Risk Factors for Complications Following Staged Alveolar Ridge Augmentation and Dental Implantation: A Retrospective Evaluation of 151 Cases with Allogeneic and 70 Cases with Autogenous Bone Blocks

Frank R Kloss, Peer W Kämmerer, Anita Kloss-Brandstätter

Full text link: https://pubmed.ncbi.nlm.nih.gov/36614811/

Risk Factors for Complications Following Staged Alveolar Ridge Augmentation and Dental Implantation: A Retrospective Evaluation of 151 Cases with Allogeneic and 70 Cases with Autogenous Bone Blocks

1. Scientific Reference

• Study Title: Risk Factors for Complications Following Staged Alveolar Ridge Augmentation and Dental Implantation: A Retrospective Evaluation of 151 Cases with Allogeneic and 70 Cases with Autogenous Bone Blocks
• Authors: Frank R. Kloss, Peer W. Kämmerer, Anita Kloss-Brandstätter
• Scientific Journal: Journal of Clinical Medicine
• Year of Publication: 2023
• DOI: 10.3390/jcm12010006

2. Scientific Background

Reconstruction of alveolar bone defects is a common step in implant dentistry when the residual bone volume does not allow predictable implant placement. Block bone grafts represent a widely used strategy for restoring the horizontal and vertical dimensions of the ridge prior to implant rehabilitation.

Historically, autogenous bone blocks have been considered a clinical reference standard because of their biological properties. However, harvesting these grafts requires an additional donor site and exposes the patient to specific morbidity. Allogeneic bone substitutes have progressively become an attractive alternative in order to reduce these surgical constraints.

In this context, understanding the factors likely to increase the risk of complications following pre-implant bone augmentation is of major interest. Identifying these factors could help optimize surgical planning and improve the predictability of implant treatments.

3. Study Objective

The primary objective of this study was to identify factors associated with the occurrence of complications following alveolar ridge augmentation performed using autogenous or allogeneic bone blocks prior to dental implant placement.

The authors sought to determine which surgical, anatomical, or patient-related parameters could influence the risk of complications during the bone reconstruction phase.

4. Methodology

This was a retrospective study based on the analysis of records from patients treated in a private oral and maxillofacial surgery clinic between 2013 and 2019.

The cohort included 164 consecutive patients who underwent 221 bone augmentation procedures, performed using 151 allogeneic blocks and 70 autogenous blocks. All surgical procedures were carried out by the same surgeon.

Patients were followed at regular intervals to identify possible complications such as wound dehiscence, partial or complete graft loss, infection, or implant failure.

The statistical analysis was based in particular on ROC curves and multiple logistic regression models designed to determine independent risk factors.

5. Main Results

The majority of procedures were completed without adverse events. Of the 221 augmentations performed, 88.2% showed no complications.

Complications were observed more frequently in the group treated with autogenous grafts. A complication occurred in 20% of autogenous augmentations compared with 7.9% of allogeneic augmentations.

The most frequently reported complication was partial loss of the bone graft, which was significantly more common with autogenous blocks.

Multivariate analysis identified four factors associated with a significant increase in the risk of complications:

• use of an autogenous bone block;
• smoking;
• vertical augmentation greater than 2.55 mm;
• over-contouring of the reconstructed bone volume.

Among these factors, over-contouring appeared to exert the greatest influence on the risk of complications.

Despite these events, the authors indicate that the observed complications remained essentially minor and did not compromise the final implant rehabilitation.

6. Clinical Analysis

This study provides particularly interesting insight into an aspect of pre-implant surgery that is sometimes underestimated: the geometry of bone reconstruction.

The results suggest that the amount of reconstructed volume is not the only factor to consider. The manner in which this volume is integrated into the natural architecture of the ridge appears to play a determining role. The concept of over-contouring, defined as augmentation extending beyond the bony profile of adjacent structures, emerges here as a factor strongly associated with postoperative complications.

The study also challenges a practice sometimes adopted in anticipation of future bone resorption. The presented data indicate that excessive augmentation could instead increase the risk of graft exposure or partial material loss.

From a clinical perspective, the results also highlight the importance of smoking control before bone reconstruction surgery. The impact observed in smokers is consistent with the classical concerns regarding tissue vascularization and healing.

Finally, the authors show that allogeneic grafts may present a favorable complication profile in this cohort. However, this observation should be interpreted with caution given the retrospective nature of the study and the existing differences between the treated groups.

7. Clinical Applications

The results of this study may be particularly useful during the planning of bone reconstruction treatments intended for implant rehabilitation.

They are especially relevant to:

• horizontal and vertical alveolar ridge augmentations;
• block bone grafting protocols prior to dental implant placement;
• situations involving localized bone deficiency following tooth loss;
• cases requiring bone reconstruction before implant-supported rehabilitation;
• assessment of surgical risk in smoking patients.

These data may also help refine volumetric reconstruction objectives in order to avoid excessive correction likely to increase biological complications.

8. Level of Evidence, Limitations and Transparency

This publication corresponds to a retrospective observational study, which constitutes an intermediate level of evidence lower than that of a randomized controlled trial.

The analyzed cohort is relatively large for this type of clinical evaluation, with 221 bone reconstruction procedures. Nevertheless, several limitations should be taken into account.

The retrospective design exposes the study to a risk of selection bias and limits control over confounding variables. Furthermore, the autogenous and allogeneic groups presented certain baseline differences, particularly regarding the type and extent of bone defects.

No specific conflict of interest involving the authors is mentioned in the information provided. The available data do not allow further assessment of this point.

9. Key Study Points

• Study Type: Retrospective observational study.
• Level of Evidence: Moderate.
• Population Analyzed: 164 patients.
• Number of Bone Grafts: 221 augmentations.
• Graft Distribution: 151 allogeneic blocks and 70 autogenous blocks.
• Mean Follow-up Duration: 3.5 years.
• Primary Outcome Evaluated: Occurrence of complications following alveolar bone augmentation.
• Main Result: Complications were more frequent with autogenous blocks.
• Independent Risk Factors: Smoking, over-contouring, vertical augmentation > 2.55 mm, and use of autogenous blocks.
• Scientific Conclusion: Complications remain globally infrequent, but certain surgical characteristics significantly increase their likelihood.
• Potential Limitations: Retrospective study, absence of randomization, differences between groups.

10. Scientific Impact

This study makes an original contribution to the literature on pre-implant bone grafting by focusing not only on the type of material used but also on the morphology of the reconstruction achieved.

The identification of a threshold of 2.55 mm for vertical augmentation represents an interesting element for clinical consideration, although this value will need to be confirmed by further prospective studies.

The results also reinforce the importance of three-dimensional planning of bone reconstructions and control of reconstructed volumes. The study highlights a technical factor—over-contouring—that has rarely been quantified with such precision in clinical publications.

Beyond the comparison between autogenous and allogeneic grafts, this work therefore contributes to a better understanding of the surgical determinants likely to influence healing and the stability of bone reconstructions prior to implantation.

11. Editorial Conclusion

This retrospective study suggests that complications following alveolar ridge augmentation remain relatively uncommon when surgical protocols are properly mastered. However, the presented data draw attention to several modifiable risk factors, particularly smoking, substantial vertical augmentation, and graft over-contouring. For clinicians involved in pre-implant bone reconstruction, these observations underscore the importance of measured surgical planning that respects the surrounding bone anatomy.