Slot Prep Dentistry

Slot Prep Restorations Home/Blog / Slot Prep Restorations. November 17, 2020 (Afternoon tea pics 1416.2: Voco Grandio SO). See all Dental Services.

These may or may not be included in an actual appointment book. These slots are prep and seating, dismissal of the patient, and disinfection of the operatory. The dental assistant is primarily responsible for these required functions. Operatory appointment booking.
Slot preparation – done in cases where there is a proximal lesion without the involvement of the occlusal surface. With a small round bur access is gained to the proximal lesion from the lingual or the buccal side and caries excavation is done, the cavosurface margins are kept at 90º or more.
“slot” preparation. Modified class II cavity design for the. placement of RMGIs. CLASS II PREPARATION COMPARISON. AMALGAM - 0.5 mm into dentin - no cavo-surface bevel - 0.5 mm prox.clearance - isthmus 1.0+ - no gingival bevel - occlusal dovetail. COMPOSITE - 0.5 mm into dentin - cavo-surface bevel - 0.5 mm prox.

OUTLINE FORM:

G .V. Black has described the outline form as being “the form of the area of the tooth surface to be included within the outline or enamel margins of the finished cavity”. It is the placement of cavity margins in the positions they will occupy in the final preparation, except for finishing enamel walls and margins and preparing an initial depth of 0.2 – 0.8mm pulpally of DEJ or normal root surface position.

Two outline forms can be appreciated

External outline form-which dictates the external perimeter of the outline form.
Internal outline form-which dictates the inner dimension and detail of the cavity.

The factors that determine outline form are the following:

Extent of the carious lesion.
Extend the cavity margin until sound tooth structures obtained and no unsupported enamel remains.
Margins should be paced in easily cleansable areas.
Average depth of the cavity should be 0.5 mm into dentin.
Extend the cavity margins into fissures that cannot be eliminated by appropriate enameloplasty.

PIT AND FISSURE CAVITIES

The general factors mentioned above are to be followed. In addition the following are considered:
Avoid terminating the margin on extreme eminences such as cusp heights and ridge crests.
Circumventing of cusps should be followed resulting in a smooth free flowing outline form.
In case of conservative cavity preparation shallow supplemental grooves and fissure crossing lingual or facial ridge can be eliminated by enameloplasty.
When two pit and fissure cavities have been separated by less than 0.5 mm of sound tooth structure, they should be joined to eliminate a weak enamel wall between them.

PROXIMAL SMOOTH SURFACE CAVITIES

Occlusal cavity outline is same as above.

Gingival margins

According to G.V.Black’s concept the gingival margin should be placed 0.5 to 1.0 mm apical to the crest of healthy free gingival. Because this area was thought to be sterile due to the alkalinity of crevicular fluid and less chances of food impaction in this area, moreover the knife edge relationship of the healthy free gingival to the adjacent tooth surface will discourage food accumulation on the adjacent restored surface occlusal to the sulcus for considerable periods during and after food ingestion. But, Dr. John Me Call has shown that mechanical causes, systemic conditions and traumatic occlusion change the alkalinity of the crevicular fluid to an acidic form making it more prone to aciduric environment.

Emphasis is made to place the margin occlusal to or just clear of the margin of the gingival crest.

Facial margin and lingual margin

The following factors govern them:

Flare and mesiodistal width of embrasures.
Wider and more flared the faciolingual embrasures are, less are the chances of food accumulation and therefore requires less extension facially and lingually.
Caries index and oral hygiene.
Faciolingual extension of the cavity in the corresponding embrasure is directly proportional to the caries index.
Occlusal and masticatory forces.
The more ideal the relationship between the adjacent and opposing teeth is, the better is the cleansability of the facial and lingual embrasures. Therefore, less extension is required.
Age of patient and tooth structure and attrition of contact areas.
An older tooth has higher fluoride content, is more resistant to caries and requires less extension.
Creation of a more convex restoration.
More convex restorations lead to wider embrasures and therefore less extension and better self cleansable areas.

Gingival margin is placed as in class II cavities. In young patients the margin is covered by the gingival whereas in patients with gingival recession the margins are kept supragingival. The mesiodistal extension is obtained considering the occluso-gingival convexity, occlusion and masticatory forces, caries index, and age of the patient.

Occlusal extension should not include the height of contour of facial and lingual surfaces.

MODIFICATIONS DUE TO THE TYPE OF RESTORATIVE MATERIAL

AMALGAM:

With the introduction of modern alloys, the modern concept of cavity preparation can be compared to the conventional G V Black’s design which are less time consuming, conserving and with decreased chances of failure.

CONVENTIONAL

OCCLUSAL PORTION- extension for prevention, mortise shaped with definite line angles and point angles.
PROXIMAL PORTION– either box type or truncated cone.
ISTHMUS-will not exceed 1/3rd intercuspal distance, atleast 1.5mm.
SWEEPING CURVES-given to the proximal and occlusal walls where they meet.
ACCESSORY RETENTION– proximal grooves are not so critical.

MODERN

OCCLUSAL PORTION:

More conservative approach. Here G V Black’s concept of extension for prevention does not apply.
Going around the cusps to conserve tooth structure.
Not extending the facial and lingual more than midway between the central grooves and cusp tips.
Using enameloplasty on the terminal ends of shallow fissures to conserve tooth structure.
Margins of the facial and lingual class I involve the entire facial and lingual groove to avoid feather edged marginal amalgam.

PROXIMAL PORTION:

Only a unilateral inverted truncated cone on functional side of marginal angles to preserve tooth structure. The gingival margin should be located occlusal to the height of contour.

ISTHMUS:

Not to exceed 1/4th intercuspal distance.

SWEEPING CURVES:

Universal sweeping curve is exaggerated and more bulk is accommodated.

ACCESSORY RETENTION:

Proximal grooves are used more often due to limited occlusal width.

TOOTH COLORED RESTORATIONS

Emphasis is more on conservative tooth preparation. G.V.Black’s concept of “extension for prevention” does not apply. With the introduction of acid etching phenomena by Buonocore, coupled with the use of synthetic resins has revolutionized the concept of cavity design.

Butt joint marginal configuration and placement of floor in dentin for retention were the characteristic features of conventional method. The modern concept is to include all faulty areas and conserve more tooth structure. Floor is not routinely placed in dentin. It depends on the caries extent and depth. Bevel is given on the enamel cavosurface margin. As in the conventional types, when a butt joint is made, a white halo is seen after the restoration is complete. This can be avoided by beveling the margin.

The ends of the enamel rods are more effectively etched than when only the sides are exposed to the etchant.

In case of composite resins the contact area should be maintained, left untouched as this material cannot maintain contact integrity, these materials can accommodate undermined enamel as long as it is not carious, discolored directly loaded in centric or eccentric contact or cracked.

CAST GOLD RESTORATION

The main characteristic feature in these restorations is taper and bevel incorporation in the outline form. The gingival to occlusal divergence of these cavity walls may range from 2 to 5 degree taper on each wall. The taper should be minimum in shallow cavities for better retention and resistance. The taper should be more in deep cavities for proper seating of the restoration. The taper prevents the undisturbed withdrawal of the wax pattern and subsequent seating of the casting.

Resistance form may be defined as that shape and form of cavity walls that best enable both the restoration and the tooth to withstand occlusal forces without fracture.

Fundamental principles involved are:

Box shape or mortise shaped with flat floor, which helps the tooth to resist occlusal loading by virtue of being at right angles to the forces of mastication.
Slightly curved than acute line angles decrease the stress concentration of stresses and hence reduce the incidence of fracture.
Conservation of strong cusps and ridges with sufficient dentin support. Weakened areas should be included in cavity preparation to prevent fractures (capping of the weakened cusps).
To provide enough thickness of restorative material to prevent fracture under load.
Slight roundening of the line angles to prevent stress concentration.

STRESS PATTERNS OF TEETH

According to Gabel application of mechanical principles to the design of restorations will help conceive favorable stress patterns for the teeth and the restorations. These principles vary according to the type of restoration and cavity.

TYPE OF RESTORATION:

The minimal thickness of amalgam and cast gold to resist fracture is approximately 1.5mm, though a little more depth is required for amalgam to achieve the requisite bulk. However in composite and glass ionomer, the depth is not the criteria for achieving resistance form. Porcelain also requires a depth of 2mm for inlays and 1.5mm for crowns.

Slot Prep Dental

TYPE OF CAVITY:

CLASS I:

A flat pulpal floor is appropriate. In case of deep caries where a rounded pulpal floor may result, the stress is doubled in the deepest portion of the cavity. Fractures in these rezsstorations are due to insufficient dentinal thickness in the center. Bending stresses are proportional to square of depth. Therefore for large restorations depth should be increased with increase in diameter.

CLASS II:

A proximo-occlusal inlay restoration acts like a curved beam of cantilever type. Due to differences in modulus of elasticity of dentin and the material there will be displacement of the restoration in the gingival seat area with the axio-pulpal line angle as axis of restoration. This is prevented by a lock in the form of groove pins, etc in the gingival floor. In M.O.D. cavity axio-pulpal line angle should be more rounded.

CLASS III:

Due to the thickness of incisal edge the cavity is extended lingually as close to the incisal edge as possible.

CLASS V:

The functional cusp and functional fossa relationship dictates the stress pattern.

EFFECT OF GROOVES:

Grooves provide resistance to a certain degree. Courdadee and Jimmerman have shown that localized areas of stress are produced in tooth tissue by provision of supplemental intracoronal retention in the form of pins.

In this monthly feature, Dr. Gordon Christensen addresses the most frequently asked questions from Dental Economics readers. If you would like to submit a question to Dr. Christensen, please send an email to info@pccdental.com.

Question...

Frequently, I see patients who have interproximal caries, but no occlusal caries on the same teeth. I use the Kavo DIAGNOdent, and I feel relatively confident that only interproximal carious lesions are present. I thought the G.V. Black Classification I meant that Class I was the most commonly occurring lesion. Why am I seeing interproximal caries and no occlusal caries, and what type of restoration is indicated for these lesions? Should I be placing typical Class II restorations in these situations?

Answer from Dr. Christensen...

You are not the only person seeing the clinical situation you described, and yes, G.V. Black did number the types of dental caries as Class I through Class IV, based on the most commonly occurring to least commonly occurring lesions. But caries activity has changed since G.V. Black's classification system was accepted. Animal and human research has shown that due to the widespread use of many methods to carry fluoride to teeth, occlusal surfaces have fewer grooves, and carious lesions are observed less frequently than without the use of fluoride. It is a fact that many posterior teeth have interproximal caries and no occlusal caries. I assume that the occlusal surfaces have some immunity to caries due to their fluoride content and relatively natural self-cleansing characteristics because of chewing food. On the other hand, the interproximal surfaces in the same mouth may have significant plaque and debris which probably overwhelms the fluoride resistance on the interproximal surfaces. This condition often is observed in teenagers as they go through their normal maturation, eating significant quantities of junk food and often resisting instruction from authority figures such as dentists or parents.

What should be done with these carious lesions? Proximal slot preparations are indicated. These preparations may be approached from the facial surface of the tooth if the tooth is fully erupted and has a long clinical crown. A challenge with the facial approach is the necessity of placing a metal matrix strip between the teeth as the facial slot preparation is made to avoid nicking the adjacent tooth. If the gingiva is not receded and the clinical crown is short, I suggest an occlusal approach for the slot preparation. This preparation looks like the proximal slot of a Class II tooth preparation without an occlusal cut.

The profession is using bonding agents routinely; however, they have questionable resistance to debonding. In these small preparations, I still suggest some mechanical retention should be placed with a small round bur (1/2-inch or 1/4-inch size). The preparations can be easily restored with resin-based composite. The result is a MO, DO, FM, or FD restoration, with the patient fee the same as a more aggressively cut Class II. If I had such a carious lesion in my own mouth, I would prefer to have the slot restoration instead of a typical Class II restoration. I also would prefer a facial approach instead of an occlusal approach, if possible, since the occlusal restoration is subjected to more wear than the proximal restoration.

Question...

In view of the limited ability of either conventional or digital dental radiographs to demonstrate caries, as reported by you and others and recognized by my own personal observations, and the unacceptability of direct vision to detect dental caries, how should devices such as the Kavo DIAGNOdent be used in typical practice?

Answer from Dr. Christensen...

The Kavo DIAGNOdent has proven itself to be a useful instrument to assist in the detection of Class I and Class V dental caries. However, using it can be time-consuming, and interpretation of results requires clinical judgment. I suggest the following staff-oriented technique. Designate a hygienist or assistant to learn about and use the DIAGNOdent. Have an in-service training session on its use. Assign caries-suspect patients to the designated dental hygienist or assistant, and have that person accomplish diagnostic data collection with the DIAGNOdent. Remember the phrase, 'diagnostic data collection.' Assistants and hygienists can collect data for later interpretation by dentists, but by law, in most states, they cannot do diagnosis or treatment-planning. I suggest the following staff procedure, which is a valuable service for the patient and a source of income for the practice.

1) Clean the suspect teeth with an air slurry polisher, such as a Prophy Jet, Cavi Jet, or many other similar devices. The DIAGNOdent will not provide an accurate reading in the presence of calculus or stain.
2) Wash and dry the teeth.
3) Use the DIAGNOdent on all of the questionable occlusal or Class V surfaces.
4) Record this information in the patient's record.
5) After these procedures have been performed by a staff person, the dentist should observe the data and make a decision about whether or not to restore the teeth, based on the numerical values obtained from the DIAGNOdent, the age of the patient, the apparent degree of caries activity, the patient's health status, and other potential caries stimulating factors.

The DIAGNOdent is useful if used correctly and with good clinical judgment. It has made dentists aware of the inability of dental radiographs of any type to accurately indicate the presence of dental caries, especially initial caries.

One of our newest videos, V1502, 'The New Generation of Tooth-Colored Inlays and Onlays,' shows conservative restoration of teeth, and will motivate dentists to provide more tooth-colored inlays and onlays. There are several excellent ceramic and polymer restorative materials available for this service. Additionally, two other videos relate directly to the questions asked above: V1180, 'Diagnostic Data Collection by Auxiliaries,' and C501A ,'DiagnoDent - Scientific Diagnosis of Caries.' For more information, contact Practical Clinical Courses at (800) 223-6569 or go to www.pccdental.com.

Slot Preparation Dentistry

Dr. Christensen is a practicing prosthodontist in Provo, Utah. He is the founder and director of Practical Clinical Courses, an international continuing-education organization for dental professionals initiated in 1981. Dr. Christensen is a cofounder (with his wife, Rella) and senior consultant of Clinical Research Associates which, since 1976, has conducted research in all areas of dentistry and publishes its findings to the dental profession in the well-known CRA Newsletter. He is an adjunct professor at Brigham Young University and the University of Utah. Dr. Christensen has educational videos and hands-on courses on the above topics available through Practical Clinical Courses. Call (800) 223-6569 or (801) 226-6569.