Andreas Faltermeier

The two main theories on dental bruxism

Bruxism is characterized by non-functional contact of mandibular and maxillary teeth resulting in clenching or grating of teeth. Theories on factors causing bruxism are a matter of controversy in current literature. The dental profession has predominantly viewed peripheral local morphological disorders, such as malocclusion, as the cause of clenching and gnashing. This etiological model is based on the theory that occlusal maladjustment results in reduced masticatory muscle tone. In the absence of occlusal equilibration, motor neuron activity of masticatory muscles is triggered by periodontal receptors. The second theory assumes that central disturbances in the area of the basal ganglia are the main cause of bruxism. An imbalance in the circuit processing of the basal ganglia is supposed to be responsible for muscle hyperactivity during nocturnal dyskinesia such as bruxism. Some authors assume that bruxism constitutes sleep-related parafunctional activity (parasomnia). A recent model, which may explain the potential imbalance of the basal ganglia, is neuroplasticity. Neural plasticity is based on the ability of synapses to change the way they work. Activation of neural plasticity can change the relationship between inhibitory and excitatory neurons. It seems obvious that bruxism is not a symptom specific to just one disease. Many forms (and causes) of bruxism may exist simultaneously, as, for example, peripheral or central forms.

Bacterial adhesion of Streptococcus mutans to esthetic bracket materials

INTRODUCTION The formation of white spot lesions and enamel demineralization might be intensified by enhanced bacterial adhesion and formation of dental plaque on brackets. Our aim in this in-vitro study was to investigate the susceptibility of various plastic bracket materials to the adherence of Streptococcus mutans. METHODS The esthetic bracket raw materials included in this study were polyoxymethylene, polycarbonate, high-density polyethylene, and an experimental polymer (90% polyethylene). Surface roughness was assessed by perthometer. S mutans suspension was incubated with test specimens and examined with fluorescence dye and an automated multi-detection reader. The oxidation-reduction fluorescence dye Alamar Blue/resazurin (0.007536 g per 10 mL distilled water) was used to determine the quantity of bacterial adhesion. RESULTS The median values of fluorescence intensity varied between approximately 600 and 1600. The lowest fluorescence with median values below 700, indicating low bacterial adhesion, was found for polyoxymethylene (median of relative fluorescence intensity, 635). The highest relative fluorescence intensity, with median values of more than 1500, was for high-density polyethylene (1565). No statistical alteration of fluorescence intensity was measured between the polymeric bracket materials. CONCLUSIONS The investigated polymeric bracket materials had no significant differences in the quantities of S mutans adhering to them. Regardless of the polymer, plastic bracket materials have similar bacterial colonization and plaque accumulation properties.

Influence of filler level on the bond strength of orthodontic adhesives.

OBJECTIVE To evaluate the effect of different filler contents of orthodontic adhesives on shear bond strength and Adhesive Remnant Index (ARI). MATERIALS AND METHODS Four experimental adhesive groups were created: group 1 was an unfilled urethane-dimethacrylate (UDMA) adhesive, group 2 consisted of UDMA and a filler content of 30 vol%, group 3 consisted of UDMA and a filler content of 50 vol%, and group 4 was manufactured with a filler level of 70 vol% in a UDMA matrix. The embedded filler was silicon dioxide. After etching and priming, stainless steel brackets were bonded to extracted human third molars (n = 60) with the experimental adhesives (15 teeth per group). After storage in distilled water for 72 hours, shear bond strength and ARI scores were evaluated. Kruskal-Wallis and post hoc test were performed for statistical analysis. RESULTS Shear bond strength of UDMA-based adhesives depends on filler content. Higher adhesive filler levels reveal greater bond strength between enamel and stainless steel brackets. ARI scores showed no significant difference among the groups. However, higher filled adhesives (filler content 70 vol%) seem to present higher ARI scores. CONCLUSION Highly filled UDMA adhesives offer greater bond strength than do lower filled or unfilled resins.

Conventionally ligated versus self-ligating metal brackets—a comparative study

The purpose of this study was to compare the frictional properties of four self-ligating metal brackets, Speed, Damon 2, In-Ovation, and Time, with those of three conventionally ligated metal brackets, Time, Victory Twin, and Discovery. The self-ligating Time bracket can also be used as a conventionally ligated bracket. Friction was tested 20 times for each bracket/wire combination using a Zwick testing machine with stainless steel wires in three different wire dimensions (0.017 x 0.025, 0.018 x 0.025, and 0.019 x 0.025 inches). All brackets had a 0.022 inch slot and the prescription of an upper first premolar. The data were statistically analysed with unsigned comparisons of all bracket/wire combinations using the Mann-Whitney U-test and the Games-Howell post hoc test. The results showed almost all brackets to have the lowest frictional force with a wire dimension of 0.018 x 0.025 inch. Friction of the self-ligating brackets using wire with a dimension of 0.018 x 0.025 inches was 45-48 per cent lower than with 0.017 x 0.025 and 0.019 x 0.025 inch wires. Friction of the conventionally ligated brackets showed a 14 per cent or less reduced friction with 0.018 x 0.025 inch wire compared with 0.017 x 0.025 and 0.019 x 0.025 inch wires. The self-ligating metal brackets showed lower frictional forces with a 0.018 x 0.025 inch wire than conventionally ligated brackets, whereas conventionally ligated brackets showed lower friction with 0.017 x 0.025 and 0.019 x 0.025 inch wire. Friction values vary with different bracket/archwire combinations and, therefore, the choice of a bracket system for treatment should consider the correct wire dimension to produce the lowest possible frictional forces.

Strontium promotes cell proliferation and suppresses IL-6 expression in human PDL cells

This study was designed to investigate the effect of strontium on human PDL cells in vitro. Strontium is used to treat osteoporosis because of its bone formation promoting effect on osteoblast cells. This investigation presents evidence that strontium promotes PDL cell proliferation. Simultaneously, strontium suppresses the expression of the inflammation-promoting cytokine IL-6. The observed effect of strontium on PDL cells supports its use it in guided dental tissue regeneration.

Effect of bracket base conditioning

INTRODUCTION The aim of this study was to compare the effect of a silicoating system, the influence of sandblasting, and the effect of a silane-coupling agent after sandblasting on the shear bond strength of stainless steel foil-mesh brackets. To simulate the oral environment, all specimens were thermocycled (6000 times at 5 degrees C and 55 degrees C) in a mastication device before testing. METHODS Four bracket groups were tested: group 1 consisted of 20 metal brackets that were sandblasted on the base; group 2 contained 20 brackets that were sandblasted, and a silane-coupling agent was applied; in group 3, the surface of the base of 20 metal brackets was treated by using a tribochemical system; and group 4 was the control group. The brackets were bonded with a light-curing adhesive to extracted third molars, and the shear bond strength and the adhesive remnant index score were determined. The brackets of group 1 were reconditioned after debonding with sandblasting and tested again (group 5). RESULTS Sandblasting and tribochemical treatment of brackets improved the shear bond strength of stainless steel brackets. Combined sandblasting and silane-coupling treatment offers no benefit of increased in-vitro strength. CONCLUSIONS The bond of resins to tribochemically silicoated stainless steel brackets seems to be sufficient to strengthen the bond between the adhesive and the metal bracket. This treatment is mainly indicated for low-compliance patients or teeth that are difficult to bond.

Effects of hypodontia on craniofacial structures and mandibular growth pattern

IntroductionThis study was performed to examine craniofacial structures in persons with hypodontia and to reveal any differences, that may occur, when agenetic teeth are only found in the maxilla, the mandible or in both jaws. The groups consistent of 50 children (33 girls, 17 boys) aged between 9 and 13.5 years were analyzed and assigned to three subgroups. Group 1 = upper jaw hypodontia. Group 2 = lower jaw hypodontia. Group 3 = hypodontia in both jaws.Materials and methodsEleven angular and three index measurements from lateral encephalographs and two linear measurements from dental blaster casts were calculated. All data was statistically analyzed, parameters with p < 5% were investigated for each subgroup respectively.ResultsIn comparison with standards the study group showed bimaxillary retrognathism and a reduction of the lower anterior facial height. Moreover both overbite and overjet significantly increased. Other values laid within the normal ranges. Evaluating results of the subgroups, differences in the means of SNA, SNB and overjet between the groups were observed.Analysis of the mandibular growth pattern revealed, that neither vertical nor horizontal patterns are dominant in hypodontia patients.ConclusionsIn certain dentofacial parameters differences between persons with hypodontia and such with full dentition exist. According to our findings agenetic teeth may have a negative influence on the saggital development of a jaw and the lower face and may be responsible for increased overbites. This should receive attention in orthodontic treatment of hypodontia patients.

Variations in the inclination of the condylar path in children and adults.

OBJECTIVE To test the null hypothesis that there are no differences between children and adults in the condylar path inclination angle on the right and left sides. MATERIALS AND METHODS A group of 80 children aged 6 to 10 years (subgroups I through V, according to chronologic age) was compared with an adult group with regard to the condylar path inclination angle (CPIA) on the right and left sides. The CPIA was measured using the ultrasonic JMA-System for registration. RESULTS During development of the temporomandibular joint the condylar path inclination angle increased with age in the subgroups of children. A significant difference was found in the CPIA between the groups of adults and children. In the group with the oldest children (mean age: 10.3 years) the condylar path inclination angle had reached 81.87% on the right side and 78.85% on the left side compared with the adult group at a 5 mm protrusive path. In the pooled group of children the CPIA amounted to 73.08% on the right side and 72.13% on the left side compared with the values for the adults. No significant difference was found between the right and left CPIA in any group. CONCLUSION The hypothesis is rejected. The CPIA on the right and left sides increased with age in the group of children and was significantly smaller in the group of children compared with the group of adults.

Outcomes of temporomandibular joint disorder therapy: observations over 13 years

Objective. To evaluate the outcome of temporomandibular joint (TMJ) disorder therapy with different kinds of splints. Methods. One-hundred-and-twenty-nine patients with TMJ disorders and meeting the primary selection criterion of reporting pain in the TMJ region were clinically evaluated. Magnetic resonance imaging of the TMJ was performed at baseline 1993–94. A protrusion splint was used whenever joint clicking could be eliminated by protrusion. In the other cases, a pivot or a Michigan splint was inserted. Re-evaluation of the patients after 12 months included a clinical examination. After 5 and 13 years, all patients were examined by means of a questionnaire. Results. Pain was significantly reduced in the case of more than two-thirds of the patients 1 year after the first consultation. After 5 and 13 years, the percentages of patients with reported pain had increased only slightly. However, the therapy did not reduce joint noises or mouth opening. The prevalence of joint noises was reduced to less than a quarter after 1 year, but during the next 13 years increased to the former level. Initially, one-third of the patients had mouth-opening reduction. This proportion dropped to one-third of these cases after 1 year, but increased to 40% after 13 years. Conclusions. Treatment using splints reduced pain in approximately two-thirds of the patients, but with no difference between the three types of splints used.

Effect of strontium on human Runx2+/- osteoblasts from a patient with cleidocranial dysplasia.

Strontium represents a new generation of anti-osteoporotic agents that exert anti-catabolic and anabolic effects on bone cells at once. We used strontium in vitro in order to examine its potential to stimulate bone marker transcription and hydroxyapatite formation on isolated Runx2(+/-) osteoblasts from a patient with cleidocranial dysplasia. This disease is evoked by heterozygous mutations of Runx2, an important transcription factor for osteoblast maturing and transcription of osteogenic genes, which results in insufficient gene dosage of Runx2. This genetic defect is responsible, for example, for patent fontanels, sometimes throughout the life, supernumerary teeth, and aplasia or hypoplasia of clavicles and mimics symptoms of hypophosphatasia. In this trial, we investigated the effect of strontium on gene expression of bone marker proteins, the formation of hydroxyapatite and the cell proliferation of strontium-treated Runx2(+/-)-osteoblasts. Unlike normal osteoblasts, gene expression of bone marker proteins was not affected in strontium-treated Runx2(+/-) osteoblasts, while improved hydroxyapatite formation was noted in the extracellular matrix. A WST-1 cell proliferation assay with strontium-treated Runx2(+/-)-osteoblasts showed that strontium induces cell proliferation and growth. This effect might be responsible for the improved mineralisation of the extracellular matrix of strontium-treated Runx2(+/-)-osteoblasts observed.