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News - Nothing but the tooth

{ May 2015 }

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May 2015
28th
28th of May 2015

Dental Implant Systems at Progressive Dentistry

We have recently been asked which types of dental implant systems we use at Progressive Dentistry.

The answer is: 

1. Nobel Biocare Implant System.

2. Astra Tech Dental Implant System.

3. Implant Direct System.

4. Ankylos Implant System.

5. Southern Dental Implant System.

We also have restorative capability for the Straumann implant system. However, we are happy to accommodate any implant system. 

If you have a problem with your dental implants and need some help, contact us. We will not simply dismiss your case because we do not use that particular implant.

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Tagged with:   Dental implants Nobel biocare Implant direct Anklos Astra tech dental
May 2015
19th
19th of May 2015

Tooth Wear - Grinding Or Bruxism

Our case of the month for May is one involving tooth wear. Tooth wear is a very common problem caused buy a number of factors and usually a combination of them all. The most common cause is night time grinding or bruxism. This can be hugely damaging to teeth. Did you know that on average our teeth make contact for only about 10-20 minutes of the day. During night grinding, the average contact time is 4 hours! It does not take a rocket scientist to figure out this is far too much contact which will lead to loss of tooth enamel. Just take a look at our case:
 

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Tagged with:   Tooth wear Fractured teeth Dahl technique Repairing tooth wear
May 2015
14th
14th of May 2015

Screw Retained Dental Implant Crowns

The great advantage of screw retained dental implant crowns is that there is no cement at all. Therefore any of the potential problems of excess cement extruding beyond the crown margin and instigating Peri-implantitis is negated. 

Another advantage is that if the crown needs to be removed, it is relatively easy to do so and there is no damage to the porcelain work by forcibly removing the crown.
 

Planning for Screw Retained Implant Crowns

In general, the screw access hole should be down the long axis of the implant. This is important in relation to ease of placement, avoiding damaging lateral tension forces when torquing the screw which could lead to screw loosening and avoiding the issue of possibly threading the screw if proper access has not been made. Therefore, prior to placing the dental implant, it is important to plan what type of restoration is to be placed. 

However, recent advances in prosthetic design have evolved and Nobel Biocare now have an angulated screw channel. This allows a angulation difference of 25 degrees, which is significant. This can be applied to the posterior and anterior regions. This is possibly a game changer in dental implant prosthetics.
 

Placing Screw Retained Dental Implant Crowns

The placement is generally quite simple. The crown and abutment is a one piece prosthetic device. The crown is then placed within the dental implant. There is only one path of insertion and therefore a placement jig is not required. Initially, screw down gently until the crown is stable and in it's fully seating position. Check the marginal adaptation, contacts, embrasure space and occlusion. Take a peri-apical radiograph to ensure correct seating. If so, make any necessary adjustments. 

Once all of the relevant checks have been made and verified, torque the screw to 20Ncm using a prosthetic torque wrench. The screw should be covered with sterile cotton wool and the access cavity restored with composite. 

Tip: for metal based substructures, to avoid a grey shadow use an opaque flowable composite around the periphery and on the base. Voco have an excellent one which I routinely use to block out dark areas whilst placing composites.
 

Removing Screw Retained Implant Crowns

Simply remove the composite and cotton wool carefully and unscrew the abutment screw. Simple. 

Tip: be very careful not to damage the abutment screw! Use an ultrasonic to remove the final layer of composite.
 

Conclusion

In many cases, screw retained implant crowns are the desired option. With the evolution of the Nobel Biocare angulated screw access, the scope for these restorations has increased hugely. With the huge advantage of no cement, I would suggest considering screw retained restorations for single implant crowns as the first choice option.

An article for dentists by Dr Nissit Patel

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Tagged with:   Dental implants Screw retained crowns Nobel biocare angulated screw access Screw retained implant crowns
May 2015
3rd
3rd of May 2015

Cement Retained Dental Implant Crowns

When restoring dental implants, the choice is screw retained or cement retained. Cement retained crowns will often be used when the screw access hole is not positioned down the long axis of the implant. There may be angulation issues or aesthetic issues that arise from this. Cement retained crowns may also be preferred by the patient due to the unaesthetic appearance of the access cavity for screw retained crowns, which often looks grey and discoloured if the underlying crown has a metal sub structure. Patients now often regard premolar and molar teeth as being in the aesthetic zone and are highly dental aware. Quite rightly, they expect dental implant crowns to look like natural teeth.
 

What Abutment Is Best for Cement Retained Crowns?

In my experience, Atlantis abutments are far superior to any other system. Think about how you would prepare a tooth for a crown and amplify the precision ten fold. With the digital age we live in, technology should be used to enhance the outcomes for our patients. This is one system that certainly does that. There are also other scanning centres which produce excellent abutments. It is worth talking with your dental implant technician and using a few systems. Of course, there is a cost implication involved and Atlantis may not be suitable for all.
 

How To Fit The Cement Retained Crown

When fitting cement retained crowns it is imperative that excess cement does not exude the margins and act as a plaque trap. This is one the main causes of Peri-implantitis and is avoidable. 

There is an excellent technique which will help you to avoid any issues with excess cement: 

1. Once you have verified the margins, occlusion, contacts, embrasure space and aesthetics you are ready to cement the crown. 

2. Use your PVS bite registration material and insert within the crown creating a tag at the end to act as a handle. 

3. Remove this index. 

4. Mix the cement, which is usually a temporary cement (Tempbond NE) or a dedicated implant cement and place within the crown. Do not overfill. Make sure the abutment screw is covered. I use pre sterilised cotton wool. 

5. Insert the index into the crown to remove the excess. This will leave a very fine layer of cement. 

6. Place the crown and wait for setting. There should be no excess at the margins.

7. Perform the usual checks and take a PA radiograph to verify. There should be no exudate whatsoever. 

8. A useful tip for removing any fine smears of Tempbond on the crown is orange solvent. Spray some onto a ball of cotton wool and clean any fine residue. 

9. Review as required.
 

How To Remove Cement Retained Implant Crowns

There are times when implant crowns will need to be removed. For example, if the abutment screw loosens. This is why temporary cements are used. In my experience, cement retained crowns can be removed with minimal fuss. However, you must pre warn the patient that some force is required. I would over emphasise this fact. To avoid damage to the porcelain, use rubber coated crown removing pliers. GC have an excellent one. Grip the crown firmly and exert pressure in a bucco-lingual direction initially and then rotational. The crown should ease off within a few seconds.
 

How To Maintain Dental Implant Crowns

Dental implant crowns, screw or cement retained, require maintenance just as natural teeth. However, your hygienist must be trained in this field. Regular scalers, hand or ultrasonic, should not be used for fear of scratching the titanium. Satelec have introduced some excellent ultrasonic tips for implants. We have invested in these with great success. Specific implant hand scalers can also be used. We are also keen on adjunctive methods of cleaning such as Philips Airfloss.
 

Feedback

Article for dentists written by Dr Nissit Patel. 

I hope this article has been of use. It comes from many years of experience of placing implant crowns, cement and screw retained. I welcome any feedback that you may have, please e-mail me: nissit@progressivedentistry.co.uk 

My next article will focus on screw retained crowns.

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Tagged with:   Cement retained dental implant crowns Dental implants Dental implant crowns