Sigmar Kopp

Effects of radiation therapy on craniofacial and dental implants: a review of the literature

OBJECTIVES The theories of the effects of radiation therapy on craniofacial and dental implants have been challenged by new models. Animal and clinical studies differ on the importance of dose effect and implant location regarding implant survival. Our purpose was to explore the risks of irradiation regarding dose levels, timing of radiation, implant location, and material. STUDY DESIGN A systematic search of the literature was performed to identify studies reporting animal and human data on the success of implants in irradiated versus nonirradiated bone. RESULTS Eleven animal studies exploring histomorphometric, biomechanical, and histologic features of implants in irradiated bone were summarized. Sixteen human clinical studies evaluating craniofacial (n = 8) and dental (n = 8) implants in irradiated bone were summarized. No meta-analyses of dental implants in irradiated bone were found. Efficacy studies comparing different implant types in irradiated bone were not found. CONCLUSION Studies from both animal subjects and human patients indicate that irradiated bone has a greater risk of implant failure than nonirradiated bone. This increase in risk may be up to 12 times greater; however, studies making these comparisons are of poor to moderate quality, so the magnitude of this difference should be accepted with caution.

Section plane selection influences the results of histomorphometric studies: the example of dental implants

Abstract Objectives: This study was designed to determine and statistically analyze bone-to-implant contact (BIC) values for human specimens segmented in at least two different locations. Materials and methods: Samples of human bone with fractured osseointegrated implants were obtained from six patients. Sections were prepared, dehydrated, and resin infiltrated. Undecalcified bone sections were produced using the thin-section technique according to Donath, ultimately obtaining a section thickness of approximately 20 μm. Fifteen specimens were available for histomorphometry. The bone sections were digitized and analyzed. The bone-to-metal contact (BMC) parameter was determined histomorphometrically. The BMC was returned in terms of the visibly bone-covered implant surfaces as a percentage of the total implant surface shown. Results: The values obtained for the six implants were arranged as six maximum-distance pairs and tested for significance using the t-test for dependent samples. The mean difference in BIC was 11.69±9.79%. The two-sided test showed a significant difference (p=0.033). Conclusion: The accidental or deliberate choice of section plane for a bone-implant block has an influence on the BIC value. To make BIC values more comparable, a standardization of section planes is desirable.

Differential diagnosis of stafne idiopathic bone cyst with Digital Volume Tomography (DVT)

ObjectivesThe distinction between a pseudocyst and an intervention demanding cyst or process cannot always be found by 2D radiology. The differential diagnosis of a pseudocyst may become more difficult when adjacent processes are present.CaseA symptom free 67-years-old man presented with a periapical radiolucency around the mandibular left second molar as well as at the impacted 3rd molar. A comparison with an older panoramic x-ray showed no expansion during a 27 months period. The new panoramic x-ray and addtional Digital Volume Tomography (DVT) showed asymptomatic separate dental cyst at the impacted wisdom tooth and the missing lingual cortical border in the apical region of the 2nd lower molar. This finding along with clinical vitality of the 1st and 2nd left molars led to the conclusion that the presented pathology was a Stafne Idiopathic Bone Cyst (SIBC) which needed no surgical intervention.DiscussionThe additional use of DVT 3D examination may help in diagnosis of SIBC prior to surgical interventions thus avoiding unwanted surgical intervention.

Dental implants and immediate loading: multivariate analysis of success factors.

OBJECTIVES The authors had for aim to examine factors potentially influencing the success of immediate implant placement and loading. MATERIALS AND METHODS One hundred and ninety-five consecutive patients (16.5 to 80.4 years of age) were provided with 310 prostheses supported by 896 immediately loaded implants. The mean follow-up was 27.5 months. Univariate and multivariate Cox regression was performed to analyze potential modifiers of implant success. RESULTS The overall implant success rate was 96.7%. The statistically significant modifiers of success on multivariate analysis (P<0.05) were duration of functional use (P<0.001), type of superstructure (P<0.001), implant-abutment connection (P<0.001), and maxilla versus mandible (P=0.026). None of the other investigated factors (age, gender, implant location/design/length) were statistically significant modifiers of success. DISCUSSION Our study results demonstrate high success rates for immediately loaded implants whatever types and superstructure used. Prosthetic designs and their implementation have a significant effect on the success rate of implant-supported restoration, with adjusted hazard ratios of up to 51. Maxilla versus mandible was the only significant non-external modifier when using an adjusted hazard ratio of 2.75.

No influence of simultaneous bone-substitute application on the success of immediately loaded dental implants: a retrospective cohort study.

Abstract Purpose: To examine the influence of bone-substitute application during implantation on the success of immediately placed and loaded dental implants. Materials and methods: A total of 147 consecutive patients (age, 16.5–80.4 years) were provided with 696 immediately loaded implants. The mean follow-up time was 34.1 months. Of these implants, 50.4% (n=351) were immediately placed into extraction sockets. A total of 119 implants were added by simultaneous bone-substitute application (NanoBone, Artoss GmbH, Rostock Germany), whereas the other implants were placed in healed bone. Univariate and multivariate analysis was performed using IBM SPSS V.20. Results: The overall implant success rate was 96.1%. Implants with simultaneous bone replacement had a hazard ratio of 0.877 (p=0.837); 95% CI, 0.253–3.04). Factors found to be statistically significant modifiers of success on multivariate analysis (p<0.05) included type of superstructure (p<0.001), implant-abutment connection (p<0.001), membrane use (p=0.010), and jaw (p=0.026). None of the other factors investigated were significant modifiers. Conclusions: The present study demonstrates high success rates for immediately loaded implants and their superstructures independent of the simultaneous application of bone substitute. The declared aim of socket preservation, the prevention avoiding bone loss, is achieved in the immediate implant placement scenario under immediate-loading conditions.

Modeling of load transmission and distribution of deformation energy before and after healing of basal dental implants in the human mandible.

Abstract The purpose of this study was to present the amount and distribution of pressure, stress, and deformation energy when basal implants in the mandible are restored with a bridge which is loaded at two different stages of bone healing. The model geometry and material properties of the mandible were gained from CT scans of a human mandible. The material model used in this study defined bone as an inhomogeneous, linear elastic isotropic material. The masseter and temporal muscles were considered as rigid connections between the bones in typical positions and directions. The rotation axis was simulated in the temporomandibular joint. The loading force of 450 N was assumed to be in the middle between the left molar and left canine implant. In freshly operated bone, the total deformation energy is 30% higher than in healed bone, due to the defined energy absorbing soft bone areas. Approximately 90% of the deformation energy is absorbed by the bone, regardless of the healing state of the bone. The immediate rigid implant splinting distributes peak forces. To cope with these energies, the necessity of a reduction of total masticatory forces or the use of additional implants for force distribution should be considered individually.

Comparison of implant survival with implants placed in acceptable and compromised bone: a literature review

BackgroundSurvival rates for conventional dental implant systems are relatively high in normal healthy bone. However, there are subgroups of patients that are at an increased risk of implant failure. In particular, patients with compromised quantity or quality of bone present a significant challenge to the dental implantologist.ObjectiveTo perform a review of the literature in an attempt to quantify the relative risk of implant failure in compromised bone compared to good or acceptable bone and to identify whether certain anatomical regions are at greater risk.Search StrategyWe conducted a systematic electronic database search of Medline, Cinhahl and the Cochrane Library through March 2006 identifying articles meeting the eligibility criteria.ResultsWe calculated an increased risk of implant failure in compromised bone compared to healthy bone in both the maxilla and the mandible using conventional dental implant systems. Relative risks ranged from 2 to 12 with the highest risk of failure in the maxilla. Conventional systems are often used in combination or after bone augmentation procedures or more innovative methods for stimulating bone growth in patients with compromised bone. These approaches do have their limitations including high costs, the accumulation of the surgical risks, and delayed time to loading.DiscussionQuantifying the risk of implant failure in patients with compromised bone should assist the implantologist in treatment decision making and patient counseling. Alternative methods for treating patients with compromised bone include zygomatic and lateral implants, neither of which typically require bone augmentation procedures. More studies are needed to evaluate their safety and efficacy.