Dr Declan Corcoran
Dr Carville R.
Bone Grafting of the Incisal Canal to allow for the Aesthetically Driven Implant Placement
Introduction: The presence of the Incisal canal in the premaxillary bone between the two maxillary central incisors very often precludes the accurate placement of dental implants in this area. This report describes bone grafting of the incisal canal to allow for the restoratively driven placement of two implants to replace Teeth Nos. 11 and 21.
A 61 year old female presented with a debonded Maryland Splint extending from Teeth Nos. 13 – 23 . The splint had been in place for over 30 years and during that time had debonded several times. The prosthesis had served as a periodontal splint for Teeth Nos. 11 and 21. The patient complained of a dark hue shining through the teeth as a result of the metal framework of the splint. In addition the patient was unhappy with the dimensions of Teeth Nos. 11 and 21, i.e. that they were too wide.
She was medically fit and intra orally there were no muco-cutaneous lesions present.
There was no evidence of excessive para-functional habits.
With the splint removed, mobility of teeth was assessed. Teeth Nos. 13,12, 22 and 23 had Grade I mobility and Teeth Nos. 11 and 21 had Grade III mobility. There was evidence of decay developing on the palatal surfaces of the laterals and canines underneath the metal framework.
A radiographic survey of the area (Figs 1 – 4) showed evidence of angular periodontal bone loss affecting Teeth Nos. 13, 11 and 21.
Fig 1, preoperatively
Figs 2 – 4, preoperatively
It was deemed that Teeth Nos. 11 and 21 had a hopeless prognosis and extraction was advised. An immediate acrylic temporary denture was fitted following the extractions. The wide dimension of the two central incisors is evident from Fig 5.
Fig 5, Temporary Acrylic denture in place showing the wide mesio-distal width of Teeth Nos.11 and 21 and the need for pink acrylic interdentally
Treatment options were discussed with the patient and implant crowns to replace Teeth Nos. 11 and 21 were recommended as the treatment of choice in view of the compromised periodontal status of the remaining teeth. It was also advised that an improvement in tooth colour could be expected with the removal of the palatal metal backing of the Maryland splint. A cat scan radiograph of the area (Fig 6) revealed
(a) the presence of a large incisal canal,
(b) a narrow bucco-palatal width of bone and
(c) a buccal concavity of the premaxillary bone.
Fig 6, CT Scan images showing presence of large incisal canal
The treatment plan offered to the patient was to place two implants relatively close to the midline and to widen the mesio-distal width of the lateral incisors to overcome the dental disharmony between the centrals and the laterals.
In order to create an appropriate volume of bone and to allow for restoratively driven implant placement it was decided
(i) to augment the premaxillary bone with particulate bone graft material.
(ii) to enucleate the contents of the incisal canal and place a bone graft in it.
(iii) to carry out delayed placement of the implants.
Surgical Procedure 1
The first surgical procedure involved reflection of a buccal full thickness muco periosteal flap extending from the disto buccal aspect of Tooth No.12 to the disto buccal aspect of Tooth No.21 with two releasing incisions. Palatally, a full thickness muco periosteal flap was raised from the distal aspect of Tooth No.13 to the distal aspect of Tooth No.23 while preserving the interdental papillae between the laterals and the canines. The contents of the incisal canal was incised to allow for full reflection of the palatal flap. The remaining contents of the incisal canal was enucleated using a spoon curette and a surgical round bur.
Following enucleation of the incisal canal and full flap reflection the clinical findings corroborated the radiographic findings of the presence of a large incisal canal and narrow alveolar bone (Fig 7). Particulate bovine bone (Botiss Cerabone, Granule size 0.5-1.0mm) was placed in the incisal canal and placed facially to augment the bone following decortication of the bone. (Fig 8).
The area was covered with a collagen membrane (Jason Membrane, Pericardium Collagen Membrane)(Fig 9). Following periosteal release of the buccal flap complete coaption of the flaps without tension was achieved.
Fig 7, showing the large incisal canal and the presence of concavities of the premaxillary bone. Both these features would preclude restoratively driven implant placement.
Fig 8, particulate bovine bone in place filling incisal canal and augmenting the facial bone.
Fig 9, collagen membrane in place over bone graft
Healing following surgery was without complications and no symptoms of altered sensation was experienced by the patient.
The clinical appearance six months following the bone grafting procedure showed evidence of ridge augmentation in a bucco-palatal dimension, as is seen in Fig 10 and the wide mesio-distal width of the edentulous area is evident in Fig 11.
Fig 10, the bucco-palatal dimension of the ridge developed
Fig 11, the wide mesio-distal dimension of the central incisor sites is evident.
Surgical Procedure 2
The second surgical procedure involved the flapless placement of two implants in the Nos.11 and 21 sites. The implants ( Nobelbiocare, Replace Select Tapered, Regular Platform x 11.5mm long) were placed relatively close to the midline and not in a central location between the mesial aspects of Teeth Nos.12 and 22. (Figs 12 and 13).
Fig 12, Implant placement in a relatively central location.
Fig 13, Implant placement in a relatively central location allowing for the possibility of the development of a papilla in the midline.
Restorative Phase
Some six months later with radiographic evidence of osseointegration of the implant taking place, the implants were restored with screw retained crowns and the laterals and canines were restored with composite restorations. The mesio-distal width of the laterals was widened and this allowed for narrower central incisor crowns, than had heretofore been present, to be fitted. This allowed the teeth to be restored giving due consideration to the Golden Proportion principles of Incisor Teeth. (Figs 14,15 and 16).
Fig 14, palatal view of screw retained crowns
Fig 15, buccal view of implant crowns in place and Teeth Nos. 12 and 21 restored to a wider mesio-distal dimension.
It also set the stage for:
(i) the development of a gradual emergence profile of the implant crowns.
(ii) the fabrication of the implant crowns without the use of pink porcelain interdentally.
(iii) the development of an interdental papilla between the two implant crowns in time.
(Figs 16,17)
Fig 16, Post operative radiograph showing evidence of good bone height around the implants and evidence of bone fill of the incisal canal.
Fig 17, Lip line showing harmonious dimensions to the central and lateral incisors.
Summary
The presence of the Incisal Canal in the anterior palate behind the central incisors, if large enough, can preclude the accurate placement of dental implants.
Various techniques have been devised to overcome the surgical dilemma that a large canal presents. This technique describes the enucleation of the contents of the canal and the filling of the canal with a bovine particulate graft material.
This surgical procedure allowed for the accurate, restoratively driven placement of two implants in the area.
No adverse postoperative reaction in the form of altered sensation was experienced by the patient. A search of the literature shows that adverse reactions to this procedure are a rarity. The fact that complications are a rarity does not absolve the clinician of his/her responsibility in obtaining clinical consent for this procedure.
The enucleation of the Incisal Canal should be considered to achieve accurate placement of implants in this aesthetic zone.
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