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Biomedical subjects

P M Sinclair

Publications and source records attributed to P M Sinclair.

At least 37 records · Page 2Linked to original sources
PubMed1995

The accuracy of video imaging in orthognathic surgery.

Video imaging is an important emerging technology in planning orthognathic surgery and educating patients about the esthetic effects of treatment. The presurgical cephalograms of 56 patients, 41 with mandibular advancement alone and 15 with mandibular advancement plus genioplasty, were digitized, and the computer-generated soft tissue "line drawing" predictions were compared with the actual posttreatment cephalograms. Video images of the patients' presurgical lateral view were obtained, and two experienced clinicians compared the computer generated video image predictions with the actual posttreatment profile. Video images judged very good or excellent were considered acceptable for treatment planning; 60% to 83% met this criterion, depending on the profile area viewed. The percentage of acceptable images in the lower lip, labiomental fold, and chin area decreased with the addition of a genioplasty. The predicted and actual posttreatment soft tissue line drawings were quite similar for all areas except for the lower lip region, where statistically significant differences were noted, with the predicted lower lip more retrusive and thinner than the actual contours. For the lower lip and chin, a 2 mm or more discrepancy was observed in 20% of the patients. In all cases, the actual image was judged more esthetic than the predicted image, allaying fears of unrealistically optimistic computer generated predictions.

Adult↗
PubMed1994

Clinical ramifications of posterior and anterior facial height changes between treated and untreated Class II samples.

Some clinicians have suggested that one primary difference between successful and unsuccessful Class II treatment outcomes is the relative change of anterior and posterior facial heights. Successfully treated cases are claimed to exhibit greater increases in posterior facial height (PFH, articulare to gonion) than in the anterior facial height (AFH, menton to palatal plane). This conjecture was tested here by recalling a treated Class I sample and a treated Class II sample and by comparing the differences found in these samples to an untreated Class II sample at the same ages. The PFH/AFH ratio increased significantly more in the treated Class I and Class II samples during the active phase of treatment than in the untreated Class II sample at the same ages. During the years from posttreatment to recall (mean = 6 yrs), there was a significant increase in the PFH/AFH ratio in the treated Class II sample due to a greater increase in PFH than AFH. This ratio continued to improve after all appliance therapy had been discontinued, and it did not occur in the treated Class I sample nor in the untreated Class II sample. The conclusion was that the patient with a Class II malocclusion, if treated, continues to change favorably over time. This favorable change, in turn, helps maintain the Class II correction.

Adolescent↗
PubMed1992

Soft tissue changes associated with double jaw surgery.

The purpose of this study was to evaluate the amount, direction, and predictability of the soft tissue changes associated with simultaneous maxillary impaction and mandibular advancement surgery. The results suggested that the soft tissue responses were similar to those seen in single jaw procedures, with the exception of the changes seen in the nasolabial angle and in the area of the lower lip and chin. The type of soft tissue manipulation employed, in particular the use of the alar base cinch suture and V-Y closure techniques, were important factors in determining the response of the upper lip to the surgery. The maxillary soft tissues moved forward 90% of the hard tissue change and showed 20% shortening of the upper lip, with the changes in the nasolabial angle being due primarily to the degree of the maxillary rotation. A predictable progressive increase was seen in the horizontal movement of the mandibular soft tissues ranging from 73% of the hard tissue change at the lower lip to 100% at pogonion. The vertical movement of the mandibular soft tissue was greater than that of underlying hard tissues, particularly in the area of the lower lip as it was freed from the effects of the maxillary incisors.

Adult↗
PubMed1991

A clinical evaluation of temporomandibular joint disk plication surgery.

Clinical and radiographic examinations were performed preoperatively and an average of 18 1/2 months postoperatively on 33 patients who had undergone TMJ disk plication surgery because of significant TMJ dysfunction symptoms that had not been resolved by previous conservative therapy. The results indicated that the disk plication procedure reduced the overall frequency of symptoms by 75%. The frequency of TMJ intracapsular, otologic, and head and shoulder symptoms was reduced by more than 80% after surgery whereas dental symptoms such as bruxing and clenching showed only a 28% reduction in incidence. Of the sample 77% were either free of pain or experiencing only mild symptoms at their postoperative recall, with only nine joints still experiencing moderate or severe symptoms, compared with the 31 joints that were in this category before surgery.

Adolescent↗
PubMed1991

The stability of double jaw surgery: a comparison of rigid versus wire fixation.

The subjects of this study were 35 patients who underwent simultaneous surgery for superior repositioning of the maxilla and advancement of the mandible. They were studied cephalometrically for a comparison of the postsurgical stability of two commonly used fixation techniques: (1) rigid fixation with bone plates and (2) skeletal-wire fixation. One surgeon performed the operations on all 35 patients, and both groups were studied for an average of 15 months after surgery. Results showed that, although the maxilla remained relatively stable after surgery with both fixation techniques, rigid fixation tended to improve stability, primarily by eliminating relapse in excess of 2 mm. Mandibular stability was much greater with rigid fixation: the amount of relapse of the horizontal projection of B point with this method was 6%, while in the skeletal-wire sample it was 26%. Increased rotational stability between the proximal and distal segments of the mandible appeared to be a major factor in the improved overall stability of the rigid-fixation sample. The amount of mandibular relapse was found to be correlated to the amount of advancement in the wire-fixation sample, but not in the rigid-fixation sample.

Adult↗
PubMed1991

A cephalometric evaluation of anterior openbite correction with the magnetic active vertical corrector.

The purpose of this study was to evaluate treatment effects of the magnetic active vertical corrector appliance (AVC) when used to treat anterior openbites in a sample of growing patients. Twenty-five patients with a mean age of 10 years 8 months underwent AVC treatment for an average of almost 8 months. They had an average of 3 mm of anterior openbite closure during the treatment period, primarily due to maxillary and mandibular molar intrusion. Additional contributions to correction of the openbite were related to maxillary incisor eruption and lingual tipping combined with mandibular incisor lingual movement. A small amount of mandibular rotation with closure of the bite and decrease in anterior force height was observed. Anteroposterior skeletal change attributed to the AVC therapy was minimal.

Activator Appliances↗
PubMed1990

Development of the nose and soft tissue profile.

Cephalometric radiographs from a sample of 64 untreated persons (32 Class I and 32 Class II) were evaluated to determine the amount, direction and timing of facial soft tissue development. Twenty-five parameters were evaluated in the mixed dentition (7 to 9 years), the early permanent dentition (11 to 13 years), and early adulthood (16 to 18 years). Results showed that anteroposterior growth and subsequent increased anterior projection of the nose continued in both males and females after skeletal growth had subsided. However, females had concluded a large proportion of their soft tissue development by age 12 while in males continued growth was noted until age 17 resulting in their having greater soft tissue dimensions for many of the parameters evaluated. During the developmental period, the angular shapes and positional relationships of the nose, lips and chin remained relatively constant for both sexes and was relatively independent of the underlying hard tissues. Treatment planning implications may be drawn from the amounts and timing of the soft tissue development found in this study.

Adolescent↗
PubMed1989

A comparison of the Ricketts and Tweed-type arch leveling techniques.

The purpose of this study was to compare the effectiveness and long-term stability of arch leveling and overbite correction carried out by the Ricketts and modified Tweed techniques. The sample comprised 60 Class II, deep bite, low-angle adolescent nonextraction cases, 30 each from the offices of Robert Ricketts and Fred Schudy, with cephalograms taken before and immediately after treatment and an average of more than 4 years after treatment. Both techniques were successful in overbite correction, producing only minimal increases in mandibular plane angle and anterior facial height. Mandibular incisors in the Ricketts group demonstrated more flaring and anterior bodily movement during treatment, with a greater amount of posttreatment uprighting and overbite relapse than the Schudy group. The Ricketts group demonstrated slightly more than 1 mm of true lower incisor intrusion; this change was relatively stable after treatment. Both techniques produced similar amounts of mandibular molar extrusion during treatment; these changes remained stable after treatment.

Adolescent↗
PubMed1989

Treatment effects of the Herbst appliance.

The purpose of this study was to examine the results of treatment with a modified Herbst appliance. The pretreatment and posttreatment cephalometric and dental cast records of 32 consecutively treated Class II, Division 1 cases were evaluated. Results showed that the skeletal Class II correction was achieved by an average 1.5 mm of greater than normal forward mandibular growth in conjunction with a minimal "headgear" effect inhibiting maxillary growth. Dental Class II correction was achieved by significant amounts of distal bodily movement and tipping of the maxillary first molars combined with bodily forward movement of the mandibular first molars. Significant increases were seen in maxillary arch length and maxillary intercanine and intermolar widths, while the mandibular arch demonstrated few changes. Slight forward movement of the mandibular incisors was noted with no significant change occurring in the maxillary incisors.

Activator Appliances↗
PubMed1988

The local use of vitamin D to increase the rate of orthodontic tooth movement.

The purpose of the study was to determine if the rate and amount of orthodontic tooth movement in a sample of cats could be enhanced by the injection of a vitamin D metabolite 1,25-dihydroxycholecalciferol (1,25D) into the periodontal ligament. After 21 days of canine retraction with a light-wire retraction spring, the teeth that had received weekly intraligamentous injections of a solution of 1,25D in dimethylsulfoxide (DMSO) had moved 60% further than matched control teeth (P less than 0.05). At the histologic level, increased numbers of mononuclear osteoclasts were recruited and activated, resulting in greater amounts of alveolar bone resorption on the pressure side of the periodontal ligament. No obvious clinical, microscopic, or biochemical side effects were noted.

Animals↗
PubMed1988

Orthodontic considerations in adult surgical orthodontic cases.

The orthodontic considerations in orthognathic cases are based on a detailed understanding of the malocclusion, particularly a differential diagnosis of its facial, skeletal, and dental components, along with a recognition of the limitations of current orthodontic therapy. The goal is to develop a treatment plan that produces the optimal in esthetics, function, and stability while addressing the patient's chief complaint. Attention must be paid to the need to integrate the orthodontic component of treatment with the general dental and surgical phases of the patient's care.

Adult↗
PubMed1987

A computerized analysis of the shape and stability of mandibular arch form.

To determine whether a particular ideal orthodontic arch form could be identified, the mandibular dental casts of 30 untreated normal cases, 30 Class I nonextraction cases, and 30 Class II nonextraction cases were examined. Following computerized digitizing and the use of a mathematic function called polynomial of the fourth degree, arch forms were generated for each sample and then compared to 17 commercially produced arch forms. Results showed that no particular arch form predominated in any of the three samples. A shape representing a combination of the "Par" and "Vari-Simplex" arch forms approximated to only 50% of the cases in the three samples. The remaining 50% of the cases displayed a wide variety of arch forms. Cases that had changes in arch form during nonextraction treatment frequently were not stable; almost 70% showed significant long-term posttreatment changes. Customizing arch forms appears to be necessary in many cases to obtain optimum long-term stability because of the great individual variability in arch form found in this study.

Adolescent↗
PubMed1987

A cephalometric, tomographic, and dental cast evaluation of Fränkel therapy.

The purpose of this study was to evaluate the skeletal, dental, and condylar positional changes induced by Fränkel FR-2 therapy. The pre- and posttreatment cephalometric, tomographic, and dental cast records of 25 consecutively treated cases were evaluated. Results showed little Class II skeletal correction with no headgear-type restraining effect on the maxilla or mandibular growth stimulation noted. Significant amounts of maxillary incisor retraction and mandibular incisor proclination were observed. The maxillary intermolar width along with the mandibular intercanine and intermolar widths were significantly increased during treatment. No significant changes in condylar position were found during Fränkel therapy and only a small increase in mandibular plane angle was noted.

Activator Appliances↗
PubMed1987

Nonextraction orthodontic therapy: posttreatment dental and skeletal stability.

To assess the long-term stability of nonextraction orthodontic treatment, the dental cast and cephalometric records of 28 cases were evaluated. Thirty cephalometric and seven cast parameters were examined before treatment, posttreatment, and an average of almost 8 years postretention. Results showed overall long-term stability to be relatively good. Relapse patterns seen were similar in nature, but intermediate in extent, between untreated normals and four first premolar extraction cases. Significant decreases were seen in arch length and intercanine width during the postretention period despite minimal changes during treatment. Incisor irregularly increased slightly postretention; intermolar width, overjet, and overbite displayed considerable long-term stability. Mandibular incisor mesiodistal and faciolingual dimensions were not associated with either pretreatment or posttreatment incisor crowding. Class II malocclusions with large ANB values and shorter mandibular lengths showed increased incisor irregularity, shorter arch lengths, and deeper overbites at the postretention stage, suggesting that the amount and direction of facial growth may have been partially responsible for maturational changes seen during the postretention period.

Adolescent↗