EFFECT OF CAST RECTIFIERS ON THE MARGINAL FIT OF UCLA ABUTMENTS

Objectives:

This study assessed the effect of cast rectifiers on the marginal misfit of cast UCLA abutments compared to premachined UCLA abutments. The influence of casting and porcelain baking on the marginal misfit of these components was also investigated.

Methods:

Two groups were analyzed: test group – 10 cast UCLA abutments, finished with cast rectifier and submitted to ceramic application; control group – 10 premachined UCLA abutments, cast with noble metal alloy and submitted to ceramic application. Vertical misfit measurements were performed under light microscopy. In the test group, measurements were performed before and after the use of cast rectifiers, and after ceramic application. In the control group, measurements were performed before and after casting, and after ceramic application. Data were submitted to statistical analysis by ANOVA and Tukey''s test (α= 5%).

Results:

The use of cast rectifiers significantly reduced the marginal misfit of cast UCLA abutments (from 25.68μm to 14.83μm; p<0.05). After ceramic application, the rectified cylinders presented misfit values (16.18μm) similar to those of premachined components (14.3 μm). Casting of the premachined UCLA abutments altered the marginal misfit of these components (from 9.63 μm to 14.6 μm; p<0.05). There were no significant changes after porcelain baking, in both groups.

Conclusion:

The use of cast rectifiers reduced the vertical misfit of cast UCLA abutments. Even with carefully performed laboratory steps, changes at the implant interface of premachined UCLA abutments occurred. Ceramic application did not alter the marginal misfit values of UCLA abutments.     

Tooth mobility and resolution of experimental periodontitis

Abstract The aim of the present experiment was to study alterations in the mobility of teeth that occurred during resolution of experimentally induced periodontitis lesions in the dog. 5, 1-year-old, beagle dogs were used in the study. The left and right 4th, 3rd, and 2nd mandibular premolars (₄P₄, ₃P₃, ₂P₂) served as experimental teeth. Periodontal tissue breakdown was initiated by placing plaque-collecting cotton-floss ligatures around the neck of the experimental teeth. The ligatures were replaced to the level of the receding gingival margin 1 × every month. On Day 120, the ligatures were removed and debridement was performed. A groove, parallel to the long axis of the mesial root, was prepared in the mesio-buccal surface of the crowns of ₂P and P₂. Guided by the groove and with a probing force of 0.5 N, a probe was inserted into the buccal gingival pocket of the mesial root and was attached to the buccal surface. Biopsies including both the mesial and distal root of ₂P and P₂ and the surrounding hard and soft tissues were harvested. The biopsy procedure was repeated in a similar manner 15 days (i.e. Day 135) and 3 months (i.e. Day 225) after ligature removal in the 4th (₄P₄) and 3rd (₃P₃) premolar regions. After fixation, decalcification and sectioning, the biopsy material was exposed to histometric and morphometric measurements. Assessment of the mobility of the experimental teeth was performed on Days 120, 135 and 225 using the Periotest system. The amount of remaining bone at the experimental teeth was evaluated in radiographs obtained in a standardized manner. The findings of the present experiment disclosed that in dogs allowed to form plaque, the placement of cotton-floss ligatures at the neck of mandibular premolars initiated a process that resulted in (i) the formation of an inflammatory lesion which extended deep into the supracrestal connective tissue; (ii) extensive loss of alveolar bone; (iii) markedly increased tooth mobility. It was also observed that, within a 4-month period the removal of the ligature and, as a consequence, a substantial portion of the subgingival microbiota, reduced the size and the apical extension of the inflammatory lesion in the supracrestal connective tissue. The alterations in the soft supracrestal tissue were accompanied by a marked decrease in the mobility of the experimental teeth and a reduced probing pocket depth. It was suggested that the reduced penetration of the probe was the result of the change in the size and position of the infiltrate as well as of a reduced mobility of the experimental teeth.     

Evaluation of the biomechanical behavior of maxillary central incisors restored by means of endocrowns compared to a natural tooth: a 3D static linear finite elements analysis.

OBJECTIVE: The present study aimed at evaluating different restoring configurations of a crownless maxillary central incisor, in order to compare the biomechanical behavior of the restored tooth with that of a sound tooth. MATERIALS AND METHODS: A 3D FE model of a maxillary central incisor is presented. An arbitrary static force of 10 N was applied with an angulation of 125 degrees to the tooth longitudinal axis at level of the palatal surface of the crown. Different material configurations were tested: composite, syntered alumina, feldspathic ceramic endocrowns and glass post resorations with syntered alumina and feldspathic ceramic crown. RESULTS: High modulus materials used for the restoration strongly alter the natural biomechanical behavior of the tooth. Critical areas of high stress concentration are the restoration-cement-dentin interface both in the root canal and on the buccal and lingual aspects of the tooth-restoration interface. Materials with mechanical properties underposable to that of dentin or enamel improve the biomechanical behavior of the restored tooth reducing the areas of high stress concentration. SIGNIFICANCE: The use of endocrown restorations present the advantage of reducing the interfaces of the restorative system. The choice of the restorative materials should be carefully evaluated. Materials with mechanical properties similar to those of sound teeth improve the reliability of the restoartive system.     

Influence of different surface treatments on surface zirconia frameworks

Objectives

To evaluate the effect of different chemo-mechanical surface treatments of zirconia ceramic in the attempt to improve its bonding potential.

Methods

Sintered zirconium oxide ceramic discs (Lava™ Ø10 mm × 1 mm height) were treated with (n = 4): (1) airborne particle abrasion with 125 μm Al₂O₃ particles; (2) 9.5% HF acid etching; (3) selective infiltration etching (SIE); (4) experimental hot etching solution applied for 10, 30 and 60 min; (5) no treatment.Ceramic discs surfaces were analyzed by atomic force microscopy (AFM) recording average surface roughness measurements of the substrate. Data were statistically analyzed by Kruskall–Wallis analysis of variance and Mann–Whitney tests (α = 0.05). The same discs were used for bi-dimensional zirconia ceramic surface characterization with scanning electron microscope (SEM).

Results

Ceramic surface treatments significantly influenced surface topography and roughness (p < 0.001). Bi-dimensional changes in ceramic surface morphology were assessed on a nanometric scale. The experimental hot etching solution improved surface roughness, independently from the application time.

Conclusion

Zirconia conditioning with the experimental hot etching solution may enhance ceramic roughness and improve the surface area available for adhesion allowing the formation of micromechanical retention. The influence of this surface treatment with regard to bond strength of zirconia needs to be addressed.     

Histological and immunohistochemical analysis of initial and early osseous integration at chemically modified and conventional SLA titanium implants: preliminary results of a pilot study in dogs

OBJECTIVES: The aim of the present pilot study was to investigate initial and early tissue reactions to modified (mod) and conventional sand-blasted, large grit and acid-etched (SLA) titanium implants. MATERIAL AND METHODS: Implantation of modSLA and SLA implants was performed bilaterally in both the mandible and maxilla of dogs. The animals were sacrificed after a healing period of 1, 4, 7 and 14 days, respectively. Peri-implant tissue reactions were assessed in non-decalcified tissue sections using conventional histology (Toluidine blue-TB and Masson Goldner Trichrome stain-MG) and immunohistochemistry using monoclonal antibodies to transglutaminase II (TG) (angiogenesis) and osteocalcin (OC). Bone density (BD) and bone to implant contact (BIC) were assessed histomorphometrically. RESULTS: Day 1 revealed an early TG antigen reactivity in the provisional fibrin matrix adjacent to both implant surfaces. Day 4 was characterized by the formation of a collagen-rich connective tissue (MG), which revealed the first signs of OC synthesis adjacent to modSLA surfaces. Immunohistochemical staining for TG revealed a direct correlation between angiogenesis and new bone formation, which was clearly identifiable after 7 days by means of increasing BD, BIC and OC values. After 14 days, modSLA surfaces seemed to be surrounded by a firmly attached mature, parallel-fibered woven bone. CONCLUSIONS: Within the limits of the present study, it might be concluded that the combination of immunohistochemical and conventional histological stainings in non-decalcified tissue sections is a valuable technique to evaluate the initial and early stages of wound healing around endosseous titanium implants.     

Clinical and microbiologic effects of subgingival controlled-release delivery of chlorhexidine chip in the treatment of periodontitis: a multicenter study

BACKGROUND: The main therapeutic approach for periodontal diseases is mechanical treatment of root surfaces via scaling and root planing (SRP). Multicenter clinical trials have demonstrated that the adjunctive use of a chlorhexidine (CHX) chip is effective in improving clinical results compared to SRP alone. However, some recent studies failed to confirm these clinical results, and conflicting results were reported regarding the effects of the CHX chip on subgingival microflora. The aim of this study was to provide further data on the clinical and microbiologic effects of CHX chips when used as an adjunct to SRP. METHODS: A total of 116 systemically healthy individuals with moderate to advanced periodontitis, aged 33 to 65 years, were recruited from the Departments of Periodontology of four Italian universities. For each subject, two experimental sites were chosen that had probing depths (PD) > or =5 mm and bleeding on probing (BOP) and were located in two symmetric quadrants. These two sites were randomized at the split-mouth level, with one receiving SRP treatment alone and the other receiving treatment with SRP plus one CHX chip (SRP + CHX). PD, relative attachment level (RAL), and BOP were evaluated at baseline, prior to any treatment, and after 3 and 6 months. Supragingival plaque and the modified gingival index were evaluated at baseline and after 15 days and 1, 3, and 6 months. Subgingival microbiologic samples were harvested at baseline and after 15 days and 1, 3, and 6 months, cultured for total bacterial counts (TBCs), and investigated by polymerase chain reaction analysis for the identification of eight putative periodontopathogens. RESULTS: When all of the pockets were considered, the PD and RAL were significantly less at 3 and 6 months compared to the baseline scores (P <0.01) for both treatments. Moreover, the PD was reduced in the SRP + CHX treatment group compared to the SRP treatment group at 3 and 6 months, whereas the RAL was similar for both treatments at 3 months and was reduced in the SRP + CHX treatment group at 6 months. The differences in PD reductions between the treatments were 0.30 and 0.55 mm at 3 and 6 months, respectively (P <0.01); for the RAL gain, the differences were 0.28 and 0.64 mm, respectively (P <0.001). The TBCs decreased significantly with both treatments. A similar, although less evident, pattern was noted when only the pockets with an initial PD > or =7 mm were considered. The percentage of sites positive for BOP was similar between the treatments at each time point. At 15 days and 1 month, the TBC for the SRP + CHX treatment group was significantly lower than for the SRP treatment group (P <0.01 and P <0.05, respectively). Over time, both treatments generally reduced the percentages of sites positive for the eight putative periodontopathic bacteria, although greater reductions were seen often for the SRP + CHX treatment group. CONCLUSIONS: The adjunctive use of the CHX chip resulted in a significant PD reduction and a clinical attachment gain compared to SRP alone. These results were concomitant with a significant benefit of SRP + CHX treatment on the subgingival microbiota.     

Long-term results of mandibular reconstruction with autogenous bone grafts and oral implants after tumor resection

Objectives: (a) To evaluate retrospectively the clinical outcome of non‐vascularized bone grafts used for the reconstruction of mandibular defects following tumor resection; (b) to evaluate the clinical outcome of implants and implant‐supported prostheses placed in the reconstructed areas; and (c) to evaluate patients' satisfaction regarding function and esthetics after oral rehabilitation. Material and methods: In a 9‐year period (1995–2003), 29 patients affected by mandibular tumors involving to tooth bearing areas were treated by means of tumor resection and immediate or delayed reconstruction with autogenous non‐revascularized calvarial or iliac bone grafts. Among these patients, 16 patients were selected for dental rehabilitation of the lost dentition with implant‐supported 3fixed prosthese333s. For to 7 months later, the patients received 60 oral implants for the prosthetic rehabilitation of the reconstructed edentulous areas. Results: No total failure of the graft was observed, while partial loss of the graft was observed in one patient. The mean follow‐up of patients after the start of prosthetic loading of implants treated was 94 months (range: 36–132 months). Two patients dropped out of the follow‐up after 3 and 4 years of observation, respectively. Two implants were removed due to loss of osseointegration, while two implants, although still integrated, presented peri‐implant bone resorption values higher than those proposed by Albrektsson et al. for successful implants. Cumulative survival and success rates of implants were 96.7% and 93.3%, respectively. Conclusion: Results from this study demonstrated that bone defects following resection of mandibular tumors can be predictably reconstructed with autogenous bone grafts taken from the calvarium or the anterior iliac crest. It has also been shown that the long‐term survival and success rates of implants placed in the reconstructed areas (96.7% and 93.3%, respectively) may guarantee an excellent prognosis of implant‐supported prostheses.     

A preliminary protocol for multi-professional centers for the determination of signs and symptoms of temporomandibular disorders

The objective of the present study was to test a protocol for the quantification of the frequency and severity of signs and symptoms of temporomandibular disorders (TMD) according to patient perception during two phases of investigation. The protocol was developed based on the signs and symptoms most frequently reported in the literature and on the circumstances in which they produce discomfort. Eighty-four patients diagnosed with TMD by functional examination of the masticatory system responded to the protocol questions and indicated the severity of signs and symptoms using an eleven point numerical scale (Phase 1). Forty-two patients were fitted with an occlusal splint (treated group) and the remaining participants did not use a splint (control group). The protocol questions were asked after 50 days of treatment (Phase 2). Based on the results of nonparametric statistical analysis, the incidence of signs and symptoms was high in Phase 1 and significant, with no difference between the groups, whereas the treated and control groups differed in Phase 2. A comparison between Phases 1 and 2 showed that only the treated group presented a reduction in the severity of signs and symptoms. The study showed that using this protocol, it is possible to define the frequency and severity of symptoms as well as the effect of the treatment. The advantage of this protocol is that it would complement the data obtained using clinical examination with information provided by the patient in a measurable manner.     

Prevalence and distribution of developmental enamel defects in the primary dentition of pre-school children

Developmental defects of the enamel (D.D.E.) are changes in the deciduous dentition that have been little studied in Brazil, although they lead to aesthetic problems, dental sensitivity and may be predictors of dental caries. The objective of this study was to estimate the prevalence and distribution of D.D.E. in the deciduous dentition of pre-school children in the municipality of Itajaí, Santa Catarina, in 2003. A cross-sectional study was carried out with a sample of 431 children aged 3 to 5 enrolled in public day care centres. All of the teeth were examined and the enamel defects were assessed according to the Modified DDE Index (FDI, 1992). The prevalence of D.D.E. was 24.4% (CI 95% 20.3-28.5). Diffuse opacities were the most common defects found (17.9%), followed by hypoplasia (11.1%) and demarcated opacities (6.1%). The most affected teeth were the second molars (44.4%), followed by the first molars (23.5%). Defects were observed more frequently in the upper arch (58.2%). Assessing enamel hypoplasia separately, a prevalence of 15.1% (CI 95% 11.7-18.5) was observed, with the most affected teeth being the canines (33.6%) and second molars (33.6%). One quarter of the pre-school children presented enamel defects, with diffuse opacities being the most prevalent ones.