Microcomputed tomography (microCT) and histology of the mandibular canal in human and laboratory animals.

The inferior alveolar nerve (IAN) is a sensitive branch of the trigeminal nerve. It has an intra-bone path in the mandible, inside the mandibular canal, where it is accompanied by lymph, venous and arterial vessels. We have studied the mandibular canal in human mandibles and in some laboratory animals (mice, rats, rabbits and cats). Microcomputed tomography evidenced that the walls of the canal are made with thin plates of trabecular bone with numerous fenestrations. This aspect is evidenced in dentate subjects and become more evident in edentulous subjects with atrophy of the alveolar bone. In rats and mice, the wall of the canal is also clearly composed of trabecular plates coming from the surrounding alveolar bone of the mandible. In the rabbit, similar findings are also observed but the trajectory of the canal is more difficult to identify. In the cat, the floor of the canal is composed of the cortical bone from the basilar cortex of the mandible and the roof has a trabecular nature. Vascular injections of gelatin-barium evidenced the arterial trajectories inside the bone in rats and humans. Undecalcified bone sections in human evidenced the histological aspect of the IAN and its connective sheets. Some nervous bundles can be observed outside the epineurium. Bone remodeling is observed on the wall of the mandibular canal. These descriptive findings have a clinical relevance in dental implantology or mandibular surgery.

Asymptomatic impacted teeth in edentulous jaws undergoing preprosthetic surgery. A long-term evaluation.

A long-term evaluation is made of 15 patients with asymptomatic impacted teeth in edentulous jaws. Seventeen impacted teeth in 15 patients were recorded and analysed. They were located in denture-bearing areas and in areas undergoing preprosthetic surgery. All patients, except one lost after 1-year period, were followed clinically and radiographically for 1 to 10 years with an average of 4 years. The asymptomatic impacted teeth in edentulous jaws embedded in bone or covered with mucosa did not cause any problem to the patients. The findings of this study support the view that removal of asymptomatic impacted teeth in denture-bearing areas, or in areas undergoing preprosthetic surgery, is unnecessary as long as the integrity of the covering tissues is preserved. A policy or radiological surveillance is recommended.

Low incidence of severe adverse effects after mandibular ridge reconstruction using hydroxylapatite.

The short and long term adverse effects after ridge reconstruction using hydroxylapatite (HA) are presented in this study. The HA was inserted using a modified tunnelling technique, followed by a lowering of the floor of the mouth and a vestibuloplasty using split thickness skin graft, 4-6 weeks later. The study comprised 637 patients followed for a period of 1 to 10 years (mean 6.0+/-2.6 years). Major loss of HA was seen in 17 patients (2.7%). Donor site visibility (skin graft) appeared to improve greatly over the years from 29.2% to 8.8% at the latest follow-up. Neurosurgery deficits also improved from 11.6% (paraesthesia and dysaesthesia) to 4.6%. Long term follow-up revealed a high percentage of patient satisfaction (97%), indicating that the low incidence of severe adverse effects of the procedure does play a significant role in the appreciation of the procedure and prosthetic care.

Risks and benefits of removal of impacted third molars. A critical review of the literature.

A critical review of the literature about risks and benefits of the removal of impacted 3rd molar teeth is presented in 4 categories: risk of non-intervention, risk of intervention, benefit of non-intervention and benefit of intervention. There are well-defined criteria for removal of impacted 3rd molar teeth. Absolute indications and contra-indications for the removal of asymptomatic 3rd molar teeth cannot be established because no long-term studies exist which validate the benefit to the patient either of early removal or of deliberate retention of these teeth. The prudent course of action for the clinician to follow is based on rational clinical decision-making using traditional methods of evaluation to effect the optimal outcome, keeping the interests of the individual patient above all else.

Failures in ridge reconstruction with hydroxyapatite. Analysis of cases and methods for surgical revision.

Misuse of hydroxyapatite for ridge reconstruction leads to problems in denture construction. The object of this article is to analyze cases that have failed to provide acceptable results and to discuss methods for surgical revision. The group under study was made of 30 patients treated originally in different centers (with one exception) with 34 attempts at ridge reconstruction for the 27 mandibular cases and 3 maxillary ones. Only two mandibular cases received a skin graft. Three major problems were identified: (1) improper location of hydroxyapatite over the vestibular instead of the lingual or palatal sides of the ridge (27 of 30 cases); (2) poorly defined ridge form (26 of 30 cases); and (3) submucosal hydroxyapatite extrusion (15 of 30 cases). Splints or binding agents did not prevent these complications. Mandibular revision was accomplished by adding hydroxyapatite over the old material and onto the lingual side of the ridge. At a second stage, the floor of the mouth was lowered. As the vestibule was extended, material in excess was removed before skin graft application. Maxillary revision involved material removal from the vestibular side to allow the lining mucosa of the vestibule to return to a normal position.

[Comparative study of 3 implanted micrografts placed in the abdominal aorta of the rat]. / Etude comparative de trois microgreffes implantées en position aortique abdominale chez le rat.

A comparative study was conducted on three micrografts of 2 mm diameter: a frozen umbilical artery, a bovine heterograft and an inert P.T.F.E. material graft. These were implanted in the infrarenal aorta of 158 Wistar rats. Each graft was examined on eight occasions: after 4, 24 and 48 hours, one and two weeks, and 1, 2 and 6 months. Excluding 46 animals that died within 24 hours, the overall permeability rate for all grafts was 87.7% (88.9% for umbilical arteries, 82.8% for bovine heterografts and 85.4% for P.T.F.E.). All grafts were examined by optical and electron microscopy. The inert material showed excellent parietal stability. In contrast, alteration and resorption of the primary matrix were moderate in extent for bovine heterografts, and major for frozen umbilical arteries which appear to be a very unstable grafts.

[Treatment of retinal detachment caused by posterior pole dehiscence]. / Le traitement des décollements de rétine par déhiscence au pôle postérieur.

20 eyes have been treated for a retinal detachment due to a posterior pole break. Three successive, different operative techniques were used: macular silastic sponge, vitrectomy plus internal tamponade by silicone oil, vitrectomy plus internal tamponade by air or by a mixture of air 60% and SF6 40%. Macular sponges obtained a good rate of retinal reattachment (83.3%) but fonctionnal results are poor (no measurable visual acuity in the macular break cases). Vitrectomy plus silicone oil does not yield better anatomical results than sponges (66.6% succes rate) but the visual function is better preserved (2 measureable visual acuities on 3 macular break cases). Vitrectomy plus gas gave us the best anatomical (100% success rate) and functional results (4 measurable usual acuities on 6 macular break cases). Retinopexy is not necessary when the vitrectomy-gas technique is used. On the contrary, retinopexy is recommended when the vitrectomy-silicone technique is used in order to remove the silicone oil as safely as possible: this causes a dilemma in the case of a macular break. We think at the present time that vitrectomy-gas is the best way to treat these particular retinal detachments.

Ridge reconstruction with hydroxylapatite. Part 2. Ridge reconstruction based on residual anatomic structure.

The second part of this article shows how the problems of atrophy and resorption of the residual ridge can be corrected with hydroxylapatite to obtain ideal ridge form and maximal prosthetic rehabilitation. The high degree of efficiency of the system is based on a thorough knowledge of the anatomic structures involved, on the use of the cephalogram as a guide, on the correction of adverse intermaxillary relationships and on the recourse to a staging of procedures when required.

Ridge reconstruction with hydroxylapatite. Part 1. Anatomy of the residual ridge.

The first part of this article serves to describe the anatomy of the residual ridge with the causes of atrophy and the patterns of resorption. The problems of treatment in prosthetics and surgery resulting from the anatomic changes are then presented.

Ridge reconstruction with hydroxylapatite: potential and shortcomings.

Residual ridge resorption leading to masticatory difficulties does not only modify eating habits but may also affect the gastrointestinal system. Facing such a serious problem, the dental profession has the responsibility of proposing effective methods that can be applied to most individuals. Over and above socio-economic reasons, ridge reconstruction with hydroxylapatite has other distinct advantages over implants. This material does preserve the residual bone as it is placed over existing structures without any bone loss, and can thus be applied to any atrophy case. It can be molded to create a very retentive ridge form for dentures and to correct abnormal ridge relationships. Finally, it is totally isolated from oral microbiotics. Most of the complications reported can be avoided by proper surgical techniques. The most serious one is occasional resorption of the material itself for which newer osteogenic materials now in the process of being developed might afford a solution.

Ridge form in preprosthetic surgery.

In preprosthetic surgery there is a need for improved methods of diagnosis that are based on the recognition of the anatomy of the deficient residual ridge. These methods enable the surgeon to direct his attention to obtaining the ideal ridge form for denture construction. To this end, characteristics and patterns of resorption as well as a cephalometric method of assessment are presented. A problem-oriented classification of deficient residual ridges will also permit the clinician to select the most effective method of treatment.

Gastrointestinal symptoms and masticatory dysfunction.

One hundred and forty-two female patients consulting a prosthodontic clinic for masticatory disturbances and suffering from mandibular ridge atrophy were systematically interrogated for the presence of digestive symptoms. Eight-five subjects (60% of the studied population) reported current digestive complaints; 32 had abdominal pain (burning sensation, bloating or cramps), 12 presented stool transit alteration (constipation or diarrhoea) and 41 reported both abdominal pain and stool transit abnormalities. A prospective evaluation of the digestive symptoms was obtained following surgical reconstruction of the atrophic mandibular ridge and insertion of functional dental prostheses to correct masticatory dysfunction. One year after jaw surgery, 62 of 73 patients (85%) initially complaining of abdominal pain reported symptomatic improvement of their condition, while a marked amelioration in stool habits was noted in 34 of 53 patients (64%) initially suffering intestinal transit alteration. The high incidence of digestive complaints in our patients with dental deficits and the improvement of these symptoms after jaw reconstruction support a case for masticatory failure in the development of digestive symptoms.

[Mandibular ridge augmentation with hydroxylapatite and its extension].

The results of 5 years follow-up of 84 cases of mandibular residual ridge augmented with hydroxlapatite (HA), followed by ridge extension, are reported. The first surgical procedures, subperiosteal HA insertion, and the second stage of total lowering of the floow of the mouth, vestibuloplasty and skin graft are detailedly described. The ridge is augmented by the first surgery, disturbance of the fraenums of the lip, buccal and tongue and muscles are eliminated by the second surgery, to increase denture retention and stability, improve wear resisting of tissue covered over the artifical ridge and eliminate pain and uncomfort when wearing denture. The results of five years follow-up show that two stages reconstruction are better than HA insertion only. HA is a kind of ideal material of bone replacement, which is not resorbed in most cases.

Residual alveolar ridge atrophy: classification and influence of facial morphology.

A method for grading residual alveolar ridge atrophies of edentulous maxillae and mandible has been devised for men and women. Comparisons were made in women and in men between the degree of atrophy and the vertical facial morphology. The study suggests some relationship between the total facial height (TFH), the vertical facial type determined by the Frankfort horizontal mandibular plan (FMA), and the atrophy of the alveolar ridges, especially for the mandible. Certain practical applications of these findings were suggested.

Surgical and prosthodontic reconstruction of the severely handicapped edentulous patient.

There is among some prosthodontists a negative attitude toward preprosthetic reconstructive surgery because of previous poor experience with reconstructive or preprosthetic surgical procedures. Such experiences may have resulted from the limitations of techniques previously used; and, therefore, the prosthodontist may resort to conventional prosthodontic techniques. There are, however, limits to what can be achieved with special impression techniques, tooth form and placement, and so forth. This article was written not only to present the rationale of current techniques but to encourage the prosthodontist to consider and present to the severely handicapped edentulous patient the choice of preprosthetic reconstructive surgery.

Visor osteotomy augmentation of the mandible with posterior onlay bone graft or with hydroxylapatite: a comparative study.

A frequent and severe ridge atrophy, the anterior spheroid basal bone with posterior bilateral concavities of the mandible, has been defined. Two groups of sixteen patients who had residual ridge augmentation of the mandible with two different techniques were studied. The visor osteotomy with posterior hydroxylapatite was superior to the visor with posterior onlay bone graft in terms of ridge form, bone resorption, patient satisfaction, and neurosensory disturbances. Nevertheless, there remained some problems of anterior resorption and backward rotation of the visor segment for both techniques and of posterior resorption with the partial onlay bone graft.

Mastication after surgical reconstruction of the mandibular residual ridge.

A group of thirty-one female denture patients who underwent surgical reconstruction of their deficient residual ridges with ridge extension and skin graft or ridge augmentation with bone graft were evaluated with regard to their masticatory function before surgery, then at 8 months and 12 months post-operative with their new dentures. Two objectives tests of masticatory efficiency were used. The masticatory efficiency index (MEI), based on the size of chewed almond particles, determined the potential capacity of patients to masticate while the masticatory performance (MP) based on the time required to masticate food before swallowing assessed the individual ability of each patient to chew food. A subjective index of difficulty (SD) provided information on the patient's own assessment of chewing difficulty of certain foods selected for their hard texture. The evolution of each index and their interrelationship were statistically evaluated. It was shown that the masticatory performance (MP) and the subjective index of difficulty (SD) both improved significantly during the rehabilitation period and even more rapidly than the masticatory efficiency index (MEI). The discrepancy between the objective and the subjective tests and the overestimation from the patients indicate that the real benefit of the rehabilitation is not limited to improved chewing, but also to an acquired self-confidence in mastication.

[Risks and benefits of removal of impacted third molars: critical review of the literature. 1]. / Risques et bénéfices de l'ablation des troisième molaires incluses: revue critique de la littérature--Partie 1.

Because of the ever-increasing enthusiasm that new graduates have demonstrated for practising minor oral surgery procedures, the authors believed that it would be useful to translate the results of a research project done in 1990 by Drs. David S. Precious and Paul Mercier, who are well-known oral and maxillofacial surgeons. This paper is about the risks and benefits associated with the removal of impacted third molars.

[Risks and benefits of extraction of impacted third molars: A critical review of the literature. 2]. / Risques et bénéfices de l'ablation des troisième molaires incluses: revue critique de la littérature--Partie 2.

In part I of this critical review of the literature on the risks and benefits of removing impacted third molars, we have dealt with: I--Risks of non-intervention. This second part is about: II--Risks of intervention, III--Benefits of non-intervention, and, finally, IV--Benefits of intervention.

Surgical and prosthodontic residual ridge reconstruction with hydroxyapatite.

The ultimate goal of a ridge augmentation procedure is to form a bearing surface for the denture that will provide stability, retention, and support. Residual ridge reconstruction with an implanted material must be based on an understanding of the variations of ridge atrophy. A problem-oriented classification describes the different forms of residual ridges. This classification of similar types of resorbed residual ridges can be used to establish a rational plan of treatment. The proper placement of hydroxyapatite is critical to obtain the desired reconstructed residual ridge. In the mandible, a lingualized placement of the alloplast is suggested. Careful use of an anatomic matrix to support and contain the hydroxyapatite particles eliminates the need for a splint. The surgical stage includes vestibuloplasty and skin grafting to provide the patient with an increased denture-bearing surface. The ridge created in the form of a comma posteriorly enhances retention and stability. The broad residual ridge with an improved interarch relation also enhances the support and provides a better foundation for balanced occlusion.