Michele Cassetta

Platelet Rich Fibrin (P.R.F.) in reconstructive surgery of atrophied maxillary bones: clinical and histological evaluations.

Introduction. Maxillary bone losses often require additional regenerative procedures: as a supplement to the procedures of tissue regeneration, a platelet concentrate called PRF (Platelet Rich Fibrin) was tested for the first time in France by Dr. Choukroun. Aim of the present study is to investigate, clinically and histologically, the potential use of PRF, associated with deproteinized bovine bone (Bio-Oss), as grafting materials in pre-implantology sinus grafting of severe maxillary atrophy, in comparison with a control group, in which only deproteinized bovine bone (Bio-Oss) was used as reconstructive material. Materials and Methods. 60 patients were recruited using the cluster-sampling method; inclusion criteria were maxillary atrophy with residual ridge < 5mm. The major atrophies in selected patients involved sinus-lift, with a second-look reopening for the implant insertion phase. The used grafting materials were: a) Bio-Oss and b) amorphous and membranous PRF together with Bio-Oss. We performed all operations by means of piezosurgery in order to reduce trauma and to optimize the design of the operculum on the cortical bone. The reopening of the surgical area was scheduled at 3 different times. Results. 72 sinus lifts were performed with subsequent implants insertions. We want to underline how the histological results proved that the samples collected after 106 days (Early protocol) with the adding of PRF were constituted by lamellar bone tissue with an interposed stroma that appeared relaxed and richly vascularized. Conclusions. The use of PRF and piezosurgery reduced the healing time, compared to the 150 days described in literature, favoring optimal bone regeneration. At 106 days, it is already possible to achieve good primary stability of endosseous implants, though lacking of functional loading.

How accurate is CBCT in measuring bone density? A comparative CBCT-CT in vitro study.

PURPOSE Recently, cone beam computed tomography (CBCT) has become widely used for oral and maxillofacial imaging. Twenty dry mandibles were CBCT and conventional multislice CT scanned to evaluate if there is a statistically significant difference between the bone density values they produce, defined as gray density values, and to determine any correlation between them. MATERIALS AND METHODS Using software and a radiographic template, the CT and CBCT scan images were overlapped, and two data sets were created, each one giving the respective gray values (voxel value [VV] or Hounsfield unit [HU]) of the same area with the same spatial coordinates. For the statistical analysis, t-test, Pearsons correlation, and Pearsons r were used. RESULTS The differences between the CBCT (VV) and CT (HU) gray density values were statistically significant (p ≤ .05), whereas the Pearsons correlation coefficients and Pearsons r-values demonstrated a statistically significant linear correlation between VV and HU gray density values. CONCLUSION The lower radiation dose and reduced costs of CBCT make this a useful substitute for CT; however, this study has shown that, in order to more accurately define the bone density with CBCT, a conversion ratio needs to be applied to the VV.

Accuracy of two stereolithographic surgical templates: A retrospective study

BACKGROUND The use of computer software and stereolithography for dental implant therapy has significantly increased during the last few years. The aim of this study was to evaluate and compare the mean accuracy and maximum deviations values of dental implant placement using two stereolithographic (SLA) guide systems. MATERIALS AND METHODS Twenty patients were selected and 227 implants were inserted using bone-, tooth- and mucosa-supported SLA surgical guides. Thirty-one guides, both single- and multiple-type, were used. Some of the single-type surgical guides were fixed with osteosynthesis screws. A postoperative computer tomography (CT) was performed and an iterative closest point algorithm was used to match the jaw of the CT preoperative with the jaw of the postoperative CT. Quantitative data of each group were described. The t-test was used to determine the influence of the utilization of the different types of SLA on accuracy values. RESULTS t-Test demonstrated a better accuracy of the multiple-type guides in almost all deviation values when the mucosa-supported guides were considered. Regarding the bone-supported template, the single-type fixed group showed a better accuracy while the highest values of deviation were registered by the multiple-type guides. The single-type group showed a better accuracy when the tooth support was considered. CONCLUSIONS The results of the present study indicated best accuracy of the single-type guide using a bone or tooth support. The multiple-type guide recorded the best accuracy data when the mucosa support was considered comparing either a fixed and a not-fixed single-type guide.

Depth deviation and occurrence of early surgical complications or unexpected events using a single stereolithographic surgi-guide §

The purpose of this study was to determine the accuracy of depth implant insertion and to describe the frequency of early surgical complications or unexpected events, recorded using a single, totally guided, stereolithographic surgi-guide (bone-, mucosa- and teeth-supported) for both osteotomy site preparation and implant delivery. Ten adults were included in this study. Six patients were treated in both arches, and the number of computer aided implantology (CAI) interventions was 16, which equalled the number of guides used, for a total of 111 implants inserted. Complications and unexpected events occurred during the positioning of the surgical guide and whilst preparing the implant site and installing implants. In order to minimize the risk of complications and unexpected events, attention must be paid to every stage of treatment, including checking computed tomography (CT) images, guide manufacturing, proper guide positioning in the mouth, guide fixation, rotational allowance of drill in tubes, shape and sharpness of the drills, first entry point, mouth opening and guided implant insertion.

Dental anomalies and clinical features in patients with maxillary canine impaction.

OBJECTIVE To analyze the prevalence, distribution, clinical features, and relationship with dental anomalies of maxillary canine impaction. MATERIALS AND METHODS The complete pretreatment records of 1674 orthodontic patients were examined. Subjects with maxillary impacted canines were divided into two study groups: a palatally displaced canine (PDC) group (114 patients) and a buccally displaced canine (BDC) group (37 patients). These were compared to a control group of 151 patients who were randomly selected from the initial sample without maxillary canine impaction. The significance of associations between canine impaction and dental and clinical features and anomalies was examined with the chi-square test. RESULTS PDC patients presented with normal overjet and facial profile and a lower degree of dental arch crowding in comparison to the control patients. PDC patients showed a higher prevalence of impaction of other teeth, dental aplasia, transposition, and peg-shaped maxillary lateral incisors (odds ratios 3.3, 2.6, 8.3, and 5.8, respectively). CONCLUSION PDC was frequently the only orthodontic problem of patients. BDC group patients did not present with notable differences in clinical and dental features or dental anomalies compared to control subjects.

Minimally invasive corticotomy in orthodontics: a new technique using a CAD/CAM surgical template

Accelerating orthodontic tooth movement is a topical issue. Despite the different techniques described in the literature, the corticotomy is the only effective and safe means of accelerating orthodontic tooth movement. Although effective, the corticotomy presents significant postoperative discomfort. The aggressive nature of these particular methods, related to the elevation of mucoperiosteal flaps and to the length of the surgery, has resulted in reluctance to proceed with this technique among both patients and the dental community. To overcome the disadvantages of the corticotomy, this technical note describes an innovative, minimally invasive, flapless procedure combining piezoelectric surgical cortical micro-incisions with the use of a 3D Printed CAD/CAM surgical guide.

Impaction of permanent mandibular second molar: A retrospective study

Objective: To determine the prevalence of impacted mandibular second molar (MM2) and the association between MM2 impaction and crowding. The clinical significance of the angle between first and second mandibular molar and of the space between the first mandibular molar (MM1) and the anterior margin of mandibular ramus in MM2 impaction were also evaluated. Material and Methods: In this retrospective study , from the dental records of 2,945 caucasian young orthodontics patients, 40 subjects with MM2 impaction were included in a study group (SG) and compared with a control group (CG) of 200 subjects without MM2 impactions. The crowding, the angle of inclination of MM2, the distance between MM1 and mandibular ramus, the canine and molar relationships, and the lower centre line discrepancy were measured. For the statistical analysis , descriptive statistics and t-Student for independent sample groups were used. Results: The prevalence of impacted MM2 was 1.36%. The independent-Samples t-Test between SG and CG showed: the presence of crowding (P≤0.001), an higher angle values of MM2 inclination (P≤0.001) and a smaller distance between MM1 and the anterior margin of mandibular ramus (P≤0.001) in the SG. Conclusion: The impaction of MM2 is a relatively rare occurrence in orthodontic caucasian populations. The crowding, a higher angle values of MM2 inclination and a reduced distance between MM1 and the anterior margin of mandibular ramus, at the time of one third of MM2 root formation (T1), characterize MM2 impaction. Key words:Impacted mandibular second molar, impaction, orthodontics.

Evaluation of alveolar cortical bone thickness and density for orthodontic mini-implant placement.

Objective: Mini-implant stability is primarily related to bone quality and quantity. This study evaluated alveolar cortical bone thickness and density differences between interradicular sites at different levels from the alveolar crest, and assessed the differences between adolescents (12-18 years of age) and adults (19-50 years of age), males and females, upper and lower arch, anterior and posterior region of jaws and buccal and oral side. Study Design: In this retrospective study, 48 Computed Tomography scans, performed for oral surgery purposes were selected from dental records of 3,223 Caucasian orthodontic patients. The SimPlant software (Materialise, Leuven, Belgium) was used to measure cortical bone thickness and density at 13 interradicular sites and four bone levels ( 2,4,6 and 8 mm ). For the statistical analysis descriptive statistics, Student’s t-test and Pearson correlation coefficient were used. Results: Statistically significant differences in alveolar cortical bone thickness and density between age, gender, sites and sides were found (P<0.05). The Pearson correlation coefficient demonstrated a significant linear increasing of thickness and density from crest to base of alveolar crest (P≤0.05). Conclusion. Adults show a thicker alveolar cortical bone than adolescents. Alveolar cortical bone thickness and density were greater in males than in females, in mandible than in maxilla, in the posterior region than the anterior, in oral than buccal side. There is an increase of thickness and density from crest to base of alveolar crest. Key words:Orthodontics, cortical bone thickness, cortical bone density, mini-implant, computed tomography, temporary anchorage devices.

Early peri-implant bone loss: a prospective cohort study

The aim of this study was to measure the early peri-implant bone level changes before the completion of an implant-abutment connection and to evaluate the influence of demographic, biologically relevant, anatomical, and implant-specific variables on these changes. A prospective cohort study design was used. STROBE guidelines were followed. The sample comprised 493 implants placed using a two-stage surgical procedure. Random allocation was used to determine the implant placement depth. Peri-apical radiographs taken at implant insertion and at the second surgery 2 months later were matched. Kappa statistics were used to compute intra- and inter-examiner reliability. The statistical analysis was performed at the implant level. Two-way analysis of variance (ANOVA) with the Bonferroni adjusted post hoc test was used to evaluate the influence of variables. One-way ANOVA with Tukeys range test and unpaired Student t-tests were used to analyze significant variables. Early marginal bone remodelling was -0.86 mm. The timing of implant placement (P=0.00) and the depth of implant placement (P≤0.05) significantly influenced early bone remodelling. Relevant radiographic early bone loss was found, but implants initially positioned below the alveolar crest and inserted ≥3 months after tooth extraction showed statistically significant higher marginal bone loss during the healing phase.

The Influence of the Tolerance between Mechanical Components on the Accuracy of Implants Inserted with a Stereolithographic Surgical Guide: A Retrospective Clinical Study

BACKGROUND The stereolithographic-guided surgery system involves a sequence of diagnostic and therapeutic events, and errors can arise at different stages. In these systems, one of the potentially clinically relevant errors may be the mechanical errors caused by the bur-guide gap due to the presence of a rotational allowance of the drills in the tubes. PURPOSE The purpose of this retrospective clinical study is to determine if it is possible to reduce the total error by limiting the tolerance among the mechanical components and to evaluate its clinical incidence. MATERIALS AND METHODS Sixty-six implants were inserted using the External Hex Safe® (Materialise Dental, Leuven, Belgium) system (Group A), and 71 implants were inserted using the same system with mechanical components modified to minimize the tolerance (Group B). Regarding only the angular deviation values, the t-test was used to determine the influence of reduced tolerance among the mechanical components on the accuracy values. RESULTS t-Test showed that there is a statistically significant better accuracy with the modified system (Group B). CONCLUSIONS Limiting the error that originates from mechanical components, total error could be statistically significantly reduced. Mechanical error is one of the most important source of error using External Hex Safe stereolithographic surgical guide.