MANAGING THE LINGUAL REDUCTION IN A DEEP OVERBITE CASE WHEN PLACING A INLAY MARYLAND RETAINER: DR PETER WALFORD FEBRUARY 28 2026
Here is a strategy for establishing the correct lingual reduction in a deep overbite case. We want 1.5 mm to produce a stiff flange. We will obtain a 1mm reduction on the maxillary tooth and 0.5 mm from ameloplasty on the lower facial surface of the opposing lower incisors. We start with a trial prep on the stone models.
First, make duplicates of both models so that you can reference between preop and postop after trial preps.
Soak one set of stone models in water for a few minutes: we will be using Kerr Occlusal Indicator Wax and wetting the model will keep it from sticking to the stone. Warm the wax under warm water, apply it to the soaked upper model and bring the models tightly together in full articulation. Have Shimstock between the posterior teeth in advance to ensure you have fully seated the models and have reached an accurate assessment in the occlusal indicator wax. Separate the models and take a photo of the centric contacts on the upper anterior teeth in the wax. Leave the wax there for the stone to dry.
Once the first stone model has dried, take a fine pencil and outline the contact areas through the wax. Then remover the wax and take a photo of the marked model.
Repeat the above sequence on the lower model, to see where the incisors make contact. Let model dry, pencil the contact area. Take a photo of that.
You now have 4 photos to help guide you through the design and take it to the clinical appointment. In previous times we would just use the models but now we can take photos so readily and use them to communicate to the lab, dental assistant, and perhaps the patient.
Next, take a VPS impression of an unprepared upper model. This VPS will create a matrix to fabricate a depth index to confirm the reduction after the trial prep. We will use conventional C&B temporary material to make this index, as if you were making a temp for a crown. We will caliper it to verify the desired reduction. For this use a pinch C&B caliper, image below.
Next step, take a #2 FG bur and use a machinist’s caliper (from Amazon, image below)
to measure its diameter. We want it to be 1mm in diameter. Because of the deep OB, we will prep the abutment to 1mm of depth and gain the extra 0.5 mm from the opposing tooth/teeth.
BTW, a dial caliper like this measures all our small objects- RCT files, posts, tooth dimensions- wherever we need to engage our left brain. The fact that most dentists don’t own, much less use such a guage tells me that we utilize only half our brain day to day. This ensures that dentistry remains a cottage industry practicing an art form, not even a pretense to objectivity. However, using this guage and both sides of your brain, we can confidently make an accurate and consistent reduction.
The depth of the desired reduction on the maxillary is 1 mm. In a normal overbite case, we usually only have to reduce selected occlusal stops. In a deep OB case, we likely will need to reduce a great deal of the lingual enamel. The diameter of bur we want is 1mm. Insert the chosen bur to its full diameter all over the lingual surface of the tooth, making little “dimples” of that depth- accurate initial depth cuts. Do not prepare perimeter margins yet. The tooth will look like a colander after all these depth cuts.
Here is a trick to ensure you keep the reduction consistent: after these depth cuts, etch the enamel with phosphoric acid, rinse, dry, apply Caries Detector, wash, and dry. All the enamel will now be pink!
Reduce the lingual surface enamel with a round bur, a #6 diamond for example, joining the little “islands” of unreduced enamel. If the cut becomes deeper than the dimples, this over-reduction becomes obvious -because the tooth changes color from pink to white once fresh enamel is reached. Cease reduction when the surface turns white! Simple!
PERIPHERAL MARGINS
The peripheral margins are next.
Paint the tooth entirely to the gingival line and proximal margin areas with an indelible black laundry marking pen.
This makes it extremely easy to identify the margins as you cut. If you guide the handpiece with the fingers of both hands, it produces an exceptionally clean margin. Don’t be embarrassed. This is a “Hot Tip” –it is Dr. Richard Tucker’s method in his exceptional, internationally recognized cast gold work.
The margins do not need to be 1 mm thick if they are not in occlusion. They are only a definitive end point to the lingual reduction. The CEJ margin needs to be conservative because the enamel is thinnest at the CEJ. The incisal margin needs to be conservative because the dark metal or the light hue of the opaque cement can transmit through the incisal aspect of the abutment, either darkening the appearance of the tooth or losing translucency. The proximal margins need to be conservative to avoid transparency issues as the incisal.
A final unifying pass with our familiar 12- bladed 7406 bur makes the diamond reduction smooth, unified to the peripheral margins and not appreciably deeper. When the black ink is completely gone it indicates that the reduction has been polished.
CREATE INLAY
With the lingual reduction complete, create the inlay. The method for this is well-described in the PowerPoint.
LOWER MODEL AMELOPLASTY
Next, we go to the lower model. Articulate the prepared models and examine where you still need space. We should have achieved a consistent 1mm from the maxillary reduction. We will gain the final 0.5mm from adjusting the lower incisor. Again make #2 dimples where you will need reduction, just shallower, i.e., half the diameter of the bur. Primarily in most cases the needed reduction is in the incisal third of the opposing teeth, where the incisor enamel is thick..
IMPORTANT: Routine reduction of the opposing tooth is not recommended. However, in deep OB case we have to push the envelope without risking dentin perforation. If the lab is given the room in the impressions to make the casting, you should not have any worries. Between the two reductions-the abutment and ameloplasty of the lower(s) we should have created space for a strong inflexible casting. This care in the design stage provides another benefit. If the lab has made an error, and made the flange too thick, then the casting will test high upon insertion. If have established everything correctly in the trial preps on stone models, then we know we can adjust the lingual surface with impunity. Be sure to check how the lab mounted the case in case there was a mounting error. So, armed with preop confidence, we have no worry about weakening or perforating the casting if it needs spot reduction. Another safeguard is to verify the metal thickness with our pinch caliper.
In planning enamel reduction, one needs to remember dental anatomy. Enamel is thickest at the incisal portion of the tooth. But if we need more casting thickness at the cingulum of the upper incisor, as in this case, we can obtain it through reducing the labioincisal area of the lower incisor. This manages the fatal error of over-reducing the cingulum and perforating to .dentin
To repeat, the thing we must avoid on the abutment is exposing dentin anywhere. Dentin bond strength is half that of enamel bond strength. As well, dentin bonding degrades more rapidly than enamel bonding. The rule for a successful Mayland flange is that 95% of the bonding substrate must be enamel. We learned that lesson in Porcelain Laminate Veneers. Now it’s time to learn the lesson again for Inlay Maryland retainers.
Yes, it is possible that in some deep OB cases with worn incisors, ameloplasty may cut into the dentin of the lower incisor. It is not the end of the world if you do so., We can restore the perforation invisibly with a low-shrinkage, hard-wearing, metameric and high polishing composite such as 3M Espe Z-250 or Tokuyama Estelite Sigma Quick. It will look and wear acceptably.
The goal of this workup is to avoid surprises. We do not want to land in a situation without proper anticipation. It may prove after this workup that we must discard the flange Maryland retainer, and proceed to a full coverage crowns instead, where we are permitted to prep into dentin.
VERIFICATION OF LINGUAL REDUCTION WITH AN INDEX
Final confirmation: On the stone model, make a depth-index temporary with your usual material in the VPS matrix taken preoperatively – as if you were making a normal C&B temp. Lubricate the model with something like KY Jelly, (glycerine) or Liquid Lens to eliminate the tendency for the temp material to lock onto the surface of the stone model.
A NOTE ABOUT TEMPORIZING THE FLANGE/INLAY ABUTMENT.
In the F/I clinical procedure I do not recommend making a flange for the temp- these fingernail- thick temps are too thin and seldom survive. At this planning stage we are only making a flange as an index to verify that we have reduced enough.
Caliper the index for thickness. It should be 1mm of thick. If it’s correct, put the temporary back on the prepared model, and articulate it against the prepared lower to check that there is the half millimetre clearance between it and the clearance you generated with the ameloplasty. Use Occlusal indicator Wax between the trial flange on the upper model and the ameloplastied lower to ensure that you have the extra 0.5mm space – you can’t readily see it in a deep OB case.
As a side issue, If you are wondering about how we temp the inlay in clinical practice, we use a blue-tinted composite temp material, Spident Temp-it Blu. It works well, is very quick, and is inexpensive, https://kdentalsupplies.com
Without a temp for the flange, the patient’s tongue will feel the flange portion of the prep. This is why we do not leave it rough after the diamond reduction, but polish it with the 7406 bur. Then it will feel smooth – not the same as pre-op, but tolerable. Being enamel, there will be no associated sensitivity.
I have not seen a tendency of teeth to over-erupt in a two- or three-week period while the case is being fabricated.
At the cementation appointment, the blue tint assists in removing the inlay temp completely before trying in the casting. If the inlay temp falls out, it will feel rough to the patient’s tongue. But there will be no sensitivity, because the dentin was desensitized with Microprime B before dismissal.
You may be tempted to use conventional LC composite to temp the inlay. Don’t! It is difficult to remove, residues are difficult to see, it will frustrate you and waste time at insertion.
COUNSELLING THE PATIENT AT DISMISSAL
I normally tell each patient not to be concerned if a temp falls out, which occurs about 20% of the time. They need assurance that there will be no impact on the outcome. This should alleviate psychological stress and a sense of impotent annoyance, and they will not feel compelled and panicked to call the office.
MAKING THE INLAY, IMPRESSIOIN, LAB PRESCRIPTION, FEE GUIDE CODES AND CEMENTATION INCLUDING SUB-TISSUE PONTIC (EMERGENCE PONTIC) AND BONE GRAFTING IN EXTRACTION SOCKETS
The above treatment steps are covered in a PowerPoint…but In these deep OB cases, indicate to the lab that you expect the flange casting to be 1.5 mm thick. Ask the lab to not use die spacer and insist they retain the sharpness of the inlay form.