Bench Mastery: Implant-retained overdentures

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Dental Lab Products | January 2008

Bench Mastery
Kreyer on Removables

Getting to the root of implant-retained overdentures

Analysis of models during treatment planning is critical to revealing variables and solving prosthetic problems.

There are two aspects of treatment planning: the clinical treatment plan, driven by biological factors, and the technical treatment plan, impelled by biomechanical factors. For cases where a mandibular complete denture is being transitioned to an implant-retained overdenture, the technical biomechanical factors that require a technician’s expertise are key in this first stage of planning. The second technical stage—creating a surgical guide stent for a clinical diagnostic aid—will be addressed in the March Bench Mastery article.

Robert Kreyer, CDT

The complete dentures (Fig. A) were sent to evaluate an existing mandibular denture for an implant-retained overdenture. To conduct a proper analysis, it is necessary to create models (Figs. B, C), which enable the technician to evaluate the current edentulous relationships. Existing dentures and the newly created models must be mounted with a centric occlusal record (Fig. D) to evaluate occlusal relationships.

Analysis

The mandibular denture is set in a Class III occlusal scheme (Fig. E). If implants are to be placed in the anterior mandible, what effect will this type of occlusion have on the implant abutments? If the anterior arrangement is duplicated, there will be severe lateral forces placed on implant abutments through the existing Class III anterior incisal lever.

In Fig. F, we see the maxillary and mandibular residual ridge relationship. Note the Class I skeletal relationship compared to the existing one that was set in a Class III. Through this analysis we see that the new dentures can be designed with a Class I or Class II occlusal scheme, and biomechanical forces can be redistributed to decrease lateral forces on implant abutments.

Set-up

To proceed with this technical redesign of an existing occlusal scheme, we start by setting the maxillary anteriors (Fig. G). A flat plane template is used on the Stratos 100 average value articulator (Ivoclar Vivadent) to establish an even plane of occlusion and smile line.

The maxillary incisal edge position was duplicated by measuring the existing incisive papilla to

incisal edge space with a denture gauge, alma gauge, or Boley gauge. The posterior denture teeth are not set, and a wax bite rim is created for stabilization.
The mandibular teeth have been reset in a Class I relationship (Fig. H) using SR Vivo TAC radiopaque anterior teeth (Ivoclar Vivadent). The corrected anterior relationship (Fig. I) will decrease lateral forces on implant abutments and allow proper positioning of teeth in relation to implants during this technical planning phase of treatment.
The teeth and wax were processed into clear acrylic using a Denture Duplicator (Lang Dental Mfg. Co.) with self-curing resin (Fig. J). The maxillary anterior teeth as well as posterior bite rim then were processed in clear acrylic resin for stabilization of the mandibular stent during the CT Scanning procedure.
Fig. K shows the occlusal view of the radiopaque CT Scan stent, which will be a diagnostic aid for implant angulations and placement in relation to the mandibular bone.

SUMMARY

Comprehensive complete denture/overdenture treatment must involve collaboration between the clinician and technician to provide optimal patient care during prosthetic treatment. Prosthetic services such as technical treatment planning add a higher level of value to a dental laboratory’s prosthetic product line.

The ability to conduct an analysis of existing mounted dentures and edentulous models for diagnostic CT Scan stents with radiopaque denture teeth will enable the clinician and technician to exceed expectations while enjoying predictable success with implant retained removable prosthetics.
For information on prosthetic courses and consulting by Robert Kreyer, CDT, go to www.PersonalizedDenture.com.

Fig. A Existing complete dentures and triple tray bite as sent from dental office.

Fig. B Complete conventional dentures with VPS Sil-Tech Super Master models and stone bases.

Fig. C Edentulous VPS casts of existing complete dentures.

Fig. D Mounting of existing dentures with bite registration on Stratos 100 average value articulator.

Fig. E Mounted dentures. Note anterior and posterior tooth arrangement in centric occlusion. Existing denture was set in a Class III occlusal scheme in centric relation.

Fig. F Residual ridge relationship of patient in centric relation, with mandibular anterior ridge set in a Class I skeletal relationship.

Fig. G Maxillary anterior teeth set on a plane analyzer for proper incisal arrangement.

Fig. H Mandibular radiopaque anterior teeth arranged and set to maxillary anteriors.

Fig. I Buccal view of new anterior arrangement shows the Class I occlusion.

Fig. J Maxillary and mandibular tooth arrangements with gingival waxing processed in clear acrylic, creating a CT Scan stent for clinical diagnosis of implant placement.

Fig. K Occlusal view of mandibular CT Scan stent with radiopaque teeth.

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