Karsten K.H. Gundlach

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.

Expansion of the socket and orbit for congenital clinical anophthalmia.

Background: Congenital clinical anophthalmia requires fitting an artificial eye, achieving a pleasing aspect of the palpebral apparatus, and stimulating growth of the orbit, as well as of the entire midface. Methods: Out of 25 patients with clinical anophthalmia, 22 were treated according to a new protocol (first described by Wiese et al. in 1999) and followed for up to 6 years. In 10 patients, anophthalmia was bilateral, in nine patients, it was on the right side only and in three it was on the left side only. Treatment consisted of implantation of an osmotic expander to first stimulate growth of the conjunctival sac and eyelids followed by serial implantation of osmotic expanders to stimulate growth of the orbit (and thus of the midface). The material used was a copolymer of methylmethacrylate and N-vinylpyrrolidone. Results: Fitting of an artificial eye was without any problem within the first year of life for the most part. Growth of the orbit was stimulated by more than 65 percent of a healthy one. Aesthetically, the results were very largely pleasing. Complications were encountered, especially when the wrong expander sizes had been implanted. Conclusion: Using osmotic expanders of this type, through a staged therapy of minor operations, promises to achieve all goals before the child enters school.

Treatment of congenital anophthalmos with self-inflating polymer expanders: a new method

Congenital anophthalmos is a rare malformation in which the optic vesicle fails to develop. This leads to a small bony orbit, a constricted mucosal socket, short eyelids, reduced palpebral fissure and malar hypoplasia. The treatment includes both aesthetic and functional aspects. Therefore, a two-step procedure is described using a new self-inflating hydrogel expander. A lens-shaped expander with a diameter of 8 mm expands the lids and the mucosal socket to allow insertion of an eye prosthesis. As a second step, orbital expansion is performed with a spherical device. The expanders absorb lacrimal fluid from the mucosal socket or tissue fluid and start swelling when implanted in the orbital tissue. The insertion of an expander into the orbit as well as into the conjunctival pocket including its fixation by a single suture took only a few minutes and was an easy procedure. The expansion of the small conjunctival sockets was successfully completed in all cases within a period of 2-4 weeks. The weight (= volume in ml) of devices increased from 0.15-1.5 g (lens-shaped expander; weight in grams = volume in ml) respectively, 0.3-3.5 g (spherical device). The expanders inserted in orbital tissue increased from 0.4-4.4 g. This is equivalent to a 10 to 11 fold increase in their water-free volumes. Orbital expansion with spherical devices in combination with the inserted eye prosthesis enlarges the lid and palpebral fissures also. In contrast to conventional silicon balloon expanders, the procedure using self-inflating hydrogel expanders is simple and highly efficient.

Perioperative antibiotic prophylaxis in maxillofacial surgery: penetration of clindamycin into various tissues.

Although clindamycin is recommended for prophylactic use in oral and maxillofacial surgery, there is little data available regarding its ability to provide sufficient tissue concentrations at the operative site. We investigated tissue samples from 31 patients, who had to undergo oral and maxillofacial surgery and who received at least one dose of 600 mg clindamycin i.v. preoperatively, to determine clindamycin tissue concentrations in muscle, oral mucosa, fatty tissue, skin and bone between 15 min and 8 h after administration. After homogenization, clindamycin concentration was determined by bioassay. It was demonstrated that clindamycin concentrations above the MIC90 of those pathogens most likely to cause contamination were reached in all kinds of tissues investigated. Already 15 min after administration, tissue concentrations above the MIC90 were reached and were still detectable in the last samples taken between 4 and 8 h after the last clindamycin administration. From the pharmacokinetic point of view, clindamycin is suitable for perioperative prophylaxis during oral and maxillofacial surgery providing sufficient tissue concentrations with no intraoperative additional dosage necessary unless procedures exceed 4 h duration.

Ankylosis of the temporomandibular joint

INTRODUCTION True ankylosis of the temporo-mandibular joint must be differentiated from other reasons why a patient is unable to open his mouth properly. It can be treated by various methods. It is the purpose of this paper to (a) Present various cases with different disorders that had lead to a restricted mouth opening and (b) Report upon the long-term post-operative results achieved by having applied various treatment options for true ankylosis of the temporomandibular joint (TMJ). MATERIAL AND METHODS In 40 patients a true ankylosis was treated surgically by applying one of the two protocols: Either by interposing silastic sheetings or by implanting a TMJ prosthesis made of metal and consisting of 2 parts, a condylar head and a temporal fossa. Twenty patients could be followed up after 113 months on average - 13 patients of these have been treated by interposition of silastic and 7 have received endoprostheses. In 7 other patients, different reasons were found inhibiting freely opening the mouth. Congenital bony ankylosis of upper and lower alveolar processes, congenital or acquired bony fusion of the coronoid process with the zygomatic arch and/or temporal bone, acquired ankylosis between mandible and lateral pterygoid plate, ossifying myositis, or fibrosis of masticatory muscles following tumour irradiation. Not all of these could be operated upon and not all of these could be followed up. However, all patients operated upon followed a strict postoperative physiotherapeutic regimen. RESULTS Long-term follow-up maximum interincisal distances (MiDs) were callipered: 34mm (mean; min. 22, max. 52) following silastic sheeting; 18mm (mean; min. 10, max. 23) following endoprosthesis implantation. In the one of the two patients who could be followed up after ankylosis of the coronoid with the temporal bone, the MiD measured 49mm 1 year postoperatively. In that one of the two patients who could be operated because of a unilateral bony fusion between the mandible and the pterygoid plate, MiD was only 26mm 8 years postoperatively. And in the one of the two males who could be followed up 8 years after operation of myositis ossificans, MiD measured 50mm. CONCLUSION There are several possible reasons why a patient cannot open his mouth widely. Six of these have been touched upon, 4 of these have been operated upon. For true ankylosis silastic (sheeting or blocks) is felt to be the best material for interposition following osteotomy. Postoperative physiotherapy is a conditio sine qua non - it is the second most important part for every type of treatment for ankylosis.

A preliminary study in osteoinduction by a nano-crystalline hydroxyapatite in the mini pig.

To test the probable osteoinductive properties of NanoBone, a new highly non-sintered porous nano-crystalline hydroxylapatite bone substitute embedded into a silica gel matrix, granules were implanted subcutaneously and intramuscularly into the back region of 18 mini pigs. After periods of 5 and 10 weeks as well as 4 and 8 months, implantation sites were investigated using histological and histomorphometric procedures. Signs of early osteogenesis could already be detected after 5 weeks. The later periods were characterized by increasing membranous osteogenesis in and around the granules leading to the formation of bone-like structures showing periosteal and tendon-like structures with bone marrow and focal chondrogenesis. Bone formation was better in the subcutaneous than in the intramuscular implantation sites. This ectopic osteogenesis is discussed with regard to the nanoporosity and microporosity of the material, physico-chemical interactions at its surface, the differentiation of osteoblasts, the role of angiogenesis and the probable involvement of growth factors. The results of this preliminary study indicate that this biomaterial has osteoinductive potential and induces the formation of bone structures, mainly in subcutaneous adipose tissue in the pig.

Long-term results following surgical treatment of internal derangement of the temporomandibular joint

The long-term results achieved in 31 joints by means of discoplasty or (temporary) implantation of silastic for treatment of internal derangements are presented. These data support the philosophy of preserving the disc whenever possible. If, however, discectomy is inevitable this fibrous plate should be replaced. Interposition of a sheet of silastic for a period of 3-6 months has proven very useful as it has in surgery for ankylosis. Silastic induces formation of a scar located between fossa and condyle which is necessary for the preservation of both rotational and translatory movements. Our postoperative results have been stable for many years and the disadvantages noted by other authors have not been found in these patients.

Is It Possible to Prevent Cleft Palate by Prenatal Administration of Folic Acid? An Experimental Study

OBJECTIVE In this study, folic acid was tested for its antiteratogenic effects on experimentally induced cleft palate in animals. DESIGN Eleven pregnant Lew 1 A dams (75 fetuses) received 200 mg/kg procarbazine via gastric tubing on postconception (p.c.) day 14 to induce a cleft palate (CP); seven of the pregnant dams (45 fetuses) were additionally given 4 mg/kg folic acid subcutaneously from the 14th to the 17th day p.c. As a control group, three more pregnant dams (24 fetuses) were not treated with the drugs mentioned above. All fetuses were delivered by Caesarian section on day 20 p.c. OUTCOMES MEASURED All fetuses were weighed and examined macroscopically with a stereomicroscope. Each fetal head was cut into 35 frontal sections and scrutinized histologically. RESULTS None of the control fetuses (n = 24) exhibited a cleft. Without folate administration, 90% of the fetuses (27 of 30) that received procarbazine exhibited a CP. After additional prenatal folate administration, this rate remained virtually unchanged (91%; 41 of 45). However, the proportion of complete (total) CP (4%) was significantly (p <.0001) lower than in the group without folate (53%). Cleft-associated microgenia and microglossia were also significantly less frequent when folate was administered prenatally: microgenia was reduced by 22% (p =.029) and microglossia by 24% (p =.032). CONCLUSIONS On the basis of these results, folate has a partial ameliorating effect on the teratogenicity of procarbazine given to pregnant rats. Additional studies are necessary on the effect of folate in different species, also taking cleft lip and CP into consideration.

New osmotically active hydrogel expander for enlargement of the contracted anophthalmic socket

Abstract · Background: Clinical anophthalmia is characterized by the absence of an eyeball within the orbit and can result in overall growth retardation of the facial skeleton. The goal of treatment consists of fitting a serial prosthesis following rapid expansion of the contracted socket as soon as possible to achieve cosmetically acceptable eyelid and orbital symmetry. · Methods: Four children, aged 3–11 months, were treated by implantation of an anhydrous, highly hydrophilic tissue expander into the rudimentary conjunctival sac. With hydration of up to 98% in 72 h, the copolymer of methylmethacrylate and vinylpyrrolidone acts like an osmotically self-inducing socket expander. · Results: In the course of 2 months the previous contracted socket was enlarged, the horizontal lid length increased and the hydrated expander could be exchanged for a custom-made glass prosthesis. · Conclusion: Preliminary results suggest that this new device can be used to avoid early plastic surgery of the eyelid. In addition, it also may enlarge the volume of the bony orbit.

Presurgical orthopaedic treatment of newborns with clefts – functional treatment with long-term effects

AIM Presentation of an orthopaedic/orthodontic treatment protocol within the framework of complex rehabilitation of patients with clefts of lip, alveolus and palate. Presurgical orthopaedic treatment aims at reduction of cleft size by guiding growth and functional rehabilitation. Long-term results of maxillary development and occlusion at young adult age are reported. PATIENTS AND METHODS 43 newborns with unilateral (19) or bilateral (24) clefts of lip, alveolus and palate were examined until their deciduous dentition was complete. In 29 patients a late follow-up was performed at age 17.3 years (mean). Maxillary dental casts were evaluated prior to and following presurgical orthopaedic treatment at the time the deciduous dentition was complete and at young adult age (2 to 5 years after termination of orthodontic treatment). Parameters were width of the alveolar and palatal cleft as well as width and length of the dental arch. In the adults occlusion was studied and the occlusal outcome was related to the therapeutical input. RESULTS Presurgical orthopaedic treatment reduced the cleft width by taking advantage of normal growth. At the age of 3 to 4 years the development of the upper dental arch was in line with that of non-cleft children. CONCLUSION Maxillary growth may be guided in almost physiological terms even in patients with a cleft of lip, alveolus and palate. Prerequisite is functional rehabilitation by means of orthopaedic treatment at age 1 to 12 months in terms of functional orthodontic therapy and a surgical protocol saving tissues with growth potential.