Winter 2000 Presentation Summary:

One can argue that orthodontics is the specialty that has the greatest ability to save teeth. We can change local factors in a tremendous way by repositioning teeth, thereby changing the subgingival microbiology. This significantly improves the longevity of the teeth. Our specialty used to be considered simply as the cosmetic side of dentistry. This is no longer true. Work done at the University of Pennsylvania on the beneficial changes in the subgingival microbiology attests to the value of proper alignment. And the results are impressive.

However, orthodontists must face one area of periodontal health, in particular: How many times do you finish a crowded case to exacting standards only to see the patient 5 to 10 years later with significant recession in the buccal segments? Would this pathologic change occur even without orthodontic treatment? Is it toothbrush abrasion, or does expansion of the bone done years earlier predispose a patient to later gingival recession? To answer this question, Dr. Vanarsdall spoke of his concerns and diagnostic methods for evaluating and treating transverse problems.

The envelope of change possible in the transverse dimension is significant in the growing patient where orthopedic expansion can be done. In the non-growing patient, mild alveolar bone remodeling can accomplish half of that change. Beyond that, surgery is needed for correction of deficient maxillary arch width. Unfortunately, even in adult cases treated with surgery, we cannot guaranteelong–term maintenance.

Diagnosing Transverse Problems

Dr. Vanarsdall evaluates transverse skeletal discrepancies by first measuring the maxillary width (JR to JL). JR and JL are the bilateral points on the jugal process at the intersection of the outline of the tuberosity of the maxilla and the zygomatic buttress. He then subtracts the lower arch width measured at the antigonial notch (AgR to AgL) to determine the differential index. This technique was published in Seminars in Orthodontics (September 1999). The differential index should be about 20mm in an adult Caucasian. In a nine-year-old, the maxilla should be about 62mm and the mandible about 76mm with a differential index of 14mm. An adult with a differential of 30 mm has a significant transverse problem regardless of how the transverse dental relation appears. This patient has a 10mm discrepancy beyond the differential index and needs surgically assisted palatal expansion, not lateral alveolar expansion done with archwires. Dr. Vanarsdall does surgically assisted expansion when the expansion needed is 5mm or more.

Interestingly, Dr. Vanarsdall has been involved with studies that show that the patient’s Angle classification correlates to the width of the dental arches. A Class I maxilla in the male is 2mm wider than a Class II at age eight and 3mm wider at age 18. Three millimeters is large considering that surgery is done for a 5mm discrepancy.

Gingival Recession and Transverse Deficiency

Gingival recession is multi factorial and cannot be blamed on tooth position alone; but tooth position must be carefully evaluated in a patient susceptible to recession. Thin tissues, genetic factors, stress, etc. can cause gingival recession. Preexisting mild recession is a tipoff that further recession is likely.

In general, gingival recession first occurs in the maxilla and, later, in the mandible. This is because the maxilla was not designed to receive forces like the mandible, but to transmit forces to the cranial bones. If the teeth are proclined significantly, they tend to receive rather than transmit forces and gingival recession can occur.

For the same reason, implants angled more than 20 degrees tend to lose bone and eventually fail. Building up bone with membranes or other periodontal techniques to provide for greater width of the alveolus in the buccal direction for an implant is only a short-term solution. In nine months, the implant will be out of the bone as the alveolar bone remodels to the width of the basal bone. The width of the basal bone is the ultimate determining factor in implant placement. Therefore, to increase the transverse dimension in adults, we need to rely more heavily on surgical expansion and, in the growing child, on orthopedic expansion of the basal bone..

Surgical Correction of Transverse Discrepancies

Two different techniques, multi-segmented maxillary surgery or surgical assisted palatal expansion, can be used for surgical expansion. Knowing which to use, and when, is critical to minimizing the possibility of gingival recession. Dr. Vanarsdall reports that three-piece maxilla surgeries are very unstable, at least on the East Coast. He quipped, "Perhaps you have more skillful surgeons here on the West Coast, but this procedure is not working well for us on the East Coast." He prefers surgically assisted palatal expansion, which he feels is more stable. To support this position he cited an article by Bill Proffitt at UNC published in 1996 in International Journal of Adult Orthodontics and Orthognathic Surgery. In this study, the most stable maxillary surgery was a maxillary impaction, and the least was a segmental upper jaw used to widen the maxilla.

If surgery is needed, Dr. Vanarsdall prefers to do surgically assisted palatal expansion at the beginning of treatment, followed later by a two-jaw procedure. In a 1995 article in the same journal, Dr. Vanarsdall reported that surgically assisted palatal expansion should be done for discrepancies of five or more millimeters. The one surgery technique, a three-piece maxilla, is done for cases with less than 5mm of maxillary deficiency.

Orthopedic Correction of Transverse Discrepancies

A younger patient who is stable is an ideal candidate for orthopedic expansion. This is when we would like to treat as many patients as possible. The upper limit for orthopedic expansion, according to Dr. Vanarsdall, is 15 years old in females (skeletal age) and 15 to 16 years old in males. For orthopedic expansions, Dr.Vanarsdall uses lip bumpers in the lower arch and Haas-type appliances with acrylic on the palate in the upper arch.

Perio-Orthodontic Issues

Dr. Vanarsdall illustrated the above points with cases from his practice and continued by discussing periodontal susceptibility and its relation to orthodontic treatment. He detailed the results of work at the University of Pennsylvania that showed decreased numbers of pathologic bacteria around teeth after alignment. These decreases brought the number of harmful bacteria below the threshold where damage occurs to the tissues! So, after orthodontic treatment, the teeth not only look better, but they are healthier too.

We need to advise patients of this when they ask us the question, "Does my child really need orthodontic treatment?" Indeed, if one considers maintenance and longevity of the teeth, without a doubt orthodontic treatment provides considerable benefit to the patient, particularly, the periodontally susceptible patient. These benefits have been reported in the literature for decades.

The maxillary transverse deficiency with thin, friable tissue is a risk marker for periodontal susceptibility and makes it difficult to treat for such a patient. In a recent NIDR study, 50% of untreated 18 to 19-year-old patients will exhibit 1–2mm of bone loss, as will 80% in those in their 30s, and 87% in their 40s. Aging, per se, is not a risk factor for gingival recession, but we see the accumulated results of gingival recession from other factors in older individuals.

Stress is a tremendous risk factor causing gingival recession and is likely tied to changes in the immune system. These individuals need scaling and root planing far more frequently than those not experiencing stressful conditions.

Establishment of ideal overbite and overjet is very important in the periodontally compromised patients in order to minimize their ability to rock their posterior teeth, increasing their mobility. However, excessively mobile teeth need scaling and root planing to remove the harmful bacteria prior to orthodontic treatment.

Studies done at Columbia University showed no increased susceptibility to periodontal breakdown based on a patient having a Class I or II or III malocclusion. However, studies done on 19-year-old cadets and reported in August 1994 show that those individuals with a Class II Div I malocclusion with an overjet of over 8mm have significant bone loss compared to ideal occlusions. Dr. Vanarsdall showed cases where patients with an untreated Class II Div I occlusion are on a downhill course periodontally because the posterior teeth are taking the full brunt of the bite. These individuals need coupling of the incisors to distribute the forces of the bite. So while the Angle classification is not a predisposing factor to periodontal breakdown, ideal overbite and overjet is an important factor to periodontal health.

Finally, Dr. Vanarsdall showed instances where orthodontic treatment extrusion was done to significantly decrease pocket depth in periodontally compromised teeth.

Conclusion

Orthodontic treatment can be particularly beneficial to the periodontally susceptible individual. Proper attention to diagnosing skeletal transverse discrepancies and knowing which procedures to use for each patient is essential in the modern orthodontic practice.

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