The three-dimensional stability and accuracy of 3D printing surgical templates: An In Vitro study

OBJECTIVE

To evaluate the three-dimensional (3D) stability and accuracy of additively manufactured surgical templates fabricated using two different 3D printers and materials.

MATERIALS AND METHODS

Forty surgical templates were designed and printed using two different 3D printers: the resin group (n = 20) used a digital light processing (DLP) 3D printer with photopolymer resin, and the metal group (n = 20) employed a selective laser melting (SLM) 3D printer with titanium alloy. All surgical templates were scanned immediately after production and re-digitalized after one month of storage. Similarly, the implant simulations were performed twice. Three-dimensional congruency between the original design and the manufactured surgical templates was quantified using the root mean square (RMS), and the definitive and planned implant positions were determined and compared.

RESULTS

At the postproduction stage, the metal templates exhibited higher accuracy than the resin templates (p < 0.001), and these differences persisted after one month of storage (p < 0.001). The resin templates demonstrated a significant decrease in three-dimensional stability after one month of storage (p < 0.001), whereas the metal templates were not affected (p > 0.05). No significant differences in implant accuracy were found between the two groups. However, the resin templates showed a significant increase in apical and angular deviations after one month of storage (p < 0.001), whereas the metal templates were not affected (p > 0.05).

CONCLUSION

Printed metal templates showed higher fabrication accuracy than printed resin templates. The three-dimensional stability and implant accuracy of printed metal templates remained unaffected by one month of storage.

CLINICAL SIGNIFICANCE

With superior three-dimensional stability and acceptable implant accuracy, printed metal templates can be considered a viable alternative technique for guided surgery.

Effects of Implant Diameter on Implant Stability and Osseointegration in the Early Stage in a Dog Model

Purpose: To determine the optimal implant diameter under limited bone width by comparing the effects of implants with different diameters on implant stability, peri-implant bone stability, and osseointegration. In addition, to evaluate the reliability of resonance frequency analysis (RFA) in detecting osseointegration and marginal bone level (MBL). Materials and Methods: Mandibular premolars and first molars of seven beagle dogs were extracted. After 8 weeks, their mandibular models and radiographic information were collected to fabricate implant templates. Implant sites were randomly divided into three groups according to diameter: Ø3.3, Ø4.1, and Ø4.8 mm. Implant stability quotient (ISQ) measurement and radiographic evaluation were performed after surgery (baseline) and at 4, 8, and 12 weeks. Three dogs were euthanized at 4 weeks to observe osteogenesis and implant-tissue interface biology. Four dogs were euthanized at 12 weeks to observe osseointegration. Hard tissue sections were prepared to analyze osteogenesis (fluorescence double labeling) and osseointegration (methylene blue-acid fuchsin staining). Results: At baseline and at 4, 8, and 12 weeks, the ISQ values of Ø4.1- and Ø4.8-mm implants did not differ (P > .05), but both had higher values than the Ø3.3-mm implants (P < .05). The mean marginal bone resorption (MBR) associated with Ø3.3-, Ø4.1-, and Ø4.8-mm implants was 0.65 ± 0.58 mm, 0.37 ± 0.28 mm, and 0.73 ± 0.37 mm, respectively. The buccal MBR of Ø4.8-mm implants was significantly higher than that of Ø4.1-mm implants (P < .05). The bone-to-implant contact (BIC) percentage at 12 weeks did not differ for any group (P > .05). The correlation coefficients between the ISQ and MBL of the Ø3.3-, Ø4.1-, and Ø4.8-mm implants were -0.84 (P < .01), -0.90 (P < .001), and -0.93 (P < .001), respectively, while that between the ISQ and BIC was 0.15 (P > .05). Conclusions: During the early healing stage, the performance of Ø4.1- and Ø4.8-mm implants in terms of implant stability was better than that of Ø3.3-mm implants. Implant diameter may not influence BIC percentage. RFA can be used to evaluate implant stability and MBL but is not suitable to assess the degree of osseointegration.

Ultrasonic Propagation in a Dental Implant

Ultrasound techniques can be used to characterize and stimulate dental implant osseointegration. However, the interaction between an ultrasonic wave and the implant-bone interface (IBI) remains unclear. This study-combining experimental and numerical approaches-investigates the propagation of an ultrasonic wave in a dental implant by assessing the amplitude of the displacements along the implant axis. An ultrasonic transducer was excited in a transient regime at 10 MHz. Laser interferometric techniques were employed to measure the amplitude of the displacements, which varied 3.2-8.9 nm along the implant axis. The results demonstrated the propagation of a guided wave mode along the implant axis. The velocity of the first arriving signal was equal to 2110 m.s^-1, with frequency components lower than 1 MHz, in agreement with numerical results. Investigating guided wave propagation in dental implants should contribute to improved methods for the characterization and stimulation of the IBI.

Do Dietary Supplements and Nutraceuticals Have Effects on Dental Implant Osseointegration? A Scoping Review

Several factors affect dental implant osseointegration, including surgical issues, bone quality and quantity, and host-related factors, such as patients' nutritional status. Many micronutrients might play a key role in dental implant osseointegration by influencing some alveolar bone parameters, such as healing of the alveolus after tooth extraction. This scoping review aims to summarize the role of dietary supplements in optimizing osseointegration after implant insertion surgery. A technical expert panel (TEP) of 11 medical specialists with expertise in oral surgery, bone metabolism, nutrition, and orthopedic surgery performed the review following the PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews) model. The TEP identified micronutrients from the "European Union (EU) Register of nutrition and health claims made on foods" that have a relationship with bone and tooth health, and planned a PubMed search, selecting micronutrients previously identified as MeSH (Medical Subject Headings) terms and adding to each of them the words "dental implants" and "osseointegration". The TEP identified 19 studies concerning vitamin D, magnesium, resveratrol, vitamin C, a mixture of calcium, magnesium, zinc, and vitamin D, and synthetic bone mineral. However, several micronutrients are non-authorized by the "EU Register on nutrition and health claims" for improving bone and/or tooth health. Our scoping review suggests a limited role of nutraceuticals in promoting osseointegration of dental implants, although, in some cases, such as for vitamin D deficiency, there is a clear link among their deficit, reduced osseointegration, and early implant failure, thus requiring an adequate supplementation.

Neutral zone recording in computer-guided implant prosthesis: A new digital neuromuscular approach

Background

Neutral zone (NZ) is a specific area in the oral cavity where muscular opposite forces are null. NZ represents the ideal zone for prosthesis placement. In this study, we compared digital implant planning using conventional technique and using NZ registration through piezography.

Methods

Sixty-tree implants were digitally planned. Angular deviation differences between traditional planned and NZ-planned implants were calculated. In addition, interferences with soft tissues (i.e., tongue and cheeks) were evaluated.

Results

We observed a significant difference between traditional technique and piezographic approach in terms of implants angulation (p = .003), independent of site. A 4.7% of the planned abutments with traditional technique were placed outside the NZ, causing conflict with soft tissues in the digital model.

Conclusions

Compared with traditional technique, piezography allows a significantly different exploitation of the nonconflict area, which potentially translates into better management of soft tissues and improved functionality of the implants.

Does intraoperative bone density testing correlate with parameters of primary implant stability? A pilot study in minipigs

Objectives

Bone density, surgical protocol, and implant design are the major determinants of primary stability. The goal of this animal trial was to investigate potential correlations of intraoperative bone density testing with clinical and histologic parameters of primary implant stability.

Material and methods

Following extractions of all mandibular premolars and subsequent healing, four implants each were placed in a total of four minipigs. Bone density was determined by applying intraoperative compressive tests using a device named BoneProbe whereas measurements of implant insertion torque and resonance frequency analysis were used for evaluating implant stability. Bone mineral density (BMD) and bone to implant contact were quantified after harvesting mandibular block sections. Spearman rank correlation tests were performed for evaluating correlations (α = .05).

Results

Due to variation in clinical measurements, only weak correlations could be identified. A positive correlation was found between the parameters bone to implant contact and BMD (Spearman's rho .53; p = .05) whereas an inverse correlation was observed between BMD and implant stability (Spearman's rho -.61; p = .03). Both BoneProbe measurements in the cortical and trabecular area positively correlated with implant insertion torque (Spearman's rho 0.60; p = .02). A slightly stronger correlation was observed between the average of both BoneProbe measurements and implant insertion torque (Spearman's rho.66; p = .01).

Conclusions

While establishing exact relationships among parameters of implant stability and the measurement techniques applied would require greater sample size, intraoperative compressive testing of bone might, despite the weak correlations seen here, be a useful tool for predicting primary implant stability.

Crestal module design optimization of dental implants: finite element analysis and in vivo studies

The aim of this study was to evaluate the biomechanical behavior of Bone Level dental implants with four different neck designs in contact with cortical bone. Numerical simulations were performed using a Finite Element Method (FEM) based-model. In order to verify the FEM model, the in silico results were compared with the results obtained from histological analysis performed in an in vivo study with New Zealand rabbits. FEM was performed using a computerized 3D model of Bone Level dental implants inserted in the lower jaw bone with an applied axial load of 100 N. The analysis was performed using four different implant neck designs: even surfaced, screwed, three-ring design and four-ring design. Interface are of bone growth was evaluated by analyzing the Bone-Implant-Contact (BIC) parameter obtained from in vivo histological process and analyzed by Scanning Electron Microscopy (SEM). Bone Level implants were inserted in the rabbit tibia, placing two implants per tibia. The BIC was evaluated after three and six weeks of implantation. FEM studies showed that the three-ring design presented lower values of stress distribution compared to the other studied designs. The lower levels of mechanical stress were then correlated with the in vivo studies, showing that the three-ring design presented the highest BIC value after 3 and 6 weeks of implantation. In silico and in vivo results both concluded that the implants with three-ring neck design presented the best biomechanical and histological behavior in terms of new bone formation, enhanced mechanical stability and optimum osseointegration.

Evaluation of the Peri-Implant Bone Level around Platform-Switched Dental Implants: A Retrospective 3-Year Radiographic Study

OBJECTIVE

To describe remodeling of the mesial and distal marginal bone level around platform-switched (PS) and platform-matched (PM) dental implants that were sandblasted with large grit and etched with acid over a three-year period.

MATERIALS AND METHODS

Digital periapical radiographs were obtained at the following time-points: during Stage I of the surgical placement of dental implants, before loading, immediately after loading (baseline), and one, three, six, 12, and 36 months after loading for measuring the horizontal and vertical marginal bone levels.

RESULTS

Sixty implants were successfully osseointegrated during the overall observation period. Vertical marginal bone levels for the PS and PM dental implants were 0.78 ± 0.77 and 0.98 ± 0.81 mm, respectively, whereas the horizontal marginal bone levels for the PS and PM implants were 0.84 ± 0.45 and 0.98 ± 0.68 mm, respectively. During the time leading up to the procedure until 36 months after the procedure, the average vertical marginal bone level resulted in less bone loss for the PS and PM groups-0.96 ± 1.28 and 0.30 ± 1.15 mm, respectively (p < 0.05). The mean levels of the horizontal marginal bone also showed increases of 0.48 ± 1.01 mm in the PS and 0.37 ± 0.77 mm in the PM groups from the time before loading until 36 months after the procedure. However, these increases were not statistically significant (p > 0.05).

CONCLUSION

PS dental implants appeared to be more effective than PM implants for minimizing the mean marginal vertical and horizontal marginal bone loss during the three-year period. Regardless of which abutment connection was used, the dental implant in the present retrospective investigation exhibited minimal marginal bone remodeling, thus indicating long-term stability.

Survival of Dental Implants Replacing Previously Failed Implants: A Retrospective Study in a University Setting

PURPOSE

The rate of dental implant failures ranges from 3% to 8%, with that number increasing as the number of implants placed increases. When an implant fails, the survival rate drops significantly when a second or third attempt is performed. The aim of this study was to evaluate the survival rate of an implant placed in a previously failed implant site and to explore the risk factors that might affect the outcome of the second procedure.

MATERIALS AND METHODS

A retrospective chart review was conducted for patients receiving dental implants at the University of Texas, School of Dentistry from 1985 to 2017. Exclusion criteria included patients with genetic diseases, radiation and chemotherapy, or an age less than 18 years. Data on age, sex, race, tobacco use, diabetes, cardiovascular, osteoporosis, implant brand, anatomical location of the implant, implant length and width, respective information on the replacement implant, and professional maintenance were collected for analysis.

RESULTS

A total of 1,234 patients with 2,742 implants were included. A chart review found that of the 247 failed implants, replacement of implants was performed in 85 patients with 99 implants. More than half of the initial implants failed within the first year of placement. Based on the 12-month performance of each brand, the initially failed implants were categorized as high, medium, or low survival rates. Based on this categorization, the replacement implants that belonged to the medium survival rate category showed higher survival rates than the high survival group of the initially failed implants.

CONCLUSION

The cumulative survival rates of the replacement implants were 91% at 1 year, 88% at 5 years, and 83% at 10 years. Implant failures were more common prior to functional loading.

[The pink and white aesthetics of a new zirconia implant]

Zirconia implants can offer a good alternative to titanium implants. Due to their specific material properties, they have the potential for a more appealing aesthetic result, which can be particularly important in the anterior zone. In the present study, the pink and white aesthetics of immediately placed zirconia implants in the anterior maxillary zone in 20 patients were assessed on the basis of Pink and White Esthetic Scores (PES and WES). To this end, two clinical photographs were compared: one taken immediately after placement of the permanent crown (mean PES = 12.8; mean WES = 8.5) and the other one taken at a later time (mean PES = 12.8; mean WES = 8.6). No statistically significant difference was found between the two moments. Volunteers found it difficult to correctly identify the implant among the other front teeth. Patients completed a questionnaire regarding the aesthetics of the pink and white implant and they graded the final result with an 8.5 score on a point scale of 0 to 10. The aesthetic appearance of a zirconia implant is excellent and stable over time. Patients are generally satisfied with the result.

Osseoincorporation of Porous Tantalum Trabecular-Structured Metal: A Histologic and Histomorphometric Study in Humans

Porous tantalum trabecular-structured metal (PTTM) has been applied to titanium orthopedic and dental implants. This study evaluated the healing pattern of bone growth into experimental PTTM cylinders (N = 24; 3.0 × 5.0 mm) implanted in the partially edentulous jaws of 23 healthy volunteers divided into four groups. Six PTTM cylinders per group were explanted, prepared, and analyzed histologically/metrically after 2, 3, 6, and 12 weeks of submerged healing. PTTM implant osseoincorporation resulted from the formation of an osteogenic tissue network that over the course of 12 weeks resulted in vascular bone volume levels in PTTM that are comparable to clinically observed mean trabecular volumes in edentulous posterior jaws.

Precision of sleeveless 3D drill guides for insertion of one-piece ceramic implants: a prospective clinical trial

OBJECTIVE

The insertion of implants through template-guided surgery is an established method. At the present time, the static navigation is based on sleeves integrated into the guides, through which drill bits of the corresponding size are passed. The present clinical trial is designed to test a new sleeveless system to determine the precision of implant insertion for one-piece ceramic implants.

MATERIALS AND METHODS

For 12 patients, implant bed preparation and the insertion of the implants were done using a sleeveless implant guide. Twenty implants were inserted in this way and checked for precision. The check was done using a noninvasive method, which permitted comparison of the planning data with the actually realized positions after superimposition.

RESULTS

The mean deviations were 0.52 mm (95% CI: 0.37 to 0.67 mm) at the crestal position of the implant, and 0.82 mm (95% CI: 0.56 to 1.08 mm) at the apical tip of the implant. The height deviation was 0.35 mm (95% CI: 0.01 to 0.68 mm). The mean angular deviation was measured as 2.85 degrees (95% CI: 2.18 to 3.51 degrees).

CONCLUSION

The values showed good precision in all the parameters measured. The results were thus in a range equal to or better than the mean precision found in numerous clinical trials described in the literature. In particular, the method showed little deviation, as illustrated by the confidence interval (CI), but also by the clinically critical maximum deviations.

Opinions Regarding Reuse or Replacement of Implant Prosthesis Retaining Screws: A Systematic Review

PURPOSE

To identify whether reuse or replacement is better for managing loose screws.

MATERIALS AND METHODS

An electronic search was performed utilizing PubMed, and a further manual search of the reference lists of relevant reviews and articles was conducted. Selected inclusion and exclusion criteria were used to limit the search.

RESULTS

The electronic and manual search provided 243 titles and abstracts. Full-text analysis was performed for 98 articles, resulting in a total of 15 articles that qualified for inclusion in this study. All the included articles reported that loose screws were reused and retightened or were replaced by new screws. The time of screw loosening ranged from 1 month to 3 years after delivery. Available details of numbers and frequency of screw loosening permitted only limited analysis from very few articles. A total of 44 loose screws reported in two articles did not loosen again after retightening once.

CONCLUSION

From the very limited available literature, it appears that retightening an occlusal screw or abutment screw is an acceptable procedure, as the evidence shows that retightened screws seem to remain tight. Replacement of screws as a routine procedure cannot be recommended. Routine assessment of screw tightness is recommended to minimize additional and more severe complications.

Influence of acid treatment on surface properties and in vivo performance of Ti6Al4V alloy for biomedical applications

The purpose of this work was to investigate the influence of acid treatment on the surface properties and in vivo performance of titanium grade 5 (Ti6Al4V) alloy. Mini-implants with surface treatment were inserted into New Zealand rabbit tibia for 1, 4 and 8 weeks. SEM analysis showed intercommunicated micropores in acid treated samples. AFM showed micron and sub-micron roughness. The thickness of the titanium oxide layer increased with surface treatment, with a significant reduction of Al and V concentration. Acid treated implant removal torque was larger than without treatment. The implants/bone interface of acid treated implants showed dense adhered Ca/P particles with spreading osteoblasts after 4 weeks and newly formed bone trabeculae after 8 weeks. Analysis of rabbit blood that received treated implant showed lower Al and V contents at all times. Acid treatment improved surface morphology and mechanical stability, which allowed initial events of osseointegration, while Al-V ion release was reduced. GRAPHICAL ABTSRACT.

Clinical Applications of an Atraumatic Osteotome

Osteotomes have long been used in the formation of osteotomies for the placement of dental implants. Their ability to manipulate and compress existing bone without generating heat makes them particularly useful for expanding narrow ridges, elevating delicate sinus membrane, and increasing relative bone density around the osteotomy. Common concerns with these devices include the traumatic force communicated to the patient during use and difficulty controlling force vectors. A new type of osteotome has been developed that is designed to enable the clinician to eliminate the concerns found with traditional osteotomes yet it preserves the best qualities and functionality of this class of device. This article will present several case reports that illustrate the usefulness of this instrumentation in clinical settings.

Influence of Laser-Microtextured Surface Collar on Marginal Bone Loss and Peri-Implant Soft Tissue Response: A Systematic Review and Meta-Analysis

BACKGROUND

A laser-microtextured surface (LMS) dental implant collar appears to promote a more tooth-like gingival collagen fiber attachment, which may help to stabilize peri-implant tissues. The purpose of this systematic review is to assess the clinical effect of an LMS versus non-LMS collar on crestal bone level and peri-implant soft tissue response.

METHODS

Electronic and manual literature searches were performed by two independent reviewers for articles written in English up to December 2016. Studies were included if they were human clinical trials with the purpose of evaluating the impact of an LMS collar on peri-implant hard and soft tissues. Cumulative marginal bone loss (MBL), probing depth (PD), and survival rate (SR) with 95% confidence intervals (CIs) were calculated to show the performance of LMS implant collars. MBL, PD, and SR data were analyzed with a random effects model to compare the influence of LMS collars with non-LMS collars (e.g., roughened surface and machined surface).

RESULTS

Fifteen human clinical studies (three randomized controlled trials, six cohort studies, and six case series) with 772 implants met the inclusion criteria. For the overall data, the weighted mean MBL was 0.72 mm (95% CI: 0.59 to 0.85 mm), PD was 1.81 mm (95% CI: 1.13 to 2.49 mm), and SR was 0.97 (95% CI: 0.95 to 0.98). MBL around an LMS collar was significantly less than around machined-surface collars (weighted mean difference [WMD]: -0.77; 95% CI: -1.01 to -0.52; I2 = 95.2%; P <0.001). PD in the LMS group was significantly shallower than in the machined-surface group (WMD: -1.34; 95% CI: -1.62 to -1.05; I2 = 81.4%; P <0.001). However, no statistically significant difference was detected for MBL between the LMS and roughened-surface groups (WMD: -0.04; 95% CI: -0.16 to 0.08; I2 = 0.0%; P = 0.75). No statistically significant difference was found for SR between the LMS and non-LMS groups (risk ratio: 1.01; 95% CI: 0.97 to 1.04; I2 = 0.0%; P = 0.91).

CONCLUSIONS

Meta-analysis showed that an LMS collar can reduce the amount of MBL and PD compared with a machined-surface collar. Due to high heterogeneity between the included studies, results should be interpreted cautiously.

Influence of Connection Types and Implant Number on the Biomechanical Behavior of Mandibular Full-Arch Rehabilitation

PURPOSE

To evaluate the influence of different implant numbers and connection types on the biomechanical behavior of mandibular full-arch implant-supported rehabilitation.

MATERIALS AND METHODS

Computed tomography-based finite element models comprising a totally edentulous mandible and 3.8 × 13-mmdiameter implants, abutments, abutment screws, bar retaining screw, and bar were constructed. Different implant numbers (three, four, and five implants) and loading conditions (symmetrical/balanced, unilateral, and posterior with diverse loading magnitudes) were simulated for both external hex and Morse-taper connections. The peak equivalent strain (EQV strain) in the bone and the peak of von Mises stress (EQV stress) in the abutment screw and bar retaining screw were evaluated.

RESULTS

Lower strain values were observed for a symmetrical loading distribution. Considering the same loading conditions, significantly higher bone strain levels were observed for external hex, compared with the Morse-taper connection. The number of implants had no significant influence on strain levels in bone, irrespective of the connection types. Compared with the external hex connection, the Morse-taper connection type presented significantly lower EQV stress values in abutment screws, but significantly higher stress in the bar retaining screw. Increasing the number of implants significantly reduced the EQV stress in the abutment screw and bar retaining screw.

CONCLUSION

The Morse-taper connection type significantly decreased the strain levels in peri-implant bone, while increasing the stress in bar retaining screws. A smaller number of implants in an inferior full-arch rehabilitation slightly increased the stress in the abutment and bar retaining screws. Balanced adjustments of the loading improve the biomechanics of a mandibular full-arch rehabilitation.

Influence of Implant Length and Diameter, Bicortical Anchorage, and Sinus Augmentation on Bone Stress Distribution: Three-Dimensional Finite Element Analysis

PURPOSE

Clarification of the protocol for using short implants is required to enable widespread use of short implants as an available treatment option. The purpose of this study was to investigate the influences of implant length and diameter, bicortical anchorage, and sinus augmentation on peri-implant cortical bone stress by three-dimensional finite element analysis.

MATERIALS AND METHODS

For bone models with bone quantity A and C in the maxillary molar region, three-dimensional finite element analysis was performed using different lengths and diameters of implant computer-aided design models, and the degree of maximum principal stress distribution for each model was calculated.

RESULTS

For bone quantity A models, the degree of stress distribution of the 4-mm-diameter, 6-mm-length implant was the greatest. For bone quantity C models, the degree of stress distribution of the 5-mm-diameter, 6-mm-length implant with bicortical anchorage was much smaller than that for the 4-mm-diameter, 13-mm-length implant with sinus augmentation.

CONCLUSION

The results of this study suggest that 6-mm-length implants should be selected in cases with bone quantity C where the bone width permits increasing implant diameter from 4 mm to 5 mm.

Influence of Drilling Speed on Stability of Tapered Dental Implants: An Ex Vivo Experimental Study

PURPOSE

The aim of this study was to evaluate whether the drilling speed used during implant site preparation influences primary stability.

MATERIALS AND METHODS

Eighty tapered designed implants (3.8 × 10 mm) were inserted following osteotomies created in solid rigid polyurethane foam (simulating bone type II) and cellular rigid polyurethane foam (simulating bone type IV). Half were prepared using drilling speeds of 800 rpm (low speed), and the other half were prepared using speeds of 1,500 rpm (high speed). Following insertion, implant primary stability was measured using Periotest and Osstell (resonance frequency analysis [RFA]) devices.

RESULTS

Two-way analysis of variance (ANOVA) used for this study found that the drilling speed used to create the osteotomies appeared to have no significant impact on primary stability.

CONCLUSION

The bone quality and not the osteotomy drilling speed seems to influence the implant primary stability.

Comparative Clinical and Histologic Assessments of Dental Implants Delivered with a Manual Torque Limiting Wrench Versus with an Electronically Controlled Torque Limiting Device

The goal of this preclinical investigation was to evaluate the healing of tapered roughened surfaced dental implants that were delivered by either a manual torque limiting wrench or an electronically controlled torque limiting device. Three canines underwent bilateral extraction of third and fourth premolars and first molar. The extraction sites were allowed to heal for 2 months before two dental implants were placed bilaterally. All animals underwent a normal healing process. One animal was sacrificed at 1 month and the remaining two animals were sacrificed at 2 months to perform histologic evaluations including bone-to-implant contact (BIC) and soft tissue healing. The clinical stability and histologic osseointegration were similar when the results obtained with the manual torque limiting wrench were compared to those delivered by the electronically controlled torque limiting device. However, BIC and maintenance of the crestal bone level achieved appeared to be higher in the electronically controlled torque limiting device groups.

Temporal sequence of hard and soft tissue healing around titanium dental implants

The objective of the present review was to summarize the evidence available on the temporal sequence of hard and soft tissue healing around titanium dental implants in animal models and in humans. A search was undertaken to find animal and human studies reporting on the temporal dynamics of hard and soft tissue integration of titanium dental implants. Moreover, the influence of implant surface roughness and chemistry on the molecular mechanisms associated with osseointegration was also investigated. The findings indicated that the integration of titanium dental implants into hard and soft tissue represents the result of a complex cascade of biological events initiated by the surgical intervention. Implant placement into alveolar bone induces a cascade of healing events starting with clot formation and continuing with the maturation of bone in contact with the implant surface. From a genetic point of view, osseointegration is associated with a decrease in inflammation and an increase in osteogenesis-, angiogenesis- and neurogenesis-associated gene expression during the early stages of wound healing. The attachment and maturation of the soft tissue complex (i.e. epithelium and connective tissue) to implants becomes established 6-8 weeks following surgery. Based on the findings of the present review it can be concluded that improved understanding of the mechanisms associated with osseointegration will provide leads and targets for strategies aimed at enhancing the clinical performance of titanium dental implants.

A Customized Healing Abutment for Immediate and Delayed Implant Cases

Anatomically contoured healing abutments have been shown to contain and protect slow-resorbing substitution grafts, resulting in bone and soft-tissue volume augmentation. Even in healed sites customized healing abutments have demonstrated favorable outcomes compared to standard healing abutments. Through two separate cases, this article describes a technique that enables simple chairside fabrication of precisely contoured customized healing abutments and exact 3-dimensional intraoral positioning. With this technique, the soft tissues upon maturation closely resemble the natural root contour, which allows for the generation of esthetic and functional implant-supported restorations.

Surgery-related factors affecting the stability of orthodontic mini implants screwed in alveolar process interdental spaces: a systematic literature review

The ambiguous results of scientific researches on surgical factors affecting the stability of mini implants (MI) impels the physicians to constantly analyze this problem. The objective of this article was to conduct a systematic literature review about surgery related factors affecting the stability of MI screwed in alveolar process buccal surface between the second premolar and first molar roots based on peer reviewed publications of 2009-2015. The Cochrane and PRISMA references were used while searching for scientific literature. Two data bases and scientific publications were browsed in the Lithuanian University of Health Sciences library. Criteria for article selection were: 1) research in which surgical factors affecting MI stability were analyzed, 2) research in which stability of MI screwed in alveolar process between adjacent teeth roots was analyzed, 3) research in which MI stability was analyzed in clinical practice, 4) articles which were published in 2009-2015. Selected articles were evaluated in accordance with methodical quality. 13 articles met the selection criteria of the research. 2652 MI screwed in 1205 people jawbones' alveolar processes were analyzed in selected articles. The MI success rate was 87.7-97%. Root proximity was identified to be the main determinant of all MI success influencing surgical factors (MI and root contact determined a 9-26.7% failure rate). The results of this article confirm the sufficient MI stability rate in clinical practice and specifies root proximity as the main surgical factor affecting the MI stability.

Intended and Achieved Torque of Implant Abutment's Screw using Manual Wrenches in Simulated Clinical Setting

OBJECTIVE

To measure the difference between the intended torque and the achieved torque by the operator using the spring-style mechanical torque-limiting device (MTLD).

MATERIALS AND METHODS

Inexperienced and experienced clinicians used one spring-type MTLD to torque two abutment screws of each anterior and posterior implants, which were attached to two digital torque meters through a jaw model. The jaw model was part of a preclinical bench manikin attached to a dental chair. The intended torque value was 35 N cm (recommended by manufacturer) and the technique of torquing was observed for all the participants (instantaneous and repeated). The mean torque value was calculated for each subject for the anterior and posterior implants independently; t-test was used to compare between the intended and achieved torque values and to compare between the experienced and inexperienced clinicians (p ≤ 0.05).

RESULTS

Thirty-seven clinicians participated, with an overall mean torque value of 34.30 N cm. The mean torque value of the achieved torque (34.30 ± 4.13 N cm) was statistically significantly less than the intended torque (p = 0.041). The male clinicians produced more statistically significantly accurate torque value (34.54 ± 3.78 N cm) than the female clinicians (p = 0.034), and the experienced clinicians produced more accurate torque values (34.9 ± 5.13 N cm) than the inexperienced clinicians (p = 0.048).

CONCLUSION

Within the limitation of this study, the use of MTLDs did not always produce consistent torque values and the technique by which the operators use the MTLD might affect the torque value.

Planning Implant Placement on 3D Stereolithographic Models Applied with Immediate Loading of Implant-Supported Hybrid Prostheses After Multiple Extractions: A Case Series

PURPOSE

The aim of this noninterventional, retrospective case series was to evaluate the outcome of immediately loaded implants in patients with failing dentitions that require bone tabling using a bone reduction guide and a surgical guide manufactured directly on three-dimensional (3D) stereolithographic models.

MATERIALS AND METHODS

Consecutive patients with failing dentition and at least two remaining teeth who were treated in a single center between December 14, 2009 and September 23, 2013 were eligible. All patients receiving implants loaded with a hybrid prosthesis on the same day as extraction with their surgery planned on 3D models and performed using a surgical guide manufactured in a laboratory on the planning model were included. Patients who had undergone bone grafting procedures were excluded. Descriptive statistical analyses of available data were performed, including life-table calculations to derive a cumulative survival rate (CSR).

RESULTS

Two hundred twenty-eight patients (105 females and 123 males) received 1,657 implants (NobelActive) in 321 arches, in most cases 5 implants (range, 5 to 7) per arch. Ten preexisting implants were used. The mean insertion torque was 60.02 ± 13.1 Ncm (range, 15 to 75 Ncm). The definitive abutment was placed on the same day as surgery in all cases, and the definitive prosthesis (n = 304) was delivered after a mean of 7.9 ± 2.6 months. All implants were followed for 20.01 ± 11.3 months (range, 0 to 52 months) from implant insertion. Four implants (3 patients) had delayed loading, and one implant was left as a sleeping implant. Eight implants among six patients failed, two of the implants after prosthesis delivery. The CSR of the placed implants was 99.4% at implant level and 96.2% at patient level.

CONCLUSION

Planning on 3D models to remove bone and place implants using custom-made bone reduction and surgical guides with immediate loading on the same day as extraction of remaining teeth was safe and effective for implant survival and rehabilitation of patients with periodontitis and failing dentition.

Insertion Torques of Self-Drilling Mini-Implants in Simulated Mandibular Bone: Assessment of Potential for Implant Fracture

PURPOSE

Fracture of orthodontic mini-implants during insertion is a limiting factor for their clinical success. The purpose of this study was to determine the fracture potential of commonly used self-drilling orthodontic mini-implants when placed into simulated thick, dense mandibular bone.

MATERIALS AND METHODS

Six mini-implant systems were assessed for the potential for fracture (Aarhus, Medicon; Dual-Top, Jeil Medical; OrthoEasy, Forestadent; tomas-pin, Dentaurum; Unitek, 3M; and VectorTAS, Ormco). First, mini-implants were inserted manually, without predrilling, into bone substitutes (Sawbones) with a 3-mm-thick, dense (1.64 g/cm(3)) cortical layer. A custom-made insertion device was used for placement of mini-implants. A sixaxis force/torque transducer was secured at the base of the bone blocks to measure the maximum torque experienced during insertion. Measured insertion torques were compared with previously reported fracture torques, yielding a torque ratio (insertion torque as a percentage of fracture torque), which was used as an indicator of the potential for mini-implant fracture. Mini-implants that experienced torque ratios ≥ 75% upon insertion underwent further testing, following the manufacturer's recommendations for predrilling in thick, dense bone conditions.

RESULTS

Significant differences in torque ratios were found among all mini-implants, except between OrthoEasy and Dual-Top, and OrthoEasy and VectorTAS. Overall, Aarhus had the highest torque ratio (91% ± 3%), with Unitek showing the lowest ratio (37% ± 3%). Aarhus and tomas-pin mini-implants displayed torque ratios ≥ 75% and experienced fracture upon insertion. When the manufacturer's specific predrilling recommendations were followed, no changes in torque ratio were found for Aarhus and tomas-pin. However, while Aarhus continued to fracture upon insertion, all tomas-pin mini-implants were inserted fully without fracture following predrilling.

CONCLUSION

These findings support the safe use of Unitek, VectorTAS, Dual-Top, and OrthoEasy self-drilling mini-implants in areas of 3-mm-thick, 1.64 g/cm(3) dense cortical bone without predrilling. Following predrilling, fractures did not occur with tomas-pin. For implants that continued to fracture after predrilling, other strategies may be required, such as the use of larger-diameter mini-implants in thick, dense bone conditions.

Influence of Palatal Coverage and Implant Distribution on Denture Strain in Maxillary Implant Overdentures

PURPOSE

As maxillary implant overdentures are being increasingly used in clinical practice, prosthodontic complications related to these dentures are also reported more often. The purpose of this study was to examine the influence of palatal coverage and implant distribution on the shear strain of maxillary implant overdentures.

MATERIALS AND METHODS

A maxillary edentulous model with implants inserted in the anterior, premolar, and molar areas was fabricated. Two kinds of experimental overdentures, with and without palatal coverage, were also fabricated, and two strain gauges were attached at the midline of the labial and palatal sides. A vertical occlusal load of 98 N was applied through a mandibular complete denture, and the shear strain in each denture was compared by analysis of variance (P = .05).

RESULTS

In all situations, the shear strain in palateless dentures was significantly higher than in dentures with palate on both sides (P < .05). In dentures with palate, the shear strain was lower when anterior implants were present.

CONCLUSION

Palateless maxillary implant overdentures exhibited much higher strain than overdentures with palate regardless of the implant distribution; this may cause more prosthodontic and implant complications. The most favorable configuration to prevent complications in maxillary implant overdentures was palatal coverage that was supported by more than four widely distributed implants.

Loss of Accuracy of Torque Wrenches Due to Clinical Use and Cleaning Procedure: Short Communication

PURPOSE

The aim of this study was to investigate the way intensive use and multiple cleanings of torque wrenches may interfere with accurary over time.

MATERIALS AND METHODS

Three different brands (one spring-style and two friction-style types) were tested at baseline and after enduring mechanical testing (1,000 cycles) and cleaning in a thermal disinfector (150 cycles). Torque wrenches were tested at a predetermined value of 30 Ncm at given intervals, and true values were registered by means of a digital torque gauge.

RESULTS

All measured values varied between 28.3 Ncm and 31.1 Ncm. Only the spring-style torque wrench revealed values that differed significantly from baseline after both mechanical testing (P < .001) and cleaning (P < .05).

CONCLUSION

The spring-style torque wrench produced values that changed significantly after multiple mechanical and multiple cleaning cycles. However, the differences were small and the measured values from all tested specimens were close to the predetermined value of 30 Ncm.

Auto-stop Drilling Device for Implant Site Preparation: In Vitro Test of Eccentric Sensor Position

PURPOSE

To quantify the reliability of a new drilling system for implant osteotomy characterized by an eccentric sensor that automatically stops the drill upon contact with soft tissue. This safety mechanism aims to minimize surgical trauma to nerves, vessels, and the maxillary sinus mucosa. The benefits of the eccentric sensor position on planar and angulated surfaces were tested in vitro.

MATERIALS AND METHODS

Predicted drill protrusion after auto-stop was validated against experiments on four human cadaver mandibles (30 osteotomies with varying angles). Measurement of the drill's exit holes allowed calculation of the amount of drill protrusion, and postoperative computed tomographic scans of the mandibles were acquired to determine the drill's exit angles.

RESULTS

Mean drill protrusion into human jawbone was 0.46 ± 0.26 mm and differed significantly from expected drill protrusion, which was based on mathematical modeling, of 0.64 ± 0.3 mm. Detection of bone passage on angulated walls was seen up to 71 degrees. A central sensor position, by contrast, may result in significantly greater drill protrusion into soft tissue (mean difference: 0.55 ± 0.49 mm) that increases with the drill's exit angle (r = 0.93).

CONCLUSION

Auto-stop drills may significantly enhance safety for the patient during osteotomy. The benefits of eccentric sensor positioning were particularly apparent when applied on angulated surfaces, whereas drill angulation was not found to influence this safety mechanism.

Comparison of design and torque measurements of various manual wrenches

PURPOSE

Accurate torque application and determination of the applied torque during surgical and prosthetic treatment is important to reduce complications. A study was performed to determine and compare the accuracy of manual wrenches, which are available in different designs with a large range of preset torques.

MATERIALS AND METHODS

Thirteen different wrench systems with a variety of preset torques ranging from 10 to 75 Ncm were evaluated. Three different designs were available, with a spring-in-coil or toggle design as an active mechanism or a beam as a passive mechanism, to select the preset torque. To provide a clinically relevant analysis, a total of 1,170 torque measurements in the range of 10 to 45 Ncm were made in vitro using an electronic torque measurement device.

RESULTS

The absolute deviations in Ncm and percent deviations across all wrenches were small, with a mean of -0.24 ± 2.15 Ncm and -0.84% ± 11.72% as a shortfall relative to the preset value. The greatest overage was 8.2 Ncm (82.5%), and the greatest shortfall was 8.47 Ncm (46%). However, extreme values were rare, with 95th-percentile values of -1.5% (lower value) and -0.16% (upper value). A comparison with respect to wrench design revealed significantly higher deviations for coil and toggle-style wrenches than for beam wrenches.

CONCLUSION

Beam wrenches were associated with a lower risk of rare extreme values thanks to their passive mechanism of achieving the selected preset torque, which minimizes the risk of harming screw connections.

A retrospective report on three implant devices used to restore posterior partial edentulism: overall performance and changes in crestal bone levels

Three implant designs were used to treat posterior partial edentulism. A total of 799 implants (563 Osseotite, 65 Straumann SLA,171 Endopore SPS) were placed in 345 patients. SPS implants were used in sites with less bone, had shorter lengths, and functioned longer than the threaded implant designs. Comparing implant losses, SPS implants had a higher failure rate (9.3%) compared with Osseotite (4.0%) or SLA (0%) implants. SPS implant losses generally occurred as late failures, while Osseotite losses were early failures. However, among surviving implants, SPS implants had less crestal bone loss at all time intervals compared with both of the threaded implant designs.

Development of a Drilling Simulator for Dental Implant Surgery

The aim of this study was to develop and evaluate a dental implant surgery simulator that allows learners to experience the drilling forces necessary to perform an osteotomy in the posterior mandibular bone. The simulator contains a force-sensing device that receives input and counteracts this force, which is felt as resistance by the user. The device consists of an actuator, a load cell, and a control unit. A mandibular bone model was fabricated in which the predicted forces necessary to drill the cortical and trabecular bone were determined via micro CT image-based 3D finite element analysis. The simulator was evaluated by five dentists from the Department of Implantology at Tokyo Dental College. The ability of the evaluators to distinguish the drilling resistance through different regions of the mandibular bone was investigated. Of the five dentists, four sensed the change in resistance when the drill perforated the upper cortical bone. All five dentists were able to detect when the drill made contact with lingual cortical bone and when the lingual bone was perforated. This project successfully developed a dental implant surgery simulator that allows users to experience the forces necessary to drill through types of bone encountered during osteotomy. Furthermore, the researchers were able to build a device by which excessive drilling simulates a situation in which the lingual cortical bone is perforated--a situation that could lead to negative repercussions in a clinical setting. The simulator was found to be useful to train users to recognize the differences in resistance when drilling through the mandibular bone.

Guided surgery with tooth-supported templates for single missing teeth: A critical review

AIM

To systematically scrutinise the scientific literature to evaluate the accuracy of computer-guided implant placement for single missing teeth, as well as to analyse the eventual clinical advantages and treatment outcomes.

MATERIAL AND METHODS

The electronic and manual literature search of clinical studies published from January 2002 up to November 2015 was carried out using specified indexing terms. Outcomes were accuracy; implant and prosthetic failures; biological and mechanical complications; marginal bone loss (MBL); sulcus bleeding index (SBI); plaque score (PS); pink esthetic score [PES]; aesthetic and clinical outcomes.

RESULTS

The search yielded 1027 relevant titles and abstracts, found during the electronic (n = 1020) and manual (n = 7) searches. After data extraction, and screening of titles, abstracts, and full-texts, 32 studies fulfilled inclusion criteria and were included in the critical review: two randomised controlled clinical trials, six prospective observational single cohort studies, one retrospective observational study, three in vitro comparative studies, 10 case reports and 10 systematic reviews. A total of 209 patients (18 to 67 years old) were treated with 342 implants using computer-guided implant surgery. The follow-up ranged from 12 to 52 months. The cumulative survival rate ranged from 96.5% to 100%. Eleven implant planning softwares and guided surgery systems were used and evaluated.

CONCLUSIONS

Computer-guided surgery for single missing teeth provides comprehensive treatment planning, reliable implant positioning, favourable clinical outcomes and aesthetics. A tooth-supported template for the treatment of single missing teeth results in greater accuracy of implant positioning than with mucosa-supported or bone-supported templates. The limited scientific evidence available suggests that guided surgery leads to implant survival rates as good as conventional freehand protocols. Computer-guided surgery implies additional costs, that should be analysed in terms of cost-effectiveness, considering the reduction of surgery time, postoperative pain and swelling, as well as, the potential increased accuracy. Long-term randomised clinical trials are eagerly needed to investigate the clinical performance of guided surgery in partially edentate patients.

Accuracy of dental torque wrenches

The aim of this in vitro study was to compare the actual torque of 2 manual wrench systems to their stated (target) torque. New spring- (Nobel Biocare USA, LLC) and friction-style (Zimmer Dental, Inc.) manual dental torque wrenches, as well as spring torque wrenches that had undergone sterilization and clinical use, were tested. A calibrated torque gauge was used to compare actual torque to target torque values of 15 and 35 N/cm. Data were statistically analyzed via mixed-effects regression model with Bonferroni correction. At a target torque of 15 N/cm, the mean torque of new spring wrenches (13.97 N/cm; SE, 0.07 N/cm) was significantly different from that of used spring wrenches (14.94 N/cm; SE, 0.06 N/cm; P < 0.0001). However, the mean torques of new spring and new friction wrenches (14.10 N/cm; SE, 0.07 N/cm; P = 0.21) were not significantly different. For torque measurements calibrated at 35 N/cm, the mean torque of new spring wrenches (35.29 N/cm; SE, 0.10 N/cm) was significantly different (P < 0.0001) from the means of new friction wrenches (36.20 N/cm; SE, 0.08 N/cm) and used spring wrenches (36.45 N/cm; SE, 0.08 N/cm). Discrepancies in torque could impact the clinical success of screw-retained dental implants. It is recommended that torque wrenches be checked regularly to ensure that they are performing to target values.

Histologic and Radiographic Comparison of Bone Scraper and Trephine Bur for Autologous Bone Harvesting in Maxillary Sinus Augmentation

PURPOSE

The aims of this study were to investigate the best two of five common methods of collecting autologous bone (preliminary study [PS]) and to test clinically the effects of autografts harvested using a trephine bur or bone scraper for sinus augmentation surgery (main study [MS]).

MATERIALS AND METHODS

In the PS, five autograft samples from five patients (n = 25) were harvested with a bone scraper, round bur, piezoelectric device, implant bur, and trephine bur and were processed for histomorphometric analysis. In the MS, sinus augmentation was performed on 20 patients using bovine-derived bone substitute and autograft collected with a trephine bur (group A, n = 10) or collected with a bone scraper (group B, n = 10). Narrow implants were also placed. At 6 months, changes in graft volume were evaluated with cone beam computed tomography. The amounts of regenerated bone, residual graft, and osseointegration of the implants were assessed histologically.

RESULTS

In the PS, the trephine bur and bone scraper harvested bone chips that were medium to large and more vital than those obtained with the other tools. In the MS, no significant differences were seen between groups in terms of the amount of residual biomaterial, regenerated bone, change in graft volume, and osseointegration.

CONCLUSION

Biologic differences between these two bone particulates may not influence regeneration and implant osseointegration in sinus augmentation when mixed with xenograft bone.

The Precision of Mechanical Torque Wrenches Used for Implants in Dental Offices

PURPOSE

This study aimed to investigate the precision of mechanical torque wrenches used for implants in dental offices.

MATERIALS AND METHODS

Mechanical torque wrenches (n = 138) with two functional designs and made by three manufacturers were tested by three groups of investigators. Potential influences on accuracy were tested. Relative deviations from targeted torque values and the precision of recorded torque values were analyzed.

RESULTS

Most abutment screws were tightened too tightly rather than too weakly. Differences were apparent in the influence of the functional design of torque wrenches on their precision. No significant correlation between absolute frequency of use and relative deviation or precision was detected. Investigators with different levels of experience exhibited significantly different deviations from targeted torque values.

CONCLUSIONS

Average deviation from intended torque values, and levels of imprecision, are evidently not major problems in implant prosthetics; however, high torque values are a cause for concern.

Cone Beam Computed Tomography for the Dental Implant Patient

Cone beam computed tomography offers many advantages over 2-D imaging for the evaluation of potential implant sites. With the use of CBCT scans becoming more commonplace, it is important for clinicians to be knowledgeable and to use this new technology appropriately and judiciously. The purpose of this article is to describe the advantages and limitations of CBCT imaging for the presurgical and postsurgical evaluations of implant treatment and assessment of implant-related complications.