The purpose of this observational, clinical study was to introduce a new classification 81 system for anterior maxilla tooth position with guidelines for immediate implant placement. Data 82 for facial and palatal bone wall height and thickness are also presented.

 

 

Each tooth was classified 85 according to its position and inclination within its alveolus (class I, middle of the alveolus; IA, thick 86 facial bone; IB, thin facial bone; class II, retroclined; IIA, thick crestal bone; IIB, thin crestal bone; class 87 III, proclined; class IV, facially outside bone envelope; class V, both thin facial and palatal bone with 88 apical isthmus). Bone thickness was measured for both facial and palatal walls at the following 89 points: crestal (A), mid-root (B), apex (C), and 4 mm beyond the apex. Bone wall height was also 90 evaluated.

 

Maxillary anterior teeth have predominantly thin facial bones, making palatal bone 96 thickness a crucial variable. The new classification system for radial plane tooth position is a 97 pragmatic clinical analysis for immediate implant treatment planning. (J Prosthet Dent 2017;

 

Recommendations for IIP
stipulate ideal anatomic con-
ditions (thick facial wall
phenotype, thick gingival
phenotype) and treatment by
well-trained, experienced cli-
nicians.2-6

 

Gingival recession and bucco-
palatal collapse are among the
most common long-term complications of immediate implants, although these may also occur with the delayed approach.7,9-11

 

 

long-term esthetic stability.12-14

 

 

Key anatomic factors that influence the outcomes of 99 IIP include gingival phenotype, facial bone thickness and 100 height, amount of bone beyond the apex, and buccal 101 gap.7,8,12,14-16 Among these factors, the alveolar bone 102 dimensions and extraction socket have received much 103 attention,6,16-18 as marked post-extraction ridge changes

 

are expected.5,12,19,20 Although most of these variables have been evaluated, the tooth root position and incli- nation, which have a significant effect on IIP, have been investigated to a lesser extent.21-23 Current guidelines for 3-dimensional (3D) IIP suggest osteotomy preparation into the sloping palatal socket wall.12 This approach does not apply to all clinical situations as tooth root position and inclination differ, and thus the residual tooth socket structure varies.

 

The classification proposed by Lau et al24 included 2 descriptions, 1 for root angulation and the other for root position in relation to the facial and palatal walls. Although the authors did provide clinical guidelines, the double-classification sys- tem appears complex. Another pioneering classification by Kan et al,22 although insightful, does not provide for anatomic variants and the concepts learned over the last 5 years.

 

 

Digital Imaging and Communi- cations in Medicine (DICOM) format

 

The results showed that between 83% and 92% of all teeth had facial bone <1 mm be- tween the crest and mid-root point. El Nahass and Naiem16 reported 86% of maxillary anterior teeth as having <1 mm at the facial crest. Wang et al23 reported that 80% of maxillary anterior teeth had thin facial bone. Chappuis et al5 also reported that a majority of maxillary anterior teeth (69%) had thin facial bone at the midfacial point. The results of all these studies are in accordance with those of the present studydthin facial bone pre- dominates in the esthetic zone.

 

Bone thickness at the palatal walls was also recorded in the present study. Most patients had thin palatal bone at crestal point A (63% <1 mm), increasing on average in thickness toward the mid-root position B (98% !1 mm) and to the apex point C (99% !1 mm). These findings are comparable with those published by Lee et al17 and Lau et al.24 Hyung-Ba et al6 also showed that 60.2% of all teeth presented palatal crests between 0.5 and 1 mm, and the results of these studies are in accordance with those of the present study.

 

Sex, however, affected bone height in the present study. The alveolar ridge was, on average, approximately 2 mm higher on the facial and palatal walls of canines and on the palatal walls of lateral incisors for men than women.

 

 

. Class I represents only 6% of maxillary anterior teeth. This clinical situation with thick facial bone (subtype IA) is rare. In such cases, the pilot osteotomy preparation may be initiated at the socket apex, and the apical bone will contribute largely to primary stability.

 

Class II represents the majority (76.5%), with 2 variations, thick (subtype IIA) or thin (subtype IIB) bone crest. The unpredictability of the facial bone, especially in type IIB, as with type IB, must be approached with caution.

Class III represents only 9.5%, with a thin facial bone 616 crest. In accordance with current studies, a delayed 617 approach may be better, and the high risk of facial 618 resorption must give caution. If IIP is selected, class III- 619 positioned tooth sites may benefit from a palatally posi- 620 tioned osteotomy. Palatal bone will contribute largely to 621 primary stability. Class IV represents only 7.3%, with a 622 thin facial bone wall. In accordance with current studies, 623 a delayed approach may be better. If IIP is selected, class 624 IV-positioned tooth sites should be prepared even more 625 palatally, as palatal and apical bone will provide the 626 entire primary stability. Class V represents 0.7%, with 627 neither bone facially, palatally, or apically to provide 628 primary stability. We regard class V tooth root position as 629 a contraindication to IIP.

 

 

 

The ideal indication for IIP would be thick facial 631 bone; however, results from this study and from pre- 632 vious studies indicate this is a rare clinical finding. The 633 next best situation would be the presence of a thick 634 palatal wall. Studies demonstrate at least 50% loss of 635 the overall alveolar ridge width after extraction,19 and a 636 7.5-mm vertical loss of the facial bone wall in the 637 esthetic zone5 of most patients. Bearing this in mind, 638 IIP dictates prudent planning and the appropriate 639 caution to best manage long-term peri-implant tissue

 

 

 

 

stability. Within the limits of the planned restoration,

9. Cosyn J, Eghbali A, Hermans A, Vervaeke S, De Bruyn H, Cleymaet R. A 5-
year prospective study on single immediate implants in the aesthetic zone.
J Clin Periodontol 2016;43:702-9. 694

10. Kan JY, Rungcharassaeng K, Sclar A, Lozada JL. Effects of the facial osseous
defect morphology on gingival dynamics after immediate tooth replacement 695 and guided bone regeneration: 1-year results. J Oral Maxillofac Surg 2007;65: 696 13-9.

11. Chen ST, Darby IB, Reynolds EC. A prospective clinical study of non- 697 submerged immediate implants: clinical outcomes and esthetic results. Clin 698 Oral Implants Res 2007;18:552-62.

12. Buser D, Chappuis V, Belser UC, Chen S. Implant placement post extraction 699 in esthetic single tooth sites: when immediate, when early, when late? 700 Periodontol 2000;2017(73):84-102.

IIP should be as far palatally as possible (except for class

641 I and possibly class IIA).11,20 This study emphasizes the

642 importance of the palatal bone for IIP as the key factor

643 for the initial osteotomy, for anchorage, for the final

 

644 implant positioning, and possibly for overall long-term

645 success. Studies are still required to further elucidate

646 the role of the palatal bone and its post-extraction

647 behavior.

CONCLUSIONS 650

. 651  Based on the findings of this study, the following con-

 

. 652  clusions were drawn:

 

14. Ferrus J, Cecchinato D, Pjetursson EB, Lang NP, Sanz M, Lindhe J. Factors 703 influencing ridge alterations following immediate implant placement into 704 extraction sockets. Clin Oral Implants Res 2010;21:22-9.

653 1. 654
655
656

657 2. 658
659
660

Most maxillary anterior teeth have thin facial bone walls, which may negate the benefits of immediate implant placement if management of these tissues is not adequately planned for.

The classification system proposed here is a straightforward, didactic clinical tool for evaluating the radial tooth root position to help select place- ment timing as well as osteotomy positioning for immediate implant placement.