Percussion Action

Colt single actions, Designed by a lefty????

In a right handed world It seems strange. The most popular revolvers from the percussion era Walkers throught the 1873 SAA Have ergonomics that suit a lefty? The loading gates & cap loading areas on these guns require a hand switch to load for most. Why does every one still make copies with the same “error.”

Some people believe Col. Sam Colt was left-handed and site some old black n white photo where he appears to be holding a gun left-handed. Since he is not actually shooting this gun it is difficult to determine why the gun is in his left hand. Was he just casually holding it in his left hand when the picture was taken? Then they point out your own observation to assert that he was a leftie (as if that were important!).

Actually, it does make sense if you think about it, IF you are already shooting left handed opening the loading gate with your Right Hand and reloading right-handed would make for faster reloading and your revolver would NEVER leave your shooting hand.

The other way to look at it is that it is easier for a right-handed person to load right-handed so he/she isn’t going to hold his revolver in his right hand and load with his left. Think about it.

I guess that this is just one of those… Unsolved mysteries. I am not going to loss any sleep over it and continue shooting my old .38-40 revolver right-handed, switch to my left to reload with my right. Its just easier that way and I’m right-handed. LOL!

H

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Calcium hydroxide

CALCIUM HYDROXIDE CEMENT

 

 

 

 

COMMERCIAL NAMES :

 

 

Self cured : Dycal (L. D. Caulk company in 1962),

                   Life, Care, calcidor

 

Light cured – Prisma, VLC dycal                                               Dycal

 

 

INTRODUCTION

 

Calcium hydroxide should be stored in tightly closed and sealed bottles. This is because of exposed to air, it changes into calcium carbonate and loses its therapeutic properties. Some spore forming bacteria also flourish in alkaline medium present in the calcium hydroxide and contaminate it. Hence, preferably every time fresh and properly sealed calcium hydroxide should be used and the rest should be discarded. Calcium hydroxide has a definite characteristic of producing calcium concentration resulting in less leakage at the capillary junction. It causes contraction of the pericapillary sphincters, thus resulting in less plasma outflow. This could account for the clinical use of the material in controlling periodical exudation. Many workers are of the opinion that if concentration of ions increased locally, the phosphate enzyme in presence of calcium salts can accelerate bone formation.

 

HISTORY:

 

Herman (1930) introduced calcium hydroxide for pulp capping.

 

In 1938 Teuscher and Zander introduced calcium hydroxide in United States.

They histologically confirmed complete dentinal bridging with healthy radicular pulp under calcium hydroxide dressings.

 

The action of hydroxyl ion from Ca (OH)2 producing a high pH, represents an essential characteristic, since it induces the formation of a mineralized barrier, as reported by Holland.

 

Estrela  et al reported the effect of Ca (OH)2 on bacteria and tissue, is directly to its ionic dissociation into Ca++ and OH- and explaining that its high pH inhibits enzyme activity that are essential to bacterial life.

 

Gordon and Alexaddre analysed two properties of Ca(OH)2 on pulpal tissue: variation in pH and Ca++ concentration. Their results suggest that the effect of Ca(OH)2 are mainly pH dependent and its efficiency may result from lower solubility.

 

Estrela & Pesce chemically analysed the release of OH- from Ca(OH)2­  in connective tissue. The percentage of the exiting OH- (45.89%) and Ca ++ (54.1%) can be obtained taking into account the molecular weight of Ca(OH)2 (74.08%).

 

 

AVAILABLE AS

 

1. Two paste system containing base

and catalyst paste in  collapsable tubes.

1. Light cured system                                                  Two paste system

2.  

   Single paste in syringe form

1. Powder form

 

  Powder form

 

COMPOSITION

 

Base paste –

 

• Glycol salicylate  40% – reacts with Ca (OH)2 and ZnO
• Calcium sulphate
• Titanium dioxide – inert fillers, pigments
• Calcium tungstate or barium sulphate – provides radiopacity

 

Catalyst paste –

 

• Calcium hydroxide 50% – principle reactive ingredient
• Zinc oxide – 10%
• Zinc stearate  – 0.5% – accelerator
• Ethylene toluene
• Sulfonamide – 39.5% – oily compound, acts as carrier

 

 

 

SETTING REACTION

 

Calcium hydroxide reacts with the salicylate ester to form a chelate viz. amorphous calcium disalicylate zinc oxide also takes part in the reaction

 

Setting time:  2.5 – 5.5 minutes

 

Factors affecting setting time :-

 

The reaction is greatly accelerated by moisture and accelerators. It therefore sets faster in the cavity.

 

PROPERTIES

 

Calcium hydroxide cements have poor mechanical properties. However, they are better than zincoxide eugenol.

 

Mechanical properties:-

 

Compressive strength – (10 – 27mpa after 24 hours)

It has a low compressive strength

The strength continues and increases with time

Tensile strength – (1.0mpso) is low

Modulus of elasticity – (0.37 Gpa/m2) the low elastic modulus limits their use to areas not critical to the support of the restoration.

 

Thermal properties:

If used in sufficiently thick layers’ they provide some thermal insulation. However, a thickness greater than 0.5mm in not recommended. Thermal protection should be providd with a separate base.

 

Biological properties:-

 

• Effect on pulp – The cement is alkaline in nature. The pH is high due to the presence of free Ca (OH)2 in the set cement. The pH range 9.2 – 11.7.
• Formation of secondary dentin:- The high alkalinity and its consequent anti bacterial and protein lysing effect helps in the formation of  reparative dentin.

 

Solubility and disintegration:-

 

• The solubility in water is high (0.4 – 7.8%).
• Some solubility of the Ca (OH)2 cement is necessary to achieve its therapeutic properties.
• Solubility is higher when exposed to phosphoric acid and ether so care should be taken during ‘Acid etching’ and during application of Varnish in the presence of this cement.

 

 

 

 

MANIPULATION

 

• Equal length of the two paste are dispensed on a paper and mixed to a uniform color.
• The material is carried and applied using a calcium hydroxide carrier or applicator (a ball ended instrument).
• The material is applied to the deep areas of cavity or directly over mildly exposed pulp (contraindicated if there is active bleeding).

 

 

 

 

RECENT ADVANCES

 

1. Light activated calcium hydroxide cement

 

• Light activated cements [Ca(OH)2] have recently become available. If consist of calcium hydroxide and barium sulphate dispersed in a urethane dimethacrylate resin.
• It also contains HEMA (hydroxy  ethylmeth acrylate) and polymerization activator.
• The light activated cement has a long working time and is less brittle than the conventional two paste system.

2. Calcium hydroxide root canal sealing pastes

 

These are similar to the once used for pulp capping but contain increased amount of retarders in order to extend the working time. They are being manipulated in the warm environment of the root canal.

 

Advantages are –

 

1. Effective antibacterial property without irritation
2. They stimulate hard tissue repair in the apical foramen.

 

USES OF CALCIUM HYDROXIDE:-

 

1. Direct and indirect pulp capping.
2. Apexification and apexogenesis.
3. To control infection in weeping canals.
4. An intracanal medicament.
5. Treatment of avulsed teeth.
6. Treating root fractures.
7. Treatment of perforations.
8. Treatment of intraoral external resorption.
9. Root canal filling material for primary molars.

 

Indirect pulp capping

 

In this procedure only gross caries is removed from the lesion and cavity is sealed for six weeks.

 

Indications  

 

• Teeth with deep caries, which are free from pulpitis.
• No history of spontaneous toothache.
• No tenderness to percussion.
• No abnormal mobility.
• No radiographic evidence of radicular disease.
• No internal or external root resorption  detectable radiographically.

 

Contraindication-

 

• Teeth with deep caries and symptoms of pulpitis.
• History of spontaneous pain.
• Tenderness to percussion.
• Abnormal mobility.
• Radiographically evidence of interradicular bone loss.
• Root resorption.

 

 

 

Procedure –

 

1. Removal of gross caries with large round bur or sharp spoon excavator.
2. If the procedure gives discomfort to the child, use of local anesthesia is necessary.
3. Cavity walls are extended to sound tooth structure with a fissures bur because carious enamel and dentin at the margins will interfere with establishment of adequate seal during repair.
4. After drying the cavity calcium hydroxide is placed.
5. The cavity is sealed with an interim restoration
6. The treated tooth should not be reentered for removal of residual caries for 6 – 8 weeks.
7. After 6-8 weeks, calcium hydroxide is removed and careful excavation of remaining caries is done.
8. The cavity preparation is completed, a fresh layer of calcium hydroxide is applied and the tooth is restored.

 

Direct pulp capping

 

This procedure involves the placement of a layer of protective material directly over the exposed pulp.

 

Indications: –

 

• Small pulp exposure produced during cavity

preparation i. e. pinpoint exposure surrounded by sound dentin.

• When the tooth is not painful, with the exception of discomfort caused by food intake.
• Minimal or no bleeding from the exposure site.

 

Contraindications: –

 

• Large pulp exposure.
• Prescence of caries surrounding the exposure site.
• In teeth with history of spontaneous pain.
• Excessive bleeding indicates hyperemia or pulpal inflammation.

 

Procedure –

 

1. Sterile condition should be maintained during the procedure.
2. Rubber dam application keeps the pulp free from contamination
3. Complete caries should be excavated
4. The exposure site is dried and calcium hydroxide is placed over the exposure. Dycal is material of choice.
5. The tooth is restored with on interim restoration
6. If the treated tooth is asymptomatic for 6-8 weeks a permanent restoration can be carried out.

 

 

 

 

 

Pulpotomy

 

It is defined as complete removal of coronal portion of dental pulp followed by a placement of suitable dressing or medicament that will promote healing and preserve vitality of tooth.

 

Objective

• Preservation of vitality of the radicular pulp
• Relief of pain in patients with acute pulpalgia

 

Indication

• Vital tooth with healthy periodontium
• A restorable tooth
• Absence of spontaneous pain
• Atleaast 2/3 of root length should be present
• During pulpotomy procedure haemorrhage at ampultation site should be pale red and easily controllable.

 

Contraindications 

• Irreversible pulpitis
• Swelling
• Presence of fistula
• External root resorption
• Internal root resorption
• Periapical abscess
• Presence of pulp calcification

 

Procedure

1. Rubber dam is applied
2. Access is gained into the pulp chamber
3. The coronal portion of pulp is removed with a sharp spoon excavator
4. The pulp chamber is irrigated with sterile water and is dried with sterile cotton pledget.
5. Calcium hydroxide paste is applied to the pulp stump.
6. A zinc phosphate cement base is applied
7. The tooth is restored by composite restoration or amalgam restoration.

 

Calcium hydroxide pulpotomy outcomes in primary teeth

 

• Calcium hydroxide pulpotomies in primary teeth only a 31% success. The failure of calcium hydroxide is the result of chronic pulpal inflammation and internal resorption.
• Internal resoption may result from overstimulation of the primary pulp by the highly alkaline calcium hydroxide.
• This alkaline induced overstimulation could cause metaplasia within the pulp tissue, leading to the formation of odontoclasts.
• In addition undetected microleakage  could allow large number of bacteria to overwhelm the pulp and nullify the beneficial effects of calcium hydroxide.

 

• Extra pulpal blood clots over the amputated sites interfered with pulpal healing and dentin bridge formation.
• At present the calcium hydroxide pulpotomy technique can not be generally recommended for the primary teeth owing to its low success rate. 

 

 

 Apexogenesis:

 

 

Apexogenesis is a physiologic development and formation

of the roots apex. Formation of apex in vital, young,

permanent teeth can be accomplished by implementing

the appropriate vital pulp therapy for teeth having

mechanical or traumatic pulp exposure.

 

 

 

Apexification:

 

Definition : it is a method of inducing apical closure          

by use of a suitable medicament formation of

osteocementum or a similar hard tissue or the

continued development of the roots of an

incompletely formed tooth in which the pulp is no longer vital.

Sometime, it is necessary for a dental surgeon to treat a tooth with incompletely developed roots. These immature teeth possess wide open apices called blunderbuss apices.

It is not possible to obturate these teeth by conventional methods using gutta percha and a sealer because there is no hard barrier apically against which the filling can be condensed.

The managements of these teeth is a challenging task requires patience, time, clinical skill and judgement.

 

Procedure-

 

1. Administration of local anesthesia
2. Application of rubber dam, following which access is gained through the lingual portion of the crown of the tooth.
3. Extirpation of pulp can be done using barbed droaches.
4. Remove the debris from the coronal portion of the canal using reamers and large files. Clean the canal and irrigate it with irrigating solution like normal saline.
5. Dry the canal with absorbent points-
6. Restoration of the tooth temporarily with glass ionomer or composite resin to prevent fracture.
7. Recall every six weeks.
8. Usually the calcium hydroxide dressing is changed every 2-3 months. However one-visit apexification procedures have also been shown to be successful.

 

The material used for root apex closure are –

 

• Calcium hydroxide + methylcellulose
• Calcium hydroxide + sterile water
• Calcium hydroxide + CMCP
• Calcium hydroxide + cresatin

 

Calcium hydroxide in RCT:-

 

“Sealapex” calcium hydroxide polymeric resin root canal sealer used in filling root canal

Healing at root apices of teeth occurs in 6 months after sealing of the canals with sealapex.  

 

Steps of RCT

Ê  Step 1 – access opening into tooth

Ê  Step 2 – File used to remove dead pulp, debris and bacteria

Ê  Step 3 – Examine by X-rays to ensure the instruments go exactly to the end of the root and not beyond the root

Ê  Step 4 – Paper point is used to absorb the moisture

Ê  Step 5 – Placement of medicament

Ê  Step 6 – Fill with gutta – percha point

Ê  Step 7 – Seal the root canal with crown

 

Calcium hydroxide as a cavity liner

 

Charbeneov described two forms of cavity liners

 

Cavity varnish suspension- cavity varnish are resinous solution in which calcium hydroxide – zinc oxide or other such materials on suspended.

 

Calcium hydroxide suspension – calcium hydroxide as a suspension in methyl cellulose is used as acid neutralizing and pulp capping agent.

 

Calcium hydroxide as a base-

 

Some time in pulpal injury which characterized by disruption and loss of dentin and localized pulpal inflammation calcium hydroxide is used as a base. It dissociates into limited degree of Ca++ and OH-  and accelerates the rate and degree of reparative dentin formation.

 

 

Calcium hydroxide as an  Intermediary base –

 For the purpose of Intermediary base a thicker layer of calcium hydroxide cavity base or liner is used.

 

It is used for the following three purpose –

A.  As protective chemical barrier under filled and unfilled resins.

1. When due to loss dentin the cavity is in close proximity to the pulp
2. The thickness of remaining pulpal dentin is about half mm or less.

Endodontic perforation   

 

Calcium hydroxide is used as nonsurgical treatment of the perforation detects  due to internal resorption and reported  excellent healing without any surgical  treatment

 

Use of calcium hydroxide in disinfection of root canal and also as an intracanal medicament:-

 

Its antiseptic action probably relates to its high pH and its leaching action on necrotic pulp tissue.

It causes a significant increase in the pH of circumpulpal dentin when the compound is placed in the root canal.

Calcium hydroxide paste is best used as an intracanal medicament when one anticepates an excessive delay between appointments because it is efficacious as long as it remains within the root canal.

 

 

 

 

 

 

 

 

 

 

 

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