The use of silicone chin implants in plastic surgery: a method of chin augmentation.
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Cephalometry↗
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[Initial results of postero-anterior extraoral traction on the mandibular dental arch with chin and lip-chin support].
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Adolescent↗
Determination of a method to predict 1-RM chin and dip from repetitive chins and dips.
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Adult↗
Crown-chin length in normal and anencephalic fetuses at 10 to 14 weeks' gestation.
OBJECTIVE: Our goal was to establish a reference range for the fetal crown-chin length at 10 to 14 weeks' gestation and to determine its usefulness in the prenatal detection of anencephaly in the first trimester. STUDY DESIGN: Women attending our center for transabdominal ultrasonographic screening at 10 to 14 weeks' gestation were prospectively recruited for this study. The crown-chin length was measured in a sagittal view of the fetal head, which included the fetal profile, from the highest point of the head to the most anterior aspect of the jaw. Nomograms for the crown-chin length and the ratio of the crown-chin length to the crown-rump length according to gestational age were generated. Additionally, the crown-chin length and the ratio of the crown-chin length to crown-rump length were obtained from a subset of 13 anencephalic fetuses and plotted against the reference range. RESULTS: In normal fetuses the crown-chin length increased (Crown-chin length = 65.2 x Gestational age in days - 28.4; r = 0.74%, p <0.0001) and the ratio of the crown-chin length to the crown-rump length decreased (Ratio of crown-chin length to crown-rump length -17.2 x Gestational age in days + 60.5; r = 0.23, p <0.0001) with advancing gestation. In anencephalic fetuses crown-chin length measurements and the ratio of the crown-chin length to the crown-rump length were below the 5th percentile in 77% and 62% of the cases, respectively. The slope of change in the ratio of the crown-chin length to the crown-rump length with gestational age was significantly different in anencephalic fetuses compared with normal fetuses (t = 2.7, p <0.003). CONCLUSION: Measurement of the crown-chin length at 10 to 14 weeks' gestation provides a technique that can assist in the early recognition of anencephaly.
Anencephaly↗
Variations in chin-marking behavior of New Zealand female rabbits throughout the whole reproductive cycle.
Chin-marking (chinning) was measured daily in intact New Zealand female rabbits across their whole reproductive cycle. In Experiment 1 does displayed during estrus (48 days studied) three phases, adaptation, growth and plateau, characterized by progressively higher chinning scores (mean +/- SE = 3.6 +/- 1.1; 17.7 +/- 6.3; 26.6 +/- 4.9 marks/10 min, respectively). Despite great quantitative differences among individuals, these 3 phases and the occurrence of chinning "peaks" at 4-6 day intervals were consistently observed in all subjects (Ss). Mating provoked, within one hour, a dramatic decrease in chinning. Both pregnant and pseudopregnant Ss showed low chinning scores for the first 13 days after mating (combined mean +/- SE = 7.3 +/- 3.8 marks/10 min). From days 14 to 30 postcoitus chinning gradually rose in the pseudopregnant Ss (mean +/- SE = 12.7 +/- 5.4 marks/10 min) while remaining low in the pregnant ones (mean +/- SE = 2.6 +/- 1.9 marks/10 min). Parturition allowed a gradual rise in chinning scores. In Experiment 2 the same Ss were explored across a second reproductive cycle that included lactation. In contrast to Experiment 1, no significant variations in chinning were displayed along estrus, Ss showing high chinning scores already on the first day of observation (mean +/- SE from 12 days = 19.2 +/- 6.7 marks/10 min). In agreement with Experiment 1, mating drastically reduced chinning scores. Low levels were maintained throughout pregnancy (mean +/- SE = 3.4 +/- 2.4 marks/10 min) and lactation (mean +/- SE = 3.3 +/- 4.8 marks/10 min). Weaning allowed a gradual increase in chinning scores.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Sex steroid regulation of chin-marking behavior in male New Zealand rabbits.
Chin-marking behavior (chinning) was evaluated daily in nine intact adult male rabbits. All subjects (Ss) displayed chinning (mean of means +/- SE = 61 +/- 7 marks/10 min) but the frequency of this behavior varied largely across them (range of mean chinning frequency = 19-84 marks/10 min). Chinning frequency showed abrupt variations at intervals of 2-3 days, but periodogram analysis did not reveal the existence of an endogenous rhythm in this behavior. Castration significantly decreased (mean of means +/- SE = 29 +/- 9 marks/10 min; p < 0.01). but did not suppress chinning. Testosterone propionate (TP; 1 mg/day for 16 days) restored chinning in castrated Ss to slightly below precastration levels (mean +/- S.E. V 53 +/- 13 marks/10 min). The daily administration of 1 microgram estradiol benzoate (EB) plus 1 mg dihydrotestosterone propionate (DHTP) stimulated chinning within 2 days (mean increase = 147%; p < 0.005). DHTP (1 mg/day) given alone stimulated chinning only after 11 days of treatment (mean increase = 475%; p < 0.01). At higher doses, both DHTP (10 mg/day) and EB (10 or 50 micrograms/day) stimulated chinning by 450%, 80%, and 100%, respectively, over baseline values. Results indicate that chinning largely depends on testicular steroids. Androgen receptor occupation by T or DHT, which is enhanced by E, optimally activates chinning.
Animal Communication↗
Chin surgery: I. Augmentation--the allures and the alerts.
The correction of sagittal deformities of the chin presents a seemingly simple surgical challenge. However, several authors have reported negative sequelae from such chin surgery, During the past 11 years, the senior author (B.M.Z.) has evaluated more than 100 such cases of adverse results after chin augmentation. Many surgeons, it seems, use chin implants unnecessarily and, thus, get into trouble. Because alloplastic chin augmentation is deceptively easy, it tends to be overused in certain situations. Either the surgeon's evaluation is too narrowly focused or his/her abilities to perform other types of surgery (e.g., osseous genioplasty) are limited. Herein, the authors present a diagnostic evaluation protocol, QUAC (Quick Analysis of the Chin), to assist in avoiding simple mistakes in alloplastic chin augmentation. This protocol will alert the surgeon to situations that, if unrecognized, will cause problems and create an unhappy patient. This article will specifically focus on (1) lower lip analysis; (2) the effect of the labiomental fold; (3) chin pad evaluation, both static and dynamic; (4) the anatomy of the cleft chin; (5) special situations; and (6) how to troubleshoot three common problems. The accompanying article, Chin Surgery II, will present a new operation that treats a chin problem that was previously difficult to correct.
Adult↗
Predicting masticatory jaw movements from chin movements using multivariate linear methods.
Previously, we have used bivariate correlations of maximum and minimum displacement, velocity and acceleration variables to compare masticatory chin and jaw movements (J. Prosthet. Dent. 81 (1999) 179). This previous study represented a first step in exploring the hypothesis that the chin contained useful information regarding jaw kinematics. The current study extends our understanding of the relationship between masticatory chin and jaw movements by: (1) reconstructing and evaluating a more continuous trajectory of chin and jaw movements, and (2) performing multivariate correlations comparing chin and jaw movements at discrete points along the trajectory in order to gain insight into the coupling of chin and jaw movements during a chewing cycle. Results indicated that chin and jaw movement trajectories were visually similar in the lateral, vertical, and anteroposterior axes. The adjusted R(2) results in the lateral, vertical, and anteroposterior dimensions averaged 0.74, 0.78, and 0.89, respectively. Within chewing cycles, the lowest correlations between chin and jaw movements in the lateral and vertical dimensions occurred when the jaw was relatively closed, whereas the lowest correlations between chin and jaw movements in the anteroposterior dimension occurred while the jaw was opening from a closed position. The results indicated that jaw and chin movements were qualitatively similar and that at least 74% of the variation in jaw movements could be accounted for by multivariate linear models of chin movement.
Adult↗
Traumatic injuries to the chin: a survey in a paediatric dental practice.
OBJECTIVE: The aim of the study was to provide data on the prevalence of clinical signs of traumatic injuries to the chin and of parental report of such injuries in a group of children visiting a private paediatric dental practice. SAMPLE AND METHODS: The study group comprised 303 children (151 boys and 152 girls) whose dental age was within the limits in which all primary molars are present. The children visited the author's private practice for purposes other than chin injury and its dental implications. Data collected included age, gender, presence and location of fractures in primary molars, presence of a scar on the child's chin, and parental report of previous chin injuries. RESULTS: Fractured primary molars were detected in 96 (31.7%) children. 79 (26%) children had a scar on the chin and previous chin injuries were reported for 110 (36.3%) children. Boys presented a higher prevalence of evidence of chin injuries than girls. The male/female ratios for fractured molars, scar on the chin and previous trauma were 1.5:1, 1.8:1 and 1.5:1 respectively. These differences were statistically significant (chi 2, P = 0.012, P = 0.002 and P = 0.008 respectively). CONCLUSIONS: It is concluded from this survey that traumatic injuries to the chin are not infrequent and the incidence of injuries to the chin is higher in boys than in girls.
Age Distribution↗
Chin-marking behavior in male and female New Zealand rabbits: onset, development, and activation by steroids.
Chin marking (chinning) frequency was determined daily in 25 male and 24 female New Zealand rabbits aged 31-150 days. Chinning appeared earlier in females (mean +/- SD = 41 +/- 16 days) than in males (47 +/- 13 days). Between days 30-50, females displayed chinning more frequently than males. Thereafter, chinning increased steadily in both sexes up to day 100. Chinning curves levelled on days 100 and 140 in males and females, respectively. Profile analysis of male and female chinning curves showed significant differences in their slopes and in their population means (p < 0.001). At 7 months of age (days 210-224), both sexes displayed adult chinning frequencies: mean of means +/- SD = 103 +/- 18 and 79 +/- 14 marks/10 min in males (n = 8) and females (n = 8), respectively. The administration of testosterone propionate (TP, 1 mg/day) or estradiol benzoate (EB, 1 microgram/day) to males and females, respectively, from days 31-50, stimulated higher chinning frequencies than those displayed by untreated animals. Results suggest that chinning frequency increases throughout development largely as a consequence of a concomitant increase in sex steroid secretion.
Aging↗
Changes in the soft tissue chin after orthodontic treatment.
The study envisages changes in the contour of the soft tissue chin immediately and 5 years after orthodontic treatment in a group of 31 male and 29 female patients. The group was classified according to facial types and whether treatment involved extraction of first premolar teeth. The average age before treatment was 10 years 7 months, immediately after treatment it was 14 years 6 months, and 5 years after treatment was 21 years 6 months. The chin contour was studied from cephalometric x-ray tracings. The facial types--mesofacial, brachyfacial, and dolichofacial--were identified on the basis of cephalometric analysis. The chin thickness was registered at six different locations around the symphysis, from the point on the soft tissue chin corresponding to B point to the chin point corresponding to menton. Statistical means and standard deviations for all of the six chin thicknesses were calculated. It was found that the overall soft tissue chin thickness increased after orthodontic treatment. The females had less increase at all levels than the males. The dolichofacial group showed a greater increase in the soft tissue chin thickness after treatment. The mesofacial and brachyfacial groups of females showed no statistically significant increases. Regression tests of independent variables, including age, sex, facial type, and such other cephalometric measurements as 1 - A Pog, 1 to A Pog, mandibular plane, mandibular arc, facial axis, lower face height, and classification of malocclusion, indicated that age, sex, and facial type were the only variables that influenced the soft tissue chin thickness.
Cephalometry↗
Sliding genioplasty for correction of chin abnormalities.
BACKGROUND: Correction of chin underprojection has a significant effect on facial symmetry. Alloplastic chin implants and sliding genioplasty represent the accepted methods of chin augmentation. While both procedures may be used for retrognathia or microgenia, the sliding genioplasty may also be used in chin asymmetry, prognathia, and vertical height discrepancies. We report our finding from a 5-year review of our experience with sliding genioplasty. OBJECTIVES: To evaluate the results of sliding genioplasties performed by residents and private practitioners, to illustrate the versatility and ease of this procedure, and to confirm the excellent clinical results obtained with minimal complications. DESIGN: Retrospective case review. SETTING: University center and private practice. PATIENTS: Forty-three patients, aged 16 to 52 years (mean age, 21 years), underwent sliding genioplasty alone (8 patients) or with concomitant orthognathic surgery (35 patients). MAIN OUTCOME MEASURES: Patient satisfaction, physician satisfaction, chin movement, bone resorption, and other complications. RESULTS: Mean value of chin advancement was 8 mm in cases of isolated sliding genioplasty and 4 mm when performed with orthognathic surgery. Average setback for prognathic correction (6 patients) was 2 mm. Less than 0.5 mm of bone resorption was encountered. Temporary unilateral mental nerve paresthesia was noted in 1 patient. Thermal injury to the lower lip occurred in 1 patient. Thirty-seven of 43 patients were extremely satisfied with their cosmetic result; 5 patients were very satisfied; and 1 patient was dissatisfied because of the resultant occlusion. Physician satisfaction correlated closely with that of the patients. Follow-up ranged from 6 months to 5 years, with an average follow-up of 2.3 years. CONCLUSIONS: Our findings indicate excellent esthetic results with minimal complications. Unlike alloplastic chin implants, sliding genioplasty allows correction of many chin abnormalities, including underprojection, overprojection, chin asymmetries, and/or vertical-height abnormalities. This underused technique is simple and effective and should be included in the options of the facial plastic surgeon.
Adolescent↗
Practical classification of chin deformities.
A visually pleasing chin is an important component of facial harmony. This study was undertaken to introduce a practical classification of chin dysmorphology, which can be used to guide the surgeon toward the appropriate surgical approach to chin repair. Analysis of life-size photography, based on standard anthropometric measurements, was completed on 2,879 patients from 1981 to 1991. Six hundred eighty-four patients were noted to have normal occlusion with some form of chin deformity. Analysis of this group of patients identified seven categories of chin dysmorphism: Class I, macrogenia (n = 170, 24.9%); Class II, microgenia (n = 435, 63.6%); Class III, combination of macrogenia in one direction and microgenia in the other direction (n = 54, 7.9%); Class IV, asymmetry (n = 4, 0.6%); Class V, soft tissue ptosis ("witch's chin") (n = 13, 1.9%); Class VI, pseudomacrogenia (normal skeletal symphysis menti with excess soft tissue covering) (n = 5, 0.73%); and Class VII, pseudomicrogenia (long-face deformity producing clockwise rotation of the normal mandible) (n = 3, 0.4%). Having diagnosed the dysmorphism, logical surgical recommendations for lower face improvement were postulated. Only patients with Class II chin deformity can be corrected with augmentation. Classes I, III, and IV require an osteotomy of the chin. Classes V and VI benefit from soft tissue correction. Class VII deformity can be corrected with a maxillary osteotomy.
Adolescent↗
The human chin and its relationship to mandibular morphology.
This study evaluated the proportion of the external chin (protuberantia mentalia) in relation to the total symphyseal area in normal jaws and those with a diverse morphology. A sample of 60 cases was randomly selected and divided into three groups of 20 each on the basis of normal growth, horizontal growth and vertical growth with an open bite. Tracings of lateral dn frontal radiographs were used to describe general mandibular form and to determine the percentage of external/total symphyseal area. Dental casts were also examined to determine a basal arch form ratio. The results of this study indicate that the amount of bony chin present is related to certain morphologic features of the mandible. The most significant findings illustrate: 1. The chin increases in size as the mandibular type varies from a vertical type, to a normal type, to a horizontal type of growth pattern. 2. With dental "hypofunction" in combination with an exaggerated vertical development of the mandible, a smaller proportion of the protruding chin is present. 3. The chin increases in size as the mandibular basal arch form varies from a tapered shape for the vertical cases to a more square form in the horizontal cases. 4. The degree of lateral ramal flair does not appear to influence the proportion of protruding chin present. Several models have been presented which attempt to explain protuberantia mentalia variation. The evidence in this study supports the concept that mandibular morphology is the result of the action of compensative adaption in a developing structure. There appears to be an implied polygenic influence on symphyseal morphology operating from the cartilaginous cranial base and mandibular basilar bone. This may be manifested in the relative proportion of mandibular basal bone to cranial base width, and to the vector of cranial base growth. The ultimate proportion of the bony chin is viewed to be the result of mandibular adaption to a functional musculoskeletal balance in the craniofacial complex. The extreme variability of chin form in man may be considered to be the result of compensative growth developing in response to the most structurally efficient jaw form, the contiguous soft and hard tissue environment, and the intrinsic genotype of the mandible.
Adolescent↗
The ptotic (witch's) chin deformity: an excisional approach.
Ptosis of the chin pad is common and can be seen in patients of all ages. It may be associated with too little or (at times) too much anterior chin projection. Often there is an associated deep submental skin crease present. Frequently, the primary concern of the patient is the appearance or exaggeration of chin ptosis in smiling ("dynamic" ptosis). This report describes a flexible approach to the correction of developmental (and some iatrogenic) ptotic chin deformities. The key element in the approach is the direct excision of sagging or excess chin fat, muscle, and skin. No attempt is made to reposition or lift ptosis-prone soft tissues. If a deep submental skin crease is present, it too is excised. If the chin needs added anterior projection, it is accomplished with a stable alloplastic chin implant. The approach is uniquely suited to correct anterior overprojection caused by an excess of soft tissue at the front of the chin and has been successful in correcting the "dynamic" ptosis that appears with smiling.
Adult↗
Head injury in facial impact--a finite element analysis of helmet chin bar performance.
The chin bar of a motorcycle helmet protects the rider from facial and head injuries. To evaluate the protective performance of chin bars against head injuries from facial impacts, an explicit finite element method was used to simulate the Snell Memorial Foundation test and a proposed drop test. The maximum acceleration and Head Injury Criterion (HIC) were employed to assess the impact-absorbing capability of the chin bar. The results showed that the proposed approach should be more practical than the Snell test, and provided more information for improving the chin bar design to protect against head injuries. The shell stiffness was important in determining the protective ability of the chin bar, but a chin bar with only an outer shell and comfort foam offered inadequate protection. An energy-absorbing liner was essential to increase the protective performance of the chin bar and the liner density should be denser than that used in the cranial portion of the helmet. For the chin bar with energy-absorbing liner, a shell design that is less stiff would provide better protection.
Craniocerebral Trauma↗
Bone quality at the implant site after reconstruction of a local defect of the maxillary anterior ridge with chin bone or deproteinised cancellous bovine bone.
The purpose of this study was to investigate the quality of bone at grafted implant sites in the anterior maxilla. Grafting of these sites was necessary because of insufficient bone volume in a buccopalatinal direction (width at the top of the crest 1-3mm). Reconstruction was performed with chin bone (N=5), chin bone and a resorbable Bio-Gide GBR membrane (N=5) or Bio-Oss spongiosa granules in combination with a Bio-Gide GBR membrane (N=5). Biopsies were taken prior to implantation, i.e. 3 months after grafting with chin bone, and 6 months after grafting with Bio-Oss. Evaluation was done by assessing the histological and histomorphometric characteristics of full-length biopsies taken from the actual implant site. Both areas with non-vital bone and areas with apposition of bone and remodelling phenomena were observed in the chin bone group at the time of placement of the implants. Similar results were observed at implant sites reconstructed with a chin bone graft covered by a membrane. In the chin bone group without and with a GBR membrane, the mean total bone volume (TBV) was 55.2+/-6.8% and 57.7+/-11.5%, respectively; the marrow connective tissue volume (MCTV) was 44.8+/-6.8% and 42.3+/-11.5%, respectively. Remnants of the resorbable GBR membrane were not detected. In the Bio-Oss((R)) group, at implant placement some newly formed bone was observed in the connective tissue surrounding the Bio-Oss((R)) particles (mean TBV (newly formed bone) 17.6+/-14.5%), but most particles were surrounded by connective tissue. No convincing signs of remodelling were observed (mean remaining Bio-Oss volume 40.5+/-9.3%; mean MCTV 41.9+/-13.1%). No implants were lost during follow up (12 months). At the time of placement of the implants the grafting material (either chin bone or Bio-Oss is still not fully replaced by new vital bone. In case of Bio-Oss, most of the grafting material is even still present. Despite these differences, the 1-year clinical results were very good and comparable between the various grafting techniques applied.
Adolescent↗
Surgical options in deep-bite mandibular deficiency with prominent chin - aesthetic considerations.
INTRODUCTION: A deep-bite hypoplastic mandible associated with a strong chin poses an aesthetic challenge. Functional correction of the distal occlusion can bring the chin point beyond the ideal or normal profile line. The aim of the study was to outline the indications and drawbacks of four approaches that are currently used to deal with this problem. MATERIAL AND METHODS: A retrospective study was done using lateral cephalograms and pre- and postoperative pictures of 40 randomly selected patients, judged by a panel of four surgeons. The following parameters were studied apart from occlusion: A-P chin position, chin height, mentolabial and submental folds, cervicomental and gonial angles, antegonial notch, lower lip position, and anterior mandibular bowing. RESULTS AND CONCLUSIONS: Procedures that involve a setback of the chin are potentially prone to create or increase submental fullness, especially the mandibular advancement/chin setback osteotomy. Procedures involving advancement of the anterior dentoalveolar segment relative to the symphyseal prominence (e.g. mandibular advancement/chin setback osteotomy, dentoalveolar mandibular advancement osteotomy) are prone to flatten the mentolabial fold excessively. The position of the chin point after mandibular advancement-posterior rotation osteotomy is difficult to predict. Maxillomandibular posterior rotation has potentially the best aesthetic outcome, provided that the chin point is not set back.
Adolescent↗