly relaxes and bolus enters the upper esophagus . Then cricopharyngeal muscle contracts and vocal cords open to allow resumption of rhythmic breathing

19. Esophageal Stage or Third Stage In esophageal stage food enters stomach from esophagus . It is an involuntary stage. The function of esophagus is to transport the bolus from the pharynx to the stomach. The movements of esophagus are specially organized for this function and the movements are called peristaltic waves.

20. Role of Lower Esophageal Sphincter The distal 2-5cm of esophagus acts like a sphincter and it is called lower esophageal spincter . Its is always constricted. It only relaxes when the food enters this part of the esophagus and constrictes as the food enters the stomach.

21. Deglutition reflex

22. APPLIED ASPECTS

23. Dysphagia Difficulty of swallowing –co exits with heartburn and vomiting . Deglutition can be restricted if the muscle of the mouth , pharynx, larynx or esophagus are weak or uncordinated .

24. ACHALASIA CARDIA It is a disease of an unknown etiology characterized by aperistalsis in the body of oesophagus and failure of relaxation of lower oesophageal sphincter on initiation of swallowing . The food collects in oesophagus resulting in dilatation of oesophagus

25. GASTROESOPHAGEAL REFLUX DISEASE It is characterised by regurgitation of acidic gastric content through esophagus. The gastric content flows into pharynx/mouth. Regurgitation is due to weakness/incompetence of lower esophageal sphincter.

26. FEATURES OF GERD Heartburn or pyrosis - painful or burning sensation in chest due to regurgitation of acidic gastric content. Esophagitis Dysphagia Cough and change of voice Esophageal ulcers and cancer (in chronic cases)

27. GAG REFLEX DENTAL IMPLICATION- Most of our patients in our day to day practice presents with gag reflex during making of impressions or carrying out restorative procedures.

28. PRESBYPHAGIA

29. CHOKING DENTAL IMPLICATIONS- Sudden aspiration of instruments or materials used in dentistry can result I chocking effects.

30. DEGLUTITION APNEA Arrest of breathing during deglutition Occurs reflexly during pharyngeal stage. When bolus is pushed into oesophagus from pharynx during pharyngeal stage , there is possibility for the bolus to enter the respiratory passage through trachea .

31. PHAGOPHOBIA – Fear of swallowing as in rabies , tetanus, pharyngeal paralysis due to fear of aspiration . GLOBUS HYSTERICUS – Sensation of lump lodges in throat . ODYNOPHAGIA – Painful swallowing .

32. Investigation X-ray chest Barium swallow Oesophagoscopy

33. ESSENTIALS OF MEDICAL PHYSIOLOGY – 5 TH EDITION K SEMBULINGAM PREM SEMBULINGAM TEXTBOOK OF PHYSIOLOGY – PROF. AK JAIN Philips- Science Of Dental Materials- Anusavice Shen Rawls- 12 th Edition REFERENCES Masseter muscle thickness in different skeletal morphology: An ultrasonographic study Sushma Rani, MS Ravi- Ab Shetty college of dental sciences ARTICLES-