occlusal rim Flashcards
lip support
the occlusal rim by the technician is placed in front of the incisal papilla (up to 9mm from the centre) this is counteract the resorption of the ridge and allow for correct lip contour (Johnson and Wood, 2012). The rim requires to be checked for displacement and stability at this point to ensure muscular harmony or dislodging forces. If the rim dislodges at this stage it may be required to compromise aesthetics for function by removing wax, this is likely in cases of excessive resorption
Occlusal Vertical Dimension-
is the height of the rims recorded together. The vertical dimension establishes the position of the posterior denture teeth, support to facial tissues and additionally prevents creasing of the lips, but additionally the lips should be allowed to form a seal. When recording the OVD the clinican must take into account the rest position (bottom right) where the patient doesn’t contact the dentition/wax rims (allows the jaw to relax). Failure to take this into account can cause poor aesthetics or TMJ issues
Occlusal plane
- this is the plane where the incisal edge of the maxillary dentition are placed and gives position for the occluding of the opposing arches dentition. Lips can be used as an initially guiding place however the rim must be adjusted to the Campers line and the relationship to the condyle must be correct for a balanced occlusion and aesthetics (Johnson et al,. 2015). In addition to this it curves upwards to incorporate the curve of Spee at the molar dentition (Johnson and Wood, 2012), in addition to this the occlusal plane being correct will influence aesthetics, phonetics and function.
Centric Relation-
the patient should be asked to touch their soft palate with the tip of the tongue, then close the rims together this produces the Retruded Contact Position (RCP)- this ensures the condyle is in the correct position in the TMJ’s the denture teeth will then be set in Intercuspal position that coincides with the RCP (Johnson et al,. 2015). The position of RCP in complete dentures is an easily reproducible position for the patient, it offers optimum load distribution, optimum for the position of muscle activity (Johnson and Wood, 2012).
Centre Line-
generally the centre of the patients face and takes into account symmetry of the denture, however unsymmetrical facial proportions can distort taking this reference point.
Smile line and Canine lines-
useful in selecting the size of the denture teeth. For the smile line the measurement from the incisal edge to the lip when smiling, failure to take this measurement into account can leave the patient with teeth that are too short which then means they have an overly ‘gummy’ profiled. Using the inner canthus of the eye running down the patients face will give the position of the canines and using a flexible rules measuring from each line can provide the width of the anterior maxilla mould of dentition
Utilising the correct material-
wax and wire is cheap and quick material of manufacture but warps easily not just in the mouth that is a warm environment but additionally in transport, a more rigid material should be utilised. Heat cure can ensure that the clinician can check the fit and stability of the resulting denture base but is expensive and time consuming.
Blocking out of undercuts-
the occlusal rim should be easy to fit and use and removing excessive undercuts may mean that the rim is not stable
Ensure the baseplate and the rim and sealed together can prevent separation in the mouth
Correct positioning of the rims-
will aid in the clinician to be able to undertake the adjustments required quickly but enhance the stability of the occlusal rim in the oral environment. Additionally the peripheral border should extend fully into the sulcus (if the working model is fully extended) but movable tissues such as the fraenum’s relieved.
Cutting of the postdam-
it is beneficial at this stage to carve the postdam as it aids in retention of the rim- correct depth is 1-2mm from hamular notch to the other. It is important to note it should be thinner at the harder tissue at the midline- this should be chamfered and deeper at the soft palate area.
Whilst the height of the rims should be constructed to ‘average’ height over extension of the resulting baseplate or the rim can result in premature contacts and prevent an accurate recording of the occlusion- therefore adjusting the baseplate to 2/3rds the height of the retromolar pad and removing wax going posterior to where the 1st molars would be positioned in both arches can prevent this premature contacting (Basker et al,. 2011; Johnson and Wood, 2012)
Width of the rim is often overlooked by technicians- wide rims can inhibit tongue space and displace the cheeks. The result of this can prevent accessing the lip support, phonetics and even vertical dimension, the rims should be slightly larger than the teeth to replace them 5-6 anterior, 8-9mm posterior (Johnson and Wood, 2012). Additionally shape from the rim to sulcus should be considered a slightly concave should be incorporated to allow for the muscular to seat correctly
Complete dentures
: ‘Balanced occlusion is present when there are simultaneous contacts between opposing artificial teeth on both sides of the dental arches. This term describes a static situation and applies when upper and lower dentures meet in any position’
This is important in partial and complete dentures to ensure that simultaneous contact is achieved if possible and functionally workable. However in partial dentures the remaining dentition will dictate the ability of balanced occlusion as the natural dentition may cause interferences. However with partial dentures the natural dentition may dictate the occlusal pattern and whilst the clinician may record the occlusion position may have to be altered somewhat to accommodate over-erupted or drifted dentition (Carr and Brown, 2015). Occlusal recording is important factor in this as well as technicians following the information.
a) The clinician can mark some notation lines into an edentulous occlusal rim.
List four different lines and identify their use for a technician in setting up. You
may draw your own diagram to aid in answering
• Centre line – where the centrals go
• Smile line – height of the teeth
• Canine line - where the canines go
• High lip line – for patients showing more gum, where you would stipple the denture
• Centre + canine line – width of teeth
b) For an edentulous patient what occlusal recording should a clinician use and why?
RCP/ Retruded Contact Position is reproducable for jaw movement
Whilst wax and wire is a common material for an occlusal rim construction as it is
cheap and quick, suggest a more appropriate material and explain why?
Light cure
• Shellac = brittle, easy to break when manipulated
• Cold cure/ orthodontic spray up cold cure
