1. Posterior Composites

  1. Dr G Christensen (2016) – “The larger the posterior composite, the shorter the longevity”
    1. The purpose of this comment is to emphasise caution in the use of direct composites, and the limitations of options in larger restorations
    Suggestion for patients with Class II restorative needs
    1. Small Class II preps (proximal only / 1/4 distance cusp-tip to cusp-tip at isthmus)
    -Directly placed CR with good technique can provide “Acceptable longevity, optimum aesthetics and tooth conservation”
    2. Medium Class II preps (1/3 cusp-tip to cusp-tip at isthmus)
    -Directly placed CR is viable choice with well-informed, co-operative patient
    -Time involved is often double the small CR, fee does not reflect extra time which can lead to cut corners
    -Tooth-coloured ceramic inlays are very good but expensive (usually 4-5x cost of CR)
    3. Large Class II preps (Over 1/2 cusp-tip to cusp-tip at isthmus)
    -If restored with CR, they will not serve for long in most situations (amalgam would have greater longevity)
    -Patients need to be informed of this
  2. Posterior composite proximal wear
    1. Tooth type and location has little influence on extent of proximal wear
    2. Proximal wear can result in a soft/absent contact, resulting in food impaction and caries
  3. Caries under Posterior composites
    1. The concern is with lack of adequate care and excessive haste in placement
    2. Posterior composites are considerably more technique sensitive than amalgam, so small mistakes or shortcuts can result in failure of restoration (Leinfelder, 1994)
    Rapid spread of caries under posterior composites
    1. 1,748 restorations evaluated at 7 years. The risk of secondary caries under composite restorations was 3.5x greater than in amalgams (Bernardo et al., 2007)
    2. Caries activity, location and type of restorative material has influence on amount & variety of bacteria (Splieth et al., 2003)
    3. Microbial variety difference – More strains of all types found under CR
    4. Similar ratios of aerobic-anaerobic flora, but more lactobacilli under failed CR
    5. Up to 8x more bacteria under failed CR (especially anaerobic rods)
    Conclusions
    1. CRs fail rapidly, therefore posterior CRs must be periodically checked to allow early caries detection and timely repair
    2. Inadequate CR placement may promote growth of cariogenic, obligate anaerobic and potentially pulpopathogenic bacteria
  4. Clinicians Report June 2018 – Epidemic of cervical caries and gaps in Class II CR restos
    3 Main causes
    1. Uncured resin at cervical margin – Could be due to excess adhesive (in resin-dentine bonding) or due to inadequate depth of cure
    2. Gaps/lack of margin integrity – Failure to place CR onto gingival margin
    3. Caries remaining at cervical margin – Haste/greed, did not remove all caries
    Gaps result in
    1. Post-op sensitivity, discomfort and pain – Because dentine tubules unsealed
    2. Caries associated with failed CR – Leakage
    3. Further loss of sound tooth structure – Because we have to replace the CR
  5. Key goals in incremental CR placement
    1. Minimise number of increments and time
    2. Seal the margins by optimising adaptation
    3. Protect/preserve previously placed increments
    4. Fill the remaining space to optimise cure
    5. Preserve margin-region enamel
    6. Restore contour (on buccal for aesthetics) and simple form (on occlusal for function)
  6. C-factor
    1. Configuration factor = Number of bonded surfaces / Number of unbonded surfaces
    2. C-factor used to provide a quick method to identify the likely interface stress between tooth and resin material
    3. Protocols designed to provide a low C-factor are likely to enhance adaptation
    4. Identifying high C-factor for a restoration, indicates need for protocols to control the effects of polymerisation contraction
    e.g.
    -High C-factor means consider reducing amount of CR in increment (So CR extends on fewer surfaces) and
    -Manage vulnerable interface so that C-factor approaches 1
  7. Managing polymerisation contraction of posterior composites
    1. Apply 1st increment to most vulnerable interface
    2. Apply first increment to one surface only
    3. Optimise adaptation to cavity walls by purposeful direction of curing light
    1. Robinson, 1987
    2. Goetsch, 1989
    3. Verslius and Douglas, 1996
    4. Engle, 1992
  8. 5 ways of achieving Rapid and Effective placement of a posterior composite
    1. Non-sticky composite
    2. Small increments (VERY small increments for ‘sealing’ increments – rapid, easily controlled, no excess)
    3. Filling the space – Larger quantities (can be with dispenser) according to depth of cure of the composite
    4. Use the best instrument for each task (No lubricants on instruments – messy)
    5. Control the CR, neat work
  9. Light curing concerns + Steps to optimise curing of posterior composites
    1. Heat generation – Dependent on time/distance from pulp (LED – 1000-1500 units vs QTH 400-600 units)
    2. Reduced time of cure – May compromise polymerisation
    3. Shortened pre-gelation time – More stress at interface with tooth
    4. Distance from CR or RMGI – Is gingival component fully cured? Loss of intensity with increasing distance
    5. Focal areas of polymerisation – uneven curing
    6. Strong recommendation to use GIC instead of RMGI for proximal portion of open sandwich due to less depth of cure in RMGI (opacity)
    Steps to optimise curing
    1. Light positioned as close as possible without touching (less than 3mm away)
    2. Stabilise & keep tip of light curing unit directly over restoration during cure
    3. Assistant – Hold light & shield, Dentist – Steady light tip at optimum angle/position
    4. Use radiometer regularly (weekly) to check intensity
  10. Use of bulk fill composites
    1. Combined technique with regular CR -> Increments placed using regular CR, remaining space filled with bulk fill
    2. High volumetric shrinkage
    3. Low modulus of elasticity/rigidity
    4. Further investigation needed to see if bulk fill CRs can perform as well as regular CRs in terms of polymerisation contraction (for margin sealing)
    Initial promotion
    1. Initially focussed on depth of cure “Placement in 5 seconds with 5mm Depth of Cure”
    2. But depth of cure was never the reason that incremental placement was used over bulk
    3. Incremental placement provides better sealing & less cusp deformation
  11. Flowables are the duct tape of dentistry
    1. Flowables have lower filler loading, lower viscosity
    2. Enhance the likelihood of leakage at margins, cause caries in proximal boxes, generally abused material
    3. 3-6% polymerisation contraction compared with 1.6-2.4% in regular CR
    4. Less rigid than regular CR
    5. Greatest thermal dimensional change (out of all materials)
    Recommendations
    6. Use flowables conservatively
    7. Don’t use in areas of high stress/occlusal loading
    8. Most common use is as a liner beneath CR, but most clinicians prefer RMGI anyway due to direct bonding to dentine & F- release
  12. Open sandwich restos
    1. Radiopaque GI restores to just gingival of contact region
    2. GI provides better seal if the margins is on root surface/very thin enamel
    3. Indications – Tooth coloured aesthetics required / Gingival wall on root surface or thin enamel
    4. Problems – GI is placed in the most inaccessable area
    Studies
    1. GI can be placed up to just short of contact region, but should not extend into the contact due to potential wear
    2. Open sandwich restos have less demin in adjacent tooth structure, more marginal discolouration, and slight concavity/loss of GI near gingival margin
    3. Slight concavity/loss of GI due to failure to adequately cure RMGI, abrasion (interdental brushes), or dissolution from early exposure to gingival fluid
    4. If RMGI is used for proximal portion, increments of less than 1.5mm (lower depth of cure because opacity) or use an auto-cured GIC