alveolar bone loss in overdentures: a 5-year study
TRANSCRIPT
REMOVABLE PROSTHODONTICS SECTKIN EDITORS
LOUIS BLATTERFEIN
5. HOWARD PAYNE GEORGE A. ZARB
Alveolar bone loss in overdentures: A S-year study
Robert J. Crum, D.D.S.,* and George E. Rooney, Jr., D.D.S.** VA Hospital, Hines, Ill., and VA Center, Wood, Wis.
S everal studies have shown that removal of all natural teeth and the wearing of complete dentures for a long time generally results in alveolar bone 10~s.“~ Tallgren 1 2 found that after removal of teeth and replacement with complete dentures, maxillary and mandibular alveolar resorption over a 7-year period was in the ratio of 1:4. In a longitudinal study, Tallgren3 observed that the average reduction of anterior mandibular ridge height was 9 to 10 mm over a 25-year denture-wearing period. Reduction of the maxillary ridge during this same period amounted to 2.5 to 3 mm.
Carlsson and Persson4 studied morphologic changes of the mandible following removal of teeth and placement of dentures. They found that the mandible lost 4 mm in height during the first year and that the resorption increased to 5 mm after 2 years and 6.7 mm 5 years following tooth removal. Carlsson and associates” also studied alveolar bone loss in 40 patients with edentulous maxillae and bilateral edentulous posterior mandibles. one group of 12 patients used only a complete maxillary denture; the second group of 16 patients used maxillary dentures and bilateral mandibular remov- able partial dentures, while a third group of 12 patients used a complete maxillary denture opposed by a removable partial denture with a Dolder Bar attached to the canines. At the 2-year follow-up no change was observed in mandibular contour in group 1; there was some change in groups 2 and 3. Also, the maxillary anterior process decreased an average of 1 mm in groups 1 and 2, while no change was observed in the group 3 patients.
Miller’ advocated overdentures as a means of preserving residual alveolar bone, and he reported lessened resorption of alveolar ridge tissue over a period of 6 years in 46 overdenture patients.
*Staff Prosthodontist, VA Hospital, Denver, Colo. **Chief, Dental Service, VA Center, Wood, Wis.
This clinical study was conducted to determine the amount of vertical residual alveolar bone loss in the anterior part of the maxillae and mandible in two groups of patients: one group with complete maxillary dentures and mandibular overdentures, and the other group with complete maxillary and mandibular dentures.
MATERIALS AND METHODS
Sixteen men aged 46 to 67 years of age who had all their natural anterior teeth prior to treatment were studied over a 5-year postextraction period. One group (group 1) of eight patients was treated with overdentures made over endodontically treated mandibular canines (Fig. 1). These canines were reduced to approximately 1.5 mm above the gingival margin, and the occlusal portion of the pulp cham- bers was sealed with silver amalgam. Group 2 was treated with complete maxillary and mandibular dentures.
Radiographic analysis was performed on cephal- ometric films made of the patients at the following intervals: (1) pie-extraction, (2) 3 weeks postextrac- tion, and (3) at l-year intervals. Each film was made with the patient’s mandible in the rest position. The postextraction radiographs were made without dentures in the mouth. Seven films were made for each patient, and the cephalometric analysis was made by the use of tracings and superimposition of films and tracings. The analysis of the amount of tissue change was confined to bone and not soft tissue.
Serial diagnostic casts were also made at the same time intervals and were analyzed by gross compari- son only. Carlsson” also used study casts to supple- ment the cephalometric radiographic analysis.
The amount of vertical bone resorption of the anterior part of the maxillary process was deter- mined by measuring a perpendicular from the NL (nasal line) to the lowest point on the alvedar
610 DECEMBER 1978 VOLUME 40 NUMBER 6
ALVEOLAR BONE LOSS IN OVERDENTURES
.Fig. 1. A patient from group 1 with two retained mandi- bular canines which have been reduced for use with an overdenture.
process (Fig. 2). Bjork8 defines the reference line NL
as the line through the spinal point and the pterygo-
maxillare.
The amount of vertical bone resorption of the
anterior part of the mandibular alveolar process was
determined by the measurement of a perpendicular
to the ML (mandibular line) (Fig. 2). Bjork defines
the ML as a tangent to the lower border of the body
of the mandible through the gnathion. The total
linear resorption of the anterior part of the maxillary
and mandibular alveolar processes was determined
by comparative analysis of the cephalometric films
made of the individual patients at the different
intervals.
The dentures were fabricated using the same
impression procedures and with cuspless acrylic resin
teeth arranged on a flat occlusal plane. Prior to
insertion of the dentures they were remounted, and
selective grinding and mill-in were performed. None
of the dentures were relined during the period of the
study.
RESULTS
Vertical bone resorption for both groups of patients is shown in Table I. The figures represent
the mean resorption of the vertical height of the
anterior portions of the maxillae and the mandible
at 5 years postextraction. The patients in group 1
with complete maxillary dentures and mandibular overdentures showed a mean vertical reduction of 1.8 mm for the anterior part of the maxillae and 0.6 mm for the anterior part of the mandible over a
period of 5 years postextraction. The patients in
Fig. 2. Landmarks used for cephalometric determination of amount of alveolar bone loss in the maxillae and mandible. NL, Nasal line, the line through the spinal point and pterygomaxillare, ML, Mandibular line, a line tangent to the lower border of mandible through the gnathion.
Table I. Vertical bone resorption
Vertical bone resorption
(mm)
Patient group Maxilla Mandible
Overdenture (group 1) Conventional dentures (group 2)
group 2 with the complete maxillary and mandibu-
lar dentures showed vertical bone loss on the maxil-
lae of 1.7 mm, while the mandible showed 5.2 mm of
bone resorption over the same 5-year period. The
individual tracings of the maxillae and mandibles in
the overdenture patients (group 1) are shown in Figs.
3 and 4. The tracings of the majiillae and mandibles
in the denture patients (group 2) are shown in Figs. 5
and 6.
The findings were taken at yearly intervals and
showed that the greatest portion of the loss of
alveolar bone (approximately 50%) occurred during
the first year after extractions.
DISCUSSION
The findings indicate that the use of the mandibu-
lar overdenture helps preserve alveolar bone in the
mandible. The reduction in the height of the anteri-
or part of the mandible in those patients wearing
complete upper and lower dentures amounted to 5.2
mm, as compared with 0.6 mm for the overdenture patients. This represents eight times more loss in the patients with complete dentures. The amount of anterior mandibular bone loss in the overdenture
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CRUM AND ROONEY
&=- ’
OVERDENTURES
3
Fig. 3. Individual cephalometric tracings of the maxillae in patients in group 1 (reduced in size). The dotted lines show bone levels after 5 years.
OVERDENTURES
Fig. 4. Individual cephalometric tracings of the mandi- bles in patients in group 1 (reduced in size). ‘TXe dotted lines show bone levels after 5 years.
CONVENTIONAL DENTURES
Fig. 5. Individual cephalometric tracings of the maxillae in group 2 patients (tracings reduced in size). Then dotted lines show bone levels after 5 years.
CONVENTIONAL DENTURES
Fig. 6. Individual cephalometric tracings of the mandi- bles in group 2 patients (tracings reduced in size). The dotted lines show bone levels after 5 years.
612 DECEMBER 1978 VOLUME 40 NUMBER 6
ALVEOLAR BONE LOSS IN OVERDENTURES
patients was similar to that observed by Tallgren* in
patients wearing mandibular bilateral free-end
partial dentures and complete maxillary dentures. Tallgren found that the reduction of the anterior
part of the mandible in these patients amounted to
0.8 mm over a 7-year period. The results of the
studies clearly indicate the advantage of retaining
teeth in the anterior part of the mandible for the
preservation of the alveolar process.
Patients in the control group (group 2), with
complete maxillary and mandibular dentures, exhib-
ited a mean vertical loss of 5.2 mm of alveolar bone
in the anterior part of the mandible and a mean
vertical loss of 1.7 mm in the anterior part of the
maxillae. This loss represents a ratio of 1:3 (maxillae
to mandible). These results are also similar to the
Tallgren findings.
The loss of bone in the maxillary process was
similar in both groups of patients. The maxillary
resorption in the overdenture group was slightly
greater than in those patients wearing complete
dentures. The maxillary loss amounted to a mean
vertical reduction of 1.8 mm in the overdenture
group and 1.7 mm in the complete denture group.
Tallgren’ also found that the mean reduction of the
maxillary process in the partial denture group was
slightly greater than in the complete denture
group.
Several articles have speculated on the role of
proprioception in the patient treated with overden-
tures.“, I” Pacer and Bowman” studied the percep-
tion of occlusal loads in overdenture patients. They
found that at load levels above 2,000 gm the over-
denture patients could discriminate loads better
than patients with complete dentures. They
reasoned that this was probably due to the fact that
the overdenture patients had more discriminatory
ability due to the discrete sensory ability of the
supporting teeth.
It may be hypothesized that the discrete proprio-
ceptive ability of the teeth under an overdenture acts
to signal against a physiologic overload of the system
and thus prevents bone resorption. In the complete
denture patients, the proprioceptive ability of the
mucosa is poor, and the constant overloading may
result in alveolar bone loss. The sensory feedback
input of the tooth may contribute to the preservation
of alveolar bone in overdenture patients, while the
absence of tooth sensory feedback in complete
denture patients may contribute to alveolar bone
destruction.
SUMMARY
The results of a 5-year clinical study show that
patients treated with complete maxillary dentures
and mandibular overdentures demonstrate less verti-
cal alveolar bone reduction than patients with
complete maxillary and mandibular dentures.
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Repmt requests to: DR. ROBERT J. CRCM
VETERANS ADMINISTRATION HOSPITAL
DENVER. Co~o. 80220
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