Effects of irradiation on bone remodelling around mandibular implants: an experimental study in dogs.

This research focuses on the effects of radiotherapy on bone remodelling around mandibular implants in dogs. After bilateral extraction of the mandibular premolars and first 2 molars, each of 11 beagles received 8 mandibular implants. Four animals were irradiated 4 weeks after implantation and 4 others 8 weeks before implantation; the remaining 3 did not receive radiotherapy. Irradiation consisted of 10 daily fractions of 4.3Gy (60)Co. Fluorochromes were given at implantation and irradiation to allow the measurement of bone apposition. The dogs were killed 6 months after implantation. Each hemi-mandible was processed according to bone-specific histological techniques. New bone formation was visible around 85 of the 88 implants. Stimulated mandibular remodelling was attested in both irradiated groups by increased porosity and numerous labelled osteons. Resorption was more pronounced in the group irradiated after implantation, but osteon formation appeared unvarying. Osseointegration was thus shown to be compatible with bone irradiation as bone turnover activities were maintained throughout the experiment. As the apposition stage of the remodelling cycle appears crucial to achieve optimal osseointegration, its normal completion should be taken into account in clinical practice by respecting a 6-month period between irradiation and implantation.

Implants placed in an irradiated dog mandible: a morphometric analysis.

The objective of this research was to evaluate the influence of radiotherapy on the osseointegration of oral implants in a canine model. After the extraction of all mandibular premolars and first and second molars, 11 male beagles were divided into 3 groups. The control group (3 dogs) received no radiation. The second group (4 dogs) was irradiated 4 weeks after implantation. The third group (4 dogs) was irradiated 8 weeks before implantation. Eight implants were placed in each dog, in an alternating pattern: 4 non-submerged ITI Bonefit titanium plasma spray-coated and 4 submerged Steri-Oss hydroxyapatite-coated. The irradiated dogs received 4.3 Gy daily for 10 days. After 6 months of osseointegration, the dogs were sacrificed and each hemimandible was dissected to isolate the implants. Quantification of the extent of the direct bone-implant contact was carried out by scanning electron microscopy backscattered electron images that reproduced each implant in its entirety, using a digitizing table connected to a computer. The results were expressed as a percentage of direct bone-implant contact versus total perimeter accessible to bone. The bone contact percentage for the control group was 87% for Steri-Oss implants and 69% for the ITI Bonefit implants; for the animals irradiated after implantation, the percentages were 82 for Steri-Oss implants and 58 for ITI Bonefit implants; and for the animals irradiated before implantation, the percentages were 62 for Steri-Oss implants and 28 for ITI Bonefit implants. A statistically significant difference appeared between the 2 types of implants (P < .001). A statistically significant difference was also seen between the 3 groups for both types of implants, except between the control group and the group irradiated after implantation (P = .14). This indicates that, overall, the timing of irradiation influences osseointegration. Osseointegration is possible before and after radiotherapy; however, the direct bone-implant contact increased when the implants were placed before irradiation.

Dental prosthetic reconstruction of osseointegrated implants placed in irradiated bone.

Nineteen patients who were treated for oncologic pathology by surgery and radiotherapy (average dose = 57 Gy) received prosthetic reconstruction with 53 implants placed in the residual mandible or maxilla and/or replacement bone graft. Implants were placed within a minimum period of 5 months after radiotherapy. The healing period before placement of the prosthesis also was at least 5 months. Two to six implants were placed as a function of tooth loss and required prosthetic design. Prostheses included both removable and fixed restorations. Two implants were lost as a result of osseointegration failure. Fifteen implants in six patients could not be followed throughout the study because of patient expiration. Patients were followed up to 68 months and for an average of 38 months. No osteoradionecrosis phenomenon was seen in this study. However, caution is urged in placing implants in irradiated bone because of the potential for osteoradionecrosis. Patients should be carefully selected and a strict therapeutic protocol should be followed.

[Prosthetic dental rehabilitation on osseointegrated implants placed in irradiated mandibular bone. Apropos of 50 implants in 17 patients treated over a period of 5 years]. / Réhabilitation prothétique dentaire sur implants ostéointégrés placés dans l'os mandibulaire irradié. A propos de 50 implants chez 17 patients traités sur une période de 5 ans.

The authors report on their experience with prosthetic dental rehabilitation of 17 patients after surgery and radiotherapy for oncologic diseases of the oral cavity. 50 implants were inserted either in the mandibular residual bone or in a bone graft. These implants were inserted at least 5 months after radiotherapy, and functionally loaded at least 5 months after implanting. Depending on the degree of edentation, 2 to 6 implants were necessary to allow for a functional removable or fixed denture. 2 implants were lost because of lack of osseointegration and 10 were lost because of death of 4 patients. The longest observation period was 56 months and the mean observation time was 29 months. Not any osteoradionecrosis occurred : nevertheless, implantation in irradiated bone must remain a carefully planned operation in selected patients with a rigourous therapeutic protocol.

[Dental prosthesis rehabilitation following oral carcinologic treatment]. / Réhabilitation prothétique dentaire après traitement carcinologique oral.

Following the different treatments applied on patients suffering of a mouth cancer, often these are confronted with a functional and esthetic handicap. Thanks to the prosthetic techniques and an eventual resort to implantation, it is possible to improve their quality of life. Different prosthetic reconstructions are considered.

[The role of implants in functional mandibular reconstruction]. / Le rôle des implants dans la reconstruction mandibulaire fonctionnelle.

More frequently after oncological resection, the mandibular reconstruction is done with microsurgically anastomosed free flaps. The titanium implants propose to the patients an oral rehabilitation with best functional and aesthetic results. It is very true in oncological surgery with or without radiotherapy.

[Corrosion of a dental acrylic resin by alkaline peroxide used for cleaning]. / Corrosion d'une résine acrylique à usage dentaire par un peroxyde alcalin proposé pour son entretien.

Some clinical observations have brought the authors to suspect a corrosion of acrylic resins by an alcaline peroxide (Steradent) proposed as a denture cleanser. By way of a laboratory simulation they have shown that standardized samples of Lucitone 199 are corroded by the main active agents issuing from Steradent: oxygen and a high level of alcalinity. A daily use of Steradent can thus badly affect the physical properties of denture acrylic bases.

[Maintenance of removable dentures. Nonexhaustive review of methods and current products]. / Entretien des prothèses amovibles: revue non exhaustive des méthodes et produits proposés.

The authors review various methods advocated to clean and disinfect removable prostheses. The effectiveness of most commercial preparations is quite relative, and some of them present definite risk for the appliance. Regular brushing of the prostheses remains absolutely necessary; it may be made easier but cannot be replaced.