Minimally invasive cavity preparation
- Definitions
- Preventive non-invasive medical dentistry
The medical model considers caries as an infectious disease whose lesions are treated by the establishment of individualized prophylactic measures aimed at remineralization of the lesions.
Its aim is to preserve the integrity of the tooth and therefore increase the chances of preservation on the arch, throughout the subjects’ lives, the average duration of which is constantly evolving.
- Adhesive dentistry:
Adhesive dentistry is based on the principle of tissue saving and adhesion using adhesive materials for aesthetic purposes.
This concept is essentially based on the achievement of a sufficiently powerful and durable adhesion to enamel and dentine in the oral environment, while preserving the maximum amount of healthy dental structures, since it is the very substrate of the adhesive systems which alone ensures adhesion to the residual dental tissues.
- Principle of minimally invasive dentistry:
The minimally invasive therapeutic approach intervenes when non-invasive remineralization techniques have failed or are no longer suitable. It concerns moderate/extensive lesions. It involves an alteration of the dental surface, whether micro-invasive (chemical) and/or surgical (instrumental), but always with maximum respect for the integrity of the original dental tissue.
It therefore aims to:
-Achieve access to the lesion as conservatively as possible, respecting the coronary anatomy;
-Exclusively remove damaged enamel and carious dentin, conforming to the lesion contours;
-Allow prevention of progression of existing lesions;
-Preserve the vitality of the pulp-dentin complex by avoiding iatrogenic maneuvers;
-Obtain a cavity configuration and an enamel-dentin substrate mechanically and biologically compatible with the long-term placement of the restorative biomaterial.
- Minimally invasive cavity preparation:
Before any intervention it is necessary to know and respect the steps
3.1 Management of the carious lesion
General recommendations state that:
– inactive carious lesions do not require treatment (except for reasons of form, function or aesthetics);
– active non-cavitated carious lesions should be managed in a non-invasive or micro-invasive manner;
– cavitary carious lesions that are not accessible to cleaning and active should be managed by ultraconservative restorative treatment.
3.2 Operating methodology
Described in the following table
Table: General recommendations for the clinical phase
3.3 Cavity layout
The shape and size of the cavity preparation depend on the progression of the carious lesion and the presence of infected and affected dentin. Curettage of the lesion should allow the removal of infected soft dentin, without exposing a living pulp (prior assessment of the pulp status is therefore a key point in the management of severe parapulpal lesions).
Affected dentin may be left in place in the parapulpal areas. If there is a risk of pulp exposure, partial/selective curettage should be considered. Several excavation techniques exist: manual, mechanical, by air abrasion, by ultrasonic or sonoabrasion, or via enzymatic systems.
Among all the tools described, it is necessary to distinguish those that are specific to the treatment or elimination of infected dentin (most often manual or mechanical) from those that are more appropriate for the preparation of the cavity (sonic, ultrasonic).
- Clinical application:
4.1 SI/STA 1•2:
A. The diagnosis
Diagnosis is based on the presence of localized enamel breakage and/or highlighted gray shadows indicative of underlying dentin involvement. Loss of enamel surface integrity is detectable without optical aids. Bitewing radiolucency under the enamel-dentin junction, extending to the middle third of the dentin, is demonstrated on the bitewing image.
B. Preparation:
In these more advanced lesions, of still moderate size, access to the lesion is achieved with spherical diamond instruments (ball or pear), the action of which begins on the sites presenting a clear cavitation.
The preparation then includes the opening of the infiltrated grooves with a fine instrument without seeking to connect the cavities together. The curettage of the carious dentine results in a rounded cavity shape, of variable depth and extension depending on the damage. Spherical blade burrs, rotary or manual, allow dentin curettage.
The overhanging enamel, not subjected to direct occlusal contacts, can be preserved as long as the curettage instruments have favorable access to the entire lesion. In general, the cavity width does not exceed a quarter of the intercuspal vestibulolingual distance. The edges of the cavity are regularized using a rotary finishing instrument (generally a fine-grain diamond bur).
Clinical schematization of site 1 lesions and treatment options proposed according to the different stages of development of carious lesions with an occlusal starting point: stage 2, punctate mini-obturations not connected to each other
4.2 SI/STA 1•3
A. The diagnosis
The diagnosis is based on the presence of an enamel-dentin cavity (filled with plaque and food debris) with a softened dentin base on probing; the gray shadows extended to the peripheral areas are indicative of unsupported enamel; in the case of so-called “hidden” caries, these grayish colorations can be extended to the entire occlusal surface without loss of the peripheral axial structures (cusps and marginal ridges), masking the underlying presence of infected dentin invading the entire coronal surface of the enamel-dentin junction, to the point of weakening the peripheral structures of the dental crown. Generally, there is an associated presence of dentino-pulpal sensitivities. The bitewing image shows a radiolucency, extended laterally under the enamel-dentin junction and deep into the inner third of the dentin.
B. Preparation:
Despite wider occlusal access involving selective removal of peripheral overhanging enamel at the level of the cusp slopes undermined by caries, the preparation will always be based on the principles of tissue economy by preserving the deep demineralized dentin and, as far as possible, the enamel envelope in order to achieve a direct restoration using a glass ionomer cement modified by the addition of resin (CVIMAR)-composite sandwich technique.
Clinical schematization of site 1 lesions and treatment options proposed according to the different stages of development of carious lesions with an occlusal starting point: stage 3, direct adhesive restoration aimed at strengthening the structures
4.3.SI/STA 1•4
A. The diagnosis
The diagnosis is based on the presence of an enamel-dentin cavity that is so extensive that it destroys part of the peripheral dental structures and induces a loss of coronal resistance; the dentin lesion being parapulpal, there is a possibility of pulp symptoms. The radiograph reveals an extensive radiolucent image revealing coronal destruction associated with a clear image of pulp retraction and/or mineralization
B. Preparation:
In the absence of symptoms of irreversible pulpitis, pulp vitality must be preserved, especially in young people, with a view to performing an onlay restoration, possibly after a temporization phase using a transitional restoration in amalgam, glass ionomer cements or composite.
However, the excision of all the carious tissues and the elimination of the weakened parts of the residual walls leave areas of undercut. To reconcile the principle of tissue economy and the mechanical principles of indirect restoration, a flowable composite or glass ionomer cement is recommended to serve as a base and internal filling. Finally, the cavity must have clean edges, rounded internal angles and walls with a slight occlusal divergence. At the level of the overlapping areas, the occlusal free space must be sufficient (approximately 2 mm). The restoration will be done by indirect technique by making an onlay bonded to the composites or ceramic
Clinical schematization of site 1 lesions and treatment options proposed according to the different stages of development of carious lesions with an occlusal starting point stage 4, extensive adhesive restoration with partial occlusal coverage (E).
SI/STA 2•1
- The diagnosis
The diagnosis is based on the objectification, on the bitewing image, of an extended enamel radiolucency under the enamel-dentin junction, in the external third of the dentin. The image remains difficult to interpret in terms of the absence or presence of a cavity.
On clinical examination, the translucency of the marginal ridge may be altered and microcavitations of the proximal surface may be revealed by tearing of the dental floss.
- Preparation:
- Posterior tooth:
The cavity is ultra conservative with conservation of the overhanging marginal ridges and preserving the proximal enamel contact.
- Proximal carious penetration zone is directly accessible
If the proximal carious penetration zone is directly accessible due to the absence or deterioration of the collateral tooth, direct access is via the initial point of election, in the altered enamel.
Diamond rotary instruments are generally well suited, but some angled sono-abrasive instruments offer increased access possibilities. Curettage of carious dentine is performed punctually, with a cylindrical-conical diamond bur at intermediate speed under air-water jet, accessibility to the lesion is dictated by the cavity located on the adjacent tooth, the progression of the caries generally being in an apical direction without reaching the marginal crest, the eviction of the carious tissues is then carried out with a small long-necked ball bur, insisting on the cavity walls.
Horizontal type mini obturation
–
In most situations, it is not possible to reach the carious site immediately. It becomes necessary to sacrifice an area of healthy tissue to access the lesion. The cavity approach must systematically respect the marginal ridges (a strategic element in the resistance of the tooth) and preserve the interproximal enamel contact. Two types of approach are proposed.
- If the location of the lesion and the anatomy of the embrasure allow it
If the location of the lesion and the anatomy of the embrasure allow it, access is made through the vestibulo-proximal or linguo-proximal angle, horizontally in the direction of the lesion to take the form of an elongated horizontal mini-cavity. This mini-cavity is described under different names in the literature: horizontal gutter or groove, horizontal box/slot
– Long-necked ball or pear-shaped diamond microburs, preferably used on a high-speed contra-angle (to limit vibrations), facilitate access to this low-visibility area. Then, diamond hemispherical inserts mounted on a sonic or ultrasonic handpiece have a clear advantage for access through the embrasures to preserve the integrity of the adjacent tooth.
Curettage of the carious dentinal tissue is continued with long-necked rotary instruments on a contra-angle. Curettage control is performed using indirect vision. The depth of the lesion sometimes requires us to widen the opening at the expense of the access face for correct removal of the damaged tissue.
tunnel type mini-obturations
If previous access is not possible, if there is caries in the occlusal marginal fossa or an occlusal restoration already present, an occlusoproximal, oblique, mini-cavity “tunnel” is then preferred. Access is made through the enamel (high-speed diamond ball bur) at the level of the occlusal fossa.
This cavity opening must respect the complete integrity of the marginal ridge: a width and height of at least 2 mm must be preserved. After crossing the thickness of the enamel tissue, it is common to distinguish a brownish coloration of the underlying proximal dentin, which advantageously serves as a guide for curetting the lesion.
The excavation of the carious dentine is continued using a low-speed round bur on a contra-angle, towards the point of penetration of the carious lesion. This progression is made obliquely to the internal zone of the proximal enamel below the point of contact
vertical type mini fillings
-Within the lesion, curettage of the infected dentine is done by internally sweeping the bur along the enamel-dentine junction, in the vestibular, lingual or cervical direction using a pendulum movement of the bur. The cavity is more extensive internally than at the level of the occlusal access and extends along the proximal face. The pulp wall of this cavity must be curetted to a minimum and with caution in order to preserve a sufficient thickness of parapulpal dentine.
-After curettage of the carious dentin, it is possible to delicately explore with a probe and check the quality of the excavation of the infected dentin. It is also necessary to observe the proximal enamel wall (which is approached internally here) which was the site of bacterial entry and which is partially demineralized. A marbled, brownish and whitish tissue is visible by indirect vision using the mirror.
If there is no cavity collapse, the enamel tissue can remineralize in contact with a bioactive filling material (glass ionomer cement and fluoride). Whenever possible, it is preferable to keep the wall like this, in order to obtain a closed tunnel minicavity, with a good prognosis.
If a cavitation already exists, it is simply regularized, thus creating an open tunnel minicavity.
-Given the proximity of the collateral tooth and the difficulty of visual inspection, it is imperative, during this procedure, to place a metal matrix strip in the interdental space to ensure protection of the surrounding tissues. There are specific angled sono-abrasive inserts with a blunt end that allows the edges to be regularized without damaging the adjacent tooth.
- Anterior tooth :
In the incisor-canine sector, the principle of mini-tunnel cavities remains the same. In addition, the aesthetic imperative is particularly well respected by the shapes of the mini-cavities.
Access to the lesion is easier due to easy visual access and the anatomy of the teeth. The approach is via the lingual surface, respecting the marginal ridge and preserving the proximal enamel in the manner of the mini-cavity tunnel, the vestibular approach is sometimes necessary in the case of crowding associated with overlaps, this situation causes difficulties of access and visibility on the lower teeth.
Access to the lesion is made by a high-speed diamond cylindro-conical bur under air-water jet. The trepanation point is located medial to the marginal ridge. The extension of the preparation is done minimally while allowing an assessment of the extent of the lesion, the proximal enamel is preserved whenever possible.
The removal of caries is done only by small round burs, the creation of retentive devices is not necessary.
Clinical schema of site 2 lesions, anterior teeth and proposed treatment options tunneled miniobturation
4.4. SI/STA 2•2
A. The diagnosis
Diagnosis is based on observation of the marginal ridge outlined by gray shadows with or without cracks. The cavity in the proximal enamel under the proximal contact area is not always clinically detectable, and here again optical aids are useful. A cavitation is clinically detectable in the enamel of the proximal contact area. A grayish coloration associated or not with a crack in the marginal ridge is generally observed. The radiograph shows involvement of the middle third of the dentin.
- Preparation:
- Posterior tooth:
Access to the lesion is from the occlusal surface, at the level of the marginal fossa, in a proximal direction, under the contact area. The tactile sensation of the passage through the softened dentin is very clear. Curettage is performed with a ball or pear bur, at low speed while leaving the demineralized dentin at the level of the axial wall in order to obtain subsequent remineralization, the cervical enamel is preserved in order to maintain the cervical edge in a supragingival position. Secondarily, the cavity is extended at the level of the occlusal marginal ridge to take a rounded hemispherical shape called a vertical minicavity.
This type of mini-cavity is commonly called “adhesive” or “vertical box/slot”; it often takes the form of a drop.
The marginal ridge overhangs are partially preserved if the enamel is resistant and the interproximal contact zones are preserved as much as possible during proximal preparations; there is an alteration of the face of the adjacent tooth in nearly 75% of cases. To improve the clinical realization, it is necessary to carry out a preliminary spacing and to protect the collateral tooth using a metal matrix.
But it is preferable to use sono- or ultrasonic abrasive inserts with a unilateral working face, which are not mutilating for the neighboring tooth as a bur would be, which is difficult to handle in this area.
These instruments allow a perfect finish of the cavity contours which thus promotes the adaptation of the obturation material and the marginal sealing Sonic-sysmicro,Kavo
Figure 38: Clinical schematic of site 2 lesions, posterior teeth and proposed stage 2 treatment options
- Anterior tooth:
Access is through the marginal fossa and will be extended to the crest, to reach a low-volume proximo-cruturating cavity. This is a teardrop-shaped form, with partial preservation of the marginal crest. The interproximal contact areas are preserved if the enamel is resistant.
If two proximal lesions coexist on the same tooth, the preparations will be separate, and we will avoid bringing them together with an occlusal preparation. Involved in occlusion and the reestablishment of interproximal contact, it will use micro-hybrid or condensable composites.
Figure 39: Clinical schematic of site 2 lesions, anterior teeth and proposed treatment options for stage 2, linguoproximal or vestibuloproximal minifillings (C);
4.2.4.SI/STA 2•3
4.2.4.1. The diagnosis
The diagnosis is easy, due to the clear cavitation of the proximal enamel if the ridge is collapsed, or due to the presence of a grayish ring due to the extension of the softened dentine under the marginal ridge. The very clear radiolucent image is suggestive of a loss of substance even before the collapse of the marginal ridge.
The radiograph highlights a radiolucent area that is lateralized over the entire proximal height, extending to the internal third of the dentin, and presents a pulpoaxial proximity. An associated image of pulp retraction is always observed
4.2.4.2. Preparation:
The cavity is opened with a high-speed diamond cylindrical bur under water jet, a search for localized cracks at the base of the cusps is then undertaken, in case of suspicion the contours of the cavity are modified by tilting the vestibular or lingual walls outwards along an oblique line directed towards the outside of the cusp summit with a cylindrical-conical bur at intermediate speed.
- Anterior tooth:
The cavity is proximo-vestibulo-lingual from side to side with preservation of the incisal angle, due to aesthetic and mechanical imperatives only composites are indicated.
An arrangement of the edges of the enamel then becomes necessary to increase the retention by bonding due to the increase in the proximal overhang and to ensure an invisible transition between the tooth and the composite, the width of this bevel is adapted according to the importance of the loss of substance on the lingual face; due to the occlusal contacts, a concave chamfer will be made which provides a greater thickness of material.
Figure 40 : Clinical schema of site 2 stage 3 lesions, three-sided adhesive restoration with preservation of the incisal angle
- Back teeth:
The search for possible cracks located at the base of the cusps is then undertaken. The cusps are weakened If a cusp crack is suspected, the contours of the cavity are modified by tilting the vestibular or lingual walls outwards along an oblique line originating from the floor of the cavity and directed towards the outside of the cusp apex; this modification of the cavity shape is carried out with a cylindro-conical bur working at intermediate speed. This cutting technique can be used to protect any weakened dental structure
Figure 41 : Clinical schema of site 2 stage 3 lesions
4.2.5.SI/STA 2•4
4.2.5.1. The diagnosis
The diagnosis is evident from the collapse of the marginal ridge and the partial destruction of the corresponding cusps, with the radiograph specifying the juxtapulpal proximity.
4.2.5.2. Preparation
a conservative attitude is preferred, and the damaged dentin on the axial wall and on the pulp floor is preserved, the cusps supported by healthy dentin will be preserved and treated, retentions in the form of pits and grooves will be made at the cervical level, finishing using a fine-grain diamond bur
- Anterior tooth:
The cavity is proximovestibulolingual including the incisal angle(s). Maximum preservation of enamel is recommended; access to the lesion is made with a cylindro-conical or cylindrical diamond bur. Unsupported enamel can to some extent be reinforced with glass ionomer, which implies a preliminary softening of the marginal limits of the preparation; the damaged dentin located on the axial wall is left in place for later remineralization.
Partial restorations bonded indirectly to laboratory composite or ceramic (extended veneer) will be preferred for better aesthetic longevity.
Figure 42 : Clinical schema of site 2 lesions, stage 4, extensive adhesive restoration with reconstruction of the free edge and incisal angle (E).
- Posterior tooth:
The restoration of a stage 4 site 2 lesion on a posterior tooth poses many difficulties, particularly when there is total loss of a cusp, whether due to significant caricusc extension or even a fracture.
In this case, the marginal limit of the lesion is located near the epithelial attachment. The shape of the cavity then becomes similar to that described for site 2 stage 3 cavities, but the restoration of a correct occlusal height is complicated by the absence of landmarks linked to the cusp loss.
Figure 43 : Clinical schema of site 2 stage 4 lesions
4.3. Preparations of site lesions 3
Site 3 concerns all carious lesions with cervical, enamel or dentin origin, on all surfaces of all teeth. Site 3 has two specificities:
•The first is that the lesion can indifferently be initiated at the level of the enamel, in young people, or at the level of the dentine in elderly patients or in the event of periodontal recession; •The second specificity is that the non-invasive treatment of inactivation of these lesions can be undertaken even in the presence of superficial cavitation, thus leaving a cavitary scar, subject to effective elimination of the plaque.
4.3.1.SI/STA 3•0
4.3.1.1. Clinical diagnosis
It is based on the presence of a white spot without cavitation, if the lesion is initiated at the level of the enamel (coronal caries) or on the observation of an exposed, colored dentinal cementum zone, more or less eroded if the caries is root.
Figure 44: Clinical schema of site 3 lesions and proposed treatment options for carious lesions with cervical, coronal or radicular origin: stage 0, non-invasive treatment by remineralization (A)
4.3.1.2. Non-invasive treatment
It consists of the remineralization of the lesion which can be obtained by application of fluoride varnish after removal of the plaque and control of the caries risk. Topical applications of antibacterial agents (chlorhexidine) and remineralizing fluorides, 4 times a year, until remineralization of the lesions.
4.3.2.SI/STA 3•1
4.3.2.1. Clinical diagnosis
It is based on the presence of a superficial cavity sparing the enamel-dentin junction, either in the enamel or in the dentin depending on whether it is a coronal or radicular lesion.
Figure 45 : Clinical schema of site 3 lesions and proposed treatment options for carious lesions with cervical, coronal or radicular starting point stage 1, mini-obturation in glass ionomer cements modified by addition of resin (CVIMAR) or in composite resin (B)
4.3.2.2. Preparation:
Access to the lesion is punctual and will aim to preserve the demineralized peripheral enamel. The cavity is shallow. The edges will be clean at the cement level while at the enamel level, the bevel is unnecessary with glass ionomers, recommended with composites
4.3.3.SISTA 3.2:
4.3.3.1. Clinical diagnosis :
The lesions are coronoradicular and extend in apical and proximal directions; the cavitation is more extensive on the surface than in depth.
Figure 46: Clinical schema of site 3 lesions and proposed treatment options for carious lesions with cervical, coronal or radicular starting point stage 2, vestibular cervical obturation in CVIMAR or composite resin (C)
4.3.3.2. Preparation:
Access is direct. The cavity is more extensive with coronal enamel and radicular dentin limits.
4.3.4.SISTA 3.3:
4.3.4.1. Clinical diagnosis
It is based on the presence of a clear cavitation, exposing the carious dentin. The lesion straddles the enamel-cement junction, and also concerns the proximal faces.
Figure 47: Clinical schema of site 3 lesions and proposed treatment options for carious lesions with cervical, coronal or radicular starting point stage 3, adhesive restoration in CVI or CVIMAR extended to the proximal faces (D)
4.3.4.2. Preparation:
access is superficial but wide. The cavity is of an atypical shape, more extensive on the surface than in depth, depending on the extent of the caries. Bioactive materials will be preferred. Glass ionomers are recommended as a first-line treatment.
4.3.5.SI/STA 3•4
4.3.5.1.Diagnosis
This is a creeping caries also called “sheet” caries with cavitation extending around the entire root perimeter and risk of root fracture.
Figure 48: Clinical schema of site 3 lesions and proposed treatment options for carious lesions with cervical, coronal or radicular starting points: stage 4, CVI temporization restoration going around the root (E).
4.3.5.2. Preparation:
Maximum tissue preservation should be sought and the approach to the axial wall is carried out with the greatest caution, demineralized dentine can be remineralized and should therefore be preserved as far as possible, the instructions of the atraumatic restorative concept will be followed, only the vertical walls of the cavity are prepared with a cylindro-conical bur while preserving the healthy enamel, the infected dentine is removed with round burs while preserving the vertical walls. The therapeutic options are the same as in the previous stage
5-Conclusion
The minimally invasive therapeutic approach to carious lesion is a clinical concept based on an updated understanding of the caries process as well as the development of diagnostic technologies, operative techniques and the use of appropriate restorative materials.
It is an operational concept of current practice with tissue economy as a fundamental precept, favoring the prophylactic attitude over any form of therapy.
The management of caries disease involves personalized caries prevention, check-ups and ultra-conservative restorative treatments. Thus, any therapy should only be initiated after an assessment of the patient’s individual caries risk (ICR). The assessment of the ICR makes it possible to adapt the preventive approach to the patient ‘s needs, to establish the right indications from a therapeutic point of view and the choice of material, and to adapt and anticipate the follow-up.
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