THE CONTACT POINT IN PROSTHESIS A KEY POINT FOR AESTHETICS AND FUNCTION

2024-04-03 16:37:34

INTERPROXIMAL CONTACT POINT IN AESTHETIC AREA

INTERPROXIMAL CONTACT POINT AND GINGIVAL AESTHETICS IN THE ANTERIOR SECTOR
Gingival aesthetics in the incisal sector is directly dependent on the point of contact between the teeth; This determines the conditions for having a good level of taste bud. This allows the gum to perfectly protect the corono-peripheral seal of our prostheses (ceramic or zirconia crowns) and to maintain a good level of interdental papilla (Tarnow).
When the inter-incisal contact point is too tight at the level of the anterior block, pain may appear linked to pressure forces similar to orthodontic forces.
This excessive tension can lead to orthodontic movement of the incisors in the short term (when their periodontal phenotype is thin) and create an arch break, i.e. a migration of the tooth with the weakest periodontium which will eventually move and exit the aesthetic arc of the incisor-canine block.
When this inter-incisal contact point is on the contrary insufficient, we often observe micromovements of the teeth due to lack of contact point.
Indeed, dynamic occlusal movements of propulsion and didduction can prove iatrogenic in the medium term and increase the risk of loosening of our ceramic crowns.
We can also sometimes see coronal fractures appear with breakage of the cosmetic element or even root fractures when the crowns are fitted with a root post.
In addition, an insufficient inter-incisal contact point can also cause periodontal disorder linked to an accumulation of biofilm and an invasion of bacterial plaque in the interdental area with an impact on the texture and volume of the inter-incisor papilla.
The papilla can thus either undergo erosion or, conversely, grow abnormally: gingival hyperplasia compared to the diastema caused by the absence of a point of contact.
These hyperplasias are often observed at the level of the papillae of the canines when the interproximal contact point is insufficient.
In the medium term, we may see migration of the incisor and an occlusal disturbance which could lead to an anomaly of anterior guidance with deleterious anterior interferences over time.
In the long term, a periodontal pocket may be observed accompanied by associated symptoms (inflammation, accumulation of plaque, gingival bleeding, pain when brushing, purplish red appearance of the marginal gum which can be very unsightly from an aesthetic point of view, etc.).

INTERPROXIMAL CONTACT POINT IN THE POSTERIOR SECTOR: OCCLUSAL AND PERIODONTAL REPERCUSSIONS

IMPACT ON FUNCTION
Ideally the marginal ridges of the molars and premolars must be perfectly aligned with “just sufficient” tension between the interproximal contact points of the teeth in order to ensure true continuity of the food bolus during chewing.
This continuity is also an important element for the self-cleaning of the teeth thanks to the absence of interruption of the bowl during the grinding of food. It is thanks to the regularity of the contact surfaces and the alignment of the height of the marginal ridges that the masticatory function is physiological.
Improper adjustment of the contact point in the molar sector risks causing both periodontal and occlusal problems in the short term.
Indeed, if the interproximal contact point lacks tension in the posterior sector, we will quickly observe food compaction associated with gingival inflammation which over time risks causing painful complications: septum syndrome.
Furthermore, if this septum syndrome is not taken care of in time, we will observe an impact on the gingival attachment next to the interproximal surfaces of the molars with the eventual occurrence of a periodontal pocket which may be associated with a lesion. intraosseous (IOL) with vertical or angular defect.
When cementing or bonding a ceramic crown, it is important to pay attention to interproximal relationships, particularly at the point of contact of the prosthetic tooth with its collateral teeth.
Indeed, if the prosthetic tooth is too wide and the contact point excessive (poor adjustment of the interproximal contact points by the prosthesis laboratory: excess tension) the tooth will not be perfectly inserted during cementing; We will then observe a sealing or sticking of the ceramic in malposition in the three directions of space with consequently an overocclusion associated with a lack of adjustment of the ceramic on its limits.
This excess interproximal pressure therefore causes a defect in the setting of the ceramic at the limits of the corono-peripheral preparation; this inaccuracy represents a risk of sealing the prosthesis with, in the medium term, an increased risk of bacterial infiltration (risk of recurrence of caries, risk of loosening following infiltration). In addition, the overhang observed between the crown and the corono-peripheral preparation can also generate in the medium term a biofilm retention zone with blockages of the food bolus under the point of contact responsible for gingival inflammation next to the papillae.
If during bonding or cementation of the ceramic, the interproximal pressure is insufficient between the
posterior teeth and the crown (ceramic too narrow delivered by the prosthesis laboratory: tension
insufficient) we will very quickly observe a food compaction which can lead to a syndrome
of the septum; the patient will consult again for pain related to this defect in the point of contact. It will be necessary
then place the new ceramic in order to rebuild a contact point with sufficient tension allowing the dental floss to be passed with appropriate pressure (the floss must not break when passing the contact point while showing a slight resistance to the passage of this one).

CONTROL OF INTERPROXIMAL TENSION AT THE CONTACT POINT

It is customary to use a pressure silicone positioned interproximally to check the interproximal contact points when trying on a ceramic crown or bridge to check the contact forces.
I find that the use of this technique of testing the tension of the interproximal contact point is quite random because very often when removing the prosthesis (once the silicone has polymerized) we often observe a tearing or stretching of the this silicone which makes the reading of the pressure zone at the ceramic level imprecise.
The challenge is to subtract the excessive tension in the right place by milling with a red then yellow ring flame cutter mounted on a turbine or red contra-angle. The subtraction must be done at low speed to avoid ending up with an insufficient contact point.
Furthermore, when the interproximal contact point is insufficient, it is the passage of dental floss which, without pressure, will allow us to decide to send the ceramic back to the prosthesis laboratory to reinflate the contact point.
It should be noted that these contact point fault problems are increasingly rare today with digital fingerprint protocols…
Furthermore, when the corono-peripheral preparations have been carried out correctly with a good reading of the stump and its prosthetic limits and when the prosthesis laboratory has respected the quantity of spacer for perfect passive insertion of the ceramic, the defect voltage at the contact point is rarer.
Indeed, when the spacing between the lower surface of the crown and the prepared stump is sufficient (80 to 100 microns), the insertion of the crown is completely passive and very often the contact point tension errors are of this nature. actually less frequent.
During the cementing appointment, if the tension at the interproximal contact point remains excessive when trying on the ceramic and if the dental floss does not pass, passes with force or tears as the clamping forces are so high , I recommend a little sleight of hand to make it easier to adjust the contact point.
I use a sheet of 80 to 100 micron occlusion marker paper positioned parallel to the contact surface when inserting the ceramic in order to precisely mark the tension area and touch up the ceramic in the area where friction is excessive. This “tip” is very simple to execute and greatly facilitates the assessment of the tension at the point of contact.
Personally, I subtract very gradually in small steps after numerous tests of reinserting the ceramic to gradually re-evaluate the pressure and obtain the ideal tension. The area to be subtracted is revealed by an excess of red or blue point of the occlusion marker paper on the contact area (proximal face) of the ceramic.

Watch the step-by-step mini-videos of this handy trick