James A. McNamara

An Improved Version of the Cervical Vertebral Maturation (CVM) Method for the Assessment of Mandibular Growth

The present study aimed to provide a version of the Cervical Vertebral Maturation (CVM) method for the detection of the peak in mandibular growth based on the analysis of the second through fourth cervical vertebrae in a single cephalogram. The morphology of the bodies of the second (odontoid process, C2), third (C3), and fourth (C4) cervical vertebrae were analyzed in six consecutive cephalometric observations (T1 through T6) of 30 orthodontically untreated subjects. Observations for each subject consisted of two consecutive cephalograms comprising the interval of maximum mandibular growth (as assessed by means of the maximum increment in total mandibular length, Co-Gn), together with two earlier consecutive cephalograms and two later consecutive cephalograms. The analysis consisted of both visual and cephalometric appraisals of morphological characteristics of the three cervical vertebrae. The construction of the new version of the CVM method was based on the results of both ANOVA for repeated measures with post-hoc Scheffés test (P < .05) and discriminant analysis. The new CVM method presents with five maturational stages (Cervical Vertebral Maturation Stage [CVMS] I through CVMS V, instead of Cvs 1 through Cvs 6 in the former CVM method). The peak in mandibular growth occurs between CVMS II and CVMS III, and it has not been reached without the attainment of both CVMS I and CVMS II. CVMS V is recorded at least two years after the peak. The advantages of the new version of the CVM method are that mandibular skeletal maturity can be appraised on a single cephalogram and through the analysis of only the second, third, and fourth cervical vertebrae, which usually are visible even when a protective radiation collar is worn.

Neuromuscular and skeletal adaptations to altered function in the orofacial region

Abstract The purpose of this study was to investigate the nature of intrinsic musculo-skeletal adaptations resulting from experimental alteration of the orofacial environment. A new occlusal configuration was devised which modified oral sensory stimuli, subsequently prompting anterior positioning of the mandible of rhesus monkeys ( Macaca mulatta ) during functional jaw movements at four defined stages of maturation. Specific skeletal, dental, and neuromuscular adaptations were studied and interrelated by means of serial electromyography, serial cephalometric radiography with metallic implants, and microscopic analysis. The study was divided into two time periods. During the 13-week control period, normal growth data were gathered from the four age groups. During the 13-week experimental period, specific neuromuscular and skeletal alterations caused by the experimental conditions were identified. Postural activity in the muscles of mastication and presumably the postural position of the mandible were altered by the induced changes in the oral environment. The superior head of the lateral pterygoid gradually increased in activity, first during functional movements and then during the maintenance of mandibular postural position. The superior head appeared to function as a principal forward positioner of the mandible. This activity decreased or disappeared by the end of the experiment. At the end of the experimental period, ten of the twelve experimental monkeys demonstrated an anteroposterior alteration in molar relationship. No single adaptive process could be isolated and identified as the sole cause of any effective alteration in maxillomandibular relationship at any age level. Rather, each resulting relationship was the composite of specific complementary (and occasionally antagonistic) adaptations throughout the craniofacial complex. Mandibular skeletal adaptations occurred primarily in the infant and juvenile animals in which the extent and direction of growth at the condyle were altered. Dentitional adjustments in the mandible were most notable in the adolescent and adult animals. In the nasomaxillary area a decrease in the vertical displacement of the maxillary complex was noted in all but three of the experimental animals. Horizontal displacement of the maxillary complex and the drift pattern of the maxillary dentition were also affected, but the expression of this effect was variable. After 13 weeks, little histologic evidence of physiologic or pathologic responses to the induced protrusive function was evident in the sacrificed animals. These histologic findings were consistent with past studies which suggest that the adult temporomandibular joint was stable and resistant while the growing articulation was responsive to functional changes. The results of this study further indicated that a chronologic correlation existed between the occurrence and disappearance of altered neuromuscular function and the re-establishment of skeletal balance. As skeletal balance was restored through specific structural adaptations, the need for compensatory muscle function was reduced. Further, the nature and extent of the specific skeletal and dental adaptations depended upon the level of maturation of the animal.

Skeletal effects of early treatment of Class III malocclusion with maxillary expansion and face-mask therapy

The effectiveness of maxillary expansion and face-mask therapy in children with Class III malocclusion was studied in a sample of 46 subjects in mixed dentition and compared with a control sample of 32 subjects with untreated Class III malocclusion. Treated and untreated samples were divided into early and late mixed-dentition groups to aid identification of the optimum timing of the orthopedic treatment of the underlying skeletal disharmony. Cephalometric analysis was based on a stable basicranial reference system, appropriate for longitudinal studies started in the early developmental ages. The level of significance for intergroup comparisons was set at a p value of 0.01. Significant forward displacement of the maxillary complex was found in the early-treatment group. The region of the pterygomaxillary suture, in particular, showed significant changes in the subjects treated during early mixed dentition. No significant maxillary modifications were recorded in the late-treatment group. Both early and late groups exhibited smaller increments in mandibular protrusion and larger increments in the intermaxillary vertical relationship compared with their respective Class III control groups. Only children treated at an early age, however, showed a significant upward and forward direction of condylar growth, leading to smaller increments in total mandibular length. These results indicate that the combination of a bonded maxillary expander and face-mask therapy is more effective in early mixed dentition than in late mixed dentition, especially with regard to the magnitude of the protraction effects on maxillary structures.

Skeletal and dental changes following functional regulator therapy on class II patients

Craniofacial growth in 100 patients treated with the functional regulator of Fränkel for about 24 months was compared with craniofacial growth seen in a matched group of untreated persons with Class II malocclusion. Both conventional and geometric cephalometric analyses were used to evaluate the skeletal and dental adaptations. This study shows several clear effects of treatment in either of two age ranges considered. The principal skeletal effect was advancement of the mandible along the direction of the facial axis. This advancement resulted in increases in mandibular length and in vertical facial dimensions. There was little effect of treatment upon maxillary skeletal structures with the exception of point A, which moved slightly posteriorly. Dentoalveolar adaptations due to treatment included a decrease in the normal forward movement of the upper molar and an increase in the normal vertical movement of the lower molar. There was a 2-mm posterior movement of the tip of the upper incisor but minimal anterior tipping of the lower incisor.

A comparison of the Herbst and Fränkel appliances in the treatment of Class II malocclusion

This study investigated the treatment effects produced by two types of functional appliance, one primarily tooth-borne (the Herbst appliance) and one primarily tissue-borne (the FR-2 of Fränkel). Serial cephalometric radiographs from 45 patients who had been treated with the acrylic splint Herbst appliance and from 41 patients who had been treated with the FR-2 appliance were compared with serial radiographs of 21 untreated persons with Class II malocclusions. Treatment effects were identified through the use of a conventional cephalometric analysis. The results of this study indicated that both appliances had influenced the growth of the craniofacial complex in treated persons. Significant skeletal changes were noted in both treatment groups, with both groups showing an increase in mandibular length and in lower facial height, as compared with controls. Greater dentoalveolar treatment effects were noted in the group wearing the tooth-borne functional appliance than in those wearing the tissue-borne appliance.

An examination of dental crowding and its relationship to tooth size and arch dimension

This investigation was undertaken to examine the extent to which tooth size and jaw size each contribute to dental crowding. Two groups of dental casts were selected on the basis of dental crowding. One group, consisting of 50 pairs of dental casts (18 males and 32 females), exhibited gross dental crowding. A second group, consisting of 54 pairs of dental casts (24 males and 30 females), exhibited little or no crowding. Means and standard deviations of the following parameters were used to compare the two groups: individual and collective mesiodistal tooth diameters, dental arch perimeters, and buccal and lingual dental arch widths. Statistically, the crowded and noncrowded groups could not be distinguished from each other on the basis of mesiodistal tooth diameters. However, significant differences were observed between the dental arch dimensions of the two groups. The crowded group was found to have smaller dental arch dimensions than the noncrowded group. The results of this study suggest that consideration be given to those treatment techniques which increase dental arch length rather than reduce tooth mass.

Early dentofacial features of Class II malocclusion: A longitudinal study from the deciduous through the mixed dentition☆☆☆★★★♢♢♢

A group of 25 untreated subjects with Class II malocclusion in the deciduous dentition (featuring the concomitant presence of distal step, Class II deciduous canine relationship, and excessive overjet) was compared with a control group of 22 untreated subjects with ideal occlusion (flush terminal plane, Class I deciduous canine relationship, minimal overbite, and overjet) at the same dentitional stage. The subjects were monitored during a 2 1/2-year period in the transition from the deciduous to the mixed dentition, during which time no orthodontic treatment was provided. Occlusal analysis of the Class II group in the deciduous dentition revealed an average interarch transverse discrepancy due to a narrow maxillary arch relative to the mandible. All occlusal Class II features were maintained or became exaggerated during the transition to the mixed dentition. The skeletal pattern of Class II malocclusion in the deciduous dentition typically was characterized by significant mandibular skeletal retrusion and mandibular size deficiency. During the period examined, cephalometric changes consisted of significantly greater maxillary growth increments and smaller increments in mandibular dimensions in the Class II sample. Moreover, a greater downward and backward inclination of the condylar axis relative to the mandibular line, with consequent smaller decrements in the gonial angle, were found in the Class II group, an indication of posterior morphogenetic rotation of the mandible in patients with Class II malocclusion occurring during the period examined. The results of this study indicate that the clinical signs of Class II malocclusion are evident in the deciduous dentition and persist into the mixed dentition. Whereas treatment to correct the Class II problem can be initiated in all three planes of space (e.g., RME, extraoral traction, functional jaw orthopedics), other factors such as patient cooperation and management must also be taken into consideration before early treatment is started.

Ethnic differences in the soft tissue profile of Korean and European-American adults with normal occlusions and well-balanced faces.

Orthodontic diagnosis typically includes comparing a patients cephalometric measurements to standard values. Lateral cephalometric norms, however, may be specific to an ethnic group and cannot always be applied to other ethnic types. The purpose of this study was to compare the soft tissue profiles obtained from Korean and European-American adults with normal occlusions and well-balanced faces, in order to understand the ethnic differences in the soft tissue profile between these two ethnic groups. The lateral cephalograms of 60 Korean (30 men and 30 women) and 42 European-American adults (15 men and 27 women) were traced and digitized by one investigator. Ten angular measurements of facial form and seven linear and angular measurements of lip position were computed. A comparison of the slope of the forehead showed no significant differences between the two groups. The Korean sample, however, had a lower angle of nasal inclination and a higher degree of lip protrusion compared to the European-American adults. Chin protrusion of the Koreans was less prominent than that of the European-Americans. These differences between ethnic groups should be taken into consideration when formulating an orthodontic treatment plan for patients of varying ethnic backgrounds.

Rapid maxillary expansion followed by fixed appliances: a long-term evaluation of changes in arch dimensions.

The purpose of this longitudinal study was to evaluate the short- and long-term changes in dental arch dimensions in patients treated with rapid maxillary expansion (RME) followed by fixed edge-wise appliances. The records of 112 patients in the treated group (TG) were compared with those of 41 untreated controls. Serial dental casts were available at three different intervals: pretreatment (T1), after expansion and fixed appliance therapy (T2), and at long-term observation (T3). The mean duration of the T1-T2 and T2-T3 periods for the TG group was three years two months +/- five months and six years one month +/- one year two months, respectively. Treatment by RME followed by fixed appliances produced significantly favorable short- and long-term changes in almost all the maxillary and mandibular arch measurements. In comparison with controls, a net gain of six mm was achieved in the maxillary arch perimeter, whereas a net gain of 4.5 mm was found for the mandibular arch perimeter of treated subjects in the long term. The duration of retention with a fixed lower appliance in the posttreatment period did not appear to affect the long-term outcomes of the treatment protocol significantly. The amount of correction in both maxillary and mandibular intermolar widths equaled two-thirds of the initial discrepancy, whereas treatment eliminated the initial deficiency in maxillary and mandibular intercanine widths. The amount of correction for the deficiency in maxillary arch perimeter was about 80%, whereas in the mandible a full correction was achieved.

Longitudinal dental arch changes in adults

This study examined changes in the dental arches that occur in untreated persons between late adolescence and the fifth or sixth decade of life. Longitudinal dental casts from 82 subjects were obtained as part of a recall study of subjects from the University of Michigan Elementary and Secondary School Growth Study. From the parent sample, three groups were identified. The untreated sample comprised 53 subjects (27 males and 26 females). A midadult sample of 10 persons, who had an additional set of records taken on average during their fourth decade of life also was analyzed, as was a sample of 13 subjects who received orthodontic treatment as adolescents and were about 30 years posttreatment. Measures of dental arch width, arch depth, and arch perimeter were evaluated with the aid of digital-imaging hardware and software. Incisor irregularity, curve of Spee, overjet, and overbite were measured directly from the dental casts. Statistically significant decrements occurred in arch width, depth, and perimeter. The mean decrement in any one dimension was less than 3 mm. At all times, males displayed significantly more mandibular incisor irregularity than females. In addition, the increase in mandibular incisor irregularity that occurred in male and female subjects was the same. However, irregularity did not increase in all subjects; it decreased in 3% of the males and 7% of the females. In general, overbite, overjet, and curve of Spee were stable during adulthood. Statistically significant correlations between the changes in dental arch measures could not be established.