Eduardo Rolim Teixeira

Preload and torque removal evaluation of three different abutment screws for single standing implant restorations

Several authors still consider the mechanical problems of fracture and component loosening as the main causes of failure of implant-supported restorations. The purpose of this in vitro study was to compare the preload of three types of screw for transmucosal abutment attachment used in single implant-supported prosthesis through strain gauge and removal torque measurements. Three external hex fixtures were used, and each received a transmucosal abutment (Cera One®), which was fixed to the implant with its respective screw: Group A- gold screw, Group B- titanium screw and Group C- surface-treated titanium screw (Ti-Tite®). Ten screws of each type were attached applying a 30.07±0.28 Ncm torque force and maintained in position for 5 minutes. After this, the preload values were measured using strain gauges and a measurement cell. Gold screws presented higher preload values (131.72±8.98 N), followed by surface-treated titanium screws (97.78±4.68 N) and titanium screws (37.03±5.69 N). ANOVA (p<0.05) and Tukeys test (p<0.05) were applied. Statistically significant differences were found among the groups for both preload and removal torque values. In conclusion, gold screws may be indicated to achieve superior longevity of the abutment-implant connection and, consequently, prosthetic restoration due to greater preload values yielded.

Comparative evaluation of bone regeneration using spherical and irregularly shaped granules of interconnected porous hydroxylapatite. A beagle dog study

PURPOSE Bone regeneration stimulated by two different shapes of interconnected porous calcium hydroxyapatite (IP-CHA) granules was evaluated in the mandibles of 3 beagle dogs. METHODS Deferent shapes of IP-CHA were used, spherical (spherical shaped IP-CHA granules) and irregular shapes (irregularly shaped IP-CHA granules). Two bone sockets (3mm in diameter and 5mm in depth) were prepared in the right edentulous mandible of each animal where right premolars had been extracted and sites healed for 3 months. The two types of IP-CHA were filled into the sockets to stimulate bone regeneration. New bone formation was evaluated histologically at 4, 8 and 12 weeks after filling. RESULTS At 4 weeks, little bone formation was apparent in any of the bony sockets. At 8 weeks, newly formed bone was detected between the granules but not in the pores. In contrast, at 12 weeks, bone formation was clearly observed not only between the granules but also inside the granule pores. Comparing the two sites at 8 and 12 weeks, more bone formation was detected in sites receiving irregularly shaped IP-CHA than in sites receiving spherical IP-CHA. CONCLUSION These results indicate that use of irregularly shaped IP-CHA may enhance bone regeneration. The results of this preliminary study suggest that irregularly shaped IP-CHA granules may have more possible usefulness than spherically shaped granules as a scaffold for bone regeneration.

Analysis of the effects of a mandibular advancement device on sleep bruxism using polysomnography, the BiteStrip, the sleep assessment questionnaire, and occlusal force.

PURPOSE This before and after study evaluated the effects of a mandibular advancement device (MAD) on sleep bruxism (SB) activity and its associated signs and symptoms. MATERIALS AND METHODS Nineteen young adults (39.9 ± 12.9 years, 58% women) with a clinical history of SB without sleep or neurologic disorders and no spontaneous temporomandibular disorder pain were selected. SB activity was assessed after a habituation period of 2 weeks. The results of a 3-month treatment with a thermoplastic monoblock MAD were compared to baseline using electromyogram polysomnography and the BiteStrip, a portable EMG device. Sleep disorders were assessed and validated against the polysomnography sleep assessment questionnaire (SAQ). Additionally, common signs and symptoms of SB were evaluated with the research diagnostic criteria for temporomandibular disorders. Occlusal force was compared to baseline using a cross-arch force transducer. RESULTS There was a significant improvement in both SB activity and sleep scores (including SB episodes per hour) according to the BiteStrip and the SAQ, respectively. There was also a significant reduction in the signs and symptoms of SB, including grinding and/or clenching, temporomandibular joint (TMJ) sounds, muscle pain, and occlusal force. None of the SB subjects experienced MAD breakage, but in 24% of patients, the MAD treatment had to be interrupted due to TMJ/muscle pain and/or discomfort. CONCLUSION The MAD treatment resulted in the reduction of SB activity, SB signs and symptoms, sleep disorders, and occlusal force.

Effect of the number of abutments on biomechanics of Branemark prosthesis with straight and tilted distal implants

Objective This study aimed to evaluate the bending moments, and compressive and tensile forces in implant-supported prostheses with three, four or five abutments. Material and Methods Ten Pd-Ag frameworks were tested over two master models with: 1) parallel vertical implants, and 2) tilted distal implants. Strain gauges were fixed on the abutments of each master model to measure the deformation when a static load of 50 N was applied on the cantilever (15 mm). The deformation values were measured when the metallic frameworks were tested over three, four or five abutments, and transformed into force and bending moment values. Data were analyzed by ANOVA and Tukey’s test for multiple comparisons at 5% level of significance. Results Abutment #1 (adjacent to the cantilever) had the highest values of force and sagittal bending moment for all tests with three, four or five abutments. Independently from the number of abutments, axial force in abutment #1 was higher in the vertical model than in the tilted model. Total moment was higher with three abutments than with four or five abutments. Independently from the inclination of implants, the mean force with four or five abutments was lower than that with three abutments. Conclusion The results suggest that in the set-ups with four or five abutments tilted distal implants reduced axial force and did not increase bending moments.

Cell Culture–Based Tissue Engineering as an Alternative to Bone Grafts in Implant Dentistry: A Literature Review

Several biomaterials and techniques for bone grafting have been described in the literature for atresic bone tissue replacement caused by edentulism, surgical resectioning, and traumas. A new technique involves tissue engineering, a promising option to replace bone tissue and solve problems associated with morbidity of autogenous grafting. This literature review aims to describe tissue-engineering techniques using ex vivo cell culture as an alternative to repair bone maxillary atresias and discuss the concepts and potentials of bone regeneration through cell culture techniques as an option for restorative maxillofacial surgery.

In vitro evaluation of cytotoxicity of hyaluronic acid as an extracellular matrix on OFCOL II cells by the MTT assay

OBJECTIVE To evaluate the cytotoxicity of hyaluronic acid (HA) on a tissue-engineered compound for bone grafting containing osteoblastic cells (OFCOL II), platelet-rich plasma (PRP) with or without thrombin (Thr), and hydroxyapatite (HP) by the MTT assay. STUDY DESIGN Studied groups were formed as follows: (A) Cells + HA + PRP with Thr + hydroxyapatite (HP); (B) Cells + HA + PRP + HP; (C) Cells + HA + HP; (D) Cells + HP; (E) Cells + HA; (F) Cells + PRP with Thr; (G) Cells + PRP; and (H) Pure Dulbeccos modified Eagles medium (DMEM) with 15% fetal bovine serum. A 2-way ANOVA and Tukeys test were applied for statistical analysis (P < .05). RESULTS Results of cell viability for each group were as follows: A: 79%, B: 67%, C: 68%, D: 99%, E: 74%, G: 89%, F: 90%, and Group H: 100%. CONCLUSIONS Results suggested a decrease in cell viability in the presence of HA.

Marginal Bone Loss in Implants Placed in the Maxillary Sinus Grafted With Anorganic Bovine Bone: A Prospective Clinical and Radiographic Study.

BACKGROUND Sinus elevation is a reliable and often-used technique. Success of implants placed in such situations, even with bone substitutes alone, prompted the authors of this study to strive for bone loss close to zero and research variables that cause higher or lower rates of resorption. The objective of this study is to evaluate survival rates and marginal bone loss (MBL) around implants placed in sites treated with maxillary sinus augmentation using anorganic bovine bone (ABB), and identify surgical and prosthetic prognostic variables. METHODS Fifty-five implants were placed in 30 grafted maxillary sinuses in 24 patients. Periapical radiographs were evaluated immediately after implant placement (baseline), 6 months, and at the most recent follow-up. MBL was calculated from the difference between initial and final measurements, taking into account a distortion rate for each radiograph compared with original implant measurements. RESULTS Survival rate was 98.2%, with only one implant lost (100% survival rate after loading) over a mean follow-up time of 2.0 ± 0.9 years. MBL ranged from 0 to 2.85 mm: 75.9% of mesial sites and 83.4% of distal sites showed <1 mm of MBL, whereas 35.2% of mesial sites and 37% of distal sites exhibited no bone loss. MBL was significantly (P <0.05) greater in open-flap compared with flapless surgery. CONCLUSIONS Within the limitations of the present study, it was concluded that maxillary sinus elevation with 100% ABB gives predictable results, and that flapless surgery results in less MBL compared with traditional open-flap surgery.

Effects of the bite splint 15-day treatment termination in patients with temporomandibular disorder with a clinical history of sleep bruxism: a longitudinal single-cohort study

OBJECTIVE The aim of this study was to assess the effects of bite splint (BS) treatment termination in patients treated for temporomandibular disorder (TMD) and sleep bruxism (SB). STUDY DESIGN This longitudinal single-cohort study assessed 30 patients (29.5 ± 7.8 years old, 86.7% women) who were successfully treated with BS for SB and TMD for 30 days to 6 months prior to termination of the use of BS. The Research Diagnostic Criteria for TMD Axes I and II, Sleep Assessment Questionnaire, Beck Depression Inventory, and BiteStrip were used to assess TMD signs and symptoms, sleep disorders, depression, and SB at baseline and after 15 days of BS disuse. RESULTS TMD symptoms, including the disability points, characteristic pain intensity, and present pain at rest, increased significantly (P < 0.05). After 15 days of BS termination, there were no significant differences in SB and depression levels, sleep quality, and TMD signs. CONCLUSIONS In patients with TMD and SB, BS treatment cessation is not recommended.

Risk factors for single crowns supported by short (6-mm) implants in the posterior region: A prospective clinical and radiographic study.

BACKGROUND The use of short implants is still not a consensus for challenging clinical situations, such as unfavorable crown-to-implant (C/I) ratio. PURPOSE This prospective study evaluated the rates of prosthetic complications and implant failure, the mean marginal bone loss of 6-mm dental implants with single crowns in posterior regions and the potential risk factors. MATERIALS AND METHODS Forty-six dental implants, 6-mm long and 4.1-mm wide, were placed in the posterior region in 20 patients. Patients were clinically and radiographically examined after the restoration with single crowns and on a yearly basis. Potential risk factors (arch, bruxism, maximum bite force, anatomical and clinical C/I ratios, and occlusal table area) were analyzed according to the following outcomes: implant survival, bone loss, and prosthetic complications. RESULTS The mean follow-up time was 45 ± 9 (16-57) months. There was no early loss of implants. After prosthetic loading, 4 implants were lost (2 in the mandible and 2 in the maxilla; 91.3% survival), and there were 13 prosthetic complications (28.3%), yielding a 65.2% success rate. The frailty term showed a 95% greater chance of loss in the mandible than the maxilla. Mean peri-implant bone loss was of 0.2 ± 0.4 mm, 0.1 ± 0.2 mm, 0.1 ± 0.3 mm, and 0.2 ± 0.4 mm in the first, second, third, and fourth years, respectively, with a mean cumulative loss of 0.3 ± 0.5 mm at 48 months. In the multilevel model, the effects of the clinical C/I ratio and time were significant for bone loss (P < .001). It was estimated that a mean bone loss of 0.1 mm is associated with both a one-unit increase in time (12 months) and a 0.1 increase in the clinical C/I ratio. The other potential risk factors showed no significant relationship with the outcomes. CONCLUSIONS The 6-mm implants supporting single crowns performed well, but the mandible shows a higher risk of failure. The time and clinical C/I ratio are predictors for bone loss.

Accuracy of periapical radiography, panoramic radiography and computed tomography for examining the mental foramen region

Purpose: To determine the accuracy of different radiographic methods for bone height estimation at the mental foramen area. Methods: Twenty dry human hemimandibles were examed by using periapical and panoramic radiography, and computed tomography. An electronic digital caliper was used to measure the tracings obtained from the radiographies in three different times (groups A1, A2 and A3) and in the cross-sectioned hemimandibles (group B). Measurements consisted of: Measure 1 - from the upper limit of the alveolar ridge to the upper limit of the mental foramen; Measure 2 - from the upper limit of the mental foramen to the inferior limit of the cortical bone of the base of the jaw; Measure 3 - from the upper limit of the alveolar ridge to the inferior limit of the cortical bone of the base of the jaw. Data were analyzed with Student-t and Friedman tests. Results: The average difference values in Measure 1 were 0.33 mm, 0.35 mm and 0.85 mm for the periapical radiography, computed tomography and panoramic radiography, respectively (confidence intervals of 0.17 mm to 0.49 mm, 0.18 mm to 0.53 mm and 0.38 mm to 1.32 mm, respectively). Panoramic radiographies showed the greatest differences in Measures 2 and 3, with average values of 1.05 mm and 1.93 mm, respectively. Conclusion: Periapical radiography and computed tomography showed the best accuracy. A safety margin for surgical purposes has been suggested.