Source Borley Textbook
STERILIZATION I
Category: prosthodontics
Mouth preparation for complete dentures (part 1)
Mouth rehabilitation is defined as restoration of form and function of the masticatory apparatus to as nearly normal as possible.
# Adjunctive care :Lesions like ulcer, abscess should be cure and be given time for healing. During their healing period adjunctive therapies like tissue massage, use of mouth washes etc. are used. For normal patients, 48 hour rest with tissue massage is sufficient.
#Removal of retained dentition : An OPG gives a clear idea whether to remove the retained dentition or not.
Removal of unerupted teeth::
The unerupted teeth lying close to ridge should be removed but the one which deeply submerged and non symptomatic can be left untouched.
Removal of retained roots::
All the retained roots should be removed but if it’s removal can cause large bony defect and is asymptomatic , then it can be left untouched.
# Correction of Hypermobile Ridge tissue :
Hypermobile tissues are caused by excessive residual ridge resorption. Small Hypermobile tissues which do not affect functioning of denture can be left untouched but the large pendulous Hypermobile tissues should be removed.
#Removal of soft tissue interfaces : Firm soft tissue interference, which do not affect the stability of the denture,can be left intact. In case of maxillary tuberosity with excessive fibrous tissue, there is need for surgical removal.
#Removal of Hypertrophic maxillary labial frenum:
In case of high frenum attachment ,where the frenum is not so close to crest of the ridge , surgery is not mandatory, only labial notch in the denture is sufficient. But when this notch breaks the peripheral seal , in that case surgical procedure is done.
( ref : Textbook of prosthodontics: Deepak nallaswamy , images : Google images)
Mouth preparation for complete dentures (part 2)
#Removal of a Hypertrophic Lingual frenum:
Frenectomy is indicated in this case. Tongue tie test is performed.Patient is asked to touch his upper lip with tongue, if the denture is displaced by doing so then frenectomy is to be done.
#Correction of prominent buccal frenum: Removal is generally not necessary as they are not present as so large. Buccal frenum is soft and it can be easily displaced by denture without any injury.
#Removal of Papillary hyperplasia:
These hyperplastic lesions occur due to irritation. It can be large or small . Small lesions are treated by curettage and large by split thickness supraperiosteal excision.
#Treatment of Epulis fissuratum:
It is an soft tissue reaction in sulcular regions due to overextension of denture flanges. No specific treatment except shortening and smoothening of denture borders.Give it time to heal.
# Removal of ridge undercuts: Small and moderate unilateral undercuts can be left untouched , while severe undercuts or bilateral moderate requires surgical correction ( alveoloplasty).
( ref: textbook of prosthodontics , Deepak nallaswamy , images: Google images.)
Mouth preparation for complete dentures ( part 3)
#Management of prominent Mylohyoid and internal oblique ridges: They are seen in lingual surfaces of mandible. Sometimes they become prominent due to ridge resorption. If there is repeated ulceration, loss of peripheral seal , they should be surgically reduced.
#Reduction of Maxillary tuberosity: Reduction of wide tuberosity is easier compared to vertically large tuberosity. Before it’s reduction, radiological evaluation is mandatory,as maxillary sinus tends to expand in tuberosity.
#Treatment of sharp spiny ridges: These type of ridges usually occur in lower anterior region due to resorption of labial and lingual cortical plates. For this ,ridge augmentation can be done.
Meyer’s classification for knife edge ridges:
⛔Saw-tooth
⛔Razor-like
⛔Ridge with discrete spiny projections
#Excision of Tori :
Tori are small bony projections of unknown etiology. Indications for maxillary Tori removal:
Interference of speech
Loss of posterior palatal seal
Poor denture stability
All the mandibular Tori should be excised .
#Vestibuloplasty:
It is the surgical procedure to increase the vestibular depth. Techniques for vestibuloplasty are::
Mucosal Advancement
Secondary Epithelialisation
Epithelial Graft Vestibuloplasty
( ref : textbook of prosthodontics,Deepak nallaswamy, image: Google images)
RUBBER DAM PLACEMENT
- Placement of Rubber Dam
- Before placement of rubber dam, following procedures should be done:
- Thorough prophylaxis of the oral cavity.
- Check contacts with dental floss.
- Check for any rough contact areas.
- Anesthetize the gingiva if required.
- Rinse and dry the operated field.
- Methods of Rubber Dam Placement.
- Method I: Clamp placed before rubber dam
- Select an appropriate clamp according to the tooth size.
- Tie a floss to clamp bow and place clamp onto the tooth
- Larger holes are required in this technique as rubber dam has to be stretched over the clamp. Usually two or three overlapping holes are made.
- Stretching of the rubber dam over the clamps can be done in the following sequence:
- – Stretch the rubber dam sheet over the clamp
- – Then stretch the sheet over the buccal jaw and allow tosettle into place beneath that jaw
- – Finally, the sheet is carried to palatal/lingual side andreleased.
This method is mainly used in posterior teeth in both adults and children except third molar.
Method II: Placement of rubber dam and clamp together
- Select an appropriate clamp according to tooth anatomy.
- Tie a floss around the clamp and check the stability.
- Punch the hole in rubber dam sheet.
- Clamp is held with clamp forceps and its wings are insertedinto punched hole.
- Both clamp and rubber dam are carried to the oral cavityand clamp is tensed to stretch the hole.
- Both clamp and rubber dam is advanced over the crown.First, jaw of clamp is tilted to the lingual side to lie on thegingival margin of lingual side.
- After this, jaw of the clamp is positioned on buccal side.
- After seating the clamp, again check stability of clamp.
- Remove the forceps from the clamp.
- Now, release the rubber sheet from wings to lie around thecervical margin of the tooth.
- Method III: Split dam technique: This method is split dam technique in which rubber dam is placed to isolate the tooth without the use of rubber dam clamp. In this technique, two overlapping holes are punched in the dam. The dam is stretched over the tooth to be treated and over the adjacent tooth on each side. Edge of rubber dam is carefully teased through the contacts of distal side of adjacent teeth.
Split dam technique is indicated:
• To isolate anterior teeth
• When there is insufficient crown structure
• When isolation of teeth with porcelain crown is required. In such cases placement of rubber dam clamp over the crown margins can damage the cervical porcelain.
• Dam is placed without using clamp.
• Here two overlapping holes are punched and dam is stretched over the tooth to be treated and adjacent tooth on each side.
REFERENCE- NISHA GARG TEXTBOOK OF ENDODONTICS
KHOURY TECHNIQUE
Written by : Dr. Urusa I Inamdar
It is also called as split bone block technique / shell technique.
- Mandibular bone blocks ( external oblique ridge ), which consists primarily of cortical bone and a low percentage of cancellous bone , are more resistant to revascularization and consequently may have poor regeneration potential . For this reason , the harvested thick bone blocks with the diamond disk according to the split bone block technique of the biologic concept of grafting procedures.
- Splitting the thick blocks into two thin blocks not only increases the number of bone blocks , offering the possibility to graft more surfaces in different forms , but also improves revascularization and regeneration.
- The thin blocks were stabilized at the recipient site with microscrews , and any gaps were filled with autogenous bone chips harvested from the donor site with a bone scraper .
- No biomaterials or membranes are used .
- This technique with pure autogenous bone , which has been used for 20 yrs , has shown a high success rate .
Reference:
- International institute of dental research
- Dental notes
- Google.com
Maxillary Posterior teeth arrangement
Steps in placement of maxillary first premolar
Placement of the maxillary first premolar in all three planes
The buccal cusp tip of the maxillary first premolar is in contact with occlusal plane (black line), and palatal cusp 1 mm short of the occlusal plane
buccal cusp corresponds with the canine tip, and
the palatal cusp corresponds to previous drawn reference line of the mandibular residual ridge line
When viewed from:
Front: Long axis parallel towards the vertical axis.
Side: Long axis parallel towards the vertical axis.
Occlusal plane: Buccal cusp is in contact with occlusal plane
and palatal cusp 1 mm short of occlusal plane
Steps in placement of the maxillary second premolar
Placement of the maxillary second premolar in all three planes
The buccal surface of the maxillary second premolar is barely visible when the patient smiles when viewed from the front
The buccal cusp of the maxillary second premolar corresponds with the buccal cusp of maxillary first premolar (blue line), and the palatal cusps of both the premolars correspond to the previous drawn line
When viewed from:
Front: Long axis parallel towards the vertical axis.
Side: Long axis parallel towards the vertical axis.
Occlusal plane: Both buccal cusp and palatal cusp is in contact
with occlusal plane
Steps in placement of maxillary first molar
Placement of the maxillary first premolar in all three planes
the mesio- and distobuccal cusps correspond with
the buccal cusp of second premolar (blue line) and the mesio- and distopalatal cusps correspond to the previous drawn line (yellow line).
When viewed from:
Front: Long axis slopes buccally.
Side: Long axis slopes distally.
Occlusal plane: Only mesiopalatal cusp is in contact with
occlusal plane
Steps in placement of maxillary second molar
The long axis of the maxillary second molar (blue line) is distally
inclined in relation to the vertical axis (red line) when viewed from the front .
All the cusps are short of the occlusal plane (black line).
The maxillary second molar is slightly buccally inclined when viewed from the front. The buccal surface of the maxillary second molar is barely visible when viewed from the front
When viewed from:
Front: Long axis slopes buccally more steeply than first molar.
Side: Long axis slopes distally more steeply than first molar.
Occlusal plane: Only mesiopalatal cusp is nearest to occlusal
plane
Source – S. Lakshmi preclinical manual of prosthodontics
Prosthesis
Prosthesis may be defined as an artificial replacement of a missing part of the human body
Types of prosthesis
i. Dental prosthesis
ii. Maxillofacial prosthesis
iii. Ancillary prosthesis
Dental prosthesis
An artificial replacement of one or more teeth and associated dental/alveolar structures.
Fixed dental prosthesis
Any dental prosthesis that is cemented, screwed or attached to the retained natural teeth or roots.
Removable prosthesis
Any dental prosthesis that replaces some of the missing teeth in a partially edentulous arch
Removable partial denture prosthesis (RPDP)
The prosthesis that replaces some of the teeth in a partially edentulous arch and that can be removed from the mouth by the patient.
It can be a simple removable partial denture fabricated in acrylic resin called temporary partial
denture.
A removable partial denture fabricated in cast metal alloy and acrylic resin is called cast partial denture
Removable complete denture prosthesis
The prosthesis that replaces the entire dentition and associated structures of maxilla and mandible
Maxillofacial prosthesis
The prosthesis that is used to replace a part or all of any stomatognathic or craniofacial structures.
Examples of the maxillofacial prosthesis are auricular
prosthesis, orbital prosthesis, nasal prosthesis and facial prosthesis.
Implant supported prosthesis
The prosthesis that is used to replace the missing teeth , retained by implant supported prosthesis.
Ancillary prosthesis
The type of dental prosthesis used in prosthodontics for a very short term of usage
example- splints ,stents and guides
source – preclinical textbook of prosthodontics by S Lakshmi and image source- google and S Lakshmi
Anterior Teeth arrangement and selection of teeth
After the registration of the maxillo-mandibular , the artificial teeth must be set in centric occlusal position.
Selecting of artificial teeth
The facial form of the patient should be classified into-
–square
–ovoid
– tapering
-The form of the teeth should be in harmony with the form of the face, square teeth are used for those with a square face and so on.
-In addition, the patient’s age, gender and personality should be taken into consideration when trying to improve to improve the appearance.
-The color is also important, dark and opaque teeth should be selected for elderly patient, light and translucent teeth for the young patients.
-The size of the teeth must also be in harmony according to the size of the face and the gender of the patient.
Objectives of setting teeth are-
to provide a comfortable and atraumatic occlusion
to assist in preparing food for deglutition
to impart a pleasing and natural appearance
to assist in speech
Teeth arrangement of anteriors and posteriors
Armamentarium
•Maxillary occlusal rim with cast
• Mandibular occlusal rim with cast
• Mean value articulator
• Teeth shade
• Measurement scale
• Wax knife
• Roach carver
• Wax spatula
• Wax sheet
• Gas torch
• Cotton
• Rubber bowl with cold water
Guidelines for anterior teeth setting are marked on the cast and the land area of the cast.
I. The centre of the incisive papilla (marked in red)
II. A line is drawn along the midline of the cast through the centre of the incisive papilla (marked in black).
III. A perpendicular line is drawn to the above line through the centre ofincisive papilla till the land area (marked in blue; CPC line).
IV. During setting of maxillary canine, the cuspid tip of the canine should be placed in line with this point
The crest of the lower residual alveolar ridge is marked in red colour along the posterior aspect of the lower cast. A corresponding line is marked on the upper cast in blue
Steps in placement of maxillary central incisor
Placement of the maxillary central incisor in relation to all three planes.
🔻The long axis of the central incisor (the blue line) is positioned parallel to the
vertical axis (the red line) when viewed from the front
🔻The incisal edge of the maxillary central incisor is positioned in line with the
anterior occlusal plane . The central pin of the articulator will point the mesioincisal line edge of the central incisor.
🔻The central pin of the articulator will
point the mesioincisal line edge of the central incisor.
When viewed from:
Front: Long axis parallel towards the vertical axis.
Side: Slopes labially about 15 degrees.
Occlusal plane: Incisal edge is in contact with occlusal plane
Steps in placement of maxillary lateral incisor
🔻The long axis of the lateral incisor (green line) is placed slightly inclined to
the vertical axis (red line).
🔻The incisal edge of the maxillary lateral incisor is placed slightly short of the
occlusal plane (marked as yellow line).
🔻The incisal edge of the maxillary lateral incisor should follow the outline of
the occlusal rim when viewed occlusally
When viewed from:
Front: Long axis slopes towards midline at incisal edge.
Side: Slopes labially about 20 degrees.
Occlusal plane: Incisal edge is 1 mm short of occlusal plane
Steps in placement of the maxillary canine.
🔻The long axis of the maxillary canine (yellow line) should be parallel to the
vertical axis (red line) when viewed from the front.
🔻The long axis of the maxillary canine (yellow line) should be parallel to the
vertical axis (red line) when viewed from the side .
Maxillary canine follows the outline of occlusal rim, and the tip of the canine
corresponds to the canine papillary line
When viewed from:
Front: Long axis parallel towards the vertical axis.
Side: Long axis parallel towards the vertical axis.
Occlusal plane: Cuspid tip is in contact with occlusal plane
Steps in placement of mandibular central incisors
🔻The incisal edge of the mandibular central incisor should follow the outline
of the occlusal rim, and the incisal edge of the mandibular central incisor tooth
should not cross over the land area when viewed occlusally
When viewed from:
Front: Long axis inclines slightly towards the vertical axis.
Side: Slopes labially.
Occlusal plane: Incisal edge is 0.5–1 mm above the occlusal
plane
Steps in placement of mandibular lateral incisor
of the occlusion rim, and the incisal edge should not cross over the land area of
the cast when viewed occlusally
When viewed from:
Front: Long axis inclines towards the vertical axis.
Side: Slopes labially less than central incisor.
Occlusal plane: Incisal edge is 0.5–1 mm above the occlusal
plane
Steps in placement of a mandibular canine
When viewed from:
Front: Long axis inclined towards midline.
Side: Slopes lingually.
Occlusal plane: Cuspid tip is 0.5–1 mm above the occlusal
plane
Maxillary and mandibular canine relation
The mesial slope of the maxillary canine should overlap the distal slope of
the mandibular canine
Complete teeth setting of maxillary and mandibular anteriors
🛑The vertical overlap (over bite) between the maxillary and mandibular
incisal edge should be 0.5–1 mm, and the horizontal overlap (over jet) between
the maxillary and mandibular incisal edges should be 1–2 mm.
🛑The horizontal overlap should be uniform from left maxillary to right maxillary canine
Source – preclinical manual of prosthodontics S . Lakshmi
Dental investments and refractory materials (part 2 )
GYPSUM BONDED INVESTMENTS
Thermal behaviour of gypsum
When gypsum is heated to a high temperature, it shrinks and fractures. At 700 °C, it shows slight expansion and then great amount of contraction. The shrinkage is due to decomposition and release of sulphur dioxide .
It contaminates the casting with sulphides of silver and copper .
Hence gypsum bonded investments are not heated above 700°C.
PHOSPHATE BONDED INVESTMENTS
EXPANSION
- Wax pattern expansion The heat during setting allows a significant expansion of the wax pattern
- Setting expansion This is around 0.7 to 1%.
- Thermal expansion Ranges from around 1 to 1.5%.
The amount of expansion is adjusted by the manufacturer for each product depending on the alloy it is intended for.
STRENGTH –
Wet strength ranges from 4-10Mpa
And dry strength is the strength under high temperatures.
SILICA BONDED INVESTMENTS
The silica is the binder. It is derived from ethyl silicate or aqueous dispersion of colloidal silica or sodium silicate.
TYPES
Based on the binder used two types may be seen. One such investment consists of silica refractory, which is bonded by the hydrolysis of ethyl silicate in the presence of hydrochloric acid.
The product of the hydrolysis is the formation of a colloidal solution of silicic acid ethyl alcohol.
Ethyl silicate has the disadvantage of containing inflammable components which are required for manufacture
Sodium silicate and colloidal silica are more commonly used as binders because of the above disadvantage.
These investments are supplied along with two bottles of special liquid. One bottle contains dilute water soluble silicate solution such as sodium silicate.
Source – basic science of dental materials manappallil
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