Marco Toia

Osseointegration in periodontitis susceptible individuals

OBJECTIVES The aim of the present study was to examine tissue integration of implants placed (i) in subjects who had lost teeth because of advanced periodontal disease or for other reasons, (ii) in the posterior maxilla exhibiting varying amounts of mineralized bone. MATERIAL AND METHODS Thirty-six subjects were enrolled; 19 had lost teeth because of advanced periodontitis (group P) while the remaining 17 subjects had suffered tooth loss from other reasons (group NP). As part of site preparation for implant placement, a 3 mm trephine drill was used to remove one or more 2 mm wide and 5-6 mm long block of hard tissue [biopsy site; Lindhe et al. (2011). Clinical of Oral Implants Research, DOI: 10.1111/j.1600-0501.2011.02205.x]. Lateral to the biopsy site a twist drill (diameter 2 mm) was used to prepare the hard tissue in the posterior maxilla for the placement of a screw-shaped, self-tapping micro-implant (implant site). The implants used were 5 mm long, had a diameter of 2.2 mm. After 3 months of healing, the micro-implants with surrounding hard tissue cores were retrieved using a trephine drill. The tissue was processed for ground sectioning. The blocks were cut parallel to the long axis of the implant and reduced to a thickness of about 20 μm and stained in toluidine blue. The percentage of (i) implant surface that was in contact with mineralized bone as well as (ii) the amount of bone present within the threads of the micro-implants (percentage bone area) was determined. RESULTS Healing including hard tissue formation around implants placed in the posterior maxilla was similar in periodontitis susceptible and non-susceptible subjects. Thus, the degree of bone-to-implant contact (about 59%) as well as the amount of mineralized bone within threads of the micro-implant (about 45-50%) was similar in the two groups of subjects. Pearsons coefficient disclosed that there was a weak negative correlation (-0.49; P < 0.05) between volume of fibrous tissue (biopsy sites) and the length of bone to implant contact (BIC) while there was a weak positive correlation (0.51; P < 0.05) between the volume of bone marrow and BIC.

The alveolar process of the edentulous maxilla in periodontitis and non‐periodontitis subjects

BACKGROUND Early implant failures may document that the bone tissue or the wound-healing process following installation surgery was compromised. Subjects who have lost teeth for periodontal reasons exhibit more earlier implant failures than subjects who had experienced tooth loss for other reasons. AIM To describe the tissue of the fully healed extraction sites in subjects who had lost teeth as a result of periodontitis or for other reasons. MATERIAL AND METHODS Thirty-six otherwise healthy, partially dentate subjects with fully healed edentulous portions in the posterior maxilla were included. Nineteen of these subjects had lost teeth because of advanced periodontitis (group P) and 17 for other reasons (group NP). Using a trephine drill, a 4-6 mm long hard tissue specimen was harvested. The biopsies were decalcified, embedded in paraffin, sectioned, stained and examined. RESULTS The edentulous posterior maxilla was comprised of 47.1 ± 11% lamellar bone, 8.1 ± 7.1% woven bone, 4.3 ± 3.1% osteoid and 16.5 ± 10.4% bone marrow. There were no significant differences in the tissue composition of post-extraction sites of (i) P and NP subjects and (ii) premolar and molar sites. CONCLUSION More than 50% of the edentulous maxilla was comprised of mineralized bone (lamellar and woven bone). The bone trabeculae frequently appeared to have a random orientation. The direction of the trabeculae rather than the lack of mineralized bone tissue may explain the clinical impression that the bone in the posterior maxilla provides limited resistance to mechanical instrumentation.

Bone tissue in different parts of the edentulous maxilla and mandible

BACKGROUND The composition of the fully healed edentulous ridge of the posterior maxilla was recently examined and was found to contain about 50% mineralized bone and 16% bone marrow. AIM The objective was to examine the composition of the tissue of the fully healed ridge in different portions of the maxilla and the mandible in partially dentate subjects. MATERIAL AND METHODS Eighty-seven healthy subjects were included. A trephine drill was used to harvest hard tissue specimens. The biopsies were decalcified, embedded in paraffin, sectioned, stained, and examined using a point-counting procedure. RESULTS The marginal portion of the jaws almost consistently contained a cortical cap that was significantly wider in the mandible than in the maxilla and twice as wide in the anterior as in the posterior segments of the mandible. Lamellar bone and bone marrow were the dominating tissue elements. Lamellar bone occupied about 63% of the tissue in the mandible and 46% in the maxilla. The maxilla contained about 23% bone marrow as compared to 16% in the mandible. In the mandible, 70% (anterior) and 57% (posterior) were made up of lamellar bone. In the maxilla, the proportion of lamellar bone in the anterior and posterior segments was similar (about 45%). Bone marrow occupied close to 40% of the anterior maxilla, while in the posterior maxilla and the anterior and posterior mandible marrow comprised between 13 and 18%. CONCLUSION Marked differences existed with respect to tissue composition of the edentulous ridge between the maxilla and the mandible. The cortical crest was wider in the mandible than in the maxilla, and widest in the symphysis region of the mandible. The proportion of bone marrow was greater in the maxilla than in the mandible. The maxillary front tooth region was poor in lamellar bone but rich in bone marrow, while the anterior mandible contained large amounts of mineralized bone but small amounts of bone marrow.

Biomechanical, Biologic, and Clinical Outcomes of Undersized Implant Surgical Preparation: A Systematic Review

PURPOSE To compile the current evidence on biomechanical, biologic, and clinical outcomes of undersized surgical preparation protocols in dental implant surgery. MATERIALS AND METHODS An electronic search using three different databases (PubMed, Web of Science, and Cochrane Library) and a manual hand search were performed including in vitro, animal, and clinical studies published prior to October 2015. Studies in which an undersized drilling protocol was compared with a nonundersized drilling protocol were included. RESULTS From an initial selection of 1,655 titles, 29 studies met the inclusion criteria, including 14 biomechanical, 7 biologic, 6 biologic and biomechanical, and 2 clinical. Due to methodologic variation, meta-analysis was not performed. Several studies showed that implants inserted with an undersized drilling approach reached a significantly higher insertion torque value than conventional drilling in low-density substrates, while this effect is less evident if a thick cortical layer is present. Similar results in terms of boneto-implant contact (BIC) were achieved in the longer term between implants inserted with undersized and nonundersized protocols. Results in the short term were inconclusive. Clinical studies did not show negative outcomes for undersized drilling, although clinical evidence was sparse. No data are available on marginal bone loss. CONCLUSION From the biomechanical standpoint, an undersized drilling protocol is effective in increasing insertion torque in low-density bone. Biologic response in long-term healing after undersized implant placement is comparable to that in the nonundersized surgical drilling protocol. Clinical studies indicate that performing an undersized drilling protocol on low-density bone is a safe procedure; however, more extensive studies are needed to confirm these data.

Dimensions of the healthy gingiva and peri-implant mucosa

OBJECTIVE To determine the dimensions of the soft tissue cuff present at various aspects of teeth and to compare these dimensions to those of the mucosa surrounding single implants. MATERIAL AND METHODS Fifty volunteers were recruited that were ≥25 years of age and exhibited no signs of (i) untreated caries; (ii) loss of periodontal tissue support in the incisor, canine, and premolar regions; (iii) systemic or local disease. Furthermore, among the 50 patients recruited (iV), 27 had one single implant in the maxilla with teeth present mesial and/or distal to the implant. Probing pocket depth (PPD) and transmucosal sounding depth (TS) were assessed by five experienced, carefully calibrated examiners and with the use of a periodontal probe at the proximal (mesial, distal) and flat (facial, buccal and palatal/lingual) surfaces of all teeth/implants. The width of the keratinized mucosa (KM) was also determined. RESULTS It was demonstrated that (i) PPD and TS were greater at proximal than at flat surfaces at both tooth and implant sites. In addition, both PPD and TS were deeper at implant than at tooth sites. The TS values documented that the cuff of healthy soft tissue that surrounded a tooth varied between 2 mm at flat surfaces and 4 mm at proximal surfaces, while at implant sites, the mucosa at proximal as well as flat surfaces was 1-1.5 mm greater. CONCLUSION The probing pocket depth (PPD) and the transmucosal sounding depth (TS) values were greater at proximal than at flat, that is, facial/palatal (lingual) surfaces at tooth sites and frequently also at implant sites. Furthermore, the PPD and the TS dimensions were greater at implant than at adjacent tooth sites.

Implant Vertical Fractures Provoked by Laboratory Procedures: A Finite Element Analysis Inspired from Clinical Cases.

Purpose:To investigate the causes for internal implant fractures, which is suggested to be one of the reasons for marginal bone loss. Materials and Methods:From a 14-year database of 6051 implants, 10 single implant vertical fractures were identified and the abutments were all castable abutments. The abutments presented contamination and irregularities at the internal connecting areas. The hypothesis was that perfect fit was disturbed by laboratory polishing procedures, and finite element analysis (FEA) using overcorrected and undercorrected castable abutment models were created and tested against a perfect fit model. Results:The results from the FEA presented that both overcorrected and undercorrected models presented nonuniform excessive plastic strain distribution in the neck portion of the implants where clinically an implant fracture was noted. Conclusions:The results suggested that laboratory procedures could induce plastic strain of the implant-abutment complex, which increases the risk of fracture.

Clinical Evidence of OsseoSpeed EV Implants: A Retrospective Study and Characterization of the Newly Introduced System

This retrospective study sought to compare a new implant (Astra Tech OsseoSpeed EV) with its predecessor (Astra Tech OsseoSpeed TX) by scanning electron microscopy and interferometry. Radiographic data from 19 patients who underwent implant restoration with EV (n = 49) with a median follow-up of 16 months were evaluated for mean bone level (MBL) changes from delivery of the definitive prosthesis. EV and TX did not differ in surface roughness, and both systems had a tight seal at the implant-abutment interface. The median MBL change of the EV was -0.02 mm mesiodistally after a median follow-up period of 16 months. Greater maintenance of MBL was found in the screw-retained restorations (n = 17) compared to cemented (0.35 ± 0.33 mm and -0.38 ± 0.76 mm, respectively; P = .03). The data suggest that EV shows minimal levels of bone loss and high implant survival.

Clinical Considerations of Adapted Drilling Protocol by Bone Quality Perception

PURPOSE To evaluate insertion torque value (ITV) and marginal bone loss (MBL) of an implant system after a clinically perceived bone quality-adapted drilling. MATERIALS AND METHODS This multicenter retrospective study included patients treated with implants, conventionally loaded, in completely healed sites. Operators customized the osteotomy preparation according to radiographic assessment and their perception of bone quality. Drilling sequence, bone quality, and ITV were recorded at the time of surgery. Radiographs were taken at the time of implant placement and permanent restoration. MBL between implant placement and permanent restoration was calculated. The implant was used as the statistical unit. Demographic and implant characteristics were shown by means of descriptive statistics. Outcome values were compared using analysis of variance (ANOVA) and Kruskal-Wallis tests. Multiple regression models were used to test the effect of independent variables on ITV and MBL. RESULTS One hundred eighty-eight implants placed in 87 patients were included in the analysis. The mean observation period was 144 ± 59 days. The mean ITV was 30.8 ± 15.1 Ncm. ITV differed significantly based on arches (mandible/maxilla) (P = .001), bone quality (P < .001), implant diameter (P = .032), and drilling protocol (P = .019). Median MBL was 0.05 mm (0.00; 0.24). A significant difference was found between the mandible and maxilla (P = .008) and between drilling protocols (P = .011). In particular, significantly higher MBL was found in the undersized drilling protocol. Multiple regression analysis showed that ITV was influenced by bone quality and implant diameter. MBL was influenced by bone quality, implant diameter, ITV, and the interaction between bone quality and ITV. It was estimated that MBL was greater with increased bone density and ITV. CONCLUSION Excessive ITV in dense bone can cause negative marginal bone responses. A presurgical radiographic assessment and the perception of bone quality are necessary to select an optimal drilling protocol and to minimize surgical trauma.