Paolo Pera

In vitro marginal adaptation of alumina porcelain ceramic crowns

This study evaluated the dimensional stability during firing of In-Ceram alumina porcelain ceramic and examined the marginal fit for three different configurations of tooth preparation. A stereomicroscope was used to measure the space between the margin of restorations and tooth preparations. The three methods of tooth preparation were statistically compared and revealed suitable dimensional stability during the firing and glazing process. A better marginal fit was recorded for artificial crowns fabricated on a chamfer or 50-degree shoulder tooth preparation.

Tooth loss and obstructive sleep apnoea

BackgroundComplete tooth loss (edentulism) produces anatomical changes that may impair upper airway size and function. The aim of this study was to evaluate whether edentulism favours the occurrence of obstructive sleep apnoea (OSA).MethodsPolysomnography was performed in 48 edentulous subjects on two consecutive nights, one slept with and the other without dentures. Upper airway size was assessed by cephalometry and by recording forced mid-inspiratory airflow rate (FIF50). Exhaled nitric oxide (eNO) and oral NO (oNO), were measured as markers of airway and oropharyngeal inflammation.ResultsThe apnoea/hypopnoea index (AHI) without dentures was significantly higher than with dentures (17·4 ± 3·6 versus 11·0 ± 2·3. p = 0·002), and was inversely related to FIF50 (p = 0·017) and directly related to eNO (p = 0·042). Sleeping with dentures, 23 subjects (48%) had an AHI over 5, consistent with OSA, but sleeping without dentures the number of subjects with abnormal AHI rose to 34 (71%). At cephalometry, removing dentures produced a significant decrease in retropharyngeal space (from 1·522 ± 0·33 cm to 1·27 ± 0·42 cm, p = 0·006). Both morning eNO and oNO were higher after the night slept without dentures (eNO 46·1 ± 8·2 ppb versus 33·7 ± 6·3 ppb, p = 0·035, oNO 84·6 ± 13·7 ppb versus 59·2 ± 17·4 ppb, p = 0·001).ConclusionThese findings suggest that complete tooth loss favours upper airway obstruction during sleep. This untoward effect seems to be due to decrease in retropharyngeal space and is associated with increased oral and exhaled NO concentration.

Systematic review of some prosthetic risk factors for periimplantitis

STATEMENT OF PROBLEM The recent literature underlines a correlation between plaque and the development of periimplantitis but neglects the importance of the prosthetic factors. PURPOSE The purpose of this systematic review was to appraise the available literature to evaluate the role played by cement excess and misfitting components on the development of periimplantitis. MATERIAL AND METHODS An electronic search restricted to the English language was performed in PubMed, Embase, and the Cochrane Register up to September 1, 2014, based on a selected search algorithm. Only cohort studies and case-control studies were included without additional restrictions. The presence of periimplantitis and implant failure were considered primary and secondary outcome variables. RESULTS The search produced 275 potentially relevant titles, of which only 2 were found eligible. They showed a correlation in cemented implant prostheses between cement excess and the presence of periimplant disease, especially in patients with a history of periodontal disease. After cement excess removal by means of debridement, disease symptoms disappeared around most of the implants. CONCLUSIONS Scientific articles on prosthetic risk factors for periimplantitis are scarce. Although the studies found on cement remnants have a high risk for bias, cement excess seems to be associated with mucositis and possibly with periimplantitis, especially in patients with a history of periodontal disease.

Adhesive strength of the luting technique for passively fitting screw-retained implant-supported prostheses: an in vitro evaluation.

PURPOSE This in vitro study evaluated the adhesive strength of a technique to lute implant cylinders to metal frameworks in implant-supported prostheses and ensure a good passive fit. MATERIALS AND METHODS Different height samples were tested: In group 1, implant cylinders were 5 mm long; in group 2, they were 10 mm long. A universal testing machine (Instron) was used to perform pullout tests. RESULTS The luting technique provided enough adhesive strength for clinical use with greater adhesive strength in group 2 (mean pull-out strength: 2.85 kN in group 1 versus 3.79 kN in group 2). CONCLUSIONS The luting technique provides enough adhesive strength for clinical use. Moreover, specimens with a larger surface for adhesion demonstrated higher adhesive strength compared with shorter specimens.

Influence of Different Surface Characteristics on Peri-implant Tissue Behavior: A Six-Year Prospective Report.

PURPOSE The aim of this study was to evaluate the behavior of hard and soft tissue around implants with different surface treatments. MATERIALS AND METHODS Eight patients were identified for this study. Each patient received at least 2 implants (1 control, 1 test) into an edentulous quadrant, for a total of 10 pairs of implants. Two types of implants were used: hybrid implants (control) with a dual acid-etched surface in their apical portion and a machined coronal part, and test implants with an acid-etched surface throughout their entire length. Standardized periapical radiographs were taken at baseline, 3 months, 6 months, and 1 year post implant placement and then annually until the 6-year follow-up. Bleeding on probing (BOP) and Plaque Index (PI) were recorded annually. Probing depth (PD) was recorded at the 6-year follow-up. RESULTS Moderate crestal bone remodeling was observed during the 1-year postimplant placement evaluation (P=.001), and test implants revealed smaller marginal bone resorption (P=.030). No significant changes in bone level were observed between the 1-year and the 6-year follow-up appointments, and a significantly smaller bone resorption was found at test implants. No statistically significant differences in bone resorption were found between maxilla and mandible. No statistically significant differences were detected between test and control implants for BOP, PI, or PD. CONCLUSIONS The preliminary results suggest that implant surface characteristics might affect the bone remodeling phase subsequent to the surgical trauma. However, once osseointegration was established, implant surfaces did not affect bone maintenance over time. Implant surfaces did not affect soft tissue behavior. The results of this pilot study need to be confirmed in a study with a larger sample size and over a longer time frame.

Consistency of performance of a new craniostat for oblique lateral transcranial radiographs of the temporomandibular joint

A new craniostat for use with OLTP radiography of the TMJ is described. In a clinical study of 20 patients the craniostat demonstrated a satisfactory consistency of radiographic reproduction.

Accuracy and repeatability of a new procedure for temporomandibular joint laminagraphy.

Abstract A new device for TMJ laminagraphy is described. Positioning the head, centering the TMJ, programming the layers, and repeatability are discussed. Repeatability is evaluated through two different methods (a measurement method and a photographic method) and found to be satisfactory.

Effect of Framework in an Implant-Supported Full-Arch Fixed Prosthesis: 3D Finite Element Analysis.

PURPOSE The aim of this study was to analyze through a three-dimensional finite element analysis (3D-FEA) stress distribution on four implants supporting a full-arch implant-supported fixed prosthesis (FFP) using different prosthesis designs. MATERIALS AND METHODS A 3D edentulous maxillary model was created and four implants were virtually placed into the maxilla and splinted, simulating an FFP without framework, with a cast metal framework, and with a carbon fiber framework. An occlusal load of 150 N was applied, stresses were transmitted into peri-implant bone, and prosthodontic components were recorded. RESULTS 3D-FEA revealed higher stresses on the implants (up to +55.16%), on peri-implant bone (up to +56.93%), and in the prosthesis (up to +70.71%) when the full-acrylic prosthesis was simulated. The prosthesis with a carbon fiber framework showed an intermediate behavior between that of the other two configurations. CONCLUSION This study suggests that the presence of a rigid framework in full-arch fixed prostheses provides a better load distribution that decreases the maximum values of stress at the levels of implants, prosthesis, and maxillary bone.

Peri-implant Tissue Health and Bone Resorption in Patients with Immediately Loaded, Implant-Supported, Full-Arch Prostheses

PURPOSE To evaluate plaque accumulation, peri-implant soft tissue inflammation, and bone resorption in patients with immediately loaded implants supporting fixed full-arch prostheses. MATERIALS AND METHODS A convenience sample of 72 patients treated with fixed full-arch prostheses supported by four to six immediately loaded implants was selected. Bleeding on probing (BOP), Plaque Index (PI), and peri-implant bone loss were measured. The Sixth European Workshop on Periodontology definitions of mucositis and peri-implantitis were used, and collected data were analyzed using a nonparametric test (Spearmans rank correlation). Correlation coefficients (ρ) were defined as follows: < 0.2 = very weak; 0.2 to 0.39 = weak; 0.4 to 0.59 = moderate; 0.6 to 0.79 = strong; 0.8 to 1.0 = very strong. RESULTS A total of 331 implants were analyzed. The mean follow-up observation time was 5.8 years (range: 1 to 14 years); mean PI and BOP were 61.7% and 21.1%, respectively; and mean bone loss was 0.89 mm (standard deviation [SD] 1.09). The mean probing depth was 1.8 mm (range: 0.5 to 5 mm). Five patients presented with one implant each affected by peri-implantitis (6.9%), and 15 patients presented with at least one implant affected by mucositis (20.8%). No correlation was found between PI and bone resorption (P = .08). Very weak correlations were found between BOP and bone resorption (ρ = 0.18; P = .001) and between PI and BOP (ρ = 0.13, P = .019). CONCLUSION The results suggest that plaque accumulation is correlated with peri-implant mucositis; however, plaque accumulation alone does not appear to be associated with bone resorption.

Evaluation of a new ultrasonic insert for prosthodontic preparation

PURPOSE This paper describes a new ultrasonic instrument (tipholder DB1 with crown prep tip inserts) designed to optimize prosthodontic margin repositioning and finishing. MATERIALS AND METHODS The insert movement was assessed, and it was demonstrated that tipholder DB1 provides its inserts with an elliptical-like movement, making the entire insert surface able to cut. Then, 20 extracted teeth were prepared using tipholder DB1, sonic instruments, and traditional drills. Dental surface roughness produced using each of the three tools was measured using a roughness tester. Results were compared using univariate analysis of variance and Bonferroni post hoc test. RESULTS The roughness produced using tipholder DB1 with crown prep insert presented no statistically significant differences compared to the roughness produced using sonic instruments and traditional drills. CONCLUSION Tipholder DB1 with crown prep inserts is a promising treatment for margin repositioning and finishing.