anatomic landmarks of the maxilla and mandible

landmarks

1. ANATOMICAL LANDMARKS OF MAXILLA (MACROSCOPIC)

2. LANDMARKS OF MAXILLA

3. LIMITING AREAS These are the sites that will guide us in having an optimal extension of the denture so as to engage maximum surface area without engaging upon the muscle action. Encroaching upon these areas will lead to dislodgement of the denture and soreness of the area while failure to cover the areas up to the limiting structure will decrease retention, stability and support of the denture.

4. LABIAL FRENUM It appears as a fold of mucous membrane extending from the mucous lining of the lip to or towards the crest of residual ridge on the labial surface. It may be single / multiple. It may be narrow / broad. It contains no muscle fibres of significance. It is fan shaped anteriorly Clinical Consideration : Sufficient relief should be given during final impression procedure and in completed prosthesis because overriding of function of frenum will cause pain and dislodgement of denture. During impression procedure the lip should be stretched horizontal outwards for the proper recording of frenum. If frenum is attached close to the crest ,frenectomy is done, failure of which will lead to the denture border being placed on the bone tissue which will cause decreased border seal.

5. LABIAL VESTIBULE T he portion of the oral cavity that is bounded on one side by the teeth, gingiva, and alveolar ridge (in the edentulous mouth, the residual ridge) and on the other by the lips anterior to the buccal frenula. (GPT9) It extends on both sides of the midline from labial frenum anteriorly to the buccal frenum posteriorly. It is bounded laterally by the labial mucosa & medially by maxillary residual alveolar ridge. Reflection of the mucous membrane superiorly reflects the height. The area of mucous membrane reflection has no muscle. Clinical Consideration : For effective border contact between denture and tissue, vestibule should be completely filled with impression material.

6. BUCCAL FRENUM Fold or folds of mucous membrane extending from mucous membrane reflection area to or towards the slope or crest of residual alveolar ridge. Significance : Levator anguli oris ( caninus muscle) lies beneath it and hence influenced by other muscles of facial expression. Clinical Consideration : During final impression procedure and in final prosthesis sufficient relief should be given for the movement of frenum because overriding of function of frenum will cause pain and dislodgement of denture. During impression procedure the cheek should be reflected laterally and posteriorly. If frenum is attached close to the crest of alveolar ridge, frenectomy is called for

7. BUCCAL VESTIBULE It is bounded anteriorly by the buccal frenum, laterally by the buccal mucosa and medially by residual alveolar ridge. Significance : In the area of buccal flange of denture base where it rounds the distobuccal area of alveolar tubercle, sometimes a small muscle attachment is seen. Clinical Consideration : During impression procedure the vestibule should be completely filled with impression material for proper border contact between denture and tissues. When the vestibular space that is distal and lateral to the alveolar tubercles is properly filled with denture flange the stability and retention of the maxillary denture is greatly enhanced. The buccal flange borders depend upon movement of ramus of mandible at the distal end of buccal vestibule and hence the patient should move the mandible laterally and protrusively to make sure the mandible does not interfere with these functions. To effectively record the maxillary buccal sulcus the mouth should be halfway closed because wide opening of the mouth narrows the space and does not allow proper contouring of sulcus because the coronoid process of mandible comes closer to the sulcus.

8. POSTERIOR PALATAL SEAL AREA The soft tissue area limited posteriorly by the distal demarcation of the movable and non movable tissues of the soft palate and anteriorly by the junction of the hard and soft palates on which pressure, within physiologic limits, can be placed; this seal can be applied by a removable complete denture to aid in its retention (GPT9) Boundaries of posterior palatal seal area : Anteriorly - anterior vibrating lines Posteriorly - posterior vibrating lines Laterally - pterygomaxillary notch Seal consist of two separate but confluent areas: Post palatal seal- extends medially from one tuberosity to another Pterygomaxillary seal- extends through hamular notch for 3-4mm anterolaterally approximating mucogingival junction

9. This landmark presents a three-dimensional seal area which supplements values of retention of maxillary denture. Anterior unit consists of as much resilient area as palpated by T-burnisher because of histologic contents. Posterior limit is revealed by the line of minimal function. Lateral limit is revealed by hamular notch area. Superior-inferior limit is revealed by the thickness of low fusing impression compound. Clinical significance : It maintains contact of denture to soft tissues during functional movements (mastication, phonation) Increase retention & stability by creating partial vacuum. Reduces gag reflex Reduce patient's discomfort when contact occurs between dorsum surface of tongue & posterior part of denture. Prevents food accumulation between posterior border of denture & soft palate.  Compensation of volumetric shrinkage that occurs during the polymerization of PMMA Clinical consideration : Under extension of denture in posterior palatal seal area- causes loss of retention Overextension- causes gag reflex, ulceration Steps to record the PPS with the novel functional swallow method: (A) Transfer of the PPS mark onto the elastomeric putty; (B) Roughening and thinning of the elastomeric putty representing the PPS; (C) Patient position for recording the PPS using the functional swallow method; (D) Low-fusing compound representing the PPS; (E) Low-viscosity elastomeric final impression; (F) Master cast with the functionally displaced PPS Krishna R, Mandokar RB, Mishra S,  et al.  A Novel Functional Swallow Method to Establish the Posterior Palatal Seal during the Maxillary Edentulous Final Impression: A Case Report. J Contemp Dent Pract 2020;21(12):1404–1407 .

10. VIBRATING LINE A n imaginary line across the posterior part of the soft palate marking the division between the movable and immovable tissues; this line can be identified when the movable tissues are functioning.(GPT9) Anterior vibrating line - Imaginary line at junction of attached tissue overlying the hard palate & the immediate movable tissue or soft palate. Shape-cupid's bow -due to the projection of posterior nasal spine. It is located by- Valsalva manoeuvre- both the nostrils are held firmly while the patient blows gently through the nose, this will place soft palate inferiorly at junction of hard palate. patient is asked to say "ah" in short vigorous bursts. Posterior vibrating line- Imaginary line at junction of aponeurosis of tensor veli palatini muscle & musculature of soft palate Located by - it can be visualised when the patient says "ah" in a normal un-exaggerated fashion

11. HAMULAR NOTCH A depression present between maxillary tuberosity & pterygoid hamulus. It is a narrow cleft of loose connective tissue which is approximately 2mm in extent anteroposteriorly and Located by using T-burnisher Significance : Constitutes the lateral boundary of posterior palatine seal area in maxillary foundation. The pterygomandibular raphe attaches to hamulus. Clinical consideration : Denture should not extend beyond the hamular notch, failure of which will result in restricted pterygomandibular raphe movement. When mouth is wide open the denture dislodges. Under extension will lead to poor retention.

12. REFERENCES Winland RD, Young JM. Maxillary complete denture posterior palatal seal: variations in size, shape, and location. J Prosthet Dent 1973;29(3):256–261. DOI:  10.1016/0022-3913(73)90004-8 . 2.  Avant WE. A comparison of the retention of complete denture bases having different types of posterior palatal seal. J Prosthet Dent 1973;29(5):484–493. DOI:  10.1016/0022-3913(73)90025-5 . 3.  Goyal S. The posterior palatal seal: its rationale and importance: an overview. Eur J Prosthodont 2014;2(2):41–47. DOI:  10.4103/2347-4610.131972 . 4.  Chen MS, Welker WA, Pulskamp FE, et al. Methods taught in dental schools for determining the posterior palatal seal region. J Prosthet Dent 1985;53(3):380–383. DOI:  10.1016/0022-3913(85)90517-7 . 5.  Petrie CS, Walker MP, Williams K. A survey of U.S. prosthodontists and dental schools on the current materials and methods for final impressions for complete denture prosthodontics. J Prosthodont 2005;14(4):253–262. DOI:  10.1111/j.1532-849X.2005.00051.x . 6.  Winkler S. Essentials of complete denture prosthodontics.New Delhi: AITBS Publishers; 2015. p. 160. 7.  Ansari IH. Establishing the posterior palatal seal during the final impression stage. J Prosthet Dent 1997;78(3):324–326. DOI:  10.1016/s0022-3913(97)70034-9 . 8.  Hardy IR, Kapur KK. Posterior border seal: its rationale and importance. J Prosthet Dent 1958;8(3):386–397. DOI:  10.1016/0022-3913(58)90064-7 . 9.   Jeannin C, Millet C. A functional impression technique for capturing the superior position of the soft palate. J Prosthet Dent 2006;96(2):145–146. DOI:  10.1016/j.prosdent.2006.05.014 .

13. THANK YOU