What's New in Dentistry

Bone grafting of extraction sockets shows promise for implant patients

If a maxillary anterior tooth is irreversibly damaged by trauma or periodontal disease, it may require extraction and replacement with an implant and crown. However, after extraction, the alveolar ridge will resorb, and this narrowing of the edentulous site can jeopardize the placement of the implant and adversely affect the esthetics of the final crown. In an attempt to overcome this problem, researchers have experimented with various types of bone grafts in extraction sockets to slow down the resorption process. A study published in the Journal of Periodontology (2001;72:152–159) documents the use of porous bovine bone mineral in the healing of human extraction sockets. The sample consisted of 15 subjects who had a hopeless tooth that was to be extracted and replaced with an implant. Immediately after extraction, porous bovine bone mineral was packed into the empty socket. The graft was covered with soft tissue and allowed to heal. After 9 months, when the implant was to be placed, a trephine of bone was removed from the socket, and was histochemically and histologically evaluated. These microscopic techniques showed that after 9 months, the bone graft was gradually resorbing and being replaced with the individual's own bone. The replacement of the graft was greatest at the deepest portion of the socket. The results of this study show that bone grafting of extraction sockets prior to implant placement can be beneficial to avoid ridge resorption and thereby, enhance the esthetic predictability of the implant restoration.

Crooked smile may be caused by lip asymmetry

A typical goal of orthodontic treatment is to produce a pleasing smile. The esthetic appearance of a patient's smile is adversely affected by asymmetries. One type of asymmetry is canting of the incisal and/or occlusal planes. If the deviation is significant, it could produce an asymmetric smile. However, some asymmetric smiles are not because of canting of the maxilla and maxillary teeth but are produced by an asymmetric upper or lower lip. The incidence of lip vs dental asymmetry was determined in a study that was published in the Journal of Oral and Maxillofacial Surgery (2001;59:396–398). The investigators evaluated the smiles of 210 dental students at a US dental school. The sample consisted of about 60% males and 40% females between the ages of 20 and 40 years. First, the subjects bit on a tongue depressor, and the relationship between the occlusal plane and interpupillary line was evaluated to screen for individuals with skeletal or dental asymmetry. This evaluation identified 15 subjects, or 7% of the overall sample, with a canted occlusal plane. The remaining 195 subjects were asked to smile repeatedly and were photographed. The distance from the incisal edge and the upper lip was measured, and any difference between the right and left sides was calculated. The authors found that 17 subjects, or about 9% of the sample, had an asymmetric upper lip. The authors pointed out that only 2 of these 17 dental students were aware that they had an asymmetric lip. So, when evaluating the symmetry of a patient's smile, remember that not all asymmetries are produced by dental or skeletal etiologies. On the basis of the results of this survey, many crooked smiles are caused by an asymmetric upper lip.

Bite force after open or closed reduction of condylar fractures is equivocal

Condylar fracture is a common traumatic injury in young individuals who receive a sharp blow to the mandible. Some of these individuals may be undergoing orthodontic treatment at the time of the fracture. The typical treatment for condylar fracture in growing individuals is closed reduction, allowing occlusal function to dictate healing and the eventual position of the condylar fragment. In some individuals, open reduction is used to surgically reposition the condylar fragment, fix it to the ramus, and allow it to heal in a more predictable position. A concern with closed reduction is that chewing function could be impaired if the condyle did not reposition itself autonomously. A study published in the Journal of Oral and Maxillofacial Surgery (2001;59:389–395) compared the bite force in patients with closed and open reduction of condylar fractures. The sample consisted of 155 subjects who had a unilateral fracture of the mandibular condyle. Two-thirds of the subjects were treated with closed reduction, and one-third were treated with open reduction. The bite force was evaluated using pressure transducers placed at varying positions between the maxillary and mandibular teeth at 6 weeks, 6 months, and 1, 2, and 3 years after the fracture. The results show that there were no significant differences between the 2 groups. The authors concluded that maximum, voluntary bite force after mandibular condylar process fractures does not differ significantly when the treatment is open or closed. The authors believe that the neuromusculature adapts to the fractured mandibular condylar process and produces similar function in both groups of individuals.

Favorable long-term outcome of resorbable plates and screws after orthognathic surgery

One of the disadvantages of rigid internal fixation after orthognathic surgery is that the metal screws and plates remain in the maxilla and mandible after the bony fragments have healed. Some patients dislike the idea of leaving these metal objects in their bones long term. In recent years, bioabsorbable screws and plates have been developed, and their compatibility with the human body is quite good. However, the long-term outcome of resorbable screws and plates was unknown. Now that they have been used for a few years, researchers are able to recall these patients to determine the effectiveness of resorbable fixation devices. A study published in the Journal of Oral and Maxillofacial Surgery (2001;59:271–276) evaluated resorbable plates and screws after 2 years. The sample consisted of 20 consecutively treated patients who underwent simultaneous maxillary and mandibular osteotomies. The bony fragments were fixed using copolymeric poly L-lactic acid/polyglycolic acid (PLLA/PGA) plates and screws. The authors report that all surgeries were accomplished uneventfully and that no problems occurred during the immediate and long-term postoperative periods. The stability of the occlusion after orthognathic surgery was not effected adversely by the use of resorbable plates and screws. In the future, these types of fixation devices can be used more routinely, if the favorable outcome of these studies continues.

Temporomandibular disorder symptoms vary with time

Many orthodontic patients have temporomandibular symptoms such as clicking, popping, pain, or limited opening. In some individuals, these symptoms can become more severe and, in others, they may subside. However, do they ever disappear? Are temporomandibular symptoms at a young age predictive of worsening problems later on in life? A study published in the Journal of Orofacial Pain (2000;14:224–232) evaluated the natural course of symptoms of temporomandibular disorders in a nonpatient population with time. The subjects selected for this study had originally participated in an initial study of temporomandibular symptoms 4 years earlier. In a follow-up study, 367 of these patients completed a second survey. The fluctuation of temporomandibular disorder (TMD) symptoms was assessed by comparing 6 pairs of answers between the first and second surveys. For all TMD symptoms, the percentage of subjects without symptoms at the second survey who had reported symptoms at the first survey was much higher than those with symptoms at the second survey who had not reported symptoms at the first survey. More than half of the subjects who reported temporomandibular joint (TMJ) or neck pain at the first survey did not report these symptoms at the second survey. Joint noise was not reduced as often as the other symptoms. The relative risks of perpetuation of TMD symptoms ranged between 0.50 and 2.81, which is very low. In conclusion, this study has shown that TMD symptoms tend to diminish with time in nearly half of the symptomatic patients.