Classification system on the selection of number of implants and superstructure design on the basis available vertical restorative space and interforaminal distance for implant supported mandibular overdenture

Abstract

Purpose: The rehabilitation of the edentulous mandible is a challenge due to various limiting factors, of which the available vertical restorative space (AVRS) has been well understood in the literature. However, other anatomic variations such as arch form, arch size, and also the interforaminal distance (IFD) (due to the presence of mandibular nerve) are influential in the selection of size and position of implants, and thereby the prosthetic design.

Materials and method: In the present study, 30 edentulous patients from a group of 300 edentulous patients, representing all the three jaw relations (Class I, II, and III) were evaluated for designing a classification that could help in a comprehensive treatment plan for the edentulous mandible. Dental panoramic radiographs of each individual with a trial or final prosthesis were made. The horizontal IFD and AVRS values were calculated.

Results: One-way analysis of variance followed by post-hoc test (multiple comparison) and Bonferroni method having P < 0.05 as significant value showed an overall mean of 38.9 mm for horizontal distance and 13.69 mm for the AVRS in 30 edentulous patients.

Conclusion: The results showed that in the majority of cases (90%) there is insufficient space to place a bar attachment supported by five implants for mandibular overdentures. This suggests that a universal treatment plan cannot be followed due to varying anatomic factors. Hence, it becomes imperative to have a set of clinical guidelines based on the AVRS and IFD, for the selection of implant number and type of attachment. The article proposes a simple classification system based on the AVRS and IFD for establishing guidelines in the treatment planning of the edentulous mandible, to aid in selection of implant size, number, and position along with the associated prosthetic design.

Keywords: Attachment; available vertical restorative space; implant; interforaminal distance; mandibular overdenture.

Figure 1

Interforaminal distance aiding the selection of number of implants for implant supported mandibular overdenture

Figure 2

Available vertical restorative space aiding the selection of type of superstructure for implant supported mandibular overdenture

Figure 3

Demonstrating the final denture of the patient, red arrow indicating the gutta-percha marked from the distal of left mandibular canine teeth to the distal of right canine, and black arrow representing the ball bearing (3 mm) on both maxillary and mandibular prosthesis

Figure 4

Digital orthopantomography of a patient, where yellow arrow indicates the gutta-percha marked over the mandibular denture teeth, black arrow representing the calibrated interforaminal distance, and red arrow shows the calibrated vertical space (from crest of alveolar ridge to occlusal plane)