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258 Australian Dental Journal, August, I966 * * Better dentistry made easier R. W. S. Cannon, M.D.Sc. (Melb.), D.D.S. (Tor.) For the average general dental practitioner to obtain the optimal results in dental prac- tice, knowledge in the fields listed below will this readily possible: Surgery design and the use of high speed equipment and mechanical aids. The standardized approach in the handling of dental materials and restorative procedures in the light of present day knowledge. Adequately trained and correct utiliza- tion of auxiliary personnel. To apply this, dental education, not only of the dental team but also of the patient, is most important. Patient education and motiva- tion commences as soon as the patient first enters, or is introduced to a practice. Thus, the overall surgery planning and movement patterns, both of the patient and staff, are important. The general theme should be one of relaxed but confident emciency. The modern concept of surgery design, to a greater or lesser extent, involves sit-down dentistry for the operator and his chairside assistants. This requires an appreciation of the import- ance of placement of equipment and economy of movement leading to greater efficiency. In time and motion study the classification of movements are: Class I: Movement of fingers only. Class 11: Movement of hand and wrist. Class 111: Movement of hand and forearm. Class IV: Movement of whole arm without bodily movement. *From a paper presented at the Canberra Dental Convention, August, 1965. Class V: Movement of arm plus bodily movement. The aim in working out techniques and the position of equipment, is to limit all move- ments to a Class I11 movement of approxi- mately a 154-inch radius circle (Fig. 1). Depending on the number of chairside assistants used, the type of practice, the number of surgeries worked, surgery design varies according to the individual require- ments. The trend is for a single main opera- tory, with longer appointments for restorative procedures. Surgery design today favours separate work areas for both operator and nurse, with separate hand basins so that work areas and movement patterns do not clash. For maximum efficiency and least stress for the operator efficient use of the chairside assistant is to be recommended. Figures on the efficiency of practices with and without chairside assistants show that: (1) With one nurse, increase in efficiency 35 per cent. (2) With two nurses, increase of 65 per cent. (3) With three nurses, increase from 75-82 per cent. Having three nurses, or two nurses and a receptionist, to a practice allows the use of two full-time chairside assistants. To gain maximum efficiency from one’s nursing staff, a planned surgery layout leads to efacient utilization and minimization of movement, with a resultant increase in efaciency range from 20-50 per cent, with a maintained optimal standard of dentistry over the whole day, rather than a decrease in efaciency from fatigue towards the end of the day.

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Page 1: Better dentistry made easier

258 Australian Dental Journal, August, I966

* * Better dentistry made easier

R. W. S. Cannon, M.D.Sc. (Melb.), D.D.S. (Tor.)

For the average general dental practitioner to obtain the optimal results in dental prac- tice, knowledge in the fields listed below will

this readily possible: Surgery design and the use of high speed equipment and mechanical aids. The standardized approach in the handling of dental materials and restorative procedures in the light of present day knowledge. Adequately trained and correct utiliza- tion of auxiliary personnel.

To apply this, dental education, not only of the dental team but also of the patient, is most important. Patient education and motiva- tion commences as soon as the patient first enters, or is introduced to a practice. Thus, the overall surgery planning and movement patterns, both of the patient and staff, are important. The general theme should be one of relaxed but confident emciency. The modern concept of surgery design, to a greater or lesser extent, involves sit-down dentistry for the operator and his chairside assistants. This requires a n appreciation of the import- ance of placement of equipment and economy of movement leading to greater efficiency. In time and motion study the classification of movements are:

Class I: Movement of fingers only. Class 11: Movement of hand and wrist. Class 111: Movement of hand and forearm. Class IV: Movement of whole arm without

bodily movement.

*From a paper presented at the Canberra Dental Convention, August, 1965.

Class V: Movement of a r m plus bodily movement.

The aim in working out techniques and the position of equipment, is to limit all move- ments to a Class I11 movement of approxi- mately a 154-inch radius circle (Fig. 1).

Depending on the number of chairside assistants used, the type of practice, the number of surgeries worked, surgery design varies according to the individual require- ments. The trend is for a single main opera- tory, with longer appointments for restorative procedures. Surgery design today favours separate work areas for both operator and nurse, with separate hand basins so that work areas and movement patterns do not clash. For maximum efficiency and least stress for the operator efficient use of the chairside assistant is to be recommended. Figures on the efficiency of practices with and without chairside assistants show that: (1) With one nurse, increase in efficiency 35 per cent. (2 ) With two nurses, increase of 65 per cent. (3) With three nurses, increase from 75-82 per cent.

Having three nurses, or two nurses and a receptionist, to a practice allows the use of two full-time chairside assistants. To gain maximum efficiency from one’s nursing staff, a planned surgery layout leads to efacient utilization and minimization of movement, with a resultant increase in efaciency range from 20-50 per cent, with a maintained optimal standard of dentistry over the whole day, rather than a decrease in efaciency from fatigue towards the end of the day.

Page 2: Better dentistry made easier

Australian Dental Journal, August. I966

Cabinet design and bench working heights, will depend to a large extent, whether the design is for flexibility or complete sit down dentistry. Working heights used in surgery design are, elbow height less 2-4” (Fig. 2 ) .

1. 38” plus or minus 1”.

2. 34” plus or minus 1”. 3. 28” plus or minus 1”.

259

......................... . , ,:. .............. ..... ...... ’..* r;.b’ ,,..: J ............ ... .....‘.‘A\ ... :.?; I/ ... ................., . . . . .

..”...

rt

4s. 4 b k a#

Fig. 1.-Working areas for the operator.

If possible it is advisable to have wet areas on a slightly lower level to dry areas to prevent moisture contamination of mixing areas. Bench heights must take into account the height of the equipment being used on these benches, the important height is from the operator or assistant’s elbow to the floor. Benches of a n even height and with a n easily cleaned surface are to be recommended.

A design which limits movement of operator and assistant must be carefully assessed. It is unwise to take a surgery plan and attempt to institute this into a practice unless the movements of the operator and staff are care- fully assessed or modified according to the design to allow maximum emciency.

Modern equipment trends

The posture type chair allows the operator to work in a seated position ranged, from 12 o’clock to 6.30, in relation to the patient’s head. A chair with very few, if any, controls behind the back rest, allows the patient to be placed i n a prone or semi-prone position with- out impingement of these controls on the knees and thighs. The closer the patient can be placed in this position, the better access, less salivation, and more relaxation, for both patient and operator. The ideal seating posi- tion for the operator is close to the back rest without having to bend and with thighs parallel to the floor with no sensation of undue weight on the legs. I t is recommended

D

that the assistant sit some four inches higher than the operator for better vision of the operating field, so stools should have either a footrest or be in such a position where she can obtain a footrest while working in close approximation to the chair. The operating stool most favoured today, is one which is completely mobile, flexible, comfortable, and favouring a correct postural position for both operator and the chairside assistant. Place- ment of the chair should allow complete flexi- bility of the operator and his assistant or assistants. Despite early recommendation the facing of the postural type chair towards the door is not favoured by many female patients.

Fig. 2.-Working heights and distances for the operator seated at chairside or bench.

The chair position should be such that i t does not hem the operator or the nurse into a corner, but allows easy egress and movement of nurse. Two chairside assistants allow un- interrupted concentration of the operator on the task in hand, removing the necessity to pick up instruments and change burs. With two chairside assistants the use of two high speed handpieces, allowing the changing of burs and cutting instruments ahead of time, is a great time saver. This is of particular importance in more extensive restorative procedures such as crown and bridgework.

Availability o f instruments

Modern equipment designers have attempted to produce equipment demanding a minimum of movement of the operator and nurse to

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260 Australian Dental Journal, August, I966

The dental materials used today (not neces-

(1 ) Silver amalgams. ( 2 ) Synthetic porcelains (silicate cement). (3) Golds: (a) condensing golds; ( b ) cast

( 4 ) Fused porcelain. (5) Combination of porcelain fused to

sarily in order of recommendation) are:

golds.

metal.

reach high speed instruments and working area bracket table. Examples of this are: (a) Split unit (Siemens, Kavo).

( b ) Unit with orbiting tray and handpieces attached to the movable t ray (Weber, S.S.W.).

(c) Chair with built-in high speed hand- pieces, triplex syringe and controls close to the operator and assistant’s work position (Morita, Spaceline).

Using a posture type chair with a fixed unit, a chair slide is to be recommended to allow handpieces and syringes to be kept in easy reaching distance of both operator and nurse, when working with a patient in a prone or semi-prone position. Units such as Chayes, which keeps the light and instruments in the same relative position t o the patient’s head no matter what movements up or down are made in position to the patient, is a n attempt to obviate this problem.

High speed evacuation High speed evacuation has revolutionized

and made the washed field technique possible to a much greater extent than before, as well as making the use of ultrasonic instru- ments such as the Cavitron, clinically accept- able. By using high speed evacuation, and a well-trained assistant, time saved In a half hour period may be as much a s 8 to 11 minutes. Work positions in using high speed evacuation should be assessed to give maxi- mum patient comfort, and clear field operation for the operator. In many practices the Vacu- Cup connected to a central high speed evacua- tion system is being used to replace the normal spitoon in unit design.

A knowledge of the standardized approach t o the handling of dental materials and restorative procedures

Over the last two decades, the understanding and knowledge of the available materials has increased greatly, although no new dental materials have been developed, or any material which will fill the requirements of the dental profession in all situations. The most clinically used materials are still the silver amalgams and the synthetic porcelain or silicate cements ; although neither of these materials fulfil modern requirements, they are the most used and probably the most abused materials in clinical handling

Rubber dam Rubber dam is not only a great time saver

in cavity preparation and restoration, but is essential for a dry field which is necessary in the placement of zinc containing amalgams, silicate cements, gold foil, and in endodontic procedures. The trend is to use heavy, or extra heavy, rubber dam along with a suitable water soluble lubricant, allowing easy place- ment with little or no necessity for ligatures, being held in place with rubber dam clamps. The use of Vaseline petroleum jelly is not recommended, but a water soluble base such as used in ointment bases (for example, Cetomacrogal or brushless shaving soap) may be used. If either of the latter two is used, only a thin smear should be applied to the rubber dam, and after placement of dam by using a n air syringe the water soluble lubri- cant is removed and the rubber dam tends to adhere to teeth without the extensive use of ligatures. In endodontics, the Ostby plastic rubber dam frame is recommended, and the Young or Woodbury frames for other restora- tive procedures.

Dental amalgams As with the silicate cements the fabrication

of good amalgam restorations with desirable strength, dimensionable stability and marginal adaptation depend more upon technique than upon choice of brand. Fine particle alloys are continually gaining in popularity, and give excellent results when used correctly in a dry field. The possibility that some clinicians may exert less than extreme care, and do not always place amalgam in a dry field, is a n unpleasant but unavoidable thought, but information indicating increased sales of rubber dam is a n encouraging sign that this requirement is being recognized by a n in- creasing number of operators. Silver amalgam is not the universal restorative material by any means, as i t is relatively brittle and has

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Australian Dental Journal, August, I966

a low tensile strength.(” I ts use is limited to medium and low stress bearing areas, preferably with support, although it is agreed that excellent results can be obtained using hand trituration and condensing by hand using a 6 to 8 lb. force on a 1.5 mm. amalgam condenser. These conditions a re dimcult to maintain, which would indicate the use of mechanical means of trituration and conden- sation.

There is a relationship between faulty mani- pulation procedures and failures of silver amalgam restorations. Investigation has shown tha t improper cavity preparation is the causative factor in approximately 56 per cent of all amalgam failures, while faulty mani- pulation of the alloy, or its contamination at the time of insertion accounts for approxi- mately 40 per cent of all failures.‘2) I t is thus essential that not only proper adherence to fundamentals in cavity preparation is essential, but also that careful standardiza- tion of all manipulative factors is imperative. It is desirable that any amalgam restoration be completely condensed within two minutes after trituration, as time between trituration and condensation increases, strength decreases. Amalgam older than three minutes should not be employed.@) By using mechanical mixers (Fig. 3) and condensers in a dry field this can easily be attained. The use of pre- dispensed alloy in pellet form and various types of dispensers (Fig. 4 ) are an aid in attaining optimal results using silver amalgam restorations.(’) It has been suggested that low mercury: alloy ratio (Eames technique) be used, but tests show that after 24 hours there is little to commend this technique, which although giving excellent results in the hands of some operators, is a technique which requires maximum attention to detail and correct condensing forces. Recent clinical studies have shown that bulk in itself is not as important a factor to clinical success of amalgam restorations as is careful removal of occlusal excess and proper finishing of the restoration. For optimal results in using

26 I

(1) Rodriguez, M. S., an@ Dickson, G.-Some tensile properties of dental amalgam. J. D. Res., 4 1 : 4, 840-852 (July-Aug.) 1962.

t2) McDonald, R. E., and Phillips, R. W.-Clinical observations on a contracting amalgam alloy. J. D. Res., 29: 4, 482-485 (Aug.) 1950.

(3) Phillips R. W.-Research on dental amalgams and i is application in practice. J.A.D.A., 54 : 3. 309-318 (Mar.) 1957.

(4) Lyell, J. S., and Wing, G.-Proportioning of dental amalgam. Austral. D. J., 6 : 3, 127-129 (June) 1961.

Fig. 3.

Fig. 4. Fig. 3, 4.-Examples of armamentarium for

amalgam preparation.

this material, correct proportioning, mixing and condensation without introduction of moisture(5) will result in a restoration with a relatively low residual mercury content giving optimal results. All this then points to the use of mechanical triturators a d condensers, the avoidance of moisture con- tamination and efficient chairside assistance if uniform excellent results are to be obtained.

Si I icate restorat ion The quality of silicate cement restorations

depends more on the operator and the nurse than on the choice between available brands of certified products. A cool slab, rapid in- corporation of large portions of powder to the liquid producing a truly thick mix, and pro- tection of the liquid from loss or gain of water, are of prime importance. The need for a dry field and protection of the restora- tion by a well adapted matrix held firmly

t6) Worner, H. K.-Excessive expansion in dental amalgams. Austral. J. Den., 45: 7, 161-163 (Ju ly) 1941.

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262

during initial step, and the application of cocoa butter, varnish or silicone, after initial step, is most important. Silicate cements, even in their hardened state, maintain their characteristics as gels, thus are susceptible to desiccation when exposed to air, therefore it is important to realize that they are contra- indicated for mouth breathers. Temporary desiccation also may result in loss of trans- lucency and increased solubility. Finishing of the restoration if necessary, should not be carried out for at least 24 hours, otherwise it may remove the intact surface (Fig. 5 ) and increase the likelihood of increased solu- bility.@) Strength and solubility is affected

Australian Dental Journal, August, 1966

( a ) Casting golds-A.S.T., T.12, and T.13. Table 1 gives data on various types of casting golds suitable for restorative procedures.

( b ) Condensing golds-( i ) Cohesive gold foil. ( i i ) Matt gold (precipitated gold). ( i i i ) Combination cohesive gold- pre- cipitated gold (Goldent).

The selection and use of golds can be de- termined to a large extent by: ( a ) the situation in the mouth; ( a ) the occlusal forces; (c) opposing surfaces and possible abrasive effects.

Where these causes are a factor, then a heat hardenable gold with a minimum BHN of 120 is to be recommended. Not all type ( c ) golds are heat hardenable, and in certain situations a denture casting gold may be the gold alloy of choice.

SURFACE FORMEDBY THE STRIP

SURFACE FORMED BY POLISHING

Fig. 5.-Diagram of surface differences in silicate restorations.

by powder:liquid ratio and the loss or gain of water in the liquid itself. Increased humi- dity may result in more rapid setting so that controlled atmospheric conditions are desir- able. Air conditioning may be necessary to achieve uniform conditions for the correct handling of dental materials. A standardized mixing technique relies heavily on the nurse being fully informed on the effects of incorrect powder: liquid ratio, moisture, and the neces- sity of correct mixing techniques, using a slab kept near the dew point if optimal results are to be obtained.

Golds

Despite a common misconception, there is not one type of gold which covers every situation occurring in restorative dentistry. Golds may be divided into:

(e) Paffenbarger, G. C.-Silicate cement and amalgam fillings, in Current advances in dentistry. Urbana, Illinois, The University of Illinois Press, 1950-51.

Condensing golds

With the introduction of the Hollenbach automatic mallet, the electro mallet of McShirley, and a n improved understanding of gold foil, the condensed gold restoration now has a very important place in restorative dentistry. I t is indicated, particularly for cavities where there are minimal external forces which would cause the restoration to wear or become dislodged, for example, Class I, Class 111, and Class V, restorations.

Gold foil should not be used where there is the possibility of the failure in marginal integrity, for example, where the margin will terminate on decalcified enamel, or in a mouth where the caries index is high. For rapid build-up of bulk, matt gold or combination gold may be used, but because of density and con- touring for tissue tolerance, i t i s usually better to finish off such a restoration with cohesive gold foil. This to my knowledge is the only gold restoration giving, when cor- rectly condensed, a VPN of 90 (compared with 24 when incorrectly condensed) which can be carried out in one visit. With efficient chair- side assistance, such a restoration can be pre- pared and inserted within a 20 to 30-minute appointment, giving a restoration with ex- cellent tissue tolerance, and has been clinically proven over the years.

Porcelain With its excellent tissue tolerance, porcelain

still has a n important place in restorative dentistry. Clinically, it must be remembered

Page 6: Better dentistry made easier

Australian Dental Journal, August, 1966

Type of gold

263

Elongation Temperature B.H.N. per cent.

TABLE 1

A B C

Denture casting gold

Min. 940°C Min. 40-75 Min. 900°C Min. 70-100 Min. 900°C Min. 90-140 Min. 900°C Soft min. 100

Hard min. 190

Min. 18 Mill. 12 Min. 12 Min. 10 Min. 2

that porcelain has a much higher surface hardness when glazed, than either gold or enamel, this must be taken into consideration in treatment planning. Clinically a better result is obtainable if the final staining and glazing is carried out with patient present. This can be easily achieved by including in every office, a simple air firing furnace.

sso.cwR 30 YINS. n

AS chsr I I FIRST SECONO L y J ( E B * l ( t

THIRD M

F W T H e4RE

FIFTH BARE

Fig. 6.-Temperature effects on hardness of gold used in porcelain-gold combinations.

Porcelain fused to gold With the advent of porcelain fused to gold,

it is most important where any occlusal forces or abrasive effects may be transmitted to the gold, that a heat hardening procedure be carried out. Despite earlier suggestions, the gold does not normally harden sufficiently during baking procedures. The recommended hardening procedure for most of these alloys is 550" C. for 30-60 minutes after final baking and soldering (Fig. 6).

Impression materials As in all clinical procedures, a standardized

approach to the handling of impression materials is most important. With particular reference to the now commonly used thiokol and hydrocolloid materials.

Thiokol (rubber base impression material) : In mixing these materials, it must be realized that any increase in humidity or addition

of moisture will decrease the setting time. A standardized mixing procedure should be carried out. The recommended mixing time being approximately 45 seconds.(7) The differ- ence between setting time of a light bodied and heavy bodied thiokol material, is usually 3 to 4 minutes; this time allows the mixing or injection of the light bodied first, with its placement in syringe, before mixing the heavy bodied material to be placed in the tray. The importance of correct mixing of this material, avoiding incorporation of a i r into the mix, cannot be over-emphasized if optimal results are to be obtained. The models should be poured immediately the impression is removed from the mouth, if maximum accuracy is to be gained.

Hydrocol loid: This material requires, more than most others, a careful check on pro- cedures, particularly in preparing, storage and tempering prior to use. A hydrocolloid condi- tioner or water bath along with water cooled trays is a necessary pre-requisite i f this technique is to be used. Recommended temper- atures and heat treatment are:

(1) Boil material for 8 minutes. When being re-used 10 minutes.

(2) Storage 145°-1500 F. (3) Tempering bath 110"-112° F. for 5-10

After impression is removed from mouth,

minutes.

model should be poured immediately.

Crown and bridgework In crown and bridgework the close co-

operation and teamwork between the tech- nician and the dentist is necessary, com- mencing with the preparation of study models which can be used for: ( a ) diagnosis and treatment planning; ( b ) cavity preparation; ( c ) the diagnostic wax-up.

(7) Skinner, E. W., and Cooper, E. N.-Desirable properties and the use of rubber impression materials. J.A.D.A., 51: 5, 523-536 (Nov.) 1955.

Page 7: Better dentistry made easier

264 Australian Dental Journal, August, I966

the assistant on the right of the patient is responsible for handing instruments, changing burs, and relieving the operator in any way possible. The assistant on the left is respon- sible for high speed evacuation, patient com- fort, and tissue protection. Time of cavity preparation can be made considerably less by the use of two high speed handpieces.

In equipping a practice, i t should be realized that any equipment which will save a nurse or technician time, increases efficiency. The main centre in any practice is the surgery, and it should have modern equipment appro- priate for the type of treatment offered. An ultrasonic cleaner is useful in the cleaning of instruments, diamonds, cutting instruments, trays, and burs, not only saving time in cleaning, but in the case of diamond cutting instruments maintaining their cutting effi- ciency over a longer period.

A well fitted-out dark room is an essential part of any practice management plan. It should have both wet and dry areas and water circulation deep tank with automatic drainage and washing. Safety lights a t the correct distance mean more uniform develop- ment and overall better results.

This allows pre-planning of surgical pro- cedures and cavity preparation for the indi- vidual case.

Time of cavity preparation can he reduced considerably by the use of two high speed handpieces. This makes i t possible for burs and cutting instruments to be ready for use, ahead of time. Quadrant preparation should be carried out in such a manner that each individual step is taken on each tooth, t o prevent unnecessary change over of burs and cutting instruments. In procedures where temporary crown protection is necessary, the preparation of these may be carried out by the technician or nurse.

Temporary crown forms may be: (a) aluminium; (Kri ) ; ( b ) tin (Surgident); ( c ) stainless steel (Rocky Mountain) ; ( d ) Pella crowns: ( e ) fabricated temporary crowns and bridges.

Training and utilization of auxiliary personnel All techniques both in surgery and office

procedures should be recorded, allowing con- tinuity with staff changeover. In the surgery, tray set-ups using colour tabs, save time usually lost in setting up. Work positions should be worked out according to whether one or two assistants are used.

With multi-instrument techniques, such as i n endodontics and oral surgery, the tray should be brought from the rear of the patient. I t is advisable that the patient is not con- fronted with an array of instruments on entering the surgery.

In restorative dentistry when carrying out the quadrant concept, and using two assistants,

Summary To attain and maintain optimal dentistry,

a standardized approach and close attention to detail is a must. This is facilitated by improved conditions and a complete under- standing within the dental team as a whole.

2 Collins Street, Melbourne, Vic.