Massimiliano Ricci

Tissue changes of extraction sockets in humans: a comparison of spontaneous healing vs. ridge preservation with secondary soft tissue healing

INTRODUCTION As a consequence of extraction, the height of the buccal wall tends to decrease and results in the disappearance of bundle bone. To modify bone remodelling after extraction, various ridge preservation techniques have been proposed. The present research was drawn up with the following considerations in mind: to evaluate and to compare changes of hard and soft tissues in post-extraction sockets which received a ridge preservation procedure, with post-extraction sockets which had healed naturally. MATERIALS AND METHODS Each patient was randomly allocated to a test or control group using a specific software package. After extraction, the sockets were carefully inspected and any granulation tissue was removed. The control sites received silk sutures to stabilize the clot without any grafting material. The test sites were grafted with corticocancellous porcine bone and a collagen membrane. All experimental sites had the membranes left exposed to the oral cavity with a secondary wound healing. The thickness of the buccal alveolar bone, if present, was carefully measured at the time of tooth extraction using a calliper at 1 mm from the edge of the wall. The following clinical parameters were evaluated at baseline and after 4 months at implant placement: vertical bone changes, horizontal bone changes and width of keratinized gingiva. The length, diameter and need for additional bone augmentation were assessed for both groups at the time of implant insertion. RESULTS The control group showed vertical bone resorption of 1 ± 0.7 mm, 2.1 ± 0.6 mm, 1 ± 0.8 mm and 2 ± 0.73 mm at the mesial, vestibular, distal and lingual sites respectively. Moreover, changes in horizontal dimension showed an average resorption of 3.6 ± 0.72 mm. The test sites showed a horizontal bone remodelling of 0.3 ± 0.76 mm, 1.1 ± 0.96 mm, 0.3 ± 0.85 mm, 0.9 ± 0.98 mm at the mesial, vestibular, distal and lingual sites respectively. The horizontal bone resorption at the test sites was 1.6 ± 0.55 mm. The keratinized gingiva showed a coronal shift of 0.7 mm in the control group when compared to 1.1 mm in the test group. In addition, 42% of sites in the control group required an additional bone augmentation at implant placement, when compared to 7% in the test sites. CONCLUSIONS This study clearly points out that an alveolar ridge preservation technique performed with collagenated porcine bone and a resorbable membrane--according to the procedure reported in this study--was able to limit the contour changes after tooth extraction. Finally, the test sites showed a better preservation of facial keratinized tissue when compared to control sites; grafted sites allowed the placement of longer and wider implants when compared to implants inserted in non-grafted sites.

Maxillary sinus augmentation using prehydrated corticocancellous porcine bone: hystomorphometric evaluation after 6 months.

BACKGROUND Insufficient alveolar bone height often prevents the placement of standard dental implants in the posterior part of edentulous maxilla. In order to increase adequately the vertical dimension of the reabsorbed alveolar process, a sinus lift procedure is often necessary. The aim of this study was to evaluate histologic results of a prehydrated corticocancellous porcine bone used in maxillary sinus augmentation. METHODS Patients (age 18-70 years) with a residual bone height requiring a maxillary sinus augmentation procedure to place dental implants were eligible for this study. All patients were treated with the same surgical technique consisting of sinus floor augmentation via a lateral approach. The space obtained by elevation of the mucosa wall was grafted with prehydrated and collagenated corticocancellous porcine bone. Biopsies were harvested 6 months after the augmentation procedures. RESULTS Twenty-four patients were enrolled. The mean percentage of new formed bone was 43.9 ± 18.6% (range 7.5-100%), whereas the mean percentage of residual graft material was 14.2 ± 13.6% (range 0-41.9%). The new bone/residual graft material ratio in the maxillary sinuses was 3.1. The mean soft tissues percentage was 41.8 ± 22.7% (range 0-92.5%). CONCLUSION The present study suggested that porcine bone showed excellent osteoconductive properties and could be used successfully for sinus augmentation. Moreover, the porcine bone showed a high percentage of reabsorption after 6 months; this might be because of the presence of collagen and the porosity of the graft material.

Flap versus flapless procedure for ridge preservation in alveolar extraction sockets: a histological evaluation in a randomized clinical trial

OBJECTIVE The aim of this study was to evaluate and compare the histological and histomorphometric features of two different procedures carried out in extraction socket grafting; namely, the flapped and flapless technique. MATERIALS AND METHODS Patients considered eligible for the study were randomized to receive tooth extraction and ridge preservation with the porcine bone and collagen membrane, with a full thickness mucoperiosteal flap and primary soft tissue closure (control group), or, with a flapless procedure and a secondary soft tissue closure (test group). After 3 months of healing, the surgical re-entry procedure was performed and implants were inserted in the test as well as in the control sites. Bone core samples were harvested from both groups and processed to be observed under light microscopy. Outcome variables were percentages of newly formed bone, residual graft particles and marrow spaces. RESULTS Thirty-four patients were enrolled in the study. All of the scheduled implants were placed. Histological and histomorphometrical analyses did not report significant differences between the two groups (with P-values ranging from 0.690 to 0.917). The mean percentages of newly formed bone, soft tissues and residual grafted particles were 22.5 and 22.5%, 59.3 and 59.4%, and 18.6 and 18.2% respectively for flap and flapless approach. CONCLUSION No histological and histomorphometrical differences were observed when comparing the flap and the flapless technique for tooth extraction and socket grafting procedures.

Buccal bone deficiency in fresh extraction sockets: a prospective single cohort study

OBJECTIVE The purpose of this prospective single cohort study was to evaluate the use of xenograft and collagen membranes in treating full or partial buccal bone defects of fresh extraction sockets in the esthetic zone. MATERIALS AND METHODS Thirty-three patients requiring tooth extraction in the anterior maxillary area and showing a complete or partial buccal bone plate deficiency (more than 2 mm) were consecutively enrolled and treated. Corticocancellous porcine bone and platelet-rich fibrin (PRF) with a collagen membrane were used to graft the extraction sockets, and the membranes were left exposed to the oral cavity with a secondary soft tissue healing. The outcome variables were as follows: width of keratinized mucosa, facial soft tissue levels, clinical bone changes (measured with a clinical splint), implant and prosthesis failures, and peri-implant marginal bone changes. RESULTS All treated sites allowed the placement of implants; the width of keratinized mucosa at the mid-facial aspect showed an increase of 2.3 mm 5 months after the grafting procedure, and its value was 3.2 ± 0.6 mm at 1-year follow-up. The mean values of the facial soft tissue level indicated an increase over time. The bone level showed an improvement of 0.8 ± 0.1 mm and 0.7 ± 0.1 mm at mesial and distal sites, respectively, when compared to the baseline measurements. Finally, in the palatal area, no bone changes were observed. No implant failed during the entire observation period. CONCLUSIONS Findings from this study showed that xenograft and PRF, used for ridge preservation of the extraction sockets with buccal bone plate dehiscence in the esthetic zone, can be considered effective in repairing bone defects before implant placement. The secondary soft tissue healing over the grafted sockets did not compromise bone formation; moreover, the soft tissue level and the width of keratinized gingiva showed a significant improvement over time.

Leader genes in osteogenesis: a theoretical study

Little is still known about the molecular mechanisms involved in the process of osteogenesis. In this paper, the leader genes approach, a new bioinformatics method which has already been experimentally validated, is adopted in order to identify the genes involved in human osteogenesis. Interactions among genes are then calculated and genes are ranked according to their relative importance in this process. In total, 167 genes were identified as being involved in osteogenesis. Genes were divided into 4 groups, according to their main function in the osteogenic processes: skeletal development; cell adhesion and proliferation; ossification; and calcium ion binding. Seven genes were consistently identified as leader genes (i.e. the genes with the greatest importance in osteogenesis), while 14 were found to have slightly less importance (class B genes). It was interesting to notice that the larger part of leader and class B genes belonged to the cell adhesion and proliferation or to the ossification sub-groups. This finding suggested that these two particular sub-processes could play a more important role in osteogenesis. Moreover, among the 7 leader genes, it is interesting to notice that RUNX2, BMP2, SPARC, PTH play a direct role in bone formation, while the 3 other leader genes (VEGF, IL6, FGF2) seem to be more connected with an angiogenetic process. Twenty-nine genes have no known interactions (orphan genes). From these results, it may be possible to plan an ad hoc experimentation, for instance by microarray analyses, focused on leader, class B and orphan genes, with the aim to shed new light on the molecular mechanisms underlying osteogenesis.

Fracture of Anterior Iliac Crest Following Bone Graft Harvest in an Anorexic Patient: Case Report and Review of the Literature

In the treatment of jaw bone atrophies, autologus bone is still considered the gold standard because of its excellent osteoconductive, osteoinductive, and osteogenetic proprieties and lack of immunogenicity, which allow better graft integration and stability. Although various donor sites are available, the iliac crest represents the best source of corticocancellous bone, and literature suggests that it has low morbidity. However, this case report emphasizes that patients with systemic diseases such as anorexia should be carefully evaluated before such an operation, because unfavorable bone conditions may jeopardize the outcome. A 47-year-old woman needing rehabilitation of the upper arch was considered for iliac crest harvesting. She stated that she had suffered from anorexia for 30 years. A corticocancellous block was harvested by a bone saw using an anterolateral approach to the outer table of the right anterior iliac crest. The postoperative course was uneventful, but 13 days later, she complained of a sudden pain in the operated area, and X rays revealed a fracture of the anterior iliac crest. So far, the literature has mentioned 50 cases of iliac crest fractures after bone harvesting, and 28 cases among these are due to harvesting in the anterior part of the iliac crest. Several factors seem to be responsible for this complication, including the area of harvesting, residual bone thickness, technique used, and age and gender of the patient. To our knowledge, our case is the first of hip fracture after bone harvesting in a patient suffering from anorexia. Both low weight and osteoporosis are probably responsible for this complication. In our opinion, patients suffering from anorexia should be considered at risk for bone harvesting, and an appropriate mini-invasive surgical technique should be carried out instead.

Periodontal dressing may influence the clinical outcome of non-surgical periodontal treatment: a split-mouth study.

INTRODUCTION After scaling and root planning (SRP), healing induces the formation of a junctional long epithelium rather than a new connective attachment. We hypothesize that the placement of a periodontal dressing will be able to prevent detachment of coagulum inducing proper healing and improving periodontal parameters. MATERIALS AND METHODS This split-mouth study included 30 patients with periodontitis with ages ranging from 35 to 70 years. Probing pocket depth (PD), probing attachment level (PAL), bleeding on probing index (BoP) and plaque index (PI) were assessed before and after therapy. The group of patients received SRP in a span of 24 h. Then, a periodontal dressing was applied on the test side and it was removed after 1 week. RESULTS CONTROL GROUP The difference between PD values at baseline and after therapy was 1.6 ± 0.6 mm. The difference in PAL (ΔPAL) measurement was 1.4 ± 0.4. Test group: there was a greater PD reduction, this being 2.4 ± 0.6 mm on average. The difference in PAL was 2.5 ± 0.4 mm. CONCLUSIONS Our results clearly suggest that the use of a periodontal dressing improves the periodontal parameters after an SRP procedure. This is probably due to clot stabilization and prevention of bacterial colonization during wound healing.

An evaluation of new designs in implant-abutment connections: a finite element method assessment.

Purpose: This research sought first to evaluate the differences in the finite element method (FEM) analysis of 4 different implant surfaces, including internal and external connections of the same manufacturer with additional modifications. Methods: In this study, 4 dental implants from the same manufacturer were compared. A connection system was modified with a collar to improve its stability. A nonlinear dynamic analysis by FEM was used to calculate the transient response of the dental implant systems. Results: The results of FEM analysis indicated that the implant-modified configuration is more efficient in loading support when compared with the others. Conclusion: In the present research, 4 different types of connections were evaluated: a modified internal hex connection with a collar (to increase stability), an internal hex connection, a standard connection without hex, and an external connection. These data demonstrated that the internal hex connection with the modification of the manufacturers original is much more resistant to loosening and/or distortion than the traditional hex.

The use of bone block allografts in sinus augmentation, followed by delayed implant placement: A case series

Purpose: This article reports the clinical outcomes observed in a large number of patients receiving block bone allograft used for sinus augmentation and delayed implant placement. Patients and Methods: In total, 28 patients (13 males) with a mean age of 49.8 ± 10.1 years (range: 33-67 years) were included in this case series. All selected patients suffered from severe alveolar ridge atrophy in the posterior maxilla and required bone augmentation procedures, followed by implant placement after 6 months. All patients were followed for 18 months after the grafting, with scheduled monthly visits and/or more frequent visits if required. The survival rates for both the bone blocks and placed implants were then evaluated. Results: A total of 42 blocks and 90 implants were placed. Only one bone graft and 5 implants failed; the survival rate was 97.2% and 95.5% for the bone grafts and implants, respectively. The graft failed due to the onset of post-surgical infectious sinusitis, while in some patients’ implants showed absence of osteointegration at the end of the healing phase. Of note, all failed implants were observed in heavy smokers; in all other patients, blocks and implants were successful. Conclusions: This preliminary case series suggests that the grafting of bone allograft followed by delayed implant placement may be a promising strategy for sinus augmentation. More extended and larger follow-up studies are needed to confirm this preliminary data.

Changes in soft tissues around immediate full-arch rehabilitations: a prospective study.

INTRODUCTION Nowadays, aesthetic appearance is receiving more and more attention from clinicians and patients. Therefore, it is of paramount importance for the surgeon to maintain or to improve the quality and the stability of the soft tissue-implant interface. The scientific literature supports the idea that the immediate placement and provisionalization of endosseus implants and abutments can indeed offer additional clinical control over the peri-implant tissue architecture. On this basis, this prospective study aims to evaluate the changes in soft tissues around immediately loaded dental implants in full-arch rehabilitations, over a period of 3 months. MATERIALS AND METHODS Fifteen subjects were treated for immediate full-arch rehabilitations. Following implant placement, provisional rehabilitations made of bisphenol-A-glycidyldimethacrylate (BIS-GMA) and resin were placed. All records were made using a periodontal probe. The facial soft-tissue level was measured evaluating the distance between the soft-tissue margin and the incisal edge of the crown. Moreover, papilla levels were measured at the mesial and distal sites from a reference line connecting the occlusal edge of the crowns. RESULTS The average value at the mesial site was -0.035 mm (±1, median 0 mm), while at the midfacial site, it was 0 mm (±0.76, median 0 mm) and at the distal site, -0.05 mm (±0.92, median 0 mm). The plaque score index showed a reduction during the follow-up period. DISCUSSION Our data indicate that no differences at the midfacial point were detectable over the observation period. This is in agreement with several studies; it is plausible that these results are linked to a correct position of the implant in the alveolar socket. Moreover, comparing our results with what has been reported by other authors, it is surprising that while other studies highlight that papilla loss at the mesial and distal aspect is an expected consequence of immediate implant restorations, our data do not show any changes. The explanation of these results remains unclear. Further studies are needed to support our data and to clarify what mechanisms are involved in the maintenance of soft tissue.