Benefits of a Seiler Microscope in Restorative Dentistry:
1.
Provides refinement in tooth and margin preparation.
2.
Allows for closer inspection of restorations and marginal tissues.
3.
Improved lighting and magnification aid in caries detection and removal.
4.
Improves detection and evaluation of coronal and root fractures and abnormalities.
5.
Facilitates cord placement for gingival retraction.
6.
Provides for better inspection of impressions.
7.
Helps with inspection of marginal fit of restoration (crowns, veneers, inlay/onlay, amalgam, composite).
8.
Facilitates in finishing and polishing of margins.
9.
Assists in gingival contouring or reshaping around teeth and implants.
10.
Assists in evaluation after cementation.
Conservative microsurgical dentistry using a microscope
Posterior Composites
Failed plastic restoration in LL6
Management of C-Shaped Canals...
LL6 has ditched amalgam. There are cracks in the enamel overlying the mesiobuccal cusp. This has resulted in secondary caries. LL5 has been provisionally restored following the repair of a root perforation
Gross Caries in LL6
Removal of the amalgam from LL6 shows the true extent of the caries.
Note how the floss ligature pulls the rubber dam subgingivally in the interproximal regions maintaining good isolation.
Cavity extent
Caries is removed using hand and rotary instruments. The colour of the dentine does not reflect the degree of demineralisation or infectivity of the remaining dentine.
The dentine is disinfected with 5% NaOCl prior to preparation for bonding.
Sectional Matrix is the first choice when placing Class II resin restorations
Sectional matrix applied and adapted with wedges.
The contact areas are burnished with a belvedere style instrument. Rings are used to separate the contact areas.
Following establishment of a glide path with stainless steel hand files [minimum ISO 20]: Protaper rotary instruments used at maximum torque but at only 150 rpm. The rotary instruments are taken to within 1mm of the canal apex [working length].
The working length is established using a combination of paper points, an electronic apex locator, radiographs, and from tactile feedback of the apical constriction if present.
Apical refinement is carried out using GT hand files.
Etching of Enamel Only
Precise etching of the enamel alone is possible with the operating field magnified. [In this instance X 6.7].
The enamel is etched for 15 seconds prior to etching the dentine.
Etching of Entire Cavity
The entire cavity, both enamel and dentine are etched for a further 15 seconds.
This ensures that the dentine is not over etched -a common cause of post operative sensitivity.
Washing of etchant
The cavity is washed copiously with an air/water mixture. To avoid over-drying of the dentine air is not used dry the cavity.
Gross pools of water are aspirated using a micro aspirator.
Drying of dentine
In order to ensure that the dentine is not overly dry, air from a standard 3-in-1 syringe is avoided.
Instead, microsponges are used to gently soak up any excess moisture. These can be held in fine tweezers.
Dentine prepared for bonding
Under magnification it can be seen that no pools of excess moisture remain within the cavity.
A common complication of air drying dentine is volumetric shrinkage by its desiccation.
Interproximal and "dentine" build up
Interproximal "enamel" contacts are developed first. Once the conversion to a Class I cavity has been completed the dentine element is built up incrementally.
By using smaller composite increments the effects of the C-factor are minimised.
Enamel build up and characterisation
The enamel layer is completed again incrementally. The rubber dam is removed and occlusal refinement made.
The tooth can then be characterised and polished.
2 years post operatively
Notice the lack of ditching or crazing in the enamel or of the resin restoration. This is achieved by the accurate placement of the composite increments. This maintains stresses at placement to a minimum.
This degree of precision is only possible with the higher levels of magnification.
2 years post operatively
Notice the occlusal morphology of the resin restoration in the LL6. Correct occlusal anatomical form distributes stresses evenly and thus minimises those within the restoration.
LL5 has been restored to function with a porcelain-fused to metal crown.
2 years post operative radiograph
Radiograph showing interproximal contacts and size of the resin restoration in LL6. LL5 has had the mesila perforation repaired with MTA.
The tooth has been restored with a non-metalic post, a resin core and porcelain fused to metal crown.
Bonded Amalgam Restoration
Bonded Amalgam Restoration
Failed Amalgam Restoration UL6
The UL6 has a ditched amalgam and recurrent caries. A piece of amalgam has fractured away from the disto-palatal cusp.
Notice the exposed dentine pin in "supporting" the disto-palatal amalgam.
The tooth is asymptomatic and responds normally to thermal stimuli. There is no sensitivity to occlusal loading of the cusps.
The tooth is isolated with rubber dam and sealed with a floss ligature.
Removal Of The Amalgam Restoration
The amalgam restoration is removed with a combination of high speed rotary and ultrasonic instruments. The use of ultrasonic instruments allows the break up of the amalgam without enlarging the cavity outline.
The dentine pin is left in situ. With the microscope: It is now possible to fully appreciate the extent of the caries.
The cavity is disinfected with 5% NaOCl prior to removing any of the caries.
Caries Removal
Caries is removed with a combination of rotary and hand instruments. The colour of the dentine is does indicate either the infectivity of the dentine or its state of demineralisation.
The cavity is periodically disinfected with 5% NaOCl to reduce the bacterial burden. Bur changes are also made to avoid contaminating deeper portions of the dentine with infected burs.
The dentine pin is still left in
Assessment of Cavity And Dentine Pin X10
Under the microscope it is plainly seen that a crack extends mesially from the dentine pin. This crack extends diagonally along the floor of the cavity towards the mesio-buccal cusp.
With the magnified well illuminated vision afforded by the microscope; cracks associated with the placement of screw-type pins are frequently observed.
The routine observation of fractures and secondary caries associated with dentine pins, has dissuaded the author from using pins for retention, even for large restorations and cores.
Removal Of Dentine Pin And Residual Caries
The pin and associated remaining caries are removed. Initial attempts at dislodging the pin is with ultrasonic instruments at low or medium power. High power will cause the pin pin to break up rather than be ejected intact.
If ultrasonic energy fails to free the pin, then a "blunt" high speed diamond bur can be gently applied perpendicular to the pin along its entire length. The clockwise motion of the bur will often persuade the pin to disengage from the dentine by rotating counter-clockwise.
In very rare instances the pin may need to be removed in sections with small rotary instruments.
Disinfection of Cavity
Following removal of the pin and remaining caries the matrix band and wedges are applied. The matrix band should be burnished after tightening to support the desired contact shape.
Notice that the rubber dam clamp is applied on the outside of the matrix band. The most suitable clamp for molars is a W56. The W56 clamp is not sufficiently stable to retain the rubbed dam. To retain the rubber dam a W8A is of better design.
The cavity is then flooded with 5%NaOCl for 60 seconds. To assist in the disinfection of the crack; micro-brushes are rubbed along its length.
Post Shaping X10
The enamel is etched for 15 seconds with phosphoric acid.
Self etching primers do not demineralise the enamel sufficiently to provide a reliable enamel bond. A poor enamel bond gives rise to marginal breakdown, microleakage and subsequent hydrolysis of the hybrid layer. All these factors contribute to reducing the prognosis of the final restoration.
The unparallel vision offered by the microscope, allows for the etching of enamel without any of the deleterious effects of etching dentine.
Priming And Bonding
The enamel and dentine can be etched and primed with a self etching primer. The enamel margins should also be covered with the etch/primer.
If using a dual cure bonding system; then in order to apply the bond, a filter must be placed over the light source. Failure to do so will result in the premature curing of the bonding agent and its failure to adhere to the amalgam.
The author has no experience of using a chemical-only cured bonding agent with amalgam.
Packing Of Amalgam
The cavity should be progressively and incrementally filled with thoroughly condensed amalgam.
Excess bonding material should be squeezed against the cavity walls in order to reduce film thickness and avoid leaving small gaps between the amalgam and tooth.
Surplus bond should be encouraged to the surface where it can be easily removed with a probe.
Carving Of Amalgam
The wedges and W56 rubber dam clamp are removed. In order to avoid damaging the marginal ridges when removing the matrix band the amalgam fillet in the marginal ridge area is removed with a probe and contoured.
The matrix band should be first displaced apically prior to its removal along the conventional occlusal path and away from the tooth. Sometimes it is necessary to section the matrix band and slide each section through the contact areas.
The rubber dam is now cut through the interproximal areas and removed. Any remaining amalgam fragments are dislodged with floss.
The occlusion is refined with a combination of excavators, and amalgam carvers. The fissure pattern is finalised with a conventional dental probe.
