WO1997025932A1

WO1997025932A1 - Carpule® for an intraligamentary syringe

Info

Publication number: WO1997025932A1
Application number: PCT/US1997/001211
Authority: WO
Inventors: Eliezer Kaufman
Original assignee: Davidson, Clifford, M.; Hadasit Medical Research Services & Development Co., Ltd.
Priority date: 1996-01-18
Filing date: 1997-01-14
Publication date: 1997-07-24
Also published as: AU1839597A; IL116815A0

Abstract

The invention provides a carpule® (10) for an intraligamentary syringe (23, 24), the carpule® (10) having a bore (12) diameter of between 5.0 mm to 6.3 mm.

Description

CARPULE® FOR AN INTRALIGAMENTARY SYRINGE

The present invention relates to a high-pressure dental carpule® for containing a liquid anesthetic or anti-inflammatory drug and to a needle for use in conjunction therewith.

More particularly, the invention provides a high-pressure dental carpule® in the form of a disposable dispenser for local anesthetic solutions as well as for delivery of anti-inflammatory drugs, and lo a disposable needle designed to penetrate the dental alveolar crest via the gingival sulcus, for use in a pressure dental syringe used in intraligamentary (PDL) anesthesia, for more efficiently depositing the local anesthetics or drugs into the site of action.

BACKGROUND OF THE INVENTION

Local anesthetic solutions are the most injectable drugs in medicine and dentistry. Almost all dental procedures performed today are accompanied by a local anesthesia injection for pain control. Traditionally, local anesthesia injection is performed either by local infiltration or by a regional nerve block. The volume injected for one tooth in one treatment session varies from 1.8 cc up to 5.4 cc, depending upon the nature of the procedure. There is an onset time of 5- 15 minutes before nerve block is in effect. A side effect associated with local anesthesia is the subjective numbness of surrounding tissues such as tongue, lips, cheek and other perioral skin, which sometimes creates postoperative inconvenience.

In the 1980's a new method, intraligamentary local anesthesia, was developed. In this technique, the local anesthetic is injected by a pressure syringe into the gingival sulcus to the crestal and periapical cancellous alveolar bone. In this procedure, significantly less anesthetic volume (0.2-0.8 cc) is required for the same clinical effect, and onset is instantaneous. Another advantage characteristic of this injection over the traditional local anesthesia is the total absence, or only minimal subjective numbness, ofthe tongue and perioral skin.

Both techniques [i.e., traditional and intraligamentary (PDL)], use the same dental carpule® which has remained basically unchanged for over 70 years. Achievement of high injection pressure has been made possible by the development of pressure syringes (pistol-like, pen-like and hydraulic) having a mechanical advantage ranging from four to one, to six to one. Such high pressure not infrequently shatters the glass carpule®.

Kaufman, in "Transligamentary Anesthesia: A Review, Anesthesia and

Pain Control," Dentistry, Vol. 2, No. 3, (1992) includes a discussion of cartridge breakage during injection:

"The protective sleeves now available in some devices prevent the shattered glass from entering the patient's oral cavity. However, the sudden noise of fracture accompanied by the need to withdraw, recharge the syringe and reinject are quite discouraging to both the patient and the operator. The more experienced an operator becomes, the less likely it is for breakage to occur. A new device, Ultraject, which limits the pressure applied on the cartridge by a clutch-like mechanism, may be one ofthe solutions ..."

When the cartridge is made of glass, the problem of carpule® breakage in response to internal pressure is sometimes experienced, and the present invention inter alia, comes to alleviate this problem.

It is therefore one of the objects of the present invention to obviate the disadvantages of the prior art carpule® and to provide a carpule® for containing a liquid anesthetic which requires less force for its operation and is thus easier to use, and is yet able to generate the required pressure for the administration of intraligamental anethesia.

It is a further object of the invention to provide a carpule® more suitable for a slower injection rate and which will thus avoid causing post-operative pain due to too rapid injection.

A still further object of the invention is to provide a carpule® more resistant to breakage under hydraulic pressure during injection.

The present invention achieves the above objectives by providing a carpule® for an intraligamentary syringe, the carpule® having a bore diameter of between 5.0-6.3 mm.

In preferred embodiments of the present invention, the carpule® will have an inner bore diameter of between 6.26-6.0 mm. In especially preferred embodiments, the carpule® will have an inner bore diameter of between about 5.5-5.0 mm.

In most preferred embodiments of the present invention, there are provided carpules® made of materials having enhanced strength, such as a strengthened glass and a sulfone polymer, and a carpule® wall made of two layers, the inner layer being of glass and the outer layer being of plastic.

In a further aspect of the present invention, said improved carpule® is used in conjunction with a needle having a diameter in the range of 25-27 gauge. In a preferred embodiment of said aspect of the present invention, said needle will preferably be provided with a needle-tip surface having a flat cross- section.

In a further preferred embodiment of said aspect of the present invention, said needle will preferably be provided with a needle-tip surface having a concave cross-section.

Preferably, said needle tip will be blade-like, rather than point-like.

The invention also provides a syringe for intraligamental dental treatment, provided with a carpule® having a bore diameter of between 5.0-6.3 mm.

In a further aspect of the present invention, the carpule® is used to inject a dental anti-inflammatory drug.

As is known, pain usually accompanies dental care. Alleviating pain in the oral cavity is a challenge for the dental profession, necessitating development of new modalities for alleviating acute orofacial pain. Acute pain is usually a sequel of tissue insult due to infection or surgical intervention leading to inflammation. Inflammation is characterized by pain, edema hypothermia and loss of function. These clinical manifestations are triggered by a cascade of numerous biochemical substances (such as prostaglandin, bradykinin, substance P and histamine) which are excreted by injured cells.

Drugs which block the action or the synthesis of inflammatory mediators should possess analgesic activity for pain of inflammatory origin. Non-steroidal anti-inllammatory drugs (NSAIDs) are potent analgesics which exert their peripheral action through blockage of prostaglandin synthesis. Oral administration is currently the accepted route for these drugs in the dental environment. However, the disadvantages of a prolonged onset time and gastrointestinal adverse reaction make this method far from ideal. Injection of these drugs into the inflamed area bears the potential for rapid pharmacological onset (analgesia), decreasing the total dose and avoiding the side effects associated with oral intake.

BRIEF SUMMARY OF THE INVENTION Thus, according to the present invention, it is now possible to modify the existing technology (periodontal ligament injection) used for injection of local anesthetic drugs to the pcriapical areas of teeth for deposition of injectable steroidal and non-steroidal anti-inflammatory drugs around inflamed teeth. Slow release injectable steroidal and non-steroidal anti-inflammatory drugs are preferred. These drugs are more viscous than local anesthetics,.

A first requirement of the invention is therefore the modification of the carpule® to withstand the high pressure generated during injection without breakage. Then, an improvement must be made in the dentist's ability to better control the rate of drug deposition into the tissue, through an improved mechanical advantage of the carpule®. The present invention accomplishes this objective by decreasing the container bore to still fit the existing syringes, and thus supplies the denial profession with a completely new and powerful tool for the quick and effective alleviation of pain.

A by-product of the present invention is the improvement o the periodontal ligament anesthetic technique, enabling the operator to deposit the local anesthetic solution in a more controlled manner. Said improvement prevents the common adverse effects associated with the current periodontal ligament technique. The disadvantages of the technique, such as initial tissue resistance resulting from an effort to inject, carpule® breakage during injection, and post¬ operative pain due to too rapid injection, are eliminated by the improvement of the present invention. Thus, dental periodontal ligament injection according to the present invention could become a very desirable method in pain-free dentistry.

A preferred steroidal anti-inflammatory drug for use in conjunction with the carpule® of the present invention is Methylprednisolone Depomedrol® (Upjohn), and preferred non-steroidal anti-inflammatory drugs for such use are selected from the group consisting of Flurbiprofen acetyl Fat-emulsified Preparation Ropion® (Kaken Pharmaceutical), Kerorlac Thromethamine [Toradole®] and Diclofenac sodium [Voltarol®] (Ciba-Geigy).

The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood.

With reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention. the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

Fig. 1 is a sectional view of a preferred embodiment of the carpule® according to the invention; Fig. 2A is an elevational view of a pen-like syringe for using said carpule®; Fig. 2B is an elevational view of a pistol-like syringe for using said carpule®; Fig. 3 is a sectional view of an embodiment of the carpule® provided with a wall made of two layers of different materials; Fig. 4A is an enlarged, perspective view of a needle for use in combination with the carpule® of the present invention; Fig. 4B is an enlarged, perspective side view of the needle shown in Fig. 4A. and Fig. 5 is an enlarged end view of a preferred needle tip.

DETAILED DESCRIPTION

There is seen in Fig. 1 a carpule® 10 for an intraligamentary syringe of the type illustrated in Fig 2. The carpule® 10 has a bore 12 with a diameter of between 5.0-6.3 mm, preferably between 6.0-6.26 mm. Carpules® having a bore diameter of at least 6 mm can be used in currently-used syringes in place of the currently-used carpules® which have an inner bore diameter of at least 6.45 mm. Thus, e.g.. a carpule® having an inner diameter of 6.02 mm can be used in the pen-type syringe of Fig. 2A, while a carpule® having an inner diameter of 6.12 mm can be used in the pistol-type syringe of Fig. 2B.

The reduction in bore diameter results in a number of important benefits. The injected fluid flows more slowly because of hydraulic decrease in piston diameter. The dental surgeon has more control and is required to exert less effort during the injection. Consequently, overly- rapid injection and excess volume are prevented, and the patient feels less post-operative pain.

The carpule® wall 14 has a thickness of between 1.20-1.24 mm. and in a first embodiment is made of glass.

Preferably, wall 14 is strengthened by thermal tempering. This process has been used many decades, and operates as follows: The carpule® is heated and then cooled. The outer surfaces cool faster than the interior; thus, the glass near the outer surface becomes rigid before the glass in the interior does. As cooling progresses to room temperature, the interior contracts over a larger temperature range and, in so doing, imposes a compressive stress on the glass near the surface.

When the carpule® is in use, before carpule® wall rupture can take place, the wall must be subjected to a tensile force high enough to overcome this compressive force, in addition to the normal wall strength. Typically, a strength

2 of 1 ,400 kg/cm is achieved by thermal tempering.

In a further embodiment, the wall 14 is made of a lithia-silica glass, and is chemically strengthened. This newer method operates by the one-for-one exchange of some sodium ions for the existing lithium ions. The glass carpule® is immersed in a molten salt bath containing the desired alkali-metal ions. As the sodium ions are considerably larger than the lithium ions near the glass surface which they are replacing, the glass structure becomes crowded by the new larger ions, and the surface area is consequently in compression. Chemical strengthening results in a glass tensile strength of at least 3,500 kg/cm^". In a further, similar embodiment, the carpule® is made of a sodium-silica glass and is chemically strengthened by the exchange of some potassium ions for existing sodium ions. The glass strength achieved is similar, i.e. at least 3,500

2 kg/cm .

Whichever method of strengthening is used, the benefit lies in opening the possibility of using a thinner carpule® wall, typically in the range of between 1- 1.2 mm, and, more importantly, in providing assurance against carpule® rupture even under pressures far in excess of those normally encountered.

While glass is considered to be chemically inert, it is far from being an ideal material for use as a cylinder under internal hydraulic pressure. Accordingly, in a further embodiment, the carpule® is made of a plastic, preferably a sulfone polymer. These polymers have a tensile strength of 840

2 kg/cm and are rigid and dimensionally stable. Their high heat resistance makes sterilization possible. The natural material transparency is useful for giving a visual indication of contents. These materials have an elongation at break of at least 40%, so that even in the unlikely case of carpule® failure, the failure is of the ductile type and no fragments are generated.

The carpule® shown has a rubber piston 16 having a free diameter of about 6.2 mm and a length of about 6.9 cm. The carpule® is sealed by a 1.5 mm thick rubber plug 20. Prior to use, the plug 20 is pierced by an 0.3 mm chamfered and hollow needle (not shown); the direction of the needle insertion into the carpule® is through the plug 20. The plug 20 is held to the carpule® by a reinforcing aluminium crimp sleeve 22. It is envisioned that, at a later stage of development, manufacturers will be persuaded to produce syringes specially adapted to receive the improved carpule® of the present invention, at which time carpules® having a bore diameter of from 5.5-5.0 mm will be preferred.

Table 1 compares the carpule® of the present invention to the conventional carpule®:

TABLE 1

Conventional Present Invention

Bore diameter, cm 0.650 0.50

Bore cross-sectional area, cm^ 0.332 0.198

Force required for 20 kg/cm^ pressure (ignoring friction) 6.64 kg 3.96 kg

Length of stroke needed to inject 0.4 mL 1.2 cm 2.02 cm

It is evident that, although the bore diameter has been reduced by only 23%. the required operating force has been reduced by 40%.

Referring now to Figs. 2A and 2B, in which like numerals have been used to describe like parts, there are seen respectively a pen-like syringe 23 and a pistol-like syringe 24, adapted for use with the carpule® described in Fig. 1. In the embodiment shown in Fig. 2B, the piston rod 32 is designed to enter a bore having a diameter of smaller than 6 mm, and preferably about 5 mm. Otherwise. the syringe is of conventional design, the main components comprising operating lever 28, needle screw-on device 30 and piston rod 32.

Referring now to Fig. 3, there is seen an embodiment of a carpule® 34. provided with a wall made of two layers of different materials 36, 38. The inner layer 36 is made of glass, thus providing inert long-term safe storage for the solution contained therein. Outer layer 38 is made of a plastic, which is assembled to inner layer 36 by use of a shrink fit, or by other available industrial assembly methods. The outer layer 38 thus greatly improves shatter resistance. If. however, the glass does break, the glass particles are safely contained within the outer layer plastic sleeve 38.

The thickness of the plastic shrink sleeve is preferably chosen to maintain the outer diameter of the carpule® to the same dimensions as found on the prior art carpule®, as shown in Example 1 :

EXAMPLE 1

mm

Carpule® bore diameter 5.0

Two glass walls, 1.2 mm each 2.4

Two 0.64 mm walls of plastic sleeve 1.3

Total outer diameter 8.7

Length of stroke needed to inject 1 mL: 50.5 mm Figs. 4A and 4B illustrate a needle 30 for use in combination with the carpule® of the present invention (not shown) and with the pistol- or pen-type syringe shown in Figs. 2A and 2B, for administration of intraligamentary anesthesia. Preferably, needle 30 has a diameter in the range of 25-27 gauge. The plastic or metallic syringe adapter 48 has an internal thread (not shown), to match the thread 50 as shown in Figs. 2A and 2B, for assembly thereto.

Needle 30 is provided with a needle tip surface 52 which has a concave cross-section. The concave shape matches the anatomical convexity of dental roots, and provides good tissue-penetration guidance.

Fig. 5 depicts an enlargement of needle tip 54, formed by a bevel forming an orifice 58. Blade thickness and orifice height are each about 0.08 mm. In operation, the orifice directs the anesthetic solution into the crestal bone of the patient without leakage.

In a further embodiment (not shown), the tip extremity has a blade-like, flat cross-section. The flat shape is preferred by some users as providing better needle mobility, in comparison to the conventional convex surface.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the essential attributes thereof, and it is therefore desired that the present embodiments be considered in all respects as illustrative and not restrictive, reference being made to the appended claims, rather than to the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

WHAT IS CLAIMED IS:

1. A carpule® for an intraligamentary syringe, said carpule® having a bore diameter of between 5.0-6.3 mm.

2. A carpule® as claimed in claim 1, wherein said bore diameter is between 6.0-6.26 mm.

3. A carpule® as claimed in claim 1, wherein the wall of said carpule® has a thickness of between 1.20-1.24 mm.

4. A carpule® as claimed in claim 3, wherein said wall is made of glass.

5. A carpule® as claimed in claim 4, wherein said wall is strengthened by thermal tempering.

6. A carpule® as claimed in claim 4, wherein said wall is made of a lithia- silica glass, and is chemically strengthened by the exchange of some sodium ions for existing lithium ions.

7. A carpule® as claimed in claim 4, wherein said wall is made of a sodium- silica glass and is chemically strengthened by the exchange of some potassium ions for existing sodium ions.

8. A carpule® as claimed in claim 4, wherein said wall is strengthened and has a thickness of between 1-1.2 mm.

9. A carpule® as claimed in claim 1, wherein the wall of said caφule® is made of a plastic.

10. A caφule® as claimed in claim 9, wherein said wall is made of sulfone polymer.

1 1. A caφule® as claimed in claim 1, wherein the wall of said caφule® is made of two layers, the inner layer being made of glass and the outer layer being made of a plastic.

12. A syringe for intraligamental dental treatment, provided with a caφule® having a bore diameter of between 5.0-6.3 mm.

13. A syringe for intraligamental dental treatment as claimed in claim 12, further comprising a needle having a diameter in the range of 25-27 gauge.

14. A syringe for intraligamental dental treatment as claimed in claim 13, wherein said needle is provided with a needle-tip surface having a concave cross- section.

15. A syringe for intraligamental dental treatment as claimed in claim 13, wherein said needle is provided with a needle-tip surface having a blade-like, flat cross-section.

16. A syringe according to claim 12, wherein said syringe is a pen-like syringe.

17. A syringe according to claim 12, wherein said syringe is a pistol-like syringe.

18. A syringe according to claim 12, in combination with a caφule® containing an anti-inflammatory drug.

19. A syringe according to claim 12, in combination with a caφule® containing a local anesthetic solution.