Maxillary Landmarks

Importance

Dentist must fully understand the anatomy of supporting and limiting structures :

• Foundations of the denture bearing areas

• Dentures and their supporting structures are to coexist for reasonable length of time

GROUPING OF LANDMARKS

These are the sites that will guide us in having an optimum extension of the denture so as to engage maximum surface area without encroaching upon the muscle actions

Encroaching upon these structures will lead to dislodgement of the denture and/or soreness of the area while failure to cover the areas upto the limiting structure will imply decreased retention stability and support.

LIMITING STRUCTURES

The limiting structures of the maxilla are:

1. Labial frenum2. Labial vestibule3. Buccal frenum4. Buccal vestibule5. Hamular notch6. Posteror palatal seal area

Labial frenum`.

• Fold of mucous membrane at the midline.• Contains no muscle.• Performs no action.

ATTACHMENT :

Superiorly: fan shapedInferiorly : attaches on labial side of ridge

Labelled as 1

CLINICALLY:

•A V shaped notch is recorded during impression making to accommodate labial frenum

•The labial notch in the labial flange of the denture should be wide & deep enough to allow the frenum to pass through it without manipulation of the lip.

2. Labial vestibule“That portion of the oral cavity bound on one side by the teeth,gingiva & alveolar ridge & on the other side by the lips & cheek”

- GPT

Vestibule is covered by the lining mucosa.

SUBMUCOSA is thick & contains areolar tissue & elastic fibres

CLINICALLY:

Main muscle of the lip – ORBICULARIS ORIS forms the outer surface of the labial vestibule.

Its tone depends on the support received from the labial flange & position of the teeth.

The fibres run horizontally & have indirect displacing effect on the denture.

Buccal frenum

It forms the dividing line between the labial & buccal vestibules.

It may be a single or double fold of mucous membrane.

It has the following attachments:

•LEVATOR ANGULI ORIS attaches beneath & effects the position of the frenum.

•ORBICULARIS ORISPulls the frenum forward

•BUCCINATORPulls it backward

Hence it requires more clearance for its action.

Buccal vestibule• It extends from the buccal frenum anteriorly to the hamular notch posteriorly.•Its size varies with the: -contraction of the buccinator -position of the mandible

-amount of bone loss in the maxilla.

The distal end of the buccal flange of the denture should be adjusted not to have any interference to the coronoid process during mouth opening .Hence the buccal vestibule should be measured with the mouth nearly as close as possible.

CLINICALLY

Hamular notchA depression between the maxillary tuberosity & hamulus of the medial pterygoid plate

It is soft area of loose areolar tissue.

The distolateral border of the denture rests in the hamular notch.

The tissues in the region can be displaced to achieve the posterior palatal seal.

So if the denture border is placed anteriorly it will loose its retentive properties.

Posterior palatal seal area

The soft tissues at or along the junction of hard & soft palate on which pressure within physiological limits of the tissues can be applied by a denture to aid in the retention of the denture,

-GPT

It prevents the air entry between the denture base & soft palate

The posterior palatal seal is divided into:

• PTERYGOMAXILLARY SEALExtends across the hamular

notch & extends 3-4 mm anterolaterally to end in the mucogingival junction on posterior part of maxillary ridge

•POST PALATAL SEALExtends between the maxillary

tuberosities.

VIBRATING LINES

Vibrating line(area)-An imaginary line drawn across thepalate that marks the beginning of the movement of soft palate when the patient says ‘ah’ extending from one hamular notch to the other hamular notch;lying usually 2mm in front of fovea palatinae.

The distal end of the denture should extend at least to the vibrating line. Functions of the posterior palatal seal:•Aids in retention•Prevents food accumulation•Compensation for polymerization shrinkage•Reduces the tendency for gag reflex due to downward movement of the denture during incising

SUPPORTING STRUCTURES

• Load bearing areas

•Show minimal ridge resorption under constant load.

•Denture should be designed such that most of the loadis concentrated on these areas.

•Two types of stress bearing areas:primary stress bearing areassecondary stress bearing areas

SUPPORTING AREAS IN THE MAXILLA

PRIMARY STRESS BEARING AREAS

1. Hard palate

The horizontal portion of the palate lateral to the midline is the primary stress bearing area.

Trabecular pattern in the bone is perpendicular to the direction of the force thus withstanding any amount of force.

2. Residual ridge

Portion of the alveolar ridge & its soft tissue covering which remains following the removal of teeth.

-GPT

Mainly the posteriolateral portion of the residual ridge is the primary stress bearing area.

SECONDARY STRESS BEARING AREAS

1. RugaeMucosal folds located in the anterior region of the palatal mucosa.

2. Maxillary tuberosityBulbous extension of the residual ridge in second & third molar region.

They are secondary stress bearing because they are least likely to resorb.

These are the areas which either resorb under constant load or have fragile structures within or are covered by thin mucosa which can be easily traumatized& hence should be relieved. They are:• incisive papilla•Mid palantine raphe•Fovea palatina•Torus palatinus

RELIEF AREAS

RELIEF AREAS

1. Incisive papilla Position

midline structure situated behind

the central incisors.

Why a relief area ?Exit point of the

nasopalatine nerves & vessels. Hence the area should be relieved to prevent necrosis of the distributive areas & parasthesia of the anterior palate.

Mid palatine raphe

Positionmedian suture area

covered by thin submocosa.

Why a relief area ?the submucosa in the

mid palatine suture is very thin. Hence relief should be provided in the denture covering the suture.

Fovea palatina

•Formed by the coalescence of ducts of several mucous glands.

•Guide to locate posterior border of the denture.

•Patients with thick ropy saliva they should be left uncovered to prevent the displacement of the denture.

TORUS PALATINUS

Hard bony enlargement in midline of roof of the mouth in 20% of people.

Covered by thin mucous membrane.

Relief should confirm accurately to the shape of the torus because the denture is robbed of the support area.