The International Journal of Oral & Maxillofacial Implants, 01/2002

Purpose: It has been hypothesized that the shock generation on implant-supported prostheses during chewing should generate higher implant loads if the veneering material is porcelain rather than acrylic resin. Materials and Methods: The present study uses strain-gauged abutments to measure the force transferred to the implant after a shock has been applied. This was measured in vitro and in vivo in 5 patients. Results: The different occlusal materials did not lead to different forces generated to the implants of the patients. Discussion: From a practical point of view, the choice of occlusal material has no bearing per se on force generation to the implants. Conclusions: The present study demonstrated that there: (a) is a difference in resilience between acrylic resin and ceramic veneering materials, but (b) this difference is only measurable in in vitro where the force is generated by a shock only and the implant is rigidly anchored. Keywords: biomechanics, dampening, resilience, strain-gauged abutment, veneering material

Purpose: To examine the effects of anodization (surface coating) and reduction of internal Morse taper surface area on the reversal torque values of Straumann ITI dental implants and abutments. Materials and Methods: Eighty ITI solid screw implants were mated with corresponding 5.5-mm solid abutments. The assemblies were divided into 4 test groups of 20 specimens. All abutments were torque tightened into the implant to 35 Ncm. Half of the abutments were anodized and half were in their as-machined state. Each of these 2 groups included half of the implants with the standard internal Morse taper configuration and half with the synOcta (Straumann USA, Waltham, MA) internal positioning interface (indexed). Torque removal testing was then performed on the assemblies. The 4 groups were compared statistically to examine the effect of the 2 variables (anodization and reduction in surface area). Scheffe's test for multiple comparisons was used to compare groups at an adjusted significance level of = .05. Results: Torque removal of all specimens revealed that the indexed implant with the non-anodized abutment demonstrated superior removal torque. Discussion: The indexed and standard implants with anodized abutments, and the standard implant with the non-anodized abutment had lower reversal torque values. Conclusion: The addition of the indexed internal surface to the ITI implant did not have deleterious effect on the resistance to loosening of standard solid abutments. Keywords: abutment loosening, dental implants, implant restorations, reverse torque, surface area

Purpose: Histomorphometry and microhardness measurements were performed after Ti6Al4V implantation in cancellous and cortical bone of healthy and ovariectomized animals to determine characterization of the bone-biomaterial interface in osteopenic bone. Materials and Methods: Nine ovariectomized and 9 sham-aged rats were used. Four months later, nails were implanted in the distal femurs, and the animals were sacrificed after 8 weeks. Moreover, 3 ovariectomized and 3 sham-aged sheep were used. Twenty-four months later, screws were implanted in the tibial diaphyses and the animals were sacrificed after 12 weeks. Results: Histomorphometry showed the development of osteopenia in both trabecular and cortical bone, and revealed a significant decrease in the osseointegration rate in osteopenic versus sham-aged animals for both trabecular (Affinity Index: -18.6%, P .001) and cortical bone (Affinity Index: -23.5%, P .005; Bone Ingrowth: -9%, P .05). At the interfaces of the shamaged animals in both trabecular and cortical bone, a decrease of bone microhardness was observed in comparison with preexisting bone (trabecular: -9.8%, P .0005; cortical: -19.3%, P .0005). In case of osteopenia, this decrease was even more extensive (trabecular: -15.5%, P .0005; cortical: -24.7%, P .0005). Discussion: The present data suggest that bone formation around Ti6Al4V was not associated with complete bone maturation, even in healthy animals. In case of osteopenia, both bone formation and maturation were delayed. Conclusion: These results apparently demonstrate the utility of investigating biomaterials in osteopenic bone and the importance of careful evaluation of the healing rate and bone maturation degree around implanted biomaterials. Keywords: bone-biomaterial interface, implant, microhardness, osseointegration, osteoporosis, titanium alloy

Purpose: Immediately loaded splinted implants can become osseointegrated when they are placed in the anterior part of the mandible. The concept of immediate loading has not been well examined in the posterior mandible. The aim of this study was to evaluate the hard tissue reactions around immediately loaded implants placed in the posterior mandible in the monkey model. Materials and Methods: Six adult M. fascicularis monkeys were used in this study. Thirty-six Ankylos implants (Degussa Dental, Hanau-Wolfgang, Germany) were placed after extraction of the second premolar, first, and second molar teeth and complete healing of the sockets. Control (C) group implants were placed and, after osseointegration, were loaded for 1 month using temporary acrylic resin prostheses and later for 2 months using splinted metal crowns. In the contralateral region of the mandible, test (T) group implants were placed and loaded immediately with the same sequence as carried out for the C implants. After sacrifice of the animals, specimens were examined histologically and evaluated histomorphometrically. Results: All implants were osseointegrated. Compact, cortical bone in contact with the implant surface without any gaps or connective tissue formation was demonstrated. Discussion: Histomorphometric findings of the bone-implant-contacts showed no significant differences between the T and C group implants. Peri-implant mineralized bone areas presented statistically significant differences and showed a higher density of bone between the threads of immediately loaded implants (P .05). Conclusions: Immediately loaded splinted implants in the posterior mandible can become osseointegrated with a hard tissue peri-implant response similar to that of delayed loaded implants. Moreover, immediate loading seems to increase the ossification of the alveolar bone around endosseous implants. Keywords: bone, immediate loading, implant, monkey, posterior mandible

Purpose: Anterior maxillary alveolar vertical distractions were followed for a 5-year period of time. Materials and Methods: A total of 30 vertical distractions were done in 28 patients. Two patients had both anterior maxilla and anterior mandibular distractions for a total of 30 distractions. Two distraction techniques were used: an implant device (3i) and an orthodontic screw device (Osteomed) for orthodontic attachment. Both devices enabled some horizontal as well as vertical movement. The average net vertical distraction was 6.5 mm, but the average anterior horizontal movement was less than 2 mm. Results: Eighty-four implants were placed, but 8 implants failed to integrate. Discussion: All failed implants had been placed in poor quality bone that needed bone grafting. The most common restoration was a fixed prosthesis supported by implants; the longest follow-up post loading was 4.4 years. Conclusion: This clinical study gives additional evidence in favor of the stability and utility of vertical distraction procedures in the maxillary esthetic alveolar zone. Keywords: alveolar distraction osteogenesis, alveolar orthognathic form, alveolar orthognathic position, alveolar projection, avascular necrosis, crestal bone, distraction screws, horizontal distraction, implant esthetics, LeFort I osteotomy, osseointegration, over

Purpose: To evaluate the influence of mandibular dentition on the performance of maxillary implants prior to definitive prosthesis attachment in maxillae that have been reconstructed with autogenous bone grafts. Materials and Methods: A retrospective review of 90 consecutive patients, 31 men and 59 women, with a mean age of 57.4 years, was conducted. All patients underwent treatment planning to receive endosseous implants in the edentulous maxilla in conjunction with autogenous bone grafting. During the time from implant and/or bone graft placement until placement of the definitive restorations in the maxillae, the mandibular dentitions were recorded and categorized into 6 groups based upon the presence and distribution of teeth. Results: Of 643 implants placed, 118 (18.4%) were lost between implant placement and definitive prosthesis placement. The type of mandibular dentition was significantly associated with implant failure during this time interval (P .001). In particular, the patients with implants opposing unilateral occlusal support showed the highest rate of implant failure (43.8%, or 28 of 64 implants). Implants that opposed a mandibular implant-supported fixed prosthesis demonstrated an implant failure rate of 14.3% (10 of 70), and in patients with a removable mandibular denture, the implant failure rate was 6.2% (4 of 65 implants failed). The overall mean patient follow-up was 64.2 months. At 60 months, the cumulative implant failure rate based on the Kaplan-Meier method was 20.2%. Discussion: Unfavorable concentration of forces on the maxilla may contribute to increased risk of implant failure. Conclusion: Effort should be made to create a favorable occlusion in the mandible, with attention being paid to broad distribution of occlusal contacts. Keywords: atrophy, autogenous bone graft, dental occlusion, dentition, endosseous dental implantation, mandible, maxilla

Purpose: This study was intended to provide a report of experience and results with Frialit-2 implants used for single-tooth replacement. Materials and Methods: Over a 7-year period (1994-2000), 146 single-tooth implants (84 maxilla, 62 mandible) were placed in 112 patients (67 females, 45 males; 31.2 ± 16.4 years). The sites included maxillary anterior teeth (n = 38) as well as the mandibular premolars and molars (n = 57). Ninety-three crowns were cemented and 53 crowns were screw mounted (22 with vertical, 31 with horizontal screws) on standard abutments. The follow-up time varied between 3 and 80 months (35.8 ± 16.5 months). Results: Two implants (1.4%) were lost, 1 during early loading and the other after 6 years. The most frequent prosthetic complication was isolated crown loosening of cemented crowns requiring recementation of 9 crowns (9.9%). Crowns with vertical screws showed no crown and/or screw loosening. Four crowns (2.8%) were replaced because of ceramic fracture. Discussion: Peri-implant soft tissue condition, bone resorption, and Periotest values indicated satisfactory results. The cumulative implant survival rate during the follow-up period was 97.3%, and that of the crowns 96.4% (total cumulative survival rate 93.7%). Conclusions: With the low number of abutment screw loosenings (3.5%), the deep internal hexagonal retention compared favorably to external retention methods. The predominant use of long implants (98.4% >= 13 mm) allowed a favorable implant/crown ratio with the potential for problem-free, long-term results. Keywords: Frialit-2 implants, implants, single tooth replacements

Purpose: To evaluate the effect of particulate dentin-plaster of Paris with and without platelet-rich plasma (PRP) on bone healing and new bone formation around titanium dental implants in a canine model. Histologic sections and histomorphometric analysis of the defects were obtained at 6 and 12 weeks after surgery. Materials and Methods: Three circular bone defects were surgically prepared in iliac crest sites in each of 10 animals. A total of 30 Avana dental implants were placed in the animals. They were self-tapping, screw-type implants, 10 mm in length and 4 mm in diameter, all made of commercially pure titanium. A titanium implant was placed centrally in each defect. In each dog, the defects were treated with 1 of the following 3 treatment modalities: (1) no treatment (control); (2) grafting with particulate dentin-plaster of Paris; (3) grafting with particulate dentin-plaster of Paris and PRP. Results: Histologic analysis showed that all of the bone defects surrounding the implants that were treated with particulate dentin-plaster of Paris, with and without PRP, were filled with new bone. The defects that were not treated (control) demonstrated new bone formation only in the inferior threaded portion of the implants. Discussion: Histomorphometric results revealed a higher percentage of bone contact with particulate dentin-plaster of Paris and PRP compared to the control and particulate dentin-plaster of Paris. Conclusions: These results suggested that bone defects around titanium implants can be treated successfully with particulate dentin-plaster of Paris, and that the outcome can be improved if PRP is also used. Keywords: implants, particulate dentin-plaster of Paris, platelet-rich plasma (PRP)

Purpose: Palatal implants have been used in the last 2 decades to eliminate headgear wear and to establish stationary anchorage. The aim of this investigation was to establish a method and easy protocol for palatal implant placement. Materials and Methods: The study comprised 8 male and 15 female patients each having a 4.5 x 8-mm stepped screw titanium implant placed in the palatal region for orthodontic purposes. A surgical template containing metal drill housing was prepared. Angulation of the drill housing was controlled according to the radiologic tracing of the maxilla transferred to a plaster cast section in the paramedian plane. Implants were placed using a noninvasive technique (incision, flap, and suture elimination) and left transmucosally to facilitate the surgical procedure and reduce operations. The paramedian region was selected so as to avoid connective tissues of the palatine suture and because it was considered to be a suitable host site for implant placement. Results: After 3 months of healing, all implants were osseointegrated and no implant was lost throughout the orthodontic treatment. Discussion: Palatal implants can be used effectively for anchorage maintenance and space-gaining procedures. Conclusion: Usage of a 3-dimensional surgical template eliminated faulty implant placement, reduced chair time, and minimized trauma to the tissues while enhancing osseointegration. Keywords: anchorage, Class II malocclusion, dental implants, molar distalization, molar slider, noncompliance therapy, orthodontics, palatal implant

Purpose: Several nerve repositioning techniques have ben presented in the literature, each with limitations. This article presents a new technique involving the use of 2 osteotomies, with minimizes particularly the potential duration of sensory disruption and the risk of nerve paresthesia and inadvertent nerve transection or compression. Materials and Methods: Ten patients ranging in age from 47 to 67 years were selected for nerve lateralization utilizing the modified technique. A total of 23 cylindrical implants were placed. An average follow-up period was 29.8 months. Results: Of the 10 patients, 4 experienced total return of sensation within 3 to 4 weeks. One patient experienced complete recovery at 6 weeks. Discussion: Creating 2 osteotomies as described minimizes the chances for postoperative neuropraxia and nerve paresthesia or anesthesia. Conclusion: When there is moderate-to-severe bone resorption of the mandible posterior to the mental foramen, repositioning the inferior alveolar nerve using both an anterior and postetrior osteotomy allows for more bone to accomodate ideal placement and greater length of implant. Keywords: dental implants, inferior alveolar nerve, nerve repositioning, nerve transpositioning, neurosensory disturbance

Purpose: Although various panoramic X-ray machines with linear tomographic functions are now frequently applied to diagnosis related to dental implant treatment, the angles of the tomographic objective planes are automatically determined and cannot be adjusted for individual patients. To resolve this problem, a direct laser positioning (DLP) system was developed. In this investigation, the measurement accuracy of images obtained by the DLP system in comparison with those from reformatted computed tomography (CT) was assessed. Materials and Methods: A rectangular parallel piped phantom was scanned with the system and the height and width were measured on linear tomograms. Ten sites in 3 dried mandibles and 21 mandibular molar sites in 15 patients were examined both with the DLP system and the reformatted CT to compare the measured values on both images. Results: The phantom experiment showed that the difference between the actual and measured heights and widths of the phantom were within 1 mm. Discussion: The difference between the values obtained by the DLP system and CT was slightly larger in the patients than those in the dried mandibles. Conclusion: The DLP measurement accuracy was deemed sufficient for clinical use. Keywords: computed tomography, dental implant, panoramic machine

Purpose: A technique is presented which utilizes a trephine with a 3.0-mm external diameter followed by an osteotome to implode a core of maxillary posterior alveolar bone prior to immediate implant placement. Materials and Methods: The technique and its indications and contraindications are described in detail. Results: One hundred sixteen implants were placed and uncovered utilizing this technique. Two implants were mobile at the time of uncovering. Discussion: One hundred fourteen implants were restored and have been functioning successfully for up to 4 years according to the Albrektsson criteria, yielding a success rate of 98.3%. Conclusion: No implants have been lost or are failing in function. Keywords: guided bone regeneration, implants, osteotome, sinus augmentation, trephine

Purpose: To clarify basic clinico-anatomic factors associated with cranio-maxillofacial rehabilitation using implants. Materials and Methods: Morphometrically evaluated were items such as the length and width of bone and the thickness of cortical bone at important sites for implant placement into cranial and maxillofacial bones in 30 cadavers at autopsy. Results: At sites corresponding to potential placement sites for implants as the fixation source for ocular epitheses, the mean length of bone was 7.8 mm, and the mean width was 8.3 mm. Conclusion: Useful data have been obtained for the selection of the placements sites, direction, length, and external diameter of cranio- and maxillofacial implants. Keywords: cadaver, clinico-anatomic study, cranio-maxillofacial implant