Effects of Implant Position on Clinical Crown Length and Papilla Fills in Implant-supported Maxillary Central Incisors

Objective To determine the effect of implant position on clinical crown length and papilla fills in implant-supported maxillary central incisors. Methods One implant replacing the 11th or 21st tooth was given to 158 patients who lost a maxillary central incisor after trauma. The contra-lateral central incisors were used as controls. The three-dimensional positional parameters were estimated using standardized photographs of the cast models, clinical photographs and peri-apical radiographs. Paired t tests were performed to examine the differences between the implants and the control teeth in clinical crown length, papilla fills, proximal bone crest levels, and the horizontal implant-teeth distance at the mesial and distal implant. Pearson correlations were used to identify the implant positional parameters associated with crown length and papilla fills. Results The implant-supported crowns were statistically longer than the controls(10.9±1.1) mm vs. (10.4±0.8) mm, P<0.05. Greater papilla fills were found in the mesial implants and distal contra-lateral teeth compared with the distal implants (P<0.000 1). The implants had higher levels of mesial proximal bone crest than the distal(2.2±1.4) mm vs. (1.2±1.5) mm, P<0.05. The oro-facial position of the implants was associated with the crown length (r=0.602, P=0.001). But the crown length was not correlated with the sagital angulation of the implants or the vertical distance from the implant fixture to the soft tissue margin. The proximal bone crest level was correlated with the papilla fill height (r=0.400,P=0.001). Conclusions An implant positioned buccally results in longer crown length. Minor buccal angulations of the implant do not necessarily result in increased crown length. Appropriate position and input depth may help avoid bone absorption and papilla shrinkage.