Space analysis of the maxillary anterior bone geometry to understand anatomical limitation: and implant simulation study using cone-beam computed tomography (CBCT)
PURPOSE: The purpose of this study was to analyze anatomical spatial limitations of the existing bone for maxillary anterior implant placement in normal subjects. MATERIALS AND METHODS: Fifty Two (52) Cone Beam Computed Tomography (CBCT) scans were selected. A 3i Osteotite (6 x 15mm) implant was superimposed on tooth positions from the right first premolar to left first premolar on reformatted cross sectional mages of maxillary anterior teeth. For the first trial, the implant was positioned following the alveolar bone axis. Utilizing Invivo 5 Software (Anatomage), the proximal overlaps between superimposed implants were evaluated at successive vertical steps of 2.5 mm. The prospective crown angulation or PCA (defined as the angulation between the crown axis and alveolar bone axis) was measured. The inter-canine distance across the arch, the palatal plane length and the palatal bony angulation (defined as the angulation between the palatal surface and the alveolar bone axis) were also measured. For the second trial, implant positioning followed a prosthetic driven position; the crown axis. The crown axis was defined as a line drawn from the midpoint of a line between the mid buccal/lingual CEJ to the incisal edge. The crest height and the apical height at which the implant's 1mm sleeve penetrated the buccal wall were calculated. RESULTS: The implant position at the central incisor and lateral incisor presented the highest percentage of overlap in both the biologically and prosthetically driven positions. The prospective crown angulation was higher at the location of the lateral incisor compared to the central incisor and canine position. The association between the remaining anatomical parameters and the prevalence of overlap was analyzed with bi-serial correlation. There was no significant relationship among any of these parameters. When the implant was simulated in a prosthetically driven position, the lateral incisor implant position frequently showed perforation at 5mm apical to the buccal crest margin demonstrating this position as highly sensitive. SUMMARY: The data demonstrated that the constriction of the alveolar bony volume in the anterior maxilla could affect implant placement. Understanding this bone morphology suggests a major limitation in the central/lateral positions which might require bone grafting. A new unique reference plane was utilized for this study.