Early load mandibular hybrid prosthesis using the Ohio State University acrylic frame requiring no final impression.

BACKGROUND: Although immediate/early loading protocols for dental implants have presented encouraging outcomes, immediate loading procedures may cause discomfort to the patient and may increase the possibility of damage to the surgical site during the impression procedures. The aim of this study was to describe an alternative technique to fabricate a mandibular hybrid prosthesis in three or four days without making any final impression and to evaluate the outcomes of this technique. METHODS: Seven patients aged 41 to 71 years (mean age, 58 +/- 11) were considered for this study. Each patient received five implants for the reconstruction of the edentulous mandible. These implants were placed in the anterior region of an edentulous mandible and restored with a final mandibular hybrid prosthesis in four days using the Ohio State University (OSU) acrylic frame requiring no final impression procedure. The patients were followed up to 19 months after implant placement. RESULTS: No implants were lost, no technical complications were observed and only minor marginal bone loss was noted after an average 15 months. CONCLUSIONS: This clinical study shows that the OSU acrylic frame, which can easily be customized and accommodates variability in arch form, may be an alternative method to restore any edentulous mandible with an early load mandibular hybrid prosthesis.

Relationship between dental implant stability determined by resonance frequency analysis measurements and peri-implant vertical defects: an in vitro study.

Resonance frequency (RF) analysis is a non-invasive and objective technique developed for implantology, where it measures the stability of the implant in the bone socket. A limited number of studies were performed to compare different stability measurement devices. The aim of the study was to evaluate the association between the implant stability and peri-implant vertical defect by using the new wireless RF analyser. Micro-textured rough-surfaced implants with diameters of 3.7 and 4.8 mm and with a length of 12 mm were used. The peak insertion torque was recorded with the help of the torque control system only during the implant placement. The peri-implant defects were created in millimetre increments ranging between 0 and 5 mm to the same extent on all implants. The RF analysis values were measured by using the RF analyser. Significant correlation was found between insertion torque (44.3 +/- 3 N cm) and implant stability quotient (ISQ) (all implants: r = 0.76, 3.7 mm diameter: r = 0.65, 4.8 mm diameter: r = 0.80). For 3.7 x 12-mm(2) implants, the mean ISQ values were 72.6 +/- 2.4, 69.8 +/- 2, 67.2 +/- 1.8, 64.3 +/- 1.9, 61.2 +/- 2 and 57.2 +/- 2.5 when peri-implant vertical defects were 0, 1, 2, 3, 4 and 5 mm; and the corresponding values were 76.5 +/- 2.2, 74.5 +/- 2.2, 72.3 +/- 2, 70 +/- 1.9, 67 +/- 1.9 and 63.4 +/- 2.3, respectively, for 4.8 x 12-mm(2) implants. All values were significantly different when compared with each other. The wireless RF analyser seems to be a suitable and reliable device to determine the implant stability. Peri-implant bone loss simulated by using acrylic models may result with a decrease in ISQ values for osseo-integrated implants measured by the RF analyser.

Occlusal contacts of edentulous patients with mandibular hybrid dentures opposing maxillary complete dentures.

The purpose of this study was to evaluate differences between the occlusal contacts of edentulous patients with mandibular implant-supported hybrid dentures opposing maxillary complete dentures and those of patients with conventional maxillary and mandibular complete dentures. Six parameters related to occlusion were measured in the 2 groups (n = 40 for each group) using pressure-sensitive film. The mean values generated by each test group for each parameter were compared using a t test. Pearson's correlation coefficients between occlusal force, age, and time in function were examined. Occlusal force and area in the implant denture wearers were larger than those in the conventional denture wearers. No significant difference was seen in occlusal force balance between the left and right sides. The center of occlusal load in the implant denture wearers was more anterior. The maxillary denture may become more unstable in implant denture wearers. It is suggested that the stability and retention of a maxillary denture be checked and the occlusion be adjusted more frequently in the hybrid denture wearer than in the conventional denture wearer.

Implant screw mechanics.

Osseointegrated implant support of dental restorations continues to be a popular option for the contemporary patient with missing natural dentition. This article focuses on the two most frequently used methods for attaching final prostheses to endosseous implants. The authors offer practical solutions for minimizing implant screw loosening and describe the factors involved in maintaining stable screw joint assembly.

Microstructures of plasma-sprayed hydroxyapatite-coated Ti-6Al-4V dental implants.

The purpose of this study was to investigate the microstructure of plasma-sprayed hydroxyapatite coatings and the elemental composition near the coating-substrate interface for two commercial implants, using the scanning electron microscope. Both coating surfaces and cross-sectioned specimens were examined. The results indicated that while the surface microstructures of both implants were consistent with the plasma-spraying process, the scale of the constituents was much finer for one product. In cross-section, both coatings exhibited minimal porosity and intimate contact with the titanium alloy substrate. It was found that limited interdiffusion of titanium and calcium occurred near the interface.

Reverse torque failure of screw-shaped implants in baboons: baseline data for abutment torque application.

Torque failure for endosseous implants has been used as a biomechanical measure of anchorage, though the significance of such data is not known. A practical understanding of the resistance to torque failure of implant-tissue interfaces at stage 2 surgery would help in assigning torque levels for implant abutment-screw fastening. The purpose of this study was to measure torque failure levels of commercially pure (CP) titanium, Ti-6Al-4V, hydroxyapatite-coated (HA-coated) screw-shaped implants placed into the maxillae and mandibles of baboons. Implants identical in size were placed into the edentulous posterior maxillae and mandibles of six female baboons (n = 37 each group) using a standardized surgical protocol. Reverse-torque data were collected at postinsertion time intervals ranging from 3 to 4 months using a counterclockwise torque driver and the data were analyzed (repeated measures ANOVA) for torque differences related to time, biomaterial, and jaw. The HA-coated implants exhibited significantly greater torque-removal values compared to both metallic implants (HA: 186.0 Ncm [50.1]; Ti-6Al-4V: 78.6 Ncm [18.1]; CP Ti 74.0 Ncm [24.4]). Analysis of torque interactions with jaw showed no significant difference; however, the mandible was found to be greater than the maxilla in torque resistance for all groups tested. Understanding the risks in inferring animal data to human application, the clinical implications of these data suggest that the recommended torque level of 35 Ncm for abutment fastening may provide a margin of safety for most implants of similar design and material as used in this study.(ABSTRACT TRUNCATED AT 250 WORDS)

Undergraduate education in implant dentistry.

A special interest group meeting devoted to clinical educational programs in implant dentistry for undergraduate students was held in March 1994 at the annual session of the American Association of Dental Schools in Seattle, Washington. Summaries of the presentations of representatives from three United States dental schools and the moderator's introductory remarks are included in this article.

New implant surgical guide.

This article describes the process of making and using a surgical guide stent. It is intended to enable the surgeon to maintain the same horizontal and vertical axes of cylindrical endosseous implants during the surgical phase of implant placement as those determined at the treatment planning stage. Furthermore, the stent can be used with the entire series of surgical drills, thereby minimizing the chance of inadvertently enlarging the implant site as a result of freehand use of the handpiece.

Soft tissue contouring for aesthetic single-tooth implant restorations.

The aesthetic replacement of a single anterior tooth has been revolutionized by the advent of dental implant technology. The learning objective of this article is to enhance the knowledge of single tooth restorations through the discussion of the restorative techniques, soft tissue management, and aesthetic considerations. The techniques presented can be used to obtain predictable results in the anterior region for aesthetic, hygienic, and functional restorations.

Keeping implant screws tight: the solution.

Retrievability is the major advantage of screw-retained implant restorations compared to cement retention; however, implant screw loosening continues to be a frequently cited disadvantage of this technique. This paper describes the factors involved in maintaining a stable screw joint assembly by maximizing preload on the retaining screw while minimizing joint-separating forces. Practical clinical solutions to minimize this clinical problem are suggested. Readers are cautioned to address both the occlusal and biomechanical etiologies of screw loosening.

Etiology of implant complications: anecdotal reports vs prospective clinical trials.

The dental profession has in the past overreacted to anecdotal reports of both positive and negative outcomes involving implants. Because implant complications usually involve multiple variables, it is necessary to isolate these variables as much as possible when structuring a study to assess implant success vs failure. The methodology used in a study of Omniloc implants is reported, including detailed criteria for patient exclusion, patient demographics, statistical method, measurement indices, control procedures, and success criteria.

A photoelastic and strain gauge analysis of angled abutments for an implant system.

This study was conducted to determine the effect of abutment angulation on the stress field near a specific dental implant. Photoelastic resin was cast directly to five 3.8 x 10-mm Steri-Oss implants in 50 x 70 x 13-mm molds. One additional model was fabricated with a strain gauge rosette embedded in the resin to allow precise determination of normal stresses. Zero-degree, 15-degree, and 20-degree abutments were assembled on each of the six implants, subjected to 178 N load, and viewed with a circular polariscope. Observed fringe patterns were photographed for all six models, and strain indicator readings were recorded for the strain gauge model. Numerical data from the strain gauges produced results that agreed with the visual interpretation of the isochromatic fringes. Strain gauge data were also used to calculate the principal stresses and strains. Although a statistically significant increase in stress and strain was found for each increase in abutment angulation, all three abutments produced principal strains that appear to be within the physiologic zone for bone. All values for stress and strain were determined at the location of the rosette, approximately 4 mm from the implant. Higher stresses and strains exist in regions closer to the fixture.

Some physical properties of implant abutment luting cements.

The dislodging force, the compressive strength at 24 hours, and the film thickness of four resin composite luting cements (UDA, UDA with fluoride, Panavia OP, and DenMat) and a conventional glass-ionomer cement (Shofu Type I) were compared. The axial force necessary to dislodge each cemented 0 degree abutment from an internally threaded Steri-Oss implant (n = 5) was then determined using a mechanical testing machine. UDA with fluoride appears to be a significantly stronger luting agent for abutment cementation than is either UDA or DenMat (P less than .05). DenMat resin composite cement exhibited the highest mean compressive strength whereas Panavia OP had the lowest value for film thickness.

Implant superstructures: a comparison of ultimate failure force.

Because of reported prosthodontic failures, alternative implant abutments and screws with suggested strength superiority have been manufactured. However, little quantitative data are available to support these claims. This study compared the force necessary to cause failure in many of the more commonly used implant and abutment combinations. An 18-mm cantilever test prosthesis was constructed for each system and loaded on an MTS machine until failure occurred (n = 5 for each sample). The mean failure forces ranged from 1.22 to 17.23 kg. The failure force and location of failure for each individual system are reported.

A comparison of the stress transfer characteristics of a dental implant with a rigid or a resilient internal element.

It has been suggested that there is a unique set of problems associated with joining an implant and a natural tooth with a fixed partial denture. The manufacturer of the IMZ implant system claims that this procedure can be accomplished successfully because of the planned stress-distributing characteristics of their resin internal (intramobile) element. This study compared the difference in the stress patterns generated in photoelastic plastic by an IMZ implant with a resilient or a rigid internal element. Under a standardized cantilever load, the stress patterns were photographed in the field of a circular polariscope. The total stress areas were calculated and a statistical comparison performed. The static load conditions of the model demonstrated no statistical difference between the area of stress pattern generated by an IMZ implant with or without a resilient internal element. Moreover, a single load produced the same deflection of the cantilever beam regardless of which element was interposed.

Ewing's sarcoma metastatic to the gingiva.

Although involvement of the jaws by Ewing's sarcoma is uncommon, when it occurs the clinical and radiographic presentation may mimic an inflammatory process, specifically pericoronitis. A case that illustrates this dilemma is presented.