Bruno Salles Sotto-Maior

A Retrospective Evaluation of the Survival Rates of Splinted and Non-Splinted Short Dental Implants in Posterior Partially Edentulous Jaws

BACKGROUND The aim of the present study is to evaluate the survival rate and bone loss around short implants (≤10 mm) supporting splinted or non-splinted posterior prostheses during a follow-up period of 3 to 16 years. METHODS A total of 453 implants from 198 patients was divided into splinted or non-splinted groups. Implant survival rate was calculated for each group, and potential risk was represented as odds ratio (OR). The final linear distance from implant platform level to the first bone-to-implant contact was compared to this same reference just after loading by digital periapical radiographs to determine the marginal bone loss (BL). RESULTS The splinted group comprised 219 implants in 86 patients, whereas the non-splinted group included 234 implants from 112 patients. The mean follow-up period was 9.7 ± 3.7 years. Although different success rates were found for splinted (97.7%) and non-splinted (93.2%) groups, they exhibited similar BL (1.22 ± 0.95 mm and 1.27 ± 1.15 mm, respectively). The success of splinted implants was associated with no other variable, whereas non-splinted implants exhibited higher risk of failure when placed in men (OR = 3.2) and when implants shorter than 10 mm were used (OR = 3.6 and 4.1 for 8.5 mm and 7 mm, respectively). Regardless of group, 71.4% of the unsuccessful implants failed before the end of the first year after loading. CONCLUSION Non-splinted posterior short implants had a somewhat lower success rate than splinted short implants, and the failure rate in non-splinted short implants appeared to be greater in males as well as in implants ≤10 mm.

Clinical accuracy of flapless computer-guided surgery for implant placement in edentulous arches.

PURPOSE Although flapless computer-guided implant placement provides important benefits, deviations from the planned implant placement in the edentulous arch may pose significant risks. This study evaluated the reliability and accuracy of a flapless computer-guided surgical approach. MATERIALS AND METHODS Computer-generated preoperative implant planning was compared to actual placement by cone-beam computerized tomography (CBCT) scanning of patients before and after surgery. A well-fitting complete denture or optimized prosthetic tooth arrangement was used and converted to a radiographic template. Prior to scanning, esthetics and functional aspects were checked clinically. The implant positions were virtually determined by the implant planning software relative to the bone structure and prospective tooth position. After implant placement, new CBCT scans were obtained for each subject. Software was used to fuse the images of the planned and placed implants, and the locations and axes were compared. The normality of the data distribution was evaluated by the Kolmogorov-Smirnov test. Mean values were compared between groups based on the upper or lower jaws with the t test for independent samples. The level of significance was fixed at 5%. RESULTS Sixty-two implants were placed in edentulous arches with stereolithographic surgical guides in 14 patients. Damage due to implant placement was not observed in any critical anatomical structure. Compared to the planned implants, placed implants showed mean and standard deviation linear measurements at the cervical, middle, and apical implant portions of 2.17 (± 0.87), 2.32 (± 1.52), and 2.86 (± 2.17) mm, for the maxilla, and 1.42 (± 0.76), 1.42 (± 0.76), and 1.42 (± 0.76) mm, for the mandible, respectively. The angular deviations were 1.93 (± 0.17) and 1.85 (± 0.75) degrees for the maxilla and mandible, respectively. The linear deviation differed significantlybetween the upper and lower jaws, but the angular deviation did not. CONCLUSION Flapless computer-guided surgery may be a viable treatment option for rehabilitating the edentulous arch.

Influence of high insertion torque on implant placement: an anisotropic bone stress analysis

The aim of this study was to evaluate the influence of the high values of insertion torques on the stress and strain distribution in cortical and cancellous bones. Based on tomography imaging, a representative mathematical model of a partial maxilla was built using Mimics 11.11 and Solid Works 2010 softwares. Six models were built and each of them received an implant with one of the following insertion torques: 30, 40, 50, 60, 70 or 80 Ncm on the external hexagon. The cortical and cancellous bones were considered anisotropic. The bone/implant interface was considered perfectly bonded. The numerical analysis was carried out using Ansys Workbench 10.0. The convergence of analysis (6%) drove the mesh refinement. Maximum principal stress (δmax) and maximum principal strain (εmax) were obtained for cortical and cancellous bones around to implant. Pearsons correlation test was used to determine the correlation between insertion torque and stress concentration in the periimplant bone tissue, considering the significance level at 5%. The increase in the insertion torque generated an increase in the δmax and εmax values for cortical and cancellous bone. The δmax was smaller for the cancellous bone, with greater stress variation among the insertion torques. The εmax was higher in the cancellous bone in comparison to the cortical bone. According to the methodology used and the limits of this study, it can be concluded that higher insertion torques increased tensile and compressive stress concentrations in the periimplant bone tissue.

Biofilm and saliva affect the biomechanical behavior of dental implants

Friction coefficient (FC) was quantified between titanium-titanium (Ti-Ti) and titanium-zirconia (Ti-Zr), materials commonly used as abutment and implants, in the presence of a multispecies biofilm (Bf) or salivary pellicle (Pel). Furthermore, FC was used as a parameter to evaluate the biomechanical behavior of a single implant-supported restoration. Interface between Ti-Ti and Ti-Zr without Pel or Bf was used as control (Ctrl). FC was recorded using tribometer and analyzed by two-way Anova and Tukey test (p<0.05). Data were transposed to a finite element model of a dental implant-supported restoration. Models were obtained varying abutment material (Ti and Zr) and FCs recorded (Bf, Pel, and Ctrl). Maximum and shear stress were calculated for bone and equivalent von Misses for prosthetic components. Data were analyzed using two-way ANOVA (p<0.05) and percentage of contribution for each condition (material and FC) was calculated. FC significant differences were observed between Ti-Ti and Ti-Zr for Ctrl and Bf groups, with lower values for Ti-Zr (p<0.05). Within each material group, Ti-Ti differed between all treatments (p<0.05) and for Ti-Zr, only Pel showed higher values compared with Ctrl and Bf (p<0.05). FC contributed to 89.83% (p<0.05) of the stress in the screw, decreasing the stress when the FC was lower. FC resulted in an increase of 59.78% of maximum stress in cortical bone (p=0.05). It can be concluded that the shift of the FC due to the presence of Pel or Bf is able to jeopardize the biomechanical behavior of a single implant-supported restoration.

Immediate implant placement, reconstruction of compromised sockets, and repair of gingival recession with a triple graft from the maxillary tuberosity: A variation of the immediate dentoalveolar restoration technique

Immediate implant placement into compromised sockets is challenging for clinicians. The 3-dimensional implant position, status of the buccal bone wall, and regeneration of the soft tissue contours all affect adequate esthetic and functional results. This clinical report presents a treatment protocol (a variation of the immediate dentoalveolar restoration concept) consisting of immediate implantation and the reconstruction of the buccal bone wall and gingival recession in a single procedure with a triple graft (cancellous and cortical bone and soft tissue graft).

Esthetic outcomes and tissue stability of implant placement in compromised sockets following immediate dentoalveolar restoration: results of a prospective case series at 58 months follow-up.

The aim of this prospective case series was to evaluate the stability of esthetic treatment after single tooth replacement in compromised sockets using the immediate dentoalveolar restoration (IDR) concept. Eighteen patients underwent immediate implant placement and IDR of bone defects. Clinical photographs were used to evaluate the gingival contour and papillae. The mean soft tissue dimensions at baseline and final follow-up were 12.85 ± 2.33 mm and 12.79 ± 2.48 mm, respectively, revealing no recession. The mean mesial and distal papillary heights increased slightly over time. Stable periimplant soft tissues and satisfactory esthetic outcomes were achieved.

Immediate occlusal loading of extrasinus zygomatic implants: a prospective cohort study with a follow-up period of 8 years.

The aim of this study was to evaluate the long-term success rate of immediate occlusal loading of extrasinus zygomatic implants after an 8-year follow-up. From 62 patients who needed implant treatment in 2003, 25 patients who presented with maxillary atrophy met the inclusion criteria and agreed to participate in the study. All patients received fixed dentures under immediate occlusal loading supported by extrasinus zygomatic implants associated with anterior standard implants. No bone grafting procedures were performed. During the 8-year follow-up period, 21 patients underwent clinical evaluation and radiographic examinations every 6 months. This study conforms to the STROBE guidelines regarding prospective cohort studies. 40 extrasinus zygomatic and 74 anterior standard implants were evaluated. All patients were clinically free of signs and symptoms of sinus disturbance at all follow-up appointments. After 8 years, the success rates of extrasinus zygomatic implants, standard anterior implants and definitive prostheses were 97.5%, 95.9% and 95.2%, respectively. Within the limits of this study, immediate occlusal loading of extrasinus zygomatic implants presents a predictable treatment option for the atrophic maxilla.

Influence of Crown-to-Implant Ratio on Stress Around Single Short-Wide Implants: A Photoelastic Stress Analysis

PURPOSE The aim of this study was to evaluate the photoelastic fringe patterns around two short-wide implants supporting single crowns with different crown-to-implant (C/I) ratios. MATERIALS AND METHODS External hexagon (EH) cylindrical implants (5 × 7 mm) or Morse Taper (MT) conical implants (5 × 6 mm) were embedded individually into photoelastic resin blocks. Each implant received a single metal-ceramic crown, with a C/I ratio of 1:1 or 2:1 (n = 10). Each set was positioned in a polariscope and submitted to a 0.5 kgf compressive load, applied axially or obliquely (30°). The polariscope images were digitally recorded, and based on isoclinal and isochromatic fringes, the shear stress was calculated at 5 predetermined points around each implant. Data were analyzed by two-way ANOVA (α = 0.05). RESULTS Under axial loading, the stress was concentrated at the crestal region, and there were no differences between C/I ratio or implant types. In contrast, under oblique loading, EH implants showed lower stress values than the MT group and the 2:1 C/I ratio showed higher stress concentration for both implant types (p < 0.05). Moreover, MT implants showed stress distribution through a higher area than the EH implant did, with a tendency to direct the stress toward the implants apex under oblique loading. CONCLUSION MT conical short-wide implants showed higher stress values that were distributed through a higher area directed to the implant apex. The C/I ratio influences the stress distribution only under oblique loading.

Evaluation of bone remodeling around single dental implants of different lengths: a mechanobiological numerical simulation and validation using clinical data

Algorithmic models have been proposed to explain adaptive behavior of bone to loading; however, these models have not been applied to explain the biomechanics of short dental implants. Purpose of present study was to simulate bone remodeling around single implants of different lengths using mechanoregulatory tissue differentiation model derived from the Stanford theory, using finite elements analysis (FEA) and to validate the theoretical prediction with the clinical findings of crestal bone loss. Loading cycles were applied on 7-, 10-, or 13-mm-long dental implants to simulate daily mastication and bone remodeling was assessed by changes in the strain energy density of bone after a 3, 6, and 12 months of function. Moreover, clinical findings of marginal bone loss in 45 patients rehabilitated with same implant designs used in the simulation (n = 15) were computed to validate the theoretical results. FEA analysis showed that although the bone density values reduced over time in the cortical bone for all groups, bone remodeling was independent of implant length. Clinical data showed a similar pattern of bone resorption compared with the data generated from mathematical analyses, independent of implant length. The results of this study showed that the mechanoregulatory tissue model could be employed in monitoring the morphological changes in bone that is subjected to biomechanical loads. In addition, the implant length did not influence the bone remodeling around single dental implants during the first year of loading.

Effect of double flasking and investing methods on artificial teeth movement in complete dentures processing.

PURPOSE The aim of this study was to evaluate linear dimensional alterations of artificial teeth for complete dentures when using different investment and flasking techniques. BACKGROUND Dimensional changes in the vertical dimension may occur owing to changes in artificial teeth positioning caused by different investing and flasking techniques. MATERIALS AND METHODS Thirty pairs of the complete dentures were manufactured and randomly divided into three groups (n = 10): (1) invested with type III stone in monomaxillary PVC flask; (2) invested with type III stone in bimaxillary PVC flask; and (3) invested with laboratory silicone in bimaxillary PVC flask. Dentures were polymerised by microwave, and 12 linear distances were measured before and after denture processing. Data were analysed by one-way anova, considering manufacturing technique as the study factor. Tukeys HSD was used as post hoc ANOVA (p = 0.05). RESULTS Most of the linear distances were comparable for all groups. All transversal maxillary and mandibular distances were higher for group 1 compared with groups 2 and 3 (p < 0.05), except the distance 3-6 for mandibular arch, in which no difference was found between groups (p < 0.05). Both maxillary diagonal distances were higher in group 1 (p < 0.05), and no differences were found among all groups for mandibular measurements. CONCLUSIONS Double flasking technique independent on the investment material is shown to be the most effective method to reduce changes in artificial teeth positioning.